U.S. patent application number 09/867983 was filed with the patent office on 2001-11-01 for apparatus for rf active compositions used in adhesion, bonding, and coating.
This patent application is currently assigned to Ameritherm, Inc.. Invention is credited to Adishian, Gary C., Gorbold, Jonathan M., Ryan, William J..
Application Number | 20010035406 09/867983 |
Document ID | / |
Family ID | 27018554 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010035406 |
Kind Code |
A1 |
Ryan, William J. ; et
al. |
November 1, 2001 |
Apparatus for RF active compositions used in adhesion, bonding, and
coating
Abstract
A susceptor composition that can bond two or more layers or
substrates to one another and that can be used to coat or cut a
substrate. The susceptor composition is activated in the presence
of radio frequency (RF) energy. In one embodiment, the susceptor
composition of the present invention comprises a susceptor and a
carrier. The carrier and susceptor are blended with one another and
form a mixture, preferably a uniform mixture. The susceptor is
present in an amount effective to allow the susceptor composition
to be heated by RF energy. In a preferred embodiment, the susceptor
also functions as an adhesive. The susceptor is an ionic or polar
compound and acts as either a charge-carrying or an
oscillating/vibrating component of the susceptor composition. The
susceptor generates thermal energy in the presence of an RF
electromagnetic or electrical field (hereafter RF field).
Inventors: |
Ryan, William J.; (Avon,
NY) ; Gorbold, Jonathan M.; (Pittsford, NY) ;
Adishian, Gary C.; (Scottsville, NY) |
Correspondence
Address: |
STERNE, KESSLER, GOLDSTEIN & FOX PLLC
1100 NEW YORK AVENUE, N.W., SUITE 600
WASHINGTON
DC
20005-3934
US
|
Assignee: |
Ameritherm, Inc.
|
Family ID: |
27018554 |
Appl. No.: |
09/867983 |
Filed: |
May 31, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09867983 |
May 31, 2001 |
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09482553 |
Jan 13, 2000 |
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09867983 |
May 31, 2001 |
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09404200 |
Sep 23, 1999 |
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09867983 |
May 31, 2001 |
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09270505 |
Mar 17, 1999 |
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60078282 |
Mar 17, 1998 |
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Current U.S.
Class: |
219/634 ;
219/660 |
Current CPC
Class: |
C09J 2467/00 20130101;
B29C 66/472 20130101; B29C 66/71 20130101; B29C 66/71 20130101;
B29C 66/72328 20130101; C09J 5/04 20130101; B29C 66/1222 20130101;
B29C 66/81871 20130101; B29C 66/1284 20130101; B29C 66/73941
20130101; B29C 66/114 20130101; B29C 66/12425 20130101; B29C
66/1122 20130101; B29C 66/71 20130101; B29C 66/1224 20130101; B29C
66/112 20130101; B29C 66/83221 20130101; B29C 66/12445 20130101;
B29C 65/3684 20130101; B29C 66/71 20130101; B29C 66/43 20130101;
B29C 66/8322 20130101; B29C 66/431 20130101; C09J 5/06 20130101;
B29C 66/71 20130101; B29K 2067/046 20130101; B29K 2023/06 20130101;
B29C 66/45 20130101; B29K 2025/06 20130101; B29C 66/53461 20130101;
B29C 66/71 20130101; B29C 66/73151 20130101; B29C 66/542 20130101;
B29C 66/71 20130101; B29C 66/71 20130101; B29C 65/00 20130101; B29K
2023/00 20130101; B29K 2827/18 20130101; B29K 2033/08 20130101;
B29K 2023/12 20130101; B29K 2067/00 20130101; B29K 2027/06
20130101; B29K 2001/00 20130101; B29K 2077/00 20130101; B29K
2023/086 20130101; B29C 66/0044 20130101; B29C 65/3676 20130101;
B29C 66/71 20130101; B29C 66/73117 20130101; B29C 66/83413
20130101; B29C 66/836 20130101; B29C 66/71 20130101; B29C 65/3656
20130101; B29C 66/71 20130101; B29C 66/7234 20130101; B29C 66/81263
20130101; C08L 67/00 20130101; C09J 167/00 20130101; B29C 66/12821
20130101; B29C 66/71 20130101; B29C 66/73921 20130101; Y10T
428/2809 20150115; B29C 65/3696 20130101; C09D 167/00 20130101;
C09J 11/00 20130101; B29C 66/8122 20130101; B29C 66/71 20130101;
B29K 2995/007 20130101; B29C 65/368 20130101; B29C 66/8122
20130101 |
Class at
Publication: |
219/634 ;
219/660 |
International
Class: |
H05B 006/06 |
Claims
What is claimed is:
1. A composition for use in adhesion or bonding, comprising: a
susceptor; and a polar carrier, wherein said susceptor and/or said
polar carrier are present in amounts effective to allow said
composition to be heated by radio frequency (RF) energy, with the
proviso that said susceptor is not a quaternary ammonium salt and
that said polar carrier comprises about 13 to about 30 weight
percent of the composition with respect to said susceptor.
2. A composition for use in coating, comprising: a susceptor; and a
polar carrier, wherein said susceptor and/or said polar carrier are
present in amounts effective to allow said composition to be heated
by RF energy, with the proviso that said susceptor is not a
quaternary ammonium salt and that said polar carrier comprises
about 13 to about 30 weight percent of the composition with respect
to said susceptor.
3. A composition for use in adhesion, bonding or coating,
consisting essentially of: a susceptor; and a polar carrier,
wherein said susceptor and/or said carrier are present in amounts
effective to allow said composition to be heated by RF energy and
that said polar carrier comprises about 13 to about 30 weight
percent of the composition with respect to said susceptor.
4. The composition of any one of claims 1-3, wherein the susceptor
and the carrier are substantially blended with one another and form
a mixture.
5. The composition of any one of claims 1-3, wherein the susceptor
and the carrier are disposed on one another.
6. The composition of any one of claims 1-3, wherein the susceptor
is an ionic compound.
7. The composition of any one of claims 1-3, wherein the susceptor
is a polar compound having a sufficiently high dipole moment that
molecular oscillations or vibrations of the compound occur when
exposed to RF energy.
8. The composition of any one of claims 1-3, wherein the polar
carrier has a dielectric constant of 13-63 (25.degree. C.)
9. The composition of any one of claims 1-, further comprising or
consisting essentially of an adhesive compound, wherein said
adhesive compound, said susceptor and said polar carrier are
blended substantially with one another to form said mixture.
10. The composition of claim 9, wherein said adhesive compound and
said susceptor are an ionomer.
11. The composition of any one of claims 1-3, wherein said
susceptor comprises or consists essentially of an aqueous
dispersion of a sulfopolyester adhesive.
12. The composition of claim 11, wherein said sulfopolyester
adhesive is present at a concentration of from about 5% to about
75%.
13. The composition of any one of claims 1-3, wherein said
susceptor is one or more ionic salts and is present in the form of
a precipitate.
14. The composition of any one of claims 1-3, wherein said
susceptor is an ionomeric polymer.
15. The composition of claim 14, wherein said ionomeric polymer is
a sulfonated polyester or copolymer thereof, or salt thereof.
16. The composition of claim 15, wherein said ionomeric polymer is
the salt of a sulfonated polyester.
17. The composition of claim 16, wherein the sulfonated polyester
is a linear polyester with a high Tg.
18. The composition of claim 15, wherein said ionomeric polymer is
a acrylic acid polymer or copolymer, or a salt thereof.
19. The composition of claim 15, wherein said ionomeric polymer is
gelatin.
20. The composition of claim 19, wherein said gelatin has a pH of
about 8 to 12.
21. The composition of claim 19, wherein said gelatin has a pH of
about 1 to about 6.
22. The composition according to any one of claims 1-3, wherein
said polar carrier is a polyol.
23. The composition according to claim 22, wherein said polyol is
selected from the group consisting of ethylene glycol;
1,2-propylene glycol; 1,3-propanediol;
2,4-dimethyl-2-ethylhexane-1,3,diol; 2,2-dimethyl-1,3-propanediol;
2-ethyl-2-butyl-1,3-propanediol;
2-ethyl-2-isobutyl-1,3-propanediol; 1,3-butanediol; 1,4-butanediol;
1,5-pentanediol; 1,6-hexanediol; 2,2-4-trimethyl-1,6-hexanediol;
thiodiethanol; 1,2-cyclohexanedimethanol;
1,3-cyclohexanedimethanol; 1,4-cyclohexanedimethanol;
2,2,4,4-tetramethyl-1,3-cyclobutanediol; and p-xylylenediol.
24. The composition according to claim 22, wherein said polyol is
glycerin.
25. The composition according to any one of claims 1-3, further
comprising or consisting essentially of a thermoplastic
polymer.
26. The composition according to any one of claims 1-3, further
comprising or consisting essentially of a thermoset resin.
27. The composition according to any one of claims 1-3, wherein the
composition is substantially transparent or translucent.
28. The composition of any one of claims 1-3, further comprising an
insoluble porous carrier saturated with said composition.
29. The composition of claim 28, wherein said insoluble porous
carrier is a thermoplastic web.
30. The composition of claim 38, wherein said insoluble porous
thermoplastic carrier web is a non-woven polypropylene (PP).
31. The composition of claim 37, further comprising a first
polyolefin layer and a second polyolefin layer disposed on said
insoluble porous carrier, wherein said first and second polyolefin
layers are bonded or adhered to the porous carrier by RF
heating.
32. A method of bonding or adhering a first substrate to a second
substrate, comprising interposing a composition between the first
and second substrates, said composition comprising a susceptor and
a polar carrier, wherein said carrier and said susceptor are
blended substantially with one another and form a mixture, and
wherein said susceptor and/or said carrier are present in amounts
effective to allow said composition to be heated by RF energy; and
applying RF energy to said composition to heat said composition,
thereby causing the first and second substrates to become adhered
or bonded, with the proviso that said susceptor is not a quaternary
ammonium salt.
33. The method of claim 32, wherein said RF energy has a frequency
in the range of from about 100 kilohertz to about 5.0
Gigahertz.
34. The method of claim 32, wherein said RF energy has a frequency
in the range from about 10 megahertz to about 30 megahertz.
35. The method of claim 32, wherein said RF energy has a power of
about 0.1 kilowatts to about 5 kilowatts.
36. The method of claim 32, wherein said polar carrier comprises
about 13 to about 30 weight percent of the composition with respect
to said susceptor.
37. A method of bonding or adhering a first substrate to a second
substrate in less than about one second, comprising interposing a
composition between the first and second substrates, said
composition comprising a susceptor and a polar carrier, wherein
said carrier and said susceptor are blended substantially with one
another and form a mixture, and wherein said susceptor and/or said
carrier are present in amounts effective to allow said composition
to be heated by RF energy; and applying RF energy to said
composition to heat said composition, thereby causing the first and
second substrates to become adhered or bonded in less than about 1
second.
38. The method of claim 37, wherein said polar carrier comprises
about 13 to about 30 weight percent of the composition with respect
to said susceptor.
39. The method of claim 37, wherein said composition melts or flows
and said first and second substrates becomes bonded or adhered in
about 100 milliseconds to about 1 second.
40. The method of claim 32 or 37, wherein said interposing further
comprises coating at least one of the first and second substrates
with said composition; and placing the first and second substrates
in contact with a uniform pressure applied to the first and second
substrates.
41. The method of claim 32 or 37, wherein said interposing
comprises interposing said composition between a first multilayer
stack of the first substrate and a second multilayer stack of the
second substrate.
42. The method of claim 32 or 37, wherein the first and second
substrates are selected from the group consisting of film,
non-woven, or foamed PP, and film, non-woven, or foamed
polyethelene (PE).
43. The method of claim 32 or 37, wherein said interposing
comprises interposing a composition between the first and second
substrates, said composition comprising said susceptor, said polar
carrier, and an adhesive compound, wherein said polar carrier, said
adhesive compound, and said susceptor are blended substantially
with one another and form said mixture.
44. The method of claim 32 or 37, wherein said susceptor is an
ionomeric adhesive.
45. The method of claim 44, wherein said ionomeric adhesive is a
sulfonated polyester or copolymer thereof, or a salt thereof.
46. The method of claim 44, wherein said ionomeric adhesive is
gelatin.
47. The method of claim 44, wherein said ionomeric adhesive is a
polyacrylic acid polymer or copolymer thereof, or a salt
thereof.
48. An adhered or bonded composition obtained according to the
method of claim 32 or 37.
49. A method of bonding or adhering a first substrate to a second
substrate, comprising: applying a first composition onto the first
substrate; applying a second composition onto the second substrate;
contacting said first composition with said second composition;
applying RF energy to said first and second compositions to heat
said compositions, thereby causing the first and second substrates
to become adhered or bonded; wherein one of said compositions
comprises a susceptor and the other of said compositions is a polar
carrier, and the susceptor and/or the carrier are present in
amounts effective to allow said first and second compositions to be
heated by RF energy.
50. The method of claim 59, wherein said susceptor is not a
quaternary ammonium salt.
51. A kit for adhering or bonding a first substrate to a second
substrate, comprising one or more containers, at least one of said
containers comprising a susceptor composition, said susceptor
composition comprising a susceptor and a polar carrier
substantially uniformly dispersed in one another to form a mixture,
wherein said susceptor and/or said carrier are present in amounts
effective to allow said composition to be heated by RF energy.
52. A kit for adhering or bonding a first substrate to a second
substrate, comprising at least two containers, wherein one of said
containers comprises a susceptor and another of said containers
comprises a polar carrier, wherein when said susceptor and said
carrier are applied to at least one of said first and second
substrates and said susceptor and carrier are interfaced, a
composition is formed that is heatable by RF energy.
53. The kit of claim 51 or 52, wherein said susceptor is an
ionomeric polymer.
54. The kit of claim 53, wherein said ionomeric polymer is a
sulfonated polyester or copolymer thereof, or a salt thereof.
55. The kit of claim 53, wherein said ionomeric polymer is an
acrylic acid polymer or copolymer thereof, or a salt thereof.
56. The kit of claim 53, wherein said ionomeric polymer is
gelatin.
57. A method of making a composition for bonding or adhering,
comprising admixing a susceptor and a polar carrier, wherein said
polar carrier and said susceptor are substantially uniformly
dispersed in one another and form a mixture, and wherein said
susceptor and/or said carrier is present in amounts effective to
allow said composition to be heated by RF energy and wherein said
polar carrier comprises about 13 to about 30 weight percent of the
composition with respect to said susceptor.
58. The method of claim 57, wherein susceptor is an ionomeric
polymer.
59. The method of claim 58, wherein said ionomeric polymer is a
sulfonated polyester or copolymer thereof, or a salt thereof.
60. The method of claim 57, wherein said ionomeric polymer is an
acrylic acid polymer or copolymer thereof, or a salt thereof.
61. The method of claim 57, wherein said admixing further comprises
admixing an adhesive compound, said carrier, and said susceptor,
wherein said carrier, said adhesive compound, and said susceptor
are substantially uniformly dispersed in one another and form said
mixture.
62. A composition obtained according to the method of claim 57.
63. A composition comprising an ionomeric polymer and a polar
carrier wherein said polar carrier comprises about 13 to about 30
weight percent of the composition with respect to said polymer.
64. The composition according to claim 63, wherein said ionomeric
polymer is a sulfonated polyester or a copolymer thereof, or a salt
thereof.
65. The composition according to claim 63, wherein said ionomeric
polymer is an acrylic acid polymer or copolymer thereof, or a salt
thereof.
66. The composition according to claim 63, wherein said ionomeric
polymer is gelatin.
67. The composition according to claim 63, wherein said polar
carrier is a polyol.
68. The composition according to claim 67, wherein said polyol is
selected from the group consisting of ethylene glycol;
1,2-propylene glycol; 1,3-propanediol;
2,4-dimethyl-2-ethylhexane-1,3,diol; 2,2-dimethyl-1,3-propanediol;
2-ethyl-2-butyl-1,3-propanediol;
2-ethyl-2-isobutyl-1,3-propanediol; 1,3-butanediol; 1,4-butanediol;
1,5-pentanediol; 1,6-hexanediol; 2,2-4-trimethyl-1,6-hexanediol;
thiodiethanol; 1,2-cyclohexanedimethanol;
1,3-cyclohexanedimethanol; 1,4-cyclohexanedimethanol;
2,2,4,4-tetramethyl-1,3-cyclobutanediol; and p-xylylenediol.
69. The composition according to claim 67, wherein said polyol is
glycerin.
70. A method of curing a thermoset, comprising combining the
thermoset with a polar carrier to give a mixture and exposing the
mixture to RF energy.
71. The method of claim 70, wherein said thermoset is an epoxy
resin, an acrylic resin, a polyester resin or a urethane resin.
72. The method of claim 70, wherein said polar carrier is a
polyol
73. The composition according to claim 72, wherein said polyol is
selected from the group consisting of ethylene glycol;
1,2-propylene glycol; 1,3-propanediol; 2,4-dimethyl-2-ethylhexane-1
,3,diol; 2,2-dimethyl-1,3-propanediol;
2-ethyl-2-butyl-1,3-propanediol;
2-ethyl-2-isobutyl-1,3-propanediol; 1,3-butanediol; 1,4-butanediol;
1,5-pentanediol; 1,6-hexanediol; 2,2-4-trimethyl-1,6-hexanediol;
thiodiethanol; 1,2-cyclohexanedimethanol;
1,3-cyclohexanedimethanol; 1,4-cyclohexanedimethanol;
2,2,4,4-tetramethyl-1,3-cyclobutanediol; and p-xylylenediol.
74. The composition according to claim 72, wherein said polyol is
glycerin.
75. An apparatus, comprising: a first portion having a first mating
surface; a second portion, having a second mating surface; a
composition disposed between said first mating surface and said
second mating surface, wherein said composition comprises a
susceptor and a polar carrier wherein said susceptor and/or said
polar carrier are present in amounts effective to allow said
composition to be heated by RF energy, and wherein said composition
adheres said first mating surface to said second mating surface
such that application of a force to separate said first mating
surface and said second mating surface results in breakage of the
apparatus unless said composition is in a melted state.
76. The apparatus of claim 75, wherein said composition is disposed
on said first mating surface and said second mating surface such
that said composition is not accessible when said first and second
mating surfaces are joined.
77. The apparatus of claim 75, wherein said portion comprises a
protrusion from said first mating surface.
78. The apparatus of claim 75, wherein said second portion
comprises a recess formed in said second mating surface.
79. The apparatus of claim 77, further comprising an electronic
circuit path disposed on said protrusion.
80. The apparatus of claim 75, wherein said first portion and said
second portion may be disassembled upon application of RF energy to
said composition.
81. A method for cutting a substrate, comprising: applying a
composition to a portion of the substrate, wherein the composition
comprises a susceptor and polar carrier wherein said susceptor
and/or said polar carrier are present in amounts effective to allow
said composition to be heated by RF energy, and wherein said
portion of the substrate defines a first section of said substrate
and a second section of said substrate; melting said portion of the
substrate, wherein said melting step includes the step of heating
said composition, wherein the step of heating said composition
includes the step of applying RF energy to said composition; after
said portion of said substrate has begun to melt, applying a force
to said substrate to separate said first section from said second
section.
82. A method for dynamically bonding a first adherand to a second
adherand, comprising: (1) creating an article of manufacture
comprising the first adherand, the second adherand, and a
composition, said composition being placed between the first
adherand and the second adherand, wherein said composition can be
activated in the presence of an RF field; (2) moving the article of
manufacture along a predetermined path; (3) generating along a
portion of said predetermined path an RF field having sufficient
energy to activate said composition, wherein said composition is
exposed to said RF field for no more than about 1 second, and
wherein said composition is activated by its less than 1 second
exposure to said RF field.
83. The method of claim 82, wherein said article passes through
said RF field at a rate of at least about one-thousand feet per
minute.
84. The method of claim 83, wherein the article passes through said
RF field at a rate of about 1000 feet per minute.
85. The method of claim 82, wherein said composition comprises a
susceptor and a polar carrier.
86. A method for applying a susceptor composition to a substrate,
comprising: (1) formulating the susceptor composition as a liquid
dispersion; (2) applying said liquid dispersion of said susceptor
composition to the substrate; (3) drying said susceptor
composition, wherein said drying step includes the step of applying
RF energy across the composition, thereby generating heat within
said liquid dispersion.
87. The method of claim 86, further comprising rolling up the
substrate after the susceptor composition has dried.
88. A method of bonding or adhering a first substrate to a second
substrate, comprising: applying a first composition onto the first
substrate; applying a second composition onto the first
composition; contacting the second substrate with the second
composition; and applying RF energy to the first and second
compositions to heat the compositions, thereby causing the first
and second substrates to become adhered or bonded, wherein one of
said compositions comprises a susceptor and the other of said
compositions is a polar carrier, and the susceptor and/or the
carrier are present in amounts effective to allow the first and
second compositions to be heated by RF energy.
89. The method according to claim 88, wherein one of the
compositions comprises at least one susceptor and the other of the
compositions comprises at least one polar carrier.
90. A method for dynamically bonding a first substrate to a second
substrate, comprising: applying a composition onto the first
substrate; after applying said composition onto the first
substrate, forming a roll of said first substrate; storing said
roll; unrolling said roll; and while unrolling said roll: joining
an unrolled portion of the first substrate with a portion of the
second substrate such that said portion of the second substrate is
in contact with a portion of said composition applied onto the
first substrate; and applying RF energy to said portion of said
composition, wherein said portion of said composition heats and
melts as a result of the RF energy being applied thereto.
91. A method for manufacturing a radio frequency (RF) active
adhesive film, comprising: formulating an RF active adhesive
composition into an extrudable resin; providing said extrudable
resin to a first extruder; providing a thermoplastic to a second
extruder; providing a sealing material to a third extruder;
layering the output of the first, second, and third extruder to
form a three layered film, wherein said thermoplastic is disposed
between said sealing material and said RF active adhesive
composition; and stretching said three layered film.
92. The method of claim 91, further comprising rolling up said
three layered film after stretching said three layered film.
93. The method of claim 91, further comprising heating said three
layered film prior to stretching said three layered film.
94. A method for manufacturing flexible packaging, comprising:
manufacturing a film comprising a first layer comprised of a
sealing material, a second layer comprised of a thermoplastic
composition, and a third layer comprised of a radio frequency (RF)
active composition, wherein said second layer is disposed between
said first layer and said third layer, and wherein said RF active
composition can be heated by applying a radio signal thereto;
applying ink to a thermoplastic film; contacting said first film
with said thermoplastic film to form an assembly, wherein said
thermoplastic film is in direct contact with said third layer;
applying a radio signal to said assembly; and nipping said
assembly.
95. The method of claim 94, wherein said radio signal has a
frequency of not more than about 20 MHz.
96. The method of claim 94, wherein said radio signal has a
frequency of not more than about 15 MHz.
97. The method of claim 94, wherein said thermoplastic film is 70
gauge oriented polypropylene.
98. The method of claim 94, wherein said radio frequency active
composition comprises a susceptor and a polar carrier.
99. The method of claim 94, wherein said radio signal is applied to
said assembly for not more than about one second.
100. A seal for sealing a container, comprising: an outer layer of
polyethylene; a layer of paper in contact with said outer layer; a
second polyethylene layer in contact with said paper layer; a layer
comprising a non-metallic susceptor composition in contact with
said second polyethylene layer; a barrier layer in contact with
said layer comprising said non-metallic composition; and an inner
layer in contact with said barrier layer, wherein said non-metallic
composition heats when a radio signal is applied thereto.
101. The seal of claim 100, wherein said non-metallic composition
comprises a susceptor and a polar carrier.
102. A bookbinding method, comprising: applying a susceptor
composition to a portion of one side of a substrate, wherein said
susceptor composition can be heated by applying a radio signal
thereto; feeding said substrate into a printing means for printing
ink onto said substrate; after said printing means prints ink on
said substrate, stacking said substrate with other substrates;
applying a radio signal to said stack of substrates, thereby
heating said susceptor composition; and nipping the stack.
103. The method of claim 102, wherein said susceptor composition
comprises a susceptor and a polar carrier.
104. The method of claim 103, wherein said susceptor composition is
transparent.
105. The method of claim 102, wherein said substrate comprises
paper.
106. A method of assembling a periodical, comprising: coating a
plurality of substrates with a composition, wherein the composition
comprises a susceptor and polar carrier wherein said susceptor
and/or said polar carrier are present in amounts effective to allow
said composition to be heated by RF energy; print ink onto said
plurality of substrates; stacking said plurality of substrates;
applying an electromagnetic field- to said plurality of substrates;
and applying pressure to said plurality of substrates.
107. An apparatus for activating a composition using radio
frequency (RF) energy, comprising: a direct current (DC) voltage
source; an RF amplifier coupled to the DC voltage source, wherein
the DC voltage source provides DC voltage to the RF amplifier; an
impedance matching circuit coupled to an output of the RF
amplifier; a first probe and a second probe connected to the
impedance matching circuit; and signal generating means, coupled to
the RF amplifier, for generating an RF signal, wherein the RF
amplifier amplifies the RF signal and the amplified RF signal is
provided to the impedance matching circuit, whereby an RF field is
generated at the probes and the RF field is used to activate the
composition.
108. The apparatus of claim 107, wherein the frequency of the RF
signal is within the about 1 kHz to about 5 GHz frequency band.
109. The apparatus of claim 107, wherein the frequency of the RF
signal is within the about 1 MHz to about 80 MHz frequency
band.
110. The apparatus of claim 107, wherein the frequency of the RF
signal is within the about 10 MHz to about 15 MHz frequency
band.
111. The apparatus of claim 107, wherein the power of the amplified
signal is between about 50 watts and 2 kilowatts.
112. The apparatus of claim 107, wherein the power of the amplified
signal is between about 500 watts and 2 kilowatts.
113. The apparatus of claim 107, wherein a DC voltage provided to
the RF amplifier by the DC voltage source is between about 50 and
200 dc volts.
114. The apparatus of claim 107, wherein a DC voltage provided to
the RF amplifier by the DC voltage source is between about 130 and
200 dc volts.
115. The apparatus of claim 107, wherein the impedance matching
circuit comprises: a connector for receiving an RF signal; a balun
transformer coupled to the connector; a first and a second variable
capacitor coupled to the balun transformer; and an inductor
connected between the first and second variable capacitor.
116. The apparatus of claim 107, wherein the RF amplifier comprises
means for amplifying a milliwatt signal up to a multiple kilowatt
continuous wave amplitude signal with greater than eighty percent
power conversion efficiency while operating directly from a 100 to
200 VDC power source, with an instantaneous bandwidth of two-thirds
of an octave in the middle High Frequency RF spectrum between 3 and
30 MHz.
117. The apparatus of claim 107, further comprising a processor for
controlling the frequency of the RF signal generated by the signal
generating means, and a power sensor coupled to the impedance
matching circuit for providing a signal to the processor, wherein
the signal is used by the processor in controlling the frequency of
the RF signal generated by the signal generating means.
118. The apparatus of claim 116, wherein the signal provided to the
processor corresponds to the amount of power reflected from the
impedance matching circuit.
119. The apparatus of claim 116, wherein the signal provided to the
processor corresponds to the amount of power provided to the
impedance matching circuit.
120. The apparatus of claim 116, wherein the signal provided to the
processor corresponds to the ratio of the amount of power provided
to the impedance matching circuit and the amount of power reflected
from the impedance matching circuit.
121. The apparatus of claim 107, wherein the first probe is a
conductive tube.
122. The apparatus of claim 121, wherein the first probe has a
diameter of about one-eighth of an inch.
123. The apparatus of claim 107, wherein one end of the first probe
is connected to the impedance matching circuit and the other end is
curled to reduce corona effects.
124. The apparatus of claim 107, wherein the first probe is
sinusoidally shaped.
125. The apparatus of claim 107, wherein the probes include a
proximal region in which the probes are spaced apart, an activation
region in which the probes are proximate to one another, and a
distal region in which the probes are spaced apart.
126. The apparatus of claim 125, wherein the probes are
substantially parallel to each other in the activation region.
127. The apparatus of claim 107, further comprising a third probe
connected to the impedance matching circuit.
128. The apparatus of claim 107, wherein the impedance matching
circuit comprises an inductor, wherein when the amplified RF signal
is provided to the impedance matching circuit an alternating
current flows through the inductor.
129. The apparatus of claim 128, wherein the first probe, the
second probe, and the inductor are connected in series such that
the inductor is connected between the first probe and the second
probe.
130. An apparatus for activating a composition using radio
frequency (RF) energy, comprising: a 100 to 200 VDC power source;
amplifier means for amplifying a milliwatt RF signal up to at least
a kilowatt continuous wave amplitude RF signal while achieving
greater than eighty percent power conversion efficiency, the
amplifying means achieving an instantaneous bandwidth of two-thirds
octave in the middle high frequency RF spectrum between 3 MHz and
30 MHz, and operating directly from the 100 to VDC power source;
signal generating means for generating the milliwatt RF signal to
be amplified by the amplification means; and an impedance matching
circuit coupled to an output of the amplification means, wherein
the amplification means amplifies the milliwatt RF signal, and the
amplified RF signal is provided to the impedance matching circuit,
whereby an RF field is produced and the RF field is used to
activate the composition.
131. The apparatus of claim 130, further comprising a first probe
and a second probe connected to the impedance matching circuit.
132. The apparatus of claim 130, wherein when the amplified RF
signal is provided to the impedance matching circuit an RF field
emanates from the probes.
133. The apparatus of claim 132, wherein the impedance matching
circuit comprises an inductor, wherein the first probe, the second
probe, and the inductor are connected in series, with the inductor
being placed between the probes.
134. The apparatus of claim 130, wherein the first probe is a
conductive tube.
135. The apparatus of claim 134, wherein the tube is circular and
has a diameter of about one-eighth of an inch.
136. The apparatus of claim 130, wherein one end of the probe is
connected to the impedance matching circuit and the other end is
curved to reduce corona effect.
137. The apparatus of claim 130, wherein the probes are
sinusoidally shaped.
138. The apparatus of claim 130, further comprising a third probe
connected to the impedance matching circuit.
139. A method for inductively liquefying a composition, comprising
the steps of: producing an RF signal; amplifying the RF signal;
providing the amplified RF signal to an impedance matching circuit
comprising a first probe and a second probe, and wherein when the
amplified RF signal is provided to the impedance matching circuit
an RF field is produced at the probes; and placing the composition
in proximity to the probes so that the composition is exposed to
the RF field, whereby the composition's exposure to the RF field
causes the temperature of the composition to increase.
140. The method of claim 139, further comprising the step of
controlling the frequency of the amplified RF signal such that the
frequency of the amplified RF signal follows the resonant frequency
of the impedance matching circuit while the composition is
heating.
141. The method of claim 139, wherein the frequency of the RF
signal is between about 1 kHz and about 5 GHz.
142. The method of claim 139, wherein the frequency of the RF
signal is between about 1 MHz and about 80 MHz.
143. The method of claim 139, wherein the frequency of the RF
signal is between about 10 MHz and 15 MHz.
144. The method of claim 139, wherein the composition is exposed to
the RF field for not more than about 1 second.
145. The method of claim 139, wherein the composition is exposed to
the RF field for not more than about 0.1 seconds.
146. The method of claim 139, wherein the composition is exposed to
the RF field for not more than about 0.075 seconds.
147. The method of claim 139, wherein the power of the RF signal
provided to the impedance matching circuit is about 50 watts to 2
kilowatts.
148. The method of claim 139, wherein the composition comprises an
ionomeric polymer and a polar carrier.
149. A method for heating a composition comprising an ionomeric
polymer and a polar carrier, the method comprising the steps of:
generating an RF signal; using the RF signal to generate an RF
field; and exposing the composition to the RF field.
150. The method of claim 149, wherein the composition is exposed to
the RF field for not more than about 1 second.
151. The method of claim 149, wherein the composition is exposed to
the RF field for not more than about 0.5 seconds.
152. The method of claim 149, wherein the composition is exposed to
the RF field for not more than about 0.1 seconds.
153. The method of claim 149, wherein the composition is exposed to
the RF field for not more than about 0.075 seconds.
154. The method of claim 149, wherein the frequency of the RF
signal is between 1 kHz and 5 GHz.
155. The method of claim 149, wherein the frequency of the RF
signal is between 1 MHz and 80 MHz.
156. The method of claim 149, wherein the frequency of the RF
signal is between 10 MHz and 15 MHz.
157. An interdigitated probe system, comprising: a first element
comprising a first conductor and one or more second conductors
connected to the first conductor; and a second element comprising a
first conductor and one or more second conductors connected to the
first conductor, wherein the first element and the second element
are orientated such that the one or more second conductors of the
first element are coplanar with the one or more second conductors
of the second element and each one of the one or more second
conductors of the first element are adjacent to at least one of the
one or more second conductors of the second element.
158. An apparatus for activating a sample, comprising: an
alternating voltage supply; a first output terminal and a second
output terminal coupled to said alternating voltage supply, wherein
an alternating voltage is produced between said first and second
output terminals; and a first probe coupled to first output
terminal and a second probe coupled to said second output
terminal.
159. The apparatus of claim 107, wherein said probes include a
proximal region in which said probes are spaced apart, an
activation region in which said probes are proximate to one
another, and a distal region in which said probes are spaced
apart.
160. The apparatus of claim 107, wherein said probes are conductive
tubes.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation-in-part of
application Ser. No. 09/404,200, filed Sep. 23, 1999, which is a
continuation-in-part of application Ser. No. 09/270,505, filed Mar.
17, 1999, which claims the benefit of U.S. provisional application
No. 60/078,282, the contents of each of which are fully
incorporated by reference herein.
[0002] This patent application is related to the following
co-pending U.S. utility patent application: "Radio Frequency
Heating System," -application Ser. No. 09/270,507, filed Mar. 17,
1999, the contents of which are incorporated by reference
herein.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention relates generally to the use of media
containing ionic compounds and/or nonionic compounds with high
dipole moments as a radio frequency (RF) susceptors in RF activated
systems.
[0005] 2. Related Art
[0006] Radio frequency (RF) heating is a well established
non-contact precision heating method that is used to generate heat
directly within RF susceptors, and indirectly within materials that
are in thermally conductive contact with RF susceptors. RF
susceptors are materials that have the ability to couple and
convert RF energy into heat energy within the material.
[0007] Conventional adhesives are not suitable RF susceptors that
can be directly heated and activated by RF heating. Rather, these
conventional adhesives are typically heated indirectly through
thermally conductive contact with an RF susceptor material. FIG. 1
illustrates two conventional methods that are currently used in
industry for indirect RF heating of conventional adhesives: The
first method is illustrated in FIG. 1A, where susceptor material
102 exists as a bulk macroscopic layer. RF susceptor material 102
is directly heated by RF energy, and adhesive layer 104 is
indirectly heated through thermally conductive contact with RF
susceptor material 102. For example, adhesive layer 104 may be
applied to a continuous surface of susceptor material 102, such as
steel or aluminum. The second method is illustrated in FIG. 1B,
where susceptor material 112 consists of discrete macroscopic
particles. Adhesive layer 114 is loaded with macroscopic particles
of a RF susceptor material 112, such as macroscopic particles or
flakes of metal oxides, metallic alloys, or aluminum. With this
conventional method, each RF susceptor particle 112 acts as a
discrete RF susceptor, generating heat throughout adhesive layer
114.
[0008] An example of a conventional RF energy activated
composition, such as that shown in FIG. 1B, is described in U.S.
Pat. No. 5,378,879, issued to Monovoukas ("Monovoukas"). Monovoukas
utilizes macroscopic "loading particles" as discrete RF susceptors.
The particles are heated by RF energy and in turn conduct heat to
the surroundings. These macroscopic loading particles are thin
flakes (i.e. in thin disk-like configuration) that are designed to
be admixed to relatively thick extruded materials. However, these
flakes are not well suited for use as susceptors in thin film
bonding applications in which physical distortions, discolorations
in the surface, or opacity of the bonded films would result from
the flakes.
[0009] Another example of a conventional inductively activated
adhesive is described in U.S. Pat. No. 3,574,031, issued to Heller
et al. ("Heller"). Heller describes a method of heat welding
thermoplastic bodies using an adhesive layer that contains
uniformly dispersed macroscopic RF susceptors, typically iron oxide
particles. These discrete RF susceptor particles are ferromagnetic
in nature. A disadvantage of this type of method is that a tradeoff
must be made between the size of the particle employed versus the
power level and duration of the inductive heating process. For
example, if susceptor particles are kept small in size, the
mechanical strength of the bond tends to increase. However, as the
size of these discrete susceptors is reduced, the power levels and
dwell times required to heat the RF susceptor material and achieve
acceptable bonds tend to increase. Another disadvantage of this
type of method is the high levels of loading of the medium with RF
susceptor particles that is required for efficient activation. Such
high loading levels detract from the physical properties and
rheology of the adhesive composition. Still another disadvantage is
the dark color and opacity of the composition, which renders the
composition undesirable for many applications.
[0010] An example of adhesive activated by a dielectric process is
described in U.S. Pat. No. 5,661,201, issued to Degrand
("Degrand"). Degrand describes a thermoplastic film including at
least one ethylene copolymer and a sufficient quantity of
N,N-ethylene-bisstearamide that is capable of being sealed
utilizing a current at a frequency of about 27.12 megahertz (MHz).
A disadvantage of this type of film and sealing process is the
inherent tendency to also heat the adherand.
[0011] U.S. Pat. No. 5,182,134, issued to Sato, discloses methods
of curing a thermoset composition by applying an RF signal having a
frequency of about 1 to 100 MHz to a composition comprising a major
portion of a thermoset and a receptor. The receptor is described as
being one of the alkali or alkaline earth metal sulfate salts (e.g.
calcium sulfate), aluminum trihydrate, quaternary ammonium salts,
phosphonate compounds, phosphate compounds, polystyrene sulfonate
sodium salts or mixtures thereof. According to this patent, all of
the exemplified compositions took longer than one second to
heat.
[0012] U.S. Pat. No. 5,328,539, issued to Sato, discloses methods
of heating thermoplastic susceptor compositions by applying an RF
signal having a frequency of about 1 to 100 MHz. The susceptors are
described as being one of the alkali or alkaline earth metal
sulfate salts (e.g. calcium sulfate), aluminum trihydrate.
quaternary ammonium salts, phosphonate compounds, phosphate
compounds. polystyrene sulfonate sodium salts or mixtures thereof.
According to this patent. all of the exemplified compositions took
longer than one second to heat.
[0013] U.S. Pat. No. 4,360,607, issued to Thorsrud, discloses a
composition suitable for sensitizing thermoplastic compositions to
the heating effects of microwave energy comprising (1) an alcohol
amine or-derivative thereof, (2) a simple or polymeric alkylene
glycol or derivative thereof, (3) silica and, optionally. (4) a
plasticizer.
[0014] U.S. Pat. No. 5,098,962, issued to Bozich, discloses a water
dispersible hot melt adhesive composition comprising:
[0015] (a) from about 40% to 95% by weight of a water dispersible
ionically substituted polyester resin having a molecular weight
from about 10,000 to about 20,000 daltons;
[0016] (b) from about 60% to about 5% by weight of one or more
compatible plasticizers; and
[0017] (c) from about 0.1% to about 1.5% of one or more compatible
stabilizers of the anti-oxidant type.
[0018] Examples of plasticizers that may be used according to this
patent include one or more low molecular weight polyethylene
glycols, one or more low molecular weight glycol ethers, glycerin,
butyl benzyl phthalate and mixtures thereof.
[0019] U.S. Pat. No. 5,750,605, issued to Blumenthal et al.,
discloses a hot melt adhesive composition comprising:
[0020] (i) 10 to 90% by weight of a sulfonated polyester
condensation polymer;
[0021] (ii) 0 to 80% by weight of a compatible tackifier;
[0022] (iii) 0 to 40% by weight of a compatible plasticizer;
[0023] (iv) 5 to 40% by weight of a compatible wax diluent with a
molecular weight below 500 g/mole containing at least one polar
functional group, said group being present at a concentration
greater than 3.times.10.sup.-3 equivalents per gram;
[0024] (v) 0 to 60% by weight of a compatible crystalline
thermoplastic polymer; and
[0025] (vi) 0 to 3% by weight of a stabilizer.
[0026] What is needed is a composition (e.g. adhesive composition
or coating) containing either dissolved or finely dispersed
susceptor constituents that are preferably colorless or of low
color. Further, the composition should be transparent or
translucent throughout an adhesive matrix or plastic layer. This
type of RF susceptor will result in more direct and uniform heating
throughout an adhesive matrix or plastic layer. Further, it is
desirable that such a composition will allow bonding with no
physical distortion or discoloration in the bonded region of thin
films. Still another desirable feature is activation of the RF
susceptors at frequencies, e.g. of about 15 MHz or below, most
preferably about 13.5 MHz, which are more economical to generate
than higher frequencies and do not substantially heat dielectric
substrates. A further desirable feature is that the composition can
be activated or melted in less than one second and that it exhibit
acceptable shear strength. It is also desirable to have a
formulation which may be optimized for a particular application,
such as cutting, coating, or bonding substrates.
SUMMARY OF THE INVENTION
[0027] The present invention generally relates to the creation and
use of a composition (also referred to as a "susceptor
composition") that can bond two or more layers or substrates to one
another and that can be used to coat or cut a substrate. The
susceptor composition is activated in the presence of radio
frequency (RF) energy.
[0028] In one embodiment, the susceptor composition of the present
invention comprises a susceptor and a carrier. The carrier and
susceptor are blended with one another and form a mixture,
preferably a substantially uniform mixture. The susceptor is
present in an amount effective to allow the susceptor composition
to be heated by RF energy. In a preferred embodiment, the susceptor
also functions as an adhesive or coating.
[0029] In another embodiment of the present invention, the
susceptor composition further comprises an adhesive compound. The
adhesive compound, susceptor, and carrier are blended with one
another to form a mixture that is activated in the presence of RF
energy. Preferably, the mixture is substantially uniform.
[0030] In another embodiment of the present invention, the
susceptor composition further comprises at least one of a
thermoplastic polymer, thermoset resin, elastomer, plasticizer,
filler or other material. The additive, susceptor, and carrier are
blended with one another to form a mixture that is activated in the
presence of RF energy.
[0031] In yet another embodiment of the present invention, the
composition can further comprise a second carrier that is an
insoluble porous carrier that is saturated with the
composition.
[0032] The susceptor is an ionic or polar compound and acts as
either a charge-carrying or an oscillating/vibrating component of
the susceptor composition. The susceptor generates thermal energy
in the presence of an RF electromagnetic or electrical field
(hereafter RF field). According to the present invention, the
susceptor can be an inorganic salt (or its respective hydrate),
such as stannous chloride (SnCl.sub.2), zinc chloride (ZnCl.sub.2)
or other zinc salt, or lithium perchlorate (LiClO.sub.4), or an
organic salt, such as lithium acetate (LiC.sub.2H.sub.3O.sub.2).
The susceptor can be a non-ferromagnetic ionic salt. The susceptor
can also be a polymeric ionic compound ("ionomer") which preferably
also functions as an adhesive or coating. Under RF power levels of
about 0.05 kilowatt (kW) to 1 kW, and frequencies of about 1 to 100
MHz, the susceptor composition of the present invention facilitates
(a) the bonding of single layers of polymeric materials such as
polyolefins, non-polyolefins, and non-polymeric materials, as well
as multilayer stacks of these materials, and (b) coating on a
substrate such as a printed pattern on plastic films, metallic
foils, etc.
[0033] Surprisingly, it has been discovered that when an ionomer is
combined with a polar carrier, much more heating occurs when
exposed to RF energy than when the ionomer or carrier is exposed
separately to RF energy. Also surprisingly, it has been discovered
that when the polar carrier is present at about 13-30% weight
percent, more preferably, about 15-25 weight percent, most
preferably, about 20-23 weight percent, very short heating times
are possible while retaining acceptable shear strength of the
bond.
[0034] According to another embodiment of the present invention, a
method of bonding a first material or substrate to a second
material or substrate comprises interposing a composition according
to the invention between the first and second materials and
applying RF energy to the composition to heat the composition,
thereby causing the first and second materials to become bonded. In
one embodiment, the composition comprises a susceptor and a carrier
that are distributed in one another to form a mixture, preferably,
a substantially uniform mixture. Optionally, the composition may
further comprise other compounds and additives as described herein.
The susceptor is present in the composition in an amount effective
to allow the composition to be heated by RF energy.
[0035] According to another embodiment of the present invention, a
method of bonding or adhering a first substrate to a second
substrate includes: applying a first composition onto the first
substrate; applying a second composition onto the second substrate;
contacting the first composition with the second composition;
applying RF energy to the first and second compositions to heat the
compositions, thereby causing the first and second substrates to
become adhered or bonded; wherein one of the compositions comprises
a susceptor and the other of the susceptors is a polar carrier, and
the susceptor and/or the carrier are present in amounts effective
to allow the first and second compositions to be heated by RF
energy.
[0036] According to yet another embodiment of the-present
invention, a method of bonding or adhering a first substrate to a
second substrate includes: applying a first composition onto the
first substrate; applying a second composition onto the first
composition; contacting the second substrate with the second
composition; and applying RF energy to the first and second
compositions to heat the compositions, thereby causing the first
and second substrates to become adhered or bonded, wherein one of
the compositions comprises a susceptor and the other of the
compositions is a polar carrier, and the susceptor and/or the
carrier are present in amounts effective to allow the first and
second compositions to be heated by RF energy.
[0037] According to another embodiment of the present invention, a
method of making a susceptor composition comprises admixing a
susceptor and a carrier, wherein, preferably, the carrier and
susceptor are substantially uniformly dispersed in one another and
form a uniform mixture. The susceptor and/or carrier are present in
the composition in an amount effective to allow the susceptor
composition to be heated by RF energy.
[0038] According to a further embodiment of the present invention,
an adhered or a bonded composition can be obtained according to the
disclosed methods.
[0039] According to a further embodiment of the present invention,
a kit for bonding a first material to a second material comprises
one or more containers, wherein a first container contains a
composition comprising a susceptor and a carrier that are dispersed
in one another and form a mixture. The kit may also contain an
adhesive or elastomeric compound or other additives as disclosed
herein. The susceptor and/or carrier are present in an amount
effective to allow the composition to be heated by radio frequency
energy.
[0040] According to a further embodiment of the present invention,
a kit for adhering or bonding a first substrate to a second
substrate, comprises at least two containers, wherein one of the
containers comprises a susceptor and another of the containers
comprises a polar carrier, wherein when the susceptor and the
carrier are applied to substrates and the susceptor and carrier are
interfaced, a composition is formed that is heatable by RF
energy.
[0041] The invention also relates to a composition comprising an
ionomeric polymer and a polar carrier.
[0042] The invention also relates to a method of curing a thermoset
resin, comprising combining the thermoset resin with a polar
carrier to give a mixture and exposing the mixture to RF
energy.
[0043] The invention relates to an apparatus, having: a first
portion having a first mating surface; a second portion, having a
second mating surface; a composition disposed between the first
mating surface and the second mating surface, wherein the
composition comprises a susceptor and a polar carrier wherein the
susceptor and/or the polar carrier are present in amounts effective
to allow the composition to be heated by RF energy, and wherein the
composition adheres the first mating surface to the second mating
surface such that application of a force to separate the first
mating surface and the second mating surface results in breakage of
the apparatus unless the composition is in a melted state.
[0044] The invention also relates to a method of applying a
protective film or printed image/ink on a substrate.
[0045] The invention also relates to a method for dynamically
bonding a first adherand to a second adherand. The method includes:
(1) creating an article of manufacture comprising the first
adherand, the second adherand, and a composition, the composition
being between the first adherand and the second adherand, wherein
the composition can be activated in the presence of an RF field;
(2) moving the article of manufacture along a predetermined path;
(3) generating along a portion of the predetermined path an RF
field having sufficient energy to activate the composition, wherein
the composition is activated by its less than one second exposure
to the RF field.
[0046] The invention also relates to a method for applying a
susceptor composition to a substrate. In one embodiment, the method
includes: (1) formulating the susceptor composition as a liquid
dispersion; (2) applying the liquid dispersion of the susceptor
composition to the substrate; (3) drying the susceptor composition,
wherein the drying step includes the step of applying RF energy
across the composition, thereby generating heat within the liquid
dispersion. In a preferred embodiment, one may roll up the
substrate after the susceptor composition has dried.
[0047] The invention also relates to a method for cutting a
substrate. The method includes: (1) applying a composition to a
portion of the substrate, wherein the composition comprises a
susceptor and polar carrier wherein the susceptor and/or said polar
carrier are present in amounts effective to allow the composition
to be heated by RF energy, and wherein the portion of the substrate
defines a first section of the substrate and a second section of
the substrate; (2) melting the portion of the substrate by heating
the composition via RF energy; and (3) after the portion of the
substrate has begun to melt, applying a force to the substrate to
separate the first section from the second section.
[0048] The method also relates to a method of dynamically bonding a
first substrate to a second substrate. The method including:
applying a composition onto the first substrate; after applying the
composition onto the first substrate, forming a roll of the first
substrate; storing the roll; unrolling the roll; and while
unrolling the roll: joining an unrolled portion of the first
substrate with a portion of the second substrate such that the
portion of the second substrate is in contact with a portion of the
composition applied onto the first substrate; and applying RF
energy to the portion of the composition, wherein the portion of
the composition heats and melts as a result of the RF energy being
applied thereto.
[0049] Further features and advantages of the present invention, as
well as the structure and operation of various embodiments of the
present invention, are described in detail below with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] The present invention is described with reference to the
accompanying drawings. In the drawings, like reference numbers
indicate identical or functionally similar elements. Additionally,
the left-most digit(s) of a reference number identifies the drawing
in which the reference number first appears.
[0051] FIGS. 1A and 1B illustrate conventional schemes for
inductively heating adhesives.
[0052] FIG. 2 shows an RF active composition according to the
present invention.
[0053] FIG. 3 shows a susceptor composition placed between two
polyolefin layers to be attached according to the present
invention.
[0054] FIG. 4 illustrates a block diagram of an RF heating system
according to a first embodiment.
[0055] FIG. 5 illustrates a block diagram of a heating system
according to a second embodiment.
[0056] FIG. 6 illustrates a two probe heating system.
[0057] FIGS. 7A and 7B further illustrate the two probe heating
system.
[0058] FIG. 7C illustrates a probe having a curled end to reduce
corona effects.
[0059] FIG. 8 illustrates one embodiment of an alternating voltage
supply.
[0060] FIG. 9 is a flow chart illustrating a process for heating a
composition according to the present invention.
[0061] FIG. 10A further illustrates one embodiment of an impedance
matching circuit.
[0062] FIG. 10B further illustrates another embodiment of an
impedance matching circuit.
[0063] FIG. 11 shows a method of bonding adherents using a
composition that is activated in the presence of RF energy.
[0064] FIGS. 12 to 17 illustrate additional embodiments of probes
602 and 604.
[0065] FIG. 18 illustrates one embodiment of an application system
for applying a composition according to the present invention to a
substrate.
[0066] FIG. 19 illustrates one embodiment of a system for bonding
or adhering various adherents.
[0067] FIGS. 20A and 20B illustrates a static bonding system for
bonding adherents.
[0068] FIG. 20C illustrates an electrically insulating block for
housing probes.
[0069] FIG. 21 illustrates an in-line bonding system.
[0070] FIG. 22 further illustrates one embodiment of the in-line
bonding system illustrated in FIG. 21.
[0071] FIGS. 23-27 illustrate alternative designs of the in-line
bonding system illustrated in FIG. 21.
[0072] FIGS. 28A and 28B illustrate one embodiment of a system for
the manufacture of flexible packaging material.
[0073] FIG. 29 further illustrates film 2815.
[0074] FIG. 30 illustrates one embodiment of film 2870.
[0075] FIG. 31 illustrates an alternative system for manufacturing
an RF activated adhesive film for use in the flexible packaging
industry.
[0076] FIG. 32 illustrates a conventional aseptic package material
construction.
[0077] FIG. 33 illustrates an aseptic package material according to
one embodiment that does not include metallic foil.
[0078] FIG. 34 illustrates another embodiment of an aseptic
packaging material construction that does not use metallic
foils.
[0079] FIG. 35 illustrates a conventional cap sealing
construction.
[0080] FIG. 36 illustrates a seal, according to one embodiment, for
sealing a bottle.
[0081] FIG. 37 illustrates a design for adhering a flexible bag to
an outer box.
[0082] FIG. 38 illustrates a step and repeat manufacturing
system.
[0083] FIG. 39 illustrates an index table bonding system.
[0084] FIG. 40 shows an example experimental set-up utilized to
test compositions according to the present invention.
[0085] FIG. 41 illustrates another experimental set-up for testing
compositions according to the present invention.
[0086] FIG. 42 illustrates test probes.
[0087] FIG. 43 illustrates a process for assembling a book,
magazine, or periodical, or the like.
[0088] FIG. 44 illustrates a paper substrate coated with a
susceptor composition.
[0089] FIG. 45 illustrates a stack of coated paper substrates.
[0090] FIGS. 46 and 47 illustrates one embodiment of an envelope or
mailer according to the present invention.
[0091] FIG. 48 illustrates a cross-section of a container sealed
with a susceptor composition of the present invention.
[0092] FIG. 49 illustrates another example of a device sealed or
otherwise joined together with a composition of the present
invention.
[0093] FIG. 50 shows another example of a device sealed or
otherwise joined together with a composition of the present
invention.
[0094] FIG. 51 illustrates still another example of a cross-section
of a container 5100 that has been sealed with the adhesive of the
present invention.
[0095] FIG. 52 illustrates a system for bonding two substrates.
[0096] FIG. 53 illustrates another embodiment of a system for
bonding two substrates.
[0097] FIG. 54 depicts a graph showing RF activation time vs. %
Glycerin for a composition comprising AQ55S.
[0098] FIG. 55 depicts a graph showing shear holding time vs. %
glycerin for a composition comprising AQ55S.
[0099] FIG. 56 depicts a graph showing RF activation time vs. %
glycerin for a composition comprising AQ35S.
[0100] FIG. 57 depicts a graph showing shear holding time vs. %
glycerin for a composition comprising AQ35S.
[0101] FIG. 58 depicts a family of curves showing RF activation
time vs. % various polar carriers.
[0102] FIG. 59 depicts a graph showing RF activation time vs. %
PARICIN 220 in a composition comprising 80% AQ55S/20% glycerin.
[0103] FIG. 60 depicts a graph showing brookfield viscosity vs. %
PARICIN 220 in a composition comprising 80% AQ55S/20% glycerin.
[0104] FIG. 61 depicts a graph showing RF activation time vs. %
glycerin in a composition comprising the sodium salt of an ethylene
acrylic acid copolymer (MICHEM Prime 48525P).
[0105] FIG. 62 illustrates a seam sealing system according to one
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0106] I. Overview and Discussion of the Invention
[0107] II. Terminology
[0108] A. Sulfonated Polymers
[0109] B. Acrylic Acid and Maleic Anhydride Polymers and
Copolymers
[0110] C. Starch/Polysaccharide Derivatives
[0111] D. Proteins
[0112] E. Others
[0113] III. The Polar Carrier
[0114] IV. Further Additives to the Susceptor Compositions
[0115] A. Adhesive/Thermoplastic Additives
[0116] B. Adhesive/Coating Thermoset Additives
[0117] C. Surfactant Additives
[0118] D. Plasticizer Additives
[0119] E. Tackifiers
[0120] F. Fillers
[0121] G. Stabilizers and Antioxidants
[0122] H. Other Additives
[0123] V. Applying the Susceptor Compositions to Substrates
[0124] VI. Apparatus For Activating the Various Compositions of the
Present Invention
[0125] VII. Method of Bonding Substrates
[0126] VIII. Additional Probe Embodiments
[0127] IX. Applicator System for Applying a Composition of the
Present Invention to a Substrate/Adherand
[0128] X. Systems for Adhering or Bonding two Adherands.
[0129] XI. Exemplary Specific Applications of the Present
Invention
[0130] A. Manufacture of Flexible Packaging
[0131] B. Food Packaging and Cap Sealing
[0132] C. Printing Applications
[0133] D. Bookbinding and Mailers
[0134] E. Security Devices
[0135] F. Thermal Destruction
[0136] G. Seam Sealing
[0137] XII. Kits
[0138] XIII. Experimental Set-up
[0139] XIV. Examples
[0140] I. Overview and Discussion of the Invention
[0141] The present invention is directed towards an RF susceptor
composition and methods and systems of bonding, cutting, and/or
coating substrates and surfaces using the susceptor composition.
The susceptor composition is a mixture of RF susceptors and/or
adhesive/coating compounds and/or other additives dissolved or
finely dispersed in a matrix. Preferably, the RF susceptors and/or
adhesive compounds and/or other additives are uniformly dissolved
or finely dispersed in the matrix. The susceptor composition is
capable of coupling efficiently in an RF field having a frequency
of about 15 MHz or below. In order to be useful in industry and
commercial products, a susceptor composition preferably has the
following characteristics: (1) an activation time in the presence
of a low power RF field on the order of 1 second or less, (2)
adequate bond or adhesive strength for the intended use, (3)
transparency or translucency and only slight coloration (if any),
(4) minimal distortion of the substrates being attached, and (5) on
demand bonding of preapplied adhesive. Further, it is desirable
that the susceptor composition have coupling ability in the absence
of volatile solvents, although the presence of nonvolatile liquids
(such as plasticizers) may be desirable. These characteristics are
important in providing sufficient heat transfer to the substrates
or layers to be bonded to one another, or for adhesion to take
place at the interface. Additionally, the susceptor composition
should not interfere with the thermal bonding or inherent adhesive
properties of the substrates or layers to be bonded or adhered to
one another.
[0142] According to the present invention, a susceptor composition
used to bond or adhere substrates or layers can be directly heated
by exposure to an RF field having frequencies ranging from 1-100
MHz. The susceptor composition comprises a susceptor, and a carrier
blended with one another to form a mixture. In addition, the
susceptor composition can further comprise one or more adhesive
compounds blended with the susceptor and carrier to form the
mixture.
[0143] Susceptors are either ionic or polar compounds introduced as
a component of a composition, such that RF heating of the resulting
susceptor composition occurs. An ionic susceptor is an ionic
compound introduced as a sufficiently charge-carrying or
oscillating component of the composition. A polar susceptor is a
polar compound which has sufficiently high dipole moment that
molecular oscillations or vibrations of the compound occur when
exposed to an RF field. As shown in FIG. 2, a susceptor composition
202 comprises a continuous mixture of susceptors such as
microscopic, ionic salts or polymeric ionic compounds or dipoles
204, which generate thermal energy in the presence of the RF field.
It has been discovered that acceptable bonding results occur with
inorganic salts such as stannous chloride (SnCl.sub.2); zinc salts
such as chloride (ZnCl.sub.2), bromide (ZnBr.sub.2) and the like;
and lithium perchlorate (LiClO.sub.4), and organic salts such as
lithium acetate (LiC.sub.2H.sub.3O.sub.2). These salts or
combination of salts, when distributed in the mixture, create an
ionic and/or polar medium capable of being heated by RF energy.
[0144] II. Terminology
[0145] "RF Energy" means an alternating electromagnetic field
having a frequency within the radio frequency spectrum.
[0146] A "susceptor composition" comprises a susceptor and a
carrier interfaced with one another and/or mixed or blended
together. Preferably, the susceptor and carrier are mixed together.
More preferably, the susceptor and carrier are substantially
uniformly mixed together. In another embodiment, the susceptor and
carrier are interfaced together by disposing a layer of the
susceptor onto a layer of the carrier or visa versa. In this
embodiment, the susceptor may be coated onto a first substrate and
the carrier, with or without added ingredients such as a wax or
other additives that prevent the carrier from evaporating
substantially, may be coated onto a second substrate. The first and
second substrates containing the susceptor and carrier layers,
respectively, may then be brought into contact or interfaced and
activated then or at a later time.
[0147] The susceptor compositions of the invention may further
comprise one or more adhesive compounds or other additives mixed,
preferably substantially uniformly mixed, together with the
susceptor and the carrier. The susceptor composition is activated
in the presence of radio frequency (RF) energy. The susceptor
composition can be used to bond two or more layers or substrates to
one another, can be used as a coating, and can be used to thermally
cut substrates.
[0148] A "carrier" provides the mobile medium in which the
susceptors are dissolved, distributed, or dispersed. Preferably,
the carrier is a polar carrier as defined below which enhances the
activation of the compositions. Carriers (also referred to as
mobile media) can be liquids, such as solvents and plastisizers, or
polymers that are utilized for their polar functionality and for
their ability to be heated by RF energy.
[0149] An "adhesive compound" refers to polymers, copolymers and/or
ionomers as described herein that are blended into the susceptor
composition to enhance its adhesive properties.
[0150] "Bonding" is defined as the joining of one substrate to
another substrate to cause a physical joining process to occur.
[0151] "Adhesion" is an interaction between two adherands at their
interface such that they become attached or joined.
[0152] A "substantially transparent" mixture refers to a mixture
that transmits greater than about 50% of incident visible
light.
[0153] "Thermal bonding" or "welding" is defined as the reflowing
of one substrate into another substrate to cause a physical joining
process to occur.
[0154] "Mechanical bonding" occurs between adherands when a
susceptor composition holds the adherands together by a mechanical
interlocking action.
[0155] An RF "susceptor" converts coupled RF energy into heat
energy in the susceptor composition. According to the present
invention, the susceptor, as described above, is either the charge
carrying or oscillating ionic compound or the oscillating polar
compound having a sufficiently high dipole moment comprising a
composition to generate thermal energy in the presence of an RF
field. Generally, the susceptor can be a salt. For example, the
susceptor can be an inorganic salt or its respective hydrate(s),
such as stannous chloride (SnCl.sub.2). stannous chloride dihydrate
(SnCl.sub.2.times.2H.sub.2O ), lithium perchlorate (LiClO.sub.4),
lithium perchlorate trihydrate (LiClO.sub.4.times.3H.sub.2- O ) or
an organic salt, such as an alkali metal salt of a C.sub.1-4
alkanoic acid such as lithium acetate (LiC.sub.2H.sub.3O.sub.2),
lithium acetate dihydrate (LiC.sub.2H.sub.3O.sub.2.times.2H.sub.2O
), or sodium acetate and the like; alkali metal salts of
arylcarboxylic acids such as lithium benzoate, sodium benzoate, and
the like; alkali metal salts of alkyl and aryl sulfonates such-as
sodium methylsulfonate and sodium p-toluenesulfonate and the like.
Other types of salts and their respective hydrates include, but are
not limited to, magnesium acetate, magnesium nitrate, sodium-based
salts (such as sodium chloride, sodium bromide and the like),
lithium-based salts (such as lithium bromide, lithium carbonate,
lithium chloride, etc.) and potassium-based salts. Many of these
salts are commercially available from Aldrich Chemical Company,
Milwaukee, Wis. See the Aldrich Catalog Handbook of Fine Chemicals
1996-1997. It is not intended that this list of salts is an
exclusive or comprehensive list. These salts are disclosed as
typical examples. The present invention is not restricted to the
listed salts, as would be apparent to those of skill in the
art.
[0156] The susceptor can also be an ionomer. Preferably, the
ionomer also functions as an adhesive and/or coating. Examples of
such ionomers include without limitation styrenated
ethylene-acrylic acid copolymer or its salts, sulfonated polyesters
and their salts, sulfonated polystyrene and its salts and
copolymers, polyacrylic acid and its salts and copolymers,
hydroxy/carboxylated vinylacetate-ethylene terpolymers,
functionalized acrylics, polyesters, urethanes, epoxies, alkyds,
latex, gelatin, soy protein, casein and other proteins, alginate,
carrageenan, starch derivatives, ionic polysacharides, and the
like. An example of an ionomer that does not function as an
adhesive is sodium polystyrenesulfonate.
[0157] Examples of ionomer adhesives are described in more detail
below.
[0158] A. Sulfonated Polymers
[0159] Sulfonated polyesters and copolymers thereof are described
in U.S. Pat. Nos. 5,750,605, 5,552,495, 5,543,488, 5,527,655,
5,523,344, 5,281,630, 4,598,142, 4,037,777, 3,033,827, 3,033,826,
3,033,822, 3,075,952, 2,901,466, 2,465,319, 5,098,962, 4,990,593,
4,973,656, 4,910,292, 4,525,524, 4,408,532, 4,304,901, 4,257,928,
4,233,196, 4,110,284, 4,052,368, 3,879,450, and 3,018,272. The
invention relates to compositions comprising sulfonated polyesters
and copolymers thereof, e.g. as described in these patents,
together with a polar carrier as described herein as well as the
adhesive compositions described in these patents (comprising the
sulfonated polyesters and copolymers thereof) together with the
polar carrier. Such sulfonated polyesters and copolymers thereof
are one preferred embodiment of the present invention, as such
materials function both as an ionomeric susceptor and as an
adhesive.
[0160] In a preferred embodiment, the sulfonated polyester is a
higher Tg (about 48.degree. C. to about 55.degree. C. or higher)
linear polyester which shows improved heat resistance compared to
lower Tg (about 35.degree. C.) linear or branched sulfonated
polyesters. Once blended with the polar carrier, the Tg of the
resulting composition should be higher than the temperature at the
intended use, e.g. higher than body temperature for diaper
adhesives. For example, a linear sulfonated polyester with a Tg of
55.degree. C. (e.g. AQ55S) blended with a sufficient amount
(greater than 10%) of polar carrier (e.g. glycerin) to achieve RF
activity will result in a Tg higher than body temperature if the
polar carrier is no more than about 35% of the composition.
[0161] In another embodiment, a salt comprising a sulfonated
polyester and a cationic dye as described in U.S. Pat. No.
5,240,780, are employed. Such salts provide a colored susceptor
composition that may be used, e.g. in printing.
[0162] Sulfonated polyesters may be prepared by the
polycondensation of the following reactants:
[0163] (a) at least one dicarboxylic acid;
[0164] (b) at least one glycol;
[0165] (c) at least one difunctional sulfomonomer containing at
least one metal sulfonate group attached to an aromatic nucleus
wherein the functional groups may be hydroxy, carboxyl, or amino
groups.
[0166] The dicarboxylic acid component of the sulfonated polyesters
comprises aliphatic dicarboxylic acids, alicyclic dicarboxylic
acids, aromatic dicarboxylic acids, or mixtures of two or more of
these acids. Examples of such dicarboxylic acids include oxalic;
malonic; dimethylmalonic; succinic; glutaric; adipic;
trimethyladipic; pimelic; 2,2-dimethylglutaric; azelaic; sebacic;
fumaric; maleic; itaconic; 1,3-cyclopentanedicarboxlyic;
1,2-cyclohexanedicarboxylic; 1,3-cyclohexanedicarboxylic;
1,4-cyclohexanedicarboxylic; phthalic; terephthalic; isophthalic;
2,5-norbornanedicarboxylic; 1,4-naphthalic; diphenic;
4,4'-oxydibenzoic; diglycolic; thiodpropionic;
4,4'-sulfonyldibenzoic; and 2,5-naphthalenedicarboxylic acids. If
terephthalic acid is used as the dicarboxylic acid component of the
polyester, at least 5 mole percent of one of the other acids listed
above may also be used.
[0167] It should be understood that use of the corresponding acid
anhydrides, esters, and acid chlorides of these acids is included
in the term "dicarboxylic acid. " Examples of these esters include
dimethyl 1,4-cyclohexanedicarboxylate; dimethyl
2,5-naphthalenedicarboxylate; dibutyl, 4,4'-sulfonyldibenzoate;
dimethyl isophthalate; dimethyl terephathalate; and diphenyl
terephthalate. Copolyesters may be prepared from two or more of the
above dicarboxylic acids or derivatives thereof.
[0168] Examples of suitable glycols include poly(ethylene glycols)
such as diethylene glycol, triethylene glycol, tetraethylene
glycol, and pentaethylene, hexaethylene, heptaethylene,
octaethylene, nonaethylene, and decaethylene glycols, and mixtures
thereof. Preferably the poly(ethylene glycol) employed in the
present invention is diethylene glycol or triethylene glycol or
mixtures thereof. The remaining portion of the glycol component may
consist of aliphatic, alicyclic, and aralkyl glycols Examples of
these glycols include ethylene glycol; propylene glycol;
1,3-propanediol; 2,4-dimethyl-2-ethylhexane-1,3,diol;
2,2-dimethyl-1,3-propanediol; 2-ethyl-2-butyl-1,3-propanediol;
2-ethyl-2-isobutyl-1,3-propanediol; 1,3-butanediol; 1,4-butanediol;
1,5-pentanediol; 1,6-hexanediol; 2,2-4-trimethyl-1,6-hexanediol;
thiodiethanol; 1,2-cyclohexanedimethanol;
1,3-cyclohexanedimethanol; 1,4-cyclohexanedimethanol;
2,2,4,4-tetramethyl-1,3-cyclobutanediol; p-xylylenediol. Copolymers
may be prepared from two or more of the above glycols.
[0169] The difunctional sulfo-monomer component of the sulfonated
polyester may advantageously be a dicarboxylic acid or an ester
thereof containing a metal sulfonate group or a glycol containing a
metal sulfonate group or a hydroxy acid containing metal sulfonate
group.
[0170] Advantageous difunctional sulfo-monomer components are those
wherein the sulfonate salt group is attached to an aromatic acid
nucleus such as benzene, naphthalene, diphenyl, oxydiphenyl,
sulfonyldiphenyl, or methylenediphenyl nucleus. Particular examples
include sulfophthalic acid, sulfoterephthalic acid,
sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid,
and their esters; metalosulfoaryl sulfonate having the general
formula. 1
[0171] wherein X is a trivalent aromatic radical derived from a
substituted or unsubstituted aromatic hydrocarbon, Y is a divalent
aromatic radical derived from a substituted or unsubstituted
aromatic hydrocarbon, A and B are carboalkoxy groups containing 1
to 4 carbon atoms in the alkyl portion or a carboxy group, the
metal ion M is Li.sup.-, Na.sup.+, K.sup.+, Mg.sup.++, Ca.sup.++,
Ba.sup.+-, Cu.sup.-+, Fe.sup.++, Fe.sup.+-- and n is 1 for
monovalent M or 2 for divalent M or 3 for trivalent M. When a
monovalent alkali metal ion is used, the resulting sulfonated
polyesters are less readily dissipated by cold water and more
rapidly dissipated by hot water. When a divalent or a trivalent
metal ion is used, the resulting sulfonated polyesters are not
ordinarily easily dissipated by cold water, but are more readily
dissipated in hot water. Depending on the end use of the polymer,
either of the different sets of properties may be desirable. It is
possible to prepare the sulfonated polyester using, for example, a
sodium sulfonate salt and later by ion-exchange replace this ion
with a different ion, for example, calcium, and thus alter the
characteristics of the polymer. In general, this procedure is
superior to preparing the polymer with divalent metal salt inasmuch
as the sodium salts may be more soluble in the polymer
manufacturing components than are the divalent metal salts.
Polymers containing divalent or trivalent metal ions are less
elastic and rubber-like than polymers containing monovalent ions.
One such metallosulfoaryl sulfonate component may be prepared as
shown by the following general reactions: 2
[0172] and other chlorinating agents (e.g., thionyl chloride,
phosphorus trichloride, phosphorous oxychloride) may be used. In
addition, the reaction between the sulfonyl chloride and the
sulfophenol may be carried out in water or an inert organic
solvent, and the base used may be an alkali metal hydroxide or a
tertiary amine. Such suitable compounds are disclosed in U.S. Pat.
No. 3,734,874.
[0173] Optionally, the polycondensation reaction may be carried out
in the presence of one or more of the following:
[0174] (d) an unsaturated mono- or dicarboxylic acid; and,
[0175] (e) a difunctional hydroxycarboxylic acid having one
--CH.sub.2--OH group. an aminocarboxylic acid having one --NRH
group, an amino alcohol having one --CR.sub.2--CH and one --NRH
group, a diamine having two --NRH groups, or a mixture thereof,
wherein each R is hydrogen or a C.sub.1-4 alkyl group.
[0176] The .alpha.,.beta.-unsaturated acids (d) are described by
the following structure:
R--CH.dbd.CH--R.sup.1
[0177] wherein R is H, alkylcarboxy, or arylcarboxy and R.sup.1 is
carboxy or arylcarboxy. Polymers derived from the above components
can be used in combination with polymers derived from other
components and/or in combination with other ethylenically
unsaturated comonomers (e.g., acrylic acid, acrylamide, butyl
acrylate, diacetone acrylamide). The comonomers can be from 1-75
parts by weight, preferably 5-25 parts by weight
.alpha.,.beta.-unsaturated acids.
[0178] Advantageous difunctional components which are
aminoalchohols include aromatic, aliphatic, heterocyclic and other
types as in regard to component (e). Specific examples include
5-aminopentanol-1,4-aminomethylc- yclo-hexanemethanol,
5-amino-2-ethyl-pentanol-1,2-(4-.beta.-hydroxyethoxyp-
henyl)-1-aminoethane, 3-amino-2,2-dimethylpropanol,
hydroxyethylamine, etc. Generally these aminoalcohols contain from
2 to 20 carbon atoms, one --NRH group and one --CR.sub.2--OH
group.
[0179] Such difunctional monomer components which are
aminocarboxylic acids include aromatic, aliphatic, heterocylic, and
other types as in regard to component (c) and include lactams.
Specific examples include 6-aminocaproic acid, its lactam known as
caprolactam, omegaaminoundecanoic acid, 3-amino-2-dimethylpropionic
acid, 4-(.beta.-aminoethyl)benzoic acid,
2-(.beta.-aminopropoxy)benzoic acid,
4-aminomethylcyclohexanecarboxylic acid,
2-(.beta.-aminopropoxy)cyclohexa- necarboxylic acid, etc. Generally
these compounds contain from 2 to 20 carbon atoms.
[0180] Examples of such difunctional monomer component (e) which
are diamines include ethylenediamine; hexamethylenediamine;
2,2,4-trimethylhexamethylenediamine; 4-oxaheptane-1,7-diamine;
4,7-dioxadecane-1,10-diamine; 1,4-cyclohexanebismethylamine;
1,3-cycloheptamethylene-diamine; dodecamethylenediamine, etc.
[0181] Greater dissipatability is achieved when the difunctional
sulfo-monomer constitutes from about 6 mole percent to about 25
mole percent out of a total of 200 mole percent of (a), (b), (c),
(d), and any (e) components of the polyester or polyesteramide. The
total of 200 mole percent can also be referred to as 200 mole
parts.
[0182] Any of the above-identified difunctional monomers generally
contain hydrocarbon moieties having from 1 to about 40 carbon atoms
in addition to their two functional groups, but they may in general
also contain up to six non-functional groups such as --O--, --S--,
--SO.sub.2--, --SO.sub.2--O--, etc. For example, the poly(ethylene
glycol) monomer used may contain from 1 to about 19 oxy groups,
such as -O-- groups.
[0183] In a preferred embodiment, the ionomer is one of the
sulfonated polyesters sold by Eastman Chemical Company, Kingsport,
Tenn. (hereafter "Eastman"). which are water dispersible, linear or
branched polyesters formed by the polycondensation of glycols with
dicarboxylic acids, some of which contain sodiosulfo groups.
Sulfopolyester hybrids may also be employed which are formed by the
in situ polymerization of vinyl and/or acrylic monomers in water
dispersions of SULFOPOLYESTER. Such Eastman sulfonated polyesters
may be purchased from Eastman under nos. AQ1045, AQ1350, AQ1950,
AQ14000, AQ35S, AQ38S, AQ55S and EASTEK 1300.
[0184] The sulfonated polyesters and copolymers thereof may range
from about 10 to about 90 weight percent, more preferably, about 60
to 80 weight percent, most preferably about 70 weight percent of
the total composition. The polar carrier may range from about 10 to
about 90 weight percent, more preferably, about 20 to about 40
weight percent, most preferably, about 30 weight percent of the
total composition. The remainder of the composition may comprise
one or more of the other additives described herein.
[0185] Compositions comprising branched sulfonated polyesters tend
to give clear, tacky and flexible films. Compositions comprising
linear polyesters tend to give clear or white, tack-free, flexible
films.
[0186] Other sulfonated polymers that can be used in the practice
of the invention include polystyrene sulfonate, acrylaminopropane
sulfonate (AMPS) based polymers (e.g.
2-acrylamido-2-methylpropanesulfonic acid and its sodium salt
available from Lubrizol Process Chemicals). In addition, urethane
ionomers can be prepared by reacting a diisocyanate with a diol
that has sulfonate functionality (e.g. butane diol sulfonate).
[0187] B. Acrylic Acid and Maleic Anhydride Polymers and
Copolymers
[0188] Other ionomers include acrylic acid polymers and copolymers
and salts thereof. Such polymers and copolymers are described in
U.S. Pat. Nos. 5,821,294, 5,717,015, 5,719,244, 5,670,566,
5,618,876, 5,532,300, 5,530,056, 5,519,072, 5,371,133, 5,319,020,
5,037,700, 4,713,263, 4,696,951, 4.692,366, 4,617,343, 4,948,822,
and 4,278,578.
[0189] The invention relates to compositions comprising the acrylic
acid polymers and copolymers thereof described in these patents
together with a polar carrier as described herein as well as the
adhesive compositions described in these patents (comprising the
acrylic acid polymers and copolymers thereof) together with the
polar carrier.
[0190] Specific examples of such acrylic acid copolymers include
ethylene acrylic acid copolymer and the ammonium (MICHEM 4983P) and
sodium (MICHEM 48525P) salts thereof available from Michelman
Incorporated, Cincinnati, Ohio. A further example is vinyl acetate
acrylic copolymers (e.g. ROVACE HP3442) available from Rohm and
Hass, Philadelphia, Pa.
[0191] The acrylic acid polymers and copolymers may range from
about 10 to about 90 weight percent, more preferably, about 40 to
80 weight percent, most preferably about 50-70 weight percent of
the total composition. The polar carrier may range from about 10 to
about 90 weight percent, more preferably, about 10 to about 40
weight percent, most preferably, about 30 weight percent of the
total composition. The remainder of the composition may comprise
one or more of the other additives described herein.
[0192] Compositions comprising ethylene acrylic acid copolymers and
a polar carrier tend to give clear, colorless, tack-free films with
very good adhesion that heat in well under one second when exposed
to RF. Vinyl acetate acrylic copolymer compositions tend to give
clear, colorless, flexible but very tacky films with very good
adhesion that heat in well under one second when exposed to RF.
[0193] In a preferred embodiment, compositions comprising acrylic
acid polymers or coplymers are applied as liquid dispersions and
dried into an RF susceptive coating.
[0194] Alternatively, maleic anhydride based copolymers such
styrene maleic anhydride, ethylene maleic anhydride, and popylene
maleic anhydride (availbe from Eastman Chemicals) may be employed
as an ionomer. Such compositions are preferably applied as an
aqueous dispersion at room temperature and dried into an RF
susceptive coating.
[0195] C. Starch/Polysaccharide Derivatives
[0196] Other ionomers include starch and polysaccharide derivatives
such as polysulfonated or polysulfated derivatives, including
dextran sulfate, pentosan polysulfate, heparin, heparan sulfate,
dermatan sulfate, chondroitin sulfate, a proteoglycan and the like.
Dextran sulfate is available from Sigma Chemical Corporation, St.
Louis, Mo., with molecular weights of 10,000, 8,000 and 5,000.
Examples of other ionic polysaccharides include carrageenan,
chitosan, xanthan gum, etc.
[0197] Phosphorylated starch as disclosed in U.S. Pat. No.
5,329,004 may be employed as a susceptor.
[0198] The starch/polysaccharide derivatives may range from about
10 to about 90 weight percent, more preferably, about 60 to 80
weight percent, most preferably about 70 weight percent of the
total composition. The polar carrier may range from about 10 to
about 90 weight percent, more preferably, about 20 to about 40
weight percent, most preferably, about 30 weight percent of the
total composition. The remainder of the composition may comprise
one or more of the other additives described herein.
[0199] D. Proteins
[0200] Other ionomers include proteins such as gelatin, soy
protein, casein, etc. Gelatin is the purified protein derived from
the selective hydrolysis if collagen. Collagen is the principal
organic component of the bones and skin of mammals. Common raw
materials include bones, cattle hides and pigskins. Gelatins are
classified as either acid type (A type) or limed (B type) according
to the process by which they are made. Particular examples of
gelatins include KNOX gelatin as well as types P, D, D-I, LB, LM
and K, available from PB Gelatins. See also the gelatin described
in U.S. Pat. No. 5,877,287. In a preferred embodiment, the gelatin
is 45Y56-853-3V0-6CS, available from Eastman Gelatin, Peabody,
Mass. Alternatively, a gelatin-modified polyurethane as disclosed
in U.S. Pat. No. 5,948,857 may be used.
[0201] In a preferred embodiment, the pH of the gelatin is raised
or lowered in order to enhance the ionomeric character of the
gelatin. The pH may be raised by the addition of aqueous base to an
aqueous solution or suspension of the gelatin. Examples of suitable
bases include alkali metal hydroxides, alkali metal carbonates and
bicarbonates, alkali metal acetates, ammonia, amino compounds such
as methylamine, dimethylamine, trimethylamine, triethylamine, and
the like. Alternatively, a basic buffer solution may be added, e.g.
a solution comprising 2-amino-2-methyl-1-propanol; or a glycine
buffer at pH 9.4 and 10.4; each of which is available from Sigma
Chemical Corporation, St. Louis, Mo. Other buffers include 0.01
borax (pH 9.2), TRIS (pH 7-9.1 depending on concentration), 0.05 M
carbonate (pH 9.93), and 0.05 M trisodium phosphate (pH 12). See
"The Chemist's Companion," A. J. Gordon and R. A. Ford, John Wiley
& Sons, New York, N.Y., 1972. The pH may be lowered by the
addition of an acid such as HCl, HBr, H.sub.2SO.sub.4,
H.sub.3PO.sub.4, or an organic acid such as C.sub.1-4 alkanoic acid
(e.g. acetic acid, propionic acid or butyric acid), an
arylcarboxylic acid (e.g. benzoic acid), or arylsulfonic acid
(e.g.p-toluenesulfonic acid). Alternatively, an acidic buffer may
be added, e.g. acetate buffer at pH 4.5, 4.9 and 5.0; citrate
buffer at pH 4.8; or a phosphate-citrate buffer at pH 5.0; each of
which is available from Sigma Chemical Corporation. Other buffers
include 0.005 M potassium tetraoxalate (pH 1.7), saturated
potassium tartrate (pH 3.6), 0.05 M potassium phthalate (pH 4.0),
and 0.05 M sodium succinate (pH 5.3). See "The Chemist's
Companion," A. J. Gordon and R. A. Ford, John Wiley & Sons, New
York. N.Y., 1972. As discussed in the Examples, it has been
discovered unexpectedly that when the pH of the gelatin composition
is shifted into the acidic or basic range, the composition exhibits
enhanced heating in an RF field compared to the untreated gelatin.
The best heating occurs when the pH is low. Such gelatin
compositions give flexible films that attach well to substrates and
heat in under one second.
[0202] In a preferred embodiment, the pH of the gelatin may range
from about 8 to about 12. In a most preferred embodiment, the pH of
the gelatin is about 10. In another preferred embodiment, the pH of
the gelatin may range from about 1 to about 6. In a most preferred
embodiment, the pH of the gelatin is about 2.
[0203] The gelatin may range from about 10 to about 90 weight
percent, more preferably, about 60 to 80 weight percent, most
preferably about 70 weight percent of the total composition. The
polar carrier may range from about 10 to about 90 weight percent,
more preferably, about 20 to about 40 weight percent, most
preferably, about 30 weight percent of the total composition. The
remainder of the composition may comprise one or more of the
other-additives described herein.
[0204] E. Others
[0205] Other ionomers that may be used in the practice of the
invention include sulfonated novolak resins obtained by a process
comprising reacting an aromatic compound with a sulfonated agent to
form a sulfonated aromatic compound, condensing the sulfonated
aromatic compound with a non-sulfonated phenolic compound and an
aldehyde or aldehyde precursor to form a sulfonated condensate, and
reacting the condensate with a monovalent or divalent metal oxide,
hydroxide, carbonic acid, boronic acid or carboxylic acid. See U.S.
Pat. No. 5,098,774. Other ionomers that can be used are
lignosulfonates and their sodium salts which are available with
different molecular weights and-levels of sulfonation from
Westvaco, North Charleson, S.C.
[0206] In addition, urethane ionomers can be prepared by reacting a
diisocyanate with a diol that has carboxy functionality (e.g.
dimethylol).
[0207] III. The Polar Carrier
[0208] In a preferred embodiment, the ionomer is combined with a
carrier that is a flowable polar compound, such as a polar solvent,
having a high dielectric constant, e.g. .epsilon. (20.degree.
C.).gtoreq. about 10, more preferably, .gtoreq. about 20. A
preferred dielectric constant range is about 13-63 (25.degree. C.),
more preferably, about 17-43 (25.degree. C.). It has been
unexpectedly discovered that compositions comprising an ionomer and
such a carrier heat much more rapidly when exposed to RF energy,
even at low levels, compared to when the ionomer or carrier are
exposed separately. Without being bound by any particular theory,
it is believed that upon exposure to RF energy, the polar carrier
allows for the migration and/or vibration of protons or metal ions
from the ionomer, resulting in the generation of heat.
[0209] Such polar carriers include, but are not limited to, water,
dimethylformamide (DMF), dimethylacetamide (DMAC),
dimethylsulfoxide (DMSO), tetrahydrofuran (THF), polypropylene
carbonates, ketones (such as acetone, acetyl acetone,
cyclohexanone, diacetone alcohol, and isophorone), alcohols (such
as ethanol, propanol, 2-methyl-1-propanol, and the like) amino
alcohols (such as ethanolamine), oxazolidines, polyols, organic
acids (such as formic, acetic, propionic, butyric and dimethylol
butyric acid and the like), anhydrides (such as acetic anhydride
and maleic anhydride), amides (such as formamide, acetamide and
propionamide), nitrites (such as acetonitrile and propionitrile),
and nitro compounds (such as nitrobenzene, nitroaniline,
nitrotoluene, nitroglycerine and any of the nitroparaffins). Any
polar carrier that can weaken, to some degree, the ionic
interaction between the anion and cation of the ionic susceptor,
even if the susceptor component is a non-ionic compound, may be
utilized in the present invention. Preferred polar carriers are
humectants (e.g., glycerin, 1,2-propanediol and
polyethyleneglycol), i.e., they retain at least a low level of
moisture after application. It is believed that the low level of
residual moisture enhances the RF activation of the
compositions.
[0210] Examples of polyols that may be used as a polar carrier
include glycols such as diethylene glycol, triethylene glycol,
tetraethylene glycol, dipropylene glycol, thioethylene glycol, and
pentaethylene, hexaethylene, heptaethylene, octaethylene,
nonaethylene, and decaethylene glycols, and mixtures thereof, as
well as aliphatic, alicyclic, and aralkyl glycols. Particular
examples of these glycols include ethylene glycol; 1,2-propylene
glycol; 1,3-propanediol; 2,4-dimethyl-2-ethylhexane- -1,3,diol;
2,2-dimethyl-1,3-propanediol; 2-ethyl-2-butyl-1,3-propanediol;
2-ethyl-2-isobutyl-1,3-propanediol; 1,3-butanediol; 1,4-butanediol;
1,5-pentanediol; 1,6-hexanediol; 2,2-4-trimethyl-1,6-hexanediol;
thiodiethanol; 1,2-cyclohexanedimethanol;
1,3-cyclohexanedimethanol; 1,4-cyclohexanedimethanol;
2,2,4,4-tetramethyl-1,3-cyclobutanediol; p-xylylenediol. Also
included are polyethylene glycols, e.g. having weight average
molecular weights ranging from about 400 to about 2,000; mixed
poly(ethylene)-poly(propylene) glycols having weight average
molecular weights ranging up to about 6,000 and containing from
about 30 to about 90 weight percent ethylene oxide; the monomethyl,
monoethyl and monobutyl ethers of ethylene glycol, propylene glycol
and diethylene glycol, the monomethyl and monoethyl ethers of
triethylene glycol; the dimethyl and diethyl ethers of diethylene
glycol, dipropylene glycol and trimethylene glycol. Examples of
polyols containing three or more hydroxy groups include glycerin
and derivatives of glycerin such as glycerol mono-, di-, and
triacetate, or monomethacrylate. Also included is polyvinylalcohol,
which also functions as an adhesive compound. Polyvinylalcohols of
molecular weights 89,000-98,000,85,000-146,000,124,0- 00-186,000,
31,000-50,000, 85,000-146,000, 124,000-186,000, 13,000-23,000.
50,000-85,000, with various levels of hydrolysis, are available
from Aldrich Chemical Company.
[0211] The polar carrier may also be an alkanolamine and
substituted alkanolamine based on ethanol and isopropanol such as
mono-, di- and triethanolamine, mono-, di- and triisopropanolamine,
methylethanolamine, dibutylethanolamine, phenyldiethanolamine,
di-(2-ethylhexyl)ethanolamine, dimethylisopropanolamine,
dibutylisopropanolamine, and the like as well as mixtures
thereof.
[0212] N-Alkyl sulfonamides are also useful carriers.
[0213] The present invention is not restricted to the listed
carriers, and mixtures of carriers may be utilized, as would be
apparent to those of skill in the art. Such polar carriers may
comprise about 10 to 90 weight percent of the composition. In a
preferred embodiment, the polar carrier comprises about 30 weight
percent of the total composition. In a more preferred embodiment,
the polar carrier comprises about 13-30% weight percent, more
preferably, about 15-25 weight percent, most preferably, about
20-23 weight percent. At these percentages, very short heating
times are possible while retaining acceptable shear strength of the
bond.
[0214] Preferable high dielectric constant carriers are those that
can generate heat without being highly volatile, in order to
preserve RF susceptor mobility in the composition. Preferred
carriers are glycols such as glycerine and N-methyl pyrrolidone
(NMP). NMP has a high dipole moment of 4.09 Debye, which produces a
dielectric constant, K, of 32.2 at 25.degree. C. NMP is
noncorrosive, biodegradable, and almost odorless. NMP has a low
order of oral toxicity and is neither a skin irritant nor a
sensitizer. NMP is also an excellent solvent both for a wide range
of organic compounds and polymers, as well as for some inorganic
salts. In short, it is a very useful medium for dissolving or
dispersing susceptors and film formers that are employed in the
bonding or adhering of substrates or layers according to the
present invention.
[0215] A farther preferred high dielectric constant carrier is
glycerine. Glycerine has a dielectric constant of 42.5 at
25.degree. C., is noncorrosive, biodegradable, and odorless.
Glycerine is nontoxic and is neither a skin irritant nor a
sensitizer. Thus, glycerine is a preferred carrier for consumer
products containing adhesives and coatings. Glycerine is also an
excellent solvent both for a wide range of organic compounds and
polymers, as well as for some inorganic salts.
[0216] A suitable susceptor composition according to the present
invention comprises a susceptor present in a concentration of from
about 10% to about 50% and a carrier present in a concentration of
from about 1% to about 75%. Additionally, another suitable
susceptor composition further comprises an adhesive compound or
other additive as described herein present in a concentration of
from about 10% to about 35%. The susceptor composition can be used
to bond or adhere substrates or layers to one another. The
substrates can include single layers of polyolefins and
non-polyolefins, as well as multilayer stacks. Such stacks may
comprise 2, 3, 4, 5 or more layers. One or more susceptor
compositions, which may be the same or different, may be between 2
or more layers of the multilayer stacks. All composition
concentrations described herein correspond to weight-weight
percentages, unless indicated otherwise.
[0217] IV. Further Additives to the Susceptor Compositions
[0218] A number of different additives may be added to the
susceptor compositions of the present invention including the
carrier or mobile medium. In order to provide uniform heating of a
susceptor composition, the susceptors are dissolved, distributed,
or dispersed, preferably substantially uniformly, in a carrier
containing either various polymers and/or solvents or plastisizers.
Some carriers, such as solvents, plastisizers, or polymers, are
utilized for their polar functionality and for their ability to
enhance the heating process.
[0219] A. Adhesive/Thermoplastic Additives
[0220] The adhesive properties of the susceptor composition of the
present invention are enhanced by the presence of one or more
thermoplastic or adhesive compounds, such as polymers or
copolymers, that are blended in the susceptor composition. Some of
the thermoplastic or adhesive compounds utilized in the present
invention include, but are not limited to, polyesters such as a
thermoplastic methylol polyester prepared from the reaction of at
least one dicarboxylic acid with a diglycidyl ether, a diglycidyl
ester or combination thereof (see U.S. Pat. No. 5,583,187) or a
cyanoacrylate/polyester adhesive composition (see U.S. Pat. No.
5,340,873); polyamides; polyurethanes (see U.S. Pat. No.
5,391,602); polysiloxanes; elastomers; polyvinylpyrrolidone;
ethylene vinyl acetate copolymers (see U.S. Pat. No. 4,460,728),
vinylpyrrolidone vinyl acetate copolymers; vinyl ether copolymers
(e.g. polyvinyl methyl ether); polyvinyl alcohol; partially
hydrolyzed polyvinyl acetate; copolymers comprising a starch ester
(see U.S. Pat. No. 5,498,224) and starch hydrolysates (see U.S.
Pat. No. 5,827,553); graft copolymer prepared from a vinyl monomer
and a polyalkylene oxide polymer, and a hydroxy-containing ester or
acid wax (see U.S. Pat. No. 5,852,080); copolymers comprising a
graft copolymer prepared from a vinyl monomer, at least one
polyalkylene oxide polymer, a polar wax and other optional
ingredients (see U.S. Pat. No. 5,453,144); thermoplastic block
copolymers comprising an aromatic vinyl copolymer block, a diene
polymer or hydrogenated derivative thereof and other additives (see
U.S. Pat. No. 5,723,222); vinyl chloride copolymers; vinylidene
chloride copolymers; vinylidene fluoride copolymers; vinyl
pyrrolidone homo- and copolymers; vinyl pyridine homo- and
copolymers; hydrolyzed polyvinyl alcohol and compositions thereof
(see U.S. Pat. No. 5,434,216); cellulose esters (e.g. cellulose
acetate and starch acetate, see U.S. Pat. No. 5,360,845) and ethers
(e.g. hydroxypropyl cellulose, methyl cellulose, ethyl cellulose,
propyl cellulose and the like; see U.S. Pat. No. 5,575,840,
5,456,936 and 5,356,963); modified starch ester containing
adhesives (see U.S. Pat. No. 5,360,845); high amylose starch
containing adhesive (see U.S. Pat. No. 5,405,437);poly-alpha
olefins; propylene homo- and copolymers; ethylene homo- and
copolymers (especially those of vinyl acetate, vinyl alcohol,
ethyl- and butyl-acrylate, carbon monoxide, acrylic and methacrylic
acid, crotonic acid, and maleic anhydride), an alkyl acrylate hot
melt adhesive (see U.S. Pat. No. 4,588,767), a hot melt adhesive
comprising an alkyl acrylate and an alpha-olefin (see U.S. Pat. No.
4,535,140), a hot melt adhesive comprising an ethylene n-butyl
acrylate copolymer (see U.S. Pat. No. 5,331,033), a hot melt
adhesive comprising a graft copolymer comprising at least one vinyl
monomer and at least one polyalkylene oxide polymer (see U.S. Pat.
No. 5,217,798), a vinyl acetate copolymer copolymerized with a
cyclic ureido compound (see U.S. Pat. No. 5,208,285), a hydrophilic
polycarbodiimide (see U.S. Pat. No. 5,100,994), a photopolymerized,
pressure sensitive adhesive comprising an alkyl acrylate, a
monethylenically unsaturated polar copolymerizable monomer,
ethylene vinylacetate copolymer and a photo initiator (see U.S.
Pat. No. 5,079,047), a hot melt adhesive comprising tackifying
resins, oil diluent, and a substantially radial styrene-butadiene
block copolymer (U.S. Pat. No. 4,944,993), an adhesive prepared
from the vinyl ester of an alkanoic acid, ethylene, a dialkyl
maleate, an N-methylol comonomer, and an ethylenically unsaturated
mono- or dicarboxylic acid (see U.S. Pat. No. 4,911,960), an
adhesive prepared from the vinyl ester of an alkenoic acid,
ethylene, a dialkyl maleate, and a monocarboxylic acid (see U.S.
Pat. No. 4,892,917), a hot melt adhesive consisting essentially of
an ethylene n-butyl acrylate copolymer (U.S. Pat. No. 4,874,804),
hot melt adhesive compositions prepared from
styrene-ethylene-butylene-styrene tri-block and/or
styrene-ethylene-butylene di-block copolymers that are tackified
(U.S. Pat. No. 4,822,653), a hot melt packaging adhesive comprising
a ethylene n-butyl acrylate copolymer with n-butyl acrylate (U.S.
Pat. No. 4,816,306), polysaccharide esters containing acetal and
aldehyde groups (U.S. Pat. No. 4,801,699), polysaccharide aldehyde
derivatives (U.S. Pat. No. 4,788,280), an alkaline adhesive
comprising a latex polymer or a halohydrin quaternary ammonium
monomer and starch (U.S. Pat. No. 4,775,706), polymeric fatty acid
polyamides (U.S. Pat. No. 4,419,494), hot melt adhesives comprising
resins containing 2-methylstyrene, styrene and a phenol (U.S. Pat.
No. 4,412,030). The present invention is not restricted to the
listed adhesive compounds and compositions, as would be apparent to
those of skill in the art.
[0221] Such adhesive additives may comprise about 1 to 50 weight
percent of the composition, more preferably, about 25 weight
percent.
[0222] B. Adhesive/Coating Thermoset Additives
[0223] It is also possible to add a thermoset resin to the
susceptor compositions of the present invention. Such thermosets
are capable of being cross-linked or cured through heat and/or
catalysts and include those described in U.S. Pat. No. 5,182,134,
e.g. epoxies, polyurethanes, curable polyesters, hybrid thermosets,
and curable acrylics. Others include bismaleimides, silicons,
phenolics, polyamids and polysulfides among others. Further
examples include maleate resins formed by the reaction of various
polyols with maleic anhydride. Orthophthalic resins may be used
which are formed by the reaction of phthalic anhydride and maleic
anhydride or fumaric anhydride as the dibasic acid. Isophthalic
resins may also be used which may be formed by reacting isophthalic
acid and maleic anhydride. Others include the bis-phenol fumarides,
chlorendic polyester resins, vinyl esters, dicyclopentadiene
resins, orthotolyl biguanine, the diglycidyl ether formed from
bis-phenol A and epichlorohydrin, triglycidyl isocyanurate
thermosetting compositions, bis-phenol A-epichlorohydrin diglycidyl
ether cured with phenolic cross-linking agents, aliphatic urethane
thermosetting compositions such as an unblocked isofuron
diisocyanate-E-caprolactam, BTDA thermosetting compositions which
are generally the reaction product of 3,3,4,4-benzophenone
tetracarboxylic dianhydride and a bis-phenol A-epichlorohydrin
diglycidyl ether, hybrid thermosetting compositions which are the
reaction product of a carboxylated saturated polyester curing
agents and bis-phenol A-epichlorohydrin diglycidyl ether, standard
bis-phenol A-epichlorohydrin diglycidyl thermosets such as those
which are cured from 2-methylimidazole, and standard bis-phenol
A-epichlorohydrin diglycidyl ether thermosets which are cured with
2-methylimidazole and dicyandiamide thermosetting compositions. See
U.S. Pat. Nos. 5,182,134, 5,387,623.
[0224] Other thermosets and adhesives/coatings that may be added to
the susceptor compositions of the invention include a reactive
polyurethane prepolymer and 2,2'-dimorpholinoethyl ether or
di(2,6-dimethylmorpholinyl- ethyl) ether catalyst (see U.S. Pat.
No. 5,550,191), a free radical polymerizable acrylic monomer,
diazonium salt/activator composition (see U.S. Pat. No. 4,602,073),
a diphenylmethane diisocyanate, a caprolactone triol, a neopentyl
adipate ester diol, and, optionally, at least one polypropylene
diol together with a catalyst (U.S. Pat. No. 5,057,568), an aqueous
polyurethane dispersion comprising an isocyanate-terminated
polyurethane prepolymer containing carboxylic acid salt groups, and
an active hydrogen containing chain extender (U.S. Pat. No.
4,801,644).
[0225] The susceptor compositions of the present invention may also
be combined with a shelf stable thermosetting resin as described in
U.S. Pat. No. 5,739,184, which is then activated by RF energy to
give coatings, e.g. for wood or paper products. This thermosetting
resin comprises an epoxy resin, a rosin and an organometallic
compound in an amount effective to provide improved adhesion to
wood or paper substrates.
[0226] Curing agents may also be combined together with the
susceptor/thermoset compositions of the invention, including
melamines such as dialkyl melamines, amides such as dicyandiamide,
adipamide, isophthalyl diamide, ureas such as ethylene thiourea or
guanylurea, azides such as thiosemicarbazide, azoles such as
guanazole or 3-amino-1,2,4-triazole, and anilines such as
dialkylanilines such as dimethyl aniline and diethyl aniline.
[0227] Such thermoset additives may comprise about 1 to 50 weight
percent of the composition, more preferably, about 25 weight
percent.
[0228] It has also been discovered that thermoset compositions may
be activated with only the polar carrier and without a susceptor.
Thus, the invention also relates to compositions comprising a
thermoset and a polar carrier. The thermoset may comprise about 60
to 95 weight percent of such a composition. The polar carrier may
comprise about 5 to 40 weight percent. The invention relates as
well to methods of bonding, adhering or coating substrates with
such thermoset/polar carrier compositions.
[0229] C. Surfactant Additives
[0230] According to another embodiment of the present invention,
surfactant additives can be added to the susceptor composition to
enhance the ability to draw down the susceptor composition of the
present invention onto the layers or substrates to be bonded,
adhered or coated. Depending on the types of materials that are to
be joined or coated, surfactant additives, such as SURFYNOL 104PA
(available from Air Products Corporation) and SURFADONE LP 300
(N-dodecyl-2-pyrrolidone, available from International Specialty
Products), can be used to wet a variety of substrates such as Mylar
and polyethylene (PE). A further plasticizer is
p-toluenesulfonamide, a good plasticizer that also dissolves
stannous chloride. The present invention is not restricted to the
listed surfactant additives, as would be apparent to those of skill
in the art. Such surfactants may comprise about 0.1 to 5 weight
percent of the composition.
[0231] D. Plasticizer Additives
[0232] The susceptor compositions of the present invention may
further comprise a plasticizer to modify the flexibility of the
adhesive or coating. Examples of such plasticizers include, but are
not limited to acetyl tributyl citrate, butyl benzyl phthalate,
butyl phthalyl butyl glycolate, dibutyl phthalate, dibutyl
sebacate, diethyl phthalate, diethylene glycol dibenzoate,
dipropylene glycol, dipropylene glycol dibenzoate, ethyl phthalyl
ethyl glycolate, ethyl-p-toluene sulfonamide, hexylene glycol,
methyl phthalyl ethyl glycolate, polyoxyethylene aryl ester,
tributoxyethyl phthalate, triethylene glycol polyester of benzoic
acid and phthalic acid, glycerin, or mixtures thereof. Other
plasticizers that may be used include N-methyl-2-pyrrolidone (NMP),
and substituted toluene sulfonamides (e.g. p-toluenesulfonamide,
RIT-CIZER #8.TM. and RIT-O-LITE MHPT from Rit-Chem Co., Inc.,
Pleasantville, N.Y.). Such plasticizers may comprise about 1 to 40
weight percent of the composition.
[0233] E. Tackifers
[0234] The tackiness of the compositions of the invention may be
increased by the addition of a suitable tackifier, e.g. one or more
of hydrogenated aromatic petroleum resins, hydrogenated aliphatic
petroleum resins, and hydrogenated terpene resins (see U.S. Pat.
No. 5,418,052), coumarone-indene, ester gum, gum rosin,
hydrogenated rosin, phenolic modified hydrocarbon resins, rosin
esters, tall oil rosins, terpene phenolic, terpene resins, toluene
sulfonamide-formaldehyde resin, wood rosin (see U.S. Pat. No.
5,442,001), distilled rosin, dimerized rosin, maleated rosin,
polymerized rosin (see U.S. Pat. No. 5,532,306). Other tackifiers
and modifiers, include (but are not limited to) styrene and alpha
methyl styrene resins, glycerol and pentaerithritol esters, etc.
Particular tackifiers include WINGTACK 95 from Goodyear, Herculin D
and PICCOLYTE C from Hercules, EASTOTACK H100 from Eastman, and ECR
149B or ECR 179A from Exxon Chemical (see U.S. Pat. No. 5,559,165).
Other tackifiers include rosin and its derivatives available from
Reichold Chemicals, Manila Copal (softening point 81-90.degree. C.
acid No.110-141), Pontianac (softening point 99-135.degree. C. acid
No. 1120129) and Sanarec (softening point 100-130.degree. C., acid
no. 117-155). Such tackifiers may comprise about 1 to 25 weight
percent of the composition.
[0235] F. Fillers
[0236] A number of different fillers may be added to the susceptor
compositions of the invention, including, but not limited to
cellulose, bentonite, calcium carbonate, calcium silicate, clay,
mica silica, talc, alumina, glass beads, fibers and the like. Such
fillers may comprise about 0 to 40 weight percent of the
composition.
[0237] G. Stabilizers and Antioxidants
[0238] Stabilizers and antioxidants may be added to the susceptor
compositions of the invention in amounts effective to achieve the
intended result. Included amoung such stabilizers include high
molecular weight hindered phenols and multifunctional phenols such
as sulfur and phosphorous-containing phenols. Representative
hindered phenols include
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene,
pentaerythritol tetrakis-3-(3,5-di-tert-butyl-4-hydroxypropionate,
n-octadecyl-3,5-di-tert-butyl-4-hydroxyphenyl)propionate,
4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-thiobis
(6-tert-butyl-o-cresol), 2,6-di-tert-butylphenol,
6-(4-hydroxyphenoxy)-2,- 4-bis(n-octylthio)-1,3,5-triazine,
di-n-octadecyl-3,5-di-tert-butyl-4-hydr- oxybenzylphosphonate,
2-(n-octylthio)ethyl -3,5-di-tert-butyl-4-hydroxyben- zoate, and
sorbitol hexa[3-(3,5-di-tert-butyl-4-hydroxylphenyl)propionate (see
U.S. Pat. No. 5,574,076). Such stabilizers and antioxidants may
comprise about 0.01 to 5 weight percent of the composition.
[0239] H. Other Additives
[0240] According to another embodiment of the present invention,
other types of additives to the susceptor composition may include
flow aids, heat and UV stabilizers, coupling agents, waxes,
pigments and other organic compounds. For example, in some
instances, waxes can facilitate lower melt temperatures. Waxes that
can be utilized include, but are not limited to, Bees wax
(SYNCHROWAX BB4), Candelilla wax, CARBOWAX 3350 (available from
Union Carbide Corporation), Carnauba wax, and CASTORWAX NF. Other
waxes include N-(2-hydroxyethyl)-2,2'-ethylene-bis-stearamide,
stearamide, 12-hydroxystearamide wax, hydrogenated castor oil,
oxidized synthetic waxes, poly(ethylene oxide) having a molar
average molecular weight of above about 1000, and functionalized
synthetic waxes such as carbonyl containing ESCOMER H101 from Exxon
(see U.S. Pat. No. 5,532,306). Preferably, the wax polar as
described in U.S. Pat. No. 5,750,605. A preferred polar wax is
Peracin 200. Also preferably, the polar wax is present at no more
than about 25%, more preferably, no more than 17% of the
composition, most preferably, no more than 10% of the
composition.
[0241] Other additives include elastomers such as those described
in U.S. Pat. No. 5,506,298, 5,739,184, 5,169,890, 5,039,744,
4,761,198 may be used, including styrene butadiene rubber,
polybutadiene rubber, rubber, nitrile rubbers, butyl rubber and
halogenated butyl rubber.
[0242] When the compositions are applied and activated as coatings,
they may further comprise one or more additives to impart color to
the composition. Such additive include, without limitation,
titanium dioxide, iron oxide pigments, carbon black and organic
pigments such as isoindoline yellow.
[0243] The present invention is not restricted to the listed
additives, as would be apparent to those of skill in the art. Such
other additives may comprise about 1 to 25 weight percent of the
composition.
[0244] V. Applying the Susceptor Compositions to Substrates
[0245] The compositions of the invention may be formulated to be
applied as a liquid at room temperature, hot melt, or powder.
Liquid compositions may be solvent borne or water-borne. The liquid
applied compositions may be applied as a liquid at room temperature
and dried down to give the desired coating. The liquid applied
coating may be applied to a substrate by any conventional method
including spraying, ink-jet, brushing, rolling, gravure printing,
dripping and the like. Methods of actively drying down liquid
compositions include but are not limited to conventional oven
drying, forced air, heat lamps, microwave heating, RF heating or
various combinations of these or other methods. When a liquid
composition is dried down, it loses some or all of its volatiles.
RF drying of a liquid applied composition may be accomplished by
applying RF energy across the composition in order to generate
sufficient heat within the liquid to facilitate or enhance the
evaporative loss of water or solvent(s). The RF energy can be
applied across the liquid at constant, intermittent, or gradient
intensities to achieve the desired rate and degree of drying.
Similarly, other methods of drying may be applied at constant,
intermittent or gradient intensities to achieve the desired drying
result.
[0246] Hot melt applied systems are applied in their molten state
at an elevated temperature and then cooled to yield the desired
solid coating. The hot melt compositions can be heated to a molten
state by various methods including but not limited to conventional
melt tanks, microwave heating and RF heating. Once the hot melt
composition is melted, it may be applied in a variety of different
types of hot melt coatings, including but not limited to spirals
and beads, hot blown, slot coat, and co-extrusion. After
application, the molten hot melt composition can be passively or
actively cooled to return to its solid form. Active cooling may be
accomplished by blowing cool air across the applied material, or by
allowing the substrate to make contact with a heat-sink
surface.
[0247] Powdered applied systems are applied in their "fine"
particle state (1-20 .mu.m) by electrostatic spray or gun. The
applied layer is activated by RF energy as in liquid or hot-melt
systems.
[0248] Once dried and/or cooled, the substrate may be stored until
activation of the composition is desired. Many of the applied
compositions of the invention are substantially non-tacky and may
be applied to a substrate which is then rolled up. Upon unrolling
and activating, the substrate may be adhered to one or more other
substrates. Those compositions that are tacky may be activated
immediately after being applied and dried if necessary.
Alternatively, they may be covered with a removable strip or dusted
with talc or similar material.
[0249] One aspect of the invention also relates to a method for
applying a susceptor composition to a substrate, comprising:
[0250] (1) formulating the susceptor composition as a liquid
dispersion;
[0251] (2) applying the liquid dispersion of the susceptor
composition to the substrate;
[0252] (3) drying the susceptor composition, wherein the drying
step includes the step of applying RF energy across the
composition, thereby generating heat within the liquid dispersion.
In a preferred embodiment, one may roll up the substrate after the
susceptor composition has dried.
[0253] The susceptor compositions may be applied to any
conventional substrates including, without limitation, woven and
nonwoven substrates such as polyolefins, such as PP and PE webs,
non-wovens, films and the like, cellulose substrates prepared from,
for example, wood pulp (such as paper, cardboard and the like),
cotton fibers (e.g. textiles such as cloth, sheeting and industrial
fabrics), glass, ceramic surfaces, rubber and synthetic polymeric
substrates such as polyester or polyolefin substrates prepared
from, for example, polypropylene and polyethylene, polyvinyl
alcohol, polyhydroxyvalerate butyrate, polylactides, cellulosics,
polyamides, polyvinyl chloride, polystyrene, acrylics, synthetic
textile products, etc. and any combination of the aforementioned.
Other substrates include metal (e.g. aluminum foil and other metal
foils), wood, composites, etc.
[0254] VI. Apparatus For Activating the Various Compositions of the
Present Invention
[0255] Generally, the compositions of the present invention may be
heated (i.e., activated) by any system capable of generating an
electromagnetic field of sufficient strength and frequency.
[0256] FIG. 4 illustrates a high level block diagram of an RE
heating system 400 that is capable of generating an electromagnetic
field for activating the NO compositions of the present invention.
Heating system 400 includes an RF power supply 402 that provides
about a 1 kW, 1 to 15 MHz, RF signal 404 to a heat station
406.Heating system 400 also includes an inductor 408 that is
coupled to RF power supply 402 through heat station 406. Generally,
heat station 406 includes a capacitor connected either in series
with or parallel to inductor 408.
[0257] RF signal 404 provided to heat station 406 by RF power
supply 402 creates an alternating current flowing through inductor
408, which creates an electromagnetic field. Heating of a sample
410, which is or includes a composition of the present invention,
occurs when sample 410 is placed in proximity to inductor 408. The
best heating takes place when sample 410 is placed near the
proximal (or "terminal") end 411 of inductor 408, and little or no
heating occurs when sample 410 is placed at the distal (or "turn")
end 412 of inductor 408. Further, there is a heating gradient from
terminal end 411 to turn end 412. In theory and without limitation,
the best heating occurs at the terminal end 411 because it is
believed that the intensity of the electric field component of the
electromagnetic field at terminal end 411 is greater than at the
distal end 412.
[0258] FIG. 5 illustrates a high level block diagram of another
embodiment of a heating system 500 that is capable of generating an
electromagnetic field for activating the compositions of the
present invention. Heating system 500 includes an alternating
voltage generator 502 and a probe 504, which is connected to an
output terminal 501 of voltage generator 502. Voltage generator 502
alternately positively charges and negatively charges probe 504,
thereby creating an electromagnetic field 506 centered at probe
504.Heating can occur when sample 410 is placed in proximity to
probe 504.How quickly and how much heating occurs depends on the
sample itself, the strength of the electromagnetic field at the
sample, and the frequency of the alternating voltage 509 produced
by voltage generator 502.
[0259] Generally, probe 504 is a conductive material, such as, but
not limited to copper, aluminum, or stainless steel. Generally,
probe 504 can have a variety of shapes, including cylindrical,
square, rectangular, triangular, etc. Preferably, probe 504 is
square or rectangular. Probe 504 can be hollow or solid, preferably
hollow. Generally, probe 504 can be straight or non-straight, such
as curved. The preferred characteristics of probe 504 ultimately
depends on the application that it is being used for.
[0260] In yet another embodiment, which is illustrated in FIG. 6,
heating system 500 includes at least two probes 602 and 604 for
activating the compositions of the present invention. Probe 602 is
connected to output terminal 610, and probe 604 is connected to
output terminal 612. Like probe 504, probes 602 and 604 are made
from conductive materials as discussed above. Probes 602 and 604
can have a variety of shapes. For example, they can be either
straight or curved. Preferably, at least a portion of probe 602 is
parallel to a portion of probe 604, although not a required.
[0261] In the system shown in FIG. 6, probe 602 has a net positive
charge when probe 604 has a net negative charge, and probe 602 has
a net negative charge when probe 604 has a net positive charge.
When probes 602 and 604 are oppositely charged, a strong
electromagnetic field 606 is present between the probes. Thus,
sample 410 is preferably heated by placing it in a region above (or
equivalently below) the region between probe 602 and probe 604, as
illustrated in FIGS. 7A and 7B. This region is referred to as an
activation region. Preferably, an insulating layer 702 (see FIG.
7A) is placed between sample 410 and probes 602 and 604, although
this is not a requirement.
[0262] Generally, the vertical distance between sample 410 and
probes 602 and 604 ranges from about 0.01 to 2 inches, more
preferably from about 0.02 to 1 inch, and most preferably from
about 0.025 to 0.185 inches. Sample 410 can also be heated by
placing it between probes 602 and 604. Generally, The center to
center distance between probes 602 and 604 ranges from about 0.1 to
3 inches, more preferably from about 0.2 to 2 inches, and most
preferably from about 0.25 to 0.75 inches. Additionally, in
general, the height and width of a rectangular probe, or the
diameter for a cylindrical probe, ranges between about 0.02 and 0.5
inches, and the length generally ranges from about 0.25 inches to
20 feet.
[0263] In one embodiment, the distal end 750 of probe 602 is curled
to reduce corona effect (see FIG. 7C). For the same reason, the
distal end of probe 604 is also curled.
[0264] An advantage that the two probe system shown in FIG. 6 has
over the system shown in FIG. 4, is that sample 410 heats equally
as well at the proximal end of probes 602, 604 as it does at the
distal end. Consequently, the system of FIG. 6 does not experience
the heating gradient problem that is encountered with the system of
FIG. 4.
[0265] Generally, the compositions of the present invention may be
activated by a frequency of the alternating voltage 509 ranging
from about 1 KHz to 5 GHz, more preferably from about 1 MHz to 80
MHz, and most preferably from about 10 to 15 MHz. The peak to peak
voltage between probes 602 and 604 generally ranges from 1 to 15
kilo volts (kV). Generally, the duration of RF energy application
to the sample 410 (also referred to as dwell time), for most
applications, ranges from about 100 milliseconds to 30 seconds.
However, there are some applications where the dwell time greatly
exceeds 30 seconds. In the case of a composition comprising a
thermoset resin, the dwell time ranges from about 1 second to 20
minutes, preferably from about 1 to 10 minutes, and most preferably
from about 2.5 to 5.0 minutes to initiate cross linking
reactions(s) leading to a high degree of thermoset character.
[0266] FIG. 8 illustrates one embodiment of alternating voltage
supply 502. The invention, however, is not limited to this or any
particular voltage supply, since any system capable of generating a
strong enough electromagnetic field could be utilized to activate
the compositions of the present invention. In one embodiment,
voltage supply 502 includes direct current (DC) voltage source 802
that is connected to a broadband amplifier 806 through DC power
rail 804. The function of DC voltage source 802 is to provide a DC
voltage to broadband amplifier 806. The DC voltage produced by DC
voltage source 802 can range from 0 volts to 200 volts. The
magnitude of the voltage provided to broadband amplifier 806 is
dependent upon an output signal 815 from a main controller 814.
Output signal 815 of main controller 814 can be controlled manually
by a user 821 through user interface 820, or automatically by a
production line control system 822.
[0267] Broadband amplifier 806 amplifies a low level RF signal 817
generated by frequency controller 816, and thus generates a high
level RF power signal 808. Preferably, the frequency of RF signal
817 ranges between 10 MHz and 15MHz. RF signal 808 is passed
through a power sensor 810 and provided to an impedance matching
circuit 812 (also referred to herein as "heat station") through an
RG393 50 ohm cable 811. Upon RF signal 808 being inputted into
impedance matching circuit 812, an electromagnetic field 606 is
generated at the probes 602 and 604; This electromagnetic field is
used to heat the compositions of the present invention.
[0268] While RF signal 808 is applied to impedance matching circuit
812, power sensor 810 continuously feeds a reflected power signal
832 to frequency controller 816 and main controller 814. Power
sensor 810 also continuously feeds a forward power signal to main
controller 814. Reflected power signal 832 represents the amount of
reflected power and forward power signal 830 represents the amount
of forward power.
[0269] Frequency controller 816 uses reflected power signal 832 to
continually adjust the frequency of RF signal 817 so as to minimize
the amount of reflected power. Main controller 814 uses forward
power signal 830 and reflected power signal 832 to maintain the
power level set by user 821 through user interface 820 or set by
production line control system 822. Main controller maintains the
correct power level by adjusting the level of DC voltage supplied
by DC voltage source 802 and by adjusting the output level of RF
signal 817 generated by frequency controller 816.
[0270] As sample 410 changes during a heating process, the
impedance on the probes 602 and 604 change, which causes a change
in the forward and reflected power. Frequency controller 816 will
detect this change in reflected power because it is receiving
reflected power signal 832 from power sensor 810. Frequency
controller 816 changes the frequency of RF signal 817 so as to
minimize reflected power, thereby achieving an optimum impedance
match and insuring a repetitive power transfer from heating system
800 to sample 410.
[0271] DC voltage source 802, sensor 810, frequency controller 416,
and main controller 814 are further described in U.S. patent
application Ser. No. 09/113,518, entitled, "RF Power Supply," which
is incorporated herein by reference in its entirety. A broadband
amplifier suitable for use in heating system 800 is described in
U.S. patent application Ser. No. 09/270,506, filed Mar. 17,1999,
entitled, "High Frequency Power Amplifier," which is incorporated
in its entirety herein by reference.
[0272] FIG. 9 is a flow chart illustrating a process for heating a
composition according to the present invention using heating system
800. The process begins with step 902 when user 821 or production
line control system 822 sends a "heat-on" signal to the main
controller 814. Upon receiving the "heat-on" signal, main
controller 814 begins an initial tunning process for determining
the frequency of RF signal 817 that produces the minimum amount of
reflected power. The initial tuning process encompasses steps
904-908. In step 904, main controller 814 directs DC voltage source
802 to output a "tune" voltage. The "tune" voltage is the lowest
voltage level that can provide a sufficient signal to measure the
reflected power over a range of frequencies. The objective is to
consume the least amount of energy during the initial tunning
process. Typically, the "tune" voltage level is 10% of the full
scale voltage, where the full scale voltage is the voltage at which
the composition is intended to be heated.
[0273] After step 904, control passes to step 906. In step 906,
heating system 800 performs course tunning. That is, heating system
800 determines a course estimate (i.e., rough estimate) of the
frequency that produces the minimum reflected power. Hereafter this
frequency shall be referred to as the resonant frequency. The
course estimate of the resonant frequency can be determined by
sampling reflected power over a first predetermined frequency
range. After step 906, control passes to step 908. In step 908, the
heating system 800 performs fine tunning. That is, the heating
system 800 determines a fine estimate (i.e., more precise estimate)
of the resonant frequency. The fine estimate can be determined by
sampling the reflected power over a second frequency range, which
includes the course estimate of the resonant frequency. After step
908, control passes to steps 910 and 912 in parallel. In step 910,
main controller 814 ramps (i.e., rapidly increases) the voltage
output by the DC voltage source 802 such that within approximately
30 milliseconds the voltage increases from the "tuning" voltage
level to approximately the full scale voltage level. In step 912,
the heating system 800 continuously tracks the resonant frequency
until a power off indication is received. The methods for course
tuning, fine tuning, and tracking resonant frequency are described
in U.S. patent application Ser. No. 09/113,518.
[0274] FIG. 10A further illustrates one embodiment of impedance
matching circuit 812. Impedance-matching circuit 812 is used to
match the impedance of 50 ohms on the input to the variable
impedance of the probes 602 and 604 and sample 410. The impedance
of the probes 602 and 604 and sample 410 is typically in the order
of 200 to 500 ohms. The impedance of the sample has an equivalent
circuit of a resistance between 500 Ohms and 50 Kilo Ohms in
parallel with a 0.1 picofarad capacitor.
[0275] Circuit 812 includes a connector 1001, two capacitors 1002
and 1004, and an inductor 1006. Capacitor 1002 is a variable
capacitor, which is adjustable from 10 to 50 picofarades (pf) to
achieve impedance match to the varying impedance of probes 602 and
604 and sample 410. The capacitance of capacitor 1004 is preferably
100 pf, and the inductance of inductor 1006 is preferably 1.0 micro
henries (.mu.H). Capacitor 1004 and inductor 1006 form a parallel
resonance circuit that will resonate typically at a frequency
between 12.5 and 14.5 MHz. Capacitor 1004 and inductor 1006 are
water cooled with a flow rate of approximately half a gallon per
minute. Probe 602 is connected to a node 1020 of circuit 812, and
probe 604 is connected to a node 1022 of circuit 812. The high
power RF input 411 (typically less than 1 kilowatt) from a 50 ohm
source generator is connected to connector 1001.
[0276] A process for setting the capacitance of variable capacitor
1002 will now be described. The process begins by applying a low
level RF signal (typically 10 watts) to input 1001 of circuit 812.
The frequency of the applied RF signal is adjusted until the amount
of reflected power is minimized. The capacitance of capacitor 1002
is then adjusted to optimize the reflected power minima. To achieve
the least amount of reflected power that is practical to achieve,
which is about two percent reflected power (or 1.25 voltage
standing wave ratio (VSWR)). the frequency of the applied RF signal
and the capacitance of capacitor 1002 are adjusted in an iterative
process. Once the process is completed, sample 410 is placed in
proximity to probes 602 and 604. At this point it may be necessary
to adjust the frequency of operation and capacitor 1002 in order to
achieve an optimum reflected power. Once optimum reflected power is
achieved, the power level of the input RF signal is increased. As
the input RF power level is increased the resonant frequency of the
matching circuit and probes 602 and 604 and sample 410 will change
requiring a change of operating frequency to continue to minimize
the reflected power.
[0277] FIG. 10B illustrates another embodiment of impedance
matching circuit 812. In this embodiment, impedance matching
circuit 812 includes a connector 1051, a 1:1 balun transformer
1052, two variable capacitors 1054 and 1056, and one inductor 1060.
Capacitors 1054 and 1056 are adjustable from about 3 to 25
picofarades (pf) to achieve impedance match to the varying
impedance of probes 1082 and 1084 and sample 410. The inductance of
inductor 1060 is preferably about 5 micro henries (mH). Capacitor
1058 is not an actual circuit element of the impedance matching
circuit 812. Capacitor 1058 represents the capacitance associated
with the inductor system, which consists of the inductor 1060, the
leads (not shown) connecting the inductor 1060 to the capacitors
1054 and 1056, and the leads (not shown) connecting the probes 1082
and 1084 to the inductor 1060. The capacitance of capacitor 1058 is
preferably less than about 15 pf. One advantage the impedance
matching circuit 812 shown in FIG. 10B has over the impedance
matching circuit shown in FIG. 10A, is that the impedance matching
circuit 812 shown in FIG. 10B provides a balanced signal on the
probes 1082 and 1084 relative to ground.
[0278] VII. Method of Bonding Substrates
[0279] The compositions of the present invention may be employed in
a variety of bonding methods, including but not limited to adhesive
bonding, thermal bonding and mechanical bonding.
[0280] Adhesive bonding is accomplished when a susceptor
composition is interposed between two substrates that are to be
joined (adherands) and activated by RF energy to undergo adhesive
attachment to each of the adherands.
[0281] In the case of thermoplastic adhesive compositions such as
hot melts, RF energy causes the composition to melt and wet-out
onto adherands that are in close contact. Upon cooling, the
composition returns to a solid state with sufficient cohesive
strength and adhesion to each of the adherands to form a good bond.
The degree of heating and melting of the adhesive composition is
controlled by the intensity and duration of the applied RF energy
and the formulation of the adhesive composition. Such control is
required to prevent undesired results stemming from under-heating
or over-heating the adhesive composition. For example,
under-heating can result in a weak bond due to insufficient wet-out
of the adhesive onto the adherands. Also, over-heating can result
in undesirable bond, with thermal distortion or destruction of the
adherands, as well as thermal degradation of the thermoplastic
composition.
[0282] In the case of thermoset adhesive compositions, RF energy
causes the composition to become cured, resulting in sufficient
increase in cohesive strength and adhesion to adherands to form a
strong bond. As in the case of thermoplastic compositions, the
degree of heating and curing of thermoset compositions is
controlled by the intensity and duration of the applied RF energy.
Such control is required to prevent undesired results from
under-heating or over-heating. For example, under-heating can
result in a weak bond due to insufficient cross-linking.
Over-heating can cause effects such as thermal distortion or
destruction of the adherands, as well as thermal degradation and
excessive shrinkage of the thermosetting composition.
[0283] Thermal bonding is accomplished when the composition is used
to generate sufficient heat to cause one or more adherands to
become thermally fused to each other.
[0284] One example of thermal bonding involves saturating a porous
thermoplastic material, such as a non-woven polypropylene web, with
an RF-heatable composition, and then interposing the saturated web
of material between two adherands and RF-heating the composition to
cause the saturated web and adjacent adherands to melt and fuse to
each other.
[0285] Another example of thermal bonding involves saturating a
porous, first thermoplastic adherand with an RF-heatable
composition, and then placing the first adherand against a second
thermoplastic adherand and RF-heating the composition to cause the
first and second adherands to melt and fuse together.
[0286] FIG. 11 shows a method of bonding polyolefin and
non-polyolefin materials using a composition that is activated in
the presence of RF energy according to the present invention.
[0287] In step 1102, adherands that are to be bonded or adhered are
chosen. Once the materials or layers are chosen, an appropriate
composition is prepared in step 1104. For example, if nonwoven PP
layers are chosen to be bonded, a susceptor, which includes an
ionomer as described herein, is combined with a polar carrier. The
type of composition may depend on whether a transparent,
translucent, or lightly colored adhesive obtained by the method of
the present invention is needed for a particular application. After
the composition is prepared in step 1104, control can pass to step
1106, 1109, or 1110.
[0288] In step 1106, a second carrier, such as an insoluble porous
carrier (e.g., nonwoven PP), is saturated with the prepared
composition. In step 1108, the saturated insoluble porous carrier
is then placed in between the layers chosen to be bonded. RF energy
is applied in step 1120. The RF energy applied in step 1120 can be
applied for 100 milliseconds to several minutes; The application of
RF energy allows for the precision heating of the layers to be
bonded, without the unwanted side effects of non-uniform bonding,
or damage to the bonded layers.
[0289] In step 1110, one or both of the layers to be bonded are
coated with the composition. In step 1112, the composition is
allowed to dry or the hot melt to congeal depending on the type of
composition created. Alternatively, a heat source (e.g. an oven or
lamp) and fan may be used to dry the coating or RF energy may be
applied to drive off any water or other solvents. According to step
1114, the layers to be bonded are placed together, such that the
coated surfaces are in contact. Uniform pressure placed on the
contacted layers helps enhance the bonding or adhesion process
activated by the applied RF energy (step 1120). Such uniform
pressure may be applied while the composition is being activated or
immediately thereafter by use of conventional nip rollers.
[0290] In step 1109, a film of the composition is created. Such a
film can be created according to film making processes well known
in the art. The film made in step 1109 can then be sandwiched
between the two materials to be bonded in step 1111. RF power is
then applied in accordance with step 1120.
[0291] In a further embodiment, two or more adherands may be bonded
or adhered by a process comprising: applying a first composition,
onto a first adherand; applying a second composition onto a second
adherand; contacting the first composition with the second
composition; applying RF energy to the first and second
compositions to heat the compositions, thereby causing the first
and second adherands to become adhered or bonded; wherein one of
the compositions comprises a susceptor and the other of the
susceptors is a polar carrier, and the susceptor and/or the carrier
are present in amounts effective to allow the first and second
compositions to be heated by RF energy.
[0292] In this embodiment of the invention, the susceptor and
carrier components of the composition are applied separately to the
adherands prior to placing the adherands together. FIG. 52 shows a
susceptor-coated adherand 5201 assembled to an adherand 5203 coated
with the polar carrier. After coating one or both of the adherands,
one may apply a temporary release liner 5205 to the coated side to
allow the coated adherand to be rolled up or stacked.
Alternatively, one may dry one or both coatings.
[0293] After nipping the two coated adherands in the assembly
stage, the assembly is passed through an RF field 5207 for
activation. The RF energy causes the susceptor and carrier to heat
with the resulting adhesion between the two adherands. The final
nip rollers 5209 press and bonds the two adherands, while cooling
the bond line.
[0294] FIG. 53 shows the replacement of the pre-applied polar
carrier on the adherand with a polar carrier spray coated onto the
adherand just prior to the assembly nip rollers 5206. A polar
carrier is applied (e.g. sprayed or otherwise as described herein)
by a spray applicator 5302 onto adherand 5201. When assembled with
the susceptor coated adherand 5203 and exposed to RF energy, the
interfaced composition activates to form a bond.
[0295] VIII. Additional Probe Embodiments
[0296] Additional embodiments of probes 602 and 604 are described
below with reference to FIGS. 12 to 17. These additional
embodiments are in no way limiting and merely provide additional
examples of possible configurations of the probes.
[0297] In FIG. 12, probes 602 and 604 are each curvilinear and
oppositely charged. In this particular example, probes 602 and 604
are sinusoidally or "S" shaped, but any similar arrangement is
possible. Probes 602 and 604 are made from conductive materials, as
described above, preferably, but not limited to, copper, aluminum,
or stainless steel. Probe 602 includes a proximal region 1206, and
activation region 1208 and a distal region 1210. Similarly, probe
604 includes a proximal region 1212, an activation region 1214, and
a distal region 1216. In proximal regions 1206 and 1212, probes 602
and 604 are spaced apart in order to prevent arcing. The amount of
spacing depends on the size of probes 602 and 604, and in one
example, probes of 0.125 inch square cross-section should be spaced
at least 1.1875 inches apart. Similarly, distal regions 1210 and
1216 are spaced apart-to prevent arcing, the amount of such spacing
is similarly dependent upon the size of the probes. In activation
regions 1208 and 1214, probes 602 and 604 are in proximity to one
another in order to create an electromagnetic field between the
probes. How close probes 602 and 604 must be to one another again
depends on the size of the probes and the magnitude of the charge
on them. In one example, probes 602 and 604 have about a 0.125 inch
square cross-section and preferably spaced between 0.25 and 0.75
inches apart. It is preferable the space between probes 602 and 604
remains substantially equal throughout the activation region, but
it is not necessary. An activation zone 1222 is defined in
activation regions 1208 and 1214 between an outermost end 1218 of
probe 602 and an outermost end 1220 of probe 604. Activation zone
1222 is indicated in dashed lines in FIG. 12. Activation zone 1222
defines the area of sample 410 that can be heated/activated by the
system when the substrates being joined are moving in the direction
indicated. If the substrates are stationary with respect to the
probes, the activation zone is defined by the area in between the
probes.
[0298] In another embodiment, probes 602 and 604 may be repeated in
order to provide a larger activation zone. Such an arrangement is
shown in FIGS. 13A, 13B and 13C. For example, in FIG. 13A, a
pattern of one probe 602 and two probes 604 is provided. This
arrangement may include any number of probes 602 and 604, as long
as oppositely charged probes are placed next to one another. This
arrangement works equally well with multiple sets of curvilinear
probes, as shown in FIG. 13B.
[0299] FIG. 13C illustrates one embodiment of what is termed an
"interdigitated probe system." The interdigitated probe system 1301
is advantageous because it provides an extended activation zone, as
shown by the dotted rectangle 1350. Interdigitated probe system
1301 includes a first element 1302 and a second element 1304.
[0300] The first element 1302 includes a first conductor 1310 and
one or more second conductors 1322 connected to the first conductor
1310. Preferably, conductors 1322 are coplanar and uniformly spaced
apart, but this is not a requirement. Additionally, in one
configuration of element 1302, each conductor 1322 forms a right
angle with conductor 1310, but this is also not a requirement.
[0301] Similarly, the second element 1304 includes a first
conductor 1312 and one or more second conductors 1320 connected to
the first conductor 1312. Preferably, conductors 1320 are coplanar
and uniformly spaced apart, but this is not a requirement.
Additionally, in one configuration of element 1304, each conductor
1320 forms a-right angle with conductor 1312, but this is also not
a requirement.
[0302] In one embodiment, first element 1302 and second element
1304 are orientated such that conductors 1320 are coplanar with
conductors 1322 and each conductor 1320 is adjacent to at least one
conductor 1322. First element 1302 and second element 1304 are not
limited to any particular type of conductive material. However,
conductors 1310, 1312, 1320, and 1322 are preferably copper, and
more particularly, copper tubes. In one embodiment, the copper
tubes have a one-eighth of an inch diameter.
[0303] In one embodiment, the length of conductors 1310 and 1312 is
about 40 inches, and the length of conductors 1320 and 1322 is
about 2 inches. However, conductors 1310, 1312, 1320, and 1322 are
not limited to any particular length. Typically, the length of
conductors 1310 and 1312 ranges between about 3 inches and 80
inches, and the length of conductors 1320 and 1322 ranges between
about 1 inch and 70 inches.
[0304] FIG. 14 shows another embodiment of a probe system for
activating a multi-sided sample 1402. In this embodiment, sample
1402 is mounted on a block 1404. Sample 1402 may be mounted on any
similar device which allows each side of sample 1402 to be exposed
to moving probe blocks 1406. This particular example shows a
three-sided sample exposed to three moving probe blocks 1406,
however, the sample may include more sides and be exposed to an
equivalent amount of moving probe blocks. Probe blocks 1406 include
probes 602 and 604 mounted in an electrically insulating material
such as, but not limited to, polytetrafluoroethylene (TEFLON.TM.).
Probes 602 and 604 are mounted on pressure plates 1408 of probe
blocks 1406. In this particular example, three probes are used in
each probe block 1406, two negatively charged probes 604 and one
positively charged probe 602.However, more or less probes can be
used, depending on the size of the probe blocks, as long as
adjacent probes are oppositely charged. Probes 602 and 604 are
coupled to an alternating voltage supply 502, via output terminals
610 and 612 as generally shown in FIG. 6. Probe blocks 1406 are
moved into proximity of sample 1402 mounted on block 1404,
preferably between 0.125 and 0.375 inch, thereby activating the
compositions of the present invention, as previously described.
Alternatively, probe blocks 1406 could be placed at the appropriate
interval and block 1404 with sample 1402 could be moved into
position to be activated. While FIG. 14 shows the probe blocks 1406
as having a regular shape, one skilled in the art will recognize
that the probe blocks could be any three dimensional shaped
object.
[0305] FIG. 15 shows another embodiment for activating a
multi-sided sample 1502 using a stationary probe system. In this
embodiment, probes 602 and 604 are mounted on multiple sides of a
single probe block 1504, similar to the manner in which probes 602
and 604 were mounted in probe blocks 1406. described above. In this
particular example, probes 602 are mounted on three sides of a
generally square probe block 1504, but probes 602 and 604 could be
mounted on multiple sides of any polygonal block or three
dimensional object. Sample 1502 is brought into proximity of probe
block 1504 by pressure plates 1506, thereby activating the
compositions of the present invention, as previously described. In
this particular example, two negatively charged probes 604 and one
positively charged probe 602 are shown on each side of probe block
1504, however, it will be recognized that any number of probes
could be utilized, depending on the application, as long as
adjacent probes are oppositely charged. Probes 602 and 604 are
coupled to an alternating voltage source 502 via output terminals
610 and 612, as generally depicted in FIG. 6.
[0306] FIGS. 16A and 16B show yet another embodiment of a probe
system for activating a sample material including compositions of
the present invention. In FIGS. 16A and 16B, sample 1602 is draped
over a conveyor rod 1604 and generally moves along the
circumference of the conveyor rod. Conveyor rod 1604 is constructed
of electrically non-conductive material. A probe system 1606 is
disposed in proximity to a portion of the circumference of conveyor
rod 1604, e.g., 0.02 to 1.5 inches, and more preferably within
0.125 to 0.375 inch, and is shaped to conform to the shape of
conveyor rod 1604, as best seen in FIG. 16B. Probe system 1606
includes adjacent alternately charged probes 602 and 604 for
activating sample 1602. Probes 602 and 604 are coupled to an
alternating voltage source 502, as generally depicted in FIG.
6.
[0307] The probe systems described above all activate a single side
of the sample material. However, probe systems could be placed on
both sides of the material in each of the above-described
embodiments, provided that the polarity of the probes is such that
the electromagnetic fields do not cancel each other out. A
particular example of an activation system for activating both
sides of the material is shown in FIG. 17. Rather than using a
probe system, two oppositely charged conductive plates 1702
(positively charge) and 1704 (negatively charged) are disposed on
opposite sides of sample material 1706. Plates 1702 and 1704 are
preferably constructed of copper, but may be constructed of any
suitable conductive material, such as the aforementioned conductive
materials of probes 602 and 604. Sample material 1706 may be
stationary or moving when exposed to the activation region between
plates 1702 and 1704. Plates 1702 and 1704 are preferably spaced
between 0.02 and 24 inches, more preferably between 0.02 and 15
inches, and most preferably between 0.05 and 0.375 inches. Plates
1702 and 1704 are coupled to an alternating voltage source 502 via
output terminals 610 and 612, as generally depicted in FIG. 6.
[0308] IX. Applicator System for Applying a Composition of the
Present Invention to a Substrate/Adherand
[0309] FIG. 18 illustrates one embodiment of an application system
1800 for applying a composition according to the present invention
to an adherand 1810. The manufacturing system includes an
applicator 1815. Applicator 1815 applies a hot melt or liquid
dispersion or powder of the composition 1812 to one side of
adherand 1810. Composition 1812 may be applied via a hot melt by
applying heat to the composition 1812 so that it reaches its
melting point and can be applied to an adherand. In a hot melt
application heat is applied to the composition 1812 in the
applicator 1815, arid the composition 1812 is applied to the
adherand at a temperature between 200 and 325 degrees Fahrenheit,
preferably 250 degrees Fahrenheit.
[0310] Composition 1812 may also be formulated as a liquid
dispersion. The composition 1812 can then be applied to the
adherand at room temperature. Once the liquid dispersion
composition 1812 is applied to the adherand, the coated material
1810 is passed through a heating system 1820.Heating system 1820
acts to dry the composition 1812.Heating system 1820 can be any
conventional heating system, like an oven, or heating system 1820
can be an RF heating system, such as heating system 500 described
above. Other drying means that may be employed include, for
example, a heat lamp with or without a fan to remove volatiles, or
microwave heating system.
[0311] Composition 1812 can be applied in powder form by
conventional electrostatic gun/spray.
[0312] In one embodiment, the coated adherand 1810 is rolled onto a
roller 1830 after composition 1812 is sufficiently dried.
Alternatively, the coated adherand 1810 can be cut into pieces and
stacked. The coated susceptor 1810 can be used at a later point in
time in the bonding process described above. The bonding process
can occur anytime within a few seconds up to many months after the
adherand 1810 has been coated with composition 1812.
[0313] X. Systems for Adhering or Bonding Two Adherands.
[0314] FIG. 19 illustrates one embodiment of a system for bonding
or adhering various adherands or layers. The system utilizes RF
heating system 400, including power supply 402, cable 404, heat
station 406, and coil 408, and clamp 1902. The adherands to be
bonded by RF heating 400, shown as layers 1910, pass through or in
proximity to coil 408. Layers 1910 can either be coated with a
suitable susceptor composition, can sandwich a film made from a
susceptor composition or can sandwich an insoluble, porous carrier
(such as a thermoplastic carrier web) that is saturated with a
susceptor composition as described above. A clamp 1902 provides
uniform pressure to the adherands to be bonded or adhered.
Alternatively, coil 408 can be implemented to provide a uniform
pressure to the adherands to be bonded or adhered; Precision
bonding or adhering takes place as the layers 1910 are exposed to
the electromagnetic field generated when an alternating current
flows through coil 408. The electromagnetic field has sufficient RF
energy to activate the bonding composition. Preferably, layers 1910
are exposed to the electromagnetic field for at least 100
milliseconds to several seconds or minutes. In the case of
thermoset compositions, in general, longer times are needed, e.g.
from 1 second to several minutes or hours.
[0315] FIGS. 20A and 20B illustrates a static bonding system 2000
for bonding or adhering adherands 2090 and 2092 (see FIG. 20B).
Bonding system 2000 is referred to as a static because the
adherands to be bonded do not substantially move while they are
being exposed to the electromagnetic field that activates an RF
activatable composition which is located between the adherands.
[0316] Referring now to FIG. 20A, bonding system 2000 includes a
power supply, such as voltage supply 502, for generating an
alternating voltage between output terminal 612 and output terminal
610. Connected to output terminal 612 is a probe 2006, and
connected to output terminal 610 is a probe 2008. The
characteristics of probe 2006 and probe 2008 are described above
with reference to probes 602 and 604. In one embodiment, probe 2006
and 2008 are rectangular hollow tubes made from a conductive
material, preferably copper. Preferably, the height (H) and width
(W) of each probe is about equal, and the length (L) is generally
larger than the height and width. For example, in one embodiment,
the height and width of each probe is about {fraction (1/8)} of an
inch, whereas the length of each probe is about 10 inches. In
general, the height and width of a rectangular probe, or the
diameter for a cylindrical probe, ranges between about 0.02 and 0.5
inches, and the length generally ranges from about 0.25 inches to
20 feet.
[0317] System 2000 is not limited to two probes. A third probe (not
shown) could be placed adjacent to probe 2006 such that probe 2006
will then be between the new probe and probe 2008. With this
configuration, the new probe would be connected to the output
terminal that probe 2008 is connected to, which in this case is
terminal 610. An exemplary three probed system is illustrated in
FIG. 13A. One skilled in the art should recognize that any number
of probes could be used, provided that no two adjacent probes are
connected to the same output terminal of voltage supply 502.
[0318] In one embodiment, probes 2006 and 2008. are placed in an
electrically insulating block 2010. Insulating block 2010 is
composed of an electrically insulating material, such as, but not
limited to polytetrafluoroethylene (TEFLON.TM.). An optional
electrically insulating layer 2012 (see FIG. 20B) may be placed on
top of probes 2006 and 2008. Preferably, electrically insulating
layer is made from polytetrafluoroethylene or other like material
which resists adhesion of the substrates or adherands thereto.
[0319] An alternative electrically insulating block 2050 is
illustrated in FIG. 20C. FIG. 20C shows a cross-sectional view of
probes 2006 and 2008 housed within the insulating block 2050.
Insulating block 2050 is formed from two elements, insulating
element 2052 and insulating element 2054.
[0320] Insulating element 2052 has two U shaped recesses 2056 and
2058 for receiving probes 2006 and 2008, respectively. In one
embodiment, a low dielectric encapsulate 2060 is placed with the
probes in the recesses. Insulating element 2054 has two protrusions
2062 and 2064 for mating with the recesses 2056 and 2058 of
insulating element 2052. Preferably, both insulating element 2052
and insulating element 2054 consist primarily of
polytetrafluoroethylene (TEFLON.TM.).
[0321] Referring now to FIG. 20B, to bond adherand 2090 to adherand
2092, adherand 2090 and/or adherand 2092 is coated with a suitable
composition 2091, or a film of the composition 2091 is sandwiched
between adherand 2090 and adherand 2092, or an insoluble porous
carrier is saturated with composition 2091 and placed between
adherand 2090 and adherand 2092. Adherands 2090 and 2092 are then
placed over probes 2006 and 2008 such that composition 2091 is
between the adherands and over the region between probe 2006 and
probe 2008, as shown. Power supply 502 is then activated, which
creates an alternating voltage between terminals 612 and 610, which
creates an electromagnetic field between probes 2006 and 2008. The
composition 2091 is exposed to the electromagnetic field for a
predetermined amount of time. The predetermined amount of time can
range between about 100 milliseconds to about one second, several
minutes, or hours depending on the composition and/or the strength
of the electromagnetic field. The electromagnetic field causes
composition 2091 to heat. When composition 2091 reaches a given
temperature, the composition will begin to melt and flow, causing
an impedance change on the matching circuit 812. The impedance
change can be detected by a change in reflected power signal 832.
This change in reflected power signal 832 can be used to control
the intensity of the RF energy. Other methods of detecting when
composition 2091 melts is to detect displacement of a pressure
plate 2020 with a feed back loop. After the predetermined amount of
time has expired or while the composition is exposed to the
electromagnetic field, the adherand can be pressed together using
pressure plate 2020, pressure roller (not shown), or any other
pressure delivery apparatus or means, thereby assuring a good
bond.
[0322] The resulting bond can be an adhesive bond, mechanical bond,
thermal bond, or any combination of aforementioned bonds. For
example, composition 2091 may have adhesive properties to create an
adhesive bond between adherands 2090 and 2092, and/or composition
2091 may be used as a source of thermal energy for welding the
adherands together.
[0323] An advantage of the present invention is that
non-electrically conductive materials can be stacked on top of an
adherand without affecting the bonding process. Only composition
2091 is directly heated when the layers are exposed to RF energy
having the preferred frequency range of 10 to 15 MHz. Thus, by
selectively heating only the composition 2091, multiple layers may
be assembled prior to forming the bond between adherands 2090 and
2092. This allows the assembly of complex laminates prior to
bonding.
[0324] Another advantage of the present invention is that RF energy
can be re-applied to the bonded product and the two (or more)
adherands 2090 and 2092 can be disassembled. This is known as
de-activating the composition 2091. In fact, the composition 2091
can be activated and de-activated a number of times.
[0325] FIGS. 38 and 39 illustrate two exemplary manufacturing
systems in which static bonding system 2000 could be utilized. FIG.
38 illustrates a step and repeat manufacturing system. There are
many applications in general manufacturing where adherands are
joined or bonded together using an adhesive. In a conventional step
and repeat joining (or bonding) system there is a gluing station
immediately followed by a joining station. The gluing station
applies an adhesive to an adherand. After the adhesive is applied,
the adherand moves immediately to a joining station where it is
brought together with the other adherand to which it is to be
joined. The joining station then nips the adherands together to
form a bond.
[0326] The adhesive compositions according to the present invention
allow the adhesive to be applied to the adherand(s) prior to the
adherand(s) entering the manufacturing line. For example, the
adhesive compositions according to the present invention may be
applied at the part supplier's facility with on-demand bonding
occurring for, example, days, weeks, or months later, by RF
activation.
[0327] Referring now to FIG. 38, a step and repeat manufacturing
process as applied to a continuous production line 3802 with base
adherand 3806 and top adherand 3808 being supplied to bonding
system 2000 on a conveyor system 3804. In one embodiment, base
adherand 3806 is pre-coated with an adhesive composition 3805
according to the present invention. Base adherand 3806 could have
been coated minutes, days, weeks, or months prior to base adherand
3806 entering continuous production line 3802. Base adherand 3806
travels along the conveyor 3804 and top adherand 3808 is assembled
to base adherand 3806 by hand or automatic system (not shown). The
assembled adherands 3810 are placed onto a pressure plate 2010 in
which probes 2006 and 2008 are embedded. The bonding process begins
when an electromagnetic field is created between probes 2006 and
2008 by power supply 502. The electromagnetic field activates the
adhesive composition 3805, which then creates a bond between
adherands 3806 and 3808. Pressure plate 2020 is used to nip the
bond during and/or after RF activation. After the bond is nipped,
the assembly 3810 is removed from bonding system 2000 and placed
back on the conveyor 3804.
[0328] FIG. 39 illustrates an index table bonding system. Index
table bonding systems are used in many manufacturing industries to
automate the bonding process. Examples include the bonding of
labels onto bottles. The index table process allows for setting up
multiple stations where different processes in the assembly process
are performed. The time the index table stops at each station is
the same, thus it is dependent upon the slowest process. An
advantage of using an adhesive composition according to the present
invention includes the pre-application to one or both of the parts
to be bonded prior to loading the parts onto the index table. Other
advantages are fast activation and curing time. Consequently, by
removing the adhesive application from the index table, one less
station is used and a higher production throughput is achieved.
[0329] Referring now to FIG. 39, an index table bonding system is
described. The index table bonding system includes an index table
3902, which is generally round and rotates either clockwise or
counter-clockwise. Base parts3904(1)-(N) having a pre-applied
adhesive composition 3906 are placed onto index table 3902. When
index table 3902 moves base part 3904(1) to the next station
(station 2), a top part 3908 is placed onto base part 3904 to form
assembly 3910. Assembly 3910 then moves to station 3 where it is
exposed to an RF field, which activates adhesive composition 3906.
In station 3, the RF field is generated by probes (not shown)
positioned so that adhesive composition 3906 is activated. The
probes may be configured to either contact the assembly 3910 and
apply some pressure to aid in the bonding process. Alternatively,
the probes could be configured so there is no contact with the
assembly 3910. After activation of the adhesive 3906, the assembly
3910 moves to station 4 for a nip or cure portion of the bonding
process. After station 4, the assembly 3909 moves to station 5
where it is unloaded from the index table 3902.
[0330] FIG. 21 illustrates a dynamic bonding system 2100 (also
referred to as an in-line bonding system) for bonding or adhering
adherands. Bonding system 2100 is referred to as dynamic because
the adherands to be adhered, adherands 2110 and 2112, continuously
move through an electromagnetic field; which is generated by
heating system 2140. In one embodiment, adherand 2110 is pre-coated
with a composition 2104 according to the system shown in FIG.
18.
[0331] Bonding system 2100 includes a roll 2102 of coated adherand
2110 and plurality of rollers 2120, 2122, 2124, 2126, and 2128 for,
among other things, continuously guiding coated adherand 2110 and
adherand 2112 through an electromagnetic field generated by heating
system 2140. In one embodiment, coated adherand 2110 and adherand
2112 move through the electromagnetic field at a rate of about 0.01
to 2000 feet per minute, most preferably, about 1000 feet per
minute (ft/minute).
[0332] The bonding process begins when coated adherand 2110 is fed
onto roller 2120. Coated adherand 2110 is then passed over roller
2122. A pressure activated construction bond may be formed by
passing the two adherands 2110 and 2112 between roller 2122 and nip
roller 2124. A construction bond may be required in this process to
maintain the proper location of coated adherand 2110 and adherand
2112 prior to and/or during activation. Preferably, the composition
2104 is formulated to provide a pressure sensitive tack when a
construction bond is needed. Coated adherand 2110 and adherand 2112
are not limited to any particular thickness. As should be readily
apparent to one skilled in the art, the system can be designed to
accommodate any reasonable thickness of adherand.
[0333] In this embodiment, the invention relates to a method for
dynamically bonding a first adherand to a second adherand,
comprising:
[0334] (1) creating an article of manufacture comprising the first
adherand, the second adherand, and a composition, the composition
being placed between the first adherand and the second adherand,
wherein the composition can be activated in the presence of an RF
field;
[0335] (2) moving the article of manufacture along a predetermined
path;
[0336] (3) generating along a portion of the predetermined path an
RF field having sufficient energy to activate the composition,
wherein the composition is activated by its less than one second
exposure to the RF field.
[0337] In a preferred embodiment, the article passes through the RF
field at a rate of at least about one-thousand feet per minute. In
a more preferred embodiment, the article passes through the RF
field at a rate of about 1000 feet per minute.
[0338] Referring now to FIG. 22, after the construction bond is
formed, the construction bonded coated adherand 2110 and adherand
2112 are passed through an RF field 2230, which is generated by
heating system 2140. FIG. 22 further illustrates heating system
2140 for use in dynamic bonding system 2100.
[0339] Heating system 2140 includes a power supply, such as power
supply 502, for generating an alternating voltage between terminal
612 and terminal 610. Connected to terminal 612 is a probe 2210,
and connected to terminal 610 is a probe 2220. The characteristics
of probes 2210 and 2220 are described above with reference to
probes 602 and 604 and probes 2006 and 2008. In one embodiment,
probe 2210 has a distal section 2211, a center section 2212 and a
proximal section 2213. Similarly, in one embodiment probe 2220 has
a distal section 2221, a center section 2222 and a proximal section
2223. Preferably, center section 2212 is parallel with center
section 2222, and they both have a length of about 48 inches when
the adherands 2110 and 2112 are traveling at about 1000 feet/minute
in the direction indicated by arrow 2130. This configuration
results in about a preferred 240 millisecond dwell time. Dwell time
refers to the maximum amount of time that any given point on
adherands 2110 and 2112 is positioned beneath (or over) probes 2210
and 2220 (i.e., within the activation region). If the speed of the
adherands 2110 and 2112 is increased, the preferred dwell time can
remain constant by increasing the length of probes 2210 and 2212.
For example, if it is desired for the adherands 2110 and 2112 to
move at a rate of about 2000 feet/min over probes 2210 and 2220,
and the preferred dwell time is about 100 milliseconds, then the
minimum length of probes 2210 anc 2220 would be about 40 inches.
Although a preferred dwell time is 600 milliseconds, the dwell time
can be increased to several minutes if desired by increasing the
length of probes 2210 and 2220, e.g., from about the 20 inches to
20 feet, and/or decreasing the speed at which adherands 2112 and
2110 travel over probes 2210 and 2220. Shorter probes are also
contemplated, for example from about 0.25 inches to about 20
inches.
[0340] Preferably, probes 2210 and 2220 are positioned with respect
to coated adherand 2110 such that the composition that coats coated
adherand 2110 is beneath (or above) an activation region. The
activation region is the area between the center section 2212 and
center section 2222.
[0341] The frequency of the alternating voltage generated by power
supply 502 can range from the low Kilohertz to high Gigahertz
range. In one embodiment the frequency ranges between about 1 MHz
to about 5 GHz, most preferably about 10 MHz and 15 MHz. The peak
to peak level of the voltage generated by power supply 502 may
range from about 500 V to 20 kV, most preferably about 1 to 15 kV.
The composition 2104 will remain activated as long as the RF energy
is delivered.
[0342] After the adherands 2110 and 2112 pass over (or under)
probes 2210 and 2220 they are nipped by non-destructive nip rollers
2126 and 2128, which assure that a good bond is created between
adherand 2110 and adherand 2112. For optimal performance, the nip
rollers 2126 and 2128 apply pressure immediately after re-flow
temperatures are achieved within the adhesive material.
Additionally, nip roller 2126 and/or nip roller 2128 may be cooled
to remove thermal energy from the adherands. Upon cooling, the
composition forms a strong bond between the adherands 2110 and
2112. The bonded adherands can then be subsequently processed in
accordance with a particular application.
[0343] There are a number of benefits of the above system. First,
the system provides a finished bond in less than about one second
of activation. Second, the activation process does not produce
harmful emissions or by-products that may interfere with the
bonding of two thin films. Third, the activation only occurs in the
activation region.
[0344] FIGS. 23-27 illustrate alternative designs for heating
system 2140. As shown in FIG. 23, curved probes 2310 and 2320 can
be used in place of straight probes 2210 and 2220. An advantage of
curved probes 2310 and 2320 is that the width 2390 of the
activation region is greater then the distance 2311 between probes
2310 and 2320, whereas the width of the activation region provided
by probes 2210 and 2220 equals the distance between center section
2212 of probe 2210 and center section 2222 of probe 2220.
[0345] The heating system shown in FIG. 24 includes probe 2410 in
addition to probes 2210 and 2220. Probe 2410 is positioned between
probes 2210 and 2220. Probe 2410 is parallel with probes 2210 and
2220. Preferably, the distance (d) between probe 2410 and 2210 is
equal to the distance (d) between probe 2410 and probe 2220. Probes
2210 and 2220 are both connected to the same output terminal of
voltage supply 502, whereas probe 2410 is connected to the other
output terminal. An advantage of the probe design illustrated in
FIG. 24. is that it provides a larger activation region. The width
2420 of the activation region is greater than the distance (d)
between any two of the probes. Based on the above description, one
skilled in the art will recognize that any number of probes can be
used in heating system 2140, provided that no two adjacent probes
are connected to the same output terminal of voltage supply
502.
[0346] The heating system shown in FIG. 25 is similar in concept to
the one shown in FIG. 24. A curved probe 2510 is placed between
curved probes 2310 and 2320. Curved probes 2310 and 2320 are both
connected to the same output terminal of voltage supply 502,
whereas probe 2510 is connected to the other output terminal.
Again, an advantage of the heating system shown in FIG. 25 is that
it can provide a larger activation region than the similar heating
system shown in FIG. 23.
[0347] FIG. 26 illustrates another heating system. The heating
system shown in FIG. 26 includes two plates 2610 and 2620. Plate
2610 is positioned above adherand 2110 and plate 2620 is positioned
below adherand 2112. Thus, composition 2104 travels between plates
2610 and 2620. Plate 2610 is connected to output terminal 610 of
voltage supply 502, and plate 2620 is connected to output terminal
612 of voltage supply 502. When voltage supply 502 is turned on, it
generates an electromagnetic field between plates 2610 and 2620,
which is used to activate composition 2104. FIG. 27 illustrates
another perspective of plates 2610 and 2620. As is apparent from
FIG. 27, the width of the activation region for this design is
simply the width (W) of the plates. The center to center distance
(d) between plate 2610 and plate 2620 can range from 0.02 inches to
20 inches. In one embodiment, the distance ranges between 0.25
inches and 1.5 inches. The length (L) of course depends on the
desired dwell time and the rate at which any given point on
adherand 2110 or 2112 travels between any two points along the
length of one of the plates.
[0348] XI. Exemplary Specific Applications of the Present
Invention
[0349] The susceptor compositions may be employed for many purposes
including bonding, cutting, and coating. Thus, the susceptor
compositions may be employed for packaging applications, e.g. to
bond or adhere cases or cartons as described in U.S. Pat. No.
5,018,337, but with the additional step of RF activation.
Applications for the RF cured thermoset compositions, which are
illustrative only and not to be considered limiting of the scope of
the present invention, include:
[0350] Coatings for conventional and spray applications on
plastics, metals, wood etc.
[0351] Corrosion resistance coatings.
[0352] Industrial and protective coatings.
[0353] Top coats.
[0354] Automotive coatings.
[0355] Lamination of composites.
[0356] Laminating adhesives.
[0357] Bonding of structural composites.
[0358] Inks and decorative coatings.
[0359] Barrier coatings.
[0360] Additional applications are listed below, but are likewise
illustrative and not limiting of the scope of the present
invention.
[0361] A. Manufacture of Flexible Packaging
[0362] FIGS. 28A and 28B illustrate one embodiment of a system for
the manufacture of flexible packaging. Flexible packages are used
for, among other things, packaging foods. The system includes a
system 2802 (see FIG. 28A) for manufacturing an RF activated
adhesive film 2815 and a bonding system 2804 (see FIG. 28B) for
bonding the adhesive film 2815 to another film 2850.
[0363] Referring now to FIG. 28A, film manufacturing system 2802
includes an extruding system 2810, a casting wheel 2814 a heating
system 2820, a stretching system 2830, and an optional film roller
2840. In one embodiment, extruding system 2810 includes three
extruders 2811, 2812, and 2813. An RF activated adhesive
composition according to the present invention is first formulated
into an extrudable resin (for example, ethylene vinyl acetate or
other polymer based material is added to the adhesive composition)
and then provided to extruder 2813 in a pellet or liquid form.
Polypropylene or other like similar substance, such as but not
limited to ethylene vinyl acetate (EVA), is provided to extruder
2811, and a sealing material is provided to extruder 2812. The
output of extruders 2811-2813 are cast into a film 2815 by casting
wheel 2814.
[0364] FIG. 29 illustrates film 2815. As shown in FIG. 29, film
2815 includes a first layer 2902 consisting of the sealing
material, a second layer 2904, e.g., OPP and/or EVA and/or other
similar substance, and a third layer 2906 consisting of the RF
activated adhesive. Because film 2815 includes an adhesive
composition according to the present invention, film 2815 can be RF
activated.
[0365] Referring back to FIG. 28A, film 2815 is provided to heating
system 2820. In one embodiment, heating system 2820 includes heater
rollers 2821 and 2822. The function of heating system is to heat
the film to a temperature that allows the film to be stretched.
After being processed by heating system 2820, film 2815 is
stretched by stretching system 2830. In one embodiment, stretching
system 2830 includes a plurality of stretch rollers 2831, 2832,
2833, 2834, and 2835 and a transverse stretcher 2837. Stretching
system 2830 stretches film 2815 both length and width wise. After
being stretched, film 2815 may be rolled up using film roller 2840.
Alternatively, film 2815 can be cut and stacked after being
stretched.
[0366] Referring now to FIG. 28B, bonding system 2804 is used to
bond film 2815 with film 2850. In one embodiment, film 2850 is a 70
gauge oriented polypropylene (OPP) film. Film 2850 is passed over a
print wheel 2855 and then through oven 2857. A pair of nip rollers
2860 and 2861 press film 2815 with film 2850 to form a construction
bond and thus form a single multi-layer film 2870. FIG. 30
illustrates one embodiment of film 2870.
[0367] As shown in FIG. 30, film 2870 includes layer 2902
consisting of the sealing material, layer 2904 that includes
thermoplastics and/or elastomers, for example, OPP and/or EVA
and/or other similar substance, third layer 2906 consisting of the
RF activated adhesive, a fourth layer 3002 consisting of the ink
applied by print wheel 2855, and a fifth layer 3004 consisting of
film 2850.
[0368] Referring back to FIG. 28B, an RF heating system 2875
creates an RF field that is used to heat adhesive layer
2906.Heating system 2875 defines an activation region. The
activation region is an area in which the RF field generated by
heating system 2875 is strong enough to activate adhesive layer
2906. Film 2870 can travel through the activation region in as
quickly as about 100 milliseconds. Shortly after passing through
the activation region, film 2870 is nipped by nip rollers 2880 and
2881 and then rolled by film roller 2885. FIGS. 16A and 16B
illustrate one embodiment of the probe portion of heating system
2875. Other heating systems could be used, such as those described
above with respect to FIGS. 20 and 21.
[0369] FIG. 31 illustrates an alternative system 3100 for
manufacturing an RF activated adhesive film for use in the flexible
packaging industry. System 3100 is similar to system 2802, except
that system 3100 does not include extruder 2813. In place of
extruder 2813, system 3100 includes an adhesive applicator 3101 and
a heating system 3102. An adhesive composition according to the
present invention is formulated into a liquid dispersion and
applied to film 2815 by adhesive applicator 3101. In one embodiment
adhesive applicator 3101 includes a gravure application tool (not
shown). Heating system 3102 can be a conventional heating system,
such as an oven, or it can be an RF heating system, such as heating
system 600 or any of the other heating systems described
herein.
[0370] B. Food Packaging and Cap Sealing
[0371] Conventionally, metallic foils are used as susceptors of
electromagnetic energy to generate heat for package sealing.
Typical examples include tamper evident bottle seals (i.e., cap
sealing) and food packaging. While the conventional systems are
effective in sealing the packages, the use of metallic foils
eliminates the manufacturer's ability to perform post sealing
inspection, such as metal detection, x-ray, and the like.
Additionally, there may be a recycling benefit and a cost saving to
the system by eliminating the metallic foil.
[0372] One solution is to replace the metallic foil with a
composition of the present invention. The composition may or may
not have adhesive properties. FIG. 32 illustrates a conventional
aseptic package construction. A conventional aseptic package
includes an outer polyethylene layer 3202, a paper layer 3204, a
second polyethylene layer 3206, a layer of metallic foil 3208, a
third 3210 polyethylene layer, an inner polyethylene layer 3212,
and a container 3214 that holds the food or beverage. Inner
polyethylene layer 3212 is the layer that contacts with the
container 3214, and is used to seal the container during the food
packaging process. The sealing is achieved through induction
heating of the metallic foil layer 3208 causing the inner
polypropylene layer 3212 to melt and bond to the container
3214.
[0373] FIG. 33 illustrates one embodiment of a packaging
construction that does not use metallic foils. The packaging
construction includes the outer polyethylene layer 3202, the paper
layer 3204, the second polyethylene layer 3206, a susceptor
composition according to the present invention 3302, a barrier
layer 3310, an inner layer 3212, and a container 3214 that holds
the food or beverage. Inner layer 3212 is the layer that contacts
with the container 3214, and is used to seal the container 3214
during the food packaging process. Inner layer 3212 can be a
polyethylene or EVA layer. In one embodiment, barrier layer 3310 is
an EVOH barrier layer. The sealing is achieved through RF heating
of susceptor composition 3302, which causes the inner layer 3212 to
melt and bond to the container 3214. The advantage of replacing
metallic foil 3208 with susceptor composition 3302 is that now the
container 3214 can be inspected after it is sealed by using a metal
detector or x-ray machine, and there are recycling advantages as
well.
[0374] A conventional cap sealing construction is illustrated in
FIG. 34. FIG. 34 illustrates a polyethylene bottle 3402, a seal
3401, and a bottle cap 3414. Seal 3401 includes several layers of
substrate, including a polyethylene layer 3404, a metallic foil
layer 3406, another polyethylene layer 3408, a wax layer 3410, and
a paper layer 3412. Seal 3401 is adhered to bottle 3402 by heating
foil through induction, which causes layer 3404 to weld to bottle
3402. As discussed above, it is desirable to remove metallic foil
layer 3406.
[0375] FIG. 35 illustrates an improved seal 3501 for bottle 3402.
Seal 3501 is identical to seal 3401 (see FIG. 34), except that the
metallic foil 3406 has been replaced with a composition 3502
according to the present invention. As discussed above, the
advantage of removing metallic foil 3406 is that now bottle 3402
can be inspected after it is sealed by using a metal detector or
x-ray machine, and can be more easily recycled.
[0376] Another use of the compositions described herein is to
attach a flexible bag 3602 containing dry food to an outer box
3604, as illustrated in FIG. 36. In one embodiment, flexible bag
3602 includes three layers, 3610, 3611, and 3612, and outer box
3604 is a paper product, such as a paper board. To bond flexible
bag 3602 to outer box 3604, an adhesive composition 3620 according
to the present invention is placed between outer box 3604 and layer
3610. Adhesive composition 3620 is then exposed to an RF field that
causes the composition 3620 to melt and flow and bond layer 3610 to
outer box 3604. In one embodiment, layer 3610 is a polyethylene
layer, layer 3611 is an EVOH barrier layer, and layer 3612 is an
EVA food contact layer. In another embodiment (see FIG. 37), outer
box 3604 is coated with a polyethylene layer (or other like layer)
3730. This configuration creates an improved bond.
[0377] C. Printing Applications
[0378] The susceptor compositions of the present invention may also
be applied together with one or more inks to provide writing, a
design or gr aphic, e.g. as is described in U.S. Pat. No.
4,595,611. Particular application of this aspect of the invention
is in the preparation of ink-printed substrates such as ovenable
food containers. Examples of pigments that can be combined with the
susceptor composition include titanium dioxide, iron oxide
pigments, carbon black and organic pigments such as isoindoline
yellow. In a preferred embodiment, the susceptor is a sulfonated
polyester. Alternatively, a sulfonated polyester-cationic dye salt
may be employed as disclosed in U.S. Pat. No. 5,240,780. The
substrate may be printed once or multiple times to achieve the
desired result. Once printed, the substrate may be further coated
with a clear unpigmented composition which may comprise the
susceptor composition of the invention. The same composition used
to print may be used to further coat, but without the added
pigments. The susceptor compositions may be RF activated after each
printing/coating step, or after all of the coatings are applied.
Finally, the substrate may be coated with a clear polyester sealing
resin.
[0379] An extension the printing application is high speed ink-jet
used in printers/copiers. Inks formulated as liquids (H-P/Cannon)
or solid (Tetronic) composition can contain the susceptor
compositions of this invention in amounts effective that can be
activated by RF energy for rapid drying and fixing. Current ink
formulations are too "slow in drying" or need excessive heat
energy.
[0380] D. Bookbinding and Mailers
[0381] The susceptor compositions of the present invention may be
used to bond paper substrates used in printing and/or copying. An
advantage of the present invention is that a substrate to be
printed on (such as a paper substrate) can be coated with a
susceptor composition described herein prior to printing on the
substrate. For example, FIG. 43 illustrates a process for
assembling a book, magazine, or periodical, or the like. In step
4302, a portion of one side of a substrate is coated with a
susceptor composition that functions as an adhesive. Any one of the
various methods for coating a substrate described herein can be
used to coat the substrate. FIG. 44 illustrates a preferred portion
of a substrate to be coated with the susceptor composition. As
shown in FIG. 44, a thin strip of the susceptor composition 4404
coats one edge of the substrate 4402. The portion of the substrate
that is not coated is the portion where ink will be printed.
Preferably, the susceptor composition 4404 is formulated such that
it is tack free, however, this is not a requirement.
[0382] After the substrate 4402 has been coated, the substrate may
be processed into rolls, stacks and the like and stored for later
use (step 4304). In step 4306, the coated substrate is fed into a
printing means that prints ink onto the substrate. The printing
means can be a conventional printer or conventional photocopying
machine. Further, the substrate can be fed into the printing means
as a continuous substrate or as cut pieces. For this example, we
will assume that cut pieces of the substrate are fed into the
printing means. In step 4308, after the printing means prints ink
onto a substrate, the substrate is stacked with the other
substrates that have already been fed into the printing means as
shown in FIG. 45. The stack is placed in an electromagnetic field.
The electromagnetic field causes the susceptor composition to melt
and flow. The stack is then nipped to assure a good bond (step
4312).
[0383] In one embodiment, prior to placing the stack in the
electromagnetic field, the substrate stack is pressure bonded by
applying upward and/or downward pressure on the stack. In another
embodiment, the ink that is printed on the substrates includes a
susceptor composition. In this way, the ink can be dried rapidly by
passing the substrate through an electromagnetic field.
[0384] In another embodiment, mailers or envelopes can be
constructed. Referring to FIG. 46, a portion of one side of
substrate 4602 is coated with a susceptor adhesive composition
4604. Preferably, the susceptor adhesive composition 4604 is
formulated so that it is tack-free. The substrate 4602 includes a
fold line 4610. The coated substrate 4602 can be fed into a
printing means that prints ink onto the substrate. After the ink is
printed thereon, the substrate is folded along the fold line 4610
so that-the top portion 4612 of the substrate 4602 contacts the
bottom portion 4614 of the substrate (see FIG. 47). At this point,
the substrate is passed through the electromagnetic field so as to
melt and flow the susceptor composition 4604, thereby bonding the
top portion 4612 of the substrate with the bottom portion 4614 when
the susceptor composition 4604 solidifies.
[0385] E. Security Devices
[0386] As would be apparent to one skilled in the relevant art(s),
the adhesive of the present invention can be used to seal
containers, casings, housings and the like (hereafter "container").
In particular, the adhesive of the present invention is preferably
used to seal containers that a manufacturer does not want accessed
by others. A manufacturer may want to prevent a third party from
opening certain containers for security, safety or quality control
reasons. However, the inside of the container must still be
accessible to the manufacturer or qualified repair facility. By
exposing the seal to an electromagnetic field, the manufacturer can
disassemble the container.
[0387] For example, a manufacturer may want to prevent an article
intended for one-time use from being reused. As such, the adhesive
of the present invention can be used, for example, to seal the
shell or casing of a disposable camera. The manufacturers of such
disposable cameras often do not want to have the shells reloaded
and reused by the consumer or a competitor company. If the adhesive
of the present invention is used to seal the camera shell, then
when the film developer opens the camera body to remove and process
the film, mating sections of the camera shell attached by the
adhesive would break or deform such that the camera body could not
be reused. As such, the adhesive of the present invention would
prevent tampering with and unauthorized reloading of disposable
camera shells.
[0388] FIG. 48 shows an example of a container 4800 sealed with a
susceptor composition of the present invention. Container 4800
includes a first portion 4804 and a second portion 4808. In one
embodiment, first portion 4804 is a container base and second
portion 4808 is a lid. Container 4800 can be made from a variety of
materials, including, for example, polypropylene, polystyrene,
polyolefin, wood or wood products, rubber, plastics, glass,
ceramics, paper, cardboard, natural or synthetic textile products,
aluminum or other foils, metals, or any combination of these
materials. An adhesive composition 4812, made in accordance with
the present invention, is applied to a surface of container 4800.
In the example of FIG. 48, adhesive composition 4812 is applied to
a first mating surface of first portion 4804. Second portion 4808
is then placed on top of first portion 4804, so that a second
mating surface of second portion 4808 comes in contact with
adhesive composition 4812. A suitable electromagnetic field, as
described herein, is then applied to adhesive composition 4812 to
join the first and second mating surfaces of first and second
portions 4804 and 4808.
[0389] To open container 4800, suitable RF energy must again be
applied to container 4800 to cause adhesive composition 4812 to
reflow. If a person attempts to open container 4800 without
applying the suitable electromagnetic field, the container 4800 is
designed to preferably break or catastrophically fail and so that
it cannot be reused.
[0390] FIG. 49 shows another example of a device 4900 sealed or
otherwise joined together with a composition of the present
invention. Device 4900 includes a first portion or substrate 4904
and a second portion or substrate 4908. Device 4900 can be made of
a variety of materials, as discussed above with respect to
container 4800, shown in FIG. 48. In this embodiment, first
substrate 4904 includes a male portion 4912 forming the first
mating surface. Male portion 4912 includes a narrowed section 4916
and a wider section 4920. A corresponding female portion 4924
forming a second mating surface is formed in second portion 4908
and is configured to accommodate or receive wider section 4920 of
male portion 4912. Second portion 4908 may also be configured to
accommodate a portion of narrowed section 4916.
[0391] An adhesive composition 4928, made in accordance with the
present invention, is applied to the second mating surface of
female portion 4924 of second portion 4908. First portion 4904 is
then assembled so that the first mating surface comes in contact
with adhesive composition 4928 on second portion 4908 while the
adhesive composition is within the electromagnetic field. First
portion 4904 is locked into second portion 4908 once the
application of electromagnetic filed is discontinued, causing
adhesive composition 4928 to solidify. To disassemble device 4900,
an electromagnetic field must again be applied to adhesive 4928 to
cause it to reflow and allow the portions 4904 and 4908 to
separate. If someone attempts to disassemble device 4900 without
application of a suitable electromagnetic field, narrowed section
4916 of male portion 4912 will break or otherwise catastrophically
fail resulting in device 4900 being unusable. As such, this
embodiment will prevent authorized disassembly and reuse of device
4900.
[0392] FIG. 50 shows another example of a device 5000 sealed or
otherwise joined together with a composition of the present
invention. Device 5000 is similar to device 4900 described above
with respect to FIG. 49, except that an electronic circuit path
5004 is added to male portion 4912 such that it is disposed through
narrowed section 4916. As such, should portions 4904 and 4908 of
device 5000 be disassembled without application of a suitable
electromagnetic field, electronic circuit path 5004 will be cut
during failure of narrowed section 4916, resulting in further
failure of device 5000.
[0393] FIG. 51 shows still another example of a cross-section of a
container 5100 that has been sealed with the adhesive of the
present invention. Container 5100 includes a first portion 5104 and
a second portion 5108. Container 5100 can be made of a variety of
materials, as discussed above with respect to container 4800, shown
in FIG. 48. First portion 5104 includes a protrusion 5112 which
forms a first mating surface. In the embodiment shown in FIG. 51,
protrusion 5112 extends around the entire circumference of
container 5100.However, it would be apparent to one skilled in the
relevant art that one or more discrete protrusions 5112 could be
used instead of or in addition to the continuous protrusion 5112.
Second portion 5108 includes a recess 5116 which forms a second
mating surface corresponding to the first mating surface of
protrusion 5112. Protrusion 5112 and corresponding recess 5116 are
formed slightly inward of the periphery of container 5100 to so
that when first and second portions 5104 and 5108 are joined, the
mating surfaces and an adhesive composition 5120 therebetween
cannot be accessed, thereby further reducing the risk of a person
prying apart or otherwise disassembling container 5100. Adhesive
composition 5120, made in accordance with the present invention, is
applied to the second mating surface of recess 5116. First and
second portions 5104 and 5108 can be joined together by application
of suitable electromagnetic field and similarly disassembled by
re-application of the electromagnetic field.
[0394] The invention relates to an apparatus, comprising:
[0395] a first portion having a first mating surface;
[0396] a second portion, having a second mating surface;
[0397] a composition disposed between the first mating surface and
the second mating surface, wherein the composition comprises a
susceptor and a polar carrier wherein the susceptor and/or the
polar carrier are present in amounts effective to allow the
composition to be heated by RF energy, and wherein the composition
adheres the first mating surface to the second mating surface such
that application of a force to separate the first mating surface
and the second mating surface results in breakage of the apparatus
unless the composition is in a melted state.
[0398] In this apparatus, the composition may be disposed on the
first mating surface and the second mating surface such that the
composition is not accessible when the first and second mating
surfaces are joined. In another embodiment, the first mating
surface may comprise a protrusion disposed on the first portion. In
another embodiment, the second mating surface may comprise a recess
formed in the second portion. In a further embodiment, the
apparatus may further comprise an electronic circuit path disposed
in the protrusion. In another embodiment, the first portion and the
second portion are disassembled upon application of an
electromagnetic energy to the composition.
[0399] F. Thermal Destruction
[0400] The susceptor composition of the present invention can not
only be used to coat a substrate and bond adherands, but also can
be used to cut a substrate. A substrate can be cut using a
susceptor composition described above by first applying the
susceptor composition to at least one side of the substrate. Next,
an electromagnetic field is applied to the susceptor composition
causing the susceptor composition to heat. The thermal energy
generated by the susceptor composition heats the substrate,
particularly the section of the substrate that is in contact with
the susceptor composition. The substrate is heated until a section
of the substrate melts resulting in the substrate being cut.
[0401] In this embodiment, the invention relates to a method for
cutting a substrate, comprising:
[0402] applying a composition to a portion of the substrate,
wherein the composition comprises a susceptor and polar carrier
wherein the susceptor and/or the polar carrier are present in
amounts effective to allow the composition to be heated by RF
energy, and wherein the portion of the substrate defines a first
section of the substrate and a second section of the substrate;
[0403] melting the portion of the substrate, wherein the melting
step includes the step of heating the composition, wherein the step
of heating the composition includes the step of applying RF energy
to the composition;
[0404] after the portion of the substrate has begun to melt,
applying a force to the substrate to separate the first section
from the second section.
[0405] G. Seam Sealing
[0406] The susceptor compositions of the present invention may be
used to seal the seams of products made from cloth. Conventional
cloth materials manufactured from man made or natural fibers are
sewn together to form cloth products, such as clothing, bags,
tents, awnings, covers, and the like. Typically, the seams of cloth
products such as tents, awnings, bags, etc. need to be sealed to
prevent leakage of liquids through the small holes in the products
created by a sewing needle and thread during a stitching process.
The susceptor compositions of the present invention can be used to
seal these seams.
[0407] FIG. 62 illustrates how a susceptor composition of the
present invention can be used to seal the seams of cloth products.
FIG. 62 illustrates a seam sealing system 6200 for sewing a first
cloth material 6202 to a second cloth material 6204 and for sealing
the seam. In one embodiment, a susceptor composition 6206 according
to the present invention is placed between the first and second
cloth materials 6202 and 6204. In another embodiment, either one or
both of the cloth materials 6202 and 6206 are coated with the
composition in the location where the seam will exist.
[0408] The system includes a pressure plate 6208 and a
reciprocating needle 6212, through which a thread 6210 can be
threaded, for joining the first cloth material 6202 with the second
cloth material 6204. The seam sealing system 6200 also includes an
RF heating system according to the present invention for activating
the composition 6206. The RF heating system includes a
reciprocating pressure foot 6214 and at least two probes (not
shown) placed within and near the surface of the pressure plate
6208. The probes (not shown) are connected to the power supply 502
for generating an RF field at the probes. Alternatively, the probes
can be located within the pressure foot 6214 as opposed to the
pressure plate 6208.
[0409] The cloth materials 6202 and 6204 and the composition 6206
are pulled past the reciprocating needle 6212 and then past the
reciprocating pressure foot 6214. The reciprocating needle 6212 and
thread 6210 stitch the first material 6202 to the second material
6204, thereby joining the materials together at a seam. This
stitching process creates small holes in the materials 6202 and
6204. The RF field generated at the probes within the pressure
plate 6208 activates the composition 6206, which causes the
composition 6206 to flow and thereby fill or cover the small holes
created by the needle 6212 during the stitching process. The
reciprocating pressure foot 6214 functions to evenly flow the
activated composition 6206, thereby facilitating the composition in
the filling/covering of the holes created by the needle 6212. In
this manner, the susceptor compositions of the present invention
can be used to seal seams.
[0410] XII. Kits
[0411] The invention also provides kits for use in the preparation
of the bonding composition according to the present invention. Kits
according to the present invention comprise one or more containers,
wherein a first container contains a susceptor composition of the
invention. Additional kits of the invention comprise one or more
containers wherein a first container contains a susceptor as
described above and a second container contains one or more
adhesive compounds and/or carriers, such as water, glycerine,
N-methyl pyrrolidone (NMP), dimethylformamide (DMF),
dimethylacetamide (DMAC), dimethylsulfoxide (DMSO), tetrahydrofuran
(THF), polyvinyl pyrrolidone (PVP), polyvinylpyrrolidone/vinyl
acetate copolymer (PVP/VA), and branched polyesters. The kits of
the invention may be used to produce one or more of the bonding
compositions of the present invention for use in a variety of
applications as described below.
[0412] The invention also provides for kits comprising at least two
containers, wherein one of the containers comprises a susceptor and
another of the containers comprises a polar carrier, wherein when
the susceptor and the carrier are applied to substrates and the
applied susceptor and carrier are interfaced, a composition is
formed that is heatable by RF energy.
[0413] XIII. Experimental Set-Up
[0414] FIG. 40 shows an example experimental set-up utilized to
test the susceptor compositions described above with respect to
example 4. An RF signal is generated by a signal generator 4001.
Signal generator 4001 can be an HP 8165A signal generator
(available from Hewlett Packard Corporation). The RF signal is
coupled to the input side of RF power amplifier 4002 (available
from ENI). The RF power is fed from the output side of RF power
amplifier 4002 to the input side of an impedance matching circuit
4003 that functions to match the output impedance to the combined
load impedance of coil 4004 and test sample 4005. Impedance
matching circuit 4003 can be designed according to known
electronics principles as would be apparent to those of skill in
the art. See, e.g., "The Art of Electronics," by P. Horowitz and W.
Hill, Second Ed., Cambridge University Press (1994), especially
Chapter 40, incorporated by reference herein. The RF power of load
coil 4004 was inductively coupled to test sample 4005. The
frequency of signal generator 4001 was tuned to result in resonance
at load coil 4004. This frequency was detected by a single turn, 2
inch diameter probe loop 4007, which was located just below and in
proximity to load coil 4004. Resonance was indicated by a maximum
resulting voltage drop across probe loop 4007, and was displayed on
an oscilloscope 4006, such as a model number OS7020A oscilloscope
available from Goldstar. Frequency tuning was performed at
sufficiently low RF powers in order to avoid heating of test sample
4005. Once the frequency of signal generator 4001 was tuned to
resonance, the RF power delivered to load coil 4004 was increased
to a desired power level by increasing the output level of signal
generator 4001. The front panel of RF power amplifier 4002
displayed the measured RF power level delivered to test sample
4005.
[0415] FIG. 41 illustrates another experimental heating system
4100.Heating system 4100 includes a signal generator 4102. Signal
generator 4102 can be an HP 8165A signal generator (available from
Hewlett Packard Corporation). Signal generator 4102 is used to
generate a low level radio frequency signal having a frequency
between 10 MHz and 15 MHz. Signal generator has a control panel
4103 that allows a user to manually select the frequency of the
generated radio frequency signal. The output level of the signal is
also controllable from control panel 4103, or from a controller
4114. The output level of the generated RF signal can vary from 0
Volts to 1 Volt peak to peak into 50 ohms, or 0 dBm.
[0416] Controller 4114 is interfaced to signal generator through a
general purpose interface board (GPIB) (not shown). In one
embodiment, controller 4114 is a personal computer (PC) running the
Windows.RTM. operating system. A visual C++ program that provides a
user interface for controlling the output level of signal generator
4102 is configured to run on controller 4114.
[0417] The low level RF signal generated by signal generator 4102
is provided to the input of a broadband RF amplifier 4106 using a
coaxial cable 4104. Preferably, broadband RF amplifier 4106 is the
A 1000 broadband amplifier sold by ENI of Rochester, N.Y., and
coaxial cable 4104 is a standard RG58 coaxial cable. Broadband
Amplifier 4106 amplifies the low level RF signal by 60 dB, thereby
providing a 1 Kilowatt output into a 50 ohm load for a 1 milliwatt
(0 dBm) input. If the low level RF input signal provided to
amplifier 4106 consists of a timed pulse, amplifier 4106 will
amplify the pulse to produce a high level pulse output.
[0418] Connected to the output of broadband amplifier 4106 is a
directional coupler 4110. A suitable directional coupler can be
purchased from Connecticut Microwave Corporation of Cheshire, Conn.
Directional coupler 4110 is connected to the output of amplifier
4106 through an RF cable 4107, such as an RG393 RF cable. The
output of directional coupler 4110 is connected to an impedance
matching circuit 4122 using RG393 RF cable 4112.
[0419] The function of impedance matching circuit 4122 is to match
a 50 ohm input impedance to a variable impedance of probes 602 and
604 and the sample 410. Typical impedances of probes 602 and 604 in
combination with sample 410 range from 200 ohms up to 500 ohms.
[0420] Directional coupler 4110 has a reflected power output port
4111 that is connected to an oscilloscope 4118. Preferably,
oscilloscope 4118 is a TDS210 digital real time oscilloscope
available from Tektronix, Inc. Directional coupler 4110 provides a
signal representing the amount of reflected power to oscilloscope
4118, which then displays the magnitude of the reflected power.
[0421] The process for heating sample 410 using heating system 4100
will now be described. Initially, an operator interacts with a user
interface on controller 4114 to activate signal generator 4102 so
that it produces a 50 millivolt RF signal. The reflected power is
then observed on oscilloscope 4118. The frequency of the 50
millivolt RF signal and matching circuit 4122 are adjusted such
that the reflected power is minimized. Once the frequency and the
matching circuit are adjusted such that the reflected power is
minimized, the signal generator is turned off and sample 410 is
placed close to probes 602 and 604.
[0422] Next, controller 4114 is used to turn on signal generator
4102 so that it once again produces a 50 millivolt RF signal. At
this point, the frequency and matching circuit are adjusted again
until the reflected power is minimized. On achieving the minimum
reflected power, signal generator 4102 is turned off. Next,
operator uses controller to direct signal generator to produce an
RF signal with a voltage ranging from 100 millivolts to 1000
millivolts and with a pulse time of between 20 milliseconds and
1000 milliseconds. This low level RF signal is amplified by
broadband amplifier 4106. The amplified signal is then provided to
impedance matching circuit 4122 and an a RF pulsed electromagnetic
field is produced at probes 602 and 604. The presence of the pulsed
electromagnetic field causes sample 410 to heat.
[0423] FIG. 42 illustrates probes 4202 and 4204, which were the
probes utilized to test the compositions described herein. The
present invention is not limited to this or any particular probe
design. Probe 4202 and probe 4204 are both {fraction (1/8)} inch
square copper tubes. Probe 4202 and probe 4204 both rest on a block
4250 of non-electrically conductive material, preferably, but not
limited to, TEFLON.TM.. More specifically, block 4250 has {fraction
(1/8)} inch square slots milled therein so that probes 4202 and
4204 are recessed into block 4250.
[0424] Probe 4202 has a proximal section 4209, a center section
4210, a transition section 4211, and a distal section 4212.
Similarly probe 4204 has a proximal section 4213, a center section
4214, a transition section 4215, and a distal section 4216. Center
section 4210 is parallel with center section 4212. The center to
center distance between center section 4210 and center section 4212
is on half of an inch.
[0425] Proximal section 4209 diverges away from probe 4204.
Similarly, proximal section 4213 diverges away from probe 4202. The
center to center distance between the proximal end of proximal
section 4209 and the proximal end of proximal section 4213 is about
at least one and three sixteenths of an inch.
[0426] Distal section 4212 is parallel with distal section 4216 and
parallel with center section 4210. The center to center distance
between distal section 4212 and distal section 4216 is about at
least one and three sixteenths of an inch. Transition section 4211
is between center section 4210 and distal section 4212. Similarly,
transition section 4215 is between center section 4214 and distal
section 4216.
[0427] The reason the distance between the proximal end of proximal
section 4209 and the proximal end of proximal section 4213 is about
at least one and three sixteenth of an inch is to prevent arcing at
the ends of probe 4202 and 4204. For that same reason the distance
between distal section 4212 and distal section 4216 is about at
least one and three sixteenth of an inch.
[0428] XIV. Examples
[0429] Without further elaboration, it is believed that one skilled
in the art can, using the preceding description, utilize the
present invention to its fullest extent. The following preferred
specific embodiments are, therefore, to be construed as merely
illustrative and not limitative of the remainder of the disclosure
in any way.
Example 1
[0430] Various susceptor compositions were screened for use at
frequencies from about 4 MHz to 15 MHz, and at power levels from
about 0.5 kW to 1 kW. RF frequencies of less than about 15 MHz are
much less costly to produce and operate than RF frequencies of
greater than 15 MHz. The best results consistently occurred at the
upper ends of the experimental frequency and power ranges (e.g., 15
MHz and 1 kW). See FIG. 6 for a schematic diagram of the
experimental set-up and equipment used for the various tests
described herein. According to the present invention, a preferred
composition comprises a uniform solution of PVP, NMP, and
SnCl.sub.2. A suitable susceptor composition comprises SnCl.sub.2
present in a concentration of from about 1% to about 50%, NMP in a
concentration of from about 25% to about 75%, and PVP in a
concentration of from about 1% to about 35%. These three components
are soluble in one another. These components were mixed together to
form a uniform solution that was able to be heated from about
75.degree. F. to a boiling point of about 280.degree. F. in several
seconds. Acceptable results can also be obtained, for example, by
substituting similar concentrations of PVP/vinyl acetate copolymer
for PVP, and substituting similar concentrations of lithium
perchlorate for SnCl.sub.2. In addition, other suitable
compositions include a mixture comprising ethylene/vinyl acetate
copolymer in a concentration of from about 75% to about 99% and
ethylene/acrylic acid copolymer in a concentration of from about 1%
to about 25%, a mixture comprising LiC.sub.2H.sub.3O.sub.2 in a
concentration of from about 1% to about 25%, ethylene/vinyl acetate
copolymer in a concentration of from about 50% to about 98%, and
styrenated ethylene/acrylic acid copolymer in a concentration of
from about 2% to about 25%, and a mixture comprising PVP/vinyl
acetate copolymer in a concentration of from about 5% to about 35%,
SnCl.sub.2 in a concentration of from about 5% to about 49%, and
NMP in a concentration of from about 1% to about 90%. Other
composition constituent concentrations will be apparent to those of
skill in the art based on the present description.
[0431] In this example, a preferred susceptor composition
comprising SnCl.sub.2 in a concentration of about 33%, NMP in a
concentration of about 50%, and PVP in a concentration of about 17%
was prepared to bond various combinations of thin polyolefin layers
of polypropylene (PP) and polyethylene (PE). This example susceptor
composition resulted in a uniform dispersion of salt ions in a
polymeric adhesive.
[0432] The experiment was conducted by saturating a second carrier,
a thin layer of an insoluble porous carrier (in this example
non-woven PP), with a small amount of the susceptor composition.
The example salt-based susceptor composition provides a continuous
matrix of salt ions in a polar organic medium throughout the
insoluble porous carrier. As shown schematically in FIG. 3, the
insoluble porous carrier 302 was sandwiched in-between two layers
of PP or PE, layers 304 and 306, respectively, and then
transversely heated by the application of RF energy. By RF heating
at about 14-15 MHz for about 1-2 seconds at about 0.8-1 kW of power
output, sufficient bonding occurred between the non-woven PP
carrier and the layers of PP and PE. In this example, the strength
of the bonded region was at least as strong or stronger than the PP
or PE substrates themselves. The polyolefin layers to be bonded
were chosen from combinations of (1) PP non-woven and (2) PE film.
The results of this example are shown below in Table 1.
1 TABLE 1 insoluble porous carrier (saturated with PVP, NMP and
SnCl.sub.2) bonding results PP non-woven/PP non-woven bonding
within 1-2 seconds PE film/PE film bonding within 1-2 seconds PP
non-woven/PE film bonding within 1-2 seconds
[0433] For each combination, the saturated insoluble porous carrier
bonded the outer layers in about 1-2 seconds. There was evidence of
melting in the outer layers, with some minor substrate distortion
and tiny melt holes. By using the saturated PP non-woven carrier, a
uniform matrix of the adhesive and susceptor components resulted in
intimate contact between the adhesive component and both outer
layers.
Example 2
[0434] The susceptor composition utilized in this example comprised
SnCl.sub.2 in a concentration of about 33%, dissolved in a mixture
of NMP in a concentration of about 50% and PVP in a concentration
of about 17%. Various PP and PB substrate surfaces were coated with
the RF susceptor composition, including: (1) PP non-woven and (2)
PE film. The susceptor composition was hand drawn onto each surface
as a wet layer that would eventually dry, leaving a coating which
was dry to the touch. RF heating tests were performed on the coated
substrates. In each case, two like samples were placed together
with the coated surfaces in contact with one another. The contacted
surfaces were placed in a load coil that was designed to clamp the
surfaces firmly together and transversely heat a 0.25 inch.times.8
inch strip of the susceptor composition. The operating frequency
was about 14 MHz, and the power delivered to the coil was about 1
kW. The tests were split into two parts: using a wet susceptor
composition and using a vacuum dried susceptor composition. The
results are shown in Table 2.
[0435] Vacuum drying was employed in this experiment as an extreme
experimental condition for comparison purposes, but is not expected
to represent a commercial embodiment.
2TABLE 2 Coated Substrates in Contact, Under 1.2 kW RF at 14 Mhz
WET/DRY non-woven PP/ PE film/ Substrates non-woven PP PE film WET
successfully evidence of bonded together melting, slight within 1-2
seconds bonding at edges of the coat of susceptor material VACUUM
No evidence of No evidence of DRIED heating after 1 heating after 1
minute. minute.
[0436] The results show that the wet susceptor composition
generates enough heat within 1-2 seconds at 14 MHz and 1 kW to melt
the PP non-woven or PE film in transverse heating of thin hand
drawn films. Bonding is successful between layers of PP non-woven.
As layers of PP non-woven are brought together, the susceptor
composition is displaced into the open space between the fiber of
the PP non-woven layers, allowing the two layers of PP non-woven to
come together and make intimate contact, enabling bonding during
re-flow of the layers.
[0437] Complete bonding was not demonstrated between layers of PE
film. As layers of PE film were brought together, the susceptor
mixture behaved as a hydrostatic middle layer or boundary,
preventing intimate contact between the two outer polyolefin
layers. It was observed that the material in the layers of PE was
more likely to partition away from the susceptor composition than
to cross the susceptor composition layer during melting and
re-flow. It was also observed that as the susceptor composition was
vacuum dried, it lost its ability to be RF heated effectively.
Results were likely due to one or more of the following factors:
the precipitation of ions back into an inactive salt as the solvent
volatilizes to form the dry coat; a decrease in translational
mobility of any ions still supported by the dry coating, thus
preventing RF heating from occurring; and, in the case of PE films,
an insufficient intermolecular contact due to the smoothness of the
films. According to the present invention, this problem can be
solved by introducing an additive, such as a surfactant,
nonvolatile solvent or, plasticizer to the composition, to achieve
better attachment.
Example 3
[0438] In this example, an RF activated susceptor composition was
prepared from an EASTMAN AQ branched polyester (available from the
Eastman Chemical Corporation) and an aqueous solution of
SnCl.sub.2. Various layers of PP non-woven and PE film were tested.
The susceptor composition that was used in this example comprised
SnCl.sub.2 dissolved in distilled water. This solution was blended
with a branched polyester adhesive component, EASTMAN AQ35S.
Suitable concentrations of the branched polyester ranged from about
25% to about 75%.
[0439] In a series of experiments, the susceptor composition was
used to adhere all combinations of: (1) PP non-woven and (2) PE
film substrates. In each experimental combination, the composition
was first coated onto the two substrate surfaces and dried under
ambient conditions similar to those used in commercial practice.
The two substrates were then pressed together in the work coil with
the two susceptor composition coated surfaces in contact with each
other. The coated surfaces were not tacky enough at this point to
result in contact adhesion between the substrates. All combinations
of substrates were successfully adhered to one another by RF
heating for a period of about 1 second at about 14 MHz and about 1
kW. The substrates were adhered to each other by the RF-activated
susceptor composition, instead of being bonded by re-flow of the
substrate. No apparent melting or distortion of the substrate
occurred. This example demonstrates that a susceptor composition
coating can be dry to the touch and still be activated by RF
heating.
Example 3a
[0440] Analogous to Example 3 above, the active ingredients Eastman
AQ35S and SnCl.sub.2 (in constituent concentrations consistent with
the parameters described above) were dissolved in NMP to form a
susceptor composition. The composition was coated on a PP non-woven
web and was allowed to air dry. The slightly tacky web was placed
between polyolefin substrates and the assemblies were RF heated in
the RF work station at 14.65 MHz and about 0.8 kW for 5
seconds.
[0441] Good adhesion was obtained in each case.
Example 3b
[0442] A susceptor composition capable of inductive activation was
prepared with an aqueous dispersion of a sulfopolyester, EASTEK
1300 Polymer (available from Eastman Chemical Company), by addition
of SnCl.sub.2. A precipitate was recovered from this mixture and a
film from this precipitate was obtained by pressing between hot
platens at about 200.degree. F. and 1000 psi for a short time. This
film was slightly wet and was sandwiched between a PE film and a PP
non-woven web. The assembly was RF heated in the RF work station at
14,63 MHz and about 0.8 kW for 1 second. Good adhesion without
substrate deformation was achieved.
Example 3c
[0443] Analogous to Example 3b, additional experiments were
performed in which slightly wet-to-touch thin films of the
susceptor compositions of example 3b were sandwiched between two
stacks consisting of multiple layers of non-woven PP or multiple
layers of non-woven PP laminated to PE film. Three different types
of sandwiched assemblies were tested, including: (1)8 layers of
non-woven PP/susceptor composition/8 layers of non-woven PP, (2) 2
layers of PP non-woven laminated to PE film/susceptor composition/2
layers of PP non-woven laminated to PE film (with PP non-woven
facing PE film at the stack interface), and (3) 4 layers of PP
non-woven/susceptor composition/4 layers of PP non-woven. In each
case, the assemblies were RF heated in the RF work station at 14.63
MHz and about 0.8 kW for 1 second. In all cases, good adhesion
occurred between the multilayer stacks without causing distortion
to the stacks.
[0444] In this experiment, each multilayered stack was
pre-assembled using a conventional contact adhesive, and the two
stacks were later adhered to one another using the susceptor
composition. However, it is contemplated in the practice of the
invention that each multilayer stack can be preassembled using a
susceptor composition to either simultaneously or sequentially bond
or adhere the various layers of each stack.
Example 4
[0445] Based on the success of the susceptor compositions tested in
Examples 1--3b, other susceptor compositions were made and tested.
In this example, sample compositions (in constituent concentrations
consistent with the parameters described above) were tested in
half-filled test tubes nearly centered within the coil of the RF
equipment described in FIG. 40. Various settings for voltage input
and frequency of the current were investigated. Table 3 summarizes
the results of these experiments. The effectiveness of RF heating
is shown by the time required for the samples to boil or to rise to
the indicated temperature.
3TABLE 3 Selected Test Tube Experiments with Potential Susceptors
Frequency, Input, Field, Time to boil or Materials MHz mV V
temperature rise Solid Salts SnCl.sub.2 .times. 2H.sub.2O 13.73 300
7.8 Poor heating SnCl.sub.2 .times. 2H.sub.2O 13.73 600 15 39 sec.,
122.degree. F. SnCl.sub.2 13.74 800 .about.20 Poor heating
LiClO.sub.4 .times. 3H.sub.2O 13.74 800 .about.20 10 sec. Aqueous
Solutions Distilled Water 13.75 800 80 sec., 117.degree. F.
LiClO.sub.4 13.73 800 .about.20 3 sec. SnCl.sub.2 800 .about.20 5
sec. NaCl 13.67 800 .about.2.2 3 sec. NaCl 5.833 320 .about.2.2 20
sec. NaCl 3.719 10 58 30 sec. Li-acetate 13.73 1000 10 sec.
Nonaqueous Solutions NMP 13.74 800 60 sec., 89.degree. F.
NMP/SnCl.sub.2 13.74 800 47 sec., 350.degree. F. NMP/PVP/SnCl.sub.2
13.73 685 20 8 sec., 142.degree. F. NMP/PVP/LiClO.sub.4 .times.
13.73 643 20 6 sec., 135.degree. F. 3H.sub.2O NMP/PVP/Li-acetate
.times. 13.73 600 18 18 sec. 2H.sub.2O Liquid Samples Uni-REZ 2115
13.75 1000 75 sec., 126.degree. F. MICHEM 4983 13.77 10 40 30 sec.,
178.degree. F. MICHEM ACRYLIC 1 13.73 800 4 sec.
[0446] These tests show that, as expected, aqueous solutions of
various susceptors, such as salts, coupled very well with the RF
energy. All tested susceptor compositions came to a boil within
3-30 seconds. As discussed above, SnCl.sub.2 dissolved in NMP also
coupled very effectively. Although a boiling time of 47 seconds is
shown in this experiment, the temperature of 350.degree. F. reached
by this mixture is substantially higher than is required for heat
bonding polyolefins.
[0447] In the section on nonaqueous solutions in Table 3, it can be
seen that while NMP is only a weak susceptor in its own right, it
couples very effectively with the RF energy, when a variety of
salts are dissolved in it. It was also observed that the solution's
ability to solubilize salts seems to be enhanced when PVP is
dissolved in it. Since the compositions shown in Table 3 were not
optimized, the RF heating capability of the solutions appear to be
very good.
[0448] The last section of Table 3 shows the RF heating capability
of some liquid polymers. They range from very mild coupling ability
to very powerful coupling ability in the case of MICHEM ACRYLIC 1
(available from Michelman Corporation), a styrenated
ethylene-acrylic acid polymer.
Example 5
[0449] This experiment tested the compatibility of various film
forming and adhesive polymers with modifying resins and additives
and with inorganic or organic susceptors (in constituent
concentrations consistent with the parameters described above). A
series of experiments were conducted with low-density polyethylene
(LDPE) as the substrate, as summarized in Table 4.
4TABLE 4 Bonding Feasibility Experiments With a Low Density
Polyethylene Substrate Frequency, Input, Sample Mhz mV Time
Adhesion Substrate ELVAX 40W + UNI-REZ 14.55 500 1 min. None LDPE
2641 ELVAX 40W + UNI-REZ The Li-acetate did not mix with the
polymers under 2641 + Li-acetate pressing conditions ELVAX 40W +
N,N- 14.54 500 1 min. None LDPE ethylenebis-stearamide @80/20 ELVAX
40W + N,N- 14.54 650 1 min. Slight LDPE EbSA @80/20 + MICHEM
ACRYLIC 1 MICHEM ACRYLIC 1 14.54 650 30 sec. Slight LDPE PRIMACOR
3460 + The Li-acetate did not mix with the polymers under
Li-acetate pressing conditions N,N-EbSA + ELVAX 14.6 850 30 sec.
Partial LDPE 40W + Poly (ethylene- maleic anhydride) + Li- acetate
+ MICHEM PRIME 4983 ELVAX 40W + Li-acetate + 14.6 850 30 sec.
Partial LDPE MICHEM PRIME 4983 ELVAX 40W + 14.6 850 15 sec.
Partial, LDPE MICHEM PRIME 4983 good UNI-REZ 2641 14.6 850 30 sec.
Partial, LDPE good ELVAX 40W + 14.6 850 30 sec. Partial, LDPE
UNI-REZ 2641 + good MICHEM PRIME 4983 Polyethylene (AS) + 14.6 850
15 sec. Partial, LDPE AlliedSignal GRADE A-C + good MICHEM PRIME
4983 Polyethylene (AS) + 14.6 850 30 sec. Partial, LDPE MICHEM
PRIME 4990 good ELVAX 40W + Fe.sub.2O.sub.3 14.6 850 30 sec. None
LDPE ELVAX 40W + 14.6 850 15 sec. Good LDPE MICHEM PRIME 4990 ELVAX
410 + N,N-EbSA + 14.6 850 30 sec. None LDPE PEMA ELVAX 410 +
N,N-EbSA + 14.6 850 30 sec. None LDPE PEMA + KEN-REACT LICA 44
ELVAX 410 + N,N-EbSA + 14.6 850 10 sec. Partial, LDPE PEMA + MICHEM
good ACRYLIC 1 ELVAX 40W + Li- 14.6 850 15 sec. Good LDPE
acetate/MICHEM ACRYLIC 1 (paste) ELVAX 40W + 14.6 850 15 sec. Good
LDPE MICHEM ACRYLIC 1 ELVALOY EP 4043 14.6 850 30 sec. None LDPE
MICHEM ACRYLIC 1 ELVAX 40 W + UNI-REZ 14.6 850 30 sec. None LDPE
2641 + STEROTEX HM wax + MICHEM ACRYLIC 1 SnCl.sub.2 + NMP + PVP
14.54 850 10 sec. None Mylar/dry K29-30 + 0.1% 14.54 850 30 sec.
None Mylar/dry SURFYNOL 104PA
[0450] Several susceptors which had been very effective in test
tube runs did not always lead to good bonding or adhesion in these
trials. MICHEM ACRYLIC 1 is a good example. Likely reasons include:
(a) the susceptors were only effective wet and lost their coupling
ability when used in a dry film, or (b) the susceptor itself was
not a good adhesive and formed a barrier to melted PE bonding to
itself. There was an indication that the second reason prevailed
when it was shown that the susceptors performed better when blended
with PE or EVA which could act as hot melt adhesives for the
substrates. Better results were obtained with MICHEM PRIME 4983 and
4990, MICHEM ACRYLIC 1, and UNI-REZ 2641 in combination with either
PE or EVA. However, N,N-ethylene-bisstearamide, which was described
in the Degrand reference, was not very effective in these
experiments. A number of trials provided partial adhesion, as noted
in Table 4, which were likely caused by the inability of the film
holder to clamp the substrates tightly and flat. Although the
shortest successful heating times were on the order of 10 to 15
seconds, which would be too long for a commercial operation, the
results are positive, in that both the adhesive compositions and
the operation of the film station can be further optimized without
undue experimentation.
Example 6
[0451] Another series of experiments were performed with other
polyolefin substrates, including a PP non-woven. These trials are
summarized below in Table 5. Very good bonds were obtained with
several compositions at dwell times down to about 1 second. While
this may be too long for some commercial applications, it is highly
encouraging for trials that were not optimized with regard to
either the susceptor composition or the test equipment.
5TABLE 5 Bonding Experiments With Polyolefin Substrates Frequency,
Input, Sample Mhz mV Time Adhesion Substrate ELVAX 40W 14.61 850 30
sec. None PP nonwoven (Du Pont 40% vinyl acetate to polyethylene)
ELVAX 40W + 14.61 850 15 sec. Good PP nonwoven MICHEM PRIME 4990
ELVAX 40W + UNI- 14.61 850 30 sec. None PP nonwoven REZ 2641 +
STEROTEX HM wax + MICHEM ACRYLIC 1 ELVAX 40W + UNI- 14.61 850 15
sec. Good PP nonwoven REZ 2641 + MICHEM ACRYLIC 1 SnCl.sub.2 + NMP
+ PVP 14.61 850 1 sec. Good PP nonwoven K29-30 + 0.1% SURFYNOL104PA
(Dried 90 min) 14.61 850 5 sec. Good PP nonwoven (Dried 15 hrs)
14.61 850 25 sec. None PP nonwoven (Dried 15 hrs + NMP) 14.61 850 2
sec. Good PP nonwoven SnCl.sub.2 + NMP + PVP 14.61 850 1 sec. None
PE/PE K29-30 + 0.1% SURFYNOL 104PA SnCl.sub.2 + NMP + PVP 14.61 850
1 sec. Slight PP/PP n/w K29-30 + 0.1% 14.61 850 2 sec. Good PP/PP
n/w SURFYNOL 104PA ELVAX 40W + 14.61 850 30 sec. None PP nonwoven
UNI-REZ 2641 + Indium tin oxide SURFADONE LP-300 + 14.61 850 30
sec. None PP nonwoven SnCl.sub.2 PVP/VA S-630 + SnCl.sub.2 + 14.61
850 1 sec. Good PP nonwoven NMP 14.61 850 1 sec. Slight PE/PE
PVP/VA S-630 + SnCl.sub.2 + 14.61 850 1 sec. Good PP nonwoven NMP +
Fumed silica 14.61 850 5 sec. Slight PE/PE 14.61 850 2 sec. Slight
PP/PP n/w ELVAX 40W + 14.61 850 30 sec. None PP nonwoven UNI-REZ
2641 + Li-acetate, pressed Li-acetate .times. 2H.sub.2O 14.61 850
30 sec. None No melting Mg(NO.sub.3).sub.2 .times. 6H.sub.2O 14.61
850 30 sec. None No melting MgAc .times. 4H.sub.2O 14.61 850 30
sec. None No melting Stearic acid + 14.61 850 2 sec. None PP
nonwoven Cetyl alcohol + 14.61 850 10 sec. Good PP nonwoven
Mg(NO.sub.3).sub.2 .times. 6H.sub.2O EVA AC-400 + 14.61 850 2, 5
and None PP nonwoven SURFADONE LP-300 + 10 sec. SnCl.sub.2
[0452] Some of the better results were obtained with compositions
containing PVP or PVP/VA and SnCl.sub.2 salt dissolved in NMP (in
constituent concentrations consistent with those discussed above).
It was shown, however, that thorough drying of the susceptor
composition eliminated its ability to couple with the RF field. It
appears that the mobility, provided by the presence of at least a
small amount of NMP solvent, is important for efficient coupling to
the applied RF field. This mobility function can be provided by the
selection of an appropriate nonvolatile plasticizer, such as
epoxidized oils, polyhydric alcohols, substituted amides,
sulfonamides, aryl and alkyl aryl phosphates, polyesters and a wide
variety of esters, including benzoates, phthalates, adipates,
azelates, citrates, 2-ethylbutyrates and hexoates, glycerides,
glycollates, myristates, palmitates, succinates, stearates, etc.
Plasticizers are used to solvate a material, and thus improve its
molecular mobility if it has become too rigid.
[0453] In general, ethylene co-polymers with functionality
providing (a) enhanced compatibility and (b) ionic or highly polar
constituents are effective in bonding or adhering substrates,
together with salts that are either soluble or readily dispersed in
the polymer matrix. There is also evidence that in some
compositions mobility of the dipoles must be assured. This was
achieved in the presence of such high-boiling solvents as NMP. It
can also be extrapolated that other high boiling solvents or
non-volatile plasticizers can achieve the same effects with more
reproducible results.
[0454] These example susceptor compositions utilize a combination
of polar components and hydrated salts in a polymer matrix
plasticized with high boiling and high dielectric constant
additives that are activatable at a relatively low frequency of
about 15 MHz.
[0455] The methods and experiments set forth above will allow those
of skill in the art to determine without undue experimentation that
a particular mixture would be suitable for bonding or adhering
substrates according to the present invention.
Example 7
[0456] This example demonstrates RF-heatable thermoplastic
compositions derived from the combination of various ion-containing
polymers with glycerin. These compositions are shown to be
significantly more susceptible to RF heating than either the
component ion-containing polymers or glycerin are by
themselves.
Example 7a
[0457] Several compositions comprising 70 wt % sulfonated
polyesters in 30 wt % glycerin were prepared. Each sample was
prepared by first mixing 14 grams of sulfopolyester material with 6
grams of glycerin in a 60 milliliter glass jar. The open topped jar
was heated in a convection oven at 165 C for 1 hour. After thirty
minutes, the composition was removed from the oven and hand stirred
for I minute and then immediately returned to the oven. After an
additional 30 minutes of heating at 165 C, the composition was
removed from the oven and hand stirred for 1 minute. While the
composition was still molten, it was hand-drawn into a 1 inch wide
by 3 inch long by 0.006 inch thick coating on the surface of a
0.004 inch thick sheet of transparency film (PP2500 series 3M
transparency film) that was supported on a 180.degree. F. 10
inch.times.10 inch Corning model PC620 hot plate. Immediately after
the composition was coated to the film, the coated film was removed
from the hot plate and allowed to cool to room temperature. The
samples were then evaluated for film properties and RF heating.
[0458] The RF equipment setup used for testing this example and
examples 8-16 consisted of the RF probes described in FIG. 42 and
the RF equipment described in FIG. 41. Unless otherwise noted, in
each case a 1-inch.times.3-inch sample (410) was placed over the RF
probes as shown in FIG. 41. The distance from the surface of the
probes to the sample was about 0.016 inches. The sample was heated
at about 1 KW input power into the tuned heat station 4122 (or
impedance matching circuit 4122) at about 13.5 MHz for the time
required to cause observable heating and melting in the activation
region of the RF probes.
6TABLE 6 Film Time to Melt Experiment # Composition Description
Properties (s) BRANCHED SULFONATED POLYESTERS . . . (Eastman A
Polyesters, Available from Eastman Chemical Company, Kingsport, TN,
USA) 1 70 wt % AQ1045 Clear, tacky, 0.25 30 wt % glycerin flexible.
2 70 wt % AQ1350 Clear, tacky, 0.25 30 wt % glycerin flexible. 3 70
wt % AQ1950 Clear, tacky, 0.25 30 wt % glycerin flexible. 4 70 wt %
AQ14000 Clear, tack, 0.25 30 wt % glycerin flexible. LINEAR
SULFONATED POLYESTERS . . . (Eastman A Polyesters, Available from
Eastman Chemical Company, Kingsport, TN, USA) 5 70 wt % AQ35S
White, tack- 0.5 30 wt % glycerin free, flexible. 6 70 wt % AQ38S
White, tack- 0.5 30 wt % glycerin free, flexible. 7 70 wt % AQ55S
Clear, tack- 0.2 30 wt % glycerin free, flexible.
Example 7b
[0459] Several compositions comprising 70 wt % ethylene acrylic
acid copolymers in 30 wt % glycerin were prepared. Each sample was
prepared by first mixing 52 grams of ethylene acrylic acid
copolymer material (a 25 wt % solids emulsion) with 5.57 grams of
glycerin in a 60 milliliter glass jar. The combined materials were
then mixed for 10 minutes to result in an emulsion. The resulting
emulsion was then cast onto a sheet of 0.004 inch thick
transparency film (PP2500 series 3M transparency film) at room
temperature. The cast emulsion was then allowed to dry-down under a
heat lamp to form a film. The samples were then evaluated for film
properties and RF heating.
7TABLE 7 Time to Experi- Melt ment # Composition Description Film
Properties (s) ETHYLENE ACRYLIC ACID COPOLYMERS (Acid Form) . . .
(MICHEM 4983P, Available from Michelman Incorporated, Cincinnati,
OH, USA) 1 100 wt % MICHEM 4983P Clear, colorless, 28 brittle,
tack-free. 2 70 wt % MICHEM 4983P Clear, colorless, less 0.5 30 wt
% glycerin brittle, tack-free. 3 50 wt % MICHEM 4983P Clear,
colorless, 0.4 50 wt % glycerin flexible, tack-free. ETHYLENE
ACRYLIC ACID COPOLYMERS (Sodium Salt Form) . . . (MICHEM 48525P,
Available from Michelman Incorporated, Cincinnati, OH, USA) 4 100
wt % MICHEM Clear, colorless, No Heating 48525P brittle, tack-free.
in 1 minute. 5 70 wt % MICHEM 48525P Clear, colorless, 0.5 30 wt %
glycerin flexible, tack-free, rubbery. 6 50 wt % MICHEM 48525P
Clear, colorless, 0.2-0.4 50 wt % glycerin flexible, tack-free,
rubbery.
Example 7c
[0460] Several compositions comprising 70 wt % vinyl acetate
acrylic copolymers in 30 wt % glycerin were prepared. Each sample
was prepared by first mixing 46.67 grams of vinyl acetate acrylic
copolymer material (a. 55 wt % solids emulsion) with 3 grams of
glycerin in a 60 milliliter glass jar. The combined materials were
then mixed for 10 minutes to result in an emulsion. The resulting
emulsion was then cast onto a sheet of 0.004 inch thick
transparency film (PP2500 series 3M transparency film) at room
temperature. The cast emulsion was then allowed to dry-down under a
heat lamp to form a film. The samples were then evaluated for film
properties and RF heating.
8TABLE 8 VINYL ACETATE ACRYLIC COPOLYMERS . . . (ROVACE HP3442,
Available from Rohm and Haas, Philadelphia, PA, USA) Composition
Time to Melt Experiment # Description Film properties (s) 1 100 wt
% HP3442 Clear, colorless, No Melting flexible, tack-free. in 1
minute 2 90 wt % HP3442 Clear, colorless, 0.3 10 wt % glycerin
flexible, very tacky, with good cohesion.
Example 7d
[0461] This example demonstrates how the addition of glycerin as
well as adjustments in pH to gelatin solutions can affect the
properties of derived gels.
[0462] Several compositions were prepared as solutions of a
commercially available gelatin (Eastman 45Y56-853-3V0-6CS available
from Eastman Gelatine Corporation). All compositions had water.
Some solutions had glycerin added to them. Some solutions had their
pH adjusted by the addition of ION NaOH or 6N HCl. The compositions
were prepared as follows:
[0463] Composition #1 was prepared by adding 70 grams of gelatin to
280 grams of water and stirring and heating the resulting mixture
at about 65.degree. C. for 1 hour to obtain a solution. The
solution had a pH of 6.18 at 65.degree. C.
[0464] Composition #2 was prepared by stirring 6 grams of glycerin
into 70 grams of composition #1. The solution had a pH of 5.8 at
65.degree. C.
[0465] Composition #3 was prepared by stirring drops of ION NaOH
(about 25 drops) into 125 mls of composition #1, until the
resulting solution had a pH of 10.1 at 65.degree. C.
[0466] Composition #4 was prepared by stirring 8.51 grams of
glycerin into 99.3 grams of composition #3 to result in a solution
with a pH of 10.1 at 65.degree. C.
[0467] Composition #5 was prepared by stirring drops of 6N
hydrochloric acid (about 90 drops) into 125 grams of composition
#1, until the resulting solution had a pH of 1.9 at 65.degree.
C.
[0468] Composition #6 was prepared by stirring 5.361 grams of
glycerin into 62.57.grams of composition #5 to result in a solution
with a pH of 1.9 at 65.degree. C.
[0469] Each gelatin solution was cast onto a sheet of transparency
film (3M PP2500 Transparency Film) and allowed to set-up at room
temperature to form a gel film. The gels differed in their film
properties and in their RF-heating properties as described in Table
9.
[0470] Gelatin films (susceptors) may not act as a good adhesive on
low energy surfaces, such as PE, PP, etc. However, the are expected
to perform effectively as adhesives on polar substrates, such as
paper, Kraft paper, linear boards, wood, etc.
9TABLE 9 GELATINS . . . (Eastman 45Y56-853-3V0-6CS gelatin,
Available from Eastman Gelatin, USA) Composition Time to Melt
Experiment # Description Film properties (s) 1 gelatin Brittle w/
No Heating pH 5.8 at 65.degree. C. poor adhesion to in substrate. 1
minute. 2 70 wt % gelatin Flexible w/ 10 30 wt % glycerin good
adhesion to pH 5.8 at 65.degree. C. substrate. 3 gelatin Brittle w/
No Heating pH 10.1 at 65.degree. C. poor adhesion to in substrate.
1 minute. 4 70 wt % gelatin flexible w/ 4 30 wt % glycerin good
adhesion to pH 10.1 at 65.degree. C. substrate. 5 gelatin Brittle
with poor 17 pH 1.9 at 65.degree. C. adhesion to substrate. 6 70 wt
% gelatin Flexible w/good <1 30 wt % glycerin attachment to pH
1.9 at 65.degree. C. substrate.
Example 8
[0471] Several compositions were prepared by mixing various polar
materials with a representative ionomer (Eastman AQ35S
Sulfopolyester). In each case, the compositions are demonstrated to
be more susceptible to RF heating than the component ionomer or
polar material by themselves.
[0472] Each composition is comprised of 70 wt % AQ35S in 30 wt %
polar material. Each sample was prepared by first mixing 46.67
grams of AQ35D (a 30 wt % solids emulsion) with 6 grams of polar
carrier in a 60 milliliter glass jar. The combined materials were
then mixed for 10 minutes to result in an emulsion. The resulting
emulsion was then cast onto a-sheet of 0.004 inch thick
transparency film (PP2500 series 3M transparency film) at room
temperature. The cast emulsion was then allowed to dry-down under a
heat lamp to form a film. The samples were then evaluated for film
properties and RF heating.
10TABLE 10 VARIOUS POLAR MATERIALS USED IN COMPOSITIONS COMPRISING:
70 wt % EASTMAN AQ35S/30 wt % POLAR MATERIAL. Experi- Time to ment
Film Melt # Composition Description properties (s) 1 70 wt %
EASTMAN AQ35S Clear, tack- 1 30 wt % Ethylene Glycol free,
flexible. (The DOW Chemical Company, Midland, MI, USA) 2 70 wt %
EASTMAN AQ35S White, slightly 0.150 30 wt % 1,2-propylene glycol
tacky, flexible. (The DOW Chemical Company, Midland, MI, USA) 3 70
wt % EASTMAN AQ35S Clear, yellow, 0.4 30 wt % polyethylene glycol
200 tacky, flexible. (Union Carbide Chemicals and Plastics Company
Inc., Danbury, CT, USA) 4 70 wt % EASTMAN AQ35S Cloudy, 12 30 wt %
polyethylene glycol 8000 orange, tack- (Union Carbide Chemicals and
free, w/ some Plastics Company Inc., undissolved Danbury, CT, USA)
polyethylene glycol, flexible. 5 70 wt % EASTMAN AQ35S White, tack-
1.5 30 wt % hexylene glycol free, flexible. (Shell Chemical
Company, Houston, TX, USA) 6 70 wt % EASTMAN AQ35S Clear, slightly
.25 30 wt % diethylene glycol tacky, flexible. (The DOW Chemical
Company, Midland, MI, USA) 7 70 wt % EASTMAN AQ35S Clear, tack-
<0.5 30 wt % glycerin free, flexible. (The Procter and Gamble
Company, Cincinnati, USA) 8 70 wt % EASTMAN AQ35S Slightly 2 30 wt
% sorbitol cloudy, (Sigma, St. Louis, MO, USA) slightly tacky,
flexible. 9 70 wt % EASTMAN AQ35S Clear, yellow, 10 30 wt %
NPC-ST-30, Colloidal silica slightly tacky, in ethylene glycol
monopropyl flexible. ether. (Nissan Chemical Company, Japan; New
York Office, Tarrytown, NY, USA) 10 70 wt % EASTMAN AQ35S Slightly
0.2 30 wt % EG-ST, Colloidal silica in cloudy, ethylene glycol.
slightly tacky, (Nissan Chemical Company, flexible. Japan; New York
Office, Tarrytown, NY, USA) 11 100 wt % EASTMAN AQ35S Clear, tack-
NO NO ADDED POLAR MATERIALS free, flexible. HEAT (CONTROL) in 1
minute. 12 70 wt % EASTMAN AQ35S Clear, tack- 2.8 30 wt %
N-methylpyrrolidone free, flexible. (Aldrich Chemical Co., Inc.
Milwauke, WI) 13 70 wt % EASTMAN AQ35S Clear, tack- 0.3 30 wt %
dimethyl formamide free, flexible. (Aldrich Chemical Co., Inc.
Milwauke, WI) 14 70 wt % EASTMAN AQ35S Clear, slightly 0.2 30 wt %
formamide tacky, flexible. (Aldrich Chemical Co., Inc. Milwauke,
WI) 15 70 wt % EASTMAN AQ35S Clear, slightly 0.15 30 wt % dimethyl
sulfoxide tacky, flexible. (Aldrich Chemical Co., Inc. Milwauke,
WI)
Example 9
[0473] Thermoset polymers are a class of polymeric systems formed
by chemical (usually covalent bonding) reaction of lower molecular
weight functional building blocks. For instance, epoxy thermoset
polymers are formed by the reaction of oxirane groups of epoxy
compounds with other functional groups such as hydroxyl, carboxyl,
amine etc. In the case of urethanes, isocyanate groups are reacted
with functional groups such as amines, hydroxyls etc. Chemical
reactions of the functional groups of the building blocks typically
need energy source such as heat, radiation and presence of
catalyst. The reaction product resulting from such an interaction
leads to crosslinking between the functional groups of the building
blocks which in turn gives a cured polymeric system with many
desirable properties such as improved heat, chemical and solvent
resistance, enhanced strength and mechanical properties etc. A key
feature of thermoset systems is the fact that once the crosslinks
are formed in the cured state it is very difficult to reverse
it.
[0474] A convenient way to study the crosslinking reaction in a
thermoset system is to follow the gelling reaction. At the start of
the crosslinking reaction, viscosity of the initial reaction
mixture is low. In the presence of appropriate catalyst and energy
source, chemical crosslinking starts to take place with increase in
molecular weight and viscosity. After a critical stage of the
crosslinking reaction has taken place, the system sets up to an
insoluble (in a solvent such as MEK in which the starting compounds
are soluble) gel. Physico-chemically, chemical bonds are being
formed leading to a network structure of the cured system. It has
been shown that many of the properties of a thermoset system (such
as glass transition temperature, solvent and chemical resistance,
mechanical properties etc) can be readily correlated to the gel
content of the system.
[0475] The degree of cross linking of various thermoset systems was
assessed by measuring the gel content of formulation after exposure
to RF field to different time and energy levels. Increase in gel
content of a given composition after RF exposure (compared to the
gel content of the same composition after air drying for several
hours) is taken as a measure of cure of the thermoset system.
[0476] Typical gel measurements were carried out as follows.
[0477] A sample of the formulation is applied to a glass slide. The
sample is air dried for a 1-2 hours so the applied layer is dry to
touch. Sample weight is noted as "A" after taking into account the
tare weight of glass slide. Then it is exposed to RF source (in the
case of control experiments, the sample is put in a conventional
laboratory oven at a set temperature and time). The cured sample is
cooled down to ambient temperature. The glass slide containing the
cured sample is dipped in 40 ml of MEK for 10 minutes. The slide is
taken out and air-dried prior to weighing. Sample weight is noted
as B.
% Gel content is calculated as (B/A).times.100
[0478] It is worth noting that gel content as measured by the above
procedure gives only the initial cure state of the thermoset
system. Typically, crosslinking reaction progress further upon
aging leading to a higher cured state of thermoset system.
[0479] In the following experiments, the following materials were
used:
[0480] EPON 828: Diglycidylether of bisphenol-A from Shell
Chemicals.
[0481] ANCAMINE 2441 catalyst, a modified polyamine from Air
Products & Chemicals Inc. nEpiRez dispersion, a bisphenol A
based epoxy dispersion from Shell Chemicals.
[0482] Epicure 8536-MY60, an amine curing agent from Shell
Chemicals.
[0483] MAINCOTE HYDUR, a self-reactive acrylic emulsion from Rohm
& Haas.
[0484] Aropol 7241, an isophthalic polyester (unpromoted) from
Ashland Chemical.
[0485] KELSOL 5293, a water dispersible polyester from
Reichhold.
[0486] CYMEL 385, butylated urea formaldehyde resin from Cytec
Industries.
[0487] DESMODUR-W, an aliphatic diisocyanate {CAS #5142-30-1,
(4-isocyanatocyclohexyl) methane}from Bayer
[0488] FORMREZ 11-36, a polyester diol from Witco
[0489] T-12 catalyst, dibutyltindilaurate from Air Products &
Chemicals inc.
[0490] Eastman A 35 D. sulfonated branched polyester from Eastman
Chemicals.
[0491] A. Epoxy Resins:
[0492] Epoxy resins are typically cured to a thermoset state by
application of heat in the presence of catalysts such as amines,
acids, anhydrides etc. By proper selection of epoxy resin, catalyst
(amine, acid etc.) and optionally a polar carrier such as water,
glycerin and similar high dielectric constant liquids, it is
possible to formulate RF cured thermoset epoxy systems of potential
interest in diverse applications, such as: adhesives and coatings
for conventional and spray applications on plastics, metals, wood,
etc; corrosion resistant coatings; industrial and protective
coatings; top coats; automotive coatings; lamination of composites;
laminating adhesives; bonding of structural composites; inks and
decorative coatings; barrier coatings; etc.
[0493] The effect of time and temperature on some thermally cured
epoxy resin systems using typical cure conditions is shown in this
example. The composition included:
11 EPON 828 resin 3 parts ANCAMINE 2441 catalyst 0.3 parts
[0494] The above composition was air dried without any heat and the
gel content measured. It was found to be zero showing that the
resin is not cross-linked to a cured system.
[0495] The above composition was heated to 130 deg C for 5 minutes
and the gel content of the sample was found to be 11%. This shows
that there is some crosslinking occurring under this condition.
[0496] The above composition was heated to 130 deg C for 15 minutes
and the gel content was found to be 48%. As expected, longer
exposure to higher temperature increases crosslink density and gel
content.
[0497] The above composition was heated to 120 deg C for 20 minutes
and the gel content was found to be 42.5%. This shows that longer
exposure time at a lower temperature compared to previous
experiment did not increase gel content. From this observation, one
can conclude that temperature has a more significant influence on
crosslink density and gel content of the system.
[0498] The above composition was exposed to 120 deg C for 30
minutes and the gel content was found to be 73.5%.
[0499] The main conclusion from the above experiments is that a
fairly long time (order 30 minutes) is needed to reach a high gel
content thermoset epoxy resin system, cured by conventional thermal
energy.
[0500] In the next series of experiments, similar epoxy
compositions were evaluated when exposed to RF (14.7 MHz) for
various lengths of time and energy. The composition included:
12 EPON 828 2.1 Parts ANCAMINE 2441 0.5 parts
[0501] The above composition was air-dried and the gel content of
the dried sample was found to be 10.7%. This shows that there is a
very small level of gel in the air-dried (1 hour) sample.
[0502] 10% Glycerin was added to the above composition and the
sample air-dried for 1 hour and its gel content was found to be
4.3%. This data shows that glycerin tends to solubilize the gel
under air dry condition.
[0503] The above composition (without glycerin) was applied onto a
glass slide and was exposed to 500 mv for 2.5 minutes and its gel
content was found to be 8.5%. This shows that there is not much
activation under this level of RF energy.
[0504] The 10% glycerin composition was applied to a glass slide
and the sample was exposed to 500 mV for 2.5 minutes. Gel content
of the sample was found to be 77.3%. This result shows that
addition of glycerin enhances the RF susceptibility of the resin
and high level of crosslinking is achieved.
[0505] These experiments clearly show that epoxy resins can be
activated in a very short period of time (compared to thermal
curing conditions), especially in the presence of a polar carrier
such as glycerin.
[0506] In the next series of experiments, another type of epoxy and
curing agent was tested. The composition included:
13 EPI-REZ 3520-WY-55 2 parts Epicure 8536-MY60 1 parts
[0507] The above composition was applied to a glass slide and
activated under 100 mV for 5 minutes. No heat was noted and the gel
content was found to be 19.3%
[0508] The same composition was activated under 500 mV for 5
minutes. Gel content was found to be 52.5%. This shows that higher
power compared to first experiment is needed for crosslinking to
take pace.
[0509] 10% Glycerin was added to the above composition and the
sample, after drying on a glass slide, was activated for 5 minutes
under 500 mV. The gel content was found to be 52.4%, which is very
similar to what was obtained without any glycerin. This result
shows that the presence of glycerin or other carrier is not
necessary for RF activation in all cases, especially if the resin
system is water based such as the Epi Rez resin.
[0510] B. Acrylic System:
[0511] In this series of experiments, the use of RF activation for
an acrylic class of resin is demonstrated.
[0512] MAINCOTE HYDUR 30, a water based acrylic emulsion with
carboxyl and unsaturation functionalties from Rohm and Haas was
tested. The sample was air-dried and its gel content was found to
be 37%. This result shows that the unsaturation in the acrylic
resin results in some crosslinking due to air oxidation, as seen in
drying oils and alkyd resins.
[0513] 10% glycerin was added to MAINCOTE HYDUR 30 and the gel
content of the air dried sample was found to be 4.6%. This result
shows that glycerin acts as good solvent for the air-dried
sample.
[0514] MAINCOTE HYDUR 30 was applied to a glass slide and the
sample exposed to 500 mV for 2.5 minutes. The gel content was found
to be 61.5%. This clearly shows that RF field activates the acrylic
resin leading to high levels of crosslinking.
[0515] 10% Glycerin/MAINCOTE HYDUR 30 was exposed to 500 mV for 2.5
minutes. The gel content was found to be 92.3%. This result shows
that presence of glycerin promotes RF coupling with the resin.
[0516] MAINCOTE HYDUR 30 was exposed to 700 mV for 2.5 minutes and
the gel content was found to be 81.8%. This shows that increased RF
power promotes crosslinking of acrylic resin.
[0517] 10% Glycerin/MAINCOTE HYDUR 30 was exposed to 700 mV for 2.5
minutes and the gel content of the sample was found to be 100%.
This result shows the beneficial role of glycerin in promoting RF
activation of acrylic resin.
[0518] The next experiment is a comparative example showing thermal
curing of acrylic resin. MAINCOTE HYDUR was heated to 100 deg C for
5 minutes and the gel content was found to be 93%. Note that gel
content of RF activated sample is higher even though it was exposed
only for half the duration to energy.
[0519] This series of examples show that functionalized acrylic
polymers can be activated under RF energy.
[0520] C. Polyester Resin
[0521] In this series of experiments, the RF response of
polyester/vinyl ester resins was studied.
[0522] Aropol 7241, an isophthalic polyester resin from Ashland
Chemical, was applied to a glass slide and the dried sample was
exposed to RF field at 500 mV and 5 minutes. The gel content was
found to be 51.3%.
[0523] This result shows that RF energy can activate an isophthalic
polyester resin.
[0524] KELSOL 5293, a polyester dispersion from Reichhold
Chemicals, was tested in this example. The composition
included:
14 KELSOL 5293 2 parts CYMEL 385 crosslinker 0.6 parts
[0525] The composition was exposed to RF for 2.5 minutes at 500 mV.
The gel content was found to be 8.5%.
[0526] 10% glycerin was added to the composition and exposed to RF
for 2.5 minutes at 500 mV. The gel content was found to be 21.9%.
This shows that addition of glycerin promotes RF activation.
[0527] The above composition (without glycerin) was exposed to 700
mV for 2.5 minutes and the gel content was found to be 73.7%. This
result shows that exposure to higher RF field leads to higher gel
content.
[0528] The composition comprising 10% glycerin was exposed to 700
mV for 2.5 minutes and the gel content was found to be 59.5%.
[0529] These experiments show that RF energy can be used to
activate polyester type resins.
[0530] D. Urethanes
[0531] A linear polyurethane composition based on DESMODUR-W (an
aliphatic diisocyanate from Bayer) and FORMREZ 11-36 (a polyester
diol from Witco) was evaluated. The composition included:
15 DESMODUR W 0.75 parts Formerez 11-36 3.2 parts T-12 catalyst
from Air Products & Chemicals 1-2 drops
[0532] A glass slide containing the above composition was exposed
to 700 mV RF field for 5 minutes and the gel content was measured
to be 11.4%. (Note: At 500 mV, the gel content was zero for 2.5 and
5 minute exposures without glycerin and 1.3% and 8.3% for 2.5 and 5
minute exposures with 10% glycerin).
[0533] 10% Glycerin was added to the above composition and the RF
activation repeated under the same conditions (700 mV and 5
minutes). The gel content was found to be 27%. This level of gel
content is quite good for a linear polyurethane.
[0534] This result shows that addition of glycerin promotes
urethane reaction and gel formation. It is very likely that
hydroxyl groups present in the glycerin molecule is acting as
reactive polyol in the formation of urethane. It may be possible to
increase the gel content by increasing the ratio of isocyanate in
the formulation relative to polyol. It may also be possible to
increase the gel content of the composition by partially replacing
the diisocyanate (DESMODUR W) and polyester diol (Formerez 11-36)
with multifunctional isocyanate such as polymeric MDI (methylene
bisdiphenyldisocyanate) and triols. Use of multifunctional
isocyanate and polyol should significantly increase gel content
close to 100%. Use of isocyanate terminated prepolymer of higher
molecular weight (8,000-10,000) in the urethane reaction may also
increase gel content of the system.
Example 10
Effect of "Susceptor" Addition on RF Activation of Acrylic and
Polyesters
[0535] The effect of adding 4-styrene sulfonic acid, Na salt, vinyl
sulfonic acid, Na salt and A 35 D sulfonated polyester from Eastman
Chemicals on RF activation of acrylic and polyester resins was
evaluated. A first composition included:
16 MAINCOTE HYDUR- 95 parts 4-styrene sulfonic acid, Na salt 5
parts
[0536] The above composition was evaluated as described in previous
examples at 700 mV and 2.5 minutes. The gel content was found to be
45.5%. Gel content of the sample without 4-styrene sulfonic acid,
Na salt, under the same conditions was found to be 81.8% (see
above).
[0537] 10% Glycerin was added to the above composition and the
sample evaluated under 700 mV and 2.5 minutes exposure conditions.
The gel content was found to be 66.7%. Gel content of the sample
without susceptor was 100% (see above).
[0538] This result shows that styrene sulfonate, Na salt does not
promote the RF activation of acrylic resin, with and without
glycerin.
[0539] A second composition included:
17 KELSOL 5243 polyester 2 parts CYMEL 0.6 parts Vinyl sulfonic
acid, Na salt At 25% in water 0.5 parts
[0540] The above composition was evaluated as before at 700 mV and
2.5 minutes. The gel content was found to be 67.2%. Similar
composition without susceptor had a gel content of 73.7% (see
above). This result shows that addition of vinyl sulfonic, Na salt,
does not promote RF activation of polyester resin.
[0541] 10% Glycerin was added to the above composition. The
resultant composition was evaluated as before under 700 mV and 1
second RF field. The sample became too hot and burst into flames.
The result shows that glycerin does activate under high field and
it is possible to get high degree of crosslinking reaction under
very short times, say less than 1 second.
[0542] A third composition included:
18 MAINCOTE HYDUR acrylic 1 part Eastman AD 35 D polyester
susceptor 1 part
[0543] The above composition was evaluated as before and the gel
content was found to be 79.2% at 700 mV and 2.6 minutes. The same
composition without the susceptor had a gel content of 81.8% at 700
mV and 2.5 minutes exposure (see above). In this case addition of a
susceptor does not have any effect on RF activation of acrylic
polymer.
[0544] 10% Glycerin was added to the third composition which was
exposed to 700 mV for 2 minutes. This exposure led to a very
violent reaction. This shows that susceptor was too active.
[0545] The third composition was exposed to 500 mV for 5 minutes.
Gel content was found to be 68.4%. A comparable sample without the
addition of susceptor was found to give a gel content of 61.5%
after 2.5 minutes exposure (see above). The result shows that the
susceptor had very little effect.
[0546] The third composition comprising 10% glycerin was evaluated
at 500 mV and 5 minutes. The gel content was found to be 69.7%. The
same sample with out susceptor had a gel content of 92.3% at 500 mV
and 2.5 minute exposure (see above). The result shows that the
addition of susceptor had a negative effect on RF activation.
[0547] It appears addition of known susceptors to the various
thermoset resin compositions has very little impact on RF
activation of the resins. In some cases, it seems to have a
negative impact.
[0548] In a few cases, the heat generation is quite violent
suggesting that proper tuning of frequency/power/time and other
variables will lead to conditions that would allow very short cure
times.
Example 14
[0549] The use of the carboxyl containing diol dimethylol butanoic
acid was tested as a susceptor. The composition included:
19 Formerez 11-36 3.2 parts DESMODUR W 0.75 parts Dimethylol
Butanoic acid 0.28 parts T-12 catalyst 1-2 drops
[0550] No significant activation took place when this composition
was exposed to 500 mV level (2.5 and 5 minute exposure).At 5 minute
exposure under 700 mV, the glass slide broke and no data could be
gathered. As noted above, under similar conditions without the
susceptor, a gel content of 11.4% was obtained in the absence of
glycerin and 27% in the presence of glycerin.
[0551] It may be useful to add the acid diol in N-methyl
pyrrolidone or another polar solvent and neutralize with a tertiary
amine to protonate the acid. Further use of urethane prepolymer
containing carboxyl or sulfonate groups in the presence of a
tertiary amine (to protonate the acid) may be a better susceptor
candidate for the urethane reaction.
Example 15
[0552] This example demonstrates a method of selectively activating
the compositions of the invention within a multi-layer stack of
materials.
[0553] The composition comprised 70 wt % Eastman AQ35S
sulfopolyester in 30 wt % glycerin. The composition was applied and
dried down from an aqueous dispersion to form a continuous 0.003
inch thick film on one side of a bilaminate polyolefin material.
The bilaminate polyolefin material comprised a single layer of
polypropylene (PP) non-woven material bonded to a single layer of
polyethylene (PE) film. The composition was coated onto the PP side
of the bilaminate material. The coated bilaminate-material was then
interposed between two multi-layer stacks of un-coated bilaminate
material to form a composite sandwich of materials. Each
multi-layer stack had two layers of the un-coated bilaminate
polyolefin material. The composite sandwich (410) was then placed
directly over the RF probes and compressed under a TEFLON.TM. block
at 30 psi. The composition was RF heated by applying approximately
1 kW of forward power into the tuned heat station 4122 for 200
milliseconds at approximately 13.5 MHz. After applying the RF
energy to the composite sandwich, the pressure was removed and the
sandwich was evaluated by slowly pulling the layers apart by hand.
Every layer was easily pulled apart, with no observed bonding,
except for the two layers that were in direct contact with the
bonding composition. The two layers that were in direct contact
with the bonding composition were firmly adhered by the bonding
composition. As a control experiment, the experiment was repeated,
except that no RF energy was applied to the composite sandwich.
This experiment resulted in no observable bonding between any of
the layers, including the two layers that were in direct contact
with the bonding composition. It should be understood that in this
experiment, the bonding composition was pre-applied to one surface
of one of the layers of the composite sandwich. The bonding
composition could be applied to more than one surface of more than
one layer. Bonding would occur between any layers that are each in
contact with a given layer of bonding composition.
Example 16
[0554] This example demonstrates the method of interfacing a
carrier layer onto the surface of a susceptor layer to achieve an
RF heatable composition. First, a 0.003 inch layer of a sulfonated
polyester copolymer, Eastman AQ35S (Supplied by Eastman Chemical
Company, Kingsport. Tenn.) was coated out of an aqueous dispersion
onto the polypropylene (PP) non-woven side of a bilaminate web
consisting of a layer of PP non-woven bonded to a layer of
polyethylene (PE) film. The coating was thoroughly dried down under
a heat lamp and fan. A sandwich was made by placing a sample of the
coated web against the PP side of a second piece of the same web
material which was not coated, such that the coating was between
the two webs. The sandwich was placed directly over the RF probes
(410) of the RF set-up described in FIG. 41. The distance between
the RF probes and the sandwich was about 0.010 inch; The sandwich
layers were pressed firmly together against the RF probes with 35
psi of applied pressure. About 1 kW of 13.5 MHz RF energy was
applied for 500 milliseconds and resulted in no noticeable heating
or bonding between the webs. Then the sandwich layers were
separated and the susceptor coating was moistened with distilled
water. The sandwich was re-assembled and RF energy was applied to
it for 500 milliseconds as described above, resulting in very good
bonding of the webs. As a control experiment, a sandwich consisting
of two webs of the uncoated web material was prepared by moistening
the PP side of each web and bringing the water moistened surfaces
together. RF energy was applied for 500 milliseconds to the
sandwich in the same way described above, resulting in no
noticeable heating.
Example 17
[0555] This example demonstrates the effect of varying the
concentration of the polar carrier in blends of the polar carrier
and an ionomer. The polar carrier of this example is glycerin.
Glycerin has a dielectric constant, e, of 42.5 at 25.degree. C. The
ionomer of this example is a commercially available sulfonated
polyester ionomer (Eastman AQ55S).
[0556] Several compositions were prepared as hot-melt blends of
AQ55S and glycerin. The wt. % concentration of glycerin in the
compositions was varied from 10% to 70. The compositions were
prepared as follows:
[0557] Each composition was prepared to have a total mass of 50
grams. For each composition, the respective amounts of AQ55S
pellets and glycerin were initially weighed into a resin flask and
mixed to achieve thorough wetting of the resin pellets with the
glycerin. The flask was then fit with a condenser column and sealed
stir-assembly, and partially immersed into a 335 F hot oil bath to
achieve controlled heating and melting of the mixture. After the
pellets became molten and swollen with the glycerin, the mixture
was stirred and blended into a uniform composition.
[0558] Each composition was then applied in its molten state as a
0.003 inch thick.times.1 inch wide.times.5 inch long, continuous
layer along the center line of a 4 inch wide.times.0.0035 inch
thick sheet of transparency film (3M PP2500 Transparency Film) and
allowed to set-up at room temperature. Several such draw downs were
made for each composition. A twin blade sample cutter was used to
cut strips from the draw downs, by cutting across and perpendicular
to the 5 inch long center line of each of the draw downs. This
produced 1 inch wide.times.4 inch long strips of acetate film, each
with a 1 inch.times.1 inch.times.0.003 inch thick coating of
composition in the center and 11/2 inch long tails on each end. The
resulting coatings differed in their relative RF-heating properties
as well as their relative heat resistance to bond failure in a
given shear loading condition.
[0559] RF-heating of each composition was evaluated as follows. For
each composition, several sandwiches were prepared. Each sandwich
was made by placing the polypropylene (PP) non-woven side of a 1
inch wide.times.4 inch long strip of a bilaminate web against the
coated side of the coated acetate test strip. The bilaminate web
was composed of a layer of PP non-woven bonded to a layer of
polyethylene (PE) film. Each sandwich was placed directly over the
RF probes (410) of the RF set-up described in FIG. 41, such that
the uncoated side of the acetate test strip was placed toward the
probes. The sandwich layers were pressed firmly together against a
layer of 0.010 inch thick layer of TEFLON.TM. and acetate that
separated the RF probes and sandwich. A single pulse of 0.5 kW,
13.5 MHz RF energy was applied for a controlled duration to each
sandwich. For each composition several sandwiches were activated,
each at an incrementally longer duration. This gave a range of RF
heating results. Threshold RF activation was determined from each
range of results as the minimum duration that result in sufficient
melting and wetting of the adhesive coating to the web to be
observed by the naked eye. Threshold RF activation by the specific
RF set-up (generally indicated in FIG. 41) resulted in a narrow
band of heating that was biased toward and parallel to the "high"
probe of the probe assembly (602 or 604). This was because an
"unbalanced" impedance matching network was used in the set-up.
[0560] Resistance to shear load bond failure was evaluated as
follows, For each composition, bonded specimens were prepared. The
specimens each consisted of a sandwich of a 1 inch.times.4
inch.times.0.0035 inch thick layer of acetate pressed against and
hot-melt bonded to the coated side of a coated acetate test strip.
(The coated acetate test strips were prepared as described earlier
in this example.) Each hot-melt bond was facilitated by pressing
the sandwich on a 275 F hot plate surface under a 0.5 Kg load for
30 seconds, and then removing the sandwich and allowing it to cool
and solidify into a bonded specimen. Each sandwich had a pair of
"tails" of unbonded acetate on each side of a centered 1
inch.times.1 inch bonded area of the sandwich. One tail from each
of the two pairs and on opposite sides of the sandwich was cut off.
This resulted in the final bonding specimen, consisting of two 1
inch.times.3 inch layers of 0.0035 inch thick acetate bonded
together across a 1 inch by 1 inch overlap by an interposed 0.003
inch thick layer of the composition being tested. The specimens
were then placed under a shear load of 0.5 Kg in a temperature
controlled chamber at 100 F. The time required to result in total
bond failure (disassembly of the specimen) at 100 F was measured
for each specimen and is referred to herein as "Shear Holding
Time".
[0561] The following observations were made:
[0562] (1) As the percentage of glycerin was increased from 10% to
70%, a sharp increase in relative rates of RF heating began to
occur at about 10% glycerin. (See FIG. 54.)
[0563] (2) As the percentage of glycerin was decreased from 70% to
10% a sharp increase in relative heat resistance began to occur at
about 30% glycerin. (See FIG. 55.)
Example 18
[0564] This example demonstrates the effect of varying the
concentration of the polar carrier in blends of the polar carrier
and an alternative sulfonated polyester ionomer to the AQ55S of
Example 17. The polar carrier of this example is glycerin. Glycerin
has a dielectric constant of 42.5 at 25.degree. C. The ionomer of
this example is a commercially available sulfonated polyester
ionomer (Eastman AQ35S).
[0565] Several compositions were prepared as hot-melt blends AQ35S
and glycerin. The wt. % concentration of glycerin in the
compositions was varied from 10% to 70%.
[0566] The compositions were prepared as follows:
[0567] Each composition was prepared to have a total mass of 50
grams. For each composition, the respective amounts of AQ35S
pellets and glycerin were initially weighed into a resin flask and
mixed to achieve thorough wetting of the resin pellets with the
glycerin. The flask was then fit with a condenser column and sealed
stir-assembly, and partially immersed into a 335 F hot oil bath to
achieve controlled heating and melting of the mixture. After the
pellets became molten and swollen with the glycerin, the mixture
was stirred and blended into a uniform composition.
[0568] RF-heating and resistance to shear load bond failure was
evaluated for each composition as described in Example 17.
[0569] The following observations were made:
[0570] (1) As the percentage of glycerin was increased from 10% to
30%, a sharp increase in relative rates of RF heating began to
occur at about 10% glycerin. (See FIG. 56.)
[0571] (2) As the percentage of glycerin was decreased from 30% to
20% a sharp increase in relative heat resistance began to occur at
about 30% glycerin. (See FIG. 57.) These results agreed closely
with the results of Example 17.
Example 19
[0572] This example demonstrates the effects of dielectric constant
and concentration of various polar carriers on the ability to
achieve significantly improved RF activation times in compositions
comprising blends of ionomers and polar carriers, as compared to
compositions comprising the ionomer without sufficient presence of
polar carrier.
[0573] The polar carriers and respective measured dielectric
constants of this example are:
[0574] (1) Propylene carbonate; .epsilon.=62.67 at 25.degree.
C.
[0575] (2) Glycerin; .epsilon.=42.5 at 25.degree. C.
[0576] (3) N-methyl-2-pyrrolidone; .epsilon.=32.2 at 20.degree.
C.
[0577] (4) 1,2-propyleneglycol .epsilon.=32 at 25.degree. C.
[0578] (5) Polyethylene glycol 200; .epsilon.=17.70 at 23.5.degree.
C.
[0579] (6) Benzoflex 9-88 (dipropylene glycol benzoate);
.epsilon.=12.28 at 25.degree. C.
[0580] The ionomer of this example is a commercially available 30%
solids aqueous dispersion of sulfonated polyester ionomer (Eastman
AQ35D). Several compositions were prepared as aqueous mixtures of
AQ35D and each of the polar carriers. The wt. % concentration of
polar carrier in each of the compositions was varied from 0% up to
50%, where total weight is based on total weight of ionomer solids
combined with total weight of polar carrier.
[0581] The compositions were prepared as follows:
[0582] Each composition was prepared to have a total mass of 50
grams. For each composition, the respective amounts of AQ35D
ionomer dispersion and glycerin were initially weighed into ajar
and mixed for about 10 minutes. The jars were sealed with tops
until castings were made.
[0583] Each composition was then applied as a liquid at room
temperature into castings onto a 0.0035 inch thick sheet of
transparency film (3M PP2500 Transparency Film) and allowed to dry
down into 0.003 inch thick coatings. The resulting coatings
differed in their relative RF-heating properties. RF activation was
evaluated as described in Example 17.
[0584] The following observations were made:
[0585] As the percentage of each polar carrier was increased from
0% to 50%, a sharp increase in relative rates of RF heating began
to occur at about 10% glycerin (except for the composition that was
prepared from Benzoflex 9-88, which experienced a relatively slow
and gradual increase). (See FIG. 58.).
[0586] While Benzoflex 9-88 gave a compatible composition with the
AQ35S polymer, it resulted in a significantly less RF-active
composition than any of the compositions that were prepared from
more polar materials with relatively high dielectric constants.
(See FIG. 58.).
Example 20
[0587] This example demonstrates the effect of varying the
concentration of a microcrystalline wax in the composition, X %
(80% AQ55S/20% Glycerin)/Y % wax. The microcrystalline wax in this
example was PARICIN 220
[N-(2-hydroxyethyl)-12-hydroxystearamide].
[0588] The compositions were prepared as follows:
[0589] Each composition was prepared to have a total mass of 50
grams. A 300 gram batch of 80% AQ55S/20% glycerin was prepared. 240
grams of AQ55S pellets and 60 grams of glycerin were initially
weighed into a resin flask and mixed to achieve thorough wetting of
the resin pellets with the glycerin. The flask was then fit with a
condenser column and sealed stir-assembly, and partially immersed
into a 335 F hot oil bath to achieve controlled heating and melting
of the mixture. After the pellets became molten and swollen with
the glycerin, the mixture was stirred and blended into a uniform
composition. After a total of 4 hours of heating, the flask was
removed from the hot oil bath. Several glass jars were each filled
with 20 grams of the molten composition. Incrementally increasing
amounts of PARICIN 220 were weighed into the hot contents of each
jar, to result in a concentration series of X % (80% AQ55S/20%
Glycerin)/Y % PARICIN 220, where Y=0, 1, 2, 3,4, 5, 10, 15, 20, 25
and 30, and X=100-Y. Each open jar was placed in an oven at 300 F
for 30 minutes and allowed to become molten. The molten contents
were then hand stirred with wooden stir sticks for 2 minutes to
form a smooth and uniform blend.
[0590] Each-composition was then applied in its molten state as a
0.003 inch thick.times.1 inch wide.times.5 inch long, continuous
layer along the center line of a 4 inch wide.times.0.0035 inch
thick sheet of transparency film (3M PP2500 Transparency Film) and
allowed to set-up at room temperature. Several such draw downs were
made for each composition. A twin blade sample cutter was used to
cut strips from the draw downs, by cutting across and perpendicular
to the 5 inch long center line of each of the draw downs. This
produced 1 inch wide.times.4 inch long strips of acetate film, each
with a 1 inch.times.1 inch.times.0.003 inch thick coating of
composition in the center and 11/2 inch long tails on each end.
[0591] The resulting coatings differed in their relative RF-heating
properties and melt viscosities.
[0592] RF-heating was evaluated for each composition as described
in Example 17. The Brookfield viscosity of each composition was
measured at 275 F, using an S27 spindle.
[0593] The following observations were made:
[0594] As the wt % of PARICIN 220 was increased from 0 to 10%,
there was a slight increase (<5%) in the time required to heat
each composition to the same degree as required at 0% PARICIN 220.
As the wt % of PARICIN 220 was increased from 10% to 30%, there was
a significant increase in the time required to heat each
composition to the same degree as required at 0% PARICIN 220. (See
FIG. 59.).
[0595] As the wt % of PARICIN 220 decreased from 10% to 0%, the
melt viscosity at 275 F increased by a factor of 6 from 6800 cP to
42000 cP.
Example 21
[0596] This example demonstrates the effect of varying the
concentration of the polar carrier in blends of the polar carrier
and an ionomer, where the ionomer is the sodium salt of an ethylene
acrylic acid copolymer. The polar carrier of this example is
glycerin. Glycerin has a dielectric constant, .epsilon., of 42.5 at
25.degree. C. The ionomer of this example is a commercially
available aqueous dispersion of the sodium salt of an ethylene
acrylic acid copolymer (MICHEM 48525P).
[0597] Several compositions were prepared as aqueous mixtures of
MICHEM 48525P and glycerin. The wt. % concentration of glycerin in
each of the compositions was Xvaried from 0% up to 50%, where total
weight is based on total weight of ionomer solids combined with
total weight of glycerin.
[0598] The compositions were prepared as follows:
[0599] Each composition was prepared to have a total mass of 50
grams. For each composition, the respective amounts of MICHEM
48525P ionomer dispersion and glycerin were initially weighed into
a jar and mixed for about 10 minutes. The jars were sealed with
tops until castings were made. Each composition was then applied as
a liquid at room temperature into castings onto a 0.0035 inch thick
sheet of transparency film (3M PP2500 Transparency Film) and
allowed to dry down into 0.003 inch thick coatings. The resulting
coatings differed in their relative RF-heating properties. RF
activation was evaluated as described in Example 17.
[0600] The following observations were made:
[0601] As the percentage of each polar carrier was increased from
0% to 50%, a sharp increase in relative rates of RF heating began
to occur at about 10% glycerin (See FIG. 61). This result agrees
well with the results of Examples 17, 18 and 19.
Example 22
[0602] This example demonstrates the relative heat resistance to
bond failure in a given shear loading condition of four separate
compositions that are composed of four different sulfonated
polyesters respectively (AQ14000, AQ35S, AQ48S and AQ55S) and the
same polar material in each case(glycerin). The polar carrier of
this example is glycerin. Glycerin has a dielectric constant,
.epsilon., of 42.5 at 25.degree. C. The ionomers of this example
are commercially available sulfonated polyester ionomers (Eastman
AQ14000, AQ35S, AQ48S and AQ55S).
[0603] The four compositions were prepared to have 80 wt %
ionomer/20 wt % glycerin. Each composition was prepared to have a
total mass of 50 grams. For each composition, the respective
amounts of ionomer pellets and glycerin were initially weighed into
a resin flask and mixed to achieve thorough wetting of the resin
pellets with the glycerin. The flask was then fit with a condenser
column and a sealed stir-assembly, and then partially immersed into
a 335 F hot oil bath to achieve controlled heating and melting of
the mixture. After the pellets became molten and swollen with the
glycerin, the mixture was stirred and blended into a uniform
composition.
[0604] Each composition was then applied in its molten state as a
0.003 inch thick.times.1 inch wide.times.5 inch long, continuous
layer along the center line of a 4 inch wide.times.0.0035 inch
thick sheet of transparency film (3M PP2500 Transparency Film) and
allowed to set-up at room temperature. Several such draw downs were
made for each composition. A twin blade sample cutter was used to
cut strips from the draw downs, by cutting across and perpendicular
to the 5 inch long center line of each of the draw downs. This
produced 1 inch wide.times.4 inch long strips of acetate film, each
with a 1 inch.times.1 inch.times.0.003 inch thick coating of
composition in the center and 11/2 inch long tails on each end. The
resulting coatings were each evaluated for their relative
RF-heating properties as well as their relative heat resistance to
bond failure in a given shear loading condition, as described in
Example 17.
[0605] The following observations were made for the four
compositions:
[0606] 80% AQ14000/20% Glycerin
[0607] Tg of AQ14000=7.degree. C.
[0608] Threshold RF Activation Time=130 ms
[0609] Shear Holding Time=1,604 sec
[0610] 80% AQ35S/20% Glycerin
[0611] Tg of AQ35S=35.degree. C.
[0612] Threshold RF Activation Time=310 ms
[0613] Shear Holding Time=68,252 sec
[0614] 80% AQ48S/20% Glycerin
[0615] Tg of AQ48S=48.degree. C.
[0616] Threshold RF Activation Time=90 ms
[0617] Shear Holding Time=40,346 sec
[0618] 80% AQ55S/20% Glycerin
[0619] Tg of AQ55S=55.degree. C.
[0620] Threshold RF Activation Time=100 ms
[0621] Shear Holding Time=1,450,000 sec
Example 23
[0622] This example demonstrates a hot melt composition prepared
from a sulfonated polyester ionomer (AQ55S) and a polar plasticizer
(RIT-CIZER #8). The composition was prepared to have 80 wt %
ionomer/20 wt % RIT-CIZER #8. The composition was prepared to have
a total mass of 50 grams. The respective amounts of ionomer pellets
and glycerin were initially weighed into a resin flask and mixed to
achieve thorough wetting of the resin pellets with the glycerin.
The flask was then fit with a condenser column and a sealed
stir-assembly, and then partially immersed into a 335 F hot oil
bath to achieve controlled heating and melting of the mixture.
After the pellets became molten and swollen with the glycerin, the
mixture was stirred and blended into a uniform composition. The
composition was then applied in its molten state as a 0.016 inch
thick.times.1 inch wide.times.1 inch long, continuous layer along
the center line of a 4 inch wide.times.0.0035 inch thick sheet of
transparency film (3M PP2500 Transparency Film). The resulting
coating was evaluated for relative RF-heating as described in
Example 17.
[0623] The following observations were made for the
composition:
[0624] The composition was very thick and stiff at 335.degree. F.
It was not possible to measure the Brookfield viscosity at
275.degree. F. At room temperature, the composition was clear,
tough and brittle. There seemed to be very good compatibility
between the polymer and RIT-CIZER #8. The threshold RF activation
time was measured to be approximately 4 seconds.
Example 24
[0625] This example demonstrates a composition that comprises an
ionomer-type susceptor, a polar material and an adhesive compound.
First, several different RF susceptor compositions were prepared by
blending various ionomers and polar material. Then, each of the RF
susceptor compositions were blended with an adhesive compound.
[0626] Preparation of the RF-Susceptor Compositions:
[0627] Several different RF susceptor compositions were prepared by
blending various commercially available sulfonated polyester
ionomers (Eastman AQ35 S, AQ48S and AQ55S, AQ1045, AQ1350, AQ14000)
with a polar material (glycerin). The RF-susceptor compositions of
this example include but are not limited to:
[0628] 70 wt % AQ35S/30 wt % Glycerin
[0629] 70 wt % AQ48S /30 wt % Glycerin
[0630] 70 wt % AQ55S/30 wt % Glycerin
[0631] 70 wt % AQ1045/30 wt % Glycerin
[0632] 70wt %AQ1350/30wt %Glycerin
[0633] 70 wt % AQ 14000/30 wt % Glycerin.
[0634] Each RF-susceptor composition was prepared to have a total
batch mass of 300 grams. For each composition, the respective
amounts of ionomer and glycerin were initially weighed into a resin
flask and mixed to achieve thorough wetting of the resin pellets
with the glycerin. The flask was then fit with a condenser column
and sealed stir-assembly, and partially immersed into a 335 F hot
oil bath to achieve controlled heating and melting of the mixture.
After the polymer became molten and swollen with the glycerin, the
mixture was stirred and blended into a uniform composition. The
compositions that comprised linear polymers (AQ35S, AQ48S and
AQ55S) were each blended at 335 F for 3 hours. The composition
comprising AQ1045 was blended at 335 F for 1 hour. The compositions
comprising AQ 1350 and 14000 were each blended at 335 F for 1.5
hours. Each of the RF-susceptor compositions was cooled and stored
at room temperature for later use.
[0635] Preparation of the Compositions Comprising Blends of
RF-Susceptor Compositions and an Adhesive Compound:
[0636] Each of the RF susceptor compositions was blended with an
adhesive compound. The adhesive compound of this example is a
random copolymer of ethylene vinyl acetate (EVA). The commercially
available EVA that was used is DuPont Polymer's ELVAX 210, Lot
#90204492.
[0637] Each composition was prepared to have a total mass of 17
grams. For each composition, 7 grams of ELVAX 210 and 10 grams of
the respective RF-susceptor composition was added to a glass jar at
room temperature. The open jar was then heated in a convection oven
at 335 F for 40 minutes. After 40 minutes of heating, the jar was
removed from the oven to the surface of a 330 F hot plate and
stirred by hand for 1 minute to result in a uniform smooth
blend.
[0638] A total of six compositions were prepared. The
RF-susceptor/Adhesive compositions of this example include but are
not limited to:
[0639] A. 41wt % AQ35S/18wt % Glycerin/41wt % ELVAX210
[0640] B. 41 wt % AQ48S/18 wt % Glycerin/41 wt % ELVAX 210
[0641] C. 41 wt % AQ55S/18 wt % Glycerin/41 wt % ELVAX 210
[0642] D. 41 wt % AQ1045/18 wt % Glycerin /41 wt % ELVAX 210
[0643] E. 41 wt % AQ1350/18 wt % Glycerin! 41 wt % ELVAX 210
[0644] F. 41 wt % AQ14000/18 wt % Glycerin 41 wt % ELVAX 210
[0645] Evaluation of the Blends of RF-Susceptor Compositions with
ELVAX 210.
[0646] Immediately after stirring the composition into a uniform
blend, each composition was then applied in its molten state as a
0.003 inch thick.times.1 inch wide.times.5 inch long, continuous
layer along the center line of a 4 inch wide.times.0.0035 inch
thick sheet of transparency film (3M PP2500 Transparency Film) and
allowed to set-up at room temperature. Several such draw downs were
made for each composition. A twin blade sample cutter was used to
cut strips from the draw downs, by cutting across and perpendicular
to the 5 inch long center line of each of the draw downs. This
produced 1 inch wide.times.4 inch long strips of acetate film, each
with a 1 inch.times.1 inch.times.0.003 inch thick coating of
composition in the center and 11/2 inch long tails on each end.
[0647] The resulting coatings were each evaluated for their
relative coat properties as well RF-heating properties, as
described in Example 17.
[0648] The following observations were made for the six
compositions:
20 TABLE 11 Coating Properties RF Com- Activation position
Toughness Clarity Color Tackiness Time (ms) A Soft Translucent
White Slight Tack 520 B Tough Translucent White Tacky 100 C Very
Tough Translucent White Very Slight 280 Tack D Very Soft Clear None
Tacky 430 E Soft Clear None Tacky 380 F Soft Clear None Tacky
340
Example 25
[0649] This example demonstrates compositions comprising an
ionomer, a polar material and various low molecular weight
polyolefin additives.
[0650] First, an RF heatable hot melt composition was prepared by
blending 70 wt % AQ35 (a sulfonated polyester, commercially
available from Eastman Chemical Company) with 30 wt % glycerin for
about 3 hours at 335 F. Then, several compositions were prepared by
blending small samples of the molten AQ35/glycerin blend,
separately with various grades of EPOLENE (low molecular weight
polyolefins, commercially available from Eastman Chemical
Company).
[0651] The polyolefin polymers of this example are Eastman
Chemical's: EPOLENE N-10 (lot #11478), EPOLENE N-11 (lot #89352),
EPOLENE N-14 (lot #12877), EPOLENE N-15 (lot #491104), EPOLENE N-20
(lot #87023), EPOLENE N-21 (lot #13018), and EPOLENE N-34 (lot
#12710). EPOLENE polymers are low molecular-weight polyolefins that
can be useful as base polymers for hot-melt adhesives.
[0652] Each composition was then applied in its molten state as a
0.003 inch thick.times.1 inch wide.times.5 inch long, continuous
layer along the center line of a 4 inch wide.times.0.0035 inch
thick sheet of transparency film (3M PP2500 Transparency Film) and
allowed to set-up at room temperature. Several such draw downs were
made for each composition. A twin blade sample cutter was used to
cut strips from the draw downs, by cutting across and perpendicular
to the 5 inch long center line of each of the draw downs. This
produced 1 inch wide.times.4 inch long strips of acetate film, each
with a 1 inch.times.1 inch.times.0.003 inch thick coating of
composition in the center and 11/2 inch long tails on each end.
[0653] The resulting coatings were each evaluated for their
relative RF-heating properties as well as their relative heat
resistance to bond failure in a given shear loading condition, as
described in Example 17.
[0654] Table 12 summarizes the observations that were made for the
various compositions:
21TABLE 12 EPOLENE# mw viscosity rftime hangtime 70% AQ35/30%
Glycerin + 5% EPOLENE N-10 10000 8675 210 3.91 N-11 6000 7450 210
2.99 N-14 4000 7750 220 4.77 N-15 12000 13500 210 2.60 N-20 15000
10020 220 6.01 N-21 6500 6125 210 1.91 N-34 6200 8100 210 2.95 70%
AQ35/30% Glycerin + 10% EPOLENE N-10 10000 10220 250 3.30 N-11 6000
7975 240 1.94 N-14 4000 8725 250 3.33 N-15 12000 17900 250 1.46
N-20 15000 9450 240 2.28 N-21 6500 7112 240 1.59 N-34 6200 8212 240
1.78 70% AQ35/30% Glycerin + X % EPOLENE N-10 % EPOLENE viscosity
rftime hangtime 0 6362 200 4.46 2.5 8337 210 2.10 5 8675 210 3.91
10 10220 250 3.30 15 11570 280 5.03 20 12250 280 5.99 25 14620 300
7.55 30 15250 825 5.35
Example 26
[0655] This example demonstrates a series of compositions that
comprise: 9% polyethylene glycol and 91% (75% AQ55/25%
glycerin).
[0656] First, a blend of 75% AQ55 and 25% glycerin was made by
blending AQ55 and glycerin for 3 hours at 335 F. Then, a series of
compositions was prepared in which each composition was prepared as
a molten blend of 9% polyethylene glycol (PEG) and 91% (75%
AQ55/25% glycerin).
[0657] Each composition was then applied in its molten state as a
0.003 inch thick.times.1 inch wide.times.5 inch long, continuous
layer along the center line of a 4 inch wide.times.0.0035 inch
thick sheet of transparency film (3M PP2500 Transparency Film) and
allowed to set-up at room temperature. Several such draw downs were
made for each composition. A twin blade sample cutter was used to
cut strips from the draw downs, by cutting across and perpendicular
to the 5 inch long center line of each of the draw downs. This
produced 1 inch wide.times.4 inch long strips of acetate film, each
with a 1 inch.times.1 inch.times.0.003 inch thick coating of
composition in the center and 11/2 inch long tails on each end. The
resulting coatings were each evaluated for their relative
RF-heating properties as well as their relative heat resistance to
bond failure in a given shear loading condition, as described in
Example 17.
[0658] Table 13 summarizes the observations that were made for the
various compositions:
22TABLE 13 hangtime PEG # tack Rftime hrs for 1 sq. inch (PEG200
Brookfield 1 = very slight time required bond area to fail at
through Viscosity tack; 2 = slight to melt sample 100 F. under a
0.5 kg PEG8000) (cP at 275 F.) tack; 3 = tacky (ms). shear load.
200 15650 1 130 12.94 300 12500 1 150 11.35 400 14600 1 130 5.34
600 13700 3 140 7.23 900 12250 1 150 5.76 1000 12800 1 150 6.82
1450 11700 1 210 4.85 3350 15070 1 200 5.70 4000 14620 2 250 5.51
4600 16400 2 220 9.34 8000 17320 1 230 6.35
Example 27
[0659] This example demonstrates a composition comprising 10%
IGEPAL (a commercially available additive from Rhodia) and 90% (75%
AQ55/25% glycerin).
[0660] A first composition comprising 75% AQ55 and 25% glycerin was
prepared by blending AQ55 and glycerin for 6 hours at 335 F. A
second composition was prepared by blending IGEPAL CO-880 at 10 wt
% with a sample of the first composition.
[0661] Each composition was then applied in its molten state as a
0.003 inch thick.times.1 inch wide.times.5 inch long, continuous
layer along the center line of a 4 inch wide.times.0.0035 inch
thick sheet of transparency film (3M PP2500 Transparency Film) and
allowed to set-up at room temperature. Several such draw downs were
made for each composition. A twin blade sample cutter was used to
cut strips from the draw downs, by cutting across and perpendicular
to the 5 inch long center line of each of the draw downs. This
produced 1 inch wide.times.4 inch long strips of acetate film, each
with a 1 inch.times.1 inch.times.0.003 inch thick coating of
composition in the center and 11/2 inch long tails on each end.
[0662] The resulting coatings were each evaluated for their
relative RF-heating properties as well as their relative heat
resistance to bond failure in a given shear loading condition, as
described in Example 17.
[0663] Table 14 summarizes the observations that were made for the
various compositions:
23TABLE 14 RF Activation Time Viscosity Time required to melt the
Composition (cP at 275 F.) sample (ms). 5% AQ55/25% glycerin 28,200
180 90% (AQ55/glycerin)/ 9,750 360 10% IGEPAL CO-880
Example 28
[0664] This example demonstrates an RF heatable composition
comprising 75% AQ48 (a commercially available sulfonated polyester
from Eastman Chemical Company) and 25% glycerin.
[0665] The composition was prepared by blending 75 wt % AQ48 with
25 wt % glycerin for 4 hours at 335 F. The resulting molten
composition was fluid and clear. When this composition was cast
onto layers of acetate and allowed to cool, the resulting solid
draw-downs were clear and had cold-tack. This composition is ideal
for applications where parts are to be initially adhered with a
green strength bond by the composition and subsequently fused by
the heat that is generated from within the composition as it is
exposed to RF energy.
[0666] The molten composition had a Brookfield viscosity of 5,750
cP at 275 F, using an S27 spindle at 20 RPM. The composition was
then applied in its molten state as a 0.003 inch thick.times.1 inch
wide.times.5 inch long, continuous layer along the center line of a
4 inch wide.times.0.0035 inch thick sheet of transparency film (3M
PP2500 Transparency Film) and allowed to set-up at room
temperature. Several such draw downs were made. A twin blade sample
cutter was used to cut strips from the draw downs, by cutting
across and perpendicular to the 5 inch long center line of each of
the draw downs. This produced 1 inch wide.times.4 inch long strips
of acetate film, each with a 1 inch.times.1 inch.times.0.003 inch
thick coating of composition in the center and 11/2 inch long tails
on each end. The resulting coatings were each evaluated for their
RF-heating properties, as described in Example 17. RF activation
was achieved in 160 ms.
[0667] The composition was then drawn into flat beads (0.10 inches
wide by 0.01 inches thick at the maximum thickness--the beads were
crowned in the middle and feathered at the edges). Three sandwiches
of materials were made. Each sample was made by placing a single
bead of the composition between two identical layers of thin-film
bilaminate polyolefin material. Each layer of bilamninate material
was composed of two layers--one layer of polypropylene non-woven
(PP) and one layer of polyethylene film (PE).
[0668] The first sandwich (sample 1) was assembled such that the
bead was in direct contact with the PP side of one of the layers of
bilaminate, and the PP side of the other layer of bilaminate. The
second sandwich (sample 2) was assembled such that the bead was in
direct contact with the PP side of one of the layers of bilaminate,
and the PE side of the other layer of bilaminate. The third
sandwich (sample 3) was assembled such that the bead was in direct
contact with the PE side of one of the layers of bilaminate, and
the PE side of the other layer of bilaminate.
[0669] In each case, the bead had slight tack and was able to
gently hold the layers of the sandwich together. Each sandwich was
then activated in a 13.5 MHz RF field for 200 ms at 1000 watts. In
each case, melting of the bilaminate layers had occurred. Then the
sandwiches were each immersed and washed in MEK for several minutes
in order to remove the adhesive from the bond line. In each case,
after washing the adhesive from the sandwich, residual bonding was
observed between all layers of the sandwich in the areas where
melting had been observed.
[0670] While various embodiments of the present invention have been
described above, it should be understood that they have been
presented by way of example only, and not limitation. Thus, the
breadth and scope of the present invention should not be limited by
any of the above-described exemplary embodiments, but should be
defined only in accordance with the following claims and their
equivalents. Additionally, all patents, patent applications and
publications mentioned above are incorporated by reference
herein.
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