U.S. patent application number 10/150554 was filed with the patent office on 2003-02-06 for low application temperature hot melt adhesive for cigarette preparation.
Invention is credited to Cole, Ingrid, Morrison, Brian D., Wieczorek, Joseph JR..
Application Number | 20030027007 10/150554 |
Document ID | / |
Family ID | 23155152 |
Filed Date | 2003-02-06 |
United States Patent
Application |
20030027007 |
Kind Code |
A1 |
Wieczorek, Joseph JR. ; et
al. |
February 6, 2003 |
Low application temperature hot melt adhesive for cigarette
preparation
Abstract
A cigarette filter, process to manufacture, wherein a low
application temperature ethylene copolymer based hot melt adhesive
is applied to porous and/or nonporous plugwrap paper. As used
herein, low application temperatures are temperature between
200.degree. F. and 300.degree. F. (93.degree. C. and 149.degree.
C.), preferably, 240.degree. F. to 275.degree. F. (115.degree. C.
to 135.degree. C.).
Inventors: |
Wieczorek, Joseph JR.;
(Flemington, NJ) ; Morrison, Brian D.; (Lebanon,
NJ) ; Cole, Ingrid; (Somerville, NJ) |
Correspondence
Address: |
Cynthia L. Foulke
Intellectual Property
NATIONAL STARCH AND CHEMICAL COMPANY
10 Finderne Avenue
Bridgewater
NJ
08807-0500
US
|
Family ID: |
23155152 |
Appl. No.: |
10/150554 |
Filed: |
May 17, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10150554 |
May 17, 2002 |
|
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09299516 |
Apr 26, 1999 |
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Current U.S.
Class: |
428/514 ;
131/343; 131/88; 131/94; 428/511; 428/522 |
Current CPC
Class: |
Y10T 428/31895 20150401;
Y10T 428/139 20150115; C08L 91/06 20130101; C08L 2666/02 20130101;
C09J 123/0869 20130101; C09J 123/0869 20130101; C08L 2205/035
20130101; Y10T 428/31906 20150401; C08L 2666/02 20130101; C08L
23/0869 20130101; A24D 3/08 20130101; Y10T 428/31935 20150401 |
Class at
Publication: |
428/514 ;
131/343; 131/94; 131/88; 428/511; 428/522 |
International
Class: |
B32B 027/10; B32B
027/30 |
Claims
What is claimed is:
1. A cigarette filter comprising a low application temperature
ethylene copolymer based hot melt adhesive.
2. A cigarette filter according to claim 1 wherein the adhesive is
applied at 200 to 300.degree. F. (93.degree. C. to 149.degree.
C.).
3. A cigarette filter according to claim 1 wherein the adhesive
comprises ethylene n-butyl acrylate copolymer comprising 10 to 40
weight percent n-butyl acrylate with a melt index of at least 40
dg/min.
4. A cigarette filter according to claim 3 additionally comprising
a second ethylene n-butyl acrylate copolymer, wherein the second
ethylene n-butyl acrylate copolymer comprises 25 to 35 weight
percent n-butyl acrylate.
5. A cigarette filter according to claim 4 wherein the second
ethylene n-butyl acrylate copolymer has a melt index of 40 dg/min
and comprises 35% ethylene n-butyl acrylate.
6. A cigarette filter according to claim 1 wherein the adhesive
comprises: a) 10 to 40 weight percent ethylene n-butyl acrylate
comprising 10 to 40 weight percent n-butyl acrylate with a melt
index of at least 400 dg/min; b) 10 to 60 weight percent tackifier;
c) 0 to 35 weight percent wax; and d) optionally 1 to 25 weight
percent of a second ethylene n-butyl acrylate, wherein the second
ethylene n-butyl acrylate comprises 33 to 35 weight percent butyl
acrylate with a melt index of 40 dg/min.
7. A cigarette filter according to claim 6 wherein the adhesive
comprises: a) 15 to 45% ethylene n-butyl acrylate copolymers having
a melt index of at least 200; b) 25 to 55% .alpha.-methyl styrene
tackifying resins; and c) 15 to 40% of a low melting point paraffin
wax.
8. A cigarette filter according to claim 6 additionally comprising
a polymeric additive selected from the group consisting of ethylene
methyl acrylate polymers containing 10 to 28 weight percent by
weight methyl acrylate, ethylene acrylic acid copolymers having an
acid number of 25 to 150, methyl (meth)acrylate copolymers,
polyethylene, polypropylene, poly(butene-1-co-ethylene) polymers
and low molecular weight and/or low melt index ethylene n-butyl
acrylate copolymers, and combinations thereof.
9. A cigarette filter according to claim 1 wherein the adhesive
comprises: a) from 20 to 40 weight percent of an
ethylene/.alpha.-olefin copolymer; b) from 20 to 40 weight percent
tackifier; and c) from 10 to 40 weight percent wax.
10. A cigarette filter according to claim 9 wherein the
ethylene/.alpha.-olefin copolymer has a composition distribution
breath index greater than 50%, and Mw/Mn less than 6.
11. A cigarette filter according to claim 9 wherein the
ethylene/.alpha.-olefin copolymer has a melt index of 40 to 1000
dg/min, a melt point of 71 to 90.degree. C., a density of 0.850 to
0.92, a composition distribution breath index greater than 50%, and
Mw/Mn less than 6.
12. A cigarette filter according to claim 9 additionally comprising
polymeric additive selected from the group consisting of ethylene
methyl acrylate polymers containing 10 to 28 weight percent by
weight methyl acrylate, ethylene acrylic acid copolymers having an
acid number of 25 to 150, polyethylene, polypropylene,
poly(butene-1-co-ethylene) polymers, ethylene n-butyl acrylate
copolymers and ethylene vinyl acetate copolymers, and combinations
thereof.
13. A cigarette filter according to claim 1 wherein the adhesive
comprises ethylene vinyl acetate comprising 5 to 45 weight percent
vinyl acetate with a melt index of at least 400 dg/min.
14. A cigarette filter according to claim 13 additionally
comprising a second ethylene vinyl acetate copolymer, wherein the
second ethylene vinyl acetate copolymer comprises 28 weight percent
vinyl acetate with a melt index of 6 to 40 dg/min.
15. A cigarette filter according to claim 13 additionally
comprising a polymeric additive selected from the group consisting
of ethylene methyl acrylate polymers containing 10 to 28 weight
percent by weight methyl acrylate, ethylene acrylic acid copolymers
having an acid number of 25 to 150, methyl (meth)acrylate
copolymers, polyethylene, polypropylene, poly(butene-1-co-ethylene)
polymers and low molecular weight and/or low melt index ethylene
n-butyl acrylate copolymers, and combinations thereof.
16. A cigarette filter according to claim 1 wherein the adhesive
comprises 30 to 60 weight percent polyethylene polymer with melt
index of 5000 to 2000 dg/min at 190.degree. C., a density of 0.900
to 0.930, and a softening point less than 110.degree. C.
17. A cigarette filter according to claim 1 wherein the adhesive
comprises blends selected from the group consisting of blends of
EnBA and EVA polymers; blends of polyethylene and EVA; blends of
poly .alpha.-olefin and EVA; and combinations thereof.
18. A cigarette filter according to claim 1 wherein the hot melt
adhesive comprises: a) 31 parts paraffin wax with a softening point
of 150.degree. F.; b) 21 parts ethylene vinyl acetate copolymer
with a melt index of 400 and a vinyl acetate content of 28%; c) 11
parts or ethylene vinyl acetate copolymer with a melt index of 43
and a vinyl acetate content of 28%; d) 37 parts of alpha-methyl
styrene tackifying resins; and e) 0.5 parts of an antioxidant
stabilizer.
19. A cigarette filter according to claim 1 wherein the hot melt
adhesive comprises: a) 50 parts polyethylene; b) 40 parts of an
aliphatic-aromatic hydrocarbon tackifying resin; c) 10 parts of a
microcrystalline wax with a softening point of 195.degree. F.; and
d) 0.2 parts of an antioxidant stabilizer.
20. The process for preparing a cigarette filter comprising
applying a low application temperature ethylene copolymer based hot
melt adhesive to porous and/or nonporous plugwrap paper.
21. The process according to claim 20 wherein the adhesive is
applied at 200 to 300.degree. F. (93.degree. C. to 149.degree.
C.).
22. The process according to claim 20 wherein the adhesive
comprises ethylene n-butyl acrylate copolymer comprising 10 to 40
weight percent n-butyl acrylate with a melt index of at least 40
dg/min, and optionally a second ethylene n-butyl acrylate
copolymer, wherein the second ethylene n-butyl acrylate copolymer
comprises 25 to 35 weight percent n-butyl acrylate.
23. The process according to claim 20 wherein the adhesive
comprises: a) 10 to 40 weight percent ethylene n-butyl acrylate
comprising 10 to 40 weight percent n-butyl acrylate with a melt
index of at least 400 dg/min; b) 10 to 60 weight percent tackifier;
c) 0 to 35 weight percent wax; and d) optionally 1 to 25 weight
percent of a second ethylene n-butyl acrylate, wherein the second
ethylene n-butyl acrylate comprises 33 to 35 weight percent n-butyl
acrylate with a melt index of 40 dg/min.
24. The process according to claim 20 wherein the adhesive
comprises: a) 15 to 45% ethylene n-butyl acrylate copolymers having
a melt index of at least 200; b) 25 to 55% .alpha.-methyl styrene
tackifying resins; and c) 15 to 40% of a low melting point paraffin
wax.
25. The process according to claim 20 wherein the adhesive
comprises: a) from 20 to 40 weight percent of an
ethylene/.alpha.-olefin copolymer; b) from 20 to 40 weight percent
tackifier; and c) from 10 to 40 weight percent wax.
26. The process according to claim 25 wherein the
ethylene/.alpha.-olefin copolymer has a composition distribution
breath index greater than 50% and Mw/Mn less than 6.
27. The process according to claim 25 wherein the
ethylene/.alpha.-olefin copolymer has a melt index of 40 to 1000
dg/min, a melt point of 71 to 90.degree. C., a density of 0.850 to
0.92, a composition distribution breath index greater than 50%, and
Mw/Mn less than 6.
28. The process according to claim 20 wherein the adhesive
comprises ethylene vinyl acetate comprising 5 to 45 weight percent
vinyl acetate with a melt index of at least 400 dg/min.
29. The process according to claim 20 wherein the adhesive
comprises 30 to 60 weight percent polyethylene polymer with melt
index of 5000 to 2000 dg/min at 190.degree. C., a density of 0.900
to 0.930, and a softening point less than 110.degree. C.
30. The process according to claim 20 wherein the adhesive
comprises blends selected from the group consisting of blends of
EnBA and EVA polymers; blends of polyethylene and EVA; blends of
poly .alpha.-olefin and EVA; and combinations thereof.
31. The process according to claim 20 wherein the adhesive
comprises: a) 31 parts paraffin wax with a softening point of
150.degree. F.; b) 21 parts ethylene vinyl acetate copolymer with a
melt index of 400 and a vinyl acetate content of 28%; c) 11 parts
or ethylene vinyl acetate copolymer with a melt index of 43 and a
vinyl acetate content of 28%; d) 37 parts of alpha-methyl styrene
tackifying resins; and e) 0.5 parts of an antioxidant
stabilizer.
32. The process according to claim 20 wherein the adhesive
comprises: a) 50 parts polyethylene; b) 40 parts of an
aliphatic-aromatic hydrocarbon tackifying resin; c) 10 parts of a
microcrystalline wax with a softening point of 195.degree. F.; and
d) 0.2 parts of an antioxidant stabilizer.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention is directed to the use of low
application temperature hot melt adhesive for cigarette filters.
Specifically, the hot melt adhesives of the present invention are
used to bond filter wrap seam and to anchor the filter element in
place on the rod.
[0002] A standard filter tipped cigarette is produced by three
different operations: (1) filter or plug manufacture, (2) rod
manufacture, and (3) tipping.
[0003] The cigarette rod consists of a stream of tobacco wrapped in
a paper tube, the paper tube being glued along one longitudinal
edge or surface with a suitable adhesive. This operation takes
place at speeds varying from 2,000 to 16,000 cigarettes per minute.
The weight of the cigarette rod, diameter, and length are all
closely monitored for both cost control and tax purposes.
[0004] The filter making operation is similar in many respects to
the rod manufacture, but the materials and manufacturing equipment
used are different. Tobacco smoke filters are most commonly
manufactured from a crimped textile tow of cellulose acetate
fibers. The tow is then warmed and rolled to produce a material
about 9" wide, and containing an even distribution of fibers. The
tow is "bloomed" in a known manner to separate the fibers, and a
high boiling point solvent, commonly called a "plasticizer", i.e.,
triacetin, is applied by spraying, wicking, or other suitable
means. The treated tow is then pulled into a cylindrical form and
wrapped with paper. During an interval of time, which can be
accelerated by heating, the plasticizer first partially dissolves
the surface of the fibers causing them to become sticky and to bond
together at points of contact with each other. The plasticizer then
migrates into the fiber leaving the surface dry, but the fibers
still remain bonded.
[0005] The bloomed tow is then formed into a tube, and wrapped in
paper or plugwrap, the paper being glued along one longitudinal
edge. Before the paper meets the tow material, adhesive is applied
to the center and the edge forming the anchor and the seam. During
this process, heater bars are used to extend the open time of the
adhesive as it meets the tow. The formed filter rod is then passed
under chiller plates to set the adhesive. This is necessary as the
filter is immediately cut into smaller pieces.
[0006] In some applications, such as multi-component or charcoal
type filters, a hot melt adhesive is pre-applied onto filter paper
and then heat sealed by the filter making machine.
[0007] In conventional cigarette filter manufacture, a hot melt
adhesive, applied at 350.degree. F. (177.degree. C.), is used for
the seam and a second, aqueous adhesive, is used for the anchor. An
aqueous adhesive is chosen with triacetin resistance. Because of
the nature of the tow, there is a high degree of radial stress upon
the glued bond, so any adhesive used must be able to stick almost
instantly and hold during storage and use. This has led to the use
of hot melt type adhesives, which by formulation are fast setting,
and allow very high machine speeds to be used.
[0008] Currently polyethylene and ethylene vinyl acetate based hot
melt adhesives are used for this filter or plugwrap application.
These are preferred since they are relatively non-polar and resist
the deteriorative effects of triacetin, the most commonly used
plasticizer, which often migrates acting as a solvent for the
adhesive causing bond deterioration.
[0009] Most commercially available adhesives used in cigarette
manufacture are either hot melts which require temperatures of
350.degree. F. (177.degree. C.) or are aqueous to provide triacetin
resistance.
[0010] However there are problems associated with use of
conventional hot melt adhesives, which are applied at elevated
temperatures, usually 350.degree. F. These high temperatures
increase the operator's risks with respect both to burns and to
inhalation of residual volatiles. In addition, the high
temperatures require more energy, placing greater demands on the
manufacturing facility. The higher temperatures can also cause
premature wear and tear on the application equipment i.e., nozzles,
hoses and reservoir tanks.
[0011] The present invention uses low application temperature hot
melt adhesives, which can be applied at temperatures in the range
200 to 300.degree. F. (93.degree. C. to 149.degree. C.). The
advantages of using such lower temperatures include reduced number
of heater elements required in the adhesive reservoir, reduced
volatile emissions, and reduced risk of injury and reduced wear and
tear on the application equipment. The use of low temperature hot
melt adhesives may also eliminate the need for use of both an
aqueous and hot melt adhesive, since some of the hot melt adhesives
of the present invention exhibit excellent triacetin resistance.
Further, the lower temperatures reduce temperatures in the
reactivation section of the machinery and eliminate the need for
cooling plates. In addition, the hot melt adhesives of the present
invention have a fast set speed, low bleed through, improved
cuttability and are comparable or better than 350.degree. F. hot
melt adhesives in terms of triacetin resistance.
SUMMARY OF THE INVENTION
[0012] It has been found in accordance with the present invention,
that low application temperature ethylene copolymer based hot melt
adhesives provide unexpected advantages in cigarette filter
manufacture.
DESCRIPTION OF THE INVENTION
[0013] The present invention is directed to the use of hot melt
adhesive compositions, which can be applied at temperatures between
200 to 300.degree. F. (93.degree. C. to 149.degree. C.), in the
manufacture of cigarette filters. In particular, the present
invention is directed to a process of making cigarette filters, and
to cigarette filters, wherein a low application temperature
ethylene copolymer based hot melt adhesive is applied to at least
one longitudinal edge or surface of porous and/or non-porous plug
wrap paper. The adhesives of the present invention are also
applicable to multi-component filters or other filters which are
prepared by preapplying the hot melt to filter paper, then heating
the coated paper on the filter making machine. As used herein, low
application temperatures are temperature between 200.degree. F. and
300.degree. F. (93.degree. C. and 149.degree. C.), preferably,
240.degree. F. to 275.degree. F. (115.degree. C. to 135.degree.
C.).
[0014] The present invention is directed to the process, and to
cigarette filters, which comprise any hot melt adhesive which can
be applied at temperatures between 200 and 300.degree. F.
(93.degree. C. and 149.degree. C.). Adhesives suitable for use
herein include the hot melt adhesives prepared from ethylene,
ethylene n-butyl acrylate copolymers, ethylene/.alpha.-olefin
copolymers, and ethylene vinyl acetate copolymers.
[0015] I. Ethylene n-Butyl Acrylate Based Hot Melt Adhesives.
[0016] The ethylene n-butyl acrylate copolymers (EnBA) useful
herein are those containing at least about 10 to 40 weight percent
n-butyl acrylate and having a melt index of at least about 40
dg/min, preferably at least about 400 dg/min. The preferred
copolymers are available from Exxon under the designation XW 23-AH
and comprise approximately 33 to 37 weight percent n-butyl acrylate
by weight and have a melt index of about 400 dg/min. The amount of
the copolymer present in the adhesive varies from about 5 to 45
weight percent by weight, preferably about 10 to 40 weight percent
by weight.
[0017] Mixtures of EnBA copolymers may also be used as long as the
resultant mixture falls within the described ranges of percent
n-butyl acrylate by weight, and melt index. It is therefore
possible to mix two ethylene n-butyl acrylate copolymers having
different melt indices and different percentages of n-butyl
acrylate. In a preferred embodiment, the EnBA copolymers described
above may be used alone or as a blend with an EnBA copolymer having
a melt index of 40 dg/min.
[0018] In addition to the components described above, the adhesive
compositions of the present invention may optionally comprise a
second EnBA copolymer, specifically one containing about 30 to 35,
preferably 33 weight percent by weight of n-butyl acrylate and
having a melt index of about 6 to 40 dg/min. The preferred
copolymers are available from Elf Autochem under the designation
LOTRYL 35BA40 and contain approximately 35 weight percent n-butyl
acrylate by weight and have a melt index of about 40 dg/min. The
amount of this copolymer present in the adhesive varies from about
1 to 25 weight percent by weight, preferably 5 to 20% by
weight.
[0019] The present invention also contemplates the addition to the
adhesive of a polymeric additive selected from the group consisting
of ethylene methyl acrylate polymers containing 10 to 28 weight
percent by weight methyl acrylate, ethylene acrylic acid copolymers
having an acid number of 25 to 150, methyl (meth)acrylate
copolymers, polyethylene, polypropylene, poly(butene-1-co-ethylene)
polymers and low molecular weight and/or low melt index ethylene
n-butyl acrylate copolymers. When such additive is present, it is
present in amounts up to about 15 weight percent by weight of
composition.
[0020] Tackifying resins useful in the EnBA adhesives of the
invention include the aliphatic, aromatic or mixed
aliphatic-aromatic hydrocarbon resins, and hydrogenated derivatives
thereof, and terpenes and terpene derivatives having a Ring and
Ball softening point of between about 70.degree. C. and about
150.degree. C. One skilled in the art would recognize that these
tackifying resins are available with differing levels of
hydrogenation.
[0021] Also included are the thermoplastic hydrocarbon resin having
a Ring and Ball softening point below 130.degree. C., preferably
below 120.degree. C. Representative resins include those derived
from styrene, alpha-methylstyrene, and/or vinyltoluene, and
polymers, copolymers and terpolymers of styrene,
alpha-methylstyrene and/or vinyltoluene. Preferred is
KRYSTALEX.RTM. 3085, a low molecular weight thermoplastic
hydrocarbon polymer derived largely from alpha-methylstyrene which
has a Ring and Ball softening point of 85.degree. C. and is
available from Hercules Inc.
[0022] The thermoplastic hydrocarbon resins are present in the
adhesive compositions of the present invention in an amount of 10
to 60 weight percent by weight of the composition, preferably 20 to
40 weight percent.
[0023] The adhesive of the present invention may comprise one or
more tackifying resins. For example, an adhesive may comprise
.varies.-methyl styrene, or .varies.-methyl styrene and vinyl
toluene.
[0024] Other useful tackifying resins include those sold under the
tradenames EASTOAC from Eastman Chemical Company, which are
partially hydrogenated cycloaliphatic petroleum hydrocarbon resin,
ESCOREZ available from Exxon Chemical Company, which is also a
partially hydrogenated cycloaliphatic petroleum hydrocarbon resin,
WINGTACK which is an aliphatic, aromatic petroleum hydrocarbon
resin available from Goodyear Chemicals, HERCOLITE which is a
partially hydrogenated cycloalipbatic petroleum hydrocarbon resin
available from Hercules, ZONATAC which is a styrenated terpene
hydrocarbon resin, made from d-limonene and available from Arizona
Chemical.
[0025] Waxes may be usefully employed in the adhesive compositions
of the present invention. Waxes are commonly used to modify the
viscosity and reduce tack at concentrations up to 60% by weight,
preferably less than about 45% by weight. Waxes useful in the
adhesives of the present invention include paraffin waxes,
microcrystalline waxes, Fischer-Tropsch, polyethylene and
by-products of polyethylene wherein M.sub.w is less than 3000. More
preferably, the concentration of wax is less than 35% by weight for
high melt point waxes.
[0026] Paraffin waxes suitable for use in the present invention
include those having melting points in the range of about 130 to
200.degree. F. (54.degree. C. to 193.degree. C.), such as, for
example, PACEMAKER from Citgo, and R-2540 from Moore and Munger;
and low melting point synthetic microcrystalline or Fischer-Tropsch
waxes having a melting point of less than about 180.degree. C. The
most preferred wax is paraffin wax with a melting point of
150.degree. C.
[0027] The adhesives of the invention preferably also contain a
stabilizer or antioxidant. Among the applicable stabilizers or
antioxidants included herein are high molecular weight hindered
phenols and multifunctional phenols such as sulfur and
phosphorous-containing phenol. Hindered phenols are well known to
those skilled in the art and may be characterized as phenolic
compounds which also contain sterically bulky radicals in close
proximity to the phenolic hydroxyl group thereof. In particular,
tertiary butyl groups generally are substituted onto the benzene
ring in at least one of the ortho positions relative to the
phenolic hydroxy group. The presence of these sterically bulky
substituted radicals in the vicinity of the hydroxyl group serves
to retard its stretching frequency, and correspondingly, its
reactivity; this hindrance thus providing the phenolic compound
with its stabilizing properties. Representative hindered phenols
include; 1,3,5-trimethyl 2,4,6-tris
(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; pentaerythrityl
tetrakis-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;
n-octadecyl-3(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate;
4,4'-methylenebis (2,6-tert-butylphenol); 4,4'-thiobis
(6-tert-butyl-o-cresol); 2,6-di-tertbutylphenol;
6-(4-hydroxyphenoxy)-2,4- -bis(n-octyl-thio)-1,3,5 triazine;
di-n-octylthio)ehtyl 3,5-di-tert-butyl-4-hydroxy-benzoate; and
sorbitol
hexa[3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate].
[0028] Commercially available antioxidants include the hindered
phenols known as IRGANOX, and available from Ciba-Geigy.
[0029] The performance of these antioxidants may be further
enhanced by utilizing, in conjunction therewith known synergists
such, for example, as thiodipropionate esters and phosphites,
particularly useful is distearylthiodipropionate. These
stabilizers, if used, are generally present in amounts of about 0.1
to 1.5 weight percent, preferably 0.25 to 1.0%. Other additives
such as plasticizers, pigments, dyestuffs conventionally added to
hot melt adhesives for various end uses contemplated as well as
small amounts of additional tackifiers and/or waxes such as
paraffin wax may also be incorporated in minor amounts, i.e., up to
about 10% by weight, into the formulations of the present
invention.
[0030] The adhesive compositions are prepared by blending the
components in the melt at a temperature of about 121.degree. C.
until a homogeneous blend is obtained, approximately two hours.
Various methods of blending are known to the art and any method
that produces a homogeneous blend is satisfactory.
[0031] The resulting adhesives are characterized by viscosity less
than about 4000 cps at 135.degree. C. They may be applied at
temperatures of 121.degree. C. to 135.degree. C. to provide
superior adhesive bonds even when exposed to wide variety of
temperature conditions. The adhesives possess excellent heat
stability as characterized by the 260 hour 121.degree. C. thermal
stability test, with no signs of char, skinning or gel
formation.
[0032] A preferred formulation for a hot melt adhesive prepared
from EnBA copolymers is one comprising 15 to 45%, preferably 15 to
25%, ethylene n-butyl acrylate copolymers having a melt index of at
least 200 dg/min, preferably at least about 300, 25 to 55%,
preferably 30 to 40%, .alpha.-methyl styrene tackifying resins and
15 to 40%, preferably 25 to 35% of a low melting point paraffin wax
which can be applied at temperatures of 225 to 275.degree. F.
(107.degree. C. to 135.degree. C.). Another preferred formulation
will comprise 20% of an EnBA copolymer with a melt index of 300
dg/min and 10% of an EnBA copolymer with a melt index of 40
dg/min.
[0033] II. Ethylene .alpha.-Olefin Based Hot Melt Adhesives
[0034] Another embodiment of the present invention is directed to
hot melt adhesives prepared from:
[0035] a) 20 to 40 parts ethylene/alpha olefin polymer;
[0036] b) 20 to 40 parts tackifier; and
[0037] c) 10 to 40 parts wax.
[0038] Ethylene/alpha olefin polymers useful herein are those
having a composition distribution breath index greater than 50%,
and Mw/Mn less than 6. In another embodiment the ethylene/alpha
olefin polymers will have a melt index of 40 to 1000 dg/min, a melt
point of 71 to 90.degree. C., a density of 0.850 to 0.92, a
composition distribution breath index greater than 50%, and Mw/Mn
less than 6. Preferably, the ethylene/alpha olefin polymers will
have a melt index of 50 to 500 dg/min and a density of 0.885 to
0.90. The ethylene/alpha olefin polymers may be copolymers of
ethylene and any alpha olefin, for example butene.
[0039] As used herein, composition distribution index, or short
chain branching distribution index, refers to the weight percent of
polymer molecules having a comonomer content within 50% of the
median total comonomer content.
[0040] Tackifiers useful in the present invention include aliphatic
or cycloaliphatic hydrocarbons, aromatic hydrocarbons, aromatically
modified aliphatic or cycloaliphatic hydrocarbons and mixtures
thereof. EASTOTAC H100, a hydrogenated cyclopentadiene-based
tackifier with a softening point of 100.degree. C. is the most
preferred tackifier.
[0041] Other tackifiers useful herein include polyterpenes,
aromatic modified terpene, and combinations thereof. Also included
are the hydrogenated derivatives of modified terpene resins. An
example of a commercially available styreneated polyterpene is
ZONATAC 105L which has a Ring and Ball softening point of about
105.degree. C. and is available from Arizona Chemical Company.
[0042] The preferred tackifiers of the present invention are those
having a softening point of 90 to 150.degree. C. The present
invention contemplates that the adhesive composition of the present
invention comprise one or more of the above adhesive promoting
tackifying resins.
[0043] Waxes suitable for use in the present invention include the
low melting point synthetic paraffin waxes or polyethylene type
waxes characterized by a melting point of about 130 to 200.degree.
F. (54.degree. C. to 93.degree. C.). The most preferred wax is
PACEMAKER from Citgo.
[0044] The adhesives of the present invention may also contain a
stabilizer or antioxidant. Among the applicable stabilizers or
antioxidants included herein are high molecular weight hindered
phenols and multifunctional phenols such as sulfur and
phosphorous-containing phenol. Hindered phenols are well known to
those skilled in the art and may be characterized as phenolic
compounds which also contain sterically bulky radicals in close
proximity to the phenolic hydroxyl group thereof. In particular,
tertiary butyl groups generally are substituted onto the benzene
ring in at least one of the ortho positions relative to the
phenolic hydroxyl group. The presence of these sterically bulky
substituted radicals in the vicinity of the deprotonated hydroxyl
group serves to retard its stretching frequency, and
correspondingly, its reactivity; this hindrance thus providing the
phenolic compound with its stabilizing properties. Representative
hindered phenols include;
1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-benzene;
pentaerythrityl
tetrakis-3(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate;
n-octadecyl-3(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate;
4,4'-methylenebis (2,6-tert-butyl-phenol); 4,4'-thiobis
(6-tert-butyl-o-cresol); 2,6-di-tertbutylphenol;
6-(4-hydroxyphenoxy)-2,4- bis (n-octyl-thio)-1,3,5 triazine;
di-n-octylthio)ethyl 3,5-di-tert-butyl-4-hydroxy-benzoate; sorbitol
hexa[3-(3,5-di-tert-butyl-- 4-hydroxy-phenyl)-propionate] and
2,6-ditertbutyl 4-methylphenol ("BHT"). An example of a
commercially available antioxidant is IRGANOX 1010, a hindered
phenol, available from Ciba Geigy.
[0045] The performance of these antioxidants may be further
enhanced by utilizing, in conjunction therewith, known synergists
such as, for example, thiodipropionate esters and phosphites.
Distearylthiodipropionat- e is particularly useful. These
stabilizers, if used, are generally present in amounts of about 0.1
to 1.5 weight percent, preferably 0.25 to 1.0 weight percent.
[0046] The present invention also contemplates the addition to the
adhesive of a polymeric additive selected from the group consisting
of ethylene methyl acrylate polymers containing 10 to 28 weight
percent by weight methyl acrylate, ethylene acrylic acid copolymers
having an acid number of 25 to 150, polyethylene, polypropylene,
poly(butene-1-co-ethyle- ne) polymers, ethylene n-butyl acrylate
copolymers and ethylene vinyl acetate copolymers. When such
additive is present, it is present in amounts up to about 15 weight
percent by weight of composition.
[0047] Depending on the contemplated end uses of the adhesives,
other additives such as plasticizers, pigments and dyestuffs
conventionally added to hot melt adhesives may be included. In
addition, small amounts of additional tackifiers and/or waxes such
as microcrystalline waxes, hydrogenated castor oil, amide waxes and
vinyl acetate-modified synthetic waxes may also be incorporated in
minor amounts, i.e., up to about 10 weight percent by weight, into
the formulations of the present invention.
[0048] A preferred embodiment of the present invention is directed
to a hot melt adhesive composition comprising:
[0049] a) 0.5% IRGANOX 1010;
[0050] b) 30% of an ethylene/.varies.-olefin copolymer having a
composition distribution breath index greater than 50%, and Mw/Mn
less than 6;
[0051] c) 35% paraffin wax; and
[0052] d) 35% EASTOTAC H100, 100.degree. C. partially hydrogenated
cyclopentadiene.
[0053] III. Ethylene Vinyl Acetate Based Hot Melt Adhesives
[0054] The ethylene vinyl acetate copolymers (EVA) useful herein
are those containing at least about 15 to 45 weight percent by
weight vinyl acetate and having a melt index of at least about 6
dg/min, preferably at least about 400 dg/min. The EVA copolymers
will preferably comprise less than 40 weight percent vinyl acetate
(VA), most preferably 28% VA. The preferred copolymers are
available from Exxon under the designation UL 7710 and comprise
approximately 28 weight percent vinyl acetate by weight and have a
melt index of about 400 dg/min. The amount of the copolymer present
in the adhesive varies from about 5 to 45 weight percent by weight,
preferably about 10 to 40 weight percent by weight.
[0055] Mixtures of ethylene vinyl acetate copolymers may also be
used as long as the resultant mixture falls within the described
ranges of percent vinyl acetate by weight, and melt index. It is
therefore possible to mix two ethylene vinyl acetates having
different melt indices and different percentages of vinyl acetate.
These copolymers are useful in the range from about 20% to about
50% by weight in the adhesive, preferably from about 25% to about
40%.
[0056] In addition to the components described above, the adhesive
compositions of the present invention may optionally comprise a
second EVA copolymer, specifically one containing about 28 weight
percent by weight of vinyl acetate and having a melt index of about
6 to 40 dg/min. The preferred copolymers are available from Exxon
under the designation ESCORENE UL 7740 and contain approximately 28
weight percent vinyl acetate by weight and have a melt index of
about 40 dg/min. The amount of this copolymer present in the
adhesive varies from about 1 to 25 weight percent by weight,
preferably 5 to 20% by weight.
[0057] The present invention also contemplates the addition to the
adhesive of a polymeric additive selected from the group consisting
of ethylene methyl acrylate polymers containing 10 to 28 weight
percent by weight methyl acrylate, ethylene acrylic acid copolymers
having an acid number of 25 to 150, methyl (meth)acrylate
copolymers, polyethylene, polypropylene, poly(butene-1-co-ethylene)
polymers and low molecular weight and/or low melt index ethylene
n-butyl acrylate copolymers. When such additive is present, it is
present in amounts up to about 15 weight percent by weight of
composition.
[0058] The adhesives of the present invention preferably also
contain a stabilizer or antioxidant. Among the applicable
stabilizers or antioxidants include those discussed above in
connection with the ethylene n-butyl acrylate copolymer based
adhesives.
[0059] The adhesive may optionally comprise an organic phosphoric
acid ester selected from the group consisting of tricresyl
phosphate, tri-isopropyl phenyl phosphate, tributyl phosphate,
triethyl phosphate, trimethyl phosphate, trioctyl phosphate or
diphenyl phosphate.
[0060] The ethylene vinyl acetate based adhesive also comprise
tackifiers and wax. The tackifiers and wax for use herein are the
same as those described above for use with ethylene n-butyl
acrylate based copolymer based adhesives. Preferably the tackifier
is KRYSTALEX.RTM. 3085, a low molecular weight thermoplastic
hydrocarbon polymer derived largely from alpha-methylstyrene which
has a Ring and Ball softening point of 85.degree. C. and is
available from Hercules Inc. The preferred wax is paraffin wax with
a melting point of 150.degree. C.
[0061] Depending on the contemplated end uses of the adhesives,
other additives such as plasticizers, pigments and dyestuffs
conventionally added to hot melt adhesives may be included. In
addition, small amounts of additional tackifiers and/or waxes such
as microcrystalline waxes, hydrogenated castor oil and vinyl
acetate modified synthetic waxes may also be incorporated in minor
amounts, i.e., up to about 10 weight percent by weight, into the
formulations of the present invention.
[0062] IV. Polyethylene
[0063] The polyethylene polymers useful in this embodiment are
those having a melt index of about 5000 to 2000 at 190.degree. C.
The polymers will have a Ring and Ball softening point of
110.degree. C. or less and a density of about 0.900 to 0.930. A
preferred polymer is EPOLENE C10 from Eastman Chemical which has a
melt index of 2,250, a Ring and Ball softening point of 104.degree.
C., and a density of 0.906. The amount of the polymer present in
the adhesive will vary from 30 to 60% by weight, preferably 50% by
weight. In addition, small amounts of additional polymers may be
included.
[0064] The tackifying resins useful in these adhesive compositions
are the aliphatic or mixed aliphatic aromatic resins such as the
terpenes, and styrenated terpenes. Preferred is ECR 179G from Exxon
which has a Ring and Ball softening point of 90.degree. C.
[0065] The polyethylene adhesives also include a paraffin or
microcrystalline wax with a Ring and Ball softening point of 130 to
200.degree. F. such as, for example, MICROSERE 599 form IGI Bolder
which as a Ball and Ring of 195.degree. F. The wax component is
utilized at levels of 0 to 30% by weight, preferably 10% by weight,
of the adhesive. Other optional waxes may be included in small
amounts.
[0066] The polyethylene adhesives may also include an antioxidant,
such as those described above in Section II above.
[0067] The adhesive compositions of the present invention are
prepared by blending the components in the melt at a temperature of
about 121.degree. C. until a homogeneous blend is obtained,
approximately two hours. Various methods of blending are known in
the art and any method that produces a homogeneous blend is
satisfactory.
[0068] The resulting adhesives are characterized by a viscosity
less than about 3000 cps at 135.degree. C. They may be applied at
temperatures of 200 to 300.degree. F. (930.degree. C. to
149.degree. C.) to provide superior adhesive bonds even when
exposed to a wide variety of temperature conditions. The adhesives
possess excellent heat stability as characterized by the 260 hour
250.degree. F. (121.degree. C.) thermal stability test, which shows
no signs of char, skinning or gel formation. In fact some
formulations show thermal stability up to 400 hours at 250.degree.
F. (121.degree. C.)
[0069] V. Blends
[0070] The present invention also contemplates that the adhesives
may be a blend of any of the above described polymers or
copolymers. For example, the base polymer in the adhesive may be a
blend of EnBA and EVA polymers. Other blends include polyethylene
and EVA blends, and poly .alpha.-olefin and EVA blends. These and
any other combination of polymers could be used as the base
adhesive, with the additional ingredients chosen according to the
polymers selected.
[0071] VI. Preferred Embodiments
[0072] Any hot melt adhesive which can be applied at the relatively
lower temperatures below 300.degree. F. can be used in the present
invention wherein a low application temperature adhesive is applied
to at least one longitudinal edge of porous and/or non porous plug
wrap paper. One most preferred embodiment of an adhesive for the
present invention is an adhesive consisting of:
[0073] a) 31 parts paraffin wax with a softening point of
150.degree. F.;
[0074] b) 21 parts ethylene vinyl acetate copolymer with a melt
index of 400 and a vinyl acetate content of 28%;
[0075] c) 11 parts or ethylene vinyl acetate copolymer with a melt
index of 43 and a vinyl acetate content of 28%;
[0076] d) 37 parts of alpha-methyl styrene tackifying resins;
and
[0077] e) 0.5 parts of an antioxidant stabilizer.
[0078] Another preferred example of a hot melt adhesive usable in
the present invention is an adhesive comprising:
[0079] a) 50 parts polyethylene such as EPOLENE C-10 from Eastman
Chemicals;
[0080] b) 40 parts of an aliphatic-aromatic hydrocarbon tackifying
resin;
[0081] c) 10 parts of a microcrystalline wax with a softening point
of 195.degree. F. such as MICROSERE 5999; and
[0082] d) 0.2 parts of an antioxidant stabilizer such as LOWINOX
(BHT) from Great Lakes Chemicals.
[0083] The resultant adhesives are characterized by viscosities of
less than about 5000 cps at 121.degree. C., a Ring and Ball
softening point of about 80.degree. C. to about 115.degree. C.,
fiber tearing bonds on plugwrap paper in the range of about
0.degree. F. to about 120.degree. F. (-18.degree. C. to 51.degree.
C.).
[0084] The following examples are merely exemplary, and not
intended to limit the scope of the present invention in any
manner.
EXAMPLES
[0085] In the following examples, which are provided for
illustrative purposes only, all parts are by weight and all
temperatures in degrees Celsius unless otherwise noted.
[0086] In the examples, all adhesive formulations were prepared in
single blade miser heated to 135.degree. C. by blending the
components until homogeneous.
[0087] The adhesives were then subjected to various tests
simulating the properties needed for successful commercial
applications.
[0088] Melt viscosities of the hot melt adhesives were determined
on a Brookfield Model RVT Thermosel viscometer using a number 27
spindle.
[0089] Test specimens for determining elevated temperature peel and
shear strengths were prepared as follows: an adhesive bead was
applied at 121.degree. C. to a strip of 50 pound Kraft paper 1 inch
wide by 3 inches long across the width of the paper. A second piece
of Kraft paper of the same dimensions was immediately placed over
the first piece and 200 gram weight placed on top of the composite
construction. The compressed adhesive bead width was 1/2 inch.
[0090] Elevated temperature peel and elevated temperature shear
were determined by attaching a 100 gram weight to each specimen and
placing the specimens in a forced-draft oven. The temperature was
raised in 5.5.degree. C. (10.degree. F.) increments from 38.degree.
C. the specimens remained at a given temperature for 15 minutes for
conditioning. The heating cycle was run until the final bond
failed. Each peel and shear specimen was prepared and tested in
duplicate. The elevated peel and shear value shown is the average
temperature of failure for the two bonds. In some cases, the sample
failed as the temperature was being adjusted within the 10.degree.
increments and is noted as such.
[0091] Adhesion at various temperatures, as noted, was determined
by applying a 1/4 inch wide bead of adhesive widthwise to a 2 inch
by 3 inch piece of non porous plug wrap paper and immediately
bringing a second piece of paper into contact. The bond is aged at
each temperature for 24 hours. The bonds were separated by hand and
a determination of the amount of fiber tear (FT) was noted.
[0092] Bleed through was measured using porous plug wrap paper.
This test is done to measure staining of the paper by the adhesive.
Six 2.times.1" sheets of plug wrap paper were stacked. An adhesive
bead, 1/4" wide was applied between the center two sheets, and aged
at 110.degree. F. (43.degree. C.) for 24 hours. The bleed of the
adhesive to the top and bottom sheets was noted.
[0093] Open time/set time was measured on a automated bond tester
using a 0.04"uncompressed bead applied to corrugated single-walled
65 lb. Open time measures that amount of time the product can
remain open, i.e., achieve 100% fiber tear, with ten seconds
compression time. Set time is the amount of time necessary to
compress and achieve 100% fiber tear with 1 second open time.
[0094] Triacetin resistance was measured after soaking the adhesive
bond for 24 hours in triacetin.
Example 1
[0095] In this example, conventional plug wrap adhesives were
compared to the low application temperature adhesives of the
present invention. Comparative Samples A and B are conventional
plugwrap adhesives which are applied at 350.degree. F. (177.degree.
C.). Samples 1-4 are in accordance with the present invention, and
are applied at 250.degree. F. (121.degree. C.). The formulations of
the adhesives studied are shown below:
[0096] Sample A: is a commercially available EVA based hot melt
adhesive from National Starch and Chemical Company under the
designation 34-2760.
[0097] Sample B: is a commercially available EVA based hot melt
adhesive from National Starch and Chemical Company under the
designation 34-2757.
1 Sample 1: Amount (% by weight) Hindered phenol (antioxidant) 0.5
Paraffin wax 150.degree. F. 31 ESCORENE UL 7710 21 (EVA, MI 400
dg/min, 28% VA) ESCORENE UL 7740 11 (EVA, MI 40 dg/min, 28% VA)
KRISTALEX 3085 37 (.alpha.-methyl styrene, 85.degree. C.) Sample 2:
BHT (antioxidant) 0.5 EPOLENE C10, 104.degree. C. 50 (polyethylene
polymer) ECR 179G 40 (hydrocarbon resin) microcrystalline wax.
195.degree. F. 10 Sample 3: Hindered phenol (antioxidant) 0.5
Paraffin wax, 150.degree. C. 31 EXXON XW 23-AH 21 (EnBA, 33% BA, MI
300 dg/min) ELF AUTOCHEM 35BA40 11 (EnBA, 33% BA, MI 40 dg/min)
KRISTALEX 3085 37 (.alpha.-methyl styrene, 85.degree. C.) Sample 4:
Hindered phenol (antioxidant) 0.5 Paraffin wax, 150.degree. C. 35
Polyalpha olefin 30 EASTOTAC H100-R, 100.degree. C. 35
[0098] The results are shown below in Table 1:
2TABLE 1 Sample A Sample B Sample 1 Sample 2 Sample 3 Sample 4
Viscosity @ appl .about.4400 cps .about.2735 cps .about.2390 cps
.about.3600 cps .about.3025 cps .about.2820 cps Adhesion @ appl
temperature RT 100, 50% 100, 50% 100% 100% 100% 100% 40.degree.
100% 100% 100% 100% 100% 100% 100.degree. 100% 75, 50% 100% 100%
100% 100% Bleed Slight Slight Very Slight Very Slight Slight Slight
through @ 100.degree. F. Triacetin 0% Fiber 25% Fiber 0% Fiber 80%
Fiber 0% Fiber 0% Fiber resistance 24 hrs. Tear Tear Tear Tear Tear
Peel/Shear Adj 130.degree./ Adj 130.degree./
110.degree./150.degree. F. Adj 110.degree./ Adj 100.degree./ Adj
100.degree./ Adj 190.degree. F. Adj 190.degree. F. 190.degree. F.
150.degree. F. Adj 150.degree. F. Stability 260 hrs. @ 350.degree.
F. @ 350.degree. F. @ 250.degree. F. @250.degree. F. @250.degree.
F. Char V. Slight None None None None None ER None None None None
None None Other None SI. Hazy None None St. None Delta visc.
.vertline.51.0% -24.0% 1.4% 13.3% Separation 2.1% -0.9% 04" bead
width @appl 1.7 secs 1.0 secs 2.0 secs 4.0 secs 1.5 secs 2.0 secs
Temp Open Time with 10 sec compression Set Time with 1 sec open
time Partial FT = 1.3 Partial FT = 4.0 Partial FT = 0.7 Partial FT
= 0.7 Partial FT = 1.5 Partial FT = 2.0 secs secs secs secs secs
secs Full FT = 3.3 Full FT = NA Full FT = 2.0 Full FT = 1.1 Full FT
= 6.0 Full FT = 4.3 secs secs secs secs secs
[0099] The results in Table 1 above, show that the low application
temperature adhesives, Samples 1, 2, 3 and 4, have good adhesion
comparable to the conventional adhesives. Samples 1 and 2 are
superior in bleed through, and have good thermal stability. The
large viscosity change observed with Samples A and B at 260 hours
indicates that these adhesives are not stable; the EVA is
degrading. Sample 2 shows excellent fiber tear even after 24 hours
of exposure to triacetin.
[0100] A significant difference between the adhesives of the
present invention and conventional adhesives is that the adhesives
of the present invention have a long open time and a fast set time
allowing for wet out and quick set prior to the cutting step of the
cigarette making process.
* * * * *