U.S. patent application number 11/071088 was filed with the patent office on 2005-06-30 for cleanly removable tapes and methods for the manufacture thereof.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Kobe, James J., Narum, Timothy N., Pereyra, Rodger J., Zhou, Zhiming.
Application Number | 20050142359 11/071088 |
Document ID | / |
Family ID | 28674356 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050142359 |
Kind Code |
A1 |
Narum, Timothy N. ; et
al. |
June 30, 2005 |
Cleanly removable tapes and methods for the manufacture thereof
Abstract
The present invention provides a fire retardant, multi-layer
article, comprising: a first adhesive layer comprising a pressure
sensitive adhesive; a core layer having an outer surface, the first
adhesive layer adhered to at least a portion of the outer surface;
a fire retardant disposed in at least one of the first adhesive
layer or the core layer, the fire retardant comprising a brominated
phosphate and being essentially free of antimony fire retardants
and polybrominated biphenyls; and the tape being cleanly
removable.
Inventors: |
Narum, Timothy N.; (Lake
Elmo, MN) ; Kobe, James J.; (Newport, MN) ;
Pereyra, Rodger J.; (Cottage Grove, MN) ; Zhou,
Zhiming; (Woodbury, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
28674356 |
Appl. No.: |
11/071088 |
Filed: |
March 3, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11071088 |
Mar 3, 2005 |
|
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10118120 |
Apr 8, 2002 |
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6866928 |
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Current U.S.
Class: |
428/343 ;
428/345; 428/354 |
Current CPC
Class: |
C09J 7/22 20180101; C09J
2301/124 20200801; C09J 2301/308 20200801; Y10S 428/921 20130101;
C09J 7/38 20180101; Y10S 428/92 20130101; Y10T 428/28 20150115;
Y10T 428/2891 20150115; Y10T 428/2848 20150115; Y10T 428/14
20150115; Y10T 428/2809 20150115; C09J 9/00 20130101; Y10T 428/2813
20150115 |
Class at
Publication: |
428/343 ;
428/345; 428/354 |
International
Class: |
B32B 007/12 |
Claims
We claim:
1. A fire retardant, multi-layer article, comprising: a first
adhesive layer comprising a pressure sensitive adhesive; a core
layer having an outer surface, the first adhesive layer adhered to
at least a portion of the outer surface; a fire retardant disposed
in at least one of the first adhesive layer or the core layer, the
fire retardant comprising a brominated phosphate and being
essentially free of antimony fire retardants and polybrominated
biphenyls; and the tape being cleanly removable.
2. The article of claim 1 wherein the fire retardant is disposed in
the first adhesive layer and the core layer.
3. The article of claim 1 wherein the fire retardant further
comprises an intumescent fire retardant.
4. The article of claim 1 wherein the core layer comprises an
adhesive.
5. The article of claim 4 wherein the adhesive comprises a pressure
sensitive adhesive.
6. The article of claim 1 wherein the core layer comprises a
substrate.
7. The article of claim 1 wherein the brominated phosphate is
tris(tribromoneopentyl)phosphate.
8. The article of claim 1 further comprising a second adhesive
layer, wherein the outer surface comprises a first major surface
and a second major surface, the first adhesive layer being adhered
to the first major surface, and the second adhesive layer being
adhered to the second major surface.
9. The article of claim 8 wherein the first adhesive layer and the
second adhesive layer have differentiated adhesion.
10. The article of claim 1 wherein the article is selected from the
group consisting of a multi-layer tape, a multi-layer sheet,
adhesive transfer tape, single-sided tape, double-sided tape, and
substrate onto which the first adhesive layer has been directly
applied.
11. The article of claim 1 wherein the article is a multi-layer
tape and wherein the multi-layer tape has been exposed to radiation
from an electron beam source to crosslink the core and/or to
crosslink the first adhesive layer.
Description
[0001] This application is a continuation of U.S. Ser. No.
10/118,120, filed Apr. 8, 2002, now allowed, the disclosure of
which is herein incorporated by reference.
[0002] The invention relates to a fire retardant, multi-layer
article, that is cleanly removable and, in some embodiments,
suitable for joining two substrates or for securing a floor
covering, such as carpet, to a substrate.
BACKGROUND OF THE INVENTION
[0003] Adhesive materials, including pressure sensitive adhesives
(PSAs), are commercially available for use in any of a variety of
applications and industries such as in the construction of mounting
tapes, carpet tapes and the like. Some carpet tapes comprise a
backing, such as, for example, a cloth or film backing, with an
adhesive coating on each of the major surfaces of the backing.
Adhesives used in carpet tape applications have typically been
pressure sensitive adhesives having (1) aggressive and permanent
tack, (2) adherence to both a substrate and an adherend (e.g., a
carpet backing) with no more than finger pressure, and preferably
(3) being removable from the adherend. Pressure-sensitive adhesive
tapes, such as carpet tapes, provide a strong bond to substrates
because separation of the tapes from the substrates is neither
intended, nor desired. When removal of the carpet is desired,
pressure sensitive carpet tapes made with aggressively tacky PSAs
have been very difficult to remove from a substrate and may result
in damage to the substrate or may leave a tacky adhesive residue.
Substrate damage is especially problematic for aerospace carpet
tape applications where the substrate, e.g., a floor panel, may be
costly to replace. Moreover, during the life of a carpet, dirt is
ground into the carpet fabric and, over time, penetrates through
the carpet to damage the underlying tape by causing nicks, cuts or
small tears in the tape backing. When the carpet is subsequently
removed, the damage to the backing can cause the tape to break,
making it more difficult to remove from the substrate.
[0004] Some pressure sensitive adhesives have been specifically
formulated to allow clean and easy removal from substrates after
use, such as, for example, the adhesive used for Post-It.RTM. brand
removable notes, available from Minnesota Mining and Manufacturing
Company of St. Paul, Minn. These adhesives, however, do not possess
sufficient tack to provide a level of holding power sufficient for
use in carpeting applications, for example. In general, adhesives
that are formulated to provide a substantial level of adhesion,
e.g., for holding a carpet to a substrate, are difficult to remove
from a substrate without significant effort.
[0005] U.S. Pat. No. 4,024,312 discloses a film backed, normally
tacky and pressure-sensitive adhesive tape which is highly
extensible and highly elastic. The tape can be removed from a
surface to which it has been applied by stretching it lengthwise in
a direction substantially parallel to the plane of the surface. The
film backing is formed from a composition comprising elastomeric
and thermoplastic A-B-A block copolymers and possesses a lengthwise
elongation to break of at least about 200%, and a 50% rubber
modulus of not above about 2,000 lbs/sq. inch. This low rubber
modulus is stated to be an important factor in insuring easy
stretchability and easy removal of the tape at high elongations.
The elasticity of the backing is important for conformability and
other purposes, and the elastic recovery from 50% stretch is stated
as at least about 75%, more preferably at least about 90%.
[0006] German (OS) 3331 016 A1 discloses another adhesive tape for
removable adhesive bonds, whereby the tape exhibits high elasticity
and low plasticity. The adhesive strength is less than the cohesive
strength, and the adhesion capability essentially disappears as the
film is being stretched. The ratio of peel force to tear strength
of the tape is about 1:2 or greater, and the adhesive bond can be
released by pulling the film in the direction of the plane of the
adhesive joint. The tape is used as a load-resistant adhesive to
bond two rigid solid substrates. A separation of the adhesively
bonded materials is possible without damage to the substrate.
[0007] The pressure sensitive adhesives described in U.S. patent
application Ser. No. 09/764,478 comprise a fibrous reinforcing
material. The patent application describes the fibrous
reinforcement of pressure sensitive adhesives to provide "stretch
removable" characteristics. The fiber reinforced adhesive
composition comprises a pressure sensitive adhesive matrix with a
fibrous reinforcing material therewithin. The fiber reinforced
adhesive composition is described as providing improved cohesive
strength over the pressure sensitive adhesive alone, while the tack
of the pressure sensitive adhesive remains substantially unreduced
by the presence of the fibers.
[0008] In applications for tapes and other articles, a fire
retardant feature may be needed and, in certain applications, may
be required by applicable regulations. For example, tapes for
electric or electronic applications may be directly exposed to
electrical current, to short circuits, and/or to heat generated
from the use of the associated electronic component or electrical
device. Consequently, industry standards or regulations may impose
conditions on the use of such tape articles that require qualifying
tests be performed on the tapes such as burn tests, and the like.
For electrical and electronics applications, the industry standard
flammability test is Underwriters Laboratories (UL 94 "Standard for
Tests for Flammability of Plastic Materials for Parts in Devices
and Appliances"). For rail transit applications, the industry
standard is American Society for Testing and Materials ASTM E662
("Test Method for Specific Optical Density of Smoke Generated by
Solid Materials") and ASTM E162 ("Test for Surface Flammability of
Materials Using a Radiant Energy Source").
[0009] For aerospace applications, the testing criteria for the
Federal Aviation Administration F.A.R. .sctn. 25.853 (July 1990)
vertical burn test, subparagraph (a)(1)(i), relates to interior
compartments occupied by crews or passengers, including interior
ceiling panels, interior wall panels, partitions, galley
structures, large cabinet walls, structural flooring, and materials
used in the construction of stowage compartments. F.A.R. .sctn.
25.853 (July 1990) subparagraph (a)(1)(ii) relates to carpet tapes,
seat cushions, padding, decorative and non-decorative coated
fabrics, leather, trays and galley furnishings, electrical conduit,
thermal and acoustical insulation and insulation covering air
ducting, joint and edge covering and the like. Materials used for
these applications must be self-extinguishing when tested
vertically in accordance with the procedures of F.A.R. .sctn.
25.853 (July 1990) (a)(1)(i) and (a)(1)(ii). In addition for both
rail transit and aerospace applications, another industry standard
is Boeing Specification Support Standard, BSS 7239 ("Test Method
for Toxic Gas Generation by Materials of Combustion") which
requires analysis of combustion gases and has specified
concentration limits on toxic gases which currently include HCN,
NO.sub.x, CO, HCl, HF, and SO.sub.2.
[0010] In particular, carpet tapes for aerospace applications are
presently defined by the Boeing Material Specification BMS 5-133C
and are classified according to the following:
[0011] Type II, Class 1--Maximum weight 16 oz/yd2, white color;
[0012] Type II, Class 2--Maximum weight 16 oz/yd2, black color;
[0013] Type III--Maximum weight 24 oz/yd2, white color;
[0014] Type IV, Class 1--Differential tack, maximum weight 5.0
oz/yd2, black color on side 2; and
[0015] Type IV, Class 2--Differential tack, maximum weight 9.0
oz/yd2, black color on side 2.
[0016] This specification lists key tests and requirements for each
of the different Types. The specification includes weight,
flammability according to F.A.R. .sctn. 25.853 (July 1990)
(a)(1)(i) (12 Second Vertical Burn), tensile strength, peel
strength, lap shear strength, corrosion to aluminum, and release
liners.
[0017] In order to meet the requirements imposed on them in such
applications, tapes and other articles may be made with materials
that are naturally resistant to fire as well as materials that have
been processed or manufactured to impart a fire retarding or fire
resistant quality by incorporating fire retardant agents and the
like. Current carpet tapes for aerospace applications utilize the
fire retardants antimony trioxide and polybrominated biphenyls,
specifically, decabromodiphenylether (deca-BDE). However, European
authorities have recommended a ban of some of the polybrominated
biphenyls as soon as Jul. 1, 2003. Such a ban will necessitate
redesigned, reformulated tapes. Also in Europe, the Waste from
Electrical and Electronic Equipment directive has proposed that
halogenated flame retardants and certain other materials be phased
out by January 2004.
[0018] Two key features are driving the need for an improved fire
retardant carpet tape invention for aerospace industry.
[0019] 1. Environment regulations requiring acceptable fire
retardant systems; and
[0020] 2. Clean removable tapes which effectively and efficiently
improve the removal process and eliminate damage to floor
substrates and which do not leave adhesive residue.
[0021] Cleanly removable tapes would provide a cost saving to the
aerospace industry and would reduce or eliminate the need to use
solvents to remove adhesive residues. Fire retardant carpet tapes
will eventually be required to meet the new environmental
legislation being adopted in Europe and around the world.
[0022] It would be desirable to provide pressure sensitive adhesive
tapes and methods for the manufacture of such tapes. More
specifically, it would be desirable to provide pressure sensitive
adhesive tapes in the form of multi-layer tapes, such as,
double-sided tapes, and the like that can be easily cleanly removed
from a substrate without leaving significant adhesive residue. It
would be especially desirable to provide these pressure sensitive
adhesive tapes in a form that permits their removal from a
substrate using a stretch-release mechanism, and wherein the tapes
are fire retardant and satisfy government and/or industry
flammability regulations.
SUMMARY OF THE INVENTION
[0023] In one aspect, the invention provides a fire retardant,
multi-layer article, comprising:
[0024] a first adhesive layer comprising a pressure sensitive
adhesive;
[0025] a core layer having an outer surface, the first adhesive
layer adhered to at least a portion of the outer surface;
[0026] a fire retardant disposed in at least one of the first
adhesive layer or the core layer, the fire retardant comprising a
brominated phosphate and being essentially free of antimony fire
retardants and polybrominated biphenyls; and
[0027] the tape being cleanly removable.
[0028] In describing the features of the present invention, certain
terms used are intended to be interpreted in a manner consistent
with their usage by those skilled in the art. By way of example,
and not limitation, the following meanings are set forth:
[0029] "Substantially continuous," when referring to fibers, means
that for an at least 0.5 centimeter length sample of the adhesive
composition taken in the machine direction, a substantial number of
the fibers present in the sample are unbroken.
[0030] "Intumescent fire retardant" refers to an intumescent
substance that when applied to or incorporated within a combustible
material, reduces or eliminates the tendency of the material to
ignite when exposed to heat or flame, induces charring and
liberates non-combustible gases to form a carbonific material that
protects the surrounding matrix, cuts off the oxygen supply, and
prevents dripping. Intumescent fire retardants generally comprise
an acid source, a char former, and a blowing agent.
[0031] "Fire retardant" refers to a substance that when applied to
or incorporated within a combustible material, reduces or
eliminates the tendency of the material to ignite when exposed to
heat or flame.
[0032] "Cleanly removable" refers to the property of an adhesive
article characterized in that, when the article is pulled from a
surface at a rate of no greater than 30 centimeters/minute, the
article detaches from the surface of the substrate without leaving
significant visible residue, excluding discoloration, on the
surface.
[0033] "Stretch release" refers to the property of an adhesive
article characterized in that, when the article is pulled from a
surface or from between two surfaces at a rate of no greater than
about 30 centimeters/minute and at an angle of no greater than
about 45.degree., the article detaches from at least one of the
surfaces of the substrates.
[0034] The invention also includes multi-layer articles, such as
for example, multilayer tapes or sheets, adhesive transfer tapes,
single-sided tapes, double-sided tapes, double-sided tapes with
differentiated adhesion, and substrates onto which the adhesive has
been directly applied. The tapes described herein may include a
tab.
[0035] Other features and advantages of the invention will be
apparent from the following description of the preferred
embodiments thereof, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] In describing the various features of the preferred
embodiment, reference is made to the various Figures, in which like
reference numerals indicate like features and wherein:
[0037] FIG. 1 is a perspective drawing showing a tape, according to
the invention;
[0038] FIG. 2 is a perspective drawing showing a tape, according to
another aspect of the invention;
[0039] FIG. 3 is perspective drawing showing a tape according to
yet another aspect of the invention; and
[0040] FIG. 4 is a schematic drawing of an extrusion process line
suitable for the manufacture of the tapes of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0041] The invention provides a cleanly removable tape that can be
used as a joining and mounting tape such as, for example, a carpet
tape. The tapes are provided in layered constructions with stretch
release properties to enable removal from a substrate without
leaving significant residue on the surface of the substrate. The
tapes comprise a core layer and at least a first adhesive layer
adhered to at least a portion of the core layer. The tapes may be
single sided tapes or double sided tapes. Single sided tapes are
tapes having adhesive properties on one side only. Double sided
tapes are tapes having adhesive properties on both sides.
[0042] The first adhesive layer is provided as a skin adhesive on
at least a portion of a first major surface of the core layer while
the other major surface of the core layer may be provided with its
own adhesive properties. Alternatively, a second adhesive layer may
be provided to a portion of the core layer as another skin adhesive
which may be the same adhesive as the first adhesive layer, or it
may be a different than the first adhesive layer. The tapes of the
invention may be dual sided tapes in that they are adhesively tacky
on both sides of the core layer to permit the simultaneous adhesion
of the tape to two different surfaces such as an article (e.g., a
carpet backing) and a substrate (e.g., a floor).
[0043] A fibrous reinforcing material may be dispersed in the core
layer, the adhesive layer(s), or both the core layer and the
adhesive layer(s) to provide stretch release properties to the
construction. The tape of the invention may include a core layer
and a fire retardant in at least one of the adhesive layer, or the
core layer. The fire retardants most desired in the present
invention are those containing no antimony or polybrominated
biphenyls, such as, pentabromodiphenylether (penta-BDE),
octabromodiphenylether (octa-BDE), and decabromodiphenylether
(deca-BDE).
[0044] Referring to the drawings, a first embodiment of a tape 10
according to the invention is shown in FIG. 1. The tape includes a
core layer 14 in the form of a sheet having a first major surface
12 and a second major surface 13 opposite the first major surface
12. The major surfaces of the core layer 14 are typically smooth,
but one or both of the major surfaces of the tape 10 may be
provided with a texture or surface structures thereon. In the
described embodiment, the core layer 14 comprises a plurality of
viscoelastic and/or elastic microfibers 16 oriented in the
manufacturing machine direction of the tape. The microfibers 16
provide the core layer 14 and the tape 10 with stretch releasable
qualities when the tape 10 is adhered to a surface. A first
adhesive layer 18 is adhered to at least a portion of the first
major surface 12 of the core layer 14. Typically, the first
adhesive layer 18 comprises a pressure sensitive adhesive (normally
as a skin adhesive), but other types of adhesives may also be used.
Additional microfibers (not shown) may be included in the
formulation of the first adhesive layer 18 as desired to further
enhance the stretch release qualities of the tape by reinforcing
the tape, especially when the tape is thin, i.e., less than about
0.25 mm (10 mils) or when the adhesive layer has high adhesion to a
surface to which it is applied.
[0045] The core layer 14 may be provided with adhesive properties
so that the second major surface 13 of the core layer 14 has
adhesive tack suited for the intended use of the tape product. The
tackiness of the second major surface 13 is typically different
than the tackiness of the first adhesive layer 18. In carpet tape
applications, the tackiness of the first adhesive layer 18 is
generally formulated to provide a strong adhesive bond to a floor
or other substrate while the tackiness of the core layer 14 along
its second major surface 13 is formulated to provide a sufficiently
strong bond to the material used for the backing of the carpet, and
the bond between the carpet and the second major surface 13 is
normally somewhat weaker than the adhesive bond between the first
adhesive layer 18 and the floor or other substrate.
[0046] The tape 10 may also include a tab (not shown) positioned
thereon so that the tape 10 may be removed from a substrate by
pulling the tab and the tape in the direction of the oriented
microfibers 16, i.e., in the machine direction. In general, to
remove a stretch releasable tape of the invention from between two
substrates, the tape is moved by pulling on the tape or the tab in
a direction substantially parallel to the two surfaces. For
carpeting adhered to a floor, the carpet or other adhered material
is first removed from the tape by pulling the carpet or other
material from the second major surface 13 of the tape 10. The tape
10 will remain adhered to the floor along the first major surface
12 via first adhesive layer 18, and removal of the tape 10 from the
floor is accomplished by then stretching the tape in the machine
direction at an angle from about 20.degree. to about 45.degree.,
relative to the surface of the floor. Alternatively, when the
carpet or other material is pulled up from the surface of a floor,
the layers of the tape 10 may separate from one another leaving
portions of the tape 10 that can be removed from the material and
the substrate by the stretch-release mechanism.
[0047] In the removal process, a force is applied to the tape in a
direction substantially parallel to the surface of the floor or
other substrate. The removal force may be applied by gripping the
aforementioned removal tab or an end of the tape and pulling the
tape in the aforementioned direction. When sufficient force is
applied to overcome the initial yield strength, the backing or core
layer will deform. When the tape comprises viscoelastic
microfibers, the tape will initially deform and then yield as the
microfibers elongate and orient, thereby undergoing strain
hardening. In addition, orientation induced by stretching further
detackifies the adhesive layer. Stretching will thin the tape
significantly at the location where the adhesive pulls away from
the substrate. Thinning of the tape dramatically reduces the force
required to remove the tape from the substrate. Pulling the tape
from the substrate at an angle of less than about 45.degree. will
aid in the removal of the tape from the laminate. In certain
aerospace applications, the substrate can be a fiber reinforced
composite laminate or panel, and pulling the tape from the
substrate at the foregoing angle significantly reduces the
possibility that the panel surface will delaminate as a result of
the tape removal process. Following the removal of the tape, the
surface will be substantially clean with little or no visible
adhesive residue remaining thereon.
[0048] Referring to FIG. 2, another embodiment of a tape 100
according to the invention is shown and will now be described. The
tape 100 comprises core layer 114 having a first major surface 112
and a second major surface 113 and includes a plurality of
microfibers 116 in the core layer 114. A first adhesive layer 118
is adhered to the first major surface 112 of the core layer 114 and
a second adhesive layer 120 adhered to the second major surface 113
of the core layer 114. In this configuration, the core layer 114
need not be formulated as an adhesive. Both the first adhesive
layer 118 and the second adhesive layer 120 are normally provided
as pressure sensitive skin adhesives, and each of these adhesives
may be provided as the same as the other, or the skin adhesives may
be formulated differently from one another. The adhesive layers 118
and 120 are adhered to at least a portion of the major surfaces 112
and 113 of the core layer 114, and the adhesives may contain
microfibers and comprise any of a variety of adhesive materials as
are further described herein.
[0049] Referring to FIG. 3, another embodiment of a fire retardant,
cleanly removable carpet tape 200 according to the invention is
shown. The tape 200 comprises a first adhesive layer 214, a core
layer 215, a second adhesive layer 218, and a release liner 219.
The core layer 215 is positioned between first adhesive layer 214
and first side 212 of second adhesive layer 218. The release liner
219 is adjacent to and overlays the second side 213 of second
adhesive layer 218. In this configuration, both the first adhesive
layer 214 and the second adhesive layer 218 are formulated as
pressure sensitive adhesives. One or both of the first adhesive
layer 214 and the second adhesive layer 218 may contain
antimony-free and polybrominated biphenyls-free fire retardant.
Typically, the fire retardant comprises an intumescent fire
retardant, a brominated phosphate fire retardant, or a combination
of such fire retardants. The second adhesive layer 218 and the
first adhesive layer 214 may comprise any of a variety of materials
as are further described herein. The materials in this embodiment
may be selected so that the tape 200 prepared therefrom is cleanly
removable but not necessarily stretch-releasable as defined above.
Although not shown, another release liner similar to the release
liner 219 may be associated with the first adhesive layer 214.
[0050] Suitable materials for the core layer 215 include any of a
variety of films such as the polymeric films described herein.
Alternatively, the core layer 215 may comprise woven and nonwoven
materials, cloth, scrim, metallic foil, and the like. The core
layer 215 may be or may not be elastic or viscoelastic. Normally,
the core layer contains a fire retardant or is inherently fire
retardant. The thickness of the core layer 215 is typically from
about 0.0125 mm (0.0005 inch) to about 0.625 mm (0.025 inch), more
often from about 0.0125 mm (0.0005 inch) to about 0.125 mm (0.005
inches) and most often from about 0.0125 mm (0.0005 inch) to about
0.051 mm (0.002 inches). The fire retardant, cleanly removable
carpet tape described above can be prepared by any well known tape
processing method such as by coating, such as, hot melt coating,
solvent coating; lamination, hot melt extrusion and the like. In
the tape 200, the materials used in the core layer 215 and the skin
adhesives 214 and 218 are selected to be compatible with one
another and to provide a cleanly removable tape according to the
invention. If a microfiber forming resin is included in one of the
layers of the tape 200, the microfiber--containing layer is
processed in a manner that generates the microfibers in situ. If
the microfibers are present in the tape 200, the tape may be made
cleanly removable using a stretch release mechanism, as described
herein. However, it will be appreciated that the tape 200 may be
cleanly removable without including microfibers in any of the
layers of the tape. Moreover, the tape 200 may be cleanly removable
without necessarily being stretch releasable.
[0051] The skin adhesive layers used in the invention can be
applied to the surface of the core layer in a continuous or
discontinuous manner. One or more adhesives can be used in a single
skin adhesive layer. For example, a first adhesive may be pattern
coated on the surface of the core layer and a second adhesive is
thereafter coated onto the portions of the surface with no first
adhesive. Alternatively, a second adhesive could be pattern coated
onto a continuous coating of the first adhesive. Typically, the
adhesive is a pressure sensitive adhesive. Most often, the adhesive
is a hot melt pressure sensitive adhesive. A release liner may
optionally be applied over the adhesive to protect it prior to its
application to a substrate or the like. It will be appreciated that
other layers and/or structures may be applied or affixed to at
least a portion of one of the major surfaces of the core layer.
[0052] Any of a variety of materials may be used in the formulation
of a core layer for the tapes of the invention. For example,
polymeric resins, including adhesives as well as blends thereof,
may be used. Thermoplastic polymers and adhesives suitable for use
as a core layer include those that are compatible with, but
immiscible with the fibrous reinforcing material. It may be
desirable to blend two or more polymers having chemically different
compositions. The physical properties of the resulting core layer
can be optimized by varying the types of components used in
creating the tape and by varying their relative concentrations. A
particular resin is generally chosen or selected based upon the
desired properties of the final stretch releasable tape. The core
layer typically contains one or more fire retardants, as described
herein, and may be treated with adhesion promoters, binders,
antistatic materials, and the like to impart additional properties
thereto.
[0053] General criteria in the design of an acceptable general
purpose stretch release, cleanly removable tape include: (1) break
strength greater than the adhesion to the substrate such that the
tape does not break during removal; (2) a Shore A hardness less
than about 60, preferably, less than about 50, and more preferably
less than about 45; (3) the skin adhesive preferably does not
delaminate from the core layer; (4) the tape should stretch release
in a cleanly removable manner from between a pair of substrates;
(5) when the stretch release tape comprises viscoelastic
microfibers, the tensile break strength should be at least about
150% of the yield strength of the tape with an elongation greater
than about 200% and less than about 50% recovery after being
elongated 100%, and when the stretch release tape comprises elastic
fibers, the tape can have an elongation greater than about 200% and
have greater than about 50% recovery after being elongated 100%;
and (6) 90 degree peel adhesion to stainless steel or glass should
generally be greater than about 0.176 kN/m (I lbs/in), typically
greater than about 0.352 kN/m (2 lbs/in), and often greater than
0.528 kN/m (3 lbs/in).
[0054] Where the stretch releasable tape is a carpet tape, the
criteria includes: (1) a split strength greater than the adhesion
to the substrate such that the tape does not break during removal;
(2) a Shore A hardness less than about 60, preferably, less than
about 50, and more preferably less than about 45; (3) the skin
adhesive preferably does not delaminate from the core layer; (4)
the tape should be cleanly removable and should stretch release
from a floor; (5) when the stretch release tape comprises
viscoelastic microfibers, the tensile break strength should be at
least about 150% of the yield strength of the tape with an
elongation greater than about 200% and less than about 50% recovery
after being elongated 100%, and when the stretch release tape
comprises elastic fibers, the tape can have an elongation greater
than about 200% and have greater than about 50% recovery after
being elongated 100%; (6) 90 degree peel adhesion to stainless
steel or glass should generally be greater than about 0.352 kN/m (2
lbs/in), typically greater than about 0.704 kN/m (4 lbs/in), and
often greater than 1.056 kN/m (6 lbs/in); (7) room temperature
static sheer holding a minimum 250 g/in.sup.2 for at least 10,000
minutes; and (8) optionally fire retardant.
[0055] Criteria for a fire retardant, cleanly removable carpet tape
for aerospace applications includes: (1) satisfying the
requirements of Boeing Material Specification BMS 5-133C, revised
29-Sep.-1993; and (2) free from antimony based fire retardant
and/or polybrominated biphenyls fire retardants or other
environmentally unacceptable fire retardants. In the instance when
the fire retardant, cleanly removable carpet tape is additionally
stretch releasable, the tape will meet all the requirements of BMS
5-133C except tensile strength.
[0056] One group of polymers useful in the manufacture of the core
layer includes acrylate and methacrylate polymers and copolymers
and combinations thereof. Such polymers can be formed by
polymerizing one or more monomeric acrylic or methacrylic esters of
non-tertiary alkyl alcohols, with the alkyl groups having from 1 to
20 carbon atoms (e.g., from 3 to 18 carbon atoms). Suitable
acrylate monomers include methyl acrylate, ethyl acrylate, n-butyl
acrylate, lauryl acrylate, 2-ethylhexyl acrylate, cyclohexyl
acrylate, iso-octyl acrylate, octadecyl acrylate, nonyl acrylate,
decyl acrylate, and dodecyl acrylate. The corresponding
methacrylates are useful as well. Also useful are aromatic
acrylates and methacrylates, e.g., benzyl acrylate.
[0057] Optionally, one or more monoethylenically unsaturated
co-monomers may be polymerized with the acrylate or methacrylate
monomers. The amount of co-monomer may be based upon the desired
properties of the polymer. One group of useful co-monomers includes
those having a homopolymer glass transition temperature greater
than the glass transition temperature of the acrylate homopolymer.
Examples of suitable co-monomers falling within this group include
acrylic acid, acrylamide, methacrylamide, substituted acrylamides
such as N,N-dimethyl acrylamide, itaconic acid, methacrylic acid,
acrylonitrile, methacrylonitrile, vinyl acetate, N-vinyl
pyrrolidone, isobornyl acrylate, cyano ethyl acrylate,
N-vinylcaprolactam, maleic anhydride, hydroxyalkylacrylates,
N,N-dimethyl aminoethyl(meth)acrylate, N,N-diethylacrylamide,
beta-carboxyethyl acrylate, vinyl esters of neodecanoic,
neononanoic, neopentanoic, 2-ethylhexanoic, or propionic acids,
vinylidene chloride, styrene, vinyl toluene, and alkyl vinyl
ethers.
[0058] Another group of monoethylenically unsaturated co-monomers
which may be polymerized with the acrylate or methacrylate monomers
includes those having a homopolymer glass transition temperature
less than the glass transition temperature of the acrylate
homopolymer. Examples of suitable co-monomers falling within this
class include ethyloxyethoxy ethyl acrylate (Tg=-71.degree. C.) and
methoxypolyethylene glycol 400 acrylate (Tg of -65.degree. C.;
available from Shin Nakamura Chemical Co., Ltd. under the
designation "NK Ester AM-90G") and combinations thereof.
[0059] Another group of polymers useful for the core layer include
polymers that are immiscible in, but are compatible with acrylic
polymers. Examples include semicrystalline polymer resins such as
polyolefins and polyolefin copolymers (e.g., based upon monomers
having between 2 and 8 carbon atoms such as low density
polyethylene, linear low density polyethylene, ultra low density
polyethylene, metallocene polyethylene copolymer, terpolymer, and
tetrapolymer; atactic polypropylene, amorphous polypropylene and
isotactic polypropylene blend, ethylene-propylene copolymers,
etc.), polyesters and co-polyesters, polyamides and co-polyamides,
fluorinated homopolymers and copolymers, polyalkylene oxides (e.g.,
polyethylene oxide and polypropylene oxide), polyvinyl alcohol,
ionomers (e.g., ethylene-methacrylic acid copolymers neutralized
with base), and cellulose acetate and combinations thereof. Other
examples of acrylate-immiscible polymers include amorphous polymers
having a solubility parameter (as measured according to the Fedors'
technique) less than 8 or greater than 11 such as
polyacrylonitrile, polyvinyl chloride, thermoplastic polyurethanes,
aromatic epoxies, polycarbonate, amorphous polyesters, amorphous
polyamides, acrylonitrile-butadiene-styrene (ABS) copolymers,
polyphenylene oxide alloys, ionomers (e.g., ethylene-methacrylic
acid copolymers neutralized with salt), fluorinated elastomers, and
polydimethyl siloxane and combinations thereof.
[0060] Another group of polymers useful for the core layer include
thermoplastic elastomers containing ultraviolet radiation-activated
groups. Examples include polybutadiene, polyisoprene,
polychloroprene, random and block copolymers of styrene and dienes
(e.g., SBR), and ethylene-propylene-diene monomer rubber and
combinations thereof.
[0061] Another group of polymers useful for the core layer include
pressure sensitive and hot melt adhesives prepared from
non-photopolymerizable monomers. Such polymers can be adhesive
polymers (i.e., polymers that are inherently adhesive), or polymers
that are not inherently adhesive, but are capable of forming
pressure sensitive adhesive compositions when compounded with
tackifiers. Specific examples include poly-alpha-olefins (e.g.,
polyoctene, polyhexene, and atactic polypropylene), tackified block
copolymer-based adhesives, natural and synthetic rubbers,
silicones, ethylene-vinyl acetates, polyurethanes, and
epoxy-containing structural blends (e.g., epoxy-acrylate and
epoxy-polyester blends) and combinations of the foregoing.
[0062] As described above, the core layer includes a plurality of
elastic, viscoelastic, or combination of elastic and viscoelastic
microfibers that reinforce the core layer while also providing the
tape with stretch release properties. Optionally, the elastic,
viscoelastic, or combination of elastic and viscoelastic
microfibers may also be included in both the core layer and skin
adhesive layers. The microfibers are generated in situ from polymer
resins during the manufacture of the core layer. Suitable
microfibers include those formulated according to the teachings of
pending U.S. patent application Ser. No. 09/764,478, incorporated
in its entirety herein by reference thereto.
[0063] In specific embodiments, the reinforcing microfibers are
viscoelastic and comprise semi-crystalline polymers (e.g., having
both amorphous and crystalline domains). Specific embodiments that
incorporate semi-crystalline polymers include polycaprolactone
(PCL), polybutene (PB), copolymers derived from ethylene and at
least one other alpha-olefin monomer (e.g.
poly(ethylene-co-1-alkene) and
poly(ethylene-co-1-alkene-co-1-alkene)), ultra low density
polyethylene such as is commercially available under the trade
designation ATTANE 4202 from Dow Chemical Co. having a density
below 0.915 grams/cubic centimeter, metallocene copolymers such as
the commercially available ENGAGE series available from Dupont-Dow
Elastomers, or the metallocene polyolefins such as those known
under the trade designation EXACT 3024, 3040 and 3139 (available
from ExxonMobil Chemical Company), linear low density polyethylene
(e.g. having a density between 0.915 and 0.94 grams/cubic
centimeter, such as those available from ExxonMobil Chemical
Company under the designations LL-3003, ECD-125, 377D60, 369G09,
363C32, 361C33, 357C32, 350D65, 350D64, 350D60, LL-3013, and
LL-3001, and the those known under the trade designation DOWLEX
available from Dow Chemical Co.
[0064] In other embodiments, the reinforcing microfibers are
elastic. Examples of suitable reinforcing elastic microfibers
include thermoplastic elastomers such as for example those
comprising polyurethane, synthetic block copolymers, and
combinations of the foregoing materials.
[0065] The viscoelastic reinforcing microfiber materials will
generally have a measurable yield strength. In certain embodiments,
the yield strength of the reinforcing material is less than about
30 MPa. The tensile break strength of the viscoelastic reinforcing
microfiber material is typically at least about 150% of its yield
strength. In specific embodiments, the tensile break strength
(measured according to ASTM D 882-97 at a crosshead speed of 12
inches/minute (30 centimeters/minute)) of the reinforcing
microfiber material is higher than the tensile break strength of
the skin adhesive and/or the core layer. Elastic reinforcing
microfiber material should have greater than about 50% recovery
after being elongated 100%. The reinforcing microfiber material
should have a melting point above the use temperature of the skin
adhesive composition and should have a melting point above the
storage temperature of the adhesive composition or any tape made
with the adhesive composition.
[0066] Most typically, the reinforcing microfiber material exists
as substantially continuous fibers in the core and/or in adhesive
layer. Specifically, according to one aspect of the invention, the
microfibers are unbroken for at least about 0.5 centimeters in the
machine direction of the adhesive or the core layer, preferably at
least about 2 centimeters. In other desired embodiments, the
substantially continuous microfibers are continuous for at least
about 5 centimeters and desirably are at least about 8 centimeters.
According to another aspect of the invention, the substantially
continuous microfibers generally have a maximum diameter of about
0.05 to about 5 micrometers, typically from about 0.1 to about 1
micrometer. According to another aspect of the invention, the
aspect ratio (i.e. the ratio of the length to the diameter) of the
substantially continuous microfibers is greater than about 1000. In
general, the polymeric material of the core layer will comprise
from about 80 to about 50 weight % of the tape while the fibrous
reinforcing material will comprise from about 20 to about 50 weight
% of the tape. When the amount of fibrous reinforcing material
comprises typically from about 40 to about 50 weight % of the final
tape article, the tape may have a lower split strength or a weaker
bond between the core layer and the skin layer(s). This provides
another method of removal by splitting the tape, and stretch
releasing each portion individually. This removal method can be
advantageous when tapes are used between two large surfaces.
[0067] It has been found that a suitable stretch release chemistry
useful in the present invention comprises viscoelastic microfibers
of certain homopolymers, copolymers, terpolymers, and tetrapolymers
of polyalkylene resins including copolymers of polyoctene-ethylene
and/or polyhexene-ethylene and the like. The microfibers will form
in situ during the manufacturing process to provide a tape and/or
adhesive material that will stretch, strain-harden and release
during removal from a substrate without breakage. In general, and
without limitation, C.sub.3-C.sub.10 copolymers with ethylene are
suitable for use in the invention. The foregoing
polyoctene-ethylene and/or polyhexene-ethylene copolymers are
compatible, but immiscible with many acrylic and rubber/resin based
block copolymer adhesives and can be blended in a twin screw
extruder, as described herein, to generate the microfibers in
situ.
[0068] In certain applications such as in aerospace applications
and the like, the tapes of the invention may be provided with fire
retardant properties. Fire retardants suitable for inclusion in the
tapes of the present invention include intumescent fire retardants
and/or non-intumescent, antimony free fire retardants which can be
present in any layer of the tape, but are generally present in the
core layer and the skin adhesive layer(s) of the tape at a
concentration of between about 20 wt. % and about 60 wt. % based on
the total weight of the tape. If the fire retardant is present in
the skin adhesive layer, it is normally present in an amount less
than about 50 wt. % of the weight of the skin adhesive layer, more
typically less than about 40 wt. % and most often less than 30 wt.
%. Examples of suitable fire retardants for use in the tapes
described herein include those commercially available from Clariant
Corporation of Charlotte, N.C., under the designation EXOLIT,
including those designated IFR 23, AP 422, AP 423, AP 452(TP), AP
462, AP 740(TP), AP 750, AP 751 (TP), and AP 752(TP), all of which
are non-halogenated fire retardants comprising ammonium
polyphosphate and/or synergists. Synergists are other fire
retardant materials that, when combined with another fire
retardant, provide enhanced fire retardant properties greater than
the additive properties of the two fire retardant materials. EXOLIT
OP grade materials, such as, OP 550, OP 910, OP 920(TP), OP
921(TP), OP 1100(TP), EXOLIT 5060, EXOLIT 5073, EXOLIT 5085(VP),
and EXOLIT 5087, also from Clariant Corporation, based on
organophosphorous compounds are also useful as well as EXOLIT RP
grades of red phosphorus materials, such as, RP 622, RP 650, RP
652, RP 654, RP 658, RP 659(TP), RP 683(TP), RP 689(TP), RP 692, RP
693, and RP 694. Other non-halogenated fire retardants that may be
used include FIREBRAKE ZB and BORGARD ZB which are zinc borate and
zinc borate hydrate respectively, ammonium
borate/diborate/tetraborate tetrahydrate, ammonium
pentaborate.times.8H.sub.2O, FYREX which is a mixture of diammonium
and monoammonium phosphate, available from Akzo Nobel, Gallipolis
Ferry, West Va.; triphenyl phosphate, di-melamine phosphate,
potassium bicarbonate, potassium aluminum sulfate, MELAPUR 25 and
MELAPUR p-46 which are both melamine cyanurates; MELAPUR 200 which
is melamine polyphosphate, all three of which are available from
DSM Melamine Americas, Inc. Westwego, La.; AMGARD NH which is
melamine phosphate, ANTIBLAZE NP which is alkyl amine phosphate,
ANTIBLAZE NK which is alkyl amine phosphate salt, ANTIBLAZE MC
which is ammonium polyphosphate, and AMGARD NP which is ethylene
diamine phosphate, all of which are available from Albright &
Wilson Americas Inc., Richmond, Va.; REOGARD 1000 which is a
proprietary intumescent fire retardant which is available from
Great Lakes Chemical Corp., West Lafayette, Ind.; aluminum
trihydrate (ATH), magnesium oxide, and magnesium hydroxide. Useful
halogenated phosphate fire retardants that may be used include TCEP
(tris(2-chloroethyl)phosphate) and TCPP
(tris(2-chloroisopropyl)phosphate) both of which are available from
Clariant Corporation, and FR 370 (tris(tribromoneopentyl)phosphate)
available from Dead Sea Bromine Group, Beer Shiva, Israel. Further
examples of useful fire retardants that are non-intumescent are
described in U.S. Pat. No. 6,022,914 (Nowak et al.) and intumescent
fire retardants that are described in U.S. Pat. No. 5,851,663
(Parsons et al.) both of which are incorporated herein by
reference.
[0069] Blends of one or more fire retardants may also be used in
the tapes of the invention. Suitable blends include blends of
EXOLIT AP 750 and FR370 and EXOLIT IFR 23 and FR 370 in a weight
ratio ranging from about 5:95 to about 95:5, and blends of
mono-ammonium phosphate, ammonium sulfate, and magnesium aluminum
silicate available as FORAY from Ansul Incorporated. Blends of one
or more fire retardants and a synergist may also be used in the
tapes of the invention. Suitable synergists include talc, magnesium
compounds, zinc compounds such as zinc borate, Fe.sub.2O.sub.3,
MoO.sub.3, special zeolite, boroxo siloxane elastomer, which are
discussed in article "Influence of Modified Rheology on the
Efficiency of Intumescent Flame Retardant Systems", P. Anna et al.,
Polymer Degradation and Stability, Vol. 74 (3), 2001, pp. 423 to
426. A synergist for both brominated and phosphorus fire retardants
is CIBA FLAMESTAB NOR 116 fire retardant material available from
Ciba, Tarrytown, N.Y. There appears to be a synergy between the
ammonium polyphosphate based intumescent fire retardants with
brominated phosphate, melamine phosphate, and/or melamine
polyphosphate fire retardants. While halogenated fire retardant
materials are generally not preferred, some halogenated materials
may be effective in the present invention.
[0070] It has been discovered that FR 370, which is
tris(tribromoneopentyl) phosphate, is a very effective fire
retardant for the preparation of fire retardant, cleanly removable
carpet tapes. FR 370 has not been identified by environmental
groups, such as the European Parliament, as a troublesome substance
and has been determined to be an effective replacement for antimony
trioxide and/or polybrominated biphenyls.
[0071] The core layer may also include a number of other additives.
Examples of suitable additives include tackifiers (e.g., rosin
esters, terpenes, phenols, and aliphatic, aromatic, or mixtures of
aliphatic and aromatic synthetic hydrocarbon resins), plasticizers,
pigments, dyes, non-expandable polymeric or glass microspheres,
expandable microspheres, reinforcing agents, hydrophobic or
hydrophilic silica, calcium carbonate, toughening agents,
antioxidants, finely ground polymeric particles such as polyester,
nylon, or polypropylene, stabilizers, conductive particulates
(thermally and/or electrically conductive), antistatic agents,
fillers, blowing agents, adhesion promoters, such as silanes,
nanoparticles, such as nanoclay, non-polymeric fibers, and
combinations thereof. The foregoing additional agents and
components are generally added in amounts sufficient to obtain a
tape having the desired end properties, but not so as to interfere
with microfiber formation described herein. Preferably, the total
volume percent of all additives is less than about 70 volume
percent, more preferably, less than about 60 volume percent, and
most preferably, less than about 50 volume percent. In addition, it
is preferred that the particle size of the additive(s) is small
(i.e., no greater than about 100 micrometers, typically no greater
than about 10 micrometers, often no greater than about 5
micrometers, and most often no greater than about 1 micrometer) in
order not to interfere with microfiber formation.
[0072] Referring to FIG. 4, an extrusion process is shown for
preparing stretch release tape according to the invention.
According to the process of the invention, polymer resin or
adhesive polymer is fed into a first extruder 310 (typically a
single screw extruder) to soften, grind, or melt the resin into a
form suitable for extrusion. The resulting polymer resin will form
the core layer. The polymer resin may be added to the extruder 310
in any convenient form, such as pellets, billets, packages,
strands, pouches and ropes. Next, the polymer resin is fed to a
second extruder 312 (e.g., typically a twin screw extruder). The
polymer resin may be fed directly from the extruder 310 into second
extruder 312 through port 311. Other additives, such as fire
retardants and microfiber forming resin, can be fed into any port
and are typically fed into the second extruder 312 at entrance 313
and are well mixed in a kneading zone. The order of component
addition and mixing conditions (e.g., screw speed, screw length,
and temperature) are selected to achieve optimum mixing. Generally,
mixing is carried out at a temperature of at least about 10.degree.
C. above the melting point temperature of the microfiber forming
resin and less than about the degradation temperature of the
material to which the microfiber forming resin is added and/or the
microfiber forming resin. Generally, mixing is carried out at a
temperature between about 140.degree. C. to about 170.degree. C.
However, higher temperatures may be used. It will be appreciated
that if the polymer resin is provided in a form suitable for
extrusion, the first extrusion step may be omitted, and the resin
is added directly to extruder 312.
[0073] The appropriate resins for forming microfibers may also be
added to the extruder 312 at downstream entrance 313 or another
port (not shown). Preferably the microfiber forming resins are
added separately from the other additives. The melt-mixing step
prepares a composition in which the microfiber forming material and
other additives are distributed throughout a molten polymer resin.
Typically, the melt-mixing operation uses at least one kneading
block downstream from entrance 313 to obtain adequate mixing of the
various components. The temperature, pressure, shear rate, and
mixing time employed during melt-mixing are selected to prepare a
void-free extrudable composition suitable for use as a tape and/or
as a core layer that is part of a multilayer tape. The order of
addition, zone temperatures, pressures, shear rates, and mixing
times are also selected based upon the particular chemical
compositions being processed, and the selection of these conditions
is within the skill of those practicing in the field. When the tape
includes a fire retardant(s), the preferred order of addition is
polymer resin/adhesive, fire retardant(s) and other additives, if
any, microfiber forming resin, and tackifier, if any.
[0074] The reinforcing microfibers are desirably formed with
material having a melt viscosity (as determined with a capillary
viscometer) similar to the melt viscosity of the polymer core
material at the die 314 temperature of the above method. The
reinforcing microfiber material is selected to be immiscible in,
but compatible with the polymer material. The physical properties
of the stretch releasable tape are affected by how well the
microfibers are formed, and the formation of the microfibers are
affected by the processing conditions and compatibility with the
core layer polymer resin. It is important that the melt viscosities
of the microfiber forming resin and the core polymer are closely
matched and processing conditions are right to generate continuous
microfibers. Typically the ratio of the melt viscosities of the
microfiber forming resin and the core polymer is from about 1:30 to
about 30:1 and preferably, from about 1:20 to 20:1. The microfiber
material is typically melted, mixed and dispersed in the core
material as substantially spherical resin droplets. These droplets
generally have an average diameter less than about 20 micrometers
and sometimes less than about 10 micrometers.
[0075] Following melt mixing, the resulting extrudable composition
is metered into an extrusion die 314 (e.g., a contact or drop die)
through transfer tubing 318 using a gear pump 316. The temperature
within die 314 is maintained at substantially the same temperature
as the temperature within transfer tubing 318. While the
temperature within tubing 318 will be elevated, it is generally
maintained low enough to avoid degradation of the polymer or the
components.
[0076] The pressure within the die 314 will generally decreases as
the polymer core composition approaches the exit port 315 of the
die 314. The flow rate of the extrudable polymer composition
through the extruder 312 and the die 314 is maintained to
adequately process the core layer, as known by those skilled in the
art. The manufacturing process temperatures are typically chosen so
that the temperature of the highest or last zone is between at
least about 10.degree. C. above the melting point (low limit) of
elastic, viscoelastic, or combination of elastic and viscoelastic
polymer resins and less than about the degradation temperature of
the components. Moreover, the temperature of the die 314 is
generally no greater than about 60.degree. C. over the melting
point of the microfiber forming polymer so that the microfiber can
effectively consolidate by crystallizing upon cooling into
relatively long, substantially continuous microfibers.
[0077] The smoothness of one or both of the major surfaces of the
tape core layer, and/or adhesive layers can be increased by using a
nip roll to press the core against a smooth chill roll 317 after
the core exits die 314, or by using smooth liners on each of the
major surfaces of the multilayered tape and passing the composite
article through a nip. It is also possible to emboss a pattern on
one or both major surfaces of the multilayered tape by using a
patterned or microstructured liner such as those described in U.S.
Pat. No. 6,197,397 issued to Sher et al. on Mar. 6, 2001 or by
contacting the tape with a patterned roll, for example, a patterned
chill roll, after it exits the die 314.
[0078] The core layer may be combined with one or more skin
adhesive layers. FIG. 4 shows a co-extrusion process for use in the
present invention. In the depicted system, a layer of skin adhesive
material is introduced to the system by adding a resin or adhesive
polymer to the extruder 330 (e.g., a single screw extruder). Within
the extruder 330, the resin or adhesive material is softened,
mixed, or melted and then fed to a second extruder 332 (e.g., a
single or twin screw extruder). Additives such as the microfiber
resins, tackifiers, fire retardants, etc. may be also be included
in the skin adhesive by adding the additional components to the
extruder 332 at downstream port 329 where the additives are mixed
with the adhesive material. Preferably the microfiber forming
resins are added separately from the other additives. The
melt-mixing step prepares a composition in which the microfiber
forming material and other additives are distributed throughout a
molten adhesive polymer resin. Typically, the melt-mixing operation
uses at least one kneading block downstream from entrance 329 to
obtain adequate mixing of the various components. The temperature,
pressure, shear rate, and mixing time employed during melt-mixing
are selected to prepare a void-free extrudable composition suitable
for use as an adhesive skin layer. The additives, the order of
their addition, zone temperatures, pressures, shear rates, and
mixing times are also selected based upon the adhesive formulation,
and the selection of these conditions is within the skill of those
practicing in the field. When the skin adhesive includes a fire
retardant(s), the preferred order of addition is polymer
resin/adhesive, fire retardant(s) and other additives, if any,
microfiber forming resin, and tackifier, if any. The number of
additives, the order of their addition, and their point of addition
are selected based on the adhesive formulation to provide desired
adhesive properties suitable for the intended application of the
final tape product.
[0079] Following mixing, an extrudable adhesive composition is
metered from the extruder 332 to the appropriate chambers of die
314 through transfer tubing 334 using gear pump 336. The adhesive
composition is co-extruded with the core layer through an exit port
315 on the die 314 so that the adhesive composition is applied
directly to one of the major surfaces of the core layer. It will be
appreciated that an adhesive composition may be applied to the core
layer on either or both of the major surfaces. Co-extrusion methods
for coating an article with adhesive are known to those in the art
and are not further explained here.
[0080] Where skin adhesive is to be applied to both of the two
major surfaces of the core layer, the resulting tape is a
three-layer (ABA or ABC) construction of the kind illustrated in
FIG. 2 and described herein. For the manufacture of such a three
layer ABC construction, additional extruders and related equipment
may be added to the system of FIG. 3 in a known manner to permit
both first and second skin adhesives to be applied to the first and
second major surfaces of the core layer. Alternatively, one or both
of the adhesive compositions may be applied to the core layer by
lamination, by coating, or by spraying the adhesive onto the core.
The first and second adhesives may be continuous or discontinuous
adhesive layers applied to the major surfaces of the core layer,
and the skin adhesives may be the same or different adhesive
compositions on each of the major surfaces, and either of the
adhesive layers may be provided with a three dimensional surface
structure. Preferably, for stretch release properties, the skin
adhesive has a peel adhesion strength that is less than the tear or
tensile break strength of the core layer or composite tape
construction.
[0081] Suitable skin adhesives for use in the articles of the
present invention include any adhesive that provides acceptable
adhesion to a variety of polar and non-polar substrates while also
being compatible with the composition used in the core layer in the
manner described herein. The thickness of the skin adhesive has an
effect on peel adhesion. Consequently, the thickness of the skin
adhesive should be at least about 0.012 mm (0.5 mil), and
typically, at least about 0.051 mm (2 mils), and generally, less
than 0.25 mm (10 mils). For clean removability of the stretch
release tape in one step, it is preferred that the skin adhesive
not adhere too strongly to a substrate, i.e., have a 90 degree peel
adhesion less than about 5.25 kN/m (30 lbs/in), preferably less
than about 3.50 kN/m (20 lbs/in) and more preferably less than
about 1.75 kN/m (10 lbs/in). Pressure sensitive adhesives are
generally acceptable and may be desired. Suitable pressure
sensitive adhesives include any of a variety of adhesives such as
those based on acrylic adhesives (including copolymers,
terpolymers, and tetrapolymers of (meth)acrylate(s) and comonomers
such as (meth)acrylic acid, vinyl acetate, and dimethyl
acrylamide), polyurethanes, thermoplastic elastomers such as
styrene-isoprene-styrene, styrene-butadiene-styrene, and
combinations thereof, and other block copolymers, polyolefins such
as poly-alpha-olefins and amorphous polyolefins, silicones, rubber
based adhesives (including natural rubber, polyisoprene,
polyisobutylene, butyl rubber etc.) and combinations and blends of
the foregoing adhesives. The adhesive component may contain
tackifiers, plasticizers, rheology modifiers, adhesion promoters
such as silanes, fillers, non-polymeric fibers, crosslinking
agents, ceramic microspheres, glass microspheres, expanded and
unexpanded polymeric microspheres, conductive particulates
(thermally and/or electrically conductive), antistatic agents,
antioxidants, dyes, pigments, stabilizers, blowing agents,
surfactants, nanoparticles such as nanoclays, microfiber forming
resin, and other additives as well as active components such as an
antimicrobial agent or the like. A group of pressure sensitive
adhesives known to be useful in the present invention are, for
example, the acrylate copolymers described in U.S. Pat. No. RE
24,906, and particularly a copolymer comprising a weight ratio of
from about 90:10 to about 98:2 iso-octyl acrylate:acylic acid
copolymer and a copolymer comprising a weight ratio of from about
90:10 to about 98:2 2-ethylhexyl acrylate:acylic acid copolymer.
Also acceptable is an 65:35 2-ethylhexyl acrylate:isobornyl
acrylate copolymer. Useful adhesives are described in U.S. Pat.
Nos. 5,804,610 and 5,932,298, both of which are incorporated herein
in their entireties by reference thereto, and a blend of acrylic
adhesive and rubber based adhesive, such as identified as Hot Melt
Composition K in PCT International Publication WO 01/57152. The
inclusion of antimicrobial agents in the adhesive is also
contemplated, such as is described in U.S. Pat. Nos. 4,310,509 and
4,323,557 both of which are incorporated herein in their entireties
by reference thereto.
[0082] A release liner 320 may be applied to the skin adhesive
layer or layers associated with either or both of the major
surfaces of the core layer. A release liner 320 can be dispensed
from a feed roll 322 and applied to a surface of the skin adhesive.
Suitable materials for liner 320 include silicone release liners,
polyester films (e.g., polyethylene terephthalate films), and
polyolefin films (e.g., polyethylene films). The liner and the
adhesive may be laminated together between nip rollers 324. A
second optional release liner 340 may be applied to the other major
surface of the core layer. The liner 340 may be dispensed from a
second feed roll 342 which feed the liner 340 to the nip roll 324.
The liner is then applied to the adhesive layer as the core and
associated adhesive pass between nip rolls 324. The pressure from
the nip rolls 324 serves to laminate the release liners 320 and 340
to the multi-layer tape construction.
[0083] In another manner of attachment, the second release liner
340 may be provided with a layer of an adhesive coated or applied
to one surface of the release liner 340. In this manner, the second
adhesive layer may be applied to the second major surface of the
core material. The second adhesive layer may be the same as or
different from the aforementioned co-extruded adhesive. Typically,
the adhesive layers will comprise pressure sensitive adhesives. The
adhesive layers may or may not contain microfibers. Release liner
320 may also be provided with a layer of an adhesive coated or
applied to one of its surfaces.
[0084] Alternatively, the liner 340 can be dispensed from a feed
roll (not shown) and applied to the surface of the chill roll 317
such that extrudate from die 314 is coated onto liner 340.
[0085] Following lamination between the nip rolls 324, the tape is
optionally exposed to radiation from an electron beam source 326,
for example, to crosslink the polymeric core and/or to crosslink
the adhesive layer(s). Where the core material requires
crosslinking for improved cohesive strength, the radiation should
be energetic enough to penetrate the thickness of the core to
initiate and complete the crosslinking reaction. As known by those
skilled in the art, the extruded core layer may be of a thickness
that irradiation by e-beam exposure is needed on both sides of the
core for adequate crosslinking. Other sources of radiation (e.g.,
ion beam, gamma radiation, and ultraviolet radiation) may be used,
and the less energetic forms of radiation may be suitable if only
the outermost layer (e.g., an adhesive layer) requires
crosslinking. Following exposure to e-beam or other radiation
source, the resulting multilayer tape laminate is rolled up onto a
take-up roll 328. Optionally, the tape can be wound into a roll and
subsequently irradiated.
[0086] The release liners are typically coated with release agents
such as fluorochemicals or silicones. For example, U.S. Pat. No.
4,472,480 describes low surface energy perfluorochemical liners.
Suitable release liners include papers, polyolefin films, or
polyester films coated with silicone release materials. Examples of
commercially available silicone coated release liners are
POLYSLIK.TM. silicone release papers available from James River
Co., H. P. Smith Division (Bedford Park, Ill.) and silicone release
papers supplied by DCP-Lohja (Dixon, Ill.) now known as Loparex
Inc. (Willowbrook, Ill.). A particular release liner is that known
by the designation 1-60BKG-157, a super calendared Kraft paper with
a water-based silicone release surface, available from Daubert
Chemical Co. Other types of stable, contaminent free, release
liners are also useful in the invention such as those described in
U.S. patent application Ser. No. 09/775,955 incorporated herein by
reference.
[0087] The foregoing co-extrusion process can be conducted so that
a two-layer article is produced, or so that articles having three
or more layers are produced. Such multi-layered constructions can
be accomplished by equipping die 314 with an appropriate feed
block, or by using a multi-vaned or multi-manifold die. While an
extrusion process has been described for preparing tape according
to the invention, multilayered tapes can also be prepared by
laminating, coating, or spraying skin adhesive layers or other
additional polymer layers to the core layer, or to any of the
co-extruded polymer layers after the core exits die 314. For
example, the core layer can be extruded directly onto a backing
layer or onto a release liner bearing a skin adhesive layer. Other
techniques which can be used include pattern coating. It is
preferred that tape 200 be prepared by the processes described in
U.S. Pat. No. 5,660,922, issued Aug. 26, 1997.
[0088] The tapes of the invention are useful in a variety of
applications, and are especially useful as carpet tape in
aerospace, electronic, automotive, and medical applications as well
as in advertising and displays. The properties of the articles may
be tailored to meet the demands of the desired applications. The
tapes can also be used as attachment systems for or as a means for
mounting a wide variety of articles such as signage, reclosable
fasteners, body side molding, panels, hooks, clips, and the like.
Additional applications include closure applications such as
container closures, diaper closures, and surgical drape
closures.
[0089] The features of the embodiments of the invention are further
illustrated in the following non-limiting examples.
EXAMPLES
[0090] All amounts listed in the Examples are by weight unless
otherwise specified. In the test methods and examples below, all
the sample dimensions (typically the length) are approximate
dimensions except for the width wherein the width was measured to
the accuracy of the cutting tool.
Test Methods
[0091] Flammability Test Method
[0092] This test method is based on the criteria and procedures for
showing compliance with F.A.R. .sctn. 25.853 (July 1990) but
differs from F.A.R. .sctn. 25.853 (July 1990) in that the specimens
(samples) were conditioned at 50%+10% relative humidity for a
minimum of 24 hours instead of the specified 50%+5%.
[0093] Samples were conditioned to 21.1.degree. C..+-.2.8.degree.
C. (70.degree..+-.5.degree. F.) and at 50%+10% relative humidity
for a minimum of 24 hours. Specimens were mounted into a U-shaped
metal frame so that the two long edges and one narrow edge were
held securely in a vertical orientation, unsupported by and
unattached to a substrate. The exposed area of the specimen was at
least 50.8 mm (two inches) wide and about 304.8 mm (12 inches)
long.
[0094] The samples were exposed to the flame from a Bunsen burner.
The lower edge of the sample was about 19.1 mm ({fraction (3/4)}
inch) above the top edge of the burner. The flame was applied to
the center line of the lower edge of the sample for 12 seconds. The
flame time, burn length, and flaming time of dripping, if any, was
recorded. Burn length was the distance from the original edge of
the sample that was exposed to the flame to the point which is the
farthest evidence of damage to the test specimen due to flame
impingement including area of partial or complete consumption,
charring, or embrittlement, but not including areas sooted,
stained, warped, or discolored, nor areas where material had shrunk
or melted away from the heat.
[0095] F.A.R. .sctn. 25.853 (July 1990) subparagraphs (a)(1)(i) 60
second flame exposure require that the average burn length not
exceed 152.4 mm (six inches), the average flame time after removal
of the flame source not exceed 15 seconds, and drips not continue
to flame for more than an average of 3 seconds after falling.
F.A.R. .sctn. 25.853 (July 1990) subparagraphs (a)(1)(ii) 12 second
flame exposure require the average burn length not exceed 203 mm (8
inches), the average flame time after removal of the flame source
not exceed 15 seconds, and drips not continue to flame for more
than an average of 5 seconds after falling.
[0096] 90 Degree Peel Adhesion Test
[0097] A 12.7 mm (one-half inch) wide by about 152 mm (6 inches)
long sample was cut from the article to be tested and laminated to
an about 165 mm (6.5 inches) long by about 28.6 mm (1.125 inches)
wide by 0.051 mm (0.002 inches) thick aluminum foil by rolling down
the article onto the aluminum foil, taking care not to trap air
bubbles between the foil and the article. The foil/article laminate
was then positioned on a clean, dry, 51 mm (two inches) wide by
about 127 mm (5 inches) long, substrate panel of stainless steel or
to a Boeing composite, as specified in the Examples below, so that
the laminate was centered on the panel with a portion of the
laminate extending off the panel to serve as a tab. The laminate
was rolled down onto the panel using a 2 kg (4.5 lb) hard rubber
roller, with two passes in each direction. Care was taken not to
trap bubbles between the panel and the laminate. The sample thus
prepared was allowed to dwell at room temperature (about 22.degree.
C.) or at 70.degree. C. for about 72 hours. Then the sample was
tested at room temperature (about 22.degree. C.) for 90 Degree Peel
Adhesion according to the Pressure Sensitive Tape Council test
method PSTC-5 "Quick Stick of Pressure Sensitive Tapes" at
crosshead speed of 30 cm/minute (12 inches/minute) using an INSTRON
tensile tester. That is, the peel value obtained from the first
25.4 mm (one inch) length of peel was ignored. The peel value of
the next 89 mm (3.5 inches) or "peel area" was recorded. The values
reported were the integrated peel adhesion values. Failure mode was
also noted for 70.degree. C. aged samples.
[0098] T-Peel Adhesion Test
[0099] A 12.7 mm (one half inch) wide by about 152 mm (6 inches)
long sample was cut from the article to be tested and laminated to
an about 165 mm (6.5 inches) long by about 28.6 mm (1.125 inches)
wide by 0.051 mm (0.002 inches) thick aluminum foil by rolling down
the article onto the aluminum foil, taking care not to trap air
bubbles between the foil and the article. The foil/article laminate
was then positioned on a clean, dry, 51 mm (two inches) wide by
about 127 mm (5 inches) long, back of a carpet panel, FELTEX CARPET
Style 282131, available from Feltex Carpet Ltd, Auckland, NZ, so
that the laminate was centered on the carpet back with a portion of
the laminate extending off the carpet back to serve as a tab. The
laminate was rolled down onto the carpet back using a 2 kg (4.5 lb)
hard rubber roller, with two passes in each direction. Care was
taken not to trap bubbles between the carpet back and the laminate.
The sample thus prepared was allowed to dwell at room temperature
(about 22.degree. C.) or at 70.degree. C. for about 72 hours. Then
the sample was tested at room temperature (about 22.degree. C.)
according to ASTM D-1876-01 "Peel Resistance of Adhesives (T-Peel
Test)" at crosshead speed of 30 cm/minute (12 inches/minute) using
an INSTRON tensile tester. The peel value obtained from the first
25.4 mm (one inch) length of peel was ignored. The peel value of
the next 89 mm (3.5 inches) or "peel area" was recorded. The values
reported were the integrated peel adhesion values.
[0100] Static Shear Strength Test
[0101] A 1.27 cm (one-half inch) wide by about 15.2 cm (6 inches)
long sample was cut from the article to be tested and laminated to
a sheet of anodized aluminum foil (about 16.5 cm (6.5 inches) long
by 2.86 cm (1.125 inches) wide by 0.0127 cm (0.005 inches) thick)
by rolling down the article onto the anodized side of the aluminum
foil, taking care not to trap air bubbles between the foil and the
article. The foil/article laminate was then cut in half to give two
about 2.54 cm.times.about 7.62 cm (I inch.times.3 inches) test
specimens. The liner was removed from a test specimen and then
positioned on a clean, dry, 5.1 cm (two inches) wide by 12.7 cm (5
inches) long, stainless steel substrate panel so that the laminate
was centered on one end of the panel so that 2.54 cm (I inch)
length was adhered (i.e. 3.13 sq. cm (0.5 sq. inch) bond area) and
the 5.1 cm (2 inches) portion of the laminate extended off the
panel to serve as a tab. The laminate was rolled down onto the
panel using a 2 kg (4.5 lb) hard rubber roller, with two passes in
each direction. Care was taken not to trap bubbles between the
panel and the laminate. The 5.1 cm (2 inches) tab was then folded
around a triangular clip and stapled so that a weight could be
attached to the test specimen. The sample thus prepared was allowed
to dwell at room temperatures and approximately 50% relative
humidity for approximately 72 hours. The test specimen was then
placed in a Static Shear standard fixture having between zero and 2
degree angle back slant in a forced air oven set at 70.degree. C.
(158.degree. F.). The test specimen was then given a 10 minute warm
up period before attaching a 500 gram weight. The test was run
until the test specimen failed or 10,000 minutes elapsed. Failure
time and failure mode were recorded. Where the test specimen did
not fail, the amount of slippage was measured and recorded.
[0102] Tensile Break Strength & Elongation Test
[0103] A silicone release liner was applied to the exposed surface
of the article which already had a liner on one side. A 2.54 cm
(one inch) wide by about 12.7 cm (5 inches) long sample was cut in
the machine direction from the article to be tested to form the
test specimen. One release liner was removed and a 2.54 cm (I inch)
length was measured and marked in the center of test specimen to
provide the initial gap distance. A 2.54 cm (1 inch) wide by about
7.62 cm (3 inch) piece of masking tape was placed across the foam
article by positioning the tape edge on both marks so that the 2.54
cm (1 inch) long section that was marked off did not have tape
covering it. The other liner was then removed, and masking tape was
wrapped completely around the article. Care was taken to keep the
masking tape aligned with the marks on the article. The tape was
used to prevent the sample from adhering to the INSTRON jaws and
prevent the sample from breaking at the point where it was clamped
by the jaws. The INSTRON was set up with the following
conditions:
[0104] Jaw Gap: 2.54 cm (1 inch)
[0105] Crosshead Speed: 25.4 cm/minute (10 inches/minute)
[0106] The test specimen was then positioned in the INSTRON jaws so
that the jaws lined up with the edge of the masking tape. The
sample was tested at a crosshead speed of 25.4 cm/minute (10
inches/minute) until the sample broke. The tensile break strength
was recorded in pounds (and later converted to kilograms) and
elongation distance was recorded. The percent elongation was
determined by dividing the elongation distance by the initial gap
distance times 100. Three specimens were tested and averaged to
provide the Tensile Break Strength and Percent Elongation.
[0107] Hardness Test
[0108] The thickness of an about 5.1 cm (two inches) by 2.54 cm
(one inch) article sample was measured and recorded. The sample was
then laminated to a clean, dry glass panel taking care to avoid
trapping air bubbles between the sample and the glass. Additional
pieces of article sample were laminated to the first article until
a total thickness of at least 0.34 cm (0.135 inches) was achieved.
Using a Shore A Hardness Tester (Model CV Stand and Durometer Type
A ASTM D2240 Gauge available from Shore Instrument Mfg. Co. Inc.,
Freeport, N.Y.), the initial hardness of the article was measured
three times and the maximum hardness values obtained were
averaged.
[0109] Stretch Release Test
[0110] Two 12.5 mm (0.5 inch) wide by about 152 mm (6 inches) long
strips were cut from the test sample such that the length was cut
in the machine direction of the sample. Two strips were laminated
side by side to a 50.8 mm (2 inch) wide.times.127 mm (5 inches)
long.times.1.59 mm ({fraction (1/16)} inches) thick stainless steel
panel such that the strips was centered down the middle of the
panel with 1.27 cm (half inch) space between the strips and
approximately 25.4 mm (1 inch) of the strip extends beyond the end
of the panel. Care was taken to ensure maximum wet-out of or
contact between the strip and the panel. It was desired that 100%
contact be achieved. The bonded sample was allowed to dwell for
between 24 and 72 hours at room temperature (about 22.degree. C.).
The free end of the test strips were pulled by hand at a speed of
about 30 cm/minute (about 12 inches/minute) in a direction away
from the panels to initiate stretch release removal until the bond
failed. The test strips were pulled at an angle that was
approximately between 10 and 25 degrees above the plane of the
panel. The panels were then visually examined for the presence of
residue and the number of times the strip broke.
Materials
[0111] Certain commercially available materials were used in the
Examples of the invention. These materials are listed below and are
often referred to in the Examples with reference to their trade
designations.
1 Trade Designation Description Source IRGACURE 651
2,2-dimethoxy-2-phenylacetophenone Ciba Specialty Chemicals Corp,
Tarrytown, NY FR 370 tris(tribromoneopentyl) phosphate Dead Sea
Bromine Group, Beer Shiva, Israel EXOLIT IFR 23 intumescent
flame-retardant system Clariant Corporation, based on ammonium
polyphosphate Charlotte, NC HL2081 rubber/resin pressure sensitive
H. B. Fuller, St. Paul, MN adhesive SYVALITE RE80HP tackifying
resin Arizona Chemical, Jacksonville, FL ECR 180 tackifying resin
ExxonMobil Chemical Company, Houston, TX EXACT 3040 ethylene-based
hexene copolymer, ExxonMobil Chemical nominal tensile yield
strength (MD) Company, Houston, TX 5.4 MPa (780 psi), tensile break
strength (MD) 51.6 MPa (7490 psi), elongation at break (MD) 460%,
MI 16.5, density 0.900 g/cm3, Peak Melting temperature 96.degree.
C. (205.degree. F.).
[0112] General Preparation of Packaged Pressure Sensitive Adhesives
I-III
[0113] Three pressure-sensitive adhesive compositions were prepared
by mixing 2-ethylhexyl acrylate (2-EHA), acrylic acid (AA),
2,2-dimethoxy-2-phenylacetophenone (IRGACURE 651), and isooctyl
thioglycolate (IOTG) in the amounts listed in Table 1 below. Each
composition was formed into a "Packaged Pressure Sensitive
Adhesive" by placing the composition into packages measuring
approximately 100 mm by 50 mm by 5 mm thick as described in U.S.
Pat. No. 5,804,610 (Hamer et al). The packaging film was 0.0635 mm
(0.0025 inches) thick VA-24 film (a heat sealable, ethylene vinyl
acetate copolymer film having 6% vinyl acetate, available from CT
Film of Dallas, Tex.). The packages were immersed in a water bath
and at the same time exposed to ultraviolet radiation at an
intensity of 3.5 milliwatts per square centimeter and a total
energy of 1627 millijoules per square centimeter as measured by
NIST units to form a "Packaged Pressure Sensitive Adhesive (Pkg.
PSA)".
2TABLE 1 Parts by Parts by Parts by Parts by Wt. of Wt. of Wt. of
Wt. of 2,2-dimethoxy-2- Component 2-EHA AA IOTG phenylacetophenone
Pkg. PSA I 90 10 0.03 0.15 Pkg. PSA II 97 3 0.01 0.15 Pkg. PSA III
95 5 0.01 0.15
[0114] Packaged Pressure Sensitive Adhesive IV
[0115] Packaged Pressure Sensitive Adhesive IV was a commercial hot
melt adhesive available from H. B. Fuller Company under the
designation HL2081.
[0116] Preparation of Precompounded Skin Adhesive A:
[0117] "Pkg. PSA I" was fed to the second feed port of a 30 mm
co-rotating twin screw extruder (Werner Pfleider) operating at a
screw speed of 300 rpm through a first 51 mm single screw extruder
(Bonnot). The Bonnot zone temperatures were set at the following:
Zone 1=149.degree. C. (300.degree. F.), Zone 2=163.degree. C.
(325.degree. F.), and Zone 3=177.degree. C. (350.degree. F.). The
pump and heated hose were set at 177.degree. C. (350.degree. F.).
The temperature for the six zones in the twin screw extruder was
set in Zone 1 at 163.degree. C. (325.degree. F.), and in Zones 2
through 6 at 121.degree. C. (350.degree. F.). The adhesive was
delivered into a silicone coated paper box though a heated hose set
at 121.degree. C. (350.degree. F.). The skin adhesive was
identified as "Precompounded Adhesive A" as shown in Table 2
below.
[0118] Precompounded Skin Adhesive B:
[0119] Precompounded Adhesive B in Table 3 below was Pkg. PSA IV
used as received from the manufacturer in the precompounded form of
pillows ready for hot melt processing.
[0120] Preparation of Precompounded Skin Adhesives C-G:
[0121] Five skin adhesives containing fire retardants were
precompounded as follows:
[0122] A Pkg. PSA was fed at a rate of 12 lbs/hr (5.45 kg/hr) to
Barrel Zone 1 of a 30 mm co-rotating twin screw extruder (Werner
Pfleider) operating at a screw speed of 300 rpm through a first 51
mm single screw extruder (Bonnot). The Bonnot zone temperatures
were set at the following: Zone 1=149.degree. C. (300.degree. F.),
Zone 2=163.degree. C. (325.degree. F.), and Zone 3=177.degree. C.
(350.degree. F.). The pump and heated hose were set at 177.degree.
C. (350.degree. F.). The temperature for the six zones in the twin
screw extruder was set at Zone 1=37.8.degree. C. (100.degree. F.),
Zones 2=79.4.degree. C. (175.degree. F.), Zones 3=37.8.degree. C.
(100.degree. F.), Zones 4=160.degree. C. (320.degree. F.), Zones
5=160.degree. C. (320.degree. F.), and Zone 6=160.degree. C.
(320.degree. F.).
[0123] The flame retardant(s) was added to Barrel Zone 3 using a
KTRON weight loss feeder, Model No. F-7, available from K Tron
Corp, Pitman, N.J.
[0124] If present, the tackifying resin(s) was melted in a resin
melting system, and was added into Barrel Zone 5. The resin melting
tank temperature was set at 148.9.degree. C. (300.degree. F.), and
the pump and heated hose were set at 162.8.degree. C. (325.degree.
F.). The feed rate for both the fire retardant(s) and tackifying
resin(s), if present, was adjusted based on the set 12 lbs/hour
(5.45 kg/hr) flow rate of the Pkg. PSA to give the desired level of
parts in the formulation as shown in Table 2.
[0125] The adhesive was delivered into a silicone coated paper box
though a heated hose set at 160.degree. C. (320.degree. F.). The
skin adhesives were identified as "Precompounded Adhesive C, D, E,
F and G" as shown in Table 2 below.
3TABLE 2 Compo- Precompounded Skin Adhesives, nent Compo- Parts by
Wt. Type nent A B C D E F G Adhesive Pkg. 100 PSA I Polymer Pkg.
100 100 100 100 PSA II Pkg. PSA 100 III Pkg. PSA 100 IV Tackifying
ECR 180 39 Resin RE80HP 39 39 49 Fire EXOLIT 75 75 50 Retardant IFR
23 FR 370 49 49
[0126] Preparation of Compounded Core Adhesives H-N:
[0127] Seven core adhesives were compounded as follows:
[0128] A Pkg. PSA was fed at a rate of 2.27 kg/hr (5 lb/hr) to
Barrel Zone 1 of a 30 mm co-rotating twin screw extruder (Werner
Pfleider) operating at a screw speed of 300 rpm through a first 51
mm single screw extruder (Bonnot). The Bonnot zone temperatures
were set at the following: Zone 1=149.degree. C. (300.degree. F.),
Zone 2=163.degree. C. (325.degree. F.), and Zone 3=177.degree. C.
(350.degree. F.). The pump and heated hose were set at 177.degree.
C. (350.degree. F.). The temperature for the six zones in the twin
screw extruder was set at Zone 1=37.8.degree. C. (100.degree. F.),
Zone 2=37.8.degree. C. (100.degree. F.), Zone 3=37.8.degree. C.
(100.degree. F.), Zone 4=160.degree. C. (320.degree. F.), Zone
5=160.degree. C. (320.degree. F.), and Zone 6=160.degree. C.
(320.degree. F.).
[0129] If present, the flame retardant(s) was added to Barrel Zone
3 using a KTRON weight loss feeder.
[0130] The fiber forming resin was added to Barrel Zone 3 using a
KTRON weight loss feeder. The feed rate for both the fire
retardant(s), if present, and fiber forming resin was adjusted
based on the set 2.27 kg/hr (5 lb/hr) flow rate of the Pkg. PSA to
give the desired level of parts in the formulation as shown in
Table 3.
[0131] The core adhesives were identified as "Compounded Core
Adhesive H, I, J, K, L, M, and N" as shown in Table 3 below. The
Compounded Core Adhesive was not isolated but was fed to the middle
layer of a three layer die as described below in Examples 1-11.
4TABLE 3 Compo- Compounded Core Adhesive, nent Compo- Parts by Wt.
Type nent H I J K L M N Adhesive Pkg. 100 100 PSA I Polymer Pkg.
100 PSA II Pkg. PSA 100 100 100 III Pkg. PSA 100 IV Fiber EXACT 54
54 54 54 54 65 87 Forming 3040 Resin Fire EXOLIT 75 75 75 Retardant
IFR 23 FR 370 49 49
Examples 1-11
[0132] Compounded Core Adhesive H--N were combined with
Precompounded Skin Adhesives A-G to prepare three layer tapes as
follows:
[0133] After a core adhesive was compounded as described above, it
was pumped directly through a heated hose to the center/middle
layer of an about 203.2 mm (8 inches) wide, three layer CLOEREN die
(available from The Cloeren Company, Orange, Tex.) with a gap of
about 1 mm (0.040 inches). The die temperature was 320.degree. F.
(160.degree. C.).
[0134] Simultaneously, a Precompounded Skin Adhesive was fed to the
each of the outer layers of the die from a second 51 mm single
screw extruder (Bonnot) and coextruded with the core adhesive
extrudate above. The Bonnot zone temperatures were all set at
149.degree. C. (300.degree. F.). The pump and heated hose were set
at 163.degree. C. (325.degree. F.). The skin adhesive flow rate was
adjusted to provide a target thickness of each outer layer of 0.076
mm (3 mils). The process conditions were adjusted to provide the
tape thickness set forth in Table 4. The extruded sheet was cast
onto a chill roll that was set at 7.2.degree. C. (45.5.degree. F.),
cooled to about 25.degree. C., and then transferred onto a 0.127 mm
thick polyethylene release liner prepared according to Examples 10a
and 10b of copending U.S. patent application Ser. No. 09/775,955
"Adhesive Article and Method of Preparing." The resulting article
was wound into a roll for subsequent crosslinking.
[0135] Two approximately one meter (39 inches) long pieces were cut
from the above sample roll. A 0.051 mm (0.002 inch) thick two
sided, silicone-coated polyester liner, having different release
materials (identified as 5035 and 7200) on each side, available
from DCP-LOHJA Inc. Willowbrook, Ill. as 2-2PESTR(P2)-5035 &
7200, was carefully laminated to the uncovered side (Side 2) of
each piece with the 7200 silicone coated side contacting the
uncovered side (Side 2). The extruded sheet piece of Examples 1-3,
and 6-11 with liners on both sides were then passed through the
electron beam (e-beam) processing unit (ESI Electro Curtain)
operating at an accelerating voltage of 300 keV and at a speed of
6.1 meters per minute, once on each side. Each piece received a
measured e-beam dose of 6 megaRads on each side.
5TABLE 4 Thickness of Skin Total Skin Adhesive Thickness Total Tape
Tape Adhesive, Side 1/ of Core Thickness, Weight Ex. Side 1/ Side
2, Core Layer, mm g/m.sup.2 No. Side 2 mm (mils) Layer mm (mils)
(mils) (oz/yd.sup.2) 1 A/A 0.076/0.076 H 0.152 (6) 0.30 (12) 285.9
(3/3) (8.43) 2 A/A 0.076/0.076 H 0.229 (9) 0.38 (15) 379.5 (3/3)
(11.19) 3 A/A 0.076/0.076 H 0.33 (13) 0.48 (19) 469.3 (3/3) (13.84)
4 B/B 0.076/0.076 I 0.305 (12) 0.46 (18) 338.0 (3/3) (9.97) 5 B/B
0.076/0.076 I 0.10 (4) 0.25 (10) 345.2 (3/3) (10.18) 6 C/C
0.076/0.076 J 0.38 (15) 0.53 (21) 592.1 (3/3) (17.46) 7 D/D
0.076/0.076 K 0.13 (5) 0.28 (11) 334.4 (3/3) (9.86) 8 E/E
0.076/0.076 L 0.13 (5) 0.28 (11) 318.8 (3/3) (9.40) 9 F/F
0.076/0.076 M 0.36 (14) 0.51 (20) 554.8 (3/3) (16.36) 10 G/G
0.076/0.076 M 0.20 (8) 0.36 (14) 410.3 (3/3) (12.10) 11 F/F
0.076/0.076 N 0.28 (11) 0.43 (17) 494.4 (3/3) (14.58)
[0136] The resultant article was then tested for physical
properties, and adhesive performance properties. Results are given
in Table 5.
6 TABLE 5 Static Tensile Shear at Break 90 Degree Adhesion,
70.degree. C., Stretch Strength, kN/m (piw) minutes, Release, MPa %
Shore A Stainless Boeing failure Sample 1/ Example (psi) Elongation
Hardness Steel Composite mode Sample 2 1 0.059 710 49-30.sup.(e)
1.27 (7.26) 1.03 (5.89) >10,000 pass/fail.sup.(d) (8.6) (1
break) 2 0.066 760 23 1.58 (9.00) 1.28 (7.34) >10,000 pass/pass
(9.7) 3 0.069 840 21 1.87 (10.7) 1.61 (9.19) >10,000 pass/pass
(10.1) 4 0.069 1270 41 1.86 (10.64) NT.sup.(b) <1 C.sup.(c)
pass/pass (10.0) 5 0.048 1050 35 1.41 (8.04) NT <1 C pass/pass
(7.0) 6 0.078 840 30 0.070 (3.98) 0.56 (3.21) 69 C pass/fail (11.4)
(2 breaks) 7.sup.(a) 0.019 600 21 0.84 (4.81) 0.92 (5.28) 43 C
fail/fail (2.8) (5 breaks/ 3 breaks) 8 0.068 880 42 0.95 (5.45)
1.31 (7.51) >10,000 pass/pass (9.9) 9 0.075 730 42 0.64 (3.68)
0.45 (2.59) 992 C pass/fail (10.9) (3 breaks) 10 0.070 720
50-48.sup.(e) 0.36 (2.06) 0.30 (1.73) >10,000 pass/pass (10.2)
11 0.088 830 41 0.47 (2.71) 0.525 (3.00) 51 C pass/pass (12.9)
.sup.(a)Example 7 was very poorly coated with void and bubbles in
the construction which affected the test properties. .sup.(b)NT =
not tested. .sup.(c)C = cohesive failure .sup.(d)Presence of void
in the core layer caused failure. .sup.(e)Dial reading constantly
decreased during testing; reading did not reach a level point.
[0137] For the 90 Degree Adhesion test, all samples detached
cleanly from the surface of the test substrate without leaving a
visible residue. Examples 4 and 5 have both rubber based skin
adhesive layers and a rubber based adhesive core layer and would
not be expected to have good shear at 70.degree. C. The tensile
break strength of the tape can be increased by increasing the
concentration of the microfibers and/or the thickness of the core
layer to prevent breaking during the Stretch Release Test for the
tapes of Examples 1, 6, 7 and 9.
Examples 6-11
Flammability
[0138] The tapes of Examples 6-11 were tested for flammability
according to Flammability Test Method. Data is set forth in Table
6.
7 TABLE 6 12 Second Vertical Burn Results Dripping Burn Burn Flame
Length, Time, Time, mm Overall, Example Drippings seconds seconds
(inches) Pass/Fail 6 Yes 0 4.6 96.5 (3.8) pass 7 Yes 0 13 139.7
(5.5) pass 8 Yes 0 0 103.6 (4.08) pass 9 Yes 0 >15 >203.2
(>8) fail 10 Yes 0 >15 >203.2 (>8) fail 11 Yes 0 >15
>203.2 (>8) fail
[0139] It is believed that the flammability of Examples 9, 10, and
111 could be improved by reducing the amount of tackifying resin
used, by increasing the total amount of fire retardant, and by
substituting a brominated fire retardant, such as FR 370, for a
portion of IFR 23 fire retardant.
Example 12
[0140] A fire retardant, cleanly removable carpet tape as shown in
FIG. 3 was prepared as follows:
[0141] The skin adhesive is identified as "Compounded Skin Adhesive
0" and the core adhesive is identified as "Compounded Core Adhesive
P". Both the skin and core adhesives were not isolated, but were
individually feed to a rotary die and coated onto a release
liner.
[0142] Preparation of Compounded Skin Adhesive and Skin Adhesive
Layer O:
[0143] Pkg. PSA II was fed at a rate of 2.27 kg/hr (5 lbs/hr) to
Barrel Zone 1 of a 30 mm co-rotating twin screw extruder (Werner
Pfleider) operating at a screw speed of 300 rpm through a first 51
mm single screw extruder (Bonnot). The Bonnot zone temperatures
were set at the following: Zone 1=149.degree. C. (300.degree. F.),
Zone 2=163.degree. C. (325.degree. F.), and Zone 3=177.degree. C.
(350.degree. F.). The pump and heated hose were set at 177.degree.
C. (350.degree. F.). The temperatures for the six zones in the twin
screw extruder were set at Zone I=37.8.degree. C. (100.degree. F.),
Zones 2=37.8.degree. C. (100.degree. F.), Zones 3=37.8.degree. C.
(100.degree. F.), Zones 4=160.degree. C. (320.degree. F.), Zones
5=160.degree. C. (320.degree. F.), and Zone 6=160.degree. C.
(320.degree. F.).
[0144] The fire retardants, EXOLIT IFR 23 and FR 370, were added to
Barrel Zone 3 using a KTRON weight loss feeder. The tackifying
resin, RE 80 HP, was melted in a HELICONE resin melting system, and
added into Barrel Zone 5. The HELICONE tank temperature was set at
148.9.degree. C. (300.degree. F.), and the pump and heated hose
were set at 162.8.degree. C. (325.degree. F.). The feed rates for
both the fire retardants, and tackifying resin were adjusted based
on the set 2.27 kg/hr (5 lbs/hr) flow rate of the Pkg. PSA II to
give the desired level of parts in the formulation as shown in
Table 7 below.
[0145] After the skin adhesive was compounded as described above,
it was not isolated, but pumped directly through a heated hose to
an about 203.2 mm (6 inches) wide, rotary rod die set at about
160.degree. C. (320.degree. F.). It was coated directly onto a
differential release, silicone coated, 55# densified kraft paper
liner at target 0.125 mm (5 mils) thickness to provide Skin
Adhesive Layer O, and wound into a roll.
[0146] Preparation of Compounded Skin Adhesive and Skin Adhesive
Layer P:
[0147] Pkg. PSA III was fed at a rate of 1.36 kg/hr (3 lbs/hr) to
Barrel Zone 1 of a 18 mm co-rotating twin screw extruder (Haake
Micro 18, available from Haake, Karlsuhe, Germany) operating at a
screw speed of 200 rpm through a first 51 mm single screw extruder
(Bonnot). The Bonnot zone temperatures were all set at 121.degree.
C. (250.degree. F.). The pump and heated hose were set at about
149.degree. C. (300.degree. F.). The temperatures for the zones in
the twin screw extruder were all set at about 121.degree. C.
(250.degree. F.).
[0148] The fire retardant FR 370 was added to Barrel Zone 3 using a
weight loss feeder. The tackifying resin, RE 80 HP, was melted in a
DYNAMELT S222-G29-24-ZN grid melting system, available from ITW
Dynatec, Hendersonville, Tenn., and added into Barrel Zone 5. The
grid was set at 148.9.degree. C. (300.degree. F.), and the pump and
heated hose were set at 162.8.degree. C. (325.degree. F.). The feed
rates for both the fire retardant, and tackifying resin were
adjusted based on the set 1.36 kg/hr (3 lbs/hr) flow rate of the
Pkg. PSA III to give the desired level of parts in the formulation
as shown in Table 7 below.
[0149] After the skin adhesive was compounded as described above,
it was not isolated, but pumped directly through a heated hose to
an about 203.2 mm (6 inches) wide, rotary rod die set at about
149.degree. C. (300.degree. F.). It was coated directly onto a
differential release, silicone coated, 55# densified kraft paper
liner at target 0.125 mm (5 mils) thickness to provide a Core Layer
P and wound into a roll.
8 TABLE 7 Adhesive Composition, Parts by Wt. Skin Component
Adhesive Skin Adhesive Type Component Layer O Layer P Pkg. PSA II
100 Pkg. PSA III 100 Tackifying RE80HP 40 39 Resin Fire EXOLIT
13.33 Retardant IFR 23 FR 370 66.67 49
[0150] Preparation of Fire Retardant Multilayer Tape
[0151] Approximately one meter (39 inches) long pieces of each of
the Skin Adhesive Layers O and P were cut from the above rolls. The
differential release, silicone coated, 55# densified kraft paper
liner, described above, was carefully laminated to the uncovered
side (Side 2) of each piece. The sample, with liners on both sides,
was then passed through the electron beam (e-beam) processing unit
(ESI Electro Curtain) operating at an accelerating voltage of 180
keV and at a speed of 6.1 meters per minute, once on each side.
Each piece received a measured e-beam dose of 8 megaRads on each
side.
[0152] After removing a liner to expose one side of the skin
adhesive layer P, the exposed side was laminated to one side of a
0.025 mm (1 mil) thick polyester film which was used as the core
layer using a 2 kg (4.5 lb) rubber roller. In a similar manner, the
skin adhesive layer 0 was laminated to the other or second side of
the polyester film to form a multilayer tape.
[0153] The tape (without liners) was tested for weight,
flammability, and tensile strength according to Boeing Test Method
BMS 5-133C. The thickness of the tape was 0.30 mm (11 mils).
9 TABLE 8 BMS 5-133C Test, Type IV, Class 2 Result Requirement A.
Weight oz/yd2, max. 8.8 9.0 B. Flammability (a) Extinguish Time,
sec., 12 15 max. (b) Burn Length, inches, 5.5 8 max. (c) Drip
Extinguishing 0 5 Time, sec., max. C. Tensile Strength.sup.(a),
lb/in, 29.5 30.0 minimum .sup.(a)measured at a crosshead speed of
2.54 cm/min.
[0154] It is believed that use of a thicker polyester film in the
above tape would provide a tape that would meet the tensile
strength requirement.
Examples 1-3, 6-12
T-Peel Adhesion and 90 Degree Peel Adhesion
[0155] The tape of Example 12, along with the tapes of Examples
1-3, and 6-11, were tested for T-peel adhesion at room
temperature(RT) and after aging at 70.degree. C. for 72 hours; and
90 degree peel adhesion to Boeing floor panel BMS 4-2, Type II,
from M. C. Gill, El Monte, Calif., at both room temperature and
after aging for 72 hours at 70.degree. C. Results are in Table
9.
10 TABLE 9 90 Degree Peel Adhesion T-Peel Adhesion to to Boeing
Floor Carpet Back, Panel, kN/m (piw) kN/m (piw) Failure Mode Aged
at Aged at of 70.degree. C. Aged Example RT 70.degree. C. RT
70.degree. C. Sample 1 0.11 (0.6) 0.14 (0.8) 1.04 (5.89) 2.08
(11.81) stringy, cohesive of adhesive and/or core 2 0.14 (0.8) 0.16
(0.93) 1.29 (7.34) 2.2 (12.5) sl. stringy, clean peel 3 0.21 (1.2)
0.21 (1.2) 1.62 (9.19) 2.66 (15.1) stringy 6 0.14 (0.8) 0.13 (0.74)
0.57 (3.21) 0.65 (3.67) clean peel 7 0.25 (1.4) 0.37 (2.1) 0.93
(5.28) 0.94 (5.34) clean peel 8 0.07 (0.4) 0.09 (0.49) 1.32 (7.51)
0.77 (4.36) cohesive split of core layer 9 0.14 (0.8) 0.18 (1.025)
0.46 (2.59) 0.80 (4.56) clean peel 10 0 (0) 0 (0) 0.30 (1.72) 0.37
(2.1) clean peel 11 0.14 (0.8) 0.14 (0.78) 0.53 (3.0) 0.56 (3.175)
clean peel 12 0.14 (0.78) 0.15 (0.875) 0.38 (2.16) 0.47 (2.69)
clean peel
[0156] For the 90 Degree Adhesion RT test, all samples detached
cleanly from the test substrate without leaving a visible
residue.
[0157] From the data it can be see that for Examples 1-3, there is
significant increase in adhesion to the Boeing floor panel after
70.degree. C. aging compared to room temperature adhesion values.
It is believed that this indicates better wet out of the substrate
by these Examples compared to the other Examples tested. In
addition, it is believed that Examples 1-3 would provide tapes that
would be especially useful for general mounting applications where
it is desirable to remove the tape after use. It is also believed
that a decrease in the amount of fiber forming resin in Example 8
would improve the cohesive strength of the core.
[0158] While the features of the preferred embodiments of the
invention have been discussed and described in detail, it will be
appreciated that modifications to the described embodiments may be
made by those skilled in the art, and such modifications and
changes are within the scope and spirit of the invention as further
set forth in the appended claims.
* * * * *