U.S. patent application number 13/937275 was filed with the patent office on 2013-11-07 for electron beam cured silicone materials.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Clayton A. George, Junkang J. Liu.
Application Number | 20130295372 13/937275 |
Document ID | / |
Family ID | 41563712 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130295372 |
Kind Code |
A1 |
Liu; Junkang J. ; et
al. |
November 7, 2013 |
Electron Beam Cured Silicone Materials
Abstract
Methods of preparing silicone materials using electron beam
curing are described. The materials are hot melt processed and
cured in the absence of an effective amount of catalysts and
initiators. Both functional and nonfunctionalized silicone
materials may be used. Exemplary cured materials include silicone
pressure sensitive adhesives, silicone foams, and non-tacky
silicone films.
Inventors: |
Liu; Junkang J.; (Woodbury,
MN) ; George; Clayton A.; (Afton, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
41563712 |
Appl. No.: |
13/937275 |
Filed: |
July 9, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13125891 |
Apr 25, 2011 |
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PCT/US2009/062563 |
Oct 29, 2009 |
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13937275 |
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61109213 |
Oct 29, 2008 |
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Current U.S.
Class: |
428/317.3 ;
428/345; 524/588; 525/474; 525/477; 528/10; 528/43 |
Current CPC
Class: |
C08J 9/32 20130101; C09J
183/04 20130101; C08J 2207/02 20130101; C09J 7/38 20180101; Y10T
428/2852 20150115; C08J 2383/04 20130101; C08J 3/28 20130101; Y10T
428/2809 20150115; Y10T 428/249983 20150401; C08J 2201/024
20130101; C09J 183/08 20130101; C08L 83/00 20130101; C09J 183/04
20130101; C08L 83/00 20130101 |
Class at
Publication: |
428/317.3 ;
428/345; 528/10; 528/43; 525/477; 525/474; 524/588 |
International
Class: |
C09J 7/02 20060101
C09J007/02; C09J 183/04 20060101 C09J183/04 |
Claims
1. A crosslinked silicone-based material made according a method
comprising (a) hot melt processing a composition comprising a
silicone material; and (b) subjecting the composition to electron
beam irradiation forming the crosslinked silicone-based
material.
2. The crosslinked silicone-based material of claim 1, wherein hot
melt processing comprises extruding.
3. The crosslinked silicone-based material of claim 1, wherein the
silicone material is a nonfunctionalized silicone material.
4. The crosslinked silicone-based material of claim 1, wherein the
silicone material comprises a siloxane backbone and at least one
functional group.
5. The crosslinked silicone-based material of claim 4, wherein all
functional groups are hydroxyl groups.
6. The crosslinked silicone-based material of claim 1, wherein the
crosslinked silicone-based material is a silicone pressure
sensitive adhesive.
7. The crosslinked silicone-based material of claim 1, wherein the
silicone material is a polysiloxane.
8. The crosslinked silicone-based material of claim 7, wherein the
polysiloxane is a poly(dimethyl siloxane).
9. The crosslinked silicone-based material of claim 7, wherein the
polysiloxane is an aromatic siloxane.
10. The crosslinked silicone-based material of claim 1, wherein the
silicone material comprises a gum having a dynamic viscosity at
25.degree. C. of greater than 1,000,000 mPasec.
11. The crosslinked silicone-based material of claim 1, wherein the
composition further comprises an MQ resin tackifier.
12. The crosslinked silicone-based material of claim 1, wherein the
composition further comprises at least one of glass bubbles and
polymeric microspheres.
13. The crosslinked silicone-based material of claim 1, wherein the
silicone material comprises a silicone fluid having a dynamic
viscosity at 25.degree. C. of no greater than 600,000 mPasec.
14. The crosslinked silicone-based material of claim 1, wherein the
composition is substantially free of catalysts and initiators.
15. An adhesive article comprising a substrate having a first major
surface, and the silicone pressure sensitive adhesive according
claim 1 adhered to at least a portion of the first major surface of
the substrate.
16. The adhesive article of claim 15, wherein the substrate
comprises a foam.
17. The crosslinked silicone-based material of claim 1, wherein the
crosslinked material is non-tacky.
Description
FIELD
[0001] The present disclosure relates to silicone materials,
including silicone pressure sensitive adhesives, silicone foams,
and non-tacky silicone films. More specifically, the present
disclosure describes silicone materials cured by exposure to
electron beam irradiation.
BACKGROUND
[0002] Pressure sensitive adhesives (PSAs) are an important class
of materials. Generally, PSAs adhere to a substrate with light
pressure (e.g., finger pressure) and typically do not require any
post-curing (e.g., heat or radiation) to achieve their maximum bond
strength. A wide variety of PSA chemistries are available
including, e.g., acrylic, rubber, and silicone based systems.
Silicone PSAs offer one or more of the following useful
characteristics: adhesion to low surface energy (LSE) surfaces,
quick adhesion with short dwell times, wide use temperature (i.e.,
performance at high and low temperature extremes), weathering
resistance (including resistance to ultraviolet (UV) radiation,
oxidation, and humidity), reduced sensitivity to stress variations
(e.g., mode, frequency and angle of applied stresses), and
resistance to chemicals (e.g., solvents and plasticizers) and
biological substances (e.g., mold and fungi).
[0003] Generally, silicone pressure sensitive adhesives have been
formed by a condensation reaction between a polymer or gum and a
tackifying resin. The polymer or gum is typically a high molecular
weight silanol-terminated poly(diorganosiloxane) material e.g.,
silanol-terminated poly(dimethylsiloxane) ("PDMS") or
poly(dimethylmethylphenylsiloxane). The tackifying resin is
typically a three-dimensional silicate structure end-capped with
trimethylsiloxy groups. In addition to the terminal silanol groups
of the polymer or gum, the tackifying resin may also include
residual silanol functionality.
[0004] Such systems rely on high molecular weight starting
materials; thus, they must be diluted in solvents to achieve
viscosities suitable for coating at room temperature. Typical
coatable solutions contain less than 60% solids by weight in a
solvent (e.g., an aromatic solvent such as toluene or xylene).
Additional solvent may be added prior to coating such that volatile
organic compound (VOC) contents of greater than 50% are common when
using traditional silicone PSAs.
[0005] A number of approaches have been investigated for the low
VOC delivery of silicone PSAs. For example, water-based emulsion
systems and liquid solventless systems based on low-viscosity,
highly-functional silicone polymers have been explored, e.g.,
polymers including silicon-bonded hydrogen, silicon-bonded vinyl,
silicon-bonded epoxy, and silicon-bonded acrylate. Hot-melt,
moisture-curable, silicone PSAs that rely on silicon-bonded
hydrolysable functional groups (e.g., alkoxy, acetoxy, or oxime
groups) have also been attempted.
[0006] Despite these advances, there is still a need for more
robust methods for the low VOC delivery of silicone PSAs. There is
also a need for low VOC delivery processes that allow for a greater
diversity of silicone chemistries to be used, thus enabling a
broader range of end-use performance properties.
[0007] While some silicone PSA formulations provide acceptable
performance after solvent removal, some systems benefit from
additional crosslinking. Conventional silicone PSAs are cured by
thermal processes using specific types of catalysts. For example,
platinum catalysts have been used with addition cure systems,
peroxides (e.g., benzoyl peroxide) have been used with
hydrogen-abstraction cure systems, and tin catalysts have been used
with moisture/condensation cure systems.
[0008] Generally, some of these approaches require reactive
functional groups attached to the siloxane backbone. For example,
addition-cure, platinum-catalyzed systems generally rely on a
hydrosilation reaction between silicon-bonded vinyl functional
groups and silicon-bonded hydrogens. In general, it may be
desirable to have a silicone adhesive system that can be cured
without the use of catalysts, particularly when hot-melt coating or
in other circumstances where premature curing should be
avoided.
SUMMARY
[0009] Briefly, in one aspect, the present disclosure provides a
method of making a crosslinked silicone-based material. The method
comprises hot melt processing a composition comprising a silicone
material and subjecting the composition to electron beam
irradiation forming the crosslinked silicone-based material. The
composition is free of an effective amount of catalysts and
initiators. In some embodiments, hot melt processing comprises
extruding.
[0010] In some embodiments, the silicone material is a
nonfunctionalized silicone material. In some embodiments, the
silicone material comprises a siloxane backbone and at least one
functional group. In some embodiments, all functional groups are
hydroxy groups.
[0011] In some embodiments, the crosslinked silicone-based material
is a silicone pressure sensitive adhesive. In some embodiments, the
crosslinked silicone-based material is a silicone foam. In some
embodiments, the crosslinked silicone-based material is a non-tacky
silicone foam.
[0012] In some embodiments, the silicone material is a
polysiloxane, e.g., a poly(dialkyl siloxane) or a poly(dimethyl
siloxane). In some embodiments, the polysiloxane is an aromatic
siloxane.
[0013] In some embodiments, the composition further comprises a
tackifier, e.g., an MQ resin tackifier.
[0014] In another aspect the present disclosure provides a
crosslinked-silicone-based material made according to the methods
of the present disclosure. In some embodiments, the silicone
pressure sensitive adhesive comprises a crosslinked, silicone
elastomer, wherein the adhesive is substantially free of catalysts
and initiators. In some embodiments, the adhesive further comprises
a tackifier, e.g., an MQ resin tackifier. In some embodiments, the
material is a foam. In some embodiments, the material is a
non-tacky film.
[0015] The above summary of the present disclosure is not intended
to describe each embodiment of the present invention. The details
of one or more embodiments of the invention are also set forth in
the description below. Other features, objects, and advantages of
the invention will be apparent from the description and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 illustrates an exemplary foam core tape according to
some embodiments of the present disclosure.
[0017] FIG. 2 illustrates an exemplary crosslinked polysiloxane
foam according to some embodiments of the present disclosure.
DETAILED DESCRIPTION
[0018] Generally, the crosslinked siloxane networks of the present
disclosure can be formed from either functional or non-functional
silicone materials. Generally, the silicone materials may be oils,
fluids, gums, elastomers, or resins, e.g., friable solid resins. In
some embodiments, the nonfunctionalized silicone materials can be a
linear material described by the following formula illustrating a
siloxane backbone with aliphatic and/or aromatic substituents:
##STR00001##
wherein R1, R2, R3, and R4 are independently selected from the
group consisting of an alkyl group and an aryl group, each R5 is an
alkyl group and n and m are integers, and at least one of m or n is
not zero. In some embodiments, one or more of the alkyl or aryl
groups may contain a halogen substituent, e.g., fluorine. For
example, in some embodiments, one or more of the alkyl groups may
be --CH.sub.2CH.sub.2C.sub.4F.sub.9.
[0019] In some embodiments, R5 is a methyl group, i.e., the
nonfunctionalized silicone material is terminated by
trimethylsiloxy groups. In some embodiments, R1 and R2 are alkyl
groups and n is zero, i.e., the material is a
poly(dialkylsiloxane). In some embodiments, the alkyl group is a
methyl group, i.e., poly(dimethylsiloxane) ("PDMS"). In some
embodiments, R1 is an alkyl group, R2 is an aryl group, and n is
zero, i.e., the material is a poly(alkylarylsiloxane). In some
embodiments, R1 is methyl group and R2 is a phenyl group, i.e., the
material is poly(methylphenylsiloxane). In some embodiments, R1 and
R2 are alkyl groups and R3 and R4 are aryl groups, i.e., the
material is a poly(dialkyldiarylsiloxane). In some embodiments, R1
and R2 are methyl groups, and R3 and R4 are phenyl groups, i.e.,
the material is poly(dimethyldiphenylsiloxane).
[0020] In some embodiments, the nonfunctionalized silicone
materials may be branched. For example, one or more of the R1, R2,
R3, and/or R4 groups may be a linear or branched siloxane with
alkyl or aryl (including halogenated alkyl or aryl) substituents
and terminal R5 groups.
[0021] As used herein, "nonfunctional groups" are either alkyl or
aryl groups consisting of carbon, hydrogen, and in some
embodiments, halogen (e.g., fluorine) atoms. As used herein, a
"nonfunctionalized silicone material" is one in which the R1, R2,
R3, R4, and R5 groups are nonfunctional groups.
[0022] Generally, functional silicone systems include specific
reactive groups attached to the siloxane backbone of the starting
material (for example, hydrogen, hydroxyl, vinyl, allyl, or acrylic
groups). As used herein, a "functionalized silicone material" is
one in which at least one of the R-groups of Formula 2 is a
functional group.
##STR00002##
[0023] In some embodiments, a functional silicone material is one
is which at least 2 of the R-groups are functional groups.
Generally, the R-groups of Formula 2 may be independently selected.
In some embodiments, the only functional groups present are
hydroxyl groups, e.g., silanol terminated polysiloxanes such as
silanol terminated poly dimethyl siloxane.
[0024] In addition to functional R-groups, the R-groups may be
nonfunctional groups, e.g., alkyl or aryl groups, including
halogenated (e.g., fluorinated) alky and aryl groups. In some
embodiments, the functionalized silicone materials may be branched.
For example, one or more of the R groups may be a linear or
branched siloxane with functional and/or non-functional
substituents.
[0025] Generally, lower molecular weight, lower viscosity materials
are referred to as fluids or oils, while higher molecular weight,
higher viscosity materials are referred to as gums; however, there
is no sharp distinction between these terms. Typically, the terms
"fluid" and "oil" refer to materials having a dynamic viscosity at
25.degree. C. of no greater than 1,000,000 mPasec (e.g., less than
600,000 mPasec), while materials having a dynamic viscosity at
25.degree. C. of greater than 1,000,000 mPasec (e.g., at least
10,000,000 mPasec) are referred to as "gums".
[0026] The pressure sensitive adhesives of the present disclosure
may be prepared by combining silicone materials (e.g., silicone
gums or elastomers) with an appropriate tackifying resin, hot melt
coating the resulting combination, and curing using electron beam
(E-beam) irradiation. Generally, any known additives useful in the
formulation of pressure sensitive adhesives (e.g., dyes, pigments,
fillers, flame retardants, rheology modifiers, flow agents,
surfactants, microspheres (e.g., expandable microspheres), and the
like may be also be included.
[0027] Generally, any known tackifying resin may be used, e.g., in
some embodiments, silicate tackifying resins may be used. In some
exemplary adhesive compositions, a plurality of silicate tackifying
resins can be used to achieve desired performance.
[0028] Suitable silicate tackifying resins include those resins
composed of the following structural units M (i.e., monovalent
R'.sub.3SiO.sub.1/2 units), D (i.e., divalent R'.sub.2SiO.sub.2/2
units), T (i.e., trivalent R'SiO.sub.3/2 units), and Q (i.e.,
quaternary SiO.sub.4/2 units), and combinations thereof. Typical
exemplary silicate resins include MQ silicate tackifying resins,
MQD silicate tackifying resins, and MQT silicate tackifying resins.
These silicate tackifying resins usually have a number average
molecular weight in the range of 100 to 50,000-gm/mole, e.g., 500
to 15,000 gm/mole and generally R' groups are methyl groups.
[0029] MQ silicate tackifying resins are copolymeric resins where
each M unit is bonded to a Q unit, and each Q unit is bonded to at
least one other Q unit. Some of the Q units are bonded to only
other Q units. However, some Q units are bonded to hydroxyl
radicals resulting in HOSiO.sub.3/2 units (i.e., "TOH" units),
thereby accounting for some silicon-bonded hydroxyl content of the
silicate tackifying resin.
[0030] The level of silicon bonded hydroxyl groups (i.e., silanol)
on the MQ resin may be reduced to no greater than 1.5 weight
percent, no greater than 1.2 weight percent, no greater than 1.0
weight percent, or no greater than 0.8 weight percent based on the
weight of the silicate tackifying resin. This may be accomplished,
for example, by reacting hexamethyldisilazane with the silicate
tackifying resin. Such a reaction may be catalyzed, for example,
with trifluoroacetic acid. Alternatively, trimethylchlorosilane or
trimethylsilylacetamide may be reacted with the silicate tackifying
resin, a catalyst not being necessary in this case.
[0031] MQD silicone tackifying resins are terpolymers having M, Q
and D units. In some embodiments, some of the methyl R' groups of
the D units can be replaced with vinyl (CH2=CH--) groups
("D.sup.Vi" units). MQT silicate tackifying resins are terpolymers
having M, Q and T units.
[0032] Suitable silicate tackifying resins are commercially
available from sources such as Dow Corning (e.g., DC 2-7066),
Momentive Performance Materials (e.g., SR545 and SR1000).
[0033] The silicone material, the tackifying resin, and any
optional additives may be combined by any of a wide variety of
known means prior to being hot melt coated and cured. For example,
in some embodiments, the various components may be pre-blended
using common equipment such as mixers, blenders, mills, extruders,
and the like. In some embodiments, the hot melt coating process is
extrusion. In such embodiments, the various components may be added
together, in various combinations or individually, through one or
more separate ports of an extruder, blended (e.g., melt mixed)
within the extruder, and extruded to form the hot melt coated
composition. Regardless of how it is formed, the hot melt coated
composition is cured through exposure to E-beam irradiation.
[0034] In some embodiments, the methods and materials of the
present disclosure may be used to foam silicone foams, including
silicone adhesive foams. Silicone foams provide unique properties,
including: resilience, wide service temperature stability (e.g.,
-50.degree. C. to about 200.degree. C.), inertness, and inherent
flame retardancy. Generally, silicone foams have been made in
processes where cell growth or expansion (i.e., the foaming
process) and cell stabilization (i.e., the crosslinking process)
are happened simultaneously. Most common cell expansion chemistries
for silicone foams rely on chemical blowing agents, e.g. azo
containing compounds or condensed gas by-product from crosslinking
reactions.
[0035] In contrast, through the use of e-beam curing process of the
present disclosure, the cell expansion or foaming process and cell
stabilization or crosslinking process can be independently
optimized. In some embodiments, this can lead to improved control
over cell structures with uniform distribution of foam cell sizes.
The E-beam cured silicone foams can be made with microspheres,
including both rigid non-polymeric hollow microspheres, e.g. glass
bubbles and polymeric microspheres, including thermally expandable
polymeric microspheres.
[0036] Glass bubble are known in the art and can be obtained
commercially and/or be made by the techniques known in the art.
Useful glass bubbles include glass bubbles available from 3M
company under trade designation "3M SCOTCHILITE GLASS BUBBLES"
(e.g. grades K1, K15, S15, S22, K20, K25, S32, K37, S38HS, K46,
A16/500, A20/1000, and D32/4500); glass bubbles available from
Potters Industries under the trade designation "Q-CELL HOLLOW
SPHERES" (e.g. grades 30, 6014, 6019, 6028, 6036, 6042, 6048, 5019,
5023, and 5028); and glass bubbles available from Silbrico Corp.
under the trade designation "SIL-CELL" (e.g. grads SIL 35/34,
SIL-32, SIL-42, and SIL-43). Those glass bubbles generally have an
average density in a range of 0.1 g/cm.sup.3 to 0.5 g/cm.sup.3 and
an average bubble size in a range of 5 to 250 micrometers.
[0037] Polymeric microspheres are hollow spheres with polymeric
shells. In some embodiments, expandable polymeric microspheres
could be used. Such expandable microspheres include a polymer shell
and a core material in the form of a gas, liquid, or a combination
(e.g., propane, butane, pentane, isobutene, neopentane, and
combinations thereof). Upon heating, the shell softens and core
expands, causing the shell to expand without breaking. Upon
cooling, the shell re-hardens, and the expandable microsphere
remains expanded. Exemplary thermally expandable polymeric
microspheres have an acrylonitrile-containing shell and suitable
core materials including. Useful expandable microspheres include
microspheres available from Henkel under the designation
"MICROPEARL" (e.g. grades F30, F80, and F100) and microspheres
market by Akzo-nobel under the trade name EXPANCEL (e.g., "Expancel
551", "Expancel 461", and "Expancel 091").
[0038] The silicone material, the microsphere, and any optional
additives may be combined by any of a wide variety of known means
prior to being hot melt coated and cured. Generally, any known
additives useful for the foam (e.g., tackifiers, plasticizers,
dyes, pigments, fillers, flame retardants, rheology modifiers, and
surfactants) may be also included. For example, in some
embodiments, the various components may be pre-blended using common
equipment such as mixers, blenders, mills, extruders, and the like.
In some embodiments, the hot melt coating process is extrusion. In
such embodiments, the various components may be added together, in
various combinations or individually, through one or more separate
ports of an extruder, blended (e.g., melt mixed) within the
extruder, and extruded to form the hot melt coated composition.
Regardless of how it is formed, the hot melt coated composition is
cured through exposure to E-beam irradiation.
[0039] A variety of procedures for E-beam curing are well-known.
The cure depends on the specific equipment used to deliver the
electron beam, and those skilled in the art can define a dose
calibration model for the equipment used.
[0040] Commercially available electron beam generating equipment
are readily available. For the examples described herein, the
radiation processing was performed on a Model CB-300 electron beam
generating apparatus (available from Energy Sciences, Inc.
(Wilmington, Mass.). Generally, a support film (e.g., polyester
terephthalate support film) runs through an inert chamber. In some
embodiments, a sample of uncured material with a liner (e.g., a
fluorosilicone release liner) on both sides ("closed face") may be
attached to the support film and conveyed at a fixed speed of about
6.1 meters/min (20 feet/min). In some embodiments, a sample of the
uncured material may be applied to one liner, with no liner on the
opposite surface ("open face").
[0041] The uncured material may be exposed to E-beam irradiation
from one side through the release liner. For making a single layer
laminating adhesive type tape, a single pass through the electron
beam may be sufficient. Thicker samples, such as a foam tape, may
exhibit a cure gradient through the cross section of the tape so
that it may be desirable to expose the uncured material to electron
beam radiation from both sides.
[0042] In contrast to previous methods for curing silicone
materials, the methods of the present disclosure do not require the
use of catalysts or initiators. Thus, the methods of the present
disclosure can be used to cure compositions that are "substantially
free" of any catalysts or initiators. As used herein, a composition
is "substantially free of catalysts and initiators" if the
composition does not include an "effective amount" of a catalyst or
initiator. As is well understood, an "effective amount" of a
catalyst or initiator depends on a variety of factors including the
type of catalyst or initiator, the composition of the curable
material, and the curing method (e.g., thermal cure, UV-cure, and
the like). In some embodiments, a particular catalyst or initiator
is not present at an "effective amount" if the amount of catalyst
or initiator does not reduce the cure time of the composition by at
least 10% relative to the cure time for same composition at the
same curing conditions, absent that catalyst or initiator.
EXAMPLES
[0043] The following examples illustrate the present inventors
surprising discovery that a wide variety of silicone chemistries
can be cured with electron beam (E-Beam) irradiation to obtain
pressure sensitive adhesives. The performance of these E-beam cured
adhesives is comparable to the same adhesives cured using
traditional methods, even though none of the catalysts or
initiators required for traditional curing were used.
[0044] For purposes of comparison, three samples were prepared with
each of the silicone chemistries. A reference example in which the
silicone was uncured, a comparative example in which the silicone
was cured by the appropriate traditional method with the use of a
catalyst, and an example of the present disclosure in which the
silicone was cured with E-beam irradiation in the absence of
catalysts and initiators. Samples were tested for Peel Adhesion and
Static Shear according to the following tests.
[0045] Peel Adhesion Test. Peel adhesion was measured using an
INSTRON Tensile Tester. The adhesive sample was slit to a width of
1.27 cm and length of 11.4 cm and laminated to 0.127 mm thick and
1.6 cm wide aluminum foil backing using one of the major surfaces
of the adhesive. The resulting tape was then applied to a clean
panel using four total passes of a 2 kg (4.5 lb) hard rubber
roller. Before testing, the samples were aged at room temperature
(22.degree. C.) and 50% relative humidity before testing for either
20 minutes or 3 days. The panel was then mounted in an INSTRON
Tensile Tester and the tape was pulled off at a 90 degree angle at
a speed of 30.5 cm per minute. Results were measured in pounds per
0.5 inch, and converted to N/cm (i.e., 3.5 N/cm=1 lbf/0.5
inch).
[0046] Static Shear Test. Shear Test. A sample of tape measuring
2.54 cm by 1.27 cm was laminated to a panel measuring 2.54 cm by
5.08 cm such that the tape edges were coextensive with edges of the
panels. The panel overlapped 1.27 cm to cover the tape and the free
ends of the panels extended in opposite directions. One end of a
panel was hung on a rack in an oven set at 70.degree. C. with a 500
gram weight hanging from the bottom of the end of the other panel
so that the tape sample was under shear stress. The time for the
bottom panel to release from the hanging panel was monitored for up
to 10,000 minutes. Time to failure in minutes was recorded. For
samples that survived for 10,000 minutes, a value of "10,000+" was
recorded.
[0047] The Peel Test and Shear Test were conducted using both
polypropylene panels and painted panels. The polypropylene panels
were obtained from Standard Plaque Inc. (Melvindale, Mich.). The
painted panels were identified as APR46336 from ACT (Hilldale,
Mich.). As received, the painted panels had been prepared using a
typical automotive paint system. The automotive paint system
comprised a base electrocoat, a pigmented base coat, and a low
surface energy carbamate crosslinked unpigmented acrylic-based
clear coat was applied to a stainless steel panel. The resulting
test surface had a surface energy of 32 dynes/cm as measured using
"Accu-Dyne" solutions.
[0048] Foam Density Test Procedure. The thickness, L, of a foam
sheet was measured. The foam sheet was cut to form samples having a
cross-sectional area of 2.54 cm by 2.54 cm (one inch by one inch)
square with a knife cutter. The weight of the sample was measured
in grams. The density was calculated by dividing the weight of the
sample by its volume, wherein the volume is the product of the
sample thickness and its cross sectional area
[0049] The materials used in the preparation of the samples are
summarized in Table 1.
TABLE-US-00001 TABLE 1 Materials summary. Material Description
Source DC-7658 dispersion of PDMS gum and resin Dow Corning DC-2013
dispersion of PDMS gum and resin Dow Corning DC-7355 dispersion of
PDMS gum and resin Dow Corning Q2-7735 dispersion of PDMS gum and
resin Dow Corning DC-7678 reactive polysiloxane crosslinker Dow
Corning Syl-Off- organo-platinum complex dispersed Dow Corning 4000
in polysiloxane SID-3352-O 50% dichlorobenzoyl peroxide in PDMS
Gelest PET-3SAC primed polyester film Mitsubishi Polyester Film
Series 1: DC-7658
Reference Example RE-1
[0050] DC-7658 was coated as received using a knife coater with gap
of 127 microns (5 mil) on the PET-3SAC film. The coated sample was
immediately dried in an oven at 70.degree. C. for 15 minutes.
Comparative Example CE-1
[0051] 125 grams of DC-7658 were mixed in a glass jar with 0.5
grams of DC-7678 (crosslinker), and 0.5 grams Syl-Off-4000
(catalyst) and placed on a roller mixer for 4 hours at room
temperature. The mixed solution was coated using a knife coater
with gap of 127 microns on the PET-3SAC film. The coated sample was
immediately dried in an oven at 70.degree. C. for 15 minutes.
Examples 1A, 1B, and 1C
[0052] DC-7658 was coated as received using a knife coater with gap
of 127 microns on the PET-3SAC film. The coated sample was
immediately dried in an oven at 70.degree. C. for 15 minutes. Dried
samples were then passed through the E-beam chamber under <50
ppm oxygen level with 250 key and various dose levels: 1 Mrad
(EX-1A), 5 Mrads (EX-1B), and 9 Mrads (EX-1C).
Series 2: DC-7355
Reference Example RE-2
[0053] DC-7355 was coated as obtained using a knife coater with gap
of 127 microns on the PET-3SAC film. The coated sample was
immediately dried in an oven at 70.degree. C. for 15 minutes.
Comparative Example CE-2
[0054] 100 grams DC-7355 and 4 grams of catalyst (SID-3352-O) were
mixed in a glass jar which was later placed on a roller mixer for 4
hours at room temperature. The mixed solution was coated using a
knife coater with gap of 127 microns on the PET-3SAC film. The
coated sample was immediately dried in an oven at 70.degree. C. for
10 minutes and then cured at 150.degree. C. for another 15
minutes.
Examples 2A, 2B, and 2C
[0055] DC-7355 was coated as obtained using a knife coater with gap
of 127 microns on the PET-3SAC film. The coated sample was
immediately dried in an oven at 70.degree. C. for 15 minutes. Dried
samples were passed through the E-beam chamber under <50 ppm
oxygen level with 250 key and various dose levels: 1 Mrad (EX-2A),
5 Mrads (EX-2B), and 9 Mrads (EX-2C).
Series 3: Q2-7735
Reference Example RE-3
[0056] Q2-7735 was coated as obtained using a knife coater with gap
of 127 microns on the PET-3SAC film. The coated sample was
immediately dried in an oven at 70.degree. C. for 15 minutes.
Comparative Example CE-3
[0057] 100 grams of Q2-7735 and 4 grams of SID-3352-O (catalyst)
were mixed in a glass jar which was later placed on a roller mixer
for 4 hours at room temperature. The mixed solution was coated
using a knife coater with gap of 127 microns on the PET-3SAC film.
The coated sample was immediately dried in an oven at 70.degree. C.
for 10 minutes and then cured at 150.degree. C. for another 15
minutes.
Examples 3A, 3B, and 3C
[0058] Q2-7735 was coated as obtained using a knife coater with gap
of 127 microns on the PET-3SAC film. Coated samples were
immediately dried in an oven at 70.degree. C. for 15 minutes. Dried
samples were passed through the E-beam chamber under <50 ppm
oxygen level with 250 key and various dose levels: 1 Mrad (EX-3A),
5 Mrads (EX-3B), and 9 Mrads (EX-3C).
Series 4: DC-2013
Reference Example RE-4
[0059] DC-2013 was coated as received using a knife coater with gap
of 51 microns (2 mil) on the PET-3 SAC film.
Comparative Example CE-4
[0060] 50 grams of DC-2013, 0.3 grams of DC-7678 (crosslinker), and
0.3 grams DC-4000 (catalyst) were mixed in a glass jar which was
placed on a roller mixer for 4 hours at room temperature. The mixed
solution was coated using a knife coater with gap of 51 microns on
the PET-3SAC film. The coated sample was immediately cured in an
oven at 70.degree. C. for 15 minutes.
Examples 4A, 4B, and 4C
[0061] DC-2013 was coated as received using a knife coater with gap
of 51 microns on the PET-3SAC film. Coated samples were passed
through an E-beam chamber under <50 ppm oxygen level with 250
key and various dose levels: 1 Mrad (EX-4A), 5 Mrads (EX-4B), and 9
Mrads (EX-4C).
[0062] The Peel Adhesion and Static Shear performance of the
exemplary E-beam adhesives in comparison to the reference and
comparative examples are summarized in Table 2.
TABLE-US-00002 TABLE 2 Properties of adhesive samples. Painted
panel Polypropylene panel Peel Peel 70.degree. C. Peel Peel
70.degree. C. System Ex. Cure (20 min) (72 hr) Shear (20 min) (72
hr) Shear DC-7658 RE-1 none (c/s) (c/s) 0 (c/s) (c/s) (c/s) 0 (c/s)
CE-1 thermal 4.1 4.5 10000 1.2 1.3 10000 1A 1 Mrad 1.5 1.9 6 0.6
1.5 7 1B 5 Mrad 3.7 4.8 10000 2.2 2.5 145 1C 9 Mrad 3.7 3.9 10000
2.3 2.8 267 DC-7355 RE-2 none (c/s) (c/s) 0 (c/s) (c/s) (c/s) 0
(c/s) CE-2 thermal 3.0 3.6 10000 3.0 3.6 10000 2A 1 Mrad 4.1 3.6
447 2.2 2.7 3362 2B 5 Mrad 3.3 3.3 10000 1.7 2.0 10000 2C 9 Mrad
4.3 3.5 10000 2.1 1.8 10000 Q2-7735 RE-3 none (c/s) (c/s) 0 (c/s)
(c/s) (c/s) 0 (c/s) CE-3 thermal 3.4 3.6 6656 3.4 3.6 2752 3A 1
Mrad 4.4 4.2 3422 2.8 3.7 640 3B 5 Mrad 4.3 4.1 10000 2.6 3.2 7668
3C 9 Mrad 4.4 4.6 10000 2.5 2.9 10000 DC-2013 RE-4 none (c/s) (c/s)
0 (c/s) (c/s) (c/s) 0 (c/s) CE-4 thermal 3.0 3.6 10000 2.4 3.1
10000 4A 1 Mrad 0.6 0.8 0 0.5 0.5 0 4B 5 Mrad 0.7 0.8 0 0.6 0.6 0
4C 9 Mrad 1.2 1.3 0 1.1 1.1 0
[0063] In some embodiments, silicone PSAs of the present disclosure
may be useful as the skin adhesive layers of a foam core tape. An
exemplary foam core tape is shown in FIG. 1. Tape 10 includes foam
core 20 and silicone PSA layer 30. Optional primer layer 40 is
interposed between the PSA layer and the foam core. In some
embodiments, second adhesive layer 50 may be adhered to the
opposing surface of foam core 20. Again, in some embodiments, a
primer layer may be used to aid in bonding the adhesive layer to
the foam core or, as shown in FIG. 1, adhesive layer 50 may be
bonded directly to the foam core 20.
[0064] Exemplary foam cores comprise one or more of acrylates,
silicones, polyolefins, polyurethanes, and rubbers (e.g., block
copolymers). These materials may be foamed by any known technique,
e.g., inclusion of spheres (e.g., glass and polymeric microspheres,
including expandable microspheres), frothing, using chemical
blowing agents, and the like. In some embodiments, the foam core
(e.g., a silicone foam core) may be E-beam cured separately, or in
the same step as, the silicone PSA.
[0065] In addition to foam core tapes, some of the silicone PSAs of
the present disclosure may be used as free films, with or without
an internal support, e.g., a scrim. The silicone PSAs may be used
as part of other single-coated and double-coated tape construction
as well, i.e., bonded directly or indirectly to a support layer,
e.g., a paper, polymeric film (e.g., fluorinated polymers such as
polytetrafluoroethylene or urethane polymers), or a metal foil.
[0066] Foam core tapes with silicone skin adhesives were prepared
using a variety of commercially available silicone pressure
sensitive adhesive materials as identified by their trade names in
Table 3.
TABLE-US-00003 TABLE 3 Silicone adhesive systems. Trade name
Description Solvent Solids SILGRIP .RTM. silanol functional xylene
56% PSA518 phenyl based polysiloxane gum and resin SILGRIP .RTM.
silanol functional toluene 55% PSA529 polysiloxane gum and resin
SILGRIP .RTM. silanol functional toluene 60% PSA590 polysiloxane
gum and resin SILGRIP .RTM. silanol functional xylene 55% PSA595
polysiloxane gum and resin SILGRIP .RTM. silanol functional xylene
60% PSA610 polysiloxane gum and resin SILGRIP .RTM. silanol
functional toluene 60% PSA6573A polysiloxane gum and resin SILGRIP
.RTM. silanol functional toluene 55% PSA6574 phenyl based
polysiloxane gum and resin SILGRIP .RTM. silanol functional toluene
60% PSA910 polysiloxane gum and resin SILGRIP .RTM. silanol
functional toluene 60% PSA915 polysiloxane gum and resin SILGRIP
.RTM. silanol functional toluene 55% PSA950 phenyl based
polysiloxane gum and resin SILGRIP .RTM. silanol functional hexane
40% SCA1000 phenyl based polysiloxane gum and resin Dow Corning
.RTM. vinyl and hydride functional -- 100% 2013 dimethyl methyl
hydrogen siloxane Dow Corning .RTM. vinyl and hydride functional
xylene 55-58% Q2-7406 Poly dimethylsiloxane gum and resin Dow
Corning .RTM. non-functional xylene 55-58% Q2-7735 Poly
dimethylsiloxane gum and resin Dow Corning .RTM. vinyl and hydride
functional xylene 55-58% DC-7658 Poly dimethylsiloxane gum and
resin Dow Corning .RTM. silanol functional xylene 55-57% DC-280A
Poly dimethylsiloxane gum and resin Dow Corning .RTM. silanol
functional xylene 55-57% DC-282 Poly dimethylsiloxane gum and resin
Dow Corning .RTM. non-functional xylene/ 55-58% DC-7355 Poly
dimethylsiloxane gum and resin toluene Dow Corning .RTM.
non-functional xylene/ 55-58% DC-7358 Poly dimethylsiloxane gum and
resin toluene Dow Corning .RTM. non-functional xylene/ 55-58%
Q2-7566 Poly dimethylsiloxane gum and resin toluene
[0067] The silicone materials were knife-coated unto a primed
polyester film and dried at 70.degree. C. for 15 minutes to achieve
50 micron (2 mil) dry thickness. The resulting tapes were E-beam
irradiated at an acceleration voltage of 300 key and a dose of 6
Mrads. The E-beam units were broadband curtain type electron beam
processors (PCT Engineered Systems, LLC, Davenport, Iowa).
Uncrosslinked samples and E-beam crosslinked samples were tested
according to the Peel Test (Table 4a) and Shear Test (Table
4b).
TABLE-US-00004 TABLE 4a Peel adhesion of uncrosslinked and E- beam
crosslinked silicone adhesives. Peel (N/cm) Peel (N/cm)
uncrosslinked E-beam @ 6 Mrad Painted Painted panel PP Panel panel
PP Panel 20 72 20 72 20 72 20 72 Sample min hour min hour min hour
min hour PSA518 7.1 7.7 4.8 4.3 4.3 4.0 3.0 N/A PSA529 6.5 7.0 3.7
4.2 5.3 5.5 3.3 3.2 PSA590 5.9 6.4 3.6 4.9 5.1 4.6 4.0 3.8 PSA595
4.5 4.9 4.3 4.3 5.5 5.3 3.5 3.7 PSA610 8.9 9.8 5.0 8.4 4.5 4.3 3.0
4.0 PSA6573A 0.2 0.6 0.1 0.1 4.7 3.0 0.7 0.2 PSA6574 6.0 6.2 4.4
4.5 4.6 4.4 3.3 2.5 PSA910 4.4 5.1 4.1 4.9 4.4 4.6 2.8 3.2 PSA915
5.6 6.1 4.8 5.9 5.4 5.2 3.3 3.7 PSA950 5.5 6.4 5.1 5.8 4.3 4.3 3.0
3.0 SCA1000 3.3 4.2 2.5 3.0 2.8 3.3 2.2 2.3 DC-2013 1.0 1.3 0.7 1.1
1.1 1.4 1.3 1.3 Q2-7406 4.8 5.3 3.0 4.7 3.6 3.6 2.7 2.8 Q2-7735 4.7
5.0 3.0 4.1 4.0 3.9 2.1 2.4 DC-7658 1.3 2.1 0.5 1.6 4.0 6.4 2.9 4.0
DC-280A 4.4 5.0 3.3 3.9 3.8 3.8 2.6 2.5 DC-282 5.2 5.3 3.5 4.3 3.4
3.8 2.3 2.5 DC-7355 4.9 5.2 3.3 4.5 3.5 3.7 2.3 3.0 DC-7358 5.3 5.6
3.0 4.3 4.0 4.3 2.8 3.0 Q2-7566 5.9 6.4 3.3 5.0 3.7 3.7 2.0 2.2
TABLE-US-00005 TABLE 4b Shear adhesion of uncrosslinked and E- beam
crosslinked silicone adhesives. 70.degree. C. Shear (minutes)
70.degree. C. Shear (minutes) uncrosslinked E-beam @ 6 Mrad Sample
Painted panel PP Panel Painted panel PP Panel PSA518 3 4 10,000+ 62
PSA529 18 21 7436 1374 PSA590 7 10 10,000+ 898 PSA595 8 11 10,000+
899 PSA610 6 9 10,000+ 10,000+ PSA6573A 146 111 10,000+ 10,000+
PSA6574 5 8 6879 138 PSA910 3 7 10,000+ 723 PSA915 5 7 7700 608
PSA950 1 2 211 51 SCA1000 3 8 329 355 DC-2013 1 2 2 5 Q2-7406 25 25
10,000+ 7243 Q2-7735 62 74 10,000+ 10,000+ DC-7658 14 15 10,000+
198 DC-280A 13 13 10,000+ 10,000+ DC-282 41 15 10,000+ 10,000+
DC-7355 21 22 10,000+ 10,000+ DC-7358 7 7 6876 732 Q2-7566 12 10
10,000+ 10,000+
[0068] These same materials were then used to form foam core tapes.
The silicone materials were first knife-unto a fluorosilicone liner
and dried at 70.degree. C. for 15 minutes to achieve 50 micron (2
mil) dry thickness. The dried silicone PSAs were then coated with
ADHESION PROMOTER 4298UV (a liquid primer containing cyclohexane,
xylene, ethyl alcohol, eythylbenzene, ethyl acetate, acrylic
polymer, chlorinated polyolefins, and isopropyl alcohol; available
from 3M Company, St. Paul, Minn.) and laminated to ACRYLIC FOAM
TAPE 5344 (a tape having a medium density acrylic foam core and an
acrylic adhesive on each side of the foam core; available from 3M).
While supported by the fluorosilicone liner, these laminates were
E-beam irradiated at an acceleration voltage of 300 key and doses
of 6 and 10 Mrads. The E-beam units were broadband curtain type
electron beam processors (PCT Engineered Systems, LLC, Davenport,
Iowa). The E-beam crosslinked samples were further tested according
to the Peel Test and Shear Test. The results are summarized in
Tables 5a and 5b. No cohesive failure was observed.
TABLE-US-00006 TABLE 5a Peel force for foam core tapes with E-beam
cured silicone adhesive skins. Peel (N/cm) Peel (N/cm) E-beam @ 6
Mrad E-beam @ 10 Mrad Painted Painted panel PP Panel panel PP Panel
20 72 20 72 20 72 20 72 Sample min hour min hour min hour min hour
PSA518 20.7 20.2 14.8 16.7 19.4 12.2 11.1 6.8 PSA529 42.2 33.9 17.9
24.5 39.7 32.8 17.7 12.9 PSA590 23.3 22.1 12.8 14.6 22.8 24.5 11.9
11.4 PSA595 15.8 23.1 14.8 17.6 20.0 27.0 9.8 13.5 PSA610 27.1 22.3
16.8 13.1 32.9 34.2 14.9 23.6 PSA6573A 36.2 37.1 3.7 12.6 36.0 36.6
6.4 21.2 PSA6574 16.8 21.5 16.4 15.5 42.9 27.4 18.5 16.8 PSA910
15.6 17.4 13.5 9.7 19.5 21.4 10.9 15.8 PSA915 19.4 20.8 18.2 16.0
21.6 18.1 17.1 9.8 PSA950 10.4 17.2 11.1 6.4 20.9 15.1 13.0 7.0
SCA1000 11.7 17.9 11.7 13.4 17.0 25.8 12.4 16.1 DC-2013 24.0 17.0
11.1 8.0 23.4 16.0 11.1 6.9 Q2-7406 15.6 25.6 11.5 11.1 27.8 23.9
10.0 16.8 Q2-7735 31.1 31.1 15.7 19.0 14.9 27.6 10.7 15.3 DC-7658
39.4 33.8 19.5 16.1 36.4 37.1 16.7 18.1 DC-280A 25.9 12.0 15.5 7.9
21.9 23.5 13.0 9.6 DC-282 27.6 22.6 14.8 8.0 23.5 26.4 13.9 13.2
DC-7355 20.0 22.3 12.5 9.9 21.4 15.6 12.8 10.3 DC-7358 16.5 19.0
9.8 8.6 15.5 16.2 10.5 6.8 Q2-7566 7.5 11.2 10.4 5.9 14.0 11.3 3.6
9.7
TABLE-US-00007 TABLE 5b Shear force for foam core tapes with E-beam
cured silicone adhesive skins. 70.degree. C. Shear (min) 70.degree.
C. Shear (min) E-beam @ 6 Mrad E-beam @ 10 Mrad Sample Painted
panel PP Panel Painted panel PP Panel PSA518 1972 73 1581 35 PSA529
652 524 725 748 PSA590 358 200 183 107 PSA595 4352 365 3563 391
PSA610 1276 232 274 52 PSA6573A 10000+ 2998 10000+ 3914 PSA6574 433
144 558 60 PSA910 2240 98 1441 103 PSA915 308 85 771 173 PSA950 357
47 534 78 SCA1000 1360 576 10000+ 12 DC-2013 10000+ 740 10000+ 161
Q2-7406 2849 328 10000+ 107 Q2-7735 336 153 390 182 DC-7658 596 166
10000+ 642 DC-280A 1288 490 1156 362 DC-282 368 953 398 168 DC-7355
3089 219 1309 189 DC-7358 455 28 1251 192 Q2-7566 599 49 7183
21
Hot-Melt Coated Samples
Example HM-1
[0069] One kilogram of PSA590 (used as received from Momentive
Performance Materials) was dried in an aluminum tray at 66.degree.
C. (150.degree. F.) for a week. The dried adhesive was fed into
twin screw extruder (available from Berstorff) and coated with a
rotary rod die coater onto fluorosilicone coated PET liner (2 CL
PET 5100/5100 from Loparex) at 50 microns (2 mils) dry thickness.
The coated samples were further E-beam irradiated at 300 key and 6
Mrads.
Example HM-1F
[0070] A foam core tape was prepared by laminating the cured
adhesive of Example HM-1 to a surface of 5666 foam tape (from 3M
Company) that had been primed with ADHESION PROMOTER 4298UV (from
3M Company).
[0071] Examples HM-2 through HM-7 were prepared by mixing EL
POLYMER NA (from Wacker) and TMS-803 (from Wacker) in a Brabender
at 120.degree. C. (250.degree. F.) for 60 minutes. The mixture was
hot pressed between primed PET film and fluorosilicone coated PET
liner (2 CL PET 5100/5100 from Loparex) into 50 micron (2 mil)
thick uncured adhesive layer. The adhesive layer was then
irradiated by E-beam (300 key and 6 Mrads).
[0072] Examples HM-2F through HM-7F were prepared laminating the
uncured adhesive layers of Examples HM-2 through HM-7 to a surface
of 5666 foam tape (from 3M Company) that had been primed with
ADHESION PROMOTER 4298UV (from 3M Company). The resulting structure
was then exposed to E-beam irradiation (300 key and 6 Mrads).
TABLE-US-00008 TABLE 6 Compositions of HM-2 through HM-7. EL
Polymer NA TMS-803 Example (g) (g) HM-2 19 31 HM-3 20 30 HM-4 21 29
HM-5 23 27 HM-6 24 26 HM-7 25 25
[0073] The hot-melt coated samples were tested for peel and shear.
The results are summarized in Table 7.
TABLE-US-00009 TABLE 7 Peel and shear performance of Examples HM-1
to HM-7 and HM-1F to HM-7F. E-Beam Peel (N/cm) Shear (minutes) Ex.
(Mrad) on MAC on TPO on MAC on TPO HM-1 6 7.1 4.4 4585 431 HM-1F 6
20.1 11.3 643 76 HM-2 6 11.3 8.3 6490 393 9 9.4 9.1 10000 316 12
8.6 8.3 10000 385 15 8.4 8.1 10000 1549 HM-2F 6 34.4 26.2 1851 810
9 34.0 26.6 1398 500 12 28.7 23.5 10000 938 15 31.2 23.2 8049 1342
HM-3 6 8.4 8.1 2135 812 9 8.2 7.8 10000 424 12 7.4 7.4 10000 956 15
7.2 7.0 10000 294 HM-3F 6 29.9 28.4 551 431 9 31.6 25.8 7459 848 12
28.1 24.8 10000 561 15 31.5 24.1 7666 435 HM-4 6 7.0 6.9 10000 278
9 6.8 7.1 10000 575 12 6.7 6.4 10000 1278 15 6.3 6.1 10000 879
HM-4F 6 25.1 21.0 1181 292 9 32.8 23.6 2925 1261 12 22.9 20.3 10000
284 15 26.6 23.2 10000 175 HM-5 6 4.7 4.5 10000 416 9 4.3 4.4 10000
2891 12 4.1 3.7 10000 5966 15 3.7 3.4 10000 10000 HM-5F 6 14.9 10.1
577 97 9 14.0 11.5 939 42 12 15.1 10.5 874 57 15 16.5 11.1 1398 26
HM-6 6 5.5 5.0 10000 386 9 4.8 4.6 10000 977 12 4.5 4.2 10000 10000
15 4.2 3.7 10000 3913 HM-6F 6 14.9 11.3 661 148 9 18.3 13.4 1050
141 12 16.9 11.8 34 2 15 16.8 11.7 38 26 HM-7 6 4.6 4.3 10000 475 9
4.0 3.9 10000 906 12 3.4 3.3 10000 4349 15 3.1 3.0 10000 5593 HM-7F
6 12.6 11.0 435 195 9 15.4 11.1 343 63 12 13.7 9.9 580 12 15 11.9
10.0 1518 10
Example HM-8
[0074] 3800 g of EL polymer NA (from Wacker) and 6200 g of TMS-803
(from Wacker) were fed into twin screw extruder (available from
Berstorff) at 260.degree. C. (500.degree. F.) and coated with a
rotary rod die coater at 50 microns (2 mil) dry thickness gap onto
EX4011 foam tape (from 3M Company). The adhesive coated side of the
foam tapes were covered with a fluorosilicone coated PET liner (2
CL PET 5100/5100 from Loparex) and E-beam irradiated at 300 key and
6 or 12 Mrads.
Example HM-9
[0075] Example HM-9 was prepared according to the procedure of
Example HM-8 except that 3400 g of EL polymer NA and 6600 g of
TMS-803 were used.
[0076] Examples HM-8 and HM-9 were tested for peel adhesion on two
substrates. Peels were measured after a 20 minute dwell and after a
48 hour dwell.
TABLE-US-00010 TABLE 8 Peel results for Examples HM-8 and HM-9.
E-beam Peel on MAC Peel on TPO Ex. (Mrad) 20 min. 48 hr. 20 min. 48
hr. HM-8 6 39.6 48.6 21.4 37.0 12 26.7 39.0 19.8 25.4 HM-9 6 42.2
44.8 13.9 19.9 12 29.4 44.2 9.1 24.7
Foam Examples
[0077] The materials used to prepare electron beam cured silicone
foams are summarized in Table 9.
TABLE-US-00011 TABLE 9 Materials used in Examples F-1 through F-19.
Material Description Source EL-P-A EL POLYMER NA Wacker Chemie, AG
TMS-803 MQ tackifier Wacker Chemie, AG OHX-4040 silanol terminated
PDMS Dow Corning (XIAMETER OHX-4040) K-15 Glass bubbles 3M Company
K-37 Glass bubbles 3M Company F100 expandable microspheres Henkel
(MICROPEARL F100) R972V silica particles Cabot (AEROSIL R972V)
[0078] Example F-1 was prepared by mixing 20 g of EL POLYMER NA, 3
g of TMS803, and 2 g of F100 expandable microsphere in a Brabender
at 93.degree. C. (200.degree. F.) and 16 RPM. The mixture was then
expanded with a hot presser (Carver Laboratory Press) at
204.degree. C. (400.degree. F.). The resulting 1.65 mm (65 mil)
thick foam sheet was milky white and self tacky. This foam sheet
was then e-beamed at 300 key and 6 Mrads from both sides. The
cured, self tacky silicone foam thus made had a density of 9.75
g/in3.
[0079] Foam Examples F-2 through F-19 were prepared according to
the formulations provided in Tables 10A and 10B. The components
were mixed at 2350 RPM for 5 minutes with a speedmixer (DAC 600
FVZ). The mixture was then pressed with a hot presser (Carver
Laboratory Press) at 204.degree. C. (400.degree. F.). The resulting
1.5 mm (60 mil) thick foam sheet was milky white. These foam sheets
were then e-beamed at 300 key and 15 Mrads from both sides. The
resulting foam densities for samples using glass bubbles are
summarized in Table 10A.
TABLE-US-00012 TABLE 10A Foam compositions and densities for
Examples F-2 through F-14 (foam produced by the addition of glass
bubbles). Composition (g) Density Ex. EL-P-NA OHX-4040 K-15 K-37
R972V (g/cc) F-2 -- 60 -- 18 -- 0.67 F-3 -- 40 -- 24 -- 0.56 F-4 --
40 6 -- -- 0.61 F-5 -- 40 12 -- -- 0.64 F-6 -- 40 6 -- 1.67 0.63
F-7 -- 40 6 -- 3.33 0.66 F-8 -- 40 6 -- 6.67 0.79 F-9 40 -- 3 -- --
0.83 F-10 40 -- 6 -- -- 0.82 F-11 40 -- 12 -- -- 0.86 F-12 40 -- 6
-- 1.67 0.87 F-13 40 -- 6 -- 3.33 0.89 F-14 40 -- 6 -- 6.67
0.91
[0080] The resulting foam densities for samples using expandable
polymeric microspheres are summarized in Table 9B.
TABLE-US-00013 TABLE 10B Foam compositions and densities for
Examples F-15 through F-19 (foam produced with expandable polymeric
microspheres). Composition (g) Density Ex. EL-P-NA F-100 R972V
(g/cc) F-15 40 6 -- 0.40 F-16 30 9 -- 0.18 F-17 30 9 1.25 0.18 F-18
30 9 2.50 0.17 F-19 30 9 5.00 0.21
[0081] Exemplary crosslinked polysiloxane foam 200 is illustrated
in FIG. 2. Foam 200 comprises crosslinked polysiloxane material 210
with polymeric microspheres 220 dispersed throughout. Although not
shown, glass bubbles could be included along with or in place of
the polymeric microspheres.
[0082] In some embodiments, the materials and methods of the
present disclosure may be used to produce non-pressure sensitive
materials from non-functionalized silicone materials. Such
materials having a, E-beam crosslinked polysiloxane network include
films and coatings, including non-tacky silicone films.
Non-Tacky Film Examples
[0083] Example NTF-1 was prepared by mixing 40 g of EL POLYMER NA
and 4 g of CAB-O-SIL TS-720 fumed silica (from Cabot) in a
Brabender at 200.degree. C. and 60 RPM for about 20 minutes. The
mixture was then pressed between two fluorosilicone liners (from
Loparex as 2 CL PET 5100/5100) by a hot presser (Carver Laboratory
Press). The polysiloxane composition was electron beam at 300 key
and 10 Mrads. The resulting 0.165 mm (6.5 mil) thick silicone films
were transparent, tack-free, and elastic.
[0084] Example NTF-2 was prepared by mixing 40 g of DMS-53 (from
Gelest) and 10 g of CAB-O-SIL TS-720 fumed silica TS-720 in a
Brabender at 100.degree. C. and 60 RPM for about 30 minutes. The
mixture was then pressed between two fluorosilicone liners (from
Loparex as 2 CL PET 5100/5100) by a hot presser (Carver Laboratory
Press). The polysiloxane composition was electron beam at 300 key
and 10 Mrads. The resulting 0.05 mm (2 mil) thick silicone films
were transparent, tack-free, and elastic.
[0085] Various modifications and alterations of this invention will
become apparent to those skilled in the art without departing from
the scope and spirit of this invention.
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