U.S. patent number RE45,747 [Application Number 14/161,994] was granted by the patent office on 2015-10-13 for articles that include a polymer foam and method for preparing same.
This patent grant is currently assigned to 3M INNOVATIVE PROPERTIES COMPANY. The grantee listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Mark D. Gehlsen, Bradley S. Momchilovich.
United States Patent |
RE45,747 |
Gehlsen , et al. |
October 13, 2015 |
Articles that include a polymer foam and method for preparing
same
Abstract
Polymer foam articles prepared by melt-mixing a polymer
composition and a plurality of microspheres, at least one of which
is an expandable polymeric microsphere, under process conditions,
including temperature and shear rate, selected to form an
expandable extrudable composition; and extruding the composition
through a die.
Inventors: |
Gehlsen; Mark D. (St. Paul,
MN), Momchilovich; Bradley S. (St. Paul, MN) |
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Assignee: |
3M INNOVATIVE PROPERTIES
COMPANY (St. Paul, MN)
|
Family
ID: |
22431887 |
Appl.
No.: |
14/161,994 |
Filed: |
January 23, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
09714658 |
Sep 28, 2004 |
6797371 |
|
|
|
PCT/US99/17344 |
Jul 30, 1999 |
|
|
|
|
09127774 |
Aug 15, 2000 |
6103152 |
|
|
Reissue of: |
10835865 |
Apr 30, 2004 |
7879441 |
Feb 1, 2011 |
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C
48/495 (20190201); B29C 48/39 (20190201); B29C
48/387 (20190201); C09J 7/21 (20180101); C09J
11/08 (20130101); C09J 7/241 (20180101); C09J
7/30 (20180101); B29C 48/08 (20190201); B29C
70/66 (20130101); B29C 44/18 (20130101); B29C
48/37 (20190201); C09J 5/08 (20130101); C08J
9/32 (20130101); B29C 44/3484 (20130101); B29C
48/21 (20190201); B29C 48/00 (20190201); Y10T
428/249972 (20150401); C08J 2207/02 (20130101); C08L
33/00 (20130101); Y10T 428/2848 (20150115); B29C
48/06 (20190201); Y10T 428/28 (20150115); B29C
48/13 (20190201); B29C 48/12 (20190201); B29K
2105/165 (20130101); C08J 2203/22 (20130101); Y10T
428/249953 (20150401); Y10T 428/249954 (20150401); Y10T
428/249984 (20150401); Y10T 428/2891 (20150115); Y10T
428/249971 (20150401); Y10T 428/249978 (20150401); B29K
2105/048 (20130101); Y10T 428/249983 (20150401); C09J
2433/00 (20130101); Y10T 428/249981 (20150401); Y10T
428/249986 (20150401); B29C 48/09 (20190201); B29C
48/022 (20190201) |
Current International
Class: |
B32B
7/12 (20060101); B29C 47/56 (20060101); C09J
5/08 (20060101); C08J 9/32 (20060101); B29C
70/66 (20060101); B29C 44/18 (20060101); B29C
47/36 (20060101); B29C 44/34 (20060101); B32B
3/26 (20060101); C08L 33/00 (20060101); B29C
47/00 (20060101) |
Field of
Search: |
;428/343,355,355AC,354,304.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
747341 |
|
Nov 1966 |
|
CA |
|
2049471 |
|
Apr 1971 |
|
DE |
|
3600041 |
|
Jul 1987 |
|
DE |
|
197 30 854 |
|
Jul 1995 |
|
DE |
|
4407144 |
|
Jul 1995 |
|
DE |
|
19521520 |
|
Dec 1996 |
|
DE |
|
195 27 926 |
|
Jan 1997 |
|
DE |
|
195 31 631 |
|
Mar 1997 |
|
DE |
|
19531631 |
|
Mar 1997 |
|
DE |
|
19803362 |
|
Aug 1999 |
|
DE |
|
0 206 760 |
|
Dec 1986 |
|
EP |
|
0 084 220 |
|
Jan 1987 |
|
EP |
|
0 222 680 |
|
May 1987 |
|
EP |
|
0 257 984 |
|
Mar 1988 |
|
EP |
|
0305161 |
|
Mar 1989 |
|
EP |
|
0 324 242 |
|
Jul 1989 |
|
EP |
|
0 349 216 |
|
Jan 1990 |
|
EP |
|
0 437 068 |
|
Jul 1991 |
|
EP |
|
0437068 |
|
Jul 1991 |
|
EP |
|
0 567 837 |
|
Nov 1993 |
|
EP |
|
0 575 012 |
|
Dec 1993 |
|
EP |
|
0 681 594 |
|
Nov 1995 |
|
EP |
|
0 692 516 |
|
Jan 1996 |
|
EP |
|
0692516 |
|
Jan 1996 |
|
EP |
|
0 710 696 |
|
May 1996 |
|
EP |
|
0 717 091 |
|
Jun 1996 |
|
EP |
|
0 763 585 |
|
Mar 1997 |
|
EP |
|
0802946 |
|
Oct 1997 |
|
EP |
|
1 316 747 |
|
May 1973 |
|
GB |
|
56061467 |
|
May 1981 |
|
JP |
|
SHO 60-76583 |
|
Jan 1985 |
|
JP |
|
62087858 |
|
Oct 1988 |
|
JP |
|
HEI 5 194921 |
|
Aug 1993 |
|
JP |
|
7-70520 |
|
Mar 1995 |
|
JP |
|
07268287 |
|
Oct 1995 |
|
JP |
|
08-012888 |
|
Jan 1996 |
|
JP |
|
08 067861 |
|
Mar 1996 |
|
JP |
|
09328662 |
|
Dec 1997 |
|
JP |
|
10-152575 |
|
Jun 1998 |
|
JP |
|
10-168401 |
|
Jun 1998 |
|
JP |
|
2000-17140 |
|
Jan 2000 |
|
JP |
|
89/00106 |
|
Jan 1989 |
|
WO |
|
93/07228 |
|
Apr 1993 |
|
WO |
|
95/16754 |
|
Jun 1995 |
|
WO |
|
95/25774 |
|
Sep 1995 |
|
WO |
|
95/31225 |
|
Nov 1995 |
|
WO |
|
96/14366 |
|
May 1996 |
|
WO |
|
96/38285 |
|
Dec 1996 |
|
WO |
|
97/34958 |
|
Sep 1997 |
|
WO |
|
WO 97/47681 |
|
Dec 1997 |
|
WO |
|
98/15298 |
|
Apr 1998 |
|
WO |
|
99/03943 |
|
Jan 1999 |
|
WO |
|
WO 99/23144 |
|
May 1999 |
|
WO |
|
Other References
"Expancel.RTM., Microspheres in Thermoplastics," Technical Bulletin
No. 24, Nov. 18, 1996. cited by applicant .
"Blowing Agent Systems: Formulations and Processing, A One Day
Seminar," RAPRA Technology Ltd., Feb. 19, 1998. cited by applicant
.
U. Wagenknecht et al., "Mit zellularen Mikrohohlkugeln zu leichten
Polyolefin Compounds," Kunststoffberater 41 (1996) pp. 18-22. cited
by applicant .
A. H. Landrock, "Handbook of Plastic Foams: Types, Properties,
Manufacture, and Applications," Plastic Technical Evaluation Center
(PLASTEC), Noyes Publications, (1995), pp. 154-155. cited by
applicant .
Japan Patent Abstract of JP 56-061467, see above for date and
inventor. cited by examiner .
Derwent Abstract of JP 56-061467, see above for date and inventor.
cited by examiner .
Translation of JP 56-061467, see PTO 892 mailed Jul. 6, 2007 for
date and inventor. cited by examiner .
Translation of JP 07-268287, see above for date and inventor. cited
by examiner .
Abstract of JP 07-268287, see above for date and abstract. cited by
examiner .
Translation of JP 56-061467, see PTO-892 mailed Jul. 6, 2007 for
date and inventor. cited by examiner .
Cobbs, W., "Foaming of hot Melts", pp. 103-115. cited by applicant
.
Klempher et al., Handbook of Polymeric Foams and Foam Technology,
pp. 229-233, Hanser Pub., NY, NY (1991). cited by applicant .
Cusdin, "What Plate Thickness Really Works Best", FLEXO, pp. 90-95,
Mar. 1997. cited by applicant .
Dahl, "The FQC Plate Construction Project", FLEXO, pp. 32-40, Nov.
1996. cited by applicant .
Pocius, "The Chemistry and Physical Properties of Elastomer-Based
Adhesives", Adhesion and Adhesives Technology, An Introduction,
Hanser/Gardner Publications, Inc., Cincinnati. cited by applicant
.
Kim et al., "Viscoelastic Behavior and Order-Disorder Transition in
Mixtures of a Block Copolymer" Journal of Polymer Science, Part B,
Polymer Physics, vol. 26, pp. 677-701, John wiley & Sons, Inc.
(1988). cited by applicant .
Kraus et al., "Tack and Viscoelasticity of block Copolymer Based
Adhesives", J. Adhesion, vol. 10, pp. 221-236 (1979). cited by
applicant .
Han et al., "Viscoelastic Behavior, Thermodynamic Compatibility,
and Phase Equilibria in Block Copolymer-Based Pressure-Sensitive
Adhesives", J. Adhesion, vol. 28, pp. 201-230 (1989). cited by
applicant .
D. Satas, Handbook Of Pressure-Sensitive Adhesives, Chapter 11, pp.
220-275, van Nostrand Reinhold CO., New York (1982). cited by
applicant.
|
Primary Examiner: Lopez; Carlos
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
Parent Case Text
RELATED APPLICATIONS
.[.The present application.]. .Iadd.This application is a reissue
application of U.S. Pat. No. 7,879,441, issued on Feb. 1, 2011,
from U.S. patent application Ser. No. 10/835,865, which .Iaddend.is
a continuation of U.S. patent application Ser. No. 09/714,658,
filed Nov. 16, 2000, now U.S. Pat. No. 6,797,371, issued Sep. 28,
2004 which is a continuation of International Application
PCT/US99/17344, having an international filing date of Jul. 30,
1999, which is a continuation-in-part and which claims priority to
U.S. patent application Ser. No. 09/127,774, filed Jul. 31, 1998,
now U.S. Pat. No. 6,103,152, issued Aug. 15, 2000, all of which are
assigned to the assignee of the present application. The entire
disclosure of the prior application is considered as being part of
the disclosure of the accompanying application and is hereby
incorporated by reference therein.
Claims
What is claimed is:
1. A foam article comprising: an extruded polymer foam formed by
polymerization of one or more monomeric acrylic or methacrylic
esters of non-tertiary alkyl alcohols, said alkyl alcohols having
from 1 to 20 carbon atoms; and a homogeneous distribution of a
plurality of thermoplastic expandable polymeric microspheres within
the extruded polymer foam, said plurality of expandable polymeric
microspheres comprising unexpanded expandable polymeric
microspheres, at least partially expanded expandable polymeric
microspheres, or both.Iadd., wherein said extruded polymer foam has
a center and a uniform size distribution of said expandable
polymeric microspheres from major outer surfaces of said extruded
polymer foam to the center of said extruded polymer foam.
.Iaddend.
2. The foam article according to claim 1, wherein said extruded
polymer foam exhibits a machine (or longitudinal) direction and
crossweb (or transverse) direction standard deviation of density or
thickness over an average density or thickness (.sigma./x),
respectively, of less than about 0.2.
3. The foam article according to claim 2, wherein
.Iadd.(.Iaddend..sigma./x.Iadd.) .Iaddend.is less than about
0.05.
4. The foam article according to claim 1, wherein said extruded
polymer foam is an adhesive.
5. The foam article according to claim 1, wherein said extruded
polymer foam comprises at least one polymer having a weight average
molecular weight of at least about 10,000 g/mol.
6. The foam article according to claim 1, wherein said extruded
polymer foam comprises at least one polymer having a shear
viscosity, measured at a temperature of 175.degree. C. and a shear
rate of 100 sec.sup.-1, of at least about 100 Pa-s.
7. The foam article of claim 1, wherein said extruded polymer foam
comprises a polymer matrix comprising a blend of two or more
polymers wherein at least one of said polymers in said blend
comprises a pressure sensitive adhesive and at least one of said
polymers is an acrylate-insoluble semi-crystalline polymer.
8. The foam article of claim 1, wherein the extruded polymer foam
comprises an acrylic polymer foam formed by polymerization of a
monomer mixture comprising: one or more acrylic or methacrylic
esters of non-tertiary alkyl alcohols, wherein said alkyl alcohols
have from 1 to 20 carbon atoms; and one or more monomers selected
from acrylic acid, acrylamide, methacrylamide,
N,N-dimethylacrylamide, itaconic acid, methacrylic acid,
acrylonitrile, methacrylonitrile, vinyl acetate, N-vinyl
pyrrolidone, isobornyl acrylate, cyano ethyl acrylate, N-vinyl
caprolactam, maleic anhydride, hydroxyalkylacrylates, N,N-dimethyl
aminoethyl methacrylate, 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.
9. The foam article of claim 1, wherein the extruded polymer foam
comprises an acrylic foam formed by polymerization of a monomer
mixture comprising: one or more acrylic or methacrylic esters of
non-tertiary alkyl alcohols, wherein said alkyl alcohols have from
1 to 20 carbon atoms; and one or more monomers selected from
ethyloxyethoxy ethyl acrylate and methoxypolyethylene glycol
acrylate.
10. The foam article according to claim 1, wherein the extruded
polymer foam is capable of stretch activated release.
11. The foam article according to claim 1, further comprising at
least one layer comprising a polymer composition, said at least one
layer bonded to said extruded polymer foam.
12. The foam article according to claim 1, wherein said extruded
polymer foam is at least partially embedded within a separate
polymer composition, said separate polymer composition having a
density that differs from said extruded polymer foam.
.[.13. The foam article according to claim 1, wherein said extruded
polymer foam has a center and a uniform size distribution of said
expandable polymeric microspheres from major outer surfaces of said
extruded polymer foam to the center of said extruded polymer
foam..].
14. The foam article according to claim 1, wherein said plurality
of expandable polymeric microspheres comprises unexpanded
expandable polymeric microspheres.
15. An article comprising: an extruded adhesive layer; and a
homogeneous distribution of a plurality of thermoplastic expandable
polymeric microspheres throughout the extruded adhesive layer, said
plurality of thermoplastic expandable polymeric microspheres
comprising unexpanded expandable polymeric microspheres, at least
partially expanded expandable polymeric microspheres, or both;
wherein the extruded adhesive layer comprises a polymer matrix
comprising a blend of two or more polymers substantially free of
urethane crosslinks and urea crosslinks to eliminate the need for
isocyanates in said polymer matrix, wherein at least one of said
polymers in said blend comprises a pressure sensitive adhesive
polymer formed by polymerization of monomers comprising an
acrylate, methacrylate, or combinations thereof; and at least one
of said polymers is selected from unsaturated thermoplastic
elastomers, acrylate monomer-insoluble saturated thermoplastic
elastomers, acrylate-insoluble semicrystalline polymers,
acrylate-insoluble amorphous polymers having a solubility parameter
of less than 8 or greater than 11, elastomers containing
ultraviolet radiation-activatable groups, and pressure sensitive
and hot melt adhesives prepared from non-photopolymerizable
monomers.
16. The article according to claim 15, wherein the extruded
adhesive layer comprises a polymer matrix comprising a pressure
sensitive adhesive polymer formed by polymerization of monomers
comprising an acrylate, methacrylate, or combinations thereof.
17. The foam article according to claim 14, wherein said plurality
of expandable polymeric microspheres further comprises at least
partially expanded expandable polymeric microspheres.
18. The article according to claim 15, wherein said plurality of
expandable polymeric microspheres comprises unexpanded expandable
polymeric microspheres.
19. The article according to claim 18, wherein said plurality of
expandable polymeric microspheres further comprises at least
partially expanded expandable polymeric microspheres.
20. The article according to claim 15, further comprising at least
one layer comprising a polymer composition, said at least one layer
bonded to said extruded adhesive layer.
.Iadd.21. The foam article of claim 2, wherein the extruded polymer
foam comprises an acrylic polymer foam formed by polymerization of
a monomer mixture comprising: one or more acrylic or methacrylic
esters of non-tertiary alkyl alcohols, wherein said alkyl alcohols
have from 1 to 20 carbon atoms; and one or more monomers selected
from acrylic acid, acrylamide, methacrylamide,
N,N-dimethylacrylamide, itaconic acid, methacrylic acid,
acrylonitrile, methacrylonitrile, vinyl acetate, N-vinyl
pyrrolidone, isobornyl acrylate, cyano ethyl acrylate, N-vinyl
caprolactam, maleic anhydride, hydroxyalkylacrylates, N,N-dimethyl
aminoethyl methacrylate, 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. .Iaddend.
.Iadd.22. The foam article of claim 2, wherein the extruded polymer
foam comprises an acrylic foam formed by polymerization of a
monomer mixture comprising: one or more acrylic or methacrylic
esters of non-tertiary alkyl alcohols, wherein said alkyl alcohols
have from 1 to 20 carbon atoms; and one or more monomers selected
from ethyloxyethoxy ethyl acrylate and methoxypolyethylene glycol
acrylate. .Iaddend.
.Iadd.23. The foam article of claim 3, wherein the extruded polymer
foam comprises an acrylic polymer foam formed by polymerization of
a monomer mixture comprising: one or more acrylic or methacrylic
esters of non-tertiary alkyl alcohols, wherein said alkyl alcohols
have from 1 to 20 carbon atoms; and one or more monomers selected
from acrylic acid, acrylamide, methacrylamide,
N,N-dimethylacrylamide, itaconic acid, methacrylic acid,
acrylonitrile, methacrylonitrile, vinyl acetate, N-vinyl
pyrrolidone, isobornyl acrylate, cyano ethyl acrylate, N-vinyl
caprolactam, maleic anhydride, hydroxyalkylacrylates, N,N-dimethyl
aminoethyl methacrylate, 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. .Iaddend.
.Iadd.24. The foam article of claim 3, wherein the extruded polymer
foam comprises an acrylic foam formed by polymerization of a
monomer mixture comprising: one or more acrylic or methacrylic
esters of non-tertiary alkyl alcohols, wherein said alkyl alcohols
have from 1 to 20 carbon atoms; and one or more monomers selected
from ethyloxyethoxy ethyl acrylate and methoxypolyethylene glycol
acrylate. .Iaddend.
Description
FIELD OF THE INVENTION
This invention relates to preparing articles that include a polymer
foam.
BACKGROUND OF THE INVENTION
Articles incorporating a polymer foam core are known. The foam
includes a polymer matrix and is characterized by a density that is
lower than the density of the polymer matrix itself. Density
reduction is achieved in a number of ways, including through
creation of gas-filled voids in the matrix (e.g., by means of a
blowing agent) or inclusion of polymeric microspheres (e.g.,
expandable microspheres) or non-polymeric microspheres (e.g., glass
microspheres).
SUMMARY OF THE INVENTION
In a first aspect, the invention features an article that includes
a polymer foam having a substantially smooth surface. The foam may
be provided in a variety of shapes, including a rod, a cylinder, a
sheet, etc. In some embodiments, e.g., where the foam is provided
in the form of a sheet, the foam has a pair of major surfaces, one
or both of which are substantially smooth. The foam includes a
plurality of microspheres, at least one of which is an expandable
polymeric microsphere.
As used herein, a "polymer foam" refers to an article that includes
a polymer matrix in which the density of the article is less than
the density of the polymer matrix alone.
A "substantially smooth" surface refers to a surface having an Ra
value less than about 75 micrometers, as measured by laser
triangulation profilometry according to the procedure described in
the Examples, infra. Preferably, the surface has an Ra value less
than about 50 micrometers, more preferably less than about 25
micrometers. The surface is also characterized by the substantial
absence of visually observable macroscopic defects such as
wrinkles, corrugations and creases. In addition, in the case of an
adhesive surface, the surface is sufficiently smooth such that it
exhibits adequate contact and, thereby, adhesion to a substrate of
interest. The desired threshold level of adhesion will depend on
the particular application for which the article is being used.
An "expandable polymeric microsphere" is a microsphere that
includes a polymer shell and a core material in the form of a gas,
liquid, or combination thereof, that expands upon heating.
Expansion of the core material, in turn, causes the shell to
expand, at least at the heating temperature. An expandable
microsphere is one where the shell can be initially expanded or
further expanded without breaking. Some microspheres may have
polymer shells that only allow the core material to expand at or
near the heating temperature.
The article may be an adhesive article or a non-adhesive article.
An "adhesive article" is an article having a surface available for
bonding that is either tacky at room temperature (i.e., pressure
sensitive adhesive articles) or becomes tacky when heated (i.e.,
heat-activated adhesive articles). An example of an adhesive
article is a foam that itself is an adhesive, or an article that
includes one or more separate adhesive compositions bonded to the
foam, e.g., in the form of a continuous layer or discrete
structures (e.g., stripes, rods, filament, etc.), in which case the
foam itself need not be an adhesive. Examples of non-adhesive
articles include non-adhesive foams and adhesive foams provided
with a non-adhesive composition, e.g., in the form of a layer,
substrate, etc., on all surfaces available for bonding.
The foam preferably is substantially free of urethane crosslinks
and urea crosslinks, thus eliminating the need for isocyanates in
the composition. An example of a preferred material for the polymer
foam is an acrylic polymer or copolymer. In some cases, e.g., where
high cohesive strength and/or high modulus is needed, the foam may
be crosslinked.
The polymer foam preferably includes a plurality of expandable
polymeric microspheres. The foam may also include one or more
non-expandable microspheres, which may be polymeric or
non-polymeric microspheres (e.g., glass microspheres).
Examples of preferred expandable polymeric microspheres include
those in which the shell is essentially free of vinylidene chloride
units. Preferred core materials are materials other than air that
expand upon heating.
The foam may contain agents in addition to microspheres, the choice
of which is dictated by the properties needed for the intended
application of the article. Examples of suitable agents include
those selected from the group consisting of tackifiers,
plasticizers, pigments, dyes, solid fillers, and combinations
thereof. The foam may also include gas-filled voids in the polymer
matrix. Such voids typically are formed by including a blowing
agent in the polymer matrix material and then activating the
blowing agent, e.g., by exposing the polymer matrix material to
heat or radiation.
The properties of the article may be adjusted by bonding and/or
co-extruding one or more polymer compositions (e.g., in the form of
continuous layers or discrete structures such as stripes, rods,
filament, etc.) to or into the foam. Both foamed and non-foamed
compositions may be used. A composition may be bonded directly to
the foam or indirectly, e.g., through a separate adhesive.
The article may be used as a "foam-in-place" article. The term
foam-in-place refers to the ability of the article to be expanded
or further expanded after the article has been placed at a desired
location. Such articles are sized and placed in a recessed area or
on an open surface, and then exposed to heat energy (e.g.,
infrared, ultrasound, microwave, resistive, induction, convection,
etc.) to activate, or further activate, the expandable microspheres
or blowing agent. Such recessed areas can include a space between
two or more surfaces (e.g., parallel or non-parallel surfaces) such
as found, for example, between two or more opposing and spaced
apart substrates, a through hole or a cavity. Such open surfaces
can include a flat or uneven surface on which it is desirable for
the article to expand after being applied to the surface. Upon
activation, the foam expands due to the expansion of the
microspheres and/or blowing agent, thereby partially or completely
filling the recess or space, or thereby increasing the volume (e.g.
height) of the article above the open surface.
It can be desirable for the foam to comprise a substantially
uncrosslinked or thermoplastic polymeric matrix material. It can
also be desirable for the matrix polymer of the foam to exhibit
some degree of crosslinking. Any crosslinking should not
significantly inhibit or prevent the foam from expanding to the
degree desired. One potential advantage to such crosslinking is
that the foam will likely exhibit improved mechanical properties
(e.g., increase cohesive strength) compared to the same foam with
less or no crosslinking. In the case of foams having a curable
polymer matrix, exposure to heat can also initiate cure of the
matrix.
It can further be desirable for the foam-in-place article to
comprise multiple layers, discrete structures or a combination
thereof (See, for example, FIGS. 4-6 and the below discussion
thereof), with each layer and discrete structure having a
difference in the way it foams-in-place (e.g., using expandable
microspheres, blowing agents or a combination thereof), a
difference in the degree to which it can be expanded in place, or a
combination thereof. For example, the concentration of expandable
microspheres and/or blowing agents can be different, the type of
expandable microspheres and/or blowing agents can be different, or
a combination thereof can be used. In addition, for example, one or
more of the layers and discrete structures can be expandable in
place while one or more other layers and discrete structures can be
unexpandable in place.
In a second aspect, the invention features an article (e.g., an
adhesive article, as defined above) comprising a polymer foam (as
defined above) that includes: (a) a plurality of microspheres, at
least one of which is an expandable polymeric microsphere (as
defined above), and (b) a polymer matrix that is substantially free
of urethane crosslinks and urea crosslinks. The matrix includes a
blend of two or more polymers in which at least one of the polymers
in the blend is a pressure sensitive adhesive polymer (i.e., a
polymer that is inherently pressure sensitive, as opposed to a
polymer which must be combined with a tackifier in order to form a
pressure sensitive composition) and at least one of the polymers is
selected from the group consisting of unsaturated thermoplastic
elastomers, acrylate-insoluble saturated thermoplastic elastomers,
and non-pressure sensitive adhesive thermoplastic polymers.
The foam preferably has a substantially smooth surface (as defined
above). In some embodiments, the foam has a pair of major surfaces,
one or both of which may be substantially smooth. The foam itself
may be an adhesive. The article may also include one or more
separate adhesive compositions bonded to the foam, e.g., in the
form of a layer. If desired, the foam may be crosslinked.
The polymer foam preferably includes a plurality of expandable
polymeric microspheres. It may also include non-expandable
microspheres, which may be polymeric or non-polymeric microspheres
(e.g., glass microspheres). The properties of the article may be
adjusted by directly or indirectly bonding one or more foamed or
non-foamed polymer compositions to the foam.
The invention also features multi-layer articles that include the
above-described foam articles provided on a major surface of a
first substrate, or sandwiched between a pair of substrates.
Examples of suitable substrates include wood substrates, synthetic
polymer substrates, and metal substrates (e.g., metal foils).
In a third aspect, the invention features a method for preparing an
article that includes: (a) melt mixing a polymer composition and a
plurality of microspheres, one or more of which is an expandable
polymeric microsphere (as defined above), under process conditions,
including temperature, pressure and shear rate, selected to form an
expandable extrudable composition; (b) extruding the composition
through a die to form a polymer foam (as defined above); and (c) at
least partially expanding one or more expandable polymeric
microspheres before the polymer composition exits the die. It can
be preferable for most, if not all, of the expandable microspheres
to be at least partially expanded before the polymer composition
exits the die. By causing expansion of the expandable polymeric
microspheres before the composition exits the die, the resulting
extruded foam can be produced to within tighter tolerances, as
described below in the Detailed Description.
It is desirable for the polymer composition to be substantially
solvent-free. That is, it is preferred that the polymer composition
contain less than 20 wt. % solvent, more preferably, contain
substantially none to no greater than about 10 wt. % solvent and,
even more preferably, contain no greater 20 than about 5 wt. %
solvent.
In a fourth aspect, the invention features another method for
preparing an article that includes: (a) melt mixing a polymer
composition and a plurality of microspheres, one or more of which
is an expandable polymeric microsphere (as defined above), under
process conditions, including temperature, pressure and shear rate,
selected to form an expandable extrudable composition; and (b)
extruding the composition through a die to form a polymer foam (as
defined above). After the polymer foam exits the die, enough of the
expandable polymeric microspheres in the foam remain unexpanded or,
at most, partially expanded to enable the polymer foam to be used
in a foam-in-place application. That is, the extruded foam can
still be further expanded to a substantial degree at some later
time in the application. Preferably, the expandable microspheres in
the extruded foam retain most, if not all, of their
expandability.
In a fifth aspect, the invention features another method for
preparing an article that includes: (a) melt mixing a polymer
composition and a plurality of microspheres, one or more of which
is an expandable polymeric microsphere (as defined above), under
process conditions, including temperature, pressure and shear rate,
selected to form an expandable extrudable composition; and (b)
extruding the composition through a die to form a polymer foam (as
defined above) having a substantially smooth surface (as defined
above). It is also possible to prepare foams having a pair of major
surfaces in which one or both major surfaces are substantially
smooth.
Polymers used according to the present invention can preferably
possess a weight average molecular weight of at least about 10,000
g/mol, and more preferably at least about 50,000 g/mol. It can also
be preferable for the polymers used according to the present
invention to exhibit shear viscosities measured at a temperature of
175.degree. C. and a shear rate of 100 sec.sup.-1, of at least
about 30 Pascal-seconds (Pa-s), more preferably at least about 100
Pa-s and even more preferably at least about 200 Pa-s.
The article may be an adhesive article (as defined above), e.g., a
pressure sensitive adhesive article or a heat-activated adhesive
article. In some embodiments, the foam itself is an adhesive.
Both the expandable extrudable composition and the extruded foam
preferably include a plurality of expandable polymeric microspheres
(as defined above). The extruded foam and the expandable extrudable
composition may also include one or more non-expandable
microspheres, which may be polymeric or non-polymeric microspheres
(e.g., glass microspheres).
The expandable extrudable composition may be co-extruded with one
or more additional extrudable polymer compositions, e.g., to form a
polymer layer on a surface of the resulting foam. For example, the
additional extrudable polymer composition may be an adhesive
composition. Other suitable additional extrudable polymer
compositions include additional microsphere-containing
compositions.
The method may also include crosslinking the foam. For example, the
foam may be exposed to thermal, actinic, or ionizing radiation or
combinations thereof subsequent to extrusion to crosslink the foam.
Crosslinking may also be accomplished by using chemical
crosslinking methods based on ionic interactions.
The invention provides foam-containing articles, and a process for
preparing such articles, in which the articles can be designed to
exhibit a wide range of properties depending upon the ultimate
application for which the article is intended. For example, the
foam core may be produced alone or in combination with one or more
polymer compositions, e.g., in the form of layers to form
multi-layer articles. The ability to combine the foam with
additional polymer compositions offers significant design
flexibility, as a variety of different polymer compositions may be
used, including adhesive compositions, additional foam
compositions, removable compositions, layers having different
mechanical properties, etc. In addition, through careful control of
the foaming operation it is possible to produce a foam having a
pattern of regions having different densities.
Both thin and thick foams can be produced. In addition, both
adhesive and non-adhesive foams can be produced. In the latter
case, the foam may be combined with one or more separate adhesive
compositions to form an adhesive article. In addition, it is
possible to prepare foams from a number of different polymer
matrices, including polymer matrices that are incompatible with
foam preparation processes that rely on actinic radiation-induced
polymerization of microsphere-containing photopolymerizable
compositions. Examples of such polymer matrix compositions include
unsaturated thermoplastic elastomers and acrylate-insoluble
saturated thermoplastic elastomers. Similarly, it is possible to
include additives such as ultraviolet-absorbing pigments (e.g.,
black pigments), dyes, and tackifiers that could not be used
effectively in actinic radiation-based foam processes. It is
further possible, in contrast to solvent-based and actinic
radiation-based foam processes, to prepare foams having a
substantially homogeneous distribution of microspheres. In
addition, the present expanded foam (i.e., a foam containing
microspheres that have been at least partially expanded) can have a
uniform size distribution of the expanded microspheres from the
surface to the center of the foam. That is, there is no gradient of
expanded microsphere sizes from the surface to the center of the
foam, e.g., like that found in expanded foams which are made in a
press or a mold. Expanded foams that exhibit such a size
distribution gradient of their expanded microspheres can exhibit
weaker mechanical properties than such foams that have a uniform
size distribution of the expanded microspheres. Oven foaming of
these foam compositions require long residence times in the high
temperature oven due to the poor thermal conductivity of the foams.
Long residence times at high temperatures can lead to polymer and
carrier (e.g., release liner) degradation. In addition, poor heat
transfer can also lead to foams containing non-uniform expansion,
causing a density gradient. Such a density gradient can
significantly decrease the strength and otherwise detrimentally
impact the properties of the foam. The process associated with oven
foaming is also complicated and usually requires unique process
equipment to eliminate large scale corrugation and buckling of the
planar sheet. For a reference on oven foaming see, for example,
Handbook of Polymeric Foams & Foam Technology, eds: D. Klempner
& K. C. Frisch, Hanser Publishers, New York, N.Y., 1991.
Foams with a substantially smooth surface can be produced in a
single step. Accordingly, it is not necessary to bond additional
layers to the foam in order to achieve a smooth-surfaced article.
Substantially smooth-surfaced foams are desirable for a number of
reasons. For example, when the foam is laminated to another
substrate, the substantially smooth surface minimizes air
entrapment between the foam and the substrate. Moreover, in the
case of adhesive foams the substantially smooth surface maximizes
contact with a substrate to which the foam is applied, leading to
good adhesion.
The extrusion process enables the preparation of multilayer
articles, or articles with discrete structures, in a single step.
In addition, when foaming occurs during the extrusion, it is
possible, if desired, to eliminate separate post-production foaming
processes. Moreover, by manipulating the design of the extrusion
die (i.e., the shape of the die opening), it is possible to produce
foams having a variety of shapes.
In addition, the present method may include heating the article
after extrusion to cause further expansion. The additional
expansion may be due to microsphere expansion, activation of a
blowing agent, or a combination thereof.
It is also possible to prepare "foam-in-place" articles by
controlling the process temperature during the initial foam
preparation such that expansion of the microspheres is minimized or
suppressed. The article can then be placed at a location of use or
application, (e.g., in a recessed area or on an open surface) and
heated, or exposed to an elevated temperature to cause microsphere
expansion. "Foam-in-place" articles can also be prepared by
including a blowing agent in the expandable extrudable composition
and conducting the extrusion process under conditions insufficient
to activate the blowing agent. Subsequent to foam preparation, the
blowing agent can be activated to cause additional foaming.
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
FIG. 1(a) is a plot showing the Ra value obtained by laser
triangulation profilometry for the sample described in Example
12.
FIG. 1(b) is a photomicrograph obtained by scanning electron
microscopy (SEM) of the surface of the sample described in Example
12.
FIG. 2(a) is a plot showing the Ra value obtained by laser
triangulation profilometry for the sample described in Example
58.
FIG. 2(b) is a SEM photomicrograph of the surface of the sample
described in Example 58.
FIG. 3 is a perspective drawing showing a foam having a patterned
surface.
FIG. 4 is a perspective drawing of an article featuring a foam
combined with an additional polymer composition.
FIG. 5 is a perspective drawing of an article featuring a foam
combined with two additional polymer compositions.
FIG. 6 is a perspective drawing of an article featuring a foam
combined with multiple additional polymer compositions.
FIG. 7 is a schematic drawing of an extrusion process for preparing
articles according to the invention.
FIG. 8 is a plot showing the peel force applied in a direction (MD)
parallel to the filament direction as a function of displacement
for Examples 73, 77 and 78.
FIG. 9 is a plot showing the peel force applied in a direction (CD)
perpendicular to the filament direction as a function of
displacement for Examples 73, 77 and 78.
FIG. 10 is a plot showing the peel force applied in a direction
(MD) parallel to the filament direction as a function of
displacement for Examples 72, 79, 80 and 81.
FIG. 11 is a plot showing the peel force applied in a direction
(CD) perpendicular to the filament direction as a function of
displacement for Examples 72, 79, 80 and 81.
FIGS. 12a-12b are SEM photomicrographs of cross-sections, as viewed
in the machine direction (MD) and crossweb direction (CD),
respectively, of the unoriented foam described in Example 86.
FIGS. 12c-12d are SEM photomicrographs of cross-sections, as viewed
in the machine direction (MD) and crossweb direction (CD),
respectively, of the axially oriented foam described in Example
86.
FIGS. 13a and 13b are SEM photomicrographs of cross-sections, as
viewed in the machine direction (MD) and crossweb direction (CD),
respectively, of the polymer blend foam described in Example
23.
DETAILED DESCRIPTION
Article
The invention features articles that include a polymer foam
featuring a polymer matrix and one or more expandable polymer
microspheres. Examination of the foam by electron microscopy
reveals that the foam microstructure is characterized by a
plurality of enlarged polymeric microspheres (relative to their
original size) distributed throughout the polymer matrix. At least
one of the microspheres (and preferably more) is still expandable,
i.e., upon application of heat it will expand further without
breaking. This can be demonstrated by exposing the foam to a heat
treatment and comparing the size of the microspheres obtain by
electron microscopy to their pre-heat treated size (also obtained
by electron microscopy).
The foam is further characterized by a surface that is
substantially smooth, as defined in the Summary of the Invention,
above. Laser triangulation profilometry results and scanning
electron photomicrographs are shown in FIGS. 1 and 2 for
representative acrylic foams having substantially smooth surfaces
prepared as described in Examples 12 and 58, respectively,
described in further detail below. Each of the photomicrographs of
FIGS. 1(b) and 2(b) includes a 100 micrometer long measurement bar
B. Each of the samples in FIGS. 1(b) and 2(b) have been sectioned,
with the surface portion being light and the sectioned portion
being dark.
The foam may be provided in a variety of forms, including a sheet,
rod, or cylinder. In addition, the surface of the foam may be
patterned. An example of such a foam is shown in FIG. 3. Foam 100
is in the form of a sheet having a uniform pattern of bumps 102
arranged on the surface of the foam. Such articles are prepared by
differential foaming, as described in more detail, below. The
differential foaming process creates bumps 102 having a density
different from the density of the surrounding areas 104.
A variety of different polymer resins, as well as blends thereof,
may be used for the polymer matrix as long as the resins are
suitable for melt extrusion processing. For example, it may be
desirable to blend two or more acrylate polymers having different
compositions. A wide range of foam physical properties can be
obtained by manipulation of the blend component type and
concentration. The particular resin is selected based upon the
desired properties of the final foam-containing article. The
morphology of the immiscible polymer blend that comprises the foam
matrix can enhance the performance of the resulting foam article.
The blend morphology can be, for example, spherical, ellipsoidal,
fibrillar, co-continuous or combinations thereof. These
morphologies can lead to a unique set of properties that are not
obtainable by a single component foam system. Such unique
properties may include, for example, anisotropic mechanical
properties, enhanced cohesive strength. The morphology (shape &
size) of the immiscible polymer blend can be controlled by the free
energy considerations of the polymer system, relative viscosities
of the components, and most notably the processing & coating
characteristics. By proper control of these variables, the
morphology of the foam can be manipulated to provide superior
properties for the intended article.
FIGS. 13a and 13b show SEM photomicrographs of the microstructure
of the immiscible polymer blend of Example 23 (i.e., 80 wt % of the
Hot Melt Composition 1 and 20 wt % of Kraton.TM. D1107). The
Kraton.TM. D1107 was stained with OsO.sub.4 so as to appear white,
which enables this phase to be viewed. These Figures demonstrate
that the Kraton.TM. D1107 phase is a complex morphology consisting
of fibrillar microstructures, with sizes of approximately 1 .mu.m.
In FIG. 13a, the Kraton.TM. D1107 fibrillar phases are shown in
cross-section and appear spherical.
One class of useful polymers includes acrylate and methacrylate
adhesive polymers and copolymers. 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 form 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, isooctyl 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 and cyclobenzyl
acrylate.
Optionally, one or more monoethylenically unsaturated co-monomers
may be polymerized with the acrylate or methacrylate monomers; the
particular amount of co-monomer is selected 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
(e.g., available from Union Carbide Corp. of Danbury, Conn. under
the designation "Vynates", vinylidene chloride, styrene, vinyl
toluene, and alkyl vinyl ethers.
A second 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
a methoxypolyethylene glycol 400 acrylate (Tg=-65.degree. C.;
available from Shin Nakamura Chemical Co., Ltd. under the
designation "NK Ester AM-90G").
A second class of polymers useful for the polymer matrix of the
foam includes acrylate-insoluble 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, high density polyethylene,
polypropylene, 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. Other examples of
acrylate-insoluble 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, ABS copolymers, polyphenylene oxide alloys, ionomers
(e.g., ethylene-methacrylic acid copolymers neutralized with salt),
fluorinated elastomers, and polydimethyl siloxane.
A third class of polymers useful for the polymer matrix of the foam
includes elastomers containing ultraviolet radiation-activatable
groups. Examples include polybutadiene, polyisoprene,
polychloroprene, random and block copolymers of styrene and dienes
(e.g., SBR), and ethylene-propylene-diene monomer rubber.
A fourth class of polymers useful for the polymer matrix of the
foam includes 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
adhesive compositions when compounded with tackifiers. Specific
examples include poly-alpha-olefins (e.g., polyoctene, polyhexene,
and atactic polypropylene), block copolymer-based adhesives (e.g.,
diblock, tri-block, star-block and combinations thereof), natural
and synthetic rubbers, silicone adhesives, ethylene-vinyl acetate,
and epoxy-containing structural adhesive blends (e.g.,
epoxy-acrylate and epoxy-polyester blends).
The expandable microspheres feature a flexible, thermoplastic,
polymeric shell and a core that includes a liquid and/or gas which
expands upon heating. Preferably, the core material is an organic
substance that has a lower boiling point than the softening
temperature of the polymeric shell. Examples of suitable core
materials include propane, butane, pentane, isobutane, neopentane,
and combinations thereof.
The choice of thermoplastic resin for the polymeric shell
influences the mechanical properties of the foam. Accordingly, the
properties of the foam may be adjusted through appropriate choice
of microsphere, or by using mixtures of different types of
microspheres. For example, acrylonitrile-containing resins are
useful where high tensile and cohesive strength are desired,
particularly where the acrylonitrile content is at least 50% by
weight of the resin, more preferably at least 60% by weight, and
even more preferably at least 70% by weight. In general, both
tensile and cohesive strength increase with increasing
acrylonitrile content. In some cases, it is possible to prepare
foams having higher tensile and cohesive strength than the polymer
matrix alone, even though the foam has a lower density than the
matrix. This provides the capability of preparing high strength,
low density articles.
Examples of suitable thermoplastic resins which may be used as the
shell include acrylic and methacrylic acid esters such as
polyacrylate; acrylate-acrylonitrile copolymer; and
methacrylate-acrylic acid copolymer. Vinylidene chloride-containing
polymers such as vinylidene chloride-methacrylate copolymer,
vinylidene chloride-acrylonitrile copolymer,
acrylonitrile-vinylidene chloride-methacrylonitrile-methyl acrylate
copolymer, and acrylonitrile-vinylidene
chloride-methacrylonitrile-methyl methacrylate copolymer may also
be used, but are not preferred where high strength is desired. In
general, where high strength is desired, the microsphere shell
preferably has no more than 20% by weight vinylidene chloride, more
preferably no more than 15% by weight vinylidene chloride. Even
more preferred for high strength applications are microspheres
having essentially no vinylidene chloride units.
Examples of suitable commercially available expandable polymeric
microspheres include those available from Pierce Stevens (Buffalo,
N.Y.) under the designations "F30D," "F80SD," and "F100D." Also
suitable are expandable polymeric microspheres available from
Akzo-Nobel under the designations "Expancel 551," "Expancel 461,"
and "Expancel 091." Each of these microspheres features an
acrylonitrile-containing shell. In addition, the F80SD, F100D, and
Expancel 091 microspheres have essentially no vinylidene chloride
units in the shell.
The amount of expandable microspheres is selected based upon the
desired properties of the foam product. In general, the higher the
microsphere concentration, the lower the density of the foam. In
general, the amount of microspheres ranges from about 0.1 parts by
weight to about 50 parts by weight (based upon 100 parts of polymer
resin), more preferably from about 0.5 parts by weight to about 20
parts by weight.
The foam 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,
reinforcing agents, hydrophobic or hydrophilic silica, calcium
carbonate, toughening agents, fire retardants, antioxidants, finely
ground polymeric particles such as polyester, nylon, or
polypropylene, stabilizers, and combinations thereof. Chemical
blowing agents may be added as well. The agents are added in
amounts sufficient to obtain the desired end properties.
The properties of the article may be adjusted by combining one or
more polymer compositions with the foam. These additional
compositions may take several forms, including layers, stripes,
etc. Both foamed and non-foamed compositions may be used. A
composition may be bonded directly to the foam or indirectly, e.g.,
through a separate adhesive. In some embodiments, the additional
polymer composition is removably bonded to the foam; such
compositions can subsequently be stripped from the foam.
Examples of articles featuring combinations of a foam and one or
more additional polymer compositions are shown in FIGS. 4-6.
Referring to FIG. 4, there is shown an article 200 featuring a
plurality of foam stripes 202 arranged in a patterned and combined
within a separate polymer layer 204. The density of stripes 202 is
different from the density of polymer layer 204 surrounding the
stripes.
FIG. 5 depicts another article 300 in which a plurality of foam
stripes 302 are arranged in a pattern and combined within a
separate polymer layer 304. Layer 304, in turn, is bonded to yet
another polymer layer 306 on its opposite face. The density of
stripes 302 is different from the density of layer 304 surrounding
the stripes.
FIG. 6 depicts yet another article 400 in which a plurality of foam
stripes 402 are embedded within a multilayer structure featuring
polymer layers 404, 406, and 408. The density of stripes 402 is
different from the density of layers 404, 406, and 408.
Preferably, additional polymer compositions are bonded to the foam
core by co-extruding the extrudable microsphere-containing
composition with one or more extrudable polymer compositions, as
described in greater detail, below. The number and type of polymer
compositions are selected based upon the desired properties of the
final foam-containing article. For example, in the case of
non-adhesive foam cores, it may be desirable to combine the core
with one or more adhesive polymer compositions to form an adhesive
article. Other examples of polymer compositions prepared by
coextrusion include relatively high modulus polymer compositions
for stiffening the article (semi-crystalline polymers such as
polyamides and polyesters), relatively low modulus polymer
compositions for increasing the flexibility of the article (e.g.,
plasticized polyvinyl chloride), and additional foam
compositions.
Extrusion Process
Referring to FIG. 7, there is shown an extrusion process for
preparing an article that includes a polymer foam featuring a
polymer matrix and one or more expandable polymer microspheres.
According to the process, polymer resin is initially fed into a
first extruder 10 (typically a single screw extruder) which softens
and grinds the resin into small particles suitable for extrusion.
The polymer resin will eventually form the polymer matrix of the
foam. The polymer resin may be added to extruder 10 in any
convenient form, including pellets, billets, packages, strands, and
ropes.
Next, the resin particles and all additives except the expandable
microspheres are fed to a second extruder 12 (e.g., a single or
twin screw extruder) at a point immediately prior to the kneading
section of the extruder. Once combined, the resin particles and
additives are fed to the kneading zone of extruder 12 where they
are mixed well. The mixing conditions (e.g., screw speed, screw
length, and temperature) are selected to achieve optimum mixing.
Preferably, mixing is carried out at a temperature insufficient to
cause microsphere expansion. It is also possible to use
temperatures in excess of the microsphere expansion temperature, in
which case the temperature is decreased following mixing and prior
to adding the microspheres.
Where no mixing is needed, e.g., where there are no additives, the
kneading step may be omitted. In addition, where the polymer resin
is already in a form suitable for extrusion, the first extrusion
step may be omitted and the resin added directly to extruder
12.
Once the resin particles and additives have been adequately mixed,
expandable polymeric microspheres are added to the resulting
mixture and melt-mixed to form an expandable extrudable
composition. The purpose of the melt-mixing step is to prepare an
expandable extrudable composition in which the expandable polymeric
microspheres and other additives, to the extent present, are
distributed substantially homogeneously throughout the molten
polymer resin. Typically, the melt-mixing operation uses one
kneading block to obtain adequate mixing, although simple conveying
elements may be used as well. The temperature, pressure, shear
rate, and mixing time employed during melt-mixing are selected to
prepare this expandable extrudable composition without causing the
microspheres to expand or break; once broken, the microspheres are
unable to expand to create a foam. Specific temperatures,
pressures, shear rates, and mixing times are selected based upon
the particular composition being processed.
Following melt-mixing, the expandable extrudable composition is
metered into extrusion die 14 (e.g., a contact or drop die) through
a length of transfer tubing 18 using a gear pump 16 that acts as a
valve to control die pressure and thereby prevent premature
expansion of the microspheres. The temperature within die 14 is
preferably maintained at substantially the same temperature as the
temperature within transfer tubing 18, and selected such that it is
at or above the temperature required to cause expansion of the
expandable microspheres. However, even though the temperature
within tubing 18 is sufficiently high to cause microsphere
expansion, the relatively high pressure within the transfer tubing
prevents them from expanding. Once the composition enters die 14,
however, the pressure drops. The pressure drop, coupled with heat
transfer from the die, causes the microspheres to expand and the
composition to foam within the die. The pressure within the die
continues to drop further as the composition approaches the exit,
further contributing to microsphere expansion within the die. The
flow rate of polymer through the extruder and the die exit opening
are maintained such that as the polymer composition is processed
through the die, the pressure in the die cavity remains
sufficiently low to allow expansion of the expandable microspheres
before the polymer composition reaches the exit opening of the
die.
The shape of the foam is dictated by the shape of the exit opening
of the die 14. Although a variety of shapes may be produced, the
foam is typically produced in the form of a continuous or
discontinuous sheet. The extrusion die may be a drop die, contact
die, profile die, annular die, or a casting die, for example, as
described in Extrusion Dies: Design & Engineering Computation,
Walter Michaelis, Hanser Publishers, New York, N.Y., 1984, which is
incorporated herein by reference in its entirety.
It can be preferable for most, if not all, of the expandable
microspheres to be partially or mostly expanded before the polymer
composition exits the die. By causing expansion of the expandable
polymeric microspheres before the composition exits the die, the
resulting extruded foam can be produced to within tighter density
and thickness (caliper) tolerances. A tighter tolerance is defined
as the machine (or longitudinal) direction and crossweb (or
transverse) direction standard deviation of density or thickness
over the average density or thickness (.sigma./x), respectively.
The .sigma./x that is obtainable according to the present invention
can be less than about 0.2, less than about 0.1, less than about
0.05, and even less than about 0.025. Without any intention to be
so limited, the tighter tolerances obtainable according to the
present invention is evidenced by the following examples.
As shown in FIG. 7, the foam may optionally be combined with a
liner 20 dispensed from a feed roll 22. Suitable materials for
liner 20 include silicone release liners, polyester films (e.g.,
polyethylene terephthalate films), and polyolefin films (e.g.,
polyethylene films). The liner and the foam are then laminated
together between a pair of nip rollers 24. Following lamination or
after being extruded but before lamination, the foam is optionally
exposed to radiation from an electron beam source 26 to crosslink
the foam; other sources of radiation (e.g., ion beam, thermal and
ultraviolet radiation) may be used as well. Crosslinking improves
the cohesive strength of the foam. Following exposure, the laminate
is rolled up onto a take-up roll 28.
If desired, the smoothness of one or both of the foam surfaces can
be increased by using a nip roll to press the foam against a chill
roll after the foam exits die 14. It is also possible to emboss a
pattern on one or both surfaces of the foam by contacting the foam
with a patterned roll after it exits die 14, using conventional
microreplication techniques, such as, for example, those disclosed
in U.S. Pat. No. 5,897,930 (Calhoun et al.), U.S. Pat. No.
5,650,215 (Mazurek et al.) and the PCT Patent Publication No. WO
98/29516A (Calhoun et al.), all of which are incorporated herein by
reference. The replication pattern can be chosen from a wide range
of geometrical shapes and sizes, depending on the desired use of
the foam. The substantially smooth surface of the extruded foam
enables microreplication of the foam surface to a higher degree of
precision and accuracy. Such high quality microreplication of the
present foam surface is also facilitated by the ability of the foam
to resist being crushed by the pressure exerted on the foam during
the microreplication process. Microreplication techniques can be
used without significantly crushing the foam because the foam
includes expandable microspheres that do not collapse under the
pressure of the microreplication roll, compared to foaming agents
like gas.
The extrusion process may be used to prepare "foam-in-place"
articles. Such articles find application, for example, as gaskets
or other gap-sealing articles, vibration damping articles, tape
backings, retroreflective sheet backings, anti-fatigue mats,
abrasive article backings, raised pavement marker adhesive pads,
etc. Foam-in-place articles may be prepared by carefully
controlling the pressure and temperature within die 14 and transfer
tubing 18 such that microsphere expansion does not occur to any
appreciable extent. The resulting article is then placed in a
desired area, e.g., a recessed area or open surface and heated at,
or exposed to, a temperature sufficiently high to cause microsphere
expansion.
Foam-in-place articles can also be prepared by incorporating a
chemical blowing agent such as
4,4'-oxybis(benzenesulfonylhydrazide) in the expandable extrudable
composition. The blowing agent can be activated subsequent to
extrusion to cause further expansion, thereby allowing the article
to fill the area in which it is placed.
The extrusion process can also be used to prepare patterned foams
having areas of different densities. For example, downstream of the
point at which the article exits the die, the article can be
selectively heated, e.g., using a patterned roll or infrared mask,
to cause microsphere expansion in designated areas of the
article.
The foam may also be combined with one or more additional polymer
compositions, e.g., in the form of layers, stripes, rods, etc.,
preferably by co-extruding additional extrudable polymer
compositions with the microsphere-containing extrudable
compositions. FIG. 7 illustrates one preferred co-extrusion process
for producing an article featuring a foam sandwiched between a pair
of polymer layers. As shown in FIG. 7, polymer resin is optionally
added to a first extruder 30 (e.g., a single screw extruder) where
it is softened and melt mixed. The melt mixed resin is then fed to
a second extruder 32 (e.g., a single or twin screw extruder) where
they are mixed with any desired additives. The resulting extrudable
composition is then metered to the appropriate chambers of die 14
through transfer tubing 34 using a gear pump 36. The resulting
article is a three-layer article featuring a foam core having a
polymer layer on each of its major faces.
It is also possible to conduct the co-extrusion process such that a
two-layer article is produced, or such that articles having more
than three layers (e.g., 10-100 layers or more) are produced, by
equipping die 14 with an appropriate feed block, or by using a
multi-vaned or multi-manifold die. Tie layers, primers layers or
barrier layers also can be included to enhance the interlayer
adhesion or reduce diffusion through the construction. In addition,
we also can improve the interlayer adhesion of a construction
having multiple layers (e.g., A/B) of different compositions by
blending a fraction of the A material into the B layer (A/AB).
Depending on the degree of interlayer adhesion will dictate the
concentration of A in the B layer. Multilayer foam articles can
also be prepared by laminating additional polymer layers to the
foam core, or to any of the co-extruded polymer layers after the
article exits die 14. Other techniques which can be used include
coating the extruded foam (i.e., extrudate) with stripes or other
discrete structures.
Post processing techniques, which may include lamination,
embossing, extrusion coating, solvent coating, or orientation, may
be performed on the foam to impart superior properties. The foams
may be uni-axially or multi-axially oriented (i.e., stretched in
one or more directions) to produce foam structures that contain
microvoids between or a separation of the foam matrix and the
expandable microspheres (See Examples 85-92). FIGS. 12a-12d show
SEM micrographs of the microstructure of the foam of Example 86,
before (FIGS. 12a and 12b) and after (FIGS. 12c and 12d) uniaxial
orientation. FIGS. 12a and 12c are cross-sectional views of the
foam microstructure as seen in the machine direction (MD). That is,
for FIGS. 12a and 12c, the foam was sectioned perpendicular to the
direction the foam flows as it exits the die and viewed in the
direction of flow. FIGS. 12b and 12d are cross-sectional views of
the foam microstructure as seen in the crossweb direction (CD).
That is, for FIGS. 12b and 12d, the foam was sectioned parallel to
the direction the foam flows as it exits the die and viewed in the
direction perpendicular to the direction of flow.
The selection of the foam matrix, expandable microsphere
type/concentration and orientation conditions can affect the
ability to produce microvoided foam materials. Orientation
conditions include the temperature, direction(s) of stretch, rate
of stretch, and degree of stretch (i.e., orientation ratio). It is
believed that the interfacial adhesion between the foam matrix and
the expandable microspheres should be such to allow at least some
debonding to occur around the microspheres upon stretching (i.e.,
orientation). It is also believed that poor interfacial adhesion
can be preferable. Furthermore, it has be found desirable for the
foam matrix to be capable of undergoing relatively high elongation
(e.g., at least 100%). Orientation of the foam samples can cause a
reduction in density of the foam (e.g., up to about 50%) due to the
formation of microvoids between the foam matrix and the
microspheres that form during orientation. Microvoids can remain
after the stretching (orientation) process or they can disappear
(i.e., collapse but the interface remains unbonded). In addition,
delamination between the foam matrix and the microspheres, with or
without a noticeable density reduction, can result in a significant
alteration of the mechanical properties of the foam (e.g., increase
in flexibility, reduction in stiffness, an increase in softness of
foam, etc.). Depending on the ultimate foam application, the
material selection and the orientation conditions can be selected
to generate desired properties.
It can be desirable for the extrudable polymer composition to be
crosslinkable. Crosslinking can improve the cohesive strength of
the resulting foam. It may be desirable for the crosslinking of the
extrudable polymer to at least start between the melt mixing step
and exiting of the polymer through the die opening, before, during
or after foaming, such as by the use of thermal energy (i.e., heat
activated curing). Alternatively or additionally, the extrudable
polymer composition can be crosslinked upon exiting the die such
as, for example, by exposure to thermal, actinic, or ionizing
radiation or combinations thereof. Crosslinking may also be
accomplished by using chemical crosslinking methods based on ionic
interactions. The degree of crosslinking can be controlled in order
to influence the properties of the finished foam article. If the
extruded polymer is laminated, as described herein, the polymer
extrudate can be crosslinked before or after lamination. Suitable
thermal crosslinking agents for the foam can include epoxies and
amines. Preferably, the concentrations are sufficiently low to
avoid excessive crosslinking or gel formation before the
composition exits the die.
Use
The foam-containing articles are useful in a variety of
applications including, for example and not by way of limitation,
aerospace, automotive, and medical applications. The properties of
the articles are tailored to meet the demands of the desired
applications. Specific examples of applications include vibration
damping articles, medical dressings, tape backings, retroreflective
sheet backings, anti-fatigue mats, abrasive article backings,
raised pavement marker adhesive pads, gaskets, and sealants.
The invention will now be described further by way of the following
examples.
EXAMPLES
Test Methods
Surface Roughness
The surface topology as a function of displacement was measured
using a Laser Triangulation Profilometer (Cyberscan 200, available
from Cyberoptics of Minneapolis, Minn.) All the measurements were
collected at room temperatures using a HeNe laser (654 nm) with a
point range selector resolution of 1 micrometer (PRS-40). The laser
was programmed to move across the sample in discrete jumps of 25
micrometers with a total of 50 jumps (total length=1250
micrometers). The sample size measured 1250.times.1250 micrometers.
The roughness data was leveled by subtracting a linear regression
fit of the data and positioning the average at zero. The surface
roughness, Ra, was calculated using the following relationship:
.times..intg..times..function..times..times.d ##EQU00001## where
R.sub..alpha. is the surface roughness, L.sub.m is the total
displacement length, and z is the height at a displacement of x.
90.degree. Peel Adhesion
A foam pressure-sensitive adhesive sheet is laminated to a sheet of
0.127 mm thick anodized aluminum. A strip of tape measuring 1.27 cm
by 11.4 cm is cut from the sheet and applied to a metal substrate
that was painted with a basecoat/clear coat automotive paint
composition (RK-7072 from DuPont Co.) The strip is then rolled down
using four total passes of using a 6.8 kg metal roller. The sample
is aged at one of the following conditions before testing: 1 hour
at room temperature (22.degree. C.) 3 days at room temperature
(22.degree. C.) 7 days at 70.degree. C. 5 days at 100.degree. C.
and 100% humidity After aging, the panel is mounted in an
Instron.TM. Tensile Tester so that the tape is pulled off at a 90
degree angle at a speed of 30.5 cm per minute. Results are
determined in pounds per 0.5 inch, and converted to Newtons per
decimeter (N/dm). T-Peel Adhesion
This test is performed according to ASTM D3330-87 except as
specified. A strip of foam tape measuring 11.43 cm by 1.27 cm wide
is laminated between two anodized aluminum strips (10.16 cm long by
1.59 cm wide by 0.127 mm thick). The laminated test sample is
conditioned for at least 1 hour at room temperature (22.degree.
C.), and then tested for cohesive strength using an Instron.TM.
Tensile tester at a 180.degree. peel and a crosshead speed of 30.48
inches per minute. The test results are recorded in pounds per 1/2
inch width and results are converted to newtons/decimeter
(N/dm).
Tensile and Elongation
This test is performed according to ASTM D412-92 except as
specified. A sample of the foam is cut into a "dog bone" shape
having a width of 0.635 mm in the middle portion. The ends of the
sample are clamped in an Instron Tensile Tester and pulled apart at
a crosshead speed of 50.8 cm per minute. The test measures peak
stress (in pounds per square inch and converted to kiloPascals
(kPas)), the amount of elongation or peak strain (in % of the
original length), and peak energy (in foot pounds and converted to
joules (J).
Static shear Strength
A 2.54 cm by 2.54 cm strip of pressure-sensitive adhesive foam tape
is laminated to a 0.51 mm thick anodized aluminum panel measuring
about 2.54 cm by 5.08 cm. A second panel of the same size is placed
over the tape so that there is a 2.54 cm overlap, and the ends of
the panels extend oppositely from each other. The sample is then
rolled down with a 6.8 kg metal roller so that the total contact
area of the sample to the panel was 2.54 cm by 2.54 cm. The
prepared panel is conditioned at room temperature, i.e., about
22.degree. C. for at least 1 hour. The panel is then hung in a
70.degree. C. oven and positioned 2 degrees from the vertical to
prevent a peel mode failure. A 750 gram weight is hung on the free
end of the sample. The time required for the weighted sample to
fall off of the panel is recorded in minutes. If no failure has
occurred within 10,000 minutes, the test is discontinued and
results are recorded as 10,000+minutes.
Hot Melt Composition 1
A pressure-sensitive adhesive composition was prepared by mixing 90
parts of IOA (isooctyl acrylate), 10 parts of AA (acrylic acid),
0.15 part 2,2 dimethoxy-2-phenylacetophenone (Irgacure.TM.651
available from Ciba Geigy) and 0.03 parts of IOTG (isooctyl
thioglycolate). The composition was placed into packages measuring
approximately 10 cm by 5 cm by 0.5 cm thick packages as described
in U.S. Pat. No. 5,804,610, filed Aug. 28, 1997, issued Sep. 8,
1998 and incorporated herein by reference. The packaging film was a
0.0635 thick ethylene vinylacetate copolymer (VA-24 Film 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 in
NIST units to form a packaged pressure-sensitive-adhesive. The
resulting adhesive had an IV (intrinsic viscosity of about 1.1
deciliters/gram, Mw of 5.6.times.10.sup.5 g/mol and Mn of
1.4.times.10.sup.5 g/mol.
Hot Melt Composition 2
A packaged adhesive was prepared following the procedure for Hot
Melt Composition 1 except that 97 parts of IOA and 3 parts of AA
were used.
Hot Melt Composition 3
A packaged adhesive was prepared following the procedure for Hot
melt Composition 1 except that 80 parts IOA and 20 parts AA were
used.
Hot Melt Composition 4
A hot melt pressure-sensitive adhesive composition having 96 parts
IOA and 4 parts methacrylic acid was prepared following the
procedure described in U.S. Pat. No. 4,833,179 (Young et al.)
incorporated in its entirety herein by reference.
Hot Melt Composition 5
A packaged adhesive was prepared following the procedure for Hot
Melt Composition 1 except that 46.25 parts of isooctyl acrylate,
46.25 parts of n-butyl acrylate (nBA), and 7.5 parts of acrylic
acid were used. The packaged adhesives was then compounded in a
twin screw extruder with 17% Escorez.TM. 180 tackifier (available
from Exxon Chemical Corp.) to form Hot Melt Composition 5.
Hot Melt Composition 6
A hot melt adhesive composition was prepared following the
procedure for Hot Melt Composition 5 except that the packaged
adhesive composition was 45 parts IOA, 45 parts nBA, and 10 parts
AA were used.
Hot Melt Composition 7
A packaged hot melt composition was prepared following the
procedure for Hot Melt Composition 1 except that the composition in
the packages also included 0.25 parts of acryloxybenzophenone per
one hundred parts of acrylate.
Hot Melt Composition 8
A hot melt composition having 90 parts IOA and 10 parts AA was
prepared following the procedure for Example 1 of U.S. Pat. No.
5,637,646 (Ellis), incorporated in its entirety herein by
reference.
Hot Melt Composition 9
A hot melt composition having 95 parts IOA and 5 parts AA was
prepared following the procedure for Hot Melt Composition 1.
Hot Melt Composition 10
A hot melt composition having 90 parts 2-ethylhexyl acrylate and 10
parts AA was prepared following the procedure for Hot Melt
Composition 1.
Extrusion Process
The packaged hot melt composition was fed to a 51 mm single screw
extruder (Bonnot) and compounded. The temperatures in the extruder
and the flexible hose at the exit end of the extruder were all set
at 93.3.degree. C. and the flow rate from was controlled with a
Zenith gear pump. The compounded adhesive was then fed to a 30 mm
co-rotating twin screw extruder with three additive ports (Werner
Pfleider) operating at a screw speed of 200 rpm with a flow rate of
about 10 pounds/hour (4.5 kilograms/hour). The temperature for all
of the zones in the twin screw extruder was set at the specific
temperatures indicated in the specific examples. Expandable
polymeric microspheres were added downstream to the third feed port
about three-fourths of the was down the extruder barrel. The hose
and die temperatures were set at the temperatures indicated for the
specific examples. The extrudate was pumped to a 15.24 cm wide drop
die that was shimmed to a thickness of 1.016 mm. The resulting foam
sheets had a thickness of about 1 mm. The extruded sheet was cast
onto a chill roll that was set at 7.2.degree. C., cooled to about
25.degree. C., and then transferred onto a 0.127 mm thick
polyethylene release liner.
Examples 1-5
Foam sheets for Examples 1-5 were prepared using Hot Melt
Composition 1 in the process described above using varying amounts
of expandable polymeric microspheres having a shell composition
containing acrylonitrile and methacrylonitrile (F100D available
from Pierce Stevens, Buffalo, N.Y.). The amounts of microspheres in
parts by weight per 100 parts of adhesive composition (EMS-pph) are
shown in Table 1. The extruder temperatures were set at
93.3.degree. C., and the hose and die temperatures were set at
193.3.degree. C. After cooling, the extruded foam sheets were
transferred to a 0.127 mm thick polyethylene film and crosslinked
using an electron beam processing unit (ESI Electro Curtain)
operating at an accelerating voltage of 300 keV and at a speed of
6.1 meters per minute. The measured e-beam dose was 4 megaRads
(mrads). All of the foams were tacky. The foam sheets in Examples
1,2,4, and 5 were bonded (e.g., laminated) to a two-layer film
adhesive using pressure from a nip roll to make a tape. The first
layer of the film adhesive was prepared by dissolving 10 parts
polyamide (Macromelt 6240 from Henkel) in a solvent blend of 50
parts isopropanol and 50 parts n-propanol, coating the solution
onto a release liner, and drying and oven at 121.degree. C. for
about 15 minutes. The second layer of the film adhesive was a
solvent based pressure sensitive adhesive having a composition of
65 parts IOA, 30 parts methyl acrylate, and 5 parts AA made
according to the method disclosed in Re24906 (Ulrich), incorporated
herein by reference. A release liner was then placed over the
solvent based pressure-sensitive adhesive, and the polyamide side
of the film adhesive was pressure laminated to the foam. The tapes
were tested for 90.degree. peel adhesive, T-peel adhesion, tensile
and elongation, and static shear strength. Test results and foam
densities for all of the examples are shown in Table 1.
The foam of Example 1 had a surface roughness (R.sub..alpha.) of 29
micrometers.
Example 6
A foam sheet was prepared following the procedure for Example 3
except that the extruder temperatures were set at 121.degree. C.,
and the hose and die temperatures were set at 177.degree. C. After
cooling, the foam was crosslinked with a dose of 8 mrads.
Examples 7-9
Pressure-sensitive adhesive coated foam tapes were prepared
following the procedure for Example 1 except that the extruder
temperatures were set at 121.degree. C. and the amounts of
microspheres were 6, 8, and 10 pph for Examples 7, 8, and 9
respectively.
Examples 10-13
Foam sheets were prepared following the procedure for Example 3
except that the extruder temperatures were set at 82.degree. C.,
the hose and die temperatures were set at 104.degree. C., and
according to the conditions specified below.
For Example 10, 2 pph expandable polymeric microspheres (F50D
available from Pierce Stevens) were used and the extruder flow rate
was 4.08 kg per hour.
For Example 11, 2 pph expandable polymeric microspheres having a
shell composition containing acrylonitrile, vinylidene chloride,
and methylmethacrylate (Expancel 461 encapsulated microspheres
available from Akzo Nobel) were used.
For Example 12, 2 pph expandable polymeric microspheres having a
shell composition containing acrylonitrile, methacrylonitrile, and
methyl methacrylate (Expancel 091 available from Akzo Nobel) were
used, the extruder temperatures were set at 93.9.degree. C., and
the hose and die temperatures were set at 193.3.degree. C. The foam
was measured for mean free spacing. The surface roughness
(R.sub..alpha.) was 14 micrometers, and a portion of the foam is
shown in FIGS. 1(a) and 1(b).
Example 13 was prepared following the procedure for Example 12
except that it used 2 pph expandable polymeric microspheres having
a shell containing acrylonitrile, methacrylonitrile, and methyl
methacrylate (F80SD microspheres available from Pierce Stevens) and
the extruder temperatures were set at 93.3.degree. C. Additionally,
0.15 parts by weight per one hundred parts of acrylate of
2,4-bis(trichloromethyl)-6-4-methoxyphenyl)-s-triazine was mixed
with the expandable polymeric microspheres and added to the
extruder. The resulting foam was crosslinked with a mercury vapor
lamp with 500 milliJoules/square centimeter of energy (NIST units).
The foam had a surface roughness (R.sub..alpha.) of 33
micrometers.
Examples 14-15
Pressure-sensitive adhesive foam tapes were prepared following the
procedures for Examples 2 and 3, respectively, except that the
extruder temperatures were set at 121.degree. C., and 10% by weight
of a melted tackifier (Escorez.TM. 180 obtained from Exxon Chemical
Co.) was added to the first port in the extruder barrel. The flow
rate of the extrudate was 4.08 kg per hour of compounded acrylate
and 0.45 kg per hour of tackifier. The cooled foam was crosslinked
with a dose of 8 mrads.
Example 16
A pressure-sensitive adhesive foam tape was prepared following the
procedure for Example 2 except that 0.2 parts per one hundred parts
of acrylate of a chemical blowing agent (of 4,4'
oxybis(benzenesulfonylhydrazide) obtained as Celogen OT from
Uniroyal Chemical Co.) was mixed with the microspheres and to added
to the extruder.
Example 17
A pressure-sensitive adhesive foam tape was prepared following the
procedure for Example 2 except that the extruder temperatures were
maintained at 110.degree. C. A mixture of 50 parts by weight F80SD
expandable polymeric microspheres and 50 parts of a chemical
blowing agent mixed (BIH, a mixture of 85% sodium bicarbonate and
15% citric acid, available from Boehringer-Ingelheim) was added at
a rate of 2 pph. The extruder rate flow was 3.54 kg per hour. The
resulting foam was crosslinked with as in Example 1 at a dose of 6
mrads.
Example 18
A foam sheet was prepared following the procedure for Example 3
except that 1.6 pph of F80SD expandable polymeric microspheres were
added as well as 0.4 pph glass bubbles (S-32 available from
Minnesota Mining & Manufacturing Company). The microspheres and
glass bubbles were mixed together before adding to the
extruder.
The foam had a surface roughness (R.sub..alpha.) of 24 micrometers
on one major surface and 21 micrometers on the other major
surface.
Examples 19-20
Foam sheets were prepared following the above extrusion process
using Hot Melt Composition 3 and with 2 pph expandable polymeric
microspheres (F80SD). The extruder temperatures were set at
110.degree. C., and the hose and die temperatures were set at
193.degree. C. The extruder feed rate was 3.58 kg/hr. Example 20
also included a plasticizer (Santicizer 141 available from
Monsanto) and which was fed into the extruder at 0.36/hr. The foams
were crosslinked following the procedure in Example 1. Example 19
was further laminated to the film adhesive of Example 1.
Example 21
A foam sheet was prepared following the procedure for Example 20
except that Hot Melt Composition 4 was fed directly into the twin
screw extruder, and 4 pph F80SD expandable polymeric microspheres
were used.
Examples 22-27
Pressure-sensitive adhesive foam sheets having the film adhesive of
Example 2 were prepared following the procedure for Example 2
except that F80 expandable polymeric microspheres were used instead
of F100D and the extruder temperatures were set at 104.degree. C.
Additives were also fed to the first extruder port in the type and
amount for each example as follows:
Example 22--10% by weight of the extrudate of polyethylene
(Engage.TM.8200 available from Dow Chemical Co.) was added to the
extruder at a rate of 0.45 kg/hr in the first port.
Example 23--20% by weight of the extrudate of
styrene-isoprene-styrene block copolymer (Kraton.TM.D1107 available
from Shell Chemical Co.) was added to the extruder at a rate of 0.9
kg/hr. The foam had a surface roughness (R.sub..alpha.) of 25
micrometers on one major surface and 19 micrometers on the other
major surface.
Example 24--Same as Example 23 except that no other adhesive was
laminated to the foam.
Example 25--25% by weight of the extrudate of polyester
(Dynapol.TM.1402 (available from Huls America) was added to the
extruder at a rate of 1.13 kg/hr.
Example 26--Same as Example 25 except that no other adhesive was
laminated to the foam.
Example 27
A pressure-sensitive adhesive foam sheet was prepared using Hot
Melt Composition 7 and 2 pph expandable polymeric microspheres
(F80SD). The extruder temperatures were set at 104.degree. C. and
the hose and die temperatures were set at 193.degree. C. The
resulting foam was cooled and crosslinked with an electron beam
dose of 4 mrads at an accelerating voltage of 300 kilo-electron
volts (Kev).
Example 28
A single layer foam sheet was prepared following the procedure for
Example 3 except a 25.4 cm wide vane coextrusion die was used
instead of a drop die, the extruder temperature was set at
104.degree. C., and F80SD expandable polymeric microspheres were
used. There was no flow of material through the outer vanes. The
cooled foam was crosslinked with an electron beam dose of 6 mrads
at an accelerating voltage of 300 Kev.
Example 29
A foam sheet prepared following the procedure for Example 28 except
that Hot Melt Composition 2 was used.
Example 30
A foam sheet for was prepared following the procedure for Example
29 except that F100D expandable polymeric microspheres were
used.
Examples 31-33
Foam sheets were prepared following the procedure for Example 28
except that the outer vanes were open and a layer of Hot Melt
Composition 5 was coextruded on each major surface of the foam
sheet. The thickness of the layer of Composition 3 was 50
micrometers, 100 micrometers and 150 micrometers (i.e., 2 mils, 4
mils, and 6 mils) for Examples 31, 32, and 33 respectively. The
extruder and hose temperatures for the additional layers were set
at 177.degree. C. The foam sheet of Example 31 had a surface
roughness of (R.sub..alpha.) 24 micrometers.
Example 34
A foam sheet was prepared following the procedure for Example 31
except that the extruder temperatures were set at 93.3.degree. C.
and the hose and die temperatures were set at 171.degree. C. and a
tackifier was added. The extruder feed rate was 4.08 kg/hr for
Composition 1 and 0.45 kg/hr for a tackifier (Escorez.TM.180). Hot
Melt Composition 5 was coextruded to a thickness of 100 micrometers
on each major surface of the foam. The coextruded composite was
crosslinked with an electron beam at an accelerating voltage of 275
Kev and a dose of 8 mrads.
Example 35
A foam sheet was prepared following the procedure for Example 34
except that instead of the tackifier, low density polyethylene
(Dowlex.TM.2517 available from Dow Chemical Co.) was added to the
extruder at feed rate of 1.36 kg/hr and Composition 1 was fed in at
a rate of 3.18 kg/hr. Hot melt Composition 6 was coextruded to a
thickness of 50 micrometers on each major surface of the foam. The
resulting coextruded composite was cooled and crosslinked with an
electron beam accelerating voltage of 250 Kev and a dose of 6
mrads.
Examples 36-37
Pressure-sensitive adhesive foam sheets were prepared following the
procedure for Example 31 except that the microspheres used were a
50/50 blend of F80SD and F100D microspheres and the extruder
temperatures were set at 93.degree. C., and the hose and die
temperatures were set at 171.degree. C. Example 36 was crosslinked
with an e-beam accelerating voltage of 250 Kev and a dose of 6
mrads. The outer vanes of the die were opened for Example 37 and
the foam was coextruded with 0.15 mm thick layer of low density
polyethylene (Dowlex.TM.2517) on one major surface of the foam.
After cooling, the polyethylene layer could be removed from the
adhesive. This example illustrates the pressure-sensitive adhesive
foam with a liner. Furthermore, the two layer composite can be
crosslinked with an electron beam to bond the foam permanently to
the polyethylene.
Example 38
A pressure-sensitive adhesive foam sheet was prepared following the
procedure for Example 28 except that Hot Melt Composition 8 was fed
directly to the twin screw extruder.
Example 39
A pressure-sensitive adhesive foam sheet was prepared following the
procedure for Example 19 except that Hot Melt Composition 9 was
used and the extruder feed rate was 4.5 kg/hr.
Examples 40-42
Foam sheets were prepared by extruding Composition 1 with ethylene
vinyl acetate copolymer (EVA). The EVA used for Examples 40, 41,
and 42 were Elvax.TM.250 (melt index of 25, vinyl acetate content
of 28%), Elvax.TM.260 (melt index of 6.0, vinyl acetate content of
28%), and Elvax.TM.660 (melt index of 2.5, vinyl acetate content of
12%) respectively. All of the EVAs were obtained from DuPont Co.
Composition 1 was fed to the extruder at a rate of 2.7 kg/hr and
the EVA was fed at a rate of 1.8 kg/hr. A loading of 3 pph F100D
expandable polymeric microspheres was used. The extruder
temperatures were set at 104.degree. C. and the hose and die
temperatures were set at 193.degree. C. Additionally, Examples 40
and 41 were coextruded with a 0.064 mm thick layer of Hot Melt
Composition 1 on both major surfaces of the foam. All of the
coextruded foams were crosslinked with an electron beam
accelerating voltage of 300 Kev and a dose of 6 mrad. The surface
roughness (R.sub..alpha.) of Example 40 was 27 micrometers.
Example 43
A non-tacky foam sheet was prepared following the procedure for
Example 40 except that only EVA (Elvax.TM.250) was extruded with 3
pph expandable polymeric microspheres (F100D). The surface
roughness (R.sub..alpha.) was 23 micrometers on one major surface
of the foam and 27 micrometers on the other major surface of the
foam.
Example 44
A foam sheet was prepared following the procedure for Example 40
except that instead of EVA, a high density polyethylene
(Dowlex.TM.IP-60 available from Dow Chemical Co.). The feed rates
of Composition 1 and the polyethylene were 3.63 kg/hr and 0.91
kg/hr, respectively.
Example 45
A foam sheet was prepared following the procedure for Example 44
except that a low density polyethylene (Dowlex.TM.2517) was used.
The feed rates of Composition 1 and the polyethylene were 3.18
kg/hr and 1.36 kg/hr, respectively.
Example 46
A foam sheet was prepared following the procedure for Example 44
except that Hot Melt Composition 9 was extruded with a polyester
(Dynapol.TM.1157 available from Huls) and 3 pph expandable
polymeric microspheres (F80). The extruder temperature was set at
93.degree. C. and the hose and die temperatures were set at
171.degree. C. The end plates of the die were set at a temperature
of 199.degree. C. to form a uniform thickness across the sheet. The
feed rates of Composition 9 and the polyester were 3.18 kg/hr and
1.36 kg/hr, respectively. The resulting foam was cooled and then
crosslinked with an electron beam accelerating voltage of 275 Kev
and a dose of 6 mrads.
Example 47
A nontacky foam sheet was prepared following the procedure for
Example 46 except that only polyester (Dynapol.TM.1157) was
extruded with 4 pph expandable polymeric microspheres (F80SD). The
foam had a surface roughness (R.sub..alpha.) of 27 micrometers.
Example 48
A 2.54 cm diameter cylindrical foam was prepared following the
procedure of Example 44 except that both Hot Melt Composition 1 and
the high density polyethylene were fed to the extruder at a rate of
2.27 kg/hr with 2 pph expandable polymeric microspheres (F80SD).
The die was removed so the foam was extruded from the hose in a
cylindrical shape.
Example 49
A 1.27 cm diameter cylindrical foam was prepared following the
procedure of Example 23 except that both Hot Melt Composition 1 and
the block copolymer were fed to the extruder at a rate of 2.27
kg/hr with 2 pph expandable polymeric microspheres (F80SD). The die
was removed and the foam was extruded from the hose in a
cylindrical shape.
Examples 50-52
A foam sheet for Example 50 was prepared by feeding a
styrene-isoprene-styrene block copolymer (Kraton.TM.D1107) to the
twin screw extruder of Example 1 at a feed rate of 1.8 kg/hr. A
tackifier (Escorez.TM.1310 LC, available from Exxon Chemical Co.)
was fed into the first port at a feed rate of 1.8 kg/hr. and
expandable polymeric microspheres (F80SD) were fed to the third
port at a rate of 2 parts per one hundred parts of block copolymer
and tackifier. The extruder temperatures were set at 121.degree. C.
and the hose and die temperatures were set at 193.degree. C. The
resulting foam adhesive had a density of 33.7 lbs/ft.sup.3 (539.2
Kg/m.sup.3). This sample possessed stretch activated release (i.e.,
stretch releasable) characteristics such as that described in the
Bries et al U.S. Pat. No. 5,507,464, which is incorporated herein
by reference.
In Example 51, a foam sheet was prepared following the procedure of
Example 51 except that 8 pph of F80SD expandable polymeric
microspheres were used. The resulting foam adhesive had a density
of 16.5 lbs/cubic ft (264 kg/m.sup.3).
In Example 52, a foam sheet was prepared following the procedure of
Example 51 except that the block copolymer was
styrene-ethylene-butylene-styrene block copolymer (Kraton G1657
available from Shell Chemical Co.) and the tackifier was Arkon P-90
(available from Arakawa Chemical USA). The resulting foam adhesive
had a density of 36.9 lbs/cubic ft (590.4 kg/m.sup.3). This sample
also possessed stretch activated release characteristics as
described in the above incorporated Bries et al US Patent and
published PCT Applications.
Example 53
A foam sheet was prepared following the procedure for Example 31
except that the extruder temperatures were set at 93.degree. C.,
and the hose and die temperatures were set at 171.degree. C. The
foam was coextruded a 0.1 mm layer of adhesive on each major
surface of the sheet. The adhesive was a tackified
styrene-isoprene-styrene block copolymer (HL2646 available from HB
Fuller). The resulting foam had a density of 29 lbs/cubic foot (464
kg/m.sup.3).
Examples 54-57
Foam sheets were prepared by feeding polyhexene having an intrinsic
viscosity of 2.1 to the twin screw extruder at a rate of 4.5 kg/hr
and expandable polymeric microspheres (F100D) at a rate of 2 pph
for Example 54 and 4 pph for Example 55. Foam sheets for Examples
56 and 57 were prepared following the procedure for Examples 54 and
55, respectively, except that the polyhexene was fed to the
extruder at a rate of 3.31 kg/hr and a tackifier (Arkon P-115
available from Arakawa Chemical USA) was fed to the first port at a
rate of 1.63 kg/hr, and the expandable polymeric microspheres were
mixed with 0.3 pph
2,4-bis(trichloromethyl)-6-4-methoxyphenyl)-s-triazine before
adding to the extruder.
Example 58
Hot Melt Adhesive Composition 1 was processed in a 10.16 mm Bonnot
single screw extruder. The extruder was operated at room
temperature, relying only on mechanically generated heat to soften
and mix the composition. The mixture was then fed into Zone 1 of a
twin screw extruder (40 mm Berstorff (ZE-40) co-rotating twin screw
extruder) where it was mixed with expandable polymeric microspheres
(F100). A standard compounding screw design was used with forward
kneading in Zone 2, reverse kneading in Zone 4, Zone 6, and Zone 8
with self-wiping conveying elements in the remaining zones. Screw
speed was 125 RPM resulting in operating pressures of 52.7
kiloPascals and total flow rates of 11.3 kg/hr. The temperatures in
the extruder were set at 104.degree. C., and the hose and die
temperatures were set at 193.degree. C. This temperature profile
prevented expansion during compounding and minimize the rupturing
of the expandable polymeric microspheres. Flow of the extrudate was
controlled using a Normag gear pump. The expandable polymeric
microspheres were metered into Zone 7 of the twin screw extruder
using a Gehricke feeder (GMD-60/2) at rates of 0.23 kg/h. A 15.24
cm wide drop die shimmed at 1 mm was operated at 193.degree. C. The
web was cast onto a chilled cast roll and laminated to a release
liner at a speed of 1.5 meters per minute. Following coating, the
foam sheet was electron beam crosslinked using an ESI Electro
Curtain at dose of 8 mrad at accelerating voltage of 300 keV. The
resulting foam is shown in FIG. 2(a) and 2(b). The foam had a
surface roughness (R.sub..alpha.) of 37 micrometers.
Examples 59-61
These examples illustrate foams that are suitable for use in a
foam-in-place application. A foam sheet for Example 59 was prepared
following the procedure for Example 3 except that it contained 10
pph F80SD expandable polymeric microspheres and the extruder, hose,
and die temperatures were all set at 88.degree. C. to minimize
expansion of the foam in the die. The foam was not crosslinked and
had a density of 55 lbs/cubic foot (880 kg/m.sup.3). After
subsequent heating to a temperature of 193.degree. C. for five
minutes, the density was reduced to 13 pounds/cubic foot (208
kg/m.sup.3). A foam for Example 60 was prepared following the
procedure for Example 59 except that Hot Melt Composition 2 was
used and the extruder, hose, and die temperatures were all set at
104.degree. C. After cooling, the foam had a density of 60
lbs/cubic ft (960 kg/m.sup.3). After subsequent heating to a
temperature of 193.degree. C. for five minutes, the density was
reduced to 15 lbs/cubic foot (240 kg/m.sup.3). A foam sheet for
Example 61 was prepared following the procedure for Example 59
except that polyester (Dynapol.TM.1157) was fed to the extruder at
a rate of 9 kg/hr, and the temperatures for the extruder, hose, and
die were all set at 110.degree. C. The 1.14 mm thick foam sheet was
crosslinked with an electron beam accelerating voltage of 275 Kev
and a dose of 6 mrad.
TABLE-US-00001 TABLE 1 Tensile & Elongation Foam 90.degree.
Peel adhesion - N/dm T- Peak Peak Overlap EMS Density 1 hr 3 days 7
days 5 days peel Stress Elong Energy Shear Ex pph Kg/m.sup.3
21.degree. C. 21.degree. C. 70.degree. C. 100/100 N/dm KPas %
Joules Minutes 1 1 745.6 150.5 210 *843.5 269.5 399 758 730 1.36
10,000+ 2 2 668.8 150.5 217 *728 301 353.5 896 645 1.50 10,000+ 3 2
668.8 133 224 *598.5 353.5 353.5 896 725 1.77 10,000+ 4 3 608 143.5
217 *682.5 280 339.5 965 548 1.50 10,000+ 5 4 561.6 136.5 206.5
*612.5 332.5 203 896 499 1.28 10,000+ 6 3 672 122.5 213.5 *672 203
262.5 1172 508 1.24 10,000+ 7 6 NT 206.5 126 112 112 NT 621 201
0.39 10,000+ 8 8 NT 77 84 66.5 77 NT 586 57 0.08 10,000+ 9 10 NT 77
56 56 56 NT 689 49 0.08 10,000+ 10 2 782.4 80.5 101.5 *479.5 171.5
217 689 700 0.82 10,000+ 11 2 812.8 91 115.5 437.5 217 231 827 699
1.09 10,000+ 12 2 584 115.5 192.5 *605.5 273 231 1393 413 1.50
10,000+ 13 2 516.8 157.5 283.5 *420 241.5 213.5 634 491 0.82 14 2
651.2 171.5 231 *717.5 311.5 357 827 612 1.41 10,000+ 15 2 651.2
171.5 259 *703.5 *388.5 339.5 827 667 1.46 10,000+ 16 2 572.8 175
234.5 *595 *483 294 552 595 1.01 10,000+ 17 1 608 77 101.5 *577.5
164.5 262.5 4020 623 1.31 10,000+ 18 1.6 524.8 119 157.5 *430.5
*448 189 1027 513 1.63 10,000+ 19 2 715.2 73.5 101.5 *507.5 308 245
4254 489 3.67 10,000+ 20 2 672 52.5 *290.5 *528.5 *525 185.5 1751
652 2.45 10,000+ 21 4 436.8 80.5 77 *203 189 42 586 283 1.36
10,000+ 22 2 NT 185.5 269.5 *434 273 NT 552 504 0.73 23 2 NT 150.5
213.5 *486.5 280 NT 655 583 0.10 10,000+ 24 2 NT 154 210 *640.5
*528.5 NT NT NT NT 10,000+ 25 2 NT 157.5 220.5 *504 357 NT 620.55
490 0.08 10,000+ 26 2 NT 178.5 *469 *448 *430.5 NT NT NT NT 10,000+
27 2 NT 154 164.5 *588 241.5 NT 620.55 618 0.83 10,000+ 28 2 620.8
154 217 *458.5 *479.5 NT NT NT NT 10,000+ 29 2 587.2 91 87.5 *434
112 NT NT NT NT 10,000+ 30 2 624 77 87.5 *392 112 NT NT NT NT
10,000+ 31 2 624 192.5 252 *451.5 *395.5 NT NT NT NT 10,000+ 32 2
680 196 238 *469 *455 NT NT NT NT 10,000+ 33 2 713.6 189 248.5
*500.5 *430.5 NT NT NT NT 10,000+ 34 2 624 210 255.5 *483 *427
262.5 400 725 1.08 10,000+ 35 2 528 52.5 52.5 189 52.5 140 1703 193
0.82 10,000+ 36 2 432 80.5 101.5 259 147 133 621 370 0.54 10,000+
37 2 NT NT NT NT NT NT NT NT NT NT 38 2 400 157.5 *269.5 *161 185.5
126 496 221 0.27 10,000+ 39 2 534.4 87.5 171.5 *451.5 276.5 262.5
641 56 1.09 10,000+ *Indicates foam split; NT-sample not tested or
data unavailable
Examples 62-70 and Comparative Example C1
Pressure-sensitive adhesive foams were prepared following the
procedure for Example 3 with varying amounts of expandable
polymeric microspheres shown in Table 2. The extruder temperatures
were set at 104.degree. C., and the hose and die temperatures were
set at 193.degree. C. Examples 62-66 contained F100D microspheres
and Examples 67-70 contained F80SD microspheres. Comparative
Example C1 contained no microspheres. None of the examples were
crosslinked. The tensile (peak stress), elongation and overlap
shear test data show that the properties of the foam can be
controlled by the amount of expandable microspheres, and the
addition of the microspheres increased the strength of the foam
above the same composition that has no microspheres. The overlap
shear test used is the same as that described above except that the
sample size was 2.54 cm.times.1.27 cm, using a 1000 g load at
25.degree. C.
TABLE-US-00002 TABLE 2 EMS Density Peak Stress Overlap Shear
Example Pph Kg/m.sup.3 Kpas Elong % Minutes 62 2 590.6 634.34 1064
122 63 4 445.9 661.92 518 169 64 6 361.5 655.025 515 166 65 8 296
682.605 185 129 66 10 268.1 634.34 169 113 67 2 535.5 524.02 940
122 68 4 400.8 0 148 69 6 293 579.18 283 117 70 8 233.3 730.87 90
83 C1 0 971.7 544.7 1867 82
Example 71
A pressure-sensitive adhesive foam was prepared following the
procedure for Example 28 except that 5 pph F100D expandable
polymeric microspheres were used with Hot Melt Composition 2 and a
hydrocarbon tackifier (Foral.TM.85 available from Hercules, Inc. of
Wilmington, Del.) was added. The hot melt composition was fed to
the extruder at a rate of 2.9 kg/hr and the tackifier was fed to
the extruder at a rate of 1.7 kg/hr. The extruder temperatures were
set at 93.degree. C., and the hose and die temperatures were set at
177.degree. C. The resulting foam was approximately 0.38 mm thick,
and was subsequently crosslinked with an electron beam dose of 8
mrad at an accelerating voltage of 300 Kev. The adhesive foam was
laminated to a flexible retroreflective sheeting described in U.S.
Pat. No. 5,450,235 (Smith et al), incorporated herein in its
entirety by reference.
The retroreflective sheeting with the foamed adhesive was applied
at room temperature to a polyethylene barrel (obtained from Traffix
Devices, Inc. of San Clemente, Calif.). The barrel was placed in an
oven at about 49.degree. C. for 3 days. The barrel was removed from
the oven and kept at room temperature for about 24 hours. Then the
barrel was placed in a truck at about -1.degree. C. for a week. The
sheeting with the adhesive evaluated showed no delamination or
buckling from the barrel at the end of the test period.
Inclusion Coextrusion
Peel Adhesion
The foam inclusion coextrusion samples were laminated to a 0.127 mm
thick piece of anodized aluminum. A strip of the tape measuring
1.27 cm by 11.4 cm was cut from the sheet and applied to a
stainless steel substrate. The strip was then rolled down using
four total passes using a 6.8 kg metal roller. The samples were
aged for 1 day at 22.degree. C., 50% relative humidity. After aging
the panel is mounted in an Instron Tensile Tester so that the tape
is pulled off at a 90 degree angle at a speed of 12 inches/minute
(30.5 cm/min.). Samples were tested in both the machine direction
(i.e., the direction the foam flows out of the die or MD), with the
peel direction being parallel to the filaments, and the crossweb
direction (i.e., the direction perpendicular to the flow direction
or CD), with the peel direction being perpendicular to the
filaments. Results are determined in pounds per 0.5 inch and
converted to Newtons per cm (N/cm).
Tensile and Elongation
This test was performed according to ASTM D412-92 except as
specified. A sample of the foam was cut into a "dog bone" shape
having a width of 2.54 cm in the middle portion. The ends of the
sample were clamped in an Instron Tensile Tester and pulled apart
at a crosshead speed of 12 inches per minute (30.5 cm/min). The
test measures peak stress (in pounds per square inch and converted
to kiloPascals (kPas)), and the amount of elongation or peak strain
(in % of the original length).
Static Shear Strength
A 2.54 cm by 2.54 cm strip of pressure-sensitive adhesive foam tape
was laminated to a 0.51 mm thick stainless steel panel measuring
about 2.54 cm by 5.08 cm. A second panel of the same size was
placed over the tape so that there was a 2.54 cm overlap, and the
ends of the panels extend oppositely from each other. The sample
was then rolled down with a 6.8 kg metal roller so that the total
contact area of the sample to the panel was 2.54 cm by 2.54 cm. The
prepared panel was conditioned at room temperature, i.e., about
22.degree. C. for at least 24 hours. The panel was then hung in a
25.degree. C. oven and positioned 2 degrees from the vertical to
prevent a peel mode failure. A 1000 gram weight was hung on the
free end of the sample. The time required for the weighted sample
to fall off of the panel was recorded in minutes. The static shear
samples were tested to failure, and each sample tested exhibited a
cohesive failure mode.
Examples 72-84
Foam samples containing embedded thermoplastic filaments were
prepared by a continuous extrusion which was carried out using a
specially designed co-extrusion die as disclosed in a U.S. Pat. No.
6,447,875, which is incorporated herein by reference in its
entirety. A schematic diagram of these samples are shown in FIG. 4.
The continuous foam matrix consisted of Hot Melt Composition 1 with
IOTG concentration of 0.1 wt % and 2 pph F100D expandable
microspheres. The adhesive was added to zone 1 of a 34 mm
Leistritz.TM. fully intermeshing, co-rotating twin screw extruder
available from American Leistritz Extruder Corp., Somerville, N.J.,
fitted with a gear pump. The microspheres were added using a
Gericke feeder (GMD-60) into zone 9 of the twin screw extruder. The
temperature profile of the twin screw extruder was: zone
1=93.degree. C. (200.degree. F.) and zones 2-12=104.degree. C.
(220.degree. F.). The screw configuration of this extruder had two
kneading sections prior to microsphere addition and one kneading
section after microsphere addition, while the remainder of the
screw was conveying elements. The twin screw extruder had a screw
speed of 100 rpm, a gear pump speed of 7 rpm, and a head pressure
of 9.1 MPa (1320 psi) which provided flow rates of 13.6 kg/h (30
lb/hr). The filament material was a polyethylene-polyoctene
copolymer (Engage.TM.8200) that was fed to the coextrusion die
using a 32 mm (1.25-inch) Killion.TM. single screw extruder (Model
KTS-125 available from Davis-Standard Killion Systems, Cedar Grove,
N.J.) with a length to diameter ratio of 24:1 and three barrel
zones that were operated with a temperature profile of zone
1--193.degree. C. (380.degree. F.), zone 2--210.degree. C.
(410.degree. F.) and zones 3 and 4 --232.degree. C. (450.degree.
F.). The screw had a Saxton mixing element with a compression ratio
of 3:1. The 32 mm extruder was run at 10 rpm with a head pressure
of 5.1 MPa (740 psi) which provided flowrates of 0.9 Kg/hr (2
lb/h). The filaments were co-extruded so as to be embedded into the
foam using a 45 cm (18 in) wide Cloeren.TM. two-layer
multi-manifold die (available as Model 96-1502 from Cloeren Co.,
Orange, Tex.) that had been modified. The vane had been hollowed
out as shown in the previously incorporated case U.S. Pat. No.
6,447.875, and the leading edge or tip had been cut off to make a
vane manifold. The vane tip had circular orifices each having a
diameter of 508 microns (20 mils) and separated by a space of 4.1
mm (0.160 in) and extended from the vane tip 2.5 mm (0.100 in) into
the matrix flow. The die was operated at 193.degree. C.
(380.degree. F.). The foam was cast onto a paper liner at a
take-away speed of 1.2 m/min (4 fpm) resulting in an overall
thickness of 625 microns (25 mils). The samples were subsequently
electron beam cured using ESI Electrocure e-beam at an accelerating
voltage of 300 keV and dosage of 6 megarads.
Example 72 was prepared using the aforementioned conditions with a
foam matrix consisting of Hot Melt Composition 1 (IOTG=0.1%) and 2
pph of F100D. No filaments were present. This was accomplished by
not operating the KTS-125 satellite extruder.
Example 73 was prepared by following the procedure for Example 1
except that the concentration of F100D was 4 pph.
Example 74 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 2 pph F100D.
The filaments consisted of 10 w % DOW.TM. Engage 8200 polyolefin
elastomer.
Example 75 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 2 pph F100D.
The filaments consisted of 20 w % DOW.TM. Engage 8200 polyolefin
elastomer.
Example 76 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 2 pph F100D.
The filaments consisted of 30 w % DOW.TM. Engage 8200 polyolefin
elastomer.
Example 77 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 4 pph F100D.
The filaments consisted of 10 w % DOW.TM. Engage 8200 polyolefin
elastomer.
Example 78 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 4 pph F100D.
The filaments consisted of 20 w % DOW.TM. Engage 8200 polyolefin
elastomer.
Example 79 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 2 pph F100D.
The filaments consisted of 10 w % Shell Kraton D 1107 thermoplastic
elastomer.
Example 80 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 2 pph F100D.
The filaments consisted of 20 w % Shell Kraton D 1107 thermoplastic
elastomer.
Example 81 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 2 pph F100D.
The filaments consisted of 30 w % Shell Kraton D 1107 thermoplastic
elastomer.
Example 82 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 4 pph F100D.
The filaments consisted of 10 w % Exxon Escorene polypropylene
3445.
Example 83 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 4 pph F100D.
The filaments consisted of 20 w % Exxon Escorene polypropylene
3445.
Example 84 was prepared by the aforementioned conditions with a
foam matrix of Hot Melt Composition 1 (IOTG=0.1%) with 4 pph F100D.
The filaments consisted of 30 w % Exxon Escorene polypropylene
3445.
TABLE-US-00003 TABLE 3 Max Max Ex- Stress Elong'n am- MD Peel CD
Peel MD Static @ @ ple Density Adhesion, Adhesion, Shear Break
Break, # g/cm.sup.3 N/cm N/cm (minutes) KPAS) (%) 72 0.7348 16.5
13.7 88 650 720.0 73 0.6496 13.9 15.3 166 641 546.7 0 0 0 74 0.777
14.5 20.0 98 1055 441.3 75 0.804 9.8 11.0 95 2050 986.7 76 0.8007
8.9 10.4 138 3233 941.7 77 0.6788 16.9 13.5 164 784 720.0 78 0.709
12.2 18.4 233 2245 989.7 0 0 0 79 0.7624 10.6 13.6 124 809 823.3 80
0.7948 15.1 15.5 1050 880.0 81 0.7848 12.8 14.0 273 1108 873.3 0 0
0 82 0.6449 12.9 11.7 171 1342 4.6 83 0.6785 9.2 19.4 120 3918 7.2
84 0.698 8.8 17.2 193 6260 6.8
Discussion of Table 3 and FIGS. 8-10
Table 3 displays a summary of the density, peel adhesion, static
shear, and tensile/elongation results for Examples 72-84. Only
uncrosslinked inclusion coextrusion samples were evaluated for
static shear strength. Only crosslinked samples were evaluated for
density, peel adhesion and tensile/elongation.
FIG. 8 shows the peel force as applied in a direction (MD) parallel
to the filament direction as a function of displacement for
Examples 73, 77 and 78. This Figure demonstrates that as the
filament material increases from 0 to 20 wt % the peel adhesion
remains essentially constant. FIG. 9 displays the peel force as
applied in a direction (CD) perpendicular to the filament direction
as a function of displacement for Examples 73, 77 and 78. Example
73 shows no structure, while Example 77 and 78 show dramatically
different behavior that is characterized by a characteristic
frequency and amplitude. The frequency between maxima in Examples
77 and 78 is exactly the distance between filaments, note that this
period does not change with concentration. However, the amplitude
between minima and maxima does change dramatically as the
concentration of filament increases from 10 to 20%. Furthermore,
the adhesion values in the CD direction is higher than in the MD.
Thus by manipulation of the filament concentration and distance
between the filaments one can design peel behavior with various
qualities in both the direction parallel and perpendicular to the
filament direction.
FIG. 10 shows the peel force as applied in a direction (MD)
parallel to the filament direction as a function of displacement
for Examples 72, 79, 80 and 81. This Figure demonstrates that as
the filament material increases from 0 to 30 wt % the peel adhesion
is reduced slightly. FIG. 11 displays the peel force as applied in
a direction (CD) perpendicular to the filament direction as a
function of displacement for Examples 72, 79, 80 and 81. Example 72
shows no structure, while Example 79, 80 and 81 show dramatically
different behavior that is characterized by a characteristic
frequency and amplitude. The frequency between maxima in Examples
79, 80 and 81 is exactly the distance between filaments, note that
this period does not change with concentration. However, in
contrast to FIG. 9 the amplitude between maxima and minima of the
force does not change as the filament concentration increases.
Therefore, the filament type also plays a role in determining the
characteristics of the peel force/displacement relationship. Not to
be bound by theory, we believe that as the filament material
characteristics become more dissimilar from the foam matrix the
amplitude between maxima and minima increases.
Other unique properties not obtainable by a single component foam
system but obtainable by the inclusion co-extrusion of embedded
discrete structures may include, for example, hand tearable
lengthwise along and between filaments, stretch releasable,
enhanced tensile properties, tailored adhesion (see FIGS. 9 and 11
and the corresponding discussion).
Inclusion coextrusion of thermoplastic filaments in foam materials
can dramatically increase the tensile force and elongation
characteristics of the materials. These properties can be
manipulated by choosing the optimum filament material &
filament concentration to produce tensile properties that vary from
high stress/low elongation to low stress/high elongation. The
adhesion behavior in the direction both parallel and perpendicular
to the filament direction can be manipulated by changing the
filament material, filament spacing, and filament
concentration.
Oriented Foam Examples 85-92
Single-layer (B) and three-layer (ABA) foam samples were prepared
as in Example 1, above, except as noted below. The A layer is an
unfoamed pressure sensitive adhesive skin layer formed using the
Hot Melt Composition 10. The B layer is a foamed layer formed using
the Hot Melt Composition 10, various thermoplastic polymer blend
components, and various expandable microspheres available from
Pierce Stevens, Buffalo, N.Y. The A layer was approximately 2.5
mils thick, and the B layer was approximately 40 mils thick. The
extruder temperatures were set at 93.3.degree. C., and the hose and
die temperatures were set at 176.7.degree. C. The thermoplastic
blend components were added in various concentrations into zone 1,
hot melt composition 10 was added in zone 3, and the expandable
microspheres were was added into zone 9. The pressure sensitive
adhesive material in the A layers was fed using a 2'' Bonnot single
screw extruder (SSE).
Both the A and B layers were pumped from the extruders to a
multilayer feedblock using 0.5 inch (1.27 cm) OD flexible tubing.
The A and B layers were combined into an ABA arrangement using a
three layer Cloeren feedblock (Cloeren Company, Orange, Tex.,
Model:96-1501) with an ABA selector plug. After the layers were
combined in the feedblock the materials were formed into a planar
sheet using a 10'' (25.4 cm) wide Ultraflex 40 Die (Extrusion Dies
Incorporated, Chippewa Falls, Wis.). The feedblock and die were
both operated at temperatures of about 176.degree. C. The ABA
construction exited the die and was cast onto a
temperature-controlled stainless steel casting drum maintained at
7.degree. C. After cooling, the foam was transferred to a 0.127 mm
thick polyethylene liner and collected on a film winder. Single
layer foam constructions were made by disengaging the Bonnot SSE.
The foam samples were uniaxially oriented at a ratio in the range
of from 2.5:1 to 8:1 (i.e., stretched in the range of from 2.5 to 8
times its length) at room temperature.
Example 85 was prepared using the aforementioned conditions with a
foam matrix consisting of 80 wt % Hot Melt Composition 1, 20 wt %
Dow Engage 8200 and 4 pph of F100D. No adhesive skin layers (i.e.,
A layers) were present. The uncrosslinked foam samples were
uniaxially oriented or stretched 2.5 times its original length
(2.5:1 ratio) at room temperature.
Example 86 was prepared by following the procedure for Example 85
except that the composition of the foam matrix was 40 wt % Hot Melt
Composition 1, 60 wt % Dow Engage 8200, and 4 pph F100D.
Example 87 was prepared using the aforementioned conditions with a
foam matrix consisting of 25 wt % Hot Melt Composition 10, 75 wt %
Shell Kraton D 1107, and 4 pph of F80SD. No adhesive skin layers
were present. The uncrosslinked foam samples were uniaxially
oriented at a ratio of 8:1 at room temperature.
Example 88 was prepared using the aforementioned conditions with a
foam matrix consisting of 50 wt % Hot Melt Composition 10, 50 wt %
DuPont Elvax 260, and 4 pph of F80SD. Adhesive skin layers of Hot
Melt Composition 10 were present (ABA). The uncrosslinked foam
samples were uniaxially oriented at a ratio of 2.8:1 at room
temperature.
Example 89 was prepared by following the procedure for Example 88
except that the composition of the foam matrix was 50 wt % Hot Melt
Composition 10, 50 wt % DuPont Elvax 260, and 6 pph of F80SD. These
samples possessed minimal elongation and could not be oriented at
room temperature.
Example 90 was prepared by following the procedure for Example 88
except that the composition of the foam matrix was 50 wt % Hot Melt
Composition 10, 50 wt % DuPont Elvax 260, and 9 pph of F80SD. These
samples possessed minimal elongation and could not be oriented at
room temperature.
Example 91 was prepared using the aforementioned conditions with a
foam matrix consisting of 50 wt % Hot Melt Composition 10, 50 wt %
Shell Kraton D 1107, and 4 pph of F80SD. Adhesive skin layers of
Hot Melt Composition 10 were present (ABA). The uncrosslinked foam
samples were uniaxially oriented at a ratio of 6:1 at room
temperature.
Example 92 was prepared by following the procedure for Example 91
except that the composition of the foam matrix was 50 wt % Hot Melt
Composition 10, 50 wt % Shell Kraton D 1107, and 6 pph of F80SD.
Adhesive skin layers of Hot Melt Composition 10 were present (ABA).
The samples were uniaxially oriented at a ratio of 6:1 at room
temperature.
TABLE-US-00004 TABLE 4 Density, Orientation Post Density, Example #
g/cm3 Type/Ratio g/cm3 85 0.5249 LO-2.5:1 0.4518 86 0.523 LO-2.5:1
0.33 87 0.3382 LO-8:1 0.3489 88 0.3907 LO-2.75:1 0.3605 89 0.3067
Cannot Orient -- 90 0.2231 Cannot Orient -- 91 0.3552 LO-6:1 0.3835
92 0.2933 LO-6:1 0.3136
Thermal Crosslinker Examples 93-96
In Example 93, 100 parts of the Hot melt composition 10 was mixed
with 2 parts of F80 expandable microspheres and 5 parts of the
crosslinking agent N,N,N',N tetrakis(2-hydroxyethyl) adipamide
(available as Primid XL-552 from EMS Chemie) and extruded through a
die, at a temperature lower than the activation temperature of the
crosslinker, to a thickness of about 1 mm. The resulting foam had a
slight amount of gel particles but did not inhibit the formation
and extrusion of the foam. The foam was laminated to a silicone
coated polyester release liner and cooled. A second silicone coated
polyester release liner was laminated to the adhesive and the
laminate was baked in an oven set at 177.degree. C. for 30 minutes.
After cooling, the samples were tested for 90.degree. Peel Adhesion
according to the test described above except that the samples were
applied to a metal substrate coated with a DCT5002 automotive
paint, and aging was changed as follows. Test results in
Newtons/decimeter after aging are: 20 minutes at 22.degree.
C.--37.8 N/dm 3 days at 22.degree. C.--90.0 N/dm 3 days at
100.degree. C./100% humidity--186.3 N/dm 3 days at 70.degree.
C.--565 N/dm
In Examples 94-96, the adhesives are prepared according to the
procedure of Example 93 except that the cross-linking agents and
compositions used are as follows:
In Example 94, 50.7 grams of Hot Melt Composition 10, 1.1 grams of
F80 expandable microspheres, and 5 grams of diglycidyl ether of
bisphenol A (available as Epon.TM.828 from Shell Chemical Co.).
In Example 95, 39 grams of Hot Melt Composition 10, 0.8 grams of
F80 expandable microspheres, 4 drops of a cycloaliphatic epoxy
(available as SarCat K126 from Sartomer), 1 drop of
tris-2,4,6-(dimethylaminomethyl)phenol (available as K-54 from
Anchor Corp).
In Example 96, 39.2 grams of Hot Melt Composition 10, 0.8 grams of
F80 expandable microspheres 0.1 gram of N,N, N',N
tetrakis(2-hydroxyethyl)adipamide dissolved in 2 drops of
water.
From the above disclosure of the general principles of the present
invention and the preceding detailed description, those skilled in
this art will readily comprehend the various modifications,
re-arrangements and substitutions to which the present invention is
susceptible. Therefore, the scope of the invention should be
limited only by the following claims and equivalents thereof.
* * * * *