U.S. patent application number 09/751141 was filed with the patent office on 2002-09-26 for pressure sensitive adhesive blends comprising (meth) acrylate polymers and articles therefrom.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Bennett, Greggory S., Joseph, Eugene G., Khandpur, Ashish K..
Application Number | 20020136891 09/751141 |
Document ID | / |
Family ID | 25020665 |
Filed Date | 2002-09-26 |
United States Patent
Application |
20020136891 |
Kind Code |
A1 |
Khandpur, Ashish K. ; et
al. |
September 26, 2002 |
Pressure sensitive adhesive blends comprising (meth) acrylate
polymers and articles therefrom
Abstract
The present invention relates to a blend of at least one
(meth)acrylate polymer and at least one amorphous propylene-derived
polymer, and an optional tackifier that provide pressure sensitive
adhesive compositions in which improved peel adhesion to at least
one of low and relatively high surface energy substrates can be
achieved.
Inventors: |
Khandpur, Ashish K.; (Lake
Elmo, MN) ; Joseph, Eugene G.; (Vadnais Heights,
MN) ; Bennett, Greggory S.; (Hudson, WI) |
Correspondence
Address: |
Attention: Lisa M. McGeehan
Office of Intellectual Property Counsel
3M Innovative Properties Company
P.O. Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
25020665 |
Appl. No.: |
09/751141 |
Filed: |
December 29, 2000 |
Current U.S.
Class: |
428/355R ;
428/343; 428/355AC |
Current CPC
Class: |
Y10T 442/60 20150401;
C08L 2666/24 20130101; Y10T 428/28 20150115; D04H 1/587 20130101;
C09J 133/06 20130101; Y10T 428/2933 20150115; C09J 151/003
20130101; Y10T 442/637 20150401; C08L 51/06 20130101; C08L 2666/04
20130101; C09J 7/385 20180101; C09J 123/10 20130101; C08L 23/10
20130101; Y10T 428/2887 20150115; C09J 133/06 20130101; Y10T
428/2878 20150115; Y10T 428/2891 20150115; C09J 123/10 20130101;
C09J 151/003 20130101; Y10T 428/2852 20150115; D04H 1/64 20130101;
C08L 2666/04 20130101; C08L 2666/04 20130101; C08L 2666/24
20130101 |
Class at
Publication: |
428/355.00R ;
428/355.0AC; 428/343 |
International
Class: |
B32B 007/12; B32B
015/04 |
Claims
What is claimed is:
1. A pressure sensitive adhesive composition comprising a blend of:
at least one (meth)acrylate polymer; and at least one amorphous
propylene-derived polymer derived from at least about 60% by weight
propylene monomers, wherein the at least one propylene-derived
polymer comprises at least about 15% by weight based on total
weight of the at least one (meth)acrylate polymer and the at least
one propylene-derived polymer.
2. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer comprises
polypropylene.
3. The pressure sensitive adhesive composition of claim 2, wherein
the polypropylene is a metallocene-generated polypropylene.
4. The pressure sensitive adhesive composition of claim 1, wherein
the at least one (meth)acrylate polymer is grafted with at least
one reinforcing polymeric moiety.
5. The pressure sensitive adhesive composition of claim 4, wherein
the at least one reinforcing polymeric moiety is selected from
polymethylmethacrylate, polystyrene, and combinations thereof.
6. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer comprises a copolymer of
propylene and at least one other alpha-olefin.
7. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer is selected from
propylene/ethylene-derived copolymers and propylene/hexene-derived
copolymers.
8. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer has a weight average
molecular weight of about 10,000 grams/mole to about 1,000,000
grams/mole.
9. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer has a melt viscosity at
190.degree. C. of greater than about 10 Poise.
10. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer has a melt viscosity at
190.degree. C. of greater than about 500 Poise.
11. The pressure-sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer has a Tg of about
-50.degree. C. to about 0.degree. C.
12. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer has a Tg of about
-15.degree. C. to about 10.degree. C.
13. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer is derived from
essentially no diene monomers.
14. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer comprises at least about
20% by weight based on total weight of the at least one
(meth)acrylate polymer and the at least one propylene-derived
polymer.
15. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer comprises about 20% to
about 50% by weight based on total weight of the at least one
(meth)acrylate polymer and the at least one propylene-derived
polymer.
16. The pressure sensitive adhesive composition of claim 1, wherein
the at least one (meth)acrylate polymer comprises at least about
15% by weight based on total weight of the at least one
(meth)acrylate polymer and the at least one propylene-derived
polymer.
17. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer is
non-stereoregular.
18. The pressure sensitive adhesive composition of claim 1, wherein
the at least one propylene-derived polymer has a stereoregularity
index of about 1 to about 10.
19. The pressure sensitive adhesive composition of claim 1, wherein
the composition is crosslinked.
20. A substrate on which the pressure sensitive adhesive
composition of claim 1 is at least partially applied.
21. A fiber comprising the pressure sensitive adhesive composition
of claim 1.
22. A microfiber web comprising the pressure sensitive adhesive
composition of claim 1.
23. A tape comprising: a backing having a first and second side;
and the pressure sensitive adhesive composition of claim 1 applied
on at least a portion of the first side of the backing and,
optionally, on at least a portion of the second side of the
backing.
24. A process for preparing a pressure sensitive adhesive
composition comprising the steps of: providing at least one
(meth)acrylate polymer, providing at least one amorphous
propylene-derived polymer derived from at least about 60% by weight
propylene monomers, wherein the at least one propylene-derived
polymer comprises at least about 15% by weight based on total
weight of the at least one (meth)acrylate polymer and the at least
one propylene-derived polymer, optionally, adding at least one
tackifier to the composition, and blending the composition
comprising the at least one (meth)acrylate polymer and the least
one amorphous propylene-derived polymer to form the pressure
sensitive adhesive composition.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to polymer blends comprising
at least one (meth)acrylate polymer and at least one amorphous
propylene-derived polymer that exhibit pressure sensitive adhesive
properties. The pressure sensitive adhesives are useful in
preparing a wide variety of articles.
BACKGROUND OF THE INVENTION
[0002] Pressure sensitive adhesive (PSA) compositions are well
known to those of ordinary skill in the art to possess properties
including the following: (1) aggressive and permanent tack, (2)
adherence with no more than finger pressure, (3) sufficient ability
to hold onto an adherend, and (4) sufficient cohesive strength.
Materials that have been found to function well as PSAs are
polymers designed and formulated to exhibit the requisite
viscoelastic properties resulting in a desired balance of tack,
peel adhesion, and shear holding power. Obtaining the proper
balance of properties is not a simple process.
[0003] The most commonly used polymers for preparing PSAs are
natural rubber-, synthetic rubber- (e.g., styrene/butadiene
copolymers (SBR) and styrene/isoprene/styrene (SIS) block
copolymers), and various (meth)acrylate- (e.g., acrylate and
methacrylate) based polymers. Of these, (meth)acrylate-based
polymer PSAs have evolved as a preferred class of PSA due to their
optical clarity, permanence of properties over time, and
versatility of adhesion levels, to name just a few of the their
benefits. It is known to prepare PSAs comprising mixtures of
certain (meth)acrylate-based polymers with certain other types of
polymers.
[0004] European Patent Application No. 0 254 002 (Sumitomo Chemical
Co. Ltd.) describes PSAs comprising at least one elastomer (e.g.,
natural rubber, styrene-butadiene rubber, and acrylic rubber), at
least one tackifier, and an ethylene-propylene copolymer having
such a low molecular weight that the intrinsic viscosity is not
more than 0.5. The ethylene-propylene copolymer is obtainable by
oxidative degradation of a corresponding ethylene-propylene
copolymer containing 30-60 weight % of propylene. The amount of
ethylene-propylene copolymer is in the range of 5-40 parts by
weight based on 100 parts by weight of the elastomer. It is taught
that the PSA therein is ordinarily dissolved in toluene or the
like, coated on a substrate, and then dried to remove the
solvent.
[0005] U.S. Pat. No. 5,202,361 (Zimmerman et al.) teaches another
approach to preparing PSAs using certain (meth)acrylate polymers in
combination with certain alpha-olefin polymers. Specifically, the
alpha-olefins have a glass transition temperature (Tg) of about
-70.degree. C. to about -10.degree. C. and a weight average
molecular weight of about 25,000 to about 5,000,000. Furthermore,
at least 60 mole % of the olefin monomers used to prepare the
alpha-olefin polymers have 6 to 18 carbon atoms. The PSAs
purportedly have good adhesion to both low and high energy
surfaces. It is taught that the alpha-olefin polymer is dissolved
in a mixture of free-radically polymerizable monomers and a
photoinitiator/crosslinker. The liquid composition is then coated
on a substrate and cured by irradiating the composition using
ultraviolet radiation.
[0006] PCT Publication No. WO 97/23,577 (Minnesota Mining and
Manufacturing Co.) describes blended PSAs that include at least two
components. The first component is a PSA. Among useful PSAs
described therein are acrylics and poly alpha-olefins. The second
component is a thermoplastic material or elastomer. For example,
thermoplastic materials useful in the invention include isotactic
polypropylene and ethylene/propylene copolymers. It is also taught
that useful thermoplastic materials are essentially immiscible in
the PSA component at use temperatures. The Abstract describes the
blends therein, which are melt processable, as having a
substantially continuous domain (generally the PSA) and a
substantially fibrinous to schistose domain (generally the
thermoplastic material). Tackifiers may be added.
[0007] PCT Publication No. WO 96/25,469 (Minnesota Mining and
Manufacturing Co.) describes PSAs that are a blend of about 5 to 95
weight percent of an acrylic PSA and about 5 to about 95 weight
percent of a thermoplastic elastomeric copolymer. The thermoplastic
elastomeric materials are materials that contain at least two
segments, i.e., a hard segment and a soft segment. Useful
thermoplastic elastomeric materials include
styrene-(ethylene-propylene) block copolymers, polyolefin-based
thermoplastic elastomeric materials represented by the formula
--(CH.sub.2CHR)x, where R is an alkyl group containing 2 to 10
carbon atoms, and polyolefins based on metallocene catalysis, such
as an ethylene/1-octene copolymer. The blends are melt
processable.
[0008] Ways to effectively adhere to low surface energy materials
is a challenge that those of ordinary skill in the art are
attempting to overcome. Many times improvements in adherence to low
surface energy substrates compromises adherence to higher surface
energy substrates or compromises shear strength of the adhesive. As
such, further adhesives for adequately adhering to low surface
energy surfaces, especially those adhesives that perform without
comprising adherence to high surface energy substrates, are
desired. Similarly, adhesives with improved adherence to high
surface energy substrates are beneficial.
[0009] It is also desired that any such new adhesives will allow
for broad formulation latitude and tailorability for particular
applications. For example, in some applications it is desirable to
have a hot-melt processable composition, as opposed to those
compositions that are coated on a substrate and subsequently dried
or cured. It is also preferred to use (meth)acrylate polymers in
such adhesives, due to their desirable properties. The present
invention addresses these motivating factors.
SUMMARY OF THE INVENTION
[0010] PSA blends of the invention are particularly useful for
adhering to both relatively high and low surface energy materials.
PSA blends of the invention are capable of providing adequate or
improved peel adhesion to such substrates. Surprisingly, in
preferred embodiments of the invention, peel adhesion to low
surface energy substrates, such as polypropylene, is enhanced as
compared to peel adhesion of the (meth)acrylate polymer without the
propylene-derived polymer to low surface energy substrates or peel
adhesion of the propylene-derived polymer without the
(meth)acrylate polymer to low surface energy substrates. This
enhancement is even possible in some embodiments without causing
detrimental effects in peel adhesion to high surface energy
substrates. According to other aspects of the invention, peel
adhesion to high surface energy substrates, such as glass, is
enhanced as compared to peel adhesion of the (meth)acrylate polymer
without the propylene-derived polymer to high surface energy
substrates or peel adhesion of the propylene-derived polymer
without the (meth)acrylate polymer to high surface energy
substrates. Useful shear strengths are also realizable using the
blends of this invention.
[0011] Certain embodiments of the invention provide substrates with
the pressure sensitive adhesive composition at least partially
applied thereon. Other embodiments of the invention provide fibers
and microfiber webs comprising the pressure sensitive adhesive
composition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] Pressure sensitive adhesive (PSA) blends of the present
invention comprise at least one (meth)acrylate polymer and at least
one propylene-derived polymer. Terms used throughout to assist in
describing the invention are defined in turn below.
[0013] "Polymer" refers to macromolecular materials having at least
five repeating monomeric units, which may or may not be the same.
The term "polymer", as used herein, encompasses homopolymers and
copolymers. Copolymers of the invention refer to those polymers
derived from at least two chemically different monomers. Included
within the definition of copolymers are traditional copolymers
derived from at least five monomers, which include only two
chemically different types of monomers, as well as terpolymers,
which include at least three chemically different types of
monomers, etc.
[0014] In general, a polymer can include more than one type of
steric structure throughout its chain length. For example, polymers
can include crystalline, stereoregular isotactic and syndiotactic
structures, as well as amorphous, atactic structures, or
combinations thereof. The steric structure of a polymer can be
determined using any suitable method. For example, carbon-13
Nuclear Magnetic Resonance can be used to determine the steric
structure (i.e., tacticity) of a polymer.
[0015] "Stereoregular" structures, as defined by Hawley's Condensed
Chemical Dictionary(12th Edition), are those whose molecular
structure has a definite spatial arrangement, rather than the
random and varying arrangement that characterizes an amorphous
polymer. Stereoregular structures include isotactic and
syndiotactic structures.
[0016] "Isotactic" structures, as defined by Hawley's Condensed
Chemical Dictionary (12th Edition), are those whose structure is
such that groups of atoms that are not part of the backbone
structure are located either all above, or all below, atoms in the
backbone chain, when the latter are all in one plane.
[0017] "Syndiotactic" structures, as defined by Hawley's Condensed
Chemical Dictionary (12th Edition), are those whose structure is
such that groups of atoms that are not part of the backbone
structure are located in some symmetrical and recurring fashion
above and below the atoms in the backbone chain, when the latter
are all in one plane.
[0018] "Atactic" structures, as defined by Hawley's Condensed
Chemical Dictionary (12th Edition), are those whose structure is
such that groups of atoms are arranged randomly above and below the
backbone chain of atoms, when the latter are all in one plane.
[0019] The "Stereoregular Index (S.I.)" of a polymer is defined as
follows: In a perfectly atactic polymer, two homotactic triads, mm
and rr, are present in equal amounts (25% each). As the polymer
becomes increasingly stereoregular, the relative amounts of mm and
rr change so that one increases to be greater than the other. S.I.
is the ratio of the larger of mm or rr to the smaller of mm or rr
and is always positive and greater than 1. S.I. expresses, in a
numerical way, how the steric structure of a polymer shifts away
from 1.0 for a random, atactic polymer to larger values
characteristic of more stereoregular polymers.
[0020] "Non-stereoregular" polymers are generally mostly atactic or
mostly semi-syndiotactic polymers, rather than mostly isotactic or
mostly syndiotactic.
[0021] "Semi-syndiotactic" polymers are those having structures
between mostly syndiotactic polymers and mostly atactic
polymers.
[0022] In one embodiment, non-stereoregular polymers of the
invention have an S.I. of 1 to about 10. In another embodiment,
non-stereoregular polymers of the invention have an S.I. of 1 to
about 7. In still a further embodiment, non-stereoregular polymers
of the invention have an S.I. of 1.5 to about 7. In yet another
embodiment, non-stereoregular polymers of the invention have an
S.I. of 1 to about 1.1.
[0023] "Amorphous" polymers are those polymers that are hexane
soluble at room temperature. Recognize that such materials may have
a small degree of crystallinity, which is detectable, for example,
using x-ray or thermal analysis. Amorphous polymers lack a
well-defined melting point when measured by Differential Scanning
Calorimetry (DSC). Particularly preferred are those amorphous
polymers that are non-stereoregular (e.g., mostly atactic or mostly
semi-syndiotactic).
[0024] "Hot melt processable" refers to those adhesives having a
sufficient viscosity upon softening, such that the adhesives can be
hot melt processed (e.g., applied to a substrate). It is not
necessary for the adhesives to actually melt at the processing
temperature, but rather it must soften to the point that it can be
made to flow at the processing pressure.
[0025] Polymers that have less stereoregularity have been found to
be preferred for processing and preparing PSAs of the invention,
such as for example, by hot-melt processing. As such, hot-melt
processable adhesives are enabled by the present invention.
[0026] Hot melt processable adhesives advantageously reduce or
eliminate the use of organic solvents in adhesives and their
processing. Hot melt processable adhesive systems are essentially
100% solid systems. Usually, such systems have no more than about
5% organic solvents or water, more typically no more than about 3%
organic solvents or water. Most typically, such systems are free of
organic solvents and water. Advantageously, by reducing the use of
organic solvents, special handling concerns associated therewith
are also reduced. Furthermore, hot melt processable adhesive
systems advantageously do not require a separate processing step
after applying the composition to a substrate. Also, in some
applications, particularly melt-blown microfiber applications, the
adhesive composition must be hot-melt processable.
[0027] Another advantage to using polymers that have less
stereoregularity is that materials that are highly isotactic tend
to be opaque, while those that are less stereoregular tend to be
more transparent. The clarity (i.e., transparency) of materials
with low stereoregularity makes them preferred for use in
applications where clarity of the adhesive is important. Such
applications include, for example, bonding of glass and transparent
plastics.
[0028] One advantage of utilizing blends of the invention is the
greater formulation latitude that they provide. That is, changes in
a wide variety of physical properties of films comprising the
blends can be effectuated, for example, by varying the ratio of
individual polymers in the blends. Furthermore, cost effectiveness
is another advantage of utilizing blends. For example, less
expensive polymers can be blended with more expensive polymers. In
that way, the less expensive polymers can act as an "extender" for
the more expensive polymers. Also, using blends can provide
advantageous synergistic effects, wherein, for a certain
application, the blend can perform substantially better than either
polymer by itself for the same application.
[0029] PSA blends of the invention are particularly useful for
adhering to both relatively high and low surface energy materials.
PSA blends of the invention are capable of providing adequate or
improved peel adhesion to such substrates.
[0030] Surprisingly, in preferred embodiments of the invention,
peel adhesion to low surface energy substrates, such as
polypropylene, is enhanced as compared to peel adhesion of the
(meth)acrylate polymer without the propylene-derived polymer to low
surface energy substrates or peel adhesion of the propylene-derived
polymer without the (meth)acrylate polymer to low surface energy
substrates. This enhancement is even possible in some embodiments
without causing detrimental effects in peel adhesion to high
surface energy substrates.
[0031] According to other aspects of the invention, peel adhesion
to high surface energy substrates, such as glass, is enhanced as
compared to peel adhesion of the (meth)acrylate polymer without the
propylene-derived polymer to high surface energy substrates or peel
adhesion of the propylene-derived polymer without the
(meth)acrylate polymer to high surface energy substrates. Useful
shear strengths are also realizable using the blends of this
invention.
[0032] Preferably at least one of the polymers in the blend is a
PSA. However, more than one polymer in the blend may be a PSA. Many
polymers are inherently tacky, i.e., the polymers do not require
addition of a tackifier to render the composition pressure
sensitive. Examples of such inherently tacky polymers include many
(meth)acrylate (i.e., methacrylate and acrylate) polymers. However,
a polymer may also be made pressure sensitive by addition of a
tackifier to the polymer. Whether a polymer is inherently a PSA or
requires addition of a tackifier, it is preferred that at least one
of the polymers in the blend is a PSA.
[0033] (Meth)Acrylate Polymer
[0034] Any suitable (meth)acrylate (i.e. acrylate or methacrylate)
polymer can be used in blends of the invention. (Meth)acrylate
polymers are those derived from at least one (meth)acrylate
monomer. (Meth)acrylate polymers may also be derived from, for
example, other ethylenically unsaturated monomers and/or acidic
monomers and/or the (meth)acrylate polymers may also be grafted
with a reinforcing polymeric moiety. Specific examples of preferred
(meth)acrylate polymers are described in the Examples section,
infra.
[0035] Particularly preferred (meth)acrylate monomers include
(meth)acrylate esters of non-tertiary alkyl alcohols, the alkyl
groups of which comprise from about 1 to about 18 carbon atoms,
preferably about 4 to about 12 carbon atoms, and mixtures
thereof.
[0036] Examples of suitable (meth)acrylate monomers useful in the
present invention include, but are not limited to, methyl acrylate,
ethyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl
acrylate, decyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl
methacrylate, hexyl acrylate, isoamyl acrylate, isodecyl acrylate,
isodecyl methacrylate, isononyl acrylate, isooctyl acrylate, lauryl
acrylate, 2-methylbutyl acrylate,
[0037] 4-methyl-2-pentyl acrylate, ethoxyethoxyethyl acrylate,
isobomyl acrylate, isobomyl methacrylate, 4-t-butylcyclohexyl
methacrylate, cyclohexyl methacrylate, phenyl acrylate, pbenyl
methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, and
mixtures thereof. Particularly preferred are 2-ethylhexyl acrylate,
isooctyl acrylate, lauryl acrylate, n-butyl acrylate,
ethoxyethoxyethyl acrylate, and mixtures thereof.
[0038] Examples of other ethylenically unsaturated monomers
include, but are not limited to, vinyl esters (e.g., vinyl acetate,
vinyl pivalate, and vinyl neononanoate); vinyl amides; N-vinyl
lactams (e.g., N-vinyl pyrrolidone and N-vinyl caprolactam);
(meth)acrylamides (e.g., N,N-dimethyl acrylamide, N,N-dimethyl
methacrylamide,
[0039] N,N-diethyl acrylamide, and N,N-diethyl methacrylamide);
(meth)acrylonitrile; maleic anhydride; styrene and substituted
styrene derivatives (e.g., alpha-methyl styrene); and mixtures
thereof.
[0040] Optional acidic monomers may also be used for preparation of
the (meth)acrylate polymers. Useful acidic monomers include but are
not limited to, those selected from ethylenically unsaturated
carboxylic acids, ethylenically unsaturated sulfonic acids,
ethylenically unsaturated phosphonic acids, and mixtures thereof
Examples of such compounds include those selected from acrylic
acid, methacrylic acid, itaconic acid, fumaric acid, crotonic acid,
citraconic acid, maleic acid, beta-carboxyethyl acrylate,
2-sulfoethyl methacrylate, styrene sulfonic acid,
2-acrylamide-2-methylpropane sulfonic acid, vinyl phosphonic acid,
and the like, and mixtures thereof.
[0041] A suitable class of useful (meth)acrylate polymers is
described in U.S. Pat. No. 4,554,324. This patent discloses
reinforcement of conventional (meth)acrylate polymers by
modification of the (meth)acrylate polymeric backbone by grafting
reinforcing polymeric moieties onto the (meth)acrylate polymeric
backbone. The reinforcing polymeric moieties may be grafted, for
example, by in-situ polymerization of the reinforcing polymeric
moieties in the presence of and onto reactive sites of the
ungrafted (meth)acrylate polymer backbone, reacting prepolymerized
polymeric moieties with reactive sites of the ungrafted
(meth)acrylate polymer backbone, or by copolymerizing reinforcing
polymeric compounds with monomer used to prepare the (meth)acrylate
polymer backbone to form the (meth)acrylate polymer grafted with
reinforcing polymeric moieties.
[0042] The reinforcing polymeric moieties in this embodiment
generally have a Tg (glass transition temperature) of at least
20.degree. C. and a weight average molecular weight of at least
2,000. By contrast, the ungrafted (meth)acrylate polymer backbone
generally has a Tg of less than about -20.degree. C., usually less
than about -50.degree. C. in this embodiment. Preferred reinforcing
polymeric moieties are those based on polymethylmethacrylate and
polystyrene. The Tg of a reinforcing polymeric moiety or ungrafted
(meth)acrylate polymer backbone is measurable using Differential
Scanning Calorimetry using second heat measurements at 10.degree.
C. per minute.
[0043] Depending on the particular application, other suitable
monomers, including diene monomers, may be copolymerized with the
(meth)acrylate monomers when preparing the (meth)acrylate polymer.
However, in one embodiment, the (meth)acrylate polymer of the
invention is derived from essentially no diene monomers.
[0044] Propylene-Derived Polymer
[0045] Any suitable polymer can be used for the propylene-derived
polymer. The propylene-derived polymers themselves, may or may not
have PSA properties. Generally, the propylene-derived polymer is at
least amorphous, preferably non-stereoregular. As such, the
compositions of the invention are able to have enhanced
pressure-sensitive adhesive properties, often without the need for
using substantial amounts of additives, such as plasticizers or
liquid oils.
[0046] The propylene-derived polymer is derived from at least
propylene monomer. While other types of monomers may be used in
their preparation, typically the propylene-derived polymer is
derived from greater than 60 mole percent propylene monomers. Other
monomers that can be copolymerized with the propylene monomer
include, for example, alpha-olefin monomers (e.g., ethylene,
1-butene, 1-hexene, 1-heptene, 1-octene, 1-nonene, etc.).
[0047] It is preferred that the propylene-derived polymer contains
a saturated hydrocarbon backbone. Accordingly, preferably the
propylene-derived polymer is derived from essentially no diene
monomers. Many compositions derived from diene monomers are
relatively unstable over time, such as for example, when exposed to
weathering or higher temperatures (e.g., when hot-melt
processing).
[0048] Propylene-derived polymers of the invention are of high
enough molecular weight that they do not act as a tackifier or
plasticizer. Typically, the weight average molecular weight of the
propylene-derived polymer is at least about 5,000 grams/mole.
Preferably, the weight average molecular weight of the
propylene-derived polymer is at least about 10,000 grams/mole, even
more preferably at least about 15,000 grams/mole, and even more
preferably at least about 20,000 grams/mole. Particularly useful
are polymers with a weight average molecular weight of about
10,000-1,000,000 grams/mole, preferably about 20,000-200,000
grams/mole.
[0049] According to one aspect of the invention, the
propylene-derived polymer is a copolymer derived from at least
propylene and ethylene monomer. Any suitable amount of ethylene
monomer may be used to prepare such propylene/ethylene-derived
copolymers as long as the resulting copolymer is amorphous.
Generally, however, the greater the proportion of ethylene monomer
used, the more likely it is that the resulting copolymer will not
be amorphous.
[0050] Particularly useful are the propylene/ethylene-derived
copolymers with a glass transition temperature (Tg) of about
-50.degree. C. to about 0.degree. C., preferably greater than
-40.degree. C. to about 0.degree. C., and more preferably about
-30.degree. C. to about 0.degree. C. Generally, when the Tg of the
propylene/ethylene-derived copolymer is lower than -50.degree. C.,
it is because a larger proportion of ethylene monomer was used in
preparation of the copolymer. While some such copolymers may be
useful for certain embodiments of the invention, as discussed
above, these polymers may not be amorphous. Furthermore, it is
preferred that the Tg of the propylene/ethylene-derived copolymer
is greater than about -50.degree. C. in order to reduce the
necessity for adding a tackifier, or at least a large amount of
tackifier, to the composition in order to obtain PSA properties for
room temperature applications. The Tg of a polymer is measurable
using Differential Scanning Calorimetry using second heat
measurements at 10.degree. C. per minute.
[0051] Examples of propylene/ethylene-derived copolymers useful in
the present invention include polymers commercially available from
Eastman Chemical Co.; Kingsport, Tenn. under the EASTOFLEX
tradename and polymers commercially available from The
International Group; Wayne, Pa. under the KTAC tradename. Specific
examples of suitable propylene/ethylene-derived copolymers from
these companies are those with a Tg of about -33.degree. C. to
about -23.degree. C., such as EASTOFLEX E1060, EASTOFLEX E1200, and
KTAC 6013.
[0052] More generally, according to another embodiment of the
invention, the propylene-derived polymer is a copolymer derived
from at least propylene and one other alpha-olefin monomer, such as
1-hexene. A specific example of a commercially available
propylene/hexene-derived copolymer is that sold under the trade
designation, EASTOFLEX D127S, available from Eastman Chemical Co.;
Kingsport, TN.
[0053] According to another aspect of the invention, the
propylene-derived polymer is derived from essentially 100 percent
by weight propylene monomers. Any suitable polypropylene can be
used in accordance with this aspect of the invention.
[0054] When the propylene-derived polymer is derived from
essentially 100 percent by weight propylene, the preferred Tg of
these polymers is about -15.degree. C. to about 10.degree. C., more
preferably about -10.degree. C. to about 5.degree. C. The use of at
least one propylene-derived polymer having such a preferred Tg
facilitates formation of a composition having PSA properties.
Again, the Tg of a polymer is measurable using Differential
Scanning Calorimetry using second heat measurements at 10.degree.
C. per minute.
[0055] When higher molecular weight propylene-derived polymers,
particularly polypropylene, are preferred, those polymers prepared
using a metallocene catalyst, such as in PCT Publication No. WO
99/20,664, are particularly useful. Typically, polymers prepared
using a metallocene catalyst (i.e., metallocene-generated polymers)
have a weight average molecular weight of greater than about 70,000
grams/mole, which is typically higher than the molecular weight of
many commercially available non-stereoregular propylene-derived
polymers. A similar comparison applies when comparing melt
viscosities of the polymers. Propylene-derived polymers prepared
using metallocene catalysts may be preferred when PSA compositions
having higher shear strength are desired in addition to improved
peel adhesion properties. The higher molecular weight of the
propylene-derived polymers prepared using a metallocene catalyst
also enables them to be more usefully crosslinked, as compared to
those propylene-derived polymers having lower molecular weights.
This may be the case, when for example, the PSAs are to be used in
a high performance application.
[0056] According to one embodiment of this aspect of the invention,
the stereoregularity index (S.I.) of the propylene-derived polymer
is about 1.0 to about 5.0. Preferably, when the propylene-derived
polymer is amorphous, its S.I. is about 1.0 to about 1.05.
Preferably, when the propylene-derived polymer is
semi-syndiotactic, its stereoregularity index (S.I.) is about 1.1
to about 4.0.
[0057] As stated previously, however, one advantage of the present
invention is that the blends are tailorable for a wide variety of
applications. Higher molecular weight polymers may not always be
preferred depending on the application. For example, lower
molecular weight polymers may be preferred when using the PSA
composition to form a fiber (e.g., melt-blown fiber). PSA blends of
the invention may be advantageously used to prepare melt-blown
microfiber webs, for example. Addition of a lower molecular weight
polymer to a conventional polymer composition in accordance with
the invention tends to lower the melt viscosity of the polymer
composition at a given processing temperature. Therefore, the use
of polymer blends of the invention may facilitate hot melt
processing of fibers (e.g., microfibers) from PSA compositions at
lower temperatures than those used to hot melt process fibers from
conventional PSA compositions. Also, the use of polymer blends of
the invention may facilitate a higher throughput of hot melt
processed fibers at a given processing temperature.
[0058] The melt viscosity of the propylene-derived polymer can vary
widely. Typically, however, the melt viscosity of the
propylene-derived polymer is at least about 10 Poise when measured
at 190.degree. C. according to the Viscosity Test method in the
Examples section, infra.
[0059] In one embodiment, particularly those embodiments where the
propylene-derived polymer is derived from essentially 100 percent
by weight propylene, melt viscosity of the propylene-derived
polymer is greater than about 500 Poise, more preferably greater
than about 750 Poise, when measured at 190.degree. C. according to
the Viscosity Test method in the Examples section, infra. In a
further embodiment according to this aspect of the invention, the
melt viscosity of the propylene-derived polymer is greater than
about 2,500 Poise when measured at 190.degree. C. according to the
Viscosity Test method. In still a further embodiment of this aspect
of the invention, the melt viscosity of the propylene-derived
polymer is greater than about 10,000 Poise when measured at
190.degree. C. according to the Viscosity Test method.
[0060] Generally, the higher the melt viscosity of the
propylene-derived polymer, the more likely it is that the resulting
composition will have a higher shear strength in conjunction with
improved peel adhesion properties. This is particularly beneficial
when preparing PSA compositions of the invention for high
performance applications.
[0061] Optional Tackifier
[0062] Tackifiers of the invention have a weight average molecular
weight of less than about 10,000 grams/mole and may be a in a solid
or liquid state. The compositions of the invention may include a
tackifier, where necessary to impart the desired PSA properties.
Those of ordinary skill in the art recognize that a wide variety of
tackifier are suitable for this purpose. The amount of tackifier
used is readily appreciated by one of ordinary skill in the
art.
[0063] Preparation of Blends
[0064] PSA compositions of the invention include at least one
(meth)acrylate polymer and at least one propylene-derived polymer.
Other additives (e.g., antioxidants, crosslinking additives,
fillers, and ultraviolet stabilizers) may also be added to the PSA
compositions, depending on the desired application and as well
known to one of ordinary skill in the art.
[0065] Each of the (meth)acrylate polymer and propylene-derived
polymer components of the blend is preferably present in an amount
of about 5 weight % to about 95 weight % based on total weight of
the blend. More preferably, each of the components is present in an
amount of at least about 10 weight % based on total weight of the
blend. Typically, however, the (meth)acrylate polymer component is
present in a major portion and the propylene-derived polymer
component is present in a minor portion based on total weight of
the two components. This ratio of components contributes to
obtainment of compositions having adequate adhesion to both
relatively high surface energy substrates and low surface energy
substrates. It has also been found that this ratio facilitates
formation of compositions having useful shear strengths by, for
example, facilitating crosslinking of the pressure sensitive
adhesive composition.
[0066] No matter what proportion of the total blend each of the
polymeric components comprises, the propylene-derived polymer
component is present in at least about 15 weight % based on total
weight of the (meth)acrylate polymer and propylene-derived polymer
components. Below this amount, significant improvements in peel
adhesion to at least one of high or low surface energy substrates
is not as readily obtainable. Preferably, the propylene-derived
polymer component is present in at least about 20 weight %, more
preferably about 20 weight % to about 50 weight %, based on total
weight of the (meth)acrylate polymer and propylene-derived polymer
components.
[0067] According to a further embodiment of the invention, the
(meth)acrylate polymer component is present in at least about 15
weight % based on total weight of the (meth)acrylate polymer and
propylene-derived polymer components. Preferably, the
(meth)acrylate polymer component is present in at least about 20
weight %, more preferably about 20 weight % to about 50 weight %,
based on total weight of the (meth)acrylate polymer and
propylene-derived polymer components.
[0068] Blending of the polymers is done by any method that results
in a substantially homogeneous distribution of the polymers. The
polymers can be blended using several methods. In particular, the
polymers can be blended by melt blending, solvent blending, or any
suitable physical means.
[0069] For example, the polymers can be melt blended by a method as
described by Guerin et al. in U.S. Pat. No. 4,152,189. That is, all
solvent (if used) is removed from each polymer by heating to a
temperature of about 150.degree. C. to about 175.degree. C. at a
pressure of about 5 Torr to about 10 Torr. Then, the polymers are
weighed into a vessel in the desired proportions. The blend is then
formed by heating the contents of the vessel to about 175.degree.
C., while stirring.
[0070] Although melt blending is preferred, the PSA blends of the
present invention can also be processed using solvent blending. In
that case, the polymers in the blend should be substantially
soluble in the solvents used.
[0071] Physical blending devices that provide dispersive mixing,
distributive mixing, or a combination of dispersive and
distributive mixing are useful in preparing homogenous blends. Both
batch and continuous methods of physical blending can be used.
Examples of batch methods include those methods using BRABENDER
(e.g., a BRABENDER PREP CENTER, available from C.W. Brabender
Instruments, Inc.; South Hackensack, N.J.) or BANBURY internal
mixing and roll milling (available from FARREL COMPANY; Ansonia,
Conn.) equipment. Examples of continuous methods include single
screw extruding, twin screw extruding, disk extruding,
reciprocating single screw extruding, and pin barrel single screw
extruding.
[0072] Applications
[0073] The PSA compositions of the present invention can be readily
applied to a substrate. For example, the PSA composition can be
applied to sheeting products (e.g., decorative, reflective, and
graphical), label, stock, and tape backings. The substrate can be
any suitable type of material depending on the desired application.
Typically, the substrate comprises a nonwoven, paper, polymeric
film (e.g., polypropylene (e.g., biaxially oriented polypropylene
(BOPP)), polyethylene, polyurea, or polyester (e.g., polyethylene
terephthalate (PET)), or release liner (e.g., siliconized
liner).
[0074] PSA compositions according to the present invention can be
utilized to form tape, for example. The PSA is applied to at least
one side of the backing. The PSA may then be crosslinked to further
improve the shear strength of the PSA. Any suitable crosslinking
method (e.g., exposure to radiation, such as actinic (e.g.,
ultraviolet or electron beam) or thermal radiation) or crosslinker
additive (e.g., including photoactivated and thermally activated
curatives) may be utilized.
[0075] When double-sided tapes are formed, the PSA is applied onto
at least a portion of both sides of the backing. Alternatively, a
release material (e.g., low adhesion backsize) can be applied to
the opposite side of the backing, if desired. Advantageously, the
PSA and/or release material, for example, can be coextruded with
the film backing for ease of processing.
[0076] The PSA can be applied to a substrate using methods well
known to one of ordinary skill in the art. For example, the PSA can
be applied using melt extrusion techniques. The PSA composition can
be applied by either continuous or batch processes. An example of a
batch process is the placement of a portion of the PSA composition
between a substrate to which the PSA is to be adhered and a surface
capable of releasing the PSA to form a composite structure. The
composite structure can then be compressed at a sufficient
temperature and pressure to form a PSA layer of a desired thickness
after cooling. Alternatively, the PSA composition can be compressed
between two release surfaces and cooled to form, for example, a
transfer tape.
[0077] Continuous forming methods include drawing the PSA
composition out of a heated film die and subsequently contacting
the drawn composition to a moving plastic web or other suitable
substrate. A related continuous forming method involves extruding
the PSA composition and a coextruded release material and/or
backing from a film die and cooling the layered product to form an
adhesive tape. Other continuous forming methods involve directly
contacting the PSA composition to a rapidly moving plastic web or
other suitable preformed substrate. Using this method, the PSA
composition is applied to the moving preformed web using a die
having flexible die lips, such as a conventional film or sheeting
die. After forming by any of these continuous methods, the films or
layers can be solidified by quenching using both direct methods
(e.g., chill rolls or water baths) and indirect methods (e.g., air
or gas impingement). Hot melt processed fibers can also be prepared
using another continuous forming method. Examples of this process
can be found, for example, in PCT Publication No. WO 99/28,539.
[0078] Although coating out of solvent is not preferred, the PSA
compositions can be coated using a solvent-based method. For
example, the PSA composition can be coated by such methods as knife
coating, roll coating, gravure coating, rod coating, curtain
coating, and air knife coating. The coated solvent-based PSA
composition is then dried to remove the solvent. Preferably, the
applied solvent-based PSA composition is subjected to elevated
temperatures, such as those supplied by an oven, to expedite
drying.
[0079] The PSA compositions, coatings, and tapes therefrom are
exemplified in the following examples. These examples are merely
for illustrative purposes and are not meant to be limiting to the
scope of the appended claims. All parts, percentages, ratios, etc.
in the examples and the rest of the specification are by weight
unless indicated otherwise.
EXAMPLES
[0080] The following examples are noted as being comparatives by
using either one of the following designations: (1) numerical
designation followed by the letter "C" (e.g., 6A-C) or (2) by
starting with the letter "C" (e.g., CIA). Furthermore, the
following test methods were used to characterize the pressure
sensitive adhesive blends produced in the following examples.
[0081] Test Methods
[0082] 180.degree. Peel Adhesion
[0083] This peel adhesion test is similar to the test method
described in ASTM D 3330-90, substituting a glass or polypropylene
substrate for the stainless steel substrate described in the
test.
[0084] Adhesive-coated strips, which had equilibrated at constant
temperature (22.degree. C.) and humidity (50% relative humidity)
for at least 24 hours, were adhered to a substrate panel, either
solvent-washed glass or polypropylene (PP) (commercially available
from Aeromat Plastics; Burnsville, MN) using a 2 kilogram roller
passed once over the strip. The bonded assembly was allowed to
dwell at room temperature for less than one minute. The assembly
was then tested for 180.degree. peel adhesion using an IMASS
slip/peel tester (Model 3M90, commercially available from
Instrumentors Inc., Strongsville, Ohio) at a rate (i.e., crosshead
speed) of 30 centimeters/minute (12 inches/minute).
[0085] Shear Strength
[0086] This shear strength test is similar to the test method
described in ASTM D 3654-88. Adhesive-coated strips, which had
equilibrated at constant temperature (22.degree. C.) and humidity
(50% relative humidity) for at least 24 hours, were cut into 1.27
centimeter (0.5 inch) strips. Each strip was adhered to a stainless
steel panel such that a 1.27 centimeter (0.5 inch) by 2.54
centimeter (1 inch) portion of the strip was in firm contact with
the panel and one end of the strip hung free. The panel with the
adhesive-coated strip attached was held in a rack such that the
panel formed an angle of 178.degree. with the extended free end,
which was tensioned by application of a force of one kilogram
applied as a hanging weight. The 2.degree. less than 180.degree.
was used to negate any peel forces, thus ensuring that only shear
forces were measured, in an attempt to more accurately determine
the holding power of the tape being tested. The time elapsed for
each tape example to separate from the test panel was recorded as
the Shear Strength. Unless otherwise noted, all shear failures
reported herein were cohesive failures of the adhesive (residue
left on the panel), adhesive failure is denoted as A (no residue
left on the panel). If the test sample did not fail at 10,000
minutes, the test was stopped and a shear value of 10,000 minutes
was recorded.
[0087] An alternative method was used in certain examples. In the
alternative method, a strip measuring 1.27 centimeters by 1.27
centimeters (0.5 inch.times.0.5 inch) (or 2.54 centimeters by 2.54
centimeters (1.0 inch.times.1.0 inch)--if separately noted in the
table) was adhered to the stainless steel panel and the test
described above was performed. These examples are noted in the
tables.
[0088] Viscosity Test
[0089] Melt viscosity was measured as the complex viscosity using
Dynamic Mechanical Analysis (DMA) in a parallel plate rheometer
(RDA II, Rheometrics, Inc; Piscataway, N.J.) while the sample was
heated from room temperature to 200.degree. C. at a rate of
2.degree. C./minute, a frequency of 1 radian/second, and a maximum
strain of 10%. The melt viscosity at 190.degree. C. measured
according to this method is referenced throughout this
application.
1 Table of Abbreviations Abbreviation/ Trade Designation
Description AA acrylic acid EASTOFLEX propylene/hexene-derived
copolymer, commercially D127S available from Eastman Chemical
Company; Kingsport, TN EASTOFLEX propylene/ethylene-derived
copolymer, commercially E1060 available from Eastman Chemical
Company; Kingsport, TN ESCORENE isotactic polypropylene,
commercially available from 3860 Exxon Chemical Co.; Houston, TX
FINA 3374X isotactic polypropylene, commercially available from
Fina Oil and Chemical Co.; Deer Park, TX IOA isooctyl acrylate KTAC
6013 propylene/ethylene-derived copolymer, commercially available
from The International Group, Inc.; Wayne, PA mPP1 atactic
polypropylene prepared using metallocene catalysts as described in
PCT Publication No. WO 99/20,664, Example 18A, with an approximate
M.sub.w of 103,000 grams/mole and an approximate M.sub.w/M.sub.n
ratio of 4 mPP2 atactic polypropylene prepared using metallocene
catalysts as described in PCT Publication No. WO 99/20,664, Example
18A, with an approximate M.sub.w of 145,000 grams/mole and an
approximate M.sub.w/M.sub.n ratio of 5.4 PET an
aminated-polybutadiene primed polyester film of polyethylene
terephthalate having a thickness of 38 .mu.m PSA-1 IOA/AA-derived
copolymer grafted with a polystyrene reinforcing moiety, prepared
according to Example 11 of U.S. Pat. No. 5,057,366, except that the
weight ratio of the IOA/AA/polystyrene ("C-2") monomers used was
approximately 92/4/4 and the inherent viscosity of the resulting
polymer was 0.65 PSA-2 IOA/AA-derived copolymer grafted with a
polymethyl- methacrylate reinforcing moiety, prepared according to
Example 70 of U.S. Pat. No. 5,057,366, except that the weight ratio
of the IOA/AA/polymethylmethacrylate ("C-14") monomers was used
approximately 92/4/4 and the inherent viscosity of the resulting
polymer was 0.79 PSA-3A IOA/AA-derived copolymer PSA, prepared
using an approximate IOA/AA monomer ratio of 95/5 and prepared by
mixing 22.8 grams IOA, 1.2 grams AA, 0.28 gram carbon tetrabromide
chain transfer agent, and 36 grams ethyl acetate in a glass vessel;
then, 0.072 gram VAZO 64 was added and the vessel was made inert
using nitrogen gas; the vessel was sealed; the vessel was tumbled
in a 55.degree. C. water bath for 24 hours; the resulting polymer
was coated on a siliconized polyester release liner; the coated
sample was oven-dried for 15 minutes at 65.degree. C., and the
dried polymer was recovered PSA-3B IOA/AA copolymer PSA, prepared
using an approximate IOA/AA monomer ratio of 95/5 and prepared as
described in U.S. Pat. No. 5,804,610, Composition D-1 in Table 5,
except using isooctylthioglycolate chain transfer agent (0.015 part
by weight per 100 parts of the formulation) and an ultraviolet
radiation intensity of 3.52 mW/cm.sup.2 for 510 seconds PSA-3C
IOA/AA-derived copolymer PSA, prepared as described in U.S. Pat.
No. RE 24,906, Example 5, except using an approximate IOA/AA
monomer ratio of 95/5 PSA-4 IOA/AA copolymer PSA, prepared using an
approximate IOA/AA monomer ratio of 90/10 and as described in U.S.
Pat. No. 5,804,610, Composition D-1 in Table 5, except using
isooctylthioglycolate chain transfer agent (0.015 part by weight
per 100 parts by weight of the formulation) and an ultraviolet
radiation intensity of 3.52 mW/cm.sup.2 for 510 seconds PSA-5
KRATON-based adhesive as described in Example 20 of U.S. Pat. No.
6,083,856 VAZO 64 azo-bis(isobutyronitrile) initiator, commercially
available from E.I. duPont de Nemours & Co.; Wilmington, DE
Examples 1A-1M
[0090] In a 350-cm.sup.3-capacity BRABENDER batch mixer, PSA-1 and
EASTOFLEX D127S were blended for 10 minutes in a molten state at 50
revolutions per minute and a temperature of 115.degree. C. to
180.degree. C. according to the mix ratios shown in Table 1. The
total charge to the mixer was 250 grams. The parts noted in Table 1
are based on total weight of PSA-1 and EASTOFLEX D127S.
[0091] The lower temperatures were used when higher levels of
EASTOFLEX D127S were present. The specific temperature is noted in
Table 1. The blends were coated at approximately 150.degree. C.
onto PET at a thickness of 51 .mu.m using a 1.9 centimeter diameter
HAAKE single screw extruder (commercially available from Haake
Buchler Instruments Inc.; Saddle Brook, N.J.) having a
length-to-diameter ratio of 25 and fitted with a
12.5centimeter-wide draw die (shimmed to a 250 .mu.m die opening)
to form PSA tapes. The adhesive performance of these tapes is shown
in Table 2.
2 TABLE 1 Parts by Mixing Weight Parts by Weight Temperature
Example PSA-1 EASTOFLEX D127S (.degree. C.) 1A-C 100 0 170 1B-C 95
5 170 1C-C 90 10 170 1D 85 15 170 1E 75 25 165 1F 70 30 165 1G 65
35 165 1H 60 40 155 1I 50 50 145 1J 40 60 145 1K 25 75 130 1L 10 90
120 1M 0 100 115
[0092]
3TABLE 2 180.degree. Peel 180.degree. Peel Room Temperature
Adhesion to Glass Adhesion to PP Shear Strength Example (N/dm)
(N/dm) (minutes) 1A-C 55.6 45.3 321 1B-C 69.4 63.7 853 1C-C 80.1
78.8 72 1D 80.3 109.4 21 1E 79.4 139.6 26 1F 84.5 86.0 * 1G 54.7
90.8 39 1H 47.7 85.8 53 1I 81.0 90.4 62 1J 64.1 74.6 91 1K 73.3
77.5 155 1L 64.5 76.4 262 1M 47.9 78.3 149 *Not tested
Examples 2A-2F
[0093] In a BRABENDER batch mixer, PSA-1 and EASTOFLEX E1060 were
blended as described in Example 1 at a temperature of
165-170.degree. C. according to the mix ratios shown in Table 3.
The parts are based on total weight of PSA-1 and EASTOFLEX E1060.
The blends were coated onto PET to the thickness shown in Table 3
as described in Example 1 to form PSA tapes. The adhesive
performance of these tapes is shown in Table 4.
4 TABLE 3 Parts by Weight Parts by Weight Thickness Example PSA-1
EASTOFLEX E1060 (.mu.m) 2A-C 100 0 51 2B-C 90 10 51 2C 75 25 51
2D-C 100 0 160 2E-C 90 10 150 2F 75 25 130
[0094]
5TABLE 4 180.degree. Peel 180.degree. Peel Room Temperature
Adhesion to Glass Adhesion to PP Shear Strength* Example (N/dm)
(N/dm) (minutes) 2A-C 55.6 45.3 74 2B-C 104.4 94.4 8 2C 81.0 104.0
4 2D-C 84.7 75.0 ** 2E-C 195.1 177.3 6 2F 153.3 132.0 4 *A 1.27 cm
.times. 1.27 cm (0.5 inch .times. 0.5 inch) strip was used for this
test **Not tested
Examples 3A-3F
[0095] In a BRABENDER batch mixer, PSA-1 and KTAC 6013 were blended
as described in Example 1 at a temperature of 165-170.degree. C.
according to the mix ratios shown in Table 5. The parts are based
on total weight of PSA-1 and KTAC 6013. The blends were coated onto
PET to the thickness shown in Table 5 as described in Example 1 to
form PSA tapes. The adhesive performance of these tapes is shown in
Table 6.
6 TABLE 5 Parts by Weight Parts by Weight Thickness Example PSA-1
KTAC 6013 (.mu.m) 3A-C 100 0 51 3B-C 90 10 51 3C 75 25 51 3D-C 100
0 160 3E-C 90 10 130 3F 75 25 130
[0096]
7TABLE 6 180.degree. Peel 180.degree. Peel Room Temperature
Adhesion to Glass Adhesion to PP Shear Strength* Example (N/dm)
(N/dm) (minutes) 3A-C 55.6 45.3 74 3B-C 79.3 66.2 9 3C 95.2 89.6 4
3D-C 84.7 107.9 ** 3E-C 124.7 120.2 ** 3F 151.1 123.5 ** *A 1.27 cm
.times. 1.27 cm (0.5 inch .times. 0.5 inch) strip was used for this
test **Not tested
Examples 4A-4E
[0097] In a BRABENDER batch mixer, PSA-2 and EASTOFLEX D127S were
blended as described in Example 1 at a temperature of 160.degree.
C. according to the mix ratios shown in Table 7. The parts are
based on total weight of PSA-2 and EASTOFLEX D127S. The blends were
coated onto PET to the thickness shown in Table 7 as described in
Example 1 to form PSA tapes. The adhesive performance of these
tapes is shown in Table 8.
8 TABLE 7 Parts by Weight Parts by Weight Thickness Example PSA-2
EASTOFLEX D127S (.mu.m) 4A-C 100 0 41 4B-C 90 10 43 4C 75 25 46
4D-C 100 0 110 4E-C 90 10 120
[0098]
9TABLE 8 180.degree. Peel 180.degree. Peel Room Temperature
Adhesion to Glass Adhesion to PP Shear Strength Example (N/dm)
(N/dm) (minutes) 4A-C 41.8 43.1 596 4B-C 51.0 47.3 62 4C 118.6 92.6
15 4D-C 52.5 55.1 314 4E-C 164.1 96.3 58
Examples 5A-5C
[0099] In a BRABENDER batch mixer, 85 parts PSA-2, 15 parts
EASTOFLEX E1060, and 0.35 part (per 100 parts PSA-2) 2-tert-butyl
anthraquinone photocrosslinker were blended as described in Example
1 at a temperature of 165-170.degree. C. The blend was coated onto
PET at a thickness of 61 .mu.m as described in Example 1 to form
PSA tapes. The adhesive performance of these tapes, with or without
exposure to ultraviolet (UV)-radiation (using a "H-Bulb" UV source
from Fusion UV Curing; Rockville, Md.), is shown in Table 9.
10TABLE 9 Room UV- 180.degree. Peel 180.degree. Peel Temperature
radiation Adhesion to Adhesion to Shear Strength Example
(mJ/cm.sup.2) Glass (N/dm) PP (N/dm) (minutes) 5A 0 77.0 89.7 23 5B
200 74.4 73.1 136 5C 400 81.0 60.2 172
Examples 6A-6H
[0100] In a BRABENDER batch mixer, PSA-3A and EASTOFLEX D127S were
blended as described in Example 1 at a temperature of approximately
130.degree. C. according to the mix ratios shown in Table 10. The
parts are based on total weight of PSA-3A and EASTOFLEX D127S.
Additionally, 0.3 part by weight (per 100 parts of the PSA-3A and
EASTOFLEX D127S blend) 2-tert-butyl anthraquinone photocrosslinker
was added to the BRABENDER batch mixer and mixed with the blend.
The blends were coated onto PET to the thickness shown in Table 10
as described in Example 1 to form PSA tapes except that the die
temperature was maintained at 120.degree. C. The adhesive
performance of these tapes, with and without UV-radiation (using a
"H-Bulb" UV source from Fusion UV Curing; Rockville, Md.), is shown
in Table 11.
11TABLE 10 Parts by Weight Parts by Weight Thickness Example PSA-3A
EASTOFLEX D127S (.mu.m) 6A-C 100 0 51 6B-C 90 10 46 6C 75 25 48 6D
60 40 56 6E-C 100 0 150 6F-C 90 10 140 6G 75 25 120 6H 60 40
120
[0101]
12TABLE 11 Room UV- 180.degree. Peel 180.degree. Peel Temperature
radiation Adhesion to Adhesion to Shear Strength Example
(mJ/cm.sup.2) Glass (N/dm) PP (N/dm) (minutes) 6A-C 0 70.9 63.2 1
6B-C 0 67.8 62.4 1 6C 0 62.6 72.2 2 6D 0 56.5 72.2 3 6E-C 0 220.1
99.6 1 6F-C 0 249.9 223.6 1 6G 0 198.7 217.7 1 6H 0 155.6 195.8 2
6A-C 500 32.6 28.4 255 6B-C 500 30.4 35.9 254 6C 500 31.3 43.1 145
6D 500 37.6 69.1 34 6E-C 500 41.1 45.9 52 6F-C 500 44.0 52.3 107 6G
500 55.8 70.7 197 6H 500 63.2 123.8 27
Examples 7A-7F
[0102] In a BRABENDER batch mixer, PSA-4 and EASTOFLEX D127S were
blended as described in Example 1 at a temperature of 160.degree.
C. according to the mix ratios shown in Table 12. The parts are
based on total weight of PSA-4 and EASTOFLEX D127S. Additionally,
0.3 part by weight (per 100 parts of the PSA-4 and EASTOFLEX D127S
blend) 2-tert-butyl anthraquinone photocrosslinker was added to the
BRABENDER batch mixer and mixed with the blend. The blends were
coated onto PET to the thickness shown in Table 12 as described in
Example 1 to form PSA tapes. The adhesive performance of these
tapes, with and without UV-radiation, is shown in Table 13.
13TABLE 12 Parts by Weight Parts by Weight Thickness Example PSA-4
EASTOFLEX D127S (.mu.m) 7A-C 100 0 51 7B-C 90 10 48 7C 75 25 48
7D-C 100 0 120 7E-C 90 10 100 7F 75 25 120
[0103]
14TABLE 13 Room UV- 180.degree. Peel 180.degree. Peel Temperature
radiation Adhesion to Adhesion to Shear Strength Example
(mJ/cm.sup.2) Glass (N/dm) PP (N/dm) (minutes) 7A-C 0 * * 108 7B-C
0 * * 87 7C 0 * * 81 7D-C 0 * * 62 7E-C 0 * * 57 7F 0 * * 44 7A-C
500 42.2 5.3 10,000 7B-C 500 31.1 7.2 2,530 7C 500 29.5 37.0 225
7D-C 500 56.9 7.2 417 7E-C 500 26.7 28.2 915 7F 500 64.3 108.5 158
*Not tested
Examples 8A-8L
[0104] In a BRABENDER batch mixer, PSA-1 and mPP1 were blended as
described in Example 1 at a temperature of 165-170.degree. C.
according to the mix ratios shown in Table 14. The parts are based
on total weight of PSA-1 and mPP1. Additionally, in Examples 8B and
8C, 0.3 part by weight (per 100 parts of the PSA-1 and MPPI blend)
2-tert-butyl anthraquinone photocrosslinker was added to the
BRABENDER batch mixer and mixed with the blend. The blends were
coated onto PET to the thickness shown in Table 14 as described in
Example 1 to form PSA tapes. The adhesive performance of these
tapes is shown in Table 15.
15TABLE 14 Parts by Weight Parts by Weight Thickness Example PSA-1
mPP1 (.mu.m) 8A-C 100 0 51 8B-C 90 10 51 8C 75 25 51 8D 60 40 51 8E
30 70 51 8F-C 0 100 51 8G-C 100 0 130 8H-C 90 10 130 8I 75 25 130
8J 60 40 130 8K 30 70 130 8L-C 0 100 130
[0105]
16TABLE 15 180.degree. Peel 180.degree. Peel Room Temperature
Adhesion to Glass Adhesion to PP Shear Strength Example (N/dm)
(N/dm) (minutes) 8A-C 51.0 45.5 322 8B-C 64.3 55.8 87 8C 117.1 65.9
32 8D 106.8 63.5 16 8E 81.4 65.2 16 8F-C 33.9 69.1 18 8G-C 84.7
75.0 83 8H-C 82.1 69.8 114 8I 77.0 85.8 21 8J 191.2 92.8 13 8K
115.3 92.1 14 8L-C 39.4 96.3 14
Examples 9A-9B
[0106] The samples of examples 8B and 8C were exposed to UV
radiation using a "H-bulb" UV source from Fusion UV Curing;
Rockville, Md. The blend compositions are shown in Table 16. The
adhesive performance of these tapes, with and without exposure to
UV-radiation, is shown in Table 17.
17TABLE 16 Parts by Weight Parts by Weight Thickness Example PSA-1
mPP1 (.mu.m) 9A-C 90 10 51 9B 75 25 51
[0107]
18TABLE 17 Room UV- 180.degree. Peel 180.degree. Peel Temperature
radiation Adhesion to Adhesion to Shear Strength Example
(mJ/cm.sup.2) Glass (N/dm) PP (N/dm) (minutes) 9A-C 0 64.3 55.8 87
9A-C 200 39.8 36.5 10,000 9A-C 400 36.1 29.8 10,000 9B 0 117.1 65.9
31 9B 200 49.4 37.9 661 9B 400 43.5 32.4 10,000
Examples 10A-10G
[0108] In a BRABENDER batch mixer, PSA-3B and mPP2 were blended as
described in Example 1 at a temperature of 140.degree. C. according
to the mix ratios shown in Table 18. The parts are based on total
weight of PSA-3B and mPP2. The blends were coated onto PET to a
thickness of 90 .mu.m as described in Example 1 to form PSA tapes.
The adhesive performance of these tapes is shown in Table 19.
19 TABLE 18 Parts by Weight Parts by Weight Example PSA-3B mPP2
10A-C 100 0 10B-C 90 10 10C 85 15 10D 75 25 10E 60 40 10F 25 75
10G-C 0 100
[0109]
20TABLE 19 180.degree. Peel 180.degree. Peel Room Temperature
Adhesion to Glass Adhesion to PP Shear Strength* Example (N/dm)
(N/dm) (minutes) 10A-C 74.2 46.6 12 10B-C 101.2 52.3 16 10C 135.8
57.8 16 10D 172.4 62.6 19 10E 191.0 44.2 26 10F 25.6 44.2 183 10G-C
21.7 37.7 1,462 *A 2.54 cm .times. 2.54 cm (1.0 inch .times. 1.0
inch) strip was used for this test
Comparative Examples C1A-C1E
[0110] The formulations of Examples 23-26 and Comparative Example
C2 are described in PCT Publication No. WO 97/23,577, in which
PSA-3C, a conventional (meth)acrylate polymer, was blended with two
different commercial isotactic polypropylene compounds. The ratio
of components and type of commercial isotactic polypropylene
compound is shown in Table 20. The blend was described as being
coated onto PET at a thickness of 90 .mu.m. The described adhesive
performance of these tapes is shown in Table 21.
21TABLE 20 Parts by Parts by Weight Weight Example Additive PSA-3C
Additive C1A None 100 0 C1B FINA 3374X 90 10 C1C FINA 3374X 85 15
C1D ESCORENE 3860 90 10 C1E ESCORENE 3860 85 15
[0111]
22TABLE 21 Room Temperature 180.degree. Peel 180.degree. Peel Shear
Adhesion to Glass Adhesion to PP Strength* Example (N/dm) (N/dm)
(minutes) C1A 52 39 100 C1B 64 39 110 C1C 56 30 150 C1D 69 50 80
C1E 62 40 250 *A 2.54 cm .times. 2.54 cm (1.0 inch .times. 1.0
inch) strip was used for this test
Examples 11A-11C
[0112] Single-layer fibers and melt blown microfiber webs therefrom
were prepared using blends of PSA-1 and EASTOFLEX D127S using a
melt-blowing process and conditions as described in Example 20 of
U.S. Pat. No. 6,083,856, except that the pre-compounded blend was
made from compositions shown in Table 22. The resulting melt-blown
microfiber webs had a basis weight of 50 g/m.sup.2 and were
collected on silicone-coated kraft paper release liner (available
from Daubert Coated Products; Dixon; Ill.). Tapes were prepared by
laminating the webs on a PET backing by using 2 passes of a 2 kg
roller. The blend compositions and adhesive properties of the
melt-blown microfiber webs are presented in Table 22.
23TABLE 22 Parts by Parts by Weight 180.degree. Peel 180.degree.
Peel Weight EASTOFLEX Adhesion to Adhesion to PP Example PSA-1
D127S Glass (N/dm) (N/dm) 11A-C 100 0 18.4 14.0 11B-C 90 10 27.1 *
11C 70 30 36.8 34.2 * Not tested
Example 12
[0113] Triple-layer fibers and melt-blown microfiber webs therefrom
were prepared using a melt-blowing process and conditions as
described in Example 25 of U.S. Pat. No. 6,083,856, except that the
PSA-5 ("KRATON/ESCOREZ/ZONAREZ PSA") melt stream was replaced by
that of a pre-compounded blend of 70 parts by weight of PSA-1 and
30 parts by weight of EASTOFLEX D127S, which formed the outermost
layers of the exiting stream from the feedblock. Also, the gear
pumps were adjusted so that a 50/50 melt volume ratio of the (PSA-1
and EASTOFLEX D127S blend) and (PSA-1 and PSA-5 blend) was
delivered to the die. The resulting melt-blown microfiber web had a
basis weight of 50 g/m.sup.2 and was collected on silicone-coated
kraft paper release liner (available from Daubert Coated Products;
Dixon; Ill.). Tapes were prepared by laminating the web on the PET
backing by using 2 passes of a 2 kg roller. The adhesive properties
of the melt-blown microfiber web are shown in Table 23.
24 TABLE 23 180.degree. Peel Adhesion to Glass 180.degree. Peel
Adhesion to PP (N/dm) (N/dm) 24.7 24.1
[0114] Various modifications and alterations of the invention will
become apparent to those skilled in the art without departing from
the spirit and scope of the invention, which is defined by the
accompanying claims. It should be noted that steps recited in any
method claims below do not necessarily need to performed in the
order that they are recited. Those of ordinary skill in the art
will recognize variations in performing the steps from the order in
which they are recited.
* * * * *