Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSITE PRESSURE SENSTI?VE ADHESIVE MICROSPHERE
Field of the Invention
This invention relates to polymeric pressure sensitive adhesive microspheres
that are comprised of a mixture of two or more polymers within the discrete
boundaries of the polymeric microspheres.
Background of the Invention
Inherently tacky pressure sensitive adhesive microspheres are known in the
art to be useful in repositionable pressure sensitive adhesive applications
and there
are numerous references discussing preparation and/or use of inherently tacky,
elastomeric polymeric microspheres. Pressure sensitive adhesive microspheres
may
be solid or hollow and are generally crosslinked to an extent such that the
particulate nature of the adhesive is maintained throughout processing and
use.
Typically, pressure sensitive adhesive microspheres are prepared via
suspension
polymerization of one or more free radically polymerizable monomers in the
presence of surfactants and/or suspension stabilizers. Choice of surfactants
and/or
suspension stabilizers and their specific combinations with specific monomers
can
determine suspension stability, desired particle morphology, performance
characteristics, and the like.
One method that has been used to prepare materials with improved
properties is the synthesis of polymeric materials that are comprised of
mixtures of
two or more distinct polymers. For example, high impact polystyrene (HIPS) is
an
example of a material that is comprised of a mixture of two or more polymers
and
has improved or unique properties. HIPS is prepared by dissolving rubbers such
as
natural rubber or poly(butadiene) in styrene followed by free radical bulk,
suspension or solution polymerization. A composite material is obtained, which
has improved impact strength relative to virgin poly(styrene).
.. An illustrative example in the field of pressure sensitive adhesives is
described in EPO 352901 A wherein the addition of rubbers such as styrene-
butadiene block copolymers to poly{acrylate)-based pressure sensitive
adhesives
resulted in improved cold temperature performance. Another illustrative
example in
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the field of emulsion polymerization is described in U.S.
Patent No. 4,616,957 in which preformed polymers are
dissolved in monomers prior to polymerization.
Yet another example, is one described in U.S.
Patent No. 5,266,402, wherein a pressure sensitive adhesive
comprising an acrylate matrix and acryla.te microspheres,
wherein each microsphere has a discrete boundary and the
microspheres and the matrix form an interpenetrating network
within the boundary of the microspheres, wherein the matrix
extends beyond the boundaries of the microspheres.
Suiramary of the Invention
Briefly, in one aspect of the present invention, a
composite pressure sensitive adhesive microspheres is
provided comprising two or more water insoluble polymers
that are mixed within the boundaries of polymeric
microspheres. Furthermore, the present invention
advantageously provides unique pressure sensitive adhesive
microsphere compositions, as well as unique chemical and
physical properties that are derived from the mixtures of
polymers that reside wholly within the boundaries of the
polymeric microspheres.
According to one aspect of the present invention,
there is provided composite pressure sensitive adhesive
microspheres comprising two or more water insoluble polymers
that are present within boundaries of the microspheres
wherein the microspheres are prepared by suspension
polymerisation of solutions of at least one solute polymer
dissolved in at least one solvent monomer.
According to another aspect of the present
invention, there is provided a suspension polymerization
process of preparing composite pressure sensitive adhesive
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microspheres comprising the steps of: (a) preparing a
solute polymer; (b) dissolving the solute polymer in at
least one solvent monomer to provide a solute
polymer/solvent monomer mixture; (c) dissolving an initiator
in the solute polymer/solvent monomer mixture; (d) charging
a reaction vessel with water, a surfactant, optionally, a
stabilizer and the soI_ute polymer/solvent monomer mixture to
provide a reaction mixture; and (e) agitating the reaction
mixture to create an emulsion and heating the emulsion while
maintaining the agitation.
The range of monomers and polymers that can be
used in this invention can be chosen in order to tailor the
properties of the composite pressure sensitive adhesive
microspheres for specific performance and/or application
requirements. Additionally, the present invention provides
repositionable adhesives with improved adhesive properties,
such as cohesive strength, peel adhesion and static shear
that can be used in product applications such as removable
and repositionable labels, tapes and signs. Pressure
sensitive adhesive microspheres according to this invention
can be prepared using free radical suspension
polymerization.
As used is this application, a polymer that is
dissolved in a "solvent monomer" prior t:o carrying out
suspension polymerization is hereinafter: referred to as a
"solute polymer". A °'solvent monomer" is essentially water
insoluble and may be a mixture comprised of one or more
monomers and will dissolve the solute polymer. Furthermore,
a solvent monomer may further include one or more monomers
that may not dissolve a solute polymer, if such monomer was
the only monomer used. Further yet, a aolvent monomer may
include one or more monomers that need riot be essentially
water insoluble, provided a mixture of
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monomers are selected and the mixture is essentially water insoluble. A
"solvent
monomer" is polymerized to form a "matrix polymer".
The product of suspension polymerization is a mixture of one or more solute
polymers and one or more matrix polymers. Solvent monomers and solute
polymers used to make the pressure sensitive adhesive microspheres of this
invention can be freely selected from a wide range of polymers and monomers.
As
used in this application "monomer" may be used to include a mixture of
monomers
and "polymer" may be used to include a mixture of polymers, as well as
copolymers, terpolymers and the like.
A solute polymer useful in the practice of the present invention is a polymer
that can be dissolved in a solvent monomer. Advantageously, any polymer that
can
be dissolved into a solvent monomer or mixture of solvent monomers, as
described
below, can be used to prepare the composite microspheres of the present
invention.
Uniquely, the present invention provides composite microspheres, wherein the
solute polymer is prepared from (1) monomers that are water insoluble or water
nonreactive, (2) the combination of water soluble or water reactive and water
insoluble or water nonreactive monomers, with the proviso the solute polymer
is
essentially water insoluble (3) monomers that are not polymerizable via free
radical
polymerization. Furthermore, the present invention provides composite
microspheres, wherein the solute polymer and the matrix polymer are prepared
using the same monomer but the resultant polymers, solute and matrix
respectively,
have different molecular weights or cross-linking densities, such as, for
example a
composite microsphere comprised of a high molecular weight poly(isooctyl
acrylate) and a low molecular weight poly(isooctyl acrylate). Yet another
combination may provide a composite microsphere comprised of a high Tg,
polymer
and a low Tg polymer. Furthermore, a portion of the solute polymer may react
with
the matrix polymer. Additionally, the mixture of solute polymer and matrix
polymer
may include grafting or crosslinking between the several components.
Examples of such polymers include but are not limited to polymers prepared
. by polymerization methods that are incompatible with water such as certain
Ziegler
Natta polymerizations, anionic polymerizations, group transfer
polymerizations, ring
opening polymerizations, condensation polymerizations and step growth
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polymerization or the like. Further, the reaction products of essentially
water
soluble or water reactive monomers in combination with enough water insoluble
monomers to render the solute polymer water insoluble can be incorporated into
the
microsphere. Other such solute polymers which can be used include
poly(acrylates), poly(methacrylates), poly(styrene)s, elastomers such as
rubbers
(natural and/or synthetic) or styrene-butadiene block copolymers,
polyurethanes,
polyureas, polyesters, crystalline and non-crystalline polymers such as
crystalline
and non-crystalline poly-a.-olefins, mixtures thereof and the like. Solute
polymers
can have high molecular weight or low molecular weight or the composite
microsphere may be comprised of a mixture of polymers of varying molecular
weight.
The predominant solvent monomers) is essentially water insoluble and may
be comprised of one or more monomers. If a mixture of monomers is used, each
of
the components need not be essentially water insoluble. Monomers, which may be
water soluble or insoluble may also be used, provided that there is enough
solvent
monomers to dissolve the solute polymer.
Particularly useful solvent monomers include (meth)acryiates and vinyl
esters Other vinyl monomers, such as styrene, acrylonitrile, mixtures thereof
and
the like, as well as various combinations of such solvent monomers may be
used.
The combination of at least one solute polymer and at least one solvent
monomer is chosen such that the solute polymer can be dissolved in the solvent
monomer. The combination of solvent monomer and solute polymer results in an
inherently pressure sensitive adhesive composite polymeric microsphere. The
mixture of solute polymer and matrix polymer can have a wide range of
morphologies, which is dependent on the compatibility of the two or more
polymers
in the microsphere. Such morphologies include homogeneous mixtures of polymers
and phase-separated compositions in which the different polymers or mixtures
of
polymers exist in their own phases. The final morphology of the microspheres
may
be solid or hollow (contain one or more voids).
' Suspension polymerization of solutions of polymers dissolved in monomers
offers several distinct advantages over previously known pressure sensitive
adhesive
microspheres. One advantage of this invention is the incorporation of polymers
into
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pressure sensitive adhesive microspheres that either cannot be prepared by
free
radical polymerization or in the presence of water. Yet another advantage of
this
invention is the incorporation of water reactive moities that normally react
in the
water phase prior to carrying out suspension polymerization into pressure
sensitive
adhesive microspheres. A further advantage of this invention is the ability to
modify
the physical properties of the microsphere by the incorporation of a wide
variety of
solute polymers such as rubbers that can alter the viscoelastic/mechanical
properties
of microspheres.
Description of the Preferred Embodiments)
A pressure sensitive adhesive microspheres are provided comprising two or
more water insoluble polymers that are mixed within the boundaries of
polymeric
microspheres. Furthermore, the present invention provides pressure sensitive
adhesive microsphere compositions having chemical and physical properties that
are
derived from the mixtures of polymers that reside within the boundaries of the
polymeric microspheres. Composite pressure sensitive adhesive microspheres are
comprised of a mixture of one or more solute polymers and a matrix polymer,
wherein the matrix polymer is the reaction product of a solvent monomer.
Distinctly, the composite pressure sensitive adhesive microspheres are
comprised of
a solute component, comprising at least one solute polymer and a solvent
component, comprising a matrix polymer that is the polymerization product of
at
least one solvent monomer.
The range of monomers and polymers that can be used in this invention is
extensive and can be chosen to tailor properties of the pressure sensitive
adhesive
microspheres for specific performance and/or application requirements.
Additionally, the present invention can be tailored to provide repositionable
adhesives with improved adhesive properties such as cohesive strength, peel
adhesion and static shear and such adhesives can be used in product
applications,
such as removable and repositionable labels, tapes and signs.
.- Pressure sensitive adhesive microspheres according to this invention may be
prepared by the suspension polymerization of solutions of monomers and
essentially
water insoluble polymers. Specifically, a polymer ("solute component") is
dissolved
in at least one monomer ("solvent component"). This mixture is then emulsified
in
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an aqueous solution of surfactants and/or suspension stabilizers and
polymerized by
suspension polymerization.
Solute Component
A solute polymer, which is essentially water insoluble may be comprised of
any monomer or mixture of monomers that upon polymerization provides a polymer
that can be dissolved into a solvent monomer or a mixture of solvent monomers,
as
described below. Typically, solute polymers have a molecular weight (MW) of at
least 2000.
The solute component is comprised of various classes of polymers. Any
polymer may be used provided this solute polymer can be dissolved in a solvent
monomer. For example, the solute polymer may be branched, modified, prepared
using water reactive or water soluble monomers, monomers that are not free-
radically polymerizable and combinations thereof. Furthermore, the solute
polymers
may be prepared according to any polymerization method that may be known to
those skilled in the art and can be generally found in various references such
as
"Principles of Polymerization" Odian, 3rd ed., Wiley Interscience.
Nonlimiting examples of useful solute polymers include poly(acrylates),
poly(methacrylates), poly(styrene)s, elastomers such as rubbers (natural
and/or
synthetic) or styrene-butadiene block copolymers, polyurethanes, polyureas,
polyesters, crystalline and non-crystalline polymers such as crystalline and
non-crystalline poly-a-olefins, crystalline poly(methacrylate) and crystalline
poly(acrylate), and mixtures thereof and the like.
Advantageously, this invention provides composite pressure sensitive
adhesive microspheres that can incorporate moieties that normally react in the
water
phase when used in monomeric forms prior to suspension polymerization of such
monomers. Nonlimiting examples of solute polymers comprised of such water
reactive moieties include, but are not limited to polymers containing malefic
anhydride, itaconic anhydride, 2-vinyl-4,4-dimethyl-2-oxazoline-5-one (VDM)
and
2-(isocyanato)ethyl methacrylate.
'. Further, highly water soluble moieties, such as {meth)acrylic acid, N-vinyl
pyrrolidone, polyethylene) oxide macromonomer, (meth)acrylimide, 1,1-dimethyl-
1(2-hydroxylpropyt)amine methacrylimide, 1,1,1-trimethylamine methacrylimide,
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1,1-dimethyl-1(2,3-dihydroxypropyl)amine methacryIimide, and other water
soluble
moieties, such as, N,N-dimethyl-N-(~3-methacryloxyethyl)ammonium propionate
betaine, 4,4,9-trimethyl-4-azonia-7-oxo-8-oxa-dec-9-ene-1 sulfonate, sodium
(meth)acrylate, ammonium acrylate, and malefic anhydride, for example can also
be
incorporated into the solute polymer used in the preparation of the composite
pressure sensitive adhesive microspheres, provided that the solute polymer is
essentially water insoluble.
Alternatively, incorporation of polymers into composite pressure sensitive
adhesive microspheres that typically cannot be prepared by free radical
polymerization or in the presence of water is provided by the present
invention.
Also, copolymers of water soluble and water insoluble monomers can be used as
solute polymers. Such solute polymers would include, for example,
poly(styrene),
poly(t-butyl)styrene, poly-a-olefins, such as poly(propylene), poly(ethylene),
poly(hexene), poly(octadecene) and/or poly(octene), styrene-butadiene block
copolymers and the like (such as Kratons), polyesters, polyureas, and various
copolymers of water soluble and insoluble monomers, such as styrene/acrylic
acid,
(t-butyl)styrene/acrylic acid, (meth)acrylate/poly(styrene)
macromonomer/acrylic
acid, (meth)acrylate/acrylic acid, (meth)acrylate/N-vinyl pyrrolidone,
(meth)acrylate/poly(ethylene) oxide macromonomer, mixtures thereof, and the
like.
Examples of suitable crystalline polymeric materials having crystallizable
main chain or backbone segments include, but are not limited to, polyesters,
polytetrahydrofuran, lower polyolefins (e.g., C2-C3 olefins), higher
polyolefins (for
example, C 14-C20 olefins) and polyurethanes containing crystalline polyester
segments. Also preferred are side chain crystalline polymeric materials
derived from
higher (a-olefin monomers, such as poly( 1-decene), poly( 1-dodecene),
poly(1-tetradecene) and poly{1-hexadecene), and higher vinyl esters, such as
vinyl
tetradecanoate, vinyl hexadecanoate, and vinyl octadecanoate.
Examples of suitable crystalline polymeric materials having crystallizable
pendant moieties (i.e., side chains) include, but are not limited to,
poly(acrylate),
poly(methacrylate), poly(acrylamide), poly(methacrylamide), polyvinyl ester}
and
poly(a-olefin) polymers and copolymers having the following formula:
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--~CH2-CH~
-(CH2)n CH3
wherein X is -CH2-, -C(O)O- -O-C(O)-, and -C(O)-NH-, etc., and n is large
enough to provide sufficient side chain length and conformation to form
polymers
containing crystalline domains or regions at room temperature. Suitable
crystalline
polymeric materials include but are not limited to poly(dodecyl acrylate),
poly(isotridecyl acrylate), poly(n-tetradecyl acrylate), poly(n-hexadecyl
acrylate),
poly(n-hexadecyl methacrylate), poly(n-octadecyl acrylate),
poly(methacrylate),
poly(acrylate), poly(behenyl acrylate), poly(eicosamyl acrylate), and mixtures
thereof. Of these, pofy(n-octadecyl acrylate), poly(behenyl acrylate), and
mixtures
or copolymers thereof are preferred.
Solvent MonomerlMatrix Polymer
The second component of the composite microspheres are matrix polymers,
a polymerization product of solvent monomers. The predominant solvent
monomers) is essentially water insoluble and may be comprised of one or more
monomers.
Useful alkyl (meth)acrylate monomers are monofunctional unsaturated
(meth)acrylate esters, the alkyl groups of which have from 4 to 14 carbons
atoms.
Such (meth)acrylates are oleophilic, water dispersible, and are essentially
water
insoluble. Furthermore, useful (meth)acrylates are those that as homopolymers,
generally have a glass transition temperature below about -10°C, or if
a combination
of monomers is used, such a combination would produce a copolymer or
terpolymer generally having a glass transition temperature below about -
10°C.
Nonlimiting examples of such (meth)acrylates include but are not limited to,
isooctyl acrylate, 4-methyl-2-pentyl acrylate, 2-methylbutyl acrylate, isoamyl
acrylate, sec-butyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate,
isodecyl
methacrylate, t-butyl acrylate, t-butyl methacrylate, isobornyl acrylate,
methylmethacrylate, isononyl acrylate, isodecyl acrylate and the like, and the
-- combination thereof.
Preferred alkyl (meth)acrylate monomers include isooctyl acrylate, isononyl
acrylate, isoamyl acrylate, isodecyl acrylate, 2-ethylhexyl acrylate, t-butyl
acrylate,
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isobornyl acrylate, butyl methacrylate, n-butyl acrylate, sec-butyl acrylate
and
mixtures thereof. Various combinations of these monomers can be used.
Vinyl ester monomers suitable for use in the present invention include but
are not limited to: vinyl 2-ethylhexanoate, vinyl laurate, vinyl pelargonate,
vinyl
hexanoate, vinyl propionate, vinyl decanoate, vinyl octanoate, and other
monofunctional unsaturated vinyl esters of linear or branched carboxylic acids
comprising 1 to 14 carbon atoms, which as homopolymers have glass transition
temperatures below about -10°C. Preferred vinyl ester monomers include
vinyl
laurate, vinyl 2-ethylhexanoate, and mixtures thereof.
Additional other vinyl monomers which, as homopolymers, have glass
transition temperatures higher than about -10°C, such as vinyl acetate,
acrylonitrile,
styrene, mixtures thereof and the like, may optionally be utilized in
conjunction with
one or more of the acrylate, methacryiate and vinyl ester monomers provided
the
glass transition temperature of the resultant polymer is below about -
10°C.
Preparation of Adhesive Microspheres
For composite microspheres or composite microparticles, suspension free
radical polymerization methods, such as those described in U.S. Patent Nos.
3,691,140; 4,166, i52; 4,786,696; 5,045,569 and 5,508,313, and PCT Patent
Appl.
No.WO 96/01280 can be used with modification.
One such process of preparing composite pressure sensitive adhesive
microspheres could comprise the steps of:
(a) preparing a solute polymer;
(b) dissolving the solute polymer in at least one solvent monomer to
provide a solute polymer/solvent monomer mixture;
(c) dissolving an initiator in the solute/polymer/solvent monomer
mixture;
(d) charging a reaction vessel with water, a surfactant, optionally, a
stabilizer and the solute polymer/solvent monomer mixture to provide a
reaction
mixture; and
(e) agitating the reaction mixture to create an emulsion and heating the
emulsion while maintaining the agitation.
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For the composite microspheres, suspension polymerizations are typically
performed in the presence of a variety of emulsifiers, surfactants,
stabilizers and/or
under particular process conditions which induce the formation of, and prevent
the
agglomeration of, the particles (e.g., microspheres having a diameter of about
1-300
micrometers). The composite microspheres can be solid, hollow or a combination
thereof. As used in the present application: ( 1 ) "hollow" means containing
at least
one void or cavity, wherein "cavity " means a space within the walls of a
droplet or
microsphere when still in the suspension or dispersion medium prior to drying,
and
thus containing whatever medium was used; "void" means a space completely
within the walls of a polymerized microsphere; and "droplet" means the liquid
stage
of the microspheres prior to the completion of polymerization; and (2) "solid"
means not hollow, that is, essentially void-free or cavity-free.
Adaptation of these processes to prepare composite microspheres of the
present invention include dissolving a solute polymer into a solvent monomer
mixture at a temperature such that the solute polymer component dissolves
followed by the formation of an emuision and subsequent polymerization of the
monomer droplets.
Once polymerization takes place, the solvent monomers are converted to a
matrix polymer, wherein the matrix polymer and the solute polymer (originally
dissolved in the solvent monomer) are present within the boundary of the
microspheres. Due to reactive moieties that may be present in either one of
the
polymers, graft sites between the polymers may be observed. Further, the
matrix
polymer may be crosslinked and a variety of methods are available to
facilitate
crosslinking such as, ionizing radiation, peroxides, silanes, metal ions, or
multifunctional crosslinking agents. Preferably, multifunctional crosslinking
agents
are used, particularly for the preferred acrylate (co)polymers. Suitable
multifunctional crosslinking agents include, but are not limited to,
multifunctional
acrylates, for example, 1,6-hexanedioldi(meth)acrylate and 1,4-
butanedioldi(meth)acrylate, polymeric multifunctional (meth)acrylates, e.g.,
~ poly(ethylene oxide) diacrylate or polyethylene) oxide dimethacrylate;
polyvinylic
crosslinking agents, such as substituted and unsubstituted divinylbenzene; and
difunctional urethane acrylates. These multifunctional crosslinking agents can
be
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used in a variety of combinations. Preferred multifunctional crosslinking
agents are
those selected from the group consisting of acrylic or methacrylic esters of
diols
such as butanediol, triols such as glycerol, tetrols such as pentaerythritol,
and
mixtures thereof. When such multifiznctional crosslinking agents are used, one
or
more are used in an amount up to about 0.1 S equivalent weight percent,
preferably
up to about 0.1 equivalent weight percent, of the total polymerizable
composition.
The "equivalent weight %" of a given compound is defined as the number of
equivalents of that compound divided by the total number of equivalents in the
total
composition times 100, wherein an equivalent is the number of grams divided by
the
equivalent weight. The equivalent weight is defined as the molecular weight
divided by the number of polymerizable groups in the monomer (in the case of
those
monomers with only one polymerizable group, equivalent weight = molecular
weight).
Surfactants will typically be present in the reaction mixture, preferably in
an
amount of no greater than about 10 parts by weight per 100 parts by weight of
polymerizable monomer, more preferably no greater than about 5 parts by
weight,
and most preferably in the range of 0.5 to 3 parts by weight per 100 parts by
weight
of polymerizable monomer.
Useful surfactants (also known as emulsifiers) include anionic, cationic, or
nonionic surfactants and include but are not limited to anionic surfactants,
such as
alkylarylether sulfates and sulfonates such as sodium alkylarylether sulfate,
e.g.,
TritonTM X200, available from Rohm and Haas, alkylarylpolyether sulfates and
sulfonates such as alkylarylpoly(ethylene oxide) sulfates and sulfonates,
preferably
those having up to about 4 ethyleneoxy repeat units, and alkyl sulfates and
sulfonates such as sodium lauryl sulfate, ammonium lauryl sulfate,
triethanolamine
lauryl sulfate, and sodium hexadecyl sulfate, alkyl ether sulfates and
sulfonates such
as ammonium lauryl ether sulfate, and alkylpolyether sulfate and sulfonates
such as
alkyl polyethylene oxide) sulfates and sulfonates, preferably those having up
to
about 4 ethyleneoxy units. Alkyl sulfates, alkyl ether sulfates, and
alkylarylether
~ sulfates are preferred. Additional anionic surfactants can include, for
example,
alkylaryl sulfates and sulfonates, for example sodium dodecyIbenzene sulfate
and
sodium dodecylbenzene sulfonate, sodium and ammonium salts of alkyl sulfates,
for
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example sodium lauryl sulfate, and ammonium lauryl sulfate; nonionic
surfactants,
such as ethoxylated oleoyl alcohol and polyoxyethylene octylphenyl ether; and
cationic surfactants, such as a mixture of alkyl dimethylbenzyl ammonium
chlorides
wherein the alkyl chain contains from 10 to 18 carbon atoms. Amphoteric
surfactants are also useful in the present invention and include for example
sulfobetaines, N-alkylaminopropionic acids, and N-alkylbetaines.
Optionally, a polymeric stabilizer may be used and if used is present in an
amount of up to about 0.05 and about 3 parts by weight per 100 parts by weight
of
the microspheres, preferably about 0.1 to about 1.5 parts by weight per 100
parts by
weight of the microspheres. Advantageously, the presence of the stabilizer
permits
the use of relatively low amounts of surfactant while still obtaining
microspheres.
Any polymeric stabilizer that effectively provides sufficient stabilization of
the final polymerized droplets and prevents agglomeration within a suspension
polymerization process is useful in the present invention.
1 S Exemplary polymeric stabilizers include salts of polyacrylic acids of
greater
than 5000 weight average molecular weight (for example, ammonium, sodium,
lithium and potassium salts), poly vinyl alcohol, carboxy modified
polyacryiamides
(for example, Cyanamer'"A-370 from American Cyanamid), copolymers of acrylic
acid and dimethylaminoethylmethacrylate and the like, polymeric quaternary
amines
(for example, General Analine and Film's Gafquat'" 755, a quaternized
polyvinyl-
pyrrolidone copolymer, or Union Carbide's "JR-400", a quaternized amine
substituted cellulosic), cellulosics, and carboxy-modified cellulosics (for
example,
Hercules' Natrosof" CMC Type 7L, sodium carboxy methycellulose).
Initiators affecting polymerization are those that are normally suitable for
free-radical polymerization of acrylate monomers. Examples of such initiators
include thermally-activated initiators such as azo compounds, hydroperoxides,
peroxides and the like and photoinitiators such as benzophenone, benzoin ethyl
ether and 2,2-dimethoxy-2-phenyl acetophenone. Other suitable initiators
include
lauroyl peroxide and bis(t-butyl cyclohexyl)peroxy dicarbonate. The initiator
is
~ present in a catalytically effective amount sufficient to bring about high
monomer
conversion in a predetermined time span and temperature range. Typically, the
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initiator is present in amounts ranging from 0.05 to approximately 2 parts per
weight per 100 parts by weight of the microsphere composition starting
materials.
.Preparation of Pressure Sensitive Adhesives
The combination of at least one solute polymer .and at least one solvent
monomer is chosen such that the solute polymer ca.n be dissolved in the
solvent
monomer. Further, the combination of solvent monomt:r and solute polymer
results
in a solute polymer/matrix polymer composite polymeric microsphere that is
inherently pressure sensitive adhesive. The mixture of solute polymer and
matrix
polymer can have a wide range of morphologies, which is dependent on the
compatibility of the two or more polymers in the micro.~phere. Such
morphologies
include homogeneous mixtures of polymers and phase-separated compositions in
which the different polymers or mixtures of polymers e~;ist in their own
phases:
When crystalline solute polymers are used, a preferred morphology is one
wherein a
crystalline solute polymer is dispersed in a matrix polymer.
Optionally, adjuvants, such as, rheology modifiers, colorants, fillers,
stabilizers, tackifiers, plasticizers, latex hinders and various other
polymeric
additives can be utilized. If such adjuvants are used, the: amounts used in
the
adhesive mixture are amounts effective for the known uses of such adjuvants.
Adhesive Articles
Backings used as substrates for adhesive articles may be materials that are
conventionally used as a tape backing or may be of other flexible material.
Sucta
backings include, but are not limited to, those made from materials selected
fronn
the group consisting of poly(propylene), poly(ethylene), polyvinyl chloride),
polyester (e.g., poly(ethylene terephthalate), such as those available under
the trade
TM
designation of "Scotch" film 8050 from 3M)), polyamid~e films such as that
available
TM
from DuPont Co., Wilmington, DE, under the trade designation "KAPTON,"
cellulose acetate, and ethyl cellulose. Backings may also be of woven fabric
funned
from threads of synthetic or natural materials such as cotton, nylon, rayon,
glass, or
ceramic material, or they may be of nonwoven fabric su<;h as air laid webs of
natural
or synthetic fibers or blends of these. In addition, the backing may be formed
of
materials selected from the group consisting of metal, metallized polymeric
film, and
ceramic sheet material.
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Preferred such materials include, but are not limited to, plastics such as
polyethylene, polypropylene, polyesters, cellulose acetate, polyvinyl
chloride), and
poly(vinylidine fluoride), as well as paper or other substrates coated or
laminated
with such plastics. These coated papers or thermoplastic films are often
siliconized
or otherwise treated to impart improved release characteristics. One or both
sides
of the backings or liners could have such release characteristics. Generally
the
backing or substrate material is about 50 um to about 155 um in thickness,
although thicker and thinner backing or substrate materials are not precluded.
Typical coating methods that can be used to prepare adhesive articles
according to the present invention, include both solvent coating and water-
based
coatings and techniques commonly known to those skilled in the art.
Particularly useful articles prepared using the pressure sensitive adhesive
microspheres of the present invention include repositionable adhesive products
such
as repositionabie note and paper products, repositionable tape and tape flags,
easel
sheets, repositionable glue sticks and the like, but may also include other
non-repositionable industrial, commercial, and medical adhesive products.
Objects and advantages of this invention are further illustrated by the
following examples. The particular materials and amounts thereof recited in
these
examples as well as other conditions and details, should not be construed to
unduly
limit this invention. All materials are commercially available except where
stated or
otherwise made apparent. All parts and percentages used herein are by weight,
unless otherwise specified.
Examples
Test Methods
Adhesive Transfer
Adhesive transfer is defined as the amount of adhesive that transfers to an
applied substrate when the adhesive coated sheet is peeled or removed from the
__ substrate. The test is conducted by adhering a three-quarter inch (1.9 cm)
wide
strip of adhesive coated sheet to a clean area of a clay coated paper
commercially
available as KromekoteTM using a TLMI release and adhesion tester. The
adhesive
is allowed to remain in contact with the KromekoteTM for 30 seconds and then
is
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WO 97/46634 _ 15 _ PCT/US97/07587
removed at a 90° angle at a constant rate of 90 inches/minute. The clay
coated strip
is then analyzed by an image processor through a video camera and the percent
adhesive coverage of the viewed area is recorded. Ten fields of view are
analyzed
and then averaged for each test sample. The test is repeated and results are
reported as averages.
Peel Adhesion
Peel adhesion is~the force required to remove an adhesive coated flexible
sheet material from a test panel measured at a specific angle and rate of
removal. In
the examples, this force is expressed in grams per width of adhesive coated
sheet.
Adhesion to Polyester
Adhesion to polyester film is measured by application of a 1.25 inches (3.2
cm) wide strip of polyester film to the surface of an adhesive coated sample
which is
fixed on a horizontal test plate. A 4.5 lb {2 kg) hard rubber roller is used
to apply
the strip. The free end of the polyester film is attached to an adhesion
tester load
cell such that the angle of removal will be 90° relative to the
horizontal test plate.
The polyester strip is peeled from the adhesive at a constant rate of 12
inches (31
cm) per minute. A load cell reading in grams per 1.25 inches (3.2 cm) is
recorded.
The test is repeated and the data is reported as the average of the number of
trials.
Adhesion to Bond Paper
Peel adhesion is the force required to remove a coated sheet from a bond
paper substrate at a specific angle and rate of removal. In the examples this
force is
expressed in grams per one inch width of coated sheet. The procedure followed
is:
A strip, one inch wide, of coated sheet is applied to the horizontal surface
of
20 pound bond paper. A 4.5 lb. hard rubber roller is used to firmly apply the
strip
to the bond paper. The free end of the coated sheet is attached to the
adhesion
tester load cell such that the angle of removal will be 90°. The test
plate is then
clamped in the jaws of the tensile testing machine which is capable of moving
the
plate away from the load cell at a constant rate of 12 inches per minute. A
load cell
w reading in grams per inch of coated sheet is recorded. The test was repeated
and
the data is reported as the average of the number of trials.
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Static Shear Test
The static shear test measures the time in minutes required to pull a standard
area of adhesive coated sheet material from a flat test panel under stress of
a
constant, standard load in which the stress is in a direction parallel to the
surface of
the test panel. Stainless steel test panels are used in the examples.
The test is conducted on strips of adhesive coated sheet material which are
applied to a test panel with a 4.5 pound (2 kg) hard rubber roller such that a
either a
1.0 inch by 1.5 inch (2.54 x 3.81 cm) or a 1.0 inch by 1.0 inch (2.54 x 2.54
cm)
portion of each strip is in contact with the panel. The panel with the coated
strip
attached is held in a rack in a near vertical position such that the panel
forms an
angle of 92° relative to horizontal. The 2° offset from the
vertical position is used
to negate any peel forces, thus insuring that only shear forces are measured.
A 1 kg
weight is attached to the free end of the adhesive coated strip and the time
elapsed
for the coated strip to separate from the test panel is recorded in minutes.
The test
is repeated and the data is reported as the average of the number of trials.
Solvent Soluble Portion
To determine the solvent soluble content of the prepared microspheres, the
following process is used.
One gram of the water suspension of microspheres is dried in a vacuum
oven without heat. After drying, I OOmI of n-heptane is added and shaken for
24
hours. After shaking, the dispersion is poured through a filter paper (30
micrometer
pores) to remove the non-soluble content. The filtrate is then dried in a
100°F oven.
The weight of the dried filtrate divided by the dried suspension microspheres
is the % solvent soluble polymer content. The test is repeated and the data is
reported as the average of the number of trials.
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Glossary
IOA isooctyl acrylate
AA acrylic acid
ODA octadecyl acrylate
1,4-BDA 1,4-butanediol diacrylate
my mean volume
sd standard deviation
pm micrometers
VDM 2-vinyl-4,4,-dimethyl-2-oxazoline-5-one
NVP N-vinyl pyrrolidone
PEO-750 An acrylate terminated polyethylene
oxide)
macromonomer of molecular weight
of 750
mg milligram
"repositionable"refers to the ability to be repeatedly
adhered to
and removed from a substrate without
substantial
loss of adhesion capability
Mw weight average molecular weight
AIBN 2,2'-azobis(2-methylpropionitrile)
Examples 1-7
Preparation oJthe 80/20IOAl.4A Solute Copolymers used in F_xamples 1-7
A 36 grams portion of IOA, 9 grams of AA, 180 grams of 2-butanone and 1
ml of a solution of 0.585 grams AIBN dissolved in 10 ml of 2-butanone were
added
to three 500 ml amber bottles. The solutions were purged with nitrogen for
five to
ten minutes and the bottles were sealed with caps. The bottles were placed in
an
Atlas Launder-o-meterTM water bath, heated to 65°C and shaken
overnight. The
bottle was then cooled and the solution evaporated to dryness in a Teflon-
lined pan,
first at room temperature, and then in a forced air oven at 55°C to
ai~ord a
transparent, slightly yellow 80/20 IOA/AA copolymer.
The polymer was characterized by gel permeation chromatography and
found to have a Mw of 61,000. This polymer was used in Examples I-4. A similar
,_ IOA/AA copolymer with a Mw of 86,000 was prepared by repeating the
polymerization at slightly higher solids (33%) and with a lower amount of AIBN
(0.066% of monomer). This polymer was used in Examples 5 and 6.
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Example 1
This example describes the preparation of a composite MSA containung
25% of an 80/20 IOAIAA solute copolymer and 75% of a poiy(IOA) matrix
copolymer. A 2 L split reaction flask equipped with a mechanical stirrer,
temperature controller, heat lamps, nitrogen inlet and b~aflle was loaded with
600
TM
grams ofDI water and 4 grams of Siponate DS-i0 (tradename for sodium
dodecylbenzenesulfonate commercially available from ~4lcolac, inc) , heated to
65°C and purged with flowing nitrogen. In a separate container, 0.929
grams of
TM
Lucidol 70 (tradename for 70% active benzoyl peroxide available from Pennw~~lt
I O Corporation) and 50 grams of the 80120 IOA/AA solute copolymer were
dissolved
in 150 grams of iOA. Upon equilibration of the aqueous solution to
65°C, the stir
rate was set to 450 rpm and the IOAlcopolymerlbenzo~yl peroxide solution was
added. The solution was purged with flowing nitrogen for an additional 5
minutes,
sealed from the atmosphere via the use of a bubbler and allowed to react at
65°C
for 8 hours. A reaction exotherm was observed, having a temperature peak of
b8°C, after 24 min after the addition of the monomer solution. After
the 8 hours
time period, the solution was cooled to room temperature and fillBred through
cheese cloth. Microscopy indicated the presence of solid microspheres.
Particle
size analysis indicated a mean volume diameter of 68 microns. The solvent
soluble
portion of the microspheres was determined to be 38°~0.
Examples 2-C?
Examples 2-C7 were prepared according to the procedure described ira
Example 1 except that the amount of the 80/20 IOAIAA solute copolymer was
varied in order to make composite pressure sensitive adhesive microspher~es
compositions containing 15, 5, 3, 1.5, 0.5 and 0% of the 80/20 IOA/AA
copolymer.
Results for particle size and % solvent soluble portion are summarized in
Table 1.
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Table 1
Examples 1-C7:
Composite microspheres prepared with varying amounts of an 80/20 IOAlfIA
copolymer A.
Example Lucido170 IOA 80/20 80/20 Particle
(g) (g) IOA/AA IOA/AA Size Solvent
CopolymerCopolymer (pm) Soluble
(g) (%) Portion
1 0.929 150 50 25 68 38
2 0.831 170 30 15 40 38
3 0.929 190 10 5 34 23
4 0.978 194 6 3 34 25
0.978 197 3 1.5 34 22
6 0.978 199 1 0.5 42 22
C7 0.978 200 0 0 58 28
5
Coatingladhesive performance of adhesives prepared in Examples 1-C7
(A) Solvent Based Coatings
The adhesives described in Examples 1-C7 were evaluated for adhesive
performance. Each pressure sensitive adhesive microspheres was isolated from
water via the addition of isopropylalcohol to the suspension which resulted in
massive coagulation. The coagulated polymer was dried to approximately 80%
solids and dispersed in enough heptane to obtain an 8% solids dispersion.
Samples
were shaken overnight and then mixed with a mechanical stirrer for several
minutes
in order to ensure uniform dispersion of the microspheres. The heptane
dispersions
were coated onto primed paper using a 4 mil (0.1 mm) gap between the paper and
the coater knife. The coatings were tested for adhesion to polyester (g/1.25"
or
g/3.175cm), adhesion to bond paper (g/inch or g/2.54 cm), adhesive transfer
and
static shear to stainless steel (1.5" x 1.0" x 1 kg or 3.81 x 3.81 cm x 1 kg).
Results
are summarized in Table 2.
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Table 2
Adhesive properties jor Examples 1-C7 coated onto primed paper.
Example 80/20 Adhesicur Adhesion % Static Shear
to to
IOAIAA Polyester Bond PaperAdhesive (min)
Copolymer(gI1.25") (g/1'~ Transfer 1.5" x 1.0"
x 1 kg
(%)
1 25 2 2 0.01 0
2 15 33 12 0.5 2150
3 5 81 30
4 3 98 33 2.7 10,000+
1.5 104 42 1.2 10,000+
6 0.5 77 52 4.0 230
C7 0 88 54 13.1 144
The data in Table 1 illustrate improvements in adhesive properties that were
S obtained using the methods described in this invention. For example, static
shear
performance was greatly increased from 144 min to gr~.,ater than 10,000
minutes by
adding a small amount (1.5 or 3.0%) of 80!20 IOA/AA copolymer while adhesion
to polyester and bond remain good. Such a high shear strength, removable
adhesive
has uses in many applications such as removable labels, signs and tapes. The
adhesion data to polyester and bond paper illustrated the ability to control
adhesion
to different surfaces. For example, at low ioadings of IOA/AA copolymer,
adhesion
to polyester increased whereas adhesion to bond paper decreased. Such
"differential adhesion" is desirable for applications in which low adhesion to
delicate
substrates and higher adhesions to more durable substrates are desired.
Percent adhesive transfer was found to decrease significantly when sohate
copolymer is added to the microsphere. Only a small amount of solute copolymer
is
needed to improve adhesive transfer greatly. This is an advantage as clean
removability from substrates is improved.
(B) Waterbased Coatings
Examples 1-C7 were coated out of water in ors3er to demonstrate that
similar improvements in performance can be seen when compared to solvent based
coatings. Each adhesive was allowed to separate upon standing into a
microsphere-
rich and microsphere-poor phase. A portion of the microsphere-rich phase was
diluted to 50% solids via the addition of deioni~ed water, dispersed via
agitation
TM
and coated through a 1 mil gap onto a 3M polyester film product "Scotch 8030".
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The coated samples were tested for adhesive performance; results are
summarized
in Table 3.
Table 3
Example% AdhesionAdhesion% Static ShearStatic Shear
80/20 to to Adhesive(min) (min)
IOA/AA PolyesterBond Transfer1.0" x 1.0" 1.5" x 1.0"
Co 1 (g/1.25")Paper x 1 kg x 1 kg
er (g/inch)
1 25 55 27 0.4 40 160
2 15 84 24 1.1 70* 490
3 5.0 231 90 1.0 4660 17,000+*
4 3.0 276 107 0.2 5630 17,000+*
1.5 247 111 0.2 10110 17,000+
6 0.5 261 149 4.4 240 17,000+
C7 0 239 178 16.3 210 1060
Data in Table 3 are reported as averages of two or three replicates unless
5 the value is noted with a "*", in which case only one replicate was carried
out.
Example 8
This example describes the preparation of microspheres containing 20% of
an 80/20 IOA/NVP solute copolymer (MW = 133,000) and 80% of a poly(IOA)
matrix polymer. The IOAINVP copolymer was first prepared by solution
polymerization in a similar manner to that used for the preparation of the
IOA/AA
copolymer used in Examples 1 to 4.
A 2L split reaction flask was loaded with 325 grams of deionized water,
8.75 grams of TritonTM X-200 (tradename for a 30% solids dispersion of alkyl
aryl
polyethylene oxide sodium sulfonate commercially available from Rohm and Haas
Company) and 7.0 grams of GoodriteTM K-702 (tradename for a 25% solids
aqueous solution of polyacrylic acid, 240,000 weight average molecular weight,
commercially available from B.F. Goodrich Company) The solution was stirred at
450 rpm, neutralized to pH 7 with concentrated ammonium hydroxide, and heated
to 65~C under a nitrogen purge. In a separate container, 655 mg of LucidolTM
70
was dissolved in 58 grams of IOA; 117 grams of a 30 % solution of a 80/20
IOA/1'1VP copolymer dissolved in IOA was then added. The resulting solution
was
._ mixed for 10 minutes and then added to the heated aqueous solution. The
solution
was purged with nitrogen and allowed to react at 65°C for 45 min and
then at 80°C
for 2 hours. The solution was cooled and filtered through cheese cloth.
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-22-
No coagulum was observed. Microscopy indicated the presence of solid,
microspheres. Particle size analysis indicated a mean volume diameter of 69
um.
Elemental analysis of the adhesive indicated a nitrogen content of 0.51%,
which is
nearly identical to the theoretical amount of 0.50%.
Example 9
This example describes the preparation of microspheres containing 10% of
an IOA/PEO-750 solute copolymer and 90% of a poly(IOA) matrix polymer. PEO-
750 is an acrylate terminated polyethylene oxide) macromonomer having an
average molecular weight of 750. An IOAlPEO-750 copolymer was first prepared
TM
by adding 14 grams of IOA, 6 grams of PEO-750, 0.06 grams of Vazo 64
(tradename for 2,2'-azobis(2-methylpropanenitrile), commercially available
from
DuPont Co.), 0.3% of CBr~ and 58 grams of ethyl acetate into a bottle. The
solution was degassed with nitrogen, the bottle capped and placed in a
Launder-o-meterT~ for 22 hours at 60°C. Following the reaction, the
ethyl acetate
was removed from the bottle via evaporation.
Polymeric microspheres were prepared by loading a one liter split, baffled
reactor with 6 grams of StandapolTM A (tradename for a 29% solids ammoniurn
lauryl sulfate solution commercially available from Henkel Corp.) and 450
grams of
deionized water. In a separate container, 4.5 grams of AA., I 5 grams of the
70/30
TM
IOA/PEO-750 copolymer, 710 mg of Lucidol-75 (tradename for 7~% active
benzoyl peroxide available from Pennwalt Corporation) were dissolved in 133.5
grams of IOA. The IOA mixture was then added to the reactor and the resultant
emulsion homogenized until the average monomer. droplet size was approximately
1
W micrometer in diameter. The solution was stirred at 400 rprn, heated to
55°C,
degassed with argon and allowed to react for 22 hours.. Following the
reaction,
there was little coagulum in the reactor. Analysis by microscopy indicated the
presence of microspheres 2 to 10 micrometers in diamE;ter.
Example 10
This example describes the preparation of microspheres containing
25°~0 of a
75/25 IOAlPEO-750 solute copolymer and ?5% of a poly(IOA) matrix polymer.
First, a 75/25 IOAlPEO-750 copolymer was prepared 1'~y combining 264 gram s of
IOA, 88 grams of PEO-?50, 720 grams of 2-butanone and 0.35 grams of AIBN in a
. , .. rt..,,~... ....w. ._ . .. ........ ...-".~ ~...,~~,~~~ . ~:~,x....~~
~.~ .,.~ .~.... ..,~.~~..~~...~.w~.,p~.. ..~...q...~..___._ __. _. _ _._
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- 23 -
large beaker. The solution was stirred until the initiator was dissolved,
divided
among four 16 oz narrow-mouth amber bottles and purged with nitrogen. Each
bottle was immediately capped then placed in a Launder-o-meterTM at
65°C and
allowed to react overnight. The polymer was isolated by removal of the solvent
via
evaporation.
Polymeric microspheres were prepared by dissolving the 75I2~ IOA/7PE0-
750 copolymer in IOA at 25% solids. To a 59.75 gram portion of this solution
was
TM
added 0. 8 grams of Lucidol 70 and the mixture was stirred until the initiator
dissolved. A split reaction flask was loaded with 740 grams of DI water and 4
TM
grams of Siponate DS-10. The solution was heated to 70°C and stirred at
400 rpm.
Both solutions were purged with nitrogen and then the IOA mixture was added!
to
the flask. The temperature was increased to 80°C. After 2 hours, the
solution was
cooled to room temperature. Analysis by microscopy indicated the presence of
microspheres 3 to 40 micrometers in diameter.
~'xample 11
This example describes the preparation of microspheres containing 13% of a
80J20 IOA/VDM (VDM = 2-vinyl-4,4-dimethyl-2-oxazoline-5-one) solute
copolymer and 87% of a poly(IOA) matrix polymer. An 80/20 IOA / VDM was
first prepared by combining 240 grams of IOA, 60 grams of VDM, 600 grams of 2-
butanone and 0.6 grams of AIBN in a large beaker. The solution was stirred
until
the initiator was dissolved, divided among four 16 oz narrow-mouth amber
bottles
and purged with nitrogen. Each bottle was immediately capped then placed in a
Launder-o-meterTM at 65°C and allowed to react overnight. The
polymer was
isolated by removal of the solvent via evaporation.
Polymeric microspheres were prepared by dissolving 41 grams of the
IOA/VDM copolymer in 272 grams of IOA. A 239 grams portion of this solution
TM
was mixed with 0.8 grams of Lucidol 70 and allowed to mix at ~45°C
until
dissolved. The resultant solution was added to a reaction flask which
contained 740
TM
grams of DI water and 4.5 grams of Siponate DS-10 surfactant at 70°C.
The
resultant mixture was stirred at 450 rpm. The temperature was raised to
80°C for 2
hours and then allowed to cool to room temperature. Little or no agglomeration
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_24-
was observed. Analysis by microscopy indicated the presence of well-formed,
solid
spheres. Particle size analysis indicated a mean volume diameter of 34
micrometers.
Example 12
This example describes the preparation of a microsphere containing 10% of
a polyhexene solute polymer and 90% of a poly(IOA) matrix polymer. A 2 L.
split
T1H
reaction flask was loaded with 730 grams of DI water, 4.4 grams of Siponate DS-
TM
10, 9.6 grams of Acumer 1530 (tradename for a 25% solids aqueous solution of
poly(acrylic acid) with weight average molecular weight of 190,000
commercially
available from Rohm and iHaas) and enough concentrated ammonium hydroxide to
neutralize the solution to pH 7. The solution was stirred at 520 rpm, heated
to
65°C and purged with nitrogen. To this solution was added a solution of
24 grams
of poly(hexene) {obtained from Eastman Kodak; Mw = 96,000) and 800 mg of
TM
Lucidol 70 dissolved in 2I 5 grams of IOA. The solution was purged with
flowing
nitrogen for an additional four minutes and then the reactor was sealed to a
bubbIer.
The mixture was allowed to react at 65°C for 1 hour, arid then at
80°C for 2 hours.
The mixture was cooled to room temperature and fiitc;red through cheese cloth.
No coagulum was observed. Analysis by microscopy indicated the pr~;sence
of microspheres. Particle size analysis indicated a symmetric distribution of
sizes
with a mean volume diameter of 38 micrometers.
Example C13
Example CI3 was prepared in a similar manner to that ofExample 12
except that no polymeric stabilizer (neutralized Acumer 1530) was used. In
contrast to Example 12, Example C13 produced predominantly agglomerated
microspheres that could not be filtered through cheese: cloth.
Example C14
Example C 14 was prepared in a similar manner to that of Example C 13
except that no polyhexene was added. Suspension of microspheres which filtered
easily through cheese cloth was obtained.
Examples 12, C13, and C14 show that composite pressure sensitive
adhesive microspheres can be more difficult to produce than non-composite
microspheres.
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Example 1 S
This example describes the preparation of microspheres containing 3% of a
polyoctene solute polymer and 97% of a poly(IOA) matrix polymer. A 2 L split
TM
reaction flask was loaded with 739 grams of DI water" 9.6 grams of Acrysol A-3
(tradename for a 25% solids aqueous solution of poly(;acrylic acid) with Mw
less
than 150,000 commercially available from Rohm and I3aas Company), 4.5 grams of
2M
Siponate DS-10 and enough concentrated ammonium hydroxide to neutralize l:he
solution to pH 7. The solution was stirred at 500 rpm. A solution of 800 mg of
TM
Lucidol 70 and 7.2 grams of polyoctene (obtained frorn Eastman Kodak; Mw =_
1,100,000) dissolved in IOA was added. The mixture was heated to 70°C
and
purged with nitrogen. A reaction exotherm to a peak temperature of 76°C
wa;>
observed after about 15 minutes. The reaction was then stirred for 2 h at
80°C',
cooled to room temperature and filtered through cheese cloth. No coagulum u~as
observed. Particle size analysis indicated a mean volume diameter of 52
micrometers.
Example 16
This example describes the preparation of micnospheres containing 20% of
poly(IOA) as the solute polymer and 80% of a poly(IOA) matrix polymer.
TM
A 300 grams portion of DI water, 2 grams of Siponate DS-10 and 4 grams
of AcumerM1530 and enough concentrated ammonium lhydroxide to neutralize the
solution to pH 7 were added to 2 L split reaction flask, and heated to
65°C under
flowing nitrogen. A solution of 20 grams of poly(IOA) (M~ = 250,000,) and 2'70
TM
mg of Lucidol 70 dissolved in 80 grams of IOA was added to the aqueous
solution
and stirred at 470 rpm. Af3er 1 hour, the temperature was raised to
80°C for 2
hours. The solution was cooled to room temperature and then filtered through
cheese cloth. No coagulum was observed. Analysis by microscopy indicated the
presence of solid microspheres. Particles size analysis indicated a mean
volume
diameter of S I micrometers.
Example 17
This example describes the preparation of microspheres containing 5% o~f
TM
Kraton 1111 rubber as the solute polymer and 95% poly(IOA) as the matrix
TM
polymer. Kraton was dissolved in I0A at 10% solids bar shaking overnight. A 75
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-26-
TM
grams portion of this solution was added to a solution of 680 mg of Lueidol-T5
dissolved in 75 grams of IOA and mixed until homogeneous. A 1L split reaction
flask was then loaded with 407 grams of DI water, 30 grams of a I O% solution
of
TM
ammonium lauryl sulfate (Stepanol AM-V, which had been diluted with DI water)
and 13 grams of poly(ammonium acrylate) at 11.5% 6soodrite K-702, which has
been diluted with DI water and neutralized with concentrated ammonium
hydroxide). The IOA solution was added. The solution was stirred at 450 rpm,
heated to 65°C and degassed with nitrogen. An exothermic reaction with
a p~.ak
temperature of 67°C was detected after 30-45 mina After 5 h at
65°C, the solution
was cooled to room temperature and filtered through cheese cloth. No coagulum
was observed. Analysis by microscopy indicated the presence of microspheres
with
a small amount of voids. Particle size analysis indicated a mean volume
diameter of
72 p,m.
Example 18
This example describes the preparation of a microsphere containing 4% of
polystyrene) as the solute polymer. A 3.0 gram portion of polystyrene {Mw ~_
5000) and 0.25 grams of'fAZO 52 were dissolved in 70.25 grams of IOA. A. I L
split reaction flask was loaded with 450 grams of DI water, 3.0 grams of
acryyic
acid and 5.0 grams of Standapol A. The aqueous solution was neutralized to pH
7
with ammonium hydroxide. The IOAlpolystyrene solution was added to the
aqueous solution. The mixture was stirred at 400 rpm, heated to 55°C
and
degassed with argon. After 5 hours at 55°C, the reactor was emptied and
the
suspension filtered through cheese cloth. No coagulum was observed. Analysis
by
optical nvcroscopy indicated the presence of microspheres with an average
diameter
of 10 to 20 micrometers that contained many small inclusions approximately 2;
micrometers in diameter.
Example 19
This example describes the preparation of microspheres containing
S°/. of -
CH2CH2-OH terminated poly{styrene) as the solute polymer. A I L indented flask
was charged with 880 ml ofdeionized water and 3.60 grams of acrylic acid, and
neutralized to pH 7 with concentrated ammonium hydroxide. To this solution was
added a solution of 6.0 grams of -CFI2Chiz-OH terminated polystyrene) with a
IVIw
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-27-
of 10,000 and 0.30 grams of Vazo 52 dissolved in 110.4 grams ofIOA. The
mixture was stirred at 350 rpm and degassed with argon. A 2.0 grams portion of
TM
Siponate DS-10 was added. The solution was degassed with argon for an
additional 10 minutes and heated to 5~ to 65°C. A samF~le taken after
45 minutes
showed the presence of microspheres 10-20 micrometers in diameter that
contained
numerous small inclusions approximately 2 micrometers in diameter.
Example 20
Example 20 was repeated in a similar manner to that of 19 except that 4.4
grams of a three-arm branched polystyrene with a Mw of 120,000 was used in
place
of the -CHZCH2-OH terminated poly{styrene). Microspheres, 10-20 micrometers in
diameter, that contained numerous small inclusions approximately 2 micrometers
in
diameter were produced.
Example 21
The example describes the preparation of a microsphere containing 5% of
I S polyvinyl ethyl ether) as the solute polymer. Polyvinyl ethyl ether)
(obtained from
Scientific Polymer Products, Inc., catalog no. 638) was dissolved in IOA at
IO%
solids. A 75 gram portion of this solution was added to a solution of 680 mg
of
TM
Lucidol ?5 dissolved in 75 grams of IOA. The resultant solution was added to a
1
L split reaction flask that had been loaded with 406 grams of DI water, 30
grams. of
TM
a 10% solution of ammonium lauryi sulfate {Stepanol AM-V, which has been
diluted with DI water] and 13 grams of a I 1.5% solution of poly(ammonium
TM
acrylate) (Goodrite K702, which had been diluted with I)I water and
neutralized
with concentrated ammonium hydroxide). The mixture was heated to 65°C,
degassed with nitrogen and allowed to react for 6 hours. The solution was
cooled
to room temperature and filtered through cheese cloth. :fro coagulum was
observed. Analysis by microscopy indicated the presence of microspheres that
contained small voids or inclusions. Particle size analysis indicated a mean
volume
diameter of 55 pm. Addition of isopropyl alcohol to a small portion of the
suspension resulted in coagulationp a tacky polymeric mass was obtained.
Fxample 22
The example describes the preparation of a microsphere containing 5% of
poly(isobomylacrylate) as the solute polymer and 95% o~f a 96/4 IOA/AA matrix
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copolymer. In a 1 L split reaction flask, a 1.05 grams portion of a 10%
solution of
poly{isobornyl acrylate) (obtained from Scientific Polymer Products, Inc.)
dissolved
in IOA was added and the solution was mixed well. A 407 grams portion of DI
water, 30 grams of a 10% aqueous solution of ammonium lauryl sulfate
(StepanolTM
AM-V, which had been diluted with DI water) and 13 grams of an 11.5% solution
of poly(ammonium acrylate) (Goodrite K-702, which had been diluted with DI
water and neutralized with concentrated ammonium hydroxide) was then added.
The mixture was stirred at 450 rpm, heated at 65°C, purged with
nitrogen and then
allowed to react at 65°C for about 9 hour. An exotherm was observed
with a peak
temperature of 72°C. The reaction was cooled to room temperature and
filtered
through cheese cloth. No coagulum was observed. Analysis by microscopy
indicated the presence of microspheres which had a small amount of inclusions
approximately 1-5 micrometers in diameter. Particle size analysis indicated
mean
volume diameter of 30 micrometers.
Example C23
Example 22 was repeated except that no acrylic acid was used in Example
C23. The reaction agglomerated and could not be filtered through cheese cloth.
Example 24
This example describes the preparation of microspheres containing 2% of a
98/2 IOA/AA copolymer as the solute copolymer. A 1 L indented flask was
charged with 880 m1 of deionized water, 3.60 grams of acrylic acid and enough
concentrated ammonium hydroxide to neutralize the solution to pH 7. To this
solution was added 12.0 grams of StandapolTM A and a solution of 4.3 grams of
a
98/2 IOA/AA copolymer and 0.86 grams of LucidolTM 70 dissolved in 220 grams of
IOA. The mixture was degassed with argon, agitated vigorously, heated to 55 to
65°C, and allowed to react overnight. A suspension of hollow
microspheres with
relatively large sized single inclusions was obtained.
Example C25
This example was prepared in a similar manner to that of Example 24 except
that the 92/2 IOA/copolymer was not added. A suspension of solid microspheres
was obtained.
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-29-
Example 2G
This example describes the preparation of microspheres containing 5% of
poly(ODA) as the solute polymer and 95% of poly(IOA) as. the matrix polymer. A
one liter glass reactor was loaded with 7.5 grams of an aqueous solution of
polyacrylic acid at 20 wt ~/o solids, 450 grams of deionized 'water, enough
concentrated ammonium hydroxide to neutralize the solution to a pH of 7 and
6.0
TM
grams of Standapoi A. The reactor was heated to 65°C whsle stirring at
600 rpm.
In a glass far, 7.5 grams of poly(ODA) were dissolved in 1 ~E2.5 grams of IOA
and
0.04 grams of 1;4-BDA, with heating. After the poly(UDA,) was dissolved, 0.67
TM
grams of Lucidol 70 was dissolved in the monomer-polymer solution. When the
contents of the reactor reached 65°C, the solution of poly(ODA) in the
monomers
containing the initiator was added while keeping the rate of agitation at 600
rpm.
After 15 hours at 65°C, the contents of the reactor were allowed to
cool to room
temperature.
Several drops of the microsphere suspension were dried on a glass slide.
The microspheres were tacky to the touch. Optical microscopy showed
microspheres with an average diameter of about 40 micrometers.
examples Z7 Z8
The following examples were prepared according tcn the procedure
described in Example 26 with the amounts of, monomers and initiators shown in
Table 4.
Table 4
TM
Exam le Pol ODA IOA 1,4-BDA Lucidol 70
27_ _ _15 135 0.04 0.64
28 22.5 127.5 0.04 0.60
Various modifications and alterations of this inventis~n will become apparent
to those skilled in the art without departing from the scope .and principles
of this
invention, and it should be understood that this invention is not be unduly
limited to
the illustrative embodiments set forth hereinabove.
