CA2205432A1 - Removable pressure sensitive adhesive and article - Google Patents
Removable pressure sensitive adhesive and articleInfo
- Publication number
- CA2205432A1 CA2205432A1 CA 2205432 CA2205432A CA2205432A1 CA 2205432 A1 CA2205432 A1 CA 2205432A1 CA 2205432 CA2205432 CA 2205432 CA 2205432 A CA2205432 A CA 2205432A CA 2205432 A1 CA2205432 A1 CA 2205432A1
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- CA
- Canada
- Prior art keywords
- sensitive adhesive
- pressure sensitive
- monomer
- dihydrazide
- acrylate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
A removable pressure sensitive adhesive comprises pressure sensitive adhesive microparticles that are the polymerization product of a mono-olefinically unsaturated monomer having an aldehyde group or a ketone group, and a base monomer. By the addition of a polyhydrazide, other adhesives with improved properties can be provided.
Description
CA 0220~432 l997-0~-lS
REMOVABLE PRESSURE SE~lllV~; ADH li'SIVE A~D ARIICLE
BACKGROUND OF THE INVENTION
Field ofthe L.~e.,Lion In general, this invention relates to removable pressure sel~silive adhesives and articles made therewith. This invention further relates to removable ples~u~e sensitive adhesives and artides that have excellent shear strength, demollslla~e reduced adhesive transfer to a ~ubsllale, and are solvent Iç~
Description of the Related Art Inherently tacky, el~tomeric microspheres are known to be useful in repositionable pressure sensitive adhesives. Numerous references describe the prepa~a~ion and/or use of solid, inhelel,lly tacky repositionable or reusable microsphere-based adhesives. Ideally, these adhesives can be repeatedly adhered to and removed from a ~ul~sllale without ~bsl~ l loss of adhesion capacity. See, for r.~ ple~ U. S. Pat. Nos.
3,691~140 (Silver); 4~166~152 ~Baker et al.); 4,495~318 ~Howard); 4~598~112 (Howard);
and 4~786~696 ~Bohnel). Reportedly, "the plilllaly problem associated with these types of
REMOVABLE PRESSURE SE~lllV~; ADH li'SIVE A~D ARIICLE
BACKGROUND OF THE INVENTION
Field ofthe L.~e.,Lion In general, this invention relates to removable pressure sel~silive adhesives and articles made therewith. This invention further relates to removable ples~u~e sensitive adhesives and artides that have excellent shear strength, demollslla~e reduced adhesive transfer to a ~ubsllale, and are solvent Iç~
Description of the Related Art Inherently tacky, el~tomeric microspheres are known to be useful in repositionable pressure sensitive adhesives. Numerous references describe the prepa~a~ion and/or use of solid, inhelel,lly tacky repositionable or reusable microsphere-based adhesives. Ideally, these adhesives can be repeatedly adhered to and removed from a ~ul~sllale without ~bsl~ l loss of adhesion capacity. See, for r.~ ple~ U. S. Pat. Nos.
3,691~140 (Silver); 4~166~152 ~Baker et al.); 4,495~318 ~Howard); 4~598~112 (Howard);
and 4~786~696 ~Bohnel). Reportedly, "the plilllaly problem associated with these types of
2 0 adhesives have been microsphere loss, i.e., microsphere transfer to the substrate." (See, for example, U.S Pat. No. 4,994~322 (Delgado et al.)) There have been prior ~lle",pls to solve the problem of "microsphere loss. " Thetypical approaches have been to use a binder, a primer, an adhesion promoting monomer, or other materials that reduce adhesive lldnsrel. U.S. Pat. No. 3~857~731~ (Merrill et al.);
EPA 0209337 (Thomson et al.); DE 3~544~882 Al ~ichiban); U.S. Pat. No. 4~656~218(Kinoshita); U.S. Pat. No. 4,645,783 (Kinoshita); and U.S. Pat. No. 5~118,750 (Silver et al.) are representative ofthese approaches.
Other a~le~lpls to attack the problem of microsphere transfer focus on the use of hollow, inherently tacky microspheres as described in U.S. Patent Nos. 4~988,5673 0 (Delgado) and 5~045~569 (I)elgado). Hollow ~ crospheres have also been combined with CA 0220s432 l997-OS-lS
WO 96/18701 PCT/US95/1'1328 binders to further reduce adhesive ~ reL. See, for c~ ple, U.S. Patent No. 4,994,322 ~elgado et al.).
However, a need still exists for removable pressure-sensitive adhesives that df~ )n~l.ale reduced adhesive ll~ulsÇer without the use of binders.
Many ofthe rortgo.l.~ patents describe the resultin~ microspheres as solvent in~olllble and solvent di~ le. See, for ~ -~...pl~ U.S Pat. Nos. 3,691,140 (Silver);
4,166,152 ~Baker et al.); 4,786,696 (Bohnel); 4,988,567 (Delgado); 4,994,322 (Delgado et al.); 5,045,569 ~Delgado); and 5,118,750 (Silver et al.). The microspheres do not dissolve in solvent but will disperse in the solvent. Con~equ~ntly, an article prepared from 1 0 these adhesives, such as a tape, could be susceptible to solvent attack since the microspheres would dispel~e in the solvent. There are many applic~tion.c for which a removable ples~ult; sensitive adhesive would benefit from also being solvent reCi~t~nt>
such as spray p~inting operations and bonding to oily :iub~ les. There is especially a need for removable plessu.e sensili~e adhesives that are l~sisl~-l to non-polar organic 1 5 solvents.
SUMMARY OF THE rNVENI IO~
In general, this invention relates to removable pl es~ure sensitive adhesives. In one broad embo~im~nt the invention is for a removable ples~ule sensitive adhesive 2 0 coll.~.isil.g pressure sensitive adhesive microparticles that are the polymèrization product of a mono-ol~finiG~lly unsalul~Led monomer having an aldehyde group or a ketone group (so...t;l;...çs rt;re-led to herein as the carbonyl monomer), and a base monomer.
The mono-olefinic unsaturation in the carbonyl monomer may be provided by (meth)acrylate, (meth~acrylamide or styryl functionality. Examples of suitable carbonyl 2 5 monomers include acrolein, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, cetQne (meth)acrylamide, formylstyrol, diacetone (meth)acrylate, acetonyl acrylate, 2-Lydlo~yl~ropyl acrylate-acetyl acetate, 1,4-butanediol acrylate acetyl~çet~tç and ..,i~ es thereo Preferably, the base monomer is an alkyl (meth)acrylate ester, a vinyl ester, or3 0 .... xlu, ~s thereof. More pl ere"ed base monomers are monofunctional unsaturated (meth)acrylate esters of non-tertiary alkyl alcohols, the alkyl groups of which have from 4 to 14 carbon atoms (most p.erelably from 4 to 10 carbon atoms).
The adhesive micl ~p~ Licles may optionally include a polar monomer that is copoly...~ ble with the call,ollyl monomer and the base monomer. The mielup~licles may further include a ml~ltifi~nctional free-radically poly,n~l~ble clos.~l;.. L ;~P agent for int~rn~lly cros~linl-in~ the miclop~ulicles.
Advantageously, it has been found that by adding a polyhydrazide (i.e., a material c~ g more than one Lydl~no moiety) to the miclop~Licles, a relnovable pres~ule sensilive adhesive having eYc~ nt shear s~lellglh, reduced adhesive ll~lsrer, and improved solvent re~i~t~nce (as measured by the inrlisp~rsibility of the adhesive in solvent) can be provided. It is believed that the polyhydrazide externally (i.e., interpartically) crosslinks the micl op~ Licles together. Consequently, this invention also relates broadly to removable ples~ure sensitive adhesives that are solvent indis~el~il,le and removable pressure sensitive adhesives that are based on pressure sensitive adhesive miel~,pal licles that are croc.~lin~ l together.
Useful polyllyd,~ides have the general structure:
fi' fi' wherein R is an organic radical co~ i..;..g about 2 to 10 carbon atoms. Examples of suitable polyl,y.ll~ides include oxalyl dihydrazide, malonyl dihydrazide, succinyl dihydrazide, glutaryl dihydrazide, adipoyl dihydrazide, maleyl dihydrazide, sebacoyl dihydrazide, fumaroyl dihydrazide, isopht~lic diydl~zide, terephthalic dihydrazide, and i~Lules thereof.
In prerelled emborlim~nt~ the pressule sensitive adhesives comprise:
,. (a) pless-lle sensitive adhesive mi~;lopalLicles that are the polylll~ tion product of:
CA 0220~432 1997-o~
WO 96/18701 PCT/US9~114328 (1) about 75 to 99.9 parts by weight (more prer~,ably about 80 to 98 parts, most prerel~bly about 85 to 98 parts) of a free-radically poly..~e. ;,Able monomer selected from the group con~ictinf~ of allcyl (meth)acrylate esters, vinyl esters, and mixtures thereof;
(2) about 0.1 to 10 parts by weight (more preferably about 0.5 to 7 parts, most preferably about 1 to 5 parts) of a mono-olefinically u~salul~Led monomer having an aldehyde group or a ketone group; and
EPA 0209337 (Thomson et al.); DE 3~544~882 Al ~ichiban); U.S. Pat. No. 4~656~218(Kinoshita); U.S. Pat. No. 4,645,783 (Kinoshita); and U.S. Pat. No. 5~118,750 (Silver et al.) are representative ofthese approaches.
Other a~le~lpls to attack the problem of microsphere transfer focus on the use of hollow, inherently tacky microspheres as described in U.S. Patent Nos. 4~988,5673 0 (Delgado) and 5~045~569 (I)elgado). Hollow ~ crospheres have also been combined with CA 0220s432 l997-OS-lS
WO 96/18701 PCT/US95/1'1328 binders to further reduce adhesive ~ reL. See, for c~ ple, U.S. Patent No. 4,994,322 ~elgado et al.).
However, a need still exists for removable pressure-sensitive adhesives that df~ )n~l.ale reduced adhesive ll~ulsÇer without the use of binders.
Many ofthe rortgo.l.~ patents describe the resultin~ microspheres as solvent in~olllble and solvent di~ le. See, for ~ -~...pl~ U.S Pat. Nos. 3,691,140 (Silver);
4,166,152 ~Baker et al.); 4,786,696 (Bohnel); 4,988,567 (Delgado); 4,994,322 (Delgado et al.); 5,045,569 ~Delgado); and 5,118,750 (Silver et al.). The microspheres do not dissolve in solvent but will disperse in the solvent. Con~equ~ntly, an article prepared from 1 0 these adhesives, such as a tape, could be susceptible to solvent attack since the microspheres would dispel~e in the solvent. There are many applic~tion.c for which a removable ples~ult; sensitive adhesive would benefit from also being solvent reCi~t~nt>
such as spray p~inting operations and bonding to oily :iub~ les. There is especially a need for removable plessu.e sensili~e adhesives that are l~sisl~-l to non-polar organic 1 5 solvents.
SUMMARY OF THE rNVENI IO~
In general, this invention relates to removable pl es~ure sensitive adhesives. In one broad embo~im~nt the invention is for a removable ples~ule sensitive adhesive 2 0 coll.~.isil.g pressure sensitive adhesive microparticles that are the polymèrization product of a mono-ol~finiG~lly unsalul~Led monomer having an aldehyde group or a ketone group (so...t;l;...çs rt;re-led to herein as the carbonyl monomer), and a base monomer.
The mono-olefinic unsaturation in the carbonyl monomer may be provided by (meth)acrylate, (meth~acrylamide or styryl functionality. Examples of suitable carbonyl 2 5 monomers include acrolein, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, cetQne (meth)acrylamide, formylstyrol, diacetone (meth)acrylate, acetonyl acrylate, 2-Lydlo~yl~ropyl acrylate-acetyl acetate, 1,4-butanediol acrylate acetyl~çet~tç and ..,i~ es thereo Preferably, the base monomer is an alkyl (meth)acrylate ester, a vinyl ester, or3 0 .... xlu, ~s thereof. More pl ere"ed base monomers are monofunctional unsaturated (meth)acrylate esters of non-tertiary alkyl alcohols, the alkyl groups of which have from 4 to 14 carbon atoms (most p.erelably from 4 to 10 carbon atoms).
The adhesive micl ~p~ Licles may optionally include a polar monomer that is copoly...~ ble with the call,ollyl monomer and the base monomer. The mielup~licles may further include a ml~ltifi~nctional free-radically poly,n~l~ble clos.~l;.. L ;~P agent for int~rn~lly cros~linl-in~ the miclop~ulicles.
Advantageously, it has been found that by adding a polyhydrazide (i.e., a material c~ g more than one Lydl~no moiety) to the miclop~Licles, a relnovable pres~ule sensilive adhesive having eYc~ nt shear s~lellglh, reduced adhesive ll~lsrer, and improved solvent re~i~t~nce (as measured by the inrlisp~rsibility of the adhesive in solvent) can be provided. It is believed that the polyhydrazide externally (i.e., interpartically) crosslinks the micl op~ Licles together. Consequently, this invention also relates broadly to removable ples~ure sensitive adhesives that are solvent indis~el~il,le and removable pressure sensitive adhesives that are based on pressure sensitive adhesive miel~,pal licles that are croc.~lin~ l together.
Useful polyllyd,~ides have the general structure:
fi' fi' wherein R is an organic radical co~ i..;..g about 2 to 10 carbon atoms. Examples of suitable polyl,y.ll~ides include oxalyl dihydrazide, malonyl dihydrazide, succinyl dihydrazide, glutaryl dihydrazide, adipoyl dihydrazide, maleyl dihydrazide, sebacoyl dihydrazide, fumaroyl dihydrazide, isopht~lic diydl~zide, terephthalic dihydrazide, and i~Lules thereof.
In prerelled emborlim~nt~ the pressule sensitive adhesives comprise:
,. (a) pless-lle sensitive adhesive mi~;lopalLicles that are the polylll~ tion product of:
CA 0220~432 1997-o~
WO 96/18701 PCT/US9~114328 (1) about 75 to 99.9 parts by weight (more prer~,ably about 80 to 98 parts, most prerel~bly about 85 to 98 parts) of a free-radically poly..~e. ;,Able monomer selected from the group con~ictinf~ of allcyl (meth)acrylate esters, vinyl esters, and mixtures thereof;
(2) about 0.1 to 10 parts by weight (more preferably about 0.5 to 7 parts, most preferably about 1 to 5 parts) of a mono-olefinically u~salul~Led monomer having an aldehyde group or a ketone group; and
(3) optionally, 0 to about 20 parts by weight (more prer~l~bly O
to about 15 parts, most preferably 0 to about 10 parts) of a polar monomer di~.elll than the carbonyl monomer and the base monomer;
wherein the sum of (a)(1) + (a)(2) + (a)(3) is 100 parts by weight; and (b) about 0.5 to 150 milliequivalents (meq) per 100 grams of miclupallicles (more preferably about 1 to 100 meq, most preferably about 2 to 50 meq) of a polyhydrazide crocslin~in~ agent for cros.clin~ing the adhesive mi~i. o~ icles 1 5 together.
Various pres~ul t; sensiliv~; adhesive articles can be prepared using the pressule sensitive adhesives of the invention incl~ltlin~ single coated tapes and sheet goods, double coated tapes and sheet goods, and transfer adhesive articles.
A variety of di~e.enL methods may be used to prepare the pressure sensitive 2 0 adhesives. In general, these methods involve aqueous suspension polym~ri7:in~ the pressul e sensitive adhesive micropa- Licles and then adding to the aqueous suspension a cros.clinkin~ agent for crocclinkinE the micl op~ licles together. The various pressure sensitive adhesive articles can be plepaled by applying the aqueous suspension of mic-up~ Licles and cros.clinkin~ agent to a backing to form a wet adhesive layer and then 2 5 drying the wet adhesive. Once dried, the pl~s~ult; sensitive adhesive microparticles are crosslinked together.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In general, this invention relates to a removable pressure sensitive adhesive. By 3 0 "removable" it is meant that once the adhesive has been firmly applied to a piece of paper, = --CA 0220~432 1997-0~
WO 96/18701 PCT/US95/1~328 it can be r~moved without tearing the paper. Preferably, the adhesives of the invention are reposition~ble by which it is meant that they can be repeatedly firmly adhered to and removed from the paper substrate without tearing the paper and wilhoul s~slalll;al loss of adhesive capacity. Upon removal from the paper substrate, the adhesive still p, ese,lLs a relatively unco.. ~ ted surface for reapplication to the paper substrate. By "p~es~u~e sens;live" it is meant that the adhesives of the invention are tacky to the touch at room te"~ alule (e.g., about 20 to 22C), as can be readily dele".,illed by a finger tack test, and can easily form a useful adhesive bond with the application of light pres;,u,e.
In more prt;rti,red embo~lim~nts, the adhesives ofthe invention demonsl,~le liKle or no adhesive transfer. As a result, little or no adhesive remains on the substrate once the adhesive has been removed, thereby leaving a relatively unco..~ ted substrate surface. Other advantages afforded by the pr~rt;l,ed adhesives ofthe invention are excellent shear strength and solvent resist~nce especially re~iet~nce to non-polar organic liquid solvents.
The removable pressure sensitive adhesives of the invention are based on polymeric, pres~.lre sensitive adhesive miclopal licles. The mi~ilop~ licles comprise and, more preferably consist es~.nti~lly of, the polymerization product of: (a) a mono-olefinically unsalul~ted monomer that COI~ an aldehyde moiety or a ketone moiety(sc""~li",es referred to herein as the "carbonyl monomer") and (b) a second or base mono",er. In particularly prerelled embo-lim~nts ofthe invention, the ples~uLe sensitive adhesives further include a polyl,yd,a~ide. As eYpl~ineci in more detail below, it is believed that the polyl,y~ zide reacts with the carbonyl group on the carbonyl monomer to externally or interpartically crosslink the adhesive micropa~ Licles together, thereby ~nh~n~.ing the shear strength and solvent resi~t~nce of the pressure sensitive adhesive 2 5 while recl~l~in~ the amount of adhesive transfer.
Turning now to the specific components of the adhesive, the carbonyl monomer preferably has the following general structure:
CA 0220S432 1997-OS-lS
WO 96/18701 PCI'IUS95/14328 wherein R is an organic radical that is bonded to the carbonyl carbon atom by another carbon atom and colllai,.s a single, free-radically poly...~ hle carbon atom-to-carbon atom double bond. The mono-olefinic unsa~Lu~a~ion may be provided by (meth)acrylate, (meth)acrylamide, styryl or other vinyl functionalities. ~t;r~;lably it is provided by acrylate or acrylamide functionality. (The use ofthe term "meth" in parentheses in~ic~tes that, for example, both acrylate and meth~crylate groups are ccsn~ ted ) Rl is hydrogen or an organic radical that is bonded to the carbonyl carbon atom by another carbon atom. Both R and Rl may contain any number of carbon atoms, may be ~liph~tic or aromatic, may be branched or linear, and may contain other functionalities such as ester or amide groups.
FY~mrles of useful carbonyl monomers include acrolein, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, diacetone (meth)acrylamide, formylstyrol, cetone (meth)acrylate, acetonyl acrylate, 2-hydlo~ylJlol~yl acry-late-acetyl acet~te, 1,4-but~ne~ic)l acrylate acetyl~cet~te and ",i~lules thereo Acrolein and diacetone acrylamide are particularly prerelled In order to accommodate the pl~r~ d sllspPn~ion polymerization m~mlf~ctllring process for the adhesive mi-;,opa"icles (~ cll~sed below), the carbonyl monomer has at least some oil solubility, although it is pl ert;" ed that it be both somewhat oil soluble and water soluble.
2 0 The carbonyl monomer is employed in an amount sufflcient to provide good cros.~linkin~ of the micl opa"icles to each other upon reaction with the polyl,yd, ~zide, while b~l~nc.in~ shear strength, cohesive strength, storage modulus, pressure sensitive adhesion, and adhesive transfer. How these properties should be llltim~t~.ly b~l~n~ed will be determined in part by the int~n~ed use of the adhesive.
2 5 Within these parameters, the carbonyl monomer is typically used in an amount of about 0.1 to 10 parts by weight. If the carbonyl monomer provides less than about 0.1 part by weight, then the level of interparticle cro.~.~linking tends to be insufficient resulting in adhesives having poor cohesive strength, low shear strength, and increased adhesive transfer. If the carbonyl monomer provides more than about 10 parts by weight, then the CA 0220~432 1997-OS-l~
res..lting polymer tends to be non-tacky and loses pressure sensitive adhesive properties, due to an increased storage modulus.
The base ...ono~ r is poly ~ ~le with the carbonyl monomer, plerelably free-radically poly..lP~ ble. The base monomers are oleophilic, water em~ ifi~ble, and have limited water solubility so as to permit the formation of a stable suspension polym~ri7ahle > system for m~n--f~ct re ofthe adhesive microp~licles. As homopolymers, base monom~rs generally have glass transition tel,lpelal~lres below about -10C to f~.ilit~te the pro-vision of pres~ule se~sili~e adhesive properties.
Alkyl (meth)acrylate monomers may be used to provide the base monnm~o .
Particularly prefel,~d are monofunctional ulls~lulaLed (meth)acrylate esters of non-tertiary alkyl alcohols. The alkyl groups ofthese alcohols preferably contain from 4 to 14 (more preferably 4 to 10) carbon atoms. (Meth)acrylate esters ~It;pared from alkyl alcohols having less than 4 or more than 14 carbon atoms tend to have in~1eql~ate ples~ule sensilivt; adhesive properties.
F.~h.. ples of useful monomers include sec-butyl acrylate, n-butyl acrylate, isoamyl acrylate, 2-m~lhyll,ulyl acrylate, 4-methyl-2-pentyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl meth~rylate, isodecyl acrylate, dodecyl acrylate, tetradecyl acrylate, and IllLxlults thereo Particularly pr~;relled are n-butyl acrylate, sec-butyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, 2 0 isononyl acrylate, isodecyl acrylate, and mixtures thereof. Of these, isooctyl acrylate and 2-ethylhexyl acrylate are the most plerelled.
Also useful for providing the base monomer are monofunctional, unsaturated vinylesters derived from linear or branched carboxylic acids having 1 to 14 (preferably 7 to 12) carbon atoms (not counting the carboxyl carbon atom). Suitable vinyl ester monomers include vinyl propionate, vinyl pelal~sonale, vinyl hexanoate, vinyl caprate, vinyl 2-ethylhexanoate, vinyl oct~noate, vinyl decanoate, vinyl laurate, and mixtures thereo Particularly prt;relled are vinyl caprate, vinyl 2-ethylhexanoate, vinyl laurate, and mixtures thereof.
(Meth)acrylate or other vinyl monomers which, as homopolymers, have glass 3 0 transition tell.pelalllres higher than about -20 to 0C, e.g., ethyl acrylate, tert-butyl CA 0220s432 1997-OS-lS
acrylate, isobo.llyl acrylate, butyl rnpth~rylate~ vinyl ~cet~te, acrylonitrile, ..~u-~s thereof, and the like, may be used in conjunction with one or more of the (meth)acrylate and vinyl ester mr)n~-mPrs provided that the glass transition temperature of the res -lting polymer is below about -10C and has pressure sensitive adhesive prop~llies.
Advantageously, the pres~ure sensilive adhesive micl op~ licles of the inventionmay be prepared without polar ...ono..æls. That is, the mic~pa"icles may be prepa ed using: alkyl (meth)acrylate and/or vinyl ester base monome.(s), alone or in co...billa~ion only with other free-radically polyl..t;.i~ble vinyl functional base monomers; and carbonyl mono...t;~ ~. Polar monon.c. s can lead to a corrosive interaction with metal substrates and can render the res -ltin~ adhesive more sensitive to moisture (e.g., loss of adhesion in high hllmirlity ellvil ol~l l lr~
However, polar monomers may be bPnPfici~l in some inet~nces Consequently, the pres~u. ~ sensitive adhesives of the invention may further and optionally comprise a polar ~ono~pr dirr~ n~ than but copolym~ hlc with the carbonyl monomer and the base monomer. The polar monomer may be added to improve or modify cohesive strength, storage stability, adhesion to polar surfaces, and glass transition te---pe~Lu~e. It is p-ert;ll cd that the polar monomer be incorporated in an amount of no more than about 1 to 20 parts by weight, if it is used at all.
Polar monomers refer to monolll~ ~ that are both oil and water soluble, are 2 0 polymerizable with but dirre~ L than the carbonyl monomer and the base monomer, and include one of the following polar substituçt te: amide, nitrile, hydroxyl and carboxylic acid (inch1~1ing acid salt) groups. Suitable polar monomers include monoolefinicmonocarboxylic acids, monoolefinic dicarboxylic acids, salts thereof, acryl~mi~çe, N-substituted acryl~mi~çe N-vinyl l~ct~me and mixtures thereo RepresenlaLi~e examples 2 5 of these classes of useful polar monomers include acrylic acid, meth~crylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, sulfoethyl meth~r.rylate, N-vinyl pyrrolidone, N-vinyl caprolactam, acrylamide, t-butyl acrylamide, dimethylamino ethyl acrylamide, N-octyl acrylamide, hydloxy ethyl acrylate, and hydroxy ethyl meth~crylate.
Ionic monolllt;-~ such as sodium mP.th~.rylate, ammonium acrylate, sodium acrylate, 3 0 trimethylamine p-vinyl bPn7imi~P, N,N-dimethyl-N-(beta-methoxy-ethyl) ammonium CA 0220'432 1997-o'.-1'.
propionate betaine, l~ elllylamine meth~crylamide~ dimethyl-1-(2,3-dillydro~yl~r~yl)amine mP.th~crylamide, and ll~lures thereof are also useful. Particularly p.trelled are acrylic acid, sodium acrylate, N-vinyl pyrrolidone, and ll~xlures thereo - The pl es~urG sensitive adhesive microparticles of the invention prGerelably colll~lise: (a) about 0.1 to 10 parts by weight carbonyl monomer; (b) about 75 to 99.9 parts by weight base mr nom~r; and, optionally, (c) 0 to about 20 parts by weight polar monom~r. More prGrGIably~ the ples~re sensilivG adhesive mi~;lo~Licles comprise: (a) about 0.5 to 7.0 parts by weight carbonyl monomer; (b) about 80 to 98 parts by weight base nlonGIllel, and, optionally, (c) 0 to ~bout 15 parts by weight polar monomer. Most ~ preferably, the pressure sensitive adhesive miclop~licles comprise: (a) about 1.0 to 5.0 parts by weight carbonyl monomer; (b) about 85 to 98 parts by weight base monomer, and, optionally, (c) 0 to about 10 parts by weight polar monomer. The parts by weight ranges are based on the sum of (a) + (b) + (c) n~min~lly equalling 100 parts.
The pressure sensilive adhesive mic~,pal licles of the invention may also contain a m~lltifim~tional free-radically polylllGIi~ le crosslinking agent. Such crosslinking agents can enh~nce the cohesive ~ll englll and solvent insolubility of the individual micl ?al licles by internally crocslin'-in~ them. ''Ml~ltifimctional~ refers to crosclinl~ing agents which possess two or more free-radically polymeri7~l3le olefinically unsaturated groups. Useful m-lltifilnl .tion~l cro~.~linking agents include (meth)acrylic esters of diols (e.g., butanediol), triols (e.g., glycerol), and tetrols (e.g., pentaerythritol); polymeric mllltifi-nctional (meth)acrylates (e.g., poly(ethylene oxide) diacrylate and poly(ethylene oxide) .rylate); polyvinylic compounds (e.g., substituted and unsubstituted divinylhen7ene); difunctional ult;lhalle acrylates; and mixtures thereof.
When an internal cro.sslin~ing agent is employed, it is typically used at a level of up to about 0.15 equivalent weight percent. Above about 0.15 equivalent weight percent, the micrc,p~ licles tend to lose their pressure sensitive adhesive qualities and eventually become non-tacky to the touch at room temperature. The "equivalent weight percent" of a given compound is defined as the number of equivalents of that compound divided by the total number of equivalents of free-radically polymerizable unsaturation in the total 3 o micropal ~icle composition. An equivalent is the number of grams divided by the CA 0220~432 1997-0~
equivalent weight. The equivalent weight is defined as the molecular weight divided by the ~luml)er of polym~ri7~hle groups in the monomer (in the case of those mono,.,cl ~ with only one polymeri7able group, equivalent weight = molecular weight). Surprisingly and adv~nt~geously, it has been found that by hlcol~u~ g a polyfunctional hydra_ide into the pres~u~le sensili~c adhesives of the invention, the shear ~, cn~L}l of articles made with the adhesives can be dr~m~tir~lly i.,lpro~ed as can the solvent resiet~nr,e of such articles. The polyfilnctiQn~l hydrazide also significantly reduces the tendency of such articles to l~lsrc~ adhesive upon r~ealed ~tt~c.~lm~nt to and subsequent removal from a surface.
A polyfilnrti()n~l hydra_ide (som~times described herein as a polyl.yd,~zide) refers to a compound having more than one hydl~illo moiety; i.e, more than one -NH-NH2 moiety. Polyl.ydl~ides are typically obtained as the reaction product of hydrazine and a polyfi.nctiQn~l organic ca,l,uxylic acid (or its corresponding ester, amide, acyl halide or anhydride). The polyfimr,tion~l organic carboxylic acid may be aliphatic or aromatic in nature and may contain a branched or linear backbone. Preferably, the acid is a dicarbo-xylic acid so as to result in a polyhydrazide having the following general structure:
O O
Il 3 11 wherein R3 is an organic radical co..~ about 2 to 10 carbon atoms. As the molecular weight and size of the R3 group increases, the solubility of the polyhydrazide in water cler,lin~s.
The polyhydl~ide may also be provided by a poly(acrylhydrazide) which is typically obtained by reacting a polymer of a polyfunctional organic carboxylic acid (or its corresponding ester, amide, acyl halide or anhydride) with hyd~ine. Also useful are bis-semicarbizides, especially those which are aliphatic or cycloaliphatic and have the following general structure:
CA 0220~432 1997-0~
ll ll H2N--NH--C--NH 1~ N' I--C--NH--NH2 wllel~;ll R4 is a straight chain or branched radical having 2 to 7 carbon atoms or a CyG~ ph~tic radical having 6 to 8 carbon atoms.
F.Y~mples of useful polyllydl~zides include oxalyl dihydrazide, malonyl dihydrazide, succinyl dihydrazide, glutaryl dihydrazide, adipoyl dihydræide, maleyl dihydrazide, sebacoyl dihydrazide, fumaroyl dihydrazide, isophthalic dihydrazide, terephthalic dihydrazide, and mixtures thereo Particularly plert;lled polyhydl~ides include malonyl dihydrazide and adipoyl dihydrazide.
Broadly, the polyhydrazide is used in an amount of about 0.5 to 150 milliequivalents (meq) per 100 grams of pressure sen:,ilive adhesive mi.,l.~pa,licle (the microp~ licle being the poly~ lion product of the carbonyl monomer, the base monomer, and any optional polar monolller). The number of milliequivalents is equal to the n,-llll)er of equivalents of hydrazine functionality ml~ltiplied by 1000, and the number of equivalents is the multiplication product of the number of moles of polyllydl~ide and the functionality ofthe polyhydrazide. If the amount of polyllydl~L6ide is less than about 2 0 0.5 meq, then the level of interparticle cros~linl~ing is reduced and the pressure sensitive adhesive micl opal Licles exhibit lower shear strength and have a higher ten-1ency toward adhesive ~ srel . If the amount of polyhydl ~ide is greater than about 150 meq, then the micl opal licles are more highly crosslinked and show less pressure sensitive adhesive properties. More pl~r~ c;d is to use about 1 to 100 meq of the polyhy-ll~ide. Most prerelled is a level of about 2 to 50 meq.
The pres~ule sensitive adhesive miclupal licles of the invention may be prepared by a variety of di~l elll methods all of which rely on suspension polymerization of the microparticles. The res.llting microparticles tend to be bead or pearl shaped, although they may more spheroidal. Typically, they have an average di~m~ter of about 1 to 300 3 0 mm (more preferably, about 1 to 50 mm). The microparticles may be solid or hollow.
CA 0220~432 1997-0~
Hollow mi~lopdllicles contain one or more voids; i.e., one or more spaces co~ letely within the walls of a poly. ..~ ed miclop~ licle. Typically, the hollow portion is less than 100 mm in average ~ meter Ehollow mic,(,p~licles are desired they may be obtained via a "two-step" processcompri.cin~ the steps of:
(a) rOl"lll,~ a water-in-oil emulsion by mixing (l) an aqueous solution (which may contain some of the carbonyl monomer and/or some of the optional polar monomer) with (2) oil phase base monomers, a free radical poly...e. ;~ ;on hlili~lor, and internal crocclinking agent (if any is used);
(b) forming a water-in-oil-in-water ~mlllcion by dispersing the water-in-oil ~mlllcion from step (a) into an aqueous phase (coll~ any ofthe carbonyl monomer and/or polar monomer not added in step (a)); and (c) il,;~ g s~lspell:,ion poly"~ ion, usually by applying heat (preferably about 40 to 60C, more preferably about 50 to 60C) or radiation (e.g., ultraviolet r~ fion).
F.mlllcifi~rs having a low l~dlophilic-lipophilic balance (HLB) value are used to f~-~ilit~te the formation (usually by agitation) of the water-in-oil emulsion in the first step.
Suitable ~mlllcifiers are those having an HLB value below about 7, preferably in the range of about 2 to 7. Examples of such em--l.cifiers include sorbitan monooleate, solbil~
2 0 trioleate, and ethoxylated oleyl alcohol such as BrijO 93, available from Atlas Ch~mic~l Tn~1uctriçc Inc. A thi~ ning agent, e.g., methyl cellulose, may also be included in the aqueous phase of the water-in-oil emulsion.
The aqueous phase into which the water-in-oil emulsion is dispersed in step (b) colllaills an ~mlll.cifier having an HLB value above about 7. Examples of such çmlllcifiers 2 5 include ethoxylated sorbitan monooleate, ethoxylated lauIyl alcohol, and allyl sulfates.
The ~mlllcifier concentration (for both steps (a) and (b)) should be greater than its critical micelle concentration, which refers to the minimllm concentration of ~.mlll.cifier necessary for the formation of micelles, i.e., submicroscopic agglega~ions of ~mlllcifier molecules.
Critical micelle concentration is slightly di~lelll for each .omlllcifier, usable concentrations ranging from about 1.0 x l0 4 to about 3.0 moles/liter. Additional detail CA 0220S432 1997-OS-lS
WO 96/18701 PCT/US9511~328 con.;~rnin~ the prep&~lion of water-in-oil-in-water em.llcion.c, i.e., multiple .oml~lcionc may be found in various liLela~ e references, e.g., Surfactant Systems: Their Cht;lllislly, Pharmacy. & Biology, (D. Attwood and A. T Florence, Chapnlal~ & Hall T.imited, New York 1983).
Useful initi~tors are those which are normally suitable for free radical poly-n~ 1 ;QI- of acrylate or vinyl ester monomprs and which are oil soluble and of very low solubility in water, typically less than 1 g/100 g water at 20C. Fx~mrles of such iaLol~ include azo compounds, llydlopero~des, peroxides, and the like, and pholQi~ QI~ such as benzoph~nt ne, ben~oin ethyl ether, 2,2-~imethoxy-2-phenyl acetophenone. The il.;l;; ~or is generally used in an amount ranging from about 0.01 percent up to about 10 percent by weight of the total polymerizable composition,prerel~bly up to about 5 percent.
Use of a subst~nti~lly water soluble polymerization initiator, such as those generally used in ~ml~lcion polymeri7~tionc causes formation of sul,s~ l amounts of latex. During suspension polymerization, any si~nific~nt formation of latex is undesirable because of the extremely small particle size.
Hollow micropallicles may also be prepal~;d by a simpler "one-step" process comprising aqueous suspension polymerization of the carbonyl monomer, the base monomer, and the polar monomer (which is not optional for this process) in the presence 2 0 of an eml~lsifier which is capable of producing, inside the droplets, a water-in-oil emulsion that is sub~ 1ly stable during both formation of the emulsion and subsequent suspension polymerization.
Useful em~lcifiers are anionic materials having an ~B value greater than 25 and include alkylaryl ether sulfates such as sodium alkylaryl ether sulfate, e.g., TritonO Wt30, 2 ~ available from Rohm and Haas; alkylaryl poly(ether) sulfates such as allylaryl poly(ethylene oxide) sulf~tes, preferably those having up to about 4 ethoxy repeat units;
and alkyl slllf~tec, such as sodium lauryl sulfate, ammonium lauryl sulfate, triethanolamine Iauryl sulfate, and sodium hexadecyl sulfate; alkyl ether sulfates such as ammonium lauryl ether sulfate; and alkyl poly(ether) s--lf~tçe, such as allyl poly(ethylene oxide) s--lf~tec, CA 0220~432 1997-o~
WO 96/18701 PCTIUS95/1'1328 ~re.~bly those having up to about 4 ethoxy units. Alkyl s.llf~tP~s; alkyl ether slllf~tes;
alkylaryl ether slllf~tes; and mixtures thereof are prere,led.
Nonionic emlll~ifiers having an HLB value of between about 13 and 25 can be utilized in conjunction with the anionic Pmlll~ifiP~rs. Examples of non-ionic Pmlll~ifiPrs include SiponicO Y-500-70 (ethoxylated oleyl ~lcohol, available from Alcolac, Inc.), PLURONIC~ P103, and TweenO40 (from ICI America) As in the two-step process, the rmlllcifiP,r is utilized in a concentration greater than its critical micelle conce~ Lion.
Polymeric stabilizers may also be present but are not n~ces.s~ry.
The above-described one-step method may be varied by CGIII~ lg the base 1 0 monomer with nonionic emlll~ifiers, oil soluble polymrri7~tion initiator, and any mllltifilnr,tional internal crosslinker before the base monomer is added to the aqueous phase c~ a c~bollyl monomer, P.mlll~ifiPr and any optional polar monomer. (The polar monomer is optional for this process.) The res.llting emulsion is suspension polymPri7ed to yield hollow ples~ure sensitive adhesive miclop~icles. Anionic 1 5 çm~ ifiers with an HLB value greater than 7 may be inrlllded in the aqueous phase to stabilize the system during suspension polylll~l~Lion but are not required.
Solid pressure sensitive adhesive microparticles may be-prepared via the suspension polym~.ri7~tions disclosed in U. S. Patent Nos. 3,691,140; 4,166,152; and
to about 15 parts, most preferably 0 to about 10 parts) of a polar monomer di~.elll than the carbonyl monomer and the base monomer;
wherein the sum of (a)(1) + (a)(2) + (a)(3) is 100 parts by weight; and (b) about 0.5 to 150 milliequivalents (meq) per 100 grams of miclupallicles (more preferably about 1 to 100 meq, most preferably about 2 to 50 meq) of a polyhydrazide crocslin~in~ agent for cros.clin~ing the adhesive mi~i. o~ icles 1 5 together.
Various pres~ul t; sensiliv~; adhesive articles can be prepared using the pressule sensitive adhesives of the invention incl~ltlin~ single coated tapes and sheet goods, double coated tapes and sheet goods, and transfer adhesive articles.
A variety of di~e.enL methods may be used to prepare the pressure sensitive 2 0 adhesives. In general, these methods involve aqueous suspension polym~ri7:in~ the pressul e sensitive adhesive micropa- Licles and then adding to the aqueous suspension a cros.clinkin~ agent for crocclinkinE the micl op~ licles together. The various pressure sensitive adhesive articles can be plepaled by applying the aqueous suspension of mic-up~ Licles and cros.clinkin~ agent to a backing to form a wet adhesive layer and then 2 5 drying the wet adhesive. Once dried, the pl~s~ult; sensitive adhesive microparticles are crosslinked together.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In general, this invention relates to a removable pressure sensitive adhesive. By 3 0 "removable" it is meant that once the adhesive has been firmly applied to a piece of paper, = --CA 0220~432 1997-0~
WO 96/18701 PCT/US95/1~328 it can be r~moved without tearing the paper. Preferably, the adhesives of the invention are reposition~ble by which it is meant that they can be repeatedly firmly adhered to and removed from the paper substrate without tearing the paper and wilhoul s~slalll;al loss of adhesive capacity. Upon removal from the paper substrate, the adhesive still p, ese,lLs a relatively unco.. ~ ted surface for reapplication to the paper substrate. By "p~es~u~e sens;live" it is meant that the adhesives of the invention are tacky to the touch at room te"~ alule (e.g., about 20 to 22C), as can be readily dele".,illed by a finger tack test, and can easily form a useful adhesive bond with the application of light pres;,u,e.
In more prt;rti,red embo~lim~nts, the adhesives ofthe invention demonsl,~le liKle or no adhesive transfer. As a result, little or no adhesive remains on the substrate once the adhesive has been removed, thereby leaving a relatively unco..~ ted substrate surface. Other advantages afforded by the pr~rt;l,ed adhesives ofthe invention are excellent shear strength and solvent resist~nce especially re~iet~nce to non-polar organic liquid solvents.
The removable pressure sensitive adhesives of the invention are based on polymeric, pres~.lre sensitive adhesive miclopal licles. The mi~ilop~ licles comprise and, more preferably consist es~.nti~lly of, the polymerization product of: (a) a mono-olefinically unsalul~ted monomer that COI~ an aldehyde moiety or a ketone moiety(sc""~li",es referred to herein as the "carbonyl monomer") and (b) a second or base mono",er. In particularly prerelled embo-lim~nts ofthe invention, the ples~uLe sensitive adhesives further include a polyl,yd,a~ide. As eYpl~ineci in more detail below, it is believed that the polyl,y~ zide reacts with the carbonyl group on the carbonyl monomer to externally or interpartically crosslink the adhesive micropa~ Licles together, thereby ~nh~n~.ing the shear strength and solvent resi~t~nce of the pressure sensitive adhesive 2 5 while recl~l~in~ the amount of adhesive transfer.
Turning now to the specific components of the adhesive, the carbonyl monomer preferably has the following general structure:
CA 0220S432 1997-OS-lS
WO 96/18701 PCI'IUS95/14328 wherein R is an organic radical that is bonded to the carbonyl carbon atom by another carbon atom and colllai,.s a single, free-radically poly...~ hle carbon atom-to-carbon atom double bond. The mono-olefinic unsa~Lu~a~ion may be provided by (meth)acrylate, (meth)acrylamide, styryl or other vinyl functionalities. ~t;r~;lably it is provided by acrylate or acrylamide functionality. (The use ofthe term "meth" in parentheses in~ic~tes that, for example, both acrylate and meth~crylate groups are ccsn~ ted ) Rl is hydrogen or an organic radical that is bonded to the carbonyl carbon atom by another carbon atom. Both R and Rl may contain any number of carbon atoms, may be ~liph~tic or aromatic, may be branched or linear, and may contain other functionalities such as ester or amide groups.
FY~mrles of useful carbonyl monomers include acrolein, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, diacetone (meth)acrylamide, formylstyrol, cetone (meth)acrylate, acetonyl acrylate, 2-hydlo~ylJlol~yl acry-late-acetyl acet~te, 1,4-but~ne~ic)l acrylate acetyl~cet~te and ",i~lules thereo Acrolein and diacetone acrylamide are particularly prerelled In order to accommodate the pl~r~ d sllspPn~ion polymerization m~mlf~ctllring process for the adhesive mi-;,opa"icles (~ cll~sed below), the carbonyl monomer has at least some oil solubility, although it is pl ert;" ed that it be both somewhat oil soluble and water soluble.
2 0 The carbonyl monomer is employed in an amount sufflcient to provide good cros.~linkin~ of the micl opa"icles to each other upon reaction with the polyl,yd, ~zide, while b~l~nc.in~ shear strength, cohesive strength, storage modulus, pressure sensitive adhesion, and adhesive transfer. How these properties should be llltim~t~.ly b~l~n~ed will be determined in part by the int~n~ed use of the adhesive.
2 5 Within these parameters, the carbonyl monomer is typically used in an amount of about 0.1 to 10 parts by weight. If the carbonyl monomer provides less than about 0.1 part by weight, then the level of interparticle cro.~.~linking tends to be insufficient resulting in adhesives having poor cohesive strength, low shear strength, and increased adhesive transfer. If the carbonyl monomer provides more than about 10 parts by weight, then the CA 0220~432 1997-OS-l~
res..lting polymer tends to be non-tacky and loses pressure sensitive adhesive properties, due to an increased storage modulus.
The base ...ono~ r is poly ~ ~le with the carbonyl monomer, plerelably free-radically poly..lP~ ble. The base monomers are oleophilic, water em~ ifi~ble, and have limited water solubility so as to permit the formation of a stable suspension polym~ri7ahle > system for m~n--f~ct re ofthe adhesive microp~licles. As homopolymers, base monom~rs generally have glass transition tel,lpelal~lres below about -10C to f~.ilit~te the pro-vision of pres~ule se~sili~e adhesive properties.
Alkyl (meth)acrylate monomers may be used to provide the base monnm~o .
Particularly prefel,~d are monofunctional ulls~lulaLed (meth)acrylate esters of non-tertiary alkyl alcohols. The alkyl groups ofthese alcohols preferably contain from 4 to 14 (more preferably 4 to 10) carbon atoms. (Meth)acrylate esters ~It;pared from alkyl alcohols having less than 4 or more than 14 carbon atoms tend to have in~1eql~ate ples~ule sensilivt; adhesive properties.
F.~h.. ples of useful monomers include sec-butyl acrylate, n-butyl acrylate, isoamyl acrylate, 2-m~lhyll,ulyl acrylate, 4-methyl-2-pentyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl meth~rylate, isodecyl acrylate, dodecyl acrylate, tetradecyl acrylate, and IllLxlults thereo Particularly pr~;relled are n-butyl acrylate, sec-butyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, 2 0 isononyl acrylate, isodecyl acrylate, and mixtures thereof. Of these, isooctyl acrylate and 2-ethylhexyl acrylate are the most plerelled.
Also useful for providing the base monomer are monofunctional, unsaturated vinylesters derived from linear or branched carboxylic acids having 1 to 14 (preferably 7 to 12) carbon atoms (not counting the carboxyl carbon atom). Suitable vinyl ester monomers include vinyl propionate, vinyl pelal~sonale, vinyl hexanoate, vinyl caprate, vinyl 2-ethylhexanoate, vinyl oct~noate, vinyl decanoate, vinyl laurate, and mixtures thereo Particularly prt;relled are vinyl caprate, vinyl 2-ethylhexanoate, vinyl laurate, and mixtures thereof.
(Meth)acrylate or other vinyl monomers which, as homopolymers, have glass 3 0 transition tell.pelalllres higher than about -20 to 0C, e.g., ethyl acrylate, tert-butyl CA 0220s432 1997-OS-lS
acrylate, isobo.llyl acrylate, butyl rnpth~rylate~ vinyl ~cet~te, acrylonitrile, ..~u-~s thereof, and the like, may be used in conjunction with one or more of the (meth)acrylate and vinyl ester mr)n~-mPrs provided that the glass transition temperature of the res -lting polymer is below about -10C and has pressure sensitive adhesive prop~llies.
Advantageously, the pres~ure sensilive adhesive micl op~ licles of the inventionmay be prepared without polar ...ono..æls. That is, the mic~pa"icles may be prepa ed using: alkyl (meth)acrylate and/or vinyl ester base monome.(s), alone or in co...billa~ion only with other free-radically polyl..t;.i~ble vinyl functional base monomers; and carbonyl mono...t;~ ~. Polar monon.c. s can lead to a corrosive interaction with metal substrates and can render the res -ltin~ adhesive more sensitive to moisture (e.g., loss of adhesion in high hllmirlity ellvil ol~l l lr~
However, polar monomers may be bPnPfici~l in some inet~nces Consequently, the pres~u. ~ sensitive adhesives of the invention may further and optionally comprise a polar ~ono~pr dirr~ n~ than but copolym~ hlc with the carbonyl monomer and the base monomer. The polar monomer may be added to improve or modify cohesive strength, storage stability, adhesion to polar surfaces, and glass transition te---pe~Lu~e. It is p-ert;ll cd that the polar monomer be incorporated in an amount of no more than about 1 to 20 parts by weight, if it is used at all.
Polar monomers refer to monolll~ ~ that are both oil and water soluble, are 2 0 polymerizable with but dirre~ L than the carbonyl monomer and the base monomer, and include one of the following polar substituçt te: amide, nitrile, hydroxyl and carboxylic acid (inch1~1ing acid salt) groups. Suitable polar monomers include monoolefinicmonocarboxylic acids, monoolefinic dicarboxylic acids, salts thereof, acryl~mi~çe, N-substituted acryl~mi~çe N-vinyl l~ct~me and mixtures thereo RepresenlaLi~e examples 2 5 of these classes of useful polar monomers include acrylic acid, meth~crylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, sulfoethyl meth~r.rylate, N-vinyl pyrrolidone, N-vinyl caprolactam, acrylamide, t-butyl acrylamide, dimethylamino ethyl acrylamide, N-octyl acrylamide, hydloxy ethyl acrylate, and hydroxy ethyl meth~crylate.
Ionic monolllt;-~ such as sodium mP.th~.rylate, ammonium acrylate, sodium acrylate, 3 0 trimethylamine p-vinyl bPn7imi~P, N,N-dimethyl-N-(beta-methoxy-ethyl) ammonium CA 0220'432 1997-o'.-1'.
propionate betaine, l~ elllylamine meth~crylamide~ dimethyl-1-(2,3-dillydro~yl~r~yl)amine mP.th~crylamide, and ll~lures thereof are also useful. Particularly p.trelled are acrylic acid, sodium acrylate, N-vinyl pyrrolidone, and ll~xlures thereo - The pl es~urG sensitive adhesive microparticles of the invention prGerelably colll~lise: (a) about 0.1 to 10 parts by weight carbonyl monomer; (b) about 75 to 99.9 parts by weight base mr nom~r; and, optionally, (c) 0 to about 20 parts by weight polar monom~r. More prGrGIably~ the ples~re sensilivG adhesive mi~;lo~Licles comprise: (a) about 0.5 to 7.0 parts by weight carbonyl monomer; (b) about 80 to 98 parts by weight base nlonGIllel, and, optionally, (c) 0 to ~bout 15 parts by weight polar monomer. Most ~ preferably, the pressure sensitive adhesive miclop~licles comprise: (a) about 1.0 to 5.0 parts by weight carbonyl monomer; (b) about 85 to 98 parts by weight base monomer, and, optionally, (c) 0 to about 10 parts by weight polar monomer. The parts by weight ranges are based on the sum of (a) + (b) + (c) n~min~lly equalling 100 parts.
The pressure sensilive adhesive mic~,pal licles of the invention may also contain a m~lltifim~tional free-radically polylllGIi~ le crosslinking agent. Such crosslinking agents can enh~nce the cohesive ~ll englll and solvent insolubility of the individual micl ?al licles by internally crocslin'-in~ them. ''Ml~ltifimctional~ refers to crosclinl~ing agents which possess two or more free-radically polymeri7~l3le olefinically unsaturated groups. Useful m-lltifilnl .tion~l cro~.~linking agents include (meth)acrylic esters of diols (e.g., butanediol), triols (e.g., glycerol), and tetrols (e.g., pentaerythritol); polymeric mllltifi-nctional (meth)acrylates (e.g., poly(ethylene oxide) diacrylate and poly(ethylene oxide) .rylate); polyvinylic compounds (e.g., substituted and unsubstituted divinylhen7ene); difunctional ult;lhalle acrylates; and mixtures thereof.
When an internal cro.sslin~ing agent is employed, it is typically used at a level of up to about 0.15 equivalent weight percent. Above about 0.15 equivalent weight percent, the micrc,p~ licles tend to lose their pressure sensitive adhesive qualities and eventually become non-tacky to the touch at room temperature. The "equivalent weight percent" of a given compound is defined as the number of equivalents of that compound divided by the total number of equivalents of free-radically polymerizable unsaturation in the total 3 o micropal ~icle composition. An equivalent is the number of grams divided by the CA 0220~432 1997-0~
equivalent weight. The equivalent weight is defined as the molecular weight divided by the ~luml)er of polym~ri7~hle groups in the monomer (in the case of those mono,.,cl ~ with only one polymeri7able group, equivalent weight = molecular weight). Surprisingly and adv~nt~geously, it has been found that by hlcol~u~ g a polyfunctional hydra_ide into the pres~u~le sensili~c adhesives of the invention, the shear ~, cn~L}l of articles made with the adhesives can be dr~m~tir~lly i.,lpro~ed as can the solvent resiet~nr,e of such articles. The polyfilnctiQn~l hydrazide also significantly reduces the tendency of such articles to l~lsrc~ adhesive upon r~ealed ~tt~c.~lm~nt to and subsequent removal from a surface.
A polyfilnrti()n~l hydra_ide (som~times described herein as a polyl.yd,~zide) refers to a compound having more than one hydl~illo moiety; i.e, more than one -NH-NH2 moiety. Polyl.ydl~ides are typically obtained as the reaction product of hydrazine and a polyfi.nctiQn~l organic ca,l,uxylic acid (or its corresponding ester, amide, acyl halide or anhydride). The polyfimr,tion~l organic carboxylic acid may be aliphatic or aromatic in nature and may contain a branched or linear backbone. Preferably, the acid is a dicarbo-xylic acid so as to result in a polyhydrazide having the following general structure:
O O
Il 3 11 wherein R3 is an organic radical co..~ about 2 to 10 carbon atoms. As the molecular weight and size of the R3 group increases, the solubility of the polyhydrazide in water cler,lin~s.
The polyhydl~ide may also be provided by a poly(acrylhydrazide) which is typically obtained by reacting a polymer of a polyfunctional organic carboxylic acid (or its corresponding ester, amide, acyl halide or anhydride) with hyd~ine. Also useful are bis-semicarbizides, especially those which are aliphatic or cycloaliphatic and have the following general structure:
CA 0220~432 1997-0~
ll ll H2N--NH--C--NH 1~ N' I--C--NH--NH2 wllel~;ll R4 is a straight chain or branched radical having 2 to 7 carbon atoms or a CyG~ ph~tic radical having 6 to 8 carbon atoms.
F.Y~mples of useful polyllydl~zides include oxalyl dihydrazide, malonyl dihydrazide, succinyl dihydrazide, glutaryl dihydrazide, adipoyl dihydræide, maleyl dihydrazide, sebacoyl dihydrazide, fumaroyl dihydrazide, isophthalic dihydrazide, terephthalic dihydrazide, and mixtures thereo Particularly plert;lled polyhydl~ides include malonyl dihydrazide and adipoyl dihydrazide.
Broadly, the polyhydrazide is used in an amount of about 0.5 to 150 milliequivalents (meq) per 100 grams of pressure sen:,ilive adhesive mi.,l.~pa,licle (the microp~ licle being the poly~ lion product of the carbonyl monomer, the base monomer, and any optional polar monolller). The number of milliequivalents is equal to the n,-llll)er of equivalents of hydrazine functionality ml~ltiplied by 1000, and the number of equivalents is the multiplication product of the number of moles of polyllydl~ide and the functionality ofthe polyhydrazide. If the amount of polyllydl~L6ide is less than about 2 0 0.5 meq, then the level of interparticle cros~linl~ing is reduced and the pressure sensitive adhesive micl opal Licles exhibit lower shear strength and have a higher ten-1ency toward adhesive ~ srel . If the amount of polyhydl ~ide is greater than about 150 meq, then the micl opal licles are more highly crosslinked and show less pressure sensitive adhesive properties. More pl~r~ c;d is to use about 1 to 100 meq of the polyhy-ll~ide. Most prerelled is a level of about 2 to 50 meq.
The pres~ule sensitive adhesive miclupal licles of the invention may be prepared by a variety of di~l elll methods all of which rely on suspension polymerization of the microparticles. The res.llting microparticles tend to be bead or pearl shaped, although they may more spheroidal. Typically, they have an average di~m~ter of about 1 to 300 3 0 mm (more preferably, about 1 to 50 mm). The microparticles may be solid or hollow.
CA 0220~432 1997-0~
Hollow mi~lopdllicles contain one or more voids; i.e., one or more spaces co~ letely within the walls of a poly. ..~ ed miclop~ licle. Typically, the hollow portion is less than 100 mm in average ~ meter Ehollow mic,(,p~licles are desired they may be obtained via a "two-step" processcompri.cin~ the steps of:
(a) rOl"lll,~ a water-in-oil emulsion by mixing (l) an aqueous solution (which may contain some of the carbonyl monomer and/or some of the optional polar monomer) with (2) oil phase base monomers, a free radical poly...e. ;~ ;on hlili~lor, and internal crocclinking agent (if any is used);
(b) forming a water-in-oil-in-water ~mlllcion by dispersing the water-in-oil ~mlllcion from step (a) into an aqueous phase (coll~ any ofthe carbonyl monomer and/or polar monomer not added in step (a)); and (c) il,;~ g s~lspell:,ion poly"~ ion, usually by applying heat (preferably about 40 to 60C, more preferably about 50 to 60C) or radiation (e.g., ultraviolet r~ fion).
F.mlllcifi~rs having a low l~dlophilic-lipophilic balance (HLB) value are used to f~-~ilit~te the formation (usually by agitation) of the water-in-oil emulsion in the first step.
Suitable ~mlllcifiers are those having an HLB value below about 7, preferably in the range of about 2 to 7. Examples of such em--l.cifiers include sorbitan monooleate, solbil~
2 0 trioleate, and ethoxylated oleyl alcohol such as BrijO 93, available from Atlas Ch~mic~l Tn~1uctriçc Inc. A thi~ ning agent, e.g., methyl cellulose, may also be included in the aqueous phase of the water-in-oil emulsion.
The aqueous phase into which the water-in-oil emulsion is dispersed in step (b) colllaills an ~mlll.cifier having an HLB value above about 7. Examples of such çmlllcifiers 2 5 include ethoxylated sorbitan monooleate, ethoxylated lauIyl alcohol, and allyl sulfates.
The ~mlllcifier concentration (for both steps (a) and (b)) should be greater than its critical micelle concentration, which refers to the minimllm concentration of ~.mlll.cifier necessary for the formation of micelles, i.e., submicroscopic agglega~ions of ~mlllcifier molecules.
Critical micelle concentration is slightly di~lelll for each .omlllcifier, usable concentrations ranging from about 1.0 x l0 4 to about 3.0 moles/liter. Additional detail CA 0220S432 1997-OS-lS
WO 96/18701 PCT/US9511~328 con.;~rnin~ the prep&~lion of water-in-oil-in-water em.llcion.c, i.e., multiple .oml~lcionc may be found in various liLela~ e references, e.g., Surfactant Systems: Their Cht;lllislly, Pharmacy. & Biology, (D. Attwood and A. T Florence, Chapnlal~ & Hall T.imited, New York 1983).
Useful initi~tors are those which are normally suitable for free radical poly-n~ 1 ;QI- of acrylate or vinyl ester monomprs and which are oil soluble and of very low solubility in water, typically less than 1 g/100 g water at 20C. Fx~mrles of such iaLol~ include azo compounds, llydlopero~des, peroxides, and the like, and pholQi~ QI~ such as benzoph~nt ne, ben~oin ethyl ether, 2,2-~imethoxy-2-phenyl acetophenone. The il.;l;; ~or is generally used in an amount ranging from about 0.01 percent up to about 10 percent by weight of the total polymerizable composition,prerel~bly up to about 5 percent.
Use of a subst~nti~lly water soluble polymerization initiator, such as those generally used in ~ml~lcion polymeri7~tionc causes formation of sul,s~ l amounts of latex. During suspension polymerization, any si~nific~nt formation of latex is undesirable because of the extremely small particle size.
Hollow micropallicles may also be prepal~;d by a simpler "one-step" process comprising aqueous suspension polymerization of the carbonyl monomer, the base monomer, and the polar monomer (which is not optional for this process) in the presence 2 0 of an eml~lsifier which is capable of producing, inside the droplets, a water-in-oil emulsion that is sub~ 1ly stable during both formation of the emulsion and subsequent suspension polymerization.
Useful em~lcifiers are anionic materials having an ~B value greater than 25 and include alkylaryl ether sulfates such as sodium alkylaryl ether sulfate, e.g., TritonO Wt30, 2 ~ available from Rohm and Haas; alkylaryl poly(ether) sulfates such as allylaryl poly(ethylene oxide) sulf~tes, preferably those having up to about 4 ethoxy repeat units;
and alkyl slllf~tec, such as sodium lauryl sulfate, ammonium lauryl sulfate, triethanolamine Iauryl sulfate, and sodium hexadecyl sulfate; alkyl ether sulfates such as ammonium lauryl ether sulfate; and alkyl poly(ether) s--lf~tçe, such as allyl poly(ethylene oxide) s--lf~tec, CA 0220~432 1997-o~
WO 96/18701 PCTIUS95/1'1328 ~re.~bly those having up to about 4 ethoxy units. Alkyl s.llf~tP~s; alkyl ether slllf~tes;
alkylaryl ether slllf~tes; and mixtures thereof are prere,led.
Nonionic emlll~ifiers having an HLB value of between about 13 and 25 can be utilized in conjunction with the anionic Pmlll~ifiP~rs. Examples of non-ionic Pmlll~ifiPrs include SiponicO Y-500-70 (ethoxylated oleyl ~lcohol, available from Alcolac, Inc.), PLURONIC~ P103, and TweenO40 (from ICI America) As in the two-step process, the rmlllcifiP,r is utilized in a concentration greater than its critical micelle conce~ Lion.
Polymeric stabilizers may also be present but are not n~ces.s~ry.
The above-described one-step method may be varied by CGIII~ lg the base 1 0 monomer with nonionic emlll~ifiers, oil soluble polymrri7~tion initiator, and any mllltifilnr,tional internal crosslinker before the base monomer is added to the aqueous phase c~ a c~bollyl monomer, P.mlll~ifiPr and any optional polar monomer. (The polar monomer is optional for this process.) The res.llting emulsion is suspension polymPri7ed to yield hollow ples~ure sensitive adhesive miclop~icles. Anionic 1 5 çm~ ifiers with an HLB value greater than 7 may be inrlllded in the aqueous phase to stabilize the system during suspension polylll~l~Lion but are not required.
Solid pressure sensitive adhesive microparticles may be-prepared via the suspension polym~.ri7~tions disclosed in U. S. Patent Nos. 3,691,140; 4,166,152; and
4,636,432. In general, these suspension polymerization techniques use ionic or nonionic 2 0 emlll~ifiers in an amount greater than the critical micelle concentration and/or protective colloids, finely divided inorganic solids, or the like.
Each suspension polymerization method (whether producing hollow or solid miclopal Licles) may be modified by withholding the addition of all or some of the carbonyl monomer and/or any optional polar monomer until after polym~ri7~tion of the oil phase base monomer has been initi~tef1 In this instance, however, these components must be added to the polymerizing mixture prior to 100% conversion of the base monomer. Similarly, the internal crosslinker (if used) can be added at any time before 100% conversion to polymer ofthe monomers ofthe microparticle composition.
Preferably it is added before initiation occurs.
CA 0220s432 1997-05-lS
WO 96/18701 PCT/US95/1'1328 Once the pre~sule sensitive adhesive mic~op&llicles have been suspension poly...~ ;~e(l but while they are still dispersed in the aqueous suspension media, the polyhydrazide may be added either as an aqueous solution or as a solid powder that dissolves in the aqueous suspension media.
Other ingredients which may be optionally added to the miclol ~licle sucpçne;on following polymeri7~tion include tackifying resins, pl~cti~ rs, pi m~ntc neutralizing agents (e.g., sodium hydroxide), fillers, stabilizers, and various polymeric additives. These ingredients are incorporated in ~mountc that do not m~ter~ y adversely affect the desired propellies ofthe pressu.e sensilive adhesive miclop~licles~
Following suspension polymerization, an aqueous s.-cr~oncion ofthe plessule sensitive adhesive microp~ licles is obtained. The suspension may have a non-volatile solids col-le -ls of from about 10 to 50 percent by weight. However, as e~rl~ined more fully h~-cinbelow, the properties ofthe pressure sensitive adhesive microp~licles will be diLrerenl depending on whether a polyl.yd.~ide has been included If the mic.~,psllicles were pre~ared without polyhydrazide, then the aqueous suspension of mi~i~op~. Licles may be sprayed by conventional techniques wilhoulcol,~ ing, or they may be ~ y~d from an aerosol container with suitable propellants such as ~lk~nes, ~lkene~ and chlorofluorocarbons (e.g., FreonO halocarbons from E.I.
duPont de Nemours & Co., Inc.). Useful aerosols preferably have a solids content of 2 0 about 5% to 20%, more prerelably about 10% to 16%.
The aqueous suspension may also be coated onto an app.op.iale substrate and dried. Drying may be accompli~hed under ambient conditions or, more quickly, by heating for about 3 to 20 minutes in a 60 to 110C oven, the actual time and temperature depending on the substrate. (For systems co..~S.h~ g a poly(acylhydrazide) external crosslinker, heated drying is required.) Alt~ ali~ely, the aqueous suspension of pressure sensitive adhesive mi~;~opal licles may be dried and then redispersed (with agitation if n~ce~s~, y) in common organic liquid solvents such as ethyl ~cet~te, tetrahydrofuran, heptane, 2-but~none benzene, and cyclohexane. The solvent dispersions may be sprayed or they may be coated onto a CA 0220~432 1997-0~
suitable b~ in~ and dried. However, once the microp~ ~icles have been dried, they cannot be redi~ ed in water.
If the plt;:S~iUl e sensitive adhesive mi.ilol,~ licles have been prep~ ed with polyhy-ll~ide, then the aqueous sl-~pPn.~ion of mic~ op~ licles may be sprayed by coll~P~ ;Qn~l teÇlm;1ues without cobwel)billg or they may be sprayed from an aerosol co~ r~ as describe above. In addition, the ~queo..s suspension may be coated onto an appropliale sL~sllale and dried, as described above. However, once these microspheres have been dried, they can no longer be ledis~,el~ed, either in water or collll.loll organic liquid solvents. Thus, the dried pleS:jUl`e sensitive adhesive micropal lides of the invention that include polyhydl~zide may be regarded as solvent indispersible.
While not wishing to be bound by any particular theory, it is believed that the polyllydl~ide is e~sPnti~lly unreactive toward the micl op~ licles in s ~p~n.~i~ n However, as the water is removed from the suspension upon drying, a dehydration cQndPn~tiQn reaction occurs between the carbonyl groups provided in the miclopallicles by the carbonyl monomer and the hydrazino moieties. In pl~relled systems, this reactionproceeds at a high rate under ambient con-lition.~ and forms covalent lin~es between microparticles. In this way, the pressule sensitive adhesive micl~al licles may be regarded as inLt;ll.allically or externally cro~slin~Pd The inert nature of the polyhydra_ide when in suspension, coupled with its ability 2 0 to rapidly form interparticle covalent crosslinks between micropal ~icles when the water is removed, offers a number of important adv~nt~e~, as explained below.
As noted above, the pres~ure sensitive adhesive mi~il opal licles of the invention may be coated onto a suitable substrate. Useful substrates include paper, plastic films, cellulose acetate, ethyl cellulose, woven or nonwoven fabric formed of synthetic or 2 5 natural m~tPri~lc, metal, mPt~lli7P,d plastic films, and ceramic sheets Coating can be accomplished with a knife coater, Meyer bar coater, or an extrusion die In this manner, a wide variety of useful articles may be provided For example, a tape or a sheet which in~ ldes a flexible backing or substrate, the pressule sensitive adhesive ofthe invention on one major surface ofthe substrate, and a 3 0 low adhesion b~c~ i7P, or release coating (e.g., silicones and fluorosilicones) on the CA 0220.,432 1 997 - os - 1 ., WO 96/18701 PCTIUS9S11'1328 opposile major surface of the ~ub~l~ale can be made. The tape or sheet can be wound convolutely about itself on a core to form a sheet roll or a roll of tape. ~Ite~tively, the p.es~u-e sensilive adhesive can be applied to both major surfaces of the substrate so as to provide a double coated tape or sheet. The invention further provides a tape comprising a flexible ~ub~l-ale~ the pr~ure sensitive adhesive on one major surface ofthe sul)~llale, and a protective release liner over the exposed pressure sens;Li~te adhesive surface. A
transfer tape comprising a film of the pressure sensitive adhesive bclweell two release liners can also be made.
Because the pressu,e sensitive adhesives of the invention display eYc~ nt le ;~A~-ce to non-polar organic liquid solvents, they would be particularly desirable in providing tapes for use in e.../i.olll.lents where exposure to motor vehicle fuel is of concern, such as a fuel hose tape.
The invention will be more fully appreciated with reference to the following e~mrles which should not be viewed as limiting in scope.
Abbreviations and Tradenames Various abbreviations and tr~den~mes are used in the examples which are defined according to the following sc.he(l-lle:
AA acrylic acid 2 0 ABVN 2,2'-azobis(2,4-dimethylvaleronitrile) polymerization i~ or ACL acrolein ADH adipoyl dihydrazide BA n-butyl acrylate BDA 1,4 butanediol diacrylate BrijO-92 polyo~syt~ ylene (2) oleyl ether, available from Atlas Chemical Industries DAACM diacetone acrylamide EA ethyl acrylate 3 o 2EHA 2-ethylhexyl acrylate WO 96/18701 PCI/US95/1~1328 HDDA 1,6 hPx~netliol diacrylate INA isononyl acrylate IOA isooctyl acrylate T ~ olo-7o 70% benzoyl peroxide polymerization initiator, available from Atochem North America MDH malonyl dihy~ zlde NaAA sodium salt of acrylic acid NVP N-vinyl pyrrolidone PluronicO F-68 nonionic s lrf~-,t~nt block copolymer of propylene oxide and ethylene oxide, available from BASF
PluronicO L-81 nonionic surf~r,t~nt block copolymer of propylene oxide and ethylene oxide, available from BASF
SiponaleO DS-10 sodium dodecylb~ e~lfQn~te anionic surfactant, available from Alcolac StandapolTM Aammonium lauryl sulfate s--rf~ct~nt available from Henkel Corporation TweenO-40 polyo~ye~l.ylene (20) sorbitan monop~lmit~te nonionic surfactant, available from ICI
2 0 America VEH vinyl 2-ethylhPY~no~te VOAc vinyl acetate X-linker crosslinker 2 5 In the examples, the par~-nthetic~l information acconll)a~lying the example number provides a s~mm~ry description ofthe composition formed in that example. The abbreviations are defined by the above sched--le. The corresponding numbers state the relative amounts of each ingredient in parts by weight where the carbonyl monomer, the base monomer, and any optional polar monomer nominally sum to 100 parts. Thus, example 1 describes the prepa,~lion of p,es~ure sensitive adhesive microparticles CG~ iSillg 98 parts by weight isooctyl acrylate, 2 parts by weight ~ cetone acrylamide, and 0.025 part by weight 1,4-b~lt~ne~1iol diacrylate.
Examples Example 1 (98:2:0.025 IOA/DAACM/BDA) A 1 liter intlPnted glass lask was cl,alged with 450 ml of deioni7ed water and
Each suspension polymerization method (whether producing hollow or solid miclopal Licles) may be modified by withholding the addition of all or some of the carbonyl monomer and/or any optional polar monomer until after polym~ri7~tion of the oil phase base monomer has been initi~tef1 In this instance, however, these components must be added to the polymerizing mixture prior to 100% conversion of the base monomer. Similarly, the internal crosslinker (if used) can be added at any time before 100% conversion to polymer ofthe monomers ofthe microparticle composition.
Preferably it is added before initiation occurs.
CA 0220s432 1997-05-lS
WO 96/18701 PCT/US95/1'1328 Once the pre~sule sensitive adhesive mic~op&llicles have been suspension poly...~ ;~e(l but while they are still dispersed in the aqueous suspension media, the polyhydrazide may be added either as an aqueous solution or as a solid powder that dissolves in the aqueous suspension media.
Other ingredients which may be optionally added to the miclol ~licle sucpçne;on following polymeri7~tion include tackifying resins, pl~cti~ rs, pi m~ntc neutralizing agents (e.g., sodium hydroxide), fillers, stabilizers, and various polymeric additives. These ingredients are incorporated in ~mountc that do not m~ter~ y adversely affect the desired propellies ofthe pressu.e sensilive adhesive miclop~licles~
Following suspension polymerization, an aqueous s.-cr~oncion ofthe plessule sensitive adhesive microp~ licles is obtained. The suspension may have a non-volatile solids col-le -ls of from about 10 to 50 percent by weight. However, as e~rl~ined more fully h~-cinbelow, the properties ofthe pressure sensitive adhesive microp~licles will be diLrerenl depending on whether a polyl.yd.~ide has been included If the mic.~,psllicles were pre~ared without polyhydrazide, then the aqueous suspension of mi~i~op~. Licles may be sprayed by conventional techniques wilhoulcol,~ ing, or they may be ~ y~d from an aerosol container with suitable propellants such as ~lk~nes, ~lkene~ and chlorofluorocarbons (e.g., FreonO halocarbons from E.I.
duPont de Nemours & Co., Inc.). Useful aerosols preferably have a solids content of 2 0 about 5% to 20%, more prerelably about 10% to 16%.
The aqueous suspension may also be coated onto an app.op.iale substrate and dried. Drying may be accompli~hed under ambient conditions or, more quickly, by heating for about 3 to 20 minutes in a 60 to 110C oven, the actual time and temperature depending on the substrate. (For systems co..~S.h~ g a poly(acylhydrazide) external crosslinker, heated drying is required.) Alt~ ali~ely, the aqueous suspension of pressure sensitive adhesive mi~;~opal licles may be dried and then redispersed (with agitation if n~ce~s~, y) in common organic liquid solvents such as ethyl ~cet~te, tetrahydrofuran, heptane, 2-but~none benzene, and cyclohexane. The solvent dispersions may be sprayed or they may be coated onto a CA 0220~432 1997-0~
suitable b~ in~ and dried. However, once the microp~ ~icles have been dried, they cannot be redi~ ed in water.
If the plt;:S~iUl e sensitive adhesive mi.ilol,~ licles have been prep~ ed with polyhy-ll~ide, then the aqueous sl-~pPn.~ion of mic~ op~ licles may be sprayed by coll~P~ ;Qn~l teÇlm;1ues without cobwel)billg or they may be sprayed from an aerosol co~ r~ as describe above. In addition, the ~queo..s suspension may be coated onto an appropliale sL~sllale and dried, as described above. However, once these microspheres have been dried, they can no longer be ledis~,el~ed, either in water or collll.loll organic liquid solvents. Thus, the dried pleS:jUl`e sensitive adhesive micropal lides of the invention that include polyhydl~zide may be regarded as solvent indispersible.
While not wishing to be bound by any particular theory, it is believed that the polyllydl~ide is e~sPnti~lly unreactive toward the micl op~ licles in s ~p~n.~i~ n However, as the water is removed from the suspension upon drying, a dehydration cQndPn~tiQn reaction occurs between the carbonyl groups provided in the miclopallicles by the carbonyl monomer and the hydrazino moieties. In pl~relled systems, this reactionproceeds at a high rate under ambient con-lition.~ and forms covalent lin~es between microparticles. In this way, the pressule sensitive adhesive micl~al licles may be regarded as inLt;ll.allically or externally cro~slin~Pd The inert nature of the polyhydra_ide when in suspension, coupled with its ability 2 0 to rapidly form interparticle covalent crosslinks between micropal ~icles when the water is removed, offers a number of important adv~nt~e~, as explained below.
As noted above, the pres~ure sensitive adhesive mi~il opal licles of the invention may be coated onto a suitable substrate. Useful substrates include paper, plastic films, cellulose acetate, ethyl cellulose, woven or nonwoven fabric formed of synthetic or 2 5 natural m~tPri~lc, metal, mPt~lli7P,d plastic films, and ceramic sheets Coating can be accomplished with a knife coater, Meyer bar coater, or an extrusion die In this manner, a wide variety of useful articles may be provided For example, a tape or a sheet which in~ ldes a flexible backing or substrate, the pressule sensitive adhesive ofthe invention on one major surface ofthe substrate, and a 3 0 low adhesion b~c~ i7P, or release coating (e.g., silicones and fluorosilicones) on the CA 0220.,432 1 997 - os - 1 ., WO 96/18701 PCTIUS9S11'1328 opposile major surface of the ~ub~l~ale can be made. The tape or sheet can be wound convolutely about itself on a core to form a sheet roll or a roll of tape. ~Ite~tively, the p.es~u-e sensilive adhesive can be applied to both major surfaces of the substrate so as to provide a double coated tape or sheet. The invention further provides a tape comprising a flexible ~ub~l-ale~ the pr~ure sensitive adhesive on one major surface ofthe sul)~llale, and a protective release liner over the exposed pressure sens;Li~te adhesive surface. A
transfer tape comprising a film of the pressure sensitive adhesive bclweell two release liners can also be made.
Because the pressu,e sensitive adhesives of the invention display eYc~ nt le ;~A~-ce to non-polar organic liquid solvents, they would be particularly desirable in providing tapes for use in e.../i.olll.lents where exposure to motor vehicle fuel is of concern, such as a fuel hose tape.
The invention will be more fully appreciated with reference to the following e~mrles which should not be viewed as limiting in scope.
Abbreviations and Tradenames Various abbreviations and tr~den~mes are used in the examples which are defined according to the following sc.he(l-lle:
AA acrylic acid 2 0 ABVN 2,2'-azobis(2,4-dimethylvaleronitrile) polymerization i~ or ACL acrolein ADH adipoyl dihydrazide BA n-butyl acrylate BDA 1,4 butanediol diacrylate BrijO-92 polyo~syt~ ylene (2) oleyl ether, available from Atlas Chemical Industries DAACM diacetone acrylamide EA ethyl acrylate 3 o 2EHA 2-ethylhexyl acrylate WO 96/18701 PCI/US95/1~1328 HDDA 1,6 hPx~netliol diacrylate INA isononyl acrylate IOA isooctyl acrylate T ~ olo-7o 70% benzoyl peroxide polymerization initiator, available from Atochem North America MDH malonyl dihy~ zlde NaAA sodium salt of acrylic acid NVP N-vinyl pyrrolidone PluronicO F-68 nonionic s lrf~-,t~nt block copolymer of propylene oxide and ethylene oxide, available from BASF
PluronicO L-81 nonionic surf~r,t~nt block copolymer of propylene oxide and ethylene oxide, available from BASF
SiponaleO DS-10 sodium dodecylb~ e~lfQn~te anionic surfactant, available from Alcolac StandapolTM Aammonium lauryl sulfate s--rf~ct~nt available from Henkel Corporation TweenO-40 polyo~ye~l.ylene (20) sorbitan monop~lmit~te nonionic surfactant, available from ICI
2 0 America VEH vinyl 2-ethylhPY~no~te VOAc vinyl acetate X-linker crosslinker 2 5 In the examples, the par~-nthetic~l information acconll)a~lying the example number provides a s~mm~ry description ofthe composition formed in that example. The abbreviations are defined by the above sched--le. The corresponding numbers state the relative amounts of each ingredient in parts by weight where the carbonyl monomer, the base monomer, and any optional polar monomer nominally sum to 100 parts. Thus, example 1 describes the prepa,~lion of p,es~ure sensitive adhesive microparticles CG~ iSillg 98 parts by weight isooctyl acrylate, 2 parts by weight ~ cetone acrylamide, and 0.025 part by weight 1,4-b~lt~ne~1iol diacrylate.
Examples Example 1 (98:2:0.025 IOA/DAACM/BDA) A 1 liter intlPnted glass lask was cl,alged with 450 ml of deioni7ed water and
5.36g of StandapolO-A s~rf~ct~nt The aqueous solution was stirred at 450 RPM andheated to 70C. A monomer formulation composed of 147g of IOA, 3g of DAAC~4 and 1 0 0.0375g of BDA was prepared. 0.643g of T.~ dolO_70 was added to the monomP.r mix.
All L.glediell~s were then added to the hot aqueous solution and the telnpel~lule was reduced to 65C. The fiask was deg~se~l with argon and allowed to react for 3 hours.
Upon cooling, a suspension of solid, tacky, acrylate micl-,p~licles was obtained with a volume average ~i~m.oter of 54 ~lm.
Example 2 (79:20:1 2EEA/NVP/DAACM) The poly..,~ ;on procedure was similar to F.Y~mple 1 except that the monomer formulation was 118.5g 2EHA, 30.0g NVP, and 1.5g DAACM. 0.45g of ABVN
polymerization in"ialor was used to suspension polymerize at 45C for S hours. Upon 2 0 cooling, a suspension of solid, tacky acrylate microparticles was obtained with a volume average di~meter of 90 llm.
E~ample 3 (99.9:0.1 IOA/DAACM) The polynæliGalion procedure was similar to Example 1 except that the monomer formulation was 149.85g IOA and 0.15g DAACM The suspension polymerization was continued for 5 hours. Upon cooling, a suspension of solid, tacly acrylate miclul)alLicles was obtained with a volume average diameter of 58 ~m.
WO 96/18701 PCI/US95/1~1328 E~ample 4 (90:10 IOA/DAACM) The poly~ ion procedure was similar to F.Y~mple 1 except that the monomer formulationwas 135gIOAand 15.0gDAACM. Thesuspensionpoly~ ionwas continued for 5 hours. Upon cooling, a suspension of solid, tacky acry-late microparticles was oblained with a volume average ~ mP~tPr of 65 ~lm.
E~ample 5 (98:2:0.025 IOA/DAACM/BDA) A 1 liter in~i~nted glass flask was ~ ,ed with 450 ml of deionized water, 3g of DAACM, and 1.79g of StandapolO-A. The aqueous solution was stirred at 450 RPM and heated to 70C. Next 147g of IOA, 4g of TweenO-40, 0.0375g of BDA, and 0.643g ofLucidolO-70 were added to the hot aqueous solution and the tempe~ re was reduced to 65C. The flask was deg~.sed with argon and the contents were allowed to suspension poly...~.;,e for 5 hours. Upon cooling, a suspension of hollow, tacky-, acry-late miclopallicles was obtained with a volume average tli~mP~ter of 38 ~lm.
E~ample 6 (98:1:1 IOA/AAtI)AACM) A 1 liter inrlçnted glass flask was ch~ed with 450 ml of deionized water and 5.36g of StandapolO-A. The ~queo~ls solution was stirred at 450 RPM and heated to 70C. Next, a monomer formulation composed of 147g of IOA, 1.5g of DAACM, and 2 0 1.5g of AA, along with 0.643g of LucidolO-70, were added to the hot aqueous solution and the te ~pe-~lule was reduced to 65C. The flask was deg~.se~ with argon and the contents were allowed to suspension polymerize for 15 hours. Upon cooling, a suspension of hollow, tacky, acrylate microparticles was obtained with a volume average rli~mP,tçrofS5 ~lm.
E~ample 7 (94:3:3 IOA/VOAc/DAACM) The polymerization procedure was similar to Example 6 except that the monomer formulation was 197.4g IOA, 6.3g VOAc, and 6.3g DAACM which were Pm~ ified into 390g of deionized water (35% solids) with 6g of StandapolO-A. 0.99g of LucidolO-70 3 0 was used as an initiator. The initiation temperature was 70C and the suspension -CA 02205432 l997-05-l5 pol~ ..;,nl;on was allowed to proceed for 8 hours. Upon cooling, a susp~n.eion of hollow, tacky, acrylate lmlCI 2~ ~icles was obtained.
E~ample 8 (98~ 0.06 VE~/NVP/DAACM/~DDA) A water-in-oil emulsion was prt,~)aled by dissolving 0. lg of HDDA, 2g of NVP, and 0.9g of Pluronic~ L-81 in 152g of VEH and then by emulsify-ing 50g of deionized water with 2g of DAACM into the above monomer llliXl~
A 1 liter indçnted resin fiask was charged with 0.5g of PluronicO F-68, 0.9g of BrijO-92, and 400g of deior~ized water. A water-in-oil-in-water emulsion was then plepa~ed by adding the above water-in-oil emulsion to the flask and ~git~tinp at 300 RPM. 0.71g of LucidolO-70 was then added to the flask, which was heated to 65C,de~sed with argon, and allowed to suspension polylne,i~e for 20 hours. Upon cooling, a suspension of hollow, tacky micl ~p~ ~icles was obtained.
Example 9 (Comparative, 100:0.025 IOA/BDA) The poly...~ ;Qn procedure was similar to FY~mrle 1 except the microparticles were prep~red without the DAACM carbonyl monomer. 150g of IOA and 0.0375g of BDA were used and the suspension polymerization was run for 5 hours. Upon cooling, a sll~p~n~ion of solid, tacky, acrylate mic, opal licles was obtained with a volume average 2 0 rli~meter of 58 llm.
Example 10 (93:5:2 IOA/EA/DAACM) 1.2g of SiponateO DS-10 was dissolved in 360g of deionized water and a monomer pre-mix comprised of 220.8g of IOA, 12g of EA, and 4.8g of DAACM. The mixture was pre-homo~ni7ed in a turbine mixer for 10 mimltes and then homogenized with a Gaulin homogenizer at 200 kg/cm2. The emulsion was charged to a 1 liter in~l~nted glass flask with 0.48g of ABVN initiator. The agitation speed was set to 335 RPM and the reactor was heated to 40C. The reactor was then deg~sed with argon to start the polyn~ aLion. Following the exotherm, the temperature was increased to 60C
3 0 and kept for 3 hours from the start of the polymerization. Upon cooling, a suspension of -CA 0220S432 1997-OS-lS
solid, tacky, acrylate mic~p~licles was obtained with a volume average r~ e~r ofapp,o~ ely 2 ~lm.
Examples 11-13 (93:5:2 IOA/l~A/DAACM) These ~ rles illustrate the use Of sllrf~c~nts other than Sil)onaleO DS-10 to emulsify the mono~ r in the water before the suspension polylnc; iGalion. The monomer composition and the method to prepare the miclopal licles were the same as in F.Y~mple 10. The s.lrf~ t~nt~ used in these examples are shown in Table 1.
Table 1 Fx~ ple Surfactant 11 4.6g LevenolO-WZ, sodium polyo~y~l}lylene (20) nonylphenyl ether sulfate from KAO
12 9.6g DemolO-EP, polymeric surfactant from KAO
13 2.4g HitenolOHS-10~HS-10), copoly,l,ti,i~ble surfactant, from Dai-ichi Kogyo Seiyaku Example 14 (89:10:1 2E~A/BA/DAACM) The polymerization procedure was similar to Example 10 except that the monomer formlll~tion was 106.8g 2EHA, 12g BA, and 1.2g DAACM and that 4.6g of LevenolO-WZ were used to emulsify into 180g of deionized water. A suspension of solid, tacky, acrylate mic, op~ ~icles was oblained with a volume average ~ m~t~r of 2 llm.
E~ample 15 (99:1 INA/ACL) 2 0 The polyl"eli~lion procedure was similar to Example 10 except that the monomer formulation was 118.8g of INA, 1.2g of ACL, and that 4.6g of LevenolTM-WZ were used to emulsify into 180g of deionized water. A suspension of solid, tacky, acrylatemicroparticles was obtained with a volume average diameter of 2 llm.
Example 16 (Comparative 85:15 2EIIA/DAACM) The polym~ri7~tion procedure was similar to Example 10 except that the monoll~e formul~ti~-n was 102g 2EHA and 18g DAACM and that 4.6g of LevenolO-WZ was used - to emulsify into 180g of deionized water. A suspension of solid, acrylate micropallicles was obl~ined with a volume average di~"~ of 2 lum.
Example 17 (Comparative 98:1:1 IOA/AAIDAACM) A 0.5 liter in~l~.nted glass flask was ch~ged with 122 ml of de;oni7ed water, 3.57g of StandapolO-A, 98.0g of IOA, 1.0g of DAACM, 1.0g of AA, and 0.167g of ~mmt nil-m 1 0 persulfate, a water soluble emulsion polymerization initi~tor. The emulsion was stirred at 250 RPM and heated to 60C. The flask was degassed with argon and the colllelll~ were allowed to emulsion polyll,eliGe for 3 hours. Upon cooling, an emulsion oftacky, acry-late polymer was obtained with a volume average particle size of 0.1 llm. Example 17 is col~lposilionally the same as FY~ le 6. However, it was prepaled by emulsion 1 5 polym~ri7~tion rather than suspension polymerization. Consequently, it uses an em~lQion polyllleli~lion iniLialor rather than the s--~pencion polym~ ion initiator of Fx;...~ple 6.
E~ample 18 (Comparative, 99:1 IOA/NaAA) The polylllt;li~alion procedure was similar to FY~mple 1 except that the monomer2 0 formulation was 148.5g IOA and 1.Sgrams AA (which was neutralized with sodium hydroxide to pH 7 before poly-merization) and the reaction was continued for 12 hours.
Upon cooling, a suspension of solid, tacly acry-late micl opal licles was obtained with a volume average rii~metP~r of 43 mm.
Example 19 (Comparative, 99:1:0.025 IOA/AA/BDA) The polymerization procedure was similar to Example 1 except that the monomer formulation was 148.5g IOA, 1.5g AA and 0.0375g BDA. The rêaction was continued for S hours. Upon cooling, a suspension of hollow, tacly acry1ate micl opa~ licles was obtained with a volume average di~met~r of 52 mm.
E~mple 20 (93:5:2:0.1 IOA/EAtDAACM/HDDA) The poly...~ ;on procedure was similar to F.Y~mple 11 except that 0.24g of HDDA was added to the monomer form~ tion. Upon cooling, a suspension of solid, tacky acrylate miclup~licles was obtained with a volume average rli~met~r of 1.5 mm.
Example 21 (Comparative, 90:10 IOA/DAACM) The polyll,e,~lion procedure was similar to F.Ys.."ple 17 except that the monomer formulation was 90g IOA and 10g DAACM. Upon cooling, an emulsion of tacky acrylate polymer was obtained with a volume average particle size of 0.1 mm.
E~ample 22 (Comparative, 98:2:0.025 IOAIDAACMIBDA) The polym~ri7~tion procedure was similar to FY~mple 17 except that the monomer formlll~tion was 98g of IOA, 2g of DAACM and 0.025g of BDA. Upon cooling, an emulsion of tacky acrylate polymer was obtained with a volume average particle size of 0.1 mm.
E~ample 23 (Comparative, 79:20:1 2EEA/N~/DAACM) The polymerization procedure was similar to Exa~ )le 17 except that the monomer formulation was 79g 2EHA, 20g NVP, and lg DAACM. Upon cooling, an emulsion of 2 0 tacky acrylate polymer was obtained with a volume average particle size of 0.1 mm.
Some of the foregoing examples were evaluated to determine whether they could be externally or interpartically cro.cclink~l Evidence for external or interparticle cros.clinkin~ can be obtained by alLt;lll,uling to disperse air dried lumps of the mic,opa,licles in heptane. Mi~;lop~licles that have been externally croc.clink~d will not 2 5 disperse; microparticles that are not externally crosslinked will disperse. More specifically, Examples 1 to 3, 5, 7 to 10, 18 and 19 were dried with and without the presence of 9.46 meq/loog of microparticle (0.824 g/lOOg of miclopalLicle) of ADH
external crosslinker and put into vials of heptane and shaken for 1~ hours. The results are shown below in Table 2.
CA 0220~432 1997-05-1~
Table 2 r.Y~ le Without Crosslinker With Crosslinker Dispersed (sep~aled Swollen but not dispersed spheres) 2 Dispersed (separatedSwollen but not dispt;l~ed spheres) 3 Dispersed (separ~led Swollen but not dispersed spheres) S Dispt;l~ed (sepalaledSwollen but not dispersed spheres) 7 Dispersed (sepalaled Swollen but not dispersed spheres) 8 Dispersed (separated Swollen but not dispersed spheres) 9 Dispersed (separated Dispersed (separated spheres) spheres) Dispersed Swollen but not dispersed (se,~al~led spheres) 18 Dispersed (separated Dispersed spheres) (separated spheres) 19 Dispersed (sepal~,led Dispersed spheres) (separated spheres) Table 2 shows that without the presence of the added, external crosslinker, the microp~Licles from F.Y~mrles 1 to 3, 5, 7 to 9, 18 and 19 dispersed in heptane. FY~mple 10 appealed to be a tliuls~elll, viscous solution because the miclopallicles were very small and highly swollen. However, the entire material could not be passed through a paper filter in~lie~tin~ that a dispersion rather than a true solution had formed. When the ADH external cros~linker was added, Examples 1 to 3, 5, 7, 8 and 10 did not disperse.
The lumps of mi-irop~ licles rem~ine~l in tact and did not break up or disperse in the heptane. This can be seen with the naked eye or, for smaller micropal licles, through an optical microscope. However, Examples 9, 18 and 19 did disperse since they did not contain a ca l,ol,yl monomer.
These eY~mples show that the combined presence of the carbonyl monomer and polyhydlazide external crosslinker results in pressure sensitive adhesive compositions that are indispersible in non-polar organic liquid solvents (e.g. heptane) once dried. As a CA 0220~432 1997-0~
WO 96/18701 PCT/US95/1~1328 result, these adhesives have improved re~iet~nce to solvents (especially non-polar organic liquid solvents) since the miclul)~u Licles will not disperse in the solvent.
Preparation of Pressure Sensitive Adhesive Tapes In the following examples, s~1ected micropa. licle compositions from Examples 1 to 23 were used to prepare pressure sel~silive adhesive tapes.
Example 24 The mi~ palLicle suspension of F.Y~mple 1 was permitted to sit overnight and sep~ale into two phases. The miclop~licle rich cream (55.7% solids) that rose to the top was isolated. 0.412 g/lOOg miclop~Lides of ADH external croe.elink~r (4.73 meq/lOOg microparticle) was added to the cream in the form of a 10% aqueous solution of ADH. A pres~ure sensilive adhesive tape was prepared by coating this mixture onto 1.5 mils thick primed (with an ~ (ed polybl.t~ ne) polyester film with a knife coater to a 4 mils wet thirL~n~ss and drying in an oven at 105C for 15 I--;----les Thenficl ~Jp~ licles were observed with an optical microscope to be continuously coated on the polyester film (i.e., adjacçnt miclu?~Licles touched one another~.
E~cample 2~
2 0 The micropal licle suspension of Example 2 was allowed to sit overnight and sep~le into two phases. The miclup~licle rich sedim~nt that settled to the bottom was isolated. 4.73 meq/lOOg miclop~licles of ADH external crosslinkerwas added to the se~lim~nt in the form of a 10% aqueous solution of ADH. A pl t;S~ul e sensitive adhesive tape was pl~aled as described in Example 24 except that the polyester film was provided with a 10 mils thick wet coat.
E~ample 26 A pl es~ure sensitive adhesive tape was prepared as described in Example 24 except using the microparticle suspension of Example 3 and 52.0 meq/100 g of microparticles of 3 0 ADH eYt~rn~l crosslinker.
A
Example 27 A pressure sensitive adhesive tape was p.~ared as described in Example 24 exceptusing the mielopa licle ~u~s~clls;on of E~ plc 4 and 4.73 meq/100 g of mic.opallicles of ADH eytern~l crosslinker.
Example 28 A pleS~ule sensilive adhesive tape was prepared as described in Fx~mrle 24 except using the ~ c~op~licle ~ùs~ension of Example 5 and 4.73 meq/100 g of mi~;.opa Licles of ADH external cros~ el.
E~ample 29 A pre~u.~ sensitive adhesive tape was pl~;pared as described in F.Y~mple 24 except using the mi~;ropa Licle suspension of Ex~lplc 6 and 5.77 meq/100 g of mic-op~lides of ADH external crosslinker.
E~ample 30 (Comparative E~ample) A plt;S:iUI~ sensitive adhesive tape was p.~;pared as described in Fx~mple 24 except using the mi~ilu~icle suspension of FY~mrle 9 and without using any ADH ~Ytern~
2 0 cros~linl ~r.
Example 31 The mic~op~icle suspension of Example 11 was thi~ened with 0.2 wt% (based on the weight of the micropal Licles) of Rheology Modifier QR-708 (Rohm and Haas) and 0.5 g/1OOg mic opalLicles of MDH external crosslinker (7.58meq/lOOg polymer) wasadded. The mixture was coated onto polypropylene film with a knife coater to a wet thickness of 3 mils and dried in an oven at 1 00C for 5 minlltes CA 0220s432 lss7-o~
wo 96/18701 Pcr/uss5/l4328 Example 32 A p.es~ule se"silive adhesive tape was p,ep&ed as described in Example 31 exceptusing the miclop~licle ~l~ension of F.Y~mrle 13 and 5.74 meq/lOOg microp~licles of ADH PYtern~l cros~lil~el.
Example 33 A p-es~ule sellsiLive adhesive tape was p,~a~ed as described in FY;~ e 31 exceptusing the micl.)p~Lide sl~p~ncic)n of FY~mple 14 and 2.87 meq/lOOg microp~licles of ADH eYtPrn~l crosslin~P,r.
E~ample 34 A pres~ure sen~iLive adhesive tape was prepaled as described in Example 31 except using the miclop~Licle suspension of Example 15 and 2.87 meq/lOOg mic~op~licles of ADH eyt~rn~l crosslinker.
Example 35 (Comparative E~ample) A tape was pl~;paled as desc,il.ed in F~y~mple 31 except using the micl op~u licle suspension of FY~mple 16 and 5 74 meq/lOOg microparticles of ADH external crosslinker.
Examples 36 to 40 A series of CA~1II~1CS was plep~t;d to evaluate the effect of varying the amount of polyhydlazide external cro~linking agent. More speçific~lly, 0 5 wt% (based on the weight ofthe micropa.licles) of UCARO Poly-phobeO 104 (Union Carbide) thiçkP.ner was 2 5 added to the mic~upal licle suspension of Example 11 and neutralized with NH~OH to obtain a dispersion having a coatable viscosity. Di~l~llL levels of ADH crosslinker (see Table 4) were added to the thi~ ned microparticle suspension and the resultinp~ material was coated onto 1.5 mils primed polyester film to a wet thickness of 6 to 8 mils with a knife coater and then dried in an oven at 105C for 5 min~tes E~ample 41 0.16g of CarbopolO 690 (polyacrylic acid thir~nin~ agent from BF Goodrich) was dissolved in 50g of cleioni7ed water and the res llting thi~ ner solution was then neutralized with 6% aqueous lithium hydroxide. To the neutralized thi.~ nçr solution, 12g ofthe rl,iclop~licle s~p~n~ion (25% solids) of F.Y~mrle 5 (modified with 9.46 meq/l OOg rnicroparticles of ADH external crosclint~r) and 3.25g of the microparticle suspension (40% solids) of F.Y~mrle 10 (mo-1ified with 9.46 meq/lOOg miclopa.~icles of ADH external cros~ .L ~ ) were added. A pressure sensitive adhesive tape was prepared as ~es ~ ecl in co~ cl;Qn with FY~mrle 24 except that the polyester film was coated to 1 0 a 3 mils wet thiclfn~
Example 42 (Comparative Example) To the neutralized thickener solution in Exarnple 41, 12g of the micropA . liclesu*.ens;on (25% solids) of F.Y;~ 1e 9 (modified with 9.46 meq/lOOg miclopa.licles of ADH external crosslinker) and 3.25g ofthe miclup~licle suspension (40% solids) of Example 10 (modified with 9.46 meq/lOOg micropA~licles of ADH external cros~lin~er) were added. A pressure sensitive adhesive tape was plt;paled as described in conj~ ;on with FY~mrle 24 except that the polyester film was coated to a 4 mils wet thi~n~s~
2 0 ~ mple 43 (Comparative Example) A p.es~ule sensitive adhesive tape was prepared by adding 5.77 meq/lOOg of miclupAl licles of ADH eternal crosslinker to the emulsion of compa.~ti~re exarnple 17, coating this material onto 1.5 mils primed (with an A...i.-~ed polybutadiene) polyester film to a wet thickness of 6 mils with a knife coatèr, and oven drying at 105C for 5 minl~tes E~ample 44 A pressure sensitive adhesive tape was prepared as described in Fx~mrle 24 but - without using any ADH external crosslinker.
3 0 Example 45 (Comparative) CA 0220s432 l997-OS-lS
WO 96tl8701 PCI`NS95/14328 A presSu- e sens;livt; adhesive tape was p~pared as described in Example 24, except using the micr~p~licle suspension of Example 18 and 4.73 meq/ lOOg mic,opallicles of ADH eYt~rnAl crosslinker.
Esample 46 (Comparative) A pre~ule sel~silive adhesive tape was p-~aled as described in Example 45 but without using any ADH ~YtPrn~l c-~s~
Esample 47 (Comparative) A prtS~Ule sensitive adhesive tape was prepal-ed as described in FY~mrle 28 but will~oul using any ADH çQ~ern~l crosslinker.
Esample 48 (Comparative) A p~s~u-e sensitive adhesive tape was p.epared as described in Fx~mrle 24, except using the mic~op~licle ~usl~ension of Fx~mple 19 and 4.73 meq/ lOOg ---cropal licles of ADH external crosslinker.
E~ample 49 (Comparative) A pres~u.e sensili~e adhesive tape was prepared as described in Fx~mple 48 but 2 0 without using any ADH external cros.clin~Pr.
Esample 50 Example 50 was plepa~ed as described in Example 37, except using the microp~ licle suspension of Example 20.
l:sample 51 (Comparative) A pl~S~Ult; sensitive adhesive tape was prepaled as described in Example 43, except using the emulsion of Example 21 and 4.73 meq/ lOOg polymer of ADH P.xtern~l crosslinker.
CA 0220~432 1997-0~-15 wo 96/18701 PCT/US95/14328 Example 52 (Comparativej A pressure sensiliv~; adhesive tape was p~ared as described in FY;..~.ple 43, except using the emulsion of E~ample 22 and 4.73 meq/ lOOg pol,vmer of ADH external crosslinker.
E~ample 53 (Coml.&~dli~e) A pres~ule sensitive adhesive tape was prepared as desclil,ed in FY~mrle 43, except using the emulsion of Fx~mple 23 and 4.73 meq/ lOOg polymer of ADH ~Ytem~l crosslinker.
The tapes of examples 24 to 53 were then evaluated for tack, peel adhesion (to glass and paper), adhesive ~ srel (to glass and paper), and whether they tore paper upon removal. The test procedures are described below and the results are shown in Table 3.
Examples 36 to 40 were further evaluated for shear strength using the test method 0~ below. Results are reported in Table 4. Selected c~ r,les were evaluated for solvent rçcictance using the test method outlined below and with the results shown in Table 5.
Test Methods Tack 2 0 The tack of the pres~lre sensitive adhesive tapes was measured with a Polyken Probe Tack Tester (available from Ken-l~ll Conlpany) according to American Society for Testing and Materials Test Method ASTM D2979-88. A~er cleaning the probe with methyl ethyl ketone using a lint-free cloth, a 2 cm x 2 cm sample of the tape was placed on the annular ring weight of the Polyken appar~ s. The tack was then measured using a 2 5 10 mm stainless steel probe having a ~i~meter of 0.4975 cm with a speed of 1 cm/sec. and a dwell time of 1 sec. The pressure sensitive adhesives of the invention preferably show a probe tack of at least 25 g, more preferably at least 50 g, and most preferably at least 100 g. The tack that is ~ltim~tçly desirable will depend on the int~n~ed use for the adhesive.
3 0 Peel Adhesion and A~ e Transfer CA 0220~432 1997-o~
WO 96/18701 PCT/US95tl4328 180 peel adhesion of the tapes was measured with a model 3M90 slip/peel tester (Instrumentors, Inc.) accolding to Test Methods for P~ ule Sensitive Tapes, PSTC-1, prom~ ted by the Pl~;s~ule Sensitive Tape Council. More sperifirzlly~ the adhesive surface of a 1 in. x 6 in. strip of tape was placed in contact with a glass plate or a piece of paper (plain, 20# white bond paper used in photocopy m~r.hines) and rolled down with one pass of a 2 kg roller. The strip of tape was then imm~rli~t~ly removed at an angle of 180 to the surface of the glass plate or the piece of paper using a removal speed of 90 in./minute. The force of removal was measu.ed and recorded in oz.rmch width. Once the tape had been ~ oved, the adherend surface was observed (visually and by finger touch) to assess whether there had been any adhesive ~ sre, . An obsel v~ion of no adhesive means that no adhesive residue could be detected on the ~ubs~ e, either visuallyor by finger touch. Useful pressu,e sensitive adhesives should display a peel ~h~ion of at least 0.3 oz.~m., preferably at least 0.5 oz./in.. They should also show no adhesive Ll~l~l. The ~ y desirable peel adhesion will depend on the int~nfled use for the1 5 adhesive.
Also recorded was whether the paper tore upon removal ofthe tape. S~mp'es were tested twice. A "no" entry indicates that the paper did not tear for either sample. A
"yes" entry in~ic~tes that the paper tore for both s~mples "SometimPs" means that the paper tore once. If the paper tore both times, adhesive transfer to the paper was not 2 0 ev~ ted Shear Strength Shear strength was measured in accordance with Test Methods for Pressure Sensitive Tapes, PSTC-7, promlllg~ted by the ~es~u.~ Sensitive Tape Council. More 2 5 specifically, a 0.5 in. x 0.5 in. end portion of a tape strip measuring 5 in. x 0.5 in. was adhered to a bright, annealed steel test panel and rolled down with six passes of a 2 kg rubber roller. The panel was then mounted in a jig vertically with the 4.5 in. free end of the tape h~nging down. A 500g mass was suspended from the free end of the tape and the time that elapsed until the tape separated from the panel was recorded in mimltes 3 0 The test was discontinued if separation had not occurred after 10,000 minlltes -;rt;lably, the pre~sule sensitive adhesives of the invention display a shear sl. ~n~lh in excess of 10,000 mim-tes The u~ ely desirable shear ~ n~lh will depend on the int~n-led use for the adhesive.
Solvent 12~s;st~nce A 1 inch x 1 inch sample of tape was immersed in various solvents (hepla~e, ~ceton~, iso-propyl alcohol (IPAj, and water) for 15 hours, removed from the solvent, and dried. The condition of the adhesive layer on the bac~in~ was obse, ved with the results shown in Table 5 where a "yes" entry under the particular solvent intlie~tes that sufficient adhesive was retained on the b~ in,~ for the tape to be used again and where a "no" entry in~ tes that the adhesive layer was deteriorated by the solvent to the point that the sample was no longer useful as a pressure sensitive adhesive tape.
Table 3 Example X-linkerl Coating Probe A&esion Adhesive Adhesion Paper A&esive (meq./ Weight Tack to Transfer to Tearing Transfer 100g (~/m2) (g) Glass to Paper to micro- (oz/in) Glass(oz/in) Paper particles 24 4.73 63.0 412 15.5 No 24.2 No No (98:2:0.025IOA/
DAACM~BDA) 4.73 106.0 502 46.0 No 46.0 No No (79:20: 12EEIA~VP/
DAACM) 26 52.0 71.1 224 11.8 No 25.7 No No (99.9:0.1 IOA/DAACM) 27 4.73 54.9 127 1.9 No 5.9No No (90: 10 IOA~DAACM) 28 4.73 47.5 335 4.1 No 23.2 No No (98:2:0.025IOA/DAACM~
BDA) 29 5.77 44.0 241 7.2 No 8.1No No (98: 1: IIOA/AA/DAACM) - 57.0 356 10.3 Yes 25.4 No Yes (100:0.025 IOA/13DA) 31 7.58 29.9 593 30 No 27 No No (93 :5 :2IOA/EA/DAACM) 32 5.74 27.3 488 42 No 28 No No (93:5:2: IIOA/EA/
DAACMiIIS-10) 33 2.87 32.9 523 35 No 29 No No (89: 10: 12EHA~BA/
CA 0220~432 1997-0~
Example X-linker' Coating Probe A&esion A&esive A&esion Paper A&esive (meq./ Weight Tack to TIansferto Tearing Transfer 100g ~/m2) (g) Glass to Paper to micro- (oz/in) Glass (oz/in) Paper particles DAACM) 34 2.87 28.8 405 16 No 27 No No (99:1 INA/ACL) 5.74 22.6 0 0 No O No No (85: 15 2EHAIDAACM) 36 -- 41.1 781 40.1 No 32.8 S~ne- No (93:5:2IOA/EA/DAACM) times 37 0.5 39.6 755 38.2 No 37.1 Some- No (93:5:2IOA/EA/DAACM) times 38 10 39.2 792 37.5 No 40.2 No No (93 :5 :210A/EA/DA~
39 100 33.8 142 28.5 No 0.4 No No (93 :5 :2IOAIEA/DAACM) 200 33.6 0 0 No O No No (93 :5 :2IOA/EA/DAACM) 41 9.46 4.4 113 1.' No 1.7 No No 42 9.46 3.0 96 1.~ Yes 1.3 No Yes 43 5.77 50.1 697 29. No 17.3 Yes (98: 1: lIOA/AA/DAACM) 44 -- 55.8 290 14.4 No 20.2 Some- Yes (98:2:0.025 times IOA/DAACM/BDA) 4.73 63.0 291 8.4 No 24.9 No Yes (99:1 IOA/NaAA) 46 -- 69.5 256 6.1 No 23.5 No Yes (99:1 IOA/NaAA) 47 54.5 300 1.1 No 12.1 No Yes (98:2:0.025 IOA/DAAC~BDA) 48 4.73 51.3 321 13.1 No 21.4 No No (99:1:0.025 IOA/AA/BDA) 49 -- 61.7 384 13.0 No 26.3 No Some-(99:1:0.025 times IOA/AA/BDA) 0.5 35.6 597 22.3 No 25.6 No No (93:5:2:0.1 IOA/EA/DAACM;/
HDDA) 51 4.73 46.9 835 31.0 No 20.1 Yes *
(90:10 IOA/DAACM) 52 4.73 46.4 558 15.6 No 10.9 Yes *
(98:2:0.025 IOA/DAACI~JBDA
53 4.73 50.7 1260 49.3 No 9.5 Yes *
(79:20:1 2EHA/NVP/DAACM) =
CA 02205432 1997-os-ls WO 96/18701 PCT/US9Sl14328 I
X-linker = ~l~h~ide external ~ ' ng agent *Ol~w~ notmade Table 4 Example X-linker' (meq./lOOgShearHoldingTime polymer) (min.) (93:5:2 IOA/EA/DAACM) 37 0.5 >10,000 (93:5:2 IOA/EA~DAACM) 38 10 >10,000 (93:5:2 IOA/EA/DAACM) 39 100 >10,000 (93:5:2 IOA/EA/DAACM) (93:S:2 IOA/EA/DAACM) ~X-linker = pol~h.~ide external Cl~ ' ' g agent Table 5 F. .'- External Coating leptane IPA Acetone WaterCl~ 1 Weight ~ G R~ e Re,~ e R~
Present (g/m2) No 57.0 No No No Yes (100:0.025 IOA/BDA) Yes 63.0 No Yes Yes Yes (99:1 IOA/NaAA) 46 No 69.5 No Yes Yes Yes (99:1 IOA/NaAA) 28 Yes 47.5 Yes Yes Yes Yes (98:2:0.025 IOA/DAAC~/BDA) ,~
47 No 54.5 No No No Yes (98:2:0.025 IOA/DAAC~/BDA) 29 Yes 44.0 Yes Yes Yes Yes (98:1:1 IOA/AA/DAACM) 48 Yes 51.3 No Yes Yes Yes (99:1:0.025 IOA/AA/BDA) 49 No 61.7 No Yes Yes Yes (99:1:0.025 IOA/AA/BDA) 38 Yes 39.2 Yes Yes Yes Yes CA 0220~432 1997-o~
WO 96/18701 PCTÇUS9~tl~328 ¦ (93:5:2 The eY~mrles d~mon~trate that the co.l.bh~ed presence of a carbonyl monomer and a polyl.yd.~ide P~Prn~l croscli~ g agent results in removable pressure sensiliveadhesives that have reduced adhesive t-~u~srer~ good adhesion, and solvent re~ nr~e Example 30 which inr~ led neither the c~l,o..yl monomer nor the polyl.yd-~ide showed good adhesion and removability but suffered from adhesive ~ srcr. Fx~mple 36 which added the carbonyl monomer but lacked the polyl.yd.~ide did not have adhesive L.~.srcr but was not removable. See also Examples 24 (c~l,o.lyl monomer and external crosslinker) and 44 (carbonyl monomer but no PYtPrnRl crosslinker) Example 24 shows reduced adhesive ~.~.src. to paper, an h~Gl~ substrate. Similarly, Example 47 (carbonyl monomer but no external crosslinker) shows adhesive transfer to paper while Example 28 (which adds the external crosslinker) does not show adhesive transfer to paper. Fx~mple 35 shows that using excess carbonyl monomer results in a material not having p~c~u~e sensitive adhesive pl~pcllies Examples 29 and 43 may be co--.paled Example 29 shows a useful, removable, pres~u.c sensit*e adhesive that does not display adhesive ~.~nsrCl In Fx~mrle 43 the same composition was emulsion poly...e.i,ed (rather than suspension poly.ne.i~ed) and a removable adhesive was not obtained. Other e~mrle pairs may be similarly ço.npaled.
See Examples 27 (suspension) and 5 l (emulsion), 24 (suspension) and 52 (emulsion), and 25 (suspension) and 53 (emulsion).
2 0 Examples 36 to 40 show the effect of varying the amount of polyhydrazide cros~linkin~ agent Example 36, having no polyl-yd-~de, exhibited limited shear strength Example 40, having excess polyhydrazide, showed no shear strength Table 5 shows the improved solvent resi~t~nre to a broad spectrum of solvents shown by the adhesive compositions that include both the carbonyl monomer and the polyhydl~zide external crosslinking agent Only the pressure sensitive adhesives ofthe invention dPmnnctrated resistance to heptane, a solvent representative of non-polar organic liquids Reasonable variations and modifications are possible within the scope of the rolt;going spe~ific~tion without departing ~om the invention which is defined in the accGIl~p~yil.g claims.
All L.glediell~s were then added to the hot aqueous solution and the telnpel~lule was reduced to 65C. The fiask was deg~se~l with argon and allowed to react for 3 hours.
Upon cooling, a suspension of solid, tacky, acrylate micl-,p~licles was obtained with a volume average ~i~m.oter of 54 ~lm.
Example 2 (79:20:1 2EEA/NVP/DAACM) The poly..,~ ;on procedure was similar to F.Y~mple 1 except that the monomer formulation was 118.5g 2EHA, 30.0g NVP, and 1.5g DAACM. 0.45g of ABVN
polymerization in"ialor was used to suspension polymerize at 45C for S hours. Upon 2 0 cooling, a suspension of solid, tacky acrylate microparticles was obtained with a volume average di~meter of 90 llm.
E~ample 3 (99.9:0.1 IOA/DAACM) The polynæliGalion procedure was similar to Example 1 except that the monomer formulation was 149.85g IOA and 0.15g DAACM The suspension polymerization was continued for 5 hours. Upon cooling, a suspension of solid, tacly acrylate miclul)alLicles was obtained with a volume average diameter of 58 ~m.
WO 96/18701 PCI/US95/1~1328 E~ample 4 (90:10 IOA/DAACM) The poly~ ion procedure was similar to F.Y~mple 1 except that the monomer formulationwas 135gIOAand 15.0gDAACM. Thesuspensionpoly~ ionwas continued for 5 hours. Upon cooling, a suspension of solid, tacky acry-late microparticles was oblained with a volume average ~ mP~tPr of 65 ~lm.
E~ample 5 (98:2:0.025 IOA/DAACM/BDA) A 1 liter in~i~nted glass flask was ~ ,ed with 450 ml of deionized water, 3g of DAACM, and 1.79g of StandapolO-A. The aqueous solution was stirred at 450 RPM and heated to 70C. Next 147g of IOA, 4g of TweenO-40, 0.0375g of BDA, and 0.643g ofLucidolO-70 were added to the hot aqueous solution and the tempe~ re was reduced to 65C. The flask was deg~.sed with argon and the contents were allowed to suspension poly...~.;,e for 5 hours. Upon cooling, a suspension of hollow, tacky-, acry-late miclopallicles was obtained with a volume average tli~mP~ter of 38 ~lm.
E~ample 6 (98:1:1 IOA/AAtI)AACM) A 1 liter inrlçnted glass flask was ch~ed with 450 ml of deionized water and 5.36g of StandapolO-A. The ~queo~ls solution was stirred at 450 RPM and heated to 70C. Next, a monomer formulation composed of 147g of IOA, 1.5g of DAACM, and 2 0 1.5g of AA, along with 0.643g of LucidolO-70, were added to the hot aqueous solution and the te ~pe-~lule was reduced to 65C. The flask was deg~.se~ with argon and the contents were allowed to suspension polymerize for 15 hours. Upon cooling, a suspension of hollow, tacky, acrylate microparticles was obtained with a volume average rli~mP,tçrofS5 ~lm.
E~ample 7 (94:3:3 IOA/VOAc/DAACM) The polymerization procedure was similar to Example 6 except that the monomer formulation was 197.4g IOA, 6.3g VOAc, and 6.3g DAACM which were Pm~ ified into 390g of deionized water (35% solids) with 6g of StandapolO-A. 0.99g of LucidolO-70 3 0 was used as an initiator. The initiation temperature was 70C and the suspension -CA 02205432 l997-05-l5 pol~ ..;,nl;on was allowed to proceed for 8 hours. Upon cooling, a susp~n.eion of hollow, tacky, acrylate lmlCI 2~ ~icles was obtained.
E~ample 8 (98~ 0.06 VE~/NVP/DAACM/~DDA) A water-in-oil emulsion was prt,~)aled by dissolving 0. lg of HDDA, 2g of NVP, and 0.9g of Pluronic~ L-81 in 152g of VEH and then by emulsify-ing 50g of deionized water with 2g of DAACM into the above monomer llliXl~
A 1 liter indçnted resin fiask was charged with 0.5g of PluronicO F-68, 0.9g of BrijO-92, and 400g of deior~ized water. A water-in-oil-in-water emulsion was then plepa~ed by adding the above water-in-oil emulsion to the flask and ~git~tinp at 300 RPM. 0.71g of LucidolO-70 was then added to the flask, which was heated to 65C,de~sed with argon, and allowed to suspension polylne,i~e for 20 hours. Upon cooling, a suspension of hollow, tacky micl ~p~ ~icles was obtained.
Example 9 (Comparative, 100:0.025 IOA/BDA) The poly...~ ;Qn procedure was similar to FY~mrle 1 except the microparticles were prep~red without the DAACM carbonyl monomer. 150g of IOA and 0.0375g of BDA were used and the suspension polymerization was run for 5 hours. Upon cooling, a sll~p~n~ion of solid, tacky, acrylate mic, opal licles was obtained with a volume average 2 0 rli~meter of 58 llm.
Example 10 (93:5:2 IOA/EA/DAACM) 1.2g of SiponateO DS-10 was dissolved in 360g of deionized water and a monomer pre-mix comprised of 220.8g of IOA, 12g of EA, and 4.8g of DAACM. The mixture was pre-homo~ni7ed in a turbine mixer for 10 mimltes and then homogenized with a Gaulin homogenizer at 200 kg/cm2. The emulsion was charged to a 1 liter in~l~nted glass flask with 0.48g of ABVN initiator. The agitation speed was set to 335 RPM and the reactor was heated to 40C. The reactor was then deg~sed with argon to start the polyn~ aLion. Following the exotherm, the temperature was increased to 60C
3 0 and kept for 3 hours from the start of the polymerization. Upon cooling, a suspension of -CA 0220S432 1997-OS-lS
solid, tacky, acrylate mic~p~licles was obtained with a volume average r~ e~r ofapp,o~ ely 2 ~lm.
Examples 11-13 (93:5:2 IOA/l~A/DAACM) These ~ rles illustrate the use Of sllrf~c~nts other than Sil)onaleO DS-10 to emulsify the mono~ r in the water before the suspension polylnc; iGalion. The monomer composition and the method to prepare the miclopal licles were the same as in F.Y~mple 10. The s.lrf~ t~nt~ used in these examples are shown in Table 1.
Table 1 Fx~ ple Surfactant 11 4.6g LevenolO-WZ, sodium polyo~y~l}lylene (20) nonylphenyl ether sulfate from KAO
12 9.6g DemolO-EP, polymeric surfactant from KAO
13 2.4g HitenolOHS-10~HS-10), copoly,l,ti,i~ble surfactant, from Dai-ichi Kogyo Seiyaku Example 14 (89:10:1 2E~A/BA/DAACM) The polymerization procedure was similar to Example 10 except that the monomer formlll~tion was 106.8g 2EHA, 12g BA, and 1.2g DAACM and that 4.6g of LevenolO-WZ were used to emulsify into 180g of deionized water. A suspension of solid, tacky, acrylate mic, op~ ~icles was oblained with a volume average ~ m~t~r of 2 llm.
E~ample 15 (99:1 INA/ACL) 2 0 The polyl"eli~lion procedure was similar to Example 10 except that the monomer formulation was 118.8g of INA, 1.2g of ACL, and that 4.6g of LevenolTM-WZ were used to emulsify into 180g of deionized water. A suspension of solid, tacky, acrylatemicroparticles was obtained with a volume average diameter of 2 llm.
Example 16 (Comparative 85:15 2EIIA/DAACM) The polym~ri7~tion procedure was similar to Example 10 except that the monoll~e formul~ti~-n was 102g 2EHA and 18g DAACM and that 4.6g of LevenolO-WZ was used - to emulsify into 180g of deionized water. A suspension of solid, acrylate micropallicles was obl~ined with a volume average di~"~ of 2 lum.
Example 17 (Comparative 98:1:1 IOA/AAIDAACM) A 0.5 liter in~l~.nted glass flask was ch~ged with 122 ml of de;oni7ed water, 3.57g of StandapolO-A, 98.0g of IOA, 1.0g of DAACM, 1.0g of AA, and 0.167g of ~mmt nil-m 1 0 persulfate, a water soluble emulsion polymerization initi~tor. The emulsion was stirred at 250 RPM and heated to 60C. The flask was degassed with argon and the colllelll~ were allowed to emulsion polyll,eliGe for 3 hours. Upon cooling, an emulsion oftacky, acry-late polymer was obtained with a volume average particle size of 0.1 llm. Example 17 is col~lposilionally the same as FY~ le 6. However, it was prepaled by emulsion 1 5 polym~ri7~tion rather than suspension polymerization. Consequently, it uses an em~lQion polyllleli~lion iniLialor rather than the s--~pencion polym~ ion initiator of Fx;...~ple 6.
E~ample 18 (Comparative, 99:1 IOA/NaAA) The polylllt;li~alion procedure was similar to FY~mple 1 except that the monomer2 0 formulation was 148.5g IOA and 1.Sgrams AA (which was neutralized with sodium hydroxide to pH 7 before poly-merization) and the reaction was continued for 12 hours.
Upon cooling, a suspension of solid, tacly acry-late micl opal licles was obtained with a volume average rii~metP~r of 43 mm.
Example 19 (Comparative, 99:1:0.025 IOA/AA/BDA) The polymerization procedure was similar to Example 1 except that the monomer formulation was 148.5g IOA, 1.5g AA and 0.0375g BDA. The rêaction was continued for S hours. Upon cooling, a suspension of hollow, tacly acry1ate micl opa~ licles was obtained with a volume average di~met~r of 52 mm.
E~mple 20 (93:5:2:0.1 IOA/EAtDAACM/HDDA) The poly...~ ;on procedure was similar to F.Y~mple 11 except that 0.24g of HDDA was added to the monomer form~ tion. Upon cooling, a suspension of solid, tacky acrylate miclup~licles was obtained with a volume average rli~met~r of 1.5 mm.
Example 21 (Comparative, 90:10 IOA/DAACM) The polyll,e,~lion procedure was similar to F.Ys.."ple 17 except that the monomer formulation was 90g IOA and 10g DAACM. Upon cooling, an emulsion of tacky acrylate polymer was obtained with a volume average particle size of 0.1 mm.
E~ample 22 (Comparative, 98:2:0.025 IOAIDAACMIBDA) The polym~ri7~tion procedure was similar to FY~mple 17 except that the monomer formlll~tion was 98g of IOA, 2g of DAACM and 0.025g of BDA. Upon cooling, an emulsion of tacky acrylate polymer was obtained with a volume average particle size of 0.1 mm.
E~ample 23 (Comparative, 79:20:1 2EEA/N~/DAACM) The polymerization procedure was similar to Exa~ )le 17 except that the monomer formulation was 79g 2EHA, 20g NVP, and lg DAACM. Upon cooling, an emulsion of 2 0 tacky acrylate polymer was obtained with a volume average particle size of 0.1 mm.
Some of the foregoing examples were evaluated to determine whether they could be externally or interpartically cro.cclink~l Evidence for external or interparticle cros.clinkin~ can be obtained by alLt;lll,uling to disperse air dried lumps of the mic,opa,licles in heptane. Mi~;lop~licles that have been externally croc.clink~d will not 2 5 disperse; microparticles that are not externally crosslinked will disperse. More specifically, Examples 1 to 3, 5, 7 to 10, 18 and 19 were dried with and without the presence of 9.46 meq/loog of microparticle (0.824 g/lOOg of miclopalLicle) of ADH
external crosslinker and put into vials of heptane and shaken for 1~ hours. The results are shown below in Table 2.
CA 0220~432 1997-05-1~
Table 2 r.Y~ le Without Crosslinker With Crosslinker Dispersed (sep~aled Swollen but not dispersed spheres) 2 Dispersed (separatedSwollen but not dispt;l~ed spheres) 3 Dispersed (separ~led Swollen but not dispersed spheres) S Dispt;l~ed (sepalaledSwollen but not dispersed spheres) 7 Dispersed (sepalaled Swollen but not dispersed spheres) 8 Dispersed (separated Swollen but not dispersed spheres) 9 Dispersed (separated Dispersed (separated spheres) spheres) Dispersed Swollen but not dispersed (se,~al~led spheres) 18 Dispersed (separated Dispersed spheres) (separated spheres) 19 Dispersed (sepal~,led Dispersed spheres) (separated spheres) Table 2 shows that without the presence of the added, external crosslinker, the microp~Licles from F.Y~mrles 1 to 3, 5, 7 to 9, 18 and 19 dispersed in heptane. FY~mple 10 appealed to be a tliuls~elll, viscous solution because the miclopallicles were very small and highly swollen. However, the entire material could not be passed through a paper filter in~lie~tin~ that a dispersion rather than a true solution had formed. When the ADH external cros~linker was added, Examples 1 to 3, 5, 7, 8 and 10 did not disperse.
The lumps of mi-irop~ licles rem~ine~l in tact and did not break up or disperse in the heptane. This can be seen with the naked eye or, for smaller micropal licles, through an optical microscope. However, Examples 9, 18 and 19 did disperse since they did not contain a ca l,ol,yl monomer.
These eY~mples show that the combined presence of the carbonyl monomer and polyhydlazide external crosslinker results in pressure sensitive adhesive compositions that are indispersible in non-polar organic liquid solvents (e.g. heptane) once dried. As a CA 0220~432 1997-0~
WO 96/18701 PCT/US95/1~1328 result, these adhesives have improved re~iet~nce to solvents (especially non-polar organic liquid solvents) since the miclul)~u Licles will not disperse in the solvent.
Preparation of Pressure Sensitive Adhesive Tapes In the following examples, s~1ected micropa. licle compositions from Examples 1 to 23 were used to prepare pressure sel~silive adhesive tapes.
Example 24 The mi~ palLicle suspension of F.Y~mple 1 was permitted to sit overnight and sep~ale into two phases. The miclop~licle rich cream (55.7% solids) that rose to the top was isolated. 0.412 g/lOOg miclop~Lides of ADH external croe.elink~r (4.73 meq/lOOg microparticle) was added to the cream in the form of a 10% aqueous solution of ADH. A pres~ure sensilive adhesive tape was prepared by coating this mixture onto 1.5 mils thick primed (with an ~ (ed polybl.t~ ne) polyester film with a knife coater to a 4 mils wet thirL~n~ss and drying in an oven at 105C for 15 I--;----les Thenficl ~Jp~ licles were observed with an optical microscope to be continuously coated on the polyester film (i.e., adjacçnt miclu?~Licles touched one another~.
E~cample 2~
2 0 The micropal licle suspension of Example 2 was allowed to sit overnight and sep~le into two phases. The miclup~licle rich sedim~nt that settled to the bottom was isolated. 4.73 meq/lOOg miclop~licles of ADH external crosslinkerwas added to the se~lim~nt in the form of a 10% aqueous solution of ADH. A pl t;S~ul e sensitive adhesive tape was pl~aled as described in Example 24 except that the polyester film was provided with a 10 mils thick wet coat.
E~ample 26 A pl es~ure sensitive adhesive tape was prepared as described in Example 24 except using the microparticle suspension of Example 3 and 52.0 meq/100 g of microparticles of 3 0 ADH eYt~rn~l crosslinker.
A
Example 27 A pressure sensitive adhesive tape was p.~ared as described in Example 24 exceptusing the mielopa licle ~u~s~clls;on of E~ plc 4 and 4.73 meq/100 g of mic.opallicles of ADH eytern~l crosslinker.
Example 28 A pleS~ule sensilive adhesive tape was prepared as described in Fx~mrle 24 except using the ~ c~op~licle ~ùs~ension of Example 5 and 4.73 meq/100 g of mi~;.opa Licles of ADH external cros~ el.
E~ample 29 A pre~u.~ sensitive adhesive tape was pl~;pared as described in F.Y~mple 24 except using the mi~;ropa Licle suspension of Ex~lplc 6 and 5.77 meq/100 g of mic-op~lides of ADH external crosslinker.
E~ample 30 (Comparative E~ample) A plt;S:iUI~ sensitive adhesive tape was p.~;pared as described in Fx~mple 24 except using the mi~ilu~icle suspension of FY~mrle 9 and without using any ADH ~Ytern~
2 0 cros~linl ~r.
Example 31 The mic~op~icle suspension of Example 11 was thi~ened with 0.2 wt% (based on the weight of the micropal Licles) of Rheology Modifier QR-708 (Rohm and Haas) and 0.5 g/1OOg mic opalLicles of MDH external crosslinker (7.58meq/lOOg polymer) wasadded. The mixture was coated onto polypropylene film with a knife coater to a wet thickness of 3 mils and dried in an oven at 1 00C for 5 minlltes CA 0220s432 lss7-o~
wo 96/18701 Pcr/uss5/l4328 Example 32 A p.es~ule se"silive adhesive tape was p,ep&ed as described in Example 31 exceptusing the miclop~licle ~l~ension of F.Y~mrle 13 and 5.74 meq/lOOg microp~licles of ADH PYtern~l cros~lil~el.
Example 33 A p-es~ule sellsiLive adhesive tape was p,~a~ed as described in FY;~ e 31 exceptusing the micl.)p~Lide sl~p~ncic)n of FY~mple 14 and 2.87 meq/lOOg microp~licles of ADH eYtPrn~l crosslin~P,r.
E~ample 34 A pres~ure sen~iLive adhesive tape was prepaled as described in Example 31 except using the miclop~Licle suspension of Example 15 and 2.87 meq/lOOg mic~op~licles of ADH eyt~rn~l crosslinker.
Example 35 (Comparative E~ample) A tape was pl~;paled as desc,il.ed in F~y~mple 31 except using the micl op~u licle suspension of FY~mple 16 and 5 74 meq/lOOg microparticles of ADH external crosslinker.
Examples 36 to 40 A series of CA~1II~1CS was plep~t;d to evaluate the effect of varying the amount of polyhydlazide external cro~linking agent. More speçific~lly, 0 5 wt% (based on the weight ofthe micropa.licles) of UCARO Poly-phobeO 104 (Union Carbide) thiçkP.ner was 2 5 added to the mic~upal licle suspension of Example 11 and neutralized with NH~OH to obtain a dispersion having a coatable viscosity. Di~l~llL levels of ADH crosslinker (see Table 4) were added to the thi~ ned microparticle suspension and the resultinp~ material was coated onto 1.5 mils primed polyester film to a wet thickness of 6 to 8 mils with a knife coater and then dried in an oven at 105C for 5 min~tes E~ample 41 0.16g of CarbopolO 690 (polyacrylic acid thir~nin~ agent from BF Goodrich) was dissolved in 50g of cleioni7ed water and the res llting thi~ ner solution was then neutralized with 6% aqueous lithium hydroxide. To the neutralized thi.~ nçr solution, 12g ofthe rl,iclop~licle s~p~n~ion (25% solids) of F.Y~mrle 5 (modified with 9.46 meq/l OOg rnicroparticles of ADH external crosclint~r) and 3.25g of the microparticle suspension (40% solids) of F.Y~mrle 10 (mo-1ified with 9.46 meq/lOOg miclopa.~icles of ADH external cros~ .L ~ ) were added. A pressure sensitive adhesive tape was prepared as ~es ~ ecl in co~ cl;Qn with FY~mrle 24 except that the polyester film was coated to 1 0 a 3 mils wet thiclfn~
Example 42 (Comparative Example) To the neutralized thickener solution in Exarnple 41, 12g of the micropA . liclesu*.ens;on (25% solids) of F.Y;~ 1e 9 (modified with 9.46 meq/lOOg miclopa.licles of ADH external crosslinker) and 3.25g ofthe miclup~licle suspension (40% solids) of Example 10 (modified with 9.46 meq/lOOg micropA~licles of ADH external cros~lin~er) were added. A pressure sensitive adhesive tape was plt;paled as described in conj~ ;on with FY~mrle 24 except that the polyester film was coated to a 4 mils wet thi~n~s~
2 0 ~ mple 43 (Comparative Example) A p.es~ule sensitive adhesive tape was prepared by adding 5.77 meq/lOOg of miclupAl licles of ADH eternal crosslinker to the emulsion of compa.~ti~re exarnple 17, coating this material onto 1.5 mils primed (with an A...i.-~ed polybutadiene) polyester film to a wet thickness of 6 mils with a knife coatèr, and oven drying at 105C for 5 minl~tes E~ample 44 A pressure sensitive adhesive tape was prepared as described in Fx~mrle 24 but - without using any ADH external crosslinker.
3 0 Example 45 (Comparative) CA 0220s432 l997-OS-lS
WO 96tl8701 PCI`NS95/14328 A presSu- e sens;livt; adhesive tape was p~pared as described in Example 24, except using the micr~p~licle suspension of Example 18 and 4.73 meq/ lOOg mic,opallicles of ADH eYt~rnAl crosslinker.
Esample 46 (Comparative) A pre~ule sel~silive adhesive tape was p-~aled as described in Example 45 but without using any ADH ~YtPrn~l c-~s~
Esample 47 (Comparative) A prtS~Ule sensitive adhesive tape was prepal-ed as described in FY~mrle 28 but will~oul using any ADH çQ~ern~l crosslinker.
Esample 48 (Comparative) A p~s~u-e sensitive adhesive tape was p.epared as described in Fx~mrle 24, except using the mic~op~licle ~usl~ension of Fx~mple 19 and 4.73 meq/ lOOg ---cropal licles of ADH external crosslinker.
E~ample 49 (Comparative) A pres~u.e sensili~e adhesive tape was prepared as described in Fx~mple 48 but 2 0 without using any ADH external cros.clin~Pr.
Esample 50 Example 50 was plepa~ed as described in Example 37, except using the microp~ licle suspension of Example 20.
l:sample 51 (Comparative) A pl~S~Ult; sensitive adhesive tape was prepaled as described in Example 43, except using the emulsion of Example 21 and 4.73 meq/ lOOg polymer of ADH P.xtern~l crosslinker.
CA 0220~432 1997-0~-15 wo 96/18701 PCT/US95/14328 Example 52 (Comparativej A pressure sensiliv~; adhesive tape was p~ared as described in FY;..~.ple 43, except using the emulsion of E~ample 22 and 4.73 meq/ lOOg pol,vmer of ADH external crosslinker.
E~ample 53 (Coml.&~dli~e) A pres~ule sensitive adhesive tape was prepared as desclil,ed in FY~mrle 43, except using the emulsion of Fx~mple 23 and 4.73 meq/ lOOg polymer of ADH ~Ytem~l crosslinker.
The tapes of examples 24 to 53 were then evaluated for tack, peel adhesion (to glass and paper), adhesive ~ srel (to glass and paper), and whether they tore paper upon removal. The test procedures are described below and the results are shown in Table 3.
Examples 36 to 40 were further evaluated for shear strength using the test method 0~ below. Results are reported in Table 4. Selected c~ r,les were evaluated for solvent rçcictance using the test method outlined below and with the results shown in Table 5.
Test Methods Tack 2 0 The tack of the pres~lre sensitive adhesive tapes was measured with a Polyken Probe Tack Tester (available from Ken-l~ll Conlpany) according to American Society for Testing and Materials Test Method ASTM D2979-88. A~er cleaning the probe with methyl ethyl ketone using a lint-free cloth, a 2 cm x 2 cm sample of the tape was placed on the annular ring weight of the Polyken appar~ s. The tack was then measured using a 2 5 10 mm stainless steel probe having a ~i~meter of 0.4975 cm with a speed of 1 cm/sec. and a dwell time of 1 sec. The pressure sensitive adhesives of the invention preferably show a probe tack of at least 25 g, more preferably at least 50 g, and most preferably at least 100 g. The tack that is ~ltim~tçly desirable will depend on the int~n~ed use for the adhesive.
3 0 Peel Adhesion and A~ e Transfer CA 0220~432 1997-o~
WO 96/18701 PCT/US95tl4328 180 peel adhesion of the tapes was measured with a model 3M90 slip/peel tester (Instrumentors, Inc.) accolding to Test Methods for P~ ule Sensitive Tapes, PSTC-1, prom~ ted by the Pl~;s~ule Sensitive Tape Council. More sperifirzlly~ the adhesive surface of a 1 in. x 6 in. strip of tape was placed in contact with a glass plate or a piece of paper (plain, 20# white bond paper used in photocopy m~r.hines) and rolled down with one pass of a 2 kg roller. The strip of tape was then imm~rli~t~ly removed at an angle of 180 to the surface of the glass plate or the piece of paper using a removal speed of 90 in./minute. The force of removal was measu.ed and recorded in oz.rmch width. Once the tape had been ~ oved, the adherend surface was observed (visually and by finger touch) to assess whether there had been any adhesive ~ sre, . An obsel v~ion of no adhesive means that no adhesive residue could be detected on the ~ubs~ e, either visuallyor by finger touch. Useful pressu,e sensitive adhesives should display a peel ~h~ion of at least 0.3 oz.~m., preferably at least 0.5 oz./in.. They should also show no adhesive Ll~l~l. The ~ y desirable peel adhesion will depend on the int~nfled use for the1 5 adhesive.
Also recorded was whether the paper tore upon removal ofthe tape. S~mp'es were tested twice. A "no" entry indicates that the paper did not tear for either sample. A
"yes" entry in~ic~tes that the paper tore for both s~mples "SometimPs" means that the paper tore once. If the paper tore both times, adhesive transfer to the paper was not 2 0 ev~ ted Shear Strength Shear strength was measured in accordance with Test Methods for Pressure Sensitive Tapes, PSTC-7, promlllg~ted by the ~es~u.~ Sensitive Tape Council. More 2 5 specifically, a 0.5 in. x 0.5 in. end portion of a tape strip measuring 5 in. x 0.5 in. was adhered to a bright, annealed steel test panel and rolled down with six passes of a 2 kg rubber roller. The panel was then mounted in a jig vertically with the 4.5 in. free end of the tape h~nging down. A 500g mass was suspended from the free end of the tape and the time that elapsed until the tape separated from the panel was recorded in mimltes 3 0 The test was discontinued if separation had not occurred after 10,000 minlltes -;rt;lably, the pre~sule sensitive adhesives of the invention display a shear sl. ~n~lh in excess of 10,000 mim-tes The u~ ely desirable shear ~ n~lh will depend on the int~n-led use for the adhesive.
Solvent 12~s;st~nce A 1 inch x 1 inch sample of tape was immersed in various solvents (hepla~e, ~ceton~, iso-propyl alcohol (IPAj, and water) for 15 hours, removed from the solvent, and dried. The condition of the adhesive layer on the bac~in~ was obse, ved with the results shown in Table 5 where a "yes" entry under the particular solvent intlie~tes that sufficient adhesive was retained on the b~ in,~ for the tape to be used again and where a "no" entry in~ tes that the adhesive layer was deteriorated by the solvent to the point that the sample was no longer useful as a pressure sensitive adhesive tape.
Table 3 Example X-linkerl Coating Probe A&esion Adhesive Adhesion Paper A&esive (meq./ Weight Tack to Transfer to Tearing Transfer 100g (~/m2) (g) Glass to Paper to micro- (oz/in) Glass(oz/in) Paper particles 24 4.73 63.0 412 15.5 No 24.2 No No (98:2:0.025IOA/
DAACM~BDA) 4.73 106.0 502 46.0 No 46.0 No No (79:20: 12EEIA~VP/
DAACM) 26 52.0 71.1 224 11.8 No 25.7 No No (99.9:0.1 IOA/DAACM) 27 4.73 54.9 127 1.9 No 5.9No No (90: 10 IOA~DAACM) 28 4.73 47.5 335 4.1 No 23.2 No No (98:2:0.025IOA/DAACM~
BDA) 29 5.77 44.0 241 7.2 No 8.1No No (98: 1: IIOA/AA/DAACM) - 57.0 356 10.3 Yes 25.4 No Yes (100:0.025 IOA/13DA) 31 7.58 29.9 593 30 No 27 No No (93 :5 :2IOA/EA/DAACM) 32 5.74 27.3 488 42 No 28 No No (93:5:2: IIOA/EA/
DAACMiIIS-10) 33 2.87 32.9 523 35 No 29 No No (89: 10: 12EHA~BA/
CA 0220~432 1997-0~
Example X-linker' Coating Probe A&esion A&esive A&esion Paper A&esive (meq./ Weight Tack to TIansferto Tearing Transfer 100g ~/m2) (g) Glass to Paper to micro- (oz/in) Glass (oz/in) Paper particles DAACM) 34 2.87 28.8 405 16 No 27 No No (99:1 INA/ACL) 5.74 22.6 0 0 No O No No (85: 15 2EHAIDAACM) 36 -- 41.1 781 40.1 No 32.8 S~ne- No (93:5:2IOA/EA/DAACM) times 37 0.5 39.6 755 38.2 No 37.1 Some- No (93:5:2IOA/EA/DAACM) times 38 10 39.2 792 37.5 No 40.2 No No (93 :5 :210A/EA/DA~
39 100 33.8 142 28.5 No 0.4 No No (93 :5 :2IOAIEA/DAACM) 200 33.6 0 0 No O No No (93 :5 :2IOA/EA/DAACM) 41 9.46 4.4 113 1.' No 1.7 No No 42 9.46 3.0 96 1.~ Yes 1.3 No Yes 43 5.77 50.1 697 29. No 17.3 Yes (98: 1: lIOA/AA/DAACM) 44 -- 55.8 290 14.4 No 20.2 Some- Yes (98:2:0.025 times IOA/DAACM/BDA) 4.73 63.0 291 8.4 No 24.9 No Yes (99:1 IOA/NaAA) 46 -- 69.5 256 6.1 No 23.5 No Yes (99:1 IOA/NaAA) 47 54.5 300 1.1 No 12.1 No Yes (98:2:0.025 IOA/DAAC~BDA) 48 4.73 51.3 321 13.1 No 21.4 No No (99:1:0.025 IOA/AA/BDA) 49 -- 61.7 384 13.0 No 26.3 No Some-(99:1:0.025 times IOA/AA/BDA) 0.5 35.6 597 22.3 No 25.6 No No (93:5:2:0.1 IOA/EA/DAACM;/
HDDA) 51 4.73 46.9 835 31.0 No 20.1 Yes *
(90:10 IOA/DAACM) 52 4.73 46.4 558 15.6 No 10.9 Yes *
(98:2:0.025 IOA/DAACI~JBDA
53 4.73 50.7 1260 49.3 No 9.5 Yes *
(79:20:1 2EHA/NVP/DAACM) =
CA 02205432 1997-os-ls WO 96/18701 PCT/US9Sl14328 I
X-linker = ~l~h~ide external ~ ' ng agent *Ol~w~ notmade Table 4 Example X-linker' (meq./lOOgShearHoldingTime polymer) (min.) (93:5:2 IOA/EA/DAACM) 37 0.5 >10,000 (93:5:2 IOA/EA~DAACM) 38 10 >10,000 (93:5:2 IOA/EA/DAACM) 39 100 >10,000 (93:5:2 IOA/EA/DAACM) (93:S:2 IOA/EA/DAACM) ~X-linker = pol~h.~ide external Cl~ ' ' g agent Table 5 F. .'- External Coating leptane IPA Acetone WaterCl~ 1 Weight ~ G R~ e Re,~ e R~
Present (g/m2) No 57.0 No No No Yes (100:0.025 IOA/BDA) Yes 63.0 No Yes Yes Yes (99:1 IOA/NaAA) 46 No 69.5 No Yes Yes Yes (99:1 IOA/NaAA) 28 Yes 47.5 Yes Yes Yes Yes (98:2:0.025 IOA/DAAC~/BDA) ,~
47 No 54.5 No No No Yes (98:2:0.025 IOA/DAAC~/BDA) 29 Yes 44.0 Yes Yes Yes Yes (98:1:1 IOA/AA/DAACM) 48 Yes 51.3 No Yes Yes Yes (99:1:0.025 IOA/AA/BDA) 49 No 61.7 No Yes Yes Yes (99:1:0.025 IOA/AA/BDA) 38 Yes 39.2 Yes Yes Yes Yes CA 0220~432 1997-o~
WO 96/18701 PCTÇUS9~tl~328 ¦ (93:5:2 The eY~mrles d~mon~trate that the co.l.bh~ed presence of a carbonyl monomer and a polyl.yd.~ide P~Prn~l croscli~ g agent results in removable pressure sensiliveadhesives that have reduced adhesive t-~u~srer~ good adhesion, and solvent re~ nr~e Example 30 which inr~ led neither the c~l,o..yl monomer nor the polyl.yd-~ide showed good adhesion and removability but suffered from adhesive ~ srcr. Fx~mple 36 which added the carbonyl monomer but lacked the polyl.yd.~ide did not have adhesive L.~.srcr but was not removable. See also Examples 24 (c~l,o.lyl monomer and external crosslinker) and 44 (carbonyl monomer but no PYtPrnRl crosslinker) Example 24 shows reduced adhesive ~.~.src. to paper, an h~Gl~ substrate. Similarly, Example 47 (carbonyl monomer but no external crosslinker) shows adhesive transfer to paper while Example 28 (which adds the external crosslinker) does not show adhesive transfer to paper. Fx~mple 35 shows that using excess carbonyl monomer results in a material not having p~c~u~e sensitive adhesive pl~pcllies Examples 29 and 43 may be co--.paled Example 29 shows a useful, removable, pres~u.c sensit*e adhesive that does not display adhesive ~.~nsrCl In Fx~mrle 43 the same composition was emulsion poly...e.i,ed (rather than suspension poly.ne.i~ed) and a removable adhesive was not obtained. Other e~mrle pairs may be similarly ço.npaled.
See Examples 27 (suspension) and 5 l (emulsion), 24 (suspension) and 52 (emulsion), and 25 (suspension) and 53 (emulsion).
2 0 Examples 36 to 40 show the effect of varying the amount of polyhydrazide cros~linkin~ agent Example 36, having no polyl-yd-~de, exhibited limited shear strength Example 40, having excess polyhydrazide, showed no shear strength Table 5 shows the improved solvent resi~t~nre to a broad spectrum of solvents shown by the adhesive compositions that include both the carbonyl monomer and the polyhydl~zide external crosslinking agent Only the pressure sensitive adhesives ofthe invention dPmnnctrated resistance to heptane, a solvent representative of non-polar organic liquids Reasonable variations and modifications are possible within the scope of the rolt;going spe~ific~tion without departing ~om the invention which is defined in the accGIl~p~yil.g claims.
Claims (24)
1. A removable pressure sensitive adhesive comprising:
(a) pressure sensitive adhesive microparticles that are the suspension polymerization product of:
(1) a mono-olefinically unsaturated monomer having an aldehyde group or a ketone group; and (2) a base monomer; and (b) a polyhydrazide crosslinking agent for crosslinking the adhesive microparticles together.
(a) pressure sensitive adhesive microparticles that are the suspension polymerization product of:
(1) a mono-olefinically unsaturated monomer having an aldehyde group or a ketone group; and (2) a base monomer; and (b) a polyhydrazide crosslinking agent for crosslinking the adhesive microparticles together.
2. A removable pressure sensitive adhesive according to claim 1 wherein the base monomer is selected from the group consisting of alkyl (meth)acrylate esters, vinyl esters, and mixtures thereof.
3. A removable pressure sensitive adhesive according to claim 1 wherein the base monomer is a monofunctional unsaturated (meth)acrylate ester of a non-tertiary alkyl alcohol, the alkyl group of which has from 4 to 14 carbon atoms.
4. A removable pressure sensitive adhesive according to claim 3 wherein the base monomer is isooctyl acrylate, 2-ethylhexyl acrylate, or n-butyl acrylate.
5. A removable pressure sensitive adhesive according to claim 1 wherein the mono-olefinic unsaturation in monomer (a)(1) is provided by (meth)acrylate, (meth)acrylamide or styryl functionality.
6. A removable pressure sensitive adhesive according to claim 5 wherein monomer (a)(1) is selected from the group consisting of acrolein, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, diacetone (meth)acrylamide, formylstyrol, diacetone (meth)acrylate, acetonyl acrylate, 2-hydroxypropyl acrylate-acetyl acetate, 1,4-butanediol acrylate-acetyl acetate, and mixtures thereof.
7. A removable pressure sensitive adhesive according to claim 1 wherein monomer (a)(1) comprises about 0.1 to 10 parts by weight, based on the weight of the pressure sensitive adhesive microparticles.
8. A removable pressure sensitive adhesive according to claim 7 wherein the polyhydrazide has the general structure:
wherein R is an organic radical containing about 2 to 10 carbon atoms.
wherein R is an organic radical containing about 2 to 10 carbon atoms.
9. A removable pressure sensitive adhesive according to claim 1 wherein the polyhydrazide is selected from the group consisting of oxalyl dihydrazide, malonyl dihydrazide, succinyl dihydrazide, glutaryl dihydrazide, adipoyl dihydrazide, maleyl dihydrazide, sebacoyl dihydrazide, fumaroyl dihydrazide, isophthalic diydrazide,terephthalic dihydrazide, and mixtures thereof.
10. A removable pressure sensitive adhesive according to claim 1 wherein the polyhydrazide comprises about 0.5 to 150 milliequivalents per 100 grams of microparticles.
11. A removable pressure sensitive adhesive according to claim 1 further comprising a multifunctional free- radically polymerizable crosslinking agent for internally crosslinking the microparticles.
12. A removable pressure sensitive adhesive comprising:
(a) pressure sensitive adhesive microparticles that are the suspension polymerization product of:
(1) about 75 to 99.9 parts by weight of a free-radically polymerizable monomer selected from the group consisting of alkyl (meth)acrylate esters, vinyl esters, and mixtures thereof;
(2) about 0.1 to 10 parts by weight of a mono-olefinically unsaturated monomer having an aldehyde group or a ketone group; and (3) optionally, 0 to about 20 parts by weight of a polar monomer different than monomers (a)(1) and (a)(2);
wherein the sum of (a)(1) + (a)(2) + (a)(3) is 100 parts by weight; and (b) about 0.5 to 150 milliequivalents per 100 grams of microparticles of a polyhydrazide crosslinking agent for crosslinking the adhesive microparticles together.
(a) pressure sensitive adhesive microparticles that are the suspension polymerization product of:
(1) about 75 to 99.9 parts by weight of a free-radically polymerizable monomer selected from the group consisting of alkyl (meth)acrylate esters, vinyl esters, and mixtures thereof;
(2) about 0.1 to 10 parts by weight of a mono-olefinically unsaturated monomer having an aldehyde group or a ketone group; and (3) optionally, 0 to about 20 parts by weight of a polar monomer different than monomers (a)(1) and (a)(2);
wherein the sum of (a)(1) + (a)(2) + (a)(3) is 100 parts by weight; and (b) about 0.5 to 150 milliequivalents per 100 grams of microparticles of a polyhydrazide crosslinking agent for crosslinking the adhesive microparticles together.
13. A removable pressure sensitive adhesive according to claim 12 wherein:
monomer (a)(1) provides about 80 to 98 parts by weight;
monomer (a)(2) provides about 0.5 to 7 parts by weight;
monomer (a)(3) provides 0 to about 15 parts by weight.
monomer (a)(1) provides about 80 to 98 parts by weight;
monomer (a)(2) provides about 0.5 to 7 parts by weight;
monomer (a)(3) provides 0 to about 15 parts by weight.
14. A removable pressure sensitive adhesive according to claim 12 wherein: monomer (a)(1) provides about 85 to 98 parts by weight;
monomer (a)(2) provides about 1 to 5 parts by weight;
monomer (a)(3) provides 0 to about 10 parts by weight.
monomer (a)(2) provides about 1 to 5 parts by weight;
monomer (a)(3) provides 0 to about 10 parts by weight.
15. A removable pressure sensitive adhesive according to claim 12 wherein the polyhydrazide crosslinking agent has the general structure:
wherein R is an organic radical containing about 2 to 10 carbon atoms.
wherein R is an organic radical containing about 2 to 10 carbon atoms.
16. A removable pressure sensitive adhesive according to claim 15 wherein the polyhydrazide is selected from the group consisting of oxalyl dihydrazide, malonyl dihydrazide, succinyl dihydrazide, glutaryl dihydrazide, adipoyl dihydrazide, maleyl dihydrazide, sebacoyl dihydrazide, fumaroyl dihydrazide, isophthalic diydrazide,terephthalic dihydrazide, and mixtures thereof.
17. A removable pressure sensitive adhesive according to claim 12 wherein the polyhydrazide crosslinking agent (b) is present in an amount of about 1 to 100 milliequivalents.
18. A removable pressure sensitive adhesive according to claim 17 wherein the polyhydrafide crosslinking agent (b) is present in an amount of about 2 to 50 milliequivalents.
19. A removable pressure sensitive adhesive according to claim 12 further comprising a crosslinking agent for internally crosslinking the microparticles.
20. A removable pressure sensitive adhesive article comprising a substrate having a pressure sensitive adhesive according to claim 12 on one major surface thereof.
21. A removable pressure sensitive adhesive article according to claim 20 that has a shear strength in excess of 10,0000 minutes.
22. A method of preparing a pressure sensitive adhesive comprising the steps:(a) aqueous suspension polymerizing pressure sensitive adhesive microparticles; and (b) after step (a), adding to the aqueous suspension of pressure sensitive adhesive microparticles a polyhydrafide crosslinking agent for crosslinking the microparticles together.
23. A method according to claim 22 further comprising the steps:
(c) applying the aqueous suspension of pressure sensitive adhesive microparticles and crosslinking agent to a backing to form a wet adhesive layer; and (d) drying the wet adhesive layer.
(c) applying the aqueous suspension of pressure sensitive adhesive microparticles and crosslinking agent to a backing to form a wet adhesive layer; and (d) drying the wet adhesive layer.
24. A method according to claim 23 wherein the dried adhesive layer comprises the pressure sensitive adhesive microparticles crosslinked together.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/354644 | 1994-12-13 | ||
| US08/354,644 US5663241A (en) | 1994-12-13 | 1994-12-13 | Removable pressure sensitive adhesive and article |
| PCT/US1995/014328 WO1996018701A1 (en) | 1994-12-13 | 1995-11-02 | Removable pressure sensitive adhesive and article |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2205432A1 true CA2205432A1 (en) | 1996-06-20 |
Family
ID=29405827
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2205432 Abandoned CA2205432A1 (en) | 1994-12-13 | 1995-11-02 | Removable pressure sensitive adhesive and article |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2205432A1 (en) |
-
1995
- 1995-11-02 CA CA 2205432 patent/CA2205432A1/en not_active Abandoned
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