Note: Descriptions are shown in the official language in which they were submitted.
CA 0220~432 l997-0~-lS
WO 96/18701 PCT/US9S/14328
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
CA 02205432 1997-05-15
WO 96/18701 PCT/US95/14328
(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'
H2N--NH--C R C--NH--NH2
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:
11
R--C--R1
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~
WO 96/18701 PCT/US95/14328
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
WO 96/18701 PCT/US95/14328
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'.
WO 96/18701 PCT/US95/14328
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~
WO 96/18701 PCT/US95/14328
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
H 2N--NH--C--R--C--NH--NH2
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~
WO 96118701 PCT/US95/14328
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~
WO 96/18701 PCTIUS95114328
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.
14
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~
WO 96/18701 PCT/US95/14328
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
CA 02205432 1997-05-15
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
18
CA 02205432 1997-05-15
WO 96/18701 PCT/US95114328
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.
19
CA 02205432 1997-05-15
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
WO 96/18701 PCT/US9SJ14328
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
WO 96118701 PCT/US95/14328
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.
CA 02205432 1997-05-15
WO 96/18701 PCT/US9S/14328
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.
CA 02205432 1997-05-15
WO 96/18701 PCT/US95/14328
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.
24
CA 0220~432 1997-05-1~
WO 96/18701 PCT/US95114328
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.
26
CA 02205432 1997-05-15
WO 96/18701 PCT/US95/14328
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
28
CA 02205432 1997-05-15
WO 9G/18701 PCT/US95/14328
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)
29
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
-
CA 02205432 1997-05-15
WO 96/18701 PCT/US95114328
;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~
WO 96/18701 PCT/US95/14328
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)
34
=
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.)
36 -- 161
(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)
200 0
(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
36
CA 02205432 1997-05-15
WO 96/18701 PCT/US95/14328
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.
