CA2149399A1 - Self-stable lattices and the molecular weight control thereof - Google Patents

Abstract

A graft copolymer characterized by carboxylic-acid or amine functional macromonomers attached at a terminal end thereof to a polymeric backbone, wherein the functional groups have been neutralized, which graft copolymer was prepared in the presence of an oligomeric acrylic chain transfer agent to control the molecular weight of the graft copolymer. Such graft copolymers are useful in high performance coatings and paints.

Description

~A-0643 TlTI F.
SELF-STABLE LATTICES AND THE
MOLECULAR WEIGHT CONTROL THEREOF

C~ .n This invention relates to a graft copolymcr, r~f~,r~d to as a self-stabilized latex, having neutralized ca,l,u~l;c-acid or amino functionality in a graft segment thereof which stabilizes the aqueous graft copolymcr in dis~e.~;o--In particular, the invention relates to the molecular weight control of the graft copolymer. The invention also relates to a process for p.epdling such a graft copolymer.

BACKGROUND OF THE INVF.~TION
Automobiles and trucks receive exterior finiches for several well known reasons. First, such finishes providç barrier protection against corrosion.
Second, consumers prefer an exterior finish having an attractive aesthetic finish, including high gloss and excellent DOI (-lictinctneCc of image).
Coating compositions co~ ise one or more film-forming 2 o polymers. Acrylic polymers are typically linear polymers that cure, upon application, by reaction with crosclinking agents. However, the use of non-linear graft copolymers has been disclosed. For example, U.S. Patent No. 4,801,653 to Das et al. describes the use of hydroxy funrtio~l graft copolymers. Das et al.
disclose grafting by a condensation reaction between epoxy groups of a glycidyl ester, cont~ined in an acrylic polymer, and carboxy groups on at least a portion of vinyl monQmers which are polymerized in the pr~ so~ce of the acrylic polymer.
In prel,aring graft polymers in general, ~ s living polymerization methods have been dicclosed for o~t~ g functional ended polyrners by selective termination of living ends. Such ~ln~prn~lly cnded polymers may subsequently be ~ttarhe~l to another polyrner, that is, as so called macromonomer "arms" on a polymeric backbone to form a comb or graft copolymer. Webster, in 'l iving Polymerization Methods," 251 SCIENCE 887 (æ
February 1991) generally discloses living polyl,lel~lion ..-e!hn~ for l r~ lg architectural forms of polymers, including graft and comb copolymers.

3 5 U.S. Patent No. 4,680,352 to Janowicz et al., U.S. Patent No.

4,722,984 to Janowicz, and PCT WO 87/03605 licclose the use of cobalt (Co) 21~9399 .
chel~tes as chain transfer agents in free radical polymerization. The latter p~terltC disclose that macromonomers ~,r~ared by cobalt chain transfer can be polymerized to produce graft copolymers which are useful in co~;ng and molding resin, incl~lding high solid finiches and ~ e~o~C or solvent based fini~ es The S use of such polymers, however, have so far found only limitcd use in the ~utomntive finiches area, as for s ple disclosed in U.S. Patent No. 5,010,140.Water dispclsible polymers are well known in thc art and have - -been used to for n waterbased cQ~t;~g co ~ ;ons~ pigment dispcrsions, adhesi~res and the like. Graft copolymers con~ g c~bo.~l groups and the 10 preparation of these polymers is shown in Jar~--se I~id Open Patent Application (Kokai) No.1-182304 dated July 20,1989. This r~ferencc shows graft copolymers that have carboxyl groups and d~ ses side chains from acrylic and methacrylic acid that have hydrophilic properties. This reference [u-lher teaches the use tertiary alcohol-based ester units of acrylic or meth~^~ylic acid to form a 15 macromonomer which is used to form a graft copolymer and then is hydrolyzed to form carboxylic-acid groups on the polymer. The process taught by the reference is an inefficient process which does not form pure graft copolymer butresults in a mixture of graft copolymer and low mole~ r weight co",~o-len~
that are detriment~l to pigment dispersions formed from the graft copolymer and 2 o finishes formed from such a composition.
B ASF EP 0363723 describes an acid-fllnction~l acrylic copolymer dispersion for use in an OEM clear coat to be cros~linlr~od with a m.~l~min~
formaldehyde binder. The acrylic copolymer is pr~aled in a solvent in a two-stage process where the hydrophilic part (acid-function~ no~.er) is 25 concentrated in one of the two stages. The overall copolymer is afte.~.ards neutralized with an amine and dispersed in water. The difl~rence l~ct- een a onestage product is the solids/viscosil~ relation being most fa~o~ b!e for the two stage acrylic. A disadvantage of this teclmolD~y is the fact that the h~ hilic part needs to be over 60~o of acid f~lnctiQn~l ...o~ .er which could give 30 proble,l,s in hurnidity r~s;~l~ce.
The present invention disclosed hl pro;ed graft copol e~a useful m aqueous co?~s~ngc~

SUMMARY OF THE INVENTION
3 5 The present invention relates to a graft copolymer prepared from an acrylic copolymer macromonomer having at least 10~o, based on the weight of 3 21~9399 .
the macromonomer, of polymerizable alpha-beta ethylenicqlly ~J~ ted monomers with either a carboxylic-acid or amino group. Such _aclo-..o~ .Grs suitably may have a weight average mo~ r weight (MW) of 500 to 30,000.
About 2-98% (by weight) of the ma.;lu-~o~ er is copn~ e.~d with 9~2% of 5 a blend of other alpha, beta ethyl~ c~qlly unsalwalcd monomcrs to form a graftcopolymer with a MW of at least 3000, in the presc~cc of an ol~gomcric chain t~ùsîer agent, as described in more dctail bclow. Thc graft C~ CI can bc formed by copolyrr,cli~ng the backbone ..-o--u~ in the prcscncc of an aqueous dispersion of the maclo...o.-o-..e.r. The mac~o..-~ n~ r can be neutralized before being dispersed in water.
It has been found that illlp,o~ed ~queous or ~bate~Olne CQ~t;~-~
systems are obtained by using these graft cû~ le,~. Such c~ o~;l;onc have the advantage of providing excellent costin~ ~ropel lies desirable for an automotive finish.
One aspect of the present invention is directed to a graft copolymer having a weight average molecular weight of 3,000 to 500,000 c~lu~.ising the reaction product of:
(i) 2 to 98 percent, based on the weight of the graft polymer, of ethylenically lmc~turated mnn~merS for fo~ the 2 o polymeric backbone of the graft copolyrner, and (ii) 98 to 2 perce-l~, based on the weight of the graft polymer, of macromonomers capable of attaching to said polymeric backbone at a single terminal point of each maclo-..ol,omer, said macromonomers colllprising from about 10 to 100 2 5 percent, based on the weight of the macromonomer, of polymerized ethylenicqlly u~r~lvr~ted ...o-.t .ers cont~qin;n~
a carbo~ylic or amino filn~ tior qlity and having a weigbt average mole~llqr weight of about 500 30,000, such that the macrorno~olners are water soluble ûr ~ able when at least partially neutralized;
(iii) 1.0 to 20 percent, based on the weight of the graft copolymer, of one or more olig~meric chain ll&~fer agents having a terminal unsaturation like the macromononer of (ii) but having a subs~pnt~ y lower average molecular weight than the macromo~o~p~r of (ii) above;
wherein said carboxylic or amino functionality has been at least partially neutralized to form a stable d;~C ~ ~;Qrl of the graft copolymer, with the 5 backbone mostly in pardcle form, in water or an a ~.-cous carrier.
The present invendon is also ~l~ted to aqueous ~ Q~lc (20 to 100 percent water) of the graft copolymer and coating compositions made with such graft copolymers. Such co~t;~.~j CO~ ~S;I;QnC may fwlhcr comprise 2 to 50 pcrcel.t, based on the weight of the binder of a cro ~ agent which, when 10 the composilion is cured, can react and ~losslink with said graft ~ly~,., and 40 to 90 percent by weight, based on the weight of the co.l~posil Ol~, of an aqueous carrier complising 20 to 100 percent water. ~tingc may further coul~...se additional curable linear or br~nrhed film-fo~ polymers or binder materials, in various propGl lions. For example, the cGl~ osilion may c~ linear or branched hydroxy-functional acrylic, polyester, or pol~rurelhane copolymers.
Further binder materials, in relatively minor ~-~,o~n~ nrlude, for e~llplc thickeners, adhesion promoters, etc.
The process for m~king the graft copolymer are also part of this invention.
The present invention offers several ci~ific~nt ad~9~1ages. First, graft copolymers with acid or amine groups con-ce~ ated in one se.~ ..l require less of these functional groups to get a stable dispclsion, thus leaving fewer moicture sensitive groups when used in co~tingc~
Second, standard emulsions are stabilized by surfactants which 2 5 besides rem~ining in the film as moisture se~sili~c res;d~es migrate to the co~ting interfaces and generate weak bo~md~ry layers which lead to poor adhesion and del~min~tion. The surf~ct~ntc also sPh;li7~ foam fo.u,ed by trapped air during spraying, le~(lin~ to pinholing~ The graft oopol~ of the present invention can be used in co-"po~ nC made with lcs_cr ~- ~o~ of 3 0 surf~ ntc or even no surf~ n~c.
Third, st~nd~rd emUlc;Qnc for which water is a non-solvcnt, nccd c~nciderable solvent to allow co~lescence (film fo~ ion) aftcr bcing applicd to a surface. This leads to higher VOC. In the pl~s~nl u.~_nlion~ the h,dr~ lic macromonomers which are on the surface of tbe self-stabilized lqttices are 3 5 plasticized by the water and allow film formation with little or no solvent, thus allowing coating compositons to be formulated with much lower VOC. These and -5 2149~99 other advantages of the invention can be better understood by refere~ce to the following detailed description of the invention.

nFTATT Fn nF~SC~PIlON OF THF. I~VF.~TION
A water soluble or d~ le graft acrylic c~ . cr is dis~osed which is formed by free radical ;l~ li?tC~ co~l~ Lt;on of 2-98% (l~y wcight) alpha-beta ~unc7~ ated ~ o-~ in the prcsence of an ac~ylic rnaaornonomer.
The acrylic macromono~ ?r is ionic in character with an avcragc number ok~ r weight (MN) of bcl~.een 500 to 30,000 and containing at Icast 10~o of an acid or amino ~lnctiotl~l alpha-beta v~s~ ated monomcr. Af~er at least partial neutralization of the carboxyl or amino groups with, for ~ ple, an amine in the case of carboxyl groups, these acrylic resins form stable s~luhorlc or dispersions in water.
These graft copolymers form particles, either alone or in a,~e~,ate, in dispersions or co~ting compositions. The macromon~mers are reldlivcly hydrophilic and hence soluble or dispersible in the aqueous carrier, and the polymeric backbone (to which the macromonomers are ~tt~ e~) is relatively water insoluble. Such particles may be cros~linked or uncrosslin~e~ for example by means of diacrylate monomeric units, and suitably have an average particle size of 50 to 1000 nanometers (mn), I,refcrably 100 to 250 nm.
The molecular weight of the self-stable latex is controlled during polymerization by utili7ing oligomeric chain transfer terllnology as hereafter described. This involves very low mole~ r weight vinyl te~ te~ oligo ~ as radical chain transfer agents in the polymerization of desired monornc-rs with 2 5 higher molecular weight macromonomer (e-mulc;on st~bili7er)~
The oligomer chain transfer agents are generally a distrih~lti~n of molEclll~r weights that have a very low degree of pol~ e.;-~lion, for example, DP=2 to 8. These low mol~ r weight ma~lo~.o .~ e.s differ from the macro~nonomers used to stabilize the emlllC;on particle in that (1) they are co-~ lised of an average molecular weight lower than the s~h;li7~r macromonomers themselves, (2) the oligomer maclo..~Q~o-.-e,~ will not, or to a s~lbst~ti~lly less extent or degree, provide emlllC;on stability as does the macromonomer stabilizer, and (3) they typically co-.t~ little or no functional groups which might provide water solubility to the oligomer.
3 5 For example, a macromonomer stabilizer having an average composition of 60~o methymethacrylate and 40~o methyacrylic acid and a number average molec~llar weight of 1200 rnight be used along with an oligomer chain transfer agent co~ ,ised of 100% methylmethacrylate having a mr~ec~ sr weight of Mn equal to 315. The neutralized 60/40 l~aclo-~nnon~-r bcc~ ~es the grafted emulsion stabilizer. The oligo...er, which cannot be neutralizcd, could s not act as an ermll~;on stabilizer and can only be used in conjunction with the 60/40 macro..-o.~omer to form stable low rno'.e.~lsr wcight self-stablc cmulsions.
The chain ll~rer l).ocess, by d~ , tcrminates thc growing radical chain but does not change the kinetic chain length. The end result is the production of several, and possibly h-llldleds, of polymer chains from one 10 initi~tinE radical. The initi~tir~ radical, from a pol~l--P. ;- I:on initiator, can be taken for any common class of initiator such as azo, peroxide, pero~c~ler, or similar classes of thermal initiators as well as redox and photo~ l;Dto, ~.
Oligomeric chain transfer agents, much like other c(jl~.c-~t;on~l transfer agents, become incorporated into the polymer during the pol~ el~lion 5 process. One advantage is that the oligomer co~ >os;l;QnC- do not introduce moieties which can degrade the propel lies of the final copolymer. In cQmr~riSon~ the use of coll~e~ltional sulfur-conl~ r agents produce polymers which cont~in groups less durable than the polymer b¢ing ~..lhcc~
They often leave the resin with an offensive odor. Some cobalt chain transfer 20 agents are active in water based polymerizations as long as the bulk of the monomers are methacrylates. If self-stable latices require the use of acrylate and styrene monomers in the backbone, then cobalt chain transfer agents may not be very effective. Cobalt catalysts also have the disadvantage of not .ol~illg well with hydroxyl and/or carboxyl cont~ining monomer. This is not a factor with the 25 oligomer transfer agents.
As mentioned above, one important aspect of using oligon-er chain transfer agents for molecular weight control is that, in m~hng the self-stable latex, the oligomers do not contribute to the particle stability in the same way as the stabilizer macromonomers. Since the ol;~ t.~ are hydrophobic, either as an 30 end group, due to chain llallsfer~ or as a short graft, due to a~ ,uc.;-~;o ~, they contribute to the hydrophobic portion of the ~l~lller.
The st~bili7er macl~,lllollomers are in t' e__e!vcs l~r agents as defined by the mech~ni~m for addition-el;...;n~t;on chain t~ r. One can observe a limited reduction in molecular weight by solely inclc~sing the number 3 5 of moles of stabilizer macromonomer in the self-stable latex colllpo~ilion. The oligomer transfer agents, because of their low molecular weight, provide a novel ` 21~9399 way of increasing the number of moles of vinyl-te~ te~l mac,o ~o~nn~er in the process, hence a larger concentration of molecul~ weight control agent, with a minor impact on hydrophobic-hydrophilic b~l~nce in the l,ol~uer ~lllpo~ ;on The coIllpelilion l~e~ ell oligomer il~co,l~oIdtion and bet~ cr;o~
S (chain llans~r) defines the relative activity of thc Q~ P~r transfer agents and is largely controlled by three factors: (1) tc.l~ alur~ - the higher the ~e~lure of the polymeri7~tion~ the more chain t~ r, (2) bae~ c monomer ,osilion -- acrylates and styrene will provide oQ ~t;-~ h~ ...c for chain transfer and incorporation while .~.P llr~ lates only ~d~ o chain I.~ uafer, and10 (3) concenllation of oli~omer versus o~n---e,a in reactor - the higher the relative molar concentration of oligomer versus (meth)acrylate and/or s~Iehc monomers in the reactor during the polymerization, the larger the molec~ r weight reduction.
Oligomer chain transfer agents reduce the variables that ~illUW
the utility of commercial chain transfer agents or techniques that are c~mm(!nlyused to control molecular weight. It works with a wide variety of morlr~mers andinitiator types without adversely affecting other illlpO. t~nt polymer p.o~l Iies.
For example, it provides for the introduction of acceptable .~-o~ .-cr units into the polymer that are commonly considered, by those knowledgeable in the art, as contributing a neutral to positive effect toward artificial and natural ~.cathe.illg durability. Having control over the molecular weight of a self-stable latex provides an additional variable for particle coalesce-nces in film forrnation inaddition to other conventional variables such as co-solvents, particle size, poly~ner glass transition temperature and temperature.
2 5 The graft copolymer of the present invention is useful in co~ting compositions. Such compositions suitably conlplise about 20 to 98 ~ercenl, preferably 50 to 90%, based on the weight of the binder, of tbe ~pe~fi~d graft polymer. (In general, the total polymeric and ol;~ --P.ic co-u~ <~ of a co~tine coulposilion are col-~enIionally refe,led to as the u;ude,~ or "binder solidsn and are dissolved, emulsified or oll elwise di~pel~ed in the aqueous liquid carrier. The binder solids generally include all the normally solid ~ ~e.ic c~mponents of the coIllposilion. Generally, catalysts"~. ~"e~t~, or rl~r~
additives such as stabilizers are not considered part of the binder solids.
Non-binder solids other than pjgments usually do not amount for more than 3 5 about 10% by weight of the composition.) ~o~ting compositions, according to one aspect of the l,re~enl invention, suitably contain about 10-60%, more typically 50-70~o by weight of the binder, and about 40-90%, more typically 50-30~o by weight, of an aqueous camer.
The graft copolymer itself contai`ns about 2-98%, pr~f~lably 540%, and most preferably 1540% by weight of mawo-.~o~ er arms and cipol-din~ly about 98-2~ refcla~ly 60 95%, most pl~,~l~ 60 85% by weight of backbone polymer. The graft copolymer has a weight ...~.~e ~-olc~ r weight of about at least 3,000, "~fe,d~l~ 20,000 to 50Q000, most 10 prefe.ably 20,000 to 300,000. The side chains of the graft ~opol~cr arc fo.,ued from relatively water soluble macromonomers that have a weight a~elage mole~ r weight of about 500-30,000 and l,le~lably 2,000-10,000 aIId c~ in about 10-lOO~o by weight and preferably 15~0~o by weight, based on the weight of the macromonomer, of polymerized ethylenically l~ns~ ated acid or amino 15 monomers which are then at least partially neutralized. These side chains arerelatively hydrophilic and keep the graft polymer well d;spe,:.cd in the resultine co~ting composition.
The backbone of the graft copolymer is hydrophobic relative to the side chains, but can contain polymerized ethylenically ~ ated acid or amine 20 monomers or salts thereof. The backbone may co~ls;n polylllelized monolners selected preferably from the group col.~iC~ e of acrylates and Sl~rlene, but maycontain up to 50% alkyl methacrylates. It may also cont~in up to 50% by weight, based on the weight of the graft copolymer, of polymerized ethylenically unc~t~rated non-hydrophobic monomers which may co~ fimrtion~l groups in 2s addition to the amino or acid groups. Examples of such mon~mers are h,d~
ethyl acrylate, hydroxy ethyl meth~rrylate, acrylqmide~ nitro phenol ac~ylate, nitro phenol methacrylate, phth~limidQ methyl aclylate, and pl~thslim:~o meth~c~ylate.Still other vinyl monomers can be incoll,o.ated into the bal Ll~r e.g., ethylenic~lly unc~tnrated sulfoni~ slllfinic phos~ho. ;c or phosphonic acid and 30 csters thereof, such as styrene sulfonic acid, acrylamido methyl ~;~anc sulfonic acid, vinyl phosphonic acid and its esters and the like.
In one embodim~-nt, the watell~.nc acrylic graft copo!ymers contain ~60 or more preferably 1~40 parts by weight of h~d~uA~ functional acrylic monomers, e.g., 2-hydroxyethyl acrylate, 4-hydroxyethyl methacrylate, 2-35 hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hyd~ yl acrylate, g and 4-hydroxybutyl acrylate.- All or most of these may be present in the side chains and may serve as crosclinlcin~ sites.
As indicated earlier, the graft polymer col~,ises macro~nonomPric side chains ~tt~hed to a polymeric backbone. Each macro~no .h-nGr ideally 5 co.~lqin~ a single terminal ethylen;c~lly ~ &led group which is pol~ e- :-c~
into the backbone of the graft copolymer and typically contains ~ e~ ;-c~
monomers of methvq~ylic acid, its esters, nitriles, am;ides or mi~ctures of thcse ~-ol-o...ers.
The ethylenicvlly v~c ~ ated ~b~lic-acid or amino funcitional 10 monomers, in an S mount of at least 10% by weight of the macromonomers, can suitably include, as carboxylic-acid monomers, the following: methacrylic acid, acrylic acid, itaconic acid, maleic acid (or maleic anhydride which upon hydrolysis after polymerization gives maleic acid), and the like or ~ ures thcreo S~it~hle-amino functional monomers include t-butylamino ethyl methacrylate, diethyl 15 amino ethyl acrylate, diethyl amino ethyl methacrylate, and the like or ~I~lrcs thereof. The above acids or amines also can be used in the backbone of the graftcopolymer, hut usually in a lesser amount by weight than in the mac.~...n.~o..-~lic arms, in order to m~int~in the water-insolubility of the backbone. In this case,however, it is preferable that both the backbone and macro.... .omer arms should20 comprise the same kind of monomer, either acid ~O~O~ S or amino "~O~G ~el~.
In addition to the ...;n;n.~ amount of acid or amino fun~ion-ql monomers, up to 90~o by weight, based on the weight of the macromonomP-r, of other polymerized ethylenically ul~atu-ated monomers can be ~rcscnl in the macromonomer, for example, but not limited to acrylic and methacrylic acid 25 esters of straight-chain or branched mono~lcohols of 1 to 20 carbon atoms. The majority of these monomers should be methacrylates, plcfelably 60 80~o by weight of the macromonomer, for example, alkyl metha.;,~latcs having 1-12 CalbOllS in the alkyl group can be used such as methyl ~c~aac~ylate, ethyl methacrylate, propyl methacrylate, isopio~"l methacrylate, butyl methac~ylate, 30 pentyl methacrylate, hexyl methacrylate, 2-ethyl methacrylate, nonyl meth~çrylate, lauryl methacrylate and the like can be used. Cycl~qliph~qti~
mPth~çrylates can be used such as trimethylcyclohexyl methacrylate, t-butyl cyclohexyl methacrylate, isobornyl methacrylate, 2-ethylhexyl methacrylate, and the like. Aryl methacrylates such as benzyl meth~ylate also can be used.
Ethylenically unsaturated monomers co.. t~in;~ hydroxy functionality include hydroxy alkyl acrylates and hydroxy alkyl mPth~crylate lo 2149399 wherein the alkyl has 1 to 12 carbon atoms. Suitable n.o..o...ers inrlude hydroxy ethyl acrylate, hydroxy propyl acrylate, hydroxy isopropyl acrylate, ~ OA,~ butyl acrylate, hydroxy ethyl methacrylate, hydroxy propyl meth~ylate~ h~OAY
isopropyl methacrylate, hydroxy butyl meth ^rylate, and the like, and ~lufes - S thereof. Reactivef~m~tio~ ityrnayalsobeobt~ r~from.--Q~ crprc~
for example, tbe epoxy group of a glycidyl methacrylate unit in a polymer. Such an epoxy group may be con.c. Ied, in a post pol~ ion reaction with water or a small ~mollnt of acid, to a hydroxy group, or with g~ -o~ and/or a primary amine to give a hydroxy amine.
Suitable other olefinic~lly ~nc~ ated co ~n-~n-~c,~ inrlvde:
acrylamide and methacrylamide and del iv.llives as alkoxy methyl (meth) acrylamide monomers, such as methacryl~mi~le N-isobuto.~rll.e~
methacryl~mide, and N-methylol methacrylamide; it~conic and aleic anhydride and its half and diesters; vinyl aromatics such as styrene and vin~llol~ene;
15 polyethylene glycol monoacrylates and morlQmethacrylates; ~;.~oî~ ;on~
(meth) acrylates as, e.g., diethylaminoethylmethacrylate and t-butylaminoethylmethacrylate; glycidyl functional (meth) acrylates as glycidylmethacrylate .
Other functional monomers as acrylonitrile, acroleine, allyl 2 o methacrylate, aceto acetoxyethyl methacrylate, methylacryl qmido~!ycolate methylether, ethylene ureaethyl methacrylate, 2-acrylamide-2 methyl prop~nesnlfonic acid, trialkoxy silyl propyl methacrylate, reaction products of mono epoxyesters or monoepoxy ethers with alpha-beta ,,n~tu-ated acids and reaction products of glycidyl (meth) acrylate with mono functional acids up to 22 2 s carbon atoms.
The above monomers also can be used in the backbone of the graft copolymer.
The graft polymer may be prepared by polymerizing ethyle-nic~lly l)nc~n~rated monomers in the presence of mac~ e-~ each ha~ing a 3 o terminal ethylene ullsatul ation for g~ ar~ g. Tbe res~llting graft ~ ~er can be envisioned as being colllposed of a backbone having a pluraliq of macromonomer "arms" ~tt~e~l thereto. In the prescnt c~ n, both the macromonomer arms and the backbone may have reactive fimrtio. qlities capable of reacting with a crocclinking compound or polymer, although it is optional to 3 5 have such reactive functionalities only on the macromonomers. It is to be understood that the macromonomers referred to as having carboxylic or amine 11 21~9399 flmrtionslity may be part of a n,ul~lure of maclo~ mPrs of which a portion do not have any carboxylic or amine functions-lity or variable ~ o~nl~ of wl~lic or amine functionality. It is also unde,~lood that, in ~,epa,~g any ma~r~ o~ol.lers, there is a usually a norrnal ~ rib~l c ~ of f~n~n~sli1y~
s To enswe that the n s~llti~ macrolr~o~ er only has one tcrm cthylenicslly v~$~ rated group which will ~l~e.~ with thc backbone "~o"o~P,l~ to form the graft copol~,l er, the macromonomcr is p~ d by using a catalytic chain ll~rer agent. Typically, in the first stcp of the proocss for ~"~pali- g the macromonomer, the monomers are blcndcd with an inert organic solvent which is water miscible or water ~ ible and a cobalt or othcr chain transfer agent and heated usually to the reflux te,.ll~clalule of the rcaction ure. In subsequent steps, additional ~o~o~-el~ a nd chain ll~çcr agent a nd col-~elllional polymerization catalyst are added and pol~ eli~lio,~ is ~I;. Jed until a macromonomer is formed of tbe desired mQlt~ r weight.
The term "macromonomer" is used herein to describe polymers of limited chain length or molecular weight which have such terrninal olefinic moieties. The present macromonomers have about 10 to about 300 -~o~n-..PIic units linked to the end group, the units being independ-~ntly ~e!ecte~ f~om the monomeric units described below. The lulllber average mole~l~r weight can vary from about lO00 to S0,000, preferably l,000 to 10,000.
The concerltration of vinyl terminal ma~; o~..onr~..ers is at least about 80 mol ~o. Preferably, concentrations of at least about 85 mol %, more ~,efelably at least about 90 mol ~o, most preferably at least about 95 mol ~o and any and all concentrations and ranges of concel llations ther~ct- ec~, and up to2s about 100 mol ~o are contemplated.
The macronomoners can be prodllce~l by a cobalt chain lla~rcr agent, as described in copending U.S. Patent Appli~ti~-n S.N., berein incol l,orated by re&rence in its entirety. The macromonomers can also be produced by a process which employs, as a free radical chain t ~fer agent, 3 o relatively low molecular weight oligomers having ~--uns~ ation (which oligomers are, in fact, themselves macrom~ ncrs of a rdali~e~ m;te~ dcgree of polymerizaiton or chain length). These ~l;gc~ ..e.s may themselves bc made with a metal chelate or other suitable chain l~al~srcr cat~alyst. Ho.._.c~ hQ~
less preferred, it is contemplated that ~ nc~ ated olieo.~ , having at least 35 two monomeric units, might also be prepared without poly~eli~ation, according to a known or routine organic synthesis. Hence, the term noligomern or -"oligomeric" does not herein connote a coll,pound . ~ccss~rily pr~pared by polymerization.
The oligomeric chain transfer agents employed in the present invention may be a pure co ~o~ d or a polydispe,~e ~ lure of c4 .~ c s These materials have utility either alone or as blends when uscd as chain transfer agents for virtually any free radical pol~ll.el.~l;on ~ ererably, the present chain l~fer agents arc uscd as a polydisperse l~ ure~ which n~lure has a ~ictrib~ of molccular weights having a very low degree of pol~ el; _tJon, i.e., DP = 2 to 100, pr~fer~ 2 to 0 20, and most preferably 2 to 7.
The oligomer chain transfer agents of interest, as well as the polymers or macrorror~omers produced thereby, inrlude those having the following end group:
~CN2 CH2 C~
x where ~f is -CONR2, -COOR, ORl, -OCOR, -OCOORl, -NR~OORl, halo, cyano, or a substituted or unsubstituted phenyl or aryl, wherein each R is independently selected from the group of hydrogen, silyl, or a sl~hstit~lte~l or2 o unsubstituted alkyl, alkyl ether, phenyl, benzyl, or aryl, v~llercill said groups may be substituted with epoxy, hydroxy, isocyanato, cyano, amino, silyl, acid (-COOH), halo, or acyl; and wherein Rl is the same as R except not H; hcrein each alkyl is independently selected from the group cQnC c ;,~g of br~n~h~, unbranched, hydrocarbons having 1 to 12, preferably 1-6, and most yre&lably 1-4 2 5 carbon atoms or cyclical hydrocarbons having 4-12, p-eferably 4~ carbon atoms;
halo or halogen refers to bromo, iodo, chloro and fluoro, preferably chloro and fluoro, and silyl includes -SiR2(R3)(R4) and the like, wherein R2,R3, and R4 areindependently allyl, phenyl, alkyl ether, or phenyl cther, prcfcrably at least ~ro of R2, R3, and R4 being a hydrolyzable group, more plefelably two of which are 30 allyl ether, wherein alkyl is as defined above, pr~felably mcthyl or ethyl. Aplurality of silyl groups may be condc ce~1 for example, an ol~,allo~ e such as -Si(R2)2-o-Si(R3)2R4, wherein R2, R3, and R4 are in-~e~ .-~c...ll~ a~l.
See U.S Patent 4,518,726, hereby incorporated by reference, for further exemplification of silyl groups in general A preferred class of olieofneric chain ll~rer agents for use in t_e present invention are those oligomers accord~ , to the above structure in which X is -CONR2, -COOR, uncubstituted or substitute~ phenyl, aryl, halo, or cyano, and R is as de-fîned above.
A more prelelled class of o!;e~ . ic chain ll~cr agents for use in the present invention are those ol;go-~e.~ according to abovc structurc in which X is -COOR or phenyl and R is L~og~ll, allyl or phenyl u~nsub s~itut~d or substituted with epoxy, l~d~ r, or alko~ysilyl.
The oligomers employed in thc l,.cscn~ invcntion arc to be 10 dictin~liched from the more con~cl~ n~l ol;g . ~. ~ having thc following cnd group:

Il ~yCH2 - O--C--C

Preferably, the oligomers employed in the present invention, as well as the polymers produced thereby, are characterized by the following end group:

fH3 "CH2 ~C CH2 C~ 1 x2 wherein x1 and x2 are independently (the same or different) X as defined above.
The general chemical structure of suitable oli~o .-e.~ for use in the present invention is described below where n = 2 to 100 on ~e,~ge.

Xl~ (n-1) CH 2~
C--C H f--C H --H
CH 3 ~ n--1 wherein xl to xn is independently ~efined as above for X and n is on average 2 to 100, preferably 2 to 20.
For example, a general formula for a m~th~crylate oligom~ric chain transfer agent is as follows:

I H2 ~ ~OR~ n-1) RnO_8_C_CH2_ I CH2 H
O -CH3 - n--1 wherein R1 to Rn are independently (the same or different) and ~lel;i-ed as above for R and n is on average 2 to 20, yreferably 2 to 7.
0 As a further very specific example, a methyl methacrylate trimer, wherein n equals 3 and R equals -CH3, is as follows.

llH2 ~ ~OCH3 CH3 O--C--C--CH2--f- CH2--H
O -CH3 _ 2 As indicated above, dimers, trimers, tetramers, etc., as defined above, or mLxtures thereof, are suitably employed in the pies~nt invention.
Mixtures of varying molecular weight are probably easier to prepare in large quantities. A wide range of molecular weight oligomers may be made, which in turn may be distilled to obtain a purer or pure oligorner, for example the 2 o tetramer. The oligomers do not have to be in any particular form. The oligomers may be stored and added in bulk, as liquids or solids, mixed in a solvent, mixed with monomers.
Many of the oligomers that can be employed in the ~1~ s~nt process, are known, for example as taught in Janowicz pukliched ~u opca~l Patent Application 0 261 942, herein incoll,ora~ed by reference. The alpha-methyl styrene dimer, which is the same as the co-~po~n~
2,4-diphenyl-4-methyl-1-pentene, is known as a chain l~ r agent. Ho. ~.c., chain transfer agents with such a phenyl or aryl group may be less preferred forreasons of the properties of the resulting polymers as a con~e~uence of the 3 o presence of aromatic end groups derived from the chain transfer agent. It may be - 15 21~9399 preferred to exclude or reduce the amount of the dimer oh~o-~-cr, where n cquals2 in the above formulas, because such dimer may be somewhat less reactive than other oligomeric chain transfer agents.
Accordiag to the present invention, suits~c oligomeric chain S t,~rer agents are dimers, trimers, tctlalllcl~ and highcr oLgohlc.~ of monomers and nl Alures ILereoL Thus, oligol~.el ~ co.,~"is~g b. ~ h~ .. h~ or cyclical alkyl or aroll.atic methacrylates such as mcthyl, cthyL propyL butyl, 2-cthylhexyl, and/or decyl melhaclylate; .,~_lohe~l, phcnyL or benzyl methac~ylate;
f~mrtjonstl alkyl or ~ l&lic methaclylates such as glycidyl mcthacrylate, 10 h,.iroA;ethyl or hydroxypropyl methacrylate, metbacrylic acid, mcthacIylonitrilc, methacrylamide, 2-isocyanatoethyl methacrylate, dil~let~ ;noethyl methacrylate, N,N-dimethylamino-3-propyl methacryl~ miAP t-butyls-n-inoethyl meth~tcrylate~ and silanes such as methacryloA~,.o~,ylll;...ell.o~ysilane, or mixtures of the foregoing, and numerous others can be employed. Hetero-5 oligomers, as for example, the reaction product of meth~,l...GthA~ylate andmethacrylonitrile are suitable. These oligomers are most casily made by a metal chelate catalytic chain transfer, for example a cobalt chelste, as will be f ~ ecl below, but they could be made by other methods as well.
The present oligomeric chain ll~,srer agents can be used to 2 o control molecular weight during polymerization of the graft copolymer of the present invention, the macromonomers used in follllh,g the graft copolymer, and/or the backbone used in forming the graft copolymer. The chain t,~rer agent can be used in an effective amount of only a few ~ercenl by weight of the reactants. A suitable range of oligomeric chain transfer agent is between 0.01%
and 80% by weight, pre&rably about 0.1 to 40%, and most prefef~bly 1 to 10%
by weight of the monomer re~ c~n~c.
The free radical polymerization of v~ u~ated ~O~J ~ , some of which carry acid functional groups for st~hili7stiorl may occur in suspcnsion, emulsion or solution, in aqueous or organic media, as will be f~s~;lisr to those3 o skilled in the art.
The oligomeric chain transfer agents employed in thc prescnt invention are typically p,eparcd by standard solution pol~.~.e~ l;o-- techniques, but may also be prepared by eJm~lcion, ~ Je~sion or bulk ~ tion processes. Preferably, a metal chelate chain tlal~rer catalyst is employed in the 3 s method of preparation. (In effect, one chain transfer agent is used to make another chain transfer agent.) Such a method is disclosed in the above mentioned U.S. Patent No. 4,680,352, issued to Janowicz et al. and U.S. Patent No. 4,694,054, issued to Janowicz, both of which are cQ ~ o~ly ~csigr çd and hereby incol~,orated by reference in their entirety, as well as WO 87/3605 published on 18 June 1987.
When employing a cobalt chelate in the pr~a.alion of thc present oligoll-el~, it may be fe~cible to re~l,o.e cobalt as well as any color from there~ction product by piee;p;tation with a solvent and the subscquent use of activated charcoal. For example, the M~lition of ethyl acctate (Rhonc-Poulenc AR grade, 99.5%, 0.005% acetic acid) in various proportions ha bccn found to 0 cause snbst~nti~l plec;pitation of cobalt as a dark brown solid and thcr~fore decreased color in the final solution. Other preeil,;t~tillg sol~ e~ n~lu~e a uli~lure of acetone and water and a ll~ ule of rceto~il,;le and water. Color maybe further removed by classical techniques, for example, simple t~ ,e-~t with activated charcoal for about 15 minutes followed by filtration though a short column packed with CELITE~ 545 filter aid.
For larger scale production, colllhlùous (CSTR) production of the oligomer may be more economical.
In general, to obtain some of the relatively lower molecular weight oligomeric chain transfer agents of the present invention, one could employ 2 o higher amounts of a metal chelate chain llansrer agent than employed in the prior art for obtaining relatively higher mol~ r weight mae o-~o.~o~ rs. In other words, es~enti~lly the same prior art processes used in m~wnf~ low molecular weight macromonomers can be used in m~king the present relatively low molecular weight oligomeric chain transfer agents, such as dimers and trimers.
An initiator which produces carbon-centered r~ic~ fficiçntly mild not to destroy the metal chelate chain transfer agent, is typically also employed in preparing the oligomeric chain l.al~srer agents. Suitable ~ tor~
are azo compounds, as described below.
As will be a~a-el t to one skilled in the art, these o~;Bo;~e~ could also be prepared in situ from a~lo~liate reactants, ~llho!-gl~ thcy arc ~,Kfc,~ably made separately and then added to the polymerization reaction ~
The macromonomer polyl,lcl~ation process accar~iug to the presently claimed invention, in which macromonomers (tellllinally v~ ated polymers or copolymers) are produced employing the above described oligomeric -chain transfer agents, is suitably carried out at 20 to 20~'C, p.efelably 4~160~C, more preferably 50-145C.
Any source of radicals or any of the known class of pol~e,~tion to-, is suitable, provided the initistQr has the r~licite sol~bility in the solvent or lllol~oll.cr ~ re chosen and has an ~py,opliate half l~ife at the t~ pllature of polymeri7~tion- Pol~ I;on ;.~ to.~ may be redox or thermally or photorh~mic~lly in~-lce~l, for example azo, pero~cidc, pcro~cster, or persulfate. Preferably, the initistor has a half life of from about 1 minutc to about 1 hour at the telllpclalu-c of pol~,ll.cl; ~I;nn Some suitable ~itiators inciudePmmonium perslllfate, ~7ocl)mene; 2,2'-azobis(2-methyl)b.J~ r;le; 4,4'-azobis(4-cyanovaleric acid); and 2-(t-butylazo)-2~ oprop~le. Other non-azo initiators having the requisite solubility and a~lopliate half life may also be used.
The macromonomer pol~lllc~iLalion process carl be carried out as either a batch, semi-batch, continuous, or feed process. When carried out in thebatch mode, the reactor is typically charged with oligomeric chain tr~l~r agent and monomer, or medium and monomer. To the ll~lure is then added the desired amount of initiator, typically such that the M/I (monomer to initi~tor) ratio is 10 to 200. In typical examples, the oligomeric chain transfer catalyst is 2 o added in the amount such that the catalyst/initiator or C/I ratio is in the range of 0.10 to 20. The mixture is heated for the requisite time, usually one-half hour to ten hours. In a batch process, the reaction may be run under l,rcs~urc to avoid monomer refl~ and the medium can be viewed as absorbing the re~ction heat.
If the macromonomer polymerization is to be carried out as a feed 2 5 system, the reaction may t,vpically be carried out as follows. The reactor is charged with m~ um~ typically an organic solvent. Into a separate vessel are placed the monomer and oligomer. In a separate vessel is added initiator and rn~ lm The me-lium in the reactor is heated and stirred while the monomer, oli~omeric chain transfer agent, and initi~tor soll~tions are u~ll~hlced~ for example by a syringe pump or other pUlllp~g device. The ratc of feed is determined largely by the quantity of sollltion When the feed is complete, he~tir~ may be conlin-led for an additional half hour or more. AlteiuaL~,_ly, all of the oligomeric chain transfer agent may be placed into a reactor with l--cA;.-initially and monomers and initiator solution added over time.
3 5 In either type of process, the macromonomer product may be isolated by stripping off the medium and unreacted monomer or by pre~;~;lalion -with a non-solvent. Alternatively, the macromonomer solution may be used as such, if appro~,iate to its application.
As indicated above, the polymerization can be carried out either in the ~bsence of, or in the presence of, a polymerization ,~ ... Many common organic solvents are s~lit~ble as pol~e.i~tiGh media. These inrl~de aromatic hydrocarbons, such as l,cl~c--~c, tohle-ne and the A~lcncs; ethers, such as tetrah~dlofut~, diethyl ether and the c~ " "o-~1y available cthylene glycol and polyethylene glycol mono~llryl and dialkyl ethers, including the Ccllosolvesi and Carbitols; alkyl esters of organic acids and mixed ester-et~hers, such as monoalkyl 0 ether-nlono~ no~te esters of ethylene glycol. In ~ditio~ 1~ t~ s, such as acetone, butanone, pentanone and h~Y~none are suitable, as are ~lcoholc such as methanol, ethanol, propanol and butanol. It may be adv~nta~ollc to use mixtures of two or more solvents. Certain solvents may be prefclled for environmental or toxicological reasons.
A significant advantage of this method of p, epar;ng vinyl termin~ted macromonomers is that a wide variety of l,-ono",crs can be polymerized without adversely affecting the molecular weight of the desired macromonomer product. As indicated earlier, typical methods of piep~lion of vinyl terminated macromonomers are subject to sensitivity to active proton 2 o cont~ining monomers. An example would be cobalt porphorine and dis~yim~o catalysts. U.S. Patent 4,680,352 and subsequent patents to Janowicz et al.
demonstrate typical examples. Such cobalt catalysts are used ~AIGnsi~ely to prepare vinyl terminated macromolecules, but have the disadvantage of not working well with hydroxyl and/or carboxyl co..l~ ;ng mQnolner when used at 2 5 low levels. Also, high level use of these catalaysts may produce unacceptable color in the resin. In general, cobalt catalysts are less efficient with acrylate monomers.
After the macromonomer is fo.,lled as described above, its sollltion can be used "as is" or solvent can be optionally ~I-ip?ed off and the ba~ e 30 monomers are added to the macromonomer along with additir~n~l sol~-~l and polymerization catalyst.
Accordhlg to the present invention, the oligomeric chain t~ansfer agents described above are used to control molecular weight in fo.-..il~ tbe graft copolymer.
Azo type catalysts (0.5-5~o by weight on monomer) can be used as can other suitable catalysts such as peroxides and hydroperoxides. Typical of 21493~9 such catalysts are di-tertiarybutyl peroxide, di-cumylperoxide, tertiary. myl peroxide, cumenehydroperoxide, di(n-propyl) pelo~dicarbonate, peresters such as amyl peroxyacetate and the like. Polymerization is co ~;n~led usually at the reflux temperature of the re~ction ~ ure until a graft copolymer is fG.l,led of 5 the desired moleclllq~r weight.
Organic solvents can be used to form the macromonomer or the graft copoly-m--er~ for e~le, aro-. qt;rc, aliphqR~, L~to--cs such as mcthyl cthyl Iretonp~ isobutyl Iretone, ethyl amyl Ireto~ e, acetone, alcohols such as ~ D~-Oeth-q-nol, n-butanol, isopropanol, esters such as ethyl acctate, glycols such as10 ethylene glycol, propylene glycol, ethers such as tetral~ o&ran, clh,lcl-e glycol mono butyl ether and the like, and as mentioned above, water and ~ ~s thereof and water miscible solvents.
As indicated above, the graft polymer can be made by copolymerizing the macromonomer in solvent with the rest of the .~o-.o-..cr 15 blend, to form a graft copolymer, thereafter neutralizing it and dispel~ing in water. Solvents can eventually be stripped off after the water d-~cl~ion has been formed.
As neutralizing agents for acid groups, suitable inorganic bases include ammonium hydroxide, sodium hydroxide, and potaccium hydroxide.
2 o Typical amines that can be used as neutralizing agents inrlude amino methyl propanol, amino ethyl propanol, dimethyl ethanol amine, triethyl~minP, dimethylethanolamine, dimethyl~minorneth~lpropallol and a~..;no...cth~lpropalloland the like. One preferred amine is amino methyl propanol and the prefellcd inorganic base is ammonium hydroxide.
2 5 Suitable neutralizing agents for amine groups, if used incte~d of acid groups, include organic or inorganic acids, e.g. acetic acid, formic acid, lactic acid, hydrochloric acid, sulfuric acid, etc.
The co"~ ion of the graft polymer into a water dispcl~ion can be done by ~dmixing the graft polyrner solution with an a~,yl~.iate ncutralizing agent and ~ ting with water, or the pol~ eli~d graft co~ ~er sQl~rdon can be stirred slowly into a solution of water and the neutralizing agent. The degroe of neutralization of the dispersion can be from 10 to 150~o of the total ~ J"t of reactive groups present, preferably from 80-105~. The final pH of the di~ ion can accordingly be about 4-10, preferably 7-10 for an anionic system and 4-7 for a 3 5 cationic system. Anionic, cationic or non-ionic surf~ct~ntc can be used, but preferably not, since they might hurt humidity resict~nce afterwards. As indicated above, not having to use a surfactant is one of the cig~ific~nt advantages of the present invention.
Preferably, however, the graft copolymer is formed directly into water, wherein the macromonomer is neutralized and dissolvcd or dis~. ~d into 5 water. The graft copolymer is formed by copol~ c.i~g the rcst of the o--o ~r blend (for the bac~hone) with the ulac~ o-.~er soludon or water dispersion (for the graft or teeth part of the comb or graft oo~ r) in thc prcsence of the neric chain transfer agent ~esc~ l above. This p~ ~C has thc advantage that less cosolvent should be uscd in thc overall ~;~cc~ and s~hcul sl~ipping can be eliminated Another a.]~nlage is that higher molecular wcight graft polymers can be obtained than in solvent poiymerization.
Mixtures of suitably con-p~tible macro~ n~merS can be used as long as all are either cationic or anionic in water.
Water-soluble free radical initiators can be used, suitably in the temperature range of 20-98C, e.g., peroxides, ~mmonillm persulf~te redox initiators such as t-butylhydroperoxide/ascorbic acid. On copolymerizing the monomers with the macromonomer optionally chain transfer agents other than the cobalt chelates can be used as, e.g., mercdpla-~s: l"ercaptoethanol, t-dodecylmercaptan, N-dodecylmercaptan.
2 o In the synthesis of the g raft copolymer, small al"ounls of difunctional alpha-beta unsaturated compounds can be used as, e.g., ethyleneglycol dimethacrylate or heY~ne~ioldiacrylate. This can result in crosslinked particles.
The overall graft copolymer water borne dispel~ion should be 2 5 characterized by an acid or amine value of from 10 to about 150 (mg KOH/g resin solids), more preferably from 15 to about 70, and a hydroxyl ~ r of about 0 to about 250 (mg KOH/g resin solids), more ~J efc~ from 40 to 150.
The afore-described binder systems are l~tili7~ to produce waterborne co~tinec by blending with other s~ita~le co-~ fnts in a~
3 o with normal paint formulation techniqu~s The graft copolymers of the p.CSCl~ .C ItiOll are useful as film-forming vehicles in the ~)rcpalation of .atcll,orne coa~ co..~-oc;~io~c such as, for example, clearcoat or b~ceco~t co,l,posilions useful in a~to.~.oti~c applications. The resultant coating compositions have low volatile organic 3 5 content, preferably to a maximum of 3.50 pounds/gallon.

21~9:~99 In preparing coating col.lposilions, according to another aspect of the present invention, the graft copolymer can be c~mbined with a crosclin~ing agent in the amount of 2 to 50 percent by weight of binder, I~;cfelably 10 to 40percc,lt by weight of binder.
S~lit-s-ble curing agents C~J1;SC ",C~ fo~sldehyde or alkylated melvsmin~ forrn-s-ldehyde co~ ds or a Uocked or unblocked isocyanate co..~l~o~ ds in a one-p~^k-sge system or ,~tc eompov~dc~
,rcfe,ably a water-di~pcl~ible pol~ ate, in a two-package systcm, or other crosclinking agents such as epo~es, C;lsnes~ w~ ides, ctc, able to react with cr~sclinkine ~mctionslities on the graft copolymer.
If the binder is used in a forrm~l~s.~iQn that is cured with a curing agent cont~oinine N-methylol and/or N-methylol ether groups, the curing agent should be dispersed in the water based graft copolymer displl~.ion to form a stable overall dispersion. Examples of such curing agents are amino resins obtained by reacting an aldehyde, such as forrn~ldellyde, with a co,,l~ound cont~inin~ amino group such as melsmine, urea and ben7~l-s~ -e and total or partial etherification of the N-methylol group with an alcohol such as, e.g.,methanol, n-butanol, isobutanol.
To form a composition which will crosslink under elevated baking temperatures of about 60-180C for about S-60 mim)tes~ about 10 to 60%, preferably 10 to 25~o by weight, based on the weight of the binder, of a water-soluble water dispersible alkylated melamine form-s-ldehyde cr~scli~-lring agenthaving 1-4 carbon atoms on the alkylated group is prefellcd.
These cros~linking agents are generally partially alkylated 2 5 mel~omine formaldehyde compounds and may be mon~meric or polymeric and if polymeric have a degree of polymerization of about 1-3. Typical alcohols used toalkylate these resins are methanol, ethanol, propo~ , bl~t~no~ s~nl, and the like. Preferred allylated melamine crosslin~ing agents that are co~ cr~;allyavailable include Cymel ~ 373, 385, 1161, 350, or 1168 (M~ s-~tQ) and Resimine~ 714, ResiminesY 730 and 731, Res;.~ en' 735 and 745 (~ de).
C~oating compositions which co,-t.,;-- a m~ mine ",~ l;"L;,~e agent can cont~in about 0.1 to 1.0%, based on the weight of a binder, of a strong acidcatalyst or a salt thereof to lower curing te~ eral~rcs and time. P~o!-,ene sulfonic acid is a preferred catalyst or its ~mmoni~lm salt. Other catalysts that 3 5 can be used are dodecyl benzene sulfonic acid, phosphoric acid and amine or ammonium salts of these acids.

21~9399 If the binder is used in a form~ tiQn that is cured with a polyisocyanate, a water dispersible polyisocyanate is added to the atc,lwlue graft copolymer dispersion prior to applic~tiorl-The overall dispersion is not stable in this case and should be used 5 within a certain time period. Examples of water dispcrsable polyis~J~Icsinclude biuret and cyclotrimers of k~ . e~ lenc diisG.~ te, i~o~o,~ne diiso~ate and tetramethyl ,.ylyle,.c .liisoc~atc. Tbcse iso J~ S may be mo lified to such an extent that they CQ~IAil~ ionic groups to case dispersion into water.
0 Typically, a cure pro.. ol;.~ catalyst is l~tfli7e~ in co aj,,~lionwith an isocyanate crosslinkine or curing agent. Prefcrred catalysts are organometallics, suitably dibutyl tin dilaurate, dibutyl tin di-2-ethylheYo~te, zinc octo~te zinc napthenate, v~n~ m acetyl acetonate, or ~.~ ... acetyl r.eton~te in an effective curing amount, typically from about 0.1 to 2~o byweight 15 of binder. Such catalysts are optional, for example, elevated tel,,peralure and/or time may suffice to cure the composition.
Typical isocyanate crosslinkine agents which may be used for curing a co~tine composition include both cou,pounds and polymers, b!r~ed or unblocked. Examples of suitable polyisocyanates inrlllde mono~llrric 2 o polyisocyanates such as toluene diisocyanate and 4,4'-methylene-bis(cyclohexylisocyanate), isophorone diisocyanate and NCO-prepolymers such as the reaction products of mono~neric polyisocyanate such as those mentioned above with polyester or polyether polyols. Particularly useful isocyanates are isophorone diisocyanate and the biuret-form 2 s 1,6-hexamethylene diisocyanate commercially available from Bayer as "Desrrod~r" N or the like. Other croCclinlring agents in~lu(le 4,4'-biphenylene diisocyanate, tetramethyl diisocyanate, ethylethylene diisocyanate, 1,3-cyclopentylene diisocyanate, 1,3-phenylene dus(h~ate, l,5-..~l~h~l-clen~
diisocyanate, bis(4-isocyanatocyclohexyl)..-etl-~ne, and the like.
3 o TrifiJnçtional isocyanates may be used, for ~lc, triphenylmethane triisocyanate, 1,3,5-be-n~ne t~us~dle~ 2,4,6-toluene triisocyanate, an adduct of trimethylol and tel~a~ethyl xylene dus~uate sold under the tradename nC ythane 3160,n "Decmod~ N 3390 which is the tmner of heY~methylene diisocyanate, and the like. Optionally, one can use a 3 5 polyisocyanate acrylic copolymer derived from isocyanatoethyl methacrylate - 21~9399 (cornmercially available as TMI) and the like, as for eA~~ os~ in U.S.
Patent 4,965,317 (col. 5) hereby inco"~o.ated by referellce.
As indicated above, the polyisocyanate may optionally be bloc~ed Examples of suitable bloc~ing agents are those materials which would unblock at 5 clevated tel,lpe~alllres, for CA~11~ ; lower aliphatic 9l~h~lc such as ...~lh'..
oAimes such as methylethyl ketone onme, and lactams such as e~C;loncarrol?~t?m Blocked isc~atcs can be used to form stable one-paclcage systems. Polyf~ l;Qllal isocyanates with free iso~zte groups can be used to form two-package room te~ cr~lu~ curable ~, jte~s. In these ~ the 10 product and isocyanate curing agent are mixed just prior to their app}ication.
Other film-forming polymers, prcferably 0 to 55 ~crcc.ll by weight (and concomitantly 45 to 100% by weight of the graft c~ .,ler), based on the weight of the binder, may also be used in conjlmrtion with the graft copoly ner.Other film fol",i,lg polymers may be linear or br~nched and may inCltl~e aclylics, 15 acrylourethanes, polyesters, polyester urethanes, polyethers, and polyether urethanes that are co...p~t;ble with the graft polymer.
An organic cosolvent is also typically utili7ed in the presen~
composition, preferably in minim~l amounts, less than 20~o by weight of carrier,to facilitate formulation and application of the co~ting collll)osilion~ of the present invention. An organic solvent is utilized which is co~ t;bl~ with the components of the composition.
The amounts of graft copolymer, curing agent, and catalyst will, of course, vary widely depending upon many &ctors, among them the specific components of the composition and the intended use of the c4lll~s;l;0n In addition, a composition using the graft copolymers ac~rd~, to the present invention may cont~in a variety of other optional in~c~ o~
inrlur1ing pigment~, pearlescent flakes, fillers, p!~cb~7ers, antio~ n~, surf~ct~nt~ and flow control agents.
To hl.~ro~e weatherability of a finish prod~ by the prescnt 3 0 co~ting composition, an ultraviolet light st~hili7er or a co-.~b~ tion of ultraviolet light stabilizers can be added in the al..ounl of about 0.1-5~o by wcight, bascd on the weight of the binder. Such stabili7ers include ultra~iolet light absorbcrs, screeners, quenchers, and specific hindered amine light st~bili7ers. Also, an anitoxidant can be added, in the about 0.1-5~o by weight, based on the weight of3 s the binder.

Typical ultraviolet light stabili_ers that are useful in~ de bel-zo~henones, tri~q,7oles, tri-q7ines~ ates, hindered amines and ~lures tbereof. Specific examples of ultraviolet st~q~bili7ers are disclos,ed in U.S. Patent 4,591,533, the entire dic~lQsllre of wbich is L~co,~o.dted bercin by r~f~rc,.cc.A co~qting co.. l~os;l;o~- may also ;~cludc o~ 1 forr~ o~
addili~es such as flow control agents, for e "k Rcsiflow S
(polybutylacrylate), BYK 320 and 325 (bigh m~lec llq~ weight polya~,~t~s);
rheology control agents, such as fumed silica, microgels, and non-aqueous dispersion polymers, and the like.
When a coYqting colllposilion is used as a clcarc~at (t~ ) over a pigmente(l colorcoat (basecoat) to provide a colorcoat/clcarcoat finish, small amounts of pigment can be added to the clear coat to provide special color or aesthetic effects such as tinting.
~ o~ting compositions can be pigmented and used as the colorcoat, 15 monocoat, primer, or primer surfacer.
The following examples illustrate the invention. All parts and percentages are on a weight basis unless otherwise indicated. All molF~ r weights disclosed herein are determined by gel permeation chlo~ toL; aphr using a polystyrene standard.

This example illustrates the preparation of a methyl meth~clylate (MMA) oligomer chain transfer agent synthesis, in which the following components were used.

-Tnvredients Parts bv W~ ht Part I
Ethyl Acetate 248.7 Methylmeth?,~rlate (MMA) 499.0 Part 2 Ethyl Acetate 873 Catalyst* 0.87 Part 3 MMA 1996.0 Part 4 VazoT" 52 initiator (DuPont) 19.6 Ethyl Acetate 648.3 Catalyst = diaquobis(borodifluorodiphenyl-glyo~to) cob~lt~te (II) A dry reactor equipped with a stirrer, the.l,locoL~le, nilr~gell s positive pressure, and condenser was used. Part 1 was added to the reactor andheated to 80C. Part 2 was charged to the reactor in a single shot. When the temperature stabilized, Parts 3 and 4 were charged to the reactor over 240 and 300 minutes, respectively. After adding Part 3, the reactor was held at refl temperature for 30 minutes before cooling.

This example illustrates the preparation of a a macromono~r stabilizer made from methylmethacrylate and meth~rlic acid (MMA/MAA) in a 60:40 weight ratio. The following ingredients were used.

ln~redients Parts bv W~i~ht Part I
Methyl ethyl ketone (MEK) solvent 1447.40 Methylmethacrylate 577.91 Methacrylic Acid 14456 Part 2 MEK solvent 12632 Vazon' 67 initiqtor (DuPont) 3.16 Catalyst' 0.44 Part 3 Methylmethacrylate 1590.39 Methacrylic Acid 1300.20 Part 4 MEK solvent 284.22 Vazon' 67 initiator 18.95 Catalyst~ 0.44 Part 5 MEK solvent 243.25 Vazon' 52 initiator 9.47 Catalyst~ 0.18 Part 6 MEK solvent 243.2S
Vazon' 52 initiator 9.47 Catalyst~ 0.26 'Catalyst = diaquobis(borodifluorodiphenyl-glyoYim~te) cobqlt<qte (II).

Part 1 was charged to a reactor e~lui~ped with stirrer, thermocouple, and nitrogen positive pressure. The reactor was b.ou6Ll to refhLl~.
5 Parts 2 through 6 were prepared in separate vessels. Part 2 was cl~g~cl to thereactor in single shot. Parts 3 and 4 were co~c~ e~ y charged to the reactor at rate of 12.04 and 3.37 g/rnin, respecti~cly. After adding Part 4, Part S was added at a rate of 3.37 g/rnin. After adding Part 5, the ad~litio~ of Part 6 was carried out at a rate of 3.37 g/min. (The addition of Part 6 and Part 3 will be complete at 10 the same time.) Following the addition of Parts 3 and 6, the reactor was held at reflux for 30 minutes.

The resulting macromonomer st~bili7er (A) was characterized by the following molecular weight data: Mn = 1405, Mw = 2353, Disp. = 1.68.

F.XAl~fP! .F. 3 This cxample illu~llatcs thc preparatio., of ~ oth~r macromonomcr st~bili7er, in this casc made from MMA/MAA in the ratio of 70:30 by wcight.
The following ingredients were used.

~edients Pa~bvWe~
Part I
MEK solvent 2233.90 Methylmethacrylate 893.60 Methacrylic Acid 157.80 Part 2 MEK solvent 183.80 Vazo0 67 intiator (DuPont) 4.61 Catalyst~ 0.45 Part 3 Methylmethacrylate 2886.00 Methacrylic Acid 1462.10 Part 4 MEK solvent 413.60 Vazo0 67 initiator 27.60 Catalyst~ 0.45 Part 5 MEK solvent 354.20 Vazo~ 52 initiator 13.80 Catalyst~ 0.18 Part 6 MEK solvent 353.98 Vazo0 52 initiator 13.78 Catalyst* 0.27 ~Catalyst = diaquobis(borodifluorodiphenyl-glyoYim~t~) cobaltate (II).

- 21~93~9 Part 1 was charged to a reactor e.l~;~ed with stirrer, thermocouple, and nitrogen positive ~res~lre. The reactor was l,roughl to refl~
Parts 2 through 6 were prepared in separate vessels. Part 2 was ~L&g d to the reactor in a single shot. Parts 3 and 4 were clla ged co ~ n~ to the reactor at S a rate of 18.12 and 4.91 gjmin, res~ ely. At the complction of Part 4 addition, Part S was added at a rate of 4.91 g/min. At the completion of Part 5 addition, Part 6 was added at a rate of 4.91 g/min. (Thc addition of Part S and Part 3 will be complete at the same time.) Following thc addition of Parts 3 and5, the reactor was held at reflux for 30 ~ (es This resulted in a maclo-.~n-~o-.~er s~ i7er (B) charactcrized by the following molecular weight data: Mn = 1206, Mw = 2641, Disp. = 2.19.

FXAMPI F~ 4-7 These examples illustratate the preparation of self stable graft copolymer emulsions according to the present invention. For fo~ l.g the backbone, the reactants were 80%, based on the weight of the graft copolymer, ofa mixture of styrene (STY), 2-ethylhexylacrylate (2-EHA), mell~ll.,ell~acrylate (MMA) and the MMA oligomeric chain transfer agent in the weight ratio of 23 /
40 / (17-X) / X. For forming the graft or arms of the graft copolymer, the re~ct~nt~ were 20~o, based on the weight of the graft copolymer of macronomoners made from MMA and MAA in the weight ration of 12 / 8. The following ingredients were used.

21~9399 ~yeu~h~vr~m~) ~redients Y. 4 Ex. 5 L~ 7 Demineralized water 789.17 789.17 789.17 789.17 Macromo~o .. cr stabilizer A 55.10 55.10 55.10 55.10 Triethylamine 25.90 25.90 25.90 25.90 .Ammoni-~m Persulfate 1.74 1.74 1.74 1.74 2 Del~-.e.alized water 48.19 48.19 48.19 48.19 Demineralized water 880.90 880.90 880.90 880.90 3 Ma~;lo .o.~Qrner stabilizer A220.60 220.60 220.60 æQ60 Triethylamine 10850 108.50 108.50 108.50 Styrene 317.10 317.10 317.10 317.10 4 2-Ethylhexylacrylate 551.30 55130 55130 55130 Methylmethacrylate 234.30 206.70 165.55 131.17 pMMA Oli~omer 0.00 2750 68.75 103.13 Alll.lloniulll Persulfate 14.10 14.10 14.10 14.10 Demineralized water 258.34 2S8.34 258.34 25834 Part 1 was charged into a five liter reactor ey~ cd with stirrer, thermocouple, and nitrogen positive pres~re. The llli~lUle was heated to 85C
and purged with nitrogen for 30 minutes Part 2, 10% of Pan 3 and 10% of Part 5 4 were charged into the reactor in single shot. The reactor telllpe-ature was allowed to rise, and once stable the concurrent addition of Parts 3, 4 and S to reactor was carried out over 240, 270 and 300 minl~te~, respe~ ely. After addingPart S, the temperature in the reactor was held for 60 ...;.~)tcs.

Moleçular WeiQht and Partic e Size ~)ate for F"~z~noles 4-7 % pMMA oligomer Weight Average FY~mplein Copolymer Mo~ r WeiQht P~article (nm~
4 0 % 77,510 282 2 % 48,610 251 6 S % 2S,480 233 7 7.5% 19,340 336 - 21493~9 This example illustrates the pr~alion of ad~ on~l graft copolymers according to the present invention, which graft copo~ .el~ were the reaction product of 80%, by weight of the graft copolymcr components, of STY
(23), 2-EHA (40), MMA (17-X), MMA ol;go-.. er chain transfcr agcnt (X) and 20~o, by weight of the graft copol~luer co ~1' e"~ of MMA (14) and MAA (6) (where the n.~ ber in par~ hec;c arc the weight ratios in thc synthcsis. The following ingredients were used.

Wel~ht~mc) Part ~n~redients .~L 8 Ex.9 Delluuelalized water 273.2 181.8 Macloll-onomer stabilizer B 19.1 12.7 triethylamine 6.7 4.5 Ammonium Persul&te 0.6 0.4 2 Demineralized water 16.7 11.1 Demineralized water 505.0 345.0 3 Macromonomer stabilizer B 76.4 50.8 Triethylamine 26.9 17.9 Styrene 109;8 73.1 4 2-Ethylhexylacrylate 190.9 127.0 Methylmethacrylate 80.5 29.8 pMMA Oli~omer 0.0 23.8 Ammonium Persulfate 4.9 3.3 Demineralized water 89.5 88.2 Part 1 was charged into a two liter reactor e~ ip~)cd with stirrer, thermocouple, and nitrogen positive plcs~urc. The ~lurc was heated to 85C
and purged with nitrogen for 30 minutes. Part 2, 10~o of Part 3 and 10% of Part 4 were charged into the reactor in single shot. The reactor tem~ralulc was 15 allowed to increase, and once stable, the con. ul,enl addition of Parts 3, 4 and 5 to the reactor was carried out over 240, 270 and 300 ~ c, res~ . After completing the the addition of Part 4, the tclll~xr~lure was held in the reactor for 60 min~ltes The results are shown below.

31 214939~

Molecular Wei~ht and Partic e Size nate for ~ lPc 8-9 % pMMA oligomer Weight Average ~p~le in CODOI~Çr Moleo~ ht Pa~j~e (nm) 8 0 ~o 82, 470 233 9 75~o 23,340 249 FXAMP!.F. 10 This cY~m~pl~ slratcs a waterborne ~ rcoal based upon the 5 use of low molec~ r weight self-st~ ed latices-utilizing mct~yl mcthacrylate oligomer for molecular weight control. The following coln~>ollel~ls were used toprepare the clearcoat:

Component Amount Wt. ~o Self-stabilized Latex (from 12.50 71.43 Example 7) Triethylamine 0.20 1.14 Butyl Carbitol 0.90 5.14 Butyl Cellosolve 0.90 5.14 Carbodiimode Crosslinker 3.00 17.14 Total 17.50 100.00 Solids (~c) 37.0 lo The above components were added in order with miYine. Samples were drawn down over glass to a dry film build of applo~ tely 2.0 mils to produce a clear glossy fflm. The panels were allowed to cure at 77 F and 50 pclcelll reldli~, humidity. The results were as follows:

1 Day2 Day 3 Day4 Day Persoz Hardness 36 57 68 82 Swell Ratio - 3.12 2.5 2.57 Water Spot Resict~nce~ 8 8 10 8 15 ' Water Spot Ratings were rated on a 1-10 scale with a nlO" being perfect. An n8"
reflected the fact that the coating swelled but reco~ered.

EXAMn F. 11 The following formul~tio~ for a watell,ollle clearcoat c~n~iid~tes utili7ecl methylmethacrylate oligomer for molecl~l?r weight control:

Co~ol~cnt ~mC!llns Wt. %
Sclf-st~bil;7ed Latex (from 25.00 67.20 .lG 4) Tdethylamine o.oo o.oo Water 5.20 13.98 Butyl Cellosolve 2.00 538 Carbodiimode Crocclinker 5.00 13.44 Total 37.20 100.00 Solids (~o) 37.0 The above components were added in order with miYing Samples were drawndown over glass to a dry film build of appro-;...~tely 2.0 mils. The panels were allowed to cure at 77 F and 50 percent relative hllmi~lity. The drawdowns with the above solutions produced a clear glossy fflm with a dust freelo time of 33 minutes and a tack free time of 4 hr with the following plOpC- lies:

1 Day 2Day 3Day 6Day 7Day Persoz Hardness 20 28 - 40 MEK Res~ ce - - 35 (double rubs) EXAMPI F. 12 The following forml-l~tio~ for a watcll,ol..c clcarcoat was based 15 upon the use of low molecular weight self-stabilized latic~s uffli7ing a methylmethacrylate oligomer for molecular weight control:

In~redients .~mount Wt. ~o Self-stabilized Latex (from 75.00 68.58~o Example 6) Water 10.00 9.14%
Carbo~liimode Cro~linlr~r 24.40 2230%
Total 109A0 100.00%
Solids (~o) 39.0 BI~D~;e1d Viscosity 60 ICI Viscosity 35 The sprayout of the above solution resulted in a clear fiLrn with very good gloss over a white b~ceco~t.
5 of Part 5 hold temperature in reactor for 60 minutes.

Molecular Wei~ht and Partic e Size Date for Fy~rn~ks 4-7 ~o pMMA oligomer Weight Average Examplein Copolymer Molecular Wei~ht Particle (nm) 8 0 5'o 82470 233 9 7.5~o 23340 249 Those skilled in the art vill no doubt be able to ~l~ ose ~ ero~ls variations on the themes di~closell~ such as rh~n~ng the ~...O~ of ~C-l e~t~
0 in~ignificantly from those shown, adding innocuous or supplc l~ ~c ~ y ~.~b~ s, or substituting equivalent components for those shown. Such variations are con~idered to be vithin the inventive concept, as defined in the following claims.

Claims (10)

1. A composition for a graft copolymer having a molecular weight of 3000 to 500,000 comprising the reaction product of the following:
(a) 2 to 98 percent, by weight of the graft polymer, of polymerized ethylenically unsaturated monomers for forming the polymeric backbone of the graft copolymer; (b) 98 to 2%, by weight of the graft polymer, of macromonomers for attachment to said polymeric backbone at a single terminal point of said macromonomer, said macromonomers having an average molecular weight of 500 30,000 and comprising 10 to 100 percent, by weight of the macromonomers, of polymerized alpha-beta ethylenically unsaturated monomers having one of carboxylic-acid functionalities or amine functionalities; and (c) 1.0 to 20 percent by weight, based on the weight of the graft copolymer, of one or more terminally unsaturated oligomers having a substantially lower average molecular weight and lower water solubility than the macromonomer of (b) above;
wherein at least a portion of the carboxylic-acid or amine groups have been neutralized and wherein the macromonomers are soluble or dispersible in an aqueous carrier to stabilize the portion of the graft polymer which forms an insoluble particle and wherein said oligomer has the effect of limiting the molecular weight of the graft copolymer.

2. The composition of claim 1 wherein the oligomer, or a molecular weight distribution of oligomers, has the following end group:

where X is -CONR2, -COOR, OR1, -OCOR, -OCOOR1, -NRCOOR1, halo, cyano, or a substituted or unsubstituted phenyl or aryl, wherein each R is independently selected from the group consisting of hydrogen, silyl, or a substituted or unsubstituted alkyl, alkyl ether, phenyl, benzyl, and aryl, wherein substituted means with a substituent selected from the group consisting of epoxy, hydroxy, isocyanato, cyano, amino, silyl, acid, halo, or acyl; and wherein R1 is the same as R except not H; and wherein each alkyl is independently selected from the group consisting of branched or unbranched hydrocarbons having 1 to 12 carbon atoms or cyclical hydrocarbons having 4 to 12, preferably 5 to 6 carbon atoms; and halo or halogen is bromo, iodo, chloro or fluoro; except excluding the use of a pure dimer when X is substituted or unsubstituted phenyl or aryl.

3. The composition of claim 2, wherein said oligomer, or molecular weight distribution of oligomers, has the following formula:

wherein n is on average 2 to 100 and x1 to Xn are independently X as defined above.

4. The composition of claim 1, wherein said oligomer, or molecular weight distribution of oligomers, has the following formula:

wherein n is, on average, 2 to 20 and R1 to Rn are each independently selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, alkylether, phenyl, benzyl, or aryl, which substituent is selected from the group consisting of epoxy, hydroxy, isocyanato, cyano, amino, silyl, acid, anhdydride, halo, or acyl; and each alkyl is independently selected from the group consisting of branched, unbranched, or cyclical hydrocarbons having 1 to 12 carbons, halo is selected from the group consisting of bromo, iodo, chloro and fluoro, and silyl is -SiR2(R3)(R4), wherein R2, R3, and R4 are independently alkyl, phenyl, alkyl ether, or phenyl ether, wherein alkyl is as defined above.

5. The composition of claim 1, wherein the oligomer is comprised of alkyl methacrylate wherein the alkyl has 1 to 10 carbon atoms.

6. The composition of claim 1, wherein said macromonomers comprise between 10 and 40% by weight, based on the weight of said macromonomer, of polymerized ethylenically unsaturated monomers containing carboxylic-acid functionality.

7. The composition of claim 1, wherein said macromonomers further comprise between 5 and 30% by weight, based on the weight of said macromonomer, of polymerized ethylenically unsaturated monomers containing hydroxyl functionality.

8. The composition of claim 1, wherein said backbone further comprises polymerized ethylenically unsaturated monomers which are predominantly acrylate and/or styrene selected from the group consisting of alkyl acrylates, cycloaliphatic acrylates, aryl acrylates, styrene, alkyl styrene, andmixtures thereof; and wherein the ethylenically unsaturated monomers containing carboxylic-acid functionality comprise monomers selected from the group consisting of carboxylic alkyl acrylates, wherein the above-mentioned alkyl, cycloaliphatic, and aryl groups have 1 to 12 carbon atoms, and wherein the macromonores are predominantly methacrylates analogous to the above.

9. A coating composition comprising the graft copolymer of claim 1.

10. A method of preparing a graft copolymer having a molecular weight of 3000 to 500,000, comprising reacting simultaneously, in an aqueous solvent, the following components:
(a) 2 to 98 percent, by weight of the graft polymer, of polymerized ethylenically unsaturated monomers for forming the polymeric backbone of the graft copolymer;

(b) 98 to 2%, by weight of the graft polymer, of macromonomers for attachment to said polymeric backbone at a single terminal point of said macromonomer, said macromonomers having an average molecular weight of 500-30,000 and comprising 10 to 100 percent, by weight of the macromonomers , of polymerized alpha-beta ethylenically unsaturated monomers having one of carboxylic-acid functionalities or amine functionalities; and (c) 1.0 to 20 percent by weight, based on the weight of the graft copolymer, of one or more terminally unsaturated oligomers having a substantially lower average molecular weight and lower water solubility than the macromonomer of (b) above;
wherein at least a portion of the carboxylic-acid or amine groups have been neutralized and wherein the macromonomers are soluble or dispersed in an aqueous carrier to stabilize the portion of the graft polymer which forms an insoluble particle and wherein said oligomer has the effect of substantially reducing the molecular weight of the graft copolymer.