CA1257945A - Latexes of polymers having pendant coreactive and oxazoline groups - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Latexes containing particles having pendant coreactive groups and oxazoline groups are disclosed.
said latexes are self-curing yielding films and other articles having excellant tensile strength and resis-tance to water and other solvents. In addition, a process for making such latexes is disclosed.

Description

7~3~5i LATEXES OF POL~MERS HAVING PENDANT
COREACTIVE AND OX~20LINE GROUPS.

This invention ~elates to curing pol~meric latexes, more specifically to self-curing polymer latexes.

Diverse self-cùring polymer latexes ar~ known in the art. For e~ample, blends of a carboxylated latex such as an acrylic acid/styrene/butadien~ terpoly-mer latex with a melamine ~ormaldehyde or urea formalde-hyde resin are known to be elf-curing, i.e., they form a curing composition which cures at elevated temperatures.

Other self-curable latex systems employ a carboxylated latex which is crosslinked with a poly-valent cation or with a catio~ic pol~mer. Such latexes have the disadvantageæ of being pH dependent and of forming films which are highly sensitive to water and other agueous ~luids.

It is known tha~ acid and oxazoline gxoups will r~act under certain conditions to form an amide :

31,760-F _~_ . . .2,~

-2--ester. uIlfortunately~ however, latex particles containing both oxazoline and acid groups have not h~retofoxe been prepared.

Accordinyly, it would be desirable to provide a polymer latex which is ~elf-~curing without the forma-tion of by products and which, upon curing, for~5 ~ilms or adhesi~e6 having excellenk physical pxoperties and improved resistance to water cmd organic ~olvents.

~t would also be de~irable to provide a process by which polymers or polymer latexes containing both pendant acid and pendant o~azoline groups are prepared.

The present invention is such a polymer and proces~. In one aspect, the present invention is a curing latex composition comprisi~g disc.rete polymer particles, which polymer particles contain pendant coreactive and pendant oxazoline groups, which particles have been prepared by the polymerization of addition ~olymerizable mo~omers, which monomers comprise (a3 a coreactlve monomer containing pendant groups which are capable o~ r~acting with oxazoline groups to form a covalent bond thereto, (b) an oxazoline as represented by the general structure:

- ...... 25 R2~ R2) n Q~ N
:~: ,' C:~ -.. ... , . Rl 31,760-F -2 _3~ 34~

wherein R1 is an acyclic organic radical having addition polymerizable unsaturation; each R2 is independently hydrogen, halogen or an inertly substituted organic radical and n is 1 or 2 and ~c~ at least one other addition pol~nerizable monomer which does not contain a coreactive or oxazoline group, In another aspect, this invention i~ a process for preparing a latex comprising discrete particles containing pendant coreactive weak acid groups and pendant oxazoline groups, said process comprising khe step~ of (a) forming a latex containing particles of a polymer containing pendant weak acid ~roups by polymerizing a first monomer mix comprising an addition polymerizable monomer containing a pendant weak acid group and at lea6t o~e other addition polymerizable monomer which is copolymerizable with said monomer, said polymerization being conducted at a pH i~ the range from 1 to 6, then (b~ adjusting the pH
of the resulting latex to a value at which an additio~
ZO polymerizable oxazoline does not substantially react or hydrolyze under conditions suitable for the polymeriza-tion thereof, (c) adding to said latex a second monomer mix comprising (1) an additio~ polymerizable oxazoline as represented by the general formula:

R2 ~RZ ~
R2_C~-R2J
O N
~Cl~
p~l 31,760-F -3-_4~ 3~5 wherein R1, R2 a~d n are as defined hereinbefore and (2) ak least one other monomer which does not contain pendant coreactive weak acid or oxazoline groups, and ~ d ~ polymerizing said monomer mix under conditions such that the second monomer mix i~ polymexized within or around said particles of a polymer containing pendant coreactive weak acid groups.

Surprisingly, the laLtexes of this in~ention exhibit, upon drying and curi~Lg, excellent tensile strength and elongation, as well as superior re~istance to water and solvents. Accorclingly, such latexes are useful in a variety of applications including ~ilms, coatings, adhe~ive~ and binders for nonwoven fabrics.

The latexes o~ this~invention are advanta-geously prepared in a two-stage emulsion polymerization process. In the first stage o~ polymerization, a first monomer mix comprising a~ addition polymerizable coreactive monomer and at least one o~her monomer copolymerizable therewith i~ polymerized.

~0 Such polymerization is conveniently conducted using substantially conven~ional emulsion polymerization techni~ues in aqu ous medium with conventional additives.
Typically, the agueous phase will contain from 0.5 to 5 weight percent (based o~ the monomer charge) o~ con~
ventional nonionic or anionic emulsifiers, e.g., pota~sium N-dodecyl sulfonate, sodium isooctobenzene sulo~at~, sodium laurate and nonyl phenol ethers of polyethylene glycol~.
.

Conventional emulsion polymerization ca~alysts can be employ~d in the foregoing latex polymerization 31,760-F -4-_5_ J ~, r~J~345 and common examples thereof include peroxides, persul-fates and azo compounds such as sodium persulfate, potassium persulfate, ammonium persulfa~e, hydrogen peroxide and azodiisobutyric diamide. Also suitable are catalysts ~e.g., redo~ catalyst~) which are activated in the water phase (e.g., by a water-soluble reducing agent). The type and amount of catalyst, as well as the particular polymerization conditions employed, will typically depend on the other monomers which are used and polymerization conditions will be generally selected to favor the polymerization o~ such other monomers.
Typically, 6uch catalysts are employed in a catalytic amount, e.g., ranging from 0.01 to 5 weight percent based upon the monomer waight. In general, the pol~merization is conducted at a temperature in the range of from -10 to 110C ~pr~ferably from 50 to 90C). When the coreactive monomer is one containing pendant weakly acidic groups as described hereinbelow, such as carboxyl group~, ~he polymerization is advan-tageously conduct~d under conditions suffici~ntlyacidic to promote the copolymerization of the weakly acidic coreactive monomers with the other monomers being employed. In such case, ~he p~ is preferably between 1 and 6, more preferably be~ween 1 and 4. The polymerization may be conducted continuously, semi--continuol~sly or batch-wise.

Similarly, con~entional chain transfer agents such as, for example, n-dodecyl mercaptan, bromoform and carbon tetrachloride can also be employed in the nonmal fashion in the aforementioned first stage polymerizatio~ to regulate the molecular weiyht of the polymer formed therein, and, typically, when such chain transfer a~ants are used, they are employed in amounts 31,760-F -5--6- 1~' 57~3~5 ranging from 0.01 to 10 (preferably from 0.1 to 5) weight percent based upon the weight of the monomers employad in the polymerization. The amount of chain transfer agent employed depends somewhat on the particular trans~er agent employed and the particular monomer~ being polymeriæed.

Suitable latex polymerization procedures are taught, for instance, in U.S. Patent Nos. 4,325,856;
4,001,163; 3,513,1~1; 3,575,913; 3,634,298; 2,399,684;
2,790,735; 2,880,189; and 2,949,386.

The coreactive monomers employed herein are those which contain pendant coreactive groups which are capable o~ reacting with an oxazoline group to form a covale~t bond th~reto. It is understood that the reaction of such coreactive groups with the o~azoline group will typically, but not necessarily, cause the oxazoline ring to open.

-Typically, the pendant coreactive group on the coreactiv~ monomer will contai~ a reactive hydrogen atom. Exemplary coreactive groups containing~an active hydrogen atom include weak acid groups, aliphatic alcohols; aromatic alcohol~, i.e., phenols; amines and amides, i.e., -CON~2 and ~CON~- groups. In g~neral, the more reactive of such groups, i.~., tho5e having the more labile hydrogen, such as the acids and aromatic alcohols, are preferred herein. Such more reactive group~ will generally rea~t with the oxazoline ring more readily under milder conditions than the less reactive groups such as the amines ~nd aliph tic a~cohols. Amide groups are generally intermediate in reactivit~.

31,760-F ~6--7 ~ 5~ 3~5 Especially preferred are monomers containing pendant coreactive weak acid groups including acid anhydride groups, espe~ially ethylenically unsaturated monomers containing weak acid or acid anhydride groups.
Exemplary of suitable monomers containing carboxylic acid groups include itaconic acid, acrylic acid, methacrylic acid, fumaric acid, maleic acid, ~inyl~
benæoic acid and isopropenylbenzoic acid. The more preferred species include acrylic, methacrylic, fumaric, itaconic and maleic acids. Maleic anhydride is an example of a suitable monoMer containing an acid anhydride group.

Suitable coreactive monomers containing phenolic groups include or~ho- and meta-vinyl phenol.

15Suitable coreactive monomçrs containing aliphatic hydroxyl groups include, for example, hydroxyethylacrylate, hydroxypropylmethacrylate and ~-hydroxyethyl-N~methyl acrylamide. Derivatives of - styrene h,aving aliphatic hydroxyl groups are also useful herein.

Suitable cor~active monomers containing amide groups inclllde acrylamide, methacrylamide, vinyl acetamide and ~-chloroacxylamide. N-methylacrylamides and N-methylmethacrylamide are examples of monomers containing ~CON~ groups.

-Suitable coreactive mo~omers containing amïne groups inclu~e allyl amine~ 2-aminoethylacrylate and

3-aminoe~hylmethacrylate.
.

31,760-F -7 ~8~ 794.5 In addition to the coreactive monomer, the first monomer rnix also contains at least o~e other monomer whi~h is not a coreactive monomer and which i5 copolymerizable with the coreactive monomer. A broad range of addition polymerizable monomer~ are copol~meriz-able with said coreactive monomers and are sui~able hexei~.

Suit~ble monomers iIlclude, for example, -the monovinyl aromatics; alkenes; alkyl esters of a,~--e~hylenically u~saturated car.boxylic acid; carboxylic acid e~ters wherein the eæter group contains addikion polymerizable unsaturation; halogenated alkenes;
acyclic ali~hatic conjugated c~enes and the like.

- The term "monovinyl aromatic monomer" is intended to include those mo~omers wherei~ a radical of the formula:

R
~2=C_ (wherein R is hydrogen or a lower alkyl such-as an alk~l having from 1 to 4 carbon atoms) is attached directly to an aromatic ~uclear containing from 6 to 10 carbon atoms, including ~hose wherein the aromatic ~cleu~ is æubstituted with alkyl or halogen substitu-ents. Typical of these mo~omers are styrene; a-me~hyl-styrene; ortho-, meta- and para-methylstyrene; ortho-, meta-and para-ethylstyrene; o,p-dimethylstyrene;
o~p-diethylstyrene; isopropylstyrene; o-m ~hyl-p-iso~
propylstyrene; p-chlorostyrene; p-bromostyrene;
30 o,p-dichloro~tyre~e; o,p-dibrom~styrene; vinylnaphtha- -lepe; diverse vinyl (alkylnaphthaienes) and vi~yl 31,760-F -8 ~1 ~5~C3~5 .~

(halonaphthalenes) and comonomeric mixtures thereof.
Because of considerations such as cosk, availability and ease of use, styren~ and vinyltoluene are preferred and styrene is especially preflerred as the monovinyl aromatic monomer.

Alkenes suitably employed herein include the monounsaturated aliphatic orga:nic compounds such as ethylena, n- and isopropylene, the diverse butenes, pentenes and hexene3 as well as alke~es containing diverse substitue~t groups which are inert to the p~lymerization thereof. Preferred are unsubskituted C2~C8 alken~s with C2-C4 unsaturated alkanes being most preferred.

Alkyl esters of a,~-ethylenically unsaturated carboxylic acids useful herein include t~pically sot acrylates, those whose homopolymer~ have a glass tran~ition temperature (Tg) o~ less than 25C, such as benzyl acrylate, bukyl acrylate, sec~butyl acrylate, cyclohexyl acrylate, do~ecyl acrylate, ethyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylat~, heptyl acrylate, hexyl acrylate, isobutyl acrylate, isopropyl acrylate, methyl acrylate and propyl acrylate. Other .suitable esters include hard acrylates, those whose homopolymeræ have a Tg of greater than 25C, such as

4-biphenylyl acrylate and tert-butyl acrylate; soft methacrylates such as butyl methacrylate, and hexyl methacrylate; and hard methacrylates such 2S sec-butyl methacrylate, tert-butyl methacrylate, cyclohexyl - methacxylate, ethyl methacryIate, isobutyl me~hacrylate, -- -30 isopropyl methacrylate, methyl methacrylate and propyl -- mçthacrylate The cost, availability and known properties 31,760-F -9--lo~ 7~3~5 of butyl acrylate and ethyl acrylate make the~e monomers preferred among the acrylates. The cost, availability and known properties of methy] methacxylate make it preferred among the methacrylates.

~alogenated alkenes useful herein include, ~or example, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and the di~erse polychloro-, polyfluoro- and polybromo-alkenes.

Acyclic aliphatic conjugated dienes usefully employ~d herein include typically ~hose com~pou~ds which h~ve fxom 4 to 9 carbon atoms, for example, 1,3-butadiene;
2-methyl-1,3-butadiene; 2,3-dimethyl-1,3-~utadiene;
pe~tadiene; 2-neop~ntyl-1,3-butadiene and oth~r hydro-c~rbon analogs of 1,3-butadienes, such as 2-chloro--1,3-butadie~e and 2-cyano-1,3-butadiene; the substi-tuted straight chain conjugated pentadienes; the ~traight chain and branched chain conjugated h~xa-dienes; other straight and bra~ched chain conjuqated die~es having from 4 to 9 carbon atoms, and comonomeric mixtures thereof. The 1,3-butadiene ' hy~rocarbon monomers such as those mentioned herein before provide interpolymers having particularly desirible properties and are therefore preferred. The C08t, ready availability and the excellent properties of interpol~mers produced therefrom makes 1,3-butadiene the most preferred acyclic,aliphatic conjugated diene.

Mi~ures of two or more of ~he foregoing monomars may~ of course, b~ e~ployed herein, if desired.
of the foregoi~g mo~omers, most preferred are styrene, 30- mixtures of styrene and butadiene, butyl acrylate, methyl methacrylate and vinyl acetate.

31,760-F ' -10-... . .

~ ~3~.~

The proportion of monomers used in the first monomer mix may vary considerably depending upon the particular end-use of the composition. T~pically, however, the coreactive monomer is employed in a rela-tively minor amount, e.g., from O.l to 20, preferablyfrom l to lO, weight percent of the monomers. In general, the coreactive monomer is employed primarily to impart ~he desired sel~-curing characteristics to latex compositions and the other monomers employ~d to impart ~he other desired properties to the composi~ion.
For exampl~, in a preferred acid/oxazoline-modified styrene/butadiene latex, the oxazoline-modified polymer will advantageously exhibit properties similar to those commonly associated with styrene/butadiene polymers and the acid monomer contributes little except curing characteristics to the polymer. It is noted that weak acid-containing polymers also often exhibit enhanced colloidal stability.

Upon co~pletion o the polymerization of the first monomer mix, the p~ of the resulting coreactive late~ is adjusted, if necessary, into a range which is sufficiently high that during the subse~uent polymer-ization o~ the second monomer mix containing oxazoline monomers, the oxazoline ~ing does not significantly react or hydrolyze. Typically, adjus~ment of the p~
into the range from 3 to ll, preferably ~ to ll, more pre~erably from 7 to lO, is satisfactory. Any con-venient water-soluble alkaline material, e.g., ammonium hydroxide, sodium hydrogen carbonate or sodiwm hydroxide, is advantageously employed to raise the p~ to the a~a~us phaseO

.

31,760-F -ll-3~5 Ta the coreactive latex is added a second monomer mix compri~ing an oxazoline monomer and at least one other addition polymerizable monomer which is not a coreactive monomer or an oxazoline and which is copolymerizable with the oxazoline monomer. This second monomer mix is added to the coreactive latex under conditions such that the monomers are polymerized within or around the coreactive lat0x particles. The general pol~merization conditions employed are as described hereinbefore except that the pH o~ the aqueous phase i8 adjusted, if necessary, into the aforementioned range (i.e., sufficient to prevent substantial reaction or hydrolysis of the oxazoline monomer) during the pol~merization reaction.

If nece~sary or desired, additional amounts of agueous phase emul ifier, catalyst or initiator may be added to the coreactive la~ex prior ~o or simul-~aneously with the addition of the second monomer mix in order to facili-tate the polymerization thereof.

The second stage of the polymerization may be conducted immediately ~ollowing the preparation of the coreactive latex. ~lternatively, the coreactive latex may be prepared be~orehand and stored until the second stage polymerization is conducted.

The oxazolines employed herein are as repre-sented by the genexal structure:

R2 ~R2 ;~
R2_C~'~ J,~l :

~C~

31,760-F 12-.~ .

4~r;
-13~

wherein Rl is an acyclic organic radical having addi-tio~ polymerizable unsaturation; each RZ is independently hydrogenr halogen or an inertly substituted organic radical and n is 1 or 2. Preferably, R1 is ~2C=C-wherein R3 is hydrogen or a~ alkyl radical. Most prefexably, Rl is an isopropenyl group. Each RZ is 10 preferably hydrogen or alkyl group with hydrogen being most preferred; n is pre~erably 1. Most pre~erably, the oxazoline i~ 2-isopropenyl-2-oxazoline.

The other monomers employed in this second monomer mix are any addition polymerizable monomer which 15 is not a coreactive monomer or an oxazoline and which is copol~merizable wi~h said oxazoline. In general, tho~e monomers de~cribed hereinbefore as use~ul in the 4irst monomex mix are al50 usefully employed in the #econd monomer mix. It is often desirable to "match" t 20 the mo~omers employed in the ~ir~t monomer mix wi~h those in the second monomer mix, i.e., to employ th same or sub tantially ~i~ilar monomers in the same or substantially similar proportions in both the firs t and second monomer mixes. For e~ample, if styrene, butadiene 25 and acrylic acid are employed in the ~irst monomer mix, a second monomer mix co~taining styrene, butadiene and o~azoline monomer can be employed to match said first and second monomer mi~. Of course, it is not necessa~y or always desirable to match the backbone of ~he first 30 and second monomer mixes :in the practice of this inven~
~ionO More generally, the choice of other monamers in - bo~h the first and ~econd monomer mixes is such ~hat 31,760-F -13~

~14~ 3~.5 the resulting latex has the desired physical and chemical properties.

The proportions of monomers used in the second monomer mix may vary considerably depen~ing on the particular end-use of the c:omposition. Typically, however, oxazoline is employed in a relatively minor amount, e.g., from 0.1 to 20, 2~d preferably from 1 to 10, weight percent of the monomers. In general, the oxazoline monomer is employed ~rimarily to impart ~he sel~-curing characteristics to the latex and the other monomers are employed to impart the other desired properties to the latex.

Advantageously, the second monomer mix contains from 0.05 to 20, preferably from 0.2 ~o 5, more preferably from 0.5 to 2, moles of oxazoline monomer per mole o~ coreactive monomer employed in the first mo~omer mix. Most pre~erably, the amoun~ o~
oxazoline monomer employed is sub~tantially equivalent on a molar basis to the amount of acid mo~omer employed.

Following the polymerization of the sec~nd monomer mix, there is obtained a curable latex composi-tio~. such composition comprises discrete polymer particles which polymer particles have been prepared by the addition polymerization of mo~omers comprising (a) a coreactive monomer, (b) an o~azoline monomer as described hereinbefore and (c~ at least one other addit~on polymerizable monomer. When the other monomer in the first monomer mix is different from the other monomers employed in the second monomer mix, the resulting latex particles will have been prepared from, in addition to the oxazoline and coreacti~e mon~mers, 31,7~0-F -14--15~ 5~.~945 at least two other addition polymerizable monomers.
While not intending to be bound by theory, it is believed that the polymer particles in the late~ of this invention are structured latexes in which the polymers prepared in the seconld monomer mix ~ither encapsulate or interpenetrate the polymers prepared ~rom -the first monomer mix. ~owever, it is recognized that during the polymeriæation of said second monomer mix, certain amounts o~ graft or block copoly~ler~ may be formed. The precise polymeric structure of the polymer particles is not considered critical to this invention. Essential f~atures of the polymer particles are that such particles contain both pendant coreactive groups and pendant oxazoline groups.

Advantageously, th~ polymer particles have a particle size distribution such that, upon film formation, the particles can become relatively closely packed together to form coheren~ films.

The curing latex composition of this invention 20 ~ may be used for a variety of applications including paper coating compositions, adhesives, binders and fibrous, nonwoven fabric compositions. Such composi-tions are especially suit~ble for tho~e applications in which a self-cura~le, curing polymer composition is desired.

The latexes of this invention may be employed as adhesives, films or binders by applying the latex ~o the desired substrate and then dewatering the late2 and curing the dewatered polymers. The dewatering step may be performed by merely allowi~g the agueous phase to evaporate under ambient conditions. Alternatively, 31,760-F -15--16- ~,S~.J~3~

elevated (i.e., 50-165C3 temperature~ may be employed to dewater the latex. Curing of ~he polymer may, likewise, be performed at ambient temperature~. Such ambient temperature curing is an unexpected property of the latexe~ of this invention. Such room temperature curing is generally conducted over a period o~ several ho~rs to several days dependi~lg on the part~cular pol~mers employed, the amount~t of oxazoline and coreac-tive groups in the polymer, the ~hickness o~ the film adhesive or binder layer, ~he amount o~ cro~linking desired and like factors. Cuxing may al60 be effected by h~ating the pol~m~rs to 100 to 165C, preferably 120 ko 150C for ~hort periods. The foregoing drying and curing points may not be distinct step~ but may be carried out simultaneou~ly if desired.
.
The fol}owing examples are intended to illu6-trate ~he invention but not to limit the scope khereof.
All parts and percentage~ are by weight u~le~s othexwise indicated. ~ ~
. .
Example 1 In~o a 0.0038 cubic meter (l-gallon), jacketed reactor eguipped with Iab pumps to deliver monomer and aqusou6 ~eeds were added 593 g of ~eio~ized water, 7 g of a 1 percent active agueou~ pentasodium diethylene triamine pentace~a~e solu~ion ~ d 21.9 g o~ a 32 percent ~olids seed latex containLng polystyre~e particle~
ha~ing a volume avexage particle ~i2e 0~ about 0.026 microme~er~ (~m), i.e, 263 A.

~he reactor was purged with ~itrogen an~
heated to 90C. The~ over a 3-hour pexiod, a monomer stream co~taining 455 g of butyl acrylate, 217 g o~

31,~50-~ -16-~ IL~.~ t:~t~'34.5 --17-- .

styrene, 28 g of acryli.c acid and 3.8 g of 55 p~rcent active divinylbenzene was added. Beginning simultane-ously with the start of the mo:nomer stream was added continuously o~er a 4-hour period 245 g of deionized water, 15.S6 g of a 45 perce~t active aqueous surfac~ant ~olution, 14 g of a 10 percent aqueous ~odium hydroxide solution and 4.9 g oX sodium persulate. Following addition o~ the monomer and agueous streams, the reac-tio~ mixture was heated a~ 90C for 1 additional hour and then cooled. The product was a 45 percent solids latex o a butyl acrylate/styrene/acrylic acid/di~inyl~
benæene polymer in a 65:31:4:0.3 percent weight ratio.

A 1244.0 g portion of the resulting coreactive latex was then placed into a 0.0038 cubic m~ter (l-gallon~
stainles~ ~teol reactor toge~her with lO0 ~ of water and ~uffi~ie~t ammonium hydroxide to increase the p~
~rom 3.9 to 8.7. The reactor wa~ then ~urged wi~h ~itrogen and the monomer mi~ compri~ing ~4 g af 2-i~opropenyl-2-oxazolin~, 91 g o~ butyl acrylate and ~0 35 g of styrene was added. Al o added were 171 g of deionized wat0r and 0.7 g of ~odium persulfate. The resulting mi~ture was then polymerized at 60C for 8 hours and cooled. The re~ultant latex contai.ned polymer pa~ticles having both penda~t acid and pendant oxazoline groups, a~ confirmed by infrared spectroscopy.

:The result~nt la~e~ wa~ thickened wi~h a s~all amou~t of sodium polya~rylate and 0.51 millimet~r (20-mil) ~hick films of the latex were caæt onto a ~eflon brand coated steel plate using a film bar of 0.51 mlllimeter (20-mil~ ~hicknes-~. The ~ilms were ~hen dried at ambient temperature until they-~.ere-tr~nsparent ~nd then they were peeled ~rom the plate ~1,760-~ -17

5~.J945 -18~

and ~urther drie~ at ambient temp~ra~ure for about ~4 ho~rs, The air-dried ~llms were then ¢ured for 5 minute~ ln an oven ~et at dlver~ ourlng temperatures noted in Table I ~ollowlng. The cured film~ w~r~
then out into 13 mllllmeter tOi5-inoh) wide ~trip~ and test~ on an In~tron~ tenslle tester to mea~ure elongatlon and ten~Lle ~tr~ng~h at break. Duplicate our~d films were ~oake~ ln an exce~ o~ an aqueou~
solution oontalnlng 0.5 pereent Aero~ol OT~ br nd ~ur~aotant ~or 5 minute~ and then t~sted ~n an In~tron ~o m~a~ure elongatlon and ten~ile .~tren~th at break.
For oo~parl~on, a ~ample o~ th~ oarboxyll¢ .lat~x oontainln~ nP pendant oxazoline group wa~ formed in~P
film~ and ~e~ted as d~scribod herein. The re~ult~ w0re a~ reported a~ Sampl~ No. C-1 in Table I r~llowing.
The re~ult~ obtalned on ~ilm~ prep~ed from the latex of thi~ lnvention are reportsd ln Table I ~ollowln~ a~
S~mple No. 1. The Ten~ile ~trength value~ are givan in Mega pa~o~lA (~Pa) ~nd th~ Elonga~lon values are ln peroent.

31,760-F -18-~:Lg~ Y~ 5 ~ABLfS I
__ S:~omparative ~ 1Sample No. C-1*
R . T . Cure 1 Dry Tensile25.62 7.48 Wet Tensile36 0 27 2 0 64 Dry. }5long. 4 351 413 Wet Elong.B285 435 100C Cure6 Dry Tensile9 . 55 6 . 65 Wek Ten~ile7 . 75 3 . 25 Dr~ long. 304 395 Wet ElongO~!75 443 1~0C Cure7 iS~;~ 9 . ~S S . 87 Wet Tensile8, 96 2 O 61 Dry Elong.268 39g Wet Eïong. ~83 401 lsaoc Cure~
D.r~ Tensile10 ., 07 5 . 94 We~ Tensilell . 36 3 . 87 Dr y Elo~g . - 2:~6 403 111et Elons~ - 260 5041 * l~ot arl e~ample of the in~7entio:~.
2 5 l Fil~ns cured at room temperature for 24 hours .
2Tensile strerlgth in ~Pa of film~i; cured at designated tez~peratllre~ measured in dry ~ilms using an Instron ten~ile tester.
aTen~ile stre~ng~ in ~rea of ~ilms cured at the de~ig~ated 30 te~perature~, measured O~l films ~3oaked for 5 minuteæ
1~ a 0.5 percent ag~ueous ~urfac:tarlt solution in~edial:ely be~are testingO Testing performed on an Instron ten~ile ~ester.
4PerceT~ elongation of films cure~ at designated temper2tures measured on dry film~ using an Instro~
te~ ile tester.
~ ~ ~~ sPercent elon~ation o~ films cured at ~he desi~nated ~emperature, measur~d on ~ilm~ soaked în an aqueous ~urfactant so~ution immediately be~ore t~s~ing.
Testing performed on an Instron Tensile tester.

31,760-F -19--2 0 ~ 5 ~J ~34 .r~

TABLE I ( cont ' d ~

ff~ilms cured at 100C for 5 minutes.
7E'ilm8 cured at 120~'C ~or 5 minutes.
8Films cured at 150DC ~or 5 mix~utes.

As can be seen from 'rable I above, the latex of thi~ in~ention formed films having higher ten3ile s~reng~h ~han the ~ilms formed from ~he control latex.
More ~i~ni icantly, the tensil~ stxength of tho ~ilms O~ vention wae not ~igni~1cantly impaired upon soaking the film~ in ~ur~actan~-contaitling water. In fact, at high cuxi~g temperatur~, wetting of the ~ilms actually incr~ases their ten~ile strength. By contrast, the control sample lo~t ~ignificant tensile stren~th upon soaking in ~he sur~actan~ solution.

.
Example 2 thi~ e~ample, a coreactive latex (51 . percent solids) containing a styrene/butadiene~fumaric acid terpolymer (57.6/~0.5/1.9 weight ratio~ wa~. used a3 a starting material.
, A 1584-g portion of t~is latex was added to a 0~.0038 cu~ic metex (l-gallon) stainless steel reactor.
Sufficient of the 28 percent aqueous ammonium hydroxide so1utio~ wa~ added to the latex to increase the pH to about 8.5. Then, 198 g of deionlzed water, 2 g o~ a 1 2$ percent active sodium diethylene triamine pentaacetate l~ ~ 801ution, 1 g of s~dium persulfate, 20 g of 2-i~opropenyl-2-oxazoline, 99 y of styrene and 4 g of ~~arbon tetrachloride were added. The reactor was ~hen pu~ged wi~h ~itrogen and 81 g of butadiene were ad~ed.

31, 760-F 20-~21~ 57~t~

The reaction mixture wa~ then heated to 60C for 8 hours. The latex was the~ steam distilled to remove unreacted monomers. The resul.ting latex contained particles having both pe~dant coreac~iva and pendant 5 oxazoline groups, a~ cor~irmecl by infrared spectroscopy.
Film6 were prepared ~rom the product latex and cured a~
described in Example 1 hereinbefore. The ten~ile proper~ies o~ the reæultant ~i~ms were evaluated a~
~ described in Example 1 with ~le result~ a~ rep~rted a~
Sample ~o~ 2 in Table II ollc~wing.

For comparison, a portion o~ the coreactive latex which had not been modi~ied with the oxazoline po}y~er was ~o~med into ~ilm~, cured and tested as ~ de~crib~d in Exa~ple 1~ The re~ult~ were as repo~ted lS ~n Sample No. C-2 in Table II ~o U owing.
- : .,~, .... .

- .:
..

, - ~ ~ , . . . . . .

31,760-F -21 .

-22~ 7~45 TABLE II
CQmparative Sample No. 2Sam~le No. C-2*
R. T. Cure1 D~y Ten~ile2 6.87 7.25 W~t Tensile3 2O80 0.71 Dxy Elong.4 443 552 Wet Elong. 5 351 207 100C Cure~
~y Tensil~ 7.39 8~09 Wet Ten~ile 3.16 0.76 Dry Elong. 447 531 Wet ~long. 362 286 120C Cuxe7 Dry Tensile 8.74 8.38 --Wet Tensile 4.30 0.85 Dry Elong. 455 546 Wet Elong. 387 3~1 150C Cure~
-:20 Dry Tensile 3.7g I0.34 Wet Tensile ~ 8.24 2.70 D~ Elong. -- 435 579 - ~et ~lony. .:405 405 * Not an example o~ the in~ention.
- 25 ~ote8 1 through 8 are the ~ame a~ in TabIe 1.

~ere, i~ is seen that ~he dry tensile strength of ~he arboxylated, IP0 modi~ied latex was essentially .
eguivalenk to ~hos~ o~ ~he dry carboxylated latex.
~owevér, wh~ we~ ten~ile ~trength wa~ evalua~ed, the ` 30` ~ilm8 prepared ~rom latexes of this invention were :cl~arly superior to ~ho~e o~ the ~ontrol.

. _., ,~

-31,760-F -22-.

t~45 . -~3-xamPle 3 In this example, a 48.6 per.c:ent solid6 latex o~ a 58/38/4 ratio of -~tyrene/butadiene/acrylic acid t~rpolymer was employed aæ coreactive starting material.

A 1646-g portion of this latex wa~ added to a 0.0038 cubic meter (l-gallon) stainle~s steel reactor.
Su~icient of a 28 percent aqu.eous ammonium hydroxide Rolution was added to the latelx ~o increase ~he pH to about 8.6. Then, 198 g of deionized water, 1 ~ o~
~odium persulfak~, 2.0 g o~ a l p2rcent active sodium diethylene tetraamine pentaac~tate solution, 20 g of 2-isopropenyl-2-oxazoline, 96 g of styrene and 6 g of carbon tetrachloride w~re added to the reactor. The r~actor was the~ purged with nikrogen and 84 g of butadiene wexe added. The resulting mixture was then .p~lymeriz~d at 60C for 7 hours. The re~ulkant latex contained par~icle~ havi~g both penda~t acid a~d pendant o~azoli~g group~. Film~ wer~ ~ormed ~rom khe product l~tex according to th2 method described i~ ~xample 1 a~d were tested for t~n~le pro~erties. The results were as repoxted in Table III. For compariso~, film~
were prepared from the carbo~ylated latex containing no -- . o~azoline group~. Th~se ~ilms were tested for tensile prop~ties with the results a~ reported in Table III
follown~g a~ SampIe No. C-3.

~ ' .

- -: .
.

31,760 F 23~

1'~5'-~JI'3~.5 -2~
r AB~ ~II

Comparative ~ample No~ 3 Sample No. C-3*
R. T. Cure1 Dry Te~sile2 11.32 11~78 Wet Tensile3 6.64 9.74 Dry Elong. 4 411 370 Wet ~long.5 315 276 100C Cure~
Dry Ten~ile 12.54 .12.75 Wet Tensile 10.41 9.74 Dry Elong. 406 395 Wet Elong. 347 276 120C Cure~
Dry Tensile 13.71 1~.07 Wek Tensile ll.OZ 12.25 Dry ~long. 403 378 Wet Elong. - 348 342 150C Cure8 ~Dry ~en~ile ~ 13.~4 12.02 Wet Tensile - 13.85 12.45 : ,Dry El~ng. - 35~ 377 Wet Elong. 324 ~. 331 .
*` Not an example o ~he i~ention.
Notes 1 ~hrough 8 are the same aæ in Table I.
:
.~gain, ~he ~cellent tensile properties of wet and dry films of thi8 invention were se~n.
-:EXa~ple 4 --Into a l-liter, glass reactor immersed in a temperature controlled water bath were added 359,g of ~deionized water, 3 g of a 1 percent active agueous pentasodium~diethylene ~r~amine pentaacetate solution and 4.5 g o~ a 32 perce~t ~olids 6eed l~tex containing poly~tyre~e polymer particle~.

31,760-~ . 24-.5 The reactor was purged with nitrogen and heated to 83C. Then, over a 1-haur period was added a first monomer stream con~aining 90 g o~ butylacrylate, 53.75 g o~ methylmethyacrylate and 5.0 g of acrylic acid. A~ter this first monome.r addition, the reactor wa~ maintained at about 83C for 15 minutes~ Three grams o 28 percent ammonium hydroxide solution was added to increase the pH $rom 3.5 to 8.3, and then a s~cond monomer stream was begw~. This ~econd monomar ~tream was added over a 1-hour p~riod and co~tained 90 g o butylacrylate, 53.75 g methylm~thacrylate and 7.5 g ~ 2-isopropenyl-2-oxazoline. Beginning at the start o~ the first monomer addi~ion, was also added, over a ~ 1/4-hour period, an ~gueous stream containing 90 g deionized water, 1.5 g oX sodium ~ersul~ite, 0.3 g NaO~
and 3.3 g of a 4S percent active sur~actant solution.
~ollowi~g the addition o tho mo~om~r and aqueou~
~treams, the reactor WaB maintained at 83C for 1 addi-. tiQ~al hour, and the~ cooled.

Thi~ latex was oxmed into fiIms as descxibed in E~ample l. The films were cured by heating at 125C
- . for 5 minutes a~d t~st~d for tensile strength and elongation ~s des~ribed in Exæmple 1. The xesult~ were reported a~ Sample No. 4 i~ ~abl~ IV ~ollowing.

For com~ari~o~, films are pr~pared in like manner from ~he followi~g latex~s:

. Sample No. C 4A But~lacrylate/methylmethacrylate (60~40) Sample No. C-4B Bu~ylacrylate/methylmethacrylat~/
acrylic acid (60/38.33/1.57) 31,760~

-26 ~ 5 Sample No. C 4C Butylacrylate/methylme~hacrylate/
~-isopropenyl-2-oxazoline ~0/37.5/2.5~
Sample No. C-4D 50:50 Blend of CW4B and C-4C

S A11 films were te~ted for ten~ile trength a~d elongation a~ described hereinbe~ore with khe results as reported in Table IV following.

TAE~LE IV

__ Sample_No~
4 C-4A* C-4B* C-4C* C-4D*
Dry Tensile~ 9.79 4.90 6O62 6.76 7.45 .
Dry El~ngation2 560 730 680 780 690 Wot Tensile3 ~.48 2.62 5.10 S.93 6.25 Wet Elongation4 430 55~ 630 600 630 15 * No~ an exampl e of the invention.
~Sa~e as Note2, Table I.
2~ame As Note4, Table I.
3~ame as Not~3, Table I.
~Same as Note5 t Table I.

As can be ~een from ~he data in T~ble IV, ~ilm8 prepare~ from the latex o ~his in~ention exhibited the highest ten~ile ~rength, whether tested wet or dry. Even Sample:No. C~4D, which contained only o~azoii~e-con~aining particles and acid-containing particles, did not exhibit the tensile ~trength of films preparad ~rom th~ late~ o~ ~his in~ention.

31,7S0-F -26-

Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A curing latex composition comprising discrete polymer particles, which particles contain pendant coreactive groups and pendant oxazoline groups, which particles have been prepared by the polymerization of addition polymerizable monomers, which monomer comprise (a) a coreactive monomer containing pendant group which are capable of reacting with oxazoline groups to form a covalent bond thereto, (b) an oxazoline as represented by the general structure:

wherein R1 is an acyclic organic radical having addition polymerizable unsaturation; each R2 is independently hydrogen, halogen or an inertly substituted organic radical and n is 1 or 2 and (c) at least one other addition polymerizable monomer which does not contain a coreactive or oxazoline group.

2. The composition of Claim 1 wherein the coreactive monomer is an Q,,B-ethylenically unsaturated carboxylic acid or acid anhydride.

3. The composition of Claim 1 wherein said other addition polymerizable monomer is a monovinyl aromatic monomer or an alkyl ester of an ~
-ethylenically unsaturated carboxylic acid and/or an aliphatic conjugated diene.

4. The composition of Claim 1 wherein Rl is an isopropenyl group, each R2 is hydrogen or an alkyl group and n is 1.

5. The composition of Claim 4 wherein the oxazoline is 2-isopropenyl 2-oxazoline.

6. The composition of Claim 1 wherein the polymer particles comprise a first polymer of a coreac-tive monomer and at least one other addition polym-erizable monomer which does not contain a coreactive or oxazoline group and a second polymer of an oxazoline -and at least one other addition polymerizable monomer which does not contain a coreactive or oxazoline group.

7. The composition of Claim 1 which is self-curing at room temperature.

8., A process for preparing a latex compris-ing discrete particles containing pendant coreactive .
weak acid groups and pendant oxazoline groups, said process comprising the steps of (a) forming a latex -containing particles of a polymer containing pendant weak acid groups by polymerizing a first monomer mix comprising an addition polymerizable monomer containing a pendant weak acid group and at least one other addition polymerizable monomer which is copolymerizable with said monomer, said polymerization being conducted at a pH in the range from 1 to 6, then (b) adjusting the pH
of the resulting latex to a value at which an addition polymerizable oxazoline does not substantially react or hydrolyze under conditions suitable for the polymerization thereof, (c) adding to said latex a second monomer mix comprising (1) an addition polymerizable oxazoline as represented by the general formula:

wherein R1 is an acyclic organic radical having addition polymerizable unsaturation; each R2 is independently hydrogen, halogen or an inertly substituted organic radical and n is 1 or Z and (2) at least one other monomer which does not contain pendant coreactive weak acid or oxazoline groups, and (d) polymerizing said monomer mix under conditions such that the second monomer mix is polymerized within or around said polymer particles containing pendant coreactive weak acid groups.

9. The process of claim 8 wherein said first monomer mix comprises an .alpha.,.beta.-ethylenically unsaturated carboxylic acid and a monovinyl aromatic monomer or an alkyl ester of an .alpha.,.beta.-ethylenically unsaturated carboxylic acid or an aliphatic conjugated diene and said second monomer mix comprises an addition polymerizable oxazoline and a monovinyl aromatic monomer, an alkyl ester of an a,.beta.-ethylenically unsaturated carboxylic acid or an aliphatic conjugated diene.

10. The process of Claim 8 wherein the oxazoline is 2-isopropenyl-2-oxazoline.

11. The process of Claim 8 wherein the pH is adjusted to a value of from 7 to 11.

12. The process of Claim 8 wherein the second monomer mix contains from 0.5 to 2 moles of oxazoline per mole of coreactive monomer employed in said first monomer mix.

13. The process of Claim 9 wherein the coreactive monomer is acrylic, methacrylic, itaconic or fumaric acid, and the oxazoline is 2-isoproenyl-2-oxazoline.