CA1263491A

CA1263491A - One package aqueous latices containing alkaline- curable self-crosslinking polymers

Info

Publication number: CA1263491A
Application number: CA000487132A
Authority: CA
Inventors: Yen-Jer Shih
Original assignee: National Starch and Chemical Corp
Current assignee: Ingredion Inc
Priority date: 1984-08-02
Filing date: 1985-07-19
Publication date: 1989-11-28
Also published as: JPS6155122A; DE3577863D1; US4546140A; AU554439B2; AU4529685A; EP0170095A2; EP0170095A3; JPH0447694B2; EP0170095B1

Abstract

ABSTRACT OF THE DISCLOSURE

Shelf-stable, one-package aqueous latices, useful as adhesives, coatings or binders, which are curable with or without the application of heat, consist essentially of an alkaline-curable, self-crosslinking emulsion polymer, selected organic metal salts, and water. The alkali, alkaline earth, or heavy metal salts of C1-C6 organic acids (e.g., sodium acetate) are post-added to the polymer emulsion or present during the polymerization. The polymer typically comprises about 90-99.92 by weight of one or more vinyl polymerizable monomers (e.g., acrylates, vinyl esters, and ethylene and 0.1-10% by weight of a polymerizable non-ionic or cationic self-crosslinking monomer containing halohydrin groups (e.g., 3-chloro-2-hydroxypropyl (meth)acrylate or the reaction product of epichlorohydrin and N,N-dimethylaminopropyl methacrylamide or methacrylate).

Description

~2634gl ONE-PACKAGE AQUEOUS LATICES CONTAINING

ALKALINE-CURABLE SE U -CROSSLINKING POLYMERS

This invention relates to storage-stable, one-package, selfcross-linklng aqueous latices useful as adhesives, coatings or binders.
Vinyl ester based and ethylene-vinyl acetate based polymers have been used for some time ~n adhesives, coatings, and binders. When the polymers conta~n a functional group such as a carboxyl group, the polymers are cured by the addition of a co-reactant (i.e., crosslinker) to the polymer emulsion or solution. When the polymers contain a fun-ct~onal~ty that is self-react~ve, the use of a co-reactant species per se 1s not necessary. The advantages of self-crosslinking polymer sys-tems are the~r s~mpl~city, economy, and eff~c~ency.
Latices conta~n~ng self-crosslink~ng polymers prepared from cati-on~c funct~onal monomers are disclosed in U.S. Pat. Nos. 3,678,098, 3,694,393 and 3,702,799 issued July 18, Sept. 26, and Nov. 14, 1972 to Sheldon N. Lew1s et al. and U.S. Pat. Nos. 3,095,390 and 3,287,305 ~s-sued June 25, 1963 and Nov. 22, 1966 to A. Maeder. Lat~ces contain~ng self-crossl~nklng polymers prepared from the non-ionic functional mono-mers 3-chloro-2-hydroxypropyl methacrylate are descr~bed in the tech-n1cal data sheet of Alcolac for S~pomer~-CHPM. 3-Chloro-2-hydroxypro-pyl acrylate ~CHPA) is disclosed as useful ~n various polymers or . 20 polymer~c formulat~ons such as a polymer of butyl acrylate, methyl meth-acrylate, acrylon~tr~le, acryl~c ac~d and CHPA useful ~n a pr~nt~ng paste (see Ger. 1,282,600 ~ssued 11/14/68 to K. Craemer et al., CA 70 48583q); polymers contaln1ng CHPA and at least one functlonal monomer , , ~ 6349~

fro~ a chemically different class which are useful as curing agents for gelatin layers (see Ger. 1,109,875 issued June 29, 1961 to E. J. Birr et al., CA 56 1094b); adhesives from a proteinaceous matter, vinyl ace-tate, and CHPA (see U.S. 3,314,905 issued April 18, 1967 to S. B. Luce et al.); a polymer of methyl methacrylate, butyl acrylate, and CHPA in an aqueous dispersion which is useful for coating plasticized poly-(vinyl chloride) (see Ger. 1,231,372 issued Dec. 29, 1966 to G. Welzel et al., CA 66 56674c~; polymers of styrene, 2-ethylhexyl acrylate, N-(butoxymethyl) methacrylamide, acrylic acid, and optionally CHPA useful in printing inks as a self-crosslinkable binder (see Fr. 1,573,457 lssùed July 4, 1969 to Bad~sche Anilin- und Soda-Fabrik A.G., C.A.
42 56820 w); a polymer of butyl acrylate, acrylonitr~le, and CHPA in a cotton fabric dye composition (see Fr. 1,513,899 issued Feb. 16, 1968 to Badische Anilin- und Soda-Fabrik A.G., CA 70 97911d); a crosslink-able ethyl acrylate-CHPA copolymer useful in admixture with a solution or dispersion of another crosslinking monomer as an adhesive coating (see Ger. Offen. 1,904,743 published Sept. 10, 1970 by H. Reinhard et al., CA 73 99733h); and a polymer of 2-ethylhexyl acrylate, n- and tert-butyl acrylate, N-vinyl pyrrolldinone, acrylic acid, and CHPA useful as an aqueous adhesive coating (see Ger. Offen 1,911,306 published Sept. 10, 1970 by H. Reinhard, CA 73 110607t). The polymers are cross-linked under alkaline conditions w~th or without the use of heat.
Alkali ~e.g., sndium and ammonium hydroxide) and alkaline salts (e.g., sodium sesquicarbonate and sodium or potassium carbonate) are used for the cure.
The ma~or problem associated with these alkaline-curable latices is their short pot llfe. The need to blend the curing agent with the latlces ~ust prior to their use is inconvenlent. There is a need there-.... .. . ..

;34gl fore for a one-package latex which is shelf-stable but st~ll capable of self-crosslinking after application.
The present inventlon provides a shelf-stable, curable, one-package la~ex which consists essentially of a dispersion of an alkaline-curable, self-crosslinking emulsion polymer ~n water and a salt of an organic acid O n+
having the formula R-IC - O~ I ~ , where R is H or a Cl-C6 straight or branched chain alkyl or C2-C6 alkenyl, M is an alkali, alkaline earth, or heavy metal and n is the valence number of M; the self-cross-l~nking polymer compr~sing a vinyl polymerizable monomer and a polymer-izable cationic or non-ionic self-crossllnking monomer containing halo-hydrin groups; the salt being present in an amount effective to cure the polymer, with or without the application of heat, after application of the dispersion, and removal of the water therefrom. Suitable self-cross-llnking monomers lnclude cationic quaternary ammonium monomers hav~ng the formula ~H2C=C~C~A(CH2)n~I+_CH2_CIH_CH21 Y~
l R1 R3 OH X ~
fi and nonlonlc monomers having the formula H2C=C-C-O-CH2-CH-CH2, where R1 and R5 are hydrogen or a methyl group; A is -O- or -N- with R4 -- belng hydrogen or a C1-C3 alkyl group; R2 and R3 are independently C1-C6 alkyl groups; X is a halogen; Y ls an anion; and n is 1-4.
Typlcally the self-crossllnking polymer comprlses about 90-99.9~ by .:...........
, , , .

- ~ .

:~L 26 3LlL ~S11 weight of the ~inyl polymerizable monomer and about 0.1-10~ by weight of the halohydrin-containing monomer. As used herein, the term "stable" applies to a latex that is shelf-stable (i.e., where there is no increase in grits and/or viscosity and/or phase separation in the latex and/or coagulation of the polymer) and is still capable of curing (i.e. crosslinking) to provide the desired end use performance.
The salt may be introduced into the latex by addition to an already prepared polymer latex or by inclusion in one of the charges used in the preparation of the polymer latex. Typically a substantially equivalent amount of salt, based on the moles of cationic or non-ionic functional monomer, will be effective. The effect of the salt on the polymer may be determlned by studying the X insolubles formed after cure. With acrylate-based polymers the use of additional salt will lead to a reduction in X insolubles. With vinyl acetate-based polymers, however, salt amounts in excess of that needed to provide the equivalent amount of alkali do not reduce the ~
insolubles. Hence, the effective amount of salt to be used may vary with the salt, the type and amount of functional monomer used, and the polymer type (acrylate vs. vinyl acetate). It will also depend upon the degree of crosslinking desired, which may vary depending upon the intended end use.
Typical non-functional vinyl polymerizable monomers include vinyl esters, alkyl (meth)acrylates, styrene and mixtures thereof as well as ethylene-vinyl acetate and mixtures thereof with other vinyl polymeriz-able monomers. The monomer type and amount depends upon the end use(i.e., laminating adhesive, pressure sensitive adhesive, binder, and the like).

.~

~LZ~i34~g1 Typical functional monomers ~nclude the cationic monoethylenically unsaturated ester monomers derived from N,N-dialkylaminoalkyl esters of (meth)acrylic acid and epihalohydrins, the cationic monoethylenically unsaturated ester monomers derived from N,~-dialkylaminoalkyl amides of (meth)acrylic acid and epihalohydrins, and the non-ionic ethylenically unsaturated ester monomers derived from (meth)acrylic acid and epihalo-hydrins. It may also be possible to use other monomeric polymerizable chlorohydrin esters or amides prepared by the reaction of epichlorohydrin and other unsaturated acids such as crotonic, furmaric, maleic, and itaconlc acids or their N,N-dialkyl-aminoalkyl esters or amides.
In the vinyl ester polymers, the vinyl ester is present in amounts of at least about 5X, the functional monomer is present in amounts of about O.l-lOX, and any opt~onal vinyl polymerizable monomer is present in amounts of about 0-94.9X. In the ethylene-vinyl acetate polymers, the monomer amounts are about 0.5-40X ethylene, up to about 89.5X vinyl acetate, about O.l-lOX cationic monomer, and 0-5X of any optional vinyl polymerizable monomer. The amounts are by weight and total lOOX. As used herein, the tenm "functional" monomer refers to those monomers containing halohydrin or epoxide groups which are capable of self-cross-linking under alkaline conditions.
Suitable salts include alkali, alkaline earth, or heavy metal salts of organic acids (e.g. sodium, potassium, calcium, aluminum, or lead formate, acetate, propionate and the like). The salt acts as a latent curing agent which, after application of the latex and the removal of the water, cures the self-crosslinking monomer. Since the salt does not raise the pH of the latex during storage, the shelf-stability ls good. It is believed that during drying the pH is raised by the in situ generation of a strong alkali when the organic ac1d anion is re-...

~Z~i34:91 moved as a volatile ac~d. Dry~ng may be carried out at room tempera-ture or an elevated temperature depending upon the end use and, more importantly, the volatil~ty of the acid. For example, sodium acetate ~s capable of curing the polymers at room temperature. The volatile acetic acid is removed with the water during drying and the sodium hydroxide produced is believed to effect the cure.
The vinyl esters su~table for use herein ~nclude preferably vinyl acetate, other vinyl esters of saturated aliphatic monocarboxylic acids containing up to 6 carbon atoms such as vinyl propionate and the like, and ethylene-vinyl acetate.
Other vinyl polymerizable monomers include monomers such as esters of (meth)acryl~c acid with C1-C1g alcohols, ~ncluding Cl-Cl8 ; alkanols, benzyl alcohol, cyclohexyl alcohol, and isobornyl alcohol, such as methyl, ethyl, butyl, 2-ethylhexyl, or octadecylacrylate or methacrylate; (meth)acrylamide and their N-substituted derivatives, such as N-mono and N-dimethyl, -ethyl, -propyl, and -butyl acrylamide .. . .
or methacrylamide and N-mono- or diphenylacrylamide; vinyl ethers such as butyl vinyl ether; N-vinyl lactams such as N-vinyl pyrrolidinone;
halogenated vinyl compounds such as vinyl chloride and vinylidene chlorlde or flouride; alkyl vinyl ketones such as methyl or ethyl vinyl ketone; diesters ofc~ unsaturated dicarboxylic acids such as dimeth-yl, diethyl, dipropyl, d~butyl, diphenyl, d~benzyl, and di(phenylethyl) ~taconate, maleate, and fumarate; ~meth)allyl esters of saturated ali-. ~, phatlc monocarboxyl~c acids, such as allyl and methallyl acetates, pro-,, ~ 25 pionates, and valerates; v~nyl compounds such as v~nyl pyrrole; styrene;
;, .
and olefins such as ethylene. Minor amounts ~e.g. 0.01-2X) of ;~ crossl~nking monomers such as diallyl maleate and tr~allyl cyanurate ;. ' .,,,,,;, ~6~4gl are also useful here~n.
The functional cationic monomers suitable for use herein are quater-nary am nium compounds represented by the fonmula given above. Typi-cally the anion is Cl-, Br~, R'C02-, N03-, S04-, or like anions derived from inorganic or organic acids.
The ester monomer may be prepared according to the procedure des-cribed in U.S. Pat. No. 3,678,098 cited earlier. An epihalohydrin, preferably epichlorohydrin, is reacted under acid conditions wnth the hydrogen acid salt of a basic ester of the formula ~ R2 H2C=C-C-0-(CH2)n-N . HY, wherein R1, R2, R3, Y and n, are as de-fined hereinabove. The reaction is carried out at from ambient temper-ature to 80C., preferably 50C. or less, in an aqueous medium. The epihalohydrin, used in at least a stoichiometric amount, is generally added to the aqueous salt solution. It is essential to maintain the pH
on the acld side to avoid side reactions. A polymerization inhibitor (e.g. monomethyl ether of hydroquinone, hydroquinone, or phenothiazine) may be used. The monomers are obtained in high yield in the aqueous reaction medium. They may be stored as the aqueous solution or concen-trated or even isolated by vacuum vaporization of the water.
The cationic amide monomer may be prepared according to the pro-cedure of U.S. Pat. No. 3,095,390 cited earlier. They may be prepared using the above procedure except that the hydrogen acid salt of a suitable basic amide is used. The salt has the formula H2C=f-C-I-(CH2)n-~ . HY, wherein R1, R2, R3, R4, Y and n are ~, R1 R4 R3 .
.. . .

~Z634~91 as defined above The ester monomer can also be prepared by the re-action of methacrylic acid or acrylic acid w~th epihalohydrin.
The functional non-ionic monsmers suitable for use herein are the reaction products of (methlacrylic acid and an epihalohydrin, pre-ferably epichlorohydrin. The preparation of 3-chloro-2-hydroxypropyl methacrylate is well known and described in an article by M. Yoshino et al. ("Derivatives of Epichlorohydrin IX. Synthesis of Glycidyl Ethers. 1." in Yukagaku 15 (11), 573-8, 1966, CA 66 46073s). The reaction is carried out at up to 110C. in the presence of a catalyst such as tertiary amines (e.g., triethylamine or pyridine) or quater-nary ammonium salts. Solvents have no desirable effect on the reaction.
The order of addition of the reactants does affect the reaction and the slow addition sf epichlorohydrin to the acid is preferred.
The vinyl ester based polymers are prepared using conventiGnal aqueous emulsion polymerization techniques, i.e., w~th the use of an ini-tiator or redox system and a surfactant. The ethylene-vinyl acetate based polymerizations are likewise carried out using conventional aqueous ethylene-vinyl acetate emulsion polymerization techniques, i.e., under pressure with the use of a redox system and surfactant.
Suitable ~nitiators include azo initiators ~e.g., 2,2'-azobisisobutyl nitrile), peroxides (e.g. hydrogen peroxide), and redox systems (e.g.
t-butyl hydroperoxide with sodium formaldehyde sulfoxylate). In the pre-ferred polymerization process, a water-soluble azo ~nitiator (e.g., 2,2'-azobis(2-amidinopropane) hydrochloride or azo-N,N'-dimethylene isobutyr-~- 25 amid~ne hydrocM oride) is used in combination with a water-soluble chain transfer agent such as an amino thiol salt (e.g., cysteamine hydro-chloride also referred to as aminoethane thiol hydrochloride or 2-diethyl-~ ~:

. ' .

~ iL~i3 4~1 aminoethane thiol hydrochloride). The water-soluble azo initiator is used in amounts from about 0.05-1~, preferably in amounts of about 0.18-0.4X; the chain transfer agent is used amounts of about 0.001-0.2X, preferably about 0.002-0.12~, both by weight based on the polymer solids.
A cationic or non-ionic surfactant ls used with the cationic self-crossllnking monomer. Any surfactant may be used with the nonionic self-crosslinking monomer. The cationic and ionic surfactants useful herein are conventional and disclosed in U.S. Pat. No. 3,287,305 (cited earlier). Typically they are used in amounts of 0.5-6~ by weight based on polymer solids. Suitable cationic surfactants lnclude a compound of a higher fatty amlne with an acld selected from the group consistlng of acetlc acld, hydrochlorlc acld and sulfuric acid; a salt of diethyl-aminoethyl ester of a higher fatty acid; oleyl amldo ethyl-diethylamlne acetate; and a quaternary ammonlum compound such as cetyldimethyl-benzyl-ammonlum chlorlde, cetyl-trimethyl-ammonlum bromide, para(tri-methylammonium)benzolc acld cetyl ester methosulphate, L~-(lauroyl-amino)propyl]-trlmethylammonlum methosulfate, cetylpyridinlum metho-sulphate, octadecyltrlmethylammonlum bromlde, and the quaternary ammonlum compound from dlethyl sulphate and triethanolamlne trlstear-ate. Suitable nonlonlc surfactants lnclude polyglycol ethers of afatty acld, fatty amlne, or fatty alcohol, octylphenol polyglycol ether, and polyhydrlc alcohol partlally esterfled wlth a hlgher fatty acld.
Optlonally and preferably, the latlces wlll also include additlve amounts of compatlble addltives of the type common to the adhesive, coating, and blnder arts such as stabillzers (partially hydrolyzed polyvlnyl alcohol), fillers, plgments, plasticizers, thlckeners (water-soluble cellulose derlvatlves, polyvlnyl alcohols and polyacrylamldes), ~:~63491 dispersants, defoamers, dyes, tackifiers, and the like. The latices wi11 typically contain at least 25~ by we~ght of water (~.e., they wlll have solids content of up to about 75X by weight, preferably about 40-60X by weight) with the solids content depending upon the end use.
The following examples will more fully illustrate the embodiments herein. In the examples all parts are given by weight and all temper-atures are in degrees Celsius unless otherwise noted. Brookfield vis-cosities (20 RPM) are measured at the indicated latex solids, and in-trinsic viscosities (I-V-) are determined in dimethyl fonnamide (DMF) or tetrahydrofuran (THF) at 30C. Deionized water was used in the pre-paration of the solutions and emulsions used for the polymerizations.
The test procedure used to evaluate the perfonmance of the adhesives hereln lnclude standard tests developed by the Specif~cations and Tech-nical Committee of the Pressure Sensitive Tape Council in Glenview, Ill.
The shear adhesion (holding power) test (PSTC-7) is described at p. 30, of the 7th ed~tion of Test Methods for Pressure Sensitive Tapes 91976).
The shear adhesion at 37C (100F) and 100X relative humidity was deter-mined first. If the laminate did not fail, the shear adhesion of the same laminate at 82C (180F) was then determined. The peel adhesion test for single coated tapes 180 angle (PSTC-l) is descr1bed at pp. 22.
EXAMPLE I
This example describes the preparation of a cationic amide monomer, the preparation of a high solids aqueous polymer latex containing sodium acetate and a high molecular weight cationic polymer prepared from i - 25 ethyl acrylate (EA), 2-ethylhexyl acrylate (2-EHA), and the self-cross-linkable cationic amide monomer. It also shows the use of the latex as a laminating adhesive.

.

~L~'63491 `art A - Preparat~on of the Cationlc Monomer A 12-l. reactor equipped with a thermometer, agitator, addition funnel, and condenser was charged with 2968 9. water and 3060 9. N,N-dimethylaminopropyl methacrylamide (DMAPMA). The solution was cooled to 20C and 1820 9. of concentrated hydrochloric acid were added slowly over 2 hr. while maintalning the temperature below 30C. Then 1332 9.
epichlorohydrin (EPI) were added slowly over 2.5 hr. while maintaining the temperature at 30-35C. The solution was held overnight and then adjusted to pH 4-4.5 with hydrochlorlc acid. The unreacted EPI was re-moved by vacuum strlpping at 63-68C. and the distillate was replaced w~th the same amount of water during strlpping.
The result~ng solution (53.6X solids) contalned the quaternary ammon~um salt wh~ch is the adduct of DMAPMA and EPI and which is refer-; red to as DPE. The salt has the followlng formula:

~ 2C C-C-NH-CH2-CH2-CH2-N~-CH2-CH-CH2~ Cl-CH3 CH3 OH Cl Part B - Preparatlon of the Polymer Latex A 2-llter four-neck flask was fitted wlth a thermometer, condenser, agltator, subsurface nltrogen purge, and sultable add~tional funnels.
The followlng charges were prepared.
A. 3.4 9. 70X octylphenol with 30 moles ethylene ox~de (EO), 4.5 9. octylphenol w~th 4 moles EO, 0.003 9. ferr~c sulfate, - ~ and 0.06 9. t-butyl hydrogen perox~de (t-BHP) in 192.5 9.
water and ad~usted to pH 4 by acet~c ac~d B. 25.0 9. ethyl acrylate (EA) C. 0.06 9. sodlum formaldehyde sulfoxylate (SFS) D. 425.0 9. EA, 50.0 9. 2-ethylhexyl acrylate ~2-EHA) and 0.6 9.
t-BHP emulsif~ed ~n a mlxture of 105.0 9. water, 32.5 9. 70X
octylphenol w1th 30 moles EO, 2.5 9. octylphenol wlth 4 moles . EO, and 27.0 9. monomer solut~on of Part A
~, , ,: ', ~' ", "' .. :

, ' ~ , .

~3491 E. 0.6 9. SFS in 20.0 9. water F. 0.5 9. t-BHP in 5.0 9. water G. 0.5 9. SFS in 5.0 9. water The initial charge A was added to the flask and the mixture was purged subsurface with nitrogen for 1 hr. Agitation was started and charge B was added. The mixture was heated to 55C while charge C was added at 35C. Ten minutes later charges D and E were added separately and slowly over 4.5 hr. at 55C. The mixture was maintained at 55C
for 10 min. Then charge F was added in one shot and 5 min. later charge G was slowly added over 10 min. The batch was then held for 10 min. at 55C, cooled, and discharged.
Part C - Preparation and Use of The Thickened Latex as a Laminating Adhesive The latex of Part B was compounded with 0.3X sodium acetate ~NaOAc), thickened to 17,000 cps. with hydroxyethyl cellulose and sprayed over fiberglass. The adhesive-coated fiberglass was dried for 5 min. at 93C (200F), then passed through a hot press cycle at 93C for 30 sec., and aged for one week at room temperature. It exhibited excel-lent shear adhesion to polyurethane foam. For example, 1 square inch of the fiberglass/polyurethane foam laminate was loaded with a 300 gm.
weight. The laminate did not fail after 24 hr. at 37C and 100X
relative humidity. On further testing the same lamlnate did not fail even after 8 hours at 80C.
A comparative latex was prepared as above except that 2X sodium sesquicarbonate ~a known alkaline curing agent~ was used in place of sodium acetate. The latex was similarly thickened (16,000 vs. 17,000 cps.) with hydroxyethyl cellulose. A laminate of the adhesive-coated fiberglass and polyurethane foam did not fail in the above high humldity and high temperature tests.

~' ~

~t~ 3 4 9 JL

Another latex was prepared as in Part B except that 1.5 9. of sodium acetate was present in Charge D. The thickened latex was comparable to that prepared by adding the sodium acetate after the polymerization. A laminate of the adhesive-coated fiberglass and polyurethane foa,m did not fail in the above high humidity and high temperature tests.
A control latex prepared as above but nnthout a curing agent (i.e., no sodium acetate or sodium sesquicarbonate) and thickened to 16,000 cps with hydroxyethyl cellulose was evaluated. In the shear adhesion test a laminate of the adhesive-coated fiberglass and polyurethane foam failed after 30 minutes at 37C and 100~ relative humidity vs. no failure after 24 hours for the salt-cured latex. The control laminate was not evaluated at 82C as it did not pass the humidity test.
The results show that the latent curing agent was as effective as the prior art alkaline curing agent.
EXAMPLE II
This example demonstrates the storage stability of aqueous polymer latices containing sodium acetate as the latent curing agent.
A latex was prepared as in Example I and thickened to 17,000 cps.
The latex was used, both before and after storage for 4 weeks at 49C
(120F), to coat fiberglass and then prepare fiberglass/polyùrethane foam laminates. Both laminates exhibited excellent shear adhesion at high humidity and high temperature. The viscosity of the stored latex was approximately the same, i.e., 16,500 cps.
A portion of the comparative latex of Example I (containing 2~
sodiun sesqu~carbonate) was also aged at 49C. The viscosity increased from 16,000 to 18,000 cps. after 2 weeks and then to 19,250 cps. after 4 weeks. A fiberglass/polyurethane foam laminate prepared using the adhesive aged for 2 weeks showed only a 4 hour maximum shear adhesion at 37C and 100~ relative humidity; it was not evaluated for high tem-5 perature adhesion as it failed the high humidity test.
The results show that the sodium acetate-containing latex provided excellent shear adhesion even after storage, whereas the sodium sesqui-carbonate-containing latex did not.
EXAMPLE III
This example describes the preparation of a functional cationic ester monomer and the preparation of a high solids aqueous polymer latex containing a high molecular weight polymer prepared as in Example I but using the cationic ester monomer.
Part A - Preparation of the Cationic Monomer A 4-neck, 1-l, flask equipped with a thermometer, agitator, addition funnel, and condenser was charged with 219 9. water and 108 9. concentra-ted hydrochloric acid. The solution was cooled to 10C and 169 9. N,N-dimethylaminoethyl methacrylate (DMAEMA) was slowly added over 2 hr. at such a rate that the contents were maintained at less than 15C. Then 70 9. epichlorohydrin (EPI) were added in one shot. The solution was held overnight with stirring and then ad~usted to pH 3.5 with hydrochloric acid. The unreacted EPI was removed by vacuum stripping at about 60C.
The resulting solution ~72.2~ solids) contained the quaternary am-: monium salt which is the adduct of oMAEMA and EPI and which is referred to as DEE. The salt has the following formula:

I fH3 H2C=CI-C-O-CH2-CH2-l+-CH2-fH-fH2 Cl-CH3 CH3 OH Cl 3L~ 3 4~3~

Part B - Preparat~on of the Polymer Latex The polymerization was carr~ed out as ~n Example I except that 21.0 9. of the above monomer solution was used in charge D in place of the 27.0 9. of the cationic monomer of Part A of Example I. The resulting 5 latex was 58.0~ solids. Compounded with 0.5~ sodium acetate (slightly less than an equivalent amount), the reflux ~nsolubles of the cast film in DMF were 36%. A film cast from the control which contained no curing agent, but which was similarly oven-cured, had only 9X insolubles.
EXAMPLE 1~
The latices of Example I, but not thickened as in Example I, were compounded ~ th the indicated amount of salt and cast as films on a metal plate. The f~lms were a~r-dr~ed overnight at room temperature and then baked for 5 m~n. at 130C. The reflux insolubles of the oven-cured f~lms in DMF were detenm~ned. The results are g~ven in Table I.
TABLE I
Latent Cur~ng Agent Insolubles Amount Used Salt (wt. ~) Oven Cured (~) Control - 2*
HC02Na 0.20 20 HC02Na 0.40** 43 CH3C02Na 0.20 24 CH3CO~Na 0.50** 39 C2HsC02Na 0.30 35 C2HsC02Na 0.50 41 C3H7CO~Na 0.67** 25 CsH11C02Na 0.84** 20 C6H13C2Na 0.92** 14 C7HlsC02Na 1.00** 12 CgH1gC02Na 1.18** 19 ~ CllH~C02Na 1.34** 38 - (CR3E~2)2Ca 0.49** 52 (CH3C02)2Ca 0.98 31 ; (CH3C02)3Al 0.43** 7 (CH3C02)3Al 0.86 11 .

.

~'~634gl TABLE I - (continued) -Latent Curing A ~ U d Insolubles mount se S _ (wt. X) Oven Cured (X) (CH3c02)2pb 3H2o 1.20** 26 NaCl*** 0.50 2 Na Sulfate*** 0.50 Na Oxalate*** 0.50 2 Na Oxalate*** l.OO 2 *Control typically ran between 0.5-5X.
**Approximately equivalent amount based on self-crosslinking monomer.
***Comparative.
The results show that a number of metals can be used as the cation.
The results also show that the anions from various organic acids (up to Cl1) are suitable as latent curing agents; however, as will be shown in Example IX, not all organic salts give storage stable latices. They further show that inorganic and organic salts (sodium chloride, sodium sulfate, sodium oxalate) that form strong acids are not suitable, i.e.
they do not crosslink the polymer as indicated by the low ~ insolubles, which was about the same as the control.
-` EXAMPLE V
This example demonstrates that a non-ionic functional monomer con-ta1ning halohydrin groups can be used in the preparation of polymer latlces containing the salts as latent curing agents.
The polymer latex was prepared as in Example I except that 10.0 gm.
of 3-chloro-2-hydroxypropyl-methacrylate and 7.5 9. 60X aqueous solu-tion of dimethylaminopropyl methacrylamide were used instead of 27.0 9.
of the cationic functional monomer solution of part A of Example I. In compounding 0.5X NaOAc (~,equivalent amount) was used instead of 0.3~.
A film was cast and oven-cured as in Example Il. The reflux insolubles ` of the cast film in DMF was 21X. A film cast from the control which ~26~4gl contained no curing agent but was similarly oven-cured had only 3.0X
insolubles.
EXAMPLE YI
This example de~onstrates the preparation of additional latently curable polymer latices using vinyl acetate (YA) and butyl acrylate (BA).
It also demonstrates the use of the latex as a binder.
The polymerization was carried out as in Example I using the fol-lowing charge:
A. 0.25 9. cetyltrimethylammonium chloride (CTMAC) 3.0 9. 70X
octylphenol with 30 moles EO, 0.3 9. octylphenol ~ th 10 moles EO, 8.0 9. catlonic monomer solution of Part A of Example I, and 0.5 9. 2,2'-azobis (2-amidinopropane) hydrochloride ( MP) in 300 9. water B. 50.0 9. VA and 5 9. BA
C. 200.0 9. VA and 245 9. BA emulsified in a mixture of 100 9.
water, 21.45 9. 70X octylphenol with 30 moles EO, 2.5 9.
octylphenol with 10 moles EO, 0.5 9. CTMAC, 0.22 9. cysteamine HCl, and 32.4 9. cationic monomer solut~on of part A
D. 1.5 9. MP in 4~ 9. water The initial charge A was added to the flask and the mlxture was purged subsurface with nitrogen for 30 min. Agitation was started and charge B was added. The mixture was heated to 75C.; 5 mln. after reflux stopped, charges C & D were added separately and slowly over 4.5 hours and 5 hours, respectively. The batch was then held for 1 hour, cooled and discharged. The resulting latex was 47.1X solids.
The latex was blended with lX NaOAc and lX d~dodecyl dimethyl ammonium chloride (a cationic surfactant), diluted to 40X sol~ds with deionized water, and used to saturate a polyester web. After drum drying, the web had a strength of 0.55 lb./in. and dry strength of 1.4 lb./in. Without sodium acetate, the wet and dry strengths were 0.21 lb./ln. and 0.9 lb./in., respectively.

49~L

The results show that the latent cur~ng agent was effective with a vinyl acetate/butyl acrylate polymer containing functional cationic groups and that the crosslinked polymer imparted strength when used as a binder for polyester webs.
EXAMPLE YI I
This example demonstrates the preparation of a latently curable polymer latice using ethylene (E), vinyl acetate ~VA) and DPE.
The following charges were prepared:
A. 0.33 CTMAC, 1.5 9. 70~ octyl phenol with 30 moles EO, 0.15 g.
octylphenol wlth 10 moles EO, 0.1 g. MP, 190.0 9. water, and 3.3 9. cationic monomer solution of Example I 'j B. 170.0 9. YA emulsified in a mixture of 50.0 9. water 10.5 9.
CTMAC, 1.25 g. 70~ octylphenol with 30 moles EO, and 9.5 9.
cationic monomer solution of Example I
C. 86.6 9. water and 0.875 g. AAP
The polymerization was carried out by charging a 1-liter stainless steel reactor ~ th charge A, applying a vacuum, and purging with nitrogen i three times. Then 25.0 9. vinyl acetate were charged and the tempera-ture was brought up to 75C. The reactor was pressurized w~th ethylene to 350 psi and, 30 m1n. after initiation, the ethylene pressure was ra~sed to 800 psi while charges B and C were slowly and separately pumped ~n over 5 and 5.5 hrs. respectively. The mixture was held at 75C for

2 hrs., cooled, and discharged. The resulting latex was 40.8X solids.
The above latex was compounded with different levels of sodium ace-tate. Films were cast on a metal plate, dried overn~ght, and oven-bak-ed at 130C for 5 min. The reflux insolubles in DMF are shown below:
- Wt. X NaOAc X Insolubles 0 2.0 0 3 46.0 0 5* 46.0 1.0 41.0 *Equivalent amount of salt.
,~ , .

4gl~

The X insolubles show that the polymers were cured by the sodium acetate.
EXAMPLE YIII
This example demonstrates that compounding a pressure sensitive polymer latex with the latent curing salts herein improves the shear adhesion.
The polymer latex was prepared as in Example I except that in Charge D 180.0 9. EA and 295.0 9. 2-EHA were used instead of 425.0 EA and 50.0 9. 2-EHA. The resulting latex was 58.0X solids.
The latex was compounded with the indicated amount of salt, coated on a release paper, and oven-baked at 135C (275F) for 5 minutes. For the shear adhesion test the film was transferred to a Mylar film and 3.2 sq. cm. (0.5 sq. in.) of the Mylar film was adhered to a steel panel and loaded with 1000 gm. weight. The peel adhesion, which was measured as lb./~n. width using an Instron Tensile Tester at a 180 angle, was satisfactory for all the latices and ranged from 1.7-2.7 after 20 min.
and 2.2-4.0 after 24 hr. The shear adhesion results are shown below.
Latent CUrin9 A9eAmOunt used Shear Adhesion Salt (wt. X) (hr.) Control _ 0.4 HCO~Na 0.40 4.8 CH3~02Na 0.25 1.9 CH3C02Na o.50 2.1 CH3C02Na 1.00 2.7 C2HsCQ2Na 0.50 2.9 C3H7C02Na 0.67 2.5 CsH1lc02Na 0.84 2.2 C6H13C02Na 0.92 2.4 C7H1sC02Na 1.00 1.9 CgH1gC02Na 1.18 1.3 C11H23CO~Na 1.24 1.2 (CH3C00)2Ca 0.49 1.5 (CH3C0~2Ca 0.98 2.0 (CH3C02)3Al 0.50 1.2 (CH3C02)3Al 1.00 1.5 ~2~j 3 4 9 Latent Curinq Aqent Amouni use~ Shear Adhesion Salt (wt. X) (hr.) NaCl* 0.50 û.~
5 NaOxalate* 0.50 0.5 *Conparative.
The results show that the latent curing agents improved the shear adhesion, with sodium fonmate showing the most significant improvement.
The sodium salts containing anions from the lower acids (up to C6) were 1û somewhat better than those containing anions from the higher acids (up to C11). The results show that the salts of multi-valent cations were also effective. The results again demonstrate that inorganic and organic salts (e.g., sodium chloride and sodium oxalate) that form strong acids are not suitable.
EXAMPLE IX
This example studies the storage stability (as indicated by no significant viscosity increase) and curing (as ~ndicated by X insol-ubles after heat cure) for the lat~ces herein.
Part A - Storage Stability of Latices Containing Cationic Functional Monomer The latices of Example I, but not th1ckened as in Example I, were co0pounded with the indicated amount of salt and stored (120F) for up to 23 days. The change in viscosity with time is shown below.
Curing Agent Yiscosity (cps.) oun Salt Used O days 7 days 16 days 23 days Control - 508 560 560 575 Control - 200 230 225 225 CH3CO2Na 0.50 340 355 350 345 C3H7C02Na 0.67 342 365 350 375 C5H1lC2Na 0.84 295 400 350 350 C6H13C2Na 0.92 298 350 370 375 , ~

..

Cur~ng Agent Viscosity (cps.) Amount Salt Used O days 7 days 16 days23 days (wt. ~) S c7HlsC2Na* 1.00 CgHlgCO7Na*1.18 C11R23C2Na*1.24 Sodium Sesqui- 1.50 178 235 240 230 carbonate**
10 *Coagulated during compounding **Comparative The results show that the salts of the lower acids (up to C3) had the best storage stabllity, that salts of higher acids (up to C6) were better in storage stability than sodium sesquicarbonate but not as good as the lower acids, and that the salts of acids above C6 are unsatis-factory as they caused the latex to coagulate during compounding. This correlates w~th the shear adhesion results in the previous example where the performance of the salts of acids above C6 was inferior.
Part B - Insolubility Study of Latices Contain~ng Non-Ionic Functional Monomer Latices were prepared as in Example Y except that charges A and D
conta1ned 210.0 9. and 115.0 9. of water instead of 192.5 and 105.0 9.
The latices were compounded with the indicated salts, cast as films, and cured as in Example IV. The re~ ux insolubles of the oven-cured films in DMF were determined. The results are shown below.
Curing Agent Insolubles Salt Amount Used Oven-Cured 5 Min. at 13U~C.
~wt. %~ lX) Control - 4.9*
CH3C02Na 0.3 20.0 CH3C02Na 0.5 22.6 CH3CO7Na 0.8 3.9 C7H15C02Na0.5 4 0 C7Hl5C02Na1.0 6.0 C12R23C2Na0.5 5.0 C12H23C02Na 1.0 12.5**
*Control typically ran between 0.5-5~.
**Coagulated after standing overnight.

1 Z~i34~1 The results show that the salts of the higher acids did not cure the polymers as indicated by the percentage insolubles which were no higher than the control. The use of 0.3% and 0.5X sodium acetate was very effective (20X and 22.6X insolubles). The use of 0.8~, which is more than an equimolar amount based on the non-ionic monomer, resulted in no insolubles.
Example X
This example demonstrates that the latices are room temperature curable.
Part A - Acr~late-Based Polymer Latex The latex was prepared as in Part B of Example I except that 2.2 9.
of sodium acetate was present in charge D. The latex was cast as fllms on a metal plate. One film was dried overn~ght at room temperature and then baked for 5 min. at 130C. The other film was dried at room tem-perature and aged for 1 week at room temperature.
The reflux insolubles for the oven-cured film in DMF was 25X, while the insolubles for the room-temperature cured film was 66X.
Part B-Yinyl Acetate-Based Polymer Latex ; The latex was prepared as in Example VI except that in charge C19.0 9. of the monomer solution of Part A was used instead of 32.4 9.
- and 1.5 g. sodium acetate were present. Also charges E (0.5 9. tert-butyl hydrogen peroxide in 5 9. of water) and F (0.5 9. sodium meta-bisulfite in 10 9. of water) were post-added. Charges C and D were added separately and slowly over 4.5 hr. The batch was held ~or 10 min., then charge E was added. The batch was held for 5 min., then charge F was added over 20 min. The batch was held for 10 mln., cooled and discharged. Films were cast and dried as above except that the air-drled film was only aged overnight.
, .

3~3~

The reflux insolubles for the oven-cured film in DMF were 62~, while the insolubles for the room temperature cured film were 55~.
The results show both polymers were cured at room temperature, without extensive aging, by the sodium acetate.
In summary, the present invention is seen to provide shelf-stable, curable, one package aqueous latices containing an alkaline-curable, self-crosslinking emulsion polymer and selected organic acid salts as latent curing agents which are effective even at room temperature.

Claims

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

1. A shelf-stable, curable, one-package latex which consists essentially of a dispersion of an alkaline-curable, self-crosslinking emulsion polymer in water and a salt of an organic acid having the formula where R is H or a C1-C6 straight or branched chain alkyl or C2-C6 alkenyl, M is an alkali, alkaline earth, or heavy metal, and n is the valence number of M; the self-crosslinking polymer comprising about 90-99.9% by weight of a vinyl polymerizable monomer and about 0.1-10% by weight of a polymerizable cationic or non-ionic self-crosslinking monomer containing halohydrin groups; the salt being present in an amount effective to cure the polymer, with or without the application of heat, after application of the dispersion and removal of the water therefrom.

2. The latex of Claim 1, wherein the salt is the sodium, calcium, aluminum, or lead salt of formic, acetic, propionic, butyric, valeric, or caproic acid; wherein the vinyl polymerizable monomer is selected from the group consisting of an up to C6 saturated aliphatic mono-carboxylic acid; an ester of acrylic or methacrylic acid with a C1-C18 alcohol; an acrylamide, methacrylamide, or N-substituted derivative thereof; a vinyl ether; a N-vinyl lactam; a halogenated vinyl compound;
an alkyl vinyl ketone; a diester of an ?,.beta.-unsaturated dicarboxylic acid; an allyl or methallyl ester of a saturated aliphatic monocarboxy-lic acid: a vinyl pyrrole; styrene; and an olefin; and wherein the self-crosslinking monomer is selected from the group consisting of a cationic quaternary ammonium monomer havlng the formula and a nonionic monomer having the formula , where R1 and R5 are hydrogen or a methyl group; A is -0- or -y- with R4 being hydrogen or a C1-C3 alkyl group; R2 and R3 are independently a C1-C6 alkyl; X is a halogen; Y is an anion; and n is 1-4.

3. The latex of Claim 2, wherein the salt is present in a more or less equimolar amount based on moles of the self-crosslinking monomer present in the polymer.

4. The latex of Claim 2, wherein the vinyl polymerizable monomer is vinyl ester, alkyl acrylate, alkyl methacrylate, styrene, or ethy-lene; wherein the cationic quaternary ammonium monomer is the reaction product of N,N-dimethylaminopropyl methacrylamide and epichlorohydrin or of N,N-dimethylaminopropyl methacrylate and epichlorohydrin present in an amount of about 1-5%; and wherein the nonionic monomer is 3-chloro-2-hydroxypropyl methacrylate or 3-chloro-2-hydroxypropyl acrylate present in an amount of about 0.05-5%.

5. The latex of Claim 4, wherein the vinyl ester or acrylate monomer is at least about 5%; and wherein the ethylene monomer is present in amounts of about 0.5-40% and the vinyl ester is vinyl acetate present in amounts up to about 89.5%.

6. The latex of Claim 1, which further consists essentially of a thickener.

7. The latex of Claim 6 wherein the thickener is selected from the group consisting water-soluble cellulose derivatives, polyvinyl alcohols, and polyacrylamides.

8. The latex of Claim 1, wherein the vinyl polymerizable monomer is vinyl acetate or mixtures thereof with ethyl acrylate, butyl acrylate, and/or 2-ethylhexyl acrylate; ethyl acrylate, butyl acrylate, 2-ethyl-hexyl acrylate or mixtures thereof; or ethylene and vinyl acetate;
wherein the self-crosslinking monomer is the reaction product of N,N-dimethylaminopropyl methacrylamide and epichlorohydrin; the reaction product of N,N-dimethylaminopropyl methacrylate and epichlorohydrin;
3-chloro-2-hydroxypropyl acrylate; or 3-chloro-2-hydroxypropyl meth-acrylate; wherein the salt is sodium formate, acetate, propionate, butyrate, valerate, or caproate; calcium acetate; aluminum acetate; or lead acetate.

9. A process for preparing the latex of Claim 1, comprising adding an effective amount of the salt of the organic acid to the aqueous latex from the emulsion polymerization in water of the vinyl polymerizable monomer and the self-crosslinking monomer.

10. A process for preparing the latex of Claim 1, comprising polymer-izing the vinyl polymerizable monomer and the self-crosslinking monomer in an aqueous emulsion containing a free radical initiator, an effective amount of the salt of the organic acid, and an emulsion stabilizing amount of a compatible surfactant.

11. A shelf-stable, curable, one-package latex which consists essentially of a dispersion of an alkaline-curable, self-crosslinking emulsion polymer in water and a salt of an organic acid having the formula where R is H or a C1-C6 straight or branched chain alkyl or C2-C6 alkenyl, M is an alkali, alkaline earth, or heavy metal, and n is the valence number of M;
the self-crosslinking polymer comprising about 90-99.9% by weight of a vinyl polymerizable monomer selected from the group consisting of a vinyl ester of an up to C6 saturated aliphatic monocarboxylic acid; an ester of acrylic or methacrylic acid with a C1-C18 alcohol; an acrylamide, methacrylamide, or N-substituted derivative thereof; a vinyl ether: a N-vinyl lactam; a halogenated vinyl compound; an alkyl vinyl ketone; a diester of an a,B-unsaturated dicarboxylic acid; an allyl or methallyl ester of a saturated aliphatic monocarboxylic acid; a vinyl pyrrole, styrene, and an olefin; and about 0.1-10 by weight of a polymerizable cationic or non-ionic self-crosslinking monomer selected from the group consisting of a cationic quarternary ammonium monomer having the formula and a nonionic monomer having the formula where R1 and R5 are hydrogen or a methyl group; A is -O- or with R4 being hydrogen or a C1-C3 alkyl group; R2 and R are independently a C1-C6 alkyl group; X is a halogen; Y is an anion; and n is 1-4; the salt being present in an amount effective to cure the polymer, with or without the application of heat, after application of the dispersion and removal of the water therefrom.

12. The latex of claim 11, wherein the salt is the sodium, calcium, aluminum, or lead salt of formic, acetic, propionic, butyric, valeric, or caprioc acid.

13. The latex of claim 12, wherein the salt is present in a more or less equimolar amount based on moles of the self-crosslinking monomer present in the polymer.

14. The latex of claim 12, wherein the cationic quaternary ammonium monomer is the reaction product of N,N-dimethylaminopropyl methacrylamide and epichlorohydrin or of N,N-dimethylaminopropyl methacrylate and epichlorohydrin and wherein the nonionic monomer is 3-chloro-2-hydroxypropyl methacrylate or 3-chloro-2-hydroxypropyl acrylate.

15. The latex of claim 14, wherein the cationic monomer is present in an amount of about 1-5% and wherein the nonionic monomer is present in an amount of about 0.05-5%.

16. The latex of claim 11, wherein the vinyl polymerizable monomer is the vinyl ester, alkyl acrylate, alkyl methacrylate, styrene, or ethylene.

17. The latex of claim 16, wherein the vinyl ester or acrylate monomer is at least about 5%; or wherein the ethylene monomer is present in amounts of about 0.5-40%
and the vinyl ester, being vinyl acetate, in amounts up to about 89.5%.

18. The latex of claim 11, which further consists essentially of a thickener.

19. The latex of claim 18, wherein the thickener is selected from the group consisting water-soluble cellulose derivatives, polyvinyl alcohols, and polyacrylamides.

20. The latex of claim 11, wherein the vinyl polymerizable monomer is vinyl acetate or mixtures thereof with ethyl acrylate, butyl acrylate, and/or 2-ethylhexyl acrylate; ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate or mixtures thereof; or ethylene and vinyl acetate; wherein the self-crosslinking monomer is the reaction product of N,N-dimethylaminopropyl methacrylamide and epichlorohydrin; the reaction product of N,N-dimethylaminopropyl methacrylate and epichlorohydrin;
3-chloro-2-hydroxypropyl acrylate; or 3-chloro-2-hydroxypropyl methacrylate; wherein the salt is sodium formate, acetate, propionate, butyrate, valerate, or caproate; calcium acetate; aluminum acetate; or lead acetate.

21. The latex of claim 20, wherein the salt is sodium formate or sodium acetate present in a substantially equimolar amount.

22. The latex of claim 20, wherein the vinyl polymerizable monomer is a mixture of ethyl acrylate and 2-ethylhexyl acrylate; vinyl acetate and butyl acrylate;
or ethylene and vinyl acetate; wherein the self-crosslinking monomer is present in an amount of about 2-3%; and wherein the salt is sodium acetate.

23. The latex of claim 22, wherein the sodium acetate is present in a substantially storchiometric amount and effective to cure the polymer without the application of heat.

24. The latex of claim 20, further comprising as a thickener hydroxyethyl cellulose.