CA1194630A - Contact adhesives - Google Patents

Abstract

Abstract of the Disclosure Disclosed are contact adhesives, containing aqueous polymeric latexes, particularly acrylic latexes.
Contact adhesives are adhesives which dry to a non-tacky state but which will adhere to another surface of the same dried adhesive. A unique feature of the adhesives is that the polymer used therein has an extremely wide range of molecular weights with substantial proportions of the product having a low molecular weight and substantial portions having a very high molecular weight, preferably with fairly uniform progression from low molecular weight to high molecular weight. However, blends of a low molecular weight fraction and a high molecular weight polymer may also be used. The preferred procedure is to prepare an emulsion polymer by reacting part of the material in the reactor in such a way as to obtain a high molecular weight product and to react at least one other portion of the monomer in the same reactor in such a way as to obtain at least one low molecular weight fraction. The adhesives preferably contain an aminoplast or a phenoplast as a tackifier and crosslinker and may contain a thickening agent such as polyvinyl alcohol. Also disclosed are articles of manufacture laminated by means of the adhesives and methods of preparing the same.

Description

CONTACT ADHES IVES
The present invention ls concerned with the production of adhes;.ve compositions of aqueous character adapted to be applied as a contact cement. By contact cement is meant a cement which has the capacity to bond two substrates well enough on initia]. assembly to hold the assemb].y together without employing extended n;p-roll or clamp pressure. The present invention is also concerned with methods of preparing artic]es of manufacture employing the adhesive compositions of the present invention, and methods for their preparation.
The latex polymers of the invention have substantial.
proportions of high molecular weight fractions and low mo]ecu~.ar wel.ght fractions The divergent molecul-ar weights may be achievea by blending latexes or, preferably, by a novel pol.ymer;.zation procedure in which staged introduction of chain transfer agent is utili.zed.
Back~round of the Invention Contact cements or adhesives are polymer solutions or dispersions whl.ch are applied to two surfaces, dr;.ed, and the mating surfaces are then pressed together, usua]l.y without heat. The dried surfaces are essentia11y non-taclcy and wil.l not adhere to most materials except to another coat.ing of the same adhesive. Care must be used in aligning the two articles or surfaces to be bonded~
since the bonding is essentially instantaneous and the articles cannot be moved reiative to one another i n ord~r to put ~hem into reg ister once c:ontact has ~:ieen made .
This "instan~-grab" property of contact adhesives has the important ~dvantage that long periods of aging or oven 5 curing are not needed~ Par~icularly for on-si~e applications, such as laminating a plastic surface sheet material to a kitchen counterto~, the advantages of the use of contac~ adhesives are particu~.arly valuab:l.e~
Pressure sensi~ive adhesives are known which invo.lve blends of polymers. For example U.S. Patent No. 3,090,694 in Examples 7 and 8, disc1Ose blends of acrylic late~es O In Example 7 the first product ("Rhoplex'~ FRN 1atex~ is known ~o have a number average mo1ecular weight (M~) of about 500,000 and the second product ("Rhop1ex" B-60A
1atex~ ~o have a molec~l1ar weight of about ~000,000. In Example 8 the first product ('IRhoplex" B-15 latex) is understood to have a Mn in th~ neighborhood of 750,000 and again the second product ('IRhoplex" B-60A latex) has a M of about 1,000,000. The glass transition temperature of ~hoplex FRN is about -15C, that of ~'Rhop1ex B-60A is about 13C and that of Rhoplex B-15 is about -12~Co Additionallyr U~S~ patent Nos. 3,222 419 and 3,257,478 disclose blends of crosslinking acry1ic resins and non~crosslinking acrylic resins, in the form 25 of organic so~.vent solu~ions, used as pressure sensitive adhesives .
As is shown by U ~ S ~ patent Nos . 2, 976,203 and

2,976 ,204 to Young (assiyned to the assignee of the present applicationj it is known to u~ilize chain 30 ~ransfer agents to lower the mol.ecular weigh~ of acrylic latex polymer~ useful as pressure sensitive adhesives and as contact cements. Another referenc:e showing that chain tran~fer agents are known for making pressure sensitive adhesives is U.S. pa~ent No. 3,806,484~ in which the 35 acrylic monomers are pre-emulsiied alorlg with the chain ~'' transfer agent, or, as understood, ~he emulsion is polymerized in increments wherein the chain transfer agent is added in the same quantity to each ~tage or increment of the emulsion being polymerized.
Formulations for contact cements utilizing ~crylic late~es and phenolic resins are di~cussed in the 1975 edition, Vol. 9A, of Polymer Science and Technology on pages 233-4~ (abstracted at Chemical Abstrac~s Vol. 84 Abstract 136482a~. A review of contact adhesives i5 mentioned in Volume 81 o~ Chemica1 ~bs~racts, ~b~ract ~o. 121991e. ~erman patent publication 2,420~683, ~ited in volunne 82 of Chemical Abs~racts, ~bs~ract No. ~915~d, discl~ses a contact adhesive. Elastomers are known to have a wide range of molecular weight polymer chainsO
A paterlt relating to syn~hetic rubber, V.S. Pat~n~ No.
4rl45~494~ shows the polymerization of diolefins, optionally with minor proportions of monoethylenically un~aturated monomers such a~ acrylic acid, methacrylic 2û ac:id , itaconic acid , esters thereof, styrene, etc., dur ing wh ich larger amounts of cha in transf er agents are add~d after at least 75% of the monomers are polymerized. A shortstopping a~ent is added to preven~
complete conversion of the monomer to pol ymer . No such agent is used in the present invention.
One way of carrying out a synthesis procedure to obtain a latex polymer having a wide divergence of molecular weights is taught ~y U.S. patent No. 4,039,500 to Basset~ et al. It teaches, in one varlation, feeding a stream of unemulsif ied monomer mixture containing a chaln ~ransfer agent into a second body of unemulsif ied monomer simultaneously with continuous feeding of a 3tream of the ~econd body of monomer into a polymerization reactor which con~ains water, an emulsifying agent and an initiator. A polyunsaturated crosslink;ng monomer is preferabl.y included. Example 1 of the patent is typ;cal, y;e]ding an overall polymer composition of 45/45/5/5 styrene, ethyl. acrylate, methacrylic acid, 2-hydroxyethyl acrylate, which 'nas a calcu]ated Tg, defined hereinafter, o about 28C. The first feed would yield a polymer having a lower Tg and the second feed wou]d yield a polymer having a higher Tg, probably in a so-called shell-core relationship.
That process has deficiencies as compared with the process of Graham Swift and Richard E. Baus, discussed below and disc]osed in certain of the examples in the present case. For instance, the Bassett et al. process is difficult to control. The Swi.Et et al. process, on the other hand, allows better control of the proportions of very high molecular we;ght and very low molecul.ar weight materlals. Furthermore, Bassett et al. are concerned with getting a hard po3ymer for paints, uslng substantial proportions of monomers such as styrene and methyl methacryl.ate, which gi.ve products having a high Ty. Bassett et al. also recommend uslng substantial amounts of the unsaturated crossl;.nker monomers, which give extremely high molecular weight products as well as a high Tg.
Contact adhesives differ from pressure sens;.tive adhesives ln that they are essentially non-tacky (although they adhere to one another), while pressure sensitive adhesives retain a permanent, aggressi.ve tack.
This may be illustrated by comparing tack ratings of contact and pressure sensitive adhesives Ln conventional tack tests such as the Rol.ling Ball. Tack Test. In this test, a 7/16" steel ball is rolled down a 6 inch, 45 inclined steel sheet onto the horizonta.~ adhesive surface in the form of a dry coating of about 1. mil in th;ckness. A pressure sensitive adhesive .is expected to stop the ba3.1 after it has travelled only one or two lnches across the adhesive surface. Conversely, contact adhes;ve will permit the steel balls to roll almost indefinite]y.
Traditionally, contact adheslves have been based on so]utions of poly(ch~oroprene) or neoprene, in combinations o~ solvents such as to~uene and methyl ethyl ketone. Recent government re~ulations reskricting use o~
such solvents has sparked adhesive manufacturers to seek alternate systems which pose signifjcantly lower flammability and pollution hazards.
Aqueous adhesives seem to be ideal candidate replacements for the hazardous solvent systems. However, early aqueous neoprene latices lacked the high bond strengths shown by their solvent counterpartsl nor are they stable to freezing and thawing. In a subsequent innovation, lt was found that the defic;ency could be overcome by using specialty acrylic latices such as 87.5 ethyl acry~ate/10 methyl methacrylate/2.5 itaconic acid +
poly(vinyl alcohol) thickener and benzoguanamine-formaldehyde crosslinker. While this may be used without safety hazards to provide high strength wood~to-plastic laminates, the system requires higher lamination pressure than customers desirel and thus greater combinabi]ity was soughtO Improved combinability, as evidenced by good adheslon with low lamination pressure, can be ach;eved by incorporat;on of tackifiers and plasticizing solvents, reducing Tg, or dropping molecular weight. However, ln all cases combinability is achieved along wjth an unacceptable loss -;n elevated temperature performance.
Extensive testing of contact adhesives has indicated that per~ormance in terms of adhes;ve propert;es such as lap shear, high temperature cleavage, legginess, combinability, etc., is re]ated to the type and amounk of acid functionality 'n the polymer bac~bone and the type and amount of crosslinker. ~owever, i~ is apparent 'chat performance is even more dramatically related to mclecular we isht of the polymer . EIigh molecular we ight improves lap shear adhesion and cleavage propertie~, but downgrades :Leggine~s, combinability, and bond fusion~
The exact opposite is true of low molecular weight polymers .
Deta i led De scr ip~ ion This invention provides c:7ntact adhesives contai.ning polymers or polymer ~ractions with a range of molecular weigh~s f rom very high to very low and of th~ proper balance to give good adhesive streng h in conjunction with goc~ legginess, combinability and bond fusion. To achieve this, in a preferred embodiment of the invention a substantial portion of the monomers are polymerized to a high molecular weight~ The high molecular weight polymer provides adhesive strength and high temperature cleavage properties~ Another por~ion of the monomers is polymerized to a low molecular weight fraction, also present in a substantial proportion, which imparts legginess and combinability.
Typical molecular weight distributions, determined by gel permeation chromatography, are shown in the drawings. Fig. 1 ~oncerns the product o~ Ex. G, Fig. 2 concerns the product of Ex. N, and Fig. 3 represen~s the product of Ex. J-l.
The adhesive composition of the presen~ inven~ion are aqueous dispersions of a water-insoluble copolymer ~r mixed copolymers, preferably acryli~ in nature, and wa~er insoluble salts thereof, o 0.5 15~, preferably 1-12% by weight of a ~arb3xylic acid selected rom the group consisting of acrylic acid, itaconic acid, maleic acid, fumaric acid, methacrylic acid, and crotonic acid, and mixtures thereof, more prefe~ably a mi~ture of 5-10% of methacrylic acid with 0O5 2~ 1ta~oni~ ~cid, 0 to 25~ by w~ight of another addition-polymerizable ~ ,~ -monoethylenically unsaturated monomer, includlng one or more of an ester o~
methacrylic acid wi.th an alcohol having l to 1.8 carbon atoms such as methyl methclcrylate, and/or other addltion polymerizable monomers such as vinyl versatate, styrene, vinyl toluene, vinyl acetate, or acrylonitri]e etc., or mixtures thereof, and the balance o~ one or more esters of acrylic acid with an alcohol having from 1 to 18 carbon atoms, preferab].y 1-8 carbon atoms. The most preferred compositions consist essentiall.y of polymerized ethyl acrylate, butyl acrylate and the unsaturated acid or acids.
The acid component is needed to provide specific adhes.ion to a wide variety of substrates and especlally to those of hydrophilic or metall1c character, and as a catalyst to cause curi.ng o an aminoplast component, descrlbed herelnafter, when used.
The particular ester of acrylic acid that is employed may be chosen from a wlde group ;.ncl.uding methyl acrylate, ethyl acrylate, butyl acryl.ate, cycl.ohexyl acrylate, 2-ethy.lhexyl acrylate, t-octyl acrylate, dodecyl acrylate, and octadecyl acrylate. Preferably, the copolymers are made using methy].. acrylate, ethyl acrylate, butyl acrylate, or 2-ethylhexyl acrylate, because of the availab;.lity, efficiency and/or inexpensiveness of those monomers.
Optional crosslinking monomers such as vinyl benzene, diallyl phthalate may be .included in small amounts of 0-2%l preferably 0-0.5% of the monomers.
Acrylic copolymers are preferred, but the invention may also be applied to the preparation of other polymers of addition po3.ymerized unsaturated monomers at least predominantly composed of ~,~ -monoethyleni.ca]ly unsaturated monomers. Examples are polyvinyl acetate and a copolymer of ethylene and viny] acetate, optionally ~o with small amounts of other monomers such as hydroxy ~thyl, hydroxy propylacrylate and ~ethacrylate,N-methylol acrylam de, acrylamide, acrylic acid, ~nethacryli~ acid, or itaconic acid, and up to 20~ of another optional copolyrrerizable monomer. Sui~able ra~ios of ethylene to vinyl acetate are 30 to 70 parts of ethylene ~o 30 ~o 70 parts of vinyl aceta~ce by weight. The chain terminator may be added similarly to ~he examples in the present application, in which the vinyl acetate is emulsified and polymerized by pressuring with ethy]ene during ~he first portion of ~he polymerization ~o give a higher mole~ular weight produc~, followed by addi~ional increments of vinyl aceta~e and ethylene in the presence of chain regulators. In a continuous process, ~he initial sta~e or stages of polymerization are conducted in ~he absence of ~hain regula~or which is th~n introduced downstream in one or more subsequen~ sectio~s of the reac~or.
The composition may have a p~ of about 2 to about 7 or higher but preferably the p~ is between 5 and 7~
Proportions of the several components of the copolymer are such as to provide a Tg between 10C and -60C~
preferably from -5~C to -40C.
~Tg" or glass ~rans;.~ion temperature, is described by Flory, "Principles of Polymer ~hemistry," pp. 56 and 57 (1953), Cornell University Press~ See al50 "Polymer ~andbook", 2nd Ed., Brandrup and In~nergut, Sec. III, pp.
139 142, Interscience (1975). While actual measurement of the Tg can be used, i~ i.s dif~icult to obtain an accura~e value on low molecular weight polymers, and it may be calculated as des~ribed by Fox, Bullo AITI~ Physics 5_ lf 3~ p. 1~3 (1956), or by the use of "Rohm and EIaas Acrylic Glass Temperature Analyzer" Publication No. CM-24 L/cb, Rohm and EIaa~ Cv~npany, Philadelphla, Pa., 19105, The actual Tg's of the low ~olecular weight polymers are lower than the calculated Tg because of low molecular ~r~

3~

g we ights , e . g ., note Example E~ , wh ich product has a calculated Tg of 22C, but it is actually a viscous liquid at that temperature. The calcula~ed Tg values, which are es~entially the ~3ame as measured Tgls of high 5 mole~ular weigh~ ~ :>lOO,OûO, Mn) polymerst are relevant indicia of the relative Tg'~ of di~ferent polymer~.
The Tg value referred to is the transition temperature or infle~ion ltempera~ure which is found by plotting the modulus of xigidity against temperature, determined at 300 kgO/cm. .
An essen~ial characteristic of the copolymer is that it be of a very broad molecular weight range. The range of molecular weight~ is obtained by thP employment of a chain regulator in an emulsion polymerization procedure as described in more de~ail hereinafter, or by blending polymers of-widely vaxying molecular weigh~s. The amount of chain regulator may vary, depend ing upon the particular regulator and the particular conditions of polymerization, but in general from 0.05 ~o 5% and ~0 preferably 0.2 to 1.5% by weight of such chain regula~or is employed, such percentage being based on the weight of monomers being polymerized in the presence of free cha;n regula~or.
The polymer compositions must have an extremely wide range of molecular weights. This may be achieved by.
blending polymers having extremely l.ow molecular weights with tho~e having high molecular weights, or preferably by the method taught in U.S~ Patent No. 4 t 501,845 issued February 26, 1985, said patent being in the names of ~,raham Swift and Richard E. saus~ and ~i~led "Emulsion Polymer o~ Heterogeneous ~olecular Weight and Preparation Thereof, n A convenient way of e~pressing the wide divergence of molecular weights is by mean~ of the nheterogenei~y index~O Th;s is the ratio of the weight average molecular weight t~ ~3 . .~,.

L~30 (Mw) to ~he number average ~eight (Mn). In accordance with the presene: inven~ion the heterogeneity index is between 15 and 150, preferably 20 ~o 90 based on molecular weights de~ermined by gel permeation 5 chromatography.
Although the heterogeneity index giv s an indication of the range of ~olecular weights of the polymer fractions in the material, it does not tell the whole story. Thus the gel permeation ~hromatograms (GPC I 5) indicate relative ~uant;ties o low molecular w~ight an~
high molecular weigh~ products. ~or example, in a conventional emulsion polymerization condu~ted in the absence of the chain transfer agent, followed af~er polymeriæation by utilization of an additional quantity of catalyst or initiator in order to chase re~idual monomer, the polymer may have a wide molecular weigh~
range of polymer f ractions, but the bulk of ~he polymer, commonly more than 95~ of it, is o extremely high molecular weight, well above a million, and only a minor fra~tion has an extremely ~ow molecular weight. In view of this, in order to further d~fine the invention, another parame~er is the relative ratios of low molecular to high mole~ular weight products and limitations on ~hose mole~ular weights. Thus, the invention also requires that between about 5% and 70% by weight/
preferably between about 10% and 60~, of ~he product is a low molecular weight fraction haviny an Mn of between about 500 and about lOO,oO0, preferably from about 10,000 to 50,000 and between about 30~ and 95%, preferably between abou~ 40% and 90%~ of a high molecular weight fraction hav;ng a M~ of between about 100,000 and about 2,000,000 preferably from abou~ 500,000 ~o 1,500,000. It i~ to be understood ~hat ordinarily, aLs the preferred rqn frac~ion~, addi~ional ract:ions of lntermediate 35 molecular weight polymer rnay be present.

Althc~ugh, as indicatecl elsewhere herein, the preferred procedllre for ob~:aining produc~s having a hi~h heterogene ity index, a~ calculated f rom the ratio s:3 the MW/3~n, is by initially poly~nerizing an emulsion of monomers in the absence of a chain ~erminator, and par~
way through ~he polymerization introducing a chain transfer agent in one or more increments and quantities, an alternative procedure for obtaining sui~able products having a. wide range of molecular weights is to blend an extremely low molecular weight product with a hi~h molecular weight emulsion polymer. The low molecular we ight products may be ob~a ined by var ious procedures .
They may be post-emulsified bulk polymers or solution polymers, as well as low molec:ular weight emulsion polymers. The low molecular weight products, suitably called oligomers, can be prepared by anionic initiatîon, using a catalys~ such as potassium methoxide, as disclosed in ~.S, paten~ No. 4,103,093, and British patent 1, 431, 446 (corresponding in large part to U . S .
Patent No. 4 ,158, 736 of S.N. Lewis et al ., issued June 19, 1979) . Other procedures a~e useful for preparing ~he low molecular component (s~ of the blend.
Examples appear in the journal article by Ali, Mark, &
Mesrobian, In~ 1 Ch---. 42, 484 (1950~; ~he article by 25 Leonard, Szlachtun, and Cort, J Poly. Sci., XI, No. 6, 539 ~1953); Rehberg & Siciliano, Ind . Eng . Chem., 44 , 2864 (1962) and Bauer,_ himicha, 5, 147 (1951). A number of these low molecular we ight polymers have been disclosed as components of blends with polyvinyl chloride to plasticize the same, in the form of alkali soluble salts of high unsaturated acid level polymers to modify acrylic la~exes such as floor polishes which must provide a hard, wear-resisting surface~ and the like. In the present case, the low molecular weight polymer frac~ion should also have a low T9 in the same range as given .. ~. ~

above, that is, from -60C to lOC, preferably less than -5C and greater than -40C.
In the place of blends, it has been found that a highly desirabl.e balance of comb;nabi]ity and elevated temperature performance can be achieved through use of a graduated addition of chain transfer agent (CTA) during formation of an emulsion copolymer, partlcularl.y acry].ic polymers, prepared i.n accordance with the teaching of Swift and Baus, supra. In this way, a variety of molecular weight species is formed, and the desired combination of properties is achieved. Thus, a part of the polymerization is conducted in the absence of a free CTA, and in at least one stage of the polymerization, preferably in two stages, the polymerization i.s conducted in the presence of free chain transfer agent.
If the CTA is added in a first stage, it is used in a ~uantity such that it i.s used up by being bound ln polymer chains, thus permitting adding additional monomer in the absence of free crrA.
~0 Preferably the first stage is free of CTA. Using this method, there exists a rather narrow opti.mum range for introduct;.on of CTA. To provide the optimum property balance, CTA addition preferab].y is not begun before at l.east 30%, preferably at least 45% of the monomer mi~ has reacted to high molecular weight product. However, the chain transfer agent addition is commenced before 95%, preferably 90%, and more preferabl.y 75%r of the monomer mix has reacted to completion. Thus, preferably between 45% and 75% of the acry~.ic monomer is reacted to polymer 30 prior to gradual incorporation o the initial chain transfer agent charge al.ong w;th monomer emulsion. A
second higher amount of CTA is preferab1.y introduced with at ]east one later port.ion of monomer.
The water inso1uble salt of the copolymer may be 35 that obtained by the use of ammonia, an alkali metal, 3~

such as 80dium or po~as~ium, or a water~soluble amine such a~ a lower alipha~ic ~mine o which tr~e~hyla~ine~
diethylamine, and trimethylc~ine, dimethyl ethanolamine, diethanolamine or triethanolamine. Preferably ammonia or a ~olatile amine is employed as the cation of the sal~
of the acid copolymer.
~ xamples of anionic emul~ifying agent~ that ~ay be used for emulsifying the monomers include the higher fatty alcohol sulfates, such as sodium lauryl sulfate, lQ the alkylaryl sulfonates, such as ~he sodium sal~ of t-octylphenyl sulfonate, ~he sodium dioctyl sulfosuccinate~ and ~o onO Examples of the nonionic dispersing agents that may be used for preparing ~he monomeric emulsions before copolymerization or dispersions of the polymer after polymeri~ation include the following: alkylphenoxypolyethoxyethanols having alkyl groups of about 7 to ~.8 carbon atoms and lO to 60 or more oxyethylene units, such as heptylphenoxypoly-ethoxyethanols, octylphenoxypolyethoxyethanols, methyl-octylphenoxypolyethoxyethanols, nonylphenoxypolyethoxy-ethanols, dodecylphenoxypolyethoxyethanols, and ~he like;
polyethoxyethanol der ivatives of methylene linked alkyl phenols; sulfur-containing agents such as those made by condensing 6 or ~0 or more moles of ethylene oxide wi~h n~nylr dodecyl, tetradecyl, t-dodecylv and ~he like mercaptans or with alkylthiophenols hav;ng alkyl groups of 6 to 15 carbon atoms; ethylene oxide derivatives of lon~-chained carboxylic acids, such as lauric, myristic~
palmitic, oleic, and the like or mixtures of acids such as found in tall oil containing 10 to 60 oxyethylene units per molecule; analogous e~hylene oxide condensates of long ~hained alcohols, such as octyl, decyl, lauryl, or cetyl alcohols, ethylene oxide derivatives of etherified or esterified polyhydroxy compounds having a hydrophQbic hydrocarbon chain, such as sorbitan '~.

~ 14 monostearate con~aining 10 to 60 o~ye~hy~ene uni~s, etc.;
block copolymers of ethylene oxide and propylene oxide compri~ing a hydrophobi~ propy7ene o~ide ~ec~ion combined with one or more hydrophilic ethylene oxide sections~
For the copolymerization, peroxidic free-radical catalysts or initiators, inclu~Lng catalytic syst~ms of the thermal and the redox type, are reconMmended. Such redox systems, as is well known, are combinations of oxidizing agen~s and reducing ag2n~s such as a combination of potassium persulfate and sodium metabisulfite. Other suitable peroxidic agents include the "per-salts" such as the alkali metal and ammonium persulfa~es and perborates~
hydrogen peroxide, ~rganic hydroperoxides such as tert butyl hydroperoxide and cumene hydroperoxide, and esters such as tert-butyl perbenzoate. Other reducing agents include water~soluble thiosulfates and hydro~ulfites~ Activators or promoters in thè form of the ~alts such as the sulfates or chlorid~s of metals which are capable of existing in more ~han one valen~e state such as cobalt, iron, nickel, and copper may be used in small amounts.
In the polymerization process the greater the proportion of chain regulator (CTA) used the lower the molecular weigh~ obtained. Examples of well known chain regulators o~ chain transfer agents which may be used include short and long-chain alkyl ~ercaptans, e.g., amyl m~rcaptan, N-dodecyl ~rcaptan, t-dodecyl ~rcaptan, dialkyl ~nthogen disulfides, e.~. diisoFropyl ~anthogen disul~ide, ~ercaptocarbo~ylic acids such as ~ercaptopropionic acid, alkaryl ~ercaptans such as benzyl ~ercaptan, long-chain alcohols, such as lauryl alcohol and t-oc~yl alcohol, halo-genated hydrocarbons, such as CC14 and CBrC13, and substituted mercaptans such as hydro~yethyl m~rcaptan.
The copolymer dispersions may be made by first mixing ~he several monomers in ~he desired propoEtions ~5 into an aqueous solution of an anionic or a non-lonic di.spersing or emulsifying agent, or a mixture of both types, to form an emu:lsi.on, then pol.ymeriz;.ng the mixture, w.ith the aid of a free radlcal catalyst or initiator. The amount oE cata].yst can vary but for purposes of e~ficiency from 0.01 to 1.0%, based on the weight of the monomers, of the peroxidic agent and the same or .l.ower proport;ons of the reducing agent, if used, are recommended. In this way it ;s possible to prepare dispersions which contai.n as llttle as l% and as much as 60% or 70% of the resinous copolymer on a weight basis. It is, however, more prac~ical -- hence preferred -- to produce dispersions which contain about 30 to 60%
resin solids.
As is conventlona], after the monomer feed is 3.5 completed, residual monomer is reduced to a minimum by use of a free radical "chaser" catalyst or initiator, by the use of an adsorbent, by heat, by means of a vacuum or a combinati.on thereof.
After the polymerization, i.n the event the unsaturated acid is employed therein as a free acid, neutralization of the dispersed copolymer may be obtained, if desired, by the addition of concentrated ammonia, one of the amines mentioned hereinabove, or the hydroxide or carbonate of sodium, potassium, or lith.ium.
If desired, further adjustment of the concentration may be effected by diluting the neutralized dispersion with water. When a filler is employed, the adjustment of the concentration may be effected after the incorporation of the fill.er instead of before if desired.
The unmodified or unfil.led compositi.on may conta;n 30 to 55% water and at least 30% of the copolymer or salt thereof. For optimum resul.ts, however, the composition comprises about 50 to 60% water, about 40 -to 55% of the copolymer, copolymer mixture, or salt thereof, and small amounts, up to about 5~ total of the auxi.]iary materials, ~ ~ ~3 Lf~

~ 16 -5uch as ~he emulsifier, crosslinker~ thickener, and 50 on~
In the cc~mposition of ~he presen~ invention, a f iller m~y be employed in ,an amount ranging f rom 096 up ~o 125%, preferably by/ we;gh~ of the polymer in ~he aqueous 5 dispersion. As is known in the ar~, ~he filler increases the ~ensile s~rength of the adhesive film ob~ained from the polymer and i~ reduces the csld 10w or creep thereof~ This effect, which may be referred to as a reinfor~ing effect, is definitely no~iceable even when as small an amount as 12% of filler, based on the weigh~ of the polymer, is employed. The maximum .reinforcing effect is obtained when the filler is used in greater amounts up to 125% of the polymer wPight, the maximum depending upon the particular filler employed.
The fillers preferably have a par~icle size not over 40 microns and in op1:imum cases thei.r dimensions are 10 micron~ or less. Many types of fillers may be employed.
One is rutile titanium dioxide. Others such as anatase titanium dioxide, so-called fu~ed silica~ hopone, magnesium silicate, clay, wollastonite, zinc oxide, calcium carbonate, clays including kaolin and bentonite, walnut shell, and so on, are useful. To some exten~
fibrous fi~lers such as cellulosic fibers or nylon s~aple may be employed. Inorqanic fillers are preferred.
There may be added to the adhesive composition, to-improve the viscosi~y and flow properties thereof, from 0%, preferably 0.25% to 10% by weight, based on the total solids of the composition, of a thickenin~ agent. The amount of such thickening agent, when used, is generally selected to provide a-viscosity .in the composition of about 1/2 poise ~o about 100 poises~ ~n most cases, when a viscosity in the lower part of the range is desired in the particular application, no thickener is necessary.
Examples of ~hickening agent~ include natural gums, such as gum tragaeanth and gum arabicj polyvinyl alcohol, hydrolyzed methacryli.c acid and water soluble ~alts, thereof, and water-sol.uble cellulose ethers~ such as methyl cel~ulose, ethyl cellulose, hydroxye~hyl cellulose, carboxymethyl eellulose, and the like.
The adhesive usually contains a ~rosslinking means such as a cross~inkable aminoplast, e.g., an alkylated one. The alkylated aminoplasts which may be used includ~
those obtained by the alkylation, with an alkanol having from 1 ~o 6 carbon atoms or cyclohexanol, of a condensate of an aldehyde wi~h urea, N,~ ethyleneurea, dicyandi-amide, and aminotriazines~ Water-soluble conden~ates such as ~he methylated dimethylolurea condensates can be employed. Preerably, the alkylation products of alcohols having from 3 to 6 carbon atoms are employed and the butylated products are particularly valuable~
Among the aminotriazines which are suitable are melamine, ace~oguanamine, benzoguanamine, formoguanamine, N-(t-butyl)-melamine, N-(t-octyl)-melamine in which the t-oc~yl group has the formu]a -C(C~3)2 C~2~tcH3)3 ammeline; 2 chloro-4,6-diamino-1,3,$-tr;azine, 2-pheny~-poxy-4~6-diamino-1,3,5~triazine, 6-methyl-2,4-diamino-1,3,5-triazinet 2,4,6-trihydrazine-1,3J5-triazine~
2~496-~rie~hyl~riamino-1,3,5-triazine, and the ~,N-di (Cl-C4)alkyl melamines such as N,N-dimethylmelamine.
While any aldehyde may be employed such as acetaldehyde, crotonaldehyde, and acrolein, the condensates obtained using formaldehyde and revertible polymers thereof such as paraformaldehyde are preferably employed.
~n place of the aminoplast crosslinking system other known latent crosslinking means or mechanisms may be used. ~or e~ample, phenoplasts su~h as the water soluble phenol formaldehyde resins referred to in the A~rak et al. ~ournal article9 supra, or in German patent 2,420~6~3 may be utilizedb Crosslinkable monomers such as ~,,~

N-methylol acryl.ami.de are also of use. ~nother we]l known mechanism ls to utitize ionic crosslinking by polyvalent metal ions. An example ;s zinc ammonium carbonate or other polyvalent metal compounds or complexes having a volati.l.e J.lgand. Sti.ll another known procedure is to incl.ude an organic peroxide in the adhesive formulation at the point of use which subsequently interacts with the acrylic polymer to cause crosslinki.ng. These latent crosslinklng reactions tend to minimize col.d flow of the adhesiv~ subsequent to i-ts uti.lization. of course, other crosslinking mechanisms and procedures may be utili.zed, such as the use of polyunsaturated monomers~ Examples of such optiona].
cross-linking agents that may be used, in amounts of 0-2%, preferably 0-0.5%, include any copolymerizable compound which contains two or more non-conjugated points of ethylenic unsaturation or two or more non~conjugated vinylidene groups of the structure, CH2=C <, such as d ivinyltoluene, divinylbenzene, trivinylbenzene, diviny.lnaphthalene, ethylene glycol d iacrylate or dimethacrylatel tr;methylene glycol diacryl.ate or dimethacry.late, l,4-butylene glycol diacrylate or dimethacrylate, 2-ethylhexane-1,3- dimethacryl.ate/
divinylxylene, divinylethylbenzene, divinyl ether, divinyl sulfone, allyl ethers of polyhydric compounds such as of glycerol, pentaerythr;tol, sorbitol, sucrose and resorcinol, divinylketone, divinylsulfide, al..lyl acrylate, diallyl mal.eate, dial.l.yl fumarate, diallyl.
phthalate, dial].yl succinate, diallyl carbonate, diallyl malonate~ diallyl oxal.atel diallyl adipate, diallyl sebacate, diallyl tartrate, diall.yl s;.licate, triallyl tricarballylate, triallyl aconitate, triallyl citrate, triallyl phosphate, N,N'-methylenediacrylami.de, N,N'-methylenedimethacrylamide, and N,N'-ethylidenedi-acrylamide~

Generally, it is unnecessary to add any material otherA than the acid groups present in the emulsion polymer to catalyze the aminoplast crosslinking reaction but, if desired, an acidic catalyst may be included. The amount of such a catalyst may be from 0.l to 1% by weight, based on the weight of aminoplast condensate.
The use of the curlng catalyst may be particularly desirable when ~ower temperatures of curing or baking are needed. With such curing catalysts, insolubilization can be accomplished simply by drying and aging at room temperature. Among the curing cata]ysts that may be used are any of the organic and inorganic acid catalysts. One may use, for instance, in catalytic amounts, sulfuric acid, hydrochloric acid and their acid salts, such as ammonium sulfate, ammonium chloride, or the organic acids, such as acetic acid, phthalic acid, benzoic acid, toluene sulphonic acid, naphthalene su]phonic acid, and the mono-salt of maleic acid with triethylam;ne. Such catalysts are added at the point of use.
~'Self-contained" acid catalysts provided by the unsaturated acid in the polymer are preferred. I~aconic acid is especially valuable in that, not only is it a stronger acid than acrylic or methacrylic acid, thus accelerating the aminoplast cure, but lt also gives a stronger adhesive bond. The combination of itacon;c acid and methacrylic acid in the emuls;on polymer ;s of particular value.
The adhesive composit;ons may be applied ;n var;ous ways. For example, they may be appl;ed by brush, roller, trowel, kniEe, dipping, spraying, and so on. The adhesive is applied to both surfaces to be adhered together and then the coatings are dried. When both surfaces are porous, the cement may be appl;ed to both and then contacted very qu~ckly thereafter.
The strength of bond develops instantaneously to -- 2~ --hold the substrates ~oge~her. AS the f iller content increases ~ the bond strerlg~th develops more rapidly. If the ams:unt of filler is such as to allow only five minutes open assembly time, greater strength is o~ained 5 in one hour af ter contac~ then if lower f iller content is u s~ .
The adhesive of the present invention has been found 'co provide exceptionally good bonds with numerous substrates, including struc~ural ma~erials such as wood, 10 paper, Formica~ brand plastic sheet, other plastic ma~erials such as polymethyl methacrylate, polyvinyl chloride, saran, nylon, phenol-formaldehyde resinsr urea-formaldehyde resins, and other thermoset materials such as melamineformaldehyde resins; rayon, cotton, silk, wool, fibers of the polymeric materials mentioned above, lea~her, ~inoleum, rubber, asphalt tile, vinyl tile, ceramic tile, various silicates'such as mineral wool, asbestos, concrete, brick, asbestos cement, plaster, metals such as aluminu~,steel, iron, copper/
zinc, chromium~ nickel, as well as painted or enamelled surfaces, such as pain~ed automobile bodiesl woodwork, walls, ceilings, or floors.
The adhesive composition may be colored or sub~tantially colorless. Besides depending on ~he color of fillers mentioned above~ suitable colored pigments may be added in place of~ or in addi~ion ~o, the fillers.
Also, if de~ired~ direct dyes may be in~roduced to provide a desired color.
The molecular weights in the examples were determined by gel permeation chromatography. Gel per~eation chromatograms are run on equipment commercially marketed by Waters A~soc. of Marlboro, Mass. Styra~el ~ columns are available prepacked in a variety of poro~ities. A column set is normally composed 35 of four or f ive four foot section~ chosen to ~sver the 3~

- 21~
mol.ecular weight range to be measured. Wlth co]umn sets of this length sufficlent resolutlon ls obtalned so that axial dispers;on can be disregarded. The column set must be calibrated for the polymer type whose molecular weight is to be determined7 Narrow molecu]ar weight standards are avai]able -for polystyrene~ Calibrat;.on curves for other polymers such as polymethyl methacrylate are constructed from the chromatograms of broad samples using either an approximate dlstr;bution techniquel or a universal cali.bration curve techni.que . To calculate the molecular weights of unknown samples a tab].e is prepared of the value Wi, of the GPC curve above baseline at equal volume increments and the mo].ecular weight Mi, read from the calibration curve at these vo]umes. The weight average molecular weight Mw, and the number average molecular weight Mn, can be calculated from these values with the equations WiMi -- Wi Mw = Mn =
Wi Wi/M;.
Wi = 1 It is to be realized that the mol.ecu1.ar weight numbers given are approximate and not precise, but are validly used for comparative purposes.

1 Calibration of Gel-Permeatj.on Column w;th Unfractionacted Polymers, A. Wei.ss, E~ Ginsberg, JO
Poly. Scl., Pt. A~2, 8 (1970~

2 A note on the Universal Ca]ibration Curve for Gel Permeatlon Chromatography - A. Weiss, E. Ginsberg, Pol.y. Letters t 7, 379-381. (l969) Test Methods A. Early Grab Testi.ng 1... Measurements Usin~ Heavy Fin~er Pressure A moderately heavy brush (5-~5 mils when wet) coat of contact adhesive is applied to a 1." x 3" x 1/20" FormicaR brand melamine formaldehyde p~astic 3~

str;.p, as well as to a 3" x 5" x l/2" particle board (40 lb. denslty~. When both surfaces are dry (at c1.ear poink~, the Formica plastic str;p is placed on the particle board and l.aminated using heavy thumb pressure by rubbing the thumb (with pressure) 6x along each edge of the Formica p1astic strip (actua~ bond area is 1." x 2"~ The laminate is then qualitatively rated for strength, legs; fusion and bond area, ;mmediately after bonding.
2. Measurements Using Specified We;ghts A moderately heavy brush coat (5-15 mils when wet) of contact adhesive is appl.ied to a 2'i x 4" x 1./20" Formica plasti.c strip and a 3" x 6" x ~/2" wood particle board. At c].ear point, the Formica plastic strip is laid across the particle board and the Formi.ca plastic strip surEace is very lightly rubbed to assure some adhesive contact area. The sampl..e is then 1.iEted by the overhanging edges (actual bond area is 2" x 3") of the Formica plastic strip and suspended for 15 seconds with just the weight of the particl.e board. If the adhesive bond holds for 15 seconds, a qualitative rating of strength, 1egs and fusion is determined. The early grab test is then repeated, after roller pressure us;ng just the wei.ght from 2 passes of a 4.5 lb. rubber rol].er (7 psi.~. The entire process is then repeated using 2 passes oE a 20 lb. roller (22 psi~.
B. Lap Shear Adhesion A thin coat (1-3 mi1.s, dry~ of adhesi.ve is brush applied to plastic ~aminate (1." x 3" x l/20" Formi.ca sheet~ and to particle board (3" x 6" x ]/2"). After drying until c]ear (30-45 minutes), another thin coat (l-3 mi1s, dry) of adhesive is applied to both previously coated surfaces and again allowed to dry unt.il clear.
Within a few m;.nutes after its clear point, the two substrates are bonded together, first w.ith heavy :Einger pressure and then with l:wo heavy hand pressure passes of a small roller over the assembly. I'he actual bond area is 1 square inch with a 2 i.nch '7Formica"plastic ~trip "handle" . The samples are cond itioned for 4 days at 5 77 F. and 50~ relative humid ity (RH), and then pulled apart by a shear stress, using an ~nstron Tester at a crosshead speed of O . 2 "/min O
C ., 158 F ~ Stat i Clea a~e 5amples are prepared in essen~ially the same 10 manner as lap shear samples, but with ~he following d i f f erences:
1. The wooden substrate i s changed to 3 " x 6 " x 1/4 " Grade ~ plywood;
2. Laminate area is 1" x 21l long, with a ~ 1"
15 "Formica"plastic strip "handlen;
3. Samples are conditioned for 7 days at 77F.
and 50% RoEI~
A~ual tes~iny is done by placing ~he laminates in a 158~F. circulating air oven with a 1 kg weight 20 hanging ver~ically from the outer edge of the l"'VFormica plastic strip "handle". End point is noted at complete failure .
D. ~
A cri~erion sometimes used in ~he industry for 25 preliminary evaluation of a contact adhesive is the extent to which "legginess" appears in the adhesive upon delamination of two surfa~es adhered toyether. ~hile it is believed that the data herein show that legginess is not essential to a good contact a~hesive, it is a quality 30 desired by some users. By legginess is meant the chara~teristic of the adhesive, when the laminate is forceably delaminated to remain adhered to both surfaces while separating in the nature of stringy ~onnections be~ween ~he ~wo surf aces as they are pulled apart . If 35 ~he legs or ~trings develop s~ver a large proportion of `1 * Trademark 3~ ~

- 2~ -the area adhered together and retain their s~ring shapes when abou~ 0.1 centi~eter or more in lengthy before breaking by cohesive ailure, or before delaminating from one or the other surfaces by adhesive failure, the legginess is rated as very go~d. Of course it is a subjective ra~ing and if ~here are no legs found the ra~ing is zero9 A ra~in~ of P is poor, of F is fair, of G is good, of ~G is very good, and of Ex. is excellent.
Intermediate ratings are stated as, for example, P~F
meaning poor to air.
~. Preeze-Thaw The latex is frozen for 16 hours at -~5C and thawed for 8 hours. If the latex does not coagul.ate after from one to five such cycles, it is deemed to be freeze-thaw stable.
In the following example~ ~he Gelva~o ~ 20 30 polyvinyl alcohol has a viscosity in centipoises of a 4%
aqueous solution at 20C of 4-6, ~he percent residual polyvinyl acetate determined on a weight basis is 19.5-2105% the percen~ hydrolysis of the polyvinyl acetate is 87.7-89%, the weight average molecular weigh~
s approxi~ately tO ~OOû, and the percent ash is 0.75.
~Gelvatol is a trademark of the ~onsanto Company. The Cymel~is a be~zoguanamino or melamine-formaldehyde condensate produced by C~mid. The "~ ~ '~ res~ M~3 is ~ ~ a product of Cyanamid and is-a melamine-formaldehyde condenQate, and i5 a known crosslillker for contact adhesives and similar productsO 5uitable phenolic resins are disc~ osed in an article by Azrak et al . i n Adhesives Aqe, June, 1975, pages 23-28. Phenolic resins are useful in place of the Aerokex produc~. One such produc~ is designa~ed Bakeli~ ~ phenolic resin Cg~A-1834~ Other such phenolic tackifiers are designated BX~U-6387 and B~A-2260 t B~UA-2370~ 45-4~% aqueous dispersions, 40-50 parts of disper~ion per 100 parts of 45~60% solids ~, latex. The latter two types of products are water i.nsolubl.e and have a labile formaldehyde content of 5 to 7~, prepared hy first dissolvlng the phenolic ~esin ;n a so]vent and emulsifying the same. For example, lOO parts of the phenolic resin with 54 parts of to~uene and 6 parts of ole;c acid is combined with 6 parts of 25%
aqueous sodium hydroxide, and 30 parts of lO~ ammoniated casein i.n water, 30 parts oE 5% gum arabic ln water, and 77 parts of water. The first three ingredients are combined and then introduced into a mixture of the last four ingredients wlth h.i.gh speed agitation. Thi.s is then mixed with the latex and other conventional contact adhesive ingredients.
The following are the abbreviations utilized ;n the examp].es for monomers:
ABBREVIATION MONOMER
AA acrylic acid BA butyl acrylate BDA 1,4-butylene diacryl.ate EA ethyl acrylate EHA 2-ethylhexyl acry].ate IA itaconic acid IDA i sodecyl acry.late IDMA isodecyl. methacrylate LMA lauryl methacrylate MAA methacrylic acid MMA methyl methacrylate S styrene W -10 vinyl versatate In the fol]owing examples, which are illustrative of the invention, the parts and percentages are by weight unless otherwise noted.
~xamp]e A - Anionically Initiated Oli~omer of BA/AA, 77.5/~2.5 The end product is oligomeric butyl acrylate~acryl.ic - 2~ -acid in the appro~imate weight ra~io o 65/35. I~ is prepared in ~wo s~ages. In ~he first s~age, oligomeric butyl acrylate is prepared, which, in a second stage, is saponified with potassium hydroxide to the fina1 product. I~ has a very narrow heterogeneity index of less than 3 1. Preparation of Anionical~y Ini~iat d 01i~

Lbs./100 LbsO Product Raw Materia1s (Prior to Stri~ and Filt.ration) Butyl Acry1a~e (BA~ 5ppm 87.50 ME~Q: 0~0~% ~2) Potassi~m ~er~-Butoxid~ 1.53 (t-BuOK; powder) To1uene ( 0~04% ~2) 9.90 Sulfuric Acid (98.5-99.0%~ 0.71 ~322 g.) ~Ryflo Super-Ce1" 0.44 (199.6 g.!
Filter Aid 100.08 (Stripped, fi1tered product ~ recovery ca. 7a-80 lbs.) Buty1 acrylate (BA) monomer is added gradua11y over 1 hour to a stirred s1urry of po~assium tert-butoxide (2 mole %) in to1uene, initially at 25C., under a dry N2 atmosphere. 01igomerization occu~s upon addition and the resultant exotherm i5 allowed to carry ~he reaction temperature to 70~C. This temperature (70C + 3) is maintained throughout ~he addition, with cooling and heating as needed, and during ~he subsequent 3 hour hold.
During the initial stage of addition, the slurry ~hickens and turns orange, but within several minutes a nearly clear, orange so1ution results. Co1Or persists throu~hou~
the reaction time. Conversion at the comp1etion of he 1 hour addition is approximate1y 75%; conversion increases to about 90% during the ho1d perioæO
*Trade~ark for a filt~r aid made of "Celite"IM brand of diatomaceous earth, 5pecially processed to provide a r~pid filtration rate.
~' The ~lightly hazy~ orange, mobile reaction mixture i5 quenched w*th sulfuric acid, treated with 0.5 WtJ % ~yf~o Super-Cel and subjected to a vacuum strip ~20 mm.) at 70 75C. with a slow N2 sparge for 0.5 hours. The stripped material is filtered warm to give a clear, straw to light yellow oil at 97% solids content, having ~he following properties:
Percent Solids 97% (100/60 min., forced (Nonvolatiles) draft oven~
~0 Vi~cosi~y 50~ cps/25C.
Appearance Clear; straw ~o light yellow Carboxylic a id content 0.05 meq./g~
Molecular weight ~n (oven-driPd, 100~/60 min.
900 ~ 30; gpc maximum wt.
fra~tion ca. ~700-1800.
2. Saponification Aqueous potassium hydroxide (45 wt. %~, at a level of 57 equivalent % o~ total BA esterl is add~d over one-half hour to a stirred solution (70% solids) of the-produc~ of ~he firs~ s~age in isopropanol, initially at 40C. Mild exotherm, color formation (nearly colorless to yellow-orange), and clouding of the solu~ion accompany addition, with ~he exotherm diminishing as addi~ion progresses.
Approximate cooling is required to main~ain the system at . 40C. (~5~. Af~er addi~ion~ conversion is 85-90%~
saponification i5 ~arried to completion during the subsequent distillation step. Prior to distillation, water is added lowering solids to 30% and providing a clear, amber solution of maximum process volume. This low solids 30 sys~em is needed both to minimize foaming tendency which occurs near the end of the distilla~ion and to solubilize inorganic salts produced by subsequent aridification.
Distillation at a~mospheric pressure removes i sopropanol and butanol as their water azeo~ropes. An alcohol-free ~ystem is obtained by continuing the distillation until only water (head temp. 100C.~ is removed. The re~ultant clear 9 48~ aqueous solution of the *Trademark ~' ,3~

carboxylate salt ;s reduced to 40% solids wlth addit;onal water and then taken to 60Co The extraction./isolation sol.vents (a ~/1. toluene/MIBK mixture; salt and organic solvent are ca. 60% sol;.ds; total solids are 30%! are then added. (MIBK is methyl isobutyl. ketone.~ Acidification of the hazy system follows at 60C. with the addition oF
concentrated sul.furic acid (150 equivalent % on KOH charge~
via dip tube over a l5 minute period. Exotherm accompanies acidiflcation and the temperature ;s al.l.owed to rise to 1.0 65-70C. and is maintained with coolingO After acidification the white mixture is stirred for 3.5 minutes at 65Co Agitat.ion is stopped and clean separation of the warm layers occurs in less than 30 minutes.
Separatlon affords a nearly cl.ear, lower aqueous layer contai.ning a small. amount of fine solid and a slightly hazy greenish yellow, upper organic layer. The lower layer containing 10-15 equiv. %/5 wt. ~ of ollgomeric acid (pr;marily 3ow molecular weight oligomer of high acid content), as wel.l as potassium sul.fate and bisulfate, ;s drawn off and discarded. The MIBK/toluene solution of the crude product ( 50% solids) contain;ng residual water and inorganic salts, is subjected to vacuum azeotroping and distillation (200-250 mm Hg.; maximum pot temp. 85C., maximum head tempO 65C.), increasing sol.ids content to 80-82% Diatomaceous earth fiFter aid (0.5 wt. ~) is thoroughly mixed into the warm, mobile, slightly hazy, yellow oi.l and filtration through a warm pressure funnel at 30 psi proceeds smoothl.y ( 20 lbs./ft.2 hr.) to provide a clear yellow syrup of 80-82% solids content and 4.2-4.4 meqO carboxylic acid/g. solution. The product has properti.es falling within the following limi.ts:
Appearance. clear, light yellow % Solids (Nonvolatiles) 80-82% (methyl. isobuty3 ketone/
toluene; 125C./60 min.~ forced draft oven, 1.0 g.) V.is~o~ity 6500-70~0 cps/25C.
Carboxylic Aci.d Content 4.2-4.4 meq./g. solution Acid No. ~100% solids) 290-300 3~

_ ~9 ~.
The process described above applies to 57 eq~ ~
saponification of the oligio-~A backbone (Mn ca. 90Q).
However, the process is readily adapted o a saponiica~ion range of 42 to 57 eq. %, giving produc~s o acid numbers ranging from abQut 200 ~o 300. The saponification level chosen requires only minimal changes (i.e. base and acid charges) of the processO
These products are described in U.S. patent ~ No. 4,158,736 of S.N~ LewiS et al., issued June 19, 1979, which çorresponds in large part to Belgian patent No.
794,403 and British Patent 1,431,446.

xam~le B _- Pre~ ion of_ Free ~adical Initiated Oli~omer of Ethyl Acrylate and Acrylic ~cid.
Reaction is carried out in a five liter, four nee~ed round ~ottom flask equipped with a paddle s~irrer, addition funnel, equipment for nitrogen sparging and a Y adapter fitted with a thermometer and two reflux condensers (in line). Cellosolve'ace~ate (2000.0 g) is charged to the kettle and heated with an oil bath to reflux (156C) under a slow nitrogen sparge, the sparge being discontinued once reflux îs reached. The initiat*or and monomers are combined as follows: 64.0 y Luper~ol 70, 240 9 e~hyl acrylate 360 9 glacial acryli~ acid. The composi~ion is butyl acrylate/acry.l.i~ acid 77.5/22.5 (wt. %) and the weight of **
"Luper~ol 70,' which is 75% ~-butylperacetate, gives 3 wt. %
initiator, based on monomer. The monomer sslution is added at a constant rate over a 3 hour period to the system maintained at reflux. The solution temp~rature kept at 152~C ~ 3C. Reflux is maintained for 20 minutes after the completion of the addition and then a chaser solution of 10.6 g Lupersol 70 (0.5 wt. % ;.nitiator on monomer) in 460.0 9 CellDsolve acetate i5 added over 30 minutes. The system is kept at ref~ux for 15 minutes following the chaser addition. At thi~ point~ solids are 3906% (solids *TrademarkO l'Cellosolve" acetate is ethylene glycol monoethyl e-ther acetate.
**Trademark. "Lu~ersol" is a trademark representing various organic peroxides. "Lupersol 70" is tert-butyl peracetate.

J ~ 9~

~ ~o _ eonditions: 1 g of sample/150C/l hr.), indicatiny ~ssentially complete conversion of monomer.
The pale gold clear solution i~ cooled and thell stripped on a Buchler flask evapora~or. Stripping is started at 55C and continued until a final temperature-of 181 is reached about 4 hours later~ The clear, slightly amber produc~ ma~erial has a solids content of 98%~ The material flows at room temperature. Molecular weights as determined by gel permeation chromatography are Mw 2,700 and ~n 1~50a~ and is quite viscous, and the he~erogeneity index was 1.8O
The polymers have a calculated ~lass transition temperature of about 22C, but the actual T~ is much lower.
13xamPle C - l~re~ rA~ o~ Arionically Initia~ed EA
.
This is prepared similarly to part 1 of Example A, but i5 not saponified.
A 900 gram portion of the oligomer at 80% solids in toluene was quenched with 9.5 g of concentrated sulfuric acid. In order to insure sal~ removal, 2 weight percent, on solids, alum (as a 33% aqueous solution) was charged to the flask and stirred for one hour at 75C. Water and solvent were then azeotroped out to give a clear yellow solution with large salt crystals. The approxima~ely 100%
~olids material was fil~ered to yield a clear yellow fluid having a T~ of -48C and a viscosity of 35,500 cps at 25C. The ~ is 1200l ~he Mw is 2400 and the ratio M~n is 2 . O .
Example D - Free Radical Oli~omer of BA/MMA/AA, 78~15~7 The procedure was essentially the same as Example B.
~nstead of mixiny the t~butyl peracetate ini~iator with the monomers and solvent, it is introduced as a ~eparate stream in this exa~ple. The reaction was carried out in a four necked 3 liter 1ask fitted with a stirrer, 500 ml addition funnel (for monomer~ two in-line reflux f~

condensers~ and a Y joint wi~h thermometer and 250 ml addition funnel ~or ~a~alys~ solution). The charges were as f ollows:
Kettle 725 g of Cellosolve~) acetate Monomers 624 g butyl acrylate 120 g me~hyl me~hacrylate 56 9 acrylic acid Initiator solution 275 g'lCellosolve a~ tate 32 g Lupersol 70 (t-butyl peracetate) The solvent in the kett.~e is ~row~ht to ref lux under a nitrogen sparge and the solution temperature is 155C. The separate streams of catalyst and monomer were commenced and introduced at substantially constant rates over a period of about 2-1/2 hours, After vacuum s~ripping ~he product at about 20mm of mercury oveE a period of about 4-1/2 hours, ~he product had a solids content of 98.5~. As el~ewhere herein when "solids" is referred ~o the non-vola~ile content is meant ~0 whether or not the product is a solid or a liquid. The Mn is 1150 and the Mw i~ 850. The Mn/~W - 2.5.
Example E - Pre~aration of Free Radical Initiated Oligomer This was conducted similarly to Example~ B and D. The 25 materials used were:
A1,000 g ~ellosolve acetate B680 g Butyl acryla~e C120 g Acrylic acid D32 g ~upersol 70 Component A wa~ char~ed to a three li~er four necked flask with a nitr~gen sweep and heated to 150C with an oil bath~ The addition of premixed component~ B, C and D
~olution was commenced at a uniform rate while the temperature was maintained at between 146C and 153C~ The monomer addition was completed after 2 hour~ and 40 minutes ~-;

3~ ` ~

- 3~ 7 and the reactor contents were h~ld at bout 150C for 15 minutes. The material was stripped at a~out 20 mm Hg, increasing the solids con ent to about 95% solids after a fînal ,~trip at S mm ~9 at 150-165C~
om~ tive Example ~ - Emulsion ~olymeriza~ion of 35EA~
55B~/9MA~ with Chain Transfer A~en~
Introduced into Initial Monomer Emulsion Feed e_ _ _ _ _ A monomer emulsion is prepared of 270 gram~ of water, 350 g of e~hyl acrylate, 550 g of bu~yl acryla~e and 90 g of methacrylic acid, 10 g of ita~onic acid, and 5 g of 3-mercap~ylpropionic acid (00 5% monomers) utilizing an anionic emulsifier, using 1.4 9 of ammonium l:icarbonal:e, 50 g of ammonium persulfate. The ammonium bicarbonate and 38 grams of ~he initiator were introduced into ~he reactor fol70wed by gradual addition of the remainder of the ammonium persulfate and the monomer emulsion at a relatively constant rate over a period of about 2-1/2 hours. Residual monomer was* chased with tertiary butyl hydroperoxide and ~ormopon and the produc~ was neutralized with ammonia ~o a p~ of about 5.9 Total solids was 56.1%. The Mn is 25,500, the Mw is lil,OOO, and ~he Mw~n is 6.7.
Com~arative Example G -_Low Molecular Weight Emulsion_ Pol~mer of EA/~A/MAA/IA 35/55~9/1 with Chain Transfer A~ent added to Emulsion before ~e ~
This example is conducted similarly to Example F
u~ilizing water, 27G g; ethyl acrylate, 350 ~,o bu~yl.
acrylate, 550 g; methacrylic acid, 90 g; i~aconic a~id, 10 g; 3-mercaptopropionic acid 10 g. The polymer was neutralized to a pH of 6.3 and had a total solid~ of 54.4%. The M~ is 1.4 x 104, the ~ ~s 0.48 x 105, and the Mw ~ ~ 35- Calculated Tg i~ -30C.
o~arative_Exam~le H _ i~h Molecular Wei~ht Pol~mer of ~ r The produ~t in this example is 99~ ethyl acrylate and *Tradem~rk for sodium formaldehyde hydxosulite.

3~!

1% itaconic ac;d. It i.s made with thermal free radical lnitiation using an anionic emulsifier ancl 0.4% ammonium persulfate based on monomers. As is conventional~ a chaser catalyst is added after the completi.on o the addition of monomer emulsion.
Thi.s product has a high heterogeneity index of about 67 made without a chai.n transfer agent but made with a chaserO As has been ind;.cated elsewhere herein heterogeneity index by itse]f does not give the complete story as to the quantity of high and low molecul.ar weight materials. It gives an indication qualitatively of the molecular weight distribution but does not do so quantitatively. When a chaser catalyst, i.e., an initiator, is added after the all of the monmers are introduced and are nearly ful.ly polymerized (in order to polymerize residual monomer in the aqueous phase and diffused into the polymer particles~, such a procedure produces a very small quantity of low molecular we;.ght polymer at the end of the polymerization reaction. As is well known, a 1.arge quantlty of free radical initiator relative to remaining monomer quantity produces quite low molecular weight materials, especi.ally i.n emulsion polymerlzations. Heterogeneity index thus gives a qualitative indication of the molecular weight distribution but does not do so quanti.tatively.
To make the monomer emu3.sion~ 9000g of ethyl acrylate are added to a solution of 44g of Siponate ~ DS-4 (23~
sodium dodecylbenzene sulfonate~ and lOOg itaconic aci.d in 2700g deionized water, and the mixture emu.lsified (M;xture A). 3588g of deion;.zed water are placed in a 22 liter kettle fitted with a reflux condenser, thermometer, and facilitjes for agitation~ Agitation is begun and the contents of the kettle heated to 82-84C. A solution of 14g of ammonium bicarbonate d;ssolved in 300g deionized water i.s added to the kettl.e followed by a solution of 30g ~ 34 --of a~nonium persulf ate dissolved in 300g deionized water .
Simul~aneous addition of l!!lix~ure A and a solu~ion of lOg o~
ammonium persulfate dissol.ved in 262g deionized wa~er is begun and the ~emperature allowed ~o r ise to 32-84C where it is maintained for 'che duration of ~he pc:lymerization.
The rates of the additions are adjusted such that additions are complete in 150 minutes. Af~er ~he additions are complete, a chaser is added in the form of a free radical initiator. Thereafter, the kettle temperature is lQwered to 40C and a neutrali2ing solution consisting of a solution of 37.5 g of aqueous ammonia (28% N~3) in 77.5 g deionized water is added over a period of 15 minutes.
A post additive is next added consisting of a mix~ure of 200g of Gelvatol 20-30 (polyvinyl alcohol) and 200g of '~ero~ex M[-3 " (melamine fcsrmaldehyde resin~ dissolved in 800g of deionized water. The emulsion is cooled to 25C and filtered through a 100 mesh screen ~o give a product having a pH of 6.8, a Brookfield vi~cosity of 82 cps and a total solids of 54.3% by weight. The Mn is 3 x 104, the Mw is 2 x 106, and MW/~n is 67.
Comparative Example I ~ olecular Weigh~ Polymer Of EA~BA/MAA/IA 35/55/9/1 Thi~ product is prepared by the same method as ExampIe El~ is neutralized to a pH of 6.2 has a viscosity of 466 cps. at 25C, using a Brookfield Model LtlF Yiscometer Spindle No, 2, at 30 rpm., and a total solids content of 53.1%~ The Mw x 10 5 i5 8.1 the Mn x 10 4 is 2.0 and the heterogenei~y index is 40.5. After the product is cooled to 4n o Gelvatol 20-30 and Aerotex M-3 in the same amounts as in Example ~ are added. A similar procedure was used to prepare a produc~ designated as Example V, but using EA/~MA/IA in the ra~ios of 87 ~ 7/9 ~ 5/2n 5 Exam~e J-I - E~/~A/~ I in the Ratios 35~55/9/1 Usin~
Pro~ramed Addltion of_Chain Transfer Agent t:o Yield a Mixtu~e of Molecular Weiqhts ~n this example the chain transfer a~ent (CTA), ~ *Trademark I ~

3-mercap~opropionîc acid (~PA), i5 introdUGed in ~wo stages. The firs~ stage intercepts ~he monomer addition at 5û96 of such addition, and 005% of the chain ~ransfer agent, based on the weight of 2596 of total monomers, is in~roduced 5 at tha~ point. At the 75% intercept, 1% of ~he chain transfer agent based on the weight of the remaining monomers, is intxoduced. The emulsifier is an anionic emulsif ier in ~he form of Sipona~e DS~4 which is sodium dodecyl benzene sulfonate. ~he pol~oerization is a 10 conventional emulsion polymerization using gradual monomer addition and a~mnoniwn persul~ate catalyst.
Twenty grams (20g. ~ of itaconic acid and 8 .8g. of '~ iponate ~S-4 ll are d i ssolved i n 5 40g . of dei on i zed water .
To th is i5 added 700g . of ethyl acrylat~, llOOg, of butyl 15 acrylate, and 180g. of methacrylic acid and the mixture emulsif ied (Mixture A) ,, A sofeed initiator solution i.5 prepared consis~ing of 2g. of ammonium p~rsulfate dissolved in 90g. of de;onized water (Solution B). Four hundred eleven grams of deionized water are added to a 5000 mlO
four-necked flask fitted with a reflux eondenser, thermometer and facilities for agi~ation and heated to 83~C. Two and eigh~-tenths grams of ammonium bicarbonate d;ssolved in 6Q~. of deionized water are added to the flask ollowed by a solution of 690 of ammonium persulfate in 60g. o deionized water. The gradual addition of Mixture A
is begun alon~ with the simultaneous addition of Solution B. Polymeriza~ion ~emperature is maintained at 82-84~C.
After 1274g. of Mixture A and 469. of Solution B have been added t:Q the rea~tion flask over a 75 mimlte period~ the additions are discon~inued. After a 5 minute hold period at 82-84C., 59. of 3-mercaptopropionic acid are added to the remaining Mixture A and the simultaneous gradual addi~ion of Mixture A and Solution B to the reaction flask is resu%ted. After 640g~ of Mixture P~ and 23g. of Solution 35 B have been added to the reaction flask over a 38 mi nute 3~

period, the addltions are discontinued. AEter a 5 minute hold period at 82-84C., ~.5g. of 3-mercaptopropionic ac;d are added to the remaining Mixture A and the s;multaneous gradual addition of Mi.xture A and Solution B to the reaction flask is resumed and completed in 38 m;nutes.
Thirty minutes after the additions are complete, the temperature is lowered to 40C. and a sol~tion of 14g. of ammoni.um bicarbonate and 12g. of aqueous ammonia (23~
NH3) in 234g. of deionized water is added over a perlod of 20 minutes. The ~n ls 2 x 104, Mw is 8.] x 10 , and the ~WrMn ls 39.6. Fifteen minutes after the additlon of thls neutralizer, a mlxture conslstlng of 40g.
of Aerotex M 3 (melamlne formal.dehyde resin) and lOOg. of Gelvatol 20-30 (polyvlnyl alcohol) dissolved ln 400g. of delonized water ;.s added. After 15 m;.nutes, the emulsion ls cooled and flltered to give a product with a pH of 6.4 and a solids of 52% by weight.
Products were prepared in the same way usi.ng the monomer ratlos EA/BA/MAA/IA of 34.75/55/9/l.25, 35.5/55/9/0.5, and 41/55/2/2 whlch had si.milar propertles.
Example J-2 - Programmed CTA Addition at Dlfferent Intercepts, than Example J-]. of Monomer Feed, EA/BA/MAA/IA, 35/55/9/].
This was conducted the same way as Example J-l, but ~5 the flrst addition ls 0.33% CTA when 60~ of the monomers have been lntroducedl and the second CTA addition is after 85% of the monomers have been fed, and is l.0~ based on the remalning ]5% of monomers.
Itaconic acid, 2Lg, and 9.3 y of Slponate DS-4 ~sodium dodecy] benzene sulfonate) are dlssolved in 567g of deionized water. To thls is added 735 y of ethyl acry~.ate, 1155g of butyl acry]ate, and 189g of methacryllc acid and the mi.xture emulsif;ed (Mixture A). 563g of dei.onized water are added to a 5000 ml four-necked flask fitted w;th a refl.ux condenser, thermometer and faci.litles for agitation and heated ~o 83C. 6.3 g of ammQnium persulfate are dissolved in 45g o deionized water and added to ~he flask followed by 139 of a preform consisting of a 45%
~olids acrylic emulsion polymer having a particle ~ize of 0.09-0.1 microns and a composition consisting of bu~yl acryla~e - 52 par~s, methyl methacrylate - 46 n 7 parts and methacrylic acid - 103 parts by weight. The gradual addition of Mixture A i5 begun along with the s;multan~ous addi~ion of a cofeed ini~iator soluticn cs:nsisting of a 2 lO weight percent solution of an~nonium persulate in deionized water (Solu~ion B). Polymerization temperature is maintained at 82-84C. Af ter 1606 ~ of I~ixture A and 649 - of Solution 13 have been added to the reaction flask os7er a 90 minute period, the additions are discontinued. After a L0 minute hold period a~: 82-84C, simultaneous gradual addi~ion of ~ixture A and Solu~ion B to the reaction flask is resumed along with the simultaneous add it ion of a solution of l. 78g 3-mercaptopropionic acid in 32. 6g of deionized water (Solution C~.. After 669g of M;.xture A, 279 of Solution B and Solution C have b~en added to the reac~ion flask over a period of 40 minutes, the additions are discontinued . Af ter a lO minute hold period at 82-84C, the remaining Mixture A (401 g) and 16g of Solutlon E~ are simul~aneously added ~o the reaction flask along with the simultaneous addition of a solution of 3. llg of 3-mercaptopropionic acid in 16.4g of deioni~ed water (Solution D) over a per;.od of 20 minu~es. Af~er the addi~ions are complete, the temperature is lowered to 40C
and a solution of 23g of aqueous ammonia (28% NH3~ in 202g of deionized water is added over a period of 20 minutes. The calculated Tg is -30C. This product gave excellent results. The M~ was, at the high end of range of 15-1~0, but could not ~e preci.sely determined because a fraction thereof was insoluble in the usual solvents used ~5 ! ~

v ~:

in gel permea~ion chroma~o~raphyO
After the additiQn of the neu~ralizer, a mixture consis~ing of 42g of"Aero~ex M-3"(melamin~ formaldehyde resin) and 126g of"Gelvatol 20 30"(polyvinyl alcohol1 dissolved in 504g deionized water is added.
xam~le K ~ Preparation of Polymer with ~igh Molecular Weight First Sta~e and Low Molecular Wei~ht Second _tage of Diferent Monomer Composition; EA/BA/MAA/IA//BA/AA in the atios 31~5/49.5/8.1/0.9//8.5/I.5 The first stage emulsion was water, 292 g; ~A? 378 9;
BA, 594 g; M~A~ 97O2 g; IA, 20,8 9. The second stage was water, 32 g; BA, 102 g; AA, 18g; 3-MPA, 3.6 9 (chain transfer agent).
T~e polymerization, using'~iponate DS-4"as the emulsifier, was conducted similarly to the other emulsion polymerizations above but the firs~ emulsion was introduced over a period of about 2.5 hours, after which the second monomer emulsion feed was commenced, and completed over a period of 35 minutes. The product was cooled to 40C, and neutralized to a p~ of 6.3. It had a viscosity of 6.6 cps with spindle no. 1, 60 rpm using a ~rookfi~ld"LVF viscometer. The product had a total solids content of S3.6%~ and had properties similar to ~hose of Examples J-l and J-~.
Example L - Hi~h Molecular Weight Latex Polymer of BA~IDMA~IA in the Ratios_49.S/49.5/1 When these monomers are used similarly to Example ~, comparable results were obtained~
Similar results were obtained with BA/IDA/IA in the ra~ios 49.5/49.5/1 and BA/~MA/IA in the ratios 49.5/49O5/1 Exam le M ~ Low Molecular Weight Emulsion~ mer_ of EA/BA/MAA/IA, 35/55/9~I

This example was conducted similarly to Example G but 3~

~ 39 -utilized 0.1% mercaptopropionic acid in the emulsion feed. The Mw x 10 is 17.2, the Mn x 10 i.s 3.2, and the MW/Mn equals 53. The product, tested as described herein, had a lap shear adheslon of 177 ].b., a 158Fo stat.i.c c]eavage of 1.5 hr., with the early grab strength of fa;.r to good, legs poor and fusion, poor.
Comparative Example N - Low Heterogeneity Index Latex Polymer of EA/BA/MAA/IA, 35/55/9/1 0.3~ CTA
This 7S conducted simiarly to Example G but wlth 0.3 mercaptopropionic aci.d resulting in an Mw x 1.0 5 of 3.5, and an Mn x ].0 4 of 4.0, givi.ng a heterogenei.ty index, MW~Mn, of 8.8.
This demonstrates that when a l.arger amount of chain transfer agent is utilized it is not consumed as rapidly and results ;n a more uniform and narrow distribut;on of molecular weights.
Comparative Example O - Low Heterogeneity Index Latex Po]ymer_EA/BA/MAA/IA 35/55/9/1, 0.5% CTA
This was conducted simi.arly to Example G and the foregoing example, utilizing 0.5% mercaptopropionic acid, resulting in an M x 10 5 of 1.26 an M x 10 4 of 2.8 and a heterogeneity index of 4.5.
Exam~le P Latex Pol~mer With Staged CTA Introduction EA~A/MAA~IA, 35/55/9/1 This examp]e was conducted with the same monomers and procedures of Exampl.e K but the initial polymerization to achieve a high molecular weight polymer fraction was achieved by feeding 85% of the monomer emulsion before introduction of the chain regulator or chain -transfer agent, which was ;n the amount of 3~ based on the remaining monomer, and was 3-mercaptopropioni.c acid, with only one stage in which the chain transfer agent was used. The Mw x 10 5 is 6.8 the Mn x 1.0 4 is 1.4 and the MW/Mn was 47.
Examples Q, R, S-and_T These were conducted simi]ar~y to Examp~.e .J-l 3~

- ~o -Comparati.ve Example V- High Mo'lecular Weight Polymer of This was made si.milar7y to Examp].e H.

Add;ti.ona] examples o polymers prepared simil,arly to Example H, using no chain transfer agent but using a chaser catalyst, include the fol'Lowing. In cases where there is a double slant line (//) between monomer increments, the meaning is that a first emul.sion polymer was prepared of the composltion indicated before the double slant line and a second monomer feed was then polymerized with the monomers fol.lowing the double slant line.
COMPS:)SITION PROPORTIONS
BA/W10/IA 49.5/49.5/1 BA/W]0/IA 49.5/50/0.5 BA/Wl0/IA/BDA 47.8/50/2/0.2 BA/W10/IA/E~DA 63.5/35/1.25/0.l BA/W10/IA/BDA 77.8/20/2/0.2 BA/W10/IA/BDA 63.65/35/l.25/0.1 VA/W10/IA 79.5/20/0.5 ~A/W10/IA/BDA 79.3/20/0.5/0.2 BA/MMA/IA 49.5/49.5/1 BA/IDA/IA 41.5/49.5/1 BA/IDMA/IA 49.5/49.5/].

EA/BA/MAA/IA 34.5/55/9/1.5 These are suitable as high molecular welght (predominantly~ components of blends with low molecular weight polymers. Of course, simil.ar monomer compositions ~ 41 -are useful with programmed CTA addition.
The results are summarized i.n Table I, which gives typical examp3es within the preferred embodiments of the inventlon, and comparative examp3es I.
Table II shows the results of contact adhesives, prepared by utillzi.ngl as in Example H, the same relative quantitles of Gelvato] 20-30 and Aerotex M-3.

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Table ~II demonstra~es blends o~ oligomers with the high molecular weight pol~ner of ~xample I, as compared wi~h the polymer of Example ~, and wi~h a commercial formulated neoprene latex.
S Table IV gives compari~ons of ~xample J-2 of the invention involving programmed chain terminator, Example V, a high molecular weight latex polymer made with a chaser but without chain terminator, a commercial acrylic latex produc~ of Union Carbide, and a commercial neoprene latex, Fastbond 30, of 3M Company.

*Trademark .~

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Claims (25)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an aqueous contact adhesive which dries to an essentially non-tacky state and adheres only to another dried, non-tacky layer of the adhesive upon contact, in the form of an aqueous latex of an addition polymer or polymer mixture at least predominantly of .alpha.,.beta.-monoethylenically unsaturated monomers comprising 0.5%-15% by weight of a carboxylic acid selected from the group consisting of acrylic acid, itaconic acid, maleic acid, fumaric acid, methacrylic acid and crotonic acid, and mixtures thereof, and 0 to 25% by weight of another addition-polymerizable .alpha.,.beta.-monoethylenically unsaturated monomer, the improvement in which the molecular weight of the polymer or polymer mixture is widely divergent and has a heterogeneity index, the ratio of MW/Mn of from 15 to 150, a fraction of from about 5%
to 70% of the polymer having an Mn of between about 500 and 100,000 and a fraction of from about 30% to 95% of the polymer having a Mn of between about 100,000 to at least 2,000,000, the molecular weights being determined by gel permeation chromotography, and the Tg of the polymer or polymer mixture is between 10°C and -60°C.

2. The adhesive of claim 1 in which from about 10% to 60% of the polymer has an Mn of from about 10,000 to 50,000, from about 40% to 90% of the polymer has an n of from about 500,000 to 1,500,000, the heterogeneity index is between 20 and 90, from 12% to 125% of an inorganic filler and a crosslinker are present.

3. The composition of claim 1 prepared by blending (a) an emulsion of a low molecular weight acrylic polymer obtained by bulk or solution polymeri-zation or a low molecular weight emulsion polymer with (b) a high molecular weight emulsion polymer.

4. The adhesive of claim 1 prepared by emulsion polymerizing an acrylic emulsion in stages, in which during at least one stage a high molecular weight polymer is obtained, and in which at least one other stage a low molecular weight fraction is obtained.

5. The composition of claim 4 prepared in stages in a reactor in which at least one portion of the polymer-ization reaction is conducted in the absence of a free chain transfer agent and at least one stage of the reaction is conducted in the presence of a free chain transfer agent, said Tg being from about -5°C to about -40°C.

6. The composition of claim 5 in which a first portion of the polymerization is conducted in the absence of a chain transfer agent, or only a low level thereof, whereby a high molecular weight fraction of the polymer is obtained and at least one additional stage of the polymerization is conducted in the presence of a higher amount of a chain transfer agent, whereby at least one low molecular weight fraction is obtained.

7. The composition of claim 6 in which at least about 30% of the monomers are polymerized in said first stage in the absence of chain transfer agent.

8. The composition of claim 7 in which there are at least two stages in which monomer and chain trans-fer agent are introduced, the quantity of chain transfer agent being greater in the last stage of the reaction, there thus being a first polymerization stage in the absence of chain transfer agent, a second polymerization stage in which a chain transfer agent is utilized, and a third stage in which a larger amount of chain transfer agent is utilized.

9. The composition of claim 8 in which 30% to 90% of the monomer mix has been reacted when the initial chain transfer agent is introduced, and a second introduction of chain transfer agent takes place when between about 50% and 95% of the monomer mix has been reacted.

10. The composition of claim 9 in which the initial introduction of chain transfer agent takes place when at least 45% of the monomers have been introduced into the reactor and polymerized, and the second introduction of monomer and chain transfer agent takes place when at least 60% of the monomers have been introduced into the reactor and polymerized.

11. The composition of claim 10 in which the balance of the copolymerized monomers are one or more esters of the acrylic acid with an alcohol having from 1 to 18 carbon atoms.

12. The composition of claim 11 in which the carboxylic acid is a mixture of 5-10% of methacrylic acid with 0.5 2% of itaconic acid, and said ester or esters of acrylic acid have 1 to 8 carbon atoms.

13. The composition of claim 12 in which the monomers consist essentially of ethyl acrylate, butyl acrylate and said acids.

14. The composition of claim 13 in which the chain transfer agent is selected from long chain alkyl mercaptans, dialkyl xanthogen disulfides, mercapto-carboxylic acids, alkarylmercaptans, long chain alcohols, and halogenated hydrocarbons.

15. The adhesive of claim 2 which contains fractions of intermediate molecular weights.

16. The composition of claim 11 in which said another addition polymerizable .alpha.,.beta.-monoethylenically unsaturated monomer includes one or more of an ester of methacrylic acid with an alcohol having from 1 to 18 carbon atoms, vinyl versetate, styrene, vinyl toluene, vinyl acetate and acrylonitrile.

17. The contact adhesive composition of claim 1 which contains up to 10% by weight, based on the total solids of the composition, of a thickening agent.

18. The contact adhesive composition of claim 1 which contains a cross-linking means.

19. The contact adhesive composition of claim 1 which contains a filler, in an amount up to 125% by weight of the polymer in the aqueous latex.

20. The composition of claim 18 wherein the cross-linking means is a crosslinkable aminoplast.

21. The composition of claim 18 wherein the crosslinking means is a copolymerizable monomer containing two or more non-conjugated points of ethylenic unsaturation or two or more non-conjugated vinylidene groups of the structure CH2=C<.

22. A method of adhering two surfaces together comprising the steps of applying the composition of claim 1 to the two surfaces to be joined, curing the two coatings to a non-tacky state but a state in which the surfaces adhere to one another upon contact, and mating the surfaces with pressure, thereby bonding the two substrates to one another.

23. A laminate prepared by the method of claim 22.

24. The composition of claim 10 which includes also a thickener and a crosslinkinq means.

25. The composition of claim 24 wherein the thickener is polyvinyl alcohol and the crosslinking means is a water-soluble aminoplast.