# United States Patent [19] 

## Brabetz et ale

[54] ADHESIVE AQUEOUS DISPERSIONS OF POLYVINYLALCOHOLGRAFfPOLYMERS WITH ACIDIC HARDENERS AND PROCESS OF PRODUCfION

[75] Inventors: Hartmut Brabetz; Christof Kemenater; Franz Six; Wilhelm Kaiser, all ofBurghausen, Germany

[73] Assignee: Wacker·Chemie GmbH, Munich, Germany

[21] Appl. No.: 792,682

[22]


### [30] Filed: May 2, 1977
Foreign Application Priority Data
May 11, 1976 [DE] Fed. Rep. ofGermany

........... 2620738
[51] Int. 

### C1.2

................................................ C09J 3/14 [52] U.S. 

### C1•...................... 260/29.6 WA; 260/29.6 B; 260/29.6 BM; 260/29.6 BE; 260/29.6 M; 260/29.6 MM; 260/875 [58] Field ofSearch

................. 260/29.6 WA, 29.6 B, 260/29.6 BM, 29.6 BE, 875, 29.6 M, 29.6 MM [56]

2,843,562 3,461,052 3.563.851 3.755.234 

### [11]

[45] 

# 4,118,357
Oct. 3, 1978

References Cited
U.S. PATENT DOCUMENTS

7/1958 8/1969 2/1971 8/1973 Caldwell

..................... 260/29.6 WA Restaino et aI.

............ 260/29.6 WA Armour et aI.

............. 260/29.6 WA Chujo et aI.

................ 260/29.6 W A 

### Primary Examiner-Eugene C. Rzucidlo 

### Attorney, Agent, or Firm-Hammond & Littell
[57] ABSTRACf
An aqueous copolymer adhesive dispersion having a long pot life and giving highly waterproofbonds, comprising an acid hardener of water-soluble acids having pKsofunder 0and an aqueous dispersion ofa pre-crosslinked polyvinyl ester grafted onto polyvinyl alcohol, said polyvinyl ester being an ester ofan acid of 1 to 12 carbon atoms and said pre-crosslinking caused by the presence of small amounts of poly-ethylenicallyunsaturated compounds in the monomer mixture, as well as the aqueous dispersion and the method for its production.

.

15 Claims, No Drawings

## 1 

## 4,118,357 2 A further object ofthe presentinvention is the development of a process for the production of the above aqueous copolymer dispersion.

A still further object of the present invention is the 

### ADHESIVE AQUEOUS DISPERSIONS OF POLYVINYLALCOHOL GRAFf POLYMERS WITH ACIDIC HARDENERS AND PROCESS OF PRODUCI'ION

RELATED ART Aqueous polyvinyl ester dispersions have a number**~** development ofan aqueous copolymer adhesive dispersion havinga long potlife consisting essentially offrom 99.5% to 90% by weight ofthe above aqueous copolymer dispersion and from 0.5% to 10% by weight ofan ofexcellent properties as adhesives, such as good adhesive power,.rapid hardening colorless adhesive joints 10 and good workability. Due to the content of hydrophilic protective colloids required in the dispersions to produce stable dispersions, however, adhesive joints produced with these dispersions are not very water- 15 proof.

There has been no lack of attempts in the past to improve the waterproofness of these polyvinyl ester adhesives. Thus resorcinol-formaldehyde, phenol-formaldehyde· and urea-formaldehyde resins have been 20 added to the dispersions toimprovethe waterproofness ofthe adhesivejoints

..The resins were added to reduce the hydrophilic nature oftheprotective colloids and to reduce, in this manner, the swelling of the adhesive joints in water. However, while the waterproofness of 25 the adhesivejoints is improved by these additives, the pot-life time was found to be very short in these systems.

Anotherwayofreducingthewatersensitivity caused by the presence ofthe protective colloids in polyvinyl 30
ester adhesivesis describedinGermanPublishedApplicationDOS 1594194.Herepolyvinylacetatehomopolymer or copolymer dispersions mixed with 2% to 12% by weight polyvinyl alcohol as a protective colloid are used in mixture with acid metal salt hardeners. Prefera- 35 bly chromium nitrate and perchlorate or aluminum chloride and nitrate areused. The free acids are unsuitable as hardener additives in these mixtures. acid hardener selected from the group consisting of water-soluble acids having pKs under 0, salts ofmonobasic acids having pKs of under 0 with heavy metals selected from the group consisting of CrIll, AIIII and FellI, and zirconyl salts ofmonobasic acids having pKs ofunder 0, and mixtures thereof.

These and otherobjects ofthe present invention will become more apparent as the description thereof proceeds.

DESCRIPTION OF THE INVENTION

The invention relates to the use of aqueous copolymer dispersions in admixture.with acid water-soluble hardeneradditivestogiveadhesives ofincreased waterproofness and long pot time which are characterized in that water-soluble acids with pKs below 0 and/or chromium<lll) and/or aluminum and/or iron and/or zirconyl salts ofmonobasic acids with pKs below 0 are added to aqueous dispersions ofpre-crosslinked grafted

. polymers of vinyl esters and at least di-oleftnicallyunsaturated monomers grafted onto a partly saponified, water-soluble polyvinyl alcohol which is contained in
amounts of 2% to 14%, preferably 3% to 10% by weight in the polymer mixture, and having a degree of hydrolysis ofbetween 74 and 97 mol %, preferably 81
to94mol %, said grafted vinyl estersconsistingofvinyl
esters with 1to 18 carbon atoms in the acid radical and its mixtures, preferably vinyl acetate and not more than 30% by weight of the total monomers of additional

monomers copolymerizable therewith, which include 0.01% to 5% by weight ofthe total monomers ofcom- OBJECTSOF THE INVENTION 40 pounds having at least two ethylenically-unsaturated double bonds in the molecule, preferably triallyl cyanurate. Anobjectofthepresentinventionwasthus

### to fmd an adhesive composition whose polymer dispersion componentis to a great extent free ofthe negative effects of theprotective colloid, and where, in addition to special salts, free acids are also suitable as a hardening compo- 45
nent.

Another object ofthe present invention is the development ofan aqueous copolymer dispersion useful for**a~hesives** of**increase~ wat~rproofness**  when hardened 50 WIth water-SOluble aCIds WIth pKS ofunder 0or heavy metal salts thereof, consisting essentially of aqueous dispersions of pre-crosslinked polyvinyl esters grafted onto polyvinyl alcohol wherein said grafted polymer contains from 2% to 14% by weight ofsaid polymer of 55

a polyvinyl alcohol with a degree ofhydrolysis ofbetween 74 and 97 mol % having grafted thereon (1) at least 70% by weight of said polymer of a vinyl ester selected from the group consisting of vinyl esters of a1kanoic acids having from 1 to 12 carbon atoms and 60 mixtures thereof, (2) from 0 to 10% by weight of said polymer of at least one monoethylenically-unsaturated compound copolymerizable with said vinyl ester and (3) from 0.01% to 5% by weight of at least one cohipound having at least two ethylenically-unsaturated 65 bonds and being copolymerizable with said vinyl ester, said aqueous dispersion having a solids content offrom 40% to 60% by weight. More particularly, the present invention relates to an aqueous copolymer dispersion useful for adhesives of increased waterproofness when hardened with watersoluble acids with pKs ofunder 0 or heavy metal salts thereof, consisting essentially'ofaqueous dispersions of pre-crosslinked polyvinyl esters grafted onto polyvinyl alcohol wherein said grafted polymercontains from 2%
to 14% by.weight ofsaid polymer ofa polyvinyl alcohol with'a degree of hydrolysis ofbetween 74 and 97 mol % having grafted thereon (1) at least 70% by weightofsaidpolymerofa vinyl ester selectedfrom the group consisting ofvinyl esters ofa1kanoic acidshaving from 1 to 12 carbon atoms and mixtures thereof, (2) from 0 

### to 10% byweightofsaidpolymer ofatleast one mono-ethylenically-unsaturated compound copolymerizable withsaid vinyl esterand (3) from0.Q1% to 5% by weight of at least one compound having at least two ethylenically-unsaturated bonds and being copolymerizable with said vinyl ester,·said aqueous dispersion having a solids content offrom 40% to 60% by weight;

as well as themethod for theproductionofsaid aqueous copolymer dispersion, which consists essentially ofthe steps of copolymerizing a monomer mixture of sufficient amount to give a fmal polymer of(1) at least 70% byweight ofsaid polymer ofa vinyl ester selected from the group consisting of vinyl esters of alkanoic acids

## 3 4,118,357 

## 4 having from 1to 12 carbon atoms and mixtures thereof, (2) from 0 to 10% by weight ofsaid polymer ofat least

one mono-ethylenically-unsaturated compound copolymerizable with said vinyl ester and (3) from 0.01% to 5% by weight ofat least one compound having at least 5 two ethylenically-unsaturated bonds and being copolymerizable with said vinyl ester, onto from 2% to 14% by weight ofsaid polymerofa polyvinyl alcohol with a degree ofhydrolysis ofbetween 74 and 97 mol 

### % under polyvinyl alcohol graft polymerization conditions at a 10 temperature of from 30· C. to 80· C. in an aqueous dispersion and recovering said aqueous copolymer dispersion.

The invention also relates to the aqueous copolymer adhesive dispersion having a long pot life, consisting 15 essentially of from 99.5% to 90% by weight of said aqueous copolymer dispersion and from 0.5% to 10% by weight ofan acid hardener selected from the group consisting of water-soluble acids having pKs under 0, salts of monobasic acids having pKs of under 0 with 20 heavy metals selected from the group consisting of Crlll, AlIIl

### and FelIl

, 

### and zirconyl salts of monobasic acids having pKs ofunder 0, and mixtures thereof.

Surprisingly, it is possible, when using these precrosslinked graft copolymers which contain polyvinyl 25 alcohol, not in admixture with the polymer component

as a protective colloid, but rather with the polymer components grafted primarily onto the polyvinyl alcohol, to achieve an increase ofthe waterproofness and a higher wet binding strength of the adhesive bond on 30 treatment with free acids. It 

### is known that polyvinyl alcohol in aqueous solution is not brought into a waterinsoluble form by these acids, although this is accomplished by the addition ofaluminum salts, by crosslinking. At the same time, it becomes possible to offer wa- 35 terproofadhesive systems which attain pot-life times of

over 4 weeks.

Thegraftbase used for the pre-crosslinked graftpolymers according to the invention is a partly saponified polyvinyl alcohol with a degree of hydrolysis of be- 40 tween 74% and 91% by weight, preferably 81% to 95% by weight. In selecting the type ofpolyvinyl alcohol, it must be kept in mind that the extent of the grafting reaction depends, among others, on the degree of hydrolysis. A high content ofresidual acetate groups en- 45 hancesthegraftreaction. Theaddition ofsmall amounts ofanionic or nonionic emulsifiers in amounts ofup to 1 % by weight ofthe total monomers enhances the graft reaction further. The content of polyvinyl alcohol in thetotal graft polymer shouldbe2% to 14% by weight, 50 preferably 3% to 10% by weight.

The pre-crosslinked graft polymer dispersions are produced by using free-radical chain starters, whereby reactive radicals are formed during their decomposition. This can be caused by heat orby the introduction S5 

### of reducing agents which enhance a graft reaction on polyvinyl alcohol. These initiator systems are organic peroxides and hydroperoxides in amounts of 0.1% to 3%byweight, preferably0.5% to2%byweight, which form highly reactive radicals during their decomposi- 60 tion, such as, for example, tert.-butyl hydroperoxide (forming the methyl radical) in combination with suitable reducing agents in amounts of 0.05% to 3% by weight, such as sodium formaldehyde sulfoxylate, sodium sulfite, sodium hydrogen sulfite, dithionite. The 65 graft reactioncan also be caused bythedirectpolyvinyl alcohol radical formation by 

### Cdv 

### ions, such as ceric ammonium sulfate orceric nitrate; by manganeselllions, such as dimanganese trisulfate in the presence of sulfuric acid or manganese triacetate; by ironIIl

### ions, or by potassium permanganate. These various heavy metal ions

## are employed in 0.1 to 3molar solutions ofthe salts.

Suitable for use according to the invention are aqueous dispersions of pre-crosslinked graft polymers, where copolymers ofvinyl esters, with each other and with other ethylenically-unsaturated monomers, are grafted on polyvinyl alcohol, and where the portion of polymerized vinyl esters in the polymer is at least 70% by weight.

Suitable as vinyl esters are those·of straight or branch-chained alkanoic acids with 1 to· 12 carbon atoms. Examples ofthese vinyl esters arevinylformiate, vinyl acetate, vinyl propionate, vinyl 2-ethylhexanoate, vinyl isononoate, vinyl laurate and vinyl esters of the versatic ®acids. These are synthetic, saturated, mainly tertiary monocarboxylic acids with 9 to 11 carbon atoms. Preferably, vinyl acetate is utilized, however, particularly in amounts ofat least 70% ofthe weight of the polymer.

Other ethyleriically-unsaturated monomers which

can be copolymerized with the· vinyl esters are the monoethylenically-unsaturated monomers in amounts offrom 0 to 10% by weight ofthe polymer produced. These are, for example, alkenoic acids having 3 to 10 carbOn atoms and their esters with alkanolshaving 1to 18 carbon atoms, such as acrylic acid or methacrylic acid or their esters with primary or secondary alcohols with mostly 1 to 18 carbon atoms, preferably 1 to 12 carbon atoms, such as methyl alcohol, ethyl alcohol, propyl alcohol andbutylalcohols and mixtures ofshortchained alcohols, 2-ethylhexyl alcohol and lauryl alcohol; as well as cyclohexyl alcohol; a,/3-unsaturated alkanoic acids with a carbon·chain between 4 and 10 carbon atoms, such as crotonic acid, isocrotonic acid and their esters with methyl alcohol, ethyl alcohol, propyl alcohol and butyl alcohol and mixtures ofshortchained alcohols, as well as 2-ethylhexyl alcohol, cyclohexyl alcohol and lauryl esters or mixtures thereof; alkenes having 2 to 6 carbon atoms, like ethylene, propylene,**butylen~;** 

### vinyl halides and .vinylidene halides, such as vinyl fluoride, vinyl chloride; vinylidene fluoride, vinylidene chloride; styrene; a,/3-unsaturated alkendioic acids with from 4 to 1 () carbonatoms, such as maleic acid, fumaric acid and itaconic acid and their monoesters and diesters ofthe same alkanols with 1 to 18 carbon atoms and cyclohexanol; nitrogen-containing monoolefmically-unsaturated monomers, particularly nitrides, amides, N-methylolamides, Mannich bases of N-methylolamides, lower alkanoic acid esters of Nmethylolamides, lower alkyl ethers of N-methylolamides, ofalkenoic acids having 3 to 6carbon atoms and allyl carbamates (except for the nitrile), like acrylonitrile, acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-methylol allyl carbamate or N-methylol lower alkylethers, Mannich bases or N-methylol lower alkanoic acid esters of Nmethylolacrylamide, N-methylolmethacrylamide, and N-methylol allyl carbamatein amountsofnotmorethan 10% by weight, generally 3% to 6% by weight ofthe polymer.

In addition, the graftcopolymers contain from 0.01% to 5% byweight, related tothe total polymer, ofmonomers having at least two ethylenically-unsaturated doublebonds in the molecule. Preferably the compounds having at least two ethylenically-unsaturatedbonds and being copolymerizable with said vinyl ester are comi i 

# d

## 5 4,118,357

pounds having two and three ethylenically-unsaturated bonds and no other unsaturation, particularly lower 

## 6

EXAMPLE I alkenyl lower alkenoates, such as, preferably, vinyl In a reactor, which is provided with a reflux concrotonate, or allyl acrylate and allyl methacrylate, denser, stirrer, dosing facilities, nitrogen feed, as well as lower alkylene bis-Iower-alkenoic acid amides such as 5 a heatable and coolablejacket,29.5 parts by weight of methylene bisacrylamide, triallyl cyanurate, di-Iower water, 2partsbyweightofapartly saponified polyvinyl alkenoic acid esters of lower alkanediols such as hex- alcohol with a degreeQfhydrolysisof90 mol % and 0.1 anediol-diacrylate, tri-Iower alkenoic acid esters of partsbyweightofanethoxylatednonylphenol (23 mols lower alkanepolyols such as pentaerythritol-triacrylate ethylene oxide) were charged. After flushing the reacand trimethylolpropane-triacrylate or in addition dial- 10 tor with nitrogen, 25% byweightofthe monomer solulyl phthalate, and polyoxyethyl:ne 'glycolest:rs of tion, which consisted of45.3 parts by weight of vinyl lower alkenoic acids such as trioxyethylene glycol- acetate, 0.04 parts by,**~eight** 

### of**t~butyl** 

### hydroperoxide dimethyacrylate. Vinyl crotonate and methylene bisac- and**0.01~** 

### parts by weight of**tnallyl~yanu~ate,** 

### were rylamide are the preferred cross-linking monomers. charged mto the reactor and the reaction**~tur~** 

### was

Thepolymerdispersions used accordingto theinven- 15 heated.

### ~en the

### temI?Cra~ure of the reaction mtXture tion have a total solids content of 40% to 60% by reached 50**~.,** 

### the dosmg m ofa supply feed**w~** 

### comweight, preferably 45% to 55% by weight. menced, which**wascom~sed** 

### of6.6.partsbyweight of

Suitable as acid compounds, which ensure a good water, 0.02 parts by weight of**~odlUm fo~alde~yde**  

### waterproofness ofth.e adhesive.joint, are

### ~he water-sol- 20 sulfoxylate and

### ~.02**pa~** by weight of sodIUm blcaruble salts of chromIUm, alummum and Iron, such as bonate. The**do~mg** 

### ofthis supply feed was effected at chromiumIllnitrate, chromiumIllchloride, al\uninumlll 

### such a rate thatIt was completed one hour.after the end chloride, aluminumllI

### nitrate, ironIll

### chloride, or zirco- o.f the two

### monom~~ supply feeds,

### o~ which one

### ~on-

. hl 'd Ch .' III 

### hl'd 

### i' min III 

### slsted of the remammg 75% by weight of the vmyl**n~um** 

### oxyc on e..**I~~~um** 

### c on e, a u um acetate solution and the outer of 3 parts by weight of mtrate and chromIUm mtrate are preferred, but also 

### 25 N th 1 1 1 'd' d 10 4 art b . ht f f 

### 'd hi h dOh 'h hl -me y 0 

### acry amt 

### e an . p s y welg 0 

### wa- ree aCI s w ch ave pKs un er ,suc as ydroc 0- 

### t ' ric acid, nitric acid, perchloric acid an,d mixtures er Th · e d' of th t' 1 ti' 

### "

. osmg e wo monomer so u ons com- thereof,**ma~** 

### be used. The**~etal** 

### salts are**a~~ed** 

### m the menced when an internal temperature of 65° C. had form oftherr**.satur~ted** 

### solutions, the free aCids, as 5 N been attained. The polymerization was effected at a aqueous solutIOns, m amounts of**O.~%** 

### to 10%, prefera- 30 temperature ofthe reaction mixture of65° C. to 70° C.**b~y** 

### 2o/k to 8%,**r~lated** 

### to the weight of tl1e polYI?er The rate offlow ofihe two monomer supply feeds was**dlsperslo~.** 

### The.aCid compoun.ds**ar~** 

### added before usmg so regulated that there was no refluxing. After all dosthe adheSive mtXture ofthe**dlsper~lon.** 

### "

.. ings had been completed, the polymerization was conIn order to reduce the ftlm-formtng temperature,lt IS tinued for 1 hour at 70° C. and then the mixture was**~ustomary** 

### in**.s~me** 

### cases to add**~o th~** **di~pe.rsion** 

### addi- 35 cooled. A stable, coarsely divided and coagulate-free tionally, plastiCIZers or ftlm-formmg atds m amounts of dispersion was obtained which, with a solids content up**t~** 

### lOo/k by weight ofthe**po~ymer cont~nt.**  

### adjusted to 50%, had a viscosity of 12,000 mPa.s (EpDisperSions ofthe**pre-cr~sslink~d polyvm~l** **alc~hol** 

### precht-Rheometer at 20° 

### G., measuring cup 

### 0, stage**gra~t copol~mers** **o~** 

### the**mven~lon** 

### ll?d**dls~rslons** 

### III). The dispersion c(:>uld be modified subsequently which contam polyvmyl alcohol m admtXture With the 40 with 3% by weight ofdibutyl phthalate, related to the**r~sin** 

### dispersio? differ clearly in their solution behavior. weight ofthe dispersion, in order to reduce the ftlmFilms ofthe vmyl acetate copolymers not,grafted onto forming temperature. polyvinyl alcohol, for example, dissolve inethyl acetate ' EXAMPLE 2 in amounts offrom 80% to 100%. The**pre~rosslinked** 

### graft copolymer dispersion ftlms used according to the 45 Some ofthe graft copolymer dispersions with differinvention, however, have a solubility of OIily 30% to ent hardening agents used according to the invention 55% in this solvent. If

### pre-crosslinked graft ,?opolymers are here described. The essential mixing data are given of vinyl acetate homopolymers or copolymers onto in Table 1. 

### Forthe, graftpolymerization, as in Example polyvinyl alcohol are mixed with a suitable amount of SO 

### 1, a partly saponified polyvinyl alcohol was utilized. the acid hardening agent, adhesive joints can be pro- The finished adhesive mixture was obtained by mixing duced with these mixtures on wood which show an the dispersion directly with the respective hardeners excellent waterproofness. before it was to beused,as an adhesive. This was done

Adhesive woodjoints, as they canbe produced with onlytoprovideuniform'comparison conditionsand was the adhesives according to the invention, are used with 5S 

### not limited by the pot time ofthe mixtures. particular advantage in exterior wood constructions; Table 1 also for windows and doors which are exposed to Solids

. Polymer 

### changing climatic conditions, water ofcondensation as Conlent ' Composition % by Weight 

### well as spray and bilge water; for wood panellings in Disper- in % by in % Hardening ofthe sion No. Weight by Weight Agent 'Dispersion 

### wood constructions in swimming pools, saunas, and 60**-'------so-=---~-~--.-::~----.:~:.:::.::::::.-** 

### shower cabins; or weathered exterior wood coverings. '94.ZS VAC HC1 8



### The following examples are illustrative of the prac-S.6S PV A 

### tice of the invention without being limitative in any 2 SO

### 7~:W**~!~** respect. 23.92 VL 3.83 PYA 

### EXAMPLES
The production of a dispersion according to the invention will be described in the following example: 65 3 S2 0.48 TMPT 76.0S VAC 19.01 DAHM 4.75 PYA 0.19 PETA 7.5

ZrOCI2 S

## 7 4,118,357 

## 8

Table I-continued
Solids Polymer Content Composition Diaper- in % by in %., Hardening sion No. Weight by Weight Agent
4 '0 78.81 VAC H2SO4 17.30 E'

. 2.84 PYA O.OS VCr 4S 90.23 VAC Cr(N03 h % by Weight ofthe Dispersion
6 5 The pot.times of the mixtures are surprisingly long when the free ,acids are used, and in all cases over 4 weeks.

.The results are compiled in Table 2.

Hardening Agent
Amount in % by Weight Table 2

2.79 CS 6.'2 PYA 0.46 MBAA 10 ofthe 'NAcid -. 5 -3 5

1.96 6 50 91.61 VAC FeCI3 4.82 AA 3.37 PYA 0.20 VCr 7 SO 90.36 VAC Cr(N03 )3 5.77 NMA 3.84 PYA .' 15

VAC = vinyl acetate VL = vinyl laurate 0.03 TAC

PET A = pentaerythritol triacrylate MBAA = methylene bisacrylamide PV

A = polyvinylalcohol DAHM = diethylhexyl maleate E = ethylene es = crotonic acid TAC = triaUyl cyanurate TMPT = trimethylolpropane triacrylate VCr = vinyl crotonate AA = acrylamide NMA

- N-methylolacrylamide

All adhesive mixtures listed in the above Table

wereused successfully for gluing wood and led to adhe20



### 25

sivejoints with excellent waterproofness.

. 30 pKs-Value Tensile Strength B 3/5 kp.**cm~2** cold water Tensile Strengtli B4/9 kp. cm-2 hot water -9

27

35

. -6 1.92 -1.3 3.8

24 22 26 

### a

31 34 33 15 6

These results demonstrate that mixtures ofstrong acids with pre-crosslinked graft copolymer dispersions yield surprisingly strong, water-resistant adhesivejoints.

EXAMPLE 4
'The addition 'ofacid hydrolyzing salts ofmonobasic acids with 'pKs under 0 and metal ions of

### chromiumIII

, aluminuniIlJ,. ironIlJandzirconyl ion in admixture with the'pre-crosslinked graft copolymer dispersions on polyvinyl alcohol also yields excellent wet-strength bindEXAMPLE 3 ing values of the'adhesion joints. The values of the shows the great water-resistance of adhesive strength listed in the following Table 3 were Thi.s

### ex~ple . ,. obtained with the dispersion described in Example 2(7). adheSIve mIxtures from pre-crosslmked graft polymers Th t 0' f th dh' . t . h rt h 1 ' 11 hI df 'd h'd' ' ". '. epo' meo ea eSlvemlXUreS.1SS 0 er, ow- onpo yvmy a co 0 an ree aCI s as ar emng agents. 35' 

### th· 'th dh' . t d d 'th f Thewater-resistance achieved is themore surprising, as**eV~dr..** ahn md**~** a eSlvte m l IX ures I?ro t uce h WI ree fi 'd fi' 1

... l' 1 aCI S'8S ar emng agen s. n every ms ance, owever, ree aCI s, or examp e, cannot precIpItate po yvmy , th t f' th 48 hIll 003 alcohol solutions, as is known from certain'salt solu- e po**~mellstmofreh** dan. ours t· n a cas d es, 1'00 

### f grameqUlva en soar emng agen were use per IOns. grams ofdispersion.

Hardening Agent
Tensile Strength B4/9(kp.cm-2) hot water

The pre-crosslinked graft copolymer dispersion as described in Example 2(1) was used for the adhesive joints. 50 The production of the test pieces and the testing of the wet binding strength were effected according to DIN 68 603, requirement group B 3/5 (cold water strength) and requirement group B 4/9 (hot water strength). DIN is the published test procedures of the 55 German Industry. The test ofrequirement group B 3/5 prescribes, substantially, storage for 7 days in a normal climate (20° 

### c., 65% relative humidity) after gluing the wood panels; subsequently, the panels are stored for 4 days in cold water at 20° C. 

### ± 2° C. and tested immedi- 60 ately thereafter on the tensile testing machine at a withdrawal rate of 50 mm/min.

Requirement group B 4/9 prescribes, likewise, storage for 7 days in a normal climate after gluing; subsequently, the test provides for storage for 6 hours in 65 boiling water followed by storage for 2 hours in cold
water. Immediately thereafter, the tensile test is run with a withdrawal rate of 50 mm/min. Table 3

Cr(N03 )j Al(N03)3 CrCI3 FeCI3 ZrOCI2 Fe2(SOJ3

'47 45 43 41 41 0

EXAMPLE.A.(Comparison Example

- Uncrosslinked and Ungrafted)

. In a reactor provided with reflux condenser, stirrer, dosing facilities, nitrogen feed, as well as a heatable and coolablejacket, 35.3 partsby weight ofwater, 2.4 parts by weight of

## a: partly saponified polyvinyl alcohol with

a degree of hydrolysis of 90 mol 

### %, and 0.1 parts by weight of an ethoxylated nonylphenol (23 mols ethylene oxide) were charged. After flushing the reactor with nitrogen, a quarter of the total supply of vinyl**~cetatemon<;>mer** mixture, which consists of 54.2 parts by weight of vinyl acetate and 0.02 parts by weight H2

### 0 2(30%) werechargedinto the reactor and the reaction**~ixture** was heated. At a temperature ofthe reaction mixture of 50° C., the dosing ofa supply feed was commenced, which supply feed was composed of 7.9 parts by weight of water and 0.07 parts by weight of hydrogen peroxide (30%). The dosing of this supply feed wa(effected at such a rate that it was completed together with the supply ofvinyl acetate.

## ·9 

## 4,118,357 10 The dosing ofthe residual acetate monomer mixture 'Atestpiecewasexposed underconstant static load of '

was started at 

# an internal temperature of

### ,65' ;C. The 

### 50 N (= skp) in a warming cabinet to a rising,temperapolymerization was effected at a temperature of the ture

.. Normal. polyvinyl acetate (PV AC) wood glue reaction mixture of6S·,C

..to70' C., the rate offlow of dispersions are stable up to a maximum temperature of the two supply feeds being so'regulated·thatthere was 5 120' C., while DispersionNo.7 was stable up to 180' C.

no refluxing. After thedosings ,were ,completed" the Without the addition of chromium nitrate, the disperpolymerization was continued for 1hour at 70' C. and sion acted like a normal wood glue with a stability of then themixture was cooled. A stable, coarsely-divided ' only up to 

### 90' C. Only by the addition ofthe hardener and coagulate-free dispersion was obtained which, with solution was the increase achieved.

a solids content adjusted to 

### 50% by weight, had a**vis~** 10 The precediJig specific embodiments are illustrative cosity of 6,000 mPa.s (Epprecht-Rheometer at' 20' C., ofthe practice ofthe, invention. It is to be understood, measuring cup D, stage III). 'however, that other expedients known to those skilled inthe artordescribed herein, may.be employed without EXAMPLE B (Comparison Example, Pre-Crosslinked departingfrom thespirit oftheinventionorthe scopeof but not Grafted)' 15 the appended claims. '. We claim:



### 1. An aqueous copolymer dispersion useful for adhe.**sive~** ofincreased waterproofness when hardened with

an acid hardener selected from the group consisting of The dispersion according to this example 

## was prepared in the same manner as the dispersion in Example A, but in the vinyl acetate monomer supply feed, 0.03 parts by weight triallyl cyanurate wer'ealso employed.
EXAMPLES, 20 water-soluble acids with pKs of under 0 and salts of monobasic acids having pKs of under 0,with,heavy metals selected from the group consisting ofCr JJJ

, AIJJJ, and FellI, and zirconyl salts ofmonobasic acids having This example shows the advantages of the use of pre-crosslinked graft copolymer dispersions on polyvinyl alcohol, compared to polymer dispersions in which the polyvinyl alcohol is present in admixture with the 25 uncrosslinked polymer dispersion (Example A), and those where the polymer is pre-crosslinked but not grafted on the polyvinyl alcohol (Example B).

Theextent ofgrafting ofthe copolymer onpolyvinyl' alcohol and ofthepre-crosslinkage were determined by 30 the solubility of the copolymers in ethyl acetate. The following Table 4 shows the solubility of dispersion 

### films, which consist ofcopolymers according to Examples A and B, respectively. These solubilities are compared with those of the 

### films of the graft copolymer 35 dispersions according to the invention (C and D) from Example 2, Dispersion No. 1 and No. 

### 5
Table 4 pKs ofunder 0, and mixtures thereofconsisting essentially ofaqueous dispersions ofpre-crosslinked polyvinyl esters grafted onto polyvinyl alcohol wherein said grafted polymer contains from 2% to 14% by weightof said polymer of a polyvinyl alcohol with a degree of hydrolysis ofbetween 74 and 97 mol % having grafted thereon (1) at least 70% by weight ofsaid polymer ofa vinyl ester selected from the group consisting of vinyl esters of alkanoic acids having from 1 to 12 carbon
atoms and mixtures thereof, (2) from 0 to 10% by weight ofsaid polymer ofat least one monoethylenically-unsaturated compound copolymerizable with said vinyl ester and (3) from 0.01% to 5% by weight of at least one compound having at least two ethylenicallyunsaturated bonds and being copolymerizable with said vinyl ester, said aqueous dispersion having a solids con- _D_is:..pe.,.,rs,-io_n,-s

_____ A

____ B

___ C

____ D

__ 40 tent offrom 40% to 60% by weight. Solubility in**52~ 41~**  2. The aqueous copolymer dispersion of claim 1 Ethyl Acetate 87% 85% 7b 7b

The dispersions' investigated for their solubility in ethyl acetate were also tested for their wet'binding 45 strength when used as adhesives according to the methods described in Example 3. The dispersiops were mixed with 

### 5% by weight of aS4turated chromium JJJ nitrate solution and used for adhesive joints. The wet strength values found are compiled in Table 5. 50
Table 

### 5 Dispersions A B C D
Tensile Strengt4 B 3/5 kp. cm-2 5 10 32 34 Tensile Strengt4 55 B 4/9 kp. cm-2 15 20 48 51

Theseresults clearlyshowthat, whenpre-crosslinked graft copolymer dispersions on polyvinyl alcohol are used, the wetbinding strength values are far superiorto 60 the conventional dispersions which contain polyvinyl alcohol in admixture, and even those dispersions where thepolymeris pre-crosslinkedbutthepolyvinyl alcohol is present in admixture with the polymer dispersion. wherein said polyvinyl alcohol is present in an amount offrom 3% to 10%.

3. The, aqueous copolymer dispersion of claim 1 wherein said polyvinyl alcohol has a degree ofhydrolysis offrom 81 to 94 mol %.

4. The, aqueous copolymer dispersion of claim 1 wherein said graft component 1 vinyl ester contains at least 70% by weight ofsaid polymer ofvinyl acetate.



### 5. The aqueous copolymer dispersion of claim 

### 1 wherein said graft component 2 is present in an amount offrom 3% to 6% by weight ofsaid polymer.

6. The aqueous copolymer dispersion of claim 1 wherein said graft components 3 is methylene bisacrylamide.

7. The aqueous copolymer dispersion of claim 1 wherein said graft component 3 is triallyl cyanurate.

8. The aqueous copolymer dispersion of claim 1 wherein said solids content is from 45% to 

### 50% by weight.

9. An aqueous copolymer adhesive dispersion having

a long pot life consisting essentially of from 

### 99.5% to 90% byweightofsaid aqueous copolymerdispersion of claim 

### 1 and from 

### 0.5% to 10% by weight of an acid

EXAMPLE 6
The Dispersion No. 7 listed in Example 2 was tested for heat resistance. 65 hardener selected from the group consisting of watersoluble acids having pKs under 0, salts of monobasic acids having pKsofunder 0 with heavy metals selected from the group consisting of CrJJJ

, AIJJJand FellI, and

## 11 4,118,357 

## 12 zirconyl salts ofmonobasic acidshavingpKsofunder0, ence offrom 0.1 % t6 3% by weight based on the total and mixtures thereof. monomercontent ofatleast one organicperoxide form10. The method for the production of said aqueous ing highly reactive free-radicals on decomposition and copolymer dispersion ofclaim 1 

### which consists essen- from 0.05% t03% weight based on the total monomer tially ofthe steps ofcopolymerizing ofmonomer mix· 5 content ofat least one peroxide reducing agent; ture ofsufficient amounttogive a final polymerof(1) at 12. 

### The method of claim 11 wherein said organic least 70% by weight of said polymer of a vinyl ester peroxide is presentin an amount offrom0.5% to 2%by selected from the group consisting of vinyl esters of weight based on the total monomer content. alkanoic acids having from 1 to 12 carbon atoms and 13. 

### The method of claim 11 wherein said organic mixtures thereof, (2) from 0 to 10% by weight of said 10 peroxide is tert. butyl hydroperoxide and said peroxide polymer ofat least one mono-ethylenically-unsaturated reducing agent is sodium formaldehyde sulfoxylate. compound copolymerizable with said vinyl ester and 14. The method of claim 10 wherein said polyvinyl (3) from 0.01% to 5% by weight of at least one com- alcohol graft polymerization conditions are by direct pound having at least two ethylenically-unsaturated polyvinyl alcohol free-radical formation in the presence bonds and being copolymerizable with said vinyl ester, 15 of from 0.1 to 3 molar concentration of heavy metal onto from 2% to 14% by weight of said polymer ofa cations selected from the group consisting of 

### Cdv

, 

### polyvinyl alcohol with a degree of hydrolysis of be- Mnlll

### and Fd ll

. 

### tween 74 and 97 mol % under polyvinyl alcohol graft 15. The method of claim 10 wherein said polyvinyl polymerization conditions at a temperature offrom 30· alcohol graft polymerization conditions are by direct C. to 80· C. in an aqueous dispersion and recovering 20 polyvinyl alcohol free-radical formation in thepresence said aqueous copolymer dispersion. offrom 0.1 to 3 molar concentration ofpotassium per11. The method ofclaim 10 wherein said polyvinyl manganate. alcohol graft polymerization conditions are in the pres- 

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