United States Patent [19] 

Brabetz et ale 

[54] ADHESIVE AQUEOUS DISPERSIONS OF 

POLYVINYL ALCOHOL GRAFf POLYMERS 

WITH ACIDIC HARDENERS AND PROCESS 

OF PRODUCfION 

[75] Inventors: Hartmut Brabetz; Christof 

Kemenater; Franz Six; Wilhelm 

Kaiser, all of Burghausen, 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. of Germany ........... 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 of Search ................. 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 waterproof bonds, comprising an acid hardener of water-soluble acids having 

pKs of under 0 and an aqueous dispersion of a pre-crosslinked polyvinyl ester grafted onto polyvinyl alcohol, 

said polyvinyl ester being an ester of an 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 of the present invention 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 

POLYVINYL ALCOHOL GRAFf POLYMERS 

WITH ACIDIC HARDENERS AND PROCESS OF 

PRODUCI'ION 

RELATED ART 

Aqueous polyvinyl ester dispersions have a number 

~ development of an aqueous copolymer adhesive dispersion having a long pot life consisting essentially of from 

99.5% to 90% by weight of the above aqueous copolymer dispersion and from 0.5% to 10% by weight of an 

of excellent 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 to improve the waterproofness 

of the adhesive joints .. The resins were added to reduce 

the hydrophilic nature of the protective colloids and to 

reduce, in this manner, the swelling of the adhesive 

joints in water. However, while the waterproofness of 25 

the adhesive joints is improved by these additives, the 

pot-life time was found to be very short in these systems. 

Another way of reducing the water sensitivity caused 

by the presence of the protective colloids in polyvinyl 30 

ester adhesives is described in German Published Application DOS 1594194. Here polyvinyl acetate homopolymer 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 are used. 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 of monobasic acids having pKs of under 0 with heavy metals 

selected from the group consisting of CrIll, AIIII and 

FellI, and zirconyl salts of monobasic acids having pKs 

of under 0, and mixtures thereof. 

These and other objects of the 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 

hardener additives to give adhesives of increased 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 of monobasic acids with pKs below 0 are 

added to aqueous dispersions of pre-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 of between 74 and 97 mol %, preferably 81 

to 94 mol %, said grafted vinyl esters consisting of vinyl 

esters with 1 to 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 of the total monomers of com- OBJECTS OF THE INVENTION 40 pounds having at least two ethylenically-unsaturated 

double bonds in the molecule, preferably triallyl cyanurate. 

An object of the present invention was thus to fmd an 

adhesive composition whose polymer dispersion component is to a great extent free of the negative effects of 

the protective colloid, and where, in addition to special 

salts, free acids are also suitable as a hardening compo- 45 

nent. 

Another object of the present invention is the development of an aqueous copolymer dispersion useful for 

a~hesives of increase~ wat~rproofness when hardened 50 

WIth water-SOluble aCIds WIth pKS of under 0 or 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 of said polymer of 55 

a polyvinyl alcohol with a degree of hydrolysis of between 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 of from 

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 of under 0 or 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 of said polymer of a polyvinyl alcohol with 'a degree of hydrolysis of between 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 mixtures thereof, (2) 

from 0 to 10% by weight of said polymer of at least one 

mono-ethylenically-unsaturated compound copolymerizable with said vinyl ester and (3) from 0.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 of from 40% to 60% by weight; 

as well as the method for the production of said aqueous 

copolymer dispersion, which consists essentially of the 

steps of copolymerizing a monomer mixture of sufficient amount to give a fmal polymer of (1) at least 70% 

by weight of said polymer of a vinyl ester selected from 

the group consisting of vinyl esters of alkanoic acids 
3 

4,118,357 

4 

having from 1 to 12 carbon atoms and mixtures thereof, 

(2) from 0 to 10% by weight of said polymer of at least 

one mono-ethylenically-unsaturated compound copolymerizable with said vinyl ester and (3) from 0.01 % to 

5% by weight of at 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 of said polymer of a polyvinyl alcohol with a 

degree of hydrolysis of between 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 of an 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 of under 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 of the 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 of aluminum salts, by crosslinking. At the same time, it becomes possible to offer wa- 35 

terproof adhesive systems which attain pot-life times of 

over 4 weeks. 

The graft base used for the pre-crosslinked graft polymers 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 of polyvinyl 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 of residual acetate groups en- 45 

hances the graft reaction. The addition of small amounts 

of anionic or nonionic emulsifiers in amounts of up to 

1 % by weight of the total monomers enhances the graft 

reaction further. The content of polyvinyl alcohol in 

the total graft polymer should be 2% 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 or by 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% by weight, preferably 0.5% to 2% by weight, 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 reaction can also be caused by the direct polyvinyl 

alcohol radical formation by Cdv ions, such as ceric 

ammonium sulfate or ceric 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 3 molar solutions of the salts. 

Suitable for use according to the invention are aqueous dispersions of pre-crosslinked graft polymers, 

where copolymers of vinyl 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 of these vinyl esters are vinyl formiate, 

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 of at least 70% of the weight of 

the polymer. 

Other ethyleriically-unsaturated monomers which 

can be copolymerized with the· vinyl esters are the 

monoethylenically-unsaturated monomers in amounts 

of from 0 to 10% by weight of the polymer produced. 

These are, for example, alkenoic acids having 3 to 10 

carbOn atoms and their esters with alkanolshaving 1 to 

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 and butyl alcohols and mixtures of shortchained 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 of shortchained 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 () carbon atoms, such as 

maleic acid, fumaric acid and itaconic acid and their 

monoesters and diesters of the 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, of alkenoic acids having 3 to 6 carbon 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 carbamate in amounts of not more than 

10% by weight, generally 3% to 6% by weight of the 

polymer. 

In addition, the graft copolymers contain from 0.01 % 

to 5% by weight, related to the total polymer, of monomers having at least two ethylenically-unsaturated doublebonds in the molecule. Preferably the compounds 

having at least two ethylenically-unsaturated bonds and 

being copolymerizable with said vinyl ester are com

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 coolable jacket,29.5 parts by weight of 

methylene bisacrylamide, triallyl cyanurate, di-Iower water, 2 parts by weight of a partly saponified polyvinyl 

alkenoic acid esters of lower alkanediols such as hex- alcohol with a degree Qfhydrolysis of 90 mol % and 0.1 

anediol-diacrylate, tri-Iower alkenoic acid esters of parts by weight of an ethoxylatednonylphenol (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% by weightof the monomer solulyl phthalate, and polyoxyethyl:ne 'glycol est:rs of tion, which consisted of 45.3 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 

The polymer dispersions used according to the inven- 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 of a supply feed w~ comweight, preferably 45% to 55% by weight. menced, which wascom~sed of6.6.parts by weight of 

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

waterproofness of th.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 of this supply feed was effected at 

chromiumIll nitrate, chromiumIll chloride, al\uninumlll such a rate that It 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 erTh· 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 of therr .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 of the reaction mixture of 65° C. to 70° C. 

b~y 2o/k to 8%, r~lated to the weight of tl1e polYI?er The rate of flow 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 of the 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 of the po~ymer cont~nt. adjusted to 50%, had a viscosity of 12,000 mPa.s (EpDisperSions of the 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 of dibutyl phthalate, related to the 

r~sin dispersio? differ clearly in their solution behavior. weight of the dispersion, in order to reduce the ftlmFilms of the vmyl acetate copolymers not ,grafted onto forming temperature. 

polyvinyl alcohol, for example, dissolve in ethyl acetate ' 

EXAMPLE 2 in amounts of from 80% to 100%. The pre~rosslinked 

graft copolymer dispersion ftlms used according to the 45 Some of the 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. For the, graft polymerization, 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 wood joints, as they can be produced with only to provide uniform'comparison conditions and was 

the adhesives according to the invention, are used with 5S not limited by the pot time of the mixtures. 

particular advantage in exterior wood constructions; Table 1 

also for windows and doors which are exposed to Solids . Polymer 

changing climatic conditions, water of condensation as Conlent ' Composition % by Weight 

well as spray and bilge water; for wood panellings in Disper- in % by in % Hardening of the 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(N03h 

% by Weight 

of the 

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 of the 

'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 

V AC = 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 

were used successfully for gluing wood and led to adhe20 

25 

sive joints 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 of strong acids 

with pre-crosslinked graft copolymer dispersions yield 

surprisingly strong, water-resistant adhesive joints. 

EXAMPLE 4 

'The addition 'of acid hydrolyzing salts of monobasic 

acids with 'pKs under 0 and metal ions of chromiumIII, 

aluminuniIlJ,. ironIlJ andzirconyl 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- on po yvmy a co 0 an ree aCI s as ar emng agents. 35' th· 'th dh' . t d d 'th f 

The water-resistance achieved is the more 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. ourst· n a cas

d es, 1'00 f gram eqUlva en soar emng agen were use per 

IOns. grams of dispersion. 

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 of requirement 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 

coolable jacket, 35.3 parts by weight of water, 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 

H20 2 (30%) were charged into the reactor and the reaction ~ixture was heated. At a temperature of the reaction mixture of 50° C., the dosing of a 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 of vinyl acetate. 
·9 

4,118,357 

10 

The dosing of the residual acetate monomer mixture 'Atest piece was exposed under constant 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 of 6S·,C .. to 70' C., the rate of flow of dispersions are stable up to a maximum temperature of 

the two supply feeds being so'regulated· that there was 5 120' C., while Dispersion No.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 1 hour at 70' C. and sion acted like a normal wood glue with a stability of 

then the mixture was cooled. A stable, coarsely-divided ' only up to 90' C. Only by the addition of the 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., of the practice of the, invention. It is to be understood, 

measuring cup D, stage III). 'however, that other expedients known to those skilled 

in the art or described herein, may.be employed without 

EXAMPLE B (Comparison Example, Pre-Crosslinked departing from the spirit ofthe invention or the scope of 

but not Grafted)' 15 the appended claims. 

'. We claim: 

1. An aqueous copolymer dispersion useful for adhe. 

sive~ of increased 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 of CrJJJ, AIJJJ, 

and FellI, and zirconyl salts of monobasic 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). 

The extent of grafting of the copolymer on polyvinyl' 

alcohol and of the pre-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 of copolymers 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 of under 0, and mixtures 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 of 

said polymer of a polyvinyl alcohol with a degree of 

hydrolysis of between 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 alkanoic acids having from 1 to 12 carbon 

atoms and 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 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 of from 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 chromiumJJJ 

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 

These results clearly show that, when pre-crosslinked 

graft copolymer dispersions on polyvinyl alcohol are 

used, the wet binding strength values are far superior to 60 

the conventional dispersions which contain polyvinyl 

alcohol in admixture, and even those dispersions where 

the polymer is pre-crosslinked but the polyvinyl alcohol 

is present in admixture with the polymer dispersion. 

wherein said polyvinyl alcohol is present in an amount 

of from 3% to 10%. 

3. The, aqueous copolymer dispersion of claim 1 

wherein said polyvinyl alcohol has a degree ofhydrolysis of from 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 of said polymer of vinyl acetate. 

5. The aqueous copolymer dispersion of claim 1 

wherein said graft component 2 is present in an amount 

of from 3% to 6% by weight of said 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% by weight of said aqueous copolymer dispersion 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 pKs of under 0 with heavy metals selected 

from the group consisting of CrJJJ, AIJJJ and FellI, and 
11 

4,118,357 

12 

zirconyl salts of monobasic acids having pKs of under 0, ence of from 0.1 % t6 3% by weight based on the total 

and mixtures thereof. monomer content of at least one organic peroxide form10. The method for the production of said aqueous ing highly reactive free-radicals on decomposition and 

copolymer dispersion of claim 1 which consists essen- from 0.05% t03% weight based on the total monomer 

tially of the steps of copolymerizing of monomer mix· 5 content of at least one peroxide reducing agent; 

ture of sufficient amount to give a final polymer of (1) at 12. The method of claim 11 wherein said organic 

least 70% by weight of said polymer of a vinyl ester peroxide is present in an amount offrom 0.5% 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 of at 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 of a cations selected from the group consisting of Cdv, 

polyvinyl alcohol with a degree of hydrolysis of be- Mnlll and Fdll. 

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 the presence 

said aqueous copolymer dispersion. of from 0.1 to 3 molar concentration of potassium per11. The method of claim 10 wherein said polyvinyl manganate. 

alcohol graft polymerization conditions are in the pres- •••••• 

25 

30 

35 

40 

50 

55 

60 

65 

<