CA1068029A

CA1068029A - Aqueous dispersions paints of unsaturated acetoacetate copolymers

Info

Publication number: CA1068029A
Application number: CA258,621A
Authority: CA
Inventors: Helmut Braun; Helmut Rinno; Werner Stelzel
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1975-08-08
Filing date: 1976-08-06
Publication date: 1979-12-11
Also published as: DK146477C; AR208810A1; AT357657B; BE845023A; CH621361A5; FI64183C; FI762246A; NO153892B; AU1664176A; FR2320339B1; NO762738L; GB1541909A; SE428215B; ES450387A1; NL187403B; LU75550A1; IT1065803B; DK356176A; IE43518L; JPS5222030A

Abstract

PAINTS ON THE BASIS OF AQUEOUS PLASTICS DISPERSIONS
Abstract of the disclosure:
Dispersion paints with high wet adhesion are obtained if, as the binder , an aqueous plastics dispersion is used, the poly-mers content of which contains as a comonomer an acetoacetic acid ester of an unsaturated alcohol, especially vinyl or allyl alcohol or a diester of a dihydroxy compound in which one acyl radical is acetoacetyl and the other acyl radical is acryl or methacryl. Especially the preparation of paints with a low pig-ment content is hereby enabled.

Description

10~80Z~
The problem of the wet adhesion, i~e. ~he adhesion of dried paints on wetting, of dispersion paints on smooth non-absorbent surfaces has lim-ited for a long time the use of such dispersion paints. Dispersion paints having a low pigment content, which dry on the substrate with formation of a glossy or slightly dull film, have a poor adhesion to smooth non-absorbent surfaces when the paints are rewetted after drying. The wet adhesion is es-pecially unsatisfactory with fresh paints which have not yet undergone ageing.
Dispersion paints of low pigment content are chosen when a washable coat of paint is desired. Owing to the high binder content of the paint a closed washable film is formed. Dispersion paints drying with formation of a glossy or slightly dull film also have a concentration by volume of pigment of less than 40 %, generally the concentration is in the range of from about 10 to 25 %. They also contain about 3 to 20 % of organic solvents to improve the gloss and flow, to prolong the working time and for film consolidation, for example polyhydric alcohols miscible with water and having up to 6 carbon atoms, especially ethylene and propylene glycol, or the monomethyl to mono-butyl ethers thereof. To improve the film consolidation solvents having a restricted solubility in water are used, such as the monoglycol ethers of carboxylic acids and more particularly esters of carboxylic acids with mono-alkyl ethers of glycols or oligoglycols. Butyl diglycol acetate is one of themost widely used representatives of this group. The combination of a low pigment content with a relatively high solvent content has a very detrimental effect on the wet adhesion of the coats of dispersions paints.
With a poor wet adhesion paints formulated to give washable coats do not have this property when applied to smooth non-absorbent surfaces, for ~-example old coats of alkyd or oil paint. In moist rooms, such as kitchen, -~

-2 ~0~80'~9 bath rooms, or industrial places, where water of condensation may form, the new coat may detach from the substrate if the wet adhesion is insufficient.
Moreover, a poor wet adhesion complicates painting. When, for example, the base and the upper half of a wall or the wall and the ceiling are to be painted in different colors, the first coat of paint may be soiled with the different paint by inaccurate handling of the brush. In principle, the different paint could be wiped off with a wet cloth or sponge, but with a poor wet adhesion - the first paint may then be damaged or even removed simultaneously.
Therefore, many attempts have been made to modify plastics disper-sions in such a manner that the dispersion paints made therewith have thedesired wet adhesion. Numerous monomers containing special functional groups (for example certain cycloureides, oxazolidines, azomethines or aziridines) have been proposed as comonomers for the emulsion polymerization in order to improve the wet adhesion of dispersion paints on non-absorbent substrates.
In order to improve the wet adhesion, it has also been proposed to incorporate amino groups into the polymer chains of emulsion polymers in such a manner that comonomers having special reactive groups, for example oxirane groups or groups having nucleophilically substitutable halogen atoms are additionally used in the emulsion polymerization and the amino groups are introduced into the polymer system only after complete polymerization by reaction with ammonia or amines.
Dispersion paints containing such amino group bearing polymers as binder, however, have often a tendency to yellowing. Moreover, the wet ad-hesion is only very slightly improved. Many of these paints, at low pigment content, yield coatings having a sufficient adhesion on smooth, non-absorbent :, ~.- ,. , . -10~:i80~9 substrates, but if organic solvents are added to these paints J the coatings obtained therefrom have no wet adhesion whatsoever.
In German Offenlegungsschrift No. 1,495,706, plastics dispersions are described the polymer portion of which contains monomers having keto groups,via which cross-linking with, for example, dicarboxylic acid-bis-hydrazides can be obtained. These dispersions are used for example in textile finishing for the manufacture of sizing agents resistant to dry-cleaning, or in the paint industry for the manufacture of solvent resistant paints.
It has now been found that solvent containing paints having a low pigment content and a high wet adhesion degree are obtained when plastics dis-persions are used as binder which are prepared by polymerization in an aqueous medium of olefinically unsaturated monomers, and the polymer portion of which contains a polymerizable acetoacetic acid ester as comonomer. ~ `
More particularly, the present invention provides a paint composi-tion having improved wet adhesion and consisting essentially of an aqueous dispersion of at least one polymer, from 3 to 20 % by weight of said compositionof a gloss-improving organic solvent and from 7 to 30 % by volume of a pig-ment, the said polymer being a polymer of at least one olefinically unsaturat-ed monomer and an ethylenically unsaturated acetoacetic acid ester copoly- -~
merizable therewith.
Acetoacetic acid esters contained as comonomers in the plastics dispersions to be used in accordance with this invention are for example ace-toacetic acid vinyl or alkyl esters or diesters of the formula R - CH = C - C - O - A - C - CH2 - - CH3 wherein R is H or CH3 and A is -~CH2)n-0- or -(CH2-CH2)m-0-; n being an integer of from 1 to 4 and _ an integer of from 1 to 3.

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101j80Z9 Acetoacetic acid alkyl esters are preferred. Relative to the total weight of all monomers, the amount of acetoacetic acid ester is from 0.5 to 10 % by weight, preferably from 1 to 5 % by weight.
Instead of one single dispersion, mixtures of different dispersions may be used; however, at least one of them must contain the polymerically bound acetoacetic acid ester in an amount which ensures that, relative to the /

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total weight of all monomers contained in the mixture, the acetoacetic acid ester is present in an amount as cited above.
By dispersion paints having a low pigment content in accordance with this invention there are to be understood dispersion paints the pigment volume concentration of which is from 7 to 30 %, preferably from 10 to 20 %.
Organic solvents in accordance with this invention are glycols and the derivatives thereof, for example ethyleneglycol, propyleneglycol, butylene-glycol, hexyleneglycol, oligoglycols such as di- or triglycol, glycol or oli-goglycol ethers such as methyl, ethyl, propyl or butyl mono-, di- or triglycol ether, mono-, di- or triglycol esters such as mono-, di- or triglycol acetate, propionate or butyrate, or (oligo) glycol semiethers/semiesters, for example methyl, ethyl, propyl or butyl mono-, di- or triglycol acetate, propionate or butyrate. Also mixtures of these substances can be organic solvents according to this invention. The organic solvents are added to the paint in an amount of from 3 to 20 %, by weight, preferably from 5 to 15 % by weight, relative to the total weight of the paint.
The aqueous plastics dispersions have a solids content of from 20 to 70 %, preferably from 40 to 60 %. For the rest, the aqueous plastics dis-persions are manufactured in usual manner according to processes known to those skilled in the art.
The selection of the other monomers is not critical. All monomers generally used for making plastics dispersions, which can be combined in accordance with the requirements of practice, are suitable, for example vinyl esters of organic carboxylic acids the acid moiety of which contains 1 to 30, preferably 1 to 20 carbon atoms, for example vinyl acetate, vinyl propionate, : ~:: : -,.- . : . . . ' . .-. . . - :
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10~80;~9 isononanoic acid vinyl ester and ~inyl ester of branched monocarboxylic acids having up to 20 carbon atoms; esters of acrylic acid or methacrylic acid having from 1 to 30 and preferably 1 to 20 carbon atoms in the alcohol moiety, for example ethyl acrylate, isopropyl acrylate, butyl acrylate, 2-ethylhexyl acrylate~ methylmethacrylate, butylmethacrylate; aromatic or aliphatic ~ unsaturated hydrocarbons such as ethylene, propylene, styrene, vinyltoluene; vinyl halides such as vinyl chloride; unsaturated nitriles such as acrylonitrile; diesters of maleic acid or fumaric acid, for example dibutyl maleate or dibutyl fumarate; ~-~ unsaturated carboxylic acids such as acrylic acid, methacrylic acid, or crotoniciacid and derivatives thereof, for example acrylamide or methacrylamide.
When selecting the appropriate monomers or monomer combinations the generally acknowledged conditions for the manufacture of dispersion paints have to be considered. In the first place, care should be taken that polymers are formed which yield a coherent film under the drying conditions of the coat of paint and the monomers for making copolymers should be selected in such a manner that, depending on the respective polymerization parameters, the formation of copolymers with the halogen compounds can be expected.
Some suitable monomers combinations are listed below:
ethyl acrylate/methylmethacrylate/(meth)acrylic acid/acetoacetic acid allyl ester, butyl acrylate/methylmethacrylate/(meth)acrylic acid/acetoacetic acid allyl ester ~, . .. . . . . . ..

~0~80Z9 - isobutyl acrylate/methylmethacrylate/(meth) acrylic acid/acetoacetic acid allyl ester, 2-ethylhexyl acrylate/methylmethacrylate/(meth) acrylic acid/acetoacetic acid allyl ester, ethyl acrylate/styrene/methylmethacrylate/(meth) acrylic acid/acetoacetic acid allyl ester, ` butyl acrylate/styrene/methylmethacrylate/(meth) acrylic acid/ acetoacetic acid allyl ester, 2-ethylhexyl acrylate/styrene/(meth) acrylic acid/acetoacetic acid allyl ester, vinyl acetate/butyl acrylate/acetoacetic acid allyl ester, vinyl acetate/dibutyl maleate/acetoacetic acid allyl ester, vinyl acetate/dibutyl fumarate/ acetoacetic acid allyl ester, `
vinyl acetate/isononanoic acid vinyl ester/acetoacetic acid allyl ester, vinyl acetate/2-ethylhexanoic acid vinyl ester/acetoacetic acid allyl ester, -vinyl acetate/vinyl ester of versatic acid with 10 carbon atoms/acetoacetic i`
acid allyl ester, vinyl acetate/ethylene/acetoacetic acid allyl ester, vinyl acetate/ethylene/vinyl chloride/acetoacetic acid allyl ester.
n astics dispersions are extremely complicated systems, and the manufacture dispersions according to the present invention requires the application of all experience existing in the Pield of emulsion polymeriza-tion, including that not particularly described in this specification.
Omi~sion of the rules known to those skilled in the art of emulsion poly-merization may adversely affect important properties, i.e. water resistance, of the dispersion films or paint fil~s. Therefore, the dispersions should : ~ .: :., . ,, :: . : : : . ,. : ~ - . :- .:: ., .
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not substantially exceed the usual amounts of up to 3 %, preferably up to 2 %, of ionic emulsifiers, or of up to 6 %, preferably up to 4 %, of non-ionic emulsifiers, relative to the polymer content.
Suitable non-ionic emulsifiers are, for example, alkyl polyglycol ethers such as the ethoxylation products of lauryl, oleyl or stearyl alcohol or of mixtures such as coconut fatty alcohol; alkyl-phenol polyglycol ethers such as the ethoxylation products of octyl- or nonyl-phenol, diisopropyl-phenol, triisopropyl-phenol or di- or tri-tert butyl-phenol; or ethoxylation ;
products of polypropylene oxide.
As ionic emulsifiers anionic emulsifiers are used in the first place, for example alkali metal or ammonium salts of alkyl, aryl or alkylaryl sulfonates, sulfates, phosphates, phosphonates, or compounds having different anionic end groups, oligo- or polyethylene oxide units possibly being contained between the hydrocarbon radical and the anionic group. ~ypical representa-tives are sodium lauryl sulfate, sodium octyl-phenol glycol ether sulfate, sodium dodecyl-benzene sulfate, sodium lauryl diglycol sulfate, ammonium tri-tert. butyl-phenol penta- or octa-glycol sulfate.
As protective colloids there may be used natural substances such as gum arabic, starch, alginates, or modified natural substances such as methyl, ethyl, hydroxyalkyl, or carboxymethyl cellulose, or synthetic sub-stances, for example polyvinyl alcàhol, polyvinyl pyrrolidone, or mixtures of the aforesaid substances. Modified cellulose derivatives and synthetic pro-tective colloids are preferred.
To initiate and continue polymerization, oil-soluble and/or preferably water-soluble radical forming agents or redox systems are used, for example hydrogen peroxide, potassium or ammonium peroxydisulfate, di-benzoyl peroxide, lauryl peroxide, tri-tert. butyl peroxide, bisazodiisobu-tyronitrile, either per se or together with reducing components, for example sodium bisulfite, Rongalite( ), glucose, ascorbic acid, and other compounds having a reducing action.
To prepare the dispersion paints having a high wet adhesion the dispersions are blended with a pigment suspension. Pigment suspensions or pigment pastes of this type, which are suitable for making dispersion paints of low pigment content and especially gloss paints consist, for example, of lo titanium dioxide uniformly dispersed in water. They contain, in general, protective colloids such as cellulose derivatives, for example hydroxyethyl ~ ~-cellulose, and dispersing agents, for example salts of poly(meth)acrylic acid or sodium polyphosphate. Usual constituents of pigment suspensions are furthermore antimicrobic preserving agents, anti-foaming agents, pH stabi-lizers and fillers. Especially suitable titanium dioxide pigments are the rutile and anatase modifications. For the manufacture of gloss paints the average particle diameter of the pigment should be near the lower limit of the light wave length, i.e. at about 0.4 to 0.2 micron. For making dull paints of low pigment content special large surface silicate pigments could be concomittantly used. Dull paints of high binder content yield paint coatings that are easy to clean. The pigment paste may, of course, also contain colored pigments or the desired shade is obtained by adding a shading dyestuff to the dispersion paint containing the white pigment.
me pigment suspension can be prepared in known manner, for example by dispersing the pigment in a dissolver, a ball mill, sand mill or roll mill.

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10~8~Z9 For use in gloss paints the pigment suspension should not contain noticeable amounts of pigment aggregates which would affect the gloss.
Auxiliaries such as plasticizers, cross-linking agents, buffer substances, thickening agents, thixotropic agents, rust preventing agents, alkyd resins, or drying oils may be added to the dispersion or the finished dispersion paint. Suitable plasticizers are not the solvents initially men-; tioned as film consolidation agents having a temporary action only but com-pounds which reduce the film-forming temperature and remain in the polymer for a longer period of time, for example dibutyl phthalate.
The following examples illustrate the invention, the parts being by weight unless otherwise stated.
E X A M P L E 1:
A dispersion liquor consisting of 603 parts water 18 parts polyvinyl alcohol having a degree of hydrolysis of 88 mol %, and a viscosity of 18 cP at 20 C in a 4 % aqueous solution thereof o.9 part sodium vinylsulfonate 6 parts sodium dodecylbenzene sulfonate 0.72 part NaH~P04 2 H20 p s 2 4 2 2 1.5 parts ammonium peroxidisulfate and parts vinyl acetate was heated while stirring in a 2 liter three-necked flask placed in a heating bath and equipped with stirrer~ reflux condenser, dropping funnel and ther-,~ .

1C)~8029 mometer, whereby the polymerization was initiated. When the temperature had reached 70 C, 540 parts vinyl acetate and 18 parts acetoacetic acid allyl ester are metered in within 3 hours. Immediately after termination of the monomer addition, heating of the polymerization mixture (70 C) was continued for 2 hours while stirring, and the batch was then slowly cooled.
E X A M P L E 2:
Operations were exactly as described in Example l; however, no ace-toacetic acid allyl ester was added.
E X A M P L E 3:
In an apparatus as described in Example 1 a dispersion liquor con-sisting of 607 parts water 18 parts oleyl polyglycol ether having about 25 ethylene oxide units 0.2 part sodium dodecylbenzene sulfonate ~-12 parts hydroxyethyl cellulose having an average degree of polymerization of about 400 (molecular weight about 100,000) 1.5 parts sodium acetate 2.5 parts ammonium peroxidisulfate and 60 parts of a monomer mixture taken from a mixture of 450 parts vinyl acetate 150 parts isononanoic acid vinyl ester and 12 parts acetoacetic acid allyl ester was heated to 70 C and the remaining monomer mixture (552 parts) was metered in within a period of 3 hours at thi- te;perature. When the addition was ~,.. .
, ., 1~i8029 terminated 0.5 part ammonium peroxidisulfate in 15 parts water were added and heating was continued for a further 2 hours. The dispersion had a solids content of about 50 %.
E X A M P L E 4:

_ .
Operations were exactly as described in Example 3; however, no ace-toacetic acid allyl ester was added.
E X A M P L E 5:

.
In an apparatus as described in Example 1 a dispersion liquor con-sisting of 618 parts water 18 parts nonylphenol polyglycol ether having about 30 ethylene glycol units 1.5 parts sodium acetate 12 parts hydroxyethyl cellulose having an average degree of poly-merization of about 400 and a molecular weight of about 100,000 2.5 parts ammonium peroxidisulfate 10 % (62 parts) of the monomer mixture consisting of 480 parts vinyl acetate 120 parts dibutylmaleate and 18 parts acetoacetic acid allyl ester were heated to 70 C and at said temperature there were added, within 3 hours, the remaining monomer mixture.
When the addition was terminated 0.5 part ammonium peroxidisulfate in 15 parts water was added and the dispersion was heated for a further 2 hours. The dispersion had a solids content of about 50 %.

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E X A M P L E 6:
Operations were exactly as described in Example 5; however, no acetoacetic acid allyl ester was added. - -E X A M P L E 7: -. :
In an apparatus as described in Example 1 a dispersion liquor consisting of 636 parts water 18 parts nonylphenol polyglycol ether having about 30 ethylene oxide units 12 parts polyvinyl alcohol having a degree of hydrolysis of 88 mol % and a viscosity of a 4 % aqueous solution of 18 cP
at 20C
0.9 part sodium vinyl sulfonate 1.5 parts sodium acetate 2.5 parts ammonium peroxidisulfate 48 parts vinyl acetate, 12 parts vinyl ester of a versatic acid with 10 carbon atoms, and 1.2 part acetoacetic acid allyl e~ter was heated to 70 C and at said temperature there was added within 3 hours a mixture of 432 parts vinyl acetate 108 parts versatic-10-C-acid vinyl ester and 18 parts acetoacetic acid allyl ester -When the addition was terminated, 0.5 part ammonium peroxidisulfate in ., parts water was added and the dispersion was heated for a further 2 hours. The dispersion had a solids content of approximately 50 %.
E X A M P L E 8:

_ _ _ . _ Operations were exactly as described in Example 7; however, no ace-toacetic acid allyl ester was added.

_ _ A monomer emulsion of 308 parts water 6 parts ammonium tri-tert. butylphenol polyglycol ether sulfate having approximately 8 ethylene oxide units 12 parts methacrylic acid 6 parts acrylic acid 300 parts 2-ethylhexyl acrylate7 300 parts methylmethacrylate and 12 parts acetoacetic acid allyl ester was first prepared by rapidly stirring until a stable emulsion was obtained.
In an apparatus as described in Example 1 a mixture of 306 parts water

3 parts ammonium tri-tert. butylphenol polyglycol ether as defined above and 60 parts of the aforesaid monomer emulsion were heated to 81C
and a solution of 0.45 part ammonium peroxidisulfate in 15 parts water was added.
Next, the remaining amount of the monomer emulsion was added in dosed quanti--14_ 1~68~Z9 ties, and the polymerization was continued until it was comp~ete. me total time of addition was 2 hours, the polymerization temperature and the tempera-ture of the after-heating period was in the range of from 81 to 83 C. When the monomer addition was terminated O.lS part ammonium peroxidisulfate in 5 parts water was added, the dispersion was heated for a further 60 minutes, and then it was cooled. The solids content was about 50 %.
E X A M P L E 10:
Operations were exactly the same as in Example 9; however, no acetoa-cetic acid allyl ester was added.
E X A M P L E 11:
A monomer emulsion having the following composition 310 parts water 6 parts of the sodium salt of lauryl alcohol diglycol ether sulfate 12 parts methacrylic acid 6 parts acrylic acid 300 parts butyl acrylate 300 parts styrene and 18 parts acetoacetic acid allyl ester was first prepared by rapidly stirring the components until the emulsion was stable.
In an apparatus as described in Example 1 a mixture of 303 parts water 3 parts of the sodium salt of lauryl alcohol diglycol ether sulfate and , -, : , : : - ~
-- ,, : :: ~ - ' . . ,~ . :
.' , ~ : ~ - ~ , ~068~Z9 62 parts of the above monomer emulsion was heated to 81 C and a solution of 0.45 part ammonium peroxidisulfate in parts water was added.
Thereafter, the remaining monomer emu~sion was added in dosed quantities, and the polymerization was continued until it was complete. The total period of dosed addition was 2 hours, the polymerization temperature and the after-heating temperature were in the range of from 81 to 83 C. When the monomer addition was terminated 0.15 part ammonium peroxidisulfate in 5 parts water were added, lo the dispersion was heated for a further 60 minutes, and cooled. The solids content was about 50 %.
E X A M P L E 12:
Operations were exactly the same as in Example 11; however, no ace-toacetic acid allyl ester was added.
To test the wet adhesion gloss paints were prepared according to the following formulations:
1. 41.0 parts water 15.6 parts of a 3 % aqueous solution of Tylose ( )H 20 0.4 part Calgon( ) N (solid) 3.0 parts dispess~agent PA 30 1.0 part ammonia of 25 % strength 2.0 parts of preserving agent 3.0 parts of anti-foaming agent 175 parts of titanium dioxide having a particle size of from 0.2 to 0.4 micron - .: .- ... . :, . .......... .
- ., , . ,: . . - . . . -~0f~8ClZ9 10.0 parts 1,2-propylene-glycol were dispersed and then 2. 710 parts of the respective dispersion (with a solids contents of 50 %) which had been admixed with 2.0 parts ammonia of 25 % strength if the pH did not exceed approximately 7 were added.
; Subsequently a mixture of 3. 10 parts butyl diglycol acetate and 27.0 parts 1,2-propylene-glycol was slowly added while stirring.
The liquid or soluble components indicated sub 1., with the exception of the 1,2-propyleneglycol, were introduced in the cited sequence into a vessel provided with stirrer, and the pigment was then dispersed in this mix-ture by means of a dissolver. Subsequently, 1,2-propyleneglycol was added.
In order to ensure identical conditions for mixing with the different dis-persions to be tested, for example in view of pigment dispersion, a large amount of this pigment paste was manufactured.
For the manufacture of the individual paints a corresponding propor-tion of the pigment pastes was mixed according to the process of the above formulation, while slowly stirring, with the dispersions approximately one day old, whereupon the solvents mentioned sub 3 were added. After complete confection, the paints were passed through a sieve.
These gloss paints were allowed to stand for one day and then spread on glass plates and steel sheets onto which a pigmented glossy air-drying alkyd resin enamel had been sprayed and which had been aged after drying for ~ . .. . . .. .. . . . .

24 hours at 100C. A film applicator was used having a slit diameter of 200microns. After a drying period of 24 hours the wet adhesion of the gloss paints was tested according to the two following methods:
-~ 1) Abrasion test:
The glass plates with the dried coating of dispersion paint were in-serted in a mechanical abrasion device as described, for example, in German Dffenlegungsschrift 2,262,956 and similar to the Gardner Washability and Abrasion Machine, but having a moving length of approximately 1.20 m in a manner such that the applied films of dispersion paint were in a vertical position with respect to the moving direction of the brush. Due to the long moving distance about 15 paints could be simultaneously tested in one run.
A brush with hog's bristles was used which, at the beginning of the test, had been wetted with distilled water. During the test the area on which the brush moved was also wetted with distilled water so that the brushed areas were permanently covered with a water film. With a poor wet adhesion the dispersion paint was brushed off the substrate after a few movements of the brush and torn at the boundary between wetted and dry film. The wet adhesion is thé
better the higher the number of movements of the brush until the film is shifted aside. The dispersion paint has an optimum wet adhesion when in the wetted area the film is not damaged after 3,000 passages of the brush, one passage including a backward and forward stroke.
2) Condensation test:
A rectangular thermostat was used one half of which was filled with water of 50 C and in the gas space of which above the water level a fan was mounted. The upper opening was covered with the steel sheets with the coated _18-. ,:. ~ :~ . : : : :.

surface in do~nward position so that the thermostat was closed. The therm-ostat was kept in a room maintained at 23 C. Owing to the temperature dif-ference steam condensed on the lower surface of the sheets and acted on the coats of paint. After 15 minutes of action the sheets were removed and the coatings evaluated.
With an unsatisfactory wet adhesion blisters form between the film of dispersion paint and the alkyd resin lacquer and the film can be easily shifted aside, for example, with the finger-tip. A film having a good wet adhesion is still free of blisters after a period of 4 hours and cannot be lo shifted. The test results are listed in the following Table 1.

ExampleAbrasion test Number Stability in con-o.of double strokes of densation test brush .
1 > 3000 4 hrs.
~ 30 10 min.
3 > 3000 4 hrs.

4* 250 10 min.
> 3000 4 hrs.
6* 120 15 min.
7 > 3000 4 hrs.
~ 50 15 min.
9 > 3000 4 hrs.
10* 70 15 min.
11 > 3000 4 hrs.
12* 110 15 min.
* Comparative Examples not in accordance with this invention.

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Claims

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

1. A paint composition having improved wet adhension and consisting essentially of an aqueous dispersion of at least one polymer, from 3 to 20 % by weight of said composition of a gloss-improving organic solvent and from 7 to 30 % by volume of a pigment, the said polymer being a polymer of at least one olefinically unsaturated monomer and an ethylenically unsaturated acetoacetic acid ester copolymerizable therewith.

2. The paint composition of claim 1 wherein the acetoacetic acid ester is acetoacetic acid vinyl ester, acetoacetic acid allyl ester or a diester of the formula R-CH=?-?-O-A-?-CH2-?-CH3 wherein R is H or CH3 and A is -(CH2-O)n or -(CH2-CH2-O)m-, n being an integer of from 1 to 4 and m an integer of from 1 to 3.

3. The paint composition of claim 1 wherein the proportion of the acetoacetic acid ester units in the polymer is from 0.5 to 10% by weight.

4. The paint composition of claim 3 wherein the proportion of the acetoacetic acid ester units in the polymer is from 1 to 5 % by weight.

5. The paint composition of claim 1 wherein the dispersion contains a mixture of polymers.

6. The paint composition of claim 1 wherein the olefinically unsaturated monomer is (a) a vinyl ester of an organic carboxylic acid the acid moiety of which contains from 1 to 30 carbon atoms, (b) an ester of acrylic acid or methacrylic acid having from 1 to 30 carbon atoms in the alcohol moiety, (c) an aromatic or aliphatic .alpha.,.beta.-unsaturated hydrocarbon, (d) a vinyl halide, (e) an unstaurated nitrile, (f) a diester of maleic acid or fumaric acid, or (g) an .alpha.,.beta.-unsaturated carboxylic acid or a derivative thereof.

7. The paint composition of claim 1 wherein the organic solvent is a glycol or a derivative thereof.

8. The paint composition of claim 1 wherein the amount of organic solvent is from 5 to 15 % by weight.

9. The paint composition of claim 1 wherein the amount of pigment is from 10 to 20 % by volume.

10. The paint composition of claim 1 wherein the solids content of the dispersion is from 20 to 70 % by weight.

11. The paint composition of claim 10 wherein the solids content is from 40 to 60 % by weight.

12. The paint composition of claim 1 wherein the dispersion contains up to 3 % by weight of an ionic emulsifier, calculated on the polymer content.

13. The paint composition of claim 1 wherein the dispersion contains up to 6 % by weight of a non-ionic emulsifier, calculated on the polymer content.