CA1068429A - Process for unsaturated acetoacetate copolymers in aqueous dispersion - Google Patents

Abstract

PROCESS FOR THE MANUFACTURE OF PLASTICS DISPERSIONS
Abstract of the disclosure:
Process for the preparation of aqueous plastics dispersions suitable for making paints having a high wet adhesion by copoly-merization of a) 20 to 80 % by weight of methylmethacrylate, styrene and/or vinyl toluene, b) 20 to 80 % by weight of acrylic acid ester carrying in the alcohol radical a linear or branched alkyl radical having from 2 to 8 carbon atoms, optionally substituted by halogen, c) 0.1 to 5 % by weight of acrylic acid, methacrylic acid,acryl-amide and methacrylamide, and d) 0.5 to 10 % by weight of an acetoacetic acid ester of the formula wherein X is -O-, -O-CH2- or

Description

HOE_75 ! ~ ~ K

10~8~'~9 This invention relates to a process for the manufacture Gf plastics dispersions suitable for making dispersion paints having a good wet adhesion, i.e. when wetted after drying.
The problem of the wet adhesion, i.e. the adhesion of dried paints on wetting, of dispersion paints on smooth non-absorbent surfaces has limited 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 espe-cially unsatisfactory with fresh paints which have not yet under-qone 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. Disper--sion paints drying with formation of a glossy or slightly dull film also have a concentration by volume of pigment of less than ~0 ~, generally the concentration is in the range of from about 10 to 25 %. They also c~ntain about 3 to 15 % of organic sol-20 ~ vents to improve the gloss and flow, to prolong the working time and for film consolidation, for example polyhydric alcohols mis-cible with water and having up to 6 carbon atoms, especially ethylene and propylene glycol, or the monomethyl to monobutyl ethers thexeof. To improve the film consolidation solvents having a restricted solublility in water are used, such as the monoglycol esters of carboxylic acids and more particularly esters of carboxylic acids with monoalkyl ethers of glycols or oligoglycols. Butyl diglycol acetate is one of the most widely 29 used representatives of this group. The combination of a low

- 2 -~0~84'~9 pigment content with a relatively high solvent content has a very detrimental effect on the wet adhesion of the coats of dis-persions paints.
With a poor wet adhesion paints formulated to give washable coats do not havo 'his prop~rti whcn applicd to smooth non ab-sorbent surfaces, for example old coats of alkyd or oil paint. In moist rooms, such as kitchen, bath rooms, or industrial places, where water of condensation may form, the new coat may detach from the substrate if the wet adhesion is not sufficient. More-` 10 ~ver, a poor wet adhesion complicates painting. When, for ex-ample, 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 slipping of the brush. In principle, the different paint could be wiped off with a wet cloth, but with a poor wet adhesion the first paint may then be damaged or even removed simultaneously.
Therefore, many att~mpts have been made to modify plastics dispersion in such a manner that the dispersion paints made there-with have the desired wet adhesion. In German Offenlegungsschrift 20 ~ 1,595,501 it has been proposed to prepare plastics dispersions by polymerizing suitable monomers in aqueous emulsion using as comonomers 0.2 to 15 % by weight, calculated on the total amount of the monomers, of compounds carrying oxirane groups and then to react the copolymer at room temperature with ammonia or an amine. Suitable oxirane compounds are above all, glycidyl esters of acrylic or methacrylic acid and allyl glycidyl ethers or vinyl glycidyl ehters.
Dispersion paints prepared with plastics dispersions of this 29 type have quite a good wet adhesion, but for many applications 10~8~29 the wet adhesion is not all sufficient.
Accordingly, the present invention provides a process for the preparation of aqueous plastics dispersion suitable for making paints having a high wet adhesion, by copolymerization in an aqueous medium of the following monomers: A) from 20 to 80 % by weight, calculated on the total quantity of the monomers, of the hardening monomers methyl methacrylate, styrene and vinyl toluene or a mi~ture thereof, B) from 20 to 80 % by weight, calculated on the total quantity of the monomers, of plasticizing monomers selected from the group of acrylic acid esters carrying in the alcohol radical a linear or branched alkyl radical having from 2 to 8 carbon atoms or conjugated dienes having from 4 to 8 carbon atoms, C) from 0.1 to 5 % by weight of acrylic acid, methacrylic acid, acrylamide or methacrylamide, which comprises using additionally in the polymerization D) from 0.5 to 10 % by weight of an acetoacetic acid ester of the formula 1l 1l ~ ~
CH3 C - CH2 - C - X - C = C - H 0 wherein R is H or CH3, R' is H or CH3, and X is -0-,-OCH2 or -0-CH2-CH2-0-C-.
Preferably component A) is used in an amount from 40 to 60 % by weight. Preferably component B) is used in an amount of from 40 to 60 % by wei~ht. Preferably component C) is used in an amount of from 1 to 3 % by weight. Preferably component D) is used in an amount of from 1 to 5 % by weight.
Plasticizing monomers of the kind sub B) are for example ethyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate or butadiene or isoprene.
Suitable monomers of the kind cited sub D) are, for example acetoacetic acid vinyl ester, acetoacetic acid allyl ester or acetoacetic acid esters of ~-hydroxyethyl acrylate or methacrylate or hydroxypropylacrylate or methacrylate. Acetoacetic acid allyl ester is used preferably, as it yields the best results.
For dispersions prepared in an acid range it is often advantageous for improving their storage life and for facilitating the preparation of paints to adjust the pH to a value in the range of from 7.5 to 10 with ammonia or suitable amines for example water-soluble tertiary amines.
Plastics dispersions are extremely complex systems. The preparation of the dispersions according to the invention of high quality requires the application of the experiences made hitherto in the field of the emulsion polymerization, including those which are not described herein in detail. A
disregard of the principles known to an expert in the field of emulsion polymerization may therefore detrimentally affect important properties such as the resistance to water, of the dispersion films or the films of the coats of paint. For this reason the conventional content of ionic emulsifiers of up to 3 %, preferably of up to 2 % in the dispersions or of non-ionic emulsifiers of up to 6 %, -. _ 5 _ J .

HO~ 75~F 204 K

preferably oE up to 4 % should not be exceeded substantially.
Suitable non-ionic emulsifiers are, for example, alkyl polyglycol ether 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, triiso-propyl-phenol or di- or tri-tert.butyl-phenol or ethoxylation products of polypr~pylene 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 poly-ethylene oxide units possibly being contained between the hydro-carbon radical and the anionic group. Typical representatives are sodium lauryl sulfate, sodium octyl-phenol glycol ether sul-fate, sodium dodecyl-benzene sulfonate, sodium lauryl diglycol sulfate, ammonium tri-tert.butyl-phenol penta- or octa-glycol sulfate.
As protective colloids there may be used natural substances 20 - such as gum arabic, starch, alginates or modified natural sub-stances such as methyl, ethyl, hydroxyalkyl, or carboxymethyl cellulose, or synthetic substances, for example polyvinyl alco-hol, polyvinyl pyrrolidone, or mixtures of the aforesaid sub-stances. ~lodified cellulose derivatives and synthetic colloids are preferred.
These protective colloids can only be employed to a limited degree if the described monomer systems are used, as it is known to one skilled in the art. The quantities used are frequently 29 low, namely in the range from 0.001 to 1 % and the tolerance and HOE 75/F _04 K
- 10~;84;~9 the kind of addition must be examined in each case. When the use of protective colloids is requiîed, the principles, for ex-ample disclosed in German Auslegeschrift No. 1,570,312 may be applied.
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, dibenzoyl peroxide, lauryl peroxide, tri-tert.
butyl peroxide, bisazodiisobutyronitrile, either singly or to-gether with reducing com~onents, for example sodium bisulfite, Rongalite(~), glucose, ascorbic acid, and other compounds having a reducing action.
The special advantage of the dispersions prepared according to the invention resides in the fact that they are not only sui-table for the manufacture of gloss dispersion paints having a good wet adhesion on non-absorbent surfaces, but that they have moreover a high resistance to saponification.
The following examples illustrate the invcntion:
E X A M P L E
20 - Firstly a monomer emulsion was prepared having the following composition:
310 parts by weight water 6 parts by weight sodium salt of lauryl alcohol diglycol ether sulfate 12 parts by weight methacrylic acid 6 parts by weight acrylic acid 300 parts by weight butyl acrylate 300 parts by weight styrene and 29 12 parts by weight acetoacetic acid ally ester.

~n~75/F ?04 K
10~84~9 The components were stirred in a rapid s,irrcr until a stable emulsion was obtained.
A mixture consisting of 303 parts by weight water

3 parts by weight sodium salt of lauryl alcohol diglycol ether sulfate and 60 parts b~ weight of the monomer emulsion was heated in a 2 liter three-necked flask placed in a heating bath and equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer and a solution of 0.45 parts by weight ammonium peroxydisulfate in 15 parts by weight water was aclded .
Thereafter the resldual monomer emulsion was added and polymeri-zation was carried to completion. The total time of addition was 2 hours, the polym~rization temperature and the temperature during the second heating period were in the range from 81 to ~3 C. When the monomer addition was finished 0.15 parts by weight ammonium peroxydisulfate in 5 parts by weight water were added, heating was continued for 60 minutes and the reaction mixture was cooled.
20- The pH was adjusted to 9.5 by means of 15 ml of 25 % NH3;
the solids content was a~out 50 %.

The example was Performed as in Example 1, except aceto-acetic acid allyl ester was omitted in the polymerization.
E X A M P L E 3:
A monomer emulsion was prepared from 310 parts by weight water 9 parts by weight ammonium-tri-tertiary but~l phenol polyglycol 29 ether sulfate having about 8 ethylene oxide HOE _/F_204 K
106t34~9 units 12 parts by weight methacrylic acid 6 parts by weight acrylic acid 300 parts by weight 2-ethylhe~yl acrylate 300 parts by weight methyl methacrylate and 18 parts by weight acetoacetic acid allyl ester, by stirring in a rapid stirrer, until a stable emulsion was obtained.
In an apparatus as described in Example 1 a mixture consist-ing of 306 parts by weight water 3 parts by weight ammonium-tri-tertiary butyl phenol polygly--- col ether sulfate having about 8 ethylene oxide units and 60 parts by weight monomer emulsion was heated to 81 C and a solution of 0.45 parts by weight ammo-nium peroxydisulfate in 15 parts by weight water was added. The residual monomer emulsion was metered in and polymerization was carried to completion. The total time of addition was 2 hours, the polymerization temperature and the temperatur during the second heating period were in the range from 81 to 83 C. When the addition of monomers was terminated, 0.15 parts by weight ammonium peroxydisulfate in 5 parts by weight water was added, heating was continued for 1 hour and the reaction mixture was cooled. The pH was adjusted to 9.3 by means of 15 ml of 25 %
N~I3. The solids content was about 50 ~.
E X A M P L E 4:
The example was carried out in an analogous manner as EY.-29 -ample 3, e~cept thataCetoacetic acid allyl ester was omitted in the _ g _ HOE 75~F_~4 K
10~84;~9 polymerization.
E X A P L E 5: ¦
A monomer emulsion was prepared from 380 parts by weight water 6 parts by weight ammonium-tri-tertiary butyl phenol polygly~ol ether sulfate having about 8 ethylene oxide units 12 parts by weight methacrylic acid 6 parts by weight acrylic acid l2 parts by weight acrylamide 4S0 parts by weight ethyl acrylate 150 parts by weight vinyl toluene 18 parts by weight acetoacetic acid allyl ester by stirring in a rapid stirrer, until a stable emulsion was ob-tained.
In an apparatus as described in Example 1 a mixture consist-ing of 390 parts by weight water 3 parts by weight ammonium-tri-tertiary butyl phenol polyglycol 2a ether sulfate having about 8 ethylene oxide units 3 parts by weight nonyl phenol polyglycol ether having about 30 ethylene oxide units and 60 parts by weight monomer emulsion was heated to 81 C and a solution of 0.45 parts by weight ammonium peroxydisulfate in 15 parts by weight water was added.
The residual monomer emulsion was then metered in and Foly-merization was carried to completion. The total time of addi-29 tion was 2 hours, the polymerization temperature and the tem-HO~ 75/F 204 X
iO~8`4'~9 perature during the second heating period wer~ in ~he range fro~
81 to 83 C. When the addition of monomers was terminated 0.15 parts by weight of ammonium peroxydisu'fate in S parts by weight of water was added, heating was continued for 60 minutes and the reaction mixture was cooled. The pH was adjusted to 9.5 by means of 15 ml of NH3 /25 %). The solids content was ~out 45 ~.
E X A M P L E 6:
The procedure was the same as in Example 5, except that aceto-acetic acid allyl ester was omitted in the polymerization.
E X A M P L E 7:
In a 16 liter autoclave provided with an impeller stirrer there was introduced a liquor consisting of 3090 g of demineralized watex 80.5 g of sodium dodecylbenzene sulfonate 15 g of potassium persulfate and 3 g of NaOH (solid).
The liquor and the whole apparatus were flushed with nitro-gen. The other operations were also performed in a protective gas atmosphere.
From a recipient a mixture consisting of 1200 g of butadiene 1560 g of styrene 90 g of acetoacetic acid allyl ester was introduced by pumping into tne autoclave.
The stirrer was set in motion (about 300 r.p.m.) and heat ing was started. The mi:~ture was polymerized for 2 and a ha]f hours at 70 C (the inner pressure was about 10 bars) and a solution consisting of ~ 1 _ 10~84'~9 40 g of sodium dodecylbenzene sulfonate in 750 g of demineralized water was added by pumping.
After another 2 hours of polymerization at 70 C a solution of 15 g of potassium persulfate in 250 ~ of deminerali~ed water was added and a mixture consisting of 180 g of styrene and 60 g of acrylic acid was metered in the course of about 15 minu-tes.
The ater-reaction time was 3 hours (also at 70). There~
after the vessel was cooled, ventilated and the product was fil-tered.
The solids content was about 42 ~. The quantity of coagulate was low.
E X_A M P L E 8-The procedure was the same as in Example 7, except that the ~uantity of styrene (1740 g) was replaced by vinyl toluene.
E X A M P L E 9:
The procedure was the same as in Example 7, except that half of the quantity of styrene (780 g in the recipient and 90 g in the second addition) was replaced by vinyl toluene.
COMPARATIVE EXAMPLE 10: (not in accordance with the present invention) As described in Example 7 a disp2rsion was prepared~but the acetoacetic acid allyl was omitted and the amount of water was reduced by 90 g to 3000 g.
To prepare the dispersion paints according to the invention having a high wet adhesion the dispersions obtained according 29 to the preceding examples were blended with a pigment suspension.

_OE 75/~ 20~i K
~(~68429 Pigment suspensions Qr pigment pastes of this type, which are suitable for making dispersion paints of low pigment content and especially gloss paints consist, for example, of titanium dioxide uniformly dispersed in water. They contain, in general, protective colloids such as cellulose derivatives, for example hydroxyethyl cellulose, and dispers~ng agents, for example salts for poly(meth)acrylic a~id or sodium polyphosphate. Usual c~n-stituents of pigment suspensions are furthermore antimicrobic preserving agents, anti-foaming agents, pH stablilizers and fil-lers. Especially suitable titanium dioxide pigments are therutile and anatase modifications. For the manufacture of glo~s paints the average particle diameter of the pigment should be near the lower limit of the light wave length, i.e. at about 0.
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 easily to clean. The pi~ment paste may, of course, al-so contain colored pigments or tne desired shade is obtained by adding a shading dyestuff to the dispersion paint containing the white pigment.
The pigment suspension can be prepared in known rnanner, for e~ample by dispersing the pigment in a dissolver, a ball mill or sand mill. For use in gloss paints the pigrnent 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 29 the dispersion or the dispersion paint. Suitable plasticizers - ~3 -HOF. 7~ 204 ~

1(~684Z9 are not the solvents initially mentioned as film consolidation agents with temporary action but compounds which reduce the film forming temperature and remain in the polymer for a longer period of time, for example dibutyl phthalate.
S To test the wet adhesion dispe-~sion paints were prepared as follows:
Recipe I:
1. 41.0 parts by weight water 15.6 parts by weight of a 3 % aqueous solution of Tylose(R) 0.4 part by weight Calgon(R~N (solid) 3.0 parts by weight dispersing agent PA 30 1.0 part by weight ammonia of 25 % strength 2.0 parts by weight of preserving agent 3.0 parts by weight of anti-foaming agent 175 parts of titanium dioxide having a particle size of from 0.2 to 0.4 micron 10 parts 1,2-propylene glycol were dispersed and 2. 710.0 parts by weight of dispersion of Examples 1 - 6 having a solids con-tent of ab~ut 50 % and 843 parts by weight of dispersion of EXamples 7 to 10 having a solids content of 42 % was used, whereto 2.0 parts by weignt of ammonia of 25 ~ were added~if the pH was not superior to ab~ut 7.
3. A mixture of 10 parts by weight butyl diglycol acetate, 27.0 parts by weight 1,2-propylene glycol was slowly added while stirring.
The liquid or soluble components indicated sub 1 except 1,2-propylene glycol were introduced into a vessel provided 29 with a stirrer in the aforesaid order and the pigment was dis-1~68429 solved therein by means of a dissolver. 1,2-Propylene glycol was added thereafter. This pigment paste was prepared in a large amount so that for the blends with the dispersions to be tested equal conditions, for example as regards the pigment dispersion, were ensured.
Recipe II:
Recipe II differed from recipe I by a different composition of the mixture o solvent added to the finished paint (processing step 3 of the preparation of paint). A mixture of 36 parts by weight of 1,2-propylene glycol, 13.5 parts by weight of butyl diglycol acetate and 20 parts by weight 2,2,4-trimethylpentanediol-1,3-monoisobutyrate-1 (Texanol*) was added.
Recipe III:
Recipe III also differed from the aforesaid recipes by a different composition of the mixture of solvent added to the finished paint, i.e. a mixture of 51.1 parts by weight of 1,2-propylene glycol, 18.9 parts by weight of butyl diglycol acetate and 20 parts by weight of 2,2,4-trimethyl-pentanediol-1,3-monoisobutyrate (Texanol*) was added.
For the~manufacture of the individual paints a corresponding proportion of the pigment paste was mixed, while slowly stirring, with the dispersions approximately one day old, whereupon the solvents mention sub 3) were added.
After complete confection, the paints were passed through a sieve.
The paints were allowed to stand for one day and then spread on glass plates and steel sheets onto which a pigmented glossy air-drying alkyld resin enamel had been sprayed and which had been kept after drying for 24 hours at loo&. A film applicator was used having a slit diameter of 200 microns.

*Trade Mark HOE _5l~ 2~4 K

After a drying period ~f 2~ 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 inserted in a mechanical abrasion device as described, for example, in German Offenlegungsschrift 2,262,956 and similar to the Gardner Washability and Abrasion Machine,`but habing a movin~
length of approximately 1.20 m in a manner such that the applied ilms of dispersion paint were in a vertical position with re-spect to the moving direction of the brush. Due to the long moving distance about 15 paints could ~e simultaneousl~ 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 bru~hed areas were permanently covered with a water film. With a poor wet adhesion the dis-persion paint was brushed off the substrate after a few move-ments of the brush and torn at the boundary between wetted and dry film. The wet adhesion is the better the higher the number 20 - 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 5,000 passages of the brush one passage including a backward and forward stroke.
2) Condensation test A rectangular therm~stat 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 cov-ered with the steel sheets with the coated surface in downward 29 position so that the thermostat was closed. The thermostat was kept in a room maintained at 23 C. Owin~ to the temperature difference steaM condensed of the lower surface of the sheets and acted on the coats o~ paint. After 15 minutes of action the sheets were removed and the coatin~s evaluated.
With an ~1n~atisfactory wet adhesion blisters formed between the film of dispersion paint and the alkyd resin lacquer and the ~ilm could be easily shifted aside. A film having a good wet adhesion was still free of blisters after a period of 6 hours and could not be shifted.
The. test results are listed in the Table.

T A B L E
Summary of the test results:

Example Recipe abrasion test, number stability in con-No. No.of double strokes of densation test brush 1 I> 5000 > 6 hrs.
2* I 110 <15 min.
3 I~ 5000 ~ 6 hrs.
~I> 5000 > 6 hrs.
III> 5000 ~ 6 hrs.

4* I 70 ~15 min.
I~ 5000 > 6 hrs.
6* I 50 ~15 min.
7 I~ 3000 > 4 hrs.
, 8 I~ 3000 > 4 hrs.
9 I> 3000 > 4 hrs.
I 170 < 15 min.
* Comparative Examples (not in accordance with the present invention).

Claims (8)

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

1. A process for the preparation of aqueous plastics dispersions suitable for making paints having a high wet adhesion, by copolymerization in an aqueous medium of the following monomers:
A) from 20 to 80 % by weight, calculated on the total quantity of the monomers, of the hardening monomers methyl methacrylate, styrene and vinyl toluene or a mixture thereof, B) from 20 to 80 % by weight, calculated on the total quantity of the monomers of plasticizing monomers selected from the group of acrylic acid esters carrying in the alcohol radical a linear or branched alkyl radical having from 2 to 8 carbon atoms or conjugated dienes having from 4 to 8 carbon atoms, C) from 0.1 to 5 % by weight of acrylic acid, methacrylic acid, acrylamide or methacrylamide, which comprises using additionally in the polymerization D) from 0.5 to 10 % by weight of an acetoacetic acid ester of the formula , wherein R is H or CH3, R' is H or CH3, and X is -O-,-OCH2 or .

2. Process as claimed in claim 1, which comprises as (D) from 1 to 5 %
by weight of said acetoacetic acid ester.

3. Process as claimed in claim 1, wherein the acetoacetic acid ester is acetoacetic acid allyl ester.

4. Process as claimed in claim 1, 2 or 3 which comprises as (A) 40 to 60 % by weight of said hardening monomers.

5. Process as claimed in claim 1, 2 or 3, which comprises as (B) 40 to 60 % by weight of said plasticizing monomers.

6. Process as claimed in claim 1, 2 or 3 which comprises as (A) 40 to 60 % by weight of said hardening monomers and as (B) 40 to 60 %
by weight of said plasticizing monomers.

7. Process as claimed in claim 2 wherein the acetoacetic acid ester is acetoacetic acid allyl ester.

8. Process as claimed in claim 7 which comprises as (A) 40 to 60 %
by weight of said hardening monomers and as (B) 40 to 60 % by weight of said plasticizing monomers.