NO762738L - - Google Patents

Description

Paint based on aqueous plastic dispersions.

The problem of wet adhesion of dispersion colors or paints on smooth, non-absorbent surfaces has for a long time limited the use of certain dispersion paints. Low-pigmented dispersion paints, and among these again especially those that dry to glossy or silky-matte films, adhere poorly to smooth, non-absorbent surfaces when the coats are moistened again after drying. Wet adhesion is particularly bad for fresh coats, which have not yet aged.

Low-pigment dispersion paints are chosen when the coat must be washable. The high binder content in these paints creates a closed, washable film. Likewise, glossy or silky-matte dispersion paints have a pigment volume concentration of less than 40%, and usually approx. 10 - 25%. In addition, they contain organic solvents in larger quantities, approx. between 3 and 20%. Gloss, course and open time are affected, for example. using polyvalent, with water

in,

miscible alcohols with up to 6 C atoms, especially ethylene

and propylene glycol, or their monomethyl, monoethyl or monobutyl ethers. To improve the film consolidation, limited water-soluble solvents are used, such as monoglycol ethers of carboxylic acid, and especially esters of carboxylic acids with monoalkyl ethers and glycols or oligoglycols. Butyl diglycol acetate is one of the most widespread representatives of this group. The combination of low pigmentation and high solvent content has a particularly negative effect on the wet adhesion of dispersion paint coats.

A lack of wet adhesion means that, in and of themselves, as washable concentrated coats, they no longer have this property when they were applied to smooth, non-absorbent surfaces, e.g.

on old alkyd resin or oil paint coats. In damp rooms, such as kitchens or bathrooms, and many industrial rooms where condensation must be expected, new coats can detach from the substrate when sufficient wet bonding has not been provided. Finally, lack of wet bonding makes the painting work difficult. If, for example, the plinth and upper half of the wall or the wall and ceiling are painted in different colours, it may happen that the first coat is soiled in a different color due to inaccurate brush application. In principle, this contamination can be removed with a damp cloth or sponge. In the event of a lack of wet bonding, however, the first coat is easily damaged or completely pushed off.

For these reasons, there has been no shortage of attempts to modify dispersions so that the dispersion paints thus produced show the desired wet adhesion. Numerous monomers containing special functional groups (e.g. certain cyclorides, oxazolidines, azomethines or aziridines) have been proposed as comonomers in emulsion polymerization to improve wet adhesion of dispersion paints on non-absorbent substrates. It has also been proposed to improve the wet adhesion to incorporate amino groups in the poly chain of the emulsion polymers by co-using comonomers with special reactive groups, e.g. oxirane groups or groups with nucleophilically substitutable halogen atoms during the polymerization and only after the polymerization has been carried out introduce the amino groups by reaction with ammonia or amines in the polymer compound.

However, dispersion paints that contain such ammonium group-containing polymers as a binder often tend to yellow. Furthermore, the wet bonding is often only slightly improved. Admittedly, many of these colors give coats with low pigmentation that adhere sufficiently to smooth, non-absorbent surfaces. However, if organic solvents are added to these paints, paints produced from them have almost no wet adhesion anymore.

From DOS 1,495,706, plastic dispersions are known, the polymerized part of which contains monomers containing cathogroups, over which it is possible to form a network with e.g. dicarboxylic acid bis-hydrazides. These dispersions are used e.g. in textile processing for the production of cleaning-resistant adhesives or in painting technology for the production of solvent-resistant paints.

It has now been found that low-pigmented solvent-containing paints with high wet adhesion are obtained when plastic dispersions are used as a binder, which have been produced by polymerization of olefinically unsaturated monomers in an aqueous medium, and which contain a polymerizable acetate diester in the polymer part as comonomer. The acetic acid ester which is contained as comonomers in the plastic dispersions to be used according to the invention is e.g. acetoacetic acid vinyl or alkyl ester or diester of the general formula

in which R means H or CH^ and A means -(CH2)n-0- or -(Ch2~CK2)m_0, where n means an integer between 1 and 4 and m an integer between 1 and 3• Acetoacetic acid alkyl esters are thereby preferred . With reference to the total weight, all monomers amount to 0.5-10% by weight, preferably 1-5% by weight, of acetate diesters.

Instead of a single dispersion, mixtures of different dispersions can be used, with at least one containing the polymer-bound acetic acid ester, namely in such an amount that, referred to the total weight of all the monomers contained in the mixture, the acetic acid ester is present in the amounts specified above.

Low-pigmented dispersion paints within the scope of the invention are dispersion paints whose pigment volume concentration lies between 7 and 30%, preferably between 10 and 20%.

Organic solvents within the scope of the invention are glycols and their derivatives, such as e.g. ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, oligoglycols, such as di- or triglycol, glycol-, resp. oligoglycol ethers, such as methyl-, ethyl-, propyl- or butyl- mono, -di- or

-triglycol ethers, mono-, di- or triglycol esters, such as mono-, di- or triglycol acetate, -propionate or -butyrate as well as (oligo-) glycol half ether half esters, such as e.g. methyl-, ethyl-, propyl- or butyl-mono-,. ,-di- or triglycol acetate, -propionate or -butyrate. Mixtures of such substances must also be

organic solvents within the scope of the invention. The organic solvents are added to the paint at 3-20% by weight, preferably 5-15% by weight, referred to the total weight of the paint.

The usual plastic dispersions have a dye content between 20 and 70%, preferably between 40 and 60%. Above all, the aqueous synthetic substance dispersions are produced in the usual way according to methods known to those skilled in the art.

The choice of the other monomers is not decisive.

This includes all monomers usually used in plastic dispersions which can combine the requirements in practice in an appropriate way. Suitable is e.g. vinyl ester of organic carboxylic acids whose carbon structure contains 1-30, preferably 1-20 carbon atoms, such as vinyl acetate, vinyl propionate, isononanoic acid vinyl ester and vinyl ester of branched mono-carboxylic acids with up to 20 carbon atoms, esters of acrylic acid or methacrylic acid with 1-30, preferably 1- 20 carbon atoms in the alcohol residue, such as ethyl acrylate, isopropyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, aromatic or aliphatic α-B-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, such as dibutyl maleate or dibutyl fumarate, α-3-unsaturated carboxylic acids, such as acrylic acid, methacrylic acid or crotonic acid and their derivatives, such as acrylamide or methacrylate.

When choosing the suitable monomers or monomer combinations, the generally recognized points of view for the production of paint dispersions must be taken into account. Thus, special care must be taken to ensure that polymers are produced which, under the prescribed drying conditions for the paint, form a film, and the choice of monomers for the production of the copolymers must be made in such a way that, after the setting of the polymerization parameter, the formation of copolymers with the keto group-containing monomers is to be expected. In the following, some suitable monomer combinations are listed: ethyl acrylate/methyl methacrylate/(meth-)acrylic acid/acetoacetic acid allyl ester

isopropyl acrylate/methyl methacrylate/(meth -)acrylic acid/acetoacetic acid allyl ester

butyl acrylate/methyl methacrylate/(meth-)acrylic acid/acetoacetic acid allyl ester

isobutyl acrylate/methyl methacrylate/(meth-)acrylic acid/acetoacetic acid allyl ester

2-ethylhexyl acrylate/methyl methacrylate/(meth-)acrylic acid/acetoacetic acid allyl ester ethyl acrylate/styrene/methyl methacrylate/(meth -)acrylic acid/acetoacetic acid allyl ester butyl acrylate/styrene/methyl methacrylate/(meth-)acrylic acid/acetoacetic acid allyl ester, 2-ethylhexyl acrylate/styrene/ (meth -) acrylic acid/acetoacetic acid allyl ester

vinyl acetate/butyl acrylate/acetoacetic allyl ester vinyl acetate/dibutyl maleate/acetoacetic allyl ester vinyl acetate/dibutyl fumarate/acetoacetic allyl ester vinyl acetate/isononanoic acid vinyl ester/acetoacetic allyl ester vinyl acetate/2-ethylhexanoic acid vinyl ester/acetoacetic allyl ester vinyl acetate/versatic-10-acid vinyl ester/acetoacetic allyl ester vinyl acetate/ethylene/acetoacetic allyl ester

vinyl acetate/ethylene/vinyl chloride/acetoacetic acid allyl ester

Plastic dispersions are extremely complex systems. The production of dispersions which are suitable for the purpose of the invention requires the application of the existing experiences in the field of emulsion polymerization, also insofar as they are not specifically discussed here. Failure to comply with the rules known to professionals in the field of emulsion polymerization can therefore affect important properties, e.g. the water resistance. The dispersions should therefore, with reference to the polymer content, not significantly exceed the usually used amounts of up to 3%■, preferably up to 2% of ionic emulsifiers, resp. up to 6%, preferably up to 4% of non-ionic emulsifiers.

As non-ionic emulsifiers, for example, alkyl polyglycol ethers are used, as ethoxylation products of lauryl, oleyl or stearyl alcohol or of mixtures such as coconut fat alcohol, alkylphenol polyglycol ethers, as ethoxylation products of octyl or nonylphenol, diisopropylphenol, triisopropylphenol or of di- or tri-tert.-butylphenol or ethoxylation products of polypropylene oxide.

Ionic emulsifiers are primarily anionic emulsifiers. It may thereby be alkali or ammonium salts of alkyl, aryl or alkylaryl sulphonates,

-sulfates, -phosphates, -phosphonates or compounds with others

anionic end groups, as oligo or polyethylene oxide units can also be found between the carbonate residue and the anionic group. Typical examples are sodium lauryl sulfate, sodium octylphenol glycol ether sulfate, sodium dodecylbenzene sulfonate, sodium lauryl diglycol sulfate, ammonium tritert-butylphenol penta- or octaglycol sulfate.

As protective colloids, natural substances such as gum arabic, starch, alginates or modified natural substances such as methyl, ethyl, hydroxyalkyl or carboxymethyl cellulose or synthetic substances such as polyvinyl alcohol, polyvinyl pyrrolidone or mixtures of such substances are used as protective colloids. Preferably, modified cellulose derivatives can be used and. synthetic protective colloids.

To start and continue the polymerization, oil and/or preferably water-soluble radical generators or redox systems are used. It is suitable, for example, hydrogen peroxide, potassium or ammonium peroxydisulphate, dibenzoyl peroxide, lauryl peroxide, tri-tert.-butyl peroxide, bis-azodiisobutyronitrile alone or together with reducing components, for example sodium bisulphite, rongalite, glucose, ascorbic acid and other compounds that have a reducing effect.

To produce dispersion colors according to the invention with high wet adhesion, the dispersions are mixed with a pigment slurry. Such pigment slurries, also referred to as pigment oil or pigment pastes, which are suitable for use in low-pigmented dispersion paints and especially gloss paints, consist, for example, of titanium dioxide which is uniformly dispersed in water. They usually contain protective colloids such as cellulose derivatives, for example hydroxyethyl cellulose, and dispersing agents, for example salts of poly(meth)acrylic acid or -sodium polyphosphate. Common components of the pigment slurry are further antimicrobial preservatives, defoamers, pH stabilizers and fillers. Particularly suitable titanium dioxide pigments are rutile and anatase. For gloss paints, it is important that the average particle diameter of the pigment is close to the lower limit of the light wavelengths, i.e. at approx. 0.4 - 0.2 y. For the production of low-pigmented matt paints, special surface-rich silicate pigments can be used, for example. Matt colors rich in binders provide coatings that are easy to clean. The pigment paste can of course also contain color pigments, but the desired color tone can also be set by fading the dispersion paint made with white pigment.

The pigment slurry can be produced according to the known methods, e.g. by dispersing the pigment in a dissolver, or on ball or sand mills or using water guns. For use in gloss paints - the pigment slurry should not contain significant amounts of pigment aggregates, because these affect the gloss.

You can either add excipients to the dispersion or to the finished dispersion paint, e.g. plasticizers, net formers, buffer substances, thickeners, thixotroping agents, rust protection agents, alkyd resins or drying oils. Plasticizers are not here, with the solvents initially mentioned as film consolidating agents, only having a temporary effect, but compounds such as dibutyl phthalate, which lower the film formation temperature and remain in the polymer for a longer time.

The invention will be explained in more detail with the help of some examples.

Example 1

In a 2-liter wooden-necked flask located in a heating bath and equipped with a stirrer, reflux condenser, dropping funnel and thermometer, the mixture is heated while stirring in a dispersion bath consisting of as the polymerization begins. When the temperature has risen to 70°C, start with the addition of a mixture of 5^0 parts by weight of vinyl acetate and 18 parts by weight of acetoacetic acid allyl ester. The total dosing time is approx. 3 hours.

After completion of the monomer addition, the mixture is reheated for a further 2 hours at the polymerization temperature (70°C) with continued stirring and the mixture is then cooled. Example 2

Proceed in exactly the same way as in example 1, however, acetoacetic acid allyl ester is not added.

Example 3

In an apparatus, as described in example 1, a dispersion bath consisting of is heated to 70°C.

and at this temperature, the remaining monomer mixture (552 parts by weight) is added over the course of 3 hours. After dosing, mix with 0.5 parts by weight of ammonium peroxydisulfate in 15 parts by weight of water and reheat for 2 hours. The solids content is approx. 50%.

Example 4

Proceed in exactly the same way as in example 35, however, no acetoacetic acid allyl ester is added.

Example 5

• In an apparatus as mentioned in example 1, a dispersion bath consisting of is heated to 70°C

2.5 parts by weight of ammonium peroxydisulfate

10% (62 parts by weight) of the monomer mixture, which consists of 480

parts by weight vinyl acetate, 120 parts by weight dibutyl maleinate and 18

parts by weight of acetoacetic acid allyl ester, and the remaining monomer mixture is added during 3 hours. After the addition, 0.5 parts by weight of ammonium peroxydisulfate are mixed with 15 parts by weight of water and reheated for 2 hours. The solids content is approx. 50%.

Example 6

Proceed in exactly the same way as described in example 5, however, acetoacetic acid allyl ester is not added.

Example 7

In an apparatus as described in example 1, a dispersion bath consisting of is heated to 70°C

and at this temperature, a mixture of 432 parts by weight vinyl acetate, 108 parts by weight versatic-10-

acid vinyl ester and 18 parts by weight of acetoacetic acid allyl ester. After the addition, 0.5 parts by weight of ammonium peroxydisulfate are mixed with 15 parts by weight of water and the mixture is heated for 2 hours. The solids content is at approx. 50%.

Example 8-

Proceed in exactly the same way as described in example 7>however, acetoacetic acid allyl ester is not added.

Example 9

A monomer emulsion of the following composition is produced:

and stirred with a high-speed stirrer until a stable emulsion has formed.

In an apparatus as described in example 1, a mixture of

306 parts by weight of water

3 parts by weight ..ammonium tri-tert.butylphenol poly-glycol ether sulfate with approx. 8 ethylene oxide units and

60 parts by weight of the monomer emulsion at 81°C

and mixed with a solution of 0.45 parts by weight of ammonium peroxydisulfate in 15 parts by weight of water. You then begin with the addition of the remaining monomer emulsion and bring the polymerization to completion. The total dosing time

is 2 hours, and the polymerization temperature and the temperature during the post-heating time are between 8l and 83°C. After the end of the monomer dosage, 0.15 parts by weight of ammonium peroxydisulfate in 5 parts by weight of water are mixed, heated for a further 60 minutes and then cooled. The solids content amounts to approx. 50%.

Example 10

Proceed in exactly the same way as described in example 9, however, acetoacetic acid allyl ester is not added.

Example 11

A monomer emulsion of the following composition is first prepared:

<p>g is stirred with a high-speed stirrer until a stable emulsion is formed.

In an apparatus as described in example 1, a mixture of

303 parts by weight of water

3 parts by weight, sodium salt of lauryl alcohol digly-chole ether sulfate and

62 parts by weight of the monomer emulsion at 81°C

and mixed with a solution of 0.45 parts by weight of ammonium peroxydisulfate in 15 parts by weight of water. You then begin with the addition of the remaining monomer emulsion and bring the polymerization to completion. The total dosing time is 2 hours and the polymerization temperature and the temperature during post-heating are between 8l and 83°C. After completion of the monomer dosing, 0.15 parts by weight of ammonium peroxydisulphate are mixed with 5 parts by weight of water, heated further for 60 minutes and then cooled. The solids content amounts to approx. 50%.

Example 12

Proceed in exactly the same way as in example 11, although no acetoacetic acid allyl ester is added.

In order to investigate wet adhesion, gloss paints were produced according to the following recipe:

12-propylene glycol 10.0 parts by weight

dispersed and then inserted

2. Dispersion (at 50% solids content) 710.0 parts by weight which, when the pH value does not exceed approx. 7> is mixed with 2.0 parts by weight of 25 percent ammonia.

Then, while stirring, slowly add a mixture of: 3. Butyl diglycol acetate 10.0 parts by weight

1,2-propylene glycol 27.0 parts by weight

The floating, resp. soluble components, with the exception of 1,2-propylene glycol, are placed in a mixing vessel in the order mentioned and the pigment is dispersed therein with a dissolver. 1,2-propylene glycol is then added. A larger quantity of this pigment paste is prepared for mixing with the different dispersions to be examined in order to ensure equal conditions, e.g. with regard to pigment dispersion.

For the production of the individual paints, a corresponding amount was taken from the pigment paste, and in the method mentioned in the above-mentioned recipe, mixed with the approx. 1 day old dispersions under a slow moving stirrer. The solvents mentioned under point 3 were then added to them. After the complete confection, the paint was sieved.

These gloss paints are drawn up after 1 day's standing time on glass plates and on steel sheets, on which an air-drying pigmented shiny alkyd resin varnish had previously been sprayed and, after drying, aged for 24 hours at 100°C. A film puller with a gap height of 200 ym was used. After a 24-hour drying time for the glossy paints, these were examined according to the two wet bonding methods mentioned below.

1) ' Wear and tear test

On a mechanical wear machine, such as the is discussed in DOS 2,262,956, corresponding to the Gardner-Washability and Abrasion Machine, however with an approx. 1.20 m long running stretch, the prepared glass sheets are inserted so that the stretched dispersion paint films are perpendicular to the running direction. Due to the length of the run, approx. 15 paints. A pig bristle brush is used which is moistened with distilled water at the beginning of the test. The running length of the brushes is also moistened during the test with distilled water so that the brush track is constantly covered with a film of water. In case of insufficient wet bonding, after a few brushings, the dispersion paints are pushed off the substrate with the help of brushes and cracks at the boundary between the wetted and dry film. The wet adhesion is all the better the longer the brush runs to push off the film. Optimum wet adhesion is achieved when after 3000 brushing strokes (1 brushing stroke is a forward and backward movement) the film has not yet been pushed off in the moistened brush groove.

2) Condensation test

Hereby, a square thermostat is used which is half filled with water of 50°C and in whose gas chamber a fan is mounted above the water surface. The upper opening is covered with the prepared steel sheets, with the test surfaces downwards, and is thereby closed. The thermostat is in a room heated to 23°C. Due to the temperature difference, water vapor condenses on the underside of the tins and affects the gloss paint film. After each 15 minute exposure time, the plates are removed and evaluated.

Insufficient wet adhesion manifests itself in the formation of blisters between the dispersion paint and the alkyd resin lacquer as well as in the easy peelability of the film, e.g. with the tip of your finger. With good wet adhesion, the film is blister-free after 4 hours and does not de-cloud vb ar.

The test results appear in table 1.

Claims (4)

1. Use of plastic dispersions which have been produced by polymerization of olefinically unsaturated monomers in an aqueous medium, and which in the polymerized part as comonomer contain a polymerisable acetate diester as a binder in low-pigment solvent-containing paints. 2. - Embodiment according to claim 1, characterized in that a dispersion is used which, as a polymerizable acetate diester, contains vinyl acetate diester, allyl acetate diester or a diester with the general formula where R means H or CH^ and A is equal to -(CH2 )n -O- or -(C <H> 2 <-> CH2 )m~ 0-5 where n means an integer between 1 and 4 and m an integer between 1 and 3 • 3. Embodiment according to claim 1' or 2, characterized in that the amount of acetic acid ester in the polymer constitutes 0.5 - 10 percent by weight, - preferably 1-5 percent by weight -, referred to the total monomeric amount. 4. Embodiment according to claims 1 - 3> characterized in that a mixture of different dispersions is used as binder. at least one of which in the polymer part contains so much acetic acid ester as comonomer that the amount of acetic acid ester, calculated on the weight of all monomers present in the mixture, amounts to 0.5 - 10, preferably 1-5 percent by weight.