NO146640B - DIFFICULT PLASTIC DISPERSIONS SUITABLE FOR PREPARING PAINT OR COLOR WITH HIGH WATER ADHESION - Google Patents

Description

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

Low-pigment dispersion paints are chosen when the coat must be washable. With high binder content of these paints, a closed, washable film is formed. Likewise, glossy or silky-matte dispersion paints have a pigment concentration of less than 40% and usually approx. 10-25%. In addition, they contain to improve gloss<1>, flow and processing

time and as a film consolidation agent organic solvents in larger quantities, approximately between 3 and 15%. Gloss, flow and processing time are affected e.g. in the case of polyhydric, water-miscible alcohols with up to 6 C atoms, especially ethylene and propylene glycol or their monomethyl to monobutyl ethers. To improve the film consolidation, water-soluble solvents such as monoglycol ethers of carboxylic acids and especially the ester of carboxylic acid with monoalkyl ethers of glycols or oligoglycols are used to a limited extent. 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 wet adhesion of dispersion paint coats.

Lack of wet bonding means that the coats which

are designed to be washable no longer have this property when they were applied to smooth, non-absorbent surfaces, e.g. on old alkyd resin or oil paint. In damp rooms such as kitchens and bathrooms and many industrial rooms, where condensation must be expected, the coats can detach from the substrate when sufficient wet bonding is not provided. Finally, lack of wet adhesion makes ironing 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 stained with a different color due to inaccurate brush application. In principle, these stains can be removed with a damp cloth. In the absence of wet bonding, however, the first coat is easily damaged or completely pushed away.

For these reasons, there has been no lack of attempts to modify plastic dispersions so that the dispersion paints thus produced show the desired wet adhesion. It is known in particular from DE-off.skrift 1,595,501 the production of plastic dispersions by polymerization of suitable monomers in an aqueous emulsion by incorporating as comonomers 0.2 to 15% by weight, referred to the total amount of monomer of compounds with oxirane groups in the polymer and then at room temperature allowing ammonia or amines to act on the copolymer. Suitable oxirane compounds are above all glycidyl esters of acrylic or methacrylic acid, but also allyl glycidyl ethers or vinyl glycidyl ethers.

Dispersion paints that are produced with

such plastic dispersions already have very good wet adhesion. For many practical purposes, however, wet bonding is not sufficient.

The invention relates to aqueous plastic dispersions which are suitable for the production of paints or colors with high wet adhesion which are obtained by copolymerization of the following monomers, A) 20-80% by weight, preferably 40-60% by weight, referred to the total amount of monomers , of the hardening monomers methyl ethacrylate, styrene and/or vinyltoluene, B) 20-80% by weight, preferably 40-60% by weight, referred to the total amount of monomers, of softening monomers consisting of acrylic acid esters, which in the alcohol residue have

a linear or branched alkyl residue with 2-8 carbon atoms, C) 0.1-5% by weight acrylic acid, methacrylic acid, acrylamide and/or methacrylamide, characterized in that by

the polymerization is additionally used

D) 0.5-10% by weight, preferably 1-5% by weight, of an acetoacetic ester of the general formula

or of the acetacetic ester of the hydroxypropyl oxylate or methacrylate.

Hardening monomers of the type mentioned under point A) are e.g. methyl methacrylate, styrene or vinyl toluene.

Emollient-acting monomers of the type mentioned under B) are e.g. ethyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate or butadiene, isoprene or chloroprene.

Water-soluble monomer of the under point

C) said type is e.g. acrylic acid, methacrylic acid, acrylamide or methacrylamide.

Monomers of the type mentioned under point D) are e.g. acetoacetic acid vinyl ester, acetoacetic acid allyl ester or acetoacetic acid ester of g-hydroxyethyl acrylate or methacrylate or hydroxypropyl acrylate or methacrylate. Acetoacetic acid allyesters are preferably used, as the best results are achieved with this.

In the case of dispersions that are produced in an acidic area, it is often advantageous to increase the storage stability and to facilitate paint production to set the pH value between 7.5 and 10 with ammonia or suitable amines, e.g. water-soluble tertiary amines.

Plastic dispersions are very complex systems. The production of high-quality dispersions in accordance with the invention presupposes the application of the experiences existing in the field of emulsion polymerization, also insofar as they are not discussed here. Failure to comply with the rules known to professionals in emulsion polymerization can therefore affect important properties, e.g. water resistance, dispersion films or the iron-on films. 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 or 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 nonyl phenol, diisopropyl phenol, triisopropyl phenol or of di- or tri- tert.-butyl-phenol, or ethoxylation products of polypropylene oxide.

Ionic emulsifiers are primarily anionic emulsifiers. It may thereby be alkali or ammonium salts of alkyl-, aryl- or alkyl-aryl-sulphonates, -sulphates, -phosphates, -phosphonates or compounds with other anionic end groups, as there may also be oligo- or polyethylene oxide- units between the hydrocarbon residue and the anionic group. Typical examples are sodium lauryl sulfate, sodium octylphenol glycol ether sulfate, sodium dodecylbenzene sulfonate, sodium lauryl diglycol sulfate, ammonium tri-tert.-butylphenol penta- or octaglycol sulfate.

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 also used as protective colloids. Modified cellulose derivatives and synthetic protective colloids are preferably used.

The use of these protective colloids

however, when using the mentioned monomer systems, which are known to those skilled in the art, is only possible to a limited extent.

The applicable amounts are often small, 0.001 - 1% and compatibility and type of addition must be examined on a case-by-case basis. When the use of protective colloids is necessary, it can e.g. the guidelines mentioned in DE-off.skrift 1,570,312 are used.

For starting and continuing 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 reducing compounds.

The dispersions according to the invention have the particular advantage that they are suitable for the production of dispersion gloss paints with good wet adhesion and non-absorbent substrates which also have high saponification resistance.

Example 1:

First of all, a monomer emulsion of the following composition is produced:

The components are stirred with a high-speed stirrer until a stable emulsion is formed.

A mixture of

and mixed with a solution of 0.45 parts by weight of ammonium peroxydisulfate in 15 parts by weight of water. The remaining monomer emulsion is then dosed and the polymerization is carried to completion. The total dosing time is 2 hours, the polymerization temperature and the temperature during the post-heating time are between 81 and 83°C. After completion of the monomer dosage, 0.15 parts by weight of ammonium peroxydisulfate are mixed with 5 parts by weight of water, heated further for 60 minutes. and then cools. The pH value is set with 15 ml of 25% NH3 to 9.5; the solids content is approx. 50%. Example 2: The procedure is exactly the same as described in example 1, except that during the polymerization, acetoacetic acid allyl ester is not used.

Example 3:

stir with a high-speed stirrer until a stable emulsion appears. In an apparatus as described in example 1, a mixture of which is mixed with a solution of 0.45 parts by weight, ammonium peroxydisulfate in 15 parts by weight of water is heated. The remaining monomer emulsion is then added and the polymerization is completed. The total dosing time is 2 hours, the polymerization temperature and the temperature during the post-heating time are between 81 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, further heated for 1 hour and then cooled. The pH value is adjusted with 15 ml of 25% NH 3 to 9.3. The solids content amounts to approx. 50%. Example 4: Proceed in exactly the same way as in example 3, however, during the polymerization, acetic acid allyl ester is not used.

Example 5:

A monomer emulsion is first prepared

stir with a high-speed stirrer until a stable emulsion appears.

In an apparatus as described in example 1, a mixture of which is mixed with a solution of 0/45 parts by weight of ammonium peroxydisulfate in 15 parts by weight of water is heated. The remaining monomer emulsion is then dosed and the polymerization is brought to a close. The total dosing time is 2 hours, the polymerization temperature and the temperature during the post-heating time are between 81 and 83°C. After completion of the monomer dosage, 0.15 parts by weight of ammonium peroxydisulphate are mixed with 5 parts by weight of water, then heated for 60 minutes.

and then cools. The pH value is adjusted with 15 ml NH 3

(25%) to 9.5. The solids content amounts to approx. 45%.

Example 6:

Proceedings are carried out in exactly the same way as in example 5, although acetoacetic acid allyl ester is not co-used during the polymerization.

For the production of dispersion paints with

high wet adhesion, the dispersion is mixed with a pigment slurry. Such pigment slurries, also referred to as pigment pastes or pigment pastes which are suitable for use in low-pigment dispersion paints and especially in gloss colours, consist for example of titanium dioxide, which is dispersed

made in water. The contents are usually protective colloids such as cellulose derivatives, for example hydroxyethyl cellulose and dispersing agents, for example salts of poly(meth)acrylic acid or sodium polyphos fat. Common components of the pigment-opps leave are further antimicrobial preservatives, defoamers, pH stabilizers and fillers. Particularly suitable titanium dioxide pigments are rutile and anatase. For gloss colours, it is important that the average particle diameter of the pigment lies in the vicinity of the lower limit of the light wave range, i.e. at approx. 0.4 to 0.2^u . For the production of low-pigmented matt paints, special surface-rich silicate pigments can, for example, be inherited. Binder-rich matte colors provide

coats that are easy to clean.. The pigment pastes can of course also contain color pigments, however, the desired color tone can also be set by fading the dispersion paint made with white pigment.

The pigment slurry can be prepared according to the known methods, e.g. by dispersing the pigment in a dissolver or on ball or sand mills. 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. softeners, net formers, buffering agents, thickeners, thixotroping agents, rust protection agents, alkyd resins or drying oils. The plasticizer is not the solvent mentioned at the outset as a film consolidating agent, which only has a temperature effect, but compounds such as dibutyl phthalate, which lower the film formation temperature and remain in the polymer for a longer time.

When examining the wet adhesive, glossy paints were produced according to the following recipes.

Prescription I

is dispersed and then

2. the dispersion is used (50% solids content) 710.0 parts by weight When the pH value does not exceed approx. 7, is mixed with 2.0 parts by weight of 25% ammonia.

A mixture of is then slowly added while stirring

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

Prescription II

Recipe II differs from Recipe I Q£ by a different composition of the solvent mixture added to the finished paint (Procedure step 3 in paint production). A mixture of 36.5 parts by weight of 1,2-propylene glycol, 13.5 parts by weight of butyl diglycol acetate and 20 parts by weight of 2,2,4-trimethylpentanediol-1,3-monoisobutyrate-1 (trade name: Texanol) was added to the paint.

Prescription III:

Recipe III also differs from the first two recipes by a different composition of the solvent mixture added to the finished paint. 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, was added to the paint. 2,4-trimethylpentanediol-1,3-monoisobutyrate-1 (part name Texanol).

For the production of the individual paints, a corresponding portion was taken from the pigment paste and mixed in the methods mentioned in the above-mentioned recipes with the approx. 1

day-old dispersions under slow stirring. The solvents mentioned under point 3 were then added. After a complete confection, the paint was sieved.

After 1 day's standing time, the gloss paints were applied to glass plates and to steel sheets, after which an air-drying pigmented shiny alkyd resin varnish was sprayed beforehand and after drying it was aged for 24 hours at 100°C. A film puller with a gap height of 200 µm was used. After 24 hours of drying time for the gloss paint, this was examined for wet adhesion according to the two methods mentioned below.

1) Wear test

On a mechanical wear machine, such as the one that e.g. are discussed in DE-off script. 2,262,956 describes a Gardner-Wash-ability und Abrasin Machine, however, with approx. 1.2 0m long running stretch, the prepared glass sheets were laid in such a way that

the drawn up dispersion paint film was perpendicular to the brush's running direction. Owing to the length of the running route, approx. 15 paints. A pig bristle brush is used, which is moistened with distilled water at the beginning of the test. During the test, the running length of the brush is also dripped with distilled water, so that the brush grooves are constantly covered with a film of water. In the case of insufficient wet adhesion, after a few brushings, the dispersion paint is pushed off the substrate by the brushes and tears off at the boundary between the wetted and dry film. The wet adhesion is all the better the longer the brush for pushing off the film runs. Optimum wet adhesion is achieved when, after 5,000 brushing strokes (1 brushing stroke is a back and forth movement), the film in the moistened brush groove has not been pushed off.

2. Condensation test

Hereby, a square thermostat was used, which is half filled with water of 50°C and in whose gas space above the surface of the water a fan is mounted. The upper opening is covered with the prepared steel sheet with the test surface downwards and then closed. The thermostat is in a room kept at 2 3°C. Due to the temperature difference, water vapor condenses on the underside of the tin and affects the glossy paint film. Every 15 minutes of exposure time, the plate is taken out and assessed.

Insufficient wet adhesion is manifested by the formation of blisters between the dispersion paint and the alkyd resin varnish as well as the easy separation of the film, e.g. with the tip of your finger. With good wet adhesion, the film is also blister-free and non-removable after 6 hours.

Test results appear in table I.

Example 7

In a 16 liter pressure vessel with impeller stirrers there is a bath consisting of:

The bath and the entire apparatus are flushed with nitrogen and the other operations are also carried out under a protective gas atmosphere.

From a storage vessel, a mixture of is pumped into the pressure vessel

You start the mixer (approx. 300 rpm) and start heating. At 70°C (the internal pressure is then approx. 10 bar) polymerisation is carried out for 2 1/2 hours and then a solution of

The post-reaction time is 3 hours (also at 70°C). The vessel is then cooled, aerated and the product filtered.

The solids content amounts to approx. 42%. The amount of coagulate is small.

Example 8

Proceed as described in example 7, with the total amount of styrene (1740 g) being replaced with vinyltoluene.

Example 9

The procedure is the same as described in example 7, with half of the styrene (780 g in the original and 90 g in the subsequent dosage) being replaced with vinyltoluene.

S^ mmejil^ njjigse^ empel 10: (not according to the invention)

The procedure is the same as described in example 7, except that acetate acetic acid allyl ester is not used and the amount of water in the dispersion bath is reduced by around 90g to 3000g.

For the production of dispersion paints with

high wet adhesion, the dispersion is mixed with a pigment slurry. Such pigment slurries, also referred to as pigment doughs or pigment pastes, which are suitable for use in low-pigment dispersion paints and especially in 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 polyphos fat. 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 pigments is close to the lower limit of the light wavelengths, i.e. at approx. 0.4 to 0.2^ . For the production of low-pigmented matt paints, special surface-rich silicate pigments can be used, for example. Binder-rich matte paints produce coats that are easy to clean. The pigment pastes can of course also contain color pigments, but the desired color tone can also be adjusted by fading the dispersion paint made up of white pigment.

The pigment slurry can be produced by the known methods, e.g. by dispersing pigment dissolvers or on ball or sand mills. For use in gloss paints, the pigment slurry should not contain significant amounts of pigment aggregates, because this affects the gloss.

You can either add excipients to the dispersion or to the finished dispersion paint, e.g. plasticizers, net formers, puffing agents, thickeners, thixotroping agents, rust protection agents, alkyd resins or

drying oils. Softeners are not the initial

show as a film consolidating agent the aforementioned solvent with only a temporary effect, but compounds such as dibutyl phthalate, which lowers the film formation temperature and remains longer in the polymer.

For examination of wet bonding, gloss paints were produced according to the following recipe:

dispersed and then: then, while stirring, a mixture of is slowly added

The liquid or 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 was prepared for mixing the different dispersions to be examined and to ensure equal conditions, e.g. with regard to pigment dispersion.

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

After 1 day's standing time, this glossy paint was drawn onto glass plates and onto steel sheets, where an air-drying pigmented, shiny alkyd-resin varnish had previously been sprayed and after drying for 24 hours was aged at 100°C. A film extractor with a gap height of 200 µm was used. After 24 hours of drying time for the gloss paint, this was examined according to the previously mentioned wear and condensation tests.

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 your fingertips. With good wet adhesion, the film is still blister-free after 4 hours and cannot be pushed off.

The test results appear in Table II.

Claims (2)

1. Aqueous plastic dispersions which are suitable for the production of paints or colors with high wet adhesion and which have been obtained by copolymerizing the following monomers, A) 20-80% by weight, preferably 40-60% by weight, referred to the total amount of monomers , of the hardening monomers methyl methacrylate, styrene and/or vinyltoluene, B) 20-80% by weight, preferably 40-60% by weight, referred to the total amount of monomers, of softening monomers consisting of acrylic acid esters, which in the alcohol residue have a linear or branched alkyl residue with 2-8 carbon atoms, C) 0.1-5% by weight acrylic acid, methacrylic acid, acrylamide and/or methacrylamide, characterized in that D) 0.5-10% by weight is additionally used during the polymerization , preferably 1-5% by weight, of an acetic acid ester of the general formula where X = -O-, - O- CHy- or where R = H or CH3 and R<1> = H or CH3, or of the acetacetic ester of hydroxypropyl oxylate or methacrylate. 2. Aqueous plastic dispersion according to claim 1, characterized in that acetoacetic acid allyl ester is used as acetoacetic ester.