SK282535B6 - Coating compositions and their use - Google Patents

Abstract

Coating compositions contain 4 to 12 wt. % of at least one water-soluble polymeric dispersion, 3 to 8 wt. % of at least one linear polydimethylsiloxane containing final hydroxyl groups, 35 to 65 wt. % of at least one pigment and/ or at least one filling, respectively up to 2 wt. % of alkali metals siliconates, alkyl-alkoxypolysiloxanes and/ or other ingredients. The use of the coating compositions for coating building materials, facades and renderings of arbitrary kind.

Description

Technical field

The invention relates to novel coating compositions comprising at least one water-dilutable polymer dispersion, at least one linear polydimethylsiloxane, containing terminal hydroxyl groups, at least one pigment and / or at least one filler and optionally alkali metal siliconates, alkylalkoxypolysiloxanes and / or other additives. It further relates to their use.

BACKGROUND OF THE INVENTION

Porous mineral substrates, such as lime-based building materials and plasters, can be protected from the environment by various methods. Coating of building materials, plasters or buildings with film-forming coatings has been transposed. According to the prior art, these coatings consist essentially of the following coating materials: organic polymer dispersions (binders), pigment and fillers.

These, however, disadvantageously limit the diffusion of water vapor. Higher proportions of pigments and fillers lead to improved microporous films, but their drawback is that the water is taken up too high. The modification of the coating materials with silicones (e.g. DEOS 12 84 007) results in microporous, water-permeable and water-repellent coatings.

According to the state of the art, more or less branched polysiloxanes are used as silicones. These occur as aqueous emulsions and contain, in addition to water, up to 20% by weight of water-immiscible solvents such as xylene or higher boiling point aromatic and paraffinic products. However, the use of organic solvents is disadvantageous from an ecological point of view.

The desired water-repellent effect, water vapor permeability and weather resistance are related to a certain ratio of polymer dispersion to silicone.

According to the prior art, for example DE-OS 12 84 007, the weight ratio of the active substances from the polymer dispersion to the polysiloxane active substances is <1.

EP 287 085 describes aqueous dispersions comprising organopolysiloxanes, ethylene-vinyl chloride copolymers and optionally pigments and their use as paints. The polysiloxanes used contain resins or organofunctional polysiloxanes.

EP 163 085 describes aqueous dispersions comprising polyurethanes, thickeners with carboxyl groups, self-crosslinking polyorganosiloxanes and crosslinkers for polyurethanes, as well as carbonyl groups containing polymers. They are useful for coating or printing textiles and leather and the like. They are cross-linked on the surface and therefore form a non-porous coating.

According to EP 546 421 a process for producing water-resistant paints and plasters is described. These paints and plasters consist of silicone resins, organic polymers and inorganic fillers.

The following data always refer to weights unless otherwise stated.

However, the polysiloxanes which are used in excess (based on the active ingredient) are considerably more expensive than polymer dispersions. However, efforts to date to increase the proportion of polymer dispersion in the active ingredient and to reduce the proportion of polysiloxane while maintaining the desired properties have failed. In particular, the water vapor permeability of such coatings is impaired.

Coating systems are therefore required which have a weight ratio of active ingredient from polymer dispersion to polysiloxane of > 1, the polysiloxane emulsion used containing a strongly reduced proportion of organic solvent and even being solvent-free.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide coating systems which do not have the stated disadvantages. It has been found that paints comprising at least one water-dilutable polymer dispersion, at least one linear polydimethylsiloxane containing hydroxyl end groups, at least one pigment, filler and optionally alkali metal siliconates, alkyl alkoxypolysiloxanes and / or other additives have properties exceeding the properties of the prior art .

Accordingly, the present invention relates to paints containing

A) 4 to 12 wt. at least one water-dilutable polymer dispersion,

B) 3 to 8 wt. at least one linear hydroxyl-terminated polydimethylsiloxane,

C) 35 to 65 wt. at least one pigment and / or at least one filler, and optionally

D) up to 2 wt. alkali metal siliconates, alkylalkoxypolysiloxanes and / or other additives,

E) 7 to 58 wt. water and optionally other additives, wherein the component

B) is a compound of formula

CH, I

CH, I ’

I

CH

I CHj in which

X is hydroxyl or alkoxy; and m is 50 to 1000, wherein the sum of components A), B), C) and D) is 100% by weight, the weight ratio of A) and B) is> 1, the weight ratio of A) and C) is 1: 5 to 1: 10 and the percentages are based on the active substance.

In the coating compositions of the present invention, component A) is any polymer dispersible in water or in a mixture of water and organic solvents. Preferred are those polymers which, after removal of the aqueous weight, dry to the films. Emulsion and suspension polymers and / or mixed polymers are particularly preferred. Suitable monomers for the production of component A) are, for example:

vinyl esters such as vinyl acetate, vinyl propionate, vinyl laurate and vinyl stearate; styrene and its derivatives such as vinyltoluene and α-methylstyrene; olefins such as ethylene, propylene, isobutylene and butadiene; vinyl ethers such as vinylethyl ether; acrylonitrile; acrylates and methacrylesters such as methyl acrylate, ethyl acrylate, methyl methacrylate and butyl acrylates; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, methylmalonic acid, itaconic acid, citraconic acid and tetrahydro-naphthalic acid; and monoesters and diesters of these acids such as dimethyl maleic acid ester, diethyl maleic acid ester, di-n-butyl maleic acid ester, mono- (2-ethylhexyl) maleic acid ester, fumaric acid dimethyl ester, fumaric acid diethyl ester, di-n-butyl ester fumaric acid, fumaric acid di- (2-ethylhexyl) ester and fumaric acid di-lauryl ester.

Preferred are homopolymers and copolymers of styrene and derivatives thereof, as well as (meth) acrylic acid derivatives. In another embodiment of the present invention, component A) is a poly (meth) acrylate and / or polystyrene / (meth) acrylate dispersion. Particularly preferred are copolymers of styrene and (meth) acrylic acid derivatives. Mixtures of different polymer dispersions can also be used.

The production of linear hydroxyl-terminated polydimethylsiloxanes (component B) can be carried out by known methods, for example as described in W. Noll, Chemie und Technologie der Silicone, p. 162 ff (1968). Preferably, such polysiloxanes are emulsified in water prior to use, optionally with the addition of < 20% by weight of solvents. The emulsions contain 20 to 75% by weight, preferably 30 to 70% by weight, particularly preferably 45 to 65% by weight of polysiloxane.

Although component B) may also contain minor proportions of organic solvents, compounds which do not contain these solvents are particularly preferred. The molecular weight of component B) may be varied within a wide range. In a preferred embodiment of the present invention, component B) has an average molecular weight in the range of 6000 to 50,000, preferably 9000 to 30,000, particularly preferably 12,000 to 20,000, free of organic solvents and occurring as an aqueous emulsion. Preferably, component B) has an average molecular weight of 15,000. When the molecular weight of component B) is greater than 30,000, it is preferably emulsified by the addition of an organic solvent.

The optimum weight ratio of components A) and B) is important for the effectiveness of the coating composition of the present invention. Not only technical aspects but also economic aspects play a role in the choice. Thus, it is possible to work with the weight ratio of components A) and

However, the relatively large proportions of the more expensive component B) negatively affect the economy of use of the coating composition of the present invention.

Surprisingly, the weight ratio of A) to B) is> 1 in the coating compositions of the present invention, while maintaining the desired performance characteristics, particularly with respect to water vapor permeability for water absorption, the upper limit for the weight ratio of A) to B) being whereas it is necessary to maintain a minimum proportion of component B) of about 4: 1 to achieve the desired coating properties. In a preferred embodiment of the present invention, the weight ratio of components A) and B) is 1.1: 1 to 1.8: 1, preferably 1.2: 1 to 16: 1, particularly preferably 1.2: 1 to 1.4: 1.

Any pigments and fillers can be used as component C), as is known from the production of dispersion paints. Mixtures of different pigments and fillers are preferably used. Examples of components C) include: alumina, quartz flour, magnesium phosphate, calcium phosphate, magnesium carbonate, calcium carbonate, aluminum hydroxide, tin dioxide, zinc oxide, mica, talc, iron oxide, various spinels, carbon black, graphite , glass and enamel powder and the like. Particularly particularly preferred as component C) are iron oxides, titanium dioxide, calcium carbonate, talc and / or mica.

Component C) may also be any additive known for the production of lacquers and paints, such as lacquer additives, dispersants, flow enhancers, thickeners, defoamers, film formers and other adjuvants, fungicides, bactericides , stabilizers, inhibitors, as well as catalysts and pH regulators.

The coating compositions according to the present invention comprise 30 to 90% by weight, preferably 40 to 80% by weight, particularly preferably 50 to 70% by weight of a solid. The aqueous phase may optionally contain organic solvents.

In one embodiment of the present invention, component D) preferably corresponds to sodium siliconate and potassium siliconate. When it corresponds to a D) alkylalkoxypolysiloxane, any compound of this type may be used. However, polysiloxanes with two different alkyl radicals are preferred, mixtures of methyl radicals with C 4 -C 14 alkyl radicals being particularly preferred. Preferred alkoxy groups are methoxy and ethoxy. Especially preferred is ethoxy.

In another preferred embodiment of the present invention, component D) is preferably potassium methyl siliconate and / or an alkylalkoxysiloxane of the following statistical composition

while

R ¹ represents a methyl group, an isopropyl group, an isobutyl group or an alkyl group having 1 to 8 carbon atoms,

R is methyl or ethyl and n is 3 to 20, preferably 3 to 10, particularly preferably 4 to 6, and the weight ratio of methyl to higher alkyl groups is 8: 1 to 0.5: 1, preferably 6: 1 to 1 1: 1, particularly preferably 5: 1 to 3: 1.

The presence of component D) generally leads to an improvement in the performance of the coating compositions according to the present invention, but is not necessary. In this way, coatings can also be obtained by omitting component D) which exceeds the properties of the prior art paints.

Said coating compositions are produced by mixing the components A) to C) together. The production can be carried out by known methods using agitators, mills or the like. In one preferred form, water is introduced, optionally together with excipients. With stirring, pigments and fillers are added sequentially or together, optionally in the form of their aqueous dispersions and then polymer dispersion. Finally, the polysiloxane emulsion is added, followed by potassium methyl siliconate. The desired rheological properties can then be adjusted with organic and / or inorganic thickeners. To improve the storage stability of the coating compositions of the present invention, their pH is adjusted to > 7, preferably 8-9.

In the manufacture of coatings from said paints, the paints are applied, for example, by spraying, rolling, dipping or painting on mineral substrates such as facades, plasters and / or building materials, for example of lime-sand building materials or bricks, and then dried, preferably at temperature. surroundings. Depending on the requirements, coatings having a thickness of 10 to 500 µm, preferably 20 to 300 µm, particularly preferably 50 to 200 µm can be produced in this way.

In particular, the coatings of the present invention are characterized by high water vapor permeability and low water gain, as shown in the following examples.

It is also an object of the present invention to use said coating compositions for coating building materials, facades and plasters of any kind.

DETAILED DESCRIPTION OF THE INVENTION

The following examples illustrate the invention in more detail. However, the invention itself is not limited to these examples.

The following abbreviations and measurements are used:

PVK: weight ratio of pigments and filler to binder; expressed in% vol.

W ₂₄ : water take-up coefficient after 24 hours. Results of capillary water uptake tests on coated lime-sand slabs. Method according to DIN 52617. Dimension: kg / m ² h ^0.5 s _D : result of the determination of the diffusion resistance number μH ₂ O for water vapor according to DIN 53122 (humidity gradient 93% relative humidity> 50% relative humidity). The value of s _D is obtained from the relation μ H ₂ O xs (equivalent air layer). The thickness of the coating layer is indicated. The layer thicknesses of the coatings tested were about 200 µm.

General rules for the manufacture of paints Appropriate concentrations of active substance, chain length in the examples of polysiloxane used

CH,

I HO-Si-O

CH,

The ratio of the polymer dispersion to the polysiloxane as well as the measurement values are given in Table 1 below.

To the dispersion (see Table 1) containing the active ingredient shown in Table 1. 1, titanium dioxide (ruthenium) is mixed as pigment and calcium carbonate (calcite in both cases), talc and mica as filler. To this mixture is added potassium methyl siliconate (at a concentration of the commercial preparation) to a concentration of 0.3% by weight of the active substance potassium methyl siliconate.

Table 1

Hwtnpomer pr Ingredients % effective poly- Poiym.diíper. / W ₂ 4 • D PVK 6th Diaper · of the half-ctep. Sioxane Poiysikndin m (kg / m ^of h ¹¹ · ⁹ ) (%) 1 StyroUAkrylát 12.0 12.0 12:05 12:57 60 2 StyroUAkrylát 8.3 83: 0 0.84 12:08 687 3 Styrok / Akrylonu 8.3 200 B.3: 3.7 12:08 12:08 68.7 4 StyroVAkrytál 8.0 200 8.0: 40 12:10 12:07 89.5 5 StyroUAkryttt 80 200 8.0: 5.6 12:06 12:07 89.5 with StyroVAkiylét 8.0 100 8.0: 56 12:05 12:10 69.5 5b Styrene / Akrylét and 300 80: 5.6 008 12:08 69.5 6 Akryttt 8.0 200 8.0: 50 12:13 12:10 ΘΘ.0 7 VrytecetaUnylvemattl 8.0 200 80 5.0 12:11 12:08 69.3

Table 2

Explanation to Table 2:

1. Methyl-silicone resin as the basis for emulsion (viscosity: 2500 mPa.s at 23 ° C, solid: 75% in Solventnaptha)

2. Methyl silicone resin as the basis for the emulsion (viscosity: 450 mPa.s at 23 ° C, solid: 71% in Isopar G)

3. Dimethylpolysiloxane

4. Dimethylpolysiloxane

5. The compound of the invention under the above conditions

Claims (7)

PATENT CLAIMS Coating compositions containing: A) 4 to 12 wt. at least one water-dilutable polymer dispersion, B) 3 to 8 wt. at least one linear polydimethylsiloxane having hydroxyl end groups, C) 35 to 65 wt. at least one pigment and / or at least one filler, and optionally D) up to 2 wt. alkali metal siliconates, alkylalkoxypolysiloxanes and / or other additives, E) 7 to 58 wt. water and optionally other additives, wherein component B) is a compound of formula CH, x-si-o— CH, Si-Si-0 ---- X I CH in which X is hydroxyl or alkoxy; and m is 50 to 1000, wherein the sum of components A), B), C) and D) is 100% by weight, the weight ratio of A) and B) is> 1, the weight ratio of A) and C) is 1: 5 to 1: 10 and the percentages are based on the active substance. Paints according to claim 1, characterized in that component A) is a dispersion of poly (meth) acrylate and / or polystyrene / (meth) acrylate. Paints according to either of Claims 1 and 2, characterized in that component B) has an average molecular weight of 6000 to 50 000, is free of organic solvents and is present as an aqueous emulsion. Paints according to any one of claims 1 to 3, characterized in that the component C) is a substance selected from the group consisting of iron oxides, titanium dioxide, calcium carbonate, talc and / or mica. Paints according to one of Claims 1 to 4, characterized in that the component D) is potassium methyl siliconate and / or alkylalkoxysiloxane of the following statistical composition R ¹ I OR - ^J n where R1 represents a methyl group, an isopropyl group, an isobutyl group or an alkyl group having 1 to 8 carbon atoms, R is methyl or ethyl and n is from 3 to 20, the ratio of methyl to higher alkyl is 8: 1 to 0.5: 1. Coating compositions according to one of Claims 1 to 5, characterized in that the weight ratio of components A) and B) is 1.1: 1 to 1.8: 1. Use of the coating compositions according to any one of claims 1 to 6 for coating building materials, facades and plasters of any kind.