EP3759175A1 - Silicate coatings - Google Patents

Abstract

The invention relates to a silicate coating comprising at least one base silicate, at least one filler and/or pigment, at least one water-soluble carbohydrate, water for setting a liquid or pasty consistency, optionally at least one organic binder and optionally conventional additives.

Description

 silicate coatings

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The invention relates to silicate coatings, especially silicate paints and dispersion silicate paints, comprising at least one basic silicate, at least one filler and / or pigment, water for adjusting a pasty consistency, optionally at least one organic binder and optionally conventional additives.

Technical field of the invention

 Silicate paints are a very important special case of mineral paints. They contain, as is exemplified in detail in Wikipedia, in addition to inorganic colorants as the main component of a potassium-containing alkali metal silicate, also as

Water glass known. A coat of silicate paints connects through

Silicification insoluble with the ground. The result is a very consistent bond between paint and paint carrier. In addition, the binding agent water glass is highly resistant to UV influences. While organic binders such as acrylate or silicone resin dispersions embrittle over the years under the influence of UV radiation and lead to chalking phenomena, cracks and, as a consequence, paint damage, the inorganic binding agent water glass remains stable. The chemical bonding with the substrate and the UV stability of the binder are the main reasons for the extremely long life of

Silicate paints. For setting, silicate paints require a mineral, siliceous base. Therefore, they are suitable for mineral substrates such as mineral plasters and concrete.

Silicate paints are enormously color stable. After they are only tinted with mineral pigments and these do not change in color due to UV light, the silicate coatings also remain constant in color for decades. Basically, three types of silicate paints are historically distinguished, the definitions of which are not intended to limit the invention:

The pure silicate paint consists of two components, a dry or colorless powder mixed in water and the liquid binder water glass. The processing requires a lot of experience and know-how. It is especially popular in the historical area. Silicate paints according to the invention can be used in

Difference to this include other ingredients.

In the middle of the 20th century, the first one-component silicate paint was developed. By adding up to 5% by weight of organic additives (eg

 Acrylate dispersion, water repellents, thickeners o. Ä.), The color can be offered ready for use in the bucket. One speaks here of so-called.

"Dispersion silicate paints" The range of application of this type of silicate paint is significantly greater than that of the pure silicate paint, because even substrates with lower strengths and / or organic proportions can be coated. In addition, the processing is easier than with the pure silicate paint. invention

Dispersion silicate paints can contain more than 5% by mass of organic matter

Additives, in particular binders include. Since 2002, there is a third category of silicate paint, the so-called sol-silicate paint. It contains as a binder a combination of silica sol and water glass. The organic content is limited to 5% by mass, as in the case of the dispersion silicate paint, in order to obtain a chemical setting and the silicate-typical starches. The sol silicate paint also allows for use

non-mineral cleaning. Here the bond takes place chemically and physically. These colors are easy and safe to use on almost all common surfaces. Known silicate and dispersion silicate coatings should (also) be suitable for applications on absorbent, mineral and / or basic, cementitious substrates. However, such silicate-bound coatings have clear weaknesses here. For critical substrates (eg absorbent, mineral and / or basic, cementitious substrates) the silicate-bound coating dries too quickly due to the acceleration of the silicification reaction due to the basicity of the substrate. After contact of the silicate binder on the basic substrate, the reaction of the silicate binder with the 'reactive' components of the substrate (Ca (OH) ₂ , other basic silicates and / or (silicate) fillers with surface OH groups) occurs immediately. This Verkieselungsreaktion sets in immediately, the penetration into the substrate is disturbed.

Critical substrates, especially basic absorbent substrates, are regularly inhomogeneously critical resp. absorbent. There are places or areas that are more or less critical resp. are sucking. That's why it comes to

Staining if the substrate is not "homogenized" by pretreatment (priming and / or fluising). Flotation is the neutralization and hardening of alkaline substrates by applying a fluoride, a salt of hexafluorosilicic acid (fluoridosilicates). The use of silicate coatings or dispersion silicate coatings on purely polymcrgcbundcncn old coatings also leads to adhesion problems, if the substrate is not pretreated accordingly. The silicification with the ground can not take place.

Against this background, it is an essential object of the invention

Silicate coatings are available, which allow the spot - free drying on critical substrates, without any pretreatment of the

Underground (priming and / or fluating) is necessary.

These silicate coatings should be as easy to process as comparable conventional silicate paints or dispersion silicate paints.

Disperse silicate paints and other disperse silicate coatings are hydrous, liquid or pasty before their intended use

Mixtures. They often have to survive long periods of storage of weeks or months between their manufacture and their use, during which they may not change relevantly. Because of the content of organic binders in aqueous medium, there is a risk that the compositions will be attacked by microbes that feed on the binder and other organic additives. This can lead to the uselessness of the affected composition and must therefore be effectively prevented.

It is therefore a further object of the invention to provide silicate coatings which are effectively protected from microbial attack.

To achieve these and other objects serve the invention

Feature combinations of the appended independent claims. Advantageous developments and refinements of the invention are defined in the subclaims.

definitions:

"Basic silicates" in the sense of the invention are silicates which on contact with H ₂ O due to the presence on the surface of the silicates of at least one

Base function with a base strength less than 5 (pK _b <5) strongly alkaline react. The "basic silicates" include basic alkali and alkaline earth silicates.

Basic silicates contain on the surface at least one of the following basic groups or ions:

• free oxide ions (O ² ), pK _b = - 15

• free hydroxide ions (OH), pK _b = - 1.8

Orthosilicate groups or ions:

- Si0 ₄ ⁴ pK _b = 0

HSi0 ₄ ³ pK _b = 1 or Si0 ₄ ^{3 ~} groups

- H ₂ Si0 ₄ ² - pK _b = 2.2 or Si0 ₄ ^{2 ~} - groups

- H ₃ Si0 ₄ - pK _b = 4.3 or Si0 ₄ - groups

Metasilicate - groups or ions:

SiO ² pK _b = 2.2

 HS1O3 pKb = 4.5 or S1O3 groups

Unless otherwise expressly stated, a coating, composition, paint, plaster and the like in the sense of the invention means both the not yet processed product and the product after its processing.

Thus, "silicate paint" or "silicate coating" includes the hydrous liquid or pasty coating composition prior to its application, as well as the solid, more or less dry, coating resulting from the application. A silicate coating in the sense of the invention comprises a liquid or pasty composition which can be produced from a dry or colorless powder mixed with water and a basic silicate such as, in particular, water glass as a liquid binder, and the additives according to the invention, in particular for delaying the setting, according to the definition in claim 1.

A dispersion silicate coating in the sense of the invention comprises a one-component silicate coating with organic additives (eg.

Acrylate dispersion, water repellents, thickeners o. Ä) and additives according to the invention, in particular for delaying the setting, according to the definition in claim 1.

 A sol-silicate coating according to the invention is a silicate coating according to the invention or dispersion-silicate coating in the above sense, as defined in claim 1, but contains as binder a combination of silica sol and water glass. The organic fraction is as in the case of the dispersion silicate coating according to the invention.

 In the context of the invention, silicate paints, disperse silicate paints, similar silicate-containing compositions (eg, sol-silicate paints, others

Coatings as paints) and emulsion paints with an addition of basic silicates are collectively referred to as "silicate coatings." "Coating" and "composition" are basically synonymous.

The invention also includes compositions whose silicate content differs from the usual silicate compositions. The invention therefore also encompasses compositions with substantially lower contents of silicates, particularly basic silicates, and substantially higher contents of at least one organic binder compared to conventional (for example the abovementioned) compositions or coatings. The content of organic binder can be well over 5 wt.% And outweigh the silicate content, even far outweigh. Such compositions correspond

Dispersion coatings with an addition of basic silicates as an additive. Percentages are by weight unless otherwise specified.

Detailed illustration of the invention

The invention solves the problem of staining or streaking when applying silicate coatings to absorbent and / or strongly alkaline substrates basically by delaying the silicification reaction. These

Delay is caused by the addition of a water-soluble carbohydrate to the silicate coating not yet applied.

The invention therefore relates to silicate coatings, especially silicate paints, comprising at least one basic silicate, at least one filler and / or pigment, at least one water-soluble carbohydrate, water for adjusting a pasty consistency, optionally at least one organic binder and optionally conventional additives.

The application of silicate coatings or dispersion silicate coatings on purely polymcrgcbundcncn old coatings also leads to adhesion problems, if the substrate is not appropriate

is pretreated. The silicification with the ground can not take place.

Because of the high proportion of organic polymer binder and a relatively low proportion of basic silicates are correspondingly preferred

Embodiments of the coating compositions according to the invention can also be applied without problems to such substrates.

So it is possibly no time-consuming underground treatment necessary both in absorbent, alkaline substrates and non-silicatable substrates. The basic silicate according to the invention in preferred embodiments of the invention is an alkaline earth silicate, in particular calcium silicate, for example cement, cement clinker, granulated slag and / or hydraulic lime, and / or an alkali metal silicate, for example lithium, sodium or potassium water glass. Especially preferred embodiments of the invention contain both alkaline earth silicate and alkali silicate.

In the preparation of the compositions of the invention, the basic silicate is used in the case of alkaline earth silicates as hydrate-free silicate, i. free or at least substantially free of alkaline earth or calcium silicate hydrate (CSH) phases. By this not only the expert understands that the alkaline earth silicates or the alkaline earth silicate-containing substances such as cement are used in unbonded condition. The detection of CSH phases succeed z. B. in a known manner by means of Röntgendifffaktometrie.

Hydrate-free calcium silicates are components of cement clinker or of cement. In the context of the invention, the terms cement clinker (cement) and cement are often used as a synonym, it being correctly noted that the cement clinker is the fired component of the cement, which is responsible for the curing with the addition of water, and the carrier the basic silicates is.

Cement is made by grinding cement clinker with Ca sulfates. Cement clinker is produced by sintering at high temperatures of limestone, clay (marl) and quartz sand.

The clinker mainly consists of the following phases:

Tricalcium silicate (alite), short C3S (3 CaO * Si0 ₂ ) Dicalcium silicate (Belit), in short C2S (2 CaO * Si0 ₂ )

 Tricalcium aluminate, short C3A (3 CaO * Al2O3)

Tetracalcium short C4AF or C4 (A, F) (4 CaO * AI2O3 * Fe ₂ 0 ₃₎ and C2 (A, F).

The chemical reactions of the main clinker phase with the mixing water to calcium silicate hydrate can be simplified as follows:

2C3S + 6H - »· CSH + 3CH

Advertised:

Of particular interest according to the invention, the calcium silicate phases, because they cause the strong increase in pH when mixed with water. The aluminate phases as well as the CaO are less of interest because they do not react as strongly basic as the hydrate-free silicates. That Cement and clinker with a particularly high content of basic silicates (more C2S phases than C3S phases) are of great importance, since this basic silicate contributes significantly more to the increase in pH than CaO. It is the stronger base.

Preferably silicate "rich" cements and clinker with Si02 content greater than 10%, better> 15% even better> 20%.

However, the proportion of SiO 2 must not be too high and should be less than 50%, better less than 40%, better still less than 30%. Otherwise, the cement condenses too fast and is difficult to delay. Therefore, not only cement and clinker can serve as a source for the calcium silicate phases, but also slag sands, which are usually from about 30-45% CaO, 30 ^ 15% SiO 2, 5-15% A1203, 4-17% MgO , 0.5-1% S and traces of other elements.

Due to the high proportion of SiO2, blastfurnace slag is very well suited, but above all due to the fact that blastfurnace slag is a latent hydraulic binder. Latent means that blastfurnace slag is relatively slow to react and does not set quickly. Since a setting of the hydraulic additive is not desirable, the blastfurnace slag is very well suited. But it is much more expensive than cement / cement clinker.

 Due to the cost of using cement, Portland cement,

White cement or corresponding Komposit cements preferred.

In the broadest version can be used as basic silicates alkali silicates (Li, Na, K water glass, silica sols) and / or the hydrate-free alkali metal silicates (solid

Water glass) are used.

The basic silicate preferably comprises a hydrate-free Erdalakalisilikat, preferably calcium silicate (tricalcium silicate (Alit, 3 CaO * SiO 2),

Dicalcium silicate (Belit, 2 CaO * SiO 2). This is especially preferred

Alkaline earth silicate entirely of calcium silicate.

The basic silicate also preferably comprises an alkali silicate, especially water glass.

In preferred embodiments, the basic silicate comprises both alkaline earth and alkali silicate.

The content of basic silicate in preferred embodiments is at most 6% by weight, preferably at least 0.01% by weight, more preferably between 0.01 and 4% by weight, more preferably between 0.01% by weight and 2% by weight, more preferably between 0.01 and 1% by weight, more particularly between 0.05% by weight and 0.5% by weight, based on the total weight of the composition. The retarding or silicification of the basic silicate retarding

In preferred embodiments, substance is a water-soluble carbohydrate, which is preferably selected from saccharides, in particular mono-, di- and oligosaccharides, especially from sugars, amino sugars and deoxysugars. Monosaccharides and disaccharides as well as table sugars (sucrose) and / or glucosamine are particularly preferred. Furthermore, hydroxycarboxylic acids such as, in particular, sugar acids and their salts and derivatives can be used. Polysaccharides such as starch and other substances used as thickeners in the prior art are less suitable as retarding agents because of their poor solubility or

not suitable.

Preferred embodiments of the invention have a content of at most 1.0% by weight, preferably at least 0.001% by weight, more preferably between 0.005% by weight and 0.5% by weight, even more preferably between 0.005% by weight and 0.1 Wt.% And most preferably between 0.01 wt.% And 0.08 wt.% Of at least one water-soluble carbohydrate, based on the total weight of

Composition.

Preferred embodiments of the invention have a content of at least one organic binder between 1% by weight and 40% by weight, preferably between 2% by weight and 30% by weight, particularly preferably between 2.5% by weight and 25% by weight, each calculated as a solid.

It is preferred that compositions according to the invention have a content of at least one filler and / or pigment between 10% by weight and 90% by weight, preferably between 20% by weight and 85% by weight, particularly preferably between 25% by weight and 80% by weight. exhibit.

The water content of the compositions is preferably between 5% by weight and 50% by weight.

The at least one organic binder is preferably selected from the group consisting of homopolymers, copolymers or terpolymers of acrylic acid and / or methacrylic acid, itaconic acid and acid esters such as ethyl acrylate,

butyl acrylate; Styrene, substituted or unsubstituted vinyl chloride, vinyl acetate, vinyl propionate, ethylene, butadiene, versatate, acrylamides and acrylonitrile;

water-dilutable alkyd polymers, combinations of (meth) acrylic / alkyd polymers, polyvinyl alcohol and mixtures thereof, preference being given to homopolymers or copolymers of acrylic acid and / or methacrylic acid.

Preference is generally given to aqueous polymer dispersions which are sufficiently stable to hydrolysis.

The at least one filler or pigment is preferably selected from the group consisting of pyrogenically precipitated silica, precipitated silica, silicon-aluminum mixed oxides, alkaline earth carbonates such as calcium carbonate, silica, silicates, e.g. Aluminosilicates, sulfates, e.g. Barium sulfates, titanium dioxide, colored pigments, e.g.

Iron oxides, bismuth vanadates or mixtures thereof, with titanium dioxide, silicates and carbonates being preferred. Preferably, compositions of the invention have a content of at least one additive such as a rheology additive, a defoamer, a hydrophobing agent, a wax or wax preparation, a stabilizer, fibers, a film-forming aid, and a dispersing and wetting agent. The compositions according to the invention can be used to advantage to realize a plaster, a paint, in particular an emulsion paint, a decorative finish coating or the like.

Embodiment 1: Emulsion paint:

Water 28 parts by weight

Aqueous polymer dispersion (about 50% solids content) 30 parts by weight of fillers and pigments 37 parts by weight of basic silicates 0.5 part by weight of sugar 0.05 part by weight

Additives (in particular rheology additives, fly-dabbing agents, defoamers,

Film-forming aids, fibers, dispersants, etc.) 5 parts by weight

The pH of this dye batch was 11.6; even after 16 weeks at 11.7.

Embodiment 2: Dispersion Silicate Paint:

Water 31 parts by weight

Aqueous polymer dispersion (about 50% solids content) 9 parts by weight

Fillers and pigments 52 parts by weight Basic silicates 4 parts by weight Sugar 0.08 parts by weight of additives (in particular rheology additives, fly-dabbing agents, defoamers,

Film-forming aids, fibers, dispersants, etc.) 3.5 parts by weight

The pH of this dye batch was 11.2; after 16 weeks even at 11.3. Embodiment 3: Dispersion Silicate Paint:

Water 33 parts by weight

Aqueous polymer dispersion (about 50% solids content) 8 parts by weight of fillers and pigments 54 parts by weight of basic silicates 1, 5 parts by weight of sugar 0.05 part by weight Additives (in particular rheology additives, water repellents, defoamers,

 Film-forming aids, fibers, dispersants, etc.) 4 parts by weight

The pH of this dye batch was 11.1; after 16 weeks still at 11.0.

The rheological properties (viscosity) remained virtually unchanged during this period. It could be detected sensory no microbial infestation. The emulsion paint proved to be storage stable.

Comparative tests:

On fiber cement boards, a commercial cementitious reinforcing compound was applied. After drying under normal conditions for 24 hours, half of the specimens were also treated with a commercially available primer. After a further 24 hours, the color coats of working examples 1, 2 and 3 as well as a commercially available dispersion silicate paint and an emulsion paint were applied in a reproducible manner to all sample bodies. Previously, the pH of the surfaces of the reinforcing layer was still using

 Indicator paper determined. The pH was about 11 in all cases.

 After 48 hours later, the color coatings of the specimen with respect to staining or. Subjectively assessed the homogeneity surface, where "5" stands for an impeccable, very homogeneous appearance without staining and "1" for clearly visible staining and

 inhomogeneous appearance stands.

The coating compositions according to the invention combine the advantages of silicate coatings or dispersion silicate coatings with those of pure dispersion coatings, without having the disadvantages of the respective other genus.

Thus, like the silicate coatings, the coating compositions according to the invention are resistant to soiling and fouling and also solidify the substrate by the slow silicification.

Claims

Patent claims 1. silicate coating, comprising at least one basic silicate, at least one filler and / or pigment, at least one water-soluble carbohydrate, water to adjust a liquid or pasty consistency, optionally at least one organic binder and optionally conventional additives. 2. Composition according to claim 1,  characterized in that the basic silicate comprises an alkaline earth silicate, preferably calcium silicate. 3. Composition according to claim 1 or 2, characterized in that the alkaline earth silicate is formed by a cement, in which preferably the Si0 ₂ content greater than 10%, better> 15%, even better> 20%, and preferably below 50%, better below 40%, even better below 30%. 4. Composition according to one of claims 1 to 3,  characterized in that the basic silicate is an alkali silicate,  preferably comprises water glass. 5. Composition according to one of claims 1 to 4 characterized in that the content of basic silicate at most 6 wt.%, Preferably at least 0.01 wt.%, More preferably between 0.01 and 4 wt.%, Even more preferably between 0.01 wt.% And 2 wt. %, more preferably between 0.01 and 1% by weight, more particularly between 0.05% by weight and 0.5% by weight, based on the total weight of the composition. 6. Composition according to one of claims 1 to 5,  characterized in that the water-soluble carbohydrate is selected from saccharides such as especially mono-, di- and oligosaccharides, especially from sugars, amino sugars and deoxy sugars, more preferably from mono- and disaccharides and table sugar (sucrose) and / or glucosamine; from hydroxycarboxylic acids such as in particular sugar acids and their salts and derivatives  7. Composition according to claim 6  characterized in that the carbohydrate comprises table sugar and / or glucosamine. 8. Composition according to one of the preceding claims,  characterized by a content of at most 1.0% by weight, preferably at least 0.001% by weight, more preferably between 0.005% by weight and 0.5% by weight, even more preferably between 0.005% by weight and 0.1% by weight. and most preferably between 0.01% by weight and 0.08% by weight of water-soluble  Carbohydrate, based on the total weight of the composition. 9. Composition according to one of the preceding claims,  characterized by a content of at least one organic  Binder between 1% by weight and 40% by weight, preferably between 2% by weight and 30% by weight, particularly preferably between 2.5% by weight and 25% by weight, calculated in each case as a solid. 10. Composition according to one of the preceding claims, characterized by a content of at least one filler and / or pigment between 10% by weight and 90% by weight, preferably between 20% by weight and 85% by weight, particularly preferably between 25% by weight and 80% by weight. 11. Composition according to one of the preceding claims,  characterized by a water content between 5% by weight and 50% by weight. 12. Composition according to one of the preceding claims,  characterized by a content of at least one organic binder selected from the group consisting of homopolymers, copolymers or terpolymers of acrylic acid and / or methacrylic acid, itaconic acid and acid esters such as ethyl acrylate, butyl acrylate; Styrene, substituted or unsubstituted  Vinyl chloride, vinyl acetate, vinyl propionate, ethylene, butadiene, versatate,  Acrylamides and acrylonitrile; water-dilutable alkyd polymers,  Combinations of (meth) acrylic / alkyd polymers, polyvinyl alcohol and mixtures thereof, wherein homopolymers or copolymers of acrylic acid and / or methacrylic acid are preferred. 13. Composition according to one of the preceding claims,  characterized by a content of at least one filler or pigment selected from the group consisting of fumed silica, precipitated  Silica, silicon-aluminum mixed oxides, alkaline earth carbonates such as  Calcium carbonate, silica, silicates, e.g. Aluminosilicates, sulfates, e.g. Barium sulfates, titanium dioxide, colored pigments, e.g. Iron oxides, bismuth vanadates or mixtures thereof, wherein titanium dioxide, silicates and carbonates are preferred. 14. Composition according to one of the preceding claims,  characterized by a content of at least one additive such as  For example, a rheology additive, a defoamer, a  Water repellents, fibers, a film forming aid and a Dispersant. Composition according to any one of the preceding claims, characterized in that the composition is a plaster, a paint, in particular an emulsion paint, a decorative finish coating or the like.