EP3759178A1

EP3759178A1 - Storage-stable polymer-bonded coating compositions

Info

Publication number: EP3759178A1
Application number: EP19707327.3A
Authority: EP
Inventors: Michael Troll; Jack VAN LEUUWEN; Gerald Burgeth
Original assignee: Sto SE and Co KGaA
Current assignee: Sto SE and Co KGaA
Priority date: 2018-03-14
Filing date: 2019-02-19
Publication date: 2021-01-06
Also published as: US20190284399A1; WO2019174872A1

Abstract

The invention relates to a storage-stable composition for forming coatings on built structures and the like comprising at least one organic binder, at least one filler and/or pigment, water for establishing a pasty consistency of the composition, a buffer system comprising at least one basic silicate, at least one substance which retards condensation of the basic silicate and optionally customary additives.

Description

Storage stable polymer bound coating compositions

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The invention relates to storage-stable polymer-bound compositions for forming coatings on structures and the like, comprising at least one organic binder, at least one filler and / or pigment, water for adjusting a pasty consistency of the composition, a buffer system comprising at least one basic silicate, at least a substance which retards the condensation of the basic silicate, and optionally conventional additives.

Technical field of the invention

Compositions of the type according to the invention are hydrous, pasty

Mixtures for the formation of coatings on buildings. 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 eukaryotic 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 already known to preserve such compositions and to protect against microbial attack. The use of conventional preservatives is generally out of the question because they are increasingly subject to legal restrictions.

It has therefore already been proposed to provide storage-stable compositions of the type considered here without containing conventional preservatives by increasing the pH of the composition so that the microbial content of the composition is increased

Infestation is effectively prevented. The aim is a pH of at least 10, since at lower pH values of the microbial infestation can not be prevented with sufficient certainty. Thus, in the prior art, the pH increase by addition of

Water glass, for example, according to EP1297079 Al or EP 2905268 Al, the disclosures of which are hereby incorporated by reference into this specification.

It is not a trivial task to find a viable and economically viable pH enhancement system in such compositions.

Increasing the pH, for example, by adding lye, such as NaOH or KOH, is not enough. The pH then falls within a few days or weeks, so that the infestation protection subsides. You need a buffer with sufficient buffer capacity.

Water glass-containing coatings, as described in the documents EP 1297079 Al or EP 2905268 Al, basically include such suitable buffer systems. However, they have significant disadvantages in the application to critical

Substrates on. For critical substrates, especially absorbent, alkaline substrates, cementitious substrates in particular, it comes to a quick drying of the water glass-containing coating due to the

Acceleration of the silicification reaction due to the basicity of the

Underground. Upon contact of the waterglass with the basic substrate, it immediately reacts with the 'reactive' components of the substrate (Ca (OH) 2, basic silicates and / or (silicate) fillers with surface OH groups). 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). Fluation is the neutralization and hardening of alkaline substrates by applying a fluat, a salt of hexafluorosilicic acid (fluorosilicates).

When applying water glass-containing coatings to clean

polymer-bound old coatings also leads to adhesion problems, if the substrate is not pretreated accordingly. The silicification with the ground can not take place.

There is therefore a need for improved systems for sufficiently and permanently increasing the pH of compositions according to the invention. Such systems must provide sufficiently high pH levels in the compositions for sufficient periods of time. You have to go with the others

Components of the compositions to be compatible and may their

Not affect usability. They must comply with the legal requirements and should be as simple and inexpensive to procure and use.

Furthermore, it is an essential object of the invention, coatings

to provide the stain-free drying on critical substrates, without a pre-treatment of the substrate is necessary. These coating compositions should be as easy to process as comparable conventional dispersion silicate paints or dispersion paints.

definitions:

Under, calcareous in this application understood calcium oxide, hydroxide and / or - carbonate - containing.

The composition is considered to be stable in storage for the purposes of the invention if its pH does not change by more than 1 during storage under normal conditions for at least 30 days.

"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 (pKb <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 and / or ions: free oxide ions (O ² ), pKb = -15

Free hydroxide ions (OH), pKb = - 1.8

Orthosilicate groups or ions:

Si0 ₄ ⁴ pKb = 0

HSi0 ₄ ³ pKb = 1 or Si0 ₄ ³ - groups

H ₂ Si0 ₄ ² pKb = 2.2 or Si0 ₄ ² groups

H ₃ Si0 ₄ pKb = 4.3 or Si0 ₄ - groups

Metasilicate - groups or ions:

SiO ² pKb = 2.2 HSi0 ₃ pKb = 4,5 or Si0 ₃ - groups

Basic silicates tend to condensation reactions such as the formation of agglomerates or silicification.

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.

"Coating" thus includes the water-containing liquid or pasty

Composition before their application, as well as the solid, more or less dry coating that results from the application.

Detailed illustration of the invention

The invention provides coating compositions which, due to their high pH and high buffering capacity, permanently counteract the microbial attack and which do not have or greatly reduce the problem of staining or streaking when applied to critical substrates.

This is achieved by adding to the basic silicate-containing compositions the condensation reaction retarding substances. The

Delay of condensation is by addition of a water-soluble

Carbohydrate causes the not yet applied coating composition.

The invention therefore relates to coating compositions, especially

Dispersion coatings and emulsion paints, comprising at least one basic silicate, at least one filler and / or pigment, at least one substance which retards the condensation of the basic silicate, water for setting a pasty consistency, at least one organic binder and optionally conventional additives. The basic silicate according to the invention in preferred embodiments of the invention is a basic alkaline earth silicate, in particular calcium silicate, 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.

Also suitable are alkaline earth silicate, in particular calcium silicate-containing substances such as cement, cement clinker, granulated blastfurnace slag and / or hydraulic lime. Because of their availability, Portland cement and white cement are particularly preferred.

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.

In the aqueous composition, instead of the basic silicates, their reaction products with water, ie the corresponding weak acids, are present in the acid-base equilibrium according to their base strength.

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 setting and curing with the addition of water, and the carrier of the basic silicates. The clinker (Portland cement clinker) consists mainly of the following phases: Tricalcium silicate (alite), short mixed C3S (3 CaO * S1O2)

Dicalcium silicate (Belit), in short C2S (2 CaO * Si0 ₂ )

Tricalcium aluminate, short C3A (3 CaO * Al ₂ O ₃ )

Tetracalcium aluminate ferrite, short C4AF or C4 (A, F) (4 CaO * Al ₂ O ₃ * Fe ₂ O ₃ ) and C2 (A, F).

The chemical reactions of the main clinker phase with water too

Calcium silicate hydrate can be simplified as follows:

2C3S + 6H - »· CSH + 3CH

Specified: 2 (3 CaO * Si0 ₂ ) + 6 H ₂ O -> 3 CaO * 2 Si0 ₂ * 3 H ₂ 0 + 3 Ca ²⁺ + 6 OH

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. Preferred are silicate "rich" cements and clinker with SiO 2 content greater than 10%, better> 15% even better> 20%, such as Portland cement.

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, 30-45% 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 latently hydraulic binder. Latent means that blastfurnace slag is relatively slow to react and does not set quickly. Since the basic silicate is not used as a binder and setting this hydraulic additive is not desirable, the blast furnace slag is very well suited. But it is much more expensive than cement / cement clinker.

Due to the cost, the use of Portland cement, white cement or corresponding composite cements is 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. Waterglass (alkali silicate) -containing coating compositions have only a relatively short "open time" especially when applied to strongly basic (cement or lime-containing) substrates. The silicification, which is a condensation reaction, to the subsurface takes place very rapidly. It has been known for a very long time that water glass (alkali silicates) on cement (containing alkaline earth silicates) act as an accelerator and vice versa. The setting of the cement or the silicification of the water glass takes place in this combination immediately and quickly. That may also be the reason that

Water glass-containing coating compositions on cementitious

Silicify substrates immediately, ie immediately to the substrate in one Condensation reaction with the 'reactive' components of the substrate (Ca (OH) 2, other basic silicates and / or (silicate) fillers with surface OH groups) bind, and the "open time" is very short. The

Coating composition sets immediately, which is not always desirable in the case of a paint. The application is difficult. It comes u.a. to a "burning" of the paint and to a non-homogenous application of the paint.

There are places or areas that are more or less critical resp. are sucking. Therefore, staining occurs if the substrate does not penetrate

Pre-treatment (priming and / or fluating) is "homogenized".

Particularly problematic prove with regard to too fast setting such compositions containing both alkali and alkaline earth silicates. The combination of alkali and alkaline earth silicates is usually not practically possible. Cement- and waterglass-containing coating compositions already bind in the bucket, both the cement and the water glass.

The combination of alkali and alkaline earth silicates in aqueous paints is therefore not known. Such colors would set in the bucket. The

Use of alkaline earth silicates alone (ie of aqueous paints containing cement) is also not known. Again, the setting process of the cement would start immediately and thicken the composition in the pot.

This is a use of basic silicates as a buffer system in

inventive compositions in the way. This is true even though the amount of basic silicates needed for buffering is much lower than that required for a structural function of the silicate. Even at the low levels, which are sufficient as a buffer system, condensation or setting of the basic silicate would lead to a disruption of the consistency. The composition may not be solid, but too thick. The amounts of basic silicates used are low. A function as a binder is thus excluded. They act only as a pH-increasing additive and as a basic buffer. Preferably, the contents of the buffer system are such that they are suitable for

Adjustment and maintenance of a pH of at least 10%

Composition is sufficient for at least 30 days, preferably 60 days, more preferably 90 days, even more preferably 180 days, especially preferably 360 days and even more preferably 720 days.

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

The content of basic silicate in preferred embodiments is at most 2% by weight, preferably at least 0.01% by weight, more preferably between 0.01 and 1% by weight, most preferably between 0.01 and 0.5% by weight, based on the

Total weight of the composition.

The setting or silicification (condensation) of the basic silicate retarding substance is in preferred embodiments, a water-soluble carbohydrate, which is preferably selected from saccharides such as especially mono-, di- and oligosaccharides, especially from sugars, amino sugars and

Desoxyzuckem. Monosaccharides and disaccharides as well as table sugars (sucrose) and / or glucosamine are particularly preferred. Furthermore you can

Hydroxycarboxylic acids such as in particular sugar acids and their salts and derivatives can be used. Polysaccharides, such as starch, as well as other carbohydrates used as thickeners in the prior art are known for their poor solubility

Retarder less suitable or unsuitable.

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, 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 at least one water-soluble carbohydrate 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.

Furthermore, silicone resins and polysiloxanes can also be used as binders. 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, silicon dioxide, silicates, eg aluminosilicates, sulfates, eg barium sulfates, titanium dioxide, colored pigments, eg

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 water repellent, a wax or wax preparation, a stabilizer, fibers, a film-forming agent and a dispersing and wetting agent. The compositions of the invention can be used with advantage to a plaster, a color, in particular a dispersion paint, a decorative

Final coating or the like. To realize.

The compositions of the invention have a pH of at least 10.5, preferably at least 11, over at least 30 days, preferably at least 60 days, more preferably 90 days, even more preferably 180 days, especially preferably 360 days and even more preferably 720 days.

Embodiment 1: Emulsion paint:

Water 28 parts by weight

Aqueous polymer dispersion (about 50% solids content) 30 parts by weight

Fillers and pigments 37 parts by weight Basic silicates 0.5 parts by weight

Sugar 0.05 parts by weight Additives (in particular rheology additives, water repellents, 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 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, fly-dabbing agents, 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 compositions of the embodiments proved to be storage stable.

Claims

Patent claims

1. A storage-stable composition for forming coatings on structures and the like

comprising at least one organic binder, at least one filler and / or pigment, water to adjust a pasty consistency of the composition, a buffer system comprising at least one basic silicate, at least one substance which retards the condensation of the basic silicate, and optionally conventional additives.

The composition of claim 1, wherein the levels are such as to adjust and maintain a pH of at least 10 of the composition for at least 30 days, preferably 60 days, more preferably 90 days, even more preferably 180 days, especially preferably 360 days, and even more preferably 720 days.

3. Composition according to claim 1 or 2,

characterized in that the basic silicate comprises an alkaline earth silicate, preferably calcium silicate.

4. The composition according to any one of claims 1 to 3, wherein the

Alkaline earth silicate is present in the form of a cement, in which preferably the SiCk content is greater than 10 wt.%, More preferably> 15 wt.%, More preferably> 20 wt.%. is, and especially under 50 wt.%, More specifically under

40% by weight, more specifically below 30% by weight.

5. Composition according to one of claims 1 to 4,

characterized in that the basic silicate comprises an alkali silicate, preferably water glass.

6. Composition according to one of claims 1 to 5

characterized in that the content of basic silicate is at most 2% by weight, preferably at least 0.01% by weight, more preferably between 0.01 and 1% by weight, most preferably between 0.01 and 0.5% by weight, based on the total weight of the composition.

7. Composition according to one of claims 1 to 6,

characterized in that the condensation-retarding substance is a water-soluble carbohydrate, which is preferably selected from saccharides such as in particular mono-, di- and oligosaccharides, especially from sugars, amino sugars and deoxysugars, more preferably from mono- and disaccharides and table sugar (sucrose ) and / or glucosamine; and from hydroxycarboxylic acids such as in particular sugar acids and their salts and derivatives.

8. Composition according to claim 7

characterized in that the carbohydrate comprises table sugar and / or glucosamine.

9. 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

coagulation-delaying substance, based on the total weight of the composition.

10. Composition according to one of the preceding claims,

characterized by a pH of at least 10.5, preferably at least 11, over at least 30 days, preferably at least 60 days, preferably 60 days, more preferably 90 days, even more preferably 180 days, especially preferably 360 days and even more preferably 720 days.

11. Composition according to one of the preceding claims,

characterized by a content of at least one organic

Binder between 1 wt.% And 40 wt.%, Preferably between 2 wt.% And 30 wt.%, Particularly preferably between 2.5 wt.% And 25

% By weight, calculated in each case as a solid.

12. 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, more preferably between 25% by weight and 80% by weight.

13. Composition according to one of the preceding claims,

characterized by a water content between 5% by weight and 50% by weight.

14. 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-reducible 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.

15. 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 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, wherein titanium dioxide,

Silicates and carbonates are preferred.

16. Composition according to one of the preceding claims,

characterized by a content of at least one additive such as a rheology additive, a defoamer, a

Water repellents, fibers, a film-forming assistant and a dispersant.

17. A composition according to any one of the preceding claims, characterized

characterized in that the composition is a plaster, a paint,

in particular, an emulsion paint, a decorative finish coating or the like.