NO303627B1 - Concrete stone coated with copolymer film, as well as process for making the concrete stone - Google Patents

Description

The invention relates to a concrete stone which is coated on at least one of the surfaces with a film of a copolymer of a) 65 - 100% by weight acrylic ester of Cx to C8 alkanols, methacrylic ester of C1 to C8 alkanols and/or vinyl aromatic monomers and

b) 0-35% by weight additional copolymerizable monomers,

with a glass temperature from -25 to +30°C, characterized by that

the film contains 0.5 - 10% by weight, calculated on the copolymer, of a compound of the general formula I

where R<1> and R<2> mean hydrogen or C4- to C24-alkyl and are not hydrogen at the same time, and where X and Y can be alkali metal ions or ammonium ions.

Concrete tiles, especially concrete roof tiles, are produced from mortars whose consistency enables the final design. The shape of the roof tiles is also preserved during the curing process, which mostly takes place at temperatures between 40 and 100°C. Concrete roof tiles are prone to lime efflorescence; these arise from a reaction between calcium hydroxide on the surface of the roof tile and carbon dioxide from the air. Calcium hydroxide can occur on the roof tile's surface during curing, but also under the influence of the weather. The result is stained, unsightly ceilings.

Polymer dispersions are used as layering material (see DE-A 2 164 256). However, the results obtained with the previous copolymer layer were not as desired. The stones were also heavily soiled.

DE-A 3 901 073 describes a concrete roof tile which is coated with a copolymer, which in polymerized form contains an organic tin compound. In this patent, the emulsifier I is not mentioned.

From the German patent application P 4 003 909.9 and DE-A 3 827 975, methods for preventing blooming occurrences on mineral substrates are known, using copolymers with a glass transition temperature between -25 and +30°C. However, the method requires the addition of special substances, namely aromatic ketones, and as a further process step, irradiation of the coating with ultraviolet light.

According to this, the task was to find a concrete stone that has been simply applied with a layer that practically does not show efflorescence and which, especially at higher temperatures, only shows a small degree of soiling. The layer must also unfold its effect as quickly as possible.

It was now found that the initially defined concrete block fulfills the aforementioned requirements.

Furthermore, a method for producing such a concrete block was found. Reference is made in this context to requirement 5.

Preferred embodiments of the invention appear from the subclaims.

The copolymers consist of a) 65 - 100, preferably 80 - 100, and especially 90 - 99% by weight, calculated on the copolymer, acrylic ester of Cx to C8 alkanols, methacrylic ester of Cx to C8 alkanols and/or vinyl aromatic monomers. Preferably, at least two monomers are used. The alkanols of the acrylic and methacrylic esters can be linear, branched or cyclic. These are usually methanol, ethanol, propanol, n-, iso- and t-butanol, n-pentanol, n-hexanol, ethylhexanol, n-octanol, cyclohexanol and preferably methanol, n-butanol and ethylhexanol.

Vinylaromatic monomers with usually up to 20 C atoms are generally styrenes, which are substituted on the nucleus with Cx - C4 alkyl groups, chlorine or bromine, such as α-methylstyrene, para-methylstyrene, para-chlorostyrene or para-bromostyrene, and especially styrene itself.

Other monomers b), which can be copolymerized with the aforementioned monomers, are used in amounts of up to 35% by weight, preferably 20% by weight, especially 1-10% by weight, based on the copolymer. It can be, for example, acrylonitrile, methacrylonitrile, α-olefins, such as ethylene, propene or iso-butene, dienes, such as butadiene and isoprene, vinyl chloride, vinylidene chloride, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, amides of these acids . Acrylic acid, methacrylic acid, amides thereof, acrylonitrile and methacrylonitrile are preferred. In many cases, good results are achieved with copolymers that do not contain any monomers b.

It is essential according to the invention that the copolymer exhibits a glass transition temperature of from -25 to +30°C, especially from

-12 to +22°C.

The glass temperature can be determined according to common methods, for example by measuring the E modulus in creep tests as a function of temperature, or with differential thermoanalysis (DTA) (see in this connection A. Zosel, Farbe und Lack 82

(1976), 125-134).

Typical combinations of monomers a with glass transition temperatures that are in the range to be achieved according to the invention are e.g. (in % by weight):

65% 2-ethylhexyl acrylate, 35% styrene,

55% 2-ethylhexyl acrylate, 45% styrene,

60% 2-ethylhexyl acrylate, 20% methyl methacrylate,

2 0% styrene,

55% 2-ethylhexyl acrylate, 35% butyl methacrylate,

10% styrene,

25% butyl acrylate, 25% 2-ethylhexyl acrylate, 50% styrene, 60% butyl acrylate, 40% styrene,

50% butyl acrylate, 50% styrene,

30% butyl acrylate, 30% 2-ethylhexyl acrylate,

20% styrene, 20% methyl methacrylate,

35% butyl acrylate, 30% methyl methacrylate,

35% butyl methacrylate.

When additional monomers b are incorporated, the glass transition temperatures of the copolymers are likewise affected. Therefore, there may need to be an adjustment of the quantity ratios stated above for the monomers a.

The compounds I are preferably used in amounts of 0.5-4, especially 0.5-3 bg, especially 1-2% by weight, calculated on the copolymer.

In the formula I, R<1> and R<2> preferably mean linear or branched alkyl residues with 6-18 C atoms or hydrogen, and especially with 6, 12 and 16 C atoms, R<1> and R<2> not both at the same time are hydrogen. X and Y are preferably sodium, potassium or ammonium ions, and especially sodium. Particularly preferred are X and Y sodium, R<1> a branched alkyl radical with 12 C atoms and R<2> hydrogen or R<1>. In the technique, mixtures are often used which show a proportion of 50 - 90% by weight of the monoalkylated product, for example Dowfax' 2A1 (trademark of the Dow Chemical Company).

These compounds are generally known as emulsifiers, for example from US-A 4 269 74 9, and can be obtained commercially.

The emulsifier I is preferably added to the copolymer during its preparation. However, it can also be added in whole or in part to the copolymer after it has been polymerised. The copolymer can be prepared in the usual manner by radical copolymerization of the monomers a and b in an aqueous emulsion. Batch processes or batch processes can be used, where the initiator and/or monomers that are possibly emulsified in water can be added during the polymerization, either in portions or continuously (see, for example, Encyclopedia of Polymer Science and Engineering, vol. 6 (1986) 1-52). The resulting aqueous polymer dispersion usually has a copolymer concentration of 40 - 60% by weight. As an emulsifier, 0.5 - 4, especially 0.5 - 3, and especially 1-2% by weight of compound 1, calculated on the copolymer, is preferred. Optionally, common emulsifiers can also be used, such as anionic and/or non-ionic emulsifiers, for example sodium dialkyl sulfosuccinates, sodium salts of sulfated oils, sodium salts of alkyl sulfonic acids, sodium, potassium and ammonium alkyl sulfates, alkali salts of sulfonic acids, oxalkylated C12 to C24 fatty alcohols and oxalkylated alkylphenols, as well as oxytylated fatty acids, fatty alcohols and/or fatty amides, oxytylated alkylphenols, further sodium salts of fatty acids, such as sodium stearate and sodium oleate, or fatty alcohol sulfates and fatty alcohol ethoxylates.

The aqueous dispersions of the copolymers form shiny, clear and tough-flexible films at room temperature which take up only a little water; after 24 hours of water storage less than 10, mostly less than 5% is measured. They usually do not contain plasticizers and film-forming agents.

For the production of coating compounds, inorganic fillers and color pigments are incorporated in the known manner into the aqueous dispersions of the copolymers, and the desired viscosity is adjusted with water. As inorganic fillers, e.g. in consideration: Chalk, quartz flour and/or heavy spar. The amounts of pigments and/or fillers are usually between 50 and 450 parts by weight, calculated for the copolymer as 100 parts by weight.

When it comes to concrete blocks, it concerns e.g. about shaped designs of concrete and aerated concrete, e.g. boards, pipes and especially roof tiles, as the layers can also be applied to uncured products of this type, especially concrete roof tiles, so-called "green roof tiles". The concrete roof tile is produced in the usual way from ready-mixed concrete by extrusion. It already thereby takes its final form. Layer compound is applied in the usual way by spraying, troweling, ironing or pouring, with application quantities of 50 - 400, especially 100 - 250 g/m<2>, measured in a dry state, usually being used. Of particular interest is the application of such layers on uncured, so-called "green" concrete roof tiles. The drying of the layer or possible layers can be carried out in the usual way, possibly at room temperature or a slightly elevated temperature. For this purpose, the coated stone is usually brought into a so-called chamber. There, the concrete is hardened during a hardening process that lasts 6 - 12 hours at temperatures from 40 to 65°C, and the copolymer in the coating mass forms

a movie.

After this process, the roof tile is preferably sprayed with the coating compound a second time. The drying takes place in a tunnel oven at ambient air temperatures of approximately 100°C. The tunnel oven and subsequent cooling section are dimensioned so that complete film formation takes place.

In this way, the stones are well protected against lime efflorescence. Furthermore, the surface of the layers does not become sticky at elevated temperatures, so that the stones do not absorb dirt.

The parts and percentages given in the following examples are, unless otherwise stated, parts by weight and percentages by weight.

Compar<g>nin<q>six example IV

An emulsion of 45 parts by weight of styrene (S), 55 parts by weight of 2-ethylhexyl acrylate (EHA), 2.5 parts by weight of acrylic acid (AS), 105 parts by weight of water, and 1.5 parts by weight of the sodium salt of a sulfuric acid half-ester of an isonylphenol ethoxylate with an average number of 25 ethylene oxide units and 0.5 parts by weight of an isononylphenol ethoxylate with an average number of 25 ethylene oxide units as emulsifiers, were polymerized with the aid of 0.5 parts by weight of sodium peroxydisulfate, by the emulsion feed method at 90°C.

Example 1

The same method as in comparative example IV was used, however, with the difference that the emulsifier was not the mixture from comparative example IV, but 1.5 parts by weight of a technical mixture of approx. 80% by weight of a compound I, where X and Y are sodium, R<1> is a branched alkyl radical with 12 C atoms and R<2> is hydrogen, and approx. 20% by weight of a compound I, where X and Y are sodium and R<1> and R<2> branched alkyl residues with 12 C atoms. A copolymer dispersion was produced with a content of copolymers of 49% by weight, measured in the usual way by evaporation of the water.

As a measure of fouling propensity, the separation energy measurement for a sample of a polymer film dried at room temperature for 2 weeks was measured according to A. Zosel, J. Adhesion

(1989) 30 135-139 at 70°C used. The results in Table 1 clearly show the superiority of the emulsifier according to the present claim. All examples and comparison experiments were tested in the same way.

Comparison example 2V

An emulsion of 35 parts by weight of n-butyl acrylate (BA), 35 parts by weight of 2-butyl methacrylate (BMA), 30 parts by weight of methyl methacrylate (MMA), 2.5 parts by weight of acrylic acid, 105 parts by weight of water, and 1.5 parts by weight of the sodium salt of a Sulfuric acid half-esters of an iso-nonylphenol ethoxylate with an average number of 25 ethylene oxide units and 0.5 parts by weight of an iso-nonyl phenol ethoxylate with an average number of 25 ethylene oxide units as emulsifiers were polymerized with the aid of 0.5 parts by weight of sodium peroxydisulfate, by emulsion addition - the method at 90°C.

Example 2

The same method as in comparative example 2V was used, however, with the difference that the mixture from comparative example 2V was not used as an emulsifier, but 1.5 parts by weight of a technical mixture of approx. 80% by weight of a compound I, where X and Y are sodium, R<1>a branched alkyl residue with 12 C atoms and R2 is hydrogen, and approx. 20% by weight of a compound I, where X and Y are sodium and R<1> and R2 are branched alkyl residues with 12 C atoms.

Comparison example 3V

An emulsion of 20 parts by weight of methyl methacrylate, 60 parts by weight of 2-ethylhexyl arylate, 20 parts by weight of styrene, 2.5 parts by weight of acrylic acid, 105 parts by weight of water, and 1.5 parts by weight of the sodium salt of a sulfuric acid half-ester of an isonylphenol ethoxylate having an average number of 25 ethylene oxide units and 0.5 parts by weight of isonylphenol ethoxylate with an average number of 25 ethylene oxide units as emulsifiers were polymerized with the aid of 0.5 parts by weight of sodium peroxydisulfate, by the emulsion feed method at 90°C.

Example 3

The same method as in comparative example 3V was used, however, with the difference that the mixture from comparative example 3V was not used as an emulsifier, but 1.5 parts by weight of a technical mixture of approx. 80% by weight of a compound I, where X and Y are sodium, R<1>a branched alkyl residue with 12 C atoms and R2 is hydrogen, and approx. 20% by weight of a compound I, where X and Y are sodium and R<1> and R2 are branched alkyl residues with 12 C atoms.

Comparative example 4V

An emulsion of 35 parts by weight of n-butyl methacrylate, 10 parts by weight of styrene and 55 parts by weight of 2-ethylhexyl acrylate, 2.5 parts by weight of acrylic acid, 105 parts by weight of water, and 1.5 parts by weight of the sodium salt of a sulfuric acid half-ester of an isonylphenol ethoxylate with an average number of 25 ethylene oxide units and 0.5 parts by weight of an isononylphenol ethoxylate with an average number of 25 ethylene oxide units as emulsifiers were polymerized with the aid of 0.5 parts by weight of sodium peroxydisulfate, by the emulsion feed method at 90°C.

Example 4

The same method as in comparative example 4V was used, however, with the difference that the mixture from comparative example 4V was not used as an emulsifier, but 1.5 parts by weight of a technical mixture of approx. 80% by weight of a compound I, where X and Y are sodium, R<1> is a branched alkyl radical with 12 C atoms and R<2> is hydrogen, and approx. 20% by weight of a compound I, where X and Y are sodium and R<1> and R2 are branched alkyl residues with 12 C atoms.

Claims (6)

1. Concrete brick that is coated on at least one of the surfaces with a film of a copolymer of a) 65 - 100% by weight acrylic esters of Cx- to C8-alkanols, methacrylic esters of C1- to C8-alkanols and/or vinyl aromatic monomers and b) 0-35% by weight further copolymerizable monomers, with a glass transition temperature from -25 to +30 °C, characterized in that the film contains 0.5 - 10% by weight, calculated on the copolymer, of a compound of the general formula I where R<1> and R<2> mean hydrogen or C4 to C24 alkyl, R<1> and R2 not being hydrogen at the same time, and X and Y can be alkali metal ions or ammonium ions. 2. Concrete brick according to claim 1, characterized in that R<1> and R2 mean linear or branched alkyl residues with 6-18 C atoms or hydrogen, as R<1> and R2 are not both hydrogen at the same time, and X and Y mean sodium, potassium or ammonium ions. 3. Concrete brick according to claim 1 or 2, characterized in that the film contains 0.5 - 4% by weight, calculated on the copolymer, of compound I. 4. Concrete brick according to claims 1-3, characterized in that the copolymer is prepared by emulsion polymerization using compound I. 5. Method for producing a concrete brick according to claims 1-4 by applying to at least one surface of a green concrete brick an aqueous formulation containing an aqueous dispersion of a copolymer of a) 65 - 100% by weight acrylic ester of C±- to C8 -alkanols, methacrylic esters of Cx- to C8-alkanols and/or vinyl aromatic monomers and b) 0-35% by weight further copolymerizable monomers, with a glass transition temperature from -25 to +30°C, characterized in that the aqueous formulation used contains 0, 5 - 10% by weight, calculated on the copolymer, of a compound of the general formula I where R<1> and R<2> mean hydrogen or C4- to C24-alkyl, since R<1> and R<2> are not hydrogen at the same time, and where X and Y can be alkali metal ions or ammonium ions. 6. Method according to claim 5, characterized by applying the formulation in such amounts to the concrete block that the total dry amount applied amounts to 50 - 400 g/m<2>.