DD244350A1 - COATING MATERIALS BASED ON ALKYL SILICATES - Google Patents

Abstract

Coating materials based on alkyl silicates for the achievement of hard coatings can be obtained by simple mixing of ethyl polysilicate with glycols and / or polyhydric alcohols and monohydric alcohols and / or ether alcohols having at least 4 C atoms in the molecule and preferably zinc chloride and sulfuric acid at room temperature. The coating materials contain pigments and extenders and z. As zinc dust, are stable in storage and have a flash point over 294 K. They are suitable for the corrosion protection of steel surfaces as well as for the coating and hardening of molds.

Description

Field of application of the invention

The invention relates to coating materials based on alkyl silicates for the achievement of hard coatings on various substrates.

Characteristic of the known technical solutions

Coating materials based on alkyl silicates are known in which the binder is present in the form of a partially hydrolysed polysilicic acid ester or in totally hydrolyzed form as a solution or dispersion of polysilicic acid in a solvent. The prehydrolysis of the polysilicic acid ester is carried out under the influence of H ⁺ ions and regulated to any desired degree of hydrolysis by the use of appropriate amounts of water and acids. In the drying of prehydrolysates with a suitable degree of hydrolysis occurs under the influence of atmospheric moisture further hydrolysis and condensation to polysilicic acid.

Also known from the brochures "Dynasil H400 and H450" (Dynamit Nobel AG), "Silbond, Alkyl Silicates" (Stauffer Chemical Europe SA), "Ethylsilicate NT120" (VEB Chemiewerk Nünchritz) and "Silester ZNA" (Monsanto Germany such paints If the partial or total hydrolysis of technically available ethyl polysilicate is carried out, then binder solutions are obtained which have a flashpoint below 294K even at a low degree of hydrolysis as a result of the released ethanol Solvents, these products fall into the hazard class A1 or B1 and are therefore undesirable or unusable for many applications for safety reasons.In combination with zinc dust or other pigments and extender the described Vorhydrolysate except the low flash point, the other disadvantages that insufficient Hy drolyse degree no or only insufficient hard drying of coatings made from such mixtures. With technically satisfactory drying properties, however, the mixtures with zinc dust only pot lives of hours to days and must therefore be used as two-component paints with the known disadvantages.

It is also known, from US-PS 3917848 and US-PS 3932 339, a reaction of Ethylpolysilikates at temperatures around 370 to 410 K with higher alcohols and / or ether alcohols and ethylene glycol and / or other glycols and / or polyhydric alcohols with distilling off the resulting ethanol. This produces binders that have a flashpoint above 294K. They give storage-stable mixtures with zinc dust. The latter dry in the air to hard coatings without prior prehydrolysis of the binder. Disadvantageous is the apparatus and energy expenditure for carrying out the transesterifications.

It is also known (DD-PS 132272), Ethylpolysilikat in a two-stage reaction with ether alcohols and small amounts of water in the presence of zinc chloride at temperatures around 332 K to react, with zinc dust-drying binder are obtained. Also disadvantageous here are the production costs and the increased production temperature of the binder. Systems are also known (DE-OS 2205387, US-PS 3660119, US-PS 3653930), which consist of ethyl polysilicate, solvents, alkaline catalysts and zinc dust, air-dry, but are stable on storage only with absolute exclusion of moisture. A disadvantage of these products is the need for absolute exclusion of moisture before processing, which is difficult to achieve, especially when removing part quantities from containers.

Object of the invention

The aim of the invention is to simplify the preparation of storage-stable and hard coatings of resulting coating materials having a flash point above 294 K on the basis of technical ethyl polysilicate.

Explanation of the essence of the invention

The object of the invention is to develop coating materials which have a flash point above 294K, are stable on storage and give coatings that are hard to dry in air, while avoiding apparatus and energy-consuming process stages based on industrial ethyl polysilicate.

According to the invention the object is achieved by reacting a obtained at room temperature mixture of glycols and / or polyhydric alcohols and monohydric alcohols and / or ether alcohols having at least 4 carbon atoms halides of elements of the 2nd or 3rd group of the periodic table, preferably zinc chloride and or aluminum chloride, and an acid, preferably sulfuric acid, used with ethyl polysilicate.

It is particularly advantageous to use such a mixture which is obtained from 1 part of ethyl polysilicate 40 with 0.05 to 0.5 parts, preferably 0.1 to 0.4 parts, of ethylene glycol and / or other glycol and / or polyhydric alcohol, 0, 5 to 3 parts, preferably 1 to 1.8 parts, of a higher alcohol having at least 4 C atoms or ether alcohol, 0.005 to 0.1 parts of a halide of the 2nd or 3rd group of the periodic table, preferably 0.01 to 0.05 parts of zinc chloride and / or aluminum chloride and 0.0001 to 0.002 parts of acid, preferably sulfuric acid, and the mixture is left at room temperature.

The mixture has a flash point above 294K after 24 hours (TGL 14301/2).

A storage-stable paint is obtained from a binder thus prepared by mixing 1 part of binder with 1 to 8 parts of pigments and extenders and preferably 2 to 5 parts of zinc dust. The preparation of the mixture is carried out by conventional methods of paint production, e.g. with the help of dissolvers.

The zinc dust binder mixture also has a flash point above 294K and gives hard-coated coatings of high anti-corrosion value on iron base around 24 hours.

The above-mentioned compound group of glycols and polyhydric alcohols, in addition to the already mentioned ethylene glycol z. B. by the following individual compounds: 1,2-propylene glycol, 1,3-butylene glycol, 1,3-

Propandiol, glycerol. ,

The linking group of the higher monohydric alcohols having at least 4 C atoms and ether alcohols includes, for example, B .: butanol, hexanol, 2-ethylhexanol, ethylene glycol monomethyl ether (methyl glycol, methyl cellosolve), ethylene glycol monobutyl ether (butyl glycol, butyl cellosolve).

While the preferred form of application for the corrosion protection of iron surfaces, the coating materials of the invention are mixtures of the binder described with zinc dust, it is quite possible to prepare mixtures with other materials, such as extenders and / or pigments and / or anti-settling agents, without the essential features of the invention limit. Suitable as additives are z. Talc, kaolin, iron oxide red, titanium dioxide, chromium oxide, finely divided silica and montmorillonites.

Exemplary embodiments (details in parts by weight)

example 1

Man mixed 2 parts zinc chloride

0.075 parts of sulfuric acid

17.4 parts of ethylene glycol

156.6 parts of ethylene glycol

93 parts ethyl polysilicate NT40

and leaves the mixture for 24 hours at room temperature. It has a flashpoint of 298.5 K, which has not changed after 14 days.

1 part of the above binder solution is mixed with 3.1 parts of zinc dust. This paint dries on iron substrate in 24 hours to a hard coating and has as a liquid paint a shelf life of more than 3 months. Coatings of 50μ.ηη thickness on steel sheet withstand more than 1000 hours in the salt spray test with the degree of corrosion AO according to TGL18785. · "

Example 2

The 2 parts of zinc chloride from Example 1 are replaced by 2 parts of aluminum chloride.

The binder and the mixture with zinc dust have similar properties as in Example 1.

Example3 ... · '.

Replacing the 17.5 parts of ethylene glycol from Example 1 with 22 parts of 1,3-propanediol.

The binder and the mixture with zinc dust have the same properties as in Example 1.

Example 4

Instead of zinc dust, the binder solutions mentioned in Examples 1 to 3 contain alumina, zinc oxide, silicon carbide, aluminum silicate, zirconium silicate or magnesium silicate. They are storage-stable coating materials, give hard-drying layers and are used for the hardening or coating of casting molds.

Claims (4)

1. coating materials based on alkyl silicates and pigments, extender and zinc dust, characterized in that it contains as a binder at room temperature a mixture of glycols and / or polyhydric alcohols and monohydric alcohols and / or ether alcohols having at least 4 carbon atoms, halides of Elements of the 2nd or 3. Group of the periodic system, preferably zinc chloride and / or aluminum chloride, and an acid, preferably sulfuric acid, containing ethyl polysilicate. 2. Coating materials according to item 1, characterized in that they contain as binder a mixture obtained at room temperature of 1 part of ethyl polysilicate, 0.05 to 0.5 parts of glycols and / or polyhydric alcohols, preferably 0.1 to 0.4 parts of ethylene glycol, 0.5 to 3 parts, preferably 1 to 1.8 parts, higher monohydric alcohols and / or ether alcohols with at least 4 C atoms, 0.005 to 0.1 parts of halides of elements of the 2nd or 3rd group of the periodic table, preferably 0.01 to 0.05 parts of zinc chloride and / or aluminum chloride, and 0.0001 to 0.002 parts of acid, preferably Sulfuric acid.