DD256055A3 - METHOD FOR PRODUCING A THICKENER COMPLEX FOR SILICATIVE COATING AGENTS - Google Patents

Abstract

The process of producing a thickener complex for aqueous silicate coatings that can be applied to various substrates provides a durable and highly effective inorganic thixotropic substance. For this purpose, a dilute aqueous alkali metal silicate solution with oxides, hydroxides or carbonates of metals of the 2nd main or subgroup is added and initially by addition of acids to a p H value of 7 to 2 and then by addition of alkali hydroxide to a p H value set from 8 to 12. The preparation of the thickener complex may optionally be carried out as a precursor or together with the final product. Can be used, the thickener z. As with paints, adhesives and Impraegniermitteln.

Description

Field of application of the invention

The invention relates to a process for the preparation of a thickener complex for aqueous silicate coating compositions, for the protective, decorative and modifying surface treatment of various substrates, such as e.g. Metals, mineral materials and substrates made of fibrous materials.

Characteristic of the known technical solutions

It is known to prepare aqueous coating compositions based on alkali metal silicates for various fields of application. Due to the low viscosity of the aqueous binder phase incorporated pigments and other substances usually settle quickly, are often difficult to stir, and the coating agents tend to run on vertical surfaces. It is also known to provide aqueous paints with additives which have a thickening effect, impart intrinsic viscosity to the paints, prevent or reduce the settling of pigments and extenders, and improve the application of the paints to a substrate, especially on vertical surfaces. As additives of this type for aqueous systems z. B. known substituted celluloses, alginates and carboxyl.- and hydroxyl-containing polymers and copolymers. Some of these substances, which in other aqueous systems, eg. As latexes, perform well in paints based on alkali silicates are not or poorly soluble or redistributable, others again lead to considerable foaming. In any case, however, the said organic substances in the later coating represent non-film constituents within the inorganic, predominantly silicate, matrix. If such coatings are subjected to thermal stress in use, carbonization of the organic substance may occur and the coatings may discolor.

It is also known to use finely dispersed silicas as thickeners in aqueous paint systems. However, such products do not develop a permanent thickening effect in paints based on alkali silicates because they are dissolved or solubilized in the alkaline medium.

Object of the invention

The invention aims to improve the substitutability and durability of thickeners.

Explanation of the essence of the invention

The invention has for its object to provide a method with which a thickener complex for aqueous silicate coating compositions can be produced, which is stable and causes no manufacturing and application defects in the coating compositions.

According to the invention the object is achieved by adding a dilute aqueous alkali metal silicate solution with oxides and / or hydroxides and / or carbonates of metals of the 2nd main or subgroup and with vigorous stirring with the addition of phosphoric acid, sulfuric acid or boric acid to a pH of 7 to 2 and subsequently adjusted to a pH of 8 to 12 by the addition of alkali hydroxide. The addition of the acid to the pH value of 5 to 3 and the addition of the alkali hydroxide to the pH value of 9 to 11 are particularly advantageous for the process procedure.

In the mentioned oxides, hydroxides and carbonates of metals of the 2nd main or subgroup are particularly suitable zinc oxide, magnesium oxide and calcium oxide.

Suitable acids are those which can form water-insoluble or sparingly water-soluble salts with the abovementioned compounds of metals of the 2nd main group or subgroup. Particularly suitable is phosphoric acid, partially suitable are boric acid and sulfuric acid.

The preparation of the thickener complex can be carried out by itself and added to the coating compositions, such as paints, adhesives, impregnating agents and other mixtures. However, it is also possible to produce the thickener complex in the production of z. B. paints by pigments and fillers and the serving as a binder alkali metal silicate according to the recipe of the paint are added to the thickener complex after its preparation. The application of the method for producing the thickener complex may optionally also be such that the z. B. a paint required pigments and fillers are already present during the preparation of the thickener complex.

The coating compositions obtained are permanently thixotropic, can be stirred very easily after a relatively long time, and can be applied on vertical surfaces in relatively thick layers in a leak-proof manner.

The preparation of the coating agent is associated with the use of the method with no negative side effects.

The thickener complex enters the produced layers as an integral part without affecting the function of the coating.

The preparation of the thickener according to the specified method will be explained below.

Exemplary embodiments (quantities in parts by weight)

example 1

In a container equipped with a dissolver are stirred vigorously: 140.0 water

0.6 potassium sodium hexametaphosphate wetting for pigments 28.2 zinc oxide

32.5 potassium silicate glass (module 3.5, solids 35%)

 Thereafter, they are added and dispersed for 8 to 10 minutes:

8.7 phosphoric acid (75%).

The result is a thixotropic paste, which then with constant dispersion with:

8.8 potassium hydroxide in 25.2 of water

is offset.

This completes the production of the thickener complex.

For example, added to the above approach and dispersed to the desired particle size:

240.0 talc 81.0 iron oxide red

435.0 potassium silicate glass (module 3.5, solids 35%).

The result is a red-brown, thixotropic, soft settling and easily aufaufrührbarer paint, which can be pneumatically applied well on vertical surfaces.

Example 2

To make a paint

435.0 alkali water glass (modulus 3.5, solids 35%)

240.0Talkum 70.0 Chrome oxide green

Dispersed by dissolver to the desired particle size. To this mixture, the thickener complex of Example 1 is incorporated with further stirring. The resulting green paint has similar properties to those in Example 1.

Example 3

For the preparation of an impregnating agent for mineral substrates or fiber-containing materials, such. As fiber tile or board, as mentioned in Example 1, the amounts used for the preparation of the thickener complex, wherein instead of the stated amount of zinc oxide 14.1 Ma parts of magnesium oxide are used.

For completion as impregnating agent, alkali water glass (35% strength) or potash water glass are added to the mixture to the desired consistency.

Claims (2)

1. A process for the preparation of a thickener complex for aqueous silicate coating compositions, characterized in that a dilute aqueous alkali silicate solution with oxides and / or hydroxides and / or carbonates of metals of the 2nd main or subgroup added and first by addition of phosphoric acid, sulfuric acid or boric acid to a pH of 7 to 2 and subsequently adjusted to a pH of 8 to 12 by the addition of alkali hydroxide. 2. The method according to item 1, characterized in that the addition of the acids to the pH value 5 to 3 and the addition of the alkali hydroxide is carried out to pH 9-11.