CS251745B1 - Plaster mixture - Google Patents

Abstract

The invention relates to plaster mixtures bound with cement, lime or their mixtures and plasters based on gypsum. The purpose is to improve the useful properties of plaster mixtures by increasing their adhesion to the substrate and reducing water absorption after drying. The purpose is achieved by adding starch monophosphate and alkaline salts of carboxylic acids with a carbon chain of length C 12 to C 18, or some of these acids.

Description

The invention relates to cement-lime plaster mixtures or plaster-based plasters.

For interior and exterior plasters, plaster mixtures composed of mineral fillers such as sand or crushed and ground aggregates, and binders, mainly cement and lime, are most commonly used in the construction industry. Gypsum plasters and gypsum gravel are used to compensate for unevenness of the panels and to seal joints in residential panel construction. To increase the water chain and the adhesion of the material to the substrate, a small amount of cold-soluble cellulose ethers, such as methyl-, ethyl- or methyl-ethyl-oeluloza, are added to the plasters. Addition of a small amount of surfactant, usually based on aryl-alkyl sulfonates and the like, serves for faster wetting and aeration of the used aggregate levers. Addition of metal soaps such as calcium stearate or aluminum stearate is then added to achieve hydrophobic properties. The metal salts of stearic acid used are hydrophobic and are very difficult to disperse in the mortar to be prepared.

The above-mentioned drawbacks are eliminated with the plaster compositions according to the invention, which are characterized in that these compositions contain 0.5 to 5 wt. % starch monophosphate and, < 0.1 to 2 wt. and / or alkali salts of a carboxylic acid having a carbon chain length of C 12 to C 18 or mixtures thereof.

The starch mohophosphate used is characterized by cold water solubility and increased viscosity due to its high hydrophilicity. Its advantage is that even an excessive dose of its additive does not affect the desired effect, and yet this additive is economically more advantageous than the cellulose ethers used hitherto.

251 74 £

The addition of the sodium salt of said carboxylic acids, as a well-soluble substance, is uniformly distributed throughout the mortar mass and, in the first stage, acts as a surfactant, i.e. it wetted the aggregate and aerates the mortar. Upon reaction with calcium hydroxide Ca 2 OH 5 in the plaster mixture, it then becomes an insoluble hydrophobic calcium salt, which induces the hydrophobicity of the render. Thus, the use of a single additive, the sodium salt of said carboxylic acids, achieves the effect of two previously used additive surfactants and a hydrophobising agent.

In both cases they are dry powdered materials, which makes it possible to produce the necessary plaster mixtures in a dry state and only to adjust them to the desired consistency with the water itself.

The invention will be further elucidated by means of practical examples thereof.

Example 1

A plaster mixture consisting of 75 wt.

% silica sand, 8 wt. % cement, 15 wt. % lime hydrate, 2 wt. % starch monophosphate, 0.2 wt. % sodium salt of said carboxylic acids and 0.5 wt. copper sulfate. The copper (II) sulfate used has the function of a fungicidal agent.

This mixture was on; The mixer in the mixer was split with water and the plaster was applied to the wall in the usual way. Adhesion of the plaster was 0.35 MPa and the water absorption decreased from 18 $ to

Example 2

Gypsum was prepared from gypsum with addition of 2 wt. % starch monophosphate and 0.1% potassium salt of said carboxylic acids. After separating with water to the desired consistency, the mass was used to pair the panels. The addition of starch monophosphate prolongs the setting time of the gypsum, the material adheres very well to the substrate.

Claims (1)

A plaster mixture with cement-lime binder or gypsum based, characterized in that it contains 0.5 to 5% by weight of starch monophosphate and 0.1 to 2% by weight of an alkali metal salt of carboxylic acids of C 12 to C 18 length, optionally some of these acids.