RU2335476C1 - Complex additive for spatial hydrophobisation of plaster - Google Patents

Abstract

FIELD: chemistry; construction.

SUBSTANCE: invention can be applied in production of plaster items to render water-repellent properties to them. Complex additive for spatial hydrophobisation of plaster includes, wt %; tetraethoxysilane - 3-10, the rest is oligomethylhydridesiloxane.

EFFECT: improved water-repellency and durability of ready plaster article.

2 tbl, 1 ex

Description

The invention relates to the production of building materials and can be used in the manufacture of gypsum products to give them water-repellent properties.

For various applications of gypsum, it is essential to have a material with good mechanical properties. It is necessary that the material, even after wetting, retains its original properties (appearance, mechanical strength). To this end, gypsum should be hydrophobized, i.e. give it water-repellent properties. Distinguish between surface and volume hydrophobization. In the case of volumetric hydrophobization, it is advisable to carry out the processing in the process of manufacturing a gypsum product - by adding a hydrophobizing compound to the mixing water.

The hydrophobizing organosilicon compositions for gypsum are widely known in the form of aqueous solutions of sodium or potassium ethyl- or methylsiliconates (M.G. Voronkov et al., Hydrophobization, Kiev, 1973, p.239; M.V. Sobolevsky et al. Properties and areas use of organosilicon products. - M., 1975, p.296), or sodium aluminomethylsiliconate (Encyclopedia of Polymers (in 3 volumes) / Edited by V.A. Kargin et al. - M., 1972, T.1, p. 630).

Also known for hydrophobization of a wide range of building and other materials is an additive based on oligoethylhydridesiloxane (Andrianov K.A., Khananashvili L.M. Technology of organoelement monomers and polymers. - M., 1973, p. 174; GOST 10834-76). Typically, this compound is used in the form of an aqueous emulsion as an additive to the mixing water at the stage of production of gypsum products. The disadvantages of this emulsion are the complexity and cost of production, low storage stability, a complete loss of valuable properties after cooling below the freezing point (0 ° C). The use of pure oligoethyl hydride siloxane in economically viable amounts does not allow the necessary hydrophobization to be achieved.

Closest to the proposed invention in terms of essential features is an additive based on oligomethylhydridesiloxane (Andrianov K.A., Khananashvili L.M. Technology of organoelement monomers and polymers. - M., 1973, p. 174). This additive is introduced into the mixing water at the stage of production of gypsum products, either in pure form or also in the form of an aqueous emulsion. A disadvantage of the known additives is a decrease in the strength of the finished gypsum product and, as a consequence, its durability.

A new technical result of this invention is the creation of a complex additive, which would provide higher water repellent and strength properties of the finished gypsum product, had a relatively low cost, was as simple to manufacture and environmentally friendly.

The technical result is achieved due to the fact that the complex additive for volumetric hydrophobization of gypsum, including the oligomethylhydride siloxane, according to the invention, additionally contains tetraethoxysilane, while the content of these ingredients should be in the following ratio, wt.%:

Tetraethoxysilane 3-10 Oligomethyl Hydride Siloxane rest

The effectiveness of this complex additive is due to the fact that it simultaneously includes two organosilicon liquids that provide the simultaneous formation of polymethylsiloxane chains and three-dimensional silicate nets in the mass of gypsum, the first of which provide the necessary hydrophobicity of the product, and the second increase its strength. Thus, this structure provides higher water repellent and strength properties of the finished gypsum product.

Case Studies

1. Preparation of complex additives.

To an oligomethylhydride siloxane in an amount of 940 kg with continuous stirring at a speed of 200-250 rpm, tetraethoxysilane in an amount of 60 kg is gradually added. Stirring of the resulting liquid is continued until complete homogenization. The resulting composition is used as an additive to the mixing water at the stage of production of gypsum products. Depending on the type of gypsum and gypsum factor, the introduction of the order of 0.15-0.3% by weight of the gypsum of the proposed complex additive allows us to obtain a stable value of water absorption below 10% for finished gypsum products while maintaining or increasing the mechanical strength. 2. Testing gypsum samples for water absorption.

, где m - масса после погружения в воду; m_o - масса исходного образца.The resulting complex additive is added to gypsum mixing water. Water-gypsum factor 0.6. The resulting samples are dried to constant weight, weighed and then immersed in water for 2 hours. The water layer above the surface of the product must be at least 5 cm. Samples are removed, excess water is removed with filter paper and weighed again. Water absorption (A,%) is calculated by the formula

where m is the mass after immersion in water; m _o is the mass of the original sample.

To obtain the proposed complex additives were prepared three composition of the ingredients. Quantitative compositions, the amount of additive by weight of gypsum and the test results of the samples in comparison with the prototype are presented in tables 1 and 2.

Based on the test results presented in the tables, we can conclude that the proposed complex additive provides high water-repellent and strength properties of the finished gypsum product (gypsum water absorption of not more than 10%, strength is higher than gypsum strength with the addition of a prototype). In addition, the additive is extremely easy to prepare and use, environmentally friendly, does not change the appearance of the product, contains relatively cheap starting components, therefore, is available for large-scale use in construction.

Table 1 Water absorption of gypsum samples with the proposed complex additive (water absorption of gypsum without additives - 34%) The composition of the additive, wt.% Percentage of additive on dry gypsum mass 0.15% 0.20% 0.25% 0.30% Water absorption, A (%) Oligomethylhydridosiloxane (prototype) 12 8.1 5.3 4.2 Oligomethylhydridosiloxane - 97%, Tetraethoxysilane - 3% 9.7 7.5 4.9 3.9 Oligomethylhydridosiloxane - 94%, Tetraethoxysilane - 6% 7.6 7.0 4.7 3.7 Oligomethylhydridesiloxane - 90%, Tetraethoxysilane -10% 8.2 7.4 4.9 3.9

Claims (1)

A complex additive for volumetric hydrophobization of gypsum, including oligomethylhydride siloxane, characterized in that it additionally contains tetraethoxysilane in the following ratio of components, wt.%: Tetraethoxysilane 3-10 Oligomethyl Hydride Siloxane rest