RU2305667C1 - Complex additive for hydrophobization of gypsum - Google Patents

Abstract

FIELD: construction engineering; production of gypsum and gypsum articles possessing water-repellent properties.

SUBSTANCE: proposed complex additive for hydrophobization of gypsum contains the following components, mass-%: sodium methyl siliconate, 29-32; sodium hexafluosilicate, 0.5-1.5; aluminum chloride, 4-6; the remainder being water.

EFFECT: enhanced moisture protective and mechanical properties; enhanced durability of products made from gypsum.

2 tbl, 1 ex

Description

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

For various applications of gypsum, it is essential to have a material with persistent mechanical properties. It is also essential that the material retains its original properties (appearance, mechanical properties) after contact with moisture. To this end, gypsum should be hydrophobized, i.e. make it insensitive to water. It was in order to improve the resistance of gypsum to water that it became necessary to treat gypsum in bulk. In the case of hydrophobization in bulk, the treatment is carried out during the production of gypsum, usually by adding a hydrophobizing compound to the mixing water.

Hydrophobizing organosilicon liquids in the form of aqueous solutions of alkali metal alkyl siliconates are widely known (Voronkov MG et al. Hydrophobization, Kiev, 1973, p. 239; Sobolevsky MV and other Properties and applications of organosilicon products, M., 1975 , p. 266).

A powder composition is known for the hydrophobization of plaster formed by calcining natural or synthetic gypsum, containing alkyl polysiloxane hydride (A), hydrocolloid (B) and a polysaccharide comprising at least one gum (RU 2199500 C2, 08.28.2002). The disadvantage of this composition is the complex cooking technology, environmentally unsafe and does not have an antiseptic effect.

The closest analogue is a complex additive for hydrophobization of gypsum, including organosilicon liquid and water (NZ 508508A, 06/28/2002).

The aim of this invention is the creation of a complex additive that would have higher moisture and mechanical properties (reducing moisture absorption and increasing durability) due to the hardening of gypsum in bulk, low cost, was easy to manufacture, environmentally friendly and fireproof.

This goal is achieved due to the fact that the complex additive for hydrophobization of gypsum, including organosilicon liquid and water, additionally contains sodium hexafluorosilicate, aluminum chloride, and sodium methylsiliconate as the organosilicon liquid, in the following ratio of ingredients, wt.%:

Sodium methylsiliconate 29-32 Sodium Hexafluorosilicate 0.5-1.5 Aluminum chloride 4-6 Water Rest

The effectiveness of this complex additive is due to the formation of hydrophobic aluminomethylsiliconate networks in the mass of gypsum. Sodium hexafluorosilicate, which allows you to control the processes of structure formation in gypsum, is used as a complexing agent containing silicon in six coordination. At the same time, hydrolysis of sodium hexafluorosilicate results in the formation of silicic acid capable of reacting with sodium aluminomethylsiliconate.

Thus, these processes lead to the hardening of hydrophobic aluminomethylsiliconate networks inside gypsum. This structure has higher moisture protective properties and prevents the penetration of moisture into the mass of gypsum.

An example of a specific implementation.

1. Preparation of complex additives.

The preparation of complex additives is carried out in two stages:

Stage 1. To an aqueous solution of sodium methylsiliconate (GKZh 11) with continuous stirring at a speed of 100-150 rpm gradually add aluminum chloride grade "h" or "chda" over 30 minutes. The mixing process takes 2-2.5 hours. Without stopping mixing, sodium hexafluorosilicate “h” or “chd” is added to the prepared mixture and mixed again for 2-3 hours

2 stage. The mixture is left the next day and poured into containers. The resulting mixture is used as a hydrophobizing additive in gypsum. Depending on the type of gypsum and the percentage of water ratio when mixing gypsum, adding about 1.0-1.4% to the mass of gypsum of the proposed complex additive allows you to get a stable value of water absorption of 10%.

2. Testing gypsum samples for water absorption.

The resulting additive is introduced into gypsum mixing water. Water-gypsum factor (W / g) 0.6. The resulting samples are dried to constant weight. Weigh and then immerse in water for 2 hours. Weigh again. Water absorption (A,%) is calculated by the formula

где m - масса образца после погружения в воду; m_сух - масса высушенного образца. Для получения предложенной добавки были приготовлены три состава ингредиентов. Количественный состав добавки от массы гипса и результаты испытаний образцов представлены в табл. 1 и 2.

where m is the mass of the sample after immersion in water; m _dry - the mass of the dried sample. To obtain the proposed additives, three ingredients were prepared. The quantitative composition of the additive by weight of gypsum and the test results of the samples are presented in table. 1 and 2.

Based on the test results presented in table. 1 and 2, we can conclude that the proposed additive has high moisture and mechanical properties (moisture absorption of gypsum is not more than 10%), which indicates its high hydrophobizing properties. In addition, the additive is easy to prepare and use, water-based, environmentally friendly and fireproof, has an antiseptic effect, does not change the appearance of the product and its mechanical properties, cheap starting components, therefore, is available for large-scale use in construction.

Table 1 Water absorption of gypsum samples made with the proposed complex additive The composition of the complex additives Sodium methylsiliconate, wt.% Aluminum chloride, wt.% Sodium silicofluoride, wt.% Water, wt.% The amount of additive,% BUT, % 29th four 0.5 66.5 0 30-40 1,2 16 1.4 eleven 1,6 7 1.8 5 2,8 four 0 30-40 thirty 5 1,0 1,2 fifteen 64 1.4 10 1,6 7 1.8 5 2.0 3 0 30-40 32 6 1,5 60.5 1,2 fourteen 1.4 10 1,6 7 1.8 5 2.0 3 table 2 Mechanical properties of gypsum samples made with the proposed additive Amount of additive in% of dry gypsum mass Gypsum ratio Water absorption,% Bending Strength, MPa Compressive strength, MPA 0 0.7 38.5 5.3 6.9 1,5 0.7 3,7 4.0 6.0 1.25 0.7 8.1 4.2 7.0

Claims (1)

A complex additive for hydrophobization of gypsum, including an organosilicon liquid and water, characterized in that it additionally contains sodium hexafluorosilicate, aluminum chloride, and sodium methylsiliconate as an organosilicon liquid in the following ratios of ingredients, wt.%: Sodium methylsiliconate 29-32 Sodium Hexafluorosilicate 0.5-1.5 Aluminum chloride 4-6 Water Rest