SU1472458A1 - Method of rendering hydrophobic a silica-base heat-insulating material - Google Patents

Abstract

The invention relates to methods for producing hydrophobic thermal insulation materials based on silica, used for lining, thermal insulation, as well as for protection of products operating under the influence of moisture. In order to enhance the hydrophobic properties and the possibility of providing reusable at operating temperature above 500 ° C heat-insulating material is subjected to preliminary heat treatment at 900-1000 ° C, and then treated with an organosilicon compound of the general formula (CH _{3) 3} SIX, wherein X ₅ -OC ₂ H ₅ , OC ₃ H ₇ , OC ₄ H ₉ , OCOCF ₃ , NHSI (CH ₃ ) _3, or an arbitrary mixture thereof, the amount of organosilicon compound being 0.5-2.8% by weight of the starting material. The process is carried out at 5-40 ° C for 6-24 hours. The weight of the material after immersion in water is 0.01-0.1%

The specific surface area before and after treatment does not change and is equal to 7-30 m ² / g. 2 tab.

Description

one

The invention relates to methods for the production of hydrophobic thermal insulation materials, in particular silica materials used for lining, thermal insulation, and also for the protection of products operating under the influence of moisture.

The purpose of the invention is to increase the hydrophobic properties and provide the possibility of multiple use at operating temperatures above 500 ° C.

The method is carried out as follows.

in a way.

i. The billet of molded silica material is subjected to heat treatment at 900-1000 ° C. The material is then exposed to a silicon-organic compound by spraying it over the surface of the material or placing the material in a reactor, to which the vapors of the organosilicon compound are fed, taken in an amount of 0.5-2.8% by weight of the starting material. The product is placed in a plastic container or other closed volume and kept in it for 6-24 hours at 5-40 ° C. After

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this treatment removes the product from the closed volume and blows warm air to remove excess modifier and reaction by-products,

Example 1. A sample of a heat insulating silica material having a specific surface of 31 m / g.

LIA into the water and put it in it for 1 h. The specific surface is determined by the method of low-temperature desorption of argon (GOST 23401-78). The ability to restore (for later use) is judged by the change in specific surface area after the operation cycle (see

a weight of 100 g is subjected to heat treatment table 2).

ke, treated with a spray of 0.5 g. of a mixture of trimethylethoxysilane and silazane in the ratio 4: 1, packed in a plastic bag and held in it for 12 hours at 20 ° C. The resulting sample is kept in air for 5 hours.

The hydrophobicity of the sample, which is assessed by water absorption after forcibly immersed in water and held for 1 hour, is 0.09%. Specific surface of heat-shielding hydrophobic sample 30

PRI mme R 2. A sample of a thermally insulating silica material with a specific surface of 234 and a mass of 100 g is subjected to heat treatment at 950 ° C, then placed in a reactor and treated with vapors of a mixture of organosilicon compounds (TMBC:: HMDS 9: 1). at 40 ° C for 7 hours. The amount of water-repellent agent is 2.8 g. Then the sample is blown with warm air for 2 hours. With a weight after forced immersion it is 0.1%. Specific over Hoctb hydrophobic sample 226.

PRI me R 3. A sample of a thermally insulating silica material with a specific surface of 7 and a mass of 100 g is treated at 950 ° C and treated from a spray bottle with an amount of 1.5 g. Then it is packed in a plastic bag and kept in it. for 5 hours at 10 ° C. The obtained sample is held in air for 5 hours. The weight gain after forced immersion is Oy05%. The specimen surface is 7.

Table 1 shows the processing conditions of the silicone compounds of the silica material according to the invention, as well as the properties of the coatings obtained.

The hydrophobicity of the obtained coatings is evaluated by water absorption after the forced immersion of the product.

0

five

0

five

0

five

0

After the cycle of operation, the specific surface of the sample does not change significantly. After a cycle of operation at temperatures above the sample is subjected to re-processing modifier. The result is a material with the same structure and hydrophobic properties as before the operation, i.e. suitable for further use as a heat insulating material. When the modification is carried out according to the proposed method, the specific surface area of the heat-shielding material both after the treatment with organosilicon compounds and after the cycle of operation at temperatures above does not change significantly. At 500 ° C, the hydrophobic coating is practically destroyed and a further increase in temperature does not lead to a change in the specific surface. At the same time, during the hydrophobization according to a known method, the specific surface area of the obtained sample changes both during the modification process and after the operation cycle at a temperature of 500 ° C (temperature of destruction of the hydrophobic coating).

Thus, the proposed method allows to obtain a silica heat-insulating material with sufficiently high thermal insulation and hydrophobic properties and at the same time having the ability not to change the specific surface of the product in the process of hydrophobization and when operating at elevated temperatures. The value of the specific surface of the sample can serve as a reliable characteristic of the stability of the structure of the material.

The constancy of the specific surface of the article of silica material makes it possible to reapply the heat-shielding material after the subsequent modification, which is carried out by treating with the applied silicon

at 5–40 ° C, i.e. The method solves the problem of repeated use of a silica material directly on the structure.

Claims (1)

Invention Formula The method of hydrophobicizing a thermally insulating silica material by treating it with a silicon-organic compound of the general formula (CH3) from Six, where X is OC5. Note. Hydrophobic en ,,. on the barely operating cycle suitable for repeated hydrophobization, TMPS - trimethylpropoxysilane; TUS - trimethylethoxysilane; CJC — Hexamethyldisilazane; TMBS - trimethylbutoxysilane; TMTFAS - trimethyl trifluoroacetoxysilane. 72458 OCOCF, NHSiCCH l, or a mixture thereof, characterized in that, in order to try out the hydrophobic properties and ensure the possibility of repeated use at an operating temperature higher, before processing the organosilicon compound, the material is subjected to heat treatment at 900-1000 ° C, and the treatment is carried out with organosilicon compound taken in the amount of 0.5-2.8% of the mass of the material at 5-40 ° C for 6-24 hours. Table 1 TUS: HMDS 4: 1. TMBS; HMDS “ year 14724588 6lit2 thirty 28 7 32 28 7