PRECIPITATED SILICON DIOXIDE AND METHOD OF PREPARATION THEREOF Russian patent published in 1997 - IPC

FIELD: production of silicon and silicon compounds. SUBSTANCE: silicon dioxide provided is in the form of powder composed of virtually spherical balls or granules and is characterized with specific surface area ranged from 140 to 240 sq.m/g, high ultrasonic deagglomeration factor, low average diameter after ultrasonic deagglomeration, and, optionally, such pore distribution providing volume percentage of pores with diameter 175 to 275 less than 50% of volume of those pores having diameter as high as 400 . Powder is designed to be utilized as reinforcing filler for rubbers. Preparation procedure includes interaction of alkali metal silicate with acidifying agent to produce precipitated silicon dioxide suspension which is then separated and dried. According to invention, precipitation of product is achieved in the following way: (1) basis of initial bath is formed composed of a part of summary amount of alkali metal silicate having taken part in reaction, its concentration in bath basis expressed as silicon dioxide being below 20 g/l; (ii) acidifying agent is added to bath basis until at least 5% of alkali metal oxide contained in bath basis is neutralized; (iii) into reaction mixture, further acidifying agent and remaining amount of alkali metal silicate are added in such a way that ratio of alkali metal silicate expressed as silicon dioxide to silicon dioxide contained in initial bath basis were within the range from 4 to 100. EFFECT: optimized preparation procedure. 15 cl, 8 tbl