| 摘要 |
A toothpaste may contain as an abrading and polishing agent a silica gel having an average particle size of 1 to 30 microns and a) a surface area of 1 to 600 m<2>/g, b) a pore volume of 0.05 to 0.5 cm<3>/g, c) a product of surface area (in m<2>/g) x pore volume (in cm<3>/g) less than or equal to 240, d) a calculated pore diameter of 1.5 to 2.5 nm, and e) a water content of less than 25% by weight which is produced by gelling an aqueous silicate solution to form a silica hydrogel, washing the silica hydrogel to a purity of about 90 to 99% by weight SiO2 (based on the calcination loss-free substance) at a pH value below 6 and at a temperature of about 0 to 70 DEG C and grinding and drying the washed hydrogel so as to prevent ageing, the washing and drying conditions to prevent ageing being set so that the silica gel product has the desired properties. a |
