关键词: 牙膏磨擦剂, 二氧化硅, 合成, 电解质

Abstract: Using sodium silicate and sulphuric acid as raw materials，the silica suitable for using in transparent toothpaste has been synthesized by precipitation process. Effects of the reaction conditions on the properties of silica have been investigated，such as the concentration of sodium silicate in the reactor，reaction temperature and aging time. It was found that optimal reaction condition was determined as sodium silicate in the reactor 0.13mol/L，65 degree C and ageing time 30 min. Under the condition，the light transmittance of silica was 89%. On this basis，it was focused on the influence of the concentration of Na2SO4 and NaCl adding in reaction liquid to improve light transmittance. It turned out that the light transmittance of silica synthesized at 65 degree C has negligible influence on the concentration of Na2SO4 or NaCl adding in the reaction liquid 0.04～0.12mol/L. But at 85 degree C，the light transmittance of silica synthesized under Na2SO4 0.08mol/L was 97% and the light transmittance of silica synthesized under NaCl 0.12mol/L was 96%. The possible reason for this phenomenon could be that the electrolytes participate in the polymerization of silicic acid more effectively at a relatively high temperature，improving the transmittance of SiO2. The properties of the synthesized substance have met the standard of QB/T 2346—2007.

Key words: toothpaste abrasive, silica, electrolytes, synthesis