| 摘要 |
PURPOSE:To produce colloidal silica having extremely high purity contg. no metallic ions and having improved stability by hydrolyzing high purity silicic ester in the presence of quat. ammonium hydroxide and a dispersant. CONSTITUTION:High purity silicic ester is hydrolyzed in the presence of quat. ammonium hydroxide and a dispersant. The silicic ester is org. silicate represented by formula I (where R is 1-4C alkyl), e.g., tetramethoxysilane or tetraethoxysilane. The quat. ammonium hydroxide is represented by formula II (where each of R1-R4 is 1-4C alkyl or alkanol), e.g., tetramethylammonium hydroxide or tetraethylammonium hydroxide. The dispersant may be selected among cationic, anionic, nonionic and amphoteric water-soluble surfactants, etc., but a nonionic surfactant such as polyoxyethylene nonylphenyl ether is preferably used as the dispersant.
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