| 摘要 |
PROBLEM TO BE SOLVED: To impart a very high hydrophobic property to silica by allowing the silica to react with a trimethylsilylating agent in the presence of steam at a high temperature and a high partial pressure of the trimethylsilylating agent. SOLUTION: Silica is allowed to react with a trimethylsilylating agent in the presence of steam at 250-350 deg.C reaction temperature and 1.5-4 kg/cm2 partial pressure of the trimethylsilylating agent to obtain the objective hydrophobic silica having trimethylsilyl groups chemically bonded to the surface. The concentration of methanol in a water-methanol solution at which the proportion of suspension of the hydrophobic silica in the solution attains to 0% is >=65%. The proportion is measured while varying the ratio between water and methanol. The trimethylsilylating agent is preferably a compound of the formula [(CH3)3Si]2NR (where R is H or a lower alkyl) or the formula (CH3)3SiY [where Y is a halogen, OH, OR or NR2 (R is H or a lower alkyl)].
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