| abstract |
An oil compound is prepared by mixing and treating (A) an essentially hydrophobic organopolysiloxane having a viscosity of 10-100,000 mm 2 /s at 25°C, (B) finely divided silica, and (C) an alkaline catalyst comprising an oxide, hydroxide, alkoxide or siliconate of an alkali or alkaline earth metal at room temperature to 200°C, and neutralizing the mixture with a solid acid. The oil compound is used to form a silicone-based antifoam composition having effective foam-breaking, persistent antifoaming ability and internal addition stability even in alkaline foaming liquids. |