| 摘要 |
1525943 Silicone/treated silica antifoam compositions GENERAL ELECTRIC CO 25 Sept 1975 [12 Nov 1974] 39326/75 Heading C3T An antifoam composition comprises a liquid polydimethylsiloxane and a precipitated silica treated with hexamethydisilazane. Preferably the siloxane is triorganosiloxane-terminated and of viscosity 100-70,000 cS/25‹ C., the silica is of surface area 100-800 m<SP>2</SP>/g. and 1- 15 wt. per cent water content, and the silazane is added to the silica before the siloxane. The silica is preferably 1-40 wt. per cent of the silica/siloxane mixture, and the silazane 1-20 wt. per cent of the silica. The composition may contain conventional dispersants and be emulsified in water. In Examples 1, 3 and 4, 1À5 p.b.w. of hexamethyldisilazane are added to 7À5, 10 and 5À1 p.b.w. of a commercial precipitated silica, which is then heated at 100- 150‹ C. with 92À5, 90 and 94À9 p.b.w. of a trimethylsiloxane - terminated polydimethylsiloxane of 500 cS/25‹ C. In Example 2 the product of Example 1 is emulsified in water. |
