Abstract:
A water-proof grease or paste is made by mixing an organic polysiloxane oil with very finely divided silicon dioxide in amount at least 25 per cent of the mixture, storing the mixture for at least a week at room temperature and thereafter working the mixture to a smooth paste by crushing or grinding it between closely-disposed surfaces, as for instance by working with a spatula or in a mill. The silicon dioxide may be that obtained by p the combustion of silicon compounds such as silicon tetrachloride and ethyl silicate. In examples, silicon dioxide (1), (2) mixed with dimethyl polysiloxane is malaxated for several hours, then stored for 15 days; (3) is mixed with a methyl/phenyl polysiloxanic oil, and left in the air for several days before final grinding or crushing. In example (2) the initial dimethyl polysiloxane is freed in vacuo from volatile products, the composition being a grease for lubricating or coating parts intended to operate in vacuo. Specification 628,585 is referred to.