Method for preparing a thermal-stability additive and a thermally stabilized methylpolysiloxane and compositions therefrom

Endblocked methylpolysiloxane fluids, such as trimethylsiloxane-endblocked polydimethylsiloxanes, are made more resistant to thermally induced siloxane rearrangement by incorporating therein certain amounts of titanium-, zirconium-, or hafnium-containing compounds. Incorporation of these compounds may be accomplished either by mixing organosiloxy derivatives of Ti, Zr, or Hf with the fluid or by mixing certain organic derivatives of Ti, Zr, or Hf with the fluid and heating the mixture to decompose the added organic derivative. Furthermore, incorporation may be accomplished either by mixing the correct amount of the Ti, Zr, or Hf compound with the fluid or by mixing an excessive amount of the Ti, Zr, or Hf compound with the fluid to form a thermal-stability additive which may be diluted with additional fluid to achieve the correct amount of Ti, Zr, or Hf compound. Further improvements in the thermal stability of the fluid may be obtained by mixing with the titanium-, zirconium-, or hafnium-containing fluid a small amount of an organosilicon hydride compound. The thermally stabilized fluids are particularly useful as heat-transfer fluids in non-oxidative, anhydrous environments.