Dow Corning Corporation

Rocco Joseph Voci

Gerald A Gornowicz

Roger G Chaffee

Randall A Siegel

The invention relates to an improved distillation method wherein hexamethylcyclotrisiloxane is isolated from a crude blend thereof by mixing the crude blend with a hydrocarbon co-solvent having a normal boiling point of 125.degree. C. to 150.degree. C. and distilling the resulting mixture in an apparatus having a reboiler, a fractionating column and a condenser, whereby deposition of solid hexamethylcyclotrisiloxane in the condenser is eliminated.

Method for distilling hexamethylcyclotrisiloxane

A fluorinated polydiorganosiloxane elastomer having improved physical properties can be obtained through the use of a method which first reacts a hydroxyl endblocked trifluoropropylmethylsiloxane having a Williams Plasticity Number of greater than 225 with a methylvinyldi(N-alkylacetamido)silane to give a chain extended polymer having pendant vinyl groups only at the location of the chain extension. The polymer is then reinforced with fume silica and compounded into a stock. The cured stock has improved tensile strength and tear strength when compared to similar compositions which do not contain the same type of polymer. The polymer has pendant vinyl groups located along the polymer chain, with the distance between them being relatively large. When too many vinyl pendent groups are present along the chain, the improved results are not obtained.

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Midland, MI, United States of America

Rocco Joseph Voci