Synthesis of low silanol content, triorgano-stopped silicone flu

Details Synthesis of low silanol content, triorgano-stopped silicone flu Synthesis of low silanol content, triorgano-stopped silicone flu

1993-07-15

1995-04-18

Marquis, Melvyn I.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

528 14, 528 22, 528 23, 528 37, 556462, 556467, 556469, 556453, C08G 7708

Patent

active

054080258

ABSTRACT:
Linear triorganosiloxy-terminated polydiorganosiloxanes having a silanol content of less than about 200 ppm are prepared by condensing linear higher molecular weight polydiorganopolysiloxanediols having one Si-bonded hydroxyl group in each terminal unit and a silanol content of preferably greater than about 1000, in two separate stages, one using a fixed bed of a solid form of a conventional equilibration catalyst, and the other using a condensation/disproportionation catalyst, e.g., a phosphonitrilic halide or an oligomer thereof or a reaction product thereof with water, an alcohol, an acid, or a siloxane or silane, until the polydiorganosiloxane has reached the desired low content of silanol groups, e.g., below 200 ppm, by weight. The two stages can be carried out in either order, and a conventional monofunctional chain terminating agent can be present in either or both stages. The process preferably does not increase the cyclic byproduct content.

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