GB1436883A - Process for the production of silanol-stopped diorganopoly siloxanes - Google Patents

Abstract

1436883 Preparing higher polydiorgano- Siloxanes GENERAL ELECTRIC CO 1 June 1973 [20 July 1972] 26395/73 Heading C3T A silanol-terminated polydiorganosiloxane of viscosity 1,000-10,000,000 cP./25‹ C. and silanol content 0À001-0À5 wt. per cent is obtained by equilibrating a silanol-terminated polydiorganosiloxane of viscosity 5-900 cP./ 25‹ C. with a cyclic polysiloxane [R 2 SiO] 3-10 at 55-200‹ C. in the presence of 0À1-75 wt. per cent of the total mixture of acid activated carbon, acid activated clay or a cation exchange resin until the required viscosity is obtained, then stripping off volatiles, each R being a hydrocarbon, halohydrocarbon, or cyanoalkyl radical. In examples a mixture of cyclic [Me 2 SiO] 4 with HO(Me 2 SiO) 5 H or another dimethylpolysiloxane diol, or of cyclic with hydrolysed MePhSiCl 2 (a linear diol/ cyclic mixture), or hydrolysed alone is heated over H 2 SO 4 -activated clay, or a 70 : 30 linear : cyclic hydrolysis mixture from Me 2 SiCl 2 is heated over H 2 SO 4 -treated carbon black or cation-exchange resin. The products are cross-linked with CH 3 COOC 2 H 4 Si(OAc) 3 and (t-BuO) 2 Si(OAc) 2 or with Si(OEt) 4 , in the presence of dibutyltin dilaurate as catalyst.