Patent GB-1476834-A (GB)
Title: Process for the preparation of linear and branched chlorosilo xanes
IPC: C08G77/22
Filed: 1975-10-13
Abstract: 1476834 Chlorosiloxanes BAYER AG 13 Oct 1975 [12 Nov 1974] 41824/75 Headings C3T and C3S A process for the preparation of a chlorinesubstituted linear or branched siloxane comprises reacting one or more chlorosilanes of the formula R a R b 1 Si Cl (4-a-b) , or partial hydrolyzates thereof, wherein a = 0-3, b = 0-3 and a + b is 3, 2, 1 or 0, and R and R<SP>1</SP> are hydrogen or saturated or unsaturated aliphatic, aromatic saturated or unsaturated araliphatic, optionally halo- or cyano-substituted, monovalent hydro-carbon radicals with up to 18 carbon atoms, with one or more linear, branched or cyclic siloxane containing one or more units selected from those of the following formulae in optionally alternating arrangements [R<SP>11</SP>SiO 3/2 ] and [SiO 2 ], wherein R<SP>11</SP> is chlorine or OH or has the meaning indicated for R and R<SP>1</SP>, and wherein the number of all Si-Cl groups exceeds the number of all Si-OH groups, the reaction being carried out in the presence of a combination of one or more protic acid equilibration catalysts for siloxanes, other than a hydrogen halide, and a hydrogen halide each being present in an amount of from 0À01 to 3% wt., based on the total weight of the reaction mixture, at a temperature of from - 10 to 200 C., optionally under pressure. Suitable catalysts are sulfonic acids of the formula R f S0 3 H, or R A SO 3 H where R f  is a perfluorinated C 1 -C 10  alkyl radical and R A  is an alkyl or aryl radical with up to 18 carbon atoms, sulphuric acid, oleum, a polysulphuric acid, a polysulfonic acid, phosphoric acid, polyphosphoric acids and acid-activated bleaching earths. The protic acid and the hydrogen halide may be produced in situ. Suitable siloxanes are the direct hydrolysis product of dimethyldichlorosiloxane or a cyclosiloxane of the formula (RR<SP>1</SP>SiO)n, where n is 3-5. The equilibration reaction is stopped by the removal of the hydrogen halide e.g. by applying a vacuum. In the Examples chlorosiloxanes are prepared either (1) by reacting (A) dimethyldichloro-silane or methyltrichlorosilane with (B) either (i) octamethylcyclotetrasiloxane and optionally tetravinyl tertramethyl-cyclotetrasiloxane, or (ii) an OH- containing polydimethylsiloxane, or (iii) a trimethylsilyl-terminated silicone oil containing (C 6 H 5 ) 2 SiO, CH 3 ) 2 SiO and (CH 3 ) 3 SiO 1/2  units; or (2) by reacting (A) chloromethylmethyldichlorosilane with (B) an OH-containing polysiloxane containing chloromethylmethysiloxy units; or (3) by reacting (A) SiCl 4  with (B) an OH-containing polydimethysiloxane; in the presence of perfluorobutane sulfonic acid and HCl, the HCl being produced in situ by the addition of water or by the reaction of the Si-OH content of the OH-containing polysiloxanes with the ehlorosilanes; or HCl gas is passed through the reaction mixture. The product is freed from HCl under vacuum. In other similar Examples the protic acids used or precursors thereof are sulphuric acid, phosphoric acid, phosphorus pentoxide, 1-chloro-l-oxophospholine or an acid-actuated bleaching earth.