Patent GB-607253-A (GB)
Title: Methyl siloxanes and methods of preparing them
IPC: C08G77/00
Filed: 1946-01-29
Abstract: A partially condensed methyl siloxane having on the average 1 to 2.5 methyl radicals per silicon atom is inter-condensed with trimethyl ethoxysilane in the presence of water.  The products are particularly stable to heat.  The preferred method is to hydrolyse an ethoxysilane having 1 to 2 methyl radicals per silicon atom or a mixture of ethoxysilanes containing 1 to 2.5 methyl radicals per silicon atom, with excess water if desired in presence of sulphuric acid under conditions, e.g. in a dilute solution in presence of a water-miscible solvent and at low temperature which promotes only partial condensation.  Trimethyl siloxane is then added and the siloxanes are inter-condensed at room temperature or preferably with heat.  Acids if present are removed by washing and the product freed from solvent. Low polymers may be removed by distillation up to 200 DEG  C.  In examples (1) and (2), a mixture of dimethyldiethoxysilane and methyltriethoxysilane were refluxed with aqueous alcoholic hydrochloric acid.  Trimethylethoxysilane was added and refluxing was continued.  The product was washed and freed from low polymers by distillation.  In example (3), dimethyldiethoxysilane was hydrolysed with dilute sulphuric acid and distilled at 100 DEG  C. Trimethylethoxysilane was added to the residue and the mixture stirred at 100 DEG  C., washed and freed from low polymers by distillation at 230 DEG  C.  Example (4) is similar. In example (5), a mixture of methyltriethoxysilane and trimethylethoxysilane was hydrolysed with hydrochloric acid at a temperature not above 40 DEG C. and the mixture then heated at 60 DEG  C. for 1 hour. Trimethylethoxysilane was added, the mixture heated for another hour at 60 DEG  C., the product washed, dissolved in xylene and dried by distillation.  Solvent was then removed.ALSO:A partially condensed methyl siloxane having on the average 1 to 2.5 methyl radicals per silicon atom is inter-condensed with trimethyl ethoxysilane in the presence of water.  The products are particularly stable to heat. The preferred method is to hydrolyse an ethoxysilane having 1 or 2 methyl radicals per silicone atom or a mixture of ethoxysilane containing 1 to 2.5 methyl radicals per silicone atom, if desired in presence of sulphuric acid under conditions, e.g. in a dilute solution in presence of a water-miscible solvent and at low temperature which promotes only partial condensation. Trimethyl-siloxane is then added and the siloxanes are inter-condensed at room temperature or preferably with heat.  Acids if present are removed by washing and the product freed from solvent. Low polymers may be removed by distillation up to 200 DEG  C.  In examples (1) and (3), a mixture of dimethyldiethoxysilane and methyltriethoxysilane were refluxed with aqueous alcoholic hydrochloric acid.  Trimethylethoxysilane was added and refluxing was continued.  The product was washed and freed from low polymers by distillation.  In example (3), dimethyldiethoxysilane was hydrolysed with dilute sulphuric acid and distilled at 100 DEG  C. Trimethylethoxysilane was added to the residue and the mixture stirred at 100 DEG  C., washed and freed from low polymers by distillation at 230 DEG  C.  Example (4) is similar. In example (5) a mixture of methyltriethoxysilane and trimethylethoxysilane was hydrolysed with hydrochloric acid at a temperature not above 40 DEG C. and the mixture then heated at 60 DEG  C. for 1 hour. Trimethylethoxysilane was added, the mixture heated for another hour at 60 DEG  C., the product washed, dissolved in xylene and dried by distillation.  Solvent was then removed.