Patent GB-682541-A (GB)
Title: Improvements in or relating to the polymerisation of organosiloxanes
IPC: C08G77/00
Filed: 1950-04-06
Abstract: In polymerizing a completely condensed liquid diorganopolysiloxane in which the organic radicals are alkyl and/or monocyclic aryl, the siloxane is maintained in contact with a catalyst of the general formula ROM or (ROH)x.MOH, where R is an alkyl radical containing less than 6 carbon atoms, x has a value from 0.5 to 2.5 and M is sodium or potassium, the catalyst being present in a proportion of from one alkali metal atom per 100 silicon atoms to one alkali metal atom per 25,000 silicon atoms, until an increase in viscosity of the siloxane is obtained. The siloxane polymer or copolymer may be mixed with the catalyst in the presence or absence of a solvent, e.g. xylene, and polymerization may be effected at temperatures below room temperature to above 250 DEG  C.  In examples, the catalysts [(CH3)2.CHOH]2.3.KOH, (CH3)2CHOK, C2H5OK, CH3OH.NaOH, [(CH3)3.COH]0.87.NaOH, [(CH3)2CHOH]2.5.NaOH, [(CH3)2CHOH]1.85.KOH, and [C2H5\t OH]0.7.NaOH are used to polymerize octamethylcyclotetra-, hexamethylcyclotri- and decamethylcyclopenta-siloxanes and mixtures of octamethylcyclotetrasiloxane with phenylmethylsiloxane and octamethylcyclotetrasiloxane with octaphenylcyclotetrasiloxane. Specification 682,540 is referred to.ALSO:Compounds of the general formul  ROM and (ROH)x.MOH, where R is an alkyl radical containing less than 6 carbon atoms, x has a value from 0.5 to 2.5 and M is sodium or potassium, are used as catalysts in the polymerization of liquid diorganopolysiloxanes (see Group IV (a)).  The former compounds, e.g. potassium isopropoxide, may be prepared by reacting an alcohol with an alkali metal under substantially anhydrous conditions.  The complexes may be prepared by refluxing NaOH or KOH with an alcohol and removing excess alcohol by distillation. In a preferred method solid alkali metal hydroxides are heated with 3 to 4 mol. excess of the alcohol until the alkali has dissolved, water being removed azeotropically during refluxing. The solution is then filtered and the alcohol removed by distillation.  The resulting complexes are dry, hygroscopic, powders.  The value of x is dependent upon the relative amounts of the reactants used, the alkali employed and the temperature used to remove excess of alcohol.  Alcohols specified are ethyl, propyl, butyl and amyl.  Compounds disclosed are (CH3)2.CHOK, [(CH3)2.CHOH]2.3. KOH, C2H5OK, CH3OH.NaOH, [(CH3)3. COH]0.87 . NaOH, [(CH3)2.CHOH]2.5 . NaOH, [(CH3)2.CHOH]1.85 . KOH, and [C2H5OH]0.7 . NaOH.ALSO:Compounds of the general formula ROM and (ROH)xMOH, where R is an alkyl radical containing less than 6 carbon atoms, x has a value from 0.5 to 2.5 and M is sodium or potassium, are used as catalysts in the polymerization of liquid diorganopolysiloxanes (see Group IV(a)).  The formed compounds, e.g. potassium isopropoxide, may be made by reacting an alcohol with an alkali metal under substantially anhydrous conditions.  The complexes may be made by refluxing NaOH or KOH with an alcohol and removing p excess alcohol by distillation.  In a preferred method, solid alkali metal hydroxides are heated with 3 to 4 mol. excess of the alcohol until the alakli has dissolved, water being removed azeotropically during refluxing.  The solution is then filtered and the alcohol removed by distillation.  The resulting complexes are dry, hygroscopic powders.  The value of x is dependent upon the relative amount of the reactants used, the alkali employed and the temperature used to remove excess alcohol.  Alcohols specified are ethyl, propyl, butyl and amyl.  Compounds disclosed are (CH3)2COOK, [(CH3)2, CHOH]2 3, KOH, C2H5OK, CH3OH-NaOH, [(CH3)3COH]0,87, NaOH, [(CH3)2CHOH]2,5, NaOH, [(CH3)2CHOH]1,85, KOH and [C2H5OH]0,7, NaOH.