GB889125A - High melting point polymers - Google Patents

Abstract

A siloxane is made by heating a diarylsilanediol dissolved in diethyl carbonate in the presence of an aluminium-magnesium lower alkoxide complex, and removing the solvent. Preferably the reaction mixture contains from 25 to 50% by wt. of the diol and the catalyst is present in amount of 0,75 to 3% by wt. of the diol. The catalyst, which can be represented by the formula Mg[Al(OR)4]2, where R is an alkyl radical of 1 to 6 C atoms (see Group IV(b)), may be added as such or be formed in situ. In the example, Mg- and Al-n-butoxides were added to a solution of diphenylsilanediol in diethylcarbonate, and the reaction mixture was heated at 90 DEG to 105 DEG C. for 2 1/2 hrs. while dry nitrogen was passed therethrough. The temperature was raised to 115 DEG C. and then to 150 DEG C. to remove the solvent, and after heating at the same temperature but under reduced pressure for a period, the temperature was finally raised to 170 DEG C. while still under reduced pressure, to yield a light brown resin which did not melt under 340 DEG C.ALSO:A complex of the formula Mg[Al(OR)4]2, wherein R is an alkyl radical of 1 to 6 carbon atoms, may be made by the interaction of Mg-and Al-alkoxides in the approximate molar ratio of 1 : 2. Thus bis-(tetrabutoxy-aluminium) magnesium can be made by mixing the appropriate molar proportions of Mg- and Al-n-butoxides in a small quantity of n-butanol; or by reacting Al with a solution of Mg-n-butoxide, as described in Annalen, 1927, 455, 227 and ibid 1929, 476, 113.