members of a foerdervorrichtung for leaves from kautscuk or similar adhesive materials, especially for embedded in rubber gewebeabschnitte weird cut

摘要

The invention comprises cyclic siloxanes of the formula FORM:0804098/IV (a)/1 where x is 3 or 4, and R is an alkyl radical of 1 to 4 carbon atoms. They are prepared by thermal or catalytic cracking of the hydrolysis products of silanes of the formula ROOC.CH(CH3)CH2Si(CH3)X2 where X is a hydrolysable radical such as chlorine, bromine or alkoxy. These silanes may be prepared by reacting, e.g., CH3SiHCl2 with an alkyl methacrylate in the presence of chloroplatinic acid, as described in Specification 804,097. Thermal cracking of the hydrolysate is effected at about 300 DEG C. Catalytic cracking is effected at 200 DEG to 300 DEG C., suitable catalysts being sodium or potassium hydroxide. Small yields of the cyclics can be obtained by distillation of the hydrolysate. The compounds may be copolymerized with other siloxanes of the general formula R1mSiO 4-m/2 , where R1h is a monovalent hydrocarbon or halogenated hydrocarbon radical, by heating the two siloxanes at 140 DEG to 175 DEG C. in the presence of alkaline catalysts. The cyclics are useful as lubricants and as intermediates, e.g. by reacting with polyhydric alcohols in the production of modified alkyds. In the examples, the methyl, ethyl and butyl esters are prepared. Specifications 706,290, 769,496 and 788,842 also are referred to.