PROCESS FOR PRODUCING LOW MOLECULAR WEIGHT POLYSILOXANE POLYMER OF WHICH THE BOTH TERMINALS ARE SILANOL GROUPS

摘要

PURPOSE: A process for producing a low molecular weight polysiloxane polymer of which the both terminals are silanol groups, is provided to generate few byproducts and to use the polysiloxane polymer as a plasticizer when producing a silicon rubber and as an intermediate when producing other siloxane polymers. CONSTITUTION: The process comprises the steps of: equilibrium-reacting 100pts.wt. of a cyclosiloxane(formula 1: £SiR1R2O|n) and 30-80pts.wt. of a dialkoxy silane(formula 2: R3R4Si(OR5)2) and 0.5-5pts.wt. of an acidic catalyst at 50-130deg.C to prepare a low molecular weight polysiloxane polymer of which the both terminals are alkoxy groups; adding water to the low molecular weight polysiloxane polymer of which the both terminals are alkoxy groups to substitute the alkoxy groups for the silanol groups by a hydrolysis and then removing a solid catalyst and the byproducts. The low molecular weight polysiloxane polymer of which the both terminals are silanol groups, has a molecular weight of 300-900 and the OH content of 4-7%. In the formulas, R1-R4 are methyl, vinyl, or phenyl, R5 is C1-C10 alkyl, and n is an integer of 3-12.