METHOD FOR PREPARING POLYORGANOSILOXANES Russian patent published in 2007 - IPC C08G77/08 

FIELD: organic chemistry, chemistry of polymers.

SUBSTANCE: invention relates to a method for synthesis of polyorganosiloxanes. Invention proposes a method for synthesis of polyorganosiloxanes of the general formula: YO[Si(CH₃)₂O]_p[SiR¹R²O]_qY (wherein p = 10-10000; q = 1-5000; R¹ means methyl; R² means vinyl, phenyl; Y means hydrogen atom (H) or R³R⁴R⁵Si- and wherein R³ means methyl; R⁴ and R⁵ means methyl, vinyl). Method involves interaction of organosiloxanediols of the formula: HO[Si(CH₃)₂O]_nH wherein n = 10-10000 with organocyclosiloxanes of the formula: [SiR¹R²O]_m wherein m = 3-5; R¹ and R have abovementioned values, or their mixture and triorganosilanols of the formula: R³R⁴R⁵SiOH wherein R³, R⁴ and R⁵ have abovementioned values at the mass parts of organosiloxanediol from 0.5 to 0.995, organocyclosiloxane from 0.005 to 0.5, and triorganosilanol from 0 to 0.01. The process is carried out in the presence of catalytic amounts of hydroxides, silanolates or siloxanolates of metals of I-st group (Li, Na, K) taken in the amount (1 x 10^-3)-(5 x 10^-2) mas.% at temperatures lower the depolymerization point for 1-5 h. Under these conditions the process results to formation of statistic copolymers and significant decreasing the content of low-molecular organocyclosiloxanes relatively to their equilibrium amount. Invention provides decreasing content of low-molecular organocyclosiloxanes by 1.5-5 times that allows removing their distillation stage and provides enhancing yield of end substances.

EFFECT: improved method of synthesis.

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