Method for the redistribution of polyorganosiloxanes
AssigneeDow Corning Corporation
InventorLarry Herbert Wood
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Abstract
Linear hydroxy endblocked linear polyorganosiloxanes, linear chloro-endblocked polyorganosiloxanes, and mixtures thereof, are redistributed in a process by contacting the linear polyorganosiloxanes, with a diorganodichlorosilane having the formula R′2SiCl2, wherein R′ is an alkyl group containing 1-8 carbon atoms; in the presence of an aqueous hydrochloric acid catalyst; to form a redistributed mixture containing cyclic polyorganosiloxanes and chloro-endblocked polyorganosiloxanes. The process generates less amounts of undesired branched siloxane species than processes which utilize an alumina catalyst.
Claims8
A process for the redistribution of linear hydroxy endblocked polyorganosiloxanes, linear chloro-endblocked polyorganosiloxanes, and mixtures thereof, comprising:
- contacting (i) a linear hydroxy endblocked polyorganosiloxane having Formula I:
- (ii) a chloro-endblocked polyorganosiloxane having Formula II:
- or (iii) a mixture of (i) and (ii)
- with (iv) a diorganodichlorosilane having the formula R′2SiCl2 in the presence of a catalyst to form a redistributed mixture comprising cyclic polyorganosiloxanes and chloro-endblocked polyorganosiloxanes having Formula II;
- wherein x and y represent integers having a value of 1-5,000 and R′, R1, and R2 represent alkyl groups containing 1-8 carbon atoms;
- and wherein the catalyst comprises aqueous hydrochloric acid and it is present in an amount of 0.1-70 percent by weight based on the weight of the linear hydroxy endblocked polyorganosiloxanes, the linear chloro-endblocked polyorganosiloxanes, and the diorganodichlorosilanes;
- and the aqueous HCl catalyst contains saturated concentrations of HCl at the temperature and pressure conditions at which the redistribution is conducted.
Dependencies are inferred from the claim text.