Patent ID: 8592545

Claim:
A polymer composition curable to a water-insoluble hydrophilic polymer network, said composition comprising a polyorganosiloxane polyoxyalkylene block copolymer of the form PS-(A-PO-A-PS) n , wherein PS represents a polydimethylsiloxane block having from 4 to 40 siloxane units terminated with an alkoxy-substituted siloxane unit which is linked via oxygen to another silicon atom of the PS block and which has the formula wherein R represents an alkyl group having 1 to 4 carbon atoms and each R′ represents an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an alkoxy group of the formula —OR, PO is a polyoxyalkylene block having the general formula —(C s H 2s O) t —where each s independently has a value of from 2 to 6 and t has a value of from 4 to 40, with the proviso that at least 50% of the polyoxyalkylene units in the polyoxyalkylene block are oxyethylene units, A is a divalent radical having from 2 to 10 carbon atoms, n has a value of at least 1, and the molar ratio of oxyalkylene units to siloxane units in the polyorganosiloxane polyoxyalkylene block copolymer is in the range 0.05:1 to 0.5:1, and a branched polyorganosiloxane cross-linking agent comprising one or more siloxane Q units of the formula (SiO 4/2 ), 0 to 250 D units of the formula R b 2 SiO 2/2 and M units of the formula R a 3 SiO 1/2 wherein the R a R b and R c substituents are selected from alkyl and alkoxy groups having 1 to 6 carbon atoms, at least three R a , R b and/or R c substituents being alkoxy units.