Patent ID: 7151150

Claim:
A process for preparing an organopolysiloxane composition, comprising mixing components: (a) essentially linear organopolysiloxanes which are terminated at both ends by Si-bonded hydroxy groups, (b) optionally, plasticizers, (c) at least one chain extender of the formula (I), R 1 2 NCR 6 2 SiR 1 (OR 2 ) 2 (I) and/or partial hydrolysates thereof, where R 1 are identical or different and are each a monovalent, substituted or unsubstituted hydrocarbon radical, R 2 are identical or different and are each a monovalent, substituted or unsubstituted hydrocarbon radical and R 6 are identical or different and are each hydrogen or a monovalent, substituted or unsubstituted hydrocarbon radical, (d) at least one organic isocyanate deactivator, (e) optionally, one or more silanes of the formula (II) R 3 Si(OR 4 ) 3 (II) and/or their partial hydrolysates, where R 3 is as defined for R 1 , R 4 are identical or different and are each a monovalent, substituted or unsubstituted hydrocarbon radical or a —C(═O)—R 5 or —N═CR 5 2 radical and R 5 are identical or different and each have one of the meanings given for R 2 , and (f) optionally, catalyst(s) for accelerating the reaction of silane (e) with Si—OH groups, and allowing components to react, wherein, in a first step, dihydroxy-terminated organopolysiloxanes (a) are mixed with any plasticizer (b) used and reacted with silanes (c) of the formula (I) and/or their partial hydrolysates, and after a reaction time, in a second step, at least one deactivator (d) is added, and optionally, in a third step, Si—OH groups still present are reacted by addition of silane(s) (e) of the formula (II) and/or their partial hydrolysates, and optionally, catalyst (f), and wherein the organic isocyanate deactivator is present in an amount of 0.0084 to 0.2 weight percent based on the weights of components a)–f).