Process for producing organopolysiloxane with high polymerization degree

Claim 1

A process for producing a triorganosilyl-end blocked organopolysiloxane with a high polymerization degree of 3,000 or more, comprising mixing an organopolysiloxane having a silanol group at both terminal ends of its molecular chain represented by the following general formula (1): ##STR9## wherein R 1 and R 2 are the same or different and are each an unsubstituted or halogen atom or cyano group substituted monovalent hydrocarbon group, and n is an integer of 2 to 3,000, with a compound that functions as both the reaction catalyst and chain lengthener and is at least one member selected from the group consisting of silanes, siloxanes and their mixtures, said silanes and siloxanes each having at least two dialkylaminosilyl groups per molecule, in amounts such that the molar ratio of silanol groups to dialkylaminosilyl groups is from 0.5 to 3.0, and heating the resulting mixture to produce a chain-lengthened organopolysiloxane with a high polymerization degree, wherein said heating is carried out in the presence of an organosilicon compound having the following general formula (2): ##STR10## wherein a is 1 or 2, R 3 , R 4 and R 5 are the same or different and are each an unsubstituted or halogen atom or cyano group substituted monovalent hydrocarbon group, and Z is a hydroxyl group, a halogen atom or --NR 6 R 7 where a=1, and =NX where a=2 wherein R 6 and R 7 are the same or different and are each an unsubstituted or halogen atom or cyano group substituted monovalent hydrocarbon group, and X is a hydrogen atom or an unsubstituted or halogen atom or cyano group substituted monovalent hydrocarbon group or is followed by reacting said organosilicon compound with the chain-lengthened organopolysiloxane, said dialkylaminosilyl-containing silane or siloxane comprising a compound having the following general formula (4): ##STR11## wherein R 8 and R 9 are each an unsubstituted or halogen atom or cyano group substituted monovalent hydrocarbon group, R 10 is an alkyl group, and q is an integer of 0 to 1,000.