CURABLE COMPOSITIONS OF RESIN-LINEAR ORGANOSILOXANE BLOCK COPOLYMERS

摘要

Curable compositions of “resin-linear” organosiloxane block copolymers comprising a superbase catalyst are disclosed. The addition of a superbase catalyst to compositions of certain resin-linear organosiloxane block copolymers results in curable compositions having faster cure rates, and improved mechanical strength and/or thermal stability over similar compositions without the superbase catalyst

主权项

1. A curable composition comprising:
i) an organosiloxane block copolymer comprising:
40 to 90 mole percent disiloxy units of the formula [R12SiO2/2],10 to 60 mole percent trisiloxy units of the formula [R2SiO3/2],
0.5 to 35 mole percent silanol groups [≡SiOH]; wherein:
R1 is independently a C1 to C30 hydrocarbyl,R2 is independently a C1 to C20 hydrocarbyl; wherein:
the disiloxy units [R12SiO2/2] are arranged in linear blocks having an average of from 10 to 400 disiloxy units [R12SiO2/2] per linear block,the trisiloxy units [R2SiO3/2] are arranged in non-linear blocks having a molecular weight of at least 500 g/mole, and at least 30% of the non-linear blocks are crosslinked with each other, each linear block is linked to at least one non-linear block; andthe organosiloxane block copolymer has a weight average molecular weight (MW) of at least 20,000 g/mole; and ii) a superbase catalyst.