Patent ID: 7019020

Claim:
A compound of formula I wherein R 1 is hydrogen, C 1-20 -alkyl or C 2-20 -alkenyl; R 2 and R 3 are independently a group —C(R 4 , R 5 )C(R 6 )═C(R 7 ,R 8 ) (a) wherein R 4 , R 5 , R 6 R 7 and R 8 are independently, hydrogen, C 1-10 -alkyl or C 2-10 -alkenyl; or C 2-10 -alkyl or C 3-10 -alkenyl containing at least one oxygen atom interrupting the hydrocarbon chain; or wherein R 4 , R 5 and R 6 are hydrogen, C 1-10 -alkyl or C 2-10 -alkyl containing at least one oxygen atom interrupting the hydrocarbon chain, or alkyl substituted by a silane or oligosiloxane moiety, and one of R 7 and R 8 is a silane or oligosiloxane moiety and the other one of R 7 and R 8 is hydrogen; or a group —C(R 4′ ,R 5′ )CH(R 6′ )CH(R 7′ ,R 8′ ) (b), wherein R 4′ , R 5′ and R 6′ are hydrogen, C 1-10 -alkyl or C 2-10 -alkyl containing at least one oxygen atom interrupting the hydrocarbon chain, or alkyl substituted by silane or oligosiloxane moiety, and one of R 7′ and R 8′ is a silane or oligosiloxane moiety and the other one of R 7′ and R 8′ is hydrogen; and X is phenylene or naphthylene, or substituted phenylene or naphthylene.