Siloxane polyphotoinitiators of the substituted acetophenone type

TLDR: An organopolysiloxane photoinitiator having an average of at least two siloxane units has the formula: X.sub.b SiO(.4-a-b)/2 (I).

Abstract: An organopolysiloxane photoinitiator having an average of at least two siloxane units, of which at least an average of one siloxane unit per organopolysiloxane molecule has the formula: X.sub.a R.sub.b SiO(.sub.4-a-b)/2 (I) wherein a is an integer of 1-3, b is an integer of 0-2 and a plus b equals 1-3; R is C 1 -C 10 hydrocarbyl or halogen substituted C 1 -C 10 hydrocarbyl; and X is a substituted acetophenone photomoiety selected from: ##STR1## where R 1 is any substituent which will not interfere with hydrosilation, n is an integer between 0 and 5 in formulas (II), (IIa), (III), (IIIa), (IV) and (IVa) and between 0 and 4 in formula (III) and (IIIa); m is 0 or 1; R 2 is alkyl or substituted alkyl; R 3 is H, alkyl or aryl; R 4 is a divalent hydrocarbon group having between 2 and 10 carbon atoms or an alkylene oxy alkylene group; R 5 is a group selected from H, alkyl, aryl, organosilyl, or the reaction product of an isocyanate esterification reagent or an etherification reagent with the hydroxyl product formed when R 5 is H and R 6 is a trivalent hydrocarbon or hydrocarbon oxyhydrocarbon group. The silicones are prepared by hydrosilation of the corresponding olefinically or acetylenically unsaturated acetophenones.