Organopolysiloxane photosensitizers and methods for their preparation
AssigneeToray Silicone Company, Ltd.
InventorAkihiko Shirahata
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Abstract
Novel photosensitizers are disclosed which are particularly useful in photopolymerizable organopolysiloxane and silicone resins. The photosensitizers are themselves organopolysiloxanes which contain at least one silicon-bonded benzoin-containing radical. Synthesis methods are disclosed for preparing these photosensitizers which employ, as starting materials, an alkenyl-substituted benzoin and a silicon compound containing at least one silicon-bonded hydrogen atom.
Claims16
An organopolysiloxane photosensitizer comprising an average of at least two siloxane units, of which at least an average of one siloxane unit per organopolysiloxane molecule has the formula Q.sub.a R.sub.b.sup.5 SiO.sub.(4-a-b)/2, wherein Q denotes a benzoin-containing group having the formula ##STR17## R.sup.1 and R.sup.2 each denote, independently, a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having from 1 to 10 carbon atoms, an alkoxy group, a thioalkoxy group, an amino group or a dialkylamino group;
- R.sup.3 denotes a hydrogen atom or a monovalent hydrocarbon group having from 1 to 10 carbon atoms;
- R.sup.4 denotes a divalent hydrocarbon group having from 2 to 10 carbon atoms;
- R.sup.5 denotes a monovalent hydrocarbon group having from 1 to 10 carbon atoms or a halogenated monovalent hydrocarbon group;
- m is an integer of from 1 to 5, n is an integer of from 1 to 5, a is an integer of from 1 to 3, b is an integer of from 0 to 2 and a+b is an integer of from 1 to 3.
A method for preparing an organopolysiloxane photosensitizer comprising an average of at least two siloxane units, of which at least an average of one siloxane unit per organopolysiloxane molecule has the formula Q.sub.a R.sub.b.sup.5 SiO.sub.(4-a-b)/2, said method comprising reacting, by a hydrosilylation reaction, an alkenyl-substituted benzoin reactant having the formula ##STR19## and an organohydrogenpolysiloxane reactant containing at least than two siloxane units and at least one silicon-bonded hydrogen atom per molecule, wherein Q denotes a benzoin-containing group having the formula ##STR20## at each occurrence R.sup.1 and R.sup.2 denote, independently, a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having from 1 to 10 carbon atoms, an alkoxy group, a thioalkoxy group, an amino group or a dialkylamino group;
- R.sup.3 denotes a hydrogen atom or a monovalent hydrocarbon group having from 1 to 10 carbon atoms;
- R.sup.4 denotes a divalent hydrocarbon group having from 2 to 10 carbon atoms;
- R.sup.5 denotes a monovalent hydrocarbon group having from 1 to 10 carbon atoms or a halogenated monovalent hydrocarbon group;
- R.sup.6 denotes an aliphatically unsaturated monovalent hydrocarbon group having the same number of carbon atoms as the R.sup.4 group;
- m is an integer of from 1 to 5, n is an integer of from 1 to 5, a is an integer of from 1 to 3, b is an integer of from 0 to 2 and a+b is an integer of from 1 to 3 whereby the R.sup.6 group becomes the R.sup.4 group during said reaction.
A method for preparing an organopolysiloxane photosensitizer comprising an average of at least two siloxane units, of which an average of at least one siloxane unit per organopolysiloxane molecule has the formula Q.sub.a R.sub.b.sup.5 SiO.sub.(4-a-b)/2, said method comprising
- (A) reacting, by a hydrosilylation reaction to form an adduct, an alkenyl-substituted benzoin reactant having the formula ##STR22## and a silane bearing at least one silicon-bonded hydrogen atom and at least one silicon-bonded hydrolyzable group or a siloxane bearing at least two siloxane units and at least one silicon-bonded hydrogen atom;
- and
- (B) polymerizing the adduct or copolymerizing the adduct with another silane bearing at least one silicon-bonded hydrolyzable radical or with a siloxane, both being free of Q groups, to provide the organopolysiloxane photosensitizer, wherein Q denotes a benzoin-containing group having the formula ##STR23## at each occurrence R.sup.1 and R.sup.2 denote, independently, a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having from 1 to 10 carbon atoms, an alkoxy group, a thioalkoxy group, an amino group or a dialkylamino group;
- R.sup.3 denotes a hydrogen atom or a monovalent hydrocarbon group having from 1 to 10 carbon atoms;
- R.sup.4 denotes a divalent hydrocarbon group having from 2 to 10 carbon atoms;
- R.sup.5 denotes a monovalent hydrocarbon group having from 1 to 10 carbon atoms or a halogenated monovalent hydrocarbon group;
- R.sup.6 denotes an aliphatically unsaturated monovalent hydrocarbon group having the same number of carbon atoms as the R.sup.4 group;
- m is an integer of from 1 to 5, n is an integer of from 1 to 5, a is an integer of from 1 to 3, b is an integer of from 0 to 2 and a+b is an integer of from 1 to 3;
- the R.sup.6 group becoming the R.sup.4 group during said hydrosilylation reaction.
Dependencies are inferred from the claim text.