Silicone release coating compositions
A branched siloxane contains at least three aliphatically unsaturated hydrocarbon groups, is terminated by units of the formula R a R b 2 SiO 1/2 and otherwise consists of: i) one or more units of the formula (SiO 4/2 ); and ii) from 15 to 995 units of the formula R b 2 SiO 2/2 which units (i) and (ii) may be inter-linked in any appropriate combination. The invention includes a method of making the branched siloxane and release coating and release modifier compositions containing the branched siloxane.
1 . A method for the preparation of a branched siloxane comprising the steps of:
a) mixing a compound having the general formula (SiO 4/2 ) (R a R b 2 SiO 1/2 ) 4 with a cyclic polydiorganosiloxane, and/or a substantially linear hydroxy terminated polydiorganosiloxane wherein each R a substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms an alkenyl group having from 1 to 6 carbon atoms and an alkynyl group having from 1 to 6 carbon atoms, the R a substituent in at least part of the compound being selected from alkenyl and alkynyl, and each R b substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an aryl group, an alkoxy group, an acrylate group and a methacrylate group;
b) causing the mixture to react in the presence of an acid or phosphazene base catalyst at a temperature of up to 180° C.; and
c) neutralising the reaction mixture.
2 . The method for the preparation of a branched siloxane of claim 1 where the reaction occurs in the presence of an acid catalyst.
3 . The method for the preparation of a branched siloxane of claim 1 where the reaction occurs in the presence of a phosphazene base catalyst.
4 . The method for the preparation of the branched siloxane of claim 1 wherein there is from 1.1 to 22.1% by weight of (SiO 4/2 ) (R a R b 2 SiO 1/2 ) 4 in the mixture of step (a) with the remainder of the mixture comprising up to 100% by weight of the cyclic polydiorganosiloxane and/or the substantially linear hydroxy terminated polydiorganosiloxane.
5 . A multi-pack release coating composition comprising a first pack comprising a branched siloxane consisting of (a) at least one Q unit of the formula (SiO 4/2 ) and (b) from 15 to 995 D units of the formula R b 2 SiO 2/2 which units (a) and (b) may be inter-linked in any appropriate combination, and (c) M units of the formula R a R b 2 SiO 1/2 , wherein each R a substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having from 1 to 6 carbon atoms and an alkynyl group having from 1 to 6 carbon atoms, at least three R a substituents in the branched siloxane being alkenyl or alkynyl units, and each R b substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, an alkoxy group, an acrylate group and a methacrylate group; a hydrosilylation inhibitor; and a catalyst, a second pack comprising an organohydrogenpolysiloxane cross-linking agent, and a third pack comprising a silicone release modifier; a catalyst; and a hydrosilylation inhibitor.
6 . A multi-pack release coating composition according to claim 5 where at least 50 percent of the R a substituents are alkenyl groups.
7 . A multi-pack release coating composition of claim 5 where the branched siloxane has the general formula
where each n is independently from 1 to 100.
8 . A multi-pack release coating composition comprising a first pack comprising a branched siloxane consisting of (a) at least one Q unit of the formula (SiO 4/2 ) and (b) from 15 to 995 D units of the formula R b 2 SiO 2/2 which units (a) and (b) may be inter-linked in any appropriate combination, and (c) M units of the formula R a R b 2 SiO 1/2 , wherein each R a substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having from 1 to 6 carbon atoms and an alkynyl group having from 1 to 6 carbon atoms, at least three R a substituents in the branched siloxane being alkenyl or alkynyl units, and each R b substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, an alkoxy group, an acrylate group and a methacrylate group; a hydrosilylation inhibitor; and an organohydrogenpolysiloxane cross-linking agent, a second pack comprising a catalyst, and a third pack comprising a silicone release modifier; an organohydrogenpolysiloxane cross-linking agent; and a hydrosilylation inhibitor.
9 . A multi-pack release coating composition according to claim 8 where at least 50 percent of the R a substituents are alkenyl groups.
10 . A multi-pack release coating composition of claim 8 where the branched siloxane has the general formula
where each n is independently from 1 to 100.
11 . A multi-pack release coating composition comprising a first pack comprising a branched siloxane consisting of (a) at least one Q unit of the formula (SiO 4/2 ) and (b) from 15 to 995 D units of the formula R b 2 SiO 2/2 which units (a) and (b) may be inter-linked in any appropriate combination, and (c) M units of the formula R a R b 2 SiO 1/2 , wherein each R a substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having from 1 to 6 carbon atoms and an alkynyl group having from 1 to 6 carbon atoms, at least three R a substituents in the branched siloxane being alkenyl or alkynyl units, and each R b substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, an alkoxy group, an acrylate group and a methacrylate group; a second pack comprising an organohydrogenpolysiloxane cross-linking agent, a third pack comprising a catalyst, a fourth pack comprising a silicone release modifier, and a fifth pack comprising a hydrosilylation inhibitor.
12 . A multi-pack release coating composition according to claim 11 where at least 50 percent of the R a substituents are alkenyl groups.
13 . A multi-pack release coating composition of claim 11 where the branched siloxane has the general formula
where each n is independently from 1 to 100.
14 . A multi-pack release coating composition comprising a first pack comprising a branched siloxane consisting of (a) at least one Q unit of the formula (SiO 4/2 ) and (b) from 15 to 995 D units of the formula R b 2 SiO 2/2 which units (a) and (b) may be inter-linked in any appropriate combination, and (c) M units of the formula R a R b 2 SiO 1/2 , wherein each R a substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having from 1 to 6 carbon atoms and an alkynyl group having from 1 to 6 carbon atoms, at least three R a substituents in the branched siloxane being alkenyl or alkynyl units, and each R b substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, an alkoxy group, an acrylate group and a methacrylate group; a catalyst; a hydrosilylation inhibitor; and an organohydrogenpolysiloxane cross-linking agent, and a second pack comprising a catalyst; a silicone release modifier; an organohydrogenpolysiloxane cross-linking agent; and a hydrosilylation inhibitor.
15 . A multi-pack release coating composition according to claim 14 where at least 50 percent of the R a substituents are alkenyl groups.
16 . A multi-pack release coating composition of claim 14 where the branched siloxane has the general formula
where each n is independently from 1 to 100.
17 . A multi-pack release coating composition comprising a first pack comprising a branched siloxane consisting of (a) at least one Q unit of the formula (SiO 4/2 ) and (b) from 15 to 995 D units of the formula R b 2 SiO 2/2 which units (a) and (b) may be inter-linked in any appropriate combination, and (c) M units of the formula R a R b 2 SiO 1/2 , wherein each R a substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having from 1 to 6 carbon atoms and an alkynyl group having from 1 to 6 carbon atoms, at least three R a substituents in the branched siloxane being alkenyl or alkynyl units, and each R b substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, an alkoxy group, an acrylate group and a methacrylate group; and a catalyst, a second pack comprising an organohydrogenpolysiloxane cross-linking agent, a third pack comprising a silicone release modifier; and a catalyst, and a fourth pack comprising hydrosilylation inhibitor.
18 . A multi-pack release coating composition according to claim 17 where at least 50 percent of the R a substituents are alkenyl groups.
19 . A multi-pack release coating composition of claim 17 where the branched siloxane has the general formula
where each n is independently from 1 to 100.