Unsaturated organic adduct of an organohydrogenpolysiloxane as an improved crosslinking agent for silicone pressure-sensitive adhesives
AssigneeDow Corning Corporation
InventorsGary A. Vincent, William P. Brady
Life of this patent
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Abstract
There is disclosed a silicone pressure-sensitive adhesive composition based on a siloxane resin component, a polydiorganosiloxane polymer component having unsaturated groups in its molecule, a silicon hydride-functional crosslinking agent and a hydrosilation catalyst, wherein the crosslinking agent is a reaction product of a cyclic or linear organohydrogenpolysiloxane and an unsaturated organic compound selected from alpha-alkenes having 6 to 28 carbon atoms or aromatic compounds having the formula Ph-R.sup.4, wherein Ph represents a phenyl radical and R.sup.4 is a terminally unsaturated monovalent hydrocarbon group having 2 to 6 carbon atoms.
Claims28
In a silicone pressure-sensitive adhesive comprising a siloxane polymer having at least two olefinically unsaturated groups in its molecule, a siloxane resin, an SiH-functional crosslinking agent and a catalytic amount of a platinum group metal-containing catalyst, the improvement comprising using as said crosslinking agent a hydrosilation reaction product of
- (I) an organohydrogenpolysiloxane selected from the group consisting of a cyclic siloxane having the formula ##STR6## a linear siloxane having the formula ##STR7## and a linear siloxane having the formula ##STR8## wherein R.sup.3 is independently selected from the group consisting of alkyl radicals having 1 to 4 carbon atoms, a phenyl radical, a trifluoropropyl radical and a chloropropyl group, x has an average value of 4 to 8, y has an average value of 5 to 25 and z has an average value of 1 to 20, with the proviso that y+z .ltoreq.25;
- and
- (II) an unsaturated organic compound selected from the group consisting of an alpha-alkene having 6 to 28 carbon atoms and an aromatic compound having the formula Ph-R.sup.4, wherein Ph represents a phenyl radical and R.sup.3 is a terminally unsaturated monovalent hydrocarbon group having 2 to 6 carbon atoms.
A silicone pressure-sensitive adhesive composition consisting essentially of:
- (A) 50 to 90 parts by weight of a soluble organopokysiloxane consisting essentially of R.sub.3 SiO.sub.1/2 siloxane units and SiO.sub.4/2 siloxane units wherein each R denotes a monovalent radical selected from the group consisting of hydrocarbon and halogenated hydrocarbon radicals, at least 1/3 of all R radicals being methyl and the mole ratio of R.sub.3 SiO.sub.1/2 siloxane units to SiO.sub.4/2 siloxane units in the soluble organopolysiloxane having a value of from 0.6 to 1.6;
- (B) 10 to 50 parts by weight of a polydiorganosiloxane having the general formula R.sup.1 R.sup.2.sub.2 SiO(R.sup.2.sub.2 SiO).sub.n SiR.sup.2.sub.2 R.sup.1 wherein each R.sup.2 denotes a monovalent radical independently selected from the group consisting of hydrocarbon and halogenated hydrocarbon radicals, at least 1/2 of all R.sup.2 radicals being methyl, each R.sup.1 denotes a radical selected from the group consisting of R.sup.2 radicals and OH radicals, the subscript n has an average value of at least 50 and wherein at least two R.sup.2 radicals contain olefinic unsaturation, the sum of components (A) and (B) being 100 parts by weight;
- (C) a crosslinking agent which is a hydrosilation reaction product of
- (I) an organohydrogenpolysiloxane selected from the group consisting of a cyclic siloxane having the formula ##STR9## a linear siloxane having the formula ##STR10## and a linear siloxane having the formula ##STR11## wherein R.sup.3 is independently selected from the group consisting of alkyl radicals having 1 to 4 carbon atoms, a phenyl radical, a trifluoropropyl radical and a chloropropyl group, x has an average value of 4 to 8, y has an average value of 5 to 25 and z has an average value of 1 to 20, with the proviso that y+z.ltoreq.25, and
- (II) an unsaturated organic compound selected from the group consisting of an alpha-alkene having 6 to 28 carbon atoms and an aromatic compound having the formula Ph-R.sup.4, wherein Ph represents a phenyl radical and R.sup.4 is a terminally unsaturated monovalent hydrocarbon group having 2 to 6 carbon atoms, the amount of (C) present in the composition being sufficient to provide from 1 to about 15 SiH groups for each olefinic radical in said composition;
- and
- (D) a curing amount of a platinum group metal-containing catalyst.
A solventless silicone pressure-sensitive adhesive composition consisting essentially of:
- (A) 50 to 90 parts by weight of a soluble organopolysiloxane having a M.sub.n value of about 2,300 to 3,000 and consisting essentially of (CH.sub.3).sub.3 SiO.sub.1/2 siloxane units and SiO.sub.4/2 siloxane units in a mole ratio of 1.1/1 to 1.4/1, respectively;
- (B) 10 to 50 parts by weight of a polydiorganosiloxane having the general formula R.sup.2.sub.3 SiO(R.sup.2.sub.2 SiO).sub.n SiR.sup.2.sub.3 wherein R.sup.2 is selected from the group consisting of methyl radicals, phenyl radical, and alkenyl radicals having 2 to 14 carbon atoms, with the proviso that at least two R.sup.2 radicals per molecule are said alkenyl radicals and at least 85 percent of R.sup.2 radicals are methyl, and n has an average value of 50 to 200, the sum of components (A) and (B) being 100 parts by weight;
- (C) a crosslinking agent which is a hydrosilation reaction product of
- (I) an organohydrogenpolysiloxane selected from the group consisting of a cyclic siloxane having the formula ##STR16## a linear siloxane having the formula ##STR17## and a linear siloxane having the formula ##STR18## wherein R.sup.3 is a methyl radical, x has an average value of 4 to 8, y has an average value of 5 to 25 and z has an average value of 1 to 20, with the provisor that y+z.ltoreq.25, and
- (II) an unsaturated organic compound selected from the group consisting of an alpha-alkene having 6 to 28 carbon atoms and an aromatic compound having the formula Ph-R.sup.4, wherein Ph represents a phenyl radical and R.sup.4 is a terminally unsaturated monovalent hydrocarbon group having 2 to 6 carbon atoms, the product of (C) present in the composition being sufficient to provide from 1 to about 4 SiH groups for each alkenyl radical in (B);
- (D) a curing amount of a platinum group metal-containing catalyst;
- and, optionally,
- (E) an effective amount of an inhibitor for said catalyst (D).
Dependencies are inferred from the claim text.