Epoxy-curable silicone release coating composition and methods for its preparation and use
An epoxy-curable silicone release coating composition and methods for its preparation and use are provided. The composition contains an inhibited Lewis acid catalyst. Releasing the Lewis acid catalyst from the inhibitor allows the Lewis acid to catalyze cure of the epoxy-groups. The composition can be coated on various substrates and cured to form a release liner.
1. An epoxy-curable silicone release coating composition comprising:
(A) an epoxy-functional polyorganosiloxane comprising unit formula
(R 1 R 2 R 3 SiO 1/2 ) a (R 1 SiO 3/2 ) c (SiO 4/2 ) d (ZO 1/2 ) e , where each R 1 is independently selected from the group consisting of an alkyl group and an alkyl group functionalized with a cyclic epoxy-functional group, each R 2 is an alkyl group, each R 3 is an alkyl group, and subscript a>1, subscript c>1, subscript d>1, and e>0, and Mn is >2,000 g/mol to 200,000 g/mol;
(B) an inhibited catalyst selected from the group consisting of
(B-1) a complex comprising
(i) a fluorinated triaryl borane; and
(ii) an amine of formula R 4 R 5 R 6 N, where and where each of R 4 , R 5 , and R 6 is independently selected from the group consisting of alkyl and substituted alkyl, and each of R 4 , R 5 , and R 6 is connected to the nitrogen by a non-conjugated carbon; and
(B-2) a Bridged Frustrated Lewis Pair comprising a complex of
(i) the fluorinated triaryl borane;
(ii) a Lewis base selected from the group consisting of PR 7 3 , P(NR 7 2 ) 3 , NR 7 3 , N(SiR 7 3 ) x R 7 3-x , P(N—R 7 )R 7 3 and
where each R 7 is independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, and substituted aryl; and
(iii) a bridging molecule connecting the fluorinated triaryl borane and the Lewis base, where the bridging molecule is selected from the group consisting of carbon dioxide, H 2 , nitriles, alkenes, alkynes, ketones, esters and aldehydes.
2. The composition of claim 1 where the fluorinated triaryl borane has formula
where each R is independently selected from the group consisting of H, F and CF 3 , with the proviso that at least one instance of R per molecule is F or CF 3 .
3. The composition of claim 1 where the amine is a trialkyl amine.
4. The composition of claim 3 , where the trialkyl amine is selected from the group consisting of triethylamine, tripropylamine, tributylamine, tripentylamine and trihexylamine.
5. The composition of claim 1 , where the Lewis base is PR 7 3 , and each R 7 is an alkyl group.
6. The composition of claim 1 , where the bridging molecule is carbon dioxide.
7. A method for preparing the epoxy-curable silicone release coating composition comprising:
(A) an epoxy-functional polyorganosiloxane comprising unit formula
(R 1 R 2 R 3 SiO 1/2 ) a (R 1 SiO 3/2 ) c (SiO 4/2 ) d (ZO 1/2 ) e , where each R 1 is independently selected from the group consisting of an alkyl group and an alkyl group functionalized with a cyclic epoxy-functional group, each R 2 is an alkyl group, each R 3 is an alkyl group, and subscript a>1, subscript c>1, subscript d>1, and e>0, and Mn is >2,000 g/mol to 200,000 g/mol;
(B) an inhibited catalyst selected from the group consisting of
(B-1) a complex comprising
(i) a fluorinated triaryl borane; and
(ii) an amine of formula R 4 R 5 R 6 N, where, and where each of R 4 , R 5 , and R 6 is independently selected from the group consisting of alkyl, and substituted alkyl, and each of R 4 , R 5 , and R 6 is connected to the nitrogen by a non-conjugated carbon; and
(B-2) a Bridged Frustrated Lewis Pair comprising a complex of
(i) the fluorinated triaryl borane;
(ii) a Lewis base selected from the group consisting of PR 7 3 , P(NR 7 2 ) 3 , NR 7 3 , N(SiR 7 3 ) x R 7 3-x , P(N—R 7 )R 7 3 and
where each R 7 is independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, and substituted aryl; and
(iii) a bridging molecule connecting the fluorinated triaryl borane and the Lewis base, where the bridging molecule is selected from the group consisting of carbon dioxide, H 2 , nitriles, alkenes, alkynes, ketones, esters and aldehydes, where the method comprises mixing, under ambient conditions, starting materials comprising (A) and (B).
8. The method of claim 7 , further comprising coating the epoxy-curable silicone release coating composition on a substrate.
9. The method of claim 8 , where the substrate comprises glassine paper.
10. The method of claim 8 , where the substrate comprises thermal paper.
11. The method of claim 8 , further comprising heating the epoxy-curable silicone release coating composition at 80° C. to 95° C. for 10 seconds to 50 seconds to cure.