COAGENT FOR FREE RADICAL CURING FLUOROELASTOMERS
Disclosed herein are curable compositions comprising a free radical curable fluoroelastomer, a free radical generating compound and an unsaturated metal compound coagent. Such compositions cure well, exhibit good (i.e. low) compression set resistance and process well (i.e. have reduced polymer viscosity compared to similar compositions not containing the unsaturated metal compound coagent).
1 . A curable fluoroelastomer composition comprising:
A) a fluoroelastomer having chloro, bromo or iodo cure sites;
B) a free radical generating compound; and
C) an unsaturated metal compound coagent having the formula Y (4-n) MX n wherein Y is selected from alkyl, aryl, carboxylic acid, or alkyl ester groups; M is selected from Si, Ge, Sn, or Pb; X is an allyl group CR 1 R 2 CR 3 ═CR 4 R 5 , vinyl group CR 1 ═CR 2 R 3 , allenyl group CR 1 ═C═CR 2 R 3 , alkynyl group C≡CR 1 , or propargyl group CR 1 R 2 C≡CR 3 ; R 1 —R 5 are selected independently from the group consisting of H, F, alkyl, aryl, heterocycle, or perfluoroalkyl groups; and n is 1, 2, or 3.
2 . The curable composition of claim 1 wherein said unsaturated metal compound coagent is of the formula Y (4-n) MX n wherein M is Sn, X is allyl group CR 1 R 2 CR 3 ═CR 4 R 5 , Y is alkyl or aryl, R 1 —R 5 are H and n is 1 or 2.
3 . The curable composition of claim 2 wherein said unsaturated metal compound coagent is allyltrioctylstannane.
4 . The curable composition of claim 2 wherein said unsaturated metal compound coagent is allyltriphenylstannane.
5 . The curable composition of claim 2 wherein said unsaturated metal compound coagent is diallyldioctylstannane.
6 . The curable composition of claim 1 wherein said unsaturated metal compound coagent is of the formula Y (4-n) MX n wherein M is Sn, X is vinyl group CR 1 ═CR 2 R 3 , Y is alkyl or aryl, R 1 —R 3 are H and n is 1.
7 . The curable composition of claim 6 wherein said unsaturated metal compound coagent is vinyltrioctylstannane.
8 . The curable composition of claim 6 wherein said unsaturated metal compound coagent is vinyltriphenylstannane.
9 . The curable composition of claim 1 wherein said unsaturated metal compound coagent is of the formula Y (4-n) MX n wherein M is Ge, X is allyl group CR 1 R 2 CR 3 ═CR 4 R 5 , Y is alkyl or aryl, R 1 —R 5 are H and n is 1.
10 . The curable composition of claim 9 wherein said unsaturated metal compound coagent is allyltrioctylgermane.
11 . The curable composition of claim 9 wherein said unsaturated metal compound coagent is allyltriphenylgermane.
12 . The curable composition of one of claims 1 - 11 further comprising a multifunctional coagent.
13 . The curable composition of claim 12 wherein said multifunctional coagent is selected from the group consisting of triallyl cyanurate, trimethacryl isocyanurate, triallyl isocyanurate, trimethallyl isocyanurate, triacryl formal, triallyl trimellitate, N,N′-m-phenylene bismaleimide, diallyl phthalate, tetraallylterephthalamide, tri(diallylamine)-s-triazine, triallyl phosphite, bis-olefins and N,N-diallylacrylamide.
14 . The curable composition of claim 13 wherein said multifunctional coagent is triallyl isocyanurate.
15 . The curable composition of claim 1 wherein said free radical generating compound is an organic peroxide.
16 . The curable composition of claim 1 wherein said free radical generating compound is a photoinitiator.