Crosslinkable fluororubber composition and crosslinked rubber article
Obtaining a crosslinked rubber with high flexibility at low temperature includes crosslinking a fluororubber composition. The fluororubber composition includes a fluororubber and a compound of formula (X—) x (Z—) z Y. In the formula, X is U—(CF 2 ) a O(CF 2 CF 2 O) b —; Z is R F O(CF 2 CF 2 O) c —; Y is a (x+z) valent perfluoro saturated hydrocarbon group, optionally interrupted by an etheric oxygen atom; x is an integer of at least 3; z is an integer of at least 0; U is a monovalent group with an unsaturated hydrocarbon, a bromine atom, an iodine atom, or a combination thereof; R F is a C 1-20 linear perfluoroalkyl group, optionally interrupted by an etheric oxygen atom; a is an integer of from 0 to 20; b is an integer of from 1 to 200; and c is an integer of from 3 to 200.
1. A crosslinkable fluororubber composition comprising a fluororubber and a compound represented by the following formula (A):
(X—) x (Z—) z Y (A)
wherein X is a group represented by the following formula (X), Z is a group represented by the following formula (Z), Y is a (x+z) valent perfluoro saturated hydrocarbon group or such a group having an etheric oxygen atom inserted between carbon atoms thereof, x is an integer of at least 3, z is an integer of at least 0, x+z is an integer of at least 3,
U—CF 2 ) a O(CF 2 CF 2 O) b — (X)
R F O(CF 2 CF 2 O) c — (Z)
wherein U is a monovalent group having at least one member selected from the group consisting of an unsaturated hydrocarbon, a bromine atom and an iodine atom, R F is a C 1-20 linear perfluoroalkyl group or such a group having an etheric oxygen atom inserted between carbon atoms thereof, a is an integer of from 0 to 20, b is an integer of from 1 to 200, and c is an integer of from 3 to 200.
2. The crosslinkable fluororubber composition according to claim 1 , wherein the compound represented by the formula (A) is a compound represented by the following formula (A1):
(X—) x1 Y (A1)
wherein x1 is an integer of 3 or 4.
3. The crosslinkable fluororubber composition according to claim 2 , wherein x1 in the formula (A1) is 3, and Y is any one of the groups (Y 3 -1) to (Y 3 -4) represented by the following formulae:
4. The crosslinkable fluororubber composition according to claim 1 , wherein the compound represented by the formula (A) is a compound represented by the following formula (A2):
wherein each of b1, b2 and b3 which are independent of one another, is an integer of from 1 to 20.
5. The crosslinkable fluororubber composition according to claim 1 , wherein the compound represented by the formula (A) has a number average molecular weight (Mn) of from 500 to 100,000.
6. The crosslinkable fluororubber composition according to claim 1 , wherein the compound represented by the formula (A) has a ratio (Mw/Mn) of the mass average molecular weight (Mw) to the number average molecular weight (Mn) of from 1.0 to 2.0.
7. The crosslinkable fluororubber composition according to claim 1 , which contains the compound represented by the formula (A) in an amount of from 1 to 50 parts by mass per 100 parts by mass of the fluororubber.
8. The crosslinkable fluororubber composition according to claim 1 , wherein the fluororubber is at least one member selected from the group consisting of a tetrafluoroethylene/propylene copolymer, a vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymer and a tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer.
9. The crosslinkable fluororubber composition according to claim 1 , which further contains an organic peroxide.
10. A crosslinked rubber article formed by crosslinking the crosslinkable fluororubber composition as defined in claim 1 .
11. The crosslinked rubber article according to claim 10 , which is a sealing material.