Patent ID: 8357748

Claim:
A process for the manufacture of a curable composition comprising a peroxide curable first fluoroelastomer, dynamically cured gel particles of a second fluoroelastomer and an uncured third fluoroelastomer, said process comprising: A) forming a blend of dynamically cured gel particles of said second fluoroelastomer dispersed in said uncured third fluoroelastomer by introducing uncured second fluoroelastomer, uncured third fluoroelastomer, organic peroxide and multifunctional unsaturated coagent into an internal mixer or extruder and dynamically curing said second fluoroelastomer at a temperature above the decomposition temperature of the organic peroxide; and B) combining said blend of dynamically cured gel particles of said second fluoroelastomer dispersed in said uncured third fluoroelastomer with said first fluoroelastomer, organic peroxide and multifunctional unsaturated coagent, at a temperature below the decomposition temperature of the organic peroxide, to form a curable fluoroelastomer composition comprising i) 55 to 95 weight percent, based on total weight of all fluoroelastomers in said composition, of a first curable fluoroelastomer comprising copolymerized units of vinylidene fluoride and at least one other fluoromonomer, said first fluoroelastomer having cure sites selected from the group consisting of iodine atoms, bromine atoms, and the combination of iodine and bromine atoms; ii) 5 to 45 weight percent, based on total weight of all fluoroelastomers in said composition, of a blend comprising a) 55 to 95 weight percent, based on total weight of said blend, of cured gel particles of a second fluoroelastomer comprising copolymerized units of vinylidene fluoride and at least one other fluoromonomer, said second fluoroelastomer having cure sites selected from the group consisting of iodine atoms, bromine atoms, and the combination of iodine and bromine atoms; and b) 5 to 45 weight percent, based on total weight of said blend, of an uncured third fluoroelastomer comprising copolymerized units of vinylidene fluoride and at least one other fluoromonomer, said third fluoroelastomer having no bromine or iodine cure sites; iii) less than 1 weight percent, based on total weight of said curable composition, of filler; iv) 0. 1 to 6 parts by weight organic peroxide per hundred parts by weight of said first curable fluoroelastomer; and v) 0.1 to 10 parts by weight multifunctional unsaturated coagent per hundred parts by weight of said first curable fluoroelastomer.