PURPOSE: To obtain a fluororubber copolymer having excellent compression set over a wide temperature range from low to high temperatures by the radical copolymerization of five kinds of fluorinated monomers in the presence of a specified diiodo compound.
CONSTITUTION: The copolymer is obtained by radical polymerization in the presence of a diiodo compound represented by the formula RI2 (wherein R is a 1-16C saturated fluorohydrocarbon, etc.) and contains 0.005-1.5mol% iodinated fluorinated vinyl ether units of the formula (wherein m is 1 to 5; and n is 0 to 3), 40-90mol% vinylidene fluoride units, 3-35mol% perfluoro(methyl vinyl ether) units, 0-25mol% hexafluoropropylene units, and 0-40mol% tetrafluoroethylene units. The iodine atoms introduced into the copolymer from the diiodo compound and the iodinated compound of the formula respectively account for 0.01-1wt.% and 0.01-2wt.% of the total weight of the copolymer, and the copolymer has a Mooney viscosity [ML1+10(100°C)] of 20 to 150.
KITAICHI MASAKI
UEDA YUTAKA
KISHINE MITSURU
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