Cross-linkable fluoroelastomer, its composition and cross-linked rubber molded product

A method for producing a cross-linkable fluoroelastomer, which comprises

• heat-treating a mixture of a fluoroelastomer (A) and an organic peroxide (B) at a temperature of from 110 to 380° C. for from 10 seconds to 3 hours to form the cross-linkable fluoroelastomer,
• wherein the cross-linkable fluoroelastomer formed by the heat-treating has an absorption peak at from 1,640 to 1,700 cm−1, wherein the intensity of the absorption peak at from 1,640 to 1,700 cm−1 of the infrared absorption spectrum as represented by absorbance of a hot pressed sample having a thickness of 0.2 mm is from 0.05 to 1.5, and
• wherein after the heat treating the cross-linkable fluoroelastomer has more unsaturated carbon-carbon bonds than the fluoroelastomer (A),
• wherein the fluoroelastomer (A) is a tetrafluoroethylene/propylene copolymer.

A cross-linkable fluoroelastomer obtained by a heat-treatment of a mixture of a fluoroelastomer (A) which does not have an absorption peak at from 1,640 to 1,700 cm−1 of the infrared absorption spectrum, and an organic peroxide (B) at a temperature of from 110 to 380° C. for from 10 seconds to 3 hours, wherein the cross-linkable fluoroelastomer has a Mooney viscosity of from 20 to 300, of which the absorption peak is at from 1,640 to 1,700 cm−1 of the infrared absorption spectrum;

• the intensity of the absorption peak at from 1,640 to 1,700 cm−1 of the infrared absorption spectrum as represented by absorbance of a hot pressed sample having a thickness of 0.2 mm is from 0.05 to 1.5;
• and the infrared absorption spectrum as represented by absorbance has no absorption peak at from 1,740 to 1,800 cm−1 or has an absorption peak at from 1,740 to 1,800 cm−1 with an absorption peak intensity of at most 0.2, and
• wherein after the heat treating the cross-linkable fluoroelastomer has more unsaturated carbon-carbon bonds than the fluoroelastomer (A),
• wherein the fluoroelastomer (A) is a tetrafluoroethylene/propylene copolymer.

A process for producing a cross-linkable fluoroelastomer comprising a heat-treatment of a mixture of a fluoroelastomer (A) which does not have an absorption peak at from 1,640 to 1,700 cm−1 of the infrared absorption spectrum, and an organic peroxide (B) at a temperature of from 110 to 380° C. for from 10 seconds to 3 hours,

• wherein the cross-linkable fluoroelastomer has a Mooney viscosity of from 20 to 300, of which the absorption peak is at from 1,640 to 1,700 cm−1 of the infrared absorption spectrum;
• the intensity of the absorption peak at from 1,640 to 1,700 cm−1 of the infrared absorption spectrum as represented by absorbance of a hot pressed sample having a thickness of 0.2 mm is from 0.05 to 1.5;
• and the infrared absorption spectrum as represented by absorbance has no absorption peak at from 1,740 to 1,800 cm−1 or has an absorption peak, at from 1,740 to 1,800 cm−1 with an absorption peak intensity of at most 0.2, and
• wherein after the heat treating the cross-linkable fluoroelastomer has more unsaturated carbon-carbon bonds than the fluoroelastomer (A),
• wherein the fluoroelastomer (A) is a tetrafluoroethylene/propylene copolymer.