Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1998-06-24
2000-10-31
Zitomer, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526206, 526227, 526242, 526250, C08F 1426, C08F 1418, C08F 1624
Patent
active
061404373
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a fluorine-containing elastomeric copolymer, a curable composition comprising the same, and a sealing member prepared from the same. In particular, the present invention relates to a fluorine-containing elastomeric copolymer which is prepared by polymerizing monomers in the presence of a specific diiodide compound, a curable composition comprising the same, and a sealing member prepared from the same.
PRIOR ART
Fluorine-containing elastomeric copolymers are used in a wide variety of fields such as equipment for producing semiconductors, chemical plants, drilling rigs, space hardware, and the like, because of their excellent chemical resistance, heat resistance and compression set.
In particular, sealing members comprising the fluorine-containing elastomeric copolymers have the large merit of the reduction of running costs due to the maintenance-free. Thus, fluorine-containing elastomeric copolymers having a longer life and higher reliability are sought.
Fluorine-containing elastomeric copolymers having iodine atoms in a polymer chain, which can be cured with peroxides, can be easily vulcanized without the addition of contaminant additives such as metal oxides, and thus they are used as materials of clean sealing members which are used in the equipment for producing semiconductors. However, a copolymer of tetrafluoroethylene and a perfluorovinyl ether having a polyether-type perfluoroalkyl group has insufficient dry strength, and also inferior compression set at high temperature to commercially available cured materials of fluororubbers comprising vinylidene fluoride, as described in JP-A-62-89713 and JP-A-62-12734.
Conventional copolymers of tetrafluoroethylene-perfluoro(methyl vinyl ether) having iodine atoms, which are disclosed in JP-A-4-505345, have insufficient tensile properties and compression set.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a fluorine-containing elastomeric copolymer which can provide a clean sealing member having a long life and high reliability as desired particularly in the semiconductor field.
As the result of extensive study for achieving such an object, it has been found that a fluorine-containing elastomeric copolymer comprising tetrafluoroethylene and perfluoro (methyl vinyl ether) in a specific ratio and containing an iodine atom has good dry properties, and its compression set at high temperature, which is one of the most important properties for sealing members, is better than that of a polyol-curable fluororubber comprising vinylidene fluoride and hexafluoropropylene, which has the best compression set among commercially available rubbers.
Furthermore, it has been found that such a fluorine-containing elastomeric copolymer, which is obtained by polymerizing tetrafluoroethylene and perfluoro(methyl vinyl ether) at a specific temperature (between 40 and 60.degree. C.), has a further improved compression set.
According to the first aspect, the present invention provides a fluorine-containing elastomeric copolymer comprising 55 to 62 mole % of repeating units derived from tetrafluoroethylene (TFE) and 38 to 45 mole % of repeating units derived from perfluoro(methyl vinyl ether) (PMVE) which is obtained by radically polymerizing the monomers in the presence of a diiodide compound of the formula: having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms, preferably at a temperature in the range between 40 and 60.degree. C., and which has a Mooney viscosity (ML.sub.1+10 100.degree. C.) in the range between 20 and 150.
According to the second aspect, the present invention provides a fluorine-containing elastomeric copolymer comprising 50 to 80 mole % of repeating units derived from tetrafluoroethylene, 20 to 50 mole % of repeating units derived from perfluoro (methyl vinyl ether), and 0.01 to 1 mole %, based on the total mole of tetrafluoroethylene and perfluoro(methyl vinyl ether), of repeating units derived from an iodine-containing fluorinated vinyl ether of the
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Iwasaki Yasuji
Kishine Mitsuru
Kitaichi Masanori
Saito Hideya
Daikin Industries Ltd.
Zitomer Fred
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