Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-06-02
1999-02-09
Lipman, Bernard
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525243, C08F25900
Patent
active
058695770
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for preparing a fluorine-containing elastic copolymer being vulcanizable and excellent in molding processability, the fluorine-containing elastic copolymer prepared by the process and a vulcanizable composition having excellent molding processability and prepared by using the copolymer. Particularly, the present invention relates to the process for preparing the fluorine-containing elastic copolymer which has improved molding processability, particularly molding stability and further is excellent particularly in vulcanization properties, flowability at molding and compression set of vulcanized rubber, the fluorine-containing elastic copolymer prepared by the process and the vulcanizable composition prepared by using the copolymer.
Fluorine-containing elastic copolymers comprising vinylidene fluoride as a main component, for example, a copolymer of vinylidene fluoride-hexafluoropropylene, a terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, etc., can provide a vulcanized fluorine-containing rubber by vulcanizing with a vulcanizing agent comprising diamine, a vulcanizing agent comprising an organic peroxide or a vulcanizing agent prepared by combination use of a polyhydroxy aromatic compound with a quaternary phosphonium salt, a quaternary ammonium salt or the like. The vulcanized fluorine-containing rubber exhibits superior resistance to heat, oil, solvent, chemicals, etc., and has been used in the wide fields such as automobiles, ships, chemical industries, office automation apparatuses, semiconductor industries and food industries.
BACKGROUND ART
The present applicant has developed, prior to the present invention, a process for preparing a fluorine-containing elastic copolymer having remarkably improved vulcanization reactivity and compression set of the vulcanized rubber and a vulcanizable composition made from the copolymer. Namely, the process for preparing the fluorine-containing elastic copolymer is a process for preparing a copolymer of vinylidene fluoride containing 28 to 92% by mole of vinylidene fluoride unit and at least one other monomer comprising (a) polymerizing vinylidene fluoride and at least one other monomer by the use of a water-soluble radical polymerization initiator in the first stage to produce a copolymer and (b) then polymerizing in the second stage of the polymerization by the use of an oil-soluble radical polymerization initiator in the presence of the copolymer prepared in the first stage to produce a copolymer, and the vulcanizable composition of the fluorine-containing elastic copolymer is a composition prepared from the copolymer (JP-A-62391/1977 and JP-A-76359/1977). However, in all of their experimental examples thereof, an amount of the water-soluble polymerization initiators is as large as about 0.08 to 0.6% by weight, and the obtained fluorine-containing elastic copolymer is not enough for recent strict requirements with respect to improvement of processability of fluorine-containing rubbers.
One of particular requirements regarding the fluorine-containing rubbers is improvement of molding processability thereof. Since the fluorine-containing rubber is high in material cost as compared with other rubber materials, when the vulcanization speed is fast and its flowability is good, such a rubber makes it possible to produce a molded article of the fluorine-containing rubber having complicated shape effectively and to lower a total production cost. Particularly, in order to conduct injection molding which is more effective as compared with compression molding, it is required to exhibit more excellent flowability, rapid vulcanization and effective crosslinking, namely it is required that irrespective of a low viscous polymer, vulcanization can be conducted in a short period of time and yet sufficient physical properties at normal state are exhibited. On the other hand, the vulcanization accelerator comprising a quaternary phosphonium salt which is often used when the polyhydroxy aromatic c
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Aihara Hiroshi
Kishine Mitsuru
Morikawa Tatsuya
Tanaka Hiroyuki
Daikin Industries Ltd.
Lipman Bernard
Sarofim N.
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