Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-02-16
1999-11-16
Mulcahy, Peter D.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524368, 524370, 524546, C08J 542
Patent
active
059859660
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/ JP95 /01323 filed Jul. 3, 1995.
TECHNICAL FIELD
The present invention relates to a novel aqueous emulsion of fluorine-containing polymer having excellent mechanical stability and thermal stability.
BACKGROUND ART
Aqueous emulsions of polytetrafluoroethylene (hereinafter referred to as PTFE) are prepared by the emulsion-polymerization method disclosed in the U.S. Pat. No.2,559,752. Aqueous emulsions of other fluorine-containing polymers are also prepared by using similar process. Aqueous emulsions of fluorine-containing polymer thus prepared have being employed as coating agents for metals or the like, impregnating agents for fibers and cloths, additives for various materials, and further as dust-preventive treating agents. For adaptation to these uses, the emulsion is generally stabilized with such nonionic surfactants as p-C.sub.8-10 alkylphenylpolyethyleneglycolethers, as the emulsion itself is inferior in mechanical stability. However, even thus stabilized emulsions become unstable against thermal and mechanical actions they encounter during evaporation, concentration, dilution, transportation, weighing and others.
It is an object of the present invention to provide an aqueous emulsion of fluorine-containing polymer having excellent mechanical stability. By use of the inventive emulsion, for example, preventions become feasible for such problems caused by inferior mechanical stability as clogging of pumps, valves and nozzles with coagulated colloidal particles of fluorine-containing polymers formed during agitation, transportation and spraying, adhesion of coagulated particles to container walls and agitators, and flotation of coagulated particles in the emulsion.
It is another object of the present invention to provide an aqueous emulsion of fluorine-containing polymer having excellent thermal stability. By use of the inventive emulsion, for example, preventions become feasible for such problems caused by inferior thermal stability as deteriorated coating property and impregnation property towards metal, glass woven fabric owing to increased emulsion viscosities under high temperatures.
It is a further object of the present invention to provide an aqueous emulsion of fluorine-containing polymer having reduced environmental pollutions especially in the ground water pollution. By use of the inventive emulsion, for example, preventions become feasible for such problems as pollution of ground water caused by emulsion stabilizers in the emulsion occurring when materials treated with PTFE emulsions are used for mixing with soil or filling in the ground for reclamation. Moreover, the inventive emulsion allows concentration by evaporation or dilution thereof, thanks to its increased mechanical and thermal stabilities.
DISCLOSURE OF THE INVENTION
An aqueous emulsion of fluorine-containing polymer according to the present invention is characterized by that it contains an emulsion stabilizer represented by the formula: is a number of 1-6, and M is Na, K or NH.sub.4.
The emulsion stabilizer is added preferably not less than 1 wt % to the polymer.
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the fluorine-containing polymer includes polymers of tetrafluoroethylene, chlorotrifluoroethylene or vinylidenefluoride, or copolymers containing the aforementioned. Mention is made of the polymers including polytetrafluoroethylene, tetrafluoroethylene.hexafluoropropylene copolymer, tetrafluoroethylene.fluoroalkylvinylether copolymer, tetrafluoroethylene.ethylene copolymer, polychlorotrifluoroethylene, polyvinylidenefluoride and vinylidenefluoride.hexafluoropropylene copolymer.
In the present invention, the aqueous emulsion means those containing in water 1-75 wt % of the fluorine-containing polymer in colloidal particles having an average particle size of 0.1-0.3.mu.. The average particle size of colloidal particles is measured by the centrifugal sedimentation method. In Examples and Comparative Examples of the present invention
REFERENCES:
patent: 4329268 (1982-05-01), Chakrabarti et al.
Chiba Shizuo
Ogura Masatsune
Du Pont - Mitsui Fluorochemicals Co. Ltd.
Mulcahy Peter D.
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