Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1996-02-15
1997-12-23
Jagannathan, Vasu
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524377, 524520, 524544, 524559, 5253262, C08J 300
Patent
active
057008590
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/JP 95/01325 filed Jul. 3, 1995.
TECHNICAL FIELD
The present invention relates to a novel aqueous emulsion of fluorocarbon polymer having excellent mechanical stability and thermal stability, and to a method for producing the same.
BACKGROUND ART
Aqueous emulsion of polytetrafluoroethylene (PTFE) are prepared by the emulsion-polymerization method disclosed in U.S. Pat. No. 2,559,752. In the method, tetrafluoroethylene is charged under pressure into an aqueous medium containing a water-soluble polymerization initiator and an anionic surfactant having a fluoroalkyl hydrophobic group to result in formation of colloidal particles of PTFE in the medium. The aqueous emulsion of other fluorocarbon polymers also are prepared by similar methods. The aqueous emulsion of fluorocarbon polymer thus prepared are stabilized by addition of emulsion stabilizers because of inferior mechanical stability of the emulsion itself.
For the emulsion stabilizer, hydrocarbon-base surfactants are employed usually in place of fluorocarbon-base surfactants mainly from the economical viewpoint, and commonly used emulsion stabilizers include such nonionic surfactants as p-C.sub.8-10 alkylphenylpolyethyleneglycolethers. However, emulsions thus stabilized by such surfactants are still not satisfactory in stability, and tend to turn into unstable ones by their encounter with mechanical actions during evaporation, concentration, dilution, transportation, weighing and others.
Anionic surfactants are also proposed for use as the emulsion stabilizer, and, for example, U.S. Pat. No. 4,369,266 mentions extensively such anionic surfactants as esters or salts of alkylsulfonic acids, alkylsulfuric acids, alkylarylsulfonic acids, alkylaryl sulfuric acids, higher fatty acids, alkyl phosphoric acid esters, alkylaryl phosphoric acid esters and sulfosuccinic acid. However, commercial usages of these surfactants for emulsion stabilizers are scarcely recognized, and further no mention is made in Examples of the U.S. Patent as to those anionic surfactants being used as emulsion stabilizers.
It is an object of the present invention to provide an aqueous emulsion of fluorocarbon polymer having excellent mechanical stability. By use of the present emulsion, for example, prevention becomes feasible against such problems caused by inferior mechanical stability as clogging of pumps, valves and nozzles with coagulated colloidal particles of fluorocarbon polymer 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 fluorocarbon polymer having excellent thermal stability. By use of the present emulsion, for example, prevention becomes feasible against such problems caused by inferior thermal stability as deteriorated coating and impregnation properties towards metals, glass woven fabric because of increased emulsion viscosities under high temperatures. It is a further object of the present invention to provide a method for producing efficiently in a short period of time an aqueous emulsion of fluorocarbon polymer having excellent mechanical and thermal stabilities.
For the purpose of obtaining aqueous emulsions of fluorocarbon polymer having excellent mechanical and thermal stabilities, the present inventors conducted numerous experiments using prospective surfactants including the aforementioned as the emulsion stabilizer. The result showed that most of the surfactants were not suitable due to causing, for example, inferior emulsion stability, excessive foaming of emulsion and coloration of coated glass woven fabric owing to surfactants, however, sodium salt of a specified alkylsulfosuccinic acid was found to be an effective emulsion stabilizer for a low content aqueous emulsion of fluorocarbon polymer. As the result of further studies, successful stabilization of aqueous emulsions of fluorocarbon
REFERENCES:
patent: 2478229 (1949-08-01), Berry
patent: 4369266 (1983-01-01), Kuhes et al.
patent: 5010121 (1991-04-01), Yeates et al.
Chiba Shizuo
Ogura Masatsune
Ohtera Kayoko
Asinovsky Olga
DuPont-Mitsui Fluorochemicals Co. Ltd.
Jagannathan Vasu
LandOfFree
Aqueous emulsion of fluorocarbon polymer and method for producin does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aqueous emulsion of fluorocarbon polymer and method for producin, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous emulsion of fluorocarbon polymer and method for producin will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1803331