Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1997-08-06
1998-09-29
Schofer, Joseph L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526217, 526211, 526212, 526255, C08F 200
Patent
active
058147136
DESCRIPTION:
BRIEF SUMMARY
FILED OF THE INVENTION
The present invention relates to a method for emulsion polymerization of tetrafluoroethylene using a paraffin wax, and a method for prevention of irregular polymerization of tetrafluoroethylene.
RELATED ART
In order to obtain polytetrafluoroethylene (hereinafter sometimes referred to as "PTFE") by the emulsion polymerization of tetrafluoroethylene (hereinafter sometimes referred to as "TFE"), PTFE is generally produced by the emulsion polymerization of TFE in water in the presence of an emulsifier and a dispersion stabilizer. As the dispersion stabilizer, for example, a paraffin wax is used. When using a commercially available paraffin wax in the emulsion polymerization, various problems sometimes arise. For example, the time required for polymerization becomes long and the polymerization does not occur. Regarding PTFE obtained by the emulsion polymerization, it is difficult to obtain values of physical properties (e.g. particle diameter) which meet the standard requirements. Therefore, the extrusion pressure at the time of paste extrusion molding does not meet the standard requirements, which results in loss of the commercial value.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for emulsion polymerization of TFE using paraffin wax and a method for prevention of irregular polymerization of TFE, which give a constant polymerization time, and polytetrafluoroethylene having values of physical properties which meet the desired standard requirements.
In the emulsion polymerization of TFE, the present inventors have studied intensively with paying attention to the fact that the time required for obtaining a predetermined amount of PTFE varies due to an influence of a reducing substance contained in a paraffin wax and therefore the polymerization time is longer as an amount of the reducing substance is larger and it is difficult to obtain PTFE having predetermined values of physical properties. Thus, the present invention has been completed.
The present invention provides a method for emulsion polymerization of tetrafluoroethylene in the presence of a polymerization initiator, a paraffin wax and an emulsifier, which comprises using the paraffin wax containing a reducing substance in an amount of not larger than 100 ppm based on the paraffin wax.
The present invention also provides a method for emulsion polymerization of tetrafluoroethylene in the presence of a polymerization initiator, a paraffin wax and an emulsifier, which comprises maintaining an amount of a reducing substance derived from the paraffin wax at not larger than 60% by mol based on the polymerization initiator in the polymerization system.
The present invention also provides a method for preventing irregular polymerization of tetrafluoroethylene, which comprising using the above method for emulsion polymerization.
DETAILED DESCRIPTION OF THE INVENTION
The paraffin wax for emulsion polymerization in the present invention comprises a paraffin and a reducing substance for stabilizing the paraffin.
Specifically, the paraffin is a mixture of saturated hydrocarbons having 15 to 45 carbon atoms, and has a melting point within the range from 10.degree. to 65.degree. C.
The reducing substance serves as a stabilizer for the paraffin. The reducing substance may be usually a compound having an unsaturated bond. The reducing substance may be, for example, a hydroxybenzene compound, an amine compound and the like. Specific examples thereof include hydroxybenzene compounds such as 2,6-di-t-butyl-p-cresol (BHT), hydroquinone, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butyl-phenyl)propionate, 2,4-bis-octyl-thio-6-(4-hydroxy-3,5-di-t-butylanilino-1,3,5-triazine) and tris(3,5-di-t-butyl-4-hydroxyphenyl)isocyanurate; and amine compounds such as 4-benzoyloxy-2,2,6,6-tetramethylpiperidine and bis(2,2,6,6-tetramethyl-4-piperidine)seba
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Ichiba Shigeru
Kawamura Takuo
Sota Tomizo
Daikin Industries Ltd.
Sarofim N.
Schofer Joseph L.
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