Process for producing modified molded article, molded article, diaphragm, and diaphragm valve
The invention provides a process for producing a modified molded article capable of providing a diaphragm that is less likely to generate particles. The process for producing a modified molded article includes: molding modified polytetrafluoroethylene containing a tetrafluoroethylene unit and a modifying monomer unit based on a modifying monomer copolymerizable with tetrafluoroethylene to provide a molded article; and irradiating the molded article with not lower than 30 kGy but lower than 70 kGy of radiation at 270° C. to 310° C. to provide a modified molded article.
1. A process for producing a modified molded article, comprising:
molding modified polytetrafluoroethylene containing a tetrafluoroethylene unit and a modifying monomer unit based on a modifying monomer copolymerizable with tetrafluoroethylene to provide a molded article; and
irradiating the molded article with not lower than 30 kGy but lower than 70 kGy of radiation at 270° C. to 310° C. to provide a modified molded article,
wherein the modified polytetrafluoroethylene has non-processability and a standard specific gravity defined in ASTM D4895-89 of 2.13 to 2.23.
2. The production process according to claim 1 ,
wherein the modified polytetrafluoroethylene contains 0.001 to 1% by mass of the modifying monomer unit relative to a sum of amounts of the tetrafluoroethylene unit and the modifying monomer unit.
3. The production process according to claim 1 ,
wherein the modified polytetrafluoroethylene has a secondary melting point of 320° C. to 329° C.
4. The production process according to claim 1 , further comprising
machining the molded article after the molded article is provided and before irradiation.
5. The production process according to claim 1 , further comprising
machining the modified molded article after the modified molded article is provided.
6. The production process according to claim 1 ,
wherein the modified molded article is a diaphragm.
7. A molded article comprising modified polytetrafluoroethylene,
the modified polytetrafluoroethylene containing a tetrafluoroethylene unit, modifying monomer unit based on a modifying monomer copolymerizable with tetrafluoroethylene,
wherein the modified polytetrafluoroethylene constituting the molded article contains tertiary carbon, the tertiary carbon being present in an amount of 0.035 to 0.100 mol % relative to a sum of amounts of the tetrafluoroethylene unit and the modifying monomer unit, and
wherein the modified polytetrafluoroethylene has non-melt-processability and a standard specific gravity defined in ASTM D4895-89 of 2.13 to 2.23.
8. The molded article according to claim 7 ,
wherein the modified polytetrafluoroethylene contains 0.001 to 1% by mass of the modifying monomer unit relative to the sum of the amounts of the tetrafluoroethylene unit and the modifying monomer unit.
9. A diaphragm comprising the molded article according to claim 7 .
10. A diaphragm obtainable by irradiating modified polytetrafluoroethylene with not lower than 30 kGy but lower than 70 kGy of radiation at 270° C. to 310° C.,
wherein the modified polytetrafluoroethylene has non-melt-processability and a standard specific gravity defined in ASTM D4895-89 of 2.13 to 2.23.
11. A diaphragm valve comprising a valve seat and the diaphragm according to claim 9 .
12. The diaphragm valve according to claim 11 ,
wherein the valve seat comprises a tetrafluoroethylene/perfluoro alkyl vinyl ether copolymer.
13. The production process according to claim 1 ,
wherein the molded article is irradiated at 280° C. to 310° C. to provide the modified molded article.
14. The production process according to claim 1 ,
wherein the molded article is irradiated at 280° C. to 300° C. to provide the modified molded article.