| 摘要 |
PROBLEM TO BE SOLVED: To provide crystallization characteristics of the small size of globulite, and outstanding surface smoothness and resistance to stress cracking by molding a tube of a copolymer obtained by adding a specific quantity of perfluoroalkylvinyl ether to tetrafluoroethylene at a specific volume flow velocity. SOLUTION: In the copolymerization of tetrafluoroethylene with perfluoro(alkylvinyl ether), the volume flow velocity of a copolymer(PFA) of tetrafluoroethylene/perfluoro(alkylvinyl ether) is set as a target value by changing the addition rate of a molecular weight modifier, e.g. alcohols such as methyl alcohol and hydrocarbons such as n-heptane. The content of a polymerization unit based on the perfluoro(alkylvinyl ether) in the PFA is 2.5-10mol%. The volume flow rate of the PFA is 0.5-100mm<3> /sec. The volume flow rate is, however, that of the PFA which flows out per unit of time which is determined by flowing the molten PFA at 380 deg.C from a 2.1mm-dia. and 8mm-long nozzle under a load of 7kg, based on a flow tester. |
