Patent ID: 10252455

Abstract:
An ethylene/tetrafluoroethylene copolymer sheet obtained by extrusion, has R0/d, wherein R0 is an in-plane phase difference [unit: nm]and d is a thickness, [unit: nm], of at most 3.0×10−3, and a thickness of more than 300 μm. The ethylene/tetrafluoroethylene copolymer sheet preferably has a thickness of from 305 to 3,000 μm . A process for producing an ethylene/tetrafluoroethylene copolymer sheet includes melting an ethylene/tetrafluoroethylene copolymer to obtain a melt, continuously extruding the melt through a die for shaping the melt to a sheet, and letting the sheet pass between two rolls. One of the two rolls is a rigid roll, and the other is an elastic roll. The two rolls are pressed under a linear pressure of from 0.1 to 1,000 N/cm.