| 摘要 |
PURPOSE:To obtain a dampproof film made of PCTFE having improved stress crack resistance by extruding polychlorotrifluoroetglene (PCTFE) at a predetermined temperature or lower, and applying heat treatment after rolling it. CONSTITUTION:Temperatures for melt extrusion is set at 300 deg.C or lower, desirably 250-300 deg.C. If extrusion temperatures are higher than said temperatures, improvement in stress cracking resistance cannot be produced. Residence time is desired to be 25 minutes or shorter. If said time exceeds 25 minutes, dampproof property is lowered. There are deviations in the thickness of film and the film has rough surface, so that the thickness is uniformized and its surface is made smooth by rolling. Temperatures of rolls in rolling are preferably about 100-200 deg.C. Heat treatment is performed to increase degree of crystallinity and dampproof property. The heat treatment is performed by gradually cooling the temperature of the rolling or by heating the cooled film for a predetermined time. The crystallinity is preferably about 50% or more, practically about 85% or less. |
