| 摘要 |
PURPOSE:To obtain a film excellent in appearance and short of deviated thickness, creases, irregular strength, etc. by a method wherein a mandrel having a spiral groove on the outside is provided in a die body and the spiral grooves are bent at a bent part. CONSTITUTION:A mandrel having a spiral groove 2a is provided in a die body 4a, the spiral groove 2a is bent at a bent part 6 and an inverse spiral 7 is provided. In this manner, molten resin supplied from an extruder is divided into four passages at a branch point 1a in the mandrel and arrives at the spiral groove 2a and is separated into spiral flow and land flow. Further, when the molten resin moves from the bent part 6 to the inverse spiral groove 7, the spiral flow diffuses and moves partially to the land flow. The land flow also diffuses. Thereby, quantative inequality, temperature difference, etc. between the land flow and the spiral flow are removed. |
