| 摘要 |
PURPOSE:To obtain the sheet having uniform gauge and no surface defect by magnetizing a nozzle such that mean magnetic flux density becomes the gauss in a specified range. CONSTITUTION:A nozzle for molding is magnetized at the mean magnetic flux density of 5-200 gausses. If the value of the magnetic flux density is smaller than 5 gausses, inorganic charged particles contained in polymer or a gelling agent adheres to a specified part of the nozzle, especially to the nozzle lip, and a streaklike defect occurs, or in case of a heavy addition, the flow speed of polymer changes, whereby gauge ununiformity becomes large and the cast sheet with uniform gauge is not obtained. If the value of magnetic flux density is larger than 200 gausses, the charged particle adheres to a specified part, and the ferromagnetic substance such as iron powder, iron-antimony solid solu tion and iron ion solid solution, etc. adhere to the specified part of the nozzle, whereby the stream line of the molten polymer emitted from the nozzle irregular ly pulsates, and only a cast sheet with an ununiform gauge is obtained. |
