| 摘要 |
PURPOSE:To contrive speeding up in production of a molded sheet by removing efficiently bubbles to be generated between the molded sheet and the surface of a cooling drum, by providing a specific ventilation hole on the surface of the cooling drum. CONSTITUTION:A molten sheet is extruded through a die and stuck to a cooling drum statically by charging a static electric charge extending over the whole width of the sheet. The cooling drum is provided with a cooling surface of a porous layer whose mean opening of a ventilation hole is 50mu or smaller by measurement by a bubble point method and ventilation resistance of the cooling surface which is measured by a vacuum leakage method is 10,000sec or slower. High speeding up of casting becomes possible as air involved in a space between the sheet and cooling drum is removed efficiently. A film which does not find a defect in a state of an orange skin and is superior in smoothness is obtained. |
