| 摘要 |
1526514 Regulating thickness of extruded and drum quenched film or sheet TEIJIN Ltd 23 March 1976 [24 March 1975] 11692/76 Heading B5A A film or sheet 17 of polymeric material which is extruded from a die passage 16 and cooled, e.g. prior to biaxial stretching, by application to a quenching drum 24 by means 20 located between the extrusion die 14 and the drum 24, is maintained at a uniform thickness across its width by homogenizing the material by kneading it between the extruder 10 and the die passage 16, and by adjusting the temperature of the die by heat transfer means disposed at locations spaced across the width of the passage 6, to maintain the required uniform thickness. The kneading can be effected by varying the area or shape of the material flow path, or by means of a static mixer having a helical screw or, as shown, by a mixer comprising a rotary helical screw 12 which mixes peripheral and centrally located material. The heat transfer means may be separated by heat insulation material, or by slits in the die, and may be located on one, or preferably both sides of the passage 16 as shown, and may comprise heating and/or cooling means, and preferably comprises cartridge heaters and gaseous or liquid cooling medium jackets alternating across the width of the die. Control to maintain the required uniform thickness is effected by means 30 measuring thickness across the width of the film, e.g. by #-ray, or transmitted light, and acting electrically through an integration device, or a memory circuit. The pinning may be effected by a roller, pneumatic pressure of an air knife or, as shown, electrostatically by a charge applied to the film from a high voltage source 21 with the drum 24 being grounded at 22. The material may comprise numerous specified thermoplastics, and the examples relate to polyethylene terephalate which is biaxially stretched subsequent to quenching. |
