| 摘要 |
A method of manufacturing an oriented film of thermoplastic polymer material comprises extrusion of a film in tubular form from an extrusion die, orienting the film in a main direction of orientation during the haul-off from the die while in molten or semi-molten state, the direction being at an angle between 0 and 45-to the axis of the tube, followed by cutting of the tube at an angle to its main degree of orientation to form a web having an orientation of no less than 20 to its longitudinal direction, which method involves segmental stretching of the film to form an array of linear bosses (1), being of thicker material, integrally connected by thinner webs (2), said bosses and webs extending in a direction which is generally parallel with the direction of orientation, forming an acute angle to the longitudinal direction of the web, the method involving, after segmental stretching and cutting, shearing of the bosses along one another under re-orientation in the connecting webs, to increase the angle at which the bosses and webs extend relative to the direction of orientation. The bosses are separated from one another by no more than 3 mm. The shearing operation may be carried out by segmental rollers (5). |
