IMPROVED SYNTHETIC FILM, SYNTHETIC SHEET AND YARN, AND AN IMPROVED PROCESS FOR THE MANUFACTURE THEREOF

摘要

1,242,456. Synthetic film or sheet; extrusion. ALGERMENE KUNSTZIJDE UNIE N.V. 19 Aug., 1968 [19 Aug., 1967], No. 39649/68. Headings B5A and B5B. [Also in Division D1] Synthetic film or sheet contains at least two unmixed components in which at least one of the components occurs in the form of substantially endless threads in the longitudinal direction of the film or sheet and the threads have transverse dimensions that are at least two to five times smaller than the thickness of the film or sheet, each thread having a diameter that is smaller than 500Á, and the threads are embedded in a basic mass of a different component. The films generally have a thickness of from 10 to 100Á and the diameter of the endless threads are preferably from 0À1 to 12Á. Sheets 0À5 mm. to a few millimetres containing endless threads less than 500Á in diameter can also be made. The apparatus for producing such films or sheets comprises in sequence at least two feed channels for polymer components, means to join and then repeatedly divide the components issuing from the channels, so as to form a multi-layer stream, a gauze pack or a grid to further divide the stream and an extrusion slit through which the stream may pass to form a film or sheet In a specific embodiment two polymer streams, one being polypropylene and the other polyester are forced down compartments 4 and 5 of channel 1, so that at the end of partition 3 the two components will form two layers. The two layered main stream is then repeatedly divided by the mixing elements 6 to form a multi-layer stream which is divided further on passage through a gauze pack 8 in a direction transverse to the layers into substreams of the layer thicknesses in situ. The polymer stream then flows into space 11 in extruder die 10, and the space 11 gradually widens and ends in a casting slit 12. Film which consists of a basic mass of the one component in which the other component forms a large number of endless threads which extend in the longitudinal direction of the film issues from the casting slit 12. The film or sheet may be processed into yarns or threads by dividing the film into a large number of ribbons which extend in the longitudinal direction of the film. In one form of the process the basic mass is entirely or partially removed from the film, sheet or ribbons by using a solvent for the basic mass or a special heat treatment.