Patent GB-1109805-A (GB)
Title: Longitudinal splitting of films, sheets, strips and the like
IPC: D04H13/00
Filed: 1966-06-03
Abstract: 1,109,805. Film fibrillation. EASTMAN KODAK CO. 3 June, 1966 [7 June, 1965], No. 24826/66. Heading B5B. A process for partially splitting a polymeric film, comprises moving a longitudinally oriented polymeric film through a splitting zone, folding and compacting the film on itself while in said splitting zone, and exerting a dragging force on the film while it is being folded and compacted and thereafter while it is in said splitting zone thereby inducing a partial splitting in the direction of movement of the film. The oriented polymeric film may be continuously moved through the splitting zone. Alternatively, the polymeric film may be moved through a series of splitting zones wherein the film is folded and compacted on itself in a random manner and subjected to a dragging force within each zone. In the apparatus of Fig. 1, a longitudinally oriented polymeric film 2 is supplied from supply roll 1, or alternatively directly from a longitudinal orientation process, passes between guide rolls 3 and through longitudinal splitting means 4 whereupon the film is split into a coherent network of fibres which possess residual splittability. The film is pulled through the splitting means 4 by rolls 5, driven at the same rate as rolls 3, and the longitudinally split film 8 is thereafter guided by means of a guide member 6 on to a winder roll 7 for further processing, or alternatively the split film may be fed directly to a machine for manufacturing tying twine or cord. Fig. 2, illustrates one form of the longitudinal splitting means 4. A compacting die 20 is provided with an orifice 21 through which the film is passed thus inducing a partial splitting in the film in the longitudinal direction. A guide 22 attached to the entrance side of the compacting die 20, allows the film gradually to assume the shape of the orifice thereby eliminating edge tearing. In Fig. 3, the compacting die 20 and guide 22 are as in Fig. 2, but an extension 24 is added to the die having an internal passage corresponding to orifice 21 of die 20. Thus an increased distance is provided during which the film is compressed and worked against itself, resulting in an increase in the extent of longitudinal splitting of the film. Extension 24 thereby provides a relatively simple means of further controlling the extent of film splitting within limits. Fig. 4, illustrates another form of the longitudinal splitting means, a compacting die 30 being provided which has incorporated thereinto an orifice 31 and an initial guide surface 32 communicating with the orifice. An example illustrates the fibrillation of polypropylene film which is first longitudinally drafted at a ratio of 10 : 1, providing a film 1À5 mils. thick and 3¢ inches wide, which is passed through the device of Fig. 2, having a circular orifice of 0À1 inch diameter, and a total length of 1À0 inch. The resulting film was partially split in the longitudinal direction. Additional splitting could be obtained by again passing the partially split film through the device. The films may be of polymeric compositions including polypropylenes, polyethylenes, polyamides, polyesters, polyvinyl chlorides, polyvinylidene chlorides, polyurethanes, polyallomers, (a crystalline block copolymer that is synthesized with two or more olefins in which the individual segments exhibit degrees of crystallinity normally associated only with olefin homopolymers) polycarbonates, and linear polyacetal resins, and other compositions which may be molecularly oriented.