IMPROVEMENTS RELATING TO PLASTIC MATERIALS

摘要

1318347 Film fibrillation JAMES MACKIE & SONS Ltd 11 Sept 1970 [22 Sept 1969] 46594/69 Heading B5B A process for fibrillating a tape of a synthetic thermoplastic polymer, e.g. polypropylene, which has been longitudinally orientated comprises feeding the tape into contact with a surface, preferable a roller, which is driven in the same direction as and at a speed greater than, that of the tape and is covered with irregularly shaped particles of a hard, wear-resisting material which are at least of a size corresponding to grade 40 grit (B.S. 872). The fibrillating surface may comprise particles of grit, e.g. alumina, bonded by a layer of resin to a flexible backing. Apparatus suitable for the process of the invention comprises guide roller 2, guide plate 3, backing rollers 4 and 41 and guide plates 6 and 7 over or through which the stretched tape 1 passes prior to contact with the flexible covering of particulate material 12 on a fibrillating roller 5. After fibrillation the tape passes over guide rail 25, front rolls 11 and 111 to a normal spindle and ring twisting arrangement 14 being guided by a lappet 15. Fig. 3 (not shown) illustrates a similar arrangement in which the covered fibrillating roller 5 is replaced by a moving endless belt 20 supported by an arcuate plate 23 over the area of contact with the tape 1. In both embodiments the front rollers 11, 111 are driven at a slighter faster speed than the back roller 4, 41 to maintain tension in the tape and the fibrillating surface moves at a speed in excess of the speed of travel of the tape. In an example polypropylene tape is fibrillated by a roller covered with grade 24 grit moving with a surface speed 3À5 times that of the tape.