Patent GB-1084390-A (GB)
Title: Method of fibrillating stretched film
IPC: D01D5/42
Filed: 1965-12-15
Abstract: 1,084,390. Making fibres by film fibrillation. POLYMER PROCESSING RESEARCH INSTITUTE Ltd. Dec. 15, 1965 [June 5, 1965], No. 53235/65. Heading B5B. [Also in Division D1] In a method of fibrillating polymer film the film is longitudinally stretched and sliderubbed under longitudinal tension over a surface or surfaces having projections so as to fibrillate the film. The film may be kept under tension by passing through pairs of pinch rollers before and after slide-rubbing, the peripheral velocity of the exit rollers exceeding that of the entrance rollers. Preferably, the film is held against the surface or surfaces by a pair of turn rolls, disposed respectively before and after the said surface or surfaces, and the fibrillated film is wound up, suitably after twisting into yarn. Specified polymers include polypropylene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, a polyester, a polyamide, regenerated cellulose, cellulose acetate, polyvinylidene chloride, or a copolymer of two or more of these polymers. Apparatus as shown comprises in functional sequence a pair of entrance pinch rolls 2, 3, a turning roll 4, a fibrillating surface or surfaces 10, a second turning roll 6, and a pair of exit rolls 7, 8. A winding device 9 may also be fitted. Suitably, the entrance pinch rolls both have rubber surfaces, one exit roll has a rubber surface and the other a metal surface. The fibrillating surface or surfaces may comprise a rotatable bar file 5 (Fig. 1, not shown) or a plurality of such files arranged parallel to each other (not shown), or alternatively the files may be disposed on the same circumference in a rotatable cylindrical cage roll 10 with their axes parallel to that of the cage roll. This arrangement is shown in detail in Fig. 3. In the cage shaped file roller 10, a plurality of round bar files 5 are arranged at equal intervals on the same circumference between two circular plates 12 and 13 fixed on the axis 11. The files are in idle engagement with roller axis 11, and gears 14 fixed to each file axis are engaged in planet positions with gear 15 driven separately to axis 11. Each file 5 revolves around the axis 11 as this axis rotates and at the same time can revolve on its own axis with rotation of the gear 15. Using this arrangement, if the surface velocity of the cage shaped files is equal to the running velocity of the. stretched film, only part of the film in contact with the bar file is split into fibres and the film part not in contact with the file is not split. The higher the rotary surface velocity of the cage shaped files relative to the running velocity of the film, the smaller the proportion of unsplit film becomes, until if the rotation of the cage shaped files becomes so fast and the cage shaped files are revolved at such a high velocity that the film portion split by one file is again struck by the following bar file, the running film is split continuously. When a periodically unsplit section of film is required, this can easily be met by controlling the surface velocity of the said cage shaped files and the running velocity of the film so as to obtain a product in which an unsplit section recurs periodically in the stretched film. In place of steel files, round bars provided with needle like projections on their surfaces, or having sandpaper wrapped around them may also be used. In an alternative arrangement, not shown, the files are disposed in series on the same plane, alternating with a succession of turning rolls, and the film is passed alternately over the rolls and files while being split by the latter. Using a film or tape of narrow width, it is possible to make yarn by twisting after splitting. When the width of the film is broad, the split fibres form a broad non-woven cloth having a network structure of short fibres. Examples are given.