Patent GB-1260836-A (GB)
Title: The manufacture of filaments, fibres and yarns by fibrillation of synthetic organic thermoplastic polymers, and the resulting products
Inventor: VERNON BRIAN JAMES
IPC: B29C48/05
Filed: 1968-04-10
Abstract: 1,260,836. Fibrillating films. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 26 March, 1969 [10 April, 1968], No. 17237/68. Heading B5B. Artificial filaments (which may, if desired, be cut up into staple fibres) are made by bringing a sheet-like mass of a synthetic organic thermoplastic molecularly-orientable polymer (or a composition comprising one or more such polymers) at a temperature above its crystalline melting point into pressure contact with a profiling element to form a profiled polymer film web having a plurality of longitudinal grooves disposed in close but spaced apart relationship in at least one surface thereof, the profiling element having a plurality of closely spaced, parallel, surface ridges, each ridge having a profile (in a plane normal to the longitudinal direction of the ridge) which includes inwardly directed sides leading to a peak, chilling the profiled film web during and/or after contact with the profiling element to a temperature below the crystalline melting point of the polymer, and stretching the chilled, profiled film web longitudinally to effect longitudinal orientation thereof said stretching being effected at a stretch ratio such that the stretched film web fibrillates under the influence of fibrillation treatment to which the chilled web is subjected during and/or after stretching. The "sheet-like mass" may be a film web formed by slot-die melt extrusion in a preceding stage of the process. The profiling element may be a profiling roller or similar rotating element of circular cross-section in a plane normal to the axis of rotation and the film web may be fed to the nip between the roller or similar rotating element and a backing roller or the like having a non-yielding surface. The web may have both surfaces grooved by feeding it to the nip formed by two profiling rollers. The profile of the ridges of the profiling element or elements may be such that the pitch of the ridges is within the range 0À003 to 0À05 inch and the depths of the troughs is within the range 0À002 to 0À02 inch. The thinnest portions of the profiled film web may be less than 1/10th of the thickness of the polymer mass before profiling. The web after having been stretched may be subjected to air blast treatment to effect or complete its fibrillation. The web may consist of a laminate of two or more polymer films formed from polymers differing in chemical composition and/or physical properties, the component films of the laminate being bonded together after their extrusion prior to contacting the profiling element. A heat transfer medium may be circulated through the profiling element and/or through any further element which contacts the web during profiling thereof to maintain the element(s) at a desired surface temperature. The polymer may be propylene or high density polyethylene. The continuous filaments formed may be cut into staple fibres or twisted into a yarn. The surface ridges of the profiling element(s) may each be divided along their length into two or more sections separated by short unridged portions of the surface of the element, which unridged portions are disposed in staggered relationship across the width of the profiling element(s) whereby the fibres formed by fibrillation are incompletely separated from one another.