Patent GB-1197465-A (GB)
Title: Method of Making Fibrous Yarns and Apparatus Therefor
IPC: D01D5/42
Filed: 1967-09-01
Abstract: 1,197,465. Film fibrillation. MITSUBISHI JUKOGYO K.K. 1 Sept., 1967 [5 Sept., 1966], No. 40178/67. Heading B5B. [Also in Division D1] Fibrous yarn having a network structure is made by transporting, under predetermined tension, a film or tape or a plurality of substantially parallel films or tapes oriented in the longitudinal direction, longitudinally splitting the film in its path of travel by means of rotatable splitting elements intersecting its path of travel, and forming discontinuous slits in the film, the splitting elements being rotated at a speed relative to the speed of travel of the film to regulate the length of the slits formed therein, and the angle of contact of the path of travel of the film with the splitting elements being varied to regulate the duration of contact of the film by the splitting elements. Suitably, the film or tape is formed of polypropylene, polyethylene, or a polyester. In apparatus as shown, sets of nip rolls 5 and 6 are provided in front of and behind the splitting drum 1. These serve to maintain the tape being split in a constant position relative to the splitting elements 2, and to drive the tape 3 under tension along the predetermined path. When the tape 3 engages the splitting drum 1 carrying projections 2, it starts at point (A) indicated in Figs. 4(a) and 4(b) (not shown), to contact the pointed end of the splitting elements 2. As tape 3 continues to proceed with rotation of drum 1 the splitting elements 2 thereon penetrate the tape 3 and subsequently act to split it as it proceeds past the point of contact (B) to reach the point of contact (C) where the splitting elements 2 are released completely from tape 3. Thus as splitting is effected along the path of the tape including points (A), (B) and (C), some difference in speed always exists between the tape 3 and the splitting elements 2 engaging therewith during the passage of the tape 3 from (A) to (B) or from (B) to (C) even if, at point (B) where tape 3 comes closest to the drum 1, the tape and the drum surface proceed at the same speed. Thus a fibrous yarn having a network structure having particular physical properties can be obtained by suitable selection of a film material of appropriate thickness and width and selecting an appropriate arrangement of splitting elements on the drum and a proper relationship between the speed of film travel and that of drum rotation to give a desired slit length (1) (Fig. 3, not reproduced) and a desired filament width (t) (Figs. 5 and 6, not reproduced). Furthermore, by changing the engagement angle that the film or tape makes with the splitting drum as shown in Fig. 2, in which said angle is decreased, the same effects as shown in the embodiment of Fig. 1 can be obtained, and the slit length can readily be varied. The splitting elements 2 may be of needle shape and may be straight, or curved in an involute form, and as shown in Fig. 1 are preferably set to slope with their pointed ends extending in the direction of the axis of rotation of the drum or to extend radially thereof as in Fig. 2. The splitting elements 2 are arranged on the peripheral surface of drum 1 along predetermined leading lines (4) (Fig. 3, not shown) which proceed in the direction of rotation of the drum. Thus the spacing or pitch (p) between two aligned splitting elements 2 arranged on adjacent leading lines may be determined in accordance with the desired splitting pattern. Suitably, the leading lines are disposed obliquely to a plane extending through the drum perpendicularly to its axis of rotation. As shown, to facilitate the starting of the splitting action at the point of contact (A) the splitting elements 2 should be set so that they start to engage the tape 3 approximately at right angles thereto. Fibrous yams of network structure so made may replace multiple filament yarn and are especially suitable as the material for bags intended to hold cereal or other particulate material without the need for any further processing steps, as e.g. crimping and pretwisting. The yarns are also useful in making carpets and knitwear.