Patent GB-683510-A (GB)
Title: Method of making crinkled artificial fibres
Inventor: JONES LEROY VERNON
IPC: D01D5/22
Filed: 1950-11-23
Abstract: An extrudable organic thermoplastic material is heated in an extrusion apparatus to 5-20 DEG  C. above its melting-point, then, while advancing the material towards an extrusion orifice, cooled to 5-25 DEG  C. below its melting-point and 15-25 DEG  C. below the first temperature.  The material is extruded in the form of filaments at the lower temperature, and the filaments are cooled and stretched to obtain a filamentary product having a natural crinkle.  The material may be a normally crystalline "Saran," (Registered Trade Mark), i.e. a polymer or copolymer of vinylidene chloride having a crystalline X-ray diffraction pattern.  As shown in the illustrated embodiment of the invention such a material in granular or coarse <PICT:0683510/IV (a)/1> powder form 10 is fed from hopper 11 to the screw 12 (driven by means not shown) of a vertical extruder wherein it is compacted and advanced at 25-100 DEG  C., and preferably at about 40 DEG  C., the temperature of the material in the screw section of the extruder being controlled by water flowing through the jacket 13.  From screw 12 the material is advanced in a thin layer over a torpedo 14, continuous with the screw 12.  The torpedo rotates in a section of the extruder heated by steam in jacket 15 to a temperature 5-20 DEG  C. above the melting-point and normal extrusion temperature of the polymer.  In the course of its travel beyond torpedo 14, the molten polymer passes through constricted throat 16 and is divided at the extrusion head 17 into a plurality of fine streams and extruded through spinneret orifices 18.  The entire section of the extruder beyond torpedo 14 is held at 5-20 DEG  C. below the melting-point of the material by means of steam or other heat transfer fluid passed through the jacket 19.  The extruded filaments 20 pass through air a distance of 5-30 inches into water or other inert liquid 21 at 10-60 DEG  C. and preferably at about 25 DEG C.  The filaments pass in about 2-15 seconds through the bath 21 and are withdrawn from the bath over guide rolls 23 and 24, snubbing rolls 25 and stretching rolls 26 which are driven at a peripheral speed 1.5-3.5 or 4.0 times that of rolls 25.  The stretched filaments are found to have a definite crinkle and may be wound on drum 27 for storage or cut into short staple lengths. In an example the polymer composition consists of 91 per cent of a crystalline copolymer of about 90 per cent vinylidene chloride and 10 per cent vinyl chloride plasticized with 7 per cent di-(alpha-phenylethyl) ether and 2 per cent dibutyl phthalate and has a melting-point and normal extrusion temperature of 168 DEG  C. The temperatures in the jackets 13, 15 and 19 are 70 DEG , 187 DEG  and 160 DEG  C. respectively, the spinneret to bath distance 15 inches, the temperature of the bath 21 is 35 DEG C., the immersion period 2 seconds and the peripheral speeds of the rolls 25 and 26 are 118-130 and 350-390 feet per minute respectively. The degree of crinkle of the filaments depends upon the extent to which they are stretched and the temperature control of the jackets 15 and a number of examples are given showing the effects of varying the temperatures of these jackets.  The crinkled (i.e. crimped, kinked, curled or wool-like) condition of the filaments is unaffected by laundering and dry-cleaning.