Patent GB-1376062-A (GB)
Title: Process and apparatus for production of resilient fibre of propylene polymer
IPC: D06C29/00
Filed: 1972-01-19
Abstract: 1376062 Polypropylene fibres PHILLIPS PETROLEUM CO 19 Jan 1972 [20 Jan 1971 (2)] 2563/72 Heading B5 A continuous fibre thread composed of a single continuous filament, or a tow of continuous filaments, or a staple fibre yarn, of polymeric material selected from propylene homopolymer, propylene copolymers containing propylene as the major constituent and polymer blends containing propylene homopolymer as the major constituent is treated to improve its resilience by treatment under tension and at a temperature below the crystalline melting point of the propylene polymer component thereof with saturated steam for a period of from 0À01 to 2 seconds, preferably 0À4 to 0À6 seconds. Desirably the filaments are in the form of a filament tow having a denier of greater than 100,000 and steam is injected directly on to the filaments under a pressure of 55 to 90 p.s.i.g. the filaments reaching a temperature of 10 to 35C. below the crystalline melting point; in the case of polypropylene homopolymer the preferred temperature range is 135 to 160 C. In apparatus as shown, a tow 10 is fed through a first tensioning means, comprising rollers 12, 14, 16, which in combination with second tensioning means 18, 20 and 22 maintains tension on the tow as it passes through the treating zone 24, which is surrounded by steam jacket 30. Steam is supplied at 32 and exhausts both at end 26 and with the tow at the second end 28, passing into contact with the tow through holes (40) in the wall of chamber 24, which chamber is of generally elongated crosssection with opposed generally flat walls 36 at each end of a major axis thereof and generally flat walls 38 at opposite ends of a minor axis thereof. The contact with steam causes the tow 10 to fluff out so as to substantially fill the space within the tube 24. Fig. 4 (not reproduced), shows a cross-section of a treatment chamber of rectangular shape. Suitably, the length of the major axis to that of the minor axis of the cross-section of the tube is in the range 2 : 1 to 200 : 1, especially 25 : 1 to 200 : 1, so that the tow is shaped to a width to height ratio within such range during contact with the steam. The chamber is suitably 1-10 feet long, especially 2-5 feet, and the holes may be spaced on the chamber wall in a spiral configuration, the axial distance between successive holes being within the range 0À2 to 2 inches, especially 0À3 to 0À7 inch or alternatively may be placed in a random pattern. The holes may have a diameter of 10-200 mils. During treatment, tension is maintained on the filament, desirably such that shrinkage of 0 to 30% takes place and especially so that the final filament length is 70 to 90% of its original length. Large denier tow may be treated at speeds of 100 to 250, preferably 125 to 250, metres per min. Treatment effects little change in tenacity, elongation and modulus but enhances dye receptivity and results in improved resilience due to a re-ordering of the crystal structure. Filaments so treated show a crystal length, as determined by X-ray diffraction, of 125-200, especially 140-160 and have greater resistance to soiling than filaments of identical polymer heated in an air oven to give a similar crystal length.