GB977535A - Synthetic bast - Google Patents

Abstract

977,535. Bast-like filaments. SOC. DE LA VISCOSE SUISSE. March 20, 1962 [April 5, 1961], No. 12279/61. Addition to 864,488. Heading B5B. A synthetic bast-like material consisting of a flat, irregularly folded and at least partly agglutinated tubular filament of irregularly varying titre and width is made by extruding a molten linear high polymeric thermoplastic material through an annular orifice in a spinneret so as to form a tubular filament, maintaining a slight superatmospheric gas pressure inside the tubular filament and passing it while it is still not completely hardened, through a cooling liquid and round a deflector in the cooling liquid thereby to flatten it, and withdrawing the filament under tension, in which process either the gas pressure inside the tubular filament or the distance between the surface of the cooling liquid and the spinneret, or both, are irregularly varied. Preferably, the polymeric thermoplastic material is a polyamide or a polyester. As shown, a spinneret 1 having an annular orifice 2 is fitted with a gas supply pipe 3 through which an inert gas, e.g. nitrogen, can be fed into the emerging tubular filament 4, which passes into cooling bath 5 and then under deflecting rod 7, being thereby flattened and folded by the action of the withdrawal tension exerted by the driven rollers 9. The filament is then stretched, preferably continuously with the spinning process, or subsequently as a separate process, in known manner, and wound up. In Fig. 11, (a) shows the effect of low gas pressure and (b) that of high gas pressure, and (d) and (e) show the effect of varying the level of liquid coolant in relation to the spinneret.