Patent GB-881856-A (GB)
Title: Crimped wet-spun filamentary materials
IPC: D02G1/16
Filed: 1958-05-29
Abstract: <PICT:0881856/IV (a)/1> <PICT:0881856/IV (a)/2> <PICT:0881856/IV (a)/3> Crimped filaments are made by wet-spinning a solution of a filament-forming material in an organic solvent into a liquid coagulant to form a bundle of parallel filaments swollen by organic liquid, separating individual filaments from one another, and removing the organic liquid from the filaments while they are maintained in separated and substantially tensionless condition until the filaments are substantially non-swollen.  The filament-forming material may be a cellulose ester, e.g. cellulose nitrate or, especially, cellulose triacetate.  The coagulant may be a mixture of the organic solvent and a non-solvent for the filamentary material, and the filaments may be stretched while in the coagulant.  Both organic solvent and coagulant may be volatile, organic liquid then being removed from the filaments by evaporation.  In the wet-spinning of cellulose triacetate, the solvent may be principally methylene chloride and the coagulant a mixture of methylene chloride and a monohydric aliphatic alcohol having 1-3 carbon atoms.  Preferably the alcohol is methanol and the proportion of methylene chloride is within the range defined by C=75 1/4 -T\sB5, where C is the per cent concentration and T the temperature in  DEG C.  The crimped filaments may be brought together to form a tow of at least 1,000 filaments, the crimps in adjacent filaments being randomly disposed and out of alignment with each other.  In the preferred method, the filaments are separated by passage through a jet of evaporative gas at a temperature and pressure such that the filaments emerge separate, parallel, uncrimped and swollen.  Air at 70-140 DEG C. is specified. As shown, spinning solution is supplied from pump 19 to spinneret 11, and coagulating liquid from pump 13 via sparger 14 and a layer of metallic wool 16, to reduce turbulence, to the vessel 12.  The coagulant also fills the spin column 17.  Filaments are drawn past stripper guides 27 and vacuum strippers 28 which remove part of the adherent liquid, over pulley 22, by the driven feed roll 23, and then pass to a pre-drier 31, supplied with hot air, which may be constructed similarly to jet 32 (see below) or may consist of an elongated box fitted with perforated pipes which direct jets of air on to the tow passing through.  The liquid content of the filaments may thus be reduced to 100-250%, based on the weight of the filament-forming material, before they enter the jet 32.  Jet 32 comprises (Fig. 4) a Venturi passage 57 supplied with gas through three symmetrically-disposed inlets 58, through which the tow passes axially, entering at 61, the cross-section of the tow being considerably less than that of the Venturi passage.  After passage through the jet, removal of organic liquid from the separated and substantially tensionless filaments so that they crimp may be effected by evaporation while the filaments float in an evaporative gas, e.g. a stream of hot air passing through an enclosed drying zone 34.  The tow is then sprayed with lubricant from sprayer 37, taken up by rolls 38, 39 and collected in container 42.  Alternatively, removal of organic liquid from the filaments may be effected by evaporation while the filaments are supported on a surface.  In this modification, filaments leaving jet 32 are conveyed through a pivoted traverse tube 46 (Fig. 2) to a moving porous belt 47 through which hot air or other evaporative gas is passed from below, and are then carried through a drying oven 49.  Specifications 715,307, 767,169 and 826,098 are referred to.