Patent GB-391801-A (GB)
Title: Improvements in the spinning of artificial filaments and the like
IPC: D01F2/30
Filed: 1931-11-03
Abstract: <PICT:0391801/IV/1> In spinning solutions of cellulose acetate or other cellulose derivative such as cellulose formate, propionate, butyrate, nitrate, or nitro-acetate, or methyl, ethyl, butyl, or benzyl cellulose, or ethyl cellulose acetate or oxyethyl cellulose acetate, the extruded filaments are subjected first to evaporative treatment such that a skin-like outer layer is formed, and are then passed through a chamber or compartment of the spinning cell where a liquid solvent or softening agent is evaporated from an extended surface so as to produce an atmosphere having a softening action on the outer layer of the filaments which are then subjected to stretching.  The stretched filaments may be passed through a further evaporative medium and they may be subjected to further stretching after they have reached an elastic condition.  The stretching force may be prevented wholly or partially from extending back to the spinning nozzle.  The extended surface for evaporation of solvent or softening agent may consist of silica gel, active carbon, fireclay, or brick and may be placed in a perforated container fed at the top with the liquid agent.  The surface may comprise a fabric or loose material of cotton, wool, or felt which is fed at the top with liquid, or dips into a bath of the liquid.  The softening agent may be acetone, methyl acetone, dimethyl ethylene glycol, dioxane methylene chloride, ethylene dichloride, dichlorethylene, methyl acetate, ethyl acetate, alcohol, benzene, or mixtures thereof. Stretching of the softened filaments may be assisted by the presence in the spinning solutions of plasticizing or high boiling-point softening agents such as cyclobutanone, acetyl acetone, diacetone alcohol, esters and ethers of olefine and polyolefine glycols, or sulphonamides.  As shown in the drawing, filaments 8 are extruded from a jet 7 into a cell 9 provided with steam heating elements 10 where they undergo rapid evaporation with formation of a skin-like outer layer.  A current of air enters the cell through a perforated ring 14 and leaves together with solvent vapour through the ring 11. The filaments are then led into a softening chamber 16 formed as a compartment of the spinning cell by the provision of a partition 17. Softening liquid from a vessel 22 enters the top of an annular container 19 and drips through small holes on to porous material such as silica gel or cotton wool.  Gaseous medium is withdrawn from the chamber 16 by means of a pump 27 and after being brought to the desired temperature by passing through the coils 26 is introduced into the bottom of the vessel 19.  The gas current assists the evaporation of softening liquid from the porous material, and the vapour issues through holes 23 into the interior of the chamber 16. The filaments pass from chamber 16 to a further drying chamber 30 and thence to a cap-spinning device 40.  Hot or cold air enters chamber 30 through the ring 32 and is withdrawn through ring 33.  It may then be passed direct to a recovery system or as shown conducted through pipe 15 to the inlet ring 14 of the compartment 9.  The filaments are stretched by means of the roller 38 which has a smaller diameter portion 36 and a tapered portion 37.  When spinning is started the filaments are passed round the portion 36, little or no stretch being applied, and when stretching is to commence the guide 39 is used to direct the filaments up the slope 37 to the large diameter of the roller 38.  Specifications 203,092, 323,790, [both in Class 2 (ii), Cellulose &c.], 340,929, 340,930, and 375,425 are referred to.