GB401679A - Improvements in the treatment of artificial filaments, fibres and the like - Google Patents

Abstract

<PICT:0401679/IV/1> <PICT:0401679/IV/2> Artificial filaments, yarns, threads, foils, films and the like, especially such as contain cellulose acetate or other cellulose esters or ethers, are treated while travelling from one point to another with a moving body of liquid containing a softening agent for the materials, the concentration of softening agent in the whole or in a portion of the liquid is then altered by the incorporation of a liquid therewith, and the materials are subjected, preferably after stretching, to a further treatment with the liquid of altered concentration. The invention is applicable in processes where the materials are passed through a bath of softening agent, particularly one of high concentration, which is circulated through a suitable vessel, and is especially applicable to stretching and coagulating processes of the kind referred to in Specifications 277,089, 323,790, 336,217, [all in Class 2 (ii), Cellulose &c.], 340,324, 340,325, 340,326, 340,436, 340,437, 375,423, 378,858, and 380,819. The concentration of the solutions in such processes may be reduced in this way by the addition of a suitable diluent either in a single stage or in stages or continuously. The diluent may be incorporated with the whole of the softening medium or with a relatively large part thereof, but is preferably added to only a small proportion, especially in washing materials after a stretching process, the bulk of the treatment liquid being returned again to the first treatment bath. The volume of the liquid of altered concentration used may be greater than, equal to, or less than that of the first treatment liquid. The concentration of the solvent may also be increased, for example, in a stretching operation, so that a further softening is effected with the more concentrated softening agent. The volume of the liquid employed for the secondary treatment may be adjusted as desired, and in cases where the materials are stretched during their travel through a moving body of softening agent, this adjustment may effect or assist in effecting a variation in the degree of stretch produced along the length of the bath. For example, when the softening agent is flowing in a direction counter to the materials, at a certain point in the bath a further quantity of liquid may be introduced so as to alter the concentration of the softening agent and increase the rate of flow between that point and the liquid outlet, thus reducing the stretching force on the portion of the materials which has not reached the point of introduction of the additional liquid. Again, when materials are being stretched while travelling from one point to another, so that their velocity increases, the relative velocities of the materials and the softening bath may be adjusted by altering the velocity of the bath at intervals or continuously along its length. When the materials and the bath are travelling in the same direction, for example, the relative velocities may be maintained substantially uniform by this method. The secondary treatment may be carried out in the same bath as the first treatment, or in a separate compartment thereof, or in a separate vessel. Thus the secondary treatment bath may form a part of the coagulating bath or of the treating bath in a stretching process, and may be separated therefrom by any suitable partition. Preferably the softening medium flows from one end of the treating or coagulating bath to the other, the compartment in which the washing operation is carried out being formed at the end towards which the softening medium flows, the filaments yarns, or the like being carried into the washing compartment or vessel without leaving the softening medium at any stage, for example, by being passed over or under a suitable partition in the softening bath furnished with a fixed or rotatable roller or other smooth surface suitable for the purpose. The proportion of the softening liquid leaving the softening bath is preferably so proportioned as to be that which is required to be reconditioned for use in the softening bath. For example, if in a wet spinning process or in a softening bath for a stretching process, one hundredth of the total liquor passing through is withdrawn from the bath and reconditioned, such a proportion may be carried into the washing compartment. The concentration of the solvent in the washing bath may be adjusted by regulating the inflow of diluent. Preferably a continuous decrease of concentration is arranged in the washing bath, for example, by means of a suitable flow of diluent thereinto from inlets at different points. Filaments, yarns, or the like, may be passed from a softening bath under a suitable partition into a washing compartment, upon entering which they are still subjected to the same concentration as that existing in the softening bath. Non-solvent diluent, preferably the same as that used to dilute the softening bath, is let in at different levels or different points along the length of the compartment. The diluent, especially if water is used for this purpose, may contain salts, sugars, or other substances adapted to minimize or prevent deleterious action due to the decrease of concentration of the softening agent. Solvents or other softening agents which may be p used are aqueous solutions of thiocyanates, such as those of the alkalis, ammonium, and alkaline earths, and aqueous solutions of zinc chloride; acetic acid, formic acid, lactic acid, diacetone alcohol, acetone, and the like; the ethers, esters, or ether-esters of olefine glycols and polyolefine glycols or of other polyhydric alcohols, for instance the monomethyl and ethyl ethers of propylene glycol, and the monoethyl ether of diethylene glycol, dioxane, methyleneethylene dioxide, and their homologues and substitution products, glycol monoacetate, methyl glycol monoacetate, mono-, di-, and tri-acetins etc.; phenols, formaldehyde, acetaldehyde, dichlorethylene, methylene chloride, and the like, or mixtures of these, or solvent mixtures. The stretch imparted to the filaments or other products may be applied in a single stage or in a plurality of stages as described in Specifications 370,430 and 375,423. It is preferable that the filaments or other products should retain plasticity between stages of stretching. The process may be carried out with filaments in warp formation as described in Specification 371,461. The stretching force may be applied to the filaments prior to, during, or after their passage through the bath. The treatment may be applied not only to cellulose acetate materials, but also to those made of or containing any other cellulose ester or ether, for example, cellulose formate, propionate, or butyrate, esters containing higher fatty acid radicles, such as cellulose laurate or stearate, or mixed esters, or cellulose nitro-acetate, or ethyl, butyl, or benzyl cellulose, or mixed cellulose ethers, or mixed ether-esters such as ethyl cellulose acetate or oxyethyl cellulose acetate. Such cellulose esters or ethers may have any desired viscosity characteristics. Other artificial materials, for example, regenerated cellulose materials obtained by the viscose, cuprammonium, and nitrocellulose processes may also be treated according to the invention. In one form of apparatus for carrying out the process, a warp of threads 8 is introduced by means of a feed roller 9 into a vessel 7, passing under a guide 11. The individual threads are kept apart by means of a reed 10. At a suitable point a partition 12 is provided to which is fixed at the bottom a perforated pipe 13 through which softening agent is withdrawn by means of a circulating pump and reintroduced at the top of the bath. The height of the partition 12 is about the same as that of the guide 11 so that the top may act as a support for the warp of threads. Diluent is introduced by means of a perforated pipe 16, the rate of flow being controlled by a suitable valve. At the further end of the bath the threads pass through a reed 17 and under a draw-roller 18 rotated at a suitable speed, then through washing and drying apparatus, after which they are wound as desired. An outlet pipe 21 fitted with a valve is provided through which the liquid is withdrawn. In order to maintain the concentration of softening agent in the main bath constant additional softening agent may be added to the circulating liquid or fed by a separate pipe to the top of the bath. In another form of apparatus whereby the invention is applied to a wet spinning process, a filter candle 24 is connected to a spinning jet 23 from which a bundle of filaments 25 is extruded into a vessel 22, coagulating liquid being led in by the pipe 35. The filament bundle passes along the bath under a guide 29 and round a draw-roller 31 to a guide 34, from which it passes to a funnel 32 and a spinning pot 33. At a suitable point along the vessel the side is cut away and a channel is formed so that the liquid in the bath is maintained at a constant level, the excess being drawn off by means of the channel and through a suitable outlet therein. A pipe 28 which is perforated along its length is provided through which diluent is introduced, a portion of the coagulating medium being thus continuously withdrawn during the later stages of travel of the materials through the bath while diluent is continuously introduced. Apparatus of a similar nature may be used for the treatment of films, foils and the like products. Examples are given.