Patent GB-274521-A (GB)
Title: Manufacture of artificial materials from viscose
IPC: D06M11/53
Filed: 1926-01-11
Abstract: 274,521. Lilienfeld, L. Jan. 11, 1926. Cellulose xanthates, processes for making filaments, films, and other products from.-Artificial silk, staple fibre, artificial cotton or wool, artificial hair, ribbons, &c. showing a high dry and wet tensile strength and an increased resistance to aqueous alkalies and soap, are made from viscose by employing as the setting-bath a liquid which contains not less than 55 per cent by weight of sulphuric acid, for instance, not less than 65 per cent of acid, for example, 65-85 per cent. For the purpose of influencing favourably the tensile strength of the products it is advantageous to apply additional tension to the threads during the spinning process either in the setting-bath or between the bath and the collecting device, or in both places. As regards the viscose, this may be prepared from cotton or wood pulp, or from cellulose that has been treated with dilute acids; the alkali cellulose may be subjected to the usual maturing process, although it is preferred to use an alkali cellulose that has not been matured or has been matured to a reduced extent as by shortening the duration of the maturing process; when matured alkali cellulose is used it is preferred to raise the cellulose content of the viscose say to 8-12 per cent; there may be used a proportion of carbon disulphide greater than 40 per cent of the weight of the cellulose, for example, 40-60-150 per cent, but in such cases a longer ageing of the viscose is desirable; the viscose may be prepared by simple mixing together of the reagents, in which case a catalyst such as a soluble chromic, nickel or iron salt or a soluble peroxide, may be added; the viscose used may be prepared according to the process of Specification 212,865; to the viscose may be added glycerine, glucose, alkali sulphites, sulphate, silicate or aluminate, or ammonia; the viscose may be ripened to the usual extent, or it may he used in the unripened or partly ripened condition; and there may be used such viscoses that have a viscosity twice that of glycerine. The strength of the acid to be employed depends to some extent on the degree of maturation of the alkali cellulose, the time of ripening of the viscose, the properties of the parent cellulose material, and the viscosity and the cellulose contents of the viscose, the more matured and less viscous products generally not requiring so strong an acid. The setting- bath may be operated at room temperature, or at lower temperature, for example, 0 to -10‹ C., or at temperatures exceeding room temperature, for example, at 25-50‹C. The length of immersion of the thread may be varied within wide limits, for instance, it may range between 3 to to 60 c.ms or even more, say, 1-2 metres; as a general rule, with very strong acid a short length of immersion suffices; further, the length of immersion is also related to the temperature of the setting-bath, being shorter as the temperature is higher. After leaving the setting- bath the thread may be collected immediately on the collecting bobbin or in a centrifuge; but in some cases it is advantageous to allow the threads to travel a longer or shorter distance through the air, preferably for more than 30 c.ms, for example, 120 c.ms. To the setting-bath may be added other mineral acids, sulphates, sulphites, a nitrite, boric acid, glycerine, glucose, alcohol, salts of organic bases such as aniline, and organic acids such as acetic, formic, lactic and oxalic acids. Since sulphuric acid of the strength employed eventually destroys the threads, its action is checked after the coagulation process is completed, by cooling to a low temperature or by quenching, for example, by watering the thread as it passes over a guide roller on its way to the centrifuge, or by immersing in water the lower port of the bobbin on which the threads are being collected. After washing, the threads may be heated or steamed either before or after drying. By adjusting the amount of viscose delivered to the spinning-nozzles and by regulating the speed of spinning, threads of the fine and finest deniers can be obtained; in the examples, the production of 1.5-4 denier threads is referred to. The Provisional Specification refers to the application of the process to the manufacture of films, plates, coatings and fillings.