Patent GB-535900-A (GB)
Title: Improvements in or relating to the production of cellulose derivative filaments, films and like materials
IPC: D01F2/28
Filed: 1939-10-23
Abstract: 535,900. Artificial filaments ; films &c. ; cellulose esters. DREYFUS, H. Oct. 23, 1939, No. 28502. [Class 2 (ii)] Artificial filaments, threads and like materials having a basis of a cellulose ester are obtained by extruding in the fused condition, and while free or substantially free from volatile solvent, a cellulose ester which is substantially stable in that condition and thereafter setting the extruded materials. The cellulose ester mav be cellulose acetate, or a cellulose ester containing propionyl, butyryl, or other radicle of a higher homologue of acetic acid, especially of an acid containing up to 6 carbon atoms. A mixed ester of cellulose may be used, e.g. cellulose aceto-propionate, aceto-butyrate, or propionobutyrate. The cellulose ester may contain free nuclear hydroxyl groups. If it has been prepared in presence of a strong polybasic inorganic acid catalyst it should be subjected to careful stabilization. It may be prepared in the absence of catalysts which render it unstable. A small proportion of stearyl or other higher fatty acid radicle may be present in the cellulose molecule. If desired, the filaments produced from molten cellulose aceto-propionate may be esterified with stearyl chloride or stearic anhydride. Cellulose stearate may be incorporated with the cellulose aceto-propionate. Plasticizers may also be incorporated with the cellulose ester before or after the shaping. The cellulose ester may be fused by electrical or indirect steam heating. Extrusion may be effected by applying mechanical or fluid pressure to the fluid material. The extruded filaments are preferably subjected to a rapid and considerable drop in temperature shortly after emerging from the orifices. The cooling medium may be a gas or a liquid and it may contain a softening agent. The filaments may be stretched during or subsequently to their production, or they may be treated with a shrinking agent and allowed to shrink. The cellulose ester may contain additions of pigments, dyes, or fire-retardants. The ironing point of the filaments may be raised by submitting them, in the case where there are free hydroxyl groups, to esterification, e.g. with halides or anhydrides of adipic, phthalic, oxalic, succinic, or thionic acid. Continuous filaments may be cut to form staple fibres, and these may be subjected to crinkling treatments. In an example, stabilized cellulose butyrate is heated electrically in a stainless steel vessel fitted ,with a stirrer and tubular extensions at the lower end. These extensions contain metal gauze filters and are provided with spinning orifices. The molten cellulose ester is extruded by the application of air pressure. The extruded filaments pass through wet steam and then through water to a winding and stretching device. In another example, cellulose acetate is further esterified by heating it with butyric anhydride and the resulting solution is poured into xylene. The ester is washed and then melted and converted into filaments. In another example, cellulose butyrate filaments obtained by melt spinning are esterified with a medium containing a mixed anhydride of acetic and adipic acids, kerosene, and stannic chloride. The treated filaments are washed with petrol ether, dried, washed with sodium carbonate solution, water, dilute acetic acid, and finally with water. Specifications 317,025, 317,026, [both in Class 120 (iii)], 357,565, 384,335, 394,709, 409,519, 484,192, [all in Group IX], 523,425, 523,774, 524,897, 529,142 529,510, 532,673, 532,674, 534,273, 534,775, and 535,894 are referred to. The Provisional Specification describes also the production of films, foils, and like shaped articles and is not restricted to the production of cellulose ester materials.