GB402143A - Improvements in the manufacture of filaments, threads, yarns, ribbons and like materials made of or containing saponified cellulose esters - Google Patents

Abstract

Filaments, yarns, and the like, of organic esters of cellulose, are saponified while being drawn in the form of a warp, web, or sheet of yarns through a bath containing the saponifying agent, by rollers or the like extending over the whole warp, web, or sheet. The saponifying agent may comprise any suitable base in aqueous, alcoholic, or aqueous-alcoholic solution. When high concentrations are employed, it is advantageous to have present a buffer salt such as sodium chloride, sodium acetate, or a soap. When using alcoholic saponifying media, e.g., methyl or ethyl alcohol, glycols, or glycerine, the saponifying agent may be present in quantity less than is theoretically necessary to produce the desired amount of saponification. The extent of saponification may vary from 5 to 50 per cent up to substantially complete elimination of the ester groups, according to whether the object is to increase the safe ironing point, confer an affinity for cotton colours, or produce a reconstituted cellulose thread. The filaments may comprise cellulose esters of high viscosity characteristics, for example, in the case of cellulose acetate, viscosities of the order of 30 to 200 or more, as measured by comparing the rate of flow of a 6 per cent solution in acetone at 25 DEG C. against a standard of glycerine as 100. High viscosity esters of this nature may be obtained by the process of Specification 207,562, [Class 2 (ii), Cellulose &c.]. The filaments may also have undergone a stretching treatment continuously with, or subsequently to their manufacture by dry or wet spinning processes, preferably so as to produce an extension of the order of 200 to 500 per cent or more, and a tenacity exceeding 2 gms. per denier. Examples of such processes are those of Specifications 277,089, 323,790, [Class 2 (ii), Cellulose &c.], 340,324, 340,325, 340,326, 340,436, 340,437, 343,062, 370,430, and 378,858. If desired, the filaments may be subjected, before or after saponification, to treatments with shrinking agents as is described in Specifications 380,504, 380,505, and 389,823. In an example, yarns of cellulose acetate which have been stretched to 500 per cent of their original length are led from a creel through a reed so as to constitute a warp, through nip rollers by which a wetting out liquid is applied, and then over a further roller into a saponifying bath containing caustic soda dissolved in an aqueous solution of sodium chloride or sodium acetate. In a further example, the yarn in the previous example is replaced by yarn obtained by dry-spinning cellulose acetate having a viscosity of 55. The first Provisional Specification refers also to Specification 371,461.