Patent GB-415412-A (GB)
Title: Improvements in the manufacture of treatment of artificial filaments, threads, yarns, ribbons, fabrics and the like made from or containing organic esters of cellulose
IPC: D01F2/28
Filed: 1933-02-20
Abstract: Textile materials of high tenacity and having an affinity for cotton dyes are produced by applying to filaments, threads, ribbons, and the like comprising organic esters of cellulose, which materials at some stage in their manufacture have been subjected to a relatively high stretch and/or which are made from cellulose esters of high viscosity, a swelling agent for the p  cellulose ester, and saponifying the materials in the presence of said swelling agent with caustic soda or other relatively strong base, the swelling agent being incapable of reacting during the saponification.  Cellulose esters of high viscosity, made, for example, by the process of Specification 207,562, [Class 2 (ii)], have a viscosity of not less than 30, the figure being obtained in the case of cellulose acetate by comparison of a 6 per cent solution of the ester in acetone at 25 DEG  C. with glycerine at the same temperature taken as a standard of 100.  When stretching is contemplated, however, the viscosity may be of the order of 10--30, or even lower.  Stretching may be effected during production of the materials as described in Specifications 340,324, 340,325, 340,326, 340,436, 340,437, 343,062, and 378,858, or the stretching may be carried out on the fully formed materials as described in Specifications 323,790, [Class 2 (ii)], 370,430, and 371,461.  If desired, after stretching and before saponification, the materials may be treated with shrinking agents as described in Specification 389,823.  As saponifying agent, caustic soda or caustic potash is preferred, but other strong base such as sodium silicate, sodium carbonate, trisodium phosphate, or barium hydroxide may be employed.  The swelling agents are non-acidic organic substances which do not contain hydroxy groups or ester acidyl groups, for example, 1, 4-oxanone, dioxane, methylene ethylene ether, dimethyl ether of ethylene glycol, dimethoxy methylene, acetals, formals, acetone, methyl ethyl ketone, and cyclohexanone.  At least some of the swelling agent is preferably contained in the saponifying bath itself. Concentrations of the order of 10--40 per cent are recommended, this being sufficient to swell the material without effecting incipient solution.  It is preferred to pass the materials, whether in fabric form, or in the form of threads, ribbons, or the like, continuously through the saponifying bath.  Threads and the like are most advantageously treated in warp formation.  Again, batch methods of saponification may be employed, the materials being treated in the form of hanks, or bobbins, cheeses, or like packages, or in the form of cakes from centrifugal spinning boxes as described in Specification 402,105.  The saponification methods of Specifications 316,521 and 318,468, [both in Class 2 (ii)], may be employed.  The extent of saponification should be sufficient to impart to the materials an affinity for cotton dyes, and may be sufficient to produce a loss in weight of 5--20 per cent, or may correspond to a 50--100 per cent loss of the ester groups.  In addition to saponification, the materials may be subjected to treatment with shrinking agents to improve their extension as is described, for example, in Specifications 380,504, 380,505, and 389,823.  The following examples are included: (1) Cellulose acetate threads which have been stretched to at least 500 per cent of their original length are drawn from a creel and passed in warp formation through a bath containing 10 per cent caustic soda and 20 per cent dioxane, at 40--50 DEG  C.  (2) The process is as in (1), but with a saponifying bath comprising 5 per cent caustic soda and 20 per cent dimethyl dioxane, at 60 DEG  C. (3) Hanks of cellulose acetate yarn which has been stretched to 200 per cent of its original length are suspended for 12--16 hours in a bath comprising 0,25 per cent caustic soda and 35 per cent dioxane, at 25 DEG  C.