Patent GB-402141-A (GB)
Title: Improvements in the manufacture of filaments, yarns, fabrics and like materials
IPC: D06M11/38
Filed: 1932-02-19
Abstract: Filaments, yarns, or the like, of organic esters of cellulose, which have undergone a stretching treatment, or fabrics containing the same, are subjected to saponification by means of an alcoholic saponifying agent containing not more than 2 per cent. of caustic soda or the equivalent of another base.  The products have a high tenacity and an affinity for cotton colours.  Preferably the materials treated should have undergone a stretch of 200 per cent. or more of their original length, whereby yarns having a tenacity exceeding 1.5 gms. per denier, e.g. of 3 to 4 or more gms. per denier are obtained.  The stretching of the yarns, may take place during or after spinning by dry or wet processes.  Examples of wet stretch-spinning processes are those of Specifications 340,324, 340,325, 340,326, 340,436, 340,437, 343,062, and 378,858.  Other stretching processes are those described in Specifications 277,089, 323,790, [Class 2 (ii), Cellulose &c.], and 370,430.  The saponifying agent, e.g. caustic soda or caustic potash, is preferably present in very low concentration, i.e., of the order of 0.05 to 1 per cent. The alcoholic medium may comprise a mono-, di-, or polyhydric alcohol such as methyl or ethyl alcohol, glycols, glycerine, or cyclic alcohols.  Saponification is conveniently carried out as a bath treatment on the yarn in hank or other package form, for example, yarn proceeding from a stretching operation carried out with the yarns in warp formation as in Specification 371,461 may be separately collected and treated in centrifugal boxes.  Cakes of filaments &c. may be supported from the interior by means of a swift which is made expansible for insertion in the cake, the swift comprising an end plate perforated at the periphery with small holes for the insertion of a number of wires which after insertion in the interior of the cake may be expanded umbrella-fashion by means of a conical piece sliding on a shaft fitted to the end plate. Alternatively, a number of small segmental gauzes are fitted inside the cake, the gauzes being attached to each other in pairs by a spring distance piece. The saponifying liquid is then circulated through the cake for the required time.  If desired a wetting agent may be applied to the yarns before saponifying.  The extent of saponification may vary from 5 to 20 or 50 per cent. up to substantially complete elimination of the ester groups.  If desired, the yarns may have been subjected to treatment with shrinking agents to improve their extension, for example, by the process of Specification 380,504, 380,505, or 389,823.  The saponified yarns may be subjected to further stretching.  In an example, dry-spun cellulose acetate yarn which has been stretched to 400-500 per cent. of its original length is treated in hank or cake form by means of methyl alcohol solutions of caustic soda under various conditions as to concentration, time, temperature, and quantity.  Specifications 125,153, 177,868, 179,234, 313,404, and 330,950, [all in Class 2 (ii), Cellulose &c.], also are referred to.--The Provisional Specification is not limited as to the concentration of the saponifying-agent.