Patent GB-391480-A (GB)
Title: Improved manufacture and treatment of artificial silk and like products
IPC: D01F2/28
Filed: 1931-10-21
Abstract: When treating cellulose acetate or other cellulose ester or ether fabrics &c. with solvents or swelling agents as for the purpose of preventing slipping or laddering as described in Specification 280,990, [Class 2 (ii), Cellulose &c.], or for the purpose of relustring delustred materials as described in Specification 259,265, [Class 2 (ii), Cellulose &c.], or for the purpose of obtaining a crepe effect with fabrics containing highly twisted yarns as described in Specification 352,000, the effect of the solvent or swelling agent with which the material has been treated in a non-solvent medium, is enhanced by subsequent treatment with an agent which decreases the solubility of the solvent in the non-solvent medium.  By this means it is possible to obtain a much higher degree of softening or swelling of the material, or to permit of the employment of solutions of solvents &c. of lower concentration. Suitable agents are generally salts and sugars.  The salts preferred are non-hydrolysable salts which in aqueous solution do not swell the cellulose derivative, in particular, sodium or potassium acetates, sodium chloride and ammonium nitrate, and these may be used in concentrations of 1-10 per cent up to saturation point.  There may also be used sugars and other polyhydric alcohols such as glucose, xylose, mannitol, cellulose, and other degradation and depolymerization products of cellulose.  The agents are preferably applied in solution in the same medium as is used for the dilution of the solvent, in particular, in solution in water or alcohol.  Similar treatment may be applied to artificial filaments, yarns, ribbons, &c. containing organic derivatives of cellulose, which have been similarly treated with a solvent or swelling agent or are laden with a solvent &c., preparatory to a stretching operation as described in Specifications 277,089 and 323,790, [both in Class 2 (ii), Cellulose &c.].  The treatment in question may be applied simultaneously with or prior to the stretching, which may be performed on the material in hanks or while it is travelling as from bobbin to bobbin or from a spinning machine, or while in warp formation; and the stretching may be gradual or in stages, and between at least some of the stages a rest period may be interposed as referred to in Specification 370,430, and the number of stages may be increased so that the stretching is in fact of a very gradual character.  Local or differential stretching may be produced by local application of the solvent or of the salts, sugars, &c.  When applied to the wet spinning of artificial filaments according to the processes of Specifications 177,868, 179,234, [both in Class 2 (ii), Cellulose &c.], 340,324, and 340,437, the filaments after leaving the coagulation or after-treatment bath may be carried directly into the salt or sugar bath, and a stretch or further stretch applied to the material while in that bath.  Solvents &c. carried by the treated material may be subsequently washed out as by a further treatment with a salt solution or with a solution of the solvent of lower concentration than that in the materials, in order to obviate loss of lustre.  Specifications 336,217, [Class 2 (ii), Cellulose &c.], 351,999, and 389,823 are referred to in the Provisional Specification.