Patent GB-357169-A (GB)
Title: Improvements in or relating to textile materials
Filed: 1930-05-16
Abstract: For the manufacture of fabrics exhibiting cr<\>zepe effects there are used highly twisted threads formed of filaments of natural silk or of artificial silk composed of cellulose acetate or other cellulose esters or of cellulose ethers, but not of cellulose or regenerated cellulose, which have been provided with coatings or layers of a cellulose or a cellulose derivative capable of being easily swollen particularly by treatment with water or other aqueous liquid.  The cellulose coating may be a cellulose which has been regenerated from viscose or a solution in ammoniacal copper solution or in metal salt solutions, and it may be a degraded cellulose, in particular a cellulose intermediate as regards its properties between b -cellulose and g -cellulose, such as is produced by treatment of cellulose with acids or alkalies, as by heating with dilute or concentrated caustic soda solutions p  with or without pressure, or by the action of sulphuric acid, the acid being subsequently eliminated by dialysis; or alternatively the cellulose used may be obtained by degrading a cellulose derivative, for example, by subjecting viscose to an extended ripening, or by prolonging the after-treatment of a cellulose ester, in the case of cellulose acetate until a product soluble in dilute alcohol is obtained, from which product degraded cellulose is regenerated by saponification with alkali or steam. According to another method, the cellulose coating may in the case of filaments formed of cellulose derivatives be formed by superficial reconversion of the latter to cellulose, for example, in the case of filaments composed of cellulose acetate &c., by superficial saponification carried out, for example, according to the processes of Specifications 314,446, 314,447, 316,521, 318,468, [all in Class 2 (ii), Cellulose &c.], and 351,417, and the superficial saponification may be carried out continuously with the manufacture of the filaments, according to the process of Specification 330,950, [Class 2 (ii), Cellulose &c.].  The coatings may, however, consist of cellulose derivatives particularly such as are readily swollen by water or other aqueous agents, for example, cellulose esters or ethers which have been degraded so as to be soluble in dilute acetone, dilute alcohol, or even in water, or cellulose esters or ethers in which the esterifying or etherifying radicles contain groups conferring increased solubility or dispersibility in water &c., for example, the cellulose esters and ethers described in Specifications 166,767, 277,721, [both in Class 2 (ii), Cellulose &c.], 343,521, and 344,775.  For producing the coating, the filaments may be treated with a solution or dispersion of a suitable cellulose, and then dried; alternatively they may be coated with a solution or dispersion of a suitable cellulose derivative, for example, viscose, and the cellulose regenerated in situ; the aqueous or other dispersions of cellulose or cellulose derivatives may be prepared with the aid of dispersing agents, with or without the addition of other colloids such as gelatin and casein, and in the case of aqueous solutions may be rendered alkaline in order to facilitate the solution of the cellulose or cellulose derivative or to facilitate the adhesion of the coating particularly in the case of filaments composed of cellulose esters in which case adhesion is improved if the alkalinity is such as to cause a slight surface saponification of the material.  The coatings may be applied either to the threads or fabrics; but the best results are obtained when the coatings are formed on the individual filaments preferably before the application of twist or at least of a high twist.  After weaving, the fabrics are subjected to a scouring or other treatment capable of swelling the cellulose or cellulose derivative coating, for example, by scouring in a soap bath or by treatment with a thiocyanate or other metal salt bath capable of swelling cellulose; the treatment should not be such as to render the coatings unduly soft or yielding, and therefore the treatment liquid may be applied as a spray or in vapour form.  The cellulose or cellulose derivative coating may be finally removed from the fabric, for example, by subjecting the material to a vigorous scouring treatment, or by raising the temperature or modifying the composition of the swelling bath.  The treatment to which the fabrics are subjected after weaving, may be such as to swell both the coatings and the filaments themselves, for example, by a suitable choice of scouring baths or by suitable additions thereto; or the swelling of the filaments may be effected in the manner described in Specification 352,000.  To obtain the best cr<\>zepe effects, the final drying of the fabrics should be carried out in the absence of substantial tension.  The cr<\>zepe threads may be of one type as regards material and coatings, or they may be of two or more different kinds; thus cellulose ester or ether threads may be combined with natural silk threads, or the threads may be composed of cellulose ester or ether filaments of different deniers.  The cr<\>zepe threads may constitute the whole of or a part of the weft, and the warp may also contain them; but it is preferred to employ low twist threads for the warp, and in the weft cr<\>zepe threads of both right-hand twist and left-hand twist, for example, by arranging pairs of threads of right-hand twist to alternate with pairs of left-hand twist.  The fabrics may contain threads of cotton, or other natural or artificial cellulosic fibres.  In examples, cellulose acetate yarn of low twist is superficially saponified by treatment with thirty times its weight of a solution of caustic soda, the latter being added at such a rate that the concentration does not exceed 1,5 grams per litre, and there being used in total an amount of caustic soda equal to 20 per cent of the weight of the material treated; a cellulose acetate yarn is sized with an aqueous solution of cellulose acetate tartrate made by heating cellulose acetate with tartaric acid and a little water for several hours; in both cases the treated yarn is dried, and is highly twisted, and is then woven into a warp of cellulose acetate yarn of low twist, and the resulting fabric is scoured in a soap bath, rinsed and dried without tension. Specifications 344,528 and 348,589 also are referred to.