GB386637A - Improvements in or relating to staple fibres - Google Patents

Abstract

Spun yarn is formed by twisting together short lengths of artificial fibres which have been roughened by the incorporation of finely-divided insoluble material. The insoluble material may be added to the spinning solution from which the filaments &c. are formed; or it may be applied to the formed filaments while in transit from the spinning machine, in the form of hanks or after cutting into staples. In the latter case, the filaments &c. are treated with a dispersion of the material, or they are first treated with a solution of soluble salts of the alkaline-earth metals and then with a solution adapted to precipitate an insoluble white salt of the metal. The salt solutions may be swelling agents, e.g. barium thiocyanate, or swelling agents such as formic acid, acetic acid, acetone, &c. are added to the solution. Suitable precipitants are aqueous solutions of sulphuric or phosphoric acids or soluble salts of these acids. The filaments &c. contain cellulose or cellulose derivatives, e.g. organic esters and ethers; they may additionally contain fibres of cotton, natural wool or silk. They may be prepared by dry or wet spinning methods and may be cut into short lengths while untwisted or after associating together two or more filaments. Suitable insoluble materials include barium, strontium, or calcium sulphate, carbonate or phosphate; lithium or magnesium silicates; kaolin; mica; zinc sulphide; finely-divided starches and cellulose; also organic compounds of high melting point, e.g. acidyl derivatives of diaminodiphenyl bases such as diacetyl-benzidine and diacetyl-tolidine, condensation products of urea or thiourea and a diphenyl base such as 4 : 4<1>-diureido diphenyl and 4 : 4<1>-dithioureido diphenyl, a -dinaphthyl urea and diphenyl oxamide. The amount of material incorporated amounts to 0,2-5 per cent or more of the weight of the filaments. In an example, finely-divided titanium oxide in an amount equal to 1 per cent of the weight of cellulose acetate is added to an aqueous acetone solution of cellulose acetate and after thorough mixing and filtering, the solution is extruded into an evaporative atmosphere. The formed filaments are stretched by about 15 per cent and are cut into staples about 1,5 inches in length which are spun into yarn by operations including opening, filling, dressing, spreading, drawing, and spinning. In a further example filaments of cellulose acetate in the form of hanks are treated for 1 hour with a solution of barium thiocyanate of 25 DEG Tw. and at a temperature of 70 DEG C., and then in the cold for 20 minutes with a 1 per cent solution of sulphuric acid, after which they are rinsed, dried, and cut into staples.