GB572140A - Process for the manufacture of artificial silk resembling wool - Google Patents

Abstract

Regenerated cellulose filaments in yarn form are crimped and given a wool-like appearance by subjecting the highly twisted filaments to treatment with a strong swelling agent so as to set the twist and then twisting in the reverse direction beyond the zero point. The yarn may be washed and dried before the reversed twist is imparted. The treatment improves the dyeing affinities of the yarn, and more even dyeings are obtained. The crimp is stable to washing treatments. The filaments which are treated may have been previously matted or dyed. The highly twisted filament yarn may be wound on to perforated bobbins and subjected on these bobbins to the swelling and twist-setting treatment. Caustic soda or potash, sulphuric acid, zinc chloride, or calcium thiocyanate solutions of various strengths may be used as swelling agent and the treatment may be in the cold or at elevated temperature. The yarn may be treated in hank form, or a continuous length may be passed through a bath of the swelling agent. After the swelling treatment the swelling agent is washed out before or after a drying step. The reverse twisting may be effected without previous drying. Dyeing or matting treatments may be effected after the swelling treatment. The reverse twisted yarns may be cut into staple fibres. They may be treated with formaldehyde to reduce the capacity for swelling. In an example, viscose yarn is twisted to 1,500 turns per metre and wound on perforated bobbins which are then placed in a pressure dyeing apparatus. Hot caustic potash lye is passed through the bobbins for a few minutes. The lye is then removed from the yarn by washing. The yarn is dried, unwound, and twisted in the opposite direction to 70-80 turns per metre. In another example, artificial silk yarn dyed with a vat dye is highly twisted and then treated with caustic potash lye containing a mercerizing assistant such as a mixture of crude cresol and fat solvent. It is neutralised and washed and twisted beyond the zero point in the opposite direction. Two such yarns are then twisted together, immersed in a softening bath containing a sodium salt of the methyltauride of a higher fatty acid, washed and dried. In another example, highly twisted viscose yarn is treated with caustic soda solution containing a wetting agent and after washing is dyed with a substantive dye, e.g. Direct Sky Blue, a solution of the dye being added slowly to the dye bath containing boiling water and a softening agent, "Igepon T" (Registered Trade Mark). After dyeing, the yarn is unwound, twisted in the opposite direction and reeled. The reverse twisted yarns may be doubled with other yarn, e.g. viscose crepe yarns. In another example, the reverse twisted yarn is hardened by treatment with a solution of formaldehyde and aluminium thiocyanate. Specification 442,073, [Group IX], is referred to.