GB867607A - Process of dyeing cellulose acetate textile materials of high acetyl value, and dyebaths for use therein - Google Patents

Abstract

Textile materials comprising fibres of cellulose acetate of acetyl value at least 60% are coloured by applying thereto a dyebath in which the dyestuff is dissolved in a mixture of water, a monohydric aliphatic alcohol, an alkali metal or ammonium thiocyanate, and, if desired, acetic acid, the concentration of thiocyanate being such that the dyebath causes coalescence of fibres of acetone-soluble cellulose acetate of acetyl value 54-55% so that textile material made therefrom loses its fibrous character, but does not damage fibres of cellulose acetate of acetyl value at least 60%. Preferably the cellulose acetate has an acetyl value of at least 61% and the fabric thereof has a maximum safe ironing temperature below about 200 DEG C. Dye concentration is preferably up to about 5%, especially from about 0,01% to about 4%, based on the weight of the dyebath. A preferred dyebath comprises a dyestuff dissolved in from 5-25 parts of acetic acid, 5-55 parts of water, 25-70 parts of the alcohol and 5-12 parts of an alkali metal or ammonium thiocyanate, all parts being by weight. The dyebath may be at 10-50 DEG C., and the textile material carrying adhering dyebath may be rinsed with water and then dried. Preferably, textile material in fabric form is passed continuously into the dyebath and is then continuously rinsed and dried, e.g, fabric may be padded with the dyebath and, after a contact time of 2-30 seconds, may be rinsed in water at below 30 DEG C. An alternative dyebath comprises a dyestuff dissolved in from 5-35 parts of water, 65-95 parts of the alcohol and 8-14 parts of alkali-metal or ammonium thiocyanate. This dyebath may be at 10-50 DEG C., and the textile material carrying adhering dyebath is preferably dried at below 65 DEG C. before rinsing with water. Preferably, textile material in fabric form is passed continuously into this dyebath and is then continuously dried and rinsed, e.g. fabric may be padded with the dyebath and, after a contact time of 2-30 seconds, may be dried at below 65 DEG C. and then rinsed in water at below 30 DEG C. After dyeing the textile material may be heat-treated to increase its crystallinity and crystalline order index. In the above dyebaths, the preferred alcohol is ethyl alcohol, but methyl, isopropyl, n-butyl and isobutyl alcohols may also be used, and the preferred thiocyanate is sodium thiocyanate. Suitable dyestuffs include acid, premetallized, direct cotton and leuco vat ester dyestuffs, and cellulose acetate disperse dyestuffs of the slow-dyeing high-temperature type, which are soluble in the dyebaths used. Numerous dyestuffs are specified. Specifications 791,391 and 824,398 are referred to.