GB803021A - Continuous textile bleaching process - Google Patents

Abstract

A continuous bleaching process for textile fabrics made from vegetable fibres such as cotton comprises (i) passing the fabric, preferably in open width and for a time not exceeding 5 minutes, suitably 10-60 seconds, through a bath or series of baths containing either trichlorethylene or perchlorethylene, where it is degreased and dewaxed, the temperature of the bath being preferably 80-87 DEG C. and the solvent preferably running counter-current to the fabric; (ii) removing excess solvent, for example by mangling; (iii) passing the fabric through an aqueous bath maintained at such a temperature as will flash off solvent entrained in the fabric, for example at least 73 DEG C. and preferably at least 90 DEG C. for trichlorethylene and at least 86 DEG C. and preferably at least 90 DEG C. for perchlorethylene, the time of contact of the fabric and the "flash off" bath medium being preferably 8-60 seconds, then optionally desizing the fabric, for example by treating it with an aqueous solution of malt or subjecting it to an acid souring treatment, or both; (iv) padding the fabric in an aqueous alkaline solution, preferably one containing sodium hydroxide in an amount such that the bath has a pH of at least 10, and optionally containing also a peroxygen compound, in which case the pH is controlled in the range 10-12; (v) rapidly heating the padded fabric by passing it through an atmosphere of steam at 50-105 DEG C. in a retention device, such as a J-box, at such a rate as to provide adequate time to allow substantial action of the alkali upon the fabric, and then, where a full bleach is required and the padding liquor has not contained sufficient peroxide; (vi) rinsing the fabric; (vii) padding it with a peroxide solution of pH 10-11 containing 1-3 gms. per litre available oxygen, followed by (viii) further steaming and passage through a retention device at 50-105 DEG C. at a rate adequate to provide time for the peroxide to effect a full bleaching of the fabric. The fabric may thereafter be rinsed well with hot water, then with cold, and finally dried at ordinary temperature in air. If desired, a steaming vessel as well as a retention device may be used in either or both of steps (v) and (viii) above. Specifications 542,413, [Group IV], and 747,481 are referred to.