| 摘要 |
Cellulose textile fabrics containing vat-dyed yarns or fibres, e.g. towelling, are submitted to a pre-bleaching treatment by saturating the fabric with a scouring solution having an alkali equivalent of 0.5 to 5.0 per cent NaOH and a pH between 11.5 and 13.5, reducing the liquid contained in the fabric to 80 to 110 per cent of the weight of the fabric, and steaming with a steam-air mixture containing at least 10 per cent by weight of air, to heat the fabric to 150 to 250 DEG F. Bleeding or marking-off of the vat dye is thereby avoided. The fabric is passed through the vessel 1 containing the alkali solution, which may contain sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium pyrophosphate, sodium silicate, wetting agents and/or buffering agents, then through squeeze rollers 5 and 6 and through tubes 9 and 10 supplied with a mixture of steam and air from the injector 23. Condensed water is removed from the steam-air mixture by the baffles 19. The temperature of the fabric is controlled by means of the thermostate 21 operating the steam valve 27. The fabric is passed into the temporary storage conduit 29 from which it is withdrawn and <PICT:0611589/IV (c)/1> forwarded to conventional washing and bleaching devices. |
