| 摘要 |
Desized or unsized gray woven cotton cloth is bleached by passing it into an aqueous solution containing 1.5-5% by weight of an alkali metal hydroxide, wetting it with 50-150% by weight of the alkaline solution, passing it to a single treating zone, continuously steaming it at a temperature of 200 DEG -212 DEG F. for 15-45 minutes at one end of the treating zone, passing it directly into an aqueous solution of a peroxygen compound containing at least the equivalent of 0.7% by weight of hydrogen peroxide maintained at the other end of the treating zone and heating it while immersed in the solution of peroxygen compound for 15-45 minutes at a temperature of 150 DEG -210 DEG F. the concentration of alkali metal hydroxide in the solution of peroxygen compound being maintained at 1-1.5% by weight. The peroxygen compound may be hydrogen peroxide, an alkali metal monopersulphate, dipersulphate or perborate or a hydrogen peroxide addition compound, e.g. Na2CO3.H2O2. The solution of the peroxygen compound may also contain sodium silicate in a concentration of 1-3% by weight, tetrasodium pyrophosphate, the pentasodium salt of diethylene triamine pentacetic acid, epsom salt and a nonionic alkylphenyl polyethylene glycol ether wetting agent, and the alkali metal hydroxide solution may also contain tetrasodium pyrophosphate and a nanionic alkyl phenyl polyethylene glycol ether wetting agent. The single treating zone may be a J-box the upper section of which is provided with openings through which steam is supplied to effect steaming of the cloth and the U-shaped portion of which contains the solution of the peroxygen compound, the level of the solution in the U-shaped portion being maintained constant by means of an overflow orifice and the concentration of alkali metal hydroxide in the solution being controlled by adding fresh solution of the peroxygen compound through spray heads situated below the openings for the entry of the steam. A collecting trough may be provided at the base of the J-box to remove the solution of the peroxygen compound which is then heated by means of steam and recirculated with fresh solution. After leaving the J-box the cloth may be washed with water. Sized cloth may be desized by treatment with an aqueous enzyme solution prior to bleaching. |
