| 摘要 |
Natural cellulosic fibrous materials, e.g. cotton fabrics, are bleached in the absence of oxidising agents by treating them at 90 DEG -150 DEG C. for from 30 seconds to 5 hours with an aqueous liquor containing (1) 4-13% by weight of an alkali metal hydroxide (2) 1-4% by weight of an alkali metal polyphosphate containing two or more phosphorus atoms in the molecule and/or a complex-forming aminopolycarboxylic acid or alkali metal salt thereof and (3) 0.5-3% by weight of an anion-active and/or nonionic wetting agent which is active in alkaline solution, the treatment temperature t (in DEG C) within the range of 90 DEG -150 DEG C. being so correlated to the treatment period #t (in minutes) that it is within the limits t1 and tu (inclusive) (t1 denoting the lower limit and tu denoting the upper limit) defined by the equations:-t1=100-20 (log #t-1.5) and tu=100-20 (log #t-4) or within the limits 90 DEG C to tu or t1 to 150 DEG C should either t1 be less than 90 DEG C or tu greater than 150 DEG C., and then freeing them from alkali metal hydroxide, all percentages being with reference to the liquor. The concentration c (in % by weight) of the alkali metal hydroxide may be correlated to the treatment temperature t (in DEG C) that it is between the limits C1 and Cu (inclusive) as defined by the equations:-C1=10-0.1 (t-100) Cu=12.5-0.1 (t-100) in the temperature range of 110 DEG -150 DEG C and C1=5.5-0.1 (t-100) Cu=8.5-0.1 (t-100) in the temperature range of 90 DEG -110 DEG C. The polyphosphate may be one having the formula Mn+2PnO3n+1 in which M is an alkali metal ion and n is an integer of 2-10, e.g. sodium or potassium pyrophosphate, tripolyphosphate, tetrapolyphosphate and hexapolyphosphate and the complex-forming aminopolycarboxylic acid may be one having the formula <FORM:1073807/D1-D2/1> in which m is zero, 1 or 2 and Y is a -COOH or -CH2OH group. Suitable wetting agents are alkyl sulphonates, alkyl disulphonates, alkylaryl sulphonates, fatty acid condensates, proteinolysis products, sulphuric acid hemiesters of alkylphenol-ethylene oxide adducts or salts thereof and adducts of ethylene oxide to fatty alcohols, fatty acid amides, alkylnaphthols, and alkylphenols. Heating may be effected by steaming. The alkali metal hydroxide may be removed by rinsing first twice at boiling temperature and then once or twice at 60 DEG -80 DEG C and then acidifying with very dilute hydrochloric acid and rinsing once cold. The aqueous liquor may also contain a reducing agent, e.g. sodium dithionite, a -hydroxyalkane sulphinic acids and their salts and reaction products of a -hydroxyalkane sulphinic acids with ammonia or amines or salts thereof. |
