| 摘要 |
1277541 Bleaching GILLETTE CO 28 April 1970 [29 April 1969] 20329/70 Heading D1P Hair or wool is bleached by first impregnating it with an aqueous solution containing 0.05-0.15 molar dissolved ferrous salt and a dissolved chelating agent with a concentration of 0.2-5 times the molar concentration of the salt at 20‹C to the boiling point of the solution and then contacting it with aqueous hydrogen peroxide at pH 8-11. The chelating agent has a chelate formation constant (K ma ) with ferrous ion such that log K ma , is 2-8 and the total ionic strength of the solution is 0.5-2.5. The ferrous salt solution may also contain 0.005-0.05 molar reducing agent e.g., alkali metal formaldehyde sulphoxylates, alkali metal sulphites and alkali metal thiosulphates. Preferably in the impregnating stage a buffer system is included to maintain the pH between 3.5-6 and to maintain the total ionic strength above the minimum desired level. Examples of the chelating agents used are ascorbic acid, citric acid, serine and ethylene diamine. In the bleaching stage the fibres are maintained in contact with an aqueous solution containing 1-6 % hydrogen peroxide by weight and adjusted to pH 8-11 by a suitable base preferably ammonium hydroxide at 20-60‹C. |
