| 摘要 |
1,270,716. Bleaching wood pulp. ATLANTIC RICHFIELD CO. 12 Aug., 1969 [19 Aug., 1968; 6 Dec., 1968], No. 40365/69. Heading D1P. Ligneous cellulosic materials, e.g. wood pulp, are bleached with a composition, usually an aqueous composition containing an organic hydroperoxide either alone or with hydrogen peroxide. The composition may also contain a buffer salt for example sodium or potassium tripolyphosphate or sodium silicate, with, if desired, sodium hydroxide and an anionic surfactant, for example a linear alkylbenzene sulphonate, wherein the alkyl group contains from 11 to 14 carbon atoms. If hydrogen peroxide is used in the bleaching composition, sodium silicate with or without sodium hydroxide is the preferred buffer salt. The bleaching step may be followed by a sulphite treatment using sodium sulphite, sodium bisulphite, zinc hydrosulphite, or sodium hydrosulphite solutions. Suitable organic hydroperoxides include tert-butyl, cumene and amyl hydroperoxides. The preferred percentage weight compositions, based on the dry weight of the treated material are as follows: organic hydroperoxide, between 0.1 and 2%, hydrogen peroxide, if present between 0.5 and 2% sodium and potassium tripolyphosphate, if present, between 1 and 2%, sodium silicate, if present, between 3 and 7% and sodium hydroxide if present, between 1 and 4%. |
