| 摘要 |
The present invention relates to compositions suitable for use in the bleaching of pulps, comprising one or more particulate alkaline earth metal oxides or alkaline earth metal hydroxides or mixtures thereof; and one or more pitch control additives. The invention further concerns the use of the compositions according to the invention, as well as methods for bleaching pulps. The preferred pitch control additive is at least one of talc, bentonite, zeolite, diatomaceous earth, cationic mica, hydrophobic carbonates, resin-decomposing enzymes, cationic polymers (i.e. polyDADMAC), aluminium sulphate, polyaluminium chloride or dispersing agents. Even more preferred is micronized talc, bimodal talc or cationic talc as pitch control agent. The preferred alkaline component is calcium oxide (CaO), calcium hydroxide (Ca(OH)2), magnesium oxide (MgO) or magnesium hydroxide (Mg(OH)2). The composition may be in form of an aqueous slurry with a total solids content of 10 75 wt%. The preferred content of alkaline earth metal oxides or alkaline earth metal hydroxides and pitch control additives are 10 90 wt%, respectively. The composition may be used during the bleaching step, during the grinding step or in between bleaching and grinding step. |
