| 摘要 |
<p>The invention relates to a process for producing bleached mechanical pulp having improved strength and brightness by mechanical decomposition of material softened by thermal and/or chemical processing and bleaching with a small amount of peroxide containing bleaching agent with the formation of small amounts of oxygen consuming substances in the waste liquors. According to the invention the wood is softened in a first step at high pH with introduction of 10 - 30% of the peroxide required for the bleaching, i.e. only sufficient peroxide to prevent the pulp from darkening during the softening step. The subsequent bleaching takes place at low pH with the addition of the remainder of the peroxide, optionally with the introduction of agents which amplify the action of the peroxide on the wood, such as complexing or chelating agents and/or surfactants.</p> |
