工业级MgO的研磨及在杨木CTMP碱性H2O2漂白中的应用

Pretreatment of Industrial Grade MgO and Its Application in Alkaline Peroxide Bleaching of Poplar CTMP

关键词:  工业级MgO  研磨  杨木CTMP  碱性H₂O₂漂白

Key Words:industrial grade magnesium oxide  grinding  poplar CTMP  alkaline peroxide bleaching

摘要:采用不同的湿法研磨工艺对工业级MgO进行研磨,分析了研磨浓度、研磨转速、研磨时间、研磨介质对MgO粒径及化学反应活性的影响；分别用经不同时间研磨处理的MgO替代25% NaOH(摩尔分数)对杨木CTMP进行碱性H₂O₂漂白,研究了漂后浆料的性能。结果表明,工业级MgO湿法研磨的浓度和转速分别为10%和500 r/min,在以自来水和去离子水为研磨介质时,MgO粒径随着研磨时间的增加逐渐减小,当研磨时间40 min时MgO的化学反应活性达到最大值；而以无水乙醇为研磨介质时,MgO化学反应活性则随研磨时间的延长持续增加；与未研磨MgO相比，在H₂O₂漂白时使用研磨浓度为10%、研磨转速500 r/min、研磨时间40 min条件下获得的MgO，漂后浆张的松厚度、白度和光散射系数均下降,强度有所提高。

Abstract:Different wet grinding processes were applied for the pretreatment of industrial grade magnesium oxide (MgO), and the effects of MgO suspension concentration, grinding speed, grinding time and liquid medium on the particle size and chemical activity of the ground MgO were analyzed. The alkaline peroxide bleaching of poplar chemi-thermomechanical pulp (CTMP) was conducted by using different pretreated MgO which was substituted 25% for sodium hydroxide (NaOH), and the properties of bleached CTMP were investigated. The results showed that the smaller particle size could be achieved by a short grinding time at the consistency and grinding speed of 10% and 500 r/min respectively. The particle size of the resulted MgO decreased with the increase of grinding time, while the chemical reaction activity increased firstly and then started to decrease as the grinding time beyond 40 min by using tap water or deionized water as liquid medium. However, in anhydrous ethanol medium, the chemical reaction activity of MgO increased as the grinding time increased. Additionally, the strength properties of the bleached poplar CTMP various pretreated MgO which were ground for different time kept growing, while the bulk and brightness dropped when prolonging the grinding time.