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用碳酸钙和硫酸钙作填料或涂布颜料时,纸机白水中会含有大量的钙离子。钙离子与果胶酸(特别是高电荷的果胶酸)之间的相互作用会产生有害影响。主要研究了钙离子对浆料中果胶酸的留着、浆料滤水性能及成纸白度的影响。钙离子的存在导致果胶酸和树脂在浆料中的留着量大大增加,同时,热磨机械浆(TMP)滤液的阳离子需求量较低。酸化前在pH值为8.0的条件下洗涤浆料,能有效去除溶解与胶体物质,这种去除效果在钙离子含量较低时尤为明显。pH值为5.5时洗出的钙离子比pH值为8.0时的多。少量的钙离子能使过氧化氢漂白的TMP白度略有提高,但增加钙离子含量不会增加这种效果。钙离子对浆料滤水性能的影响较小。
When using calcium carbonate and calcium sulfate as fillers or pigments, paper machine white water contains large amounts of calcium ions. The interaction between calcium ions and pectic acids, especially highly charged pectic acids, can have detrimental effects. The effects of calcium ion on the retention of pectic acid in the slurry, the filtration performance of the slurry and the whiteness of the paper were studied. The presence of calcium ions leads to a significant increase in the retention of pectic acid and resin in the slurry while the cation demand of the hot mill mechanical pulp (TMP) filtrate is low. Washing the slurry at pH 8.0 prior to acidification effectively removes dissolved and colloidal material, especially when the calcium ion content is low. The calcium ion eluted at pH 5.5 was more than the pH at pH 8.0. A small amount of calcium ion can slightly increase the TMP whiteness of hydrogen peroxide bleaching, but increasing the calcium ion content does not increase this effect. Calcium ions have little effect on slurry drainage performance.