硅酸钠基改性体系对PCC的溶解抑制作用

Dissolution-inhibiting Effect of Silicate-based Inhibitors on Precipitated Calcium Carbonate Filler

将硅酸钠基改性体系引入至PCC填料悬浮液中,制得改性填料悬浮液,对各种改性体系的溶解抑制作用进行了比较与分析。实验结果表明,硅酸钠/硫酸铝、硅酸钠/氯化铝、硅酸钠/磷酸、硅酸钠/磷酸/六偏磷酸钠及硅酸钠/磷酸/聚丙烯酸钠均具有一定的溶解抑制作用,改性后的填料悬浮液的pH值均有所下降;对改性填料悬浮液进行稀释,悬浮液pH值随稀释倍数的增加而上升;改性后的填料在pH值为4.50和5.00的稀盐酸溶液、pH值为4.50和5.00的硫酸铝溶液、pH值为5.85的蒸馏水及pH值为7.26的自来水中的溶解性均有所降低,其中硅酸钠/硫酸铝及硅酸钠/氯化铝的溶解抑制作用较弱,硅酸钠/磷酸、硅酸钠/磷酸/六偏磷酸钠及硅酸钠/磷酸/聚丙烯酸钠的溶解抑制作用较强;对于各种溶液体系而言,硅酸钠/磷酸/六偏磷酸钠均具有较为有效的溶解抑制作用。

Calcium carbonate filler is widely used in alkaline papermaking to lower the manufacturing cost, and to improve the properties of the papers, however, the use of calcium carbonate in wood-containing or rosin-sized papers is usually not industrially feasible because of pulp darkening at alkaline pH or dissolution of calcium carbonate below pH 7. For the more cost-effective use of calcium carbonate filler in papermaking, its dissolution-inhibiting is of great significance. In order to inhibit the dissolution of papermaking grade precipitated calcium carbonate （PCC） filler, silicate-based inhibitors were used in the preparations of modified filler suspensions, and the dissolution-inhibiting effects of the relevant inhibitors were compared and analyzed. Under the controlled experimental conditions, sodium silicate/aluminum sulfate, sodium silicate/aluminum chloride, sodium silicate/phosphoric acid, sodium silicate/phosphoric acid/sodium hexametaphosphate and sodium silicate/ phosphoric acid/sodium polyacrylate were all proved to be effective in dissolution-inhibiting of PCC, and the pH values of filler suspensions consistently decreased to a certain degree after the filler modifications. When diluted, the pH of modified PCC suspensions increased with the decreasing filler concentration. After modification, the filler dissolution in distilled water with pH 5.85, diluted hydrochloric chloride solutions with pH 4.50 and pH 5.00, diluted alum solutions with pH 4.50 and pH 5.00, and tap water with pH 7.26, all decreased to a certain degree. Also, sodium silicate/aluminum sulfate and sodium silicate/aluminum chloride were proved to be less effective as compared with other inhibitors, and sodium sitjcabephosphoric acid/sodium hexametaphosphate was highly effective in inhibiting PCC dissolution in different solutions used in this work.