【作者】 李宗全；

【导师】 詹怀宇；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2005， 博士

【摘要】 近年来,废纸的回用受到越来越多的重视。其中大量的脱墨浆在许多新闻纸厂得到广泛的应用。在废纸回用过程中,来自纸张生产、加工和使用过程中引入的各种涂布粘合剂、胶粘剂和油墨粘结料等杂质以及木材中的天然树脂等都在制浆和漂白过程中释放到浆水体系中。这些物质在生产中会形成胶粘物沉积到成形网、压榨部、烘缸表面以及纸张表面上,影响生产效率和产品质量。随着废纸回用量的日益增加,胶粘物问题日益严重。 本文通过对造纸厂胶粘物的分析,确定了胶粘物的根本来源,分别选取了合适的模型物研究胶粘物沉积的各种因素以及胶粘物各组分之间的相互作用,根据所研究的胶粘物的沉积机理,提出胶粘物控制的方法。 对福建南平纸厂网前压力筛处的胶粘物进行分离和分析发现,以聚醋酸乙烯酯和聚丙烯酸酯为代表的人工合成聚合物以及机械浆中的木材树脂是产生胶粘物的根本来源,但它们在胶粘物沉积中的含量只有5%左右。胶粘物沉积中大部是无粘性的碳酸钙和细小纤维,说明碳酸钙等物质会与具有粘性的树脂类物质粘附在一起造成大量沉积物的出现。 以马尾松硫酸盐法制浆的副产物—塔罗油和水分散型聚丙烯酸树脂压敏胶作为胶粘物中的天然树脂组分和人工合成胶粘剂的模型物,研究了影响树脂沉积和胶粘物沉积的各种因素。研究表明,钙离子对树脂沉积有重要影响,钙皂的沉积量不但与生成钙皂的多少有关,还与钙皂在体系中的分散程度有关。纸浆中细小组分对树脂沉积有重要影响。纤维中的细小组分能够吸附更多的树脂/钙皂粒子,阻止了树脂/钙皂粒子之间进一步相互絮聚,降低了它们的粘性。 阳离子聚合物的加入是导致二次胶粘物失稳和沉积的重要原因。阳离子聚丙烯酰胺(CPAM)、阳离子淀粉加入后使二次胶粘物部分失稳时导致较多的沉积,而聚乙烯亚胺(PEI)加入后使二次胶粘物接近完全失稳时沉积最多。过量阳离子聚合物的加入使沉积减少,其原因并非是二次胶粘物重新稳定的结果,而是由于失稳且阳离子化的胶粘物吸附到纤维上的结果。高浓度的钙离子的存在会导致更多的胶粘物沉积。 造纸过程常用的填料重质碳酸钙(重钙)、轻质碳酸钙(轻钙)和滑石粉都会与粘性大的胶粘物一起沉积而导致胶粘物沉积量的增加,特别是在较低的阳离子聚合物加入量下,由于填料和失稳的胶粘物在纤维上的吸附较少而导致胶粘物沉积更加严重。加入填料后,沉积物增加量远远大于沉积物中所含的填料的量。不同的填料对胶粘物沉积的影响不同。在较大的阳离子聚合物加入量下,与滑石粉相比,轻钙加入后产生的胶粘物沉积较少。 通过溶胶物质DCS及溶解物质DS的加入对二次胶粘物模型物的稳定性及沉积性能更多还原

【Abstract】 The recycled fibers have become an important raw material for papermaking, and more and more deinked pulps were used in many newsprint mills in recent years. A lot of contaminants such as pressure-sensitive adhesive, hot melt adhesive, coating adhesive, ink binding adhesive from waste paper as well as the lipophilic wood resins are released and dispersed in the pulp suspension during waste paper recycling. The contaminants could form the deposit on the forming wire, press section and dryers or the surface of paper sheets, which was harmful to the production efficiency and the product quality. The deleterious stickies problem became more and more serious due to more and more secondary fibers recycling in paper mills.The deposit obtained from a paper mill was analyzed and the origin of the deposit was determined. Some substances were chosen as the model substance to study the factors that influence the stickies deposit and the interactions of the components in the deposit. Basing on the understanding of the mechanism of stickies deposition, some novel methods for the control of stickies deposit were put forward.According to the analysis of the deposit from the pressurized screen before the wire section in Nanping Paper Mill, polyvinyl acetate (PVAc), polyacrylate (PA) and the wood lipophilic extractives were taken as the representatives of the deposit, but their content in the deposit was only about 5%. Most of the substances in the deposit were the nonsticky calcium carbonate and fines that could adhere to the sticky contaminants and deposit together, resulting in a great deal of the deposit.Tall oil and a pressure-sensitive adhesive whose component was polymethacrylate wererespectively chosen as the model substances of the wood resin and the synthetic adhesives to study the factors influencing the pitch deposit and stickies deposit. The results showed that calcium ions concentration had a significant effect on the pitch deposit. The pitch deposit was correlative with both the amount of the calcium soaps and the degree of dispersion of the calcium soaps. The fines adsorbed more pitch/calcium soaps particles compared with the fibers, and the adsorption of pitch/calcium soaps particles on the fines and fibers prevented them from further aggregation and deposition.Cationic polymers addition was one of the significant causes that led to destabilization of secondary stickies and the stickies deposit. Cationic polyacrylamide(CPAM) and cationic starch led to the destabilization of secondary stickies by interparticle bridging mechanism and polyethylene imine (PEI) led to the destabilization of secondary stickies by charge patch mechanism. Both CPAM and cationic starch resulted in more stickies deposit as the secondarystickies was partly destabilized at low level addition, but PEI resulted in more deposit as the secondary stickies was nearly completely destabilized. The stickies deposit decreased with excessive cationic polymer addition because of the adhesion of the destabilized stickies to the fibers of but not the restabilization of the secondary stickies. In addition, high concentration of calcium ions exacerbated the stickies deposit.The fillers such as heavy calcium carbonate, precipitated calcium carbonate and talc could led to the increase of the deposit because they could adhere to the sticky stickies and deposit together with them, especially as the fillers and the destabilized secondary stickies were not well adsorbed to the fibers at low cationic polymers addition. The increased amount of stickies deposit was much more than that of fillers in the deposit after fillers addition. The effect of different fillers on the stickies deposit was different. Comparing with talc, precipitated calcium carbonate addition resulted in less deposit at high dosage of cationic polymers.The effect of DCS and DS in the mechanical pulp on the stabilization and the stickies deposit was studied. The results showed that the synergism of anionic trash from mechanical pulp and the stickies with high stickiness and high concentration calcium ions from the deinked pulp was the cause that led to the more deposit as the furnish of mixed DIP and mechanical pulp was used instead of only DIP or mechanical pulp. More anionic trash led to the lower efficiency of cationic polymers and high stickiness contaminants from waste paper tended to aggregate with other contaminants to deposit. In addition, high concentration of calcium ions could exacerbate the stickies deposit because they could lead to the destabilization of stickies and decreased the efficiency of the cationic polymers simultaneously.DCS especially DS from the mechanical pulp decreased the retention efficiency of CPAM, and the higher fines retention was found after the enzymatic degradation of pectic acid that was the main substance causing anionic trash. The increase of cationic polymers efficiency could reduce the stickies deposit and the treatment of DCS or the pulp (mechanical pulp or DIP) with pectinase was an effective method for the stickies control.According to the influencing factors and the mechanism of the stickies deposit, some methods for control of stickies deposit were put forward.(1) The concentration of calcium ions in pulp suspension should be controlled. The pulp should be properly refined to a higher beating degree and higher content of fines, and the retention of fines and fillers should be increased.(2) The addition of ultrafine talc in the pulp suspension would reduce the stickiness of pitch so as to achieve the control of pitch deposit(3) The cationic polymers with high charge density and low molecular weight addition could neutralize the anionic trash in the pulp suspension and enhance the efficiency of retention aids to reduce the stickies deposit.更多还原