【作者】 董元锋；

【导师】 刘温霞；

【作者基本信息】 山东轻工业学院 ， 制浆造纸工程， 2007， 硕士

【摘要】 膨润土是当今应用范围较广和经济价值较高的粘土矿物之一,被称为“千种用途土”,广泛应用于冶金、化工、农业、建筑、造纸、环保等多种领域。我国膨润土资源非常丰富,矿产几乎遍布全国,其储量居世界第一位,但我国90%以上为钙基膨润土,不适合在造纸中作为微粒助留成分使用。碳酸钠是传统的改性剂,成本低廉,但碳酸钠改性膨润土质量不佳;柠檬酸钠改性膨润土非常适于作造纸微粒助留剂,但其成本较高;实验中以中性试剂氟化钠代替传统的碳酸钠做改性剂制备钠基膨润土悬浮液,并与CPAM(阳离子聚丙烯酰胺)组成微粒助留体系,研究改性机理与方法(固体加热改性、常温液体改性),考察钠化剂种类、改性时间、钠化剂用量、干燥条件、剪切分散方法、剪切时间及放置时间对膨润土性能及微粒助留助滤效果的影响,通过X射线衍射分析、透射电镜观察及膨胀倍、胶质价、粒度、粘度、阳离子交换量、Zeta电位测定等手段研究膨润土的性能变化,同时利用动态滤水仪研究CPAM与膨润土组成的微粒助留体系对二次纤维的助留助滤效果,并与国内外不同化学品公司提供的膨润土微粒助留剂的性能及对麦草桨、针叶木桨、二次纤维和LWC纸浆的助留助滤效果进行了比较。结果表明,中性改性剂氟化钠在用量4%时可以将钙基膨润土中的Ca2+交换完全。与常规碳酸钠改性膨润土相比,氟化钠改性膨润土呈完全剥离的片状结构,具有更好的胶体与分散性能,粒度小、悬浮液流动性好且对二次纤维具有更好的助留助滤效果,尤其是放置四周后仍能保持其良好的助留助滤效果。各种改性膨润土的物化性能与助留助滤效果均与钠化剂的用量有关,且在膨润土刚好完全钠化时其粒度最小、膨胀倍和胶质价最高,助留助滤效果最好。利用氟化钠对钙基膨润土进行钠化处理可制备高浓膨润土悬浮液,该悬浮液分散性好、粘度低、贮存稳定性好,有利于产品的商业化。与固体加热氟化钠改性膨润土和碳酸钠改性膨润土悬浮液相比,具有更好的物化性能及分散性、流动性,助留助滤效果也更好,且悬浮液放置四周后助留助滤效果保持不变。与国内外化学品公司的改性膨润土微粒助留剂相比,自制氟化钠膨润土的pH值呈中性,对浆种和抄纸pH值的适应性强,对二次纤维、麦草浆、木浆及LWC浆料都具有相当好的助留助滤效果,且远好于国内化学品公司的产品,与国外化学品公司的产品对其优势浆种的助留助滤效果相当甚至或更好。在pH值3.5-8.0之间,对纸料的助留助滤效果变化不大。更多还原

【Abstract】 Bentonite, which is called“clay with thousand kinds of usages”, is an important mineral raw material used in many fields including metallurgy, chemical industry, agriculture, construction, pulp and papermaking, environment protection et al. There are many bentonite ores which distribute almost everywhere in China. However, more than 90 percent of them are Ca-bentonite, which can not be directly used as a microparticulate retention aid in paper industry.Sodium carbonate is often used as an ion-exchanger to prepare Na-bentonite. It is quiate cheap as conventional modification agent, but the resulted modified bentonite may detoriate the wet end envioronment since its alkaline pH value. Sodium citrate is an excellent ion-exchanger for preparing neutral Na-bentonite, yet it is not cost-effective for a bentonite based microparticle retention aid. In this study, sodium fluoride was selected as a neutral ion-exchanger for preparing Na-bentonite suspension. The resulted modified bentonite was used as a microparticulate retention aid together with cationic polyacryamide. The effects of modification agents, methods, time, dosage of modification agents, dry condition, shearing methds and time on properties and performances of bentonite as a microparticulate retention aid were inveistigated. The properties of bentonite are characterized by the X-ray diffraction, TEM observation, swelling capacity (SC), colloidal capacity (CC), particle size, viscidity, caion-exchange capacity and zeta potential. The synergistic retention and drainage effects of the modified bentionite with cationic polyacryamide were studied by the means of dynamic drainage jar. The differences between the fluoride modified bentionite and the commcial bentonite based microparticle retention aids were also analyzed according to their properties and synergistic retention and drainage effect with CPAM on wheat pulp, softwood pulp, secondary fiber and LWC pulp.The results show that calcium ions among the layers of bentonite are replaced completely by sodium ions when 4% of sodium fluoride (based on the weight of bentonite) is used as ion-exchanger. The sodium fluoride-modified bentonite is dispersed into single layered structures and exhibits better suspensibility and dispensability, smaller particle size as well as lower sludge viscosity than sodium carbonate-modified bentonite. Naturally, the bentonite modified by sodium fluoride behaves better on improving the retention and drainage of the secondary fibers than the bentonite modified by sodium carbonate; especially it can sustain its good performance even after four weeks as a suspension. The suspending and dispersing properties as well as retention and drainage effects of the modified bentonite on the secondary fibers are related to the dosage of the ion-exchangers. The greater improvement on the retention and drainage of the secondary fibers occurred when the calcium ions among the layers of bentonite are just completely exchanged by the sodium ions of the ion-exchangers.The properties of high solid bentonite suspension modified at ambient temperature show smaller particle size, lower viscosity as well as higher swelling and colloidal capacity than that of bentionite powders heated during drying. Consequently, it shows higher synergistic retention and drainage effects with cationic polyarcyamide on secondary fibers. It also shows better synergistic retention and drainage effects with cationic polyarcyamide than bentonite suspension modified by sodium carbonate since its higher dispersibility. Futhermore, the propertices and synergiec retention and drainage effects of fluoride modified bentionite suspenstion do not change significantly during the 4 weeks of standing time.Compared to the commcial bentonite based microparticle retention aid, the pH value of the fluoride modified bentonite suspension is neutral. It can be used to different paper stocks at different papermaking pH, showing far better synergistic retention effect with CPAM on wheat pulp, softwood pulp, secondary fiber and LWC pulp than that of both home-made and aboard-made commcial bentonite microparticle retention aid.更多还原