【作者】 宋顺喜；

【导师】 张美云； 倪永浩；

【作者基本信息】 陕西科技大学 ， 制浆造纸工程， 2014， 博士

【摘要】 矿物填料在改善成纸性能、降低生产成本与能耗方面的优势使其广泛应用于造纸工业中。近年来，以固体废弃物为主要原料制备环境友好型低成本造纸填料已经成为了制浆造纸领域的研究热点之一。粉煤灰作为火力发电厂的固体废弃物，在我国排放量大，综合利用率低，对环境与人类健康造成了严重危害。因此，提高粉煤灰资源化利用率，对我国乃至世界而言仍是一项重要的任务。在造纸工业中，粉煤灰可以作为一种潜在的造纸填料，但其白度低，粒径大的特点使其应用受到限制。论文以我国高铝粉煤灰提取氧化铝过程中产生的非晶态氧化硅所制备的新型硅酸钙作为造纸填料，与传统造纸填料沉淀碳酸钙（Precipitated Calcium Carbonate, PCC）和研磨碳酸钙（Ground Calcium Carbonate, GCC）对比，对新型多孔硅酸钙（FlyAsh basedCalcium Silicate，FACS）填料物化特性、化学组成、表面形貌、湿部性能、成纸性能和印刷适性等方面进行了研究，分析了FACS作为造纸填料的优势与不足。在此基础上，从填料特性出发，研究了加填纸结构与性能的关系，并通过填料热改性、填料与纤维共同磨浆以及填料复配等方式来改善加填纸的成纸性能，以期为优化填料的生产工艺、发挥填料应用优势以及开发高填料纸方面提供参考和借鉴。（1）FACS填料的表征与造纸性能对FACS填料特性进行了表征。FACS填料平均粒径为21.6μm，比表面积为121m2/g，堆积密度为0.31g/cm3，白度为91.5%ISO，与普通填料GCC和PCC相比，具有粒径大、比表面积高、堆积密度低，白度高的特点，该特点有利于改善成纸松厚度与光学性能，但会导致成纸的施胶性能较差。另外，该填料游离水和结合水含量较高，是造成灼烧损失较高的原因。XRD结果表明，该填料的主要成分为水化硅酸钙（C-S-H），除此之外，还有含水硫酸钙（CaSO42H2O和CaSO40.5H2O），这主要是由于在填料制备后期添加硫酸降低填料pH所致。SEM、TEM与EDAX结果显示，FACS填料包含表面多孔球状聚集体的水化硅酸钙粒子和针状的硫酸钙粒子，其中水化硅酸钙结晶程度较低，粒子由褶皱片状组成，而硫酸钙具有良好的单斜晶体结构。采用物理研磨方法制备3种不同粒径的FACS填料，并对FACS填料的造纸性能进行分析比较。结果发现，随着研磨强度的增加，水化硅酸钙的多孔结构逐渐被破坏，填料的粒径分布变宽，白度从91.5%ISO上升至93.1%ISO。在湿部特性方面，当添加助留剂CPAM时，填料的动态留着率随着粒径的增加而增大，原始FACS填料的留着率远高于GCC和PCC填料；添加CPAM后，较小粒径的FACS填料留着率较高。CPAM可明显提高FACS加填浆料的滤水速度，FACS与PCC填料加填浆料的滤水性能相近，但略低于GCC填料；粒径较低的FACS填料其滤水性能相对较差。对成纸物理性能测试结果表明，FACS填料在改善成纸松厚度方面优势明显，当FACS0填料含量为15%时，与未加填纸张相比，松厚度可提高约40%，在轻型纸领域具有较大优势。对于研磨FACS填料，成纸松厚度随填料粒径的降低而下降，但相应的抗张强度有所提高；粒径较大的FACS填料，其成纸撕裂强度也较高。FACS0加填纸的光散射系数高于GCC加填纸，这主要归因于FACS0表面多孔形貌和聚集体结构。另外，FACS加填纸的光散射系数随着填料粒径的降低而升高。FACS填料较高的比表面积以及加填纸较高的透气度导致成纸油墨需求量较高，但FACS的较好的油墨吸收性以及加填纸较高的松厚度是造成其透印值优于GCC加填纸的主要原因。粒径较小的FACS2填料（8.4μm）可在达到相同的印刷密度时降低油墨需求量与透印值。另外，FACS加填纸表面强度与GCC加填纸相近，均高于PCC和FACS2加填纸，填料在纸张的表面分布情况可能是导致表面强度不同的原因之一。（2）加填纸结构与性能的相关性研究当纤维定量固定时，增加PCC和GCC填料定量最终会提高成纸表观密度，而增加FACS定量却可显著降低成纸表观密度。表观密度的变化引起了纸张结构与性能的变化。另外发现，填料定量的提高会造成填料堆积指数（Packing index）的降低，从而影响成纸强度性能与光学性能的变化。当固定纤维定量而增加填料定量时，成纸有效抗张指数随着填料定量的增加而降低说明填料粒子通过位阻效应降低了纤维结合；然而FACS加填纸有效抗张指数损失在FACS定量超过7g/m2时逐渐降低，说明填料粒子之间的包裹能力的增加有利于降低填料对纤维结合能力的破坏作用。另外，填料堆积指数与成纸光散射系数的线性负相关关系解释了在高填料定量下，加填纸的光散射系数增加较慢的原因。对加填纸成形性能（匀度）与成纸性能相关性分析表明，加填有利于改善纸张匀度。加填纸成纸性能与不同匀度分量的相关性随着填料种类、物理性质的不同有一定差异。FACS加填纸的抗张指数和撕裂指数与匀度分量为0.6mm、0.8mm和1.3mm的PPF（Paper Perfect Formation）值（匀度）呈线性正相关，在匀度分量为0.6~0.8mm之间，其判定系数可达0.95以上。FACS加填纸白度和不透明度与匀度分量为0.6~1.3mm处PPF值相关性较高，呈负相关，该结果有利于纸厂在线快速检测产品性能变化，及时调整工艺参数以满足产品性能要求。为研究填料Z向分布对成纸结构与性能的影响，采用分层抄造的方法制备出具有不同填料Z向分布特征因子的加填纸张，通过图像分析方法对填料在纸张Z向分布进行了表征与验证，并研究了填料分布特征因子，即对称因子、形状因子和集中因子与成纸性能的关系。论文提出了与结构性能和强度性能关系密切的填料Z向分布的特征因子，集中因子（ConcentrationFactor, Fc）。结果表明，纸张的松厚度和透气度与填料分布集中因子成正相关，即集中因子越大，纸张的松厚度越高，透气度越大；纸张的抗张强度与填料分布的集中因子成负相关，即集中因子越小，抗张强度越大，当集中因子Fc=0时，与Fc>0的纸样相比，成纸抗张指数可提高70%以上，但却显著降低成纸内结合强度。在成纸光学性能方面，纸张填料含量越高，其表面填料含量也会提高，因而成纸白度也相对较高。对称因子与成纸白度的两面差呈线性正相关，其相关系数R2可达0.9802。当填料分布对称因子越小，成纸两面的白度差也越小。填料Z向分布的集中因子与层合纸页的不透明度呈正相关。当层合纸页集中因子相同时，增加上层纸页填料含量有利于提高成纸不透明度。（3）FACS加填纸性能的改善为了研究填料晶体结构对成纸性能的影响，对填料进行了热改性处理。结果发现，当温度超过840℃时，填料物理性质发生较大变化，FACS平均粒径由未改性的21.62μm减小至17.06μm；另外，由于其表面褶皱多孔形貌的消失，在900℃改性后填料热稳定性好，比表面积由原始填料121.0m2/g下降至4.0m2/g，有利于改善成纸施胶性能；化学成分也由当初的C-S-H和含水硫酸钙转变为硅灰石和无水硫酸钙。900℃改性后的FACS填料加填纸的松厚度与未改性FACS加填纸相比，在填料含量为17.5%和33.5%时分别降低了约27.2%和33.8%，而相应的透气度分别降低了约129%和79%。然而，使用900℃下热改性的填料可有效改善加填纸的抗张强度，但却降低了成纸白度与不透明度。研究采用纤维和填料共同磨浆的新方法可改善FACS加填纸的物理强度与光学性能。与常规浆内加填方式相比，采用纤维和填料共同磨浆方式可有效改善加填纸的光学性能，但却会降低成纸的松厚度。在磨浆转数为3500r时，该方法制备的手抄片的强度性能与常规加填方式相当，但却可显著改善加填纸的光散射系数和成纸白度。采用共同磨浆方式对填料粒径的降低作用是降低成纸松厚度，改善成纸光学性能的主要原因。此外，通过对填料进行复配使用有利于发挥填料各自优势，弥补自身不足。若以成纸强度与光学性能为目标时，可使用少量PCC填料与热改性FACS填料（IFACS）进行复配使用；而以成纸强度与松厚度为主要目标时，将FACS与IFACS填料复配可较好的平衡加填纸的松厚度与强度性能。更多还原

【Abstract】 Mineral filler has been widely used in paper industry because of theadvantages in improvement of paper properties, cost reduction and energy saving.In recent years, the development of filler engineering becomes an urgent need forthe papermaking industry, especially for the new filler with low cost andenvironmental-friendliness. China produces a large amount of fly ash but the rateof utilization is relatively low, which result in undesired environmentalconsequences and health concern. Therefore, how to increase the utilization offly ash with added value has become a key focus for China, even for the world.As a solid waste in power plant, fly ash can be used as paper filler. However, itslow brightness and large particle size limit its potential applications in paperindustry. In this work, a novel fly ash based calcium silicate (FACS), which is abyproduct of aluminum extraction from fly ash, is employed as a potential paperfiller. The filler characteristics, chemical composition, morphology, wet endperformance, paper properties and printability were investigated. The resultswere compared with those of using ground calcium carbonate (GCC) andprecipitated calcium carbonate (PCC) filler, which are commonly used in paperindustry. Based the characteristics of FACS, the relationship between thestructure of FACS filled paper and properties was also discussed. Besides,calcination treatment, filler-fiber co-refining and filler blending methods werealso adopted in order to improve the properties of FACS filled paper. This papermainly consists of three parts:1. Fly ash based calcium silicate paper filler: characterization and itsapplicationIn comparison with GCC and PCC commonly used as paper fillers, the original fly ash based calcium silicate filler (FACS) has a larger particle size(21.6μm)，a higher specific surface area (121m2/g), a much lower packingdensity (0.31g/cm3) and a similar brightness (91.5%ISO)，which provide benefitsfor paper bulk and optical properties but compromise the paper internal sizing. Inaddition, higher free water and bonding water content of FACS result in moreignition loss at525℃. XRD results showed that the chemical composition ofFACS were calcium silicate hydrate (C-S-H), calcium sulfate hemihydrate(CaSO40.5H2O) and gypsum (CaSO42H2O). The use of sulphuric acid in theprocess of lowering the pH of FACS slurry is the main reason of containingcalcium sulfate hemihydrate and gypsum in FACS filler. Based on the results ofSEM, TEM and EDAX, it was found that there were two types of particles inFACS filler: calcium sulfate with needle-like particles and monoclinic structurewhile C-S-H exhibited low degree of crystallinity of aggregated particles withwrinkly porous surface.Three grades of FACS fillers with different particle size were prepared byball milling; their characteristics as paper fillers and the effects on the wet-endperformance and resulting paper properties were determined. Ball millingchanged the morphology and particle size distribution while decreasing theparticle size. Regarding to filler wet-end performance, the dynamic retention rateof FACS was increased with increasing particle size and the dynamic retentionrate of original FACS was superior to GCC and PCC filler when retention aidswas not used; while filler with small particle size exhibited higher filler retentionwhen CPAM was applied. In addition, CPAM can promote the drainage ability offilled furnish. FACS and PCC showed similar drainage ability but lower thanGCC filler in this study. Besides, it was found that FACS with small particle sizehad a detrimental effect on drainage ability.Physical test showed that FACS filler had an advantage of improving paperbulk. At a15%original FACS, the paper bulk was about40%higher than that ofthe control (no filler addition). For ball milled FACS, the paper bulk of FACSfilled paper decreased because the particle size of FACS filler decreased, whilethe paper tensile strength increased. A larger FACS particle size led to higher tearstrength. Although original FACS had a large particle size, the light scatteringcoefficient was higher than that of GCC-filled paper. This can be attributed to FACS’s porous surface and morphology. The light scattering coefficient for ballmilled samples increased as the particle size decreased. Printing quality testsindicated that FACS filled paper demanded more ink than GCC and PCC filledsheets due to its porous structure and low air resistance. Thanks to its high bulk,the FACS0filled paper had a lower print through than the GCC filled paper.FACS2, which was smaller in size than FACS0, can decrease the ink demand andimprove print through. In addition, the surface strength of FACS0filled sheetswas similar to GCC filled sheets, both of which were higher than PCC andFACS2filled sheets, which can be partly explained by filler distribution.2. How filler influences paper properties: fiber bonding ability and fillerZ-distributionWhen fiber mass was fixed, the use of PCC and GCC filler can increasepaper apparent density as filler mass increased while FACS addition reducedapparent density. The change in paper apparent density caused the differences instructure and properties among filled paper samples. Besides, it was found thatfiller packing index was decreased with increasing filler grammage, whichresulted in the changes in effective tensile index of filled paper and lightscattering ability of filler. The effective tensile index decreased with increasingfiller grammage, which verified filler particles prevented fiber bonding by stericeffect. In addition, the loss of effective tensile index of FACS filled paper wasfound to be maximized at7g/m2filler and decreased with filler grammage. Thisfact illustrated that the increase of packing ability of filler particles help toalleviate the negative effect on paper strength caused by filler. The linearrelationship between filler packing index and light scattering coefficient of fillerpaper explained the nonlinearly increase of light scattering coefficient as fillergrammage increased.The correlation between formation components and paper properties wasalso analyzed. It was proved that the use of filler can improve paper formation.The differences in correlation between formation components and filled paperproperties can be varied with filler type and properties. A high positive linearcorrelation can be found between tensile and tear index of FACS filled paper andformation component at0.6mm,0.8mm and1.3mm, especially at0.6mm and0.8mm with R2>0.95. Additionally, a high negative linear correlation can be found between the brightness and opacity of FACS filled paper and formationcomponent of0.6~1.3mm. The results can help paper mill control paper qualityby rapid test formation of filled paper.In order to investigate the effect of filler distribution in Z-direction on paperproperties, the layered handsheets with various distribution factors were prepared.Filler distribution in Z-direction of FACS filled layered handsheets wascharacterized and verified by image analysis. A new factor of filler distribution inZ direction, i.e. concentration factor, was proposed, which was related to paperstructure and strength properties. The results showed that the bulk and porosityof FACS filled paper had a positive correlation with Fcwhile a negativecorrelation could be found between tensile index and Fc. An increase around70%in the tensile index of FACS filled paper with Fc=0could be observed comparedto paper sample with Fc≠0. However, the interbonding index of FACS filledpaper with Fc=0could be dramatically reduced. Regarding to optical properties,it was found that the surface filler content increased with increasing the averagefiller content of paper，resulting in the improvement in paper brightness. Apositive linear correlation between symmetrical factor (Fs) and the differences inbrightness of both sides of layered paper can be found, which the coefficient ofdetermination R2can be up to0.9802. In addition, the opacity of FACS filledpaper had a positive correlation with concentration factor, i.e. increasing fillercontent in top layer helps to improve opacity of layered paper.3. Improvement of the properties of FACS filled paperCalcination modification was applied to FACS filler based on thethermostability of FACS. The results showed that the characteristics of FACSwas changed significantly when temperature was over850℃. FACS exhibitedgood stability when filler was modified at900℃(i.e. IFACS) while the poroussurface of FACS was disappeared, the average particle size was reduced from21.6μm to17.1μm and the specific surface area decreased to4.0m2/g, which isbeneficial to internal sizing. In addition, the chemical composition was changedto wollatonite (CaSiO3) and calcium sulfate (CaSO4). In comparison withoriginal FACS filled paper, the bulk of paper filled with IFACS was decreased27.2%and33.8%at filler content of17.5%and33.5%, respectively. Meanwhile,the corresponding porosity was reduced129%and79%, respectively. Importantly, IFACS can improve paper tensile index significantly but had anegative effect on paper brightness and opacity.Fiber-filler co-refining was employed to improve the strength and opticalproperties of FACS filled paper. In comparison with regular filling method, thenew method can improve optical properties effectively but reduce paper bulk.When refining revolutions was fixed around3500r, the brightness and lightscattering coefficient of FACS filled paper were improved significantly while thetensile index was maintained well. The changes in bulk and optical propertiescan be explained by the decrease in average particle size in process ofco-refining.Besides, the concept of filler blending can be used to take full advantage offiller properties and balance the filled paper properties. Blending of PCC andIFACS can be used to balance paper optical properties and strength propertieswhile FACS and IFACS can also be blended if a good balance between paperbulk and strength become a concern factor.更多还原