基于晶体结构与形态特征因素解析的高固相高岭石超高速剪切流变性调控机制研究

The extraordinary poor rheology of kaolinite slurry with high solid content in China impedes its application in paper industry. High grade kaolinite product for paper coating in our country depends on the input of others. It is an emergent project to explore the factors affecting the rheology of kaolinite in China and improve its properties. This project chooses representive kaolinte samples from China, America and Brazil etc. as the objects and make a goal to improve the rheology of kaolinite slurry with high solid content. The methods like FESEM (Field emission scanning electron microscope), Zeta analyzer, capillary rheometer and XRD (X ray diffractometer) with Rietveld software to fit model are used in this research. The differences on the properties, such as structure, shape, particle size distribution and interactions between particles, of representative kaolinte and its samples before and after intercalation are compared to explore the correlativity of several mineralogical factors with surface potential and find the influence of surface potential on the rheology of slurry. Then, a bridge like crystallochemical and mineralogical factors-surface potential-rheology will be builded. Finally, a model will be simulated appling an existing methodology for analyzing central composite design to predict the relationship of rheology with crystallochemical and mineralogical factors. If this project could be carried on, the improvement mechanism on reology of pillar mineral and electric and dynamical theory of two phase flows with high-solid-content should be developed. Afterward, the theoretical guide and improving approach will be put out, which can be applied to resolve the problem on rheology of kaolinite for paper coating in China through controlling mineralogical parameters.

中国高岭石极差的高固相流变性能限制了其在造纸产业中的应用，致使我国优质涂料级高岭石长期依赖进口。因此，探究影响高岭石流变性的因素，进而提高我国高岭石性能成为当前的紧迫课题。本项目以中国、美国和巴西等具有代表性的高岭石样品为研究对象，以调控高固相高岭石的流变性作为研究目标，通过场发射扫描、表面电位仪、毛细管流变仪以及X射线衍射结合Rietveld拟合等手段，比较横向及插层交互前后高岭石的结构、形态、粒级及颗粒间作用力的不同，探索各种矿物学因素与表界面电性能之间的相关关系、表界面电性能与流变性能的影响关系；最终建立高岭石结晶矿物学因素-表界面电性能-流变性能的桥梁关系；利用中心复合设计方法回归拟合结晶矿物学多因素与流变性能的预测模型。通过本项目的实施，将在高固相两相流电动理论、片层矿物流变性改善机制方面取得创新；为中国涂布高岭石流动性能难题的解决，从矿物学参数调控的角度提供理论依据和改善途径。

造纸涂布中，需要高岭石浆料具有高固含量、低粘度的特性。大部分中国高岭石产品的粘浓度仅达到66%，目前中国造纸涂布用高岭石90 %依赖于粘浓度达75 %的进口产品。改变涂布用高岭石资源开发的局面，需要解决其中的科学问题。本项目研究内容：①高岭石表面电荷来源与理论和永久电荷密度（σcc，σp）、可变电荷密度（σv）的相关关系；②高岭石杂质和pH对高岭石分散稳定性的影响；③插层技术工业化生成纳米复合物，应用于轻量涂布；④ 表面改性对高岭石表面界面性能影响； ⑤世界典型涂布级高岭石结构缺陷解析及对生产加工高岭石的启示；⑥大尺寸离子液体插层高岭石及其纳米插层复合物的性能研究。研究成果：（1）σp与内部元素替代有关，通过理论计算和实验得到的样品电荷密度其趋势是一致。考虑理论或实际比表面积时，同一样品计算 得σcc 和 σp大小关系得到相反的结果。σv依赖于高岭石边缘断裂程度，与等电点pHIEP有直接关系。但内部结构的变形则与表面电荷没有直接关联。（2）高岭石浆料的稳定性在酸性和碱性区内与表面电位Zeta呈线性关系。离子种类、浓度、pH影响高岭石的电位，进而影响颗粒的面面、边面聚集状态。（3）插层技术成功应用于工业生产线，高岭石粘浓度高达74.23%，轻量纸涂敷性能优异。（4）表面改性对高岭石界面分散有影响，其应用于膜中结合界面、晶型、水处理性能得到提高。 (5)利用Rietveld解析涂布用高岭石结构，计算平均键长，四面体旋转角(α)和压平角(τ)，八面体压平角(ψ)，层厚(T)等。发现其共同特点：杂质少，结构有序，各同类键长相近，变形和扭曲较少，层较薄。（6）利用熔融插层方法，大尺寸咪唑离子液体插入高岭石层间，其工艺简单，插层率高。在理论上建立起了结晶学、矿物学因素——表界面电性能——高固相流流变性能的桥梁关系，在实践基础上为工业生产提供一种新的降粘机制，生产产品替代进口同类产品，为中国涂布用高岭石的生产提供理论和实践依据。