TiO_(2)的表面改性及其粉体流动性能评价方法的建立

Surface Modification and Establishment of Powder Flowability Evaluation Method of TiO_(2)

目的建立基于粉体流动性能和颜料性能的TiO_(2)综合性能评判方法,指导表面改性工艺的优化,获得兼具优异的流动性能与颜料性能的钛白粉产品。方法以氯化法金红石型TiO_(2)为基料,依次进行Zr/Al无机包覆和有机包覆,研究包覆关键参数对TiO_(2)产品的流动性与颜料性能的影响。采用粉体流变仪进行TiO_(2)粉体的压缩性、壁摩擦、剪切作用测试,得到Hausner比、壁摩擦角、内摩擦角等表征流动性的特征指标参数;采用X射线荧光衍射仪测定钛白粉的无机元素含量;利用X射线衍射分析仪测定钛白粉基料的晶型;采用激光粒度仪测定粉体的粒度及粒度分布;通过扫描电子显微镜对粉体的表面形貌进行分析;通过光泽、消色力、遮盖率等指标评价钛白粉的颜料性能。以主成分分析法综合上述特征参数评判TiO_(2)综合性能。结果对于Zr/Al无机包覆,当铝的添加量为2.0%~3.0%时,粉体具有较优的颜料性能和流动性能。对于有机包覆,当TMP添加量为0.4%或TME添加量为0.2%时,所得产品在保持良好颜料性能的同时具有较优的流动性能,且生产成本相对较低。结论对于同一基料的钛白粉(D50=0.354μm),Zr/Al无机包覆中铝的添加量、有机包覆剂的种类及添加量均会对其表面性质产生影响,从而造成流动性和颜料性能的差异。以本文选择的特征指标,通过主成分分析法建立的TiO_(2)粉体综合性能评判方法,能够用于指导包覆工艺的优化。

The flowability of TiO_(2)powder directly affects its pigment properties and application in subsequent fields.Currently,most of TiO_(2)products have the problem of poor flowability,which is manifested as bonding and agglomeration in blanking,packaging,transportation and subsequent application.The existing research on the flowability of powder mainly focuses on the flowability difference caused by particle size of micron powder such as food,medicine and pulverized coal,while there is little research on the flowability of submicron powder.To date,the research on the flowability of TiO_(2)powder has not been reported by scholars in China or abroad.The work aims to establish a comprehensive performance evaluation method of TiO_(2)based on powder flowability and pigment properties to guide the optimization of surface modification process and obtain titanium dioxide products with excellent flowability and pigment properties.The effects of the impact different surface properties on TiO_(2)flowability and pigment properties were compared with those on TiO_(2)of the same particle size and size distribution.With chloride rutile TiO_(2)as the base material,Zr/Al inorganic coating and organic coating were carried out in sequence.The effects of key coating parameters on the flowability and pigment properties of coated TiO_(2)products were investigated.By changing the alumina content(1.0%,2.0%,3.0%,4.0%,5.0%in terms of TiO_(2)mass)in Zr/Al inorganic coating,and maintaining the same organic coating conditions,the effect of inorganic coating on powder performance was explored.After the optimal inorganic coating was determined,the effect of organic coating on TiO_(2)powder performance was explored by maintaining the same inorganic coating condition and coating TiO_(2)samples with different additions of TMP and TME(0.0%,0.2%,0.4%,0.6%,0.8%,1.0%based on the mass of TiO_(2)).The compressibility,wall friction and shear action of TiO_(2)powder were tested by powder rheometer,and characteristic index parameters such as Hausner ratio,wall friction angle and internal friction angle were obtained to characterize flowability.The inorganic element content of TiO_(2)was measured by X-ray fluorescence diffractometer,the crystal form of TiO_(2)was determined by X-ray diffraction analyzer,the particle size and particle size distribution of powder were measured by laser particle size analyzer,and the surface morphology of powder was analyzed by scanning electron microscope.The pigment properties of TiO_(2)were evaluated by gloss,tint strength and coverage.Based on the above parameters,principal component analysis method was used to evaluate the comprehensive performance of TiO_(2).The experiment results indicated that the inorganic coating had great effect on the pigment properties of TiO_(2)powder,but small impact on its flowability.In contrast,the organic coating had great significance on the flowability of TiO_(2)powder.For Zr/Al inorganic coating,hydrated alumina firstly formed a continuous dense coating layer on the surface of powder particles due to heterogeneous nucleation and then homogeneously nucleated to form a loose and flocculent Boehmite-type coating layer.When aluminum content was 2.0%-3.0%,the powder had better pigment properties and flowability.For organic surface modification,when TMP content was 0.4%or TME content was 0.2%,the product maintained good pigment properties and excellent flowability,while the production cost was relatively low.In conclusion,for TiO_(2)with same base material(D50=0.354μm),the amount of aluminum added in Zr/Al inorganic coating and the type and amount of organic coating agent will affect the surface properties,resulting in the difference in flowability and pigment properties.With the characteristic indicators selected in this paper,the comprehensive performance evaluation method of TiO_(2)powder established by principal component analysis can be used to guide the optimization of the coating process.