Preparation Of Wollastonite/tio₂ Composite Particles Material By Mechano-chemical Method And Its Application

The mineral/TiO2 composite particles material with non-metal mineral as core material and crystallized TiO2 as coating material is new developed white pigment in recent years. It has been widely used as substitute for titanium white in paints, plastics, rubber, paper making and other industries. The preparation technique, performance characterization, application technology and mechanisms of wollastonite/TiO2 composite by wet mechanochemical method were studied in this paper. This work can provide technical supports for fully exerting excellent properties of wollastonite mineral, upgrading its application values and solving problems existed in the production and application of titanium dioxide powder.Influences of the main process factors for preparing wollastonite/TiO2 composite by wet mechanochemical method were studied in the experiments. Optimum process conditions of are: slurry concentration 35%, dosage of dispersant 0.3%, dosage of TiO2 45%, dispersion time of TiO2 in the water 30min. At the reaction stage, the ratio of ball to powder is 4.5:1, the grinding speed is 1400r/min, the reaction time is 15min, pH value is 8 (with the ratio of ball to powder 5:1, the grinding speed 1400r/min and reaction time 20min during the wet grinding stage).The pigment properties and application in building coatings of the composite were researched. The products prepared under optimal conditions have hiding power of 17.97g/m2, oil absorption of 22.72g/100g, and whiteness of 96.6. Its pigment properties are similar with that of titanate white powder and far better than products prepared by dry and wet agitating and mixing of wollastonite and TiO2. The properties of the composite particles used as interior wall coating are compatible with that of titanate white powder.The micro morphology and compositing mechanism were studied. The composite particles are composed of core material wollastonite and coating material crystalline TiO2 and TiO2 coated evenly on surface of wollastonite. The Van der waals force and electrostatic interaction between the heterogeneous particles wollastonite and TiO2 and its combining force among particles are all attracting forces. The mechanochemical effect was generated accompanying the granular refinement in the process of wet ultrafine grinding. Chemical bond was formed by surface hydroxyl groups on the surface of TiO2 and wollastonite in water medium, making TiO2 firmly bonded on the surface of wollastonite. The adsorption model of TiO2 on the surface of wollastonite was established according to the surface morphology on particle surfaces and the generated chemical binding.