Preparation And Characterization Of Barite/lead Chrome Yellow Composite Pigment

Lead chrome yellow is a yellow pigment with excellent performance and wide application. But its production needs a considerable amount of lead, chromium and may cause damage to environment and health of its producers. The preparation of composite materials with pigments characteristics by the composite particles technology to reduce the actual amount of lead chrome yellow is one of the effective ways to solve problems of lead chrome yellow in production and application. In this paper, barite was chosen as the modified matrix. The preparation conditions and mechanisms of barite/lead chrome yellow composite pigment by liquid mechano-chemical method have been studied. This work will fully utilize excellent properties of barite and promote the application value, and finally provide technical support for solving the problems existing in traditional application.The nature dispersing behavior of lead chrome yellow pigment, the effect of different pH and dispersants to adjust dispersing behavior in aqueous medium were investigated. Results indicate that the dispersion could be strengthen by appropriate pH, sodium hexametaphosphate, sodium polyacrylate added and ultrasonic wave. The optimal experimental conditions are: pH6.8, sodium hexametaphosphate used 0.5%, sodium polyacrylate used 0.5%, and ultrasonic wave is very effective to dispersing behavior.The technique conditions and influence factors of barite/lead chrome yellow composite pigment prepared by liquid mechano-chemical method were investigated. The effect degree of the conditions was obtained: the grinding time of barite>the stirring speed>the reaction time>the ball to powder mass ratio. The optimal conditions of factors are: the grinding time of barite 30min; the stirring speed 800r/min; the ball to powder mass ratio 5∶1; the reaction time 60min; the barite to lead chrome yellow ratio 4∶6 ; the grinding pulp concentration of the wetmilling of the mixture of finely ground barite and lead chrome yellow pigment 50%; sodium polyacrylate used 0.5%. The pigment performances of barite/lead chrome yellow composite pigment were investigated. The results were: hiding power 16.89g/m2, oil absorption 19.61g/100g, relative contrast ratio 96.2%, chromaticity value ?E=1.2731. The performances were similar to pure lead chrome yellow pigment. The paint experiments show that barite/lead chrome yellow composite pigment can be used to replace pure lead chrome yellow pigment to apply.The composite mechanism and micro-structure of barite/lead chrome yellow composite pigments particles were investigated. Lead chrome yellow particles have achieved effective coating on the surface of barite particles in the barite/lead chrome yellow composite pigments. The mechano chemical effect generated in process of the wet ultrafine grinding of barite enhances the reactivity and interphase competence of barite. There is the role of mutual attraction between barite and lead chrome yellow in the composite system. Lead chrome yellow and barite particles formed a solid combination of interface with combination of the surface functional groups.