High White Filler Grade Aluminum Hydroxide Preparation

High whiteness aluminum hydroxide (AH) is finding increasing applications in filler market. It is very significant to research the preparation technology of aluminum hydroxide with good crystal growth, low oil adsorption, high purity and excellent filling property in high polymers. The high whiteness AH production technologies from carbonation and seed precipitation process, the filling property of AH products and the effect of grain size gradation on oil adsorption are mainly studied in this dissertation. The main conclusions and findings can be summarized as follows:(1) The filler-grade AH can be obtained by controlling the technological conditions during discontinuous and continuous carbonation process. However, the oil adsorption of carbonation product is higher (35ml/100g) due to the fact that the crystal is looser and the crystal surface is rougher.(2) High whiteness filler-grade AH with mean diameter of 50~65um and perfect crystal structure can be prepared by controlling decomposition temperature and time, crystal seed coefficient and addition mode of purified liquor during discontinuous seed precipitation process. The decomposing rate is larger at the initial stage of discontinuous seed precipitation process due to the fact that the decomposition driving force is higher and the seeds are high-activity AH. Nevertheless the oil adsorption is still high, this may be attributed to the broad spaces between the second granules. The effect of seeds from carbonation and seed precipitation process on the particle size and oil adsorption of discontinuous seed precipitation product is not distinct.(3) The top grade high whiteness filler-grade AH with mean diameter of 60~85um and lower oil adsorption can be obtained by continuous seed precipitation technology due to that the longer decomposition time make crystal structure more perfect so that the crystal surface is smooth, the spaces between particles are tiny. The particle size of the product presents perfect normal distribution.(4) Generally, the top grade high whiteness filler-grade AH is prepared by continuous seed precipitation technology, and that middle and low-quality AH product is obtained by continuous carbonation or discontinuous seed precipitation technology.(5) The grain size gradation is an effective way to depress the oil adsorption of AH filler.