Patent ID: 6056813
Filing Date: 2000-05-02
Classification: C09D,D21H

Abstract:
A process for making white pigment directly from constituent materials without byproducts, the process comprising the steps of:inputting three material flows comprising a sulphate source, an alkali source, and an aluminum source;recycling and mixing into said three material flows a process return from a separation and wash stage and vapors from a pressure let-down stage;heating and holding a mixture of recycled process returns and said three material flows at elevated pressure in a reactor for a minimum predetermined residence time;letting down pressure in a flow from said reactor after said minimum predetermined residence time to produce a pre-wash flow; andseparating, classifying, and delaminating said pre-wash flow into a first and second pigment or filler that are differentiated by their respective average particle distribution sizes and providing for said first and second pigments or fillers that principally include a double salt of the type wK.sub.2 SO.sub.4 .multidot.xAl.sub.2 O.sub.3 .multidot.zH.sub.2 O or vNa.sub.2 SO.sub.4 .multidot.xAl.sub.2 O.sub.3 .multidot.ySO.sub.3 .multidot.zH.sub.2 O, where, ""v"" is the stoichiometric coefficient of Na.sub.2 SO.sub.4, between about zero and one; ""w"" is the stoichiometric coefficient of K.sub.2 SO.sub.4, between about zero and one ""x"" is the stoichiometric coefficient of Al.sub.2 O.sub.3, about there ""y"" is the stoichiometric coefficient of SO.sub.3 about four; and ""z"" is the stoichiometric coefficient of H.sub.2 O, about nine, and wherein using both alkali metals, K and Na, as the raw materials produces a combination double salt.