Calcium sulpho-aluminate pigment prepn. - by reacting calcium hydroxide with aluminium sulphate and stabilising with a poly:carboxylic acid salt

摘要

Calciumsulphoaluminate (I) pigment having a particle size of 0.1-2.0 mu is continuously prepd. by (1) mixing an aq. 6 plus-or-minus 2 wt. % Ca(OH)2 suspension with an aq. 6 plus-or-minus wt. % (as Al2O3) Al sulphate soln. while maintaining a CaO:N2O3 mol. ratio of 7.2 plus-or-minus 0.2 and instantaneously reacting to form a reaction system contg. at first a (I) gel and then (I) particles and (2) cooling and thinning the reaction system by mixing the water and adding a polycarboxylic acid salt to stabilise the surface of the particles. (I) is used as a paper coating pigment, and has excellent flow properties.