Treating sedimentary clays - to yield low viscosity clays for coating paper

摘要

Process involves forming a clay suspension in water contg 20-40% solids followed by decantation, oxidisation, flocculation reduction, a further flocculation each flocculation stage being followed by filtering and finally drying and crushing. A clay of low viscosity is obtd which is ideal for coating paper. The properties of whiteness and opacity of the coated paper are also excellent. The dispersant is pref. sodium hexametaphosphate added as 1.5 kg per tonne of suspension. The oxidising agent is sodium hypochlorite, the reducing agent is sodium hydrosulphite and the flocculating agent is aluminium sulphate.