preparation and expansion of perlite ore fines

摘要

Perlite ore fines (at least 50% of the particles being not greater than 74 mu ) are treated with an agglomerating agent which has a viscous liquid phase at a temperature above ambient temperature but below the critical dehydration temperature of the perlite ore fines, e.g. orthoboric acid or metaboric acid. The perlite ore fines and agglomerating agent are mixed, preferably by dry mixing, and then heated to the temperature of the viscous liquid phase and held at that temperature for a short period while the liquid coats at least a portion of the perlite ore fines and effects agglomeration. Thereafter, the agglomerated perlite ore fines can be expanded in a conventional perlite ore expander. The resulting expanded materials have properties essentially identical to standard expanded perlite ore and are useful for such purposes as insulating fillers and light weight aggregates.