Fine-grained expanded granules and process for their production

摘要

Perlite having a grain size of preferably 0.1 to 0.6 mm is mixed with a glazing material which, before reaching the expanding temperature of the perlite, forms a film of glassy melt on the individual perlite particles. If the particles are then heated up to the expanding temperature of the perlite while in constant motion, granules having a grain size of less than 3 mm and a strength of the granule particles corresponding to the strength of sand are obtained. These granules are used in particular, preferably on their own, as an aggregate for plastering mortar, with which insulating plasters with a very high insulating value can then be produced. The preferred glazing material used is a suspension of colloidal perlite in a concentrated solution of phosphates or of silicates and borates in water. The colloidal perlite is readily obtained from perlite expanded in a conventional way.