Use of closed-pore microspheres of expanded pearlite as a filler for the production of mouldings for the foundry industry

A molding for the foundry industry, produced using

• closed-pore microspheres of expanded perlite, having a closed foam structure with pores separated from one another, and wherein the microspheres are closed on their surface;
• wherein the microspheres have a particle size d50 of 200 to 250 μm;
• expanded glass;
• wherein a weight ratio of perlite to expanded glass ranges from 1:1 to 1:2;
• and an organic or inorganic binder or a mixture of organic and inorganic binder, wherein the binder is selected from the group consisting of water glass, phenol-formaldehyde resins, two-component systems comprising as reactants a polyisocyanate and a polyol component containing free hydroxyl groups (OH groups), and starch
• wherein the closed-pore microspheres of expanded perlite have a bulk density from 200 to 500 kg/m3.