PURPOSE: To prepare foamed glass beads having excellent crushing strength, by applying glass powder free of foaming agent to the surface of spherical glass powder containing foaming agent, coating the coated surface with a releasing agent, and heating at a high temperature.
CONSTITUTION: 100pts.wt. of arbitrary glass powder is mixed with 5pts.wt. of powdery foaming agent (e.g. CaCO3) evolving CO2 gas with heat, and crushed and mixed in a ball mill, etc. to obtain the size-controlled powdery mixture wherein particles finer than 325 mesh occupies ≥80% of the mixture. The mixture is mixed with a binder such as aqueous solution of starch, polyvinyl alcohol, etc. and granulated to spheres having a diameter of about 1mm. 100pts.wt. of the granules are coated with 2W10pts.wt. of fine glass powder free of foaming agent using the above binder, and a releasing agent such as talc powder is attached to the coating surface. The coated granules are heated at the foaming temperature to generate foams in the core part of the granule. Foamed glass bead having a diameter of 1W3mm, a crushing strength of 400W1,400g, and a specific gravity of 0.3W0.4 can be obtained by this process.
YAMAMOTO KOUSUKE
HAYASHI HIROAKI
TOYODA CHUO KENKYUSHO KK