To effectively utilize a broken glass cullet, to increase a glass porosity and to lighten glass by mixing a specific amount of glass fine powder, a blowing agent of wood flour obtained from wood pulp and, if required, a filler and an organic binder, granulating the mixture, heating and baking the granule at a specific temperature.
Glass powder in an amount of 35-95 wt.% is mixed with 2-10 wt.% of a blowing agent, 0-50 wt.% of a filler and 0.1-1 wt.% of an organic binder, granulated and baked at 500-1,000°C. The glass powder is preferably soda-lime glass such as glass bottle, sheet glass, etc., and a broken glass cullet is preferably pulverized into ≤300 μm. Preferably wood flour obtained from wood pulp is used as the blowing agent and has a size of about 10 μm to 2 mm fiber length and about 5 μm to 1 mm fiber diameter. An inorganic material such as Sunakira, talc, etc., is used as the filler and an organic adhesive such as carboxylmethyl cellulose, etc., is used as the organic binder. Consequently a lightweight glass foam having about 0.3-0.5 bulk specific gravity is obtained by using a waste by low-temperature baking.
KOBAYASHI YOSHIHISA
UCHIGAKI TOMOYOSHI
