Nippon Polyurethane Industry Co., Ltd.

Osamu Ishizu

Shin Konishi

Tadashi Kimura

A self-hardening mold material composition comprising 100 parts by weight of molding sand, 0.1 to 6 parts by weight of a component (a), 0.1 to 4 parts by weight of a component (b), 0.05 to 2.0 parts by weight of a component (c) as SiO.sub.2, and 0.01 to 0.5 parts by weight of a component (d) on the basis of 100 parts by weight of the component (b), wherein the component (a) is an organic polyisocyanate having at least two isocyanate groups; the component (b) is a polyetherpolyol mixtures comprising aminopolyetherpolyol, obtained by addition reaction of aliphatic or aromatic amine with alkylene oxide, and a non-aminopolyetherpolyol and containing 5 to 85% by weight of primary hydroxyl-containing polyetherpolyol, the component (c) is at least one of silicate ester, its hydrolysis products, a water dispersion-type silica sol and an alcohol dispersion-type silica sol; and the component (d) is a reaction catalyst, can produce a mold having a good strength after being left standing in the atmosphere at the ordinary temperature and after a molten metal is poured therein, a good shake-out when the mold is dismantled, without any need for mold wash at all or with a need only for simple mold wash.

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Yokohama, Japan

Osamu Ishizu