| 摘要 |
PROBLEM TO BE SOLVED: To provide an organic binding agent for a casting mold, which can improve the strength of the casting mold just after gas hardening, and also can satisfactorily secure the usable time in forming a phenol urethane casting mold by the amine cold box method, and further to provide a molding sand composition which can be obtained by using the organic binding agent for the casting mold and has an elongated usable time, and further to provide a casting mold which is formed by hardening the molding sand composition described above by a gas. SOLUTION: The organic binding agent to be used in forming the phenol urethane gas hardened casting mold is composed of a phenol resin which contains a phenol class monomer of at most 3 %, and has a number average molecular weight (Mn) of 200-700, and satisfies a variance ratio (Mw/Mn) of 1.1-1.6, wherein the variance ratio (Mw/Mn) is the ratio of a weight average molecular weight (Mw) to the number average molecular weight (Mn), in the measurement by the gel filtration chromatography. COPYRIGHT: (C)2006,JPO&NCIPI
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