| 摘要 |
PROBLEM TO BE SOLVED: To obtain a mold having excellent strength by using reconditioned molding sand after pretreating the sand with the specific ratio of water to the sand. SOLUTION: The cold hardening molding sand composition is manufactured by coating alkaline phenol resin water solution and ester groop compound on the alkaline reconditioned molding sand. The alkaline phenol resin water solution used there 5 for is a strong base phenol resin having methylol group and/or dimethylene ether group in the molecule. As the phenol group, phenol cradle, etc., is exemplified. As the suitable example of the ester group compound, oxyacid cyclic esters ofγ-butyrolactones are exemplified. To 100 pts.wt. of the alkaline phenol regin water solution, the ester group compound is used in the range of 5-40 pts.wt. In the manufacture of this molding sand, the reconditioned molding sand, the reconditioned molding sand is used by pretreating with 0.1-1.0 pts.wt. of water per 100 pts.wt. of the molding sand.
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