Patent ID: 8813829

Claim:
A method for producing a mold comprising the steps of: producing a mold with a spherical molding sand (A) having a sphericity of 0.95 or more, a binder (II) comprising an acid-hardening resin and a hardening agent (II), pouring metal into the obtained mold; disintegrating and reclaiming the mold to obtain reclaimed molding sand; mixing the reclaimed molding sand, a binder (I) comprising an acid-hardening resin and a hardening agent (I) to obtain kneaded sand; and forming the kneaded sand into a second mold, wherein the reclaimed molding sand comprises 60% by weight or more of Al 2 O 3 , and both of the hardening agents (I) and (II) comprise an organic sulfonic acid, and, in the hardening agents, a content of sulfuric acid is 2% by weight to 5% by weight and a content of phosphoric acid is not more than 5% by weight, wherein an ignition loss of the reclaimed molding sand is not more than 0.5% by weight; and an elution amount of elemental aluminum per 1 g of the reclaimed molding sand is not more than 50 μg in accordance with the following method of measurement: 25 g of the reclaimed molding sand is weighed in a beaker; to this is added 50 ml of 0.1 N—HCL aqueous solution, and stirred for 15 minutes; the mixture is allowed to stand for 5 minutes; a supernatant is filtered through a filtering paper; an elemental aluminum in the filtered supernatant is quantified by ICP analysis (Inductively Coupled Plasma Emission Spectrometry), and used to calculate an elution amount per 1 g of reclaimed molding sand.