Method of producing sand mold comprising curing a resin and a binder by the same curing agent

A method of producing a sand mold, the method comprising the steps of:

• mixing artificial sand with a furan resin composition including a furan resin precursor, whereby the furan resin composition covers surfaces of particles of the artificial sand,
• mixing a curing agent including xylene sulfonic acid with the artificial sand with which the furan resin composition is mixed,
• curing the furan resin composition with the curing agent, thereby preparing molding sand, and
• curing an added portion of a binder in the molding sand by adding the binder to the molding sand,
• wherein, in the step of preparing the molding sand, the curing agent cures the furan resin composition to form a resin cured product on the surfaces of the particles of the artificial sand, and the curing agent remains as an acid catalyst,
• the cured resin product forms a surface-modified layer,
• the remaining curing agent is attached to a surface of the surface-modified layer, and
• the molding sand includes the artificial sand, the surface-modified layer, and the curing agent,
• wherein, in the step of curing the added portion of the binder, the curing agent for curing the furan resin composition is used also as a curing agent for curing the binder.