Phenolic resin composition for shell molding, resin coated sand for shell molding, and shell mold formed of the same

Abstract

Provided are a phenolic resin composition for shell molding that has low thermal expansion properties and high flexibility, a resin coated sand for shell molding obtained by using the same, and a shell mold formed of the same. The phenolic resin composition for shell molding that is capable of exhibiting advantageous mold characteristic is obtained by a combination of a phenolic resin that is obtained by a reaction of a phenol, a naphthol, and an aldehyde, and a fatty acid amide.

Description

[0001]This application is a continuation of the International Application No. PCT / JP2010 / 061591 filed on Jul. 8, 2010, which claims the benefit under 35 U.S.C. §119(a)-(d) of Japanese Patent Application 2009-172135, filed on Jul. 23, 2009, the entireties of which are incorporated herein by reference.TECHNICAL FIELD[0002]The present invention relates to a phenolic resin composition for shell molding, a resin coated sand for shell molding, and a shell mold formed of the same. In particular, the present invention relates to a phenolic resin composition for shell molding that simultaneously solves problems related to thermal expansion and flexibility, a resin coated sand obtained by using the phenolic resin composition, and a shell mold obtained by using the resin coated sand.BACKGROUND ART[0003]Conventionally, in shell-mold casting, there is generally used a shell mold that is formed by hot-forming a resin coated sand obtained by kneading a fire-refractory particle (casting sand) and a...

AI Technical Summary

Benefits of technology

[0011]The present invention has been made in the light of the situations described above. It is therefore an object of the present invention to provide: a phenolic resin composition for shell molding that has low thermal expansion properties and high flexibility; RCS obtained by using the phenolic resin: a process for producing the RCS; and a shell mold obtained by using such RCS.

[0012]The inventors of the present invention have conducted intensive study and research about the phenolic resin composition for shell molding in an effort to solve the above-described problems and found that a phenolic resin composition having effective properties can be obtained by a reaction of phenol components including a phenol and a naphthol with an aldehyde in the presence of a reaction catalyst such as a divalent metal salt and / or an oxalic acid. Specifically, they found that in the mold produced by using RCS formed by using the above-described phenolic resin composition, low coefficient of thermal expansion and high flexibility are obtained. Thus, the present invention has been completed.

[0026]The phenolic resin composition for shell molding according to the present invention includes a phenolic resin that is obtained by a reaction of a phenol, a naphthol, and an aldehyde, and a fatty acid amide. Therefore, when a coating layer including the phenolic resin composition is formed on a surface of a predetermined fire-refractory particle so as to constitute RCS for shell molding and such RCS is used to produce a shell mold, the obtained mold has low thermal expansion properties and the flexibility of the mold can be sufficiently improved. Accordingly, a problem of casting defect of veining caused by a crack of the mold can be solved at the same time. In addition, since the phenolic resin can be produced without a corrosive component such as hydrochloric acid, a problem of corrosion of a die during mold-forming may not be caused. Thus, the present invention can have industrial advantages that the intended shell mold can be easily and safely produced.

Problems solved by technology

However, in casting process by using this kind of mold, especially by using a mold which has a complex shape, e.g., a mold for casting a molded product such as a cylinder head of an internal combustion engine, there is a problem that a fracture or a crack (hereinafter referred to as “crack” of the mold) is easily caused on the mold during the casting process using the mold.

However, although such technique has sufficiently solved the problem of crack of the mold, the technique has not sufficiently solved the problem of flexibility.

However, thermal expansion properties and flexibility are not sufficiently improved by this method, and thus further improvement is needed.

However, particularly in the production of such resin by using the hydrochloric acid as a catalyst, there is a safety problem caused by vigorous reaction during the production of the resin, and also there is a problem of corrosion of a die during the production of the mold.

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