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.

What is claimed is: 
     
         1 . A resin coated sand for shell molding, wherein a fire-refractory particle is coated with a phenolic resin composition comprising a resin consisting of a phenolic resin obtained by a reaction of a phenol, a naphthol, and an aldehyde; and a fatty acid amide. 
     
     
         2 . The resin coated sand for shell molding according to  claim 1 , wherein a ratio of the phenol to the naphthol is in a range of from 95:5 to 50:50 by mass ratio. 
     
     
         3 . The resin coated sand for shell molding according to  claim 1 , wherein a ratio of the phenol to the naphthol is in a range of from 90:10 to 60:40 by mass ratio. 
     
     
         4 . The resin coated sand for shell molding according to  claim 1 , wherein the naphthol comprises at least one of 1-naphthol and 2-naphthol. 
     
     
         5 . The resin coated sand for shell molding according to  claim 1 , wherein a reaction molar ratio among the phenol (P), the naphthol (N), and the aldehyde (F): F/(P+N) is in a range of from 0.40 to 0.80. 
     
     
         6 . The resin coated sand for shell molding according to  claim 1 , wherein the fatty acid amide is present in a range of from 1 to 15 parts by mass based on 100 parts by mass of the phenolic resin. 
     
     
         7 . The resin coated sand for shell molding according to  claim 1 , wherein the fatty acid amide is one of a monoamide, a substituted amide, and a bisamide. 
     
     
         8 . The resin coated sand for shell molding according to  claim 1 , wherein the fatty acid amide is a fatty acid bisamide. 
     
     
         9 . The resin coated sand for shell molding according to  claim 8 , wherein the fatty acid bisamide is a saturated fatty acid bisamide. 
     
     
         10 . The resin coated sand for shell molding according to  claim 1 , wherein the phenolic resin composition further comprises a silane coupling agent. 
     
     
         11 . The resin coated sand for shell molding according to  claim 1 , wherein the phenolic resin composition is present in a range of from 0.2 to 10 parts by mass based on 100 parts by mass of the fire-refractory particle. 
     
     
         12 . The resin coated sand for shell molding according to  claim 1 , wherein a mold produced by using the resin coated sand has a flexibility of at least 5.4 mm. 
     
     
         13 . The resin coated sand for shell molding according to  claim 1 , wherein the phenolic resin is obtained by a reaction of phenol, naphthol and an aldehyde in the presence of an acid catalyst. 
     
     
         14 . A shell mold obtained by forming and heat-curing the resin coated sand for shell molding according to  claim 1 .