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.

1 . A phenolic resin composition for shell molding, comprising as essential components: a phenolic resin obtained by a reaction of a phenol, a naphthol, and an aldehyde; and a fatty acid amide. 
     
     
         2 . The phenolic resin composition 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 phenolic resin composition for shell molding according to  claim 1 , wherein the naphthol comprises at least one of 1-naphthol and 2-naphthol. 
     
     
         4 . The phenolic resin composition 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. 
     
     
         5 . The phenolic resin composition 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. 
     
     
         6 . The phenolic resin composition for shell molding according to  claim 1 , wherein the fatty acid amide is one of a monamide, a substituted amide, and a bisamide. 
     
     
         7 . The phenolic resin composition for shell molding according to  claim 1 , wherein the fatty acid amide is a fatty acid bisamide. 
     
     
         8 . The phenolic resin composition for shell molding according to  claim 7 , wherein the fatty acid bisamide is a saturated fatty acid bisamide. 
     
     
         9 . The phenolic resin composition for shell molding according to  claim 1 , further comprising a silane coupling agent. 
     
     
         10 . A resin coated sand for shell molding, wherein a fire-refractory particle is coated with the phenolic resin composition for shell molding according to  claim 1 . 
     
     
         11 . The resin coated sand for shell molding according to  claim 10 , 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 . A shell mold obtained by fowling and heat-curing the resin coated sand for shell molding according to  claim 10 . 
     
     
         13 . A process for producing a resin coated sand, comprising the steps of: reacting a phenol, a naphthol, and an aldehyde in the presence of a catalyst to obtain a phenolic resin; and coating a fire-refractory particle with the phenolic resin and a fatty acid amide, which are mixed by melting. 
     
     
         14 . A process for producing a resin coated sand, comprising the steps of: reacing a phenol, a naphthol, and an aldehyde in the presence of a catalyst to obtain a phenolic resin; and coating a fire refractory particle with the phenolic resin and a fatty acid amide, which are used independently. 
     
     
         15 . The process for producing a resin coated sand for shell molding according to  claim 13 , wherein the catalyst comprises at least one of a divalent metal salt and an oxalic acid. 
     
     
         16 . The process for producing a resin coated sand for shell molding according to  claim 14 , wherein the catalyst comprises at least one of a divalent metal salt and an oxalic acid.