Polyurethane based binder system for the manufacture of foundry cores and molds

Abstract

A cold-box process for preparing a foundry shape, e.g. mold or core, that uses a binder comprising a phenolic resin component and an isocyanate component, wherein the phenolic resin component comprises (a) an alkoxy-modified phenolic resole resin and (b) an oxygen-rich polar, organic solvent component, which contains a fatty acid ester.

We claim:  
     
         1 . A process for preparing a foundry shape by the cold-box process which comprises: 
 (a) forming a foundry mix comprising a major amount of aggregate and an effectively binding amount of a binder system comprising: 
 (1) a phenolic resole resin component, and  
 (2) an isocyanate component,  
 wherein the phenolic resin component comprises (a) an alkoxy-modified phenolic resole resin component such that the mole ratio of alcohol to phenol used to prepare said alkoxy-modified phenolic resole resin is less than 0.25:1.0, and (b) at least one oxygen-rich, polar organic solvent component, wherein the solvent portion of the phenolic resin component of the binder system amounts to no more than 40% by weight, based upon the weight of the phenolic resin component, and the amount of oxygen-rich polar organic solvent is at least 50 weight percent based on the total weight of the solvent in the phenolic resin component; and  
 wherein either the phenolic resin component, isocyanate component, or both of said components contain a fatty acid ester having from 1 to 12 carbon atoms in the alcohol chain of the fatty acid ester;  
   (b) forming a foundry shape by introducing the foundry mix obtained from step (a) into a pattern;    (c) contacting foundry shape mix with a volatile tertiary amine catalyst; and    (d) removing the foundry shape of step (c) from the pattern.    
     
     
         2 . The process of  claim 1  wherein the oxygen-rich polar, organic solvent is selected from the group consisting of glycol ether esters, glycol diesters, glycol diethers, cyclic ketones, cyclic esters, cyclic carbonate, and mixtures thereof.  
     
     
         3 . The process of  claim 2  wherein the fatty acid ester is part of the phenolic resin component and is derived from an alcohol having from 4 to 10 carbon atoms.  
     
     
         4 . The process of  claim 3  wherein the fatty acid ester is the butyl ester of tall oil fatty acids.  
     
     
         5 . The process of  claim 4  wherein the amount of said binder in said foundry mix is about 0.6 percent to about 5.0 percent based upon the weight of the aggregate.  
     
     
         6 . A process of casting a metal which comprises: 
 (a) preparing a foundry shape in accordance with claims  1 ,  2 ,  3 ,  4 , or  5 ;    (b) pouring said metal while in the liquid state into and a round said shape;    (c) allowing said metal to cool and solidify; and    (d) then separating the molded article.    
     
     
         7 . A binder system comprising: 
 (a) a phenolic resole resin component, and    (b) an isocyanate component,    wherein the phenolic resin component comprises (a) an alkoxy-modified phenolic resole resin component such that the mole ratio of alcohol to phenol used to prepare said alkoxy-modified phenolic resole resin is less than 0.25:1.0, and (b) at least one oxygen-rich, polar organic solvent component, wherein the solvent portion of the phenolic resin component of the binder system amounts to no more than 40% by weight, based upon the weight of the phenolic resin component, and the amount of oxygen-rich polar organic solvent is at least 50 weight percent based on the total weight of the solvent in the phenolic resin component; and    wherein either the phenolic resin component, isocyanate component, or both of said components contain a fatty acid ester having from 1 to 12 carbon atoms in the alcohol chain of the fatty acid ester.    
     
     
         8 . The binder system of  claim 7  wherein the oxygen-rich polar, organic solvent is selected from the group consisting of glycol ether esters, glycol diesters, glycol diethers, cyclic ketones, cyclic esters, cyclic carbonate, and mixtures thereof.  
     
     
         9 . The binder system of  claim 8  wherein the fatty acid ester is part of the phenolic resin component and is derived from an alcohol having from 4 to 10 carbon atoms.  
     
     
         10 . The binder system of  claim 9  wherein the fatty acid ester is the butyl ester of tall oil fatty acids.