Foundry binder systems

Abstract

The present invention relates to foundry binder systems forming a curable polyurethane with a catalytically effective amount of a curing catalyst, comprising at least one phenolic resin component comprising at least: a phenolic resin and a solvent of triacetin type and a polyisocyanate component. The invention also relates to foundry mixtures prepared from the binder and an aggregate, to foundry forms such as cores and molds prepared via the no-bake or cold-box processes, and also to the respective processes. The foundry forms obtained by the present invention are especially used for manufacturing metallic components, especially for the casting of metallic components.

1 . Foundry binder system forming a curable polyurethane with a catalytically effective amount of a curing catalyst, comprising at least:
 A. a phenolic resin component comprising at least:   (1) a phenolic resin: and   (2) a solvent comprising at least triacetin: and   B. a polyisocyanate component   
     
     
         2 . A foundry binder system as defined by  claim 1 , in which the triacetin is obtained from a process using crude glycerol. 
     
     
         3 . A foundry binder system as defined by  claim 1 , in which the solvent is a mixture comprising at least 80% by weight of triacetin. 
     
     
         4 . A foundry binder system as defined by  claim 1 , in which the solvent is a mixture comprising 80% to 95% by weight of triacetin, 5% to 15% by weight of diacetin and less than 5% by weight of monoacetin, relative to the total weight of the mixture. 
     
     
         5 . A foundry binder system as defined by  claim 1 , in which the said component A also comprises a solvent that is a mixture of dimethyl esters, especially dimethyl adipate, dimethyl glutarate and dimethyl succinate. 
     
     
         6 . A foundry binder system as defined by  claim 5 , in which the ratio of the solvent comprising at least triacetin and of the said mixture of dimethyl esters ranges from 1:20 to 20:1. 
     
     
         7 . A foundry binder system as defined by  claim 1 , in which the said component A also comprises one or more aromatic hydrocarbon-based solvents. 
     
     
         8 . A foundry binder system as defined by  claim 1 , in which the solvent comprising at least triacetin represents from 10% to 30% by weight relative to the weight of component A. 
     
     
         9 . A foundry binder system as defined by  claim 1 , in which the said phenolic resin is a resol phenolic resin. 
     
     
         10 . A foundry binder defined by  claim 1 , in which the said polyisocyanate component comprises a polyisocyanate and a polyisocyanate solvent, 
     
     
         11 . A foundry binder system as defined by  claim 10 , in which the said polyisocyanate solvent is a mixture of aromatic hydrocarbons, chosen especially from benzene, toluene, xylene and alkylbenzenes, and mixtures thereof. 
     
     
         12 . Foundry mixture comprising a polyurethane-forming binder system as defined by  claim 1 , and an aggregate, 
     
     
         13 . A foundry mixture as defined by  claim 12 , in which the said aggregate is sand. 
     
     
         14 . Process for preparing a foundry form via the cold-box process, in which the binder is as defined by  claim 1 , and the curing catalyst is a gaseous amine. 
     
     
         15 . Process for preparing a foundry form via the no-bake process, in which the binder is as defined by  claim 1 , and the curing catalyst is a liquid amine. 
     
     
         16 . Foundry form prepared via the process as defined by  claim 14 . 
     
     
         17 . Use of a mixture comprising at least triacetin as a solvent that is useful for phenolic resins in polyurethane-forming foundry binder systems, alone or as a mixture with other solvents.