Lignite-Urethane Based Resins for Enhance Foundry Sand Performance
Described herein, in a preferred embodiment, is a leonardite-based polyurethane resin binder that may be used, among other applications, as a binder in combination with foundry aggregate, e.g., sand, for molding or casting metal parts. The binders described herein comprise a humic substance, preferably leonardite, first mixed with a foundry aggregate and then the humic-aggregate mixture is combined with a polymerizable polyol, an isocyanate, and a polymerization catalyst to make a polyurethane resin binder in situ in a foundry aggregate, such as sand. The lignite is added as a solid to the foundry aggregate, and improves the binder performance of the lignite-containing part of the binder components.
1 . A foundry shape comprising a foundry aggregate, a lignite, and a urethane resin; wherein the urethane resin is admixed with an impregnated foundry aggregate that comprises a mixture of the foundry aggregate and the lignite.
2 . The foundry shape of claim 1 , wherein the urethane resin is formed by admixing a polymerizable polyol, a polymerizable isocyanate, and a polymerization catalyst.
3 . The foundry shape of claim 2 , wherein the urethane resin is formed in situ with the impregnated foundry aggregate.
4 . The foundry shape of claim 3 , wherein a weight percent of the urethane resin in the foundry aggregate is about 0.1 to about 10, based on the weight of foundry aggregate.
5 . The foundry shape of claim 1 , wherein the impregnated foundry aggregate comprises about 0.1 wt. % to about 0.5 wt. % lignite, based on the weight of the foundry aggregate.
6 . A process of preparing a foundry shape comprising homogeneously mixing a impregnated foundry aggregate, a polymerizable polyol, a polymerizable isocyanate, and a catalysts to form a moldable mixture and forming the moldable mixture into a foundry mold or core.