Lignite urethane based resins for enhanced 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 method of making a foundry mix comprising:
admixing a solid humic substance and a foundry aggregate to form an impregnated foundry aggregate consisting of the humic substance and the foundry aggregate,
admixing a polymerizable liquid polyol with the impregnated foundry aggregate,
admixing a polymerizable isocyanate with the impregnated foundry aggregate, and
admixing a polymerization catalyst with the impregnated foundry aggregate; to yield a foundry mix.
2. The method of claim 1 , wherein the humic substance is a lignite.
3. The method of claim 2 , wherein the lignite has a moisture content of less than about 35 wt. %.
4. The method of claim 3 , wherein the lignite has a moisture content of less than about 10 wt. %.
5. The method of claim 2 , wherein the lignite is leonardite.
6. The method of claim 5 , wherein the leonardite has an average particle size of about 500 nm to about 500 μm.
7. The process of claim 1 , wherein the humic substance is a lignite having moisture content of 0 wt % to about 20 wt %.
8. The method of claim 1 , wherein the polymerizable polyol is selected from the group consisting of a glycol having a molecular formula of HO—(CH 2 CH 2 O) x —H, where x is a value between 1 and about 25, a glycerol, and a mixture thereof.
9. The method of claim 8 , wherein the polymerizable polyol is triethyleneglycol.
10. The method of claim 1 , wherein the polymerizable isocyanate is a polymeric 4,4′-methylene bis(phenylisocyanate).
11. The method of claim 1 , wherein the polymerization catalyst is selected from the group consisting of 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), pentamethyldipropylenetriamine, bis(dimethylamino ethyl)ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine, tris(3-dimethylamino) propylamine, a liquid tertiary amines, and a mixture thereof.