Lignite-based foundry resins
Described herein, in the 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, 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 mixed with the polymerizable polyol and dispersing agents as additives to improve the suspension quality and binder performance of the lignite-containing part of the binder components.
1. A lignite-polyol suspension comprising: a plurality of lignite particles that have an average diameter less than about 20 μm; a polyol; and a dispersing agent, wherein the lignite has a moisture content of 0 wt % to 20 wt % based on the dry weight of the lignite.
2. The lignite-polyol suspension of claim 1 , wherein the lignite particles have an average diameter less than about 15 μm.
3. The lignite-polyol suspension of claim 2 , wherein the lignite particles have an average diameter less than about 10 μm.
4. The lignite-polyol suspension of claim 1 ,
wherein 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; and
wherein the dispersing agent is a polymer selected from the group consisting of (A) a polymer selected from the group consisting of a monoesterified polyethylene glycol, a poly(acrylic acid), a poly(methacrylic acid), a poly(vinyl alcohol), a poly(acrylamide), a poly(ethylene imine), a poly(diallyldimethyl ammonium halide), a poly(vinyl methyl ether), and a mixture thereof; (B) a polyvinylpyrrolidone; (C) a polyvinylpyrrolidone copolymer; and (D) a copolymer of a plurality of monomers selected from the group consisting of propylene oxide, vinyl acetate, vinyl amine, vinyl chloride, acrylamide, acrylonitrile, ethylene, propylene, ethylene oxide, lauryl methacrylate, methyl methacrylate, hydroxystearate, dimethylsiloxane, diallyldimethyl ammonium halide, ethylenimine, acrylic acid, methacrylic acid, and a mixture thereof.
5. The lignite-polyol suspension of claim 4 , wherein the dispersing agent is a mixture of polymers selected from the group consisting of (A), (B), (C), and (D).
6. The lignite-polyol suspension of claim 1 further comprising a organic solvent.
7. The lignite-polyol suspension of claim 6 wherein the lignite-polyol suspension consists essentially of
about 0.1 wt. % to about 85 wt. % lignite;
about 15 wt. % to about 90 wt. % polyol;
about 0.01 wt. % to about 30 wt. % dispersing agent; and
a ratio of the organic solvent to the polyol that is about 0.01 to about 9.
8. The lignite-polyol suspension of claim 7 , wherein the polyol is triethylene glycol.
9. The lignite-polyol suspension of claim 7 , wherein the lignite is leonardite.
10. The lignite-polyol suspension of claim 7 , wherein the dispersing agent is a monoesterified polyethylene glycol.
11. The lignite-polyol suspension of claim 7 , wherein the organic solvent is propylene carbonate.