US Patent 8071656 Nylon extraction from commingled materials

The present invention provides energetically and economically efficient methods for separating polyamide polymer(s) from commingled materials. The methods generally involve precipitating a polyamide polymer dissolved in a solvent (e.g., formic acid) using dimethyl ether (DME) as an antisolvent. The methods comprise dissolving the polyamide polymer in a solvent that (i) selectively dissolves the polyamide polymer relative to the other materials and (ii) has a higher solubility for DME relative to the polyamide polymer; and then contacting the mixture of the solvent with the dissolved polyamide polymer with DME, thereby precipitating the polyamide polymer.