Method for extracting nylon from waste materials

A method for recovering nylon from a nylon-containing material, comprising:

• contacting the nylon-containing material with an alkanol-containing solvent in a mixing vessel, wherein at least a portion of the mixture of nylon-containing material and alkanol-containing solvent is withdrawn from the mixing vessel by a splitter pump and returned to the mixing vessel at a high flow rate;
• increasing the temperature and pressure of the mixture until a pressure is reached that is higher than the equilibrium pressure of the alkanol-containing solvent, and until the temperature is between 130° C. and 155° C. thereby dissolving the nylon in the alkanol-containing solvent;
• removing the alkanol-containing solvent containing dissolved nylon from any undissolved solids;
• decreasing the temperature, or pressure, or both, of the alkanol-containing solvent containing dissolved nylon to precipitate the dissolved nylon;
• concentrating, dewatering, or otherwise increasing the concentration of the precipitated nylon;
• drying the dewatered, concentrated precipitated nylon in a drier.

A method for increasing the tenacity of nylon fiber, comprising:

• dissolving a feedstock nylon fiber in a solvent comprising an alkanol at an elevated temperature between 130° C. and 155° C. and at a dissolution pressure above the equilibrium vapor pressure of the solvent at the dissolution temperature;
• filtering undissolved solids from the solution;
• precipitating nylon from solution by decreasing pressure, temperature, or both of the solution, to form a precipitated mixture;
• concentrating the precipitated nylon by removing solvent from the precipitated mixture to form a concentrated mixture;
• drying the concentrated mixture to form solid nylon;
• extruding the solid nylon into fiber having tenacity increased over that of the feedstock nylon fiber.

A method for increasing the molecular weight of feedstock nylon, comprising:

• dissolving a feedstock nylon in a solvent comprising an alkanol at an elevated temperature between 130° C. and 155° C. at a dissolution pressure above the equilibrium vapor pressure of the solvent at the dissolution temperature;
• filtering undissolved solids from the solution;
• precipitating nylon from solution by decreasing pressure, temperature, or both of the solution, to form a precipitated mixture;
• concentrating the precipitated nylon by removing solvent from the precipitated mixture to form a concentrated mixture;
• drying the concentrated mixture to form solid nylon having a molecular weight substantially increased over that of the feedstock nylon.