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mixing vessel, wherein at least a portion of the mixture of nylon-containing material and alkanol-containing solvent is withdrawn from the mixing vessel by a splitter pump and returned to the mixing vessel at a high flow rate;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 at the increased temperature, 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 elevated temperature 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 elevated temperature 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 having a molecular weight substantially increased over that of the feedstock nylon.

An apparatus for recovering nylon from a nylon-containing material, comprising:

• a mixing vessel adapted to mix nylon containing materials with a liquid solvent;
• a high flow rate splitting pump in fluid communication with the mixing vessel, adapted to withdraw a portion of the contents of the mixing vessel and return it to the mixing vessel at a high flow rate;
• a pressurized heat exchanger in fluid communication with the mixing vessel, the splitting pump, or both, adapted to heat a mixture of nylon and solvent from the mixing vessel to an elevated temperature at a pressure above the equilibrium vapor pressure of the solvent;
• a filtration system in fluid communication with the pressurized heat exchanger, adapted to remove undissolved solids from a fluid stream;
• a precipitator in fluid communication with the filtration system, the pressurized heat exchanger, or both, adapted to reduce the pressure of a fluid stream, decrease the temperature of a fluid stream, or both;
• a concentrator in fluid communication with the precipitator, adapted to remove solvent from, and increase the solids content of, a mixture of precipitated nylon and solvent;
• a drier in fluid communication with the concentrator, adapted to dry a concentrated mixture of nylon and solvent.

A splitter pump comprising:

• a progressive cavity, comprising:
• a distal end;
• a proximal end;
• a progressive cavity rotor extending through at least a portion of the progressive cavity;
• a progressive cavity stator surrounding the progressive cavity rotor and disposed between the distal and proximal ends of the progressive cavity;
• an inlet chamber in fluid communication with the proximal end of the progressive cavity;
• a lateral inlet opening in fluid communication with the inlet chamber;
• a lateral recycle outlet opening in fluid communication with the inlet chamber;
• a process stream outlet in fluid communication with the distal end of the progressive cavity;
• and
• a drive shaft linked to the progressive cavity rotor.