Method for extracting nylon from waste materials
View Patent ↗The invention relates to a method for recovering nylon from a nylon-containing material by contacting the nylon-containing material with an alkanol-containing solvent at elevated temperature and at a pressure higher than the equilibrium pressure of the alkanol-containing solvent at the elevated temperature, thereby dissolving the nylon in the alkanol-containing solvent, removing the alkanol-containing solvent containing dissolved nylon from any undissolved solids, and decreasing the temperature of the alkanol-containing solvent containing dissolved nylon to precipitate the dissolved nylon.
1. A method for recovering nylon from a waste material comprising nylon, comprising:
contacting the waste material comprising nylon with an alkanol-containing solvent at an elevated temperature between 130° C. and 155° C. and at a pressure higher than an equilibrium vapor pressure of the alkanol-containing solvent at the elevated temperature, and between 400 psig to 600 psig, and maintaining the pressure for a dissolution time sufficient to dissolve the nylon, thereby dissolving the nylon in the alkanol-containing solvent, wherein the combination of the pressure, temperature and the dissolution time provide a desired yield of nylon of at least 82%;
removing the alkanol-containing solvent containing dissolved nylon from any undissolved solids;
decreasing the temperature of the alkanol-containing solvent containing dissolved nylon to between 120° C. and 130° C. to precipitate dissolved nylon to generate precipitated nylon in remaining solution; and separating the precipitated nylon from the remaining solution.
2. The method of claim 1 , wherein the waste material comprises a floor covering material.
3. The method of claim 1 , wherein the nylon is nylon 6,6.
4. The method of claim 1 , wherein the alkanol-containing solvent is substantially free of glycols or other polyols.
5. The method of claim 1 , wherein the alkanol-containing solvent comprises an alkanol selected from the group consisting of methanol, ethanol, propanols, butanols, and mixtures thereof.
6. The method of claim 1 , wherein the alkanol-containing solvent comprises a mixture of alkanol and water.
7. The method of claim 6 , wherein the alkanol is present in an amount ranging from about 40 wt % to about 90 wt % of the solvent.
8. The method of claim 7 , wherein the alkanol-containing solvent comprises a mixture of about 80 wt % ethanol in water.
9. The method of claim 1 , wherein the pressure during the contacting ranges from 400 psig to 500 psig.
10. The method of claim 9 , wherein the elevated temperature is about 145° C.
11. The method of claim 1 , wherein the pressure higher than the equilibrium vapor pressure of the alkanol-containing solvent at the elevated temperature is attained by introducing an inert gas into the reactor.
12. The method of claim 1 , wherein the pressure higher than the equilibrium vapor pressure of the alkanol-containing solvent at the elevated temperature results at least in part from the pressure head of the alkanol-containing solvent entering the reactor.
13. The method of claim 1 , wherein the waste material comprises nylon-containing floor covering materials which comprise carpet or carpet tile, or mixtures thereof.
14. The method of claim 13 , wherein the carpet or carpet tile contains nylon 6,6.
15. The method of claim 1 , wherein the dissolution time is between 15 and 45 minutes.
16. The method of claim 15 , wherein the dissolution time is between 15 and 37 minutes.
17. The method of claim 16 , wherein the dissolution time is between 15 and 23 minutes.
18. The method of claim 1 wherein the temperature, the pressure and the dissolution time result in a yield of 82-100%.