Method of continuously recycling thermoset plastic waste

1. A method of continuously recycling thermoset plastic waste, comprising:

crushing the thermoset plastic waste into pieces with a diameter size suitable for being fed into an extruder;

purifying the thermoset plastic waste by cleaning the thermoset plastic waste using a cleaning agent to remove contaminants from the thermoset plastic waste; and

decrosslinking the thermoset plastic waste by combining a supercritical solvent and the thermoset plastic waste in the extruder and extruding the thermoset plastic waste under a temperature of 200-400° C. and an extrusion pressure of 10-150 bar.

2. The method of claim 1 , wherein a liquid solvent is introduced into the extruder and becomes the supercritical solvent under the temperature of 200-400° C. and the extrusion pressure of 10-150 bar in the extruder.

3. The method of claim 1 , wherein the thermoset plastic waste is selected from a group consisting of polyethylene (XLPE), phenolic resin, and epoxy resin.

4. The method of claim 1 , wherein the extruding the thermoset plastic waste requires only one extruder.

5. The method of claim 2 , wherein the liquid solvent and the thermoset plastic waste are introduced into the extruder simultaneously.

6. The method of claim 2 , wherein the thermoset plastic waste is introduced into the extruder at a thermoset feed rate of 1-60 g/min, and the liquid solvent is introduced into the extruder at a solvent injection rate of 1-50 mL/min.

7. The method of claim 2 , wherein the liquid solvent is selected from a group consisting of methanol, ethanol, isopropyl alcohol and a mixture thereof.

8. The method of claim 2 , wherein when the thermoset plastic waste is XLPE, the thermoset plastic waste is introduced into the extruder at a thermoset feed rate of 20-30 g/min, a screw rotating speed of the extruder is 15-20 rpm, the liquid solvent is ethanol and is introduced into the extruder at a solvent injection rate of 2-3 mL/min, the extrusion pressure is 105-115 bar, and the temperature is 240-370° C.

9. The method of claim 8 , wherein when the thermoset plastic waste is XLPE, the thermoset plastic waste is introduced into the extruder at the thermoset feed rate of 30 g/min, the screw rotating speed of the extruder is 15 rpm, the liquid solvent is ethanol and is introduced into the extruder at the solvent injection rate of 3 mL/min, the extrusion pressure is 105 bar, and the temperature is 240-310° C.

10. The method of claim 8 , wherein when the thermoset plastic waste is XLPE, the thermoset plastic waste is introduced into the extruder at the thermoset feed rate of 20 g/min, the screw rotating speed of the extruder is 20 rpm, the liquid solvent is ethanol and is introduced into the extruder at the solvent injection rate of 2 mL/min, the extrusion pressure is 115 bar, and the temperature is 250-370° C.

11. The method of claim 2 , wherein when the thermoset plastic waste is phenolic resin, the thermoset plastic waste is introduced into the extruder at a thermoset feed rate of 15-20 g/min, a screw rotating speed of the extruder is 20-30 rpm, the liquid solvent is ethanol and is introduced into the extruder at a solvent injection rate of 5 mL/min, the extrusion pressure is 80-96 bar, and the temperature is 240-320° C.

12. The method of claim 11 , wherein when the thermoset plastic waste is phenolic resin, the thermoset plastic waste is introduced into the extruder at the thermoset feed rate of 20 g/min, the screw rotating speed of the extruder is 20 rpm, the extrusion pressure is 80 bar, and the temperature is 240-300° C.

13. The method of claim 11 , wherein when the thermoset plastic waste is phenolic resin, the thermoset plastic waste is introduced into the extruder at the thermoset feed rate of 15 g/min, the screw rotating speed of the extruder is 30 rpm, the extrusion pressure is 96 bar, and the temperature is 260-320° C.

14. The method of claim 2 , wherein when the thermoset plastic waste is epoxy resin, the thermoset plastic waste is introduced into the extruder at a thermoset feed rate of 16-21 g/min, a screw rotating speed of the extruder is 15-25 rpm, the liquid solvent is ethanol and is introduced into the extruder at a solvent injection rate of 5 mL/min, the extrusion pressure is 80-96 bar, and the temperature is 230-330° C.

15. The method of claim 14 , wherein when the thermoset plastic waste is epoxy resin, the thermoset plastic waste is introduced into the extruder at the thermoset feed rate of 21 g/min, the screw rotating speed of the extruder is 15 rpm, the extrusion pressure is 80 bar, and the temperature is 230-310° C.

16. The method of claim 14 , wherein when the thermoset plastic waste is epoxy resin, the thermoset plastic waste is introduced into the extruder at the thermoset feed rate of 16 g/min, the screw rotating speed of the extruder is 25 rpm, the extrusion pressure is 96 bar, and the temperature is 260-330° C.

17. The method of claim 1 , wherein a screw rotating speed of the extruder is in a range of 1-80 rpm.

18. The method of claim 1 , wherein the thermoset plastic waste is extruded out from the extruder in less than 5 minutes.

19. The method of claim 1 , wherein purifying the thermoset plastic waste comprises:

mixing the thermoset plastic waste in the cleaning agent selected from a group consisting of water, methanol, ethanol, isopropyl alcohol and a mixture thereof;

cleaning the thermoset plastic waste in ultrasonic bath at a temperature of 40-80° C. for 10-30 minutes;

filtering the thermoset plastic waste through a filtration mesh so that contaminants in the thermoset plastic waste are removed; and

drying the thermoset plastic waste for further extrusion.