Automatic devulcanizing and plasticizing device and method for using same
Rubber to be recycled is first ground to rubber crumb and then is transferred to a plasticizing unit. The rubber to be recycled is mixed with chemicals including an aromatic, environmental-friendly, low volatility reaction oil, a thickening agent and an activator. This mixture is heated to a desired temperature under anaerobic conditions and then is maintained at that temperature for a suitable time. The processed material is then transferred to a cooling unit in which it is cooled to a temperature below 60° C. prior to being released from the machine.
1. A method of recycling rubber comprising:
(a) grinding a quantity of rubber to be recycled to a particle size between −10 mesh to −40 mesh, thereby producing rubber crumb;
(b) providing a rubber plasticizing machine comprising a plasticizing unit comprising a plasticizing conveyor and a cooling unit comprising a cooling conveyor;
(c) transferring the rubber crumb into the plasticizing unit;
(d) mixing the rubber crumb with chemicals, thereby producing a mixture, said chemicals comprising a residual aromatic extract oil, a viscosity increaser and an activator;
(e) heating the mixture in the plasticizing unit to a temperature between 200-250° C. and maintaining the mixture at said temperature for a pre-determined period of time;
(f) transferring the mixture from the heating unit to the cooling unit;
(g) cooling the mixture in the cooling unit to a temperature below 60° C.; and
(h) releasing the mixture from the cooling unit.
2. The method according to claim 1 wherein the rubber is ground such that at least 50% of the rubber crumb passes through a screen with a mesh size of 40.
3. The method according to claim 1 , wherein following step (a), calcium carbonate is added to the rubber crumb at 0.1-5% (w/w) of the rubber crumb.
4. The method according to claim 1 wherein the plasticizing unit and the cooling unit are air tight so that rubber crumb is plasticized under anaerobic conditions.
5. The method according to claim 1 wherein the chemicals and the rubber crumb are mixed by the plasticizing conveyor.
6. The method according to claim 1 wherein the aromatic oil is a low volatility aromatic oil.
7. The method according to claim 1 wherein the residual aromatic extract oil is added at 5-30% (v/w) of the rubber crumb.
8. The method according to claim 1 wherein the residual aromatic extract oil is added at 15-20% (v/w) of the rubber crumb.
9. The method according to claim 1 wherein prior to step (d) the residual aromatic extract oil is heated to a temperature between 55-65° C.
10. The method according to claim 1 where in the viscosity increaser is natural gum rosin.
11. The method according to claim 10 wherein the natural gum rosin has a chemical formula of C 19 H 29 COOH.
12. The method according to claim 10 wherein the rosin is added at 0.5-5% (v/w) of the rubber crumb.
13. The method according to claim 1 wherein the activator is a mixture of an activating agent selected from 420 or 450 and a plasticizing agent selected from 480 and 510.
14. The method according to claim 1 wherein the activator is a mixture of pentachlorothiophenol and stearic acid.
15. The method according to claim 14 wherein the activator is 30-45% pentachlorothiophenol and 55-70% stearic acid.
16. The method according to claim 1 wherein the activator is added at 0.05-0.8% (v/w) of the rubber crumb.
17. The method according to claim 1 wherein the predetermined time is 5-15 minutes.
18. The method according to claim 1 wherein at step (g) the mixture is cooled to a temperature below 50° C.
19. The method according to claim 1 wherein at step (g) the mixture is cooled to a temperature below 40° C.
20. The method according to claim 1 wherein the plasticizing unit comprises a plurality of plasticizing chambers connected in series.
21. The method according to claim 20 wherein each respective one of the plurality of plasticizing chambers is heated to a temperature lower than the adjacent next plasticizing chamber in series.
22. The method according to claim 1 wherein the cooling unit comprises a plurality of cooling chambers connected in series.
23. The method according to claim 22 wherein each respective one of the plurality of cooling chambers is cooled to a temperature lower than the adjacent next cooling chamber in series.
24. The method according to claim 1 wherein steps (c)-(g) are carried out anaerobically.