Method of continuous preparation of reclaimed rubber using multi-stage screw extruders

Method of continuous preparation of reclaimed rubber using multi-stage screw extruders, comprising:

• first, mixing waste rubber powder and softener in a mixer for 5 to 25 minutes at 60° C. to 120° C. to obtain a mixture, then the mixture being transported into a thermal insulation buffer tank kept at 60° C.˜120° C., and fed into a first counter rotating twin screw extruder through a thermal insulation and metering apparatus, which stays for 1 to 6 minutes at 100° C. to 340° C. in the extruder to complete uniform penetration of the softener into the waste rubber powder and preliminary devulcanization, cooling to 40 to 80° C. under airtight conditions in a continuous cooling apparatus to obtain a preliminary devulcanized material with Mooney viscosity of 100 to 230, adding the preliminary devulcanized material continuously into a second multi screw extruder through the thermal insulation and metering apparatus, adding a devulcanizing agent through a side feeding apparatus and controlling the temperature of a barrel and mandrel of the multi screw extruder at 20 to 110° C., proceeding devulcanization reaction for 1 to 6 minutes and extruding devulcanized rubber powder with Mooney viscosity of 70˜150, cooling the devulcanized rubber powder to 25° C. to 60° C. under airtight condition in a continuous cooling apparatus, continuously adding the devulcanized rubber powder into a third multi screw extruder, controlling the temperature of barrel and mandrel of the multi screw extruder at −5 to 50° C. and refine the devulcanized rubber powder for 1 to 10 minutes under shear condition, wherein refining process is finished as the reclaimed rubber is extruded from the third extruder and passes a molding apparatus and a cooling apparatus to cool to below 50° C., the required reclaimed rubber is obtained after package;
• wherein
• the mass ratio between waste rubber powder, softener and devulcanizing agent is 100:(2˜20):(0.01˜3);
• softener is one or several mixtures of coal tar, aromatic hydrocarbon oil, pine tar, tall oil, dipentene, paraffin oil, oleic acid, cottonseed oil, rosin, said devulcanizing agent is one of an aromatic hydrocarbon disulfide, a multi alkyl phenol sulfide, a phenylmercaptan, an amine compound, or combinations thereof;
• waster rubber powder is one kind of waste radial truck tire powder, waste passenger car tire powder, or combinations thereof.