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

Abstract

The invention relates to a method of preparing reclaimed rubber, especially using multi-stage screw extruders, which belongs to the field of recycling and reusing of waste rubber. The rubber powder and softener which were preliminarily mixed are compacted and added into first counter rotating twin screw extruder through thermal insulation and metering apparatus, the softener permeates the waste rubber powder uniformly under the action of temperature in the extruder to finish primary desulfurization of rubber waste powder; add preliminary devulcanized material continuously into second multi screw extruder after cooling by transformation device, rapid desulfurization and regeneration can be achieved by means of activator and shear action; The desulfurized rubber powder is cooled and transported into the third multi-screw extruder in series, the performance of deprocessing can be improved by shear action under low temperature; After extrusion, the recycled rubber is obtained by molding device and cooling device. The whole process is completed under closed oxygen isolation condition, realizing safe, simple and continuous desulfurization regeneration. It is energy saving and environmental protection with excellent properties.

Claims

1. 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.

2. Method of continuous preparation of reclaimed rubber using multi-stage screw extruders in claim 1, wherein the multi screw extruder is a co-rotating twin screw extruder or a parallel triple screw extruder.

3. Method of continuous preparation of reclaimed rubber using multi-stage screw extruders in claim 1, wherein in the counter rotating twin screw extruder, the temperature of heating and exhaust zone, holding zone and cooling zone is in the range of 120° C. to 200° C., 200° C. to 340° C. and 100° C. to 200° C., respectively.

4. Method of continuous preparation of reclaimed rubber using multi-stage screw extruders in claim 1, wherein in the second multi screw extruder, the temperature of mixing zone, shear zone and cooling zone is in the range of 40° C. to 70° C., 70° C. to 90° C., and 30° C. to 60° C., respectively.

5. Method of continuous preparation of reclaimed rubber using multi-stage screw extruders in claim 1, wherein in the third multi screw extruder, the temperature of first conveying zone, pre-shear zone, second conveying zone, second shear zone and third conveying zone is in the range of 0° C. to 25° C., 5° C. to 40° C., 5° C. to 25° C., −5° C. to 35° C., and 0° C. to 45° C., respectively.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a process flow diagram illustrating how multi-stage extruders connect and work to produce reclaimed rubber in the present invention.

(2) 1. Thermal insulation and metering apparatus, 2. First motor, 3. First reducer, 4. Counter rotating twin screw, 5. Counter rotating twin screw extruder barrel, 6. Cooling conveying apparatus, 7. Second motor, 8. Second reducer, 9. Multiple-screw 1, 10. Multiple-screw barrel 1, 11. Third motor, 12. Third reducer, 13. Multiple-screw 2, 14. Multiple-screw barrel 2, 15. Cooling conveying apparatus, 16. Package apparatus

(3) FIG. 2 is a counter rotating twin screw extruder diagram wherein softener permeates into the waste rubber powder.

(4) FIG. 3 is a co-rotating tri-screw extruder diagram.

(5) FIG. 4 is a co-rotating twin-screw extruder diagram.

(6) 1. Motor, 2. Coupling, 3. Reducer, 4. Counter rotating twin screw, 5. Barrel, 6. Base

DETAILED DESCRIPTION OF THE EMBODIMENT

(7) The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. The following is a further description of the invention. Phr means mass percent unless otherwise stated.

Example 1

(8) Add 10 phr coal tar and 10 phr pine tar as softener, 100 phr waste radial truck tire tread rubber powder into mixer and stir for 8 minutes at 60° C., and then the prepared material is continuously conveyed to counter rotating twin screw extruder through enclosed, thermal insulation conveying metering apparatus. The temperature of heating and exhaust zone, holding zone and cooling zone of the counter rotating twin screw extruder is at 180° C., 230° C. and 160° C. respectively. After staying in extruder for 2 minutes, preliminary devulcanized powder with Mooney viscosity 195 is obtained. The preliminary devulcanized powder is cooled down to 50° C. by the following cooling conveyor and subsequently transported into co-rotating twin screw extruder. Add 0.1 phr activator 2,2′-bisthio-bis(4-methyl-6-t-butylphenol) from side feeding. The temperature of mixing zone, shear zone and cooling zone of the co-rotating twin screw extruder are at 45° C., 70° C. and 35° C. respectively. Devulcanization reaction time lasts 3 minutes and devulcanized rubber powder with Mooney viscosity 110 is extruded. The devulcanized rubber powder is continuously feed into parallel tri-screw extruder through cooling conveying apparatus under enclosed condition. Temperature of first conveying zone, pre-shear zone, second conveying zone, second shear zone and third conveying zone of the parallel tri-screw extruder are at 15° C., 30° C., 20° C., 15° C. and 10° C. respectively, and the mandrel temperature is at 10° C. Refine the devulcanized rubber powder for 3 minutes under shear condition, and refining process is finished as the reclaimed rubber is extruded from the parallel tri-screw extruder and passes molding apparatus and cooling apparatus to 40° C. Mooney viscosity of the obtained reclaimed rubber is 53.

(9) TABLE-US-00001 Mooney viscosity Tensile Ash Acetone ML100° C. strength Elongation content % extract % (1 + 4 min) MPa % Example 1 7.5 16.8 53 16.3 535 GB/T15340- ≤10 ≤18 ≤95 ≥14 ≥420 2008, TA1

Example 2

(10) Add 2 phr tall oil and 3 phr pine tar as softener, 100 phr waste radial truck tire tread rubber powder into mixer and stir for 15 minutes at 80° C., and then the prepared material is continuously conveyed to counter rotating twin screw extruder through enclosed, thermal insulation conveying metering apparatus. The temperature of heating and exhaust zone, holding zone and cooling zone of the counter rotating twin screw extruder is at 160° C., 280° C. and 120° C. respectively. After staying in extruder for 5 minutes, preliminary devulcanized powder with Mooney viscosity 180 is obtained. The preliminary devulcanized powder is cooled down to 60° C. by the following cooling conveyor and subsequently transported into co-rotating twin screw extruder. Add 3.0 phr activator diphenyldisulfide from side feeding. The temperature of mixing zone, shear zone and cooling zone of the co-rotating twin screw extruder are at 55° C., 80° C. and 40° C. respectively. Devulcanization reaction time lasts 3 minutes and devulcanized rubber powder with Mooney viscosity 100 is extruded. The devulcanized rubber powder is continuously feed into parallel tri-screw extruder through cooling conveyor under enclosed condition. Temperature of first conveying zone, pre-shear zone, second conveying zone, second shear zone and third conveying zone of the parallel tri-screw extruder are at 15° C., 30° C., 20° C., 25° C. and 15° C. respectively, and the mandrel temperature is at 10° C. Refine the devulcanized rubber powder for 3 minutes under shear condition, and refining process is finished as the reclaimed rubber is extruded from the parallel tri-screw extruder and passes molding apparatus and cooling apparatus to 40° C. Mooney viscosity of the obtained reclaimed rubber is 53.

(11) TABLE-US-00002 Mooney viscosity Tensile Ash Acetone ML100° C. strength Elongation content % extract % (1 + 4 min) MPa % Example 2 6.2 13.5 62 15.1 480 GB/T15340- ≤10 ≤18 ≤95 ≥14 ≥420 2008, TA1

(12) Project Case 3:

(13) Add 8 phr tall oil, 6 phr pine tar and 4 phr rosin as softener, 100 phr waste radial truck tire tread rubber powder into mixer and stir for 20 minutes at 100° C., and then the prepared material is continuously conveyed to counter rotating twin screw extruder through enclosed, thermal insulation conveying metering apparatus. The temperature of heating and exhaust zone, holding zone and cooling zone of the counter rotating twin screw extruder is at 160° C., 260° C. and 140° C. respectively. After staying in extruder for 5 minutes, preliminary devulcanized powder with Mooney viscosity 160 is obtained. The preliminary devulcanized powder is cooled down to 55° C. by the following cooling conveyor and subsequently transported into co-rotating twin screw extruder. Add 0.2 phr activator n-butylamine from side feeding. The temperature of mixing zone, shear zone and cooling zone of the co-rotating twin screw extruder are at 65° C., 90° C. and 50° C. respectively. Devulcanization reaction time lasts 3 minutes and devulcanized rubber powder with Mooney viscosity 90 is extruded. The devulcanized rubber powder is continuously feed into parallel tri-screw extruder through cooling conveyor under enclosed condition. Temperature of first conveying zone, pre-shear zone, second conveying zone, second shear zone and third conveying zone of the parallel tri-screw extruder are at 5° C., 15° C., 10° C., 20° C. and 15° C. respectively, and the mandrel temperature is at 15° C. Refine the devulcanized rubber powder for 2 minutes under shear condition, and refining process is finished as the reclaimed rubber is extruded from the parallel tri-screw extruder and passes molding apparatus and cooling apparatus to 30° C. Mooney viscosity of the obtained reclaimed rubber is 50.

(14) TABLE-US-00003 Mooney viscosity Tensile Ash Acetone ML100° C. strength Elongation content % extract % (1 + 4 min) MPa % Example 3 7.0 14.2 50 15.0 485 GB/T15340- ≤10 ≤18 ≤95 ≥14 ≥420 2008, TA1