Preparation method of regenerated rubber with high tensile strength

Abstract

The invention provides a preparation method of regenerated rubber with high tensile strength, and belongs to the field of rubber production and manufacturing. The method comprises the following steps: step 1, simultaneously adding waste rubber powder and environment-friendly oil into a first co-rotating twin-screw extruder for multiple times according to a mass part ratio of 100: (4-10) to obtain mixed oil rubber powder; and 2, feeding the mixed oil rubber powder into a second planetary screw extruder, carrying out continuous desulfurization regeneration under a closed oxygen isolation condition, cooling, and carrying out a refining process to prepare the high-strength regenerated rubber. According to the invention, the environment-friendly oil with better compatibility with the waste rubber powder is selected, and the heat transfer effect of the waste rubber powder from outside to inside is accelerated under the condition that matched equipment is connected in series, so that the desulfurization uniformity is greatly improved, and the high-strength environment-friendly regenerated rubber is obtained.

Description

Technical Field

[0001] The invention relates to a regenerated rubber manufacturing technology, in particular to a method for preparing regenerated rubber with high tensile strength, and belongs to the technical field of regenerated rubber production and manufacturing. Background Art

[0002] After years of development and technological innovation, the reclaimed rubber industry has formed a desulfurization and regeneration process based on "high temperature and high pressure dynamic desulfurization". The desulfurization reaction is completed in the desulfurization tank. The regeneration agent and water are added to the desulfurization tank together. The working pressure is about 2.2MPa, the working temperature is about 220℃, and the desulfurization time is about 2.5 hours. After decompression and cooling, the desulfurized rubber powder is obtained, and then 3 to 4 high-speed double-roller refiners are used to press the reclaimed rubber to obtain the reclaimed rubber. A large amount of wastewater and waste gas is generated when the material is discharged after the reaction, so there are many safety hazards; at the same time, intermittent operation and unorganized emission of flue gas are also difficult to collect and treat. The high energy consumption and high pollution disadvantages of the "dynamic desulfurization tank" in the production of recycled rubber have become synonymous with secondary pollution in the comprehensive utilization of waste rubber industry.

[0003] Many continuously closed desulfurization and regeneration technical equipment such as high-speed mixers, screw extruders, and spiral plasticizers have emerged in the industry. The desulfurization formula generally still uses the additives used in dynamic desulfurization tanks. Changes in equipment and processes have caused them to be unable to play their original role. The prepared regenerated rubber has a certain gap with the traditional desulfurization tank in terms of smell, fineness, Mooney viscosity rebound, etc. At the same time, with the continuous improvement of environmental protection requirements, it is imperative to eliminate the original toxic and harmful additives. CN102977404B uses the linkage technology equipment of twin-screw continuous desulfurization extruder and screw continuous refining extruder to replace the traditional intermittent high-temperature and high-pressure dynamic desulfurization tank and open high-speed refiner preparation technology equipment. There is no water in the desulfurization formula, and the original intermittent operation is changed into continuous production. Regenerated rubber is prepared by continuous green desulfurization under closed conditions. However, coal tar, pine tar, tall oil, etc. are used as softeners, and the activator is still a mixture of one or more of aromatic disulfide, polyalkylphenol sulfide, phenyl mercaptan, and amino compounds. The additives used in the prior art are not environmentally friendly, and the desulfurization tank used in the past would cause unorganized emissions and unsafe production.

[0004] Therefore, only by developing new recycling equipment and matching formulas and process conditions can recycled rubber products with higher tensile strength be obtained. Summary of the invention

[0005] The invention provides a novel method for preparing recycled rubber with high tensile strength. By selecting environmentally friendly oil with better compatibility with waste rubber powder, the heat transfer effect of the waste rubber powder from the outside to the inside can be accelerated, so as to solve the technical problem that low-cost high-strength recycled rubber cannot be produced in the prior art.

[0006] The method for preparing recycled rubber with high tensile strength according to the embodiment of the present invention comprises the following steps:

[0007] In the first step, waste rubber powder and environmentally friendly oil are added into the first co-rotating twin-screw extruder at the same time in a mass ratio of 100:4 to 10 for multiple times to obtain mixed oil rubber powder;

[0008] In the second step, the mixed oil rubber powder is sent to the second planetary screw extruder for continuous desulfurization and regeneration under closed oxygen-proof conditions. After cooling and refining process, high-strength recycled rubber can be prepared.

[0009] The method for preparing recycled rubber with high tensile strength as described above, wherein the particle size of the waste rubber powder is 20 to 60 meshes; the waste rubber powder is obtained by crushing waste rubber tires and removing impurities;

[0010] The environmentally friendly oil has an aromatic content greater than 80% and a kinematic viscosity of 30 to 70 at 100°C;

[0011] The mass ratio of the waste rubber powder to the environmentally friendly oil is 100:6-8.

[0012] The method for preparing recycled rubber with high tensile strength as described above, wherein the aspect ratio of the first co-rotating twin-screw extruder is 28 to 48:1;

[0013] The temperature of the heating section is 150℃~220℃, the temperature of the mixing section is 220℃~280℃, the temperature of the insulation section is 150~220℃; the mixing time is 1-10min;

[0014] The first co-rotating twin-screw extruder has three feeding ports; the environmentally friendly oil is added to the three feeding ports in a mass ratio of 1:1.5-2:2-5 in sequence; and the time interval between additions is not less than 20 seconds.

[0015] In the method for preparing recycled rubber with high tensile strength as described above, the temperature of the second planetary screw extruder is set to 200-240° C., and the reaction time is 4-6 min.

[0016] The method for preparing recycled rubber with high tensile strength as described above, wherein a high-speed refiner or a screw extruder is used in the refining process, and the refining temperature is controlled at 0-60°C.

[0017] In the method for preparing recycled rubber with high tensile strength as described above, the screw extruder is a twin-screw or multi-screw extruder.

[0018] In the method for preparing recycled rubber with high tensile strength as described above, the waste rubber tires include any one or more combinations of all-steel load-bearing tires, passenger car tires, bias load-bearing tires and light truck tires.

[0019] The embodiments of the present invention have at least the following beneficial effects:

[0020] After comparing the traditional high-temperature and high-pressure dynamic desulfurization technology with the normal-pressure desulfurization technology, combined with the current industry status, the previous environmentally unfriendly regeneration additives were abandoned, and the acceleration of the heat transfer effect in the desulfurization process was taken as the breakthrough point. The softener with higher thermal conductivity quickly penetrated into the waste rubber powder, which greatly improved the poor thermal conductivity of the waste rubber, making the desulfurization degree more uniform, and the rubber hydrocarbon molecular weight of the prepared recycled rubber was higher, which could obtain higher tensile strength and better environmental protection indicators.

[0021] Taking advantage of the flexible and changeable geometric arrangement of the screw extruder, the first co-rotating twin-screw extruder added softener in multiple stages to achieve better mixing effect. The planetary screw extruder has a long residence time and good temperature control effect to meet the heat transfer requirements for a longer time. The entire process is isolated from the presence of oxygen. The tandem screw extruder unit has a short time, high efficiency, and a continuous and automated process, which saves labor and makes the production process stable and controllable. DETAILED DESCRIPTION

[0022] The method for preparing recycled rubber with high tensile strength of the present invention can be made of the following materials and components, but is not limited to the following materials and components, for example: environmentally friendly oil, waste rubber powder, screw extruder, etc.

[0023] The method for preparing recycled rubber with high tensile strength according to the embodiment of the present invention comprises the following steps:

[0024] In the first step, waste rubber powder and environmentally friendly oil are added into the first co-rotating twin-screw extruder at a mass ratio of 100:4 to 10 for multiple times to obtain oil-mixed rubber powder; the particle size of the waste rubber powder is 20 to 60 meshes; the waste rubber powder is obtained by crushing waste rubber tires and removing impurities;

[0025] The environmentally friendly oil has an aromatic content greater than 80% and a kinematic viscosity of 30 to 70 at 100°C;

[0026] The mass ratio of the waste rubber powder to the environmentally friendly oil is 100:6-8.

[0027] The length-to-diameter ratio of the first co-rotating twin-screw extruder is 28-48:1; the temperature of the heating section is 150-220°C, the temperature of the mixing section is 220-280°C, the temperature of the insulation section is 150-220°C; the mixing time is 1-10 min;

[0028] The first co-rotating twin-screw extruder has three feeding ports; the environmentally friendly oil is added in the three feeding ports in a mass ratio of 1:1.5~2:2~5 in order; the time interval between additions is not less than 20 seconds. When adding oil in small amounts and multiple times, a small amount of oil is added first so that it can contact with a large amount of rubber powder and quickly penetrate into the rubber powder. The gradually added oil is actually added to the rubber powder that has been "filled with oil". According to the principle of similar compatibility, the later it is added, the faster it can penetrate into the rubber powder. Because different parts of the tire contain different amounts of oil, the addition ratio is different, and the ratio of adding in three times is also different.

[0029] The waste rubber tires include any one or more combinations of all-steel load-bearing tires, passenger car tires, bias load-bearing tires and light truck tires.

[0030] In the second step, the mixed oil rubber powder is sent to the second planetary screw extruder for continuous desulfurization and regeneration under closed oxygen-proof conditions. After cooling and refining process, high-strength recycled rubber can be prepared.

[0031] The temperature of the second planetary screw extruder is set at 200-240° C., and the reaction time is 4-6 min.

[0032] In the refining process, a high-speed refiner or a screw extruder is used, and the refining temperature is controlled at 0-60°C.

[0033] The screw extruder is a twin-screw or multi-screw extruder.

[0034] Example 1

[0035] After the whole waste bias truck tire is crushed and impurities are removed to obtain 40 mesh rubber powder, 100phr of the waste rubber powder is added to the first co-rotating twin-screw extruder with a length-to-diameter ratio of 48:1, and 10phr of environmentally friendly oil with an aromatic content of 81% and a kinematic viscosity of 70 is added to the extruder in three times in a ratio of 1:2:5 through a side feeding device. After mixing for 5 minutes under the conditions of a heating section temperature of 160°C, a mixing section temperature of 160°C, and a heat preservation section temperature of 160°C, the extruder is fed into a second planetary screw extruder, reacted at 240°C for 6 minutes, and after cooling, refined at 10°C by a double-roll refiner to obtain a recycled rubber with a Mooney viscosity of 55.

[0036] Example 2

[0037] After the tire top of the waste all-steel load-bearing tire is crushed and impurities are removed to obtain 30-mesh rubber powder, 100phr of the waste rubber powder is added into the first co-rotating twin-screw extruder with a length-to-diameter ratio of 32:1, and 6phr of environmentally friendly oil with an aromatic content of 82.3% and a kinematic viscosity of 46 is added into the extruder in three times in a ratio of 1:1.7:3 through a side feeding device. After mixing for 3 minutes under the conditions of a heating section temperature of 140°C, a mixing section temperature of 150°C, and a heat preservation section temperature of 150°C, the extruder is fed into the second planetary screw extruder, reacted at 220°C for 5 minutes, cooled, and refined by a twin-screw at 30°C to obtain recycled rubber with a Mooney viscosity of 57.

[0038] Example 3

[0039] After the tread of the waste all-steel truck tire is crushed and impurities are removed to obtain 22-mesh rubber powder, 100phr of the waste rubber powder is added to the first co-rotating twin-screw extruder with a length-to-diameter ratio of 28:1, and 4phr of environmentally friendly oil with an aromatic content of 85% and a kinematic viscosity of 30 is added to the extruder in three times in a ratio of 1:1.5:2 through a side feeding device. After mixing for 1 minute under the conditions of a heating section temperature of 100°C, a mixing section temperature of 120°C, and a heat preservation section temperature of 140°C, the rubber is fed into a second planetary screw extruder, reacted at 200°C for 4 minutes, cooled, and refined by a three-screw extruder at 30°C to obtain recycled rubber with a Mooney viscosity of 60.

[0040] Comparison 1

[0041] 100 parts of 20-mesh waste all-steel truck tire tread rubber powder; 10 parts of aromatic oil asphalt; 0.5 parts of activator B480; 0.45 parts of rosin; 0.12 parts of water. Stir the rubber powder, activator and rosin evenly and put them into an electrically heated desulfurization tank, then add water, pass 1.6Mpa high-pressure steam, and keep the temperature at 225℃ for 2.5 hours to obtain desulfurized rubber powder; cool the desulfurized rubber powder to below 45℃ through a cooling conveyor; then refine the desulfurized rubber powder through a refiner and produce flakes to obtain recycled rubber with a Mooney viscosity of 55.

[0042]

[0043] The present invention has at least the following beneficial effects:

[0044] After comparing the traditional high-temperature and high-pressure dynamic desulfurization technology with the normal-pressure desulfurization technology, combined with the current industry status, the previous environmentally unfriendly regeneration additives were abandoned, and the acceleration of the heat transfer effect in the desulfurization process was taken as the breakthrough point. The softener with higher thermal conductivity quickly penetrated into the waste rubber powder, which greatly improved the poor thermal conductivity of the waste rubber, making the desulfurization degree more uniform, and the rubber hydrocarbon molecular weight of the prepared recycled rubber was higher, which could obtain higher tensile strength and better environmental protection indicators.

[0045] Taking advantage of the flexible and changeable geometric arrangement of the screw extruder, the first twin-screw extruder added softener in multiple stages to achieve better mixing effect. The planetary screw extruder has a long residence time and good temperature control effect to meet the heat transfer needs for a longer time. The entire process is isolated from the presence of oxygen. The tandem screw extruder unit has a short time, high efficiency, and a continuous and automated process, which saves labor and makes the production process stable and controllable.

[0046] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages and disadvantages of the embodiments. Through the description of the above implementation methods, those skilled in the art can clearly understand that the above embodiment methods can be implemented by means of some deformations plus the necessary general technology superposition; of course, they can also be implemented by simplifying some important technical features. Based on this understanding, the technical solution of the present invention is essentially or contributes to the prior art in the following aspects: the overall structure and connection method, and the structure described in each embodiment of the present invention.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing recycled rubber with high tensile strength, characterized in that: The following steps are involved: In the first step, waste rubber powder and environmentally friendly oil are added into the first co-rotating twin-screw extruder at the same time in a mass ratio of 100:4 to 10 for multiple times to obtain mixed oil rubber powder; In the second step, the mixed oil rubber powder is sent to the second planetary screw extruder for continuous desulfurization and regeneration under closed oxygen-proof conditions. After cooling and refining process, high-strength recycled rubber can be prepared.

2. The method for preparing recycled rubber with high tensile strength according to claim 1, characterized in that: The particle size of the waste rubber powder is 20-60 meshes; the waste rubber powder is obtained by crushing waste rubber tires and removing impurities; The environmentally friendly oil has an aromatic content greater than 80% and a kinematic viscosity of 30 to 70 at 100°C; The mass ratio of the waste rubber powder to the environmentally friendly oil is 100:6-8.

3. The method for preparing recycled rubber with high tensile strength according to claim 1, characterized in that: The first co-rotating twin-screw extruder has an aspect ratio of 28 to 48:1; The temperature of the heating section is 150℃~220℃, the temperature of the mixing section is 220℃~280℃, the temperature of the insulation section is 150~220℃; the mixing time is 1-10min; The first co-rotating twin-screw extruder has three feeding ports; the environmentally friendly oil is added to the three feeding ports in a mass ratio of 1:1.5-2:2-5 in sequence; and the time interval between additions is not less than 20 seconds.

4. The method for preparing recycled rubber with high tensile strength according to claim 1, characterized in that: The temperature of the second planetary screw extruder is set at 200-240° C., and the reaction time is 4-6 min.

5. The method for preparing recycled rubber with high tensile strength according to claim 1, characterized in that: In the refining process, a high-speed refiner or a screw extruder is used, and the refining temperature is controlled at 0-60°C.

6. The method for preparing recycled rubber with high tensile strength according to claim 5, characterized in that: The screw extruder is a twin-screw or multi-screw extruder.

7. The method for preparing recycled rubber with high tensile strength according to claim 2, characterized in that: The waste rubber tires include any one or more combinations of all-steel load-bearing tires, passenger car tires, bias load-bearing tires and light truck tires.

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