A method for continuously preparing high-performance reclaimed rubber at low cost and high efficiency

Abstract

The present application relates to a kind of low cost, high efficiency continuously preparing high performance reclaimed rubber method, belong to waste and old rubber recycling field.Utilize two double screw extruders in series to complete deep desulfurization process and mixing reaction process, in the first extruder, waste rubber is formed under the action of high shear and temperature and contains a large amount of high temperature fluid rubber mixture rich in light oil gas, good fluidity, into the second double screw extruder, part of fluid rubber mixture completes penetration reaction to rubber powder inside quickly, realizes the effective use of heat, and makes desulfurization regeneration reaction can be carried out quickly.The whole preparation process is completed under the condition of closed oxygen isolation, and the performance of the obtained reclaimed rubber is excellent;The main equipment used is double-stage double screw extruder, and has the advantages of safe and simple continuous operation, energy saving and environmental protection.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of waste and old rubber recycling, and particularly relates to a method for continuously preparing high-performance reclaimed rubber with low cost and high efficiency. BACKGROUND

[0002] Rubber is a strategic resource. In 2020, China imported a total of 7.468 million tons of natural and synthetic rubber (including latex), and the total production of natural rubber in China in 2020 was only 693,000 tons, with a very low self-sufficiency rate, far from meeting the demand of the rubber industry in China. Reclaimed rubber should be the priority and main force of resource disposal, which is also determined by the national conditions of China. Reclaimed rubber was listed as one of the three strategic resources of the rubber industry together with synthetic rubber and natural rubber by the Ministry of Industry and Information Technology of China in 2012. According to incomplete statistics, the production of reclaimed rubber in China reached 4.6 million tons in 2021.

[0003] After years of development and technological innovation, the reclaimed rubber industry has formed a desulfurization and regeneration process mainly based on "high temperature and high pressure dynamic desulfurization". The desulfurization reaction is completed in a desulfurization tank, and the regenerant and water are added together into the desulfurization tank, the working pressure is about 2.2 MPa, the working temperature is about 220℃, and after 3 hours of desulfurization, the pressure is released and cooled to obtain desulfurized rubber powder, which is then pressed into sheets by 3-4 high-speed refining machines to obtain reclaimed rubber. From the desulfurization reaction mechanism, high temperature and high pressure dynamic desulfurization belongs to chemical regeneration, that is, under the action of external heat, the activator penetrates into the waste rubber with the aid of the softener and reacts with it, destroys the crosslinked network, and becomes a quasi-linear process that can be processed again. However, the penetration of the regenerant into the waste rubber is completed in high temperature and high pressure for a long time, which has serious safety hazards and high energy consumption. Desulfurized rubber powder needs to be cooled from high temperature to room temperature by external cooling, and the refining process requires continuous low temperature, resulting in a large amount of energy consumption. According to the statistics of the association at the present stage, the energy consumption of waste tire reclaimed rubber is generally 600 degrees of electricity per ton, and the refining stage accounts for ~60%. The reclaimed rubber factory in the industry is still in the stage of "small and scattered", which cannot promote the coordinated development of the actual demand of the production and downstream use of reclaimed rubber, resulting in the disconnection between the preparation of reclaimed rubber products and the downstream use.

[0004] At present, both the products and the production methods are in an important stage of upgrading and transformation. Zhang Liqun et al. in "CN102601975B A method for continuously preparing liquid reclaimed rubber by using a screw extruder" proposed a kind of liquid reclaimed rubber product. Under the combined action of temperature, pressure, shear and desulfurizer in the extruder, the three-dimensional crosslinked network of waste rubber is broken, and liquid reclaimed rubber is obtained. The waste rubber powder is fully desulfurized and depolymerized to regenerate. The obtained liquid reclaimed rubber can be used with asphalt or instead of asphalt for paving roads, and with pure rubber for making waterproof and corrosion-resistant materials. The whole process is continuous and has low energy consumption. The mechanical properties are not mentioned, but highly cracked waste rubber is also not too likely to have high mechanical properties.

[0005] In the waste rubber modified asphalt industry, it has been recognized that the high Mooney viscosity of waste rubber powder or traditional reclaimed rubber is difficult to disperse, and the process of combining with asphalt processing makes the rubber powder degrade during the use of rubber asphalt processing, the temperature provides the energy required to destroy the main bond and crosslinking bond of rubber, the chemical activity of oxygen is improved, the strength of vulcanized rubber is reduced, and the degradation of rubber network macromolecules is promoted. Compared with the preparation of reclaimed rubber from waste rubber, although both are the treatment and utilization of waste rubber, the research mechanism and invention point are different. For example, Zhang Jianwu et al. in "A low Mooney viscosity reclaimed rubber particle and its preparation method and use" in order to solve the process problems of easy addition, fast dispersion and high content of rubber powder in asphalt at low temperature (<180℃), use a high-speed mixer to make the waste rubber powder react quickly, then mix in a kneader, then use a screw extruder to extrude, and then granulate underwater to get a low Mooney viscosity reclaimed rubber particle. The Mooney viscosity of the obtained reclaimed rubber is 15-40, which is still a traditional industry reclaimed rubber, only as an additive added to asphalt. In Jiang Kuan et al. "A kind of composite waste rubber powder particle modified asphalt which can be stored stably and its preparation method", it is hoped that the linear macromolecules in the high desulfurization degree reclaimed rubber of the composite waste rubber powder particle are uniformly wrapped on the surface of the rubber powder, and the micro-crosslinking effect of the crosslinking agent is used to form a "core-shell" structure of linear macromolecular crosslinking structure. It is beneficial to the storage stability of rubber asphalt. The composite waste rubber powder particle for modifying asphalt is prepared: the low mesh rubber powder is first deeply desulfurized and degraded by using the high temperature and strong shear action of a double screw extruder to prepare a high desulfurization degree reclaimed rubber, and then the high mesh rubber powder, the high desulfurization degree reclaimed rubber and a small amount of crosslinking agent are mixed in a certain proportion by using the low temperature and blending action of a single screw extruder to prepare a modified asphalt. More attention is paid to the compatibility of waste rubber and asphalt.

[0006] In order to adapt to the development trend of energy saving and consumption reduction, combined with various technical methods for recycling waste rubber, it is particularly urgent to develop new low-cost, low-energy-consumption and high-efficiency methods for preparing reclaimed rubber. SUMMARY

[0007] In order to solve the defects existing in the background, the purpose of the application proposes a method for continuously preparing regenerated rubber at low cost and high efficiency. The process of the method is continuous, closed and environmentally friendly, and has outstanding energy-saving effect, and the obtained regenerated rubber has excellent performance, and is suitable for popularization and use.

[0008] In order to achieve the above-mentioned purpose, the technical solution of the application is as follows:

[0009] A method for continuously preparing high-performance regenerated rubber at low cost and high efficiency, comprising a deep desulfurization process and a mixing reaction process, wherein the deep desulfurization process is to add 10-20 mesh waste rubber powder and desulfurizing agent according to 100: (0.5-5) mass parts into the first co-rotating twin screw extruder with exhaust device, and carry out desulfurization reaction, the reaction conditions are 250℃-400℃ for 1min-6min, then extruded from the first co-rotating twin screw extruder, the obtained material is directly mixed in the second co-rotating twin screw extruder, and 200-500 mass parts of 40-80 mesh waste rubber powder is mixed at 100℃-200℃ for 2min-5min, to obtain regenerated rubber with a Mooney viscosity of 40-70, and then cooled to below 50℃ by a cooling device, and finally packaged to obtain the required regenerated rubber product.

[0010] Preferably, the waste rubber powder is one or a mixture of several of waste tire tread rubber powder, waste tire whole tire rubber powder and waste tire top rubber powder.

[0011] Preferably, the desulfurizing agent is one or a mixture of two of 2-mercaptobenzothiazole and 2,2'-dithiodibenzothiazole.

[0012] Preferably, the length-diameter ratio of the first co-rotating twin screw extruder is 24:1-52:1.

[0013] Preferably, the temperature of the heating exhaust section of the first co-rotating twin screw extruder is 250℃-300℃, and the temperature of the heat preservation section is 250℃-400℃.

[0014] Preferably, the length-diameter ratio of the second twin screw extruder is 16:1-32:1, and the temperature of the mixing section is 100℃-200℃.

[0015] Beneficial effects:

[0016] 1. This invention first desulfurizes the rubber powder in a deep desulfurization process, forming a fluid rubber mixture rich in light oil and gas at high temperatures and with good flowability. In the second mixing and reaction process, this mixture, with its good compatibility with waste rubber powder, acts as a softener and desulfurizer, rapidly penetrating into the rubber powder to complete the reaction. This achieves efficient heat utilization while enabling the desulfurization and regeneration reaction to proceed quickly. Unlike the traditional reclaimed rubber industry, which involves high-temperature desulfurization followed by low-temperature refining and significant energy consumption, this method fully utilizes the oil and gas and heat generated during deep desulfurization as an aid and energy source for the second-stage desulfurization reaction, ensuring product performance while significantly reducing energy consumption in the production process.

[0017] 2. This solution, based on practical experience in rubber powder production within the industry, recognizes that finer rubber powder increases grinding costs. It rationally selects waste rubber powder of different particle sizes as raw materials. In the first co-rotating twin-screw extruder, under the combined action of high temperature and high shear, the large molecular network of coarse rubber powder is fully disrupted, minimizing "core-shell" structures or hard particles. Meanwhile, the fine waste rubber powder added in the second extruder, under weak shear conditions, can complete the thorough mixing and penetration reaction in a shorter time, avoiding the impact of high shear heat on performance. This ensures the normal operation of the regeneration process while reducing temperature rise, which helps reduce energy consumption in the subsequent cooling section. The selected desulfurizing agent is also a commonly used accelerator in the industry, capable of generating highly reactive free radicals under high temperature and high shear conditions, accelerating the reaction and improving production efficiency.

[0018] 3. By employing two different twin-screw extruders that meet the requirements of high shear and high mixing effects, multiple changes in material flow direction and velocity are achieved, realizing a closed, continuous, and automated process. Through optimized formulation and processes, and a rationally designed process flow, energy consumption is significantly reduced. The entire preparation process is completed under closed, oxygen-free conditions, resulting in reclaimed rubber with excellent performance and the advantages of safe, simple, continuous, energy-saving, and environmentally friendly operation. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] In the description of this invention, it should be understood that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," "link," "fix," etc., should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] In addition, the terms "first", "second", etc. are used only for descriptive purposes and should not be construed as implying or suggesting relative importance or an indicated number of technical features. Thus, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features, and in the description of the present application, the meaning of "a plurality" is two or more, unless otherwise explicitly and specifically limited.

[0022] The first and second same-direction double screw extruders in the application are connected in series, that is, the discharge port of the first same-direction double screw extruder is connected to the feeding port of the second same-direction double screw extruder. The two series-connected double screw extruders complete the deep desulfurization process and the mixing reaction process. The material in the first same-direction double screw extruder forms a fluid rubber mixture containing a large amount of light oil gas at high temperature and having good fluidity under the action of high shear and temperature. The fluid rubber mixture is connected to the second same-direction double screw extruder. Part of the fluid rubber mixture quickly completes the penetration reaction into the rubber powder, realizes the effective use of heat, and enables the desulfurization regeneration reaction to be quickly carried out. The entire preparation process is completed under airtight and oxygen-free conditions. The regenerated rubber has excellent performance. The main equipment used is a common double-stage double screw extruder. The selected equipment can meet the reaction conditions of the application and is not specifically limited. The present scheme has the advantages of safe and simple operation, continuity, energy saving, and environmental protection.

[0023] Example 1

[0024] 10 kg of waste tire tread rubber powder and 2-mercaptobenzothiazole were added to a first same-direction double screw extruder with an exhaust device and a length-diameter ratio of 36:1 at a mass ratio of 100:3. The heating and exhaust section of the first same-direction double screw extruder was at a temperature of 250℃, and the holding section was at a temperature of 300℃. After 1 min of reaction, the material was extruded from the first same-direction double screw extruder into a second same-direction double screw extruder with a length-diameter ratio of 24:1. The material was mixed with 300 kg of 80 mesh waste rubber powder at 130℃ for 5 min to obtain regenerated rubber with a Mooney viscosity of 60. The regenerated rubber was cooled to 43℃ by a cooling device, and finally packaged to obtain the desired regenerated rubber product.

[0025] Example 2

[0026] The 16 mesh waste tire top rubber powder and 2, 2'-dithiodibenzothiazole are added into the first co-rotating twin screw extruder with exhaust device in a mass ratio of 100:0.5, the heating exhaust section temperature of the first co-rotating twin screw extruder is 300℃, the holding section temperature is 400℃, after 5 minutes of reaction, the product is extruded from the first co-rotating twin screw extruder into the second co-rotating twin screw extruder with a length-diameter ratio of 16:1, and then mixed with 500 parts by mass of 80 mesh waste rubber powder at 150℃ for 2 minutes of reaction to obtain regenerated rubber with a Mooney viscosity of 70, and then cooled to 40℃ by a cooling device to obtain the desired regenerated rubber product.

[0027] Example 3

[0028] The 20 mesh waste tire whole tire rubber powder, 2-mercaptobenzothiazole and 2, 2'-dithiodibenzothiazole are added into the first co-rotating twin screw extruder with exhaust device in a mass ratio of 100:2.5:2.5, the heating exhaust section temperature of the first co-rotating twin screw extruder is 260℃, the holding section temperature is 370℃, after 3 minutes of reaction, the product is extruded from the first co-rotating twin screw extruder into the second co-rotating twin screw extruder with a length-diameter ratio of 32:1, and then mixed with 200 parts by mass of 40 mesh waste rubber powder at 120℃ for 3 minutes of reaction to obtain regenerated rubber with a Mooney viscosity of 40, and then cooled to 35℃ by a cooling device to obtain the desired regenerated rubber product.

[0029] Comparative Example 1

[0030] The 22 mesh waste tire whole tire rubber powder, 2-mercaptobenzothiazole and 2, 2'-dithiodibenzothiazole are added into the first co-rotating twin screw extruder with exhaust device in a mass ratio of 300:2.5:2.5, and 0.6 parts by mass of water is added into the desulfurization tank, the product is discharged after 3.2 hours of reaction at a working pressure of 2.3 MPa and a working temperature of 210℃ to obtain desulfurized rubber powder, and then refined by a refiner to obtain regenerated rubber with a Mooney viscosity of 42, and then packaged to obtain the desired regenerated rubber product.

[0031] The data of the above-mentioned Example 1, Example 2, Example 3 and Comparative Example 1 are shown in the following table:

[0032] Product performance and energy consumption

[0033]

[0034] The above examples are only for illustrating the technical concept and characteristics of the present application, the purpose is to enable the person skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application, any equivalent changes or modifications made according to the spirit and essence of the present application should be covered within the protection scope of the present application.

[0035] The present application achieves the intended effects.

Claims

1. A method for continuous production of high performance reclaimed rubber at low cost and high efficiency, characterized in that The method comprises a deep desulfurization process and a mixing reaction process, wherein the deep desulfurization process is that 10-20 mesh waste rubber powder and a desulfurizer are added into a first co-rotating twin-screw extruder with an exhaust device according to 100:(0.5-5) mass parts, a desulfurization reaction is carried out, the reaction condition is 250-400 DEG C for 1-6 min, then the obtained material is directly introduced into a second co-rotating twin-screw extruder for mixing reaction, and 200-500 mass parts of 40-80 mesh waste rubber powder is mixed at 100-200 DEG C for 2-5 min to obtain regenerated rubber with a Mooney viscosity of 40-70, then the regenerated rubber is cooled to below 50 DEG C through a cooling device, and finally the regenerated rubber product is obtained after packaging. The desulfurizer is one of 2-mercaptobenzothiazole and 2,2'-dithiodibenzothiazole or a mixture of the two.

2. The method of claim 1, characterized by The waste rubber powder is one of waste tire tread rubber powder, waste tire whole tire rubber powder and waste tire top rubber powder or a mixture of the three.

3. The method of claim 1, wherein The length-diameter ratio of the first co-rotating twin-screw extruder is 24:1-52:

1.

4. The method according to claim 1 or 3, characterized in that The temperature of the heating exhaust section of the first co-rotating twin-screw extruder is 250-300 DEG C, and the temperature of the heat preservation section is 250-400 DEG C.

5. The method of claim 1, wherein The length-diameter ratio of the second co-rotating twin-screw extruder is 16:1-32:1, and the temperature of the mixing section is 100-200 DEG C.

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