A method for preparing fine paste reclaimed rubber

Abstract

The present application relates to a kind of preparation methods of fine paste reclaimed rubber, belong to waste rubber recycling field.The preparation method is first to waste rubber powder uniform preheating penetration swelling, then by continuous closed heat preservation conveying metering device is added into same direction double screw extruder, dense material is under the action of temperature and shear force in extruder, the three-dimensional crosslinking network of waste rubber is fully broken, and the rapid devulcanization regeneration of waste rubber is realized;The obtained material is connected into millstone crusher, and the mutual friction between the moving millstone and the fixed millstone and the material is utilized at low temperature, further refinement is carried out, finally the material is cooled by forming device and cooling device, and the required fine paste reclaimed rubber product is obtained by packaging.The production process has the advantages of safe operation, simple, continuous, energy saving and environmental protection, and the paste rubber obtained has good fineness and little odor, and can be widely used in modified asphalt, waterproofing membrane and rubber products.

Description

Technical Field

[0001] This invention relates to fine paste reclaimed rubber, and more particularly to a method for preparing fine paste reclaimed rubber using a screw extruder and a grinding disc pulverizer, belonging to the field of waste rubber recycling. Background Technology

[0002] Reclaimed rubber has become the third most widely used type of rubber after natural and synthetic rubber. Since its inception, the fineness of reclaimed rubber has consistently influenced its application. In actual production, unless there are specific requirements for the product's appearance, the fineness requirements for molded rubber products are generally not very high. However, when reclaimed rubber is used in extruded products, good extrusion performance and surface smoothness are necessary, thus requiring a higher fineness of the rubber powder. This led to the concept of fine reclaimed rubber. Fineness reflects the uniformity of desulfurization in reclaimed rubber, primarily encompassing two aspects: the macroscopic uniformity of desulfurization among individual rubber particles (plasticity (Mounney viscosity value) directly affects the smoothness of the product; excessive viscosity makes mixing and extrusion difficult); and the uniformity of desulfurization within and outside individual rubber particles, i.e., the "core-shell" structure. In the traditional production of reclaimed rubber from waste tires, when high fineness is required, three methods are often employed: selecting waste rubber powder with smaller particle sizes; using a fine-pitch refining mill to further refine "underdeveloped" particles; and filtering out larger "underdeveloped" particles using a filter. The ultrafine tire reclaimed rubber produced is dense, smooth, free of impurities, and glossy, both on the surface and cross-section of the rubber block. In contrast, the surface or cross-section of ordinary tire reclaimed rubber of 30-40 mesh is much rougher. Therefore, reclaimed rubber product manufacturers can make a preliminary judgment on the fineness of the reclaimed rubber by visual inspection.

[0003] In recent years, with the gradual phasing out of traditional high-temperature and high-pressure dynamic desulfurization tank methods, atmospheric pressure continuous desulfurization and regeneration methods have been promoted. Liquid (paste) reclaimed rubber or low Mooney viscosity reclaimed rubber has gradually emerged and entered the market, but it also faces many technical challenges. Although the degree of desulfurization has increased, the different application scenarios mean that the fineness issue remains unavoidable. For example, Zhang Liqun et al., in CN102601975B "A Method for Continuous Preparation of Liquid Reclaimed Rubber Using a Screw Extruder," selected a rubber powder particle size of 0.1–10 mm, believing that the desired reclaimed rubber could be obtained directly from the screw extruder head without subsequent refining processes, greatly reducing energy consumption; however, they did not realize the unavoidable undercooked rubber particles during the desulfurization process. Zhang Jianwu et al., in CN201910308916.6 "A Low Mooney Viscosity Reclaimed Rubber Granule and Its Preparation Method and Applications," prepared reclaimed rubber granules with a Mooney viscosity (ML100℃1+4) of 15-40 and a sol content greater than 30%. These granules are suitable for use in waterproof membranes or road construction, where the fineness of the liquid adhesive is not critical. The process involves selecting a particle size of 10-80 mesh, preheating the rubber powder at high temperature using a high-speed mixer, then kneading and mixing it in a kneader and cooling it to below 160℃. The mixture is then fed into a screw extruder for further mixing, and finally granulated using a die-cutting underwater pelletizer to obtain low Mooney viscosity reclaimed rubber granules. However, under such high temperature conditions, thermo-oxidative aging of the rubber powder is inevitable.

[0004] For other types of reclaimed rubber, especially liquid reclaimed rubber which also has fineness issues, it is necessary to design solutions based on principles under new requirements in order to expand their application scope. Summary of the Invention

[0005] This invention provides a method for preparing fine paste reclaimed rubber. By rationally designing the regeneration process and adjusting the refining method, the fine paste reclaimed rubber prepared solves the problem of refining low-viscosity reclaimed rubber.

[0006] This invention is achieved through the following process: A method for preparing fine paste-like reclaimed rubber, firstly, 10-40 mesh waste rubber powder is mixed and stirred in a mixer, and the temperature is raised to 100℃-150℃ within 1-3 minutes. Then, a softener is added, and the mixture is stirred for another 3-5 minutes to reach 140℃-160℃ to ensure thorough mixing. The mass ratio of the waste rubber powder to the softener is 100:(2-8). Then, the mixed material is fed into a co-rotating twin-screw extruder through a continuous, sealed, and insulated conveyor for desulfurization reaction. The reaction conditions are 200℃-350℃, and the reaction is carried out for 1-3 minutes. The material is then extruded from the co-rotating twin-screw extruder and fed into a grinding disc crusher for fine grinding. The grinding disc temperature is 5℃-50℃. After 1-3 minutes, the paste-like reclaimed rubber is extruded. The material is then cooled to below 60℃ by a molding device and a cooling device before final packaging to obtain the desired fine paste-like reclaimed rubber product.

[0007] The preferred waste rubber powder is one of waste tire rubber powder, waste ethylene propylene rubber, or waste butyl rubber.

[0008] The preferred softener is one or a mixture of aromatic oil pitch, pine tar pitch, tall oil pitch.

[0009] The preferred co-rotating twin-screw extruder consists of a combination of threaded conveying elements, kneading elements of different structures, and a screw mandrel, with a length-to-diameter ratio of 32 to 48, and is equipped with a barrel exhaust mechanism.

[0010] The preferred co-rotating twin-screw extruder has a heating section temperature of 200℃~250℃, a reaction section temperature of 250℃~350℃, and a cooling section temperature of 200℃~250℃.

[0011] The preferred grinding disc gap of the crusher is 0.1 mm to 0.3 mm.

[0012] The preferred fine paste regenerated adhesive product has a sol content greater than 60%, a number-average molecular weight (Mn) of 7000–18000, and a molecular weight distribution of 5–10.

[0013] Beneficial effects:

[0014] This invention improves the uniformity of waste rubber powder by selecting waste rubber powder with appropriate particle size and optimizing the preheating and mixing process of waste rubber powder and softener. The uniformly mixed and preheated material, at a lower temperature, reduces the generation of hard particles and "core-shell" structures under shearing action, and also avoids excessive desulfurization degradation caused by high temperatures. This transforms most of the three-dimensional network structure of rubber hydrocarbons into short-chain hydrocarbons. Then, in a small-gap, low-temperature disc crusher, the insufficiently desulfurized "underdeveloped" particles are further refined. This invention supplements the previous method of evaluating fineness solely by examining the outer surface of the rubber compound, selecting an evaluation index with a higher correlation to fineness as the basis, thus better quantifying the uniformity of desulfurization. The resulting fine paste reclaimed rubber product is more refined and has better uniformity. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0016] Among them, 1. mixer, 2. continuous closed heat-insulated conveying device, 3. co-rotating twin-screw extruder, and 4. grinding disc crusher. Detailed Implementation

[0017] 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. The equipment described are all conventional production equipment.

[0018] A method for preparing fine paste-like reclaimed rubber involves first mixing 10-40 mesh waste rubber powder in a mixer 1, heating it to 100-150°C within 1-3 minutes, then adding a softener, and continuing mixing for 3-5 minutes to reach 140-160°C for thorough mixing. The mass ratio of waste rubber powder to softener is 100:(2-8). The mixed material is then fed through a continuous, sealed, insulated conveyor 2 into a co-rotating twin-screw extruder 3 for desulfurization. The reaction conditions are 200-350°C for 1-3 minutes, after which the material is extruded from the co-rotating twin-screw extruder 3 and fed into a grinding disc crusher 4 for fine grinding. The grinding disc temperature in the crusher 4 is 5-50°C. After 1-3 minutes, the paste-like reclaimed rubber is extruded. The material is then cooled to below 60°C by a molding and cooling device before final packaging to obtain the desired fine paste-like reclaimed rubber product. All equipment involved in this method is conventional production equipment. Figure 1 The continuous closed heat-insulated conveying device 2 shown is a pipe with an outer heat-insulating layer. One end of it is connected to the discharge end of the mixer 1, and the other end is connected to the feed end of the co-rotating twin-screw extruder 3. The discharge end of the co-rotating twin-screw extruder 3 is connected to the grinding disc crusher 4.

[0019] Example 1

[0020] 100 parts by weight of 40-mesh waste tire rubber powder were heated to 130°C in a mixer within 3 minutes. Then, 8 parts by weight of aromatic oil asphalt were added, and mixing continued for 5 minutes until the temperature reached 145°C. The mixed material was then fed into a co-rotating twin-screw extruder with a length-to-diameter ratio of 48 via a continuous, enclosed, insulated conveyor for desulfurization. The heating section was at 200°C, the reaction section at 300°C, and the cooling section at 200°C for 2 minutes. After reacting for 2 minutes, the material entered a disc crusher with a 0.1mm gap and a disc temperature of 10°C. After 1.5 minutes, a paste-like reclaimed rubber was extruded. The material was then cooled to 43°C using a molding and cooling device before final packaging to obtain the desired fine paste-like reclaimed rubber product. The resulting product had a sol content of 65%, a number-average molecular weight (Mn) of 18000, and a molecular weight distribution of 5.

[0021] Example 2

[0022] 100 parts by weight of 20-mesh waste tire tread rubber powder were heated to 100°C in a mixer within 2 minutes. Then, 6 parts by weight of aromatic oil asphalt were added, and mixing continued for 3 minutes until the temperature reached 140°C. The mixed material was then conveyed via a continuous, enclosed, insulated conveyor into a co-rotating twin-screw extruder with a length-to-diameter ratio of 40 for desulfurization. The heating section was at 200°C, the reaction section at 280°C, and the cooling section at 200°C for 1.5 minutes. After this reaction, the material entered a disc crusher with a 0.15mm gap and a disc temperature of 20°C. After 2.5 minutes, a paste-like reclaimed rubber was extruded. The material was then cooled to 40°C using a molding and cooling device before final packaging to obtain the desired fine paste-like reclaimed rubber product. The resulting product had a sol content of 80%, a number-average molecular weight (Mn) of 7000, and a molecular weight distribution of 10.

[0023] Example 3

[0024] 100 parts by weight of 10-mesh waste butyl rubber powder were heated to 150°C in a mixer within 1 minute. Then, 2 parts by weight of tall oil asphalt were added, and mixing continued for 3 minutes until the temperature reached 160°C. The mixed material was then conveyed via a continuous, enclosed, insulated conveyor into a co-rotating twin-screw extruder with a length-to-diameter ratio of 36 for desulfurization. The reaction was carried out at 220°C in the heating section, 350°C in the reaction section, and 210°C in the cooling section for 3 minutes. After 3 minutes, the material entered a disc crusher with a 0.3mm gap and a disc temperature of 50°C. After 3 minutes, a paste-like reclaimed rubber was extruded. The material was then cooled to 50°C using a molding and cooling device before final packaging to obtain the desired fine paste-like reclaimed rubber product. The resulting product had a sol content of 75%, a number-average molecular weight (Mn) of 10,000, and a molecular weight distribution of 9.

[0025] Example 4

[0026] 100 parts by weight of 20-mesh waste ethylene propylene rubber powder were heated to 120°C in a mixer within 2 minutes. Then, 4 parts by weight of pine tar pitch were added, and mixing continued for 4 minutes until the temperature reached 150°C. The mixed material was then conveyed via a continuous, enclosed, insulated conveyor into a co-rotating twin-screw extruder with a length-to-diameter ratio of 32 for desulfurization. The heating section was at 250°C, the reaction section at 320°C, and the cooling section at 200°C for 1 minute. After reacting, the material entered a 0.2mm gap disc crusher at 5°C. After 2 minutes, a paste-like reclaimed rubber was extruded. The material was then cooled to 55°C using a molding and cooling device before final packaging to obtain the desired fine paste-like reclaimed rubber product. The resulting product had a sol content of 70%, a number-average molecular weight (Mn) of 9500, and a molecular weight distribution of 6.

[0027] The results of Examples 1, 2, 3, and 4 above are shown in the table below:

[0028]

[0029] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0030] In summary, the present invention achieves the expected results.

Claims

1. A method for preparing fine paste-like reclaimed rubber, characterized in that... The method first involves mixing 10-40 mesh waste rubber powder in a mixer and heating it to 100-150°C within 1-3 minutes. Then, a softener is added, and the mixture is stirred for another 3-5 minutes until it reaches 140-160°C to ensure thorough mixing. The mass ratio of waste rubber powder to softener is 100:(2-8). The mixed material is then conveyed through a continuous, sealed, and insulated conveyor to a co-rotating twin-screw extruder for desulfurization. The reaction conditions are 200-350°C for 1-3 minutes, after which the material is extruded from the co-rotating twin-screw extruder and fed into a grinding disc crusher for fine grinding. The grinding disc temperature is 5-50°C. After 1-3 minutes, a paste-like reclaimed rubber is extruded. The material is then cooled to below 60°C by a molding and cooling device before final packaging to obtain the desired fine paste-like reclaimed rubber product. The grinding disc gap of the crusher used is 0.1 mm to 0.3 mm; The prepared fine paste reclaimed rubber product has a sol content of more than 60%, a number-average molecular weight (Mn) of 7000–18000, and a molecular weight distribution of 5–10.

2. The method according to claim 1, characterized in that... The waste rubber powder used is one of the following: waste tire rubber powder, waste ethylene propylene rubber, or waste butyl rubber.

3. The method according to claim 1, characterized in that... The softener is one or a mixture of aromatic oil asphalt, pine tar asphalt, tall oil asphalt, or a mixture thereof.

4. The method according to claim 1, characterized in that: The co-rotating twin-screw extruder has an aspect ratio of 32 to 48, a heating and exhaust section temperature of 200°C to 250°C, a reaction section temperature of 250°C to 350°C, and a cooling section temperature of 200°C to 250°C.

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