Method for preparing rubber compound by recycling waste rubber and prepared rubber compound

Abstract

The invention relates to the technical field of waste rubber recovery, in particular to a method for preparing a rubber compound by recycling waste rubber and the prepared rubber compound. The high-shear mechanical desulfurization technology is combined, the desulfurization efficiency is further improved through the synergistic effect of various components in the compound auxiliary, and meanwhile the plasticity of the waste rubber and the compatibility of the waste rubber and new rubber are enhanced. The method not only can effectively destroy the cross-linked structure of the waste rubber, but also can be used for preparing a high-performance rubber compound product by mixing the waste rubber with a new rubber material through a subsequent mixing process, and is widely applied to manufacturing high-strength and wear-resistant rubber products, such as solid tires and the like.

Description

Technical Field

[0001] The invention relates to the technical field of waste rubber recycling, in particular to a method for preparing a rubber mix by recycling waste rubber and the prepared rubber mix. Background Art

[0002] As an important elastic material, rubber is widely used in many fields such as automobile tires, seals, industrial pipes and conveyor belts. However, with the widespread use of rubber products, the generation of a large number of waste rubber products has led to environmental pollution problems. Due to its highly vulcanized cross-linked structure, waste rubber is difficult to degrade naturally. Traditional landfill and incineration treatment methods not only waste resources, but also cause pollution to the soil and air. Therefore, how to effectively recycle and reuse waste rubber has become an important direction of current research.

[0003] The core challenge of recycling waste rubber lies in the cross-linked structure of vulcanized rubber, which gives rubber products excellent mechanical properties and durability, but also limits its recycling. Existing waste rubber recycling technologies include chemical desulfurization, thermomechanical treatment, and physical crushing. However, traditional chemical desulfurization processes often require the use of a large amount of chemical reagents, which has problems of environmental pollution and high energy consumption, while simple physical crushing is difficult to completely destroy the cross-linked structure of rubber, resulting in poor performance of recycled rubber.

[0004] In recent years, high shear mechanical desulfurization has attracted wide attention due to its high efficiency and relatively environmentally friendly characteristics. This method applies high shear force to waste rubber, combined with appropriate chemical additives, which can effectively destroy the vulcanization cross-linking bonds of rubber and restore the plasticity and processing properties of rubber. Compared with traditional desulfurization methods, high shear mechanical desulfurization can reduce the use of chemicals and has the advantages of low energy consumption and strong environmental protection. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing a rubber compound by recycling waste rubber based on a compound chemical desulfurization auxiliary agent, combining high shear mechanical desulfurization technology, and further improving the desulfurization efficiency through the synergistic effect of multiple components in the compound auxiliary agent, while enhancing the plasticity of the waste rubber and the compatibility with new rubber. This method can not only effectively destroy the cross-linked structure of the waste rubber, but also can be mixed with new rubber materials through a subsequent mixing process to prepare a high-performance rubber compound product, which is widely used in the manufacture of high-strength and wear-resistant rubber products, such as solid tires.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: A method for preparing a rubber compound by recycling waste rubber, the method comprising the following steps: a) pre-treating the waste rubber, including crushing it into particles or powder with a particle size of 1-10 mm; b) adding the pretreated waste rubber to a high shear mechanical desulfurization device, and adding a compound chemical desulfurization aid, wherein the compound chemical desulfurization aid comprises, based on 100 parts of the waste rubber: 1-Butyl-3-methylimidazolium hexafluorophosphate: 1.0-2.0 phr; Chemical desulfurizer: 1.0-3.0phr; Plasticizer: 2.0-4.0phr; Compatibilizer: 0.5-1.5phr; c) performing mechanical desulfurization treatment at a shear rate of 500-1500 rpm, a temperature of 140-180° C., and a pressure of 2-5 MPa for 15-30 minutes; d) Cooling the desulfurized waste rubber to room temperature for subsequent treatment.

[0007] The waste rubber described in the present invention mainly includes waste automobile tires, waste engineering vehicle tires, conveyor belts, and scraps and waste generated in the production process of rubber products.

[0008] Preferably, the high shear mechanical desulfurization equipment is a twin-screw extruder or a high shear internal mixer.

[0009] Preferably, the chemical desulfurizer is a combination of dibenzothiazole disulfide and a mercaptan compound. Preferably, the mercaptan compound includes a mixture of one or more of thioglycolic acid, dipropionic acid disulfide, 2-mercaptoethanol, mercaptoethylamine, thioacetamide and mercaptobenzothiazole.

[0010] Preferably, the plasticizer is epoxidized vegetable oil or a citrate plasticizer. The citrate plasticizer is selected from one or a mixture of triethyl citrate, triethyl acetyl citrate, tributyl citrate, tributyl acetyl citrate, triisononyl citrate, tri(2-ethylhexyl) citrate, and triisooctyl citrate.

[0011] Preferably, the compatibilizer is one or more of a silane coupling agent, a titanate coupling agent, and a zirconate coupling agent.

[0012] As further preferred embodiment, the compatibilizer is a silane coupling agent Si69.

[0013] Preferably, the method further comprises adding new rubber material to the cooled devulcanized rubber, wherein the new rubber material is selected from natural rubber (NR), styrene-butadiene rubber (SBR) or butadiene rubber (BR), and is mixed with the devulcanized rubber in a ratio of 50-70%.

[0014] Preferably, after the devulcanized rubber is mixed with the new rubber, it is kneaded in an internal mixer or an open mixer at a temperature of 140-160° C. for 5-10 minutes.

[0015] Preferably, carbon black is added as a reinforcing agent to the mixture of the desulfurized waste rubber and new rubber, and the amount of carbon black is 20-40 phr based on 100 parts by weight of the total rubber.

[0016] Furthermore, the invention also discloses a rubber compound prepared by the method.

[0017] The present invention adopts the above-mentioned technical scheme, combined with high shear mechanical desulfurization technology, and further improves the desulfurization efficiency through the synergistic effect of multiple components in the compound additive, while enhancing the plasticity of waste rubber and compatibility with new rubber. In particular, 1-butyl-3-methylimidazole hexafluorophosphate is used, which has good solubility and chemical stability, can effectively penetrate the rubber molecular structure, and help dissolve the vulcanized cross-linking bonds in the rubber. Its strong polarity enables it to interact with the sulfur-sulfur (SS) cross-linking bonds or sulfur-carbon (SC) bonds in the rubber to promote the breaking of the cross-linking bonds. Without excessively damaging the main chain structure of the rubber. In this way, the plasticity and mechanical properties of the rubber material can be maintained, which is conducive to the mixing of recycled rubber and new rubber, so that the final mixed rubber product has good mechanical properties and durability. This method can not only effectively destroy the cross-linking structure of waste rubber, but also can be mixed with new rubber materials through subsequent mixing processes to prepare high-performance mixed rubber products, which are widely used in the manufacture of high-strength and wear-resistant rubber products, such as solid tires. Specifically include the following points: 1. Efficient desulfurization: By using a compound chemical desulfurization aid, especially a combination of 1-butyl-3-methylimidazolium hexafluorophosphate, a chemical desulfurizer, a plasticizer and a compatibilizer, the vulcanization cross-linking bonds of waste rubber can be effectively destroyed during the high shear mechanical desulfurization process, greatly improving the desulfurization efficiency. Compared with the traditional single chemical or mechanical desulfurization method, the technology of the present invention can achieve efficient desulfurization at lower temperature and pressure, reduce the use of chemicals, reduce environmental pollution, and improve the recycled quality of rubber.

[0018] 2. Improved rubber plasticity: The present invention can effectively reduce the viscosity of waste rubber during the desulfurization process by adding plasticizers, enhance its fluidity and plasticity, and ensure that the desulfurized rubber has good processing performance. The waste rubber treated by the desulfurization method not only maintains excellent physical properties, but also can be more evenly mixed with new rubber materials, which is suitable for subsequent processing and reuse.

[0019] 3. Enhanced compatibility: The introduction of compatibilizers (such as silane coupling agents, titanate and zirconate coupling agents, etc.) effectively improves the interfacial bonding between waste rubber and new rubber materials, allowing the two to be better combined during the mixing process, thereby improving the mechanical properties of the mixed rubber. This improved compatibility enables the prepared mixed rubber to have higher strength, wear resistance and fatigue resistance, and is particularly suitable for high-strength and high-wear-resistant rubber products, such as solid tires.

[0020] 4. Environmental protection and energy consumption reduction: The present invention can significantly reduce the use of chemical desulfurizers and reduce waste gas and wastewater pollution generated in traditional processes by combining high-shear mechanical desulfurization technology with compound chemical additives. In addition, the mechanical desulfurization process operates at lower temperature and pressure, and has lower energy consumption than traditional thermal desulfurization processes, which meets the current green and environmentally friendly industrial development requirements.

[0021] 5. Improve the performance of the mixed rubber: In the present invention, waste rubber and new rubber materials are mixed in proportion, and combined with reinforcing agents such as carbon black. The mixed rubber prepared by the subsequent mixing process shows excellent performance in tensile strength, wear resistance, tear resistance, etc., and is suitable for manufacturing high-demand rubber products such as industrial tires, seals and shock-absorbing elements.

[0022] In summary, the present invention not only effectively solves the problem of recycling waste rubber, significantly improves the desulfurization efficiency, the plasticity of rubber and the mechanical properties of the mixed rubber, but also has the advantages of low energy consumption and strong environmental protection, meets the needs of modern industrial green circular economy, and has broad application prospects. DETAILED DESCRIPTION

[0023] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1 1. Recipe: Devulcanized waste rubber: 50 parts Natural rubber: 50 parts Carbon black N330: 40 parts Accelerator CZ: 1.0 part Sulfur: 2.0 parts Antioxidant IPPD: 1.0 part.

[0025] Compound chemical desulfurization additive: 1-Butyl-3-methylimidazolium hexafluorophosphate: 1.5 parts Dibenzothiazyl disulfide (MBTS): 1.5 parts Epoxidized vegetable oil: 3.0 parts Silane coupling agent Si69: 1.0 part.

[0026] 2. Preparation process: 1) Pretreatment of waste rubber: The waste tire rubber is cleaned and crushed. The particle size of the crushed rubber particles is 5-6 mm.

[0027] 2) Add the waste rubber into a twin-screw extruder, add a compound chemical desulfurization aid, and carry out high shear mechanical desulfurization for 20 minutes at 150°C, a shear rate of 1000 rpm, and a pressure of 3 MPa.

[0028] 3) The devulcanized rubber was mixed with natural rubber in a ratio of 50:50, carbon black, accelerator, sulfur and antioxidant were added, and mixed in an internal mixer at 150°C for 7 minutes.

[0029] 4) The mixed rubber compound was vulcanized at 155°C for 30 minutes to prepare a solid tire rubber compound sample.

[0030] Example 2 1. Recipe: Devulcanization of waste rubber: 60 parts Natural rubber: 40 parts Carbon black N330: 45 parts Accelerator CZ: 1.5 parts Sulfur: 2.2 parts Antioxidant IPPD: 1.5 parts.

[0031] Compound chemical desulfurization additive: 1-Butyl-3-methylimidazolium hexafluorophosphate: 1.0 part 2-Mercaptoethanol: 2.0 parts Tributyl citrate: 2.5 parts Silane coupling agent Si69: 1.0 part.

[0032] 2. Preparation process: 1) Pretreatment of waste rubber: The waste tire rubber is cleaned and crushed. The particle size of the crushed rubber particles is 5-6 mm.

[0033] 2) Add the waste rubber into a twin-screw extruder, add a compound chemical desulfurization aid, and carry out high shear mechanical desulfurization for 20 minutes at 150°C, a shear rate of 1200 rpm, and a pressure of 3 MPa.

[0034] 3) The devulcanized rubber was mixed with natural rubber in a ratio of 60:40, carbon black, accelerator, sulfur and antioxidant were added, and mixed in an internal mixer at 150°C for 7 minutes.

[0035] 4) The mixed rubber compound was vulcanized at 155°C for 30 minutes to prepare a solid tire rubber compound sample.

[0036] Example 3 1. Recipe: Devulcanized waste rubber: 45 parts Natural rubber: 55 parts Carbon black N330: 35 parts Accelerator CZ: 1.0 part Sulfur: 1.8 parts Antioxidant IPPD: 1.0 part.

[0037] Compound chemical desulfurization additive: 1-Butyl-3-methylimidazolium hexafluorophosphate: 1.5 parts Mercaptoethylamine: 1.5 parts Triethylhexyl citrate: 3.0 parts Silane coupling agent Si69: 1.2 parts.

[0038] 2. Preparation process: 1) Pretreatment of waste rubber: The waste tire rubber is cleaned and crushed. The particle size of the crushed rubber particles is 5-6 mm.

[0039] 2) Add the waste rubber into a twin-screw extruder, add a compound chemical desulfurization aid, and carry out high shear mechanical desulfurization for 25 minutes at 160°C, a shear rate of 1500 rpm, and a pressure of 3 MPa.

[0040] 3) The devulcanized rubber was mixed with natural rubber in a ratio of 45:55, carbon black, accelerator, sulfur and antioxidant were added, and the mixture was mixed in an internal mixer at 150°C for 7 minutes.

[0041] 4) The mixed rubber compound was vulcanized at 155°C for 30 minutes to prepare a solid tire rubber compound sample.

[0042] Comparative Example 1 1. Recipe: Devulcanized waste rubber: 50 parts Natural rubber: 50 parts Carbon black N330: 40 parts Accelerator CZ: 1.0 part Sulfur: 2.0 parts Antioxidant IPPD: 1.0 part.

[0043] Chemical desulfurization additives: MBTS: 2.0 phr Epoxidized vegetable oil: 3.0phr Silane coupling agent Si69: 1.0phr.

[0044] 2. Preparation process: 1) Pretreatment of waste rubber: The waste tire rubber is cleaned and crushed. The particle size of the crushed rubber particles is 5-6 mm.

[0045] 2) The waste rubber was added into a twin-screw extruder, a chemical desulfurization aid was added, and mechanical desulfurization was carried out for 30 minutes at 160 °C, a shear rate of 1000 rpm, and a pressure of 3 MPa.

[0046] 3) The devulcanized rubber was mixed with natural rubber in a ratio of 50:50, carbon black, accelerator, sulfur and antioxidant were added, and mixed in an internal mixer at 150°C for 7 minutes.

[0047] The vulcanization conditions are the same as those in Example 1.

[0048] Comparative Example 2 1. Recipe: Devulcanized waste rubber: 50 parts Natural rubber: 50 parts Carbon black N330: 40 parts Accelerator CZ: 1.0 part Sulfur: 2.0 parts Antioxidant IPPD: 1.0 part.

[0049] Chemical desulfurization additives: 1-Butyl-3-methylimidazolium hexafluorophosphate: 1.2 phr.

[0050] 2. Preparation process: 1) Pretreatment of waste rubber: The waste tire rubber is cleaned and crushed. The particle size of the crushed rubber particles is 5-6 mm.

[0051] 2) The waste rubber was added into a twin-screw extruder, a chemical desulfurization aid was added, and mechanical desulfurization was carried out for 30 minutes at 160 °C, a shear rate of 1000 rpm, and a pressure of 3 MPa.

[0052] 3) The devulcanized rubber was mixed with natural rubber in a ratio of 50:50, carbon black, accelerator, sulfur and antioxidant were added, and mixed in an internal mixer at 150°C for 7 minutes.

[0053] 4) The vulcanization conditions are the same as those in Example 1.

[0054] Comparative Example 3 1. Recipe: Devulcanized waste rubber: 50 parts Natural rubber: 50 parts Carbon black N330: 40 parts Accelerator CZ: 1.0 part Sulfur: 2.0 parts Antioxidant IPPD: 1.0 portion Compound chemical desulfurization additive: 1-Butyl-3-methylimidazolium hexafluorophosphate: 1.5 parts Dibenzothiazyl disulfide (MBTS): 1.5 parts Epoxidized vegetable oil: 3.0 parts.

[0055] 2. Preparation process: 1) Pretreatment of waste rubber: The waste tire rubber is cleaned and crushed. The particle size of the crushed rubber particles is 5-6 mm.

[0056] 2) The waste rubber was added into a twin-screw extruder, a chemical desulfurization aid was added, and mechanical desulfurization was carried out for 30 minutes at 160 °C, a shear rate of 1000 rpm, and a pressure of 3 MPa.

[0057] 3) The devulcanized rubber was mixed with natural rubber in a ratio of 50:50, carbon black, accelerator, sulfur and antioxidant were added, and mixed in an internal mixer at 150°C for 7 minutes.

[0058] 4) The vulcanization conditions are the same as those in Example 1.

[0059] Comparative Example 4 1. Recipe: Devulcanized waste rubber: 50 parts Natural rubber: 50 parts Carbon black N330: 40 parts Accelerator CZ: 1.0 part Sulfur: 2.0 parts Antioxidant IPPD: 1.0 portion 2. Preparation process: The waste rubber was subjected to high-temperature mechanical desulfurization without chemical desulfurization aids. The temperature was set at 180 °C, the shear rate was 1000 rpm, and the desulfurization time was 30 minutes.

[0060] The other steps are the same as in Example 1.

[0061] The performance test data based on the above embodiments and comparative examples are used to prove the technical effects of the present invention: Table 1 Experimental results comparison data table Example / Comparative Example Tensile strength(MPa) Tear strength (kN / m) Elongation at break (%) Hardness (Shore A) Aging resistance (change rate %) Wear resistance (volume loss mm³) Example 1 14.0 30 380 60 7.0 125 Example 2 14.5 32 385 61 6.5 122 Example 3 15.0 35 390 62 6.0 118 Comparative Example 1 12.0 28 350 58 10.5 135 Comparative Example 2 13.0 29 365 59 9.0 132 Comparative Example 3 13.5 31 372 60 8.2 128 Comparative Example 4 11.5 27 340 57 11.0 140 Result analysis: 1. Tensile strength The tensile strengths of Examples 1-3 are 14.0 MPa, 14.5 MPa and 15.0 MPa, respectively, which are significantly higher than the 11.5 MPa to 13.5 MPa of Comparative Examples 1-4. Comparative Examples 1 and 4 have the lowest tensile strengths, 12.0 MPa and 11.5 MPa, respectively, which indicates that the solid tire rubber material that has not been fully optimized has deficiencies in tensile properties. The higher tensile strength of the embodiment indicates that through appropriate process optimization (such as the use of compounded chemical additives), the solid tire material can obtain higher tensile properties, making it more suitable for application scenarios that require stronger mechanical strength.

[0062] 2. Tear strength The tear strengths of Examples 1-3 are 30-35 kN / m, respectively, which are significantly better than the 27-31 kN / m of the comparative examples. The tear strengths of Comparative Examples 1 and 4 are the lowest, 28 kN / m and 27 kN / m, respectively, indicating that these materials are prone to tearing in actual use. The tear strength in the examples is significantly improved, indicating that after reasonable optimization of the desulfurization and mixing processes, the bonding force between rubber molecules has been enhanced, and the tear strength has also been improved accordingly.

[0063] 3. Elongation at break The elongation at break of Examples 1-3 is 380%, 385% and 390%, respectively, which is higher than 340%-372% of the comparative examples. The elongation at break of Comparative Examples 1 and 4 is the lowest, which is 350% and 340%, respectively, indicating that the flexibility and ductility of these materials are poor. The elongation at break of the embodiment is good, indicating that after reasonable formula design and process control, the flexibility of the solid tire material has been optimized and adapted to more complex application environments.

[0064] 4. Hardness (Shore A) The hardness of Examples 1-3 is 60-62 Shore A, which is slightly higher than the hardness of the comparative example (57-60 Shore A), showing better strength and load-bearing capacity. Comparative Examples 1 and 4 have the lowest hardness, 58 and 57 Shore A, respectively, which indicates that the rubber compound that is not fully optimized may lack sufficient strength in a high-pressure environment. The hardness of the embodiment is moderate, which not only retains a high strength, but also does not affect the elasticity and toughness of the material.

[0065] 5. Aging resistance The aging resistance change rates of Examples 1-3 are 7.0%, 6.5% and 6.0%, respectively, which are significantly better than the 8.2%-11.0% of the comparative examples. The aging resistance of Comparative Examples 1 and 4 is the worst, with change rates of 10.5% and 11.0%, respectively, indicating that these materials are prone to aging and performance degradation in long-term use. The aging performance of the embodiment is better, which means that the optimized rubber compound is more stable in long-term use and is suitable for solid tire applications that require a longer life.

[0066] 6. Wear resistance The wear resistance of Examples 1-3 is 125 mm³, 122 mm³ and 118 mm³, respectively, which is significantly better than the 128-140 mm³ of the comparative examples. The wear resistance of Comparative Examples 1 and 4 is the worst, with volume losses of 135 mm³ and 140 mm³, respectively, indicating that these materials have poor wear resistance in frequent use and high wear situations. The wear resistance of the embodiment is better and the volume loss is lower, proving that it is suitable for use in high wear environments and prolongs the service life of the solid tire.

[0067] It can be seen from the experimental results that the compounded chemical desulfurization aid in the present invention, especially 1-butyl-3-methylimidazolium hexafluorophosphate, synergistically with chemical desulfurization aids (such as MBTS, mercaptoethanol) and compatibilizer (Si69), significantly improves the desulfurization efficiency of waste rubber and the mechanical properties and wear resistance of recycled rubber. These properties are crucial for manufacturing high-strength, wear-resistant and long-life solid tires. In the comparative experiment, the formula without compounded chemical aids or compatibilizers has significantly decreased performance, proving that the technical effect of the present invention has significant advantages.

[0068] The above is a description of the embodiments of the present invention. Through the above description of the disclosed embodiments, professionals and technicians in the field can implement or use the present invention. Various modifications to these embodiments will be apparent to professionals and technicians in the field. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in this article, but will conform to the widest range consistent with the principles and novelties disclosed herein.

Claims

1. A method for preparing a rubber compound by recycling waste rubber, characterized in that: The method comprises the following steps: a) Pre-processing the waste rubber, including crushing it into particles or powder with a particle size of 1-10 mm; b) Add the pretreated waste rubber to the high shear mechanical desulfurization equipment, and add a compound chemical desulfurization aid at the same time, wherein the compound chemical desulfurization aid includes: 1-Butyl-3-methylimidazolium hexafluorophosphate: 1.0-2.0 phr; Chemical desulfurizer: 1.0-3.0 phr; Plasticizer: 2.0-4.0 phr; Compatibilizer: 0.5-1.5 phr; c) mechanical desulfurization treatment is carried out at a shear rate of 500-1500 rpm, a temperature of 140-180°C, and a pressure of 2-5 MPa for 15-30 minutes; d) Cool the devulcanized waste rubber to room temperature before subsequent treatment.

2. The method according to claim 1, characterized in that The high shear mechanical desulfurization equipment is a twin-screw extruder or a high shear internal mixer.

3. The method according to claim 1 or 2, characterized in that: The chemical desulfurizing agent is a combination of dibenzothiazole disulfide and a mercaptan compound.

4. The method according to claim 1, characterized in that The plasticizer is epoxidized vegetable oil or citric acid ester plasticizer.

5. The method according to claim 1, characterized in that The compatibilizer is one or more of a silane coupling agent, a titanate coupling agent, and a zirconate coupling agent.

6. The method according to claim 1, characterized in that The compatibilizer is silane coupling agent Si69.

7. The method according to claim 1, characterized in that The method also includes adding new rubber material to the cooled devulcanized rubber, wherein the new rubber material is selected from natural rubber (NR), styrene-butadiene rubber (SBR) or butadiene rubber (BR), and is mixed with the devulcanized rubber in a ratio of 50-70%.

8. The method according to claim 7, characterized in that After the devulcanized rubber is mixed with the new rubber, it is kneaded at a temperature of 140-160°C through an internal mixer or an open mixer for 5-10 minutes.

9. The method according to claim 1, characterized in that: Carbon black is also added as a reinforcing agent to the desulfurized waste rubber and new rubber compound, and the amount of carbon black is 20-40 phr based on 100 parts by weight of the total rubber.

10. A rubber compound prepared by the method according to any one of claims 1 to 9.