A recyclable rubber with high mechanical properties, high adhesive properties

Abstract

The present invention discloses a carboxylated rubber powder and a recyclable rubber having high mechanical properties, high bonding properties, and high recyclability. The rubber is prepared from the following raw materials in parts by weight: 5-100 parts of carboxylated rubber powder, 50-200 parts of epoxidized natural rubber, 5-100 parts of filler, 0.5-10 parts of cross-linking agent, and 0.5-10 parts of catalyst. The carboxylated rubber powder is obtained by swelling rubber powder with an organic solvent containing a free radical initiator, adding the resulting mixture to an aqueous solution of a carboxyl olefin monomer for reaction, and drying the resulting powder after the reaction is complete. The rubber prepared from the carboxylated waste rubber exhibits recyclability and strong bonding properties due to the transformable topology of the cross-linked network. The rubber has multiple application prospects and realizes high-value applications of waste rubber powder.

Description

Technical Field

[0001] The present invention particularly relates to a recyclable rubber with high mechanical properties and high bonding properties. Background Art

[0002] The rubber industry generates a large amount of scrap during the production of rubber products, and rubber products reaching the end of their service life also generate a significant amount of scrap rubber. As a major solid waste, improperly handling scrap rubber can pollute the environment and waste resources. Therefore, the recycling of scrap rubber is a global issue and a major challenge. Rubber's use requires vulcanization, which crosslinks linear rubber hydrocarbon chains into a three-dimensional covalent network. Crosslinked rubber is insoluble, infusible, and non-degradable, and its blind disposal can cause irreversible damage to the ecological environment. 25% of the widely discussed marine microplastics are scrap rubber microparticles. According to statistics from the China Rubber Industry Association in the first half of 2020, the total production of recycled rubber and rubber powder exceeded 430,000 tons. Currently, my country's natural rubber production is constrained by weather, pests, and other factors, and synthetic rubber relies heavily on imports. The impact of rubber resource shortages on economic development is becoming increasingly apparent. Promoting the green recycling of scrap rubber can not only address "black pollution" but also alleviate my country's rubber resource shortage, which is of great significance to the development of a circular economy and the establishment of a conservation-oriented society.

[0003] The main utilization methods for scrap rubber are waste rubber powder and recycled rubber. After rough processing, crushed waste rubber is called waste rubber powder, which is then processed into recycled rubber through specialized techniques. Waste rubber powder is categorized into various types based on processing methods, particle size, and modification methods. Its application areas can be primarily categorized into the asphalt, plastics, and rubber industries. When added to asphalt, waste rubber powder, through complex physical and chemical reactions, improves the asphalt's low-temperature properties, elasticity, and aging resistance. In the plastics industry, the addition of waste rubber powder can improve the toughness of PS and ABS resins. Adding waste rubber powder to rubber significantly reduces costs and improves the product's processing performance and aging resistance. The antioxidants and fillers contained in the waste rubber powder are also highly valuable. However, when waste rubber powder is directly added to rubber, the vulcanizing agent has difficulty diffusing into the waste rubber powder and co-vulcanizing with the raw rubber. This creates a weak interface between the waste rubber powder and the raw rubber, significantly reducing the mechanical properties of the added rubber. This effect is particularly severe for self-reinforcing rubber. Recycled rubber production methods are generally categorized into physical, chemical, and microbiological methods. Physical methods involve breaking down covalent networks through physical means such as high temperature, high shear force, and ultrasound. Traditional thermal and mechanical chemical methods often consume large amounts of energy, produce strong odors, and generate significant pollution. Emerging ultrasonic and microwave methods, on the other hand, require more sophisticated equipment. Chemical methods can achieve better directional treatment of crosslinked structures, generally offering superior performance compared to physical methods and shortening production times. However, due to processing limitations, they also pose significant pollution risks. Microbiological methods are environmentally friendly and rely on naturally occurring sulfur-loving bacteria for desulfurization. However, due to the lipophilicity of rubber, bacterial strains have difficulty attaching, and are currently still in the laboratory stage. Existing technologies for recycling scrap rubber powder or recycled rubber also face a fundamental problem: waste rubber products generate more waste rubber after reaching the end of their useful life. Therefore, existing measures are often "temporary" or short-lived, and do not fundamentally address the difficulty in recycling vulcanized rubber. my country's development and utilization of waste rubber developed relatively late, and the added value of the products is low. The development and utilization of waste rubber powder as raw material is far lower than that of recycled rubber. It faces problems such as insufficient system research, incomplete system development, and imperfect research system. In-depth research on new technologies for the recycling of waste rubber, development of waste rubber powder application methods and channels, and development of new high-value and long-term utilization strategies are issues that urgently need to be addressed.

[0004] In recent years, vitrimers, dynamic adaptive network materials based on dynamic covalent bonds, have attracted considerable research attention, offering promise for fundamentally resolving the recycling challenges of cross-linked polymers. Unlike traditional thermoplastic elastomers such as SBS and TPV, which rely on melting of the non-rubber phase for recycling, vitrimers utilize dynamic, reversible covalent crosslinking. They utilize thermally stimulated dynamic covalent network topology rearrangement, enabling network chain relaxation and macroscopic flow for reshaping while maintaining a constant crosslink density. This unique property of vitrimers offers properties and applications not possessed by traditional cross-linked polymers, such as shape memory, welding, reproducible molding, and basic calendering properties. Vitrimer materials can be constructed by adding functional monomers to synthetic polymers or modifying traditional polymers. Guo Baochun and colleagues from South China University of Technology grafted carboxyl functional groups onto conventional filler carbon black, mixed the resulting mixture into epoxidized natural rubber, and then hot-pressed the resulting composite interfacially cross-linked vitrimer. After adding 20 parts of carbon black, the elastomer achieves a tensile strength of 15.7 MPa and an elongation at break of 340%. Furthermore, at 180°C, the network fully relaxes within 20 minutes, and repeated molding experiments demonstrate a performance recovery rate of 70%. Zhang Liqun and colleagues from Beijing University of Chemical Technology epoxidized commercial EPDM rubber and crosslinked it with sebacic acid to create a carbon black-based vitrimer. This material achieves a tensile strength of 20 MPa and an elongation at break of 400%, exhibiting shape memory properties. When used with new rubber compounds, it can achieve a 100% recyclability. Wu Jinrong and colleagues from Sichuan University developed a naturally derived vitrimer. By blending the natural macromolecular crosslinker sodium alginate with epoxidized natural rubber latex via an emulsion blending method and then hot pressing, the resulting green and environmentally friendly intelligent vitrimer material exhibits high mechanical properties and recyclability, three-dimensional plasticity, and excellent humidity responsiveness. The research results of Vitrimer materials show that the material has a wide range of application prospects, but currently, there are no reports on waste rubber-based Vitrimer materials. Summary of the Invention

[0005] To solve the above problems, the present invention provides a carboxylated rubber powder, which is obtained by swelling rubber powder with an organic solvent containing a free radical initiator, adding the resulting mixture to an aqueous solution of a carboxyl olefin monomer for reaction, and drying the resulting powder after the reaction is complete.

[0006] Furthermore, the mass ratio of the rubber powder, free radical initiator, carboxyl olefin monomer and water is 20-50:1-5:10-50:300-750; the swelling conditions are a temperature of -20°C-2°C and a time of 4-24 hours; and the reaction is carried out in an inert atmosphere at a speed of 100-1000 RPM and a temperature of 60°C-80°C with stirring for 0.5-12 hours.

[0007] Furthermore, the rubber powder is waste rubber powder; the waste rubber powder is derived from any one or more of natural rubber, styrene-butadiene rubber, butyl rubber, polybutadiene rubber, nitrile rubber, chloroprene rubber, halogenated butyl rubber, ethylene-propylene rubber, and fluororubber;

[0008] The free radical initiator is any one or more of azobisisobutyronitrile, benzoyl peroxide, dicumyl peroxide, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane;

[0009] The organic solvent is any one or more of chloroform, tetrahydrofuran, cyclohexane, petroleum ether, carbon tetrachloride, benzene, and toluene;

[0010] The carboxyl olefin monomer is any one or more of acrylic acid, methacrylic acid, 2-carboxyethyl acrylate, itaconic acid, maleic anhydride, maleic dicarboxylic acid, and fumaric acid.

[0011] The present invention also provides a use of the carboxylated rubber powder in preparing rubber.

[0012] The present invention provides a recyclable rubber with high mechanical properties and high adhesive properties, which is prepared from the following raw materials in parts by weight:

[0013] 5-100 parts of the aforementioned carboxylated rubber powder, 50-200 parts of epoxidized natural rubber, 5-100 parts of filler, 0.5-10 parts of crosslinking agent, and 0.5-10 parts of catalyst.

[0014] Furthermore, the epoxidized natural rubber is an epoxidized natural rubber having an epoxidation degree of 25%, 30% and / or 50%;

[0015] The filler is any one or more of carbon black, white carbon black, calcium carbonate, and montmorillonite;

[0016] The cross-linking agent is any one or more of sebacic acid, azelaic acid, suberic acid, and terephthalic acid;

[0017] The catalyst is any one or more of 1,2-dimethylimidazole, dimethylaminopyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, zinc acetate, and zinc oxide.

[0018] Furthermore, it is prepared from the following raw materials in parts by weight:

[0019] 20-60 parts of the aforementioned carboxylated rubber powder, 50-200 parts of epoxidized natural rubber, 10-60 parts of carbon black, 0.5-1.5 parts of sebacic acid or azelaic acid, and 0.3-1 part of a catalyst;

[0020] The catalyst is a combination of 1,2-dimethylimidazole or dimethylaminopyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, zinc acetate or zinc oxide in a mass ratio of 0.1:0.2-0.5.

[0021] The present invention also provides a method for preparing the aforementioned rubber, characterized in that it comprises the following steps:

[0022] 1) Preparing carboxylated rubber powder: taking rubber powder, adding an organic solvent containing a free radical initiator to swell the rubber powder, and adding the swollen rubber powder to an aqueous solution of a carboxyl olefin monomer to react, thereby obtaining carboxylated rubber powder;

[0023] 2) Preparation of dynamically cross-linked rubber: The carboxylated rubber powder obtained in step 1), epoxidized natural rubber, filler, cross-linking agent and catalyst are mixed according to a certain ratio and hot pressed to obtain the dynamically cross-linked rubber.

[0024] Furthermore, in step 1), the mass ratio of the rubber powder, free radical initiator, carboxyl olefin monomer, and water is 20-50:1-5:10-50:300-750; the swelling conditions are a temperature of -20°C-2°C and a time of 4-24 hours; and the reaction is carried out in an inert atmosphere at a speed of 100-1000 RPM and a temperature of 60°C-80°C with stirring for 0.5-12 hours;

[0025] And / or, in step 2), the hot pressing temperature is 150-200° C., preferably 180° C., and the time is 0.5-1 hour.

[0026] Finally, the present invention provides a use of the aforementioned rubber in preparing adhesives or re-moldable rubber products.

[0027] The invention uses simple chemical and physical methods to modify waste rubber powder with low energy consumption and low pollution, and directly prepares vitrimer material with high added value, thereby realizing high-value recycling of waste rubber powder.

[0028] The basic idea of ​​the present invention is to use a green aqueous solution interfacial grafting method to carboxylate the surface of waste rubber powder, and compound and react it with epoxidized rubber to prepare a recyclable waste rubber-based Vitrimer material based on interfacial dynamic covalent bonds. The mechanical properties and adhesive properties of the Vitrimer material are improved by regulating the type of raw materials, chemical structure and compounding process.

[0029] Compared with the prior art, the present invention is beneficial in that:

[0030] The present invention introduces a free radical initiator into the waste rubber powder through swelling, thermally initiating the polymerization of carboxyl-containing olefin monomers at the rubber powder-water interface, achieving efficient carboxylation modification of the waste rubber powder. This avoids the use of high-concentration inorganic acids in traditional modification methods and achieves extremely high grafting efficiency, making it environmentally friendly and simple. Subsequently, the material is combined with epoxidized natural rubber to construct a β-hydroxyester bond crosslinking network, achieving uniform stress field conduction and avoiding the stress concentration problems caused by the lack of co-crosslinking and strong interactions in the use of traditional waste rubber powder. The rubber prepared from the carboxylated waste rubber in the present invention exhibits recyclability and strong bonding properties due to the transformable topology of the crosslinking network. It has multiple application prospects and realizes high-value applications of waste rubber powder.

[0031] Obviously, based on the above contents of the present invention, according to common technical knowledge and customary means in this field, without departing from the above basic technical ideas of the present invention, other various forms of modifications, replacements or changes can be made.

[0032] The following further describes the above content of the present invention in detail through specific embodiments in the form of examples. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The XPS spectra of waste rubber powder before and after carboxylation modification, 1 # The unmodified waste rubber powder in Comparative Example 2 is 2 # This is the carboxylated waste rubber powder of Example 1. The data in the figure show that after grafting, the surface oxygen content of the waste rubber powder increases significantly, proving that the waste rubber powder has successfully completed the carboxylation.

[0034] Figure 2 The stress-strain curves of Example 1, Comparative Example 1 and Comparative Example 2 are shown in FIG. # Represents dynamically cross-linked epoxy natural rubber mixed with carboxylated waste rubber powder, 2 # Represents dynamically cross-linked rubber without rubber powder, 3 # The figure shows that the unmodified waste rubber powder has a significant weakening effect on the material, while the carboxylated waste rubber powder has a significant strengthening effect on the material.

[0035] Figure 3 is the tension-displacement curve of the bonding sample of Example 13 and Comparative Example 1, 1 # For a tape made of simple dynamically cross-linked rubber, 2 #This is a dynamically cross-linked rubber tape mixed with carboxylated waste rubber powder. As can be seen from the figure, the addition of carboxylated waste rubber powder significantly improves the bonding performance. DETAILED DESCRIPTION

[0036] Example 1 Preparation of rubber with high mechanical properties, high adhesive properties and recyclability

[0037] Preparation of carboxylated waste rubber powder: A chloroform solution containing 2g of azobisisobutyronitrile was added to 50g of natural rubber waste rubber powder under mechanical stirring and kept at 2°C for 8h. The swollen waste rubber powder was then added to 500g of an aqueous solution containing 20g of maleic anhydride. The mixture was heated at 60°C for 7h under an inert atmosphere with stirring at 100RPM. The mixed solution was filtered, and the filter cake was washed repeatedly 3-5 times. It was then dried at 50°C for 12h together with the filtered solid. The powder was collected to obtain the carboxylated waste rubber powder (its XPS spectrum is shown in Figure 1 ).

[0038] Preparation of carboxylated waste rubber powder / epoxidized natural rubber: 20g of carboxylated waste rubber powder, 100g of 25% epoxidized natural rubber, 20g of carbon black, 1g of sebacic acid, 0.1g of dimethylaminopyridine, and 0.2g of zinc acetate were mixed on an open mill using a mechanical mixing method. The rubber mixture was then hot-pressed on a flat vulcanizer at 180°C for 50 minutes to form the mixture separately or bond it together. The tensile strength was 16.4MPa, the elongation at break was 430%, the repeated shaping strength retention rate at 180°C was 68%, and the bonding strength was 8.3MPa ( Figure 2 ).

[0039] Example 2 Preparation of rubber with high mechanical properties, high adhesive properties and recyclability

[0040] Preparation of carboxylated scrap rubber powder: A toluene solution containing 1g of dibenzoyl peroxide (BPO) was added to 20g of natural rubber / styrene-butadiene rubber scrap rubber powder under mechanical stirring. The mixture was then incubated at 0°C for 12 hours. The swollen scrap rubber powder was then added to 300g of an aqueous solution containing 10g of maleic anhydride. The mixture was heated at 80°C for 6 hours under an inert atmosphere at 400 RPM. The mixed solution was filtered, and the filter cake was washed 3-5 times. The filtered solid was then dried at 40°C for 48 hours. The powder was collected to obtain the carboxylated scrap rubber powder.

[0041] Preparation of a rubber mixture using carboxylated scrap rubber powder and epoxidized natural rubber: 40g of carboxylated scrap rubber powder, 80g of 30% epoxidized natural rubber, 40g of carbon black, 0.8g of sebacic acid, 0.1g of dimethylimidazole, and 0.2g of zinc acetate were mechanically mixed on an open mill. The rubber mixture was then hot-pressed at 180°C for 60 minutes on a flat-plate vulcanizer to form the mixture individually or by bonding. The resulting mixture exhibited a tensile strength of 18.8 MPa, an elongation at break of 340%, a strength retention of 49% after repeated shaping at 180°C, and a bonding strength of 8.1 MPa.

[0042] Example 3 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties and Recyclability

[0043] Preparation of carboxylated scrap rubber powder: A benzene solution containing 2g of dicumyl peroxide was added to 30g of EPDM scrap rubber powder under mechanical stirring. The mixture was then heated at 2°C for 16 hours. The swollen scrap rubber powder was then added to 300g of an aqueous solution containing 20g of methacrylic acid. The mixture was heated at 80°C for 6 hours under an inert atmosphere at 400 RPM. The mixed solution was filtered, and the filter cake was washed 3-5 times. The filter cake and the filtered solid were then dried at 50°C for 12 hours. The powder was collected to obtain the carboxylated scrap rubber powder.

[0044] Preparation of a rubber mixture using carboxylated scrap rubber powder and epoxidized natural rubber: 20g of carboxylated scrap rubber powder, 80g of 30% epoxidized natural rubber, 10g of carbon black, 1g of sebacic acid, 0.1g of dimethylaminopyridine, and 0.2g of zinc acetate were mechanically mixed on an open mill. The rubber mixture was then hot-pressed on a flat-plate vulcanizer at 180°C for 50 minutes to form the mixture individually or bond them together. The resulting mixture exhibited a tensile strength of 16.9 MPa, an elongation at break of 341%, a strength retention of 55% after repeated shaping at 180°C, and a bonding strength of 8.9 MPa.

[0045] Example 4 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties and Recyclability

[0046] Preparation of carboxylated scrap rubber powder: A toluene solution containing 2g of benzoyl peroxide was added to 20g of nitrile rubber scrap rubber powder under mechanical stirring and incubated at 0°C for 48 hours. The swollen scrap rubber powder was then added to 300g of an aqueous solution containing 30g of acrylic acid. The mixture was heated at 80°C for 4 hours under an inert atmosphere at 500 RPM. The mixed solution was filtered, and the filter cake was washed 3-5 times. The filter cake and the filtered solid were then dried at 50°C for 48 hours. The powder was collected to produce the carboxylated scrap rubber powder.

[0047] Preparation of a rubber mixture of carboxylated scrap rubber powder and epoxidized natural rubber: 60g of carboxylated scrap rubber powder, 100g of 50% epoxidized natural rubber, 35g of carbon black, 1.2g of sebacic acid, 0.1g of 1,2-dimethylimidazole, and 0.2g of zinc acetate were mechanically mixed on an open mill. The rubber mixture was then hot-pressed at 180°C for 50 minutes on a flat-plate vulcanizer to form the mixture individually or by bonding. The resulting mixture exhibited a tensile strength of 16.8 MPa, an elongation at break of 312%, a strength retention of 53% after repeated shaping at 180°C, and a bonding strength of 10.2 MPa.

[0048] Example 5 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties and Recyclability

[0049] Preparation of carboxylated scrap rubber powder: A toluene solution containing 1.5g of benzoyl peroxide was added to 30g of natural rubber scrap rubber powder under mechanical stirring, and the mixture was kept at 0°C for 18 hours. The swollen scrap rubber powder was then added to 750g of an aqueous solution containing 30g of 2-carboxyethyl acrylate. The mixture was heated at 70°C under an inert atmosphere at 250 RPM for 9 hours. The mixed solution was filtered, and the filter cake was washed 3-5 times. The filter cake and the filtered solid were then dried at 40°C for 12 hours. The powder was collected to obtain the carboxylated scrap rubber powder.

[0050] Preparation of a rubber mixture of carboxylated scrap rubber powder and epoxidized natural rubber: 40g of carboxylated scrap rubber powder, 100g of 50% epoxidized natural rubber, 50g of carbon black, 1.2g of sebacic acid, 0.1g of 1,2-dimethylimidazole, and 0.2g of zinc acetate were mechanically mixed on an open mill. The rubber mixture was then hot-pressed on a flat-plate vulcanizer at 180°C for 50 minutes to form the mixture individually or bond them together. The resulting mixture exhibited a tensile strength of 18.4 MPa, an elongation at break of 294%, a strength retention of 57% after repeated shaping at 180°C, and a bonding strength of 11.2 MPa.

[0051] Example 6 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties and Recyclability

[0052] Preparation of carboxylated scrap rubber powder: A chloroform solution containing 1g of azobisisobutyronitrile was added to 20g of styrene-butadiene rubber scrap rubber powder under mechanical stirring. The mixture was then heated at 0°C for 18 hours. The swollen scrap rubber powder was then added to 300g of an aqueous solution containing 20g of acrylic acid. The mixture was heated at 60°C for 9 hours under an inert atmosphere at 400 RPM. The mixed solution was filtered, and the filter cake was washed 3-5 times. The filter cake and the filtered solid were then dried at 50°C for 12 hours. The powder was collected to obtain the carboxylated scrap rubber powder.

[0053] Preparation of a rubber mixture of carboxylated scrap rubber powder and epoxidized natural rubber: 60g of carboxylated scrap rubber powder, 100g of 50% epoxidized natural rubber, 40g of carbon black, 1g of sebacic acid, 0.1g of dimethylaminopyridine, and 0.2g of 1,8-diazabicyclo[5.4.0]undec-7-ene were mechanically mixed on an open mill. The rubber mixture was then hot-pressed at 180°C for 50 minutes on a flat-plate vulcanizer to form the mixture individually or by bonding. The resulting mixture exhibited a tensile strength of 15.8 MPa, an elongation at break of 265%, a 59% retention of strength after repeated shaping at 180°C, and a bonding strength of 8.5 MPa.

[0054] Example 7 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties and Recyclability

[0055] Preparation of carboxylated scrap rubber powder: A toluene solution containing 1g of benzoyl peroxide was added to 20g of natural rubber scrap rubber powder under mechanical stirring and incubated at 0°C for 48 hours. The swollen scrap rubber powder was then added to 500g of an aqueous solution containing 25g of itaconic acid. The mixture was heated at 90°C for 3 hours under an inert atmosphere at 500 RPM. The mixed solution was filtered, and the filter cake was washed 3-5 times. The filter cake and the filtered solid were then dried at 50°C for 12 hours. The powder was collected to obtain the carboxylated scrap rubber powder.

[0056] Preparation of a rubber mixture of carboxylated scrap rubber powder and epoxidized natural rubber: 20g of carboxylated scrap rubber powder, 100g of 25% epoxidized natural rubber, 20g of carbon black, 1g of sebacic acid, 0.1g of dimethylaminopyridine, and 0.2g of zinc acetate were mechanically mixed on an open mill. The rubber mixture was then hot-pressed at 180°C for 50 minutes on a flat-plate vulcanizer to form the mixture individually or by bonding. The resulting mixture exhibited a tensile strength of 15.4 MPa, an elongation at break of 530%, a strength retention of 68% after repeated shaping at 180°C, and a bonding strength of 5.3 MPa.

[0057] Example 8 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties and Recyclability

[0058] Preparation of carboxylated scrap rubber powder: A chloroform solution containing 2g of benzoyl peroxide was added to 40g of natural rubber scrap rubber powder under mechanical stirring and incubated at 0°C for 18 hours. The swollen scrap rubber powder was then added to 500g of an aqueous solution containing 40g of acrylic acid. The mixture was heated at 80°C for 0.5h under an inert atmosphere with stirring at 500rpm. The mixed solution was filtered, and the filter cake was washed 3-5 times. The filter cake and the filtered solid were then dried at 50°C for 48h. The powder was collected to produce the carboxylated scrap rubber powder.

[0059] Preparation of a rubber mixture of carboxylated scrap rubber powder and epoxidized natural rubber: 40g of carboxylated scrap rubber powder, 100g of 25% epoxidized natural rubber, 40g of carbon black, 1g of azelaic acid, 0.1g of 1,2-dimethylimidazole, and 0.2g of zinc acetate were mechanically mixed on an open mill. The rubber mixture was then hot-pressed on a flat-plate vulcanizer at 180°C for 60 minutes to form the mixture individually or bond them together. The resulting mixture exhibited a tensile strength of 16.4 MPa, an elongation at break of 337%, a 47% strength retention after repeated shaping at 180°C, and a bonding strength of 8.7 MPa.

[0060] Example 9 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties and Recyclability

[0061] Preparation of carboxylated scrap rubber powder: A chloroform solution containing 2g of azobisisobutyronitrile was added to 40g of EPDM scrap rubber powder under mechanical stirring. The mixture was then heated at 0°C for 12 hours. The swollen scrap rubber powder was then added to 500g of an aqueous solution containing 40g of maleic anhydride. The mixture was heated at 60°C under an inert atmosphere with stirring at 500 RPM for 9 hours. The mixed solution was filtered, and the filter cake was washed 3-5 times. The filter cake and the filtered solid were then dried at 50°C for 48 hours. The powder was collected to obtain the carboxylated scrap rubber powder.

[0062] Preparation of a rubber mixture of carboxylated scrap rubber powder and epoxidized natural rubber: 60g of carboxylated scrap rubber powder, 100g of 25% epoxidized natural rubber, 50g of carbon black, 1g of sebacic acid, 0.1g of dimethylaminopyridine, and 0.2g of zinc acetate were mechanically mixed on an open mill. The rubber mixture was then hot-pressed on a flat-plate vulcanizer at 180°C for 50 minutes to form the mixture individually or bond them together. The resulting mixture exhibited a tensile strength of 19.8 MPa, an elongation at break of 274%, a 39% strength retention after repeated shaping at 180°C, and a bonding strength of 9.8 MPa.

[0063] Example 10 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties and Recyclability

[0064] Preparation of carboxylated scrap rubber powder: A toluene solution containing 2g of di-2-pentane was added to 30g of cis-1,4-di-1,5 ...

[0065] Preparation of a rubber mixture of carboxylated scrap rubber powder and epoxidized natural rubber: 40g of carboxylated scrap rubber powder, 100g of 25% epoxidized natural rubber, 60g of carbon black, 1g of sebacic acid, 0.1g of dimethylaminopyridine, and 0.2g of zinc acetate were mechanically mixed on an open mill. The rubber mixture was then hot-pressed at 180°C for 50 minutes on a flat-plate vulcanizer to form the mixture individually or bond them together. The resulting mixture exhibited a tensile strength of 22.3 MPa, an elongation at break of 191%, a 27% strength retention after repeated shaping at 180°C, and a bonding strength of 11.3 MPa.

[0066] Example 11 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties, and Recyclability

[0067] Preparation of carboxylated scrap rubber powder: A benzene solution containing 2g of benzoyl peroxide was added to 40g of styrene-butadiene rubber scrap rubber powder under mechanical stirring, and the mixture was kept at 0°C for 8 hours. The swollen scrap rubber powder was then added to 500g of an aqueous solution containing 20g of maleic anhydride. The mixture was heated at 70°C for 12 hours under an inert atmosphere at 100 RPM. The mixed solution was filtered, and the filter cake was washed repeatedly 3-5 times. The filter cake and the filtered solid were then dried at 40°C for 24 hours. The powder was collected to obtain the carboxylated scrap rubber powder.

[0068] Preparation of a rubber mixture of carboxylated scrap rubber powder and epoxidized natural rubber: 50g of carboxylated scrap rubber powder, 100g of 25% epoxidized natural rubber, 40g of carbon black, 1g of sebacic acid, 0.1g of 1,2-dimethylimidazole, and 0.5g of zinc oxide were mechanically mixed on an open mill. The rubber mixture was then hot-pressed at 180°C for 50 minutes on a flat-plate vulcanizer to form the mixture individually or by bonding. The resulting mixture exhibited a tensile strength of 15.6 MPa, an elongation at break of 341%, a strength retention of 55% after repeated shaping at 180°C, and a bonding strength of 7.6 MPa.

[0069] Example 12 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties, and Recyclability

[0070] Preparation of carboxylated scrap rubber powder: A tetrahydrofuran solution containing 2g of benzoyl peroxide was added to 30g of natural rubber scrap rubber powder under mechanical stirring and incubated at 2°C for 8 hours. The swollen scrap rubber powder was then added to 400g of an aqueous solution containing 40g of acrylic acid. The mixture was heated at 80°C under an inert atmosphere with stirring at 500 RPM for 6 hours. The mixed solution was filtered, and the filter cake was washed 3-5 times. The filter cake and the filtered solid were then dried at 50°C for 36 hours. The powder was collected to obtain the carboxylated scrap rubber powder.

[0071] Preparation of a rubber mixture of carboxylated scrap rubber powder and epoxidized natural rubber: 20g of carboxylated scrap rubber powder, 100g of 25% epoxidized natural rubber, 40g of carbon black, 1g of sebacic acid, 0.1g of 1,2-dimethylimidazole, and 0.2g of zinc acetate were mechanically mixed on an open mill. The rubber mixture was then hot-pressed at 180°C for 50 minutes on a flat-plate vulcanizer to form the mixture individually or by bonding. The resulting mixture exhibited a tensile strength of 17.4 MPa, an elongation at break of 530%, a strength retention of 68% after repeated shaping at 180°C, and a bonding strength of 5.3 MPa.

[0072] Example 13 Preparation of Rubber with High Mechanical Properties, High Adhesive Properties, and Recyclability

[0073] Preparation of carboxylated scrap rubber powder: A toluene solution containing 5g of benzoyl peroxide was added to 50g of natural rubber scrap rubber powder under mechanical stirring and incubated at 2°C for 8 hours. The swollen scrap rubber powder was then added to 500g of an aqueous solution containing 50g of maleic anhydride. The mixture was heated at 80°C under an inert atmosphere at 600 RPM for 4 hours. The mixed solution was filtered, and the filter cake was washed 3-5 times. The filter cake and the filtered solid were then dried at 50°C for 12 hours. The powder was collected to obtain the carboxylated scrap rubber powder.

[0074] Preparation of carboxylated waste rubber powder / epoxidized natural rubber: 30g of carboxylated waste rubber powder, 50g of 50% epoxidized natural rubber, 20g of carbon black, 0.5g of sebacic acid, 0.1g of dimethylaminopyridine, and 0.2g of zinc acetate were mixed on an open mill using a mechanical mixing method. The rubber mixture was then hot-pressed on a flat vulcanizer at 180°C for 50 minutes to form the rubber separately or bond it together. The rubber mixture had a tensile strength of 18.5MPa, an elongation at break of 240%, a strength retention rate of 57% after repeated shaping at 180°C, and a bonding strength of 11.2MPa ( Figure 3 ).

[0075] Comparative Example 1

[0076] Preparation of single dynamic cross-linked rubber: 100g of 50% epoxidized natural rubber, 30g of carbon black, 0.5g of sebacic acid, 0.1g of dimethylaminopyridine, and 0.2g of zinc acetate were mixed on an open mill using a mechanical mixing method. The rubber compound was then hot-pressed on a flat vulcanizer at 180°C for 50 minutes and then formed or bonded together. The tensile strength was 15.8MPa, the elongation at break was 740%, the repeated shaping strength retention at 180°C was 57%, and the bonding strength was 1.6MPa ( Figures 2 and 3 ).

[0077] Comparative Example 2

[0078] Preparation of unmodified waste rubber powder mixed with dynamic cross-linked rubber: 40g unmodified natural rubber waste rubber powder (its XPS spectrum is shown in Figure 1 ), 100g 50% epoxidized natural rubber, 30g carbon black, 0.5g sebacic acid, 0.1g dimethylaminopyridine, and 0.2g zinc acetate were mixed on an open mill to prepare a rubber compound, which was then hot-pressed on a flat vulcanizer at 180°C for 50min to form the compound separately or bond them together. The compound has a tensile strength of 10.5MPa, an elongation at break of 7900%, a strength retention rate of 44% after repeated shaping at 180°C, and a bonding strength of 0.7MPa ( Figure 2 ).

[0079] Comparative Example 3

[0080] Preparation of single-phase carboxylated waste rubber powder: 50g of waste natural rubber powder was directly added to 500g of an aqueous solution containing 50g of acrylic acid. The mixture was heated at 80 degrees Celsius for 4h under an inert atmosphere and stirred at 600RPM. The mixed solution was filtered, and the filter cake was washed repeatedly for 3-5 times. The mixture was dried at 50°C for 12h together with the filtered solid. The powder was collected to obtain the carboxylated waste rubber powder.

[0081] Preparation of a rubber mixture of single-phase carboxylated scrap rubber powder and epoxidized natural rubber: 60g of single-phase carboxylated scrap natural rubber powder, 100g of 50% epoxidized natural rubber, 50g of carbon black, 0.5g of sebacic acid, 0.1g of dimethylaminopyridine, and 0.2g of zinc acetate were mechanically mixed on an open mill. The rubber mixture was then hot-pressed at 180°C for 50 minutes on a flat-plate vulcanizer to form the mixture individually or bond them together. The resulting mixture exhibited a tensile strength of 9.7 MPa, an elongation at break of 713%, a 37% strength retention after repeated shaping at 180°C, and a bonding strength of 0.3 MPa.

Claims

1. A method for preparing carboxylated rubber powder, characterized in that: It is a process of swelling rubber powder with an organic solvent containing a free radical initiator, then adding the mixture to an aqueous solution of a carboxyl olefin monomer to react, and drying the mixture to obtain powder after the reaction is complete. The mass ratio of the rubber powder, free radical initiator, carboxyl olefin monomer and water is 20-50:1-5:10-50:300-750; the swelling conditions are a temperature of -20°C-2°C and a time of 4-24 hours; the reaction is carried out in an inert atmosphere at a speed of 100-1000 RPM and a temperature of 60°C-80°C with stirring for 0.5-12 hours; The rubber powder is waste rubber powder; the waste rubber powder is derived from any one or more of natural rubber, styrene-butadiene rubber, butyl rubber, polybutadiene rubber, nitrile rubber, chloroprene rubber, halogenated butyl rubber, ethylene-propylene rubber, and fluororubber; The free radical initiator is any one or more of azobisisobutyronitrile, benzoyl peroxide, dicumyl peroxide, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; The organic solvent is any one or more of chloroform, tetrahydrofuran, cyclohexane, petroleum ether, carbon tetrachloride, benzene, and toluene; The carboxyl olefin monomer is any one or more of acrylic acid, methacrylic acid, 2-carboxyethyl acrylate, itaconic acid, maleic anhydride, maleic dicarboxylic acid, and fumaric acid.

2. Use of the carboxylated rubber powder prepared by the method of claim 1 in the preparation of rubber.

3. A recyclable rubber with high mechanical properties, high adhesive properties, characterized by: It is prepared from the following raw materials in parts by weight: 5-100 parts of carboxylated rubber powder prepared by the method of claim 1, 50-200 parts of epoxidized natural rubber, 5-100 parts of filler, 0.5-10 parts of crosslinking agent, and 0.5-10 parts of catalyst.

4. The rubber according to claim 3, characterized in that: The epoxidized natural rubber is an epoxidized natural rubber with an epoxidation degree of 25%, 30% and / or 50%; The filler is any one or more of carbon black, white carbon black, calcium carbonate, and montmorillonite; The cross-linking agent is any one or more of sebacic acid, azelaic acid, suberic acid, and terephthalic acid; The catalyst is any one or more of 1,2-dimethylimidazole, dimethylaminopyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, zinc acetate, and zinc oxide.

5. The rubber according to claim 4, characterized in that: It is prepared from the following raw materials in parts by weight: 20-60 parts of carboxylated rubber powder prepared by the method of claim 1, 50-200 parts of epoxidized natural rubber, 10-60 parts of carbon black, 0.5-1.5 parts of sebacic acid or azelaic acid, and 0.3-1 part of a catalyst; The catalyst is a combination of 1,2-dimethylimidazole or dimethylaminopyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, zinc acetate or zinc oxide in a mass ratio of 0.1:0.2-0.

5.

6. A method for preparing the rubber according to any one of claims 3 to 5, characterized in that: It includes the following steps: 1) Preparing carboxylated rubber powder: taking rubber powder, adding an organic solvent containing a free radical initiator to swell the rubber powder, and adding the swollen rubber powder to an aqueous solution of a carboxyl olefin monomer to react, thereby obtaining carboxylated rubber powder; 2) Preparation of dynamically cross-linked rubber: The carboxylated rubber powder obtained in step 1), epoxidized natural rubber, filler, cross-linking agent and catalyst are mixed according to a certain ratio and hot pressed to obtain the dynamically cross-linked rubber.

7. The method according to claim 6, characterized in that: Step 1) The mass ratio of the rubber powder, free radical initiator, carboxyl olefin monomer and water is 20-50:1-5:10-50:300-750; the swelling conditions are a temperature of -20°C-2°C and a time of 4-24 hours; the reaction is carried out in an inert atmosphere at a speed of 100-1000 RPM and a temperature of 60°C-80°C with stirring for 0.5-12 hours; And / or, the hot pressing temperature in step 2) is 150-200° C. and the time is 0.5-1 hour.

8. Use of the rubber according to any one of claims 3 to 5 in the preparation of adhesives or re-moldable rubber products.

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