Rubber recovery method and heat-resistant reclaimed rubber

Abstract

The invention discloses a rubber recovery method and heat-resistant reclaimed rubber. The rubber recovery method specifically comprises the following steps: 1) recovering rubber to prepare modified SBR (Styrene Butadiene Rubber) master batch; 2) a preparation method of heat-resistant reclaimed rubber; the preparation method comprises the following steps: firstly, desulfurizing crushed colloidal particles by using ozone to generate active functional groups, then esterifying and grafting 4-bromonaphthol to obtain a modified SBR master batch, banburying and vulcanizing the modified SBR master batch, and carrying out nucleophilic substitution on bromine by a vulcanizing agent to form a cross-linked network. By modifying the waste styrene-butadiene rubber and reconstructing a molecular cross-linked network of the rubber, the mechanical property and the thermal stability of the reclaimed rubber are greatly improved, particularly, the heat resistance reaches the level of native styrene-butadiene rubber, and the method is an optimal scheme for recycling the waste rubber.

Description

Technical Field

[0001] The present invention relates to the technical field of waste rubber recycling and processing, and in particular to a rubber recycling method and heat-resistant reclaimed rubber. Background Art

[0002] About 20 million tons of waste rubber are produced every year in the world. Traditional landfill or incineration not only occupies land, but also pollutes the soil and atmosphere with polycyclic aromatic hydrocarbons and heavy metals contained in it, and causes a huge waste of rubber resources.

[0003] Natural rubber prices fluctuate significantly. While synthetic rubber is relatively inexpensive, using virgin rubber directly still faces high costs. Recycled rubber, by reprocessing waste rubber, costs only 30%-50% of virgin rubber, significantly reducing the production cost of rubber products.

[0004] As of today, although recycled rubber has been applied on a large scale, there is still a significant gap between its performance and that of virgin rubber. In particular, when recycled rubber is recycled from waste rubber for reproduction, the rubber's cross-linking network is severely damaged, causing its molecular structure to be irreversibly damaged, resulting in low mechanical strength and insufficient heat resistance of the recycled rubber.

[0005] Therefore, how to improve the mechanical strength and heat resistance of recycled rubber has become the research direction of rubber recycling and recycled rubber production. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a rubber recycling method and heat-resistant reclaimed rubber.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A rubber recycling method comprises the following steps: S1. Waste crushing The waste styrene butadiene rubber (SBR) is dried and crushed using a crusher to obtain rubber crumbs; Crushing the rubber pieces using a coarse crusher to obtain rubber granules; The rubber coarse particles were crushed with a grinder, and the metal in the rubber was removed by magnetic separation. The rubber was soaked in a 5% H2SO4 aqueous solution for 30 minutes and washed with water until neutral to obtain rubber fine particles. Soak the rubber particles in a 5% NaOH aqueous solution for 30 minutes, wash with water until neutral, and filter to obtain rubber powder; S2. Preprocessing The rubber powder is placed in a fluidized bed and O3 is introduced at 30°C with an O3 concentration of 50-80 mg / m 3 , the flow rate is 0.8m³ / h, the treatment time is 40min, and nitrogen is purged for 30min to obtain wet oxidized SBR rubber powder with a solid content of 70%; β-cyclodextrin (β-CD) was dissolved in deionized water at 60°C and stirred at 300 rpm until transparent to obtain a β-CD solution. 4-bromonaphthol was dissolved in propylene glycol methyl ether and slowly added dropwise to the β-CD solution. The mixture was stirred at 300 rpm at 70°C for 6 hours, then naturally cooled to 25°C, filtered, and vacuum-dried at 40°C for 3 hours to obtain a white powdery solid, i.e., a naphthalene inclusion complex. The mass ratio of β-cyclodextrin, deionized water, 4-bromonaphthol, and propylene glycol methyl ether was 20:100:8:15. Bromine atoms are easily replaced by sulfur nucleophiles, and the 6-position bromination selectivity is high.

[0008] Dissolving p-toluenesulfonic acid in propylene glycol methyl ether to obtain a p-toluenesulfonic acid propylene glycol methyl ether solution; wherein the mass ratio of p-toluenesulfonic acid to propylene glycol methyl ether is 1:10; S3. Aqueous grafting reaction Deionized water, wet-oxidized SBR rubber powder and naphthalene inclusion body were placed in a reactor equipped with a condensation reflux device and a stirring device, and the propylene glycol methyl ether p-toluenesulfonate solution was slowly added dropwise. The mixture was stirred at 300 rpm and heated to 80°C. After reacting for 8 hours, ethanol was added to the reactor, the precipitate was taken, and washed with water until neutral to obtain a modified SBR masterbatch.

[0009] At 80°C, the β-cyclodextrin forming the naphthalene inclusion complex is still in a dissolved state. When precipitation occurs, the naphthalene ring structure wrapped in the middle of the naphthalene inclusion complex escapes from the β-cyclodextrin.

[0010] Preferably, in S2, the β-cyclodextrin not encapsulating 4-bromonaphthol can be directly recycled after filtration.

[0011] Preferably, in S3, the mass ratio of the wet-oxidized SBR rubber powder, the naphthalene inclusion body, the propylene glycol methyl ether p-toluenesulfonate solution, and the ethanol is: 100:12-18:9-13:10.

[0012] Preferably, in S3, when adding the propylene glycol methyl ether p-toluenesulfonate solution, ensure that the system is maintained at a weak acidity, that is, pH=3-5.

[0013] The present invention also proposes heat-resistant reclaimed rubber prepared by using the modified SBR masterbatch obtained by the above-mentioned rubber recovery method, comprising the following raw materials in parts by weight: Modified SBR masterbatch: 80-120 parts; Carbon black N550: 40-50 parts; Precipitated silica: 12-18 parts; Zinc oxide ZnO: 3-7 parts; Stearic acid: 1-3 parts; Sulfur: 1-2 parts; N-cyclohexyl-2-benzothiazole sulfenamide CBS: 1-1.4 parts; 2,2,4-Trimethyl-1,2-dihydroquinoline polymer RD: 1-2 parts; Polyethylene glycol (PEG) with an average molecular weight of 400 Da: 2-4 parts; 3mm chopped carbon fiber: 3-7 parts.

[0014] In addition, the present invention also proposes a method for preparing the aforementioned heat-resistant regenerated rubber, comprising the following steps: 1) Secret refining The modified SBR masterbatch, carbon black N550 and precipitated silica were placed in an internal mixer and mixed at 120°C for 3 minutes. ZnO, stearic acid and PEG were added and the mixture was continued for 2 minutes. Carbon fiber was added and mixed for 1.5 minutes. Sulphur, CBS and RD were added and mixed for another 1 minute. The mixed SBR was then discharged to obtain the internal mixer. 2) Vulcanization Place the mixed SBR in a flat vulcanizer, heat it to 160°C at a rate of 10°C / min, and treat it for 3 minutes; The product is heat-resistant recycled rubber obtained by heating to 180°C at a rate of 10°C / min, vulcanizing at high temperature for 1 hour, and naturally cooling to room temperature.

[0015] Preferably, the long-term stable working temperature of the heat-resistant regenerated rubber obtained by the present invention is 120-150°C.

[0016] Ozone has strong oxidizing properties and can effectively attack the double bonds and sulfur cross-links in the rubber molecular chain, causing them to break. The main components of styrene-butadiene rubber, butadiene and styrene molecules, contain a large number of double bond structures, which react:

[0017] This step is carried out at room temperature (30°C), avoiding the high temperature (180-250°C) and high pressure conditions required for traditional desulfurization. However, ozone treatment significantly reduces the crosslink density and molecular weight of the rubber powder, transforming it from an unreprocessable vulcanized rubber state into a "wet-oxidized SBR rubber powder" with a certain degree of plasticity and reactivity. In essence, ozone oxidation is a mild desulfurization method.

[0018] After ozone treatment, the rubber powder is partially cross-linked, and its performance, especially mechanical properties and heat resistance, are not as good as those of traditional reclaimed rubber. Therefore, 4-bromonaphthol encapsulated in β-cyclodextrin and p-toluenesulfonic acid catalyst are introduced. Under acid catalysis, 4-bromonaphthol undergoes esterification grafting reaction with the carboxyl groups on the wet-oxidized SBR rubber powder molecular chain through its hydroxyl group:

[0019] The introduction of the large and rigid structure of 4-bromonaphthol ultimately gives the recycled rubber excellent heat resistance.

[0020] The grafting reaction process itself is also accompanied by further plasticization of the molecular chain. The grafted bromine provides a large number of active points for the formation of a new cross-linked network during subsequent vulcanization, and cooperates with the sulfur / accelerator system to participate in the formation of the cross-linked network.

[0021]

[0022] This allows sulfur and the accelerator CBS to re-establish a cross-linking network between the modified SBR masterbatch and the added rubber compounding ingredients during the subsequent vulcanization process, thereby improving the mechanical strength of the reclaimed rubber.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The present invention realizes "mild desulfurization" through ozone oxidation. Ozone (O3) selectively attacks the double bonds (C=C) and sulfur cross-linking bonds (-S) in the styrene-butadiene rubber molecular chain at a low temperature of 30°C. x -), the general reaction formula is: C=C+O3→ozonide→broken oxygen-containing chain segments (aldehyde / ketone / carboxyl) -S x -+O3→sulfonic acid / sulfoxide and other sulfur-containing oxides The process is completed at room temperature and pressure, avoiding the high temperature and high pressure environment of 180-250°C of the traditional desulfurization process, and preventing excessive degradation of the original rubber molecular chains.

[0024] The cross-linking density of the rubber powder treated with ozone is significantly reduced, the molecular chains are broken to form active sites, and it is transformed into plasticized "wet-oxidized SBR rubber powder", providing an ideal platform for subsequent grafting reactions.

[0025] In a weak acid environment, catalyzed by p-toluenesulfonic acid, the phenolic hydroxyl group (-OH) of 4-bromonaphthol and the carboxyl group (-COOH) of wet-oxidized SBR rubber powder undergo esterification grafting reaction:

[0026] The steric hindrance effect of the large and rigid naphthalene ring inhibits the thermal motion of the molecular chain, thereby improving thermal stability. The conjugated naphthalene ring system absorbs thermal vibration energy and delays the degradation of the main chain.

[0027] At the same time, the bromine on the naphthalene ring participates in the vulcanization step and reconstructs the cross-linked network that will be cut into shorter molecular chains, greatly improving the mechanical properties of the reclaimed rubber.

[0028]

[0029] Carbon fiber disperses stress and delays local overheating; white carbon black PEG400 promotes the dispersion of white carbon black, forms a silanol-rubber hydrogen bond network, and improves tear strength; sulfur and CBS rebuild a high-density sulfur cross-linking network at the grafting active point, improving the tensile strength of the reclaimed rubber; the combined effect of multiple components enables the long-term stable operating temperature of the present invention to reach 120-150°C.

[0030] In the production process of the present invention, β-cyclodextrin can be directly reused after filtration, and ozone oxidation wastewater can be discharged in compliance with standards after simple neutralization. The traditional "desulfurization → refining → modification" multi-step process is also integrated into an aqueous grafting reaction in a single tank, which has low energy consumption and little pollution, and meets the national "dual carbon goals".

[0031] In summary, the heat-resistant recycled rubber technical solution of the present invention combines ozone oxidation desulfurization with chemical grafting modification to achieve efficient regeneration and performance upgrade of waste SBR rubber at low cost. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0033] The specifications and manufacturers of the drugs used in the experiment are shown in Table 1: Table 1. Raw material drug information Example

[0034] A rubber recycling method and heat-resistant reclaimed rubber, comprising the following steps: A rubber recycling method comprises the following steps: S1. Waste crushing The waste styrene butadiene rubber (SBR) is dried and crushed using a crusher to obtain rubber crumbs; Crushing the rubber pieces using a coarse crusher to obtain rubber granules; The rubber coarse particles were crushed with a grinder, and the metal in the rubber was removed by magnetic separation. The rubber was soaked in a 5% H2SO4 aqueous solution for 30 minutes and washed with water until neutral to obtain rubber fine particles. Soak the rubber particles in a 5% NaOH aqueous solution for 30 minutes, wash with water until neutral, and filter to obtain rubber powder; S2. Preprocessing The rubber powder is placed in a fluidized bed and O3 is introduced at 30°C with an O3 concentration of 50-80 mg / m 3 , the flow rate is 0.8m³ / h, the treatment time is 40min, and nitrogen is purged for 30min to obtain wet oxidized SBR rubber powder with a solid content of 70%; β-cyclodextrin, i.e., β-CD, is dissolved in deionized water at 60°C and stirred at 300 rpm until transparent to obtain a β-CD solution; 4-bromonaphthol is dissolved in propylene glycol methyl ether and slowly added dropwise to the β-CD solution. The solution is stirred at 300 rpm at 70°C for 6 hours, then naturally cooled to 25°C, filtered, and vacuum-dried at 40°C for 3 hours to obtain a white powdery solid, i.e., a naphthalene inclusion body; wherein the mass ratio of β-cyclodextrin, deionized water, 4-bromonaphthol, and propylene glycol methyl ether is 20:100:8:15; and the β-cyclodextrin not encapsulating the 4-bromonaphthol can be directly recycled after filtration.

[0035] Dissolving p-toluenesulfonic acid in propylene glycol methyl ether to obtain a p-toluenesulfonic acid propylene glycol methyl ether solution; wherein the mass ratio of p-toluenesulfonic acid to propylene glycol methyl ether is 1:10; S3. Aqueous grafting reaction Place the wet-oxidized SBR rubber powder and 4-bromonaphthol suspension into a reactor equipped with a condensation reflux device and a stirring device, and slowly add the propylene glycol methyl ether p-toluenesulfonate solution dropwise. When adding the propylene glycol methyl ether p-toluenesulfonate solution, ensure that the system is maintained at a weak acidity, that is, pH = 3-5.

[0036] The mixture was stirred at 300 rpm and heated to 80°C. After reacting for 8 h, ethanol was added to the reactor. The precipitate was taken and washed with water until neutral to obtain a modified SBR masterbatch.

[0037] The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution and ethanol is 100:15:11:10.

[0038] The preparation method of heat-resistant regenerated rubber comprises the following steps: 1) Secret refining 80 kg of modified SBR masterbatch, 50 kg of carbon black N550, and 12 kg of precipitated silica were put into an internal mixer and mixed at 120°C for 3 min. Then, 7 kg of ZnO, 1 kg of stearic acid, and 2 kg of PEG were added and mixed for 2 min. Then, 7 kg of carbon fiber was added and mixed for 1.5 min. Then, 2 kg of sulfur, 1 kg of CBS, and 2 kg of RD were added and mixed for another 1 min. The mixed SBR was obtained by debonding. 2) Vulcanization Place the mixed SBR in a flat vulcanizer, heat it to 160°C at a rate of 10°C / min, and treat it for 3 minutes; The product is heat-resistant recycled rubber obtained by heating to 180°C at a rate of 10°C / min, vulcanizing at high temperature for 1 hour, and naturally cooling to room temperature. Example

[0039] A rubber recycling method and heat-resistant reclaimed rubber, comprising the following steps: A rubber recycling method comprises the following steps: S1. Waste crushing The waste styrene butadiene rubber (SBR) is dried and crushed using a crusher to obtain rubber crumbs; Crushing the rubber pieces using a coarse crusher to obtain rubber granules; The rubber coarse particles were crushed with a grinder, and the metal in the rubber was removed by magnetic separation. The rubber was soaked in a 5% H2SO4 aqueous solution for 30 minutes and washed with water until neutral to obtain rubber fine particles. Soak the rubber particles in a 5% NaOH aqueous solution for 30 minutes, wash with water until neutral, and filter to obtain rubber powder; S2. Preprocessing The rubber powder is placed in a fluidized bed and O3 is introduced at 30°C with an O3 concentration of 50-80 mg / m 3 , the flow rate is 0.8m³ / h, the treatment time is 40min, and nitrogen is purged for 30min to obtain wet oxidized SBR rubber powder with a solid content of 70%; β-cyclodextrin, i.e., β-CD, is dissolved in deionized water at 60°C and stirred at 300 rpm until transparent to obtain a β-CD solution; 4-bromonaphthol is dissolved in propylene glycol methyl ether and slowly added dropwise to the β-CD solution. The solution is stirred at 300 rpm at 70°C for 6 hours, then naturally cooled to 25°C, filtered, and vacuum-dried at 40°C for 3 hours to obtain a white powdery solid, i.e., a naphthalene inclusion body; wherein the mass ratio of β-cyclodextrin, deionized water, 4-bromonaphthol, and propylene glycol methyl ether is 20:100:8:15; and the β-cyclodextrin not encapsulating the 4-bromonaphthol can be directly recycled after filtration.

[0040] Dissolving p-toluenesulfonic acid in propylene glycol methyl ether to obtain a p-toluenesulfonic acid propylene glycol methyl ether solution; wherein the mass ratio of p-toluenesulfonic acid to propylene glycol methyl ether is 1:10; S3. Aqueous grafting reaction Place the wet-oxidized SBR rubber powder and 4-bromonaphthol suspension into a reactor equipped with a condensation reflux device and a stirring device, and slowly add the propylene glycol methyl ether p-toluenesulfonate solution dropwise. When adding the propylene glycol methyl ether p-toluenesulfonate solution, ensure that the system is maintained at a weak acidity, that is, pH = 3-5.

[0041] The mixture was stirred at 300 rpm and heated to 80°C. After reacting for 8 h, ethanol was added to the reactor. The precipitate was taken and washed with water until neutral to obtain a modified SBR masterbatch.

[0042] The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution and ethanol is 100:15:11:10.

[0043] The preparation method of heat-resistant regenerated rubber comprises the following steps: 1) Secret refining 100 kg of modified SBR masterbatch, 45 kg of carbon black N550, and 15 kg of precipitated silica were put into an internal mixer and mixed at 120°C for 3 min. Then, 5 kg of ZnO, 2 kg of stearic acid, and 3 kg of PEG were added and the mixture was further mixed for 2 min. Then, 5 kg of carbon fiber was added and mixed for 1.5 min. Then, 1.5 kg of sulfur, 1.2 kg of CBS, and 1.5 kg of RD were added and mixed for another 1 min. The mixed SBR was obtained by debonding. 2) Vulcanization Place the mixed SBR in a flat vulcanizer, heat it to 160°C at a rate of 10°C / min, and treat it for 3 minutes; The product is heat-resistant recycled rubber obtained by heating to 180°C at a rate of 10°C / min, vulcanizing at high temperature for 1 hour, and naturally cooling to room temperature. Example

[0044] A rubber recycling method and heat-resistant reclaimed rubber, comprising the following steps: A rubber recycling method comprises the following steps: S1. Waste crushing The waste styrene butadiene rubber (SBR) is dried and crushed using a crusher to obtain rubber crumbs; Crushing the rubber pieces using a coarse crusher to obtain rubber granules; The rubber coarse particles were crushed with a grinder, and the metal in the rubber was removed by magnetic separation. The rubber was soaked in a 5% H2SO4 aqueous solution for 30 minutes and washed with water until neutral to obtain rubber fine particles. Soak the rubber particles in a 5% NaOH aqueous solution for 30 minutes, wash with water until neutral, and filter to obtain rubber powder; S2. Preprocessing The rubber powder is placed in a fluidized bed and O3 is introduced at 30°C with an O3 concentration of 50-80 mg / m 3 , the flow rate is 0.8m³ / h, the treatment time is 40min, and nitrogen is purged for 30min to obtain wet oxidized SBR rubber powder with a solid content of 70%; β-cyclodextrin, i.e., β-CD, is dissolved in deionized water at 60°C and stirred at 300 rpm until transparent to obtain a β-CD solution; 4-bromonaphthol is dissolved in propylene glycol methyl ether and slowly added dropwise to the β-CD solution. The solution is stirred at 300 rpm at 70°C for 6 hours, then naturally cooled to 25°C, filtered, and vacuum-dried at 40°C for 3 hours to obtain a white powdery solid, i.e., a naphthalene inclusion body; wherein the mass ratio of β-cyclodextrin, deionized water, 4-bromonaphthol, and propylene glycol methyl ether is 20:100:8:15; and the β-cyclodextrin not encapsulating the 4-bromonaphthol can be directly recycled after filtration.

[0045] Dissolving p-toluenesulfonic acid in propylene glycol methyl ether to obtain a p-toluenesulfonic acid propylene glycol methyl ether solution; wherein the mass ratio of p-toluenesulfonic acid to propylene glycol methyl ether is 1:10; S3. Aqueous grafting reaction Place the wet-oxidized SBR rubber powder and 4-bromonaphthol suspension into a reactor equipped with a condensation reflux device and a stirring device, and slowly add the propylene glycol methyl ether p-toluenesulfonate solution dropwise. When adding the propylene glycol methyl ether p-toluenesulfonate solution, ensure that the system is maintained at a weak acidity, that is, pH = 3-5.

[0046] The mixture was stirred at 300 rpm and heated to 80°C. After reacting for 8 h, ethanol was added to the reactor. The precipitate was taken and washed with water until neutral to obtain a modified SBR masterbatch.

[0047] The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution and ethanol is 100:15:11:10.

[0048] The preparation method of heat-resistant regenerated rubber comprises the following steps: 1) Secret refining 120 kg of modified SBR masterbatch, 40 kg of carbon black N550, and 18 kg of precipitated silica were put into an internal mixer and mixed at 120°C for 3 min. 3 kg of ZnO, 3 kg of stearic acid, and 4 kg of PEG were added and the mixture was further mixed for 2 min. 3 kg of carbon fiber was added and mixed for 1.5 min. 1 kg of sulfur, 1.4 kg of CBS, and 1 kg of RD were added and mixed for another 1 min. The mixture was discharged to obtain the mixed SBR. 2) Vulcanization Place the mixed SBR in a flat vulcanizer, heat it to 160°C at a rate of 10°C / min, and treat it for 3 minutes; The product is heat-resistant recycled rubber obtained by heating to 180°C at a rate of 10°C / min, vulcanizing at high temperature for 1 hour, and naturally cooling to room temperature.

[0049] In the modified SBR masterbatch used in the above examples, the mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution, and ethanol is: 100:15:11:10; based on the weight parts of the raw materials used in Example 2, the ingredients of the modified SBR masterbatch are changed to obtain Examples 4-7 and Comparative Examples 1-4: Example 4: The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution, and ethanol is: 100:12:11:10; Example 5: The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution, and ethanol is: 100:18:11:10; Example 6: The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution, and ethanol is: 100:15:9:10; Example 7: The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution, and ethanol is: 100:15:13:10; Comparative Example 1: The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution, and ethanol is: 100:1:11:10; Comparative Example 2: The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution, and ethanol is: 100:30:11:10; Comparative Example 3: The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution, and ethanol is: 100:15:1:10; Comparative Example 4: The mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution, and ethanol is: 100:15:20:10; That is, as shown in Table 2 and Table 3: Table 2. Heat-resistant recycled rubber formula description table (1)

[0050] Table 3. Heat-resistant recycled rubber formula description table (2)

[0051] The tensile strength, elongation at break, Td5%, Td 50 %, and thermal deformation rate were tested. The test results are summarized in Table 4. The test method is as follows: Mechanical properties testing: After vulcanization, the reclaimed rubber prepared by the method of the present invention was made into a 2 mm thick test piece, which was then punched into a standard dumbbell-shaped specimen (type 1). The tensile strength and elongation at break were recorded using a CTM2000 tensile testing machine in accordance with the GB / T 528-2009 standard. 2. Thermal stability test: The reclaimed rubber obtained by the method of the present invention was vulcanized to prepare a cylindrical specimen with a diameter of 29 mm and a height of 12.5 mm. The specimen was subjected to a ZWK-8X rubber Vicat thermal deformation tester in accordance with the GB / T 7759-2015 standard, with the temperature increased to 150°C at a rate of 10°C / min, and then compressed by 25% and maintained for 24 hours. Table 4. Heat-resistant recycled rubber performance data test table

[0052] Data Analysis: The amount of naphthalene inclusion body determines the rigid naphthalene ring grafting density and dominates the heat resistance and high-temperature deformation of the regenerated rubber; the amount of acid catalyst can control the degree of grafting reaction, affect the reconstruction of the cross-linking network, and indirectly determine the mechanical properties.

[0053] It can be seen from Example 2, Comparative Example 1 and Comparative Example 2 that insufficient naphthalene inclusion bodies will lead to a low rubber grafting rate and a small number of modified functional groups, resulting in a weak cross-linking network. The mechanical properties and thermal stability of the obtained reclaimed rubber are not as good as those of Example 2 with reasonable addition. When excessive addition is made, the oxidation treatment of the rubber particles by ozone can only affect the surface of the rubber particles, and the number of hydroxyl groups produced is limited, and the number of effective functional groups cannot be increased, resulting in a waste of resources.

[0054] Similarly, by comparing Example 2, Comparative Example 3, and Comparative Example 4, it can be seen that insufficient acid catalyst leads to incomplete grafting reaction, reduced ability of naphthalene ring to inhibit molecular chain slippage, easy relaxation of cross-linked molecular chains, and reduced thermal stability of regenerated rubber, while excessive acid catalyst may induce side reactions, and the grafting rate will decrease instead.

[0055] In summary, the present invention modifies discarded styrene-butadiene rubber and reconstructs the molecular cross-linking network of the rubber, thereby greatly improving the mechanical properties and thermal stability of the reclaimed rubber, especially the heat resistance reaches the level of original styrene-butadiene rubber. It is an optimal solution for recycling and reusing waste styrene-butadiene rubber.

[0056] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A rubber recycling method, characterized in that: The following steps are involved: S1. Waste crushing The waste styrene butadiene rubber (SBR) is dried and crushed using a crusher to obtain rubber crumbs; Crushing the rubber pieces using a coarse crusher to obtain rubber granules; The rubber coarse particles were crushed with a grinder, and the metal in the rubber was removed by magnetic separation. The rubber was soaked in a 5% H2SO4 aqueous solution for 30 minutes and washed with water until neutral to obtain rubber fine particles. Soak the rubber particles in a 5% NaOH aqueous solution for 30 minutes, wash with water until neutral, and filter to obtain rubber powder; S2. Preprocessing The rubber powder is placed in a fluidized bed and O3 is introduced at 30°C with an O3 concentration of 50-80 mg / m 3 , the flow rate is 0.8m³ / h, the treatment time is 40min, and nitrogen is purged for 30min to obtain wet oxidized SBR rubber powder with a solid content of 70%; β-cyclodextrin (β-CD) was dissolved in deionized water at 60°C and stirred at 300 rpm until transparent to obtain a β-CD solution. 4-bromonaphthol was dissolved in propylene glycol methyl ether and slowly added dropwise to the β-CD solution. The mixture was stirred at 300 rpm at 70°C for 6 hours, then naturally cooled to 25°C, filtered, and vacuum-dried at 40°C for 3 hours to obtain a white powdery solid, i.e., a naphthalene inclusion complex. The mass ratio of β-cyclodextrin, deionized water, 4-bromonaphthol, and propylene glycol methyl ether was 20:100:8:

15. Dissolving p-toluenesulfonic acid in propylene glycol methyl ether to obtain a p-toluenesulfonic acid propylene glycol methyl ether solution; wherein the mass ratio of p-toluenesulfonic acid to propylene glycol methyl ether is 1:10; S3. Aqueous grafting reaction Deionized water, wet-oxidized SBR rubber powder and naphthalene inclusion body were placed in a reactor equipped with a condensation reflux device and a stirring device, and the propylene glycol methyl ether p-toluenesulfonate solution was slowly added dropwise. The mixture was stirred at 300 rpm and heated to 80°C. After reacting for 8 hours, ethanol was added to the reactor, the precipitate was taken, and washed with water until neutral to obtain a modified SBR masterbatch.

2. A rubber recycling method according to claim 1, characterized in that: In the S2, the β-cyclodextrin that does not encapsulate 4-bromonaphthol can be directly recycled after filtration.

3. A rubber recycling method according to claim 1, characterized in that: In S3, the mass ratio of wet-oxidized SBR rubber powder, naphthalene inclusion body, propylene glycol methyl ether p-toluenesulfonate solution, and ethanol is: 100:12-18:9-13:

10.

4. A rubber recycling method according to claim 1, characterized in that: In the above-mentioned S3, when adding the propylene glycol methyl ether p-toluenesulfonate solution, ensure that the system is maintained at a weak acidity, that is, pH=3-5.

5. Heat-resistant reclaimed rubber prepared by using the modified SBR masterbatch obtained by the rubber recycling method according to any one of claims 1 to 4, characterized in that: The invention comprises the following raw materials in parts by weight: Modified SBR masterbatch: 80-120 parts; Carbon black N550: 40-50 parts; Precipitated silica: 12-18 parts; Zinc oxide ZnO: 3-7 parts; Stearic acid: 1-3 parts; Sulfur: 1-2 parts; N-cyclohexyl-2-benzothiazole sulfenamide CBS: 1-1.4 parts; 2,2,4-Trimethyl-1,2-dihydroquinoline polymer RD: 1-2 parts; Polyethylene glycol (PEG) with an average molecular weight of 400 Da: 2-4 parts; 3mm chopped carbon fiber: 3-7 parts.

6. The method for preparing heat-resistant regenerated rubber according to claim 5, characterized in that: The steps include: 1) Secret refining The modified SBR masterbatch, carbon black N550 and precipitated silica were placed in an internal mixer and mixed at 120°C for 3 minutes. ZnO, stearic acid and PEG were added and the mixture was continued for 2 minutes. Carbon fiber was added and mixed for 1.5 minutes. Sulphur, CBS and RD were added and mixed for another 1 minute. The mixed SBR was then discharged to obtain the internal mixer. 2) Vulcanization Place the mixed SBR in a flat vulcanizer, heat it to 160°C at a rate of 10°C / min, and treat it for 3 minutes; The product is heat-resistant recycled rubber obtained by heating to 180°C at a rate of 10°C / min, vulcanizing at high temperature for 1 hour, and naturally cooling to room temperature.

7. The method for preparing heat-resistant regenerated rubber according to claim 6, characterized in that: The long-term stable working temperature of the heat-resistant recycled rubber obtained is 120-150°C.

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