Waste rubber product mixing process

Abstract

The invention discloses a waste rubber product mixing process, and belongs to the technical field of waste rubber recycling, and the waste rubber product mixing process provided by the invention comprises the following steps: shearing a waste rubber product, and then carrying out desulfurization activation and crushing to obtain waste rubber powder; then carrying out surface modification on the waste rubber powder by using a silane coupling agent to obtain modified waste rubber powder; mixing natural rubber with the modified waste rubber powder, and plastifying to obtain a mixture; mixing butadiene styrene rubber and butadiene rubber with the mixture, then adding graphene and carbon black for first mixing, then adding nano silicon dioxide for second mixing, and adding a composite surfactant for third mixing to obtain a mixed material; mixing the mixed material with a vulcanizing agent, zinc oxide and an anti-aging agent, and vulcanizing to obtain a rubber product; the composite surfactant comprises zinc stearate, Tween 80 and sodium dodecyl benzene sulfonate. The rubber product provided by the invention has good mechanical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of waste rubber recycling, and particularly relates to a mixing process for waste rubber products. Background Art

[0002] Waste rubber is known as "black pollution" due to its difficulty in degrading and potential pollution risks. Natural degradation of waste rubber takes hundreds of years, and its storage occupies land and releases heavy metals (such as zinc and lead) that contaminate soil and groundwater. Open-air storage also breeds mosquitoes and spreads diseases like dengue fever. Furthermore, waste rubber is highly flammable (having a higher calorific value than coal), making its accumulation a fire hazard and the release of toxic gases such as dioxins.

[0003] The massive scale of the automotive industry results in a vast amount of scrap tires. If not recycled, this translates to millions of tons of rubber being wasted annually. While existing technologies have attempted to recycle scrap rubber, the mechanical properties of the products produced using this technology are relatively poor, limiting its recycling.

[0004] Therefore, there is an urgent need to provide a new method for recycling waste rubber, and to make the prepared product have good mechanical properties. Summary of the Invention

[0005] The present invention aims to address at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a mixing process for waste rubber products. The rubber products obtained by the process have excellent mechanical properties, such as tensile strength and hardness, which facilitates the recycling and reuse of waste rubber, transforming waste into valuable resources while also increasing economic income.

[0006] The concept of the present invention focuses on a three-pronged approach of nano-reinforcement, interface modification, and vulcanization synergy to break through the bottleneck of mechanical properties of recycled waste rubber products. The core of the invention is: (1) using graphene and carbon black to construct a three-dimensional reinforcement network, combined with nano-silica rigid particle filling to improve the hardness and stress transfer efficiency of rubber products; (2) using silane coupling agent to graft and modify the surface of rubber powder to enhance the interface bonding between waste rubber powder and matrix and reduce defect concentration; (3) introducing a composite vulcanization system such as sulfur powder and morpholine disulfide and optimizing the step vulcanization process to form a uniform network structure with high cross-linking density. Ultimately, while maintaining a high proportion of waste rubber powder, the tensile strength exceeds 17MPa and the Shore hardness exceeds 67HA, while taking into account process compatibility and environmental protection. In addition, the composite surfactant composed of three surfactants used in the present invention includes metal soap (zinc stearate), nonionic type (Tween 80) and anionic type (sodium dodecylbenzene sulfonate), which synergistically address the polarity differences in rubber. Among them, zinc stearate leads vulcanization activation and processing lubrication, Tween 80 strengthens emulsification stability and compatibility, and sodium dodecylbenzene sulfonate provides strong dispersion and interface modification. The combination of the three avoids the limitations of a single component and ensures that the filler (graphene, carbon black, nano-silica) and the modified waste rubber powder are uniformly dispersed at a high filling amount, thereby facilitating the improvement of the mechanical properties of the rubber product finally obtained.

[0007] A mixing process for waste rubber products comprises the following steps: (1) shearing the waste rubber product, desulfurizing and activating it, and crushing it to obtain waste rubber powder, and then surface-modifying the waste rubber powder with a silane coupling agent to obtain modified waste rubber powder; (2) mixing natural rubber with the waste rubber powder modified in step (1), and performing mastication to obtain a mixture; (3) mixing styrene-butadiene rubber and butadiene rubber with the mixture prepared in step (2), then adding graphene, carbon black, and nano-silica for a first mixing, then adding nano-silica for a second mixing, then adding a composite surfactant for a third mixing to obtain a mixture; (4) mixing the mixed material prepared in step (3) with a vulcanizing agent, zinc oxide, and an anti-aging agent, and vulcanizing to obtain a rubber product; The complex surfactant comprises zinc stearate, Tween 80 and sodium dodecylbenzenesulfonate.

[0008] Preferably, in the composite surfactant, the weight ratio of zinc stearate, Tween 80 and sodium dodecylbenzenesulfonate is 1.5:(0.5-1):(0.3-1).

[0009] Preferably, in step (1), the process of surface modifying the waste rubber powder with a silane coupling agent comprises: A silane coupling agent is added to a mixture of ethanol and water, and the mixture is stirred and mixed. Then, waste rubber powder is added, the mixture is heated and stirred, washed, and dried to obtain modified waste rubber powder.

[0010] Preferably, the weight of the silane coupling agent is 1% to 3% of the weight of the waste rubber powder.

[0011] Preferably, the weight ratio of the mixed liquid to the waste rubber powder is (1.1-1.5):1.

[0012] Preferably, the volume ratio of ethanol to water is (7-9):1.

[0013] Preferably, aqueous ammonia is added to the mixture of ethanol and water to adjust the pH to 9-10.

[0014] Preferably, the heating and stirring is carried out at a temperature of 40 to 50° C. and for a time of 30 to 60 minutes.

[0015] Preferably, the washing is performed with ethanol.

[0016] Preferably, the drying is carried out under vacuum conditions at 50-60°C.

[0017] Preferably, in step (1), the mesh size of the waste rubber powder is 60 to 100 meshes, more preferably 70 to 80 meshes.

[0018] Preferably, in step (1), the desulfurization activation is performed using 1-pentanethiol.

[0019] Preferably, in step (1), the weight ratio of the waste rubber product to 1-pentanethiol is 100:(2-5).

[0020] Preferably, in step (1), the temperature of the desulfurization activation is 140-150° C., and the time is 0.5-1 h.

[0021] Preferably, in step (2), the weight ratio of the natural rubber to the waste rubber powder modified in step (1) is 30:(50-100), more preferably 30:(70-100).

[0022] Preferably, in step (2), the temperature of the mastication is 120-130° C., and the time of the mastication is 22-30 min.

[0023] Preferably, in step (2), the mastication is carried out in an internal mixer.

[0024] Preferably, in step (2), the particle size of the natural rubber is less than 5 mm.

[0025] Preferably, in step (3), the weight ratio of the styrene-butadiene rubber and butadiene rubber to the mixture prepared in step (2) is 10:(5-15):(50-100).

[0026] Preferably, in step (3), the weight ratio of the mixture prepared in step (2) to graphene and carbon black is 80:(0.5-2):(30-45), and more preferably 80:(0.5-1.5):(35-40).

[0027] Preferably, in step (3), the weight ratio of the mixture prepared in step (2) to the nano-silicon dioxide and the composite surfactant is 80:(0.2-5):(0.5-3).

[0028] Preferably, in step (3), the temperature of the first mixing is 90-100° C., and the time is 3-6 minutes.

[0029] Preferably, in step (3), the temperature of the second mixing is 90-100° C., and the time is 2-4 minutes.

[0030] Preferably, in step (3), the temperature of the third mixing is 90-100° C., and the time is 2-5 minutes.

[0031] Preferably, in step (4), the vulcanizing agent includes sulfur powder and morpholine disulfide.

[0032] Preferably, in step (4), the weight ratio of the mixed material to the vulcanizing agent and zinc oxide is 100:(0.8-2):(1-5).

[0033] Preferably, the weight ratio of the sulfur powder to morpholine disulfide is 1:(0.8-1.2).

[0034] Preferably, in step (4), the vulcanization process is: keeping the temperature at 90-100°C for 2-4 minutes, then keeping the temperature at 130-145°C for 5-8 minutes, and then keeping the temperature at 146-150°C for 3-5 minutes. The use of step-by-step temperature vulcanization is beneficial to improving the mechanical properties of the prepared rubber product.

[0035] Preferably, in step (3), after adding carbon black, single-walled carbon nanotubes modified with a silane coupling agent are also added. The single-walled carbon nanotubes modified with the silane coupling agent form electron channels with graphene through π-π conjugation, thereby improving stress transfer efficiency. In addition, the silane coupling agent achieves molecular-level interface bonding between the single-walled carbon nanotubes and the rubber through covalent bond bridging, thereby optimizing stress transfer efficiency and inhibiting defect propagation. Ultimately, a breakthrough is achieved in tensile strength and elongation at break, so that the tensile strength of the final rubber product prepared is ≥18.5 MPa and the elongation at break is ≥390%.

[0036] Preferably, in step (3), the weight ratio of the mixture prepared in step (2) to the single-walled carbon nanotubes modified with a silane coupling agent is 80:(0.2-0.6).

[0037] Preferably, the preparation process of the silane coupling agent-modified single-walled carbon nanotubes comprises: S1, mixing single-walled carbon nanotubes with an acid solution, ultrasonically treating, then centrifuging, washing, and drying to obtain oxidized single-walled carbon nanotubes; S2. Add a silane coupling agent to an alcohol-water mixed solution, adjust the pH to acidic, heat to react, then add the oxidized single-walled carbon nanotubes, raise the temperature to reflux and react under a protective gas atmosphere, centrifuge, then wash alternately with toluene and ethanol, and dry to obtain the single-walled carbon nanotubes modified with the silane coupling agent.

[0038] Preferably, in S1, the acid solution is obtained by mixing water, sulfuric acid and nitric acid in a weight ratio of 10:(2-3):(0.5-1). The function of S1 is to carboxylate the surface of the single-walled carbon nanotubes.

[0039] Preferably, in step S1, the weight ratio of the single-walled carbon nanotubes to the acid solution is 1:(8-12).

[0040] Preferably, in step S1, the temperature of the ultrasound is 50-60° C., and the time is 1-2 hours.

[0041] Preferably, in step S1, the washing is performed by washing with water until the water becomes neutral.

[0042] Preferably, in step S1, the drying is performed under vacuum at 50-60°C.

[0043] Preferably, in step S2, the weight ratio of the silane coupling agent to the alcohol-water mixed solution is 1.5 to 3:100.

[0044] Preferably, in step S2, the weight ratio of the oxidized single-walled carbon nanotubes to the alcohol-water mixed solution is 1:(15-30).

[0045] Preferably, in step S2, the silane coupling agent includes KH550.

[0046] Preferably, in step S2, the alcohol-water mixed solution includes ethanol and water, and the volume ratio of the ethanol to water is (7-9):1.

[0047] Preferably, in step S2, the pH is adjusted to 4 to 5 by acidifying the solution, for example, by using acetic acid solution to adjust the pH.

[0048] Preferably, in step S2, the heating reaction temperature is 55-65° C. and the time is 40-60 min.

[0049] Preferably, in step S2, the protective gas includes nitrogen or a rare gas, such as argon or helium.

[0050] Preferably, in step S2, the temperature of the heating reflux reaction is 100-110° C., and the time is 12-24 hours.

[0051] Preferably, in step S2, the drying is performed under vacuum at 50-60°C.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses graphene and carbon black to construct a three-dimensional reinforcement network, combined with nano-silica rigid particle filling to improve the hardness and stress transfer efficiency of rubber products; through the grafting and modification of the rubber powder surface by silane coupling agent, the interface bonding between the waste rubber powder and the matrix is ​​enhanced, and the concentration of defects is reduced; a composite vulcanization system such as sulfur powder and morpholine disulfide is introduced and the step vulcanization process is optimized to form a uniform network structure with a high cross-linking density. Ultimately, while maintaining a high proportion of waste rubber powder, a tensile strength exceeding 17MPa and a Shore hardness exceeding 67HA are achieved, while taking into account process compatibility and environmental protection. The composite surfactant has the effect of improving the mechanical properties of the final rubber product.

[0053] (2) After adding carbon black, single-walled carbon nanotubes modified with silane coupling agents are also added. The single-walled carbon nanotubes modified with silane coupling agents form electron channels with graphene through π-π conjugation, improving the stress transfer efficiency. In addition, the silane coupling agent achieves molecular-level interface bonding between single-walled carbon nanotubes and rubber through covalent bond bridging, optimizing stress transfer efficiency and inhibiting defect expansion. Ultimately, a breakthrough is achieved in tensile strength and elongation at break, making the final rubber product have a tensile strength of ≥18.5MPa and an elongation at break of ≥390%. DETAILED DESCRIPTION

[0054] Below in conjunction with the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, it is obvious that described embodiment is only a part of embodiment of the present invention, rather than whole embodiment. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise all fall within the scope of protection of the present invention. Meanwhile, raw materials, reagents or devices used in the following examples, unless otherwise specified, can be obtained from conventional commercial channels, or can be obtained by existing known methods.

[0055] Example 1

[0056] A mixing process for waste rubber products comprises the following steps: (1) The waste rubber product is sheared and then mixed with 1-pentanethiol for desulfurization activation (the weight ratio of the waste rubber product to 1-pentanethiol is 100:3), the desulfurization activation temperature is 140°C, the time is 45 minutes, and then the waste rubber powder is crushed to 80 mesh to obtain waste rubber powder, and then the waste rubber powder is surface-modified with a silane coupling agent to obtain modified waste rubber powder; The process of surface modification of waste rubber powder using silane coupling agent includes: Silane coupling agent KH550 was added to a mixture of ethanol and water (volume ratio of 9:1) (the pH of the mixture was adjusted to 9 with ammonia water), and the mixture was stirred. Then, waste rubber powder was added, and the mixture was heated to 60°C and stirred for 40 minutes. The mixture was washed with ethanol and dried at 60°C to obtain modified waste rubber powder. The weight of the silane coupling agent KH550 is 2% of the weight of the waste rubber powder, and the weight ratio of the mixed liquid to the waste rubber powder is 1.2:1.

[0057] (2) mixing natural rubber (particle size less than 5 mm) with the waste rubber powder modified in step (1), wherein the weight ratio of natural rubber to the waste rubber powder modified in step (1) is 30:80, and performing mastication in an internal mixer at a mastication temperature of 120° C. and a mastication time of 25 min to obtain a mixture; (3) taking styrene-butadiene rubber and butadiene rubber and mixing them with the mixture prepared in step (2) (the weight ratio of styrene-butadiene rubber and butadiene rubber to the mixture prepared in step (2) is 10:10:80), then adding graphene and carbon black for the first mixing, the temperature of the first mixing is 90°C, the time is 5 minutes, then adding nano-silica and mixing at 95°C for 2 minutes, then adding a composite surfactant and mixing at 95°C for 4 minutes to obtain a mixture, the weight ratio of the mixture to graphene and carbon black is 80:1:40; the weight ratio of the mixture to nano-silica and composite surfactant is 80:0.8:1; (4) mixing the mixture prepared in step (3) with a vulcanizing agent, zinc oxide, and 2-mercaptobenzimidazole (the weight ratio of the mixture to the vulcanizing agent, zinc oxide, and 2-mercaptobenzimidazole is 100:2:3:3), wherein the vulcanizing agent is composed of sulfur powder and morpholine disulfide in a weight ratio of 1:1.2, and the mixture is kept warm at 100° C. for 2 minutes, then kept warm at 140° C. for 6 minutes, and then kept warm at 150° C. for 4 minutes to obtain a rubber product; The composite surfactant is composed of zinc stearate, Tween 80 and sodium dodecylbenzene sulfonate in a weight ratio of 1.5:0.8:0.5.

[0058] Example 2

[0059] A mixing process for waste rubber products comprises the following steps: (1) The waste rubber product is sheared and then mixed with 1-pentanethiol for desulfurization activation (the weight ratio of the waste rubber product to 1-pentanethiol is 100:3.5), the desulfurization activation temperature is 145°C, the time is 45 minutes, and then the waste rubber powder is crushed to 80 mesh to obtain waste rubber powder, and then the waste rubber powder is surface-modified with a silane coupling agent to obtain modified waste rubber powder; The process of surface modification of waste rubber powder using silane coupling agent includes: Silane coupling agent KH550 was added to a mixture of ethanol and water (volume ratio of 9:1) (the pH of the mixture was adjusted to 10 with ammonia water), and the mixture was stirred. Then, waste rubber powder was added, and the mixture was heated to 50°C and stirred for 40 minutes. The mixture was washed with ethanol and dried at 60°C to obtain modified waste rubber powder. The weight of the silane coupling agent KH550 is 2% of the weight of the waste rubber powder, and the weight ratio of the mixed liquid to the waste rubber powder is 1.1:1.

[0060] (2) mixing natural rubber (particle size less than 5 mm) with the waste rubber powder modified in step (1), wherein the weight ratio of natural rubber to the waste rubber powder modified in step (1) is 30:80, and performing mastication in an internal mixer at a mastication temperature of 125° C. and a mastication time of 25 min to obtain a mixture; (3) taking styrene-butadiene rubber and butadiene rubber and mixing them with the mixture prepared in step (2) (the weight ratio of styrene-butadiene rubber and butadiene rubber to the mixture prepared in step (2) is 10:15:80), then adding graphene and carbon black for the first mixing, the temperature of the first mixing is 90°C, the time is 5 minutes, adding nano-silica and mixing at 90°C for 2 minutes, and then adding a composite surfactant and mixing at 90°C for 3 minutes to obtain a mixture, the weight ratio of the mixture to graphene and carbon black is 80:0.9:41; the weight ratio of the mixture to nano-silica and composite surfactant is 80:0.9:1; (4) mixing the mixture prepared in step (3) with a vulcanizing agent, zinc oxide, and 2-mercaptobenzimidazole (the weight ratio of the mixture to the vulcanizing agent, zinc oxide, and 2-mercaptobenzimidazole is 100:1.5:3:3), wherein the vulcanizing agent is composed of sulfur powder and morpholine disulfide in a weight ratio of 1:1.1, and heating at 100° C. for 2 minutes, then heating at 145° C. for 6 minutes, and then heating at 155° C. for 4 minutes to obtain a rubber product; The composite surfactant is composed of zinc stearate, Tween 80 and sodium dodecylbenzene sulfonate in a weight ratio of 1.5:0.6:0.5.

[0061] Example 3

[0062] A mixing process for waste rubber products comprises the following steps: (1) The waste rubber product is sheared and then mixed with 1-pentanethiol for desulfurization activation (the weight ratio of the waste rubber product to 1-pentanethiol is 100:3), the desulfurization activation temperature is 140°C, the time is 45 minutes, and then the waste rubber powder is crushed to 80 mesh to obtain waste rubber powder, and then the waste rubber powder is surface-modified with a silane coupling agent to obtain modified waste rubber powder; The process of surface modification of waste rubber powder using silane coupling agent includes: Silane coupling agent KH550 was added to a mixture of ethanol and water (volume ratio of 9:1) (the pH of the mixture was adjusted to 9 with ammonia water), and the mixture was stirred. Then, waste rubber powder was added, and the mixture was heated to 60°C and stirred for 40 minutes. The mixture was washed with ethanol and dried at 60°C to obtain modified waste rubber powder. The weight of the silane coupling agent KH550 is 2% of the weight of the waste rubber powder, and the weight ratio of the mixed liquid to the waste rubber powder is 1.2:1.

[0063] (2) mixing natural rubber (particle size less than 5 mm) with the waste rubber powder modified in step (1), wherein the weight ratio of natural rubber to the waste rubber powder modified in step (1) is 30:80, and performing mastication in an internal mixer at a mastication temperature of 120° C. and a mastication time of 25 min to obtain a mixture; (3) taking styrene-butadiene rubber and butadiene rubber and mixing them with the mixture prepared in step (2) (the weight ratio of styrene-butadiene rubber and butadiene rubber to the mixture prepared in step (2) is 10:10:80), then adding graphene, carbon black, and single-walled carbon nanotubes modified by silane coupling agent for the first mixing, the temperature of the first mixing is 90° C., the time is 5 min, nano-silica is added and mixed at 95° C. for 2 min, and then a composite surfactant is added and mixed at 95° C. for 4 min to obtain a mixture, the weight ratio of the mixture to the graphene, carbon black, and single-walled carbon nanotubes modified by silane coupling agent is 80:1:40:0.5; the weight ratio of the mixture to the nano-silica and composite surfactant is 80:0.8:1; The preparation process of single-walled carbon nanotubes modified with silane coupling agents includes: S1, mixing single-walled carbon nanotubes with an acid solution (the acid solution is composed of water, sulfuric acid and nitric acid in a weight ratio of 10:2:0.5), ultrasonically treating at 60° C. for 1.5 h, then centrifuging, washing with water until neutral, and vacuum drying at 60° C. to obtain oxidized single-walled carbon nanotubes; S2. Adding silane coupling agent KH550 to an alcohol-water mixed solution (composed of ethanol and water in a volume ratio of 9:1), wherein the weight ratio of silane coupling agent KH550 to the alcohol-water mixed solution is 2:100, adjusting the pH to 4 with acetic acid, heating at 60° C. for 50 min, then adding oxidized single-walled carbon nanotubes, heating and reflux under a nitrogen atmosphere, the temperature of the heating and reflux reaction being 110° C. for 24 h, centrifuging, and then washing alternately with toluene and ethanol three times, and drying under vacuum at 60° C. to obtain single-walled carbon nanotubes modified with silane coupling agent; (4) mixing the mixture prepared in step (3) with a vulcanizing agent, zinc oxide, and 2-mercaptobenzimidazole (the weight ratio of the mixture to the vulcanizing agent, zinc oxide, and 2-mercaptobenzimidazole is 100:2:3:3), wherein the vulcanizing agent is composed of sulfur powder and morpholine disulfide in a weight ratio of 1:1.2, and the mixture is kept warm at 100° C. for 2 minutes, then kept warm at 140° C. for 6 minutes, and then kept warm at 150° C. for 4 minutes to obtain a rubber product; The composite surfactant is composed of zinc stearate, Tween 80 and sodium dodecylbenzene sulfonate in a weight ratio of 1.5:0.8:0.5.

[0064] Example 4

[0065] Compared with Example 1, the difference of Example 4 is only step (4). The content of step (4) of Example 4 is as follows: The mixed material prepared in step (3) is mixed with a vulcanizing agent, zinc oxide, and 2-mercaptobenzimidazole (the weight ratio of the mixed material to the vulcanizing agent, zinc oxide, and 2-mercaptobenzimidazole is 100:2:3:3), the vulcanizing agent is composed of sulfur powder, and the mixture is kept warm at 140° C. for 12 minutes to obtain a rubber product.

[0066] Comparative Example 1

[0067] Compared with Example 1, the only difference of Comparative Example 1 is that an equal amount of sodium dodecyl sulfate is used instead of sodium dodecylbenzenesulfonate, and the other processes are the same as those of Example 1.

[0068] Comparative Example 2

[0069] Compared with Example 1, the difference of Comparative Example 2 is that an equal amount of carbon black is used instead of nano-silicon dioxide, and the other processes are the same as those of Example 1.

[0070] Product effect test: The rubber products prepared in the above examples and comparative examples were tested for Shore hardness with reference to GB / T 531.1-2019 "Rubber, vulcanized or thermoplastic rubber - Indentation hardness test - Part 1: Shore durometer method", and the tensile strength and elongation at break were tested with reference to GB / T 528-2009 "Rubber, vulcanized or thermoplastic rubber - Determination of tensile stress-strain properties". The results are shown in Table 1: Table 1

[0071] As can be seen from Table 1, the mechanical properties of the rubber products prepared in Examples 1 to 4 of the present invention are significantly better than those in Comparative Examples 1 to 2.

[0072] As can be seen from Example 1 and Comparative Example 1, replacing sodium dodecylbenzenesulfonate with sodium dodecyl sulfate results in a deterioration in the dispersion stability and interfacial bonding strength of the system. This is because the benzene ring structure of sodium dodecylbenzenesulfonate generates a π-π interaction with carbon black / graphene, enhancing the filler-rubber interface. Furthermore, the sulfonic acid group also stabilizes the filler dispersion. However, sodium dodecyl sulfate lacks this π-π interaction, resulting in a decrease in filler-rubber stress transfer efficiency and a tendency to cause graphene / carbon black agglomeration, which in turn leads to a decrease in the mechanical properties of the resulting rubber product.

[0073] It can be seen from Example 1 and Comparative Example 2 that the performance of the rubber product prepared in Comparative Example 2 is significantly reduced. The reason may be that after carbon black replaces nano-silica, the surface of nano-silica is rich in silanol (-SiOH), which forms a strong interface bond (Si-O-Si covalent bond) with the waste rubber powder modified with the silane coupling agent through chemical bonding, significantly improving the stress transfer efficiency. Carbon black only relies on physical adsorption (van der Waals force) and π-π stacking, and cannot provide the same interface strength, resulting in an increase in stress concentration points and a decrease in mechanical properties. The cross-linking bridge points formed by the silane coupling agent structure on the surface of the nano-silica are eliminated, the integrity of the vulcanization network is destroyed, and the elongation at break is directly reduced.

[0074] It should be noted that, in this document, terms such as "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0075] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A mixing process for waste rubber products, characterized in that: The following steps are involved: (1) shearing the waste rubber product, desulfurizing and activating it, and crushing it to obtain waste rubber powder, and then surface-modifying the waste rubber powder with a silane coupling agent to obtain modified waste rubber powder; (2) mixing natural rubber with the waste rubber powder modified in step (1), and performing mastication to obtain a mixture; (3) mixing styrene-butadiene rubber and butadiene rubber with the mixture prepared in step (2), then adding graphene and carbon black for a first mixing, then adding nano-silica for a second mixing, then adding a composite surfactant for a third mixing to obtain a mixture; (4) mixing the mixed material prepared in step (3) with a vulcanizing agent, zinc oxide, and an anti-aging agent, and vulcanizing to obtain a rubber product; The complex surfactant comprises zinc stearate, Tween 80 and sodium dodecylbenzenesulfonate.

2. A waste rubber product mixing process according to claim 1, characterized in that: In the composite surfactant, the weight ratio of zinc stearate, Tween 80 and sodium dodecylbenzenesulfonate is 1.5:(0.5-1):(0.3-1).

3. A waste rubber product mixing process according to claim 1, characterized in that: In step (1), the process of surface modifying the waste rubber powder with a silane coupling agent comprises: A silane coupling agent is added to a mixture of ethanol and water, and the mixture is stirred and mixed. Then, waste rubber powder is added, the mixture is heated and stirred, washed, and dried to obtain modified waste rubber powder.

4. A waste rubber product mixing process according to claim 3, characterized in that: The weight of the silane coupling agent is 1% to 3% of the weight of the waste rubber powder; and / or the weight ratio of the mixed liquid to the waste rubber powder is (1.1 to 1.5):1; and / or the temperature of the heating and stirring is 40 to 50° C., and the time is 30 to 60 minutes.

5. A waste rubber product mixing process according to claim 1, characterized in that: In step (2), the weight ratio of the natural rubber to the waste rubber powder modified in step (1) is 30:(50-100).

6. A waste rubber product mixing process according to claim 1, characterized in that: In step (2), the plasticizing temperature is 120-130° C., and the plasticizing time is 22-30 min; and / or, in step (3), the weight ratio of the styrene-butadiene rubber and butadiene rubber to the mixture prepared in step (2) is 10:(5-15):(50-100).

7. The process for mixing waste rubber products according to claim 1, wherein: In step (3), the weight ratio of the mixture prepared in step (2) to graphene and carbon black is 80:(0.5-2):(30-45).

8. A waste rubber product mixing process according to claim 1, characterized in that: In step (3), the weight ratio of the mixture prepared in step (2) to the nano-silica and the composite surfactant is 80:(0.2-5)(0.5-3); and / or, in step (4), the vulcanizing agent includes sulfur powder and morpholine disulfide.

9. A waste rubber product mixing process according to claim 1, characterized in that: In step (4), the vulcanization process is: keeping warm at 90-100°C for 2-4 minutes, then keeping warm at 130-145°C for 5-8 minutes, and then keeping warm at 146-150°C for 3-5 minutes.

10. A mixing process for waste rubber products according to any one of claims 1 to 9, characterized in that: In step (3), after adding carbon black, single-walled carbon nanotubes modified with a silane coupling agent are also added.

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