A mixing process for waste rubber products

Abstract

The application discloses a kind of waste and old rubber product mixing processes, belong to waste and old rubber recycling technical field, the waste and old rubber product mixing process provided by the application, including the following steps: waste and old rubber product is sheared, then desulfurization is activated, is crushed, and waste and old rubber powder is obtained, then waste and old rubber powder is surface modified using silane coupling agent, and modified waste and old rubber powder is obtained;Take natural rubber and modified waste and old rubber powder and mix, and plasticize, and obtain mixed material;Take styrene-butadiene rubber and butadiene rubber and mixed material and mix, then add graphene, carbon black and carry out first mixing, then add nano silicon dioxide and carry out second mixing, add composite surfactant and carry out third mixing, and obtain mixing material;Mixing material is mixed with vulcanizing agent, zinc oxide and anti-aging agent, and vulcanized, and obtain rubber product;Composite surfactant includes zinc stearate, tween 80 and sodium dodecyl benzene sulfonate.The rubber product of the application has good mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of waste rubber recycling, and particularly relates to a waste rubber product mixing process. BACKGROUND

[0002] Waste rubber is called "black pollution" due to its non-degradability and potential pollution risk. It takes hundreds of years for waste rubber to degrade naturally, occupies land when stacked, and releases heavy metals (such as zinc and lead) to pollute soil and groundwater. Open-air stacking is also prone to breeding mosquitoes and spreading diseases such as dengue fever. In addition, waste rubber is highly flammable (with a higher heat value than coal), and stacking can easily cause fires and release toxic gases such as dioxin.

[0003] Due to the large scale of the automobile industry, the amount of waste tires is extremely large. If not recycled, it is equivalent to wasting millions of tons of rubber resources every year. The existing technology also attempts to recycle waste rubber, but the mechanical properties of the products obtained by the existing technology using waste rubber are poor, which limits the recycling of waste rubber to some extent.

[0004] Therefore, it is urgent to provide a new waste rubber recycling method, and the mechanical properties of the products prepared are good. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a waste rubber product mixing process. The rubber product obtained by the process has good mechanical properties, such as good tensile strength and hardness, which is beneficial to the recycling of waste rubber, not only can it turn waste into treasure, but also can increase economic income.

[0006] The present invention focuses on a ternary technical path of synergistic nano-reinforcement, interface modification and vulcanization, which breaks through the mechanical performance bottleneck of waste rubber regeneration products. The core is: (1) using graphene and carbon black to build a three-dimensional reinforcing network, combined with nano-silica rigid particle filling to improve the hardness and stress transfer efficiency of the rubber product; (2) the surface of the rubber powder is modified by silane coupling agent, which enhances the interface bonding force between the waste rubber powder and the matrix and reduces the defect concentration; (3) introduce sulfur powder, disulfide morpholine and other composite vulcanization systems and optimize the step vulcanization process to form a uniform network structure with high crosslinking density. Finally, under the premise of maintaining a high proportion of waste rubber powder, the tensile strength exceeds 17 MPa, the Shore hardness exceeds 67HA, while taking into account the process compatibility and environmental friendliness. In addition, the composite surfactant composed of the three surfactants used in the present invention respectively covers metal soap (zinc stearate), non-ionic (Tween 80) and anionic (sodium dodecyl benzene sulfonate), which synergistically treats the polarity difference in rubber. Among them, zinc stearate dominates the vulcanization activation and processing lubrication, Tween 80 strengthens the emulsification stability and compatibility, and sodium dodecyl benzene sulfonate provides strong dispersion and interface modification. The combination of the three avoids the limitations of single components, ensuring that the fillers (graphene, carbon black, nano-silica) and modified waste rubber powder are uniformly dispersed under high filling amount, thereby facilitating the improvement of the mechanical properties of the final rubber product.

[0007] A waste rubber product mixing process, comprising the following steps:

[0008] (1) Shearing the waste rubber product, then devulcanizing and activating, crushing to obtain waste rubber powder, then surface modifying the waste rubber powder with silane coupling agent to obtain modified waste rubber powder;

[0009] (2) Mixing natural rubber with the modified waste rubber powder of step (1) to obtain a mixture;

[0010] (3) Mixing styrene-butadiene rubber and butadiene rubber with the mixture prepared in step (2), then adding graphene, carbon black and nano-silica for the first mixing, adding nano-silica for the second mixing, and adding a composite surfactant for the third mixing to obtain a mixed material;

[0011] (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;

[0012] The composite surfactant comprises zinc stearate, Tween 80 and sodium dodecyl benzene sulfonate.

[0013] Preferably, in the composite surfactant, the weight ratio of zinc stearate, Tween 80 and sodium dodecyl benzene sulfonate is 1.5:(0.5-1):(0.3-1).

[0014] Preferably, the surface modification of the waste rubber powder in step (1) is carried out by adding a silane coupling agent to the waste rubber powder.

[0015] The silane coupling agent is added to a mixture of ethanol and water, stirred, and then the waste rubber powder is added, heated and stirred, washed, and dried to obtain the modified waste rubber powder.

[0016] Preferably, the weight of the silane coupling agent is 1% to 3% of the weight of the waste rubber powder.

[0017] Preferably, the weight ratio of the mixture to the waste rubber powder is (1.1 to 1.5): 1.

[0018] Preferably, the volume ratio of ethanol to water is (7 to 9): 1.

[0019] Preferably, ammonia is added to the mixture of ethanol and water to adjust the pH to 9 to 10.

[0020] Preferably, the temperature of the heating and stirring is 40 to 50°C, and the time is 30 to 60 minutes.

[0021] Preferably, the washing is carried out with ethanol.

[0022] Preferably, the drying is carried out under vacuum at 50 to 60°C.

[0023] Preferably, in step (1), the mesh size of the waste rubber powder is 60 to 100 mesh, and further preferably 70 to 80 mesh.

[0024] Preferably, in step (1), the devulcanization is carried out using 1-pentanethiol.

[0025] Preferably, in step (1), the weight ratio of the waste rubber product to 1-pentanethiol is 100:(2 to 5).

[0026] Preferably, in step (1), the temperature of the devulcanization is 140 to 150°C, and the time is 0.5 to 1 hour.

[0027] Preferably, in step (2), the weight ratio of the natural rubber to the modified waste rubber powder of step (1) is 30:(50 to 100), and further preferably 30:(70 to 100).

[0028] Preferably, in step (2), the temperature of the mastication is 120 to 130°C, and the time of the mastication is 22 to 30 minutes.

[0029] Preferably, in step (2), the mastication is carried out in an internal mixer.

[0030] Preferably, in step (2), the particle size of the natural rubber is less than 5mm.

[0031] Preferably, in step (3), the weight ratio of the butadiene styrene rubber and cis-butadiene rubber to the mixture prepared in step (2) is 10: (5-15): (50-100).

[0032] Preferably, in step (3), the weight ratio of the mixture prepared in step (2) to the graphene and carbon black is 80: (0.5-2): (30-45), and further preferably 80: (0.5-1.5): (35-40).

[0033] Preferably, 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).

[0034] Preferably, in step (3), the temperature of the first mixing is 90-100℃, and the time is 3-6min.

[0035] Preferably, in step (3), the temperature of the second mixing is 90-100℃, and the time is 2-4min.

[0036] Preferably, in step (3), the temperature of the third mixing is 90-100℃, and the time is 2-5min.

[0037] Preferably, in step (4), the vulcanizing agent includes sulfur powder and dimorpholine disulfide.

[0038] 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).

[0039] Preferably, the weight ratio of the sulfur powder to the dimorpholine disulfide is 1: (0.8-1.2).

[0040] Preferably, in step (4), the vulcanization process is: keeping at 90-100℃ for 2-4min, then keeping at 130-145℃ for 5-8min, and then keeping at 146-150℃ for 3-5min. The stepwise temperature rising vulcanization is beneficial to improve the mechanical properties of the prepared rubber product.

[0041] Preferably, in step (3), after the addition of carbon black, single-walled carbon nanotubes modified by silane coupling agents are also added. The single-walled carbon nanotubes modified by silane coupling agents form an electron channel with graphene through π-π conjugation, improve the stress transfer efficiency, in addition, the silane coupling agent realizes molecular-level interface bonding of single-walled carbon nanotubes-rubber through covalent bond bridging, optimizes the stress transfer efficiency, inhibits defect propagation, and finally achieves breakthroughs in tensile strength and elongation at break performance, so that the tensile strength of the finally prepared rubber product is ≥18.5 MPa, and the elongation at break is ≥390%.

[0042] Preferably, in step (3), the weight ratio of the mixture prepared in step (2) to the single-walled carbon nanotubes modified by silane coupling agents is 80:(0.2-0.6).

[0043] Preferably, the preparation process of the single-walled carbon nanotubes modified by silane coupling agents comprises:

[0044] S1, mixing single-walled carbon nanotubes with acid solution, ultrasonic treatment, then centrifugation, washing, drying, to obtain oxidized single-walled carbon nanotubes;

[0045] S2, adding a silane coupling agent to an alcohol-water mixed solution, adjusting the pH to be acidic, heating and reacting, then adding the oxidized single-walled carbon nanotubes, and refluxing and reacting under a protective gas atmosphere, centrifuging, then washing with toluene and ethanol alternately, and drying, to obtain the single-walled carbon nanotubes modified by silane coupling agents.

[0046] Preferably, in S1, the acid solution is a mixture of water, sulfuric acid and nitric acid in a weight ratio of 10:(2-3):(0.5-1). The role of S1 is to carboxylate the surface of the single-walled carbon nanotubes.

[0047] Preferably, in step S1, the weight ratio of the single-walled carbon nanotubes to the acid solution is 1:(8-12).

[0048] Preferably, in step S1, the ultrasonic temperature is 50-60°C, and the time is 1-2h.

[0049] Preferably, in step S1, the washing is water washing to neutral.

[0050] Preferably, in step S1, the drying is vacuum drying at 50-60°C.

[0051] Preferably, in step S2, the weight ratio of the silane coupling agent to the alcohol-water mixed solution is 1.5-3:100.

[0052] Preferably, in step S2, the weight ratio of the oxidized single-walled carbon nanotubes to the alcohol-water mixed solution is 1:(15-30).

[0053] Preferably, in step S2, the silane coupling agent comprises KH550.

[0054] Preferably, in step S2, the alcohol and water mixed solution comprises ethanol and water, and the volume ratio of the ethanol to water is (7-9):1.

[0055] Preferably, in step S2, the acidity is to pH 4-5. For example, adjust the pH with acetic acid solution.

[0056] Preferably, in step S2, the heating reaction temperature is 55-65°C, and the time is 40-60 min.

[0057] Preferably, in step S2, the protective gas comprises nitrogen or a noble gas. For example, argon, helium.

[0058] Preferably, in step S2, the temperature of the temperature rising reflux reaction is 100-110°C, and the time is 12-24 h.

[0059] Preferably, in step S2, the drying is vacuum drying at 50-60°C.

[0060] Compared with the prior art, the application has the following beneficial effects:

[0061] (1) The application uses graphene and carbon black to construct a three-dimensional reinforcing network, combines with nano-silicon dioxide rigid particle filling to improve the hardness and stress transfer efficiency of the rubber product; the surface of the rubber powder is modified by grafting with a silane coupling agent to enhance the interface bonding force between the waste rubber powder and the matrix and reduce defect concentration; a composite vulcanization system such as sulfur powder and dimorpholine disulfide is introduced and the step vulcanization process is optimized to form a uniform network structure with high crosslinking density. Finally, under the premise of maintaining a high proportion of waste rubber powder, the tensile strength exceeds 17 MPa, the Shore hardness exceeds 67HA, while the process compatibility and environmental friendliness are taken into account. The composite surfactant has the effect of improving the mechanical properties of the final rubber product.

[0062] (2) After adding carbon black, single-walled carbon nanotubes modified by a silane coupling agent are also added. The single-walled carbon nanotubes modified by the silane coupling agent form an electronic channel with graphene through π-π conjugation, improve the stress transfer efficiency, in addition, the silane coupling agent realizes molecular-level interface bonding between single-walled carbon nanotubes and rubber through covalent bond bridging, optimizes the stress transfer efficiency, and inhibits defect propagation, finally realizes breakthrough in tensile strength and elongation at break performance, so that the tensile strength of the finally prepared rubber product is ≥18.5 MPa, and the elongation at break is ≥390%. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present application will be clearly and completely described below with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work are within the protection scope of the present application. Meanwhile, the raw materials, reagents or devices used in the following embodiments are commercially available or can be obtained by the known methods, if not specifically stated.

[0064] Embodiment 1

[0065] A waste rubber product mixing process, comprising the following steps:

[0066] (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 temperature of the desulfurization activation is 140℃, the time is 45 min, and then the waste rubber product is crushed to 80 meshes to obtain waste rubber powder, and then the waste rubber powder is surface modified by using a silane coupling agent to obtain modified waste rubber powder;

[0067] The process of surface modification of the waste rubber powder by using the silane coupling agent comprises:

[0068] The silane coupling agent KH550 is added into a mixture of ethanol and water (the volume ratio is 9:1) (the mixture is adjusted to pH 9 by using ammonia water), the mixture is stirred, then the waste rubber powder is added, heated to 60℃ and stirred for 40 min, washed by using ethanol, and dried at 60℃ to obtain the modified waste rubber powder;

[0069] The weight of the silane coupling agent KH550 is 2% of the weight of the waste rubber powder, and the weight ratio of the mixture to the waste rubber powder is 1.2:1.

[0070] (2) The natural rubber (the particle size is less than 5 mm) is mixed with the modified waste rubber powder of step (1), the weight ratio of the natural rubber to the modified waste rubber powder of step (1) is 30:80, and plasticizing is performed in a banbury mixer, the temperature of the plasticizing is 120℃, and the time of the plasticizing is 25 min to obtain a mixture;

[0071] (3) take the butadiene rubber and cis-butadiene rubber and the mixture prepared in step (2) (the weight ratio of butadiene rubber and cis-butadiene rubber to the mixture prepared in step (2) is 10:10:80) to mix, then add graphene, carbon black to mix for the first time, the temperature of the first mixing is 90℃, the time is 5min, then add nano-silicon dioxide 95℃ mix for 2min, then add composite surfactant 95℃ mix for 4min, to get the mixed material, the weight ratio of the mixed material to graphene, carbon black is 80:1:40; the weight ratio of the mixed material to nano-silicon dioxide, composite surfactant is 80:0.8:1;

[0072] (4) mix the mixed material prepared in step (3) with vulcanizing agent, zinc oxide, 2-mercaptobenzimidazole (the weight ratio of the mixed material to vulcanizing agent, zinc oxide, 2-mercaptobenzimidazole is 100:2:3:3), the vulcanizing agent is composed of sulfur powder and morpholine disulfide according to the weight ratio of 1:1.2, heat at 100℃ for 2min, then heat at 140℃ for 6min, and then heat at 150℃ for 4min, to get the rubber product;

[0073] The composite surfactant is composed of zinc stearate, tween 80 and sodium dodecyl benzene sulfonate according to the weight ratio of 1.5:0.8:0.5.

[0074] Example 2

[0075] A waste rubber product mixing process, comprising the following steps:

[0076] (1) cut the waste rubber product, then mix with 1-pentanethiol to activate desulfurization (the weight ratio of waste rubber product to 1-pentanethiol is 100:3.5), the temperature of desulfurization activation is 145℃, the time is 45min, then crush to 80 mesh, to get waste rubber powder, then modify the surface of the waste rubber powder with silane coupling agent, to get modified waste rubber powder;

[0077] The process of modifying the surface of the waste rubber powder with silane coupling agent includes:

[0078] Add silane coupling agent KH550 to the mixture of ethanol and water (volume ratio is 9:1) (adjust the pH of the mixture to 10 with ammonia water), stir and mix, then add waste rubber powder, heat to 50℃ and stir for 40min, wash with ethanol, dry at 60℃, to get modified waste rubber powder;

[0079] The weight of silane coupling agent KH550 is 2% of the weight of waste rubber powder, the weight ratio of the mixture to waste rubber powder is 1.1:1.

[0080] (2) Take natural rubber (particle size less than 5 mm) and step (1) modified waste rubber powder mixed, the weight ratio of natural rubber and step (1) modified waste rubber powder is 30:80, plasticizing in the internal mixer, the temperature of plasticizing is 125℃, the time of plasticizing is 25min, get the mixed material;

[0081] (3) Take styrene butadiene rubber and butadiene rubber and step (2) prepared mixed material mixed (styrene butadiene rubber and butadiene rubber and step (2) prepared mixed material weight ratio is 10:15:80), then add graphene, carbon black for the first time mixing, the temperature of the first time mixing is 90℃, the time is 5min, add nano silicon dioxide 90℃ mixing 2min, add composite surfactant 90℃ mixing 3min, get the mixing material, the weight ratio of mixed material and graphene, carbon black is 80:0.9:41; The weight ratio of mixed material and nano silicon dioxide, composite surfactant is 80:0.9:1;

[0082] (4) The mixing material prepared in step (3) is mixed with vulcanizing agent, zinc oxide, 2-mercaptobenzimidazole (the weight ratio of mixing material, vulcanizing agent, zinc oxide, 2-mercaptobenzimidazole is 100:1.5:3:3), the vulcanizing agent is composed of sulfur powder and morpholine disulfide according to the weight ratio of 1:1.1, heat preservation at 100℃ for 2min, then heat preservation at 145℃ for 6min, and heat preservation at 155℃ for 4min, get the rubber product;

[0083] The composite surfactant is composed of zinc stearate, tween 80 and sodium dodecyl benzene sulfonate according to the weight ratio of 1.5:0.6:0.5.

[0084] Example 3

[0085] A waste rubber product mixing process, comprising the following steps:

[0086] (1) The waste rubber product is sheared, then mixed with 1-pentanethiol for desulfurization activation (the weight ratio of waste rubber product and 1-pentanethiol is 100:3), the temperature of desulfurization activation is 140℃, the time is 45min, then crushed to 80 mesh, get the waste rubber powder, then the surface of the waste rubber powder is modified with silane coupling agent, get the modified waste rubber powder;

[0087] The process of modifying the surface of the waste rubber powder with silane coupling agent includes:

[0088] Add silane coupling agent KH550 to the mixture of ethanol and water (volume ratio is 9:1) (the mixture is adjusted to pH 9 with ammonia water), stir and mix, then add waste rubber powder, heat to 60℃ and stir for 40min, wash with ethanol, dry at 60℃, get the modified waste rubber powder;

[0089] 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 solution to the waste rubber powder is 1.2:1.

[0090] (2) The natural rubber (particle size less than 5 mm) is mixed with the modified waste rubber powder of step (1), and the weight ratio of the natural rubber to the modified waste rubber powder of step (1) is 30:80. Plastication is carried out in a plasticator, the plastication temperature is 120°C, and the plastication time is 25 min, to obtain a mixture;

[0091] (3) The butadiene styrene rubber and butadiene rubber are mixed with the mixture prepared in step (2) (the weight ratio of butadiene styrene rubber and butadiene rubber to the mixture prepared in step (2) is 10:10:80), then graphene, carbon black, and silane coupling agent modified single-walled carbon nanotubes are added for first mixing, the first mixing temperature is 90°C, and the first mixing time is 5 min. Nano-silicon dioxide is added at 95°C for 2 min, and then composite surfactant is added at 95°C for 4 min to obtain a mixed material. The weight ratio of the mixture to graphene, carbon black, and silane coupling agent modified single-walled carbon nanotubes is 80:1:40:0.5. The weight ratio of the mixture to nano-silicon dioxide and composite surfactant is 80:0.8:1;

[0092] The preparation process of the silane coupling agent modified single-walled carbon nanotube includes:

[0093] S1, mixing single-walled carbon nanotubes with acid solution (the acid solution is composed of water, sulfuric acid, and nitric acid in a weight ratio of 10:2:0.5), ultrasonic treatment at 60°C for 1.5 h, then centrifugation, water washing to neutral, and vacuum drying at 60°C to obtain oxidized single-walled carbon nanotubes;

[0094] S2, adding silane coupling agent KH550 into alcohol-water mixed solution (composed of ethanol and water in a volume ratio of 9:1), the weight ratio of silane coupling agent KH550 to alcohol-water mixed solution is 2:100, adjusting pH to 4 with acetic acid, heating at 60°C for 50 min, then adding oxidized single-walled carbon nanotubes, heating and refluxing under nitrogen atmosphere, the heating and refluxing temperature is 110°C, and the time is 24 h, centrifugal separation, then washing with toluene and ethanol alternately for 3 times, and vacuum drying at 60°C to obtain silane coupling agent modified single-walled carbon nanotubes;

[0095] (4) Mixing the mixed material prepared in step (3) with vulcanizing agent, zinc oxide, and 2-mercaptobenzimidazole (the weight ratio of the mixed material to vulcanizing agent, zinc oxide, and 2-mercaptobenzimidazole is 100:2:3:3), the vulcanizing agent is composed of sulfur powder and morpholine disulfide in a weight ratio of 1:1.2, heating at 100°C for 2 min, then heating at 140°C for 6 min, and heating at 150°C for 4 min to obtain a rubber product.

[0096] The composite surfactant is composed of zinc stearate, tween 80 and sodium dodecyl benzene sulfonate in a weight ratio of 1.5:0.8:0.5.

[0097] Example 4

[0098] Compared with Example 1, the difference of Example 4 is only in step (4), and the content of step (4) of Example 4 is as follows:

[0099] The mixing material prepared in step (3) is mixed with vulcanizing agent, zinc oxide and 2-mercaptobenzimidazole (the weight ratio of the mixing material, vulcanizing agent, zinc oxide and 2-mercaptobenzimidazole is 100:2:3:3), and the vulcanizing agent is composed of sulfur powder, and the rubber product is obtained by keeping at 140℃ for 12 min.

[0100] Comparative Example 1

[0101] Compared with Example 1, the difference of Comparative Example 1 is only that an equal amount of sodium dodecyl sulfate is used instead of sodium dodecyl benzene sulfonate, and the other processes are the same as those of Example 1.

[0102] Comparative Example 2

[0103] Compared with Example 1, the difference of Comparative Example 2 is only 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.

[0104] Product effect test:

[0105] The rubber products prepared in the above examples and comparative examples are taken to test the Shore hardness according to GB / T 531.1-2019 “Vulcanized or thermoplastic rubber compression hardness test Part 1: Shore hardness tester method”, and the tensile strength and elongation at break are tested according to GB / T 528-2009 “Determination of tensile stress-strain properties of vulcanized or thermoplastic rubber”, and the results are shown in Table 1:

[0106] Table 1

[0107]

[0108] As can be seen from Table 1, the mechanical properties of the rubber products prepared in Examples 1-4 of the present application are obviously better than those of Comparative Examples 1-2.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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 process for mixing waste rubber products, characterized in that, The method comprises the following steps: (1) cutting waste rubber products, then carrying out devulcanization and activation, crushing to obtain waste rubber powder, and then carrying out surface modification on the waste rubber powder by using a silane coupling agent to obtain modified waste rubber powder; (2) mixing natural rubber and the modified waste rubber powder of step (1) to carry out plasticizing 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 to carry out first mixing, adding nano-silicon dioxide to carry out second mixing, and adding a composite surfactant to carry out third mixing to obtain a mixed material; (4) mixing the mixed material prepared in step (3) with a vulcanizing agent, zinc oxide and an anti-aging agent to vulcanize to obtain a rubber product. The composite surfactant comprises zinc stearate, Tween 80 and sodium dodecyl benzene sulfonate. In the composite surfactant, the weight ratio of zinc stearate, Tween 80 and sodium dodecyl benzene sulfonate is 1.5:(0.5-1):(0.3-1). 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). In step (3), the weight ratio of the mixture prepared in step (2) to nano-silicon dioxide and the composite surfactant is 80:(0.2-5):(0.5-3).

2. The mixing process of waste rubber products according to claim 1, characterized in that, In step (1), the process of surface modification of the waste rubber powder by using a silane coupling agent comprises: adding a silane coupling agent into a mixture of ethanol and water, stirring and mixing, then adding waste rubber powder, heating and stirring, washing and drying to obtain modified waste rubber powder.

3. A process for mixing waste rubber products according to claim 2, characterized in that, The weight of the silane coupling agent is 1%-3% of the weight of the waste rubber powder; and / or, the weight ratio of the mixture to the waste rubber powder is (1.1-1.5):1; and / or, the temperature of the heating and stirring is 40-50 DEG C, and the time is 30-60 min.

4. The process of claim 1, wherein the waste rubber product is mixed with the solvent at a temperature of 100- 150°C. In step (2), the weight ratio of the natural rubber to the modified waste rubber powder of step (1) is 30:(50-100).

5. The process of claim 1, wherein the waste rubber product is mixed with the solvent at a temperature of 100- 150°C. In step (2), the temperature of the plasticizing is 120-130 DEG C, and the time of the plasticizing 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).

6. The process of claim 1, wherein the waste rubber product is mixed with the solvent at a temperature of 100- 150°C. In step (4), the vulcanizing agent comprises sulfur powder and dimorpholine disulfide.

7. The process of claim 1, wherein the waste rubber product is mixed with the solvent at a temperature of 100- 150°C. In step (4), the vulcanizing process is: keeping at 90-100 DEG C for 2-4 min, then keeping at 130-145 DEG C for 5-8 min, and then keeping at 146-150 DEG C for 3-5 min.

8. The process according to any one of claims 1 to 7, characterized in that, In step (3), after adding carbon black, single-walled carbon nanotubes modified by a silane coupling agent are also added.

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