Natural rubber composite, wet-mixing masterbatch, and method for preparing the same

Abstract

The application discloses a natural rubber composite material, a wet-mixing masterbatch and a preparation method thereof. Firstly, filler slurry and natural rubber latex are respectively delivered to different nozzles; the nozzles are arranged uniformly around the same spraying collision center and form a free collision area, and instantaneous contact dispersion occurs; then, the wet-mixing masterbatch is obtained through subsequent dehydration, washing and drying; and finally, the natural rubber composite material is obtained through mixing and vulcanization molding. The natural rubber composite material comprises a rubber matrix and functional fillers, the dispersion uniformity of the functional fillers is above 9, and the contact area of the fillers and the rubber matrix forms a hierarchical interface structure including a tightly combined rubber layer and a loosely combined rubber layer in sequence. The application can not only obtain the natural rubber composite material with excellent comprehensive performance, but also shorten the process and improve the process efficiency.

Description

Technical Field

[0001] This invention relates to the field of natural rubber composite materials and their preparation technology, specifically to a wet mixing method of nanofillers with natural rubber latex and / or other latexes and the resulting natural rubber composite material. Background Technology

[0002] Natural rubber is the only bio-based polymer elastomer among the world's four major industrial raw materials that possesses the attribute of being renewable throughout its entire life cycle. It has a series of core advantages that cannot be completely replaced by synthetic rubber materials. It is a core basic material for emerging industries such as aircraft (including helicopters and low-altitude aircraft), ships, marine engineering, rail transportation, wind power, and automobiles. It has been included in the list of key materials related to industrial security and the security of industrial and supply chains by major industrial countries around the world and is subject to key control.

[0003] As the world's largest consumer and importer of natural rubber, my country has a higher dependence on foreign high-performance specialty natural rubber, which has driven up rubber costs. If we can make fuller use of locally produced Eucommia ulmoides rubber, TPI or TBIR modified natural rubber, it will be of great significance to reduce rubber production costs and increase product profit margins.

[0004] Existing preparation processes for natural rubber composite materials mainly include dry mixing and wet mixing.

[0005] Dry mixing typically relies on the mechanical shearing of an internal mixer or open mill to mix the filler with the rubber. The prolonged and intense shearing during the mixing process can easily reduce the molecular weight of natural rubber. Furthermore, dry mixing also has problems such as high dust pollution and high energy consumption.

[0006] Wet mixing, which involves pre-dispersing fillers in an aqueous phase before mixing with natural rubber latex, helps improve the initial dispersion state of the fillers. However, existing wet mixing technologies still have the following problems:

[0007] 1. Existing pretreatment methods for fillers can only reduce the size of the fillers to the micrometer level; further dispersion is required to prepare nanomaterials. 2. The contact efficiency between the filler slurry and natural rubber latex is limited, resulting in insufficient mixing in some areas; 3. The dispersed structure established in the early stage is easily destroyed during the coagulation stage; 4. Existing wet mixing processes lack sufficient coordinated control over key parameters such as pressure, flow rate, temperature, and pH, resulting in poor process stability and repeatability during continuous and large-scale preparation. 5. Insufficient interfacial bonding between the filler and the rubber matrix, resulting in an imperfect stress transfer structure; 6. Existing wet mixing methods require the synthetic rubber obtained from bulk polymerization to be dissolved in organic solvents before blending with natural rubber, which poses significant environmental pollution and safety risks.

[0008] Existing technologies for preparing natural rubber nanocomposites are not comprehensive and effective in controlling the size, dispersion level, interfacial gradient morphology, and network construction perfection of filler aggregates, making it difficult to suppress subsequent re-agglomeration of fillers. Summary of the Invention

[0009] The technical problem to be solved by this invention is to overcome the shortcomings and defects mentioned in the background art above, and to provide a method for preparing wet-process compounding masterbatch of natural rubber composite materials based on center-jet collision, so as to solve at least one of the problems of insufficient dispersion of nanofillers in natural rubber systems, easy re-agglomeration, insufficient interfacial bonding, and poor process stability in the prior art. Another objective of this invention is to provide a natural rubber composite material prepared based on the above method and its preparation method, in which the filler can be dispersed in a more uniform state in the natural rubber matrix and form a more stable filler-rubber interface structure, thereby improving the comprehensive performance of the composite material.

[0010] To solve the above-mentioned technical problems, the technical solution proposed in this invention is a method for preparing wet-process compounding masterbatch of natural rubber composite materials, comprising the following steps: (a) Preparation of filler slurry and natural rubber latex; (b) The filler slurry and natural rubber latex are respectively conveyed to different nozzles through independent conveying devices; the filler slurry and natural rubber latex are sprayed out through the nozzles after being driven by pressure to form multiple solid cone mists; The different nozzles are configured to be evenly arranged around the same spray collision center. The multiple solid cone mists form a free collision zone in the vicinity of the spray collision center (there are no other objects or components around the spray to limit its diffusion path, that is, to provide a certain amount of free space for the center-to-center collision), and contact dispersion occurs in the free collision zone. (c) The composite masterbatch slurry obtained after step (b) is introduced into a collection device, and then dehydrated, washed and dried to obtain wet-mixed masterbatch of natural rubber composite material.

[0011] The above technical solution enables the filler slurry and natural rubber latex to undergo instantaneous contact and high-intensity mixing in the free collision zone under the action of a high-pressure jet with opposing impacts. The latex particles undergo controlled instability under the action of high shear and local flow field disturbance, and form a coating and co-aggregated structure with the filler.

[0012] In the above-mentioned preparation method, preferably, the cone angle of the solid cone mist is 30° to 70°, the number of nozzles is 2 to 4, the nozzle orifice diameter is 0.5 to 2.0 mm, and the nozzle spacing is 20 to 80 mm.

[0013] In the above-described preparation method, preferably, the different nozzles are configured to be uniformly arranged around the same jet collision center. Specifically, when there are two nozzles, the two nozzles are arranged coaxially and centered relative to each other; when there are three or more nozzles (preferably no more than four), the multiple nozzles are uniformly arranged around the same jet collision center on the entire circumference. More preferably, the number of nozzles is two, and the two nozzles are arranged coaxially and centered relative to each other.

[0014] In the above preparation method, preferably, the filler slurry and natural rubber latex are respectively transported by a high-pressure metering pump, the pipeline transport pressure is 2-15 MPa, the average flow velocity at the nozzle outlet is 30-150 m / s, and the momentum ratio J of the jets ejected from different nozzles is controlled between 0.8 and 1.2 (more preferably 0.9-1.1), wherein the momentum ratio J is expressed by the following formula: J = (ρ1v1²A1): (ρ2v2²A2):…… (ρ n v n ²A n ); Where ρ1, ρ2, ρ n These represent the fluid densities ejected from nozzles 1, 2, and n, respectively. v1, v2, v n These represent the average flow velocities at the outlets of nozzles 1, 2, and n, respectively. A1, A2, A n These represent the outlet cross-sectional areas of nozzles 1, 2, and n, respectively.

[0015] In the above preparation method, preferably, the system temperature in the free collision zone is controlled at 15℃~30℃ (more preferably 20℃~25℃); the pH of the natural rubber latex feeding section is maintained at 8.5~10.5.

[0016] Preferably, by setting up an online detection and closed-loop control system in the above process, the feed pressure, feed flow rate, system temperature, and pH before the nozzle can be monitored online, and the feed state can be adjusted in real time according to the feedback results. This ensures that the collision mixing process around the spray collision center is stabilized within a preset process window. Through the coordinated control of key parameters, the consistency of the flow field in the collision mixing region can be improved, enhancing process repeatability and batch stability. The feed flow rates of the filler slurry and natural rubber latex can be determined based on their respective solid content and target formulation. The amount of nanofiller relative to 100 parts of dry rubber is preferably 5 to 120 parts, more preferably 10 to 80 parts.

[0017] The above-described preparation method, preferably, includes the following steps: adding nanofillers to a dispersion medium, and pretreating with surfactants and coupling agents, thereby obtaining a stable filler slurry under multi-stage dispersion operations; the amount of nanofillers relative to 100 parts of natural rubber latex dry rubber is 5-120 parts, preferably 10-80 parts; the total amount of surfactants added is 1%-50% of the mass of the nanofillers; and the total amount of coupling agents added is 1%-25% of the mass of the nanofillers. The dispersion medium contains deionized water; The nanofiller comprises at least one of carbon black, silica, graphene oxide, carbon nanotubes, clay, aluminum hydroxide, and magnesium hydroxide. The surfactant includes at least one of anionic surfactants, cationic surfactants, and nonionic surfactants.

[0018] As a further improvement in the preparation of nanofillers, the surface of the nanofillers contains hydroxyl, carboxyl, or alkoxy groups, or is modified with reactive groups after pretreatment; a coupling agent is also added to the dispersion medium; the coupling agent is a silane coupling agent; and the surfactant is an anionic surfactant. More preferably, the coupling agent includes at least one of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, γ-aminopropyltriethoxysilane, and γ-mercaptopropyltriethoxysilane, and its amount is 1% to 25% of the mass of the nanofillers. Through the above-mentioned formulation optimization and subsequent multi-stage dispersion measures, the present invention can achieve the effect of fully dispersing the nanofillers without adding other types of dispersants.

[0019] As a further improvement in the preparation of nanofillers, the surfactant includes a compound of anionic surfactants, cationic surfactants, and nonionic surfactants to balance filler wetting and latex interfacial compatibility; more preferably, the anionic surfactant is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, fatty acid soap, and rosin soap; the cationic surfactant includes at least one of hexadecyltrimethylammonium bromide, quaternary ammonium salts, and ammonium salts; the nonionic surfactant includes at least one of polyoxyethylene sorbitan fatty acid ester, polyvinylpyrrolidone, polydopamine, alkylphenol polyoxyethylene ether, and polyvinyl alcohol; the total amount of surfactant added is 1% to 50% of the mass of the nanofiller.

[0020] As a further improvement in the preparation of nanofillers, the multi-stage dispersion operation includes two steps: pre-dispersion and graded depolymerization; the graded depolymerization includes three steps: high-shear stirring, ball milling dispersion, and ultrasonic dispersion.

[0021] By employing a three-stage dispersion process of "high-shear stirring-ball milling-ultrasonic dispersion" in combination with pre-dispersion, the filler agglomerates in the filler slurry can be completely broken up, ensuring that the nanofillers exist in the form of monodisperse or small-sized aggregates, thus providing a guarantee for the instantaneous mixing and uniform coating with the latex in the subsequent process. During the three-stage dispersion process, the turbulence intensity of the slurry flow field can be controlled throughout, avoiding the destruction of the filler structure caused by incomplete or excessive dispersion.

[0022] As a further improvement in the preparation of nanofillers, the pre-dispersion process is achieved by stirring, with a stirring speed of 500-2000 r / min, a stirring time of 10-60 min, and the temperature of the stirring system controlled below 35℃; after pre-dispersion, the resulting filler slurry has good fluidity and transport stability.

[0023] As a further improvement in the preparation of nanofillers, the high-shear stirring involves adding the pre-dispersed filler slurry into a high-speed shear disperser, controlling the rotation speed at 3000–20000 r / min, the temperature at 20–35℃, and the dispersion time at 0.5 h–2 h, thereby forming a preliminary stable suspension system.

[0024] As a further improvement in the preparation of nanofillers, the ball milling dispersion involves feeding the high-shear stirred filler slurry into a ball mill, using zirconia microspheres with a particle size of 0.05–0.3 mm as the grinding media; the ball mill's filling rate is 65%–75%, the ball milling speed is 2500–3000 r / min, and the circulating ball milling time is 0.5–5 h. By optimizing and controlling the ball milling and ultrasonic conditions, excessive damage to the nanofiller structure can be avoided, and the primary agglomerates and soft agglomerates of the filler can be further broken down.

[0025] As a further improvement in the preparation of nanofillers, the ultrasonic dispersion involves feeding the ball-milled and dispersed filler slurry into a high-frequency ultrasonic disperser, controlling the frequency at 25–35 kHz, the power at 8–12 kW, and the ultrasonic time at 15–25 min. The ultrasonic dispersion employs intermittent ultrasonic dispersion (e.g., ultrasonication for 5 min, followed by cooling for 2 min, repeated 3–5 times), with the ultrasonic dispersion temperature controlled at 20℃–30℃ to further break down micro-agglomerates and ensure the stability of the filler dispersion system. After ultrasonic dispersion, the solid content of the filler slurry is controlled at 20%–60%. A filter screen of 200 mesh or finer (filtration pressure 0.1 MPa, filtration speed 50 mL / min) is preferably used for filtration to remove impurities and grinding media residue, resulting in a uniform and stable multi-filler dispersion.

[0026] By controlling the pre-dispersion and graded deagglomeration processes described above, the particle size D50 of the nanofiller dispersion is achieved to be 0.5–5 μm. This structural design enhances the network structure of subsequent products. Simultaneously, the pre-dispersion and graded deagglomeration processes effectively break down primary aggregates and agglomerates of the filler, reducing the risk of clogging during subsequent jetting. Furthermore, it improves the uniformity of filler dispersion, providing a prerequisite and foundation for subsequent high-pressure jet instantaneous dispersion and mixing, and uniform coating after latex demulsification.

[0027] In the preferred embodiment of the above preparation method, the natural rubber latex comprises pure natural rubber (NR) latex, or a combination of pure natural rubber (NR) latex and eucommia ulmoides latex, or pure natural rubber (NR) latex and one or two synthetic latexes (such as chloroprene latex, styrene-butadiene latex, nitrile latex, and polybutadiene latex) in a mass ratio of 95:5 to 50:50, with a total solid content of 20% to 60%; and its pH is adjusted to 8.5 to 10.5 to improve storage stability and process stability during transportation. The pH adjustment can be achieved using ammonia or other suitable latex stabilizers.

[0028] In the above preparation method, preferably, the dehydration can be carried out by pressing dehydration, centrifugal dehydration, or a combination thereof, but preferably by staged pressing, with a pressing pressure of 0.2 to 2.0 MPa and a pressing time of 5 to 30 min; after dehydration, the moisture content of the composite masterbatch slurry is not higher than 35%; The washing method can be to directly stir or rinse with an aqueous solution, preferably to wash with an aqueous solution with a pH of 6-8 at least twice; The drying method is preferably vacuum drying, hot air drying, or a combination of vacuum and hot air drying, with staged heating vacuum drying being the most preferred. The vacuum degree is -0.06 to -0.095 MPa, the drying temperature is 50℃ to 80℃, and the drying time is 8 to 30 hours. To reduce rapid surface crusting and maintain the micro-dispersed structure, the moisture content of the composite masterbatch slurry after drying is not greater than 1.0%, more preferably not greater than 0.5%.

[0029] By using gentle dehydration and staged drying processes, the dispersed and interfacial structures formed in the preceding stages can be preserved as much as possible while removing moisture, thus reducing the adverse effects of post-processing on the composite system.

[0030] In the above-mentioned preparation method, preferably, after the composite masterbatch slurry is introduced into the collection device, it is no longer subjected to an acid coagulation process, so as to reduce the adverse effects of localized rapid coagulation on the dispersion structure of the filler.

[0031] As a general technical concept, the present invention also provides a method for preparing a natural rubber composite material, comprising the following steps: Step 1: Using the above preparation method, wet-process compound masterbatch is prepared; Step 2: Put the wet-mixed masterbatch and modifier obtained in Step 1 into an internal mixer for mixing; (the mixing temperature during mixing is preferably controlled at 110℃~160℃, and the time is 3~10 min) By using mixing, the coupling agent and filler and rubber undergo an in-situ grafting reaction, thereby improving the interfacial bonding level between the filler and rubber. Step 3: After the mixture from Step 2 is evenly mixed, cool it down to below 80°C, add activator and antioxidant, and continue mixing (preferably 3-8 min); then cool the compound to below 50°C again, add sulfur and accelerator, and continue mixing. When the temperature of the compound reaches above 100°C, discharge the compound to obtain the desired compound. Step 4: After the compounded rubber is left to stand, it is vulcanized and molded (preferably left to stand for 24 hours, then vulcanized at 130℃~150℃ and 20 MPa at t90) to obtain a natural rubber composite material.

[0032] In the above preparation method, preferably, the modifier includes a crystalline polymer modifier (preferably at least one of eucommia gum, TBIR, and TPI), and the mass ratio of the crystalline polymer modifier to natural rubber is 5-100%, preferably 10-50%. In this case, the mixing temperature during step 2 is controlled at 140℃-150℃. High-temperature mixing can reduce the viscosity of the crystalline rubber modifier, which is beneficial to improving the blending and dispersion level with natural rubber, thereby promoting further homogenization of the masterbatch and meeting the softening and dispersion requirements of the crystalline modifier. Since the crystalline rubber modifier has a high viscosity, it is necessary to increase the temperature to dissolve and crystallize it, thereby reducing viscosity and dispersing it. Simple wet mixing processes cannot dissolve it. At the same time, in order to further provide interfacial interaction between fillers, modifiers, and rubber, a high-temperature mixing method is preferred.

[0033] As a general technical concept, the present invention also provides a natural rubber composite material prepared by the above-described preparation method, the natural rubber composite material comprising: Rubber matrix, a network structure formed by rubber molecular chains; Functional filler, comprising a plurality of filler polymers filled in the network structure; The functional filler is uniformly dispersed in the rubber matrix, and the uniformity of filler dispersion characterized by the carbon black dispersion method is above level 9. The core of the filler polymer forms a hierarchical interface structure with the rubber matrix in the contact area between the core and the rubber matrix, which includes a tightly bonded rubber layer and a loosely bonded rubber layer. The tightly bonded rubber layer refers to the region where the molecular chains of the filler polymer and the rubber matrix achieve interfacial load transfer or structural anchoring through physical bonding points (e.g., physical adsorption, physical embedding) or chemical bonding points (e.g., hydrogen bonding / polar adsorption, chemical coupling adsorption). The loosely bonded rubber layer refers to the transition zone where the molecular chains of the filler polymer and the rubber matrix are not in direct contact (e.g., through mechanical entanglement of tightly bonded rubber chains and loosely bonded rubber chains).

[0034] Preferably, the rubber matrix of the above-mentioned natural rubber composite material is prepared by mixing pure natural rubber latex and eucommia gum latex in a mass ratio of 95:5 to 50:50; the mixed raw material also contains a modifying component formed by at least one of eucommia gum, TBIR, and TPI.

[0035] Compared with the prior art, the advantages of the present invention are as follows: 1. The aqueous wet mixing route of this invention adopts a continuous, center-to-center, high-pressure jet mixing method, which reduces dust pollution, high-energy mechanical shearing, and local overheating problems in traditional dry mixing. It also enables controlled demulsification and online closed-loop control, reducing process fluctuations and ineffective energy input. Through instantaneous center-to-center, high-pressure jet mixing of the latex, the uniformity of filler dispersion and local enrichment in the natural rubber matrix can be significantly improved.

[0036] 2. The preferred embodiment of this invention employs microscopic topological structure control technology for filler-rubber. Through optimization measures such as filler pre-dispersion in the aqueous phase and three-stage depolymerization, the original aggregates and agglomerates of the filler are effectively broken down, reducing the risk of clogging during subsequent jetting. Simultaneously, the uniformity of filler dispersion is further improved, achieving uniform coating after subsequent high-pressure jet instantaneous dispersion and mixing, and latex demulsification. In the optimal embodiment, this invention, through a combination of wet mixing (including three-stage depolymerization, instantaneous mixing with high-pressure jetting, multi-parameter closed-loop control, and gentle drying), high-temperature mixing (including interface-induced reactions and dispersion of crystalline polymers), room-temperature vulcanization, and high-pressure vulcanization, can further enhance the high performance and multifunctionality of natural rubber composite materials.

[0037] 3. This invention is particularly applicable to natural rubber systems filled with functional fillers such as flame retardants. By fully depolymerizing and controlling the interface before the functional filler enters the latex system, and by using a high-pressure jet with a counter-current flow to achieve more efficient dispersion and coating, it can maintain high mechanical properties as much as possible while imparting flame retardant and other functions to the composite material, thereby alleviating the technical contradiction that it is difficult to balance functionalization and high mechanical properties.

[0038] 4. This invention enables continuous production and improves process repeatability and batch stability by coordinating and controlling key parameters such as pipeline conveying pressure, nozzle structural parameters, feed flow rate, temperature, pH and jet flow rate ratio; combined with mild post-treatment, it can effectively maintain the molecular weight of natural rubber.

[0039] 5. This invention relates to a high-performance and multifunctional modification and preparation technology for natural rubber used in vibration reduction and noise reduction. By controlling the chemical reaction between natural rubber, modifier, filler, and coupling agent through subsequent high-temperature mixing, the interfacial bonding level between filler and rubber is improved, and the further crushing and dispersion of filler aggregates is promoted. At the same time, since the crystalline rubber modifier has a high viscosity, the viscosity is reduced by increasing the temperature to melt and crystallize, which is beneficial to improving the blending and dispersion level with natural rubber.

[0040] 6. This invention, through high-pressure vulcanization combined with a preceding mixing process, can effectively establish a filler-rubber interface gradient layer, orderly construct and stably maintain the filler network structure, and help reduce material defects, thereby obtaining high-performance and multifunctional natural rubber composite materials. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a process flow diagram of the preparation method of the natural rubber composite material of the present invention.

[0043] Figure 2 This is a schematic diagram of the structure of the dual-nozzle concentric high-pressure jet mixing device selected in the embodiment of the present invention.

[0044] Figure 3 The above is a schematic top view of the structure in which the nozzles are arranged around the same collision center in an embodiment of the present invention, wherein (a), (b), and (c) are schematic diagrams of the structure in which two, three, and four nozzles are arranged around the same collision center, respectively.

[0045] Figure 4 This is a schematic diagram of the online detection and closed-loop control system of the dual-nozzle center-to-center high-pressure jet mixing device in an embodiment of the present invention.

[0046] Figure 5 The following is a schematic diagram comparing the effects of center-to-center high-pressure jet mixing, conventional stirring mixing, and dry mixing on the microstructure of the product in the embodiments of the present invention: (a) is dry mixing; (b) is conventional stirring mixing; (c) is center-to-center high-pressure jet mixing; and (d) is a schematic diagram of the interfacial interaction mode of natural rubber composite filler in rubber matrix.

[0047] Figure 6 for Figure 5 The middle d-image is a magnified view of a portion of the area around the central particle.

[0048] Figure 7 This is a particle size distribution diagram of the packing material after three-stage dispersion in Example 1 of the present invention.

[0049] Figure 8 The graph shows a comparison of the carbon black dispersion of the natural rubber composite materials prepared in Example 3 and Comparative Example 3 of the present invention. In Figure (a), the carbon black dispersion of the traditional dry mixing process is grade 6, while in Figure (b), the carbon black dispersion of Example 3 of the present invention reaches grade 9.

[0050] Figure 9 The graph shows a comparison of the carbon black dispersion of the natural rubber composite materials prepared in Example 1 and Comparative Example 1 of the present invention. In Figure (a), the carbon black dispersion is grade 6 in the conventional dry mixing process, while in Figure (b), the carbon black dispersion in Example 1 of the present invention reaches grade 9.

[0051] Figure 10 This is a comparison diagram of the preparation process of the present invention with other existing rubber compounding processes in terms of process time.

[0052] Legend: 1. Filler slurry storage tank; 2. Natural rubber latex storage tank; 3. Filler slurry conveying pipeline; 4. Latex conveying pipeline; 5. Filler high-pressure metering pump; 6. Latex high-pressure metering pump; 7. Filler-side nozzle; 8. Latex-side nozzle; 9. Free collision zone; 10. Collection chamber; 11. Wet compound discharge port; 12. Pressure sensor; 13. Flow meter; 14. Temperature sensor; 15. pH sensor; 16. PLC controller; 17. Actuator unit; 18. Cooling jacket; 23. Collision center; 24. Spray cone coverage area. Detailed Implementation

[0053] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0054] It should be noted that when a component is described as being "fixed to, attached to, connected to or connected to" another component, it can be directly fixed to, attached to, connected to or connected to the other component, or it can be indirectly fixed to, attached to, connected to or connected to the other component through other intermediate connectors.

[0055] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0056] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0057] Unless otherwise specified, "parts" in the following examples and comparative examples refer to parts by weight; when taking 100 parts of dry adhesive, "100 parts" can be converted to 100 g, 1 kg or other proportional mass benchmarks, and each component is scaled up or down proportionally by parts by weight. Unless otherwise specified, if commercially available nano-sized filler powders are available in the examples, nano-sized fillers are preferred.

[0058] In this invention, Si69 is bis-[γ-(triethoxysilyl)propyl]tetrasulfide; 6PPD is N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine; RD is 2,2,4-trimethyl-1,2-dihydroquinoline polymer; CBS is N-cyclohexyl-2-benzothiazole sulfenamide; and TBzTD is tetrabenzylthiuram disulfide.

[0059] In this invention, the modifier ATD is 2-aminoethyl-2-[(3-triethoxysilylpropyl)amino]ethyl disulfide, which belongs to the category of multifunctional silane coupling interface modifiers containing ethoxysilane, amino, and disulfide bonds; the modifier DBDA is 3,4-diamino-(1,1'-biphenyl)-3,5-dicarboxylic acid, which belongs to the category of aromatic biphenyl dicarboxylic acid interface modifiers containing amino and carboxyl bifunctional groups.

[0060] Example 1: A method for preparing a natural rubber composite material includes the following steps (where steps a to c are the preparation of wet-mixed masterbatch): (a) Based on 100 parts of dry natural rubber, the raw material formulation includes: 100 parts of natural rubber latex (dry weight), 30 parts of silica (containing hydroxyl groups on the surface or modified with reactive groups after pretreatment), 0.9 parts of sodium dodecylbenzenesulfonate, and 2.4 parts of Si69; the downstream formulation consists of: 10 parts of trans-butadiene rubber TBIR, 2 parts of modifier ATD, 5.0 parts of zinc oxide, 2.0 parts of stearic acid, 2.0 parts of 6PPD, 2.0 parts of RD, 3.0 parts of microcrystalline wax, 1.2 parts of accelerator CBS, and 2.0 parts of sulfur.

[0061] Add 30 parts of silica to 170 parts of deionized water, add 0.9 parts of sodium dodecylbenzenesulfonate and 2.4 parts of Si69, stir at 1000 r / min for 25 min, and control the temperature of the stirring system at 25℃ to obtain a pre-dispersed silica slurry.

[0062] The pre-dispersed silica slurry was subjected to high-shear stirring and then added to a high-speed shear disperser. The high-shear speed was controlled at 6000 r / min, the dispersion time was 30 min, and the dispersion temperature was 26℃. The high-shear treated slurry was then fed into a ball mill for ball milling, using 0.10 mm zirconium oxide beads as the grinding medium with a filling rate of 70%. The ball milling speed was 2800 r / min, and the ball milling time was 2.0 h. After ball milling, the slurry was then fed into a high-frequency ultrasonic disperser for ultrasonic dispersion. The ultrasonic frequency was 28 kHz, the ultrasonic power was 9 kW, the ultrasonic time was 20 min, and the treatment temperature was controlled at 25℃. Intermittent ultrasonic dispersion was used. After ultrasonic treatment, the slurry was filtered through a 300-mesh filter to obtain a silica dispersion slurry. The particle size D50 of the filler dispersion was reduced to 2.11 μm (see...). Figure 7 ).

[0063] Take 100 parts of natural rubber latex (dry weight), adjust its total solids content to 60%, and adjust the pH to 9.5 with ammonia water. Maintain this pH value during the feeding process.

[0064] (b) Using as Figure 2 The dual-nozzle, concentrically aligned, high-pressure jet mixing device shown is used for mixing. The nozzles are solid conical mist nozzles with a nozzle orifice diameter of 1.0 mm, a spray cone angle of 50°, and a nozzle spacing of 50 mm. The aforementioned silica dispersion slurry stored in the filler slurry storage tank 1 and the pretreated natural rubber latex stored in the natural rubber latex storage tank 2 are respectively fed into two coaxially aligned nozzles through the filler slurry conveying pipe 3 and the latex conveying pipe 4. The silica slurry conveying pressure of the filler-side nozzle 7 is 6.0 MPa, and the silica slurry density is 1106 kg / m³. 3 The actual average flow velocity is 97.1 m / s, and the outlet cross-sectional area is 7.854 × 10⁻⁶. -7 m 2 The latex delivery pressure of the latex-side nozzle 8 is 6.0 MPa, and the latex density is 954 kg / m³. 3 The actual average flow velocity is 104.7 m / s, and the outlet cross-sectional area is 5.027 × 10⁻⁶. -7 m 2 The jet flow ratio J is controlled at 1.00, and the mixing temperature is 23℃. The silica dispersion slurry and natural rubber latex are driven by the filler high-pressure metering pump 5 and the latex high-pressure metering pump 6, respectively, and then sprayed out through nozzles on both sides to form two conical mists. The two conical mists form a free collision zone 9 near the jet collision center 23 (see...). Figure 3 The mixture undergoes instantaneous contact dispersion at the spray cone coverage area 24 in the free collision zone 9, and is collected in the collection chamber 10 to obtain the composite masterbatch slurry, which is then discharged from the wet compound outlet 11.

[0065] During the counter-mixing process, pressure sensor 12, flow meter 13, temperature sensor 14, and pH sensor 15 respectively collect the feed pressure before the nozzle, feed flow rate, system temperature, and pH of the latex feed section, and feed the detection signals back to PLC controller 16. PLC controller 16 adjusts execution unit 17 according to preset process window to stabilize the feed state of filler slurry and latex, and controls the temperature of the counter-mixing zone through cooling jacket 18, thereby improving the repeatability and batch stability of the instantaneous mixing process in free collision zone 9 (see...). Figure 4 ).

[0066] (c) The obtained composite masterbatch slurry was subjected to staged pressing and dehydration at a pressing pressure of 1.0 MPa for 15 min. The moisture content of the wet masterbatch after dehydration was 30%. Subsequently, the dehydrated composite masterbatch slurry was washed three times with an aqueous solution of pH 7, and then vacuum dried at a vacuum degree of -0.08 MPa, a drying temperature of 65℃, and a drying time of 16 h, resulting in a wet-process compounded masterbatch with a moisture content of 0.6%.

[0067] (d) Mixing process: The obtained wet-process masterbatch is fed into an internal mixer for post-mixing according to the aforementioned post-processing formula. First, the wet-process masterbatch, TBIR, and modifier ATD are added to the internal mixer and mixed at 145°C for 5 min; after cooling to below 80°C, activators (zinc oxide, stearic acid) and antioxidants (RD, 6PPD, microcrystalline wax) are added, and mixing continues for 5 min; then the compound is cooled to below 50°C, accelerator CBS and sulfur are added, and mixing continues. When the compound temperature reaches above 100°C, the compound is discharged to obtain the desired compound. This compound is left to stand for 24 h and then vulcanized at 145°C and 20MPa at t90 to obtain a silica / TBIR / natural rubber composite material.

[0068] Comparative Example 1: A conventional dry mixing method for preparing silica / natural rubber composite materials.

[0069] The formula is as follows: 100 parts natural rubber, 30 parts silica, 10 parts trans-butadiene rubber (TBIR), and the other functional additives and their proportions are the same as in Example 1.

[0070] The mixing process is as follows: Natural rubber dry rubber and trans-butadiene rubber (TBIR) are mixed evenly in an internal mixer. Then, activators and antioxidants are added and mixed evenly. Next, silica, Si69, and modifiers are added, and the mixture is further mixed at a high temperature of 145°C for 5 minutes. Finally, the mixed rubber is cooled to below 50°C, and accelerators and sulfur are added. Mixing continues until the rubber compound temperature reaches above 100°C, at which point the rubber is discharged, yielding the desired mixed rubber. After the mixed rubber is left to stand for 24 hours, it is vulcanized at 150°C and 20 MPa at a t90 setting.

[0071] Comparative Example 2: A method for preparing silica / natural rubber composite materials by mechanical stirring, mixing and acid coagulation.

[0072] The raw material formulation of this comparative example is the same as that of Example 1. The pre-dispersion of the silica slurry, the three-stage depolymerization steps, and the pretreatment steps of the natural rubber latex are also the same as those of Example 1.

[0073] The only difference is that instead of using a high-pressure jet mixing device, the silica dispersion slurry and natural rubber latex were added to a mixing tank and mechanically stirred at 800 r / min for 20 min. Then, 18 parts of a 10 wt% formic acid aqueous solution were added, allowing the system to coagulate until the final pH reached 4.8, resulting in a composite masterbatch slurry. The subsequent dehydration, washing, drying, post-mixing, and vulcanization conditions of the obtained composite masterbatch slurry were the same as in Example 1.

[0074] Example 2: The raw material formulation in this embodiment is the same as that in Example 1. The only difference is that the silica is only subjected to the pre-dispersion and high-shear treatment of Example 1, and is not subjected to subsequent ball milling and ultrasonic dispersion. The specific dispersion process is as follows: silica is added to deionized water and stirred at 1000 r / min for 25 min to obtain pre-dispersed silica slurry; the pre-dispersed silica slurry is subjected to high-shear stirring treatment and added to a high-speed shear disperser. The high-shear speed is controlled at 6000 r / min, the dispersion time is 30 min, and the dispersion temperature is 26℃.

[0075] The remaining natural rubber latex pretreatment, core-to-core high-pressure jet mixing, dehydration, washing, drying, post-mixing and vulcanization conditions are the same as in Example 1.

[0076] The performance test results of the rubber composite materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2 are compared in Table 1 below.

[0077] Table 1: Performance test results of rubber composite materials in Examples 1 and 2 and Comparative Examples 1 and 2

[0078] The above examples and comparative examples retain only two comparison routes: traditional dry mixing and mechanically stirred emulsion blending-acid coagulation wet mixing. The traditional dry mixing of Comparative Example 1 is used to reflect the level of filler dispersion and interfacial bonding under conventional mechanical shear mixing conditions; the mechanically stirred emulsion blending-acid coagulation wet mixing of Comparative Example 2 is used to reflect the technical state of the filler slurry and latex after stirring and mixing to form masterbatch by acid flocculation in conventional wet mixing.

[0079] A comparison of Example 1 with Comparative Examples 1 and 2 shows that, in the silica / natural rubber / TBIR system, the center-to-center high-pressure jet mixing enables the silica dispersion slurry and natural rubber latex to rapidly contact in the free collision zone and form a more uniform coated co-aggregate structure. After the addition of TBIR and ATD in the later stage, high-temperature mixing softens and disperses TBIR, allowing it to participate in the construction of the rubber interphase transition layer. The ethoxysilane, amino, and disulfide bonds in ATD enhance the interfacial coupling between silica and rubber, thereby reducing energy loss and the risk of fatigue crack initiation caused by filler network inhomogeneity (see [link to relevant documentation]). Figure 5 Compared to the traditional dry mixing method of Comparative Example 1, the DIN wear, compression heat generation, Payne effect, and fatigue index of Example 1 were significantly improved. Compared to the mechanical stirring acid coagulation wet method of Comparative Example 2, Example 1 further avoided the re-agglomeration of fillers caused by local rapid coagulation. Compared to the absence of tertiary dispersion in Example 2, Example 1 more effectively broke up the original aggregates and agglomerates of fillers, reduced the risk of blockage in the subsequent jetting process, and further improved the uniformity of filler dispersion, providing a prerequisite and foundation for the subsequent high-pressure jet instantaneous dispersion mixing and uniform coating after latex demulsification. The various performance parameters of the product were also better than those of Example 2.

[0080] Example 3: One such Figure 1 The method for preparing the natural rubber composite material shown includes the following steps: (a) Based on 100 parts of dry natural rubber, the raw material formulation includes: 100 parts of natural rubber latex (dry weight), 40 parts of carbon black N234, and 0.7 parts of sodium dodecylbenzene sulfonate; the downstream formulation consists of: 10 parts of trans-1,4-polyisoprene rubber TPI, 5.0 parts of zinc oxide, 2.0 parts of stearic acid, 2.0 parts of 6PPD, 2.0 parts of RD, 3.0 parts of microcrystalline wax, 1.2 parts of accelerator CBS, and 2.0 parts of sulfur.

[0081] Add 40 parts of carbon black N234 to 180 parts of deionized water, add 0.7 parts of sodium dodecylbenzenesulfonate, stir at 1200 r / min for 20 min, and control the temperature of the stirring system at 25℃ to obtain a pre-dispersed carbon black slurry.

[0082] The pre-dispersed carbon black slurry was subjected to high-shear stirring and then added to a high-speed shear disperser. The high-shear speed was controlled at 7000 r / min, the dispersion time was 30 min, and the dispersion temperature was 26℃. The slurry after high-shear treatment was then fed into a horizontal ball mill for ball milling. Zirconia beads with a particle size of 0.10 mm were used as the grinding medium, with a filling rate of 70%. The ball milling speed was 2800 r / min, and the ball milling time was 1.5 h. After ball milling, the slurry was then fed into a high-frequency ultrasonic disperser for ultrasonic dispersion. The ultrasonic frequency was 28 kHz, the ultrasonic power was 8 kW, the ultrasonic time was 15 min, and the treatment temperature was controlled at 25℃. Intermittent ultrasonic dispersion was used. After ultrasonic treatment, the slurry was filtered through a 300-mesh filter to obtain a carbon black dispersion slurry. The particle size D50 of the filler dispersion was reduced to 4.52 µm.

[0083] Take 100 parts of natural rubber latex (dry weight), adjust its total solids content to 60%, and adjust the pH to 9.3 with ammonia water. Maintain this pH value during the feeding process.

[0084] (b) Using as Figure 2 The dual-nozzle concentric high-pressure jet mixing device shown is used for mixing. The nozzles are solid conical mist nozzles with a nozzle orifice diameter of 0.8 mm, a spray cone angle of 45°, and a nozzle spacing of 45 mm. The carbon black dispersion slurry stored in the filler slurry storage tank 1 and the pretreated natural rubber latex stored in the natural rubber latex storage tank 2 are respectively fed into two relatively coaxial and concentrically arranged nozzles through the filler slurry conveying pipe 3 and the latex conveying pipe 4. The carbon black slurry conveying pressure of the filler-side nozzle 7 is 5.0 MPa, and the carbon black slurry density is 1093 kg / m³. 3 The actual average outlet velocity is 89.4 m / s, and the outlet cross-sectional area is 5.027 × 10⁻⁶. -7 m 2 The latex delivery pressure of the latex-side nozzle 8 is 5.1 MPa, and the latex density is 954 kg / m³. 3 The actual average flow velocity is 94.6 m / s, and the outlet cross-sectional area is 5.027 × 10⁻⁶. -7 m 2 The jet flow ratio J is controlled at 1.02, and the mixing temperature is 22℃. The carbon black dispersion slurry and natural rubber latex are driven by the filler high-pressure metering pump 5 and the latex high-pressure metering pump 6, respectively, and then sprayed out through nozzles on both sides to form two conical mists. The two conical mists form a free collision zone 9 in the area near the jet collision center 23 (see...). Figure 3 The mixture undergoes instantaneous contact dispersion at the spray cone coverage area 24 in the free collision zone 9, and is collected in the collection chamber 10 to obtain the composite masterbatch slurry, which is then discharged from the wet compound outlet 11.

[0085] During the counter-mixing process, pressure sensor 12, flow meter 13, temperature sensor 14, and pH sensor 15 respectively collect the feed pressure before the nozzle, feed flow rate, system temperature, and pH of the latex feed section, and feed the detection signals back to PLC controller 16. PLC controller 16 adjusts execution unit 17 according to preset process window to stabilize the feed state of filler slurry and latex, and controls the temperature of the counter-mixing zone through cooling jacket 18, thereby improving the repeatability and batch stability of the instantaneous mixing process in free collision zone 9 (see...). Figure 4 ).

[0086] (c) The obtained composite masterbatch slurry was subjected to staged pressing and dehydration at a pressing pressure of 1.0 MPa for 15 min. The moisture content of the dehydrated composite masterbatch slurry was 31%. Subsequently, the dehydrated composite masterbatch slurry was washed three times with an aqueous solution of pH 7, and then vacuum dried at a vacuum degree of -0.08 MPa, a drying temperature of 65℃, and a drying time of 14 h, resulting in a wet-process compounded masterbatch with a moisture content of 0.7%.

[0087] (d) The mixing process is as follows: The obtained wet-process masterbatch is fed into an internal mixer for post-mixing. First, the wet-process masterbatch and TPI are added to the internal mixer and mixed at 130°C for 7 minutes to soften the TPI under high-temperature shear and fully mix it with the carbon black / natural rubber wet-process masterbatch. After cooling to below 80°C, activators and antioxidants are added, and mixing continues for 6 minutes. Then, the compound is cooled to below 50°C, accelerators and sulfur are added, and mixing continues. When the temperature of the compound reaches above 100°C, the compound is discharged to obtain the desired compound. This compound is left to stand for 24 hours and then vulcanized at 150°C and 20MPa at t90 to obtain the carbon black / TPI / natural rubber composite material.

[0088] Comparative Example 3: A conventional dry mixing method for preparing carbon black / natural rubber composite materials.

[0089] The formulation of this comparative example is as follows: 100 parts natural rubber, 40 parts carbon black N234, 10 parts trans-1,4-polyisoprene rubber TPI, 5.0 parts zinc oxide, 2.0 parts stearic acid, 2.0 parts 6PPD, 2.0 parts RD, 3.0 parts microcrystalline wax, 1.2 parts accelerator CBS, and 2.0 parts sulfur.

[0090] The preparation process for this comparative example is as follows: First, natural rubber dry rubber and TPI are put into a mixer and mixed evenly. Then, activators and antioxidants are added, and mixing continues. Next, carbon black N234 is added, and mixing continues for 5 minutes. Finally, the compound is cooled to below 50°C, accelerators and sulfur are added, and mixing continues. When the rubber compound temperature reaches above 100°C, the rubber is discharged to obtain the desired compound. After the compound is left to stand for 24 hours, it is vulcanized at 150°C and 20 MPa according to t90.

[0091] Comparative Example 4: A method for preparing natural rubber composite materials by non-centric high-pressure jet mixing emulsion blending and acid coagulation.

[0092] The raw material formulation of this comparative example is the same as that of Example 3. The pre-dispersion, graded depolymerization steps of the carbon black slurry, and the pretreatment steps of the natural rubber latex are also the same as those of Example 3. However, this comparative example does not use concentric high-pressure jet mixing. Instead, the composite filler dispersion slurry and natural rubber latex are uniformly atomized at an atomization pressure of 2 MPa, a liquid flow diameter of 1.5 mm, and a spray angle of 60-120°. The atomized materials diffuse, contact, and mix in a mixing chamber, and a rubber mixture is collected. The rubber mixture is stirred at a stirring speed of 500 rpm for 10 min. A 10 wt% formic acid aqueous solution is added to the stirred mixture for flocculation, washing, and dehydration to obtain the rubber masterbatch. The subsequent mixing and vulcanization conditions are the same as those of Example 3.

[0093] The performance test results of the rubber composite materials prepared in Example 3 and Comparative Examples 3 and 4 are compared in Table 2 below.

[0094] Table 2: Performance test results of rubber composite materials in Example 3 and Comparative Examples 3 and 4

[0095] Example 3 is a carbon black / TPI / natural rubber system, mainly verifying the applicability of this invention to conventional reinforcing carbon black systems and post-modification systems of crystalline polymers. The reinforcing effect between carbon black and rubber mainly relies on physical adsorption, mechanical entanglement, and interfacial frictional energy dissipation. The center-to-center high-pressure jet mixing can improve the uniformity of filler distribution in the carbon black wet-process masterbatch, reduce local high-concentration agglomeration areas, and make the carbon black network more continuous and stress transmission more uniform. TPI, as trans-1,4-polyisoprene rubber, is a crystalline polymer modification component. During the subsequent high-temperature shear mixing, it can soften and disperse, forming an interphase transition region with the continuous phase of natural rubber. After cooling and vulcanization, TPI segments can provide certain crystallization constraints and rigidity contributions to the local rubber phase, which is beneficial for increasing the degree of constraint on the rubber segments around the carbon black, reducing ineffective internal friction and local stress concentration during dynamic deformation. Therefore, Example 3 outperforms Comparative Examples 3 and 4 (dry process and conventional wet process) in terms of tear strength, DIN abrasion, compression heat generation, Payne effect, and fatigue performance. The performance improvement is mainly due to the synergistic effect of the above-mentioned embodiment schemes, rather than a single carbon black dispersion factor (see [link]). Figure 8 ).

[0096] Example 4: One such Figure 1 The method for preparing the natural rubber composite material shown includes the following steps: (a) Based on 100 parts of dry natural rubber, the raw material formulation includes: 100 parts of natural rubber latex (dry weight), 3 parts of carbon nanotubes, 25 parts of silica, 1.2 parts of sodium dodecylbenzenesulfonate, and 1.8 parts of Si69; the downstream formulation consists of: 5.0 parts of zinc oxide, 2.0 parts of stearic acid, 2.0 parts of 6PPD, 2.0 parts of RD, 3.0 parts of microcrystalline wax, 1.2 parts of CBS, and 2.0 parts of sulfur.

[0097] Add 3 parts of carbon nanotubes and 25 parts of fumed silica to 200 parts of deionized water, then add the aforementioned sodium dodecylbenzenesulfonate and Si69, and stir at 1500 r / min for 30 min. The temperature of the stirring system is controlled at 25℃ to obtain a pre-dispersed filler slurry.

[0098] The pre-dispersed filler slurry was subjected to high-shear stirring and then added to a high-speed shear disperser. The high-shear speed was controlled at 10,000 r / min, the dispersion time was 40 min, and the dispersion temperature was 26℃. The high-shear treated slurry was then fed into a horizontal ball mill for ball milling. Zirconia beads with a particle size of 0.08 mm were used as the grinding medium, the filling rate was 68%, the ball milling speed was 2600 r / min, and the ball milling time was 1.5 h. After ball milling, the slurry was then fed into a high-frequency ultrasonic disperser for ultrasonic dispersion. The ultrasonic frequency was 30 kHz, the ultrasonic power was 10 kW, the ultrasonic time was 15 min, and the treatment temperature was controlled at 24℃. Intermittent ultrasonic dispersion was used. After ultrasonic treatment, the slurry was filtered through a 300-mesh filter to obtain a composite filler dispersion slurry. The particle size D50 of the filler dispersion was reduced to 1.92 μm.

[0099] Take 100 parts of natural rubber latex (dry weight), adjust its total solids content to 58%, and adjust the pH to 9.6 with ammonia water. Maintain this pH value during the feeding process.

[0100] (b) Using as Figure 2 The dual-nozzle, concentrically aligned, high-pressure jet mixing device shown uses solid conical mist nozzles with a nozzle orifice diameter of 1.0 mm, a spray cone angle of 50°, and a nozzle spacing of 48 mm. The composite filler dispersion slurry stored in filler slurry storage tank 1 and the pretreated natural rubber latex stored in natural rubber latex storage tank 2 are respectively fed into two coaxially aligned nozzles via filler slurry conveying pipe 3 and latex conveying pipe 4. The composite filler dispersion slurry conveying pressure of the filler-side nozzle 7 is 8.0 MPa, and the density of the composite filler dispersion slurry is 1084 kg / m³. 3 The actual average flow velocity is 113.8 m / s, and the outlet cross-sectional area is 7.854 × 10⁻⁶ m / s. -7 m 2 The latex delivery pressure of the latex-side nozzle 8 is 8.1 MPa, and the latex density is 956 kg / m³. 3 The actual average flow velocity is 121.6 m / s, and the outlet cross-sectional area is 7.854 × 10⁻⁶ m / s. - 7 m 2 The jet flow ratio J is controlled at 1.0, and the mixing temperature is 22℃. The composite filler dispersion slurry and natural rubber latex are driven by the filler high-pressure metering pump 5 and the latex high-pressure metering pump 6, respectively, and then sprayed out through nozzles on both sides to form two conical mists. The two conical mists form a free collision zone 9 in the area near the jet collision center 23 (see...). Figure 3 The mixture undergoes instantaneous contact dispersion at the spray cone coverage area 24 in the free collision zone 9, and is collected in the collection chamber 10 to obtain the composite masterbatch slurry, which is then discharged from the wet compound outlet 11.

[0101] During the counter-mixing process, pressure sensor 12, flow meter 13, temperature sensor 14, and pH sensor 15 respectively collect the feed pressure before the nozzle, feed flow rate, system temperature, and pH of the latex feed section, and feed the detection signals back to PLC controller 16. PLC controller 16 adjusts execution unit 17 according to preset process window to stabilize the feed state of filler slurry and latex, and controls the temperature of the counter-mixing zone through cooling jacket 18, thereby improving the repeatability and batch stability of the instantaneous mixing process in free collision zone 9 (see...). Figure 4 ).

[0102] (c) The obtained composite masterbatch slurry was dehydrated by pressing at a pressure of 1.2 MPa for 18 min. The moisture content of the dehydrated composite masterbatch slurry was 29%. Subsequently, the dehydrated composite masterbatch slurry was washed three times with an aqueous solution of pH 7, and then vacuum dried at a vacuum of -0.085 MPa, a drying temperature of 60℃, and a drying time of 18 h, resulting in a wet-process compounded masterbatch with a moisture content of 0.5%.

[0103] (d) The mixing process is as follows: The obtained wet-process masterbatch is fed into an internal mixer for post-mixing. First, the wet-process masterbatch is added to the internal mixer and mixed at 160°C for 10 min; after cooling to below 80°C, activators, antioxidants, etc. are added, and mixing continues for 7 min; then the compound is cooled to below 50°C, accelerators and sulfur are added, and mixing continues. When the temperature of the compound reaches above 100°C, the compound is discharged to obtain the desired compound. This compound is left to stand for 24 h and then vulcanized at 150°C and 20 MPa according to t90 to obtain a carbon nanotube / fumed silica / natural rubber composite material.

[0104] Comparative Example 5: A conventional dry mixing method for preparing carbon nanotube / fumed silica / natural rubber composite materials.

[0105] The formulation of this comparative example is as follows: 100 parts natural rubber, 3 parts carbon nanotubes, 25 parts silica, 1.8 parts Si69, 5.0 parts zinc oxide, 2.0 parts stearic acid, 2.0 parts 6PPD, 2.0 parts RD, 3.0 parts microcrystalline wax, 1.2 parts CBS, and 2.0 parts sulfur.

[0106] The preparation process for this comparative example is as follows: First, dry natural rubber is added to a mixer and plasticized for 1 minute. Then, activators and antioxidants are added and mixed evenly. Next, carbon nanotubes, silica, and Si69 are added, and the mixture is further mixed at a high temperature of 145-155℃ for 8 minutes. Finally, the mixed rubber is cooled to below 50℃, accelerators and sulfur are added, and mixing continues. When the rubber compound temperature reaches above 100℃, the rubber is discharged to obtain the desired mixed rubber. After the mixed rubber is left to stand for 24 hours, it is vulcanized at 150℃ and 20 MPa at t90.

[0107] Comparative Example 6: A method for preparing carbon nanotube / fumed silica / natural rubber composite materials by mechanical stirring emulsion blending and acid coagulation.

[0108] The raw material formulation for this comparative example is the same as that of Example 4. The pre-dispersion, graded depolymerization steps of the carbon nanotube / fumed silica composite filler slurry, and the pretreatment steps of the natural rubber latex are also the same as those in Example 4. The difference is that the composite filler dispersion slurry and the natural rubber latex are added to a stirred tank and mechanically stirred at 800 r / min for 20 min. Then, 10 wt% formic acid aqueous solution is added to allow the acid in the system to coagulate to the endpoint pH of 4.8, thus obtaining the composite masterbatch slurry. The dehydration, washing, drying, post-mixing, and vulcanization conditions of the obtained composite masterbatch slurry are all the same as those in Example 4.

[0109] The performance test results of the rubber composite materials prepared in Example 4 and Comparative Examples 5 and 6 are compared in Table 3 below.

[0110] Table 3: Performance test results of rubber composite materials in Example 4 and Comparative Examples 5 and 6

[0111] Example 4 introduces a carbon nanotube / fumed silica composite filler to verify the applicability of the present invention to high-structure or lamellar nanofiller systems. Carbon nanotubes have a one-dimensional high aspect ratio structure, which easily forms a directional reinforcing network, but is also prone to entanglement and aggregation. The present invention, through graded depolymerization and concentric high-pressure jet instantaneous mixing, enables the above-mentioned high-structure filler to be more uniformly embedded in the rubber phase when entering the latex system, reducing the number of large-size defect sources. Therefore, Example 4 is significantly superior to Examples 5 and 6 in terms of tensile, tear, abrasion, Payne effect, and fatigue performance.

[0112] Example 5: One such Figure 1 The method for preparing the natural rubber composite material shown includes the following steps: (a) Based on 100 parts of dry natural rubber, the raw material formulation includes: 100 parts of natural rubber latex (dry weight), 2 parts of graphene oxide, 25 parts of silica, 1.0 part of sodium dodecylbenzenesulfonate, and 1.8 parts of Si69; the downstream formulation consists of: 5.0 parts of zinc oxide, 2.0 parts of stearic acid, 2.0 parts of 6PPD, 2.0 parts of RD, 3.0 parts of microcrystalline wax, 1.2 parts of CBS, and 2.0 parts of sulfur.

[0113] First, graphene oxide is pre-exfoliated in deionized water for 20 min. Then, silica and other additives are added, with a total water volume of 190 parts. The mixture is stirred at 1200 r / min for 25 min, and the temperature of the stirring system is controlled at 25℃ to obtain a pre-dispersed filler slurry.

[0114] The pre-dispersed filler slurry was subjected to high-shear stirring and then added to a high-speed shear disperser. The high-shear speed was controlled at 9000 r / min, the dispersion time was 35 min, and the dispersion temperature was 26℃. The high-shear treated slurry was then fed into a horizontal ball mill for ball milling, using 0.05 mm zirconia beads as the grinding medium, with a filling rate of 70%, a ball milling speed of 2500 r / min, and a ball milling time of 1.0 h. After ball milling, the slurry was then fed into a high-frequency ultrasonic disperser for ultrasonic dispersion. The ultrasonic frequency was 30 kHz, the ultrasonic power was 9 kW, the ultrasonic time was 18 min, and the treatment temperature was controlled at 24℃. Intermittent ultrasonic dispersion was used. After ultrasonic treatment, the slurry was filtered through a 400-mesh filter to obtain a composite filler dispersion slurry, with the filler dispersion particle size D50 reduced to 2.38 μm.

[0115] Take 100 parts of natural rubber latex (dry weight), adjust its total solids content to 60%, and adjust the pH to 9.4 with ammonia water. Maintain this pH value during the feeding process.

[0116] (b) Using as Figure 2 The dual-nozzle, concentrically aligned, high-pressure jet mixing device shown uses solid conical mist nozzles with a nozzle orifice diameter of 1.0 mm, a spray cone angle of 50°, and a nozzle spacing of 50 mm. The composite filler dispersion slurry stored in filler slurry storage tank 1 and the pretreated natural rubber latex stored in natural rubber latex storage tank 2 are respectively fed into two coaxially aligned nozzles via filler slurry conveying pipe 3 and latex conveying pipe 4. The composite filler dispersion slurry conveying pressure of the filler-side nozzle 7 is 7.0 MPa, and the density of the composite filler dispersion slurry is 1085 kg / m³. 3 The actual average flow velocity is 106.1 m / s, and the outlet cross-sectional area is 7.854 × 10⁻⁶ m / s. -7 m 2The latex delivery pressure of the latex-side nozzle 8 is 7.1 MPa, and the latex density is 954 kg / m³. 3 The actual average flow velocity is 113.9 m / s, and the outlet cross-sectional area is 7.854 × 10⁻⁶ m / s. -7 m 2 The jet flow ratio J is controlled at 0.98, and the mixing temperature is 22℃. The composite filler dispersion slurry and natural rubber latex are driven by the filler high-pressure metering pump 5 and the latex high-pressure metering pump 6, respectively, and then sprayed out through nozzles on both sides to form two conical mists. The two conical mists form a free collision zone 9 in the area near the jet collision center 23 (see...). Figure 3 The mixture undergoes instantaneous contact dispersion at the spray cone coverage area 24 in the free collision zone 9, and is collected in the collection chamber 10 to obtain the composite masterbatch slurry, which is then discharged from the wet compound outlet 11.

[0117] During the counter-mixing process, pressure sensor 12, flow meter 13, temperature sensor 14, and pH sensor 15 respectively collect the feed pressure before the nozzle, feed flow rate, system temperature, and pH of the latex feed section, and feed the detection signals back to PLC controller 16. PLC controller 16 adjusts execution unit 17 according to preset process window to stabilize the feed state of filler slurry and latex, and controls the temperature of the counter-mixing zone through cooling jacket 18, thereby improving the repeatability and batch stability of the instantaneous mixing process in free collision zone 9 (see...). Figure 4 ).

[0118] (c) The obtained composite masterbatch slurry was dehydrated by pressing at a pressure of 1.0 MPa for 15 min. The moisture content of the dehydrated composite masterbatch slurry was 30%. The dehydrated composite masterbatch slurry was then washed three times with an aqueous solution of pH 7, and then vacuum dried at a vacuum of -0.085 MPa, a drying temperature of 62℃, and a drying time of 16 h to obtain a wet-process compounded masterbatch with a moisture content of 0.6%.

[0119] (d) Mixing process: The obtained wet-process masterbatch is fed into an internal mixer for post-mixing. First, the wet-process masterbatch is added to the internal mixer and mixed at 150°C for 10 min; then cooled to below 80°C, activator and antioxidant are added, and mixing continues for 7 min; then the mixture is cooled to below 50°C, accelerator and sulfur are added, and mixing continues. When the temperature of the rubber compound reaches above 100°C, the rubber is discharged to obtain the desired compound. This compound is left to stand for 24 h and then vulcanized at 150°C and 20 MPa according to t90 to obtain a graphene oxide / fumed silica / natural rubber composite material.

[0120] Comparative Example 7: A conventional dry mixing method for preparing graphene oxide / fumed silica / natural rubber composite materials.

[0121] The formulation of this comparative example is as follows: 100 parts natural rubber, 2 parts graphene oxide, 25 parts silica, 1.8 parts Si69, 5.0 parts zinc oxide, 2.0 parts stearic acid, 2.0 parts 6PPD, 2.0 parts RD, 3.0 parts microcrystalline wax, 1.2 parts CBS, and 2.0 parts sulfur.

[0122] The preparation process for this comparative example is as follows: First, dry natural rubber is added to a mixer and plasticized for 1 minute. Then, activators and antioxidants are added and mixed evenly. Next, graphene oxide, silica, and Si69 are added, and the mixture is further mixed at a high temperature of 145-155℃ for 8 minutes. Finally, the compound is cooled to below 50℃, accelerators and sulfur are added, and mixing continues. When the temperature of the rubber compound reaches above 100℃, the compound is discharged to obtain the desired compound. After the compound is left to stand for 24 hours, it is vulcanized at 150℃ and 20 MPa at t90.

[0123] Comparative Example 8: A method for preparing graphene oxide / fumed silica / natural rubber composite material by mechanical stirring emulsion blending and acid coagulation.

[0124] The raw material formulation for this comparative example is the same as that of Example 5. The pre-dispersion, graded depolymerization steps of the graphene oxide / fumed silica composite filler slurry, and the pretreatment steps of the natural rubber latex are also the same as those in Example 5. The main difference is that the composite filler dispersion slurry and the natural rubber latex are added to a mixing tank and mechanically stirred at 800 r / min for 20 min. Then, a 10wt% formic acid aqueous solution is added to allow the acid in the system to coagulate to the endpoint pH of 4.8, thus obtaining the composite masterbatch slurry. The dehydration, washing, drying, post-mixing, and vulcanization conditions of the obtained composite masterbatch slurry are all the same as those in Example 5.

[0125] The performance test results of the rubber composite materials prepared in Example 5 and Comparative Examples 7 and 8 are compared in Table 4 below.

[0126] Table 4: Performance test results of rubber composite materials in Example 5 and Comparative Examples 7 and 8

[0127] Example 5 introduces a graphene oxide / fumed silica composite filler to verify the applicability of this invention to high-structure or sheet-like nanofiller systems. Graphene oxide possesses a two-dimensional sheet structure and oxygen-containing functional groups, providing strong polar interfacial interactions; however, it is prone to sheet overlap and local enrichment under acid coagulation or uneven dry shearing. This invention, through graded depolymerization and jet instantaneous mixing, enables the aforementioned high-structure filler to be more uniformly embedded in the rubber phase when entering the latex system, reducing the number of large-size defect sources. Therefore, the corresponding embodiment significantly outperforms corresponding examples 7 and 8 in tensile, tear, abrasion, Payne effect, and fatigue performance.

[0128] Example 6: One such Figure 1 The method for preparing the natural rubber composite material shown includes the following steps: (a) Based on 100 parts of dry natural rubber, the raw material formulation includes: 100 parts of natural rubber latex (dry weight), 60 parts of aluminum hydroxide, 20 parts of silica, 1.5 parts of sodium dodecylbenzenesulfonate, and 1.2 parts of Si69; the downstream formulation consists of: 10 parts of TBIR, 2.0 parts of modifier DBDA, 5.0 parts of zinc oxide, 2.0 parts of stearic acid, 2.0 parts of 6PPD, 2.0 parts of RD, 3.0 parts of microcrystalline wax, 1.2 parts of CBS, 0.5 parts of accelerator TBzTD, and 2.0 parts of sulfur.

[0129] Aluminum hydroxide and silica were added together to 220 parts of deionized water, followed by sodium dodecylbenzenesulfonate and Si69. The mixture was stirred at 1300 r / min for 30 min, with the temperature of the stirring system controlled at 25℃, to obtain a pre-dispersed filler slurry.

[0130] The pre-dispersed filler slurry was subjected to high-shear stirring and then added to a high-speed shear disperser. The high-shear speed was controlled at 8000 r / min, the dispersion time was 35 min, and the dispersion temperature was 26℃. The high-shear treated slurry was then fed into a horizontal ball mill for ball milling, using 0.1 mm zirconia beads as the grinding medium, with a filling rate of 70%, a ball milling speed of 2700 r / min, and a ball milling time of 2.0 h. After ball milling, the slurry was then fed into a high-frequency ultrasonic disperser for ultrasonic dispersion. The ultrasonic frequency was 28 kHz, the ultrasonic power was 9 kW, the ultrasonic time was 20 min, and the treatment temperature was controlled at 25℃. Intermittent ultrasonic dispersion was used. After ultrasonic treatment, the slurry was filtered through a 300-mesh filter to obtain a composite filler dispersion slurry, with the filler dispersion particle size D50 reduced to 4.88 μm.

[0131] Take 100 parts of natural rubber latex (dry weight), adjust its total solids content to 58%, and adjust the pH to 9.5 with ammonia water. Maintain this pH value during the feeding process.

[0132] (b) Using as Figure 2 The dual-nozzle concentric high-pressure jet mixing device shown is used for mixing. The nozzles are solid conical mist nozzles with a nozzle orifice diameter of 1.2 mm, a spray cone angle of 60°, and a nozzle spacing of 55 mm. The composite filler dispersion slurry stored in the filler slurry storage tank 1 and the pretreated natural rubber latex stored in the natural rubber latex storage tank 2 are respectively fed into two relatively coaxial and concentrically arranged nozzles through the filler slurry conveying pipe 3 and the latex conveying pipe 4. The composite filler dispersion slurry conveying pressure of the filler-side nozzle 7 is 6.0 MPa, and the density of the composite filler dispersion slurry is 1191 kg / m³. 3The actual average flow velocity is 94.9 m / s, and the outlet cross-sectional area is 1.131 × 10⁻⁶ m / s. -6 m 2 The latex delivery pressure of the latex-side nozzle 8 is 6.1 MPa, and the latex density is 956 kg / m³. 3 The actual average flow velocity is 105.5 m / s, and the outlet cross-sectional area is 1.131 × 10⁻⁶ m / s. -6 m 2 The jet flow ratio J is controlled at 1.01, and the mixing temperature is 23℃. The composite filler dispersion slurry and natural rubber latex are driven by the filler high-pressure metering pump 5 and the latex high-pressure metering pump 6, respectively, and then sprayed out through nozzles on both sides to form two conical mists. The two conical mists form a free collision zone 9 in the area near the jet collision center 23 (see...). Figure 3 The mixture undergoes instantaneous contact dispersion at the spray cone coverage area 24 in the free collision zone 9, and is collected in the collection chamber 10 to obtain the composite masterbatch slurry, which is then discharged from the wet compound outlet 11.

[0133] (c) The obtained composite masterbatch slurry was dehydrated by pressing at a pressure of 1.0 MPa for 15 min. The moisture content of the dehydrated composite masterbatch slurry was 30%. The dehydrated composite masterbatch slurry was then washed three times with an aqueous solution of pH 7, and then vacuum dried at a vacuum of -0.085 MPa, a drying temperature of 62℃, and a drying time of 16 h to obtain a wet-process compounded masterbatch with a moisture content of 0.6%.

[0134] (d) The mixing process is as follows: The obtained wet-process masterbatch, TBIR, and modifier are added to an internal mixer for post-mixing. First, the wet-process masterbatch, TBIR, and modifier are added to the internal mixer and mixed at 145°C for 7 minutes; after cooling to below 80°C, activators and antioxidants are added, and mixing continues for 5 minutes; then the compound is cooled to below 50°C, accelerators and sulfur are added, and mixing continues. When the compound temperature reaches above 100°C, the compound is discharged to obtain the desired compound. This compound is left to stand for 24 hours and then vulcanized at 150°C and 20MPa according to t90 to obtain a flame-retardant filler / fumed silica / natural rubber composite material.

[0135] Comparative Example 9: A conventional dry mixing method for preparing flame-retardant filler / fumed silica / natural rubber composite materials.

[0136] The formulation of this comparative example is as follows: 100 parts natural rubber, 10 parts TBIR, 2.0 parts modifier DBDA; 60 parts aluminum hydroxide, 20 parts silica, 1.2 parts Si69; 5.0 parts zinc oxide, 2.0 parts stearic acid, 2.0 parts 6PPD, 2.0 parts RD, 3.0 parts microcrystalline wax, 1.2 parts CBS, 0.5 parts accelerator TBzTD, and 2.0 parts sulfur.

[0137] The preparation process for this comparative example is as follows: First, natural rubber dry rubber and TBIR are put into a mixer and mixed evenly. Then, activators and antioxidants are added and mixed for 2-3 minutes. Next, aluminum hydroxide, silica, modifier DBDA, and Si69 are added and the mixture is further mixed at a high temperature of 130℃-140℃ for 5 minutes. Finally, the compound is cooled to below 50℃, accelerators and sulfur are added, and mixing continues. When the temperature of the rubber compound reaches above 100℃, the rubber is discharged to obtain the desired compound. After the compound is left to stand for 24 hours, it is vulcanized at 150℃ and 20MPa at t90.

[0138] Comparative Example 10: A method for preparing flame-retardant filler / fumed silica / natural rubber composite material by non-central high-pressure jet mixing emulsion blending and acid coagulation.

[0139] The raw material formulation for this comparative example is the same as that of Example 6. The pre-dispersion, graded depolymerization steps of the aluminum hydroxide / fumed silica composite filler slurry, and the pretreatment steps of the natural rubber latex are also the same as in Example 6. The difference lies in the uniform atomization of the composite filler dispersion slurry and the natural rubber latex. The atomization pressure is 2 MPa, the liquid flow diameter is 1.5 mm, and the spray angle is 60-120°. The atomized materials diffuse, contact, and mix in a mixing chamber, and a rubber mixture is collected. The rubber mixture is stirred at 500 rpm for 10 minutes. A 10 wt% formic acid aqueous solution is added to the stirred mixture for flocculation, washing, and dehydration to obtain the rubber masterbatch. The subsequent mixing and vulcanization conditions are the same as in Example 6.

[0140] The performance test results of the rubber composite materials prepared in Example 6 and Comparative Examples 9 and 10 are compared in Table 5 below.

[0141] Table 5: Performance test results of rubber composite materials in Example 6 and Comparative Examples 9 and 10

[0142] Example 6 describes an aluminum hydroxide / fumed silica flame retardant system, focusing on verifying the dispersion and interface control effects in a high-polarity, high-filling functional filler system. Aluminum hydroxide has abundant hydroxyl groups on its surface and strong polarity; high filling levels can easily cause interface defects and a decrease in mechanical properties. DBDA contains a rigid framework of amino, carboxyl, and aromatic biphenyl groups, which can enhance the interfacial bonding between aluminum hydroxide / fumed silica and the rubber matrix through hydrogen bonding, acid-base interactions, polar adsorption, or coordination. In Example 6, the process method of this invention, combined with the subsequent high-temperature mixing of TBIR / DBDA, helps to reduce compression heat generation and abrasion while maintaining the flame retardant rating and improving fatigue performance.

[0143] Example 7: One such Figure 1The method for preparing the natural rubber / Eucommia ulmoides latex composite material includes the following steps: (a) Based on 100 parts of dry natural rubber, the raw material formulation includes: 90 parts of natural rubber latex (dry weight), 10 parts of Eucommia ulmoides latex (dry weight), 25 parts of silica, 10 parts of carbon black N234, 0.9 parts of sodium dodecylbenzene sulfonate, and 2.0 parts of Si69; the downstream formulation consists of: 5.0 parts of zinc oxide, 2.0 parts of stearic acid, 2.0 parts of 6PPD, 2.0 parts of RD, 3.0 parts of microcrystalline wax, 1.2 parts of CBS, 0.5 parts of accelerator TBzTD, and 2.0 parts of sulfur.

[0144] Silica and carbon black N234 were added together to 190 parts of deionized water, followed by sodium dodecylbenzenesulfonate and Si69. The mixture was stirred at 1200 r / min for 25 min, and the temperature of the stirring system was controlled at 25℃ to obtain a pre-dispersed filler slurry.

[0145] The pre-dispersed filler slurry was subjected to high-shear stirring and then added to a high-speed shear disperser. The high-shear speed was controlled at 7000 r / min, the dispersion time was 30 min, and the dispersion temperature was 26℃. The high-shear treated slurry was then fed into a horizontal ball mill for ball milling, using 0.1 mm zirconia beads as the grinding medium, with a filling rate of 70%, a ball milling speed of 2800 r / min, and a ball milling time of 2.0 h. After ball milling, the slurry was then fed into a high-frequency ultrasonic disperser for ultrasonic dispersion. The ultrasonic frequency was 28 kHz, the ultrasonic power was 8 kW, the ultrasonic time was 18 min, and the treatment temperature was controlled at 25℃. Intermittent ultrasonic dispersion was used. After ultrasonic treatment, the slurry was filtered through a 300-mesh filter to obtain a composite filler dispersion slurry, with the filler dispersion particle size D50 reduced to 3.34 μm.

[0146] After mixing natural rubber latex with Eucommia ulmoides latex, the total solid content is adjusted to 60%, and the pH is adjusted to 9.4 with ammonia water. This pH value is also maintained during the feeding process.

[0147] (b) Using as Figure 2 The dual-nozzle, concentrically aligned, high-pressure jet mixing device shown is used for mixing. The nozzles are solid conical mist nozzles with a nozzle orifice diameter of 1.0 mm, a spray cone angle of 50°, and a nozzle spacing of 50 mm. The composite filler dispersion slurry stored in the filler slurry storage tank 1 and the pretreated composite rubber latex stored in the natural rubber latex storage tank 2 are respectively fed into two relatively coaxially aligned nozzles through the filler slurry conveying pipe 3 and the latex conveying pipe 4. The composite filler dispersion slurry conveying pressure of the filler-side nozzle 7 is 7.0 MPa, and the density of the composite filler dispersion slurry is 1101 kg / m³. 3The actual average flow velocity is 105.2 m / s, and the outlet cross-sectional area is 7.854 × 10⁻⁶ m / s. -7 m 2 The latex delivery pressure of the latex-side nozzle 8 is 7.0 MPa, and the latex density is 953 kg / m³. 3 The actual average flow velocity is 113.0 m / s, and the outlet cross-sectional area is 7.854 × 10⁻⁶ m / s. -7 m 2 The jet flow ratio J is controlled at 1.0, and the mixing temperature is 23℃. The composite filler dispersion slurry and composite rubber latex are driven by the filler high-pressure metering pump 5 and the latex high-pressure metering pump 6, respectively, and then sprayed out through nozzles on both sides to form two conical mists. The two conical mists form a free collision zone 9 in the area near the jet collision center 23 (see...). Figure 3 The mixture undergoes instantaneous contact dispersion at the spray cone coverage area 24 in the free collision zone 9, and the composite masterbatch slurry collected by the collection chamber 10 is discharged from the wet compound outlet 11.

[0148] (c) The obtained composite masterbatch slurry was dehydrated by pressing at a pressure of 1.0 MPa for 15 min. The moisture content of the dehydrated composite masterbatch slurry was 30%. The dehydrated composite masterbatch slurry was then washed three times with an aqueous solution of pH 7, and then vacuum dried at a vacuum of -0.08 MPa, a drying temperature of 65℃, and a drying time of 16 h to obtain a wet-process compounded masterbatch with a moisture content of 0.6%.

[0149] (d) Mixing process: The obtained wet-process masterbatch is fed into an internal mixer for post-mixing. First, the wet-process masterbatch is added to the internal mixer and mixed at 140°C for 6 minutes; then cooled to below 80°C, activators and antioxidants are added, and mixing continues for 5 minutes; then the mixture is cooled to below 50°C, accelerators and sulfur are added, and mixing continues. When the temperature of the rubber compound reaches above 100°C, the rubber is discharged to obtain the desired compound. This compound is left to stand for 24 hours and then vulcanized at 150°C and 20MPa according to t90 to obtain a natural rubber / Eucommia ulmoides latex composite material.

[0150] Comparative Example 11: A conventional dry mixing method for preparing natural rubber / Eucommia ulmoides latex composite materials.

[0151] The formulation of this comparative example is as follows: 90 parts natural rubber, 10 parts eucommia gum, 25 parts silica, 10 parts carbon black N234, 2.0 parts Si69, 5.0 parts zinc oxide, 2.0 parts stearic acid, 2.0 parts 6PPD, 2.0 parts RD, 3.0 parts microcrystalline wax, 1.2 parts CBS, 0.5 parts accelerator TBzTD, and 2.0 parts sulfur.

[0152] The preparation process for this comparative example is as follows: First, natural rubber and Eucommia ulmoides rubber are mixed evenly in a Banbury mixer. Then, activators and antioxidants are added and mixed for 2-3 minutes. Next, carbon black, silica, and Si69 are added and the mixture is further Banburyed at a high temperature of 140-150℃ for 5 minutes. Finally, the compound is cooled to below 50℃, and accelerators and sulfur are added. The mixture is then further mixed until the temperature of the compound reaches above 100℃, at which point the compound is discharged to obtain the desired compound. After the compound is left to stand for 24 hours, it is vulcanized at 150℃ and 20 MPa at a t90 setting.

[0153] Comparative Example 12: A method for preparing a natural rubber / Eucommia ulmoides latex composite material by mechanical stirring emulsion blending and acid coagulation.

[0154] The raw material formulation for this comparative example is the same as that in Example 7. The pre-dispersion, graded depolymerization steps of the silica / carbon black composite filler slurry, and the pretreatment steps of the natural rubber / Eucommia ulmoides composite latex are also the same as in Example 7. The difference is that the composite filler dispersion slurry and the composite rubber latex are added to a mixing tank and mechanically stirred at 800 r / min for 20 min. Then, a 10wt% formic acid aqueous solution is added to allow the acid in the system to coagulate to the endpoint pH of 4.8, thus obtaining the composite masterbatch slurry. The dehydration, washing, drying, post-mixing, and vulcanization conditions of the obtained composite masterbatch slurry are all the same as those in Example 7.

[0155] The performance test results of the rubber composite materials prepared in Example 7 and Comparative Examples 11 and 12 are compared in Table 6 below.

[0156] Table 6: Performance test results of rubber composite materials in Example 7 and Comparative Examples 11 and 12

[0157] Example 7 is a natural rubber / Eucommia ulmoides latex blend system, mainly verifying the applicability of the present invention to multi-latex blend systems. Natural rubber provides a high elasticity and fatigue resistance foundation, while Eucommia ulmoides latex helps to improve fatigue resistance. Through the process of the present invention, the composite filler and blended latex are fully and uniformly mixed in the latex stage, which can reduce the phase inhomogeneity and filler segregation caused by subsequent dry blending, thereby improving strength, reducing compression heat generation, and improving fatigue life.

[0158] As shown in the table above, under conditions where the final formulations are similar or identical, the embodiments of the present invention, compared with the comparative examples of traditional dry mixing and mechanically stirred emulsion blending-acid coagulation wet mixing, exhibit higher overall tensile strength, tear strength, resilience, tensile fatigue life, and flexural fatigue life, as well as lower DIN abrasion, compression heat generation, and Payne effect ΔG′. These results indicate that the pre-dispersion of the filler in the aqueous phase, staged depolymerization, instantaneous mixing with high-pressure jets, dehydration and drying, and subsequent mixing have a synergistic effect, which can improve the filler dispersion quality, the filler-rubber interface bonding level, and dynamic service stability.

[0159] In general, the embodiments do not simply pursue the maximization of a single performance, but rather verify the applicability of the invention by focusing on different filler types and different rubber matrix combinations: Examples 1 and 2 highlight the interface coupling of silica / TBIR / ATD; Example 3 highlights the carbon black / TPI reinforcement and crystalline polymer post-modification system; Examples 4 and 5 highlight the high-structure nanofiller system; Example 6 highlights the flame-retardant functional filler system; and Example 7 highlights the natural rubber / Eucommia ulmoides latex blend system. The performance differences of each system mainly stem from the filler morphology, filler polarity, filler network construction method, rubber phase composition, and the synergistic effect of post-modifiers or crystalline polymer modifiers. Through the characterization and verification of these different embodiments, the method of the present invention can be widely applied to blending systems of different types of filler slurries and natural rubber latex.

[0160] The above embodiments further demonstrate that the wet mixing process of the present invention is low-carbon, environmentally friendly, and energy-efficient, equivalent to the pre-dispersion of fillers and some additives. Combined with subsequent high-temperature mixing, the interfacial forces are strengthened through temperature, pressure, and shear flow fields via interface-induced chemical reactions, further promoting the nano-sizing of filler aggregates into smaller, more stable aggregates. A dense binding adhesive (including chemical grafting and physical penetration) is formed on the surface of the filler aggregates, causing the crystalline blend components (such as TPI and TBIR) to melt and their viscosity adjusted to be close to NR, thus achieving better dispersion. This promotes interfacial rubber grafting, transition layer molecular chain entanglement, and the formation of a complete filler network and rubber crosslinking network (see [link to relevant documentation]). Figure 5 , Figure 6 and Figure 9 Moreover, compared to existing traditional dry or wet mixing processes, the entire process is shorter and takes less time, while further improving efficiency. For example... Figure 10 As shown, traditional mixing disperses fillers through high-temperature internal mixing. While achieving dispersion, high-temperature internal mixing also shears the molecular chains of rubber, leading to deterioration in performance. However, the process of this invention can compress the high-temperature mixing time and retain molecular weight as much as possible.

[0161] like Figure 5 , Figure 6As shown in the diagram, compared to traditional processes, this schematic reveals the regulatory effect of high-pressure jet dispersion mixing on the microstructure of the filler-reinforced rubber system. The strong shearing, strong turbulence, and instantaneous collisions generated by the high-pressure jet process effectively break up filler agglomerates, promote uniform dispersion of the filler in the rubber matrix, and increase the contact area between the filler and rubber chain segments. After high-temperature mixing, the filler surface forms a hierarchical interface structure composed of a tightly bound rubber layer (red area in the diagram) and a loosely bound rubber layer (blue area in the diagram), further exhibiting an interface layer gradient characteristic that gradually decreases from a strongly constrained interface region to a flexible transition region. Among them, the red tightly bound rubber chains bear the role of interface load transfer and structural anchoring, while the blue loosely bound rubber chains serve as a flexible transition region, coordinating the deformation differences between the filler and the free rubber chains. At the same time, the effective connection between the filler and the rubber network is improved through embedded bonding points (green marks in diagram d) and coupling bonding points (yellow marks in diagram d) around the filler particles, transforming the dispersed filler from an isolated reinforcing phase into a functional structural node in the rubber network. This multi-scale interfacial structure with gradient interfacial layer characteristics helps improve the effectiveness of the filler network, load transfer efficiency, and deformation stability, providing a structural basis for enhancing the mechanical strength and fatigue resistance of rubber composites. Specifically, in different filler embodiments, based on our research on the final product, nanofiller carbon black mainly interacts with rubber molecular chains through physical adsorption and mechanical entanglement, forming a relatively large interfacial interaction zone around the particles; while coupling agent-modified silica relies on the coupling agent to construct a bridging structure between the filler surface and the rubber molecular chains, accompanied by certain polar interactions, thereby enhancing interfacial bonding and stress transfer; and for highly polar inorganic fillers such as aluminum hydroxide, the interfacial interaction mainly originates from hydrogen bonds or polar interactions initiated by surface hydroxyl groups, resulting in a relatively more localized interfacial interaction zone.

[0162] In addition to relying on the dispersive mixing effect of the high-pressure jet to regulate the microstructure of the filler-reinforced rubber system, the preparation of this invention also optimizes the control parameters of three-stage depolymerization and instantaneous mixing of the high-pressure jet. In particular, through the synergy of inverse-structure rubbers such as TBIR and TPI, the uniformity of filler dispersion and interfacial bonding in the natural rubber matrix can be further improved, reducing large-size agglomerates and local enrichment. This effectively forms a natural rubber composite material with smaller filler aggregate size, uniform dispersion, reasonable interfacial layer gradient, complete network, and stable structure. This is beneficial to improving the tensile strength, tear strength, tensile stress, abrasion resistance, and dynamic performance of the natural rubber composite material, and realizing the high-performance utilization of domestic natural rubber.

[0163] The preferred embodiment of this invention utilizes a synergistic process of "three-stage depolymerization - instantaneous mixing with counter-jet flow - multi-parameter closed-loop control," combined with optimized flow field dynamics parameters, step-by-step drying, and high-temperature hot refining to further improve the interfacial bonding and micro / mesostructure of the filler and rubber. High-pressure vulcanization further enhances the final product, resulting in high-performance and high-stability natural rubber composite materials. These composite materials can be used in aerospace, rail transportation, high-speed rail, wind power, automotive, shipbuilding, and marine engineering. The natural rubber composite materials prepared by this invention have the potential for comprehensive improvement in one or more of the following properties: mechanical properties, abrasion resistance, dynamic properties, and flame retardancy. Specific effects can be adjusted according to the selected filler type, formulation, and process conditions. The preferred formulation and process parameters of the above embodiments do not constitute a limitation on the scope of protection of this invention.

[0164] Unless otherwise stated, the performance parameters of the above embodiments and comparative examples were obtained by testing as follows: 1. Mooney viscosity: Tested according to GB / T 1232.1; 2. Dynamic mechanical properties: The dynamic thermomechanical analyzer (DMA test) was used for testing, and tanδ was taken as the value at 60℃; 3. Payne effect: The change in storage modulus ΔG' was measured using a rubber processing analyzer; 4. Particle size D50 of the filler slurry: measured using a laser particle size analyzer; 5. Compression heat generation: Tested using a compression heat generation apparatus, in accordance with GB / T 1687.3; 6. Carbon black dispersion: Tested according to ASTM D7723.

Claims

1. A method for preparing a wet-process masterbatch for natural rubber composite materials, characterized in that, Includes the following steps: (a) Preparation of filler slurry and natural rubber latex; (b) The filler slurry and natural rubber latex are respectively conveyed to different nozzles through independent conveying devices; the filler slurry and natural rubber latex are sprayed out through the nozzles after being driven by pressure to form multiple solid cone mists; The different nozzles are configured to be evenly arranged around the same spray collision center, and the multiple solid cone mists form a free collision zone in the area near the spray collision center and undergo contact dispersion in the free collision zone; (c) The composite masterbatch slurry obtained after step (b) is introduced into a collection device, and then dehydrated, washed and dried to obtain wet-mixed masterbatch of natural rubber composite material.

2. The preparation method according to claim 1, characterized in that, The solid conical mist has a cone angle of 30° to 70°, the number of nozzles is 2 to 4, the nozzle orifice diameter is 0.5 to 2.0 mm, and the nozzle spacing is 20 to 80 mm.

3. The preparation method according to claim 1, characterized in that, The different nozzles are configured to be evenly arranged around the same jet collision center. Specifically, when there are two nozzles, the two nozzles are set coaxially and centered relative to each other; when there are three or more nozzles, the multiple nozzles are evenly arranged around the same jet collision center on the entire circumference.

4. The preparation method according to claim 1, characterized in that, The filler slurry and natural rubber latex are respectively transported by high-pressure metering pumps, with a pipeline transport pressure of 2-15 MPa and an average flow velocity at the nozzle outlet of 30-150 m / s. The momentum ratio J of the jets ejected from different nozzles is controlled between 0.8 and 1.2, and the momentum ratio J is expressed by the following formula: J = (ρ1v1 2 A1) : (p2v2 2 A2) : …… (p n v n 2 A n ) in, ρ1, ρ2, ρ n These represent the fluid densities ejected from nozzles 1, 2, and n, respectively. v1, v2, v n These represent the average flow velocities at the outlets of nozzles 1, 2, and n, respectively. A1, A2, A n These represent the outlet cross-sectional areas of nozzles 1, 2, and n, respectively.

5. The preparation method according to claim 1, characterized in that, The system temperature in the free collision zone is controlled between 15°C and 30°C; the pH of the natural rubber latex feeding section is maintained between 8.5 and 10.

5.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The preparation of the filler slurry includes the following steps: adding nanofillers to a dispersion medium, and pretreating with surfactants and coupling agents, and obtaining a stable filler slurry under multi-stage dispersion operation; the amount of nanofillers relative to 100 parts of natural rubber latex dry rubber is 5 to 120 parts; the total amount of surfactants added is 1% to 50% of the mass of nanofillers; the total amount of coupling agents added is 1% to 25% of the mass of nanofillers. The dispersion medium contains deionized water; The nanofiller comprises at least one of carbon black, silica, graphene oxide, carbon nanotubes, clay, aluminum hydroxide, and magnesium hydroxide. The surfactant includes at least one of anionic surfactants, cationic surfactants, and nonionic surfactants.

7. The preparation method according to claim 6, characterized in that, The surface of the nanofiller contains hydroxyl, carboxyl, alkoxy groups, or is modified with reactive groups after pretreatment; a coupling agent is also added to the dispersion medium; the coupling agent is a silane coupling agent.

8. The preparation method according to claim 7, characterized in that, The coupling agent includes at least one of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, γ-aminopropyltriethoxysilane, and γ-mercaptopropyltriethoxysilane, and its amount is 1% to 25% of the mass of the nanofiller.

9. The preparation method according to claim 6, characterized in that, The surfactant comprises a blend of anionic surfactant, cationic surfactant, and nonionic surfactant; the anionic surfactant comprises at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, fatty acid soap, and rosin soap; the cationic surfactant comprises at least one of hexadecyltrimethylammonium bromide, quaternary ammonium salt, and ammonium salt; the nonionic surfactant comprises at least one of polyoxyethylene sorbitan fatty acid ester, polyvinylpyrrolidone, polydopamine, alkylphenol polyoxyethylene ether, and polyvinyl alcohol; the total amount of surfactant added is 1% to 50% of the mass of the nanofiller.

10. The preparation method according to claim 6, characterized in that, The multi-stage dispersion operation includes two steps: pre-dispersion and graded depolymerization; the graded depolymerization includes three steps: high-shear stirring, ball milling dispersion, and ultrasonic dispersion. The pre-dispersion process is achieved by stirring, with a stirring speed of 500-2000 r / min, a stirring time of 10-60 min, and the temperature of the stirring system controlled below 35℃.

11. The preparation method according to claim 10, characterized in that, The high-shear mixing involves adding the pre-dispersed filler slurry into a high-speed shear disperser, controlling the rotation speed at 3000–20000 r / min, the temperature at 20℃–35℃, and the dispersion time at 0.5 h–2 h.

12. The preparation method according to claim 10, characterized in that, The ball milling dispersion involves feeding the high-shear stirred filler slurry into a ball mill, using zirconia microspheres as the grinding medium with a particle size of 0.05–0.3 mm; the ball mill filling rate is 65%–75%, the ball milling speed is 2500–3000 r / min, and the circulating ball milling time is 0.5–5 h.

13. The preparation method according to claim 10, characterized in that, The ultrasonic dispersion involves feeding the ball-milled and dispersed filler slurry into a high-frequency ultrasonic disperser, controlling the frequency at 25–35 kHz, the power at 8–12 kW, and the ultrasonic time at 15–25 min. The ultrasonic dispersion is performed intermittently, with the ultrasonic dispersion temperature controlled at 20℃–30℃. The particle size D50 of the filler dispersion is reduced to 0.5–5 μm.

14. The preparation method according to any one of claims 1 to 5, characterized in that, The natural rubber latex comprises pure natural rubber latex, or a combination of pure natural rubber latex and Eucommia ulmoides gum latex, or pure natural rubber latex and synthetic latex in a mass ratio of 95:5 to 50:50, with a total solid content of 20% to 60% and a pH adjusted to 8.5 to 10.

5.

15. The preparation method according to any one of claims 1 to 5, characterized in that, After the composite masterbatch slurry is introduced into the collection device, it will no longer undergo acid coagulation processing.

16. A method for preparing a natural rubber composite material, characterized in that, Includes the following steps: Step 1: Prepare a wet-mixed masterbatch using the preparation method described in any one of claims 1 to 15; Step 2: Add the wet-mixed masterbatch and modifier obtained in Step 1 into an internal mixer for mixing; Step 3: After the mixture in Step 2 is evenly mixed, cool it down to below 80°C, add activator and antioxidant, and continue mixing; then cool the compound to below 50°C again, add sulfur and accelerator, and continue mixing. When the temperature of the compound reaches above 100°C, discharge the compound to obtain the required compound. Step 4: After the rubber compound is left to stand, it is vulcanized and molded to obtain a natural rubber composite material.

17. The preparation method according to claim 16, characterized in that, The modifier includes a crystalline polymer modifier, which is selected from at least one of Eucommia ulmoides gum, TBIR, and TPI. The mixing temperature during step 2 is controlled at 140℃~150℃, and the time is 3min~10min. The mass ratio of the crystalline polymer modifier to natural rubber is 5~100%.

18. A natural rubber composite material, said natural rubber composite material comprising: Rubber matrix, a network structure formed by rubber molecular chains; Functional filler, comprising a plurality of filler polymers filled in the network structure; Its features are: The functional filler is uniformly dispersed in the rubber matrix, and the uniformity of filler dispersion characterized by the carbon black dispersion method is above level 9. The core of the filler polymer forms a hierarchical interface structure with the rubber matrix in the contact area between the core and the rubber matrix, which includes a tightly bonded rubber layer and a loosely bonded rubber layer. The tightly bonded rubber layer refers to the region where the molecular chains of the filler polymer and the rubber matrix achieve interfacial load transfer or structural anchoring through physical or chemical bonding points. The loosely bonded rubber layer refers to the transition zone where the molecular chains of the filler polymer and the rubber matrix are not in direct contact.

19. The natural rubber composite material according to claim 18, characterized in that, The rubber matrix is ​​prepared from a mixture of pure natural rubber latex and Eucommia ulmoides latex in a mass ratio of 95:5 to 50:50; the mixture also contains a modifying component formed from at least one of Eucommia ulmoides, TBIR, and TPI.

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