Sepiolite-loaded zinc oxide material and high-activity natural rubber composite material thereof

Abstract

The invention discloses a sepiolite-loaded zinc oxide material and a high-activity natural rubber composite material thereof, relates to the technical field of natural rubber composite materials, and covers the whole process of preparing a sepiolite suspension, adding divalent zinc salt and alkali, filtering and drying, and treating in a high-temperature atmosphere furnace. In addition, the scheme also comprises a method for preparing high-activity natural rubber / zinc oxide masterbatch by using the material, and the accurate control of operation parameters and a mixing process of natural latex and loaded zinc oxide are emphasized. According to the invention, zinc oxide is uniformly loaded to the fiber surface through the structure of sepiolite, a stable three-dimensional network is constructed in a water phase system, and the dispersibility and stability of zinc oxide are significantly improved. Traditional grinding and surfactants are abandoned, the production process is simplified, the energy consumption is reduced, and the economic efficiency and the environmental protection property are improved. Zinc oxide in the obtained rubber master batch is dispersed in a nanoscale, vulcanization crosslinking is effectively promoted, and the performance of a rubber product is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of natural rubber composites, and particularly relates to a sepiolite-supported zinc oxide material and a highly active natural rubber composite material thereof. Background Art

[0002] The vulcanization of rubber composites is a necessary stage to achieve their applicable physical and mechanical properties. Improving the vulcanization efficiency and shortening the vulcanization time can also save resources and energy consumption. The rubber vulcanization system includes activators, accelerators, and vulcanizing agents. Among them, zinc oxide is considered the best activator for the vulcanization crosslinking of rubber materials. During the vulcanization process, zinc oxide first forms an intermediate complex with stearic acid, then reacts with the accelerator to form a particularly active zinc chelate, and then interacts with sulfur to form a polysulfide zinc complex, which further combines with the rubber precursor chain to form a crosslinked structure. At the same time, only Zn 2+ attached to the surface of zinc oxide particles can participate in and promote the vulcanization reaction. Therefore, the dosage, size, specific surface area of zinc oxide particles, and their dispersion in the rubber matrix all have a great impact on the vulcanization characteristics of rubber composites. 2+

[0003] As an indispensable additive in the rubber formulation system, zinc oxide is also the rubber compounding additive with the largest demand in the rubber industry except for reinforcing fillers. However, research shows that zinc oxide can cause reproductive toxicity to aquatic organisms. During the production, decomposition, and recycling of rubber products, or under usage conditions such as landfill leaching and tire wear, zinc oxide will be released into the environment, which will undoubtedly bring a series of ecological and environmental problems. Therefore, relevant researchers have explored various ways to reduce the usage amount of zinc oxide. These mainly include using nano-zinc oxide with different structural forms, active zinc oxide with a high specific surface area and low particle size, and core-shell structure nano-zinc oxide to replace the application of traditional indirect method zinc oxide. Although these methods are theoretically effective, there are still problems of poor dispersion of zinc oxide under the current traditional dry mixing process, and at the same time, it is impossible to avoid the loss of zinc oxide particles during the processing.

[0004] As is well known, rubber wet mixing is an energy-saving and environmentally friendly process method to improve the dispersion of fillers and additives in the rubber matrix. For additives such as zinc oxide with a relatively large density, a large amount of surfactant often needs to be added and supplemented with a long-time grinding process to prepare an aqueous zinc oxide slurry that can be used for rubber wet mixing. This method can effectively crosslink latex products, but it is not suitable for rubber products such as tires and conveyor belts for dynamic applications. Therefore, it will be a very meaningful work to achieve the wet mixing of zinc oxide and rubber latex without using organic surfactants.

[0005] ​Sepiolite is a natural magnesium-rich hydrated silicate clay mineral with a special one-dimensional fibrous crystal morphology. Its crystal lattice is generally considered to be composed of Si-O tetrahedral sheets and Mg-O octahedral sheets, and it also has a 2:1 type banded structure parallel to the C axis. Moreover, the discontinuous octahedral sheets are connected to the reverse tetrahedral sheets through alternating bonds formed by oxygen atoms. This alternating connection method enables sepiolite to form a large number of channel and tunnel pore structures and a rich surface of silanol groups (Si-OH), endowing it with excellent adsorption, reinforcement, and aqueous suspension stability. Additionally, it can stabilize inorganic fillers such as carbon nanotubes and graphene without adding surfactants.

[0006] In the traditional dry mixing process, when nano-zinc oxide, active zinc oxide, and core-shell structured zinc oxide replace conventional indirect method zinc oxide, there are still problems of poor zinc oxide dispersion, and at the same time, the harm caused by the loss of zinc oxide particles during the processing cannot be avoided; in the existing technology, to achieve the mixing of zinc oxide and natural latex, a large amount of surfactants and a long-time grinding process are required to prepare a zinc oxide aqueous suspension, with high energy consumption and poor suspension stability during the process. Moreover, this method is not applicable to rubber products for dynamic applications such as tires and conveyor belts.

[0007] In the present invention, sepiolite is used as a carrier, and zinc oxide is loaded onto the surface of sepiolite. Utilizing the unique structural properties of sepiolite, a sepiolite aqueous suspension containing zinc oxide with stable suspension is prepared, which can be directly wet-mixed with natural latex to obtain a highly active natural rubber / zinc oxide masterbatch. During the preparation process, surfactants and long-time grinding processes are abandoned, and the zinc oxide in the obtained masterbatch is uniformly dispersed at the nanoscale, with a wider application range.

[0008] In the present invention, using the unique structural properties of sepiolite, zinc oxide is uniformly loaded onto the surface of sepiolite fibers to prepare a sepiolite-supported zinc oxide material. In an aqueous phase system, after the fibers are defibrillated, with the assistance of weak chemical interactions, they physically overlap with each other to form a stable three-dimensional network structure. At the same time, the pore structure of sepiolite also binds some free water, thus forming a stable suspension system. After wet-mixing it with natural latex, a highly dispersed and highly active natural rubber / zinc oxide masterbatch is prepared. Summary of the Invention

[0009] In order to achieve the above-mentioned invention purpose and address the above-mentioned technical problems,

[0010] The present invention provides a sepiolite-supported zinc oxide material, which is prepared by the following steps:

[0011] A1 Add sepiolite powder to water, and prepare a sepiolite suspension with a certain solid content under the action of high-speed stirring or ultrasonic dispersion;

[0012] A2 Under heating and stirring, a divalent zinc salt is added to the sepiolite suspension obtained in A1, and the addition amount is 10% - 100% of the mass of sepiolite. After complete dissolution, a quantitative base is added in batches, and the addition amount is 2 times the molar amount of the divalent zinc salt used. After the reaction is complete, a sepiolite-supported zinc hydroxide suspension is obtained;

[0013] A3 The sepiolite-supported zinc hydroxide suspension in A2 is pressure-filtered, washed, dried, and crushed to obtain sepiolite-supported zinc hydroxide powder;

[0014] A4 The sepiolite-supported zinc hydroxide powder obtained in A3 is placed in a high-temperature air atmosphere furnace for reaction to obtain a sepiolite-supported zinc oxide material.

[0015] Preferably, in step A1, the speed of high-speed stirring is 1000 rpm - 20000 rpm; the energy required for ultrasonic dispersion is 0.1 - 5 J / g per gram of sepiolite suspension; the sepiolite solid content of the sepiolite suspension is 1% - 5%.

[0016] Preferably, in step A2, the heating temperature is 25°C - 100°C; the divalent zinc salt added is one of zinc chloride, zinc acetate, and zinc sulfate; the quantitative base is one of sodium hydroxide, potassium hydroxide, and ammonia water.

[0017] Preferably, in step A3, the particle size of the sepiolite-supported zinc hydroxide powder is 1 μm - 100 μm.

[0018] Preferably, in step A4, the heating temperature of the high-temperature atmosphere furnace is 100°C - 550°C.

[0019] The present invention also provides a high-activity natural rubber / zinc oxide masterbatch, and the masterbatch is prepared by the following steps:

[0020] B1 The sepiolite-supported zinc oxide material is added to water, and a sepiolite aqueous suspension loaded with zinc oxide with a certain solid content is obtained under the action of high-speed stirring or ultrasonic dispersion;

[0021] B2 Natural latex is added to the aqueous suspension obtained in B1, and after stirring at 10 - 500 rpm for 10 - 60 min, a mixed slurry of natural latex and sepiolite suspension loaded with zinc oxide is obtained, where the dry rubber mass in the natural latex is counted as 100 parts, and the total addition amount of sepiolite loaded with zinc oxide is 10 parts - 100 parts;

[0022] B3 A diluted flocculant is slowly added to the mixed slurry obtained in B2, and the addition amount is 0 - 1.0% of the dry weight of the natural latex; after stirring and flocculation, extrusion dehydration and washing are carried out, and then after crushing and drying, a high-activity natural rubber / zinc oxide masterbatch is obtained.

[0023] Preferably, the sepiolite-loaded zinc oxide material is a sepiolite-loaded zinc oxide material prepared by the above-mentioned preparation method.

[0024] Preferably, the speed of high-speed stirring in step B1 is 1000rpm-20000rpm; the energy required for ultrasonic dispersion of each gram of zinc oxide-loaded sepiolite suspension is 0.1-5J / g; and the solid content of the zinc oxide-loaded sepiolite aqueous suspension is between 1% and 10%.

[0025] Preferably, in step B2, the natural latex is a mixture of one or more of field natural latex, concentrated natural latex, and epoxidized natural latex with a solid content of 20% to 50%.

[0026] Preferably, in step B3, the added flocculant is one or more of formic acid, calcium chloride, methanol and protease.

[0027] The beneficial effects brought by the technical solution provided by the present invention are:

[0028] The present invention utilizes the unique structural properties of sepiolite to uniformly load zinc oxide onto the surface of sepiolite fibers. In the aqueous phase system, after the fibers are unbundled, they are physically overlapped with each other with the aid of weak chemical action to form a stable three-dimensional network structure, which effectively improves the dispersibility of zinc oxide. The pore structure of sepiolite binds part of the free water, and the formed suspension system is extremely stable, which avoids the loss of zinc oxide during the processing process and solves the problem of poor dispersibility of zinc oxide in the traditional dry mixing process.

[0029] The preparation process of the present invention abandons the use of traditional surfactants and long grinding processes, which not only simplifies the production process but also significantly reduces energy consumption. Through the physical and chemical structural characteristics of sepiolite, the stable loading and dispersion of zinc oxide are directly achieved, which effectively reduces the input of complex chemical treatment and mechanical energy, thereby improving the economic efficiency and environmental friendliness of the entire preparation process.

[0030] The resulting natural rubber / zinc oxide masterbatch has zinc oxide uniformly dispersed at the nanometer level. This high dispersion greatly improves the performance of rubber products in dynamic applications (such as tires and drive belts). Nano-dispersed zinc oxide more effectively promotes the vulcanization cross-linking reaction, thereby reducing the amount of zinc oxide used and improving the durability and elasticity of rubber products. This effect directly corresponds to the technical requirements of improving product performance and reducing material costs.

[0031] Compared with the zinc oxide aqueous suspension that requires surfactant treatment, the sepiolite-supported zinc oxide material of the present invention is not only applied to the preparation of traditional rubber products, but also can be widely applied to various high-performance composite materials that require high dispersibility and stability. The generalization of this material and the expansion of its scope of application are important supplements and optimizations to the existing technology. Description of the Drawings

[0032] Figure 1 is the X-ray diffraction pattern of the sepiolite-supported zinc oxide material, raw sepiolite and zinc oxide in the present invention;

[0033] Figure 2 is the scanning electron microscope (SEM) image of the sepiolite-supported zinc oxide material in the present invention;

[0034] Figure 3 is the transmission electron microscope (TEM) image of the sepiolite-supported zinc oxide material in the present invention;

[0035] Figure 4 is the scanning electron microscope (SEM) image of the brittle fracture surface of the vulcanizate of the high-activity natural rubber composite material prepared by the wet method using the sepiolite-supported zinc oxide material in the present invention, which characterizes the dispersion state of zinc oxide in the rubber matrix;

[0036] Figure 5 is the transmission electron microscope (TEM) image of the brittle fracture surface of the vulcanizate of the high-activity natural rubber composite material prepared by the wet method using the sepiolite-supported zinc oxide material in the present invention, which characterizes the dispersion state of zinc oxide in the rubber matrix;

[0037] Figure 6 is the scanning electron microscope (SEM) image of the brittle fracture surface of the vulcanizate of the natural rubber composite material obtained by dry mixing zinc oxide in the prior art;

[0038] Figure 7 is the transmission electron microscope (TEM) image of the brittle fracture surface of the vulcanizate of the natural rubber composite material obtained by dry mixing zinc oxide in the prior art. Detailed Embodiments

[0039] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with embodiments. Of course, the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] Example 1

[0041] A preparation method of a nano-scale super anti-slip ceramic tile, the implementation steps are as follows:

[0042] Example 1:

[0043] Take 10 g of sepiolite and add it to 490 g of water. Stir at a speed of 10,000 rpm for 20 min to obtain a sepiolite suspension with a solid content of 2%. Subsequently, add 0.840 g of ZnCl2 and stir at 60 °C. Meanwhile, take 0.494 g of NaOH and dissolve it in 100 ml of deionized water. After the ZnCl2 is completely dissolved, add the prepared NaOH solution to the sepiolite suspension containing ZnCl2 in 5 portions at intervals of 10 min. After the addition is completed, continue heating and stirring for 2 h. Then, perform suction filtration and washing 3 times to remove the salts generated in the system. After the washing is completed, place it in an oven at 60 °C and dry for 24 h, and then grind it into a powder. Finally, place the powder in a vacuum atmosphere furnace and heat it at 300 °C for 2 h to obtain sepiolite loaded with 0.5 g of zinc oxide. Add the above sepiolite loaded with zinc oxide to water and disperse it under ultrasonic action of 3 J / g for 15 min to prepare a suspension with a solid content of 4%. Subsequently, add 333.4 g of concentrated natural rubber latex diluted to a solid content of 30% and stir at 500 rpm for 30 min. Then, flocculate with a 2% calcium chloride solution, soak and wash several times, and then vacuum dry at 60 °C for 48 h to obtain a highly active natural rubber / zinc oxide masterbatch containing 0.5 g of zinc oxide, 10 g of sepiolite, and 100 g of natural rubber. Mix the above masterbatch with 2 phr of stearic acid, 1.35 phr of accelerator NS, and 1.5 phr of sulfur on an open mill to obtain a mixed rubber. After standing for 12 h, measure the vulcanization curve at 150 °C, and the results are shown in Table 1. The mixed rubber is vulcanized under the vulcanization conditions of 150 °C, 10 MPa, and t90 + 3 min, and the results of testing the physical and mechanical properties and crosslink density are shown in Table 2.

[0044] Example 2:

[0045] Take 10 g of sepiolite and add it to 490 g of water. Stir at a speed of 10000 rpm for 20 min to obtain a sepiolite suspension with a solid content of 2%. Subsequently, add 1.679 g of ZnCl₂ and stir at 60 °C. At the same time, take 0.988 g of NaOH and dissolve it in 100 ml of deionized water. After ZnCl₂ is completely dissolved, add the prepared NaOH solution to the sepiolite suspension containing ZnCl₂ in 5 portions, with an interval of 10 min each time. After the addition is completed, continue heating and stirring for 2 h. Then, perform suction filtration and washing 3 times to remove the salts generated in the system. After the washing is completed, place it in an oven at 60 °C and dry for 24 h, and grind it into a powder. Finally, place the powder in a vacuum atmosphere furnace and heat it at 300 °C for 2 h to obtain sepiolite loaded with 1.0 g of zinc oxide. Add the above sepiolite loaded with zinc oxide to water, disperse it under ultrasonic action of 3 J / g for 15 min to prepare a suspension with a solid content of 4%. Subsequently, add 333.4 g of concentrated natural rubber latex diluted to a solid content of 30%, and stir at 500 rpm for 30 min. Then, flocculate with a 2% calcium chloride solution, soak and wash several times, and vacuum dry at 60 °C for 48 h to obtain a highly active natural rubber / zinc oxide masterbatch containing 1.0 g of zinc oxide, 10 g of sepiolite, and 100 g of natural rubber. The mixing, processing, testing steps, and results of the obtained masterbatch are the same as those in Example 1.

[0046] Example 3:

[0047] Take 10 g of sepiolite and add it to 490 g of water. Stir at a speed of 10000 rpm for 20 min to obtain a sepiolite suspension with a solid content of 2%. Subsequently, add 2.591 g of ZnCl₂ and stir at 60 °C. At the same time, take 1.481 g of NaOH and dissolve it in 100 ml of deionized water. After ZnCl₂ is completely dissolved, add the prepared NaOH solution to the sepiolite suspension containing ZnCl₂ in 5 portions, with an interval of 10 min each time. After the addition is completed, continue heating and stirring for 2 h. Then, perform suction filtration and washing 3 times to remove the salts generated in the system. After the washing is completed, place it in an oven at 60 °C and dry for 24 h, and grind it into a powder. Finally, place the powder in a vacuum atmosphere furnace and heat it at 300 °C for 2 h to obtain sepiolite loaded with 1.5 g of zinc oxide. Add the above sepiolite loaded with zinc oxide to water, disperse it under ultrasonic action of 3 J / g for 15 min to prepare a suspension with a solid content of 4%. Subsequently, add 333.4 g of concentrated natural rubber latex diluted to a solid content of 30%, and stir at 500 rpm for 30 min. Then, flocculate with a 2% calcium chloride solution, soak and wash several times, and vacuum dry at 60 °C for 48 h to obtain a highly active natural rubber / zinc oxide masterbatch containing 1.5 g of zinc oxide, 10 g of sepiolite, and 100 g of natural rubber. The mixing, processing, testing steps, and results of the obtained masterbatch are the same as those in Example 1.

[0048] Example 4:

[0049] Take 10 g of sepiolite and add it to 490 g of water. Stir at a speed of 10,000 rpm for 20 min to obtain a sepiolite suspension with a solid content of 2%. Then add 3.358 g of ZnCl2 and stir at 60 °C. At the same time, take 1.975 g of NaOH and dissolve it in 100 ml of deionized water. After the ZnCl2 is completely dissolved, add the prepared NaOH solution to the sepiolite suspension containing ZnCl2 in 5 portions at intervals of 10 min. After the addition is completed, continue heating and stirring for 2 h. Then filter and wash 3 times to remove the salts generated in the system. After the washing is completed, place it in an oven at 60 °C and dry for 24 h, and grind it into a powder. Finally, place the powder in a vacuum atmosphere furnace and heat it at 300 °C for 2 h to obtain sepiolite loaded with 2.0 g of zinc oxide. Add the above zinc oxide-loaded sepiolite to water and disperse it under ultrasonic action of 3 J / g for 15 min to prepare a suspension with a solid content of 4%. Then add 333.4 g of concentrated natural rubber latex diluted to a solid content of 30% and stir at 500 rpm for 30 min. Subsequently, flocculate with a 2% calcium chloride solution, soak and wash several times, and then vacuum dry at 60 °C for 48 h to obtain a highly active natural rubber / zinc oxide masterbatch containing 2.0 g of zinc oxide, 10 g of sepiolite and 100 g of natural rubber. The mixing, processing, testing steps and results of the obtained masterbatch are the same as those in Example 1.

[0050] Example 5:

[0051] Take 10 g of sepiolite and add it to 490 g of water. Stir at a speed of 10,000 rpm for 20 min to obtain a sepiolite suspension with a solid content of 2%. Then add 5.037 g of ZnCl2 and stir at 60 °C. At the same time, take 2.963 g of NaOH and dissolve it in 100 ml of deionized water. After the ZnCl2 is completely dissolved, add the prepared NaOH solution to the sepiolite suspension containing ZnCl2 in 5 portions at intervals of 10 min. After the addition is completed, continue heating and stirring for 2 h. Then filter and wash 3 times to remove the salts generated in the system. After the washing is completed, place it in an oven at 60 °C and dry for 24 h, and grind it into a powder. Finally, place the powder in a vacuum atmosphere furnace and heat it at 300 °C for 2 h to obtain sepiolite loaded with 3.0 g of zinc oxide. Its X-ray diffraction pattern (XRD) is as Figure 1 shown, and the scanning electron microscope SEM is as Figure 2 shown, and the transmission electron microscope TEM is as Figure 3As shown; add the above-mentioned sepiolite loaded with zinc oxide into water, disperse it under ultrasonic action of 3 J / g for 15 min to prepare a suspension with a solid content of 4%, then add 333.4 g of concentrated natural latex diluted to a solid content of 30%, and stir at 500 rpm for 30 min. Then, flocculate with a 2% calcium chloride solution, soak and wash several times, and vacuum dry at 60 °C for 48 h to obtain a highly active natural rubber / zinc oxide masterbatch containing 3.0 g of zinc oxide, 10 g of sepiolite and 100 g of natural rubber; the mixing process, testing steps and results of the obtained masterbatch are the same as those in Example 1. In addition, the SEM and TEM of the brittle fracture surface of the vulcanizate of the obtained masterbatch are respectively as Figure 4 and Figure 5 shown.

[0052] Example 6:

[0053] Take 10 g of sepiolite and add it to 490 g of water, stir at a speed of 10000 rpm for 20 min to obtain a sepiolite suspension with a solid content of 2%. Then add 8.395 g of ZnCl2 and stir at 60 °C; at the same time, take 4.938 g of NaOH and dissolve it in 100 ml of deionized water. After ZnCl2 is completely dissolved, add the prepared NaOH solution to the sepiolite suspension dissolved with ZnCl2 in 5 portions, with an interval of 10 min each time. After the addition is completed, continue to heat and stir for 2 h. Then filter and wash 3 times to remove the salts generated in the system. After washing, place it in an oven at 60 °C and dry for 24 h, and grind it into powder. Finally, place the powder in a vacuum atmosphere furnace and heat it at 300 °C for 2 h to obtain sepiolite loaded with 5.0 g of zinc oxide; add the above-mentioned sepiolite loaded with zinc oxide into water, disperse it under ultrasonic action of 3 J / g for 15 min to prepare a suspension with a solid content of 4%, then add 333.4 g of concentrated natural latex diluted to a solid content of 30%, and stir at 500 rpm for 30 min. Then, flocculate with a 2% calcium chloride solution, soak and wash several times, and vacuum dry at 60 °C for 48 h to obtain a highly active natural rubber / zinc oxide masterbatch containing 5.0 g of zinc oxide, 10 g of sepiolite and 100 g of natural rubber; the mixing process, testing steps and results of the obtained masterbatch are the same as those in Example 1.

[0054] Comparative Example 1:

[0055] Take 1.679 g of ZnCl₂ and add it to 500 ml of water, and stir at 60 °C until completely dissolved; meanwhile, take 0.988 g of NaOH and dissolve it in 100 ml of deionized water; add the prepared NaOH solution to the ZnCl₂ solution in 5 portions at intervals of 10 min each. After the addition is completed, continue heating and stirring for 2 h. Then, perform suction filtration and wash 3 times to remove the salts generated in the system. After the washing is completed, place it in an oven at 60 °C and dry for 24 h, and grind it into a powder. Finally, place the powder in a vacuum atmosphere furnace and heat it at 300 °C for 2 h to obtain 0.5 g of zinc oxide particles (equivalent to 1 phr of zinc oxide) for use; take 10 g of sepiolite and add it to 240 g of water, disperse it under ultrasonic action of 3 J / g for 15 min to prepare a sepiolite suspension with a solid content of 4%, then add 333.4 g of concentrated natural rubber latex diluted to a solid content of 30%, and stir at 500 rpm for 30 min. Subsequently, flocculate with a 2% calcium chloride solution, soak and wash several times, and then dry in vacuo at 60 °C for 48 h to obtain a masterbatch containing 10 g of sepiolite and 100 g of natural rubber; mix the above masterbatch with the prepared 1 phr of zinc oxide, 2 phr of stearic acid, 1.35 phr of accelerator NS, and 1.5 phr of sulfur on an open mill to obtain a mixed rubber. After standing for 12 h, measure the vulcanization curve at 150 °C, and the results are shown in Table 1; vulcanize the mixed rubber under the vulcanization conditions of 150 °C, 10 MPa, and t90 + 3 min, and test the physical and mechanical properties and crosslink density, and the results are shown in Table 2.

[0056] Comparative Example 2:

[0057] Take 3.358 g of ZnCl₂ and add it to 500 ml of water, and stir at 60 °C until completely dissolved; meanwhile, take 1.975 g of NaOH and dissolve it in 100 ml of deionized water; add the prepared NaOH solution to the ZnCl₂ solution in 5 portions at intervals of 10 min each. After the addition is completed, continue heating and stirring for 2 h. Then, perform suction filtration and wash 3 times to remove the salts generated in the system. After the washing is completed, place it in an oven at 60 °C and dry for 24 h, and grind it into a powder. Finally, place the powder in a vacuum atmosphere furnace and heat it at 300 °C for 2 h to obtain 2.0 g of zinc oxide particles (equivalent to 2 phr of zinc oxide) for use; the preparation method of the natural rubber / sepiolite masterbatch and the mixing, processing, and testing steps with the prepared zinc oxide and other additives are the same as those in Comparative Example 1.

[0058] Comparative Example 3:

[0059] Take 5.037 g of ZnCl2 and add it to 500 ml of water, and stir at 60 °C until completely dissolved; at the same time, take 2.963 g of NaOH and dissolve it in 100 ml of deionized water; add the prepared NaOH solution to the ZnCl2 solution in 5 portions, with an interval of 10 min each time. After the addition is completed, continue heating and stirring for 2 h. Then filter with suction and wash 3 times to remove the salts generated in the system. After the washing is completed, place it in an oven at 60 °C and dry for 24 h, and grind it into a powder. Finally, place the powder in a vacuum atmosphere furnace and heat it at 300 °C for 2 h to obtain 2.0 g of zinc oxide particles (equivalent to 2 phr of zinc oxide) for use; the preparation method of natural rubber / sepiolite masterbatch and its mixing, processing and testing steps with other additives such as the prepared zinc oxide are the same as those in Comparative Example 1. Among them, the SEM and TEM images of the vulcanized fracture surface of the obtained composite material are respectively as Figure 6 and Figure 7 shown.

[0060] Comparative Example 4:

[0061] Take 8.395 g of ZnCl2 and add it to 500 ml of water, and stir at 60 °C until completely dissolved; at the same time, take 4.938 g of NaOH and dissolve it in 100 ml of deionized water; add the prepared NaOH solution to the ZnCl2 solution in 5 portions, with an interval of 10 min each time. After the addition is completed, continue heating and stirring for 2 h. Then filter with suction and wash 3 times to remove the salts generated in the system. After the washing is completed, place it in an oven at 60 °C and dry for 24 h, and grind it into a powder. Finally, place the powder in a vacuum atmosphere furnace and heat it at 300 °C for 2 h to obtain 2.0 g of zinc oxide particles (equivalent to 2 phr of zinc oxide) for use; the preparation method of natural rubber / sepiolite masterbatch and its mixing, processing and testing steps with other additives such as the prepared zinc oxide are the same as those in Comparative Example 1.

[0062] Table 1 Vulcanization characteristics of the mixed rubbers obtained in the examples and comparative examples

[0063]

[0064] Table 2 Physical and mechanical properties and crosslinking density of the composite materials obtained in the examples and comparative examples

[0065]

[0066] From the above performance data, it can be seen that the wet mixing application of sepiolite-supported zinc oxide material enables zinc oxide to be dispersed at the nanoscale in the rubber matrix. At the same time, when the amount of zinc oxide is the same, the vulcanization efficiency, crosslink density, modulus at a specified elongation, tensile strength, tear strength and other properties of the natural rubber composites obtained by wet mixing of sepiolite-supported zinc oxide are higher than those of the natural rubber composites obtained by traditional dry mixing. In addition, when the amount of supported zinc oxide is 2 phr, the application effect can reach the application effect of traditional zinc oxide at 3 - 5 phr, indicating that it can effectively reduce the usage amount of zinc oxide.

[0067] From Figure 1 the JCPDS#36 - 1451 standard card of zinc oxide, it can be seen that the characteristic diffraction peaks of ZnO are at 2θ = 31.7°, 34.4°, 36.2°, 47.5°, 56.6°, 62.8°, 67.9°; while the main characteristic peaks of sepiolite are at 2θ = 7.3° etc., as shown in the Sep pattern in the figure. For the sepiolite-supported zinc oxide material, it can be seen that it still has a strong characteristic peak at 2θ = 7.3°, indicating that the loading of zinc oxide does not change the original interplanar spacing of sepiolite and destroy its original crystal structure. And the characteristic peaks at 2θ = 31.7°, 34.4°, 36.2°, 47.5°, 56.6°, 62.8°, 67.9° still exist, and no additional diffraction peaks appear, indicating that the zinc oxide loaded on sepiolite has good crystallinity, showing that zinc oxide has been successfully loaded on sepiolite.

[0068] Figure 2 Some nanoscale particles can be clearly observed to be relatively evenly distributed among the sepiolite bundle-like fibers, making the bundle-like fiber structure of sepiolite look looser. It can be seen from the enlarged SEM image that these particles are deposited on the fiber surface individually or in clusters.

[0069] From Figure 3 the TEM image, it can be seen that there are many dense irregular nanoparticles on the surface of the sepiolite fibers that are cylindrical and have a pore structure, and they closely adhere to the surface of the rod-like fibers. The individual size of these particles is about 20 - 30 nm, and the size of the clusters ranges from dozens of nanometers to hundreds of nanometers.

[0070] From Figure 4 it can be seen that in the natural rubber composites obtained by direct wet mixing, all the filler particles are relatively evenly dispersed in the rubber matrix, and there are no obvious aggregated particles, indicating that both sepiolite and the loaded zinc oxide particles are well dispersed in the rubber matrix.

[0071] From Figure 5 it can be seen that the sepiolite fibers in the composite material are relatively evenly dispersed, and the fiber length is all below 1 μm. At the same time, the zinc oxide particles are also evenly dispersed in the form of dozens of nanometers, and there is no aggregation of larger zinc oxide particles.

[0072] It can be seen from Figure 6 that in the cross-section of the vulcanizate, there are obviously some aggregated particles. It is analyzed that since the sepiolite particles are mixed into the rubber matrix by a wet process and are relatively evenly dispersed, these aggregated particles should mainly be zinc oxide particles.

[0073] Through Figure 7 the TEM images, it can be seen that there are large aggregated zinc oxide particles in the cross-section of the composite material. This shows that in the composite material obtained by dry mixing zinc oxide, the dispersion of zinc oxide particles is relatively poor.

[0074] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A sepiolite-loaded zinc oxide material, characterized in that: The material is prepared by the following steps: A1: adding sepiolite powder into water, and preparing a sepiolite suspension with a certain solid content under the action of high-speed stirring or ultrasonic dispersion; A2 adds divalent zinc salt to the sepiolite suspension obtained in A1 under heating and stirring, the added amount is 10% to 100% of the mass of the sepiolite, and after it is completely dissolved, a certain amount of alkali is added in batches, the added amount is twice the molar amount of the divalent zinc salt, and after the reaction is complete, a suspension of sepiolite loaded with zinc hydroxide is obtained; A3 filters and washes the sepiolite-loaded zinc hydroxide suspension in A2, and then dries and crushes it to obtain sepiolite-loaded zinc hydroxide powder; A4: placing the sepiolite-loaded zinc hydroxide powder obtained in A3 in a high-temperature air atmosphere furnace for reaction to obtain a sepiolite-loaded zinc oxide material.

2. The sepiolite-loaded zinc oxide material according to claim 1, characterized in that: The speed of high-speed stirring in step A1 is 1000rpm-20000rpm; the energy required for ultrasonic dispersion per gram of sepiolite suspension is 0.1-5J / g; and the sepiolite solid content of the sepiolite suspension is 1%-5%.

3. The sepiolite-loaded zinc oxide material according to claim 1, characterized in that: In step A2, the heating temperature is 25° C.-100° C.; the added divalent zinc salt is one of zinc chloride, zinc acetate and zinc sulfate; and the quantitative base is one of sodium hydroxide, potassium hydroxide and ammonia water.

4. The sepiolite-loaded zinc oxide material according to claim 1, characterized in that: In the step A3, the particle size of the sepiolite-loaded zinc hydroxide powder is 1 μm-100 μm.

5. The sepiolite-loaded zinc oxide material according to claim 1, characterized in that: The heating temperature of the high temperature atmosphere furnace in step A4 is 100°C-550°C.

6. A highly active natural rubber / zinc oxide masterbatch, characterized in that: The masterbatch is prepared by the following steps: B1: adding sepiolite loaded with zinc oxide into water, and obtaining a sepiolite aqueous suspension loaded with zinc oxide with a certain solid content under high-speed stirring or ultrasonic dispersion; B2: adding natural rubber latex to the aqueous suspension obtained in B1, stirring at 10-500 rpm for 10-60 min to obtain a mixed slurry of natural rubber latex and zinc oxide-loaded sepiolite suspension, wherein the total amount of zinc oxide-loaded sepiolite added is 10 to 100 parts based on 100 parts of dry rubber in the natural rubber latex; B3 slowly adding the diluted flocculant to the mixed slurry obtained in B2, the added amount being 0-1.0% of the dry weight of natural latex; after stirring and flocculating, squeezing, dehydrating and washing, and then crushing and drying to obtain a highly active natural rubber / zinc oxide masterbatch.

7. The highly active natural rubber / zinc oxide masterbatch according to claim 6, characterized in that: The sepiolite-loaded zinc oxide material is a material prepared according to any one of claims 1-5.

8. The highly active natural rubber / zinc oxide masterbatch according to claim 6, characterized in that: The speed of high-speed stirring in step B1 is 1000rpm-20000rpm; the energy required for ultrasonic dispersion of each gram of zinc oxide-loaded sepiolite suspension is 0.1-5J / g; the solid content of the zinc oxide-loaded sepiolite aqueous suspension is between 1% and 10%.

9. The highly active natural rubber / zinc oxide masterbatch according to claim 6, characterized in that: In the step B2, the natural latex is a mixture of one or more of field natural latex, concentrated natural latex, and epoxidized natural latex with a solid content of 20% to 50%.

10. The highly active natural rubber / zinc oxide masterbatch according to claim 7, characterized in that: In step B3, the added flocculant is one or more of formic acid, calcium chloride, methanol, and protease.

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