A multi-component collaborative high-performance natural rubber sheet and its industrial preparation method

Abstract

The present invention discloses a multi-component synergistic high-performance natural rubber sheet and its industrial preparation method. The multi-component synergistic high-performance natural rubber sheet, by weight, comprises the following components: 150 - 175 parts of natural rubber latex, 20 - 35 parts of carbon black, 7 - 12 parts of nano-silica, 5 - 10 parts of modified short aramid fibers, 3 - 5 parts of zinc oxide, 1 - 1.5 parts of stearic acid, 1 - 2 parts of vulcanizing agent, 2 - 5 parts of coupling agent, 1.2 - 1.8 parts of accelerator, 0.5 - 1.5 parts of antioxidant and 5 - 16 parts of auxiliary agent. The present invention provides a rubber sheet with high abrasion resistance, high tear resistance, high strength and low hardness that can be industrially produced, including a preparation method of wet-mixed rubber and a complete process of a feasible industrial mass production process, so as to overcome the deficiencies of existing dry rubber sheets in terms of comprehensive multi-performance and the drawback that the current high-performance wet-mixing technology can only achieve its comprehensive excellent performance in the laboratory.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber materials, and particularly relates to a multi-component synergistic high-performance natural rubber rubber sheet and an industrial preparation method thereof. Background Art

[0002] In many industrial fields, such as machinery manufacturing, mining, transportation, etc., there are strict requirements for the performance of rubber sheets. Traditional dry rubber rubber sheets often have difficulty in balancing multiple characteristics such as high wear resistance, high tear resistance, high strength and low hardness. In addition, some domestic wet mixing technologies with similar high wear resistance and high tear resistance can only achieve their comprehensive excellent performance in the laboratory. When scaled up to industrial production, all performances are greatly reduced, and the large-scale production process route is imperfect, which cannot meet the market demand. For example, rubber components used in mining equipment need high wear resistance and high tear resistance to cope with the impact and friction of ores. However, the existing products have a high hardness, which is easy to cause damage to other components of the equipment, and are prone to tearing or damage due to stress concentration during long-term use, unable to meet the production requirements of high efficiency, safety and long life. In the field of sanitation sweeper manufacturing, rubber sheets are used for parts such as scrapers, which require both low hardness, high elasticity and high tear resistance, and high wear resistance to maintain a long service life and reduce the use cost. At present, the comprehensive performance of the existing rubber sheets is not satisfactory. Therefore, it is urgent to develop a multi-component synergistic high-performance rubber sheet and successfully promote it to industrial production. Summary of the Invention

[0003] The present invention aims to provide a rubber sheet with high wear resistance, high tear resistance, high strength and low hardness that can be industrially produced, including a preparation method of a wet mixing rubber and a complete process of a feasible industrial large-scale production process, so as to overcome the deficiencies of the existing dry rubber rubber sheets in terms of comprehensive performance of multiple properties and the disadvantage that the current high-performance wet mixing technology can only achieve its comprehensive excellent performance in the laboratory, and provide a perfect solution for research and development and production transfer. Meet the special needs of the rubber materials in various industrial fields and improve the quality and performance of related products.

[0004] The present invention is implemented through the following technical solutions:

[0005] On the one hand, the present invention discloses a multi-component synergistic high-performance natural rubber rubber sheet, which, by weight, includes the following components: 150-175 parts of natural rubber latex, 20-35 parts of carbon black, 7-12 parts of nano-silica, 5-10 parts of modified short aramid fibers, 3-5 parts of zinc oxide, 1-1.5 parts of stearic acid, 1-2 parts of vulcanizing agent, 2-5 parts of coupling agent, 1.2-1.8 parts of accelerator, 0.5-1.5 parts of antioxidant and 5-16 parts of auxiliary agent.

[0006] Further, the solid content of the natural rubber latex is 60±2%.

[0007] Further, the preparation method of the modified chopped aramid fiber specifically includes the following steps:

[0008] (1) Pretreatment of chopped aramid fiber: Soak the washed and dried chopped aramid fiber in a 2 wt% sodium hydroxide solution at 40 °C for 15 min, then wash it until neutral and dry to obtain pretreated chopped aramid fiber;

[0009] (2) Dopamine modification: Add dopamine to a buffer solution to prepare a dopamine solution with a concentration of 1 - 3.5 g / L, adjust the pH of the dopamine solution to 8.3 - 8.8 with an inorganic base, immerse the pretreated chopped aramid fiber in the dopamine solution, let it stand overnight at room temperature, take it out, wash it, and dry it to obtain dopamine-modified chopped aramid fiber;

[0010] (3) In-situ growth of LDHs: Prepare a precursor solution of 0.04 - 0.06 mol / L Mg(NO 3 ) 2 ·6H 2 O, 0.02 - 0.03 mol / L Al(NO 3 ) 3 ·9H 2 O and 0.4 - 0.5 mol / L urea. Immerse the dopamine-modified chopped aramid fiber in the precursor solution, place it in a closed reaction kettle, under nitrogen protection, heat it to 85 - 90 °C, stir at a low speed for 4 - 12 h. After the reaction is completed, wash it and dry it to obtain the modified chopped aramid fiber.

[0011] Further, the length of the chopped aramid fiber is 0.5 - 3 mm.

[0012] Further, in step (2), the buffer solution is any one of Tris-HCl, sodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution, sodium hydrogen phosphate-sodium dihydrogen phosphate buffer solution, or potassium dihydrogen phosphate-sodium hydroxide buffer solution.

[0013] Further, in step (3), the stirring rate is 100 - 180 r / min.

[0014] Further, the vulcanizing agent is vulcanizing agent S-80;

[0015] The coupling agent is silane coupling agent Si-69;

[0016] The accelerator is composed of accelerator TBBS and accelerator DPG in a mass ratio of 1:2;

[0017] The antioxidant is composed of antioxidant RD and antioxidant 4020 in a mass ratio of 1:1.5.

[0018] Further, the auxiliary agent is composed of emulsified naphthenic oil and emulsified aromatic oil in a mass ratio of 4:1.

[0019] The second aspect of the present invention discloses a method for preparing the multi-component synergistic high-performance natural rubber rubber sheet, comprising the following steps:

[0020] S1. Add carbon black and nano-silica into deionized water, then continue to add a silane coupling agent, and perform high-speed shear dispersion to form a homogeneous slurry. Then continue to add modified short aramid fibers and perform low-speed stirring dispersion to obtain a filler slurry;

[0021] S2. Mix the natural rubber latex and the auxiliary agent evenly, add the filler slurry, zinc oxide and stearic acid, stir evenly, then add a promoter and an antioxidant in sequence, and continue to stir evenly to obtain a mixed latex;

[0022] S3. Add a calcium chloride solution as a coagulant to the mixed latex, stir until the colloid flocculates, filter, wash with water, and dry to obtain a masterbatch of the mixed rubber;

[0023] S4. Add the masterbatch of the mixed rubber into a mixer, perform mixing at room temperature for 5 - 10 min, add a vulcanizing agent, and continue to mix for 5 - 10 min to obtain a uniformly mixed rubber compound. Then use a calendering or extrusion process to form a rubber sheet blank;

[0024] S5. Feed the rubber sheet blank into a vulcanizing press for vulcanization molding to obtain the multi-component synergistic high-performance natural rubber rubber sheet.

[0025] Further, in step S1, the rotation speed of the high-speed shear dispersion is 8000 - 10000 r / min, and the shear dispersion time is 30 - 40 min; the rotation speed of the low-speed stirring is 150 - 200 r / min, and the stirring time is 10 - 20 min;

[0026] In step S3, the concentration of the calcium chloride solution is 5 wt%;

[0027] In step S5, the vulcanization temperature is 120 - 160 °C, and the pressure is 15 MPa.

[0028] Advantages of the present invention:

[0029] 1. In the present invention, traditional carbon black filler and nano-silica are added in a coordinated manner, which can form a homogeneous dispersion system in the rubber matrix, thereby improving the wear resistance and tear resistance of the rubber sheet. The short aramid fibers are synergistically modified by LDHs / dopamine to form a functional layer on the fiber surface, improving the interfacial bonding with the rubber matrix, effectively transmitting stress, further enhancing the overall impact resistance and tensile strength, and at the same time controlling the vulcanization network structure to keep the rubber sheet at a relatively low hardness.

[0030] 2. The present invention adopts the wet mixing technology. By directly dispersing each component in the rubber latex, the problem of filler agglomeration in traditional dry mixing is avoided, and the dispersion uniformity is significantly improved, especially for the dispersion effect of nano-scale fillers. In addition, the compounded accelerator and antioxidant system provides excellent vulcanization characteristics and aging protection ability. The compounding of naphthenic oil and aromatic oil not only improves the processing performance of the rubber compound, but also improves the dynamic performance of the product to a certain extent. This multi-component synergistic formulation design and innovative preparation process not only achieves wear resistance, tear resistance and high strength performance, but also maintains the low hardness and high flexibility of the rubber sheet, thus meeting the requirements for comprehensive performance in different fields. Detailed Embodiments

[0031] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0032] In the embodiments and comparative examples of the present invention, the solid content of the natural rubber latex is 60 ± 2%;

[0033] The vulcanizing agent is vulcanizing agent S-80;

[0034] The coupling agent is silane coupling agent Si-69;

[0035] The accelerator is composed of accelerator TBBS and accelerator DPG in a mass ratio of 1:2;

[0036] The antioxidant is composed of antioxidant RD and antioxidant 4020 in a mass ratio of 1:1.5;

[0037] The auxiliary agent is composed of emulsified naphthenic oil and emulsified aromatic oil in a mass ratio of 4:1.

[0038] Example 1

[0039] A multi-component synergistic high-performance natural rubber sheet, by weight, comprises the following components: 160 parts of natural rubber latex, 30 parts of carbon black, 10 parts of nano-silica, 8 parts of modified short-cut aramid fiber, 4 parts of zinc oxide, 1.2 parts of stearic acid, 1.5 parts of vulcanizing agent, 3 parts of coupling agent, 1.5 parts of accelerator, 1.0 part of antioxidant and 12 parts of auxiliary agent.

[0040] The preparation of the modified short-cut aramid fiber specifically includes the following steps:

[0041] (1) Pretreatment of short-cut aramid fiber: The washed and dried short-cut aramid fiber (length 2 - 3 mm) is soaked in a 2 wt% sodium hydroxide solution at 40 °C for 15 min, and then washed to neutral and dried to obtain pretreated short-cut aramid fiber;

[0042] (2) Dopamine modification: Add dopamine to the disodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution to prepare a dopamine solution with a concentration of 2.0 g / L. Adjust the pH of the dopamine solution to 8.5 with an inorganic base. Immerse the pretreated short aramid fibers in the dopamine solution, let it stand overnight at room temperature, take it out, wash it, and dry it to obtain dopamine-modified short aramid fibers;

[0043] (3) In-situ growth of LDHs: Prepare a precursor solution of 0.06 mol / L Mg(NO 3 ) 2 ·6H 2 O, 0.03 mol / L Al(NO 3 ) 3 ·9H 2 O and 0.45 mol / L urea. Immerse the dopamine-modified short aramid fibers in the precursor solution, place them in a closed reaction kettle, under nitrogen protection, heat to 90 °C, stir at 120 r / min for 6 h. After the reaction is completed, wash and dry to obtain modified short aramid fibers.

[0044] A preparation method of a multi-component synergistic high-performance natural rubber rubber sheet includes the following steps:

[0045] S1. Add carbon black and nano-silica to deionized water, then add a silane coupling agent, and shear and disperse at a high speed of 10000 r / min for 30 min to form a uniform slurry. Then add the modified short aramid fibers and stir and disperse at 150 r / min for 20 min to obtain a filler slurry;

[0046] S2. Mix the natural rubber latex and additives evenly, add the filler slurry, zinc oxide and stearic acid, stir evenly, then add the accelerator and antioxidant in sequence, and continue to stir evenly to obtain a mixed latex;

[0047] S3. Add a 5 wt% calcium chloride solution as a coagulant to the mixed latex, stir until the colloid flocculates, filter, wash with water, and dry to obtain a masterbatch of the mixed rubber;

[0048] S4. Add the masterbatch of the mixed rubber to an internal mixer, mix at room temperature for 10 min, add a vulcanizing agent, and continue to mix for 10 min to obtain a uniformly mixed rubber compound. Use the calendering process to make the rubber compound into a rubber sheet blank with a thickness of 1.8 mm and a width of 250 mm;

[0049] S5. Feed the rubber sheet blank into a vulcanizing press, set the vulcanization temperature to 150 °C, the pressure to 15 MPa, and the vulcanization time to T90 + 3 min for vulcanization molding to obtain a multi-component synergistic high-performance natural rubber rubber sheet.

[0050] Example 2

[0051] A multi-component synergistic high-performance natural rubber rubber sheet, by weight, comprises the following components: 160 parts of natural rubber latex, 27 parts of carbon black, 9 parts of nano-silica, 10 parts of modified short-cut aramid fiber, 4 parts of zinc oxide, 1.2 parts of stearic acid, 1.5 parts of vulcanizing agent, 3 parts of coupling agent, 1.5 parts of accelerator, 1.0 part of antioxidant and 12 parts of auxiliary agent.

[0052] The preparation method of the modified short-cut aramid fiber and the multi-component synergistic high-performance natural rubber rubber sheet is the same as that of Example 1.

[0053] Example 3

[0054] A multi-component synergistic high-performance natural rubber rubber sheet, by weight, comprises the following components: 160 parts of natural rubber latex, 33 parts of carbon black, 11 parts of nano-silica, 6 parts of modified short-cut aramid fiber, 4 parts of zinc oxide, 1.2 parts of stearic acid, 1.5 parts of vulcanizing agent, 3 parts of coupling agent, 1.5 parts of accelerator, 1.0 part of antioxidant and 12 parts of auxiliary agent.

[0055] The preparation method of the modified short-cut aramid fiber and the multi-component synergistic high-performance natural rubber rubber sheet is the same as that of Example 1.

[0056] Based on Examples 1-3, further, when adjusting the pH of the dopamine solution to 8.5 with an inorganic base, the pH is adjusted to 8.5 through the following steps:

[0057] Obtain a preset number of specific portions of the inorganic base in the inorganic base to obtain multiple small portions of the inorganic base;

[0058] Add the small portions of the inorganic base to the dopamine solution in sequence, and after each addition of a small portion of the inorganic base to the dopamine solution, perform real-time monitoring of the pH value of the dopamine solution to obtain the pH change information of the dopamine solution, and obtain the pH change information of the dopamine solution;

[0059] Analyze the data after the pH change of the dopamine solution is stable after adding the small portions of the inorganic base according to the pH change information of the dopamine solution to determine multiple pH adjustment data, and obtain the first pH data; wherein, the pH adjustment data is the pH data after the pH change of the dopamine solution is stable after adding the small portions of the inorganic base;

[0060] Analyze the pH change characteristics during the pH adjustment of the dopamine solution for the first pH data to obtain the pH adjustment characteristics, including:

[0061] Calculate the pH difference for the pH adjustment data in the first pH data in combination with the adjacent pH adjustment data to obtain the pH change data;

[0062] Analyze the change law of the pH change data to determine the change characteristics of the pH change data, and obtain the first pH adjustment characteristics;

[0063] Analyze the variation characteristics by combining the PH change data with the amount of a small portion of inorganic base to obtain the sub-variation data characteristics, and form the target analysis data sequence according to the acquisition order of the PH change data;

[0064] In the target analysis data sequence, analyze the variation characteristics of the first two, three,..., N data in turn to determine multiple data variation sub-characteristics; where N is the number of sub-variation data characteristics in the target analysis data sequence;

[0065] Analyze the variation rules based on multiple data variation sub-characteristics to determine the variation characteristics of the data variation sub-characteristics and obtain the second PH adjustment characteristic;

[0066] Analyze whether the first PH adjustment characteristic is the same as the second PH adjustment characteristic. If the first PH adjustment characteristic is the same as the second PH adjustment characteristic, then the first PH adjustment characteristic or the second PH adjustment characteristic is the final PH adjustment characteristic. If the first PH adjustment characteristic is different from the second PH adjustment characteristic, then comprehensively analyze the first PH adjustment characteristic and the second PH adjustment characteristic to determine the third PH adjustment characteristic, and use the third PH adjustment characteristic as the final PH adjustment characteristic;

[0067] Obtain the current PH data of the dopamine solution, analyze the difference between the current PH data and 8.5 to obtain the target PH difference;

[0068] Obtain the inorganic base again according to the PH adjustment characteristic in combination with the target PH difference and the preset fine-tuning threshold to obtain the target amount of inorganic base;

[0069] Add the target amount of inorganic base to the dopamine solution, and obtain the PH data after the PH change stabilizes to obtain the second PH data;

[0070] Perform fine-tuning based on the second PH data, add a small amount of inorganic base to the dopamine solution, wait for a while and then obtain the PH data of the dopamine solution to obtain the PH fine-tuning data, and repeat multiple times until the PH fine-tuning data is equal to 8.5.

[0071] The above technical solution can not only improve the efficiency of adjusting the pH of the dopamine solution, but also ensure the accuracy of pH adjustment, guarantee the properties of the dopamine solution, provide a guarantee for impregnating the pretreated short aramid fibers into the dopamine solution, enable better acquisition of dopamine-modified short aramid fibers, improve the quality of the modified short aramid fibers, and then form a functional layer on the fiber surface, improve the interfacial bonding with the rubber matrix, effectively transfer stress, further enhance the overall impact resistance and tensile strength, and at the same time control the vulcanization network structure to keep the rubber sheet at a lower hardness. By using multiple small portions of inorganic base, the characteristics of the pH change of the dopamine solution during pH adjustment can be initially understood, and then the pH can be continuously adjusted according to the pH adjustment characteristics. The pH is continuously adjusted in two stages: the target amount of inorganic base and micro-adjustment. This can not only quickly bring the pH of the dopamine solution close to the target pH (8.5), but also avoid excessive one-time adjustment causing the pH of the dopamine solution to exceed the target pH, reduce the time for pH adjustment, improve the efficiency of pH adjustment of the dopamine solution, and at the same time avoid excessive pH adjustment beyond the target pH by means of a preset fine-tuning threshold, resulting in the dopamine solution not meeting the requirements, and reduce unnecessary waste of time and resources. In addition, when analyzing the pH change characteristics of the dopamine solution during pH adjustment based on the first pH data, after obtaining the first pH adjustment characteristic and the second pH adjustment characteristic by two methods respectively, the final pH adjustment characteristic is determined, reducing the large error of the pH adjustment characteristic caused by one-sided factors, improving the accuracy of the pH adjustment characteristic, thus providing a guarantee for obtaining the inorganic base again according to the pH adjustment characteristic in combination with the target pH difference and the preset fine-tuning threshold, improving the suitability of the target amount of inorganic base, and further improving the adjustment effect of the target amount of inorganic base in subsequent adjustments, enabling more efficient pH adjustment when continuously adjusting the pH in two stages: the target amount of inorganic base and micro-adjustment.

[0072] Further, when adding carbon black and nano-silica into deionized water and then adding a silane coupling agent in S1, a detection device is used to detect and analyze the slurry during the high-speed shear dispersion process at 10,000 r / min, including:

[0073] Statistical time of the high-speed shear dispersion process is carried out to obtain the high-speed shear dispersion statistical time, and at the same time the state information of the slurry is obtained in real time to get the real-time slurry state information;

[0074] Analysis of the dispersion situation of the slurry is carried out according to the real-time slurry state information to determine whether the slurry is evenly dispersed, and the slurry analysis result is obtained;

[0075] When the slurry analysis result shows that the slurry is unevenly dispersed, analyze and determine whether the high-speed shear dispersion statistical time has reached the preset time. If the high-speed shear dispersion statistical time has reached the preset time, an uneven slurry dispersion warning is issued. If the high-speed shear dispersion statistical time has not reached the preset time, continue to perform 10000r / min high-speed shear dispersion until the high-speed shear dispersion statistical time has reached the preset time, or the slurry analysis result shows that the slurry is evenly dispersed.

[0076] When the slurry analysis result shows that the slurry is evenly dispersed, continue to perform high-speed shear dispersion at 10000r / min according to the preset blending time, then stop the high-speed shear dispersion, obtain the statistical time of the high-speed shear dispersion at this time, obtain the current statistical time of the high-speed shear dispersion, analyze the difference between the current statistical time of the high-speed shear dispersion and the preset time, obtain the target surplus time, and then give a prompt for the target surplus time.

[0077] The above-mentioned detection and analysis of the slurry during the 10000r / min high-speed shear dispersion process by the detection device ensures that the slurry is evenly dispersed after the carbon black and nano-silica are added to the deionized water and the silane coupling agent is further added, thereby providing convenient conditions for adding modified chopped aramid fibers to the slurry, ensuring the properties of the filler slurry, avoiding agglomeration of the filler slurry, and thereby improving the performance of the multi-synergistic high-performance natural rubber sheet. By performing time statistics on the high-speed shear dispersion process, the 10000r / min high-speed shear dispersion time can be measured to avoid wasting time and resources caused by long-term high-speed shear dispersion. At the same time, by analyzing the slurry dispersion situation, the final slurry dispersion is guaranteed to be uniform, and the uneven slurry dispersion will not affect the subsequent use of the slurry. When the slurry analysis result shows that the slurry dispersion is uneven, the preset time (30min) is combined with the preset time to issue an uneven slurry dispersion warning, so that relevant personnel can understand the situation after the 10000r / min high-speed shear dispersion process ends, so that the slurry can be processed again according to the actual situation. At the same time, when the slurry analysis result shows that the slurry dispersion is uniform, the blending time is used to further ensure that the slurry is fully dispersed. By analyzing the difference between the current statistical time and the preset time of the high-speed shear dispersion, the gap between the preset time (30min) and the actually required high-speed shear dispersion time is clarified, reducing unnecessary time waste. At the same time, the preset time for the subsequent 10000r / min high-speed shear dispersion can also be optimized.

[0078] Comparative Example 1

[0079] In this comparative example, no modified chopped aramid fiber was added.

[0080] A natural rubber rubber sheet, by weight, comprises the following components: 160 parts of natural rubber latex, 30 parts of carbon black, 10 parts of nano-silica, 4 parts of zinc oxide, 1.2 parts of stearic acid, 1.5 parts of vulcanizing agent, 3 parts of coupling agent, 1.5 parts of accelerator, 1.0 part of antioxidant and 12 parts of auxiliary agent.

[0081] The preparation method of the natural rubber rubber sheet comprises the following steps:

[0082] S1. Add carbon black and nano-silica into deionized water, then continue to add silane coupling agent, and disperse at a high speed of 10000 r / min by shearing for 30 min to obtain a filler slurry.

[0083] S2. Mix the natural rubber latex and the auxiliary agent evenly, add the filler slurry, zinc oxide and stearic acid, stir evenly, then add the accelerator and antioxidant in sequence, and continue to stir evenly to obtain a mixed latex.

[0084] S3. Add a 5wt% calcium chloride solution as a coagulant to the mixed latex, stir until the colloid flocculates, filter, wash with water, and dry to obtain a masterbatch of the kneaded rubber.

[0085] S4. Add the masterbatch of the kneaded rubber into a mixer, knead at room temperature for 10 min, add the vulcanizing agent, and continue to knead for 10 min to obtain a uniformly kneaded rubber compound. Then use a calendering process to make the rubber compound into a rubber sheet blank with a thickness of 1.8 mm and a width of 250 mm.

[0086] S5. Feed the rubber sheet blank into a vulcanizing press, set the vulcanization temperature at 150 °C, the pressure at 15 MPa, and the vulcanization time at T90 + 3 min for vulcanization molding to obtain the natural rubber rubber sheet.

[0087] Comparative Example 2

[0088] In this comparative example, unmodified short aramid fibers are added.

[0089] A natural rubber rubber sheet, by weight, comprises the following components: 160 parts of natural rubber latex, 30 parts of carbon black, 10 parts of nano-silica, 8 parts of short aramid fibers, 4 parts of zinc oxide, 1.2 parts of stearic acid, 1.5 parts of vulcanizing agent, 3 parts of coupling agent, 1.5 parts of accelerator, 1.0 part of antioxidant and 12 parts of auxiliary agent.

[0090] The preparation method of a multi-component synergistic high-performance natural rubber rubber sheet comprises the following steps:

[0091] S1. Add carbon black and nano-silica into deionized water, then continue to add silane coupling agent, disperse at a high speed of 10000 r / min by shearing for 30 min to form a homogeneous slurry, and then continue to add short aramid fibers, and disperse by stirring at 150 r / min for 20 min to obtain a filler slurry.

[0092] S2. Mix the natural rubber latex and additives evenly, add the filler slurry, zinc oxide and stearic acid, stir evenly, add the accelerator and antioxidant in sequence, and continue to stir evenly to obtain the mixed latex;

[0093] S3. Add a 5wt% calcium chloride solution to the mixed latex as a coagulant, stir until the colloid flocculates, filter, wash with water, and dry to obtain the masterbatch of the mixed rubber;

[0094] S4. Add the masterbatch of the mixed rubber to a mixer, mix at room temperature for 10 min, add the vulcanizing agent, and continue to mix for 10 min to obtain a uniformly mixed rubber compound. Process the rubber compound into a rubber sheet blank by calendering, with a thickness of 1.8 mm and a width of 250 mm;

[0095] S5. Feed the rubber sheet blank into a vulcanizing press, set the vulcanization temperature at 150 °C, the pressure at 15 MPa, and the vulcanization time at T90 + 3 min for vulcanization molding to obtain the multi-component synergistic high-performance natural rubber sheet.

[0096] Comparative Example 3

[0097] In this comparative example, dopamine-modified short aramid fibers are added.

[0098] A multi-component synergistic high-performance natural rubber sheet, by weight, comprises the following components: 160 parts of natural rubber latex, 30 parts of carbon black, 10 parts of nano-silica, 8 parts of modified short aramid fiber A, 4 parts of zinc oxide, 1.2 parts of stearic acid, 1.5 parts of vulcanizing agent, 3 parts of coupling agent, 1.5 parts of accelerator, 1.0 part of antioxidant and 12 parts of additives.

[0099] The preparation of the modified short aramid fiber A specifically comprises the following steps:

[0100] (1) Pretreatment of the short aramid fiber: Immerse the cleaned and dried short aramid fiber (with a length of 2 - 3 mm) in a 2wt% sodium hydroxide solution at 40 °C for 15 min, then wash until neutral and dry to obtain the pretreated short aramid fiber;

[0101] (2) Dopamine modification: Add dopamine to a disodium hydrogen phosphate - potassium dihydrogen phosphate buffer solution to prepare a dopamine solution with a concentration of 2.0 g / L. Adjust the pH of the dopamine solution to 8.5 with an inorganic base. Immerse the pretreated short aramid fiber in the dopamine solution, let it stand overnight at room temperature, take it out, wash, and dry to obtain the modified short aramid fiber A.

[0102] A method for preparing a multi-component synergistic high-performance natural rubber sheet comprises the following steps:

[0103] S1. Add carbon black and nano-silica into deionized water, then continue to add silane coupling agent, and disperse them by high-speed shearing at 10000 r / min for 30 min to form a homogeneous slurry. Then continue to add modified short aramid fiber A and disperse it by stirring at 150 r / min for 20 min to obtain a filler slurry.

[0104] S2. Mix natural rubber latex and additives evenly, add the filler slurry, zinc oxide and stearic acid, stir evenly, then add accelerator and antioxidant in turn, and continue to stir evenly to obtain a mixed latex.

[0105] S3. Add a 5 wt% calcium chloride solution as a coagulant into the mixed latex, stir until the colloid flocculates, filter, wash with water, and dry to obtain a masterbatch of the mixed rubber.

[0106] S4. Add the masterbatch of the mixed rubber into a mixer, knead it at room temperature for 10 min, add a vulcanizing agent, and continue to knead for 10 min to obtain a uniformly kneaded rubber compound. Then use a calendering process to make the rubber compound into a rubber sheet blank with a thickness of 1.8 mm and a width of 250 mm.

[0107] S5. Feed the rubber sheet blank into a vulcanizing press, set the vulcanization temperature at 150 °C, the pressure at 15 MPa, and the vulcanization time at T90 + 3 min for vulcanization molding, thus obtaining a multi-component synergistic high-performance natural rubber sheet.

[0108] Test Example

[0109] Perform performance tests on the natural rubber sheets prepared in Examples 1 - 3 and Comparative Examples 1 - 3, and the results are shown in Table 1.

[0110] Hardness: Refer to the standard GB / T 531.1 - 2008 Test Method for Durometer Hardness of Vulcanized Rubber or Thermoplastic Rubber.

[0111] Rotating drum abrasion: Refer to the standard GB / T 9867 - 2008 Determination of Abrasion Resistance of Vulcanized Rubber or Thermoplastic Rubber (Rotating Drum Abrasion Machine Method).

[0112] Tear strength: Refer to the standard GB / T 529 - 2008 Determination of Tear Strength of Vulcanized Rubber or Thermoplastic Rubber (Trouser, Right Angle and Crescent Specimens).

[0113] Tensile strength and elongation at break: Refer to the standard GB / T 528 - 2009 Test for Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber.

[0114] Table 1 Performance Test Results of Natural Rubber Sheets Prepared in Examples 1 - 3 and Comparative Examples 1 - 3

[0115] Group Hardness (degree) Rotating drum abrasion (mg / 40m) Tear strength (KN / m) Tensile strength (MPa) Elongation at break (%) Example 1 40 136 73 23 930 Example 2 37 135 75 24 910 Example 3 42 139 69 21 900 Comparative example 1 38 168 52 17 840 Comparative example 2 40 154 57 18 860 Comparative example 3 39 149 63 20 870

[0116] As can be seen from the results in Table 1, the performance indicators of Examples 1-3 are significantly better than those of Comparative Examples 1-3, fully confirming the feasibility and advancement of the technical solution of the present invention. The natural rubber rubber sheet prepared by the method of the present invention realizes the unity of high strength, high wear resistance and low hardness, which is difficult to balance in traditional formulations.

[0117] In the present invention, a dual modification process of dopamine and LDHs is used to treat short aramid fibers. From the data of Comparative Example 2 and Comparative Example 3, it can be seen that the enhancement effect of unmodified or only dopamine-modified fibers is significantly inferior to that of dual modification (Examples 1-3). This is because dopamine modification provides preliminary interfacial activity, and the in-situ growth of LDHs constructs a more complex interfacial structure on this basis. The synergistic effect of the two significantly improves the interfacial bonding strength between the fiber and the rubber matrix.

[0118] In addition, the compound reinforcement system of carbon black and nano-silica used in the present invention exhibits good synergistic effects. The data comparison of Examples 1-3 shows that by adjusting the ratios of modified fibers, carbon black and nano-silica, the material properties can be regulated within a certain range. This provides a practical formula optimization range, which has important guiding significance. From the perspective of industrial application, this solution not only realizes the comprehensive improvement of performance indicators, but also has a clear process route, good repeatability and controllability.

[0119] Finally, it should be noted that the above-described embodiments only represent several implementation manners of the present invention, and are not intended to limit the present invention. For those of ordinary skill in the art, any modifications, equivalent replacements, improvements, etc. made without departing from the concept of the present invention shall be included within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A multi-component synergistic high-performance natural rubber sheet, characterized in that: The composition comprises the following components by weight: 150-175 parts of natural rubber latex, 20-35 parts of carbon black, 7-12 parts of nano silicon dioxide, 5-10 parts of modified chopped aramid fiber, 3-5 parts of zinc oxide, 1-1.5 parts of stearic acid, 1-2 parts of vulcanizing agent, 2-5 parts of coupling agent, 1.2-1.8 parts of accelerator, 0.5-1.5 parts of antioxidant and 5-16 parts of auxiliary agent; The preparation method of the modified chopped aramid fiber specifically comprises the following steps: (1) Pretreatment of chopped aramid fibers: The cleaned and dried chopped aramid fibers were immersed in a 2 wt % sodium hydroxide solution at 40° C. for 15 min, then washed to neutrality and dried to obtain pretreated chopped aramid fibers; (2) Dopamine modification: dopamine is added to a buffer solution to prepare a dopamine solution with a concentration of 1-3.5 g / L, the pH of the dopamine solution is adjusted to 8.3-8.8 with an inorganic base, the pretreated chopped aramid fibers are immersed in the dopamine solution, and the fibers are allowed to stand overnight at room temperature. After being taken out, they are washed and dried to obtain dopamine-modified chopped aramid fibers. (3) In situ growth of LDHs: prepare a precursor solution of 0.04-0.06 mol / L Mg(NO3)2·6H2O, 0.02-0.03 mol / L Al(NO3)3·9H2O and 0.4-0.5 mol / L urea, immerse the dopamine-modified chopped aramid fibers in the precursor solution, place in a closed reactor, heat to 85-90°C under nitrogen protection, stir at a low speed, react for 4-12 h, and after the reaction is completed, wash and dry to obtain the modified chopped aramid fibers.

2. The multi-component synergistic high-performance natural rubber sheet according to claim 1, characterized in that: The solid content of the natural rubber latex is 60±2%.

3. The multi-component synergistic high-performance natural rubber sheet according to claim 1, characterized in that: The length of the chopped aramid fibers is 0.5-3 mm.

4. The multi-component synergistic high-performance natural rubber sheet according to claim 1, characterized in that: The buffer solution in step (2) is any one of Tris-HCl, disodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution, disodium hydrogen phosphate-sodium dihydrogen phosphate buffer solution or potassium dihydrogen phosphate-sodium hydroxide buffer solution.

5. The multi-component synergistic high-performance natural rubber sheet according to claim 1, characterized in that: The stirring rate in step (3) is 100-180 r / min.

6. The multi-component synergistic high-performance natural rubber sheet according to claim 1, characterized in that: The vulcanizing agent is vulcanizing agent S-80; The coupling agent is silane coupling agent Si-69; The accelerator is composed of accelerator TBBS and accelerator DPG in a mass ratio of 1:2; The antioxidant is composed of antioxidant RD and antioxidant 4020 in a mass ratio of 1:1.

5.

7. The multi-component synergistic high-performance natural rubber sheet according to claim 1, characterized in that: The auxiliary agent is composed of emulsified cycloalkane oil and emulsified aromatic oil in a mass ratio of 4:

1.

8. A method for preparing a multi-component synergistic high-performance natural rubber sheet as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Add carbon black and nano-silica to deionized water, continue to add silane coupling agent, high-speed shear dispersion to form a uniform slurry, continue to add modified chopped aramid fiber, stir and disperse at low speed to obtain a filler slurry; S2. The natural rubber latex and additives are mixed evenly, filler slurry, zinc oxide and stearic acid are added, stirred evenly, accelerators and antioxidants are added successively, and stirring is continued to obtain a mixed latex; S3. Add calcium chloride solution as a coagulant to the mixed latex, stir until the colloid flocculates, filter, wash, and dry to obtain a rubber masterbatch; S4. The rubber masterbatch was added to an internal mixer, mixed at room temperature for 5-10 min, a vulcanizing agent was added, and mixing was continued for 5-10 min to obtain a uniformly mixed rubber, and the rubber was calendered or extruded to form a rubber sheet blank; S5. The rubber sheet blank is fed into a vulcanizing press for vulcanization and molding to obtain a multi-component synergistic high-performance natural rubber sheet.

9. The method for preparing the multi-component synergistic high-performance natural rubber sheet according to claim 8, characterized in that: In step S1, the rotation speed of high-speed shear dispersion is 8000-10000 r / min, and the shear dispersion time is 30-40 min; the rotation speed of low-speed stirring is 150-200 r / min, and the stirring time is 10-20 min; The concentration of the calcium chloride solution in step S3 is 5wt%; In step S5, the vulcanization temperature is 120-160° C. and the pressure is 15 MPa.