Tread rubber and method for producing the same, agricultural tire

Abstract

The application provides a tread rubber and a preparation method thereof and an agricultural tire. In the preparation method, the raw materials include a first rubber, a second rubber, a first filler, a second filler, a vulcanization aid, a silane coupling agent, a protective wax, a tear-resistant resin, a first vulcanizing agent and a first vulcanization accelerator; the vulcanization aid is obtained by pre-reaction of an antioxidant and a vulcanization system medicine; the preparation method comprises the following steps: S1, mixing the vulcanization aid with the first filler, the second filler, the first rubber, the silane coupling agent and a first solvent, performing wet mixing, separating the solvent and obtaining a master batch; S2, performing internal mixing on the master batch, performing first dry mixing on the obtained rubber material, the second rubber, the protective wax and the tear-resistant resin to obtain a first-stage master batch; and S3, performing second dry mixing on the first-stage master batch, the first vulcanizing agent and the first vulcanization accelerator, and performing vulcanization treatment on the second dry mixing product to obtain a vulcanized rubber. The tread rubber has improved wear resistance, flex resistance and other properties.

Description

Technical Field

[0001] This invention relates to the field of tread rubber technology, and more specifically, to a tread rubber and its preparation method, and to agricultural tires. Background Technology

[0002] Although agricultural tires travel at slow speeds, they are used on harsh surfaces such as field roads or crop stubble fields, making them prone to cuts and punctures. Agricultural machinery often operates intermittently and has long periods of downtime, thus requiring high levels of resistance to punctures, cuts, compression heat generation, dynamic fatigue, and heat aging. Working in paddy fields or driving on muddy roads after rain makes them extremely slippery and prone to excessive wear. Furthermore, agricultural vehicles are often used for short-distance transport, necessitating that agricultural tires also possess a certain level of wear resistance.

[0003] Traditional tire rubber compounding processes are energy-intensive, time-consuming, and generate significant dust pollution, resulting in poor filler dispersion. Increasing filler content is a common method to improve the abrasion resistance of rubber compounds. However, increasing filler content inevitably increases energy consumption during the mixing process, generates substantial heat, and subjects rubber molecules to intense shear at high temperatures, making them prone to plasticization and affecting the tensile and tear properties of the compound. To ensure the puncture resistance and abrasion resistance of agricultural tires, the filler content in agricultural tire tread compounds is generally high. High-filler compounds typically have increased hysteresis loss factors and heat generation, as well as decreased filler dispersion and flexural resistance. To avoid the deterioration of filler dispersion due to increased filler content, the filler particle size is usually increased, such as with semi-reinforcing 2-series or 3-series carbon black. The flexural resistance, puncture resistance, abrasion resistance, and heat generation of rubber compounds are mutually restrictive, and conventional technical solutions cannot simultaneously satisfy all these properties.

[0004] In recent decades, wet mixing (liquid-phase mixing) technology has developed rapidly. It can reduce the number of mixing stages, lower energy consumption, avoid dust pollution, and solve the problem of poor dispersion of high specific surface area fillers in conventional mixing. However, most wet mixing technologies use latex and filler slurries, followed by chemical coagulation to produce masterbatch. CN106750389 A discloses a wet method for preparing silica / solution-polymerized styrene-butadiene rubber masterbatch. First, silica is uniformly dispersed in an organic solvent, then a silane coupling agent is added to modify the silica. This is then mixed with the solution-polymerized styrene-butadiene rubber solution. The organic solvent is removed by co-evaporation of water vapor and solvent to obtain the silica / solution-polymerized styrene-butadiene rubber masterbatch. However, the dehydration time is relatively long, and it is only applicable to silica and solution-polymerized styrene-butadiene rubber systems. The paper "Application of Liquid-Phase Mixed NR / Carbon Black Composite Material in Tread Rubber" (Tire Industry, 2005, 25(2):4) discloses the application of carbon black composite material (CEC). The carbon black composite material is produced by Cabot Corporation of the United States using a liquid-phase continuous process to manufacture natural rubber carbon black masterbatch using natural rubber latex and carbon black slurry. This method of preparing rubber filler masterbatch by liquid-phase continuous mixing simplifies the rubber mixing process, mixing time, and reduces energy consumption and labor. However, the types and contents of rubber and fillers used in the preparation of masterbatch are limited, and additives such as masterbatch chemicals still need to be added during the tread rubber mixing process.

[0005] On the other hand, zinc oxide from tire debris entering the water cycle has been proven to cause environmental water pollution. European Commission Directive 2400 / 73 / EC and California's SB1260 bill proposed in 2016 both recommend restricting the use of zinc or zinc oxide in tires. Companies in the rubber and tire industry are facing pressure to transition to green practices and strive to reduce the environmental impact of their production processes. Summary of the Invention

[0006] The main objective of this invention is to provide a tread rubber and its preparation method, as well as an agricultural tire, to solve the problems of existing rubber compounds having difficulty in simultaneously possessing good flexural resistance, abrasion resistance, and heat generation properties, which are insufficient to meet the requirements of agricultural tires, and the presence of zinc pollution.

[0007] To achieve the above objectives, according to one aspect of the present invention, a method for preparing tread rubber is provided, wherein the raw materials for the tread rubber include a first rubber, a second rubber, a first filler, a second filler, a vulcanizing aid, a silane coupling agent, a protective wax, an anti-tear resin, a first vulcanizing agent, and a first vulcanization accelerator; the vulcanizing aid is obtained by pre-reaction of an antioxidant and a vulcanization system reagent; the preparation method includes: step S1, mixing the vulcanizing aid with the first filler, the second filler, the first rubber, the silane coupling agent, and a first solvent, performing wet mixing, and separating the solvent to obtain a masterbatch; step S2, internally mixing the masterbatch, and performing a first dry mixing with the obtained rubber compound and the second rubber, the protective wax, and the anti-tear resin to obtain a first-stage masterbatch; step S3, performing a second dry mixing with the first vulcanizing agent and the first vulcanization accelerator, and performing vulcanization treatment on the second dry mixing product to obtain a vulcanized rubber.

[0008] Furthermore, the pre-reaction temperature is 100-190°C, preferably 110-170°C; the pre-reaction time is 1 min-120 min, preferably 5 min-50 min;

[0009] The vulcanization system chemicals include any one or more of the second vulcanizing agent and the second vulcanization accelerator;

[0010] Preferably, the pre-reaction is carried out in a second organic solvent;

[0011] Preferably, the pre-reaction is carried out in the presence of a catalyst, including stearic acid;

[0012] Preferably, 1-10 parts by weight of stearic acid, 0.5-15 parts by weight of antioxidant, and 0.5-12 parts by weight of vulcanization system chemicals are added to the pre-reaction process;

[0013] Preferably, the pre-reaction is carried out in a second organic solvent, and the catalyst further includes 1 to 10 parts by weight of zinc oxide. After the pre-reaction is completed, the zinc oxide is removed by filtration.

[0014] Furthermore, the first filler and the second filler are each independently any one or more of reinforcing agents or fillers;

[0015] Preferably, the first filler is precipitated silica and the second filler is carbon black;

[0016] Preferably, the mass ratio of the first packing to the second packing is 1:1 to 1:100.

[0017] Furthermore, the first rubber and the second rubber are each independently selected from any one or more of natural rubber and synthetic rubber;

[0018] The synthetic rubber is selected from one or more of the following: polybutadiene rubber, polyisoprene rubber, polystyrene-butadiene rubber, ethylene propylene rubber, butyl rubber, nitrile rubber, chloroprene rubber, silicone rubber, fluororubber, polyurethane rubber, chlorosulfonated polyethylene rubber, and acrylate rubber.

[0019] Preferably, the mass ratio of the first rubber to the second rubber is 95:5 to 50:50.

[0020] Furthermore, the first rubber is synthetic rubber, the second rubber is natural rubber, the first filler is silica, and the second filler is carbon black;

[0021] Preferably, the synthetic rubber comprises 30-80 parts by weight, the natural rubber comprises 20-70 parts by weight, the silica comprises 5-50 parts by weight, and the carbon black comprises 20-80 parts by weight.

[0022] Furthermore, the raw materials for the tread rubber include 30-80 parts by weight of first rubber, 20-70 parts by weight of second rubber, 5-40 parts by weight of first filler, 30-60 parts by weight of second filler, 5-15 parts by weight of vulcanizing agent, 0.1-10 parts by weight of silane coupling agent, 0.5-5 parts by weight of protective wax, 0.1-15 parts by weight of tear-resistant resin, 0.5-5 parts by weight of first vulcanizing agent and 0.5-5 parts by weight of first vulcanizing accelerator.

[0023] Furthermore, the first solvent is selected from any one or more of aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, chlorinated hydrocarbon solvents, ketone solvents, ether solvents, and ester solvents;

[0024] Wet mixing methods include at least one of the following: latex / filler co-precipitation method, powder rubber preparation method, latex / filler continuous liquid phase mixing method, and rubber solution / filler continuous liquid phase mixing method;

[0025] Solvent separation methods include any one or more of the following: atmospheric pressure evaporation, low-pressure vacuum drying, heating, spray drying, expansion drying, and flash evaporation.

[0026] Furthermore, the Mooney viscosity ML(1+4)@125℃ of the first stage of masterbatch rubber needs to be below 70.

[0027] According to another aspect of this application, a tread rubber is provided, which is prepared by any of the above-described preparation methods.

[0028] According to another aspect of this application, an agricultural tire is provided, which contains the tread rubber described above.

[0029] By applying the technical solution of this invention, the above-mentioned method for preparing tread rubber, through wet mixing of the first rubber and filler, and dry mixing of the second rubber and a first stage of wet masterbatch, not only reduces the amount of solvent used, lowers energy consumption, and simplifies solvent removal, but also improves the wear resistance, flexural resistance, and heat generation properties of the tread rubber by combining wet and dry mixing. Furthermore, the tread rubber preparation method of this application also incorporates a vulcanization aid generated by the reaction of an antioxidant and a vulcanization system chemical. This vulcanization aid contains an active intermediate that promotes vulcanization and can replace zinc oxide. In other words, the tread rubber prepared by the method of this application does not contain zinc, achieving zinc-free emissions and being environmentally friendly. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0031] As disclosed in the background section of this application, the prior art has the problem that rubber compounds are difficult to combine good flexural resistance, abrasion resistance and heat generation properties, which makes it difficult to meet the needs of agricultural tires, and there is also the problem of zinc pollution. In order to solve this problem, this application provides a tread rubber and its preparation method, as well as an agricultural tire.

[0032] According to a typical embodiment of this application, this application provides a method for preparing tire tread rubber, wherein the raw materials for the tire tread rubber include a first rubber, a second rubber, a first filler, a second filler, a vulcanizing agent, a silane coupling agent, a protective wax, an anti-tear resin, a first vulcanizing agent, and a first vulcanization accelerator; the vulcanizing agent is obtained by pre-reaction of stearic acid and a vulcanization system reagent; the preparation method includes: step S1, mixing the vulcanizing agent with the first filler, the second filler, the first rubber, the silane coupling agent, and the first solvent, performing wet mixing, and separating the solvent to obtain a masterbatch; step S2, internally mixing the masterbatch, and performing a first dry mixing with the obtained rubber compound, the second rubber, the protective wax, and the anti-tear resin to obtain a first-stage masterbatch; step S3, performing a second dry mixing with the first vulcanizing agent and the first vulcanization accelerator, and performing vulcanization treatment on the second dry mixing product to obtain a vulcanized rubber.

[0033] The aforementioned method for preparing tread rubber involves wet mixing of the first rubber and filler, followed by dry mixing of the second rubber and a first-stage wet masterbatch. This not only reduces solvent usage, lowers energy consumption, and simplifies solvent removal, but also improves the tread rubber's wear resistance, flexural strength, and heat generation properties through the combination of wet and dry mixing. Furthermore, the tread rubber preparation method of this application incorporates a vulcanization aid generated from the reaction of an antioxidant and a vulcanization system chemical. This vulcanization aid contains an active intermediate that promotes vulcanization and can replace zinc oxide. In other words, the tread rubber prepared by this method does not contain zinc, achieving zinc-free emissions and being environmentally friendly.

[0034] In some embodiments of this application, to further promote the pre-reaction, the pre-reaction is carried out in the presence of a catalyst, including stearic acid. Taking a phenylenediamine antioxidant and a 2-thiobenzothiazole sulfurization system as an example, the reaction occurring in the pre-reaction is shown in the following reaction equation, and the product has the effect of promoting the sulfurization reaction.

[0035]

[0036] In some embodiments of this application, the pre-reaction temperature is 100-190°C, and the pre-reaction time is 1 min-120 min. For example, the pre-reaction temperature can be 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, or 185°C, etc. Preferably, the pre-reaction temperature is 110-170°C, which generates more active intermediates, resulting in tread rubber with better performance. For example, the pre-reaction time can be 3 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, etc. Preferably, the pre-reaction time is 5 min-50 min.

[0037] In some preferred embodiments of this application, the above-mentioned vulcanization system includes any one or more of a second vulcanizing agent and a second accelerator. The second vulcanizing agent and the second vulcanization accelerator can be selected from existing technologies. For example, the vulcanizing agent can be sulfur, and the vulcanization accelerator includes, but is not limited to, any one or more of sulfonamide vulcanization accelerators, sulfenamide vulcanization accelerators, and thiazole vulcanization accelerators. Specifically, the vulcanization accelerator is selected from any one or more of CZ, DZ, DM, M, and NS.

[0038] In some preferred embodiments of this application, the above-mentioned vulcanization system contains a second vulcanization accelerator, which is more likely to react with antioxidants to generate active intermediates that can promote vulcanization, thereby further improving the overall performance of the tread rubber.

[0039] In some embodiments of this application, the antioxidant is a p-phenylenediamine antioxidant, such as any one or more of 4020, 4010NA, and 7PPD. In some preferred embodiments of this application, the antioxidant is a compound having the structure of Formula I. Antioxidants having this structure can not only form highly active intermediates with the sulfurized chemical system, but also have low toxicity and minimal environmental impact.

[0040] Formula I

[0041] In formula I, R 1 Selected from C1-C 18 chain hydrocarbon group, C3-C 18 alicyclic hydrocarbon group or C6-C 18 aromatic group, R 2 R 3 R 4 R 5 Selected from C1-C 18 The chain hydrocarbon group, R 2 With R 3 Or R 4 With R 5 They can also form adipose rings individually or simultaneously, R 6 Selected from H, C1-C 18 chain hydrocarbon group, C3-C 18 alicyclic hydrocarbon group or C6-C 18 The aromatic group; x=0 or 1, y=0 or 1, z=0 or 1, w=0 or 1, and at least one of x and w is 1, and at least one of y and z is 1.

[0042] In some embodiments of this application, the pre-reaction is carried out in a second organic solvent. Preferably, the second solvent is any one or more of butanol, octanol, N-methylpyrrolidone, octane, nonane, decane, toluene, and xylene. These solvents not only have good solubility for stearic acid, antioxidants, and vulcanizing agents, but also facilitate the pre-reaction and improve reaction efficiency. The second solvent can be separated and removed after the pre-reaction is complete, or the vulcanizing agent solution obtained after the pre-reaction can be directly used in step S1 and removed together with the first solvent during the solvent separation stage. The amount of the second solvent is not particularly required; it only needs to be sufficient to dissolve the antioxidant, vulcanizing agents, and stearic acid.

[0043] In some typical embodiments of this application, 1-10 parts by weight of stearic acid, 0.5-15 parts by weight of antioxidant, and 0.5-12 parts by weight of vulcanization system chemicals are added to the pre-reaction process. The resulting vulcanization aid has a good vulcanization promoting effect and further improves the performance of the tread rubber.

[0044] In some embodiments of this application, the above-mentioned pre-reaction is carried out in a second organic solvent. The catalyst also includes 1 to 10 parts by weight of zinc oxide. After the pre-reaction is completed, the zinc oxide is filtered out. Adding zinc oxide can also promote the formation of active intermediates. Since zinc oxide is insoluble in organic solvents, it can be separated by filtration after the pre-reaction. The prepared vulcanizing agent also does not contain zinc oxide, and zinc-free tread rubber can also be achieved.

[0045] The first and second fillers described above can be the same or different, and the specific types can be selected from existing technologies. For example, the first and second fillers can each be independently any one or more of reinforcing agents or fillers. In some preferred embodiments, the first and / or second fillers include carbon black.

[0046] In some preferred embodiments of this application, to further improve the flexural and abrasion resistance of the rubber, making it more suitable for the preparation of agricultural tires, the first filler is precipitated silica and the second filler is carbon black. Preferably, the mass ratio of the first filler to the second filler is 1:1 to 1:100, specifically 5:75, 10:70, 15:65, 20:60, 25:55, 30:50, 40:60, 30:70, 20:80, 10:90, or 5:95, or other ratios within the above range. Preferably, the mass ratio of the first filler to the second filler is 1:1 to 1:6.

[0047] In some preferred embodiments of this application, the specific surface area of ​​the silica is 10~500m². 2 / g, more preferably 10~300m 2 / g, more preferably 100~300m 2 / g; preferably, the oil absorption value of silica is 20~350mL / 100g, more preferably 25~300mL / 100g, and even more preferably 30~290mL / 100g.

[0048] In some embodiments of this application, the specific surface area of ​​the carbon black is 10~500m². 2 / g, preferably 10~300m 2 / g, further preferably 100~300m 2 / g.

[0049] The first rubber mentioned above can be the same or different, and the specific type can be selected from the existing technology. For example, the first rubber and the second rubber can be independently selected from any one or more of natural rubber and synthetic rubber. Preferably, the synthetic rubber is selected from one or more of polybutadiene rubber, polyisoprene rubber, polystyrene-butadiene rubber, ethylene propylene rubber, butyl rubber, nitrile rubber, chloroprene rubber, silicone rubber, fluororubber, polyurethane rubber, chlorosulfonated polyethylene rubber, and acrylate rubber.

[0050] Preferably, the mass ratio of the first rubber to the second rubber is 95:5 to 50:50, which better balances energy consumption and rubber performance. Specifically, the mass ratio of the first rubber to the second rubber can be 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:45, 60:40, 55:45, 50:50, or other values ​​within the above range. Preferably, the mass ratio of the first rubber to the second rubber is 70:30 to 50:50.

[0051] In some preferred embodiments of this application, the first rubber is a synthetic rubber, the second rubber is a natural rubber, the first filler is silica, and the second filler is carbon black. That is, the synthetic rubber is wet-mixed with silica, carbon black, silane coupling agent, vulcanizing agent, etc., and the natural rubber is dry-mixed. This not only makes the above components more uniformly mixed, but also allows the above components to play a better role.

[0052] In some preferred embodiments of this application, the raw materials of the tread rubber contain 30-80 parts by weight of natural rubber, 20-70 parts by weight of silica, 5-50 parts by weight of fumed silica, and 20-80 parts by weight of carbon black, which can better exert their synergistic effect and further improve the flexural resistance and heat generation properties of the prepared rubber.

[0053] In some typical embodiments of this application, in order to better leverage the synergistic effect of the components in the raw materials, the raw materials for the tread rubber include 30-80 parts by weight of a first rubber, 20-70 parts by weight of a second rubber, 5-40 parts by weight of a first filler, 30-60 parts by weight of a second filler, 5-15 parts by weight of a vulcanizing agent, 0.1-10 parts by weight of a silane coupling agent, 0.5-5 parts by weight of a protective wax, 0.1-15 parts by weight of a tear-resistant resin, 0.5-5 parts by weight of a first vulcanizing agent, and 0.5-5 parts by weight of a first vulcanizing accelerator, wherein the vulcanizing agent does not include solvents in its weight parts.

[0054] In the above-mentioned method for preparing tread rubber, step S1 involves wet mixing of some raw materials to ensure that the first filler, the second filler, the first rubber, the vulcanizing agent, and the silane coupling agent are mixed relatively evenly and thoroughly. By combining this with subsequent dry mixing, the rubber and filler are evenly dispersed, and the rubber is fully cross-linked.

[0055] In some embodiments of this application, the first solvent is selected from any one or more of aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, chlorinated hydrocarbon solvents, ketone solvents, ether solvents, and ester solvents; specifically, aliphatic hydrocarbon solvents include, but are not limited to, various solvent gasolines, cycloalkanes and substituted cycloalkanes, n-alkanes, etc.; aromatic hydrocarbon solvents include, but are not limited to, benzene, toluene, xylene, and styrene, etc.; chlorinated hydrocarbon solvents include, but are not limited to, dichloromethane, trichloromethane, carbon tetrachloride, dichloroethane, chlorobenzene, tetrachloroethylene, chlorotoluene, etc.

[0056] The specific methods for wet mixing described above can be selected from existing technologies. In some embodiments of this application, the wet mixing methods include, but are not limited to, at least one of the following: latex / filler co-precipitation method, powdered rubber preparation method, continuous liquid-phase mixing method for latex / filler, and continuous liquid-phase mixing method for rubber solution / filler. The preferred wet mixing method is the continuous liquid-phase mixing method for rubber solution / filler, which is more conducive to improving the performance of the rubber compound and is easier to implement.

[0057] After wet mixing, solvent separation is performed to obtain wet dry rubber, i.e., masterbatch. The solvent separation method can also be selected from existing technologies, such as any one or more of atmospheric pressure evaporation, low-pressure vacuum drying, heating, spray drying, expansion drying, and flash evaporation.

[0058] In some embodiments of this application, solvent separation is performed by evaporation, using an oven or drying plate. In some embodiments of this application, solvent separation is performed by spray drying, using centrifugal atomization, pressure atomization, or two-fluid atomization. In some embodiments of this application, solvent separation is performed by expansion drying, wherein the expansion drying method involves heating followed by a sudden release of pressure. In some embodiments of this application, solvent separation is performed by flash evaporation, which can be at least one of atmospheric pressure flash evaporation or reduced pressure flash evaporation, with 1 to 3 flash stages. In some embodiments of this application, solvent separation is performed by low-pressure vacuum drying, specifically by evaporating the solvent or filtering it under vacuum to a pressure below one atmosphere, with the pressure ranging from -0.1 MPa to 0, preferably from -0.09 MPa to 0, and more preferably from -0.08 MPa to 0. In some embodiments of this application, the above-mentioned expansion drying is to flash vaporize the solvent using a screw expansion dryer. Preferably, the screw expansion dryer pushes along the shaft at 0-20 MPa, more preferably 1-10 MPa, with decreasing screw pitch, generating heat through friction, causing a sudden drop in outlet pressure, relaxing the expansion of the rubber strip, and flash vaporizing the solvent inside the rubber strip.

[0059] In some embodiments of this application, when the solid content in the rubber compound after solvent separation is less than 98 wt%, the rubber compound is dried to remove residual solvent from the solvent separation process. Specifically, the drying process can be heat drying and / or mechanical drying. As an example, mechanical drying is performed using an open mill, kneader, internal mixer, or screw extruder, and the operating temperature of the mechanical drying is 20℃-250℃.

[0060] The above-mentioned drying process can be performed by first heating and then mechanical drying, or by first mechanical drying and then heating. When mechanical drying is selected, heating can be performed simultaneously at a temperature of 10°C to 250°C; when heating is selected, heating can be carried out in a gaseous medium, which includes at least one of air, nitrogen, water vapor, and CO2.

[0061] During the solvent separation or drying process described above, the solvent can be recovered and recycled. The recovery method can be selected from existing technologies, such as recovery via condensers and distillation towers. The solvent recovery method can use any method known in the art, such as recovering the vaporized solvent through surface condensation or direct contact condensation. When using direct contact condensation, water can be used as the coolant.

[0062] Steps S2 and S3 above involve dry mixing, and the process for dry mixing can be referenced from existing technologies. The first dry mixing includes primary mixing, secondary mixing, and possible remixing, i.e., dry mixing before final mixing; the second dry mixing represents final mixing and is distinct from the first dry mixing. For example, the apparatus used for dry mixing includes at least one of a two-roll mill, internal mixer, kneading mill, continuous mixer, or screw mill, and this application is not limited to this.

[0063] In order to further improve the performance of the final prepared rubber compound, in some preferred embodiments of this application, the temperature of the first dry mixing process is 130~170℃ and the time is 2~8min, and the temperature of the second dry mixing process is 90~110℃ and the time is 2~5min.

[0064] In some typical embodiments of this application, in order to better control the performance of the product rubber, the Mooney viscosity ML(1+4)@125℃ of the above-mentioned masterbatch needs to be lower than 70; if the above condition is not met, the rubber compound that has been dry-mixed in the first process will be re-mixed, and the re-mixing process is the same as the initial mixing process.

[0065] In some preferred embodiments of this application, the vulcanization temperature is 130~160℃ and the vulcanization time is 0.5~3 hours, resulting in a better vulcanization effect.

[0066] According to another typical embodiment of this application, a tread rubber is provided, which is prepared by any of the above-described preparation methods.

[0067] The tread rubber of this application, prepared using the aforementioned method, exhibits superior flexural and heat-generating properties, and is relatively inexpensive, making it particularly suitable for agricultural tires. Furthermore, the tread rubber of this application does not contain zinc, achieving zinc-free emissions and thus being environmentally friendly.

[0068] According to another typical embodiment of this application, an agricultural tire is provided, which contains the aforementioned tread rubber. This agricultural tire not only has good flexural resistance and heat generation properties, but is also environmentally friendly and has broad market application prospects.

[0069] The beneficial effects that this application can achieve will be further illustrated below with reference to embodiments and comparative examples.

[0070] The specific sources of the materials used in the embodiments and comparative examples of this application are as follows:

[0071] Styrene-butadiene rubber, ESBR1502, TSRC Corporation;

[0072] Natural rubber (NR), STR20#, standard rubber;

[0073] Carbon black: N134, Shanghai Cabot Co., Ltd.; specific surface area 143 m² 2 / g, oil absorption value 127mL / 100g;

[0074] Silica: 165MP, manufactured by Quecheng Silicon Chemical Co., Ltd.; specific surface area 179m² 2 / g, oil absorption value 245mL / 100g;

[0075] Si69, a silane coupling agent, is produced by Nanjing Shuguang Silane Chemical Co., Ltd.

[0076] Stearic acid, a product of Tyco Brown Chemical (Zhangjiagang) Co., Ltd.

[0077] Protective wax, a product of Qingdao Jinxian Chemical Co., Ltd.

[0078] Antioxidant RD, a product of Nanjing Chemical Industry Co., Ltd., China Petrochemical Corporation;

[0079] Antioxidant 4020, a product of Jiangsu Shengao Chemical Technology Co., Ltd.

[0080] Anti-aging agents ,self made;

[0081] Tear-resistant resin, Jiangsu Qixiang High-Tech Materials Co., Ltd.;

[0082] CZ, a vulcanization accelerator, is a product of Shandong Shangshun Chemical Co., Ltd.

[0083] DPG, a vulcanization accelerator, is a product of Shandong Shangshun Chemical Co., Ltd.

[0084] Sulfur, a product of Liaoning Chaoyang Tianming Industry and Trade Co., Ltd.

[0085] Comparative Example 1

[0086] In a mixer, 40 parts (by weight, the same below) of 165MP silica, 20 parts of N134 carbon black and 4 parts of Si69 are added to 70 parts of ESBR1502 and 30 parts of natural rubber. After mixing for 1 minute, 3.5 parts of zinc oxide, 2 parts of stearic acid, 1.5 parts of antioxidant 4020, 1.5 parts of antioxidant RD, 1 part of protective wax and 2 parts of tear-resistant resin are added. After mixing for 3 minutes, the mixture is discharged at 150°C. After standing for 8 hours, 1.8 parts of vulcanization accelerator CZ, 1.3 parts of vulcanization accelerator DPG and 1.3 parts of sulfur are added to the mixer. After mixing for 2 minutes, the mixture is discharged at 100°C. After standing for 8 hours, the mixture is vulcanized at 150°C for 40 minutes using a flat vulcanizing machine to obtain dry vulcanized rubber a.

[0087] Comparative Example 2

[0088] 40 parts of 165MP silica, 20 parts of N134 carbon black and 4 parts of Si69 were added to a hexane solution of 70 parts of ESBR1502 and 30 parts of natural rubber. After mixing, the mixture was continuously injected into a coagulant for coagulation. Then, the solvent was flash vaporized and desolvated by a screw expander and dried to obtain masterbatch A. After adding masterbatch A to a mixer and mixing for 1 minute, add 3.5 parts zinc oxide, 2 parts stearic acid, 1.5 parts antioxidant 4020, 1.5 parts antioxidant RD, 1 part protective wax, and 2 parts tear-resistant resin. Mix for 3 minutes and discharge the mixture at 150°C. After standing for 8 hours, add the mixture back to the mixer and mix evenly. Then add 1.8 parts vulcanization accelerator CZ, 1.3 parts vulcanization accelerator DPG, and 1.3 parts sulfur. Mix for 2 minutes and discharge the mixture at 100°C. After mixing, roll the mixture onto a sheet. After standing for 8 hours, vulcanize the mixture at 150°C for 40 minutes using a flat vulcanizing machine to obtain continuous vulcanized rubber aa.

[0089] Example 1

[0090] 1) Preparation of vulcanizing aid: 2 phr stearic acid, 3 phr environmentally friendly antioxidant 1.8 phr of vulcanization accelerator CZ was mixed in octanol and pre-reacted at 160 °C for 25 min to obtain a zinc-free vulcanization aid.

[0091] 2) The above-mentioned zinc-free vulcanizing aid, 20 parts of carbon black, 40 parts of 165MP silica, and 4 parts of Si69 were added to a hexane solution of 70 parts of ESBR1502 (the mass concentration of the rubber was 25%). After mixing, the solution was continuously injected into the reactor to evaporate and separate the solvent, and then heated and dried to obtain masterbatch A.

[0092] 3) Add masterbatch A to the internal mixer and mix for 1 minute. Then add 30 parts of natural rubber, 1 part of protective wax, and 2 parts of tear-resistant resin. Mix for 3 minutes and discharge the rubber at 150°C to obtain a first-stage compound. The Mooney viscosity ML(1+4)@125°C of this compound is less than 70.

[0093] 4) After the above-mentioned compound has been left to stand for 8 hours, add 1.3 parts of sulfur and 1.3 phr of DPG vulcanization accelerator to the internal mixer, mix for 2 minutes and discharge the rubber at 100°C. After standing for 8 hours, vulcanize at 150°C for 40 minutes using a flat vulcanizing machine to obtain continuous vulcanized rubber A.

[0094] Example 2

[0095] The difference from Example 1 is that the antioxidant was replaced with 1.5 parts antioxidant 4020 and 1.5 parts antioxidant RD in the preparation of the vulcanizing agent.

[0096] Example 3

[0097] The difference from Example 1 is that the amount of silica added is 10 parts, Si69 is 1 part, and carbon black is 60 parts.

[0098] Example 4

[0099] The difference from Example 1 is that in step 2), 50 parts of hexane solution of ESBR1502 are added; and in step 3), 20 parts of ESBR1502 and 30 parts of natural rubber are added.

[0100] The vulcanizates prepared in the above examples and comparative examples were tested according to the following methods, and the test results are listed in Table 1.

[0101] The filler dispersion grade was determined according to GB / T 6030-2006 Rapid Comparative Method for Evaluation of Carbon Black and Carbon Black / Silica Dispersion in Rubber;

[0102] The hardness of the rubber compound was determined according to GB / T 531.1-2008 Test method for indentation hardness of vulcanized rubber or thermoplastic rubber - Part 1: Shore hardness tester method (Shore hardness)

[0103] The physical properties (tensile strength and elongation at break) of the rubber compound were determined in accordance with GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0104] The vulcanization characteristics of rubber compounds were determined according to GB / T 16584-1996 "Determination of vulcanization characteristics using a rotorless vulcanizing apparatus for rubber".

[0105] The elastic modulus of the rubber compound at 60°C was determined according to GB / T 9870.1-2006 Determination of dynamic properties of vulcanized rubber or thermoplastic rubber - Part 1: General rules, and the tanδmax of the rubber compound was determined using a rotational rheometer.

[0106] Table 1

[0107]

[0108] A comparison of the physical and dynamic properties of tread compounds obtained using continuous and dry preparation processes in the examples and comparative examples shows that, under similar formulations, the continuous preparation process improves the dispersion of fillers in the rubber, resulting in excellent tensile properties of the vulcanizate, reduced heat generation during compression, and significantly improved DIN abrasion. Furthermore, this application achieves properties similar to those of compounds containing zinc oxide by adding a vulcanizing agent that does not contain zinc.

[0109] In addition, extraction experiments were conducted on tire wear debris from Examples 1 and 2, and HRMS analysis of the extract confirmed that the self-synthesized environmentally friendly antioxidant does not produce highly toxic quinone compounds. Toxicity testing of the extract confirmed that the environmentally friendly antioxidant is less toxic to zebrafish and silver salmon than commercial antioxidants such as 4020 (6PPD), and is environmentally friendly.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing a tread rubber, characterized by, The raw material of the tread rubber comprises a first rubber, a second rubber, a first filler, a second filler, a vulcanization aid, a silane coupling agent, a protective wax, a tear-resistant resin, a first vulcanizing agent and a first vulcanization accelerator; The vulcanization aid is obtained by pre-reaction of an antioxidant and a vulcanization system medicine; the pre-reaction temperature is 100-190°C, the pre-reaction time is 1 min-120 min; the pre-reaction is carried out in the presence of a catalyst, and the catalyst comprises stearic acid; the vulcanization system medicine comprises a second vulcanization accelerator selected from any one or more of CZ, DZ, DM, M and NS; the antioxidant is a p-phenylenediamine antioxidant; The preparation method comprises: Step S1, mixing the vulcanization aid with the first filler, the second filler, the first rubber, the silane coupling agent, the first solvent, wet mixing, solvent separation, and obtaining a masterbatch; Step S2, performing internal mixing on the masterbatch, and performing first dry mixing on the obtained rubber compound with the second rubber, the protective wax and the tear-resistant resin to obtain a first-stage masterbatch, Step S3, performing second dry mixing on the first-stage masterbatch with the first vulcanizing agent and the first vulcanization accelerator, and performing vulcanization treatment on the second dry mixing product to obtain a vulcanized rubber; In the pre-reaction, 1-10 parts by weight of stearic acid, 0.5-15 parts by weight of an antioxidant and 0.5-12 parts by weight of a vulcanization system medicine are added; The first filler and the second filler are each independently any one or more of a reinforcing agent or a filler; The first rubber and the second rubber are each independently any one or more of natural rubber and synthetic rubber.

2. The production method according to claim 1, characterized by, The pre-reaction temperature is 110-170°C, and the pre-reaction time is 5 min-50 min.

3. The method of claim 1, wherein, The pre-reaction is carried out in a second organic solvent.

4. The method of claim 1, wherein, The pre-reaction is carried out in a second organic solvent, and the catalyst further comprises 1-10 parts by weight of zinc oxide, which is removed by filtration after the pre-reaction is completed.

5. The preparation method according to claim 1, characterized in that, The first filler is white carbon black, and the second filler is carbon black.

6. The method of claim 1, wherein, The mass ratio of the first filler to the second filler is 1:1-1:

100.

7. The preparation method according to claim 1, characterized in that, The synthetic rubber is selected from one or more of polybutadiene rubber, polyisoprene rubber, polystyrene-butadiene rubber, ethylene-propylene rubber, butyl rubber, nitrile rubber, chlorobutyl rubber, silicone rubber, fluororubber, polyurethane rubber, chlorosulfonated polyethylene rubber and acrylate rubber.

8. The production method according to claim 7, characterized by, The mass ratio of the first rubber to the second rubber is 95:5-50:

50.

9. The preparation method according to claim 7, characterized in that, The first rubber is synthetic rubber, the second rubber is natural rubber, the first filler is white carbon black, and the second filler is carbon black.

10. The method of claim 9, wherein, The synthetic rubber is 30-80 parts by weight, the natural rubber is 20-70 parts by weight, the white carbon black is 5-50 parts by weight, and the carbon black is 20-80 parts by weight.

11. The production method according to any one of claims 1 to 10, characterized by, The raw material of the tread rubber comprises 30-80 parts by weight of a first rubber, 20-70 parts by weight of a second rubber, 5-40 parts by weight of a first filler, 30-60 parts by weight of a second filler, 5-15 parts by weight of a vulcanization aid, 0.1-10 parts by weight of a silane coupling agent, 0.5-5 parts by weight of a protective wax, 0.1-15 parts by weight of a tear-resistant resin, 0.5-5 parts by weight of a first vulcanizing agent, and 0.5-5 parts by weight of a first vulcanization accelerator.

12. The production method according to any one of claims 1 to 10, characterized by, The first solvent is selected from any one or more of aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, chlorinated hydrocarbon solvents, ketone solvents, ether solvents, and ester solvents; The wet mixing method comprises at least one of a latex / filler co-precipitation method, a powder rubber preparation method, a latex / filler continuous liquid phase mixing method, and a rubber solution / filler continuous liquid phase mixing method. The solvent separation method comprises any one or more of atmospheric evaporation, low-pressure vacuum drying, heating, spray drying, expansion drying, and flash evaporation.

13. The production method according to any one of claims 1 to 10, characterized by, The Mooney viscosity ML (1+4) @ 125℃ of the one-stage masterbatch is less than 70.

14. A tread rubber characterized by, Prepared by the preparation method of any one of claims 1-13.

15. An agricultural tire characterized in that, Containing the tread rubber of claim 14. Containing the tread rubber of claim 14.

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