Tread rubber, preparation method thereof and agricultural tire

Abstract

The invention provides tread rubber, a preparation method thereof and an agricultural tire. In the preparation method, raw materials comprise first rubber, second rubber, a first filler, a second filler, a vulcanizing aid, a silane coupling agent, protective wax, tear-resistant resin, a first vulcanizing agent and a first vulcanization accelerator; the vulcanizing aid is obtained by pre-reaction of an anti-aging agent and a vulcanizing system drug; the preparation method comprises the following steps: S1, mixing a vulcanizing aid with a first filler, a second filler, first rubber, a silane coupling agent and a first solvent, and carrying out wet mixing and solvent separation to obtain a rubber master batch; the preparation method comprises the following steps: S1, preparing master batch, S2, internally mixing the master batch, and carrying out first dry-process mixing on the obtained rubber material, second rubber, protective wax and tear-resistant resin to obtain first-stage master batch, and S3, carrying out second dry-process mixing on the first-stage master batch, a first vulcanizing agent and a first vulcanization accelerator, and carrying out vulcanization treatment on a second dry-process mixing product to obtain vulcanized rubber. And the properties of wear resistance, deflection resistance and the like of the tread rubber are improved.

Description

Technical Field

[0001] The invention relates to the technical field of tread rubber, and in particular to a tread rubber and a preparation method thereof, and an agricultural tire. Background Art

[0002] Although agricultural tires travel at a slow speed, they work on harsh roads, such as field roads or crop stubble fields, which are easily cut and punctured. Agricultural machinery often works intermittently and is parked for a long time, so they have high requirements for puncture resistance, cutting resistance, compression heat generation, good dynamic fatigue, and heat aging resistance. Paddy field operations or driving on muddy roads after rain are very easy to slip and excessively wear. In addition, agricultural vehicles are often used as short-distance transportation tools, which requires agricultural tires to have certain wear resistance.

[0003] The traditional tire rubber compound mixing process is energy-consuming, time-consuming, and has high dust pollution, and the filler dispersion is poor. Increasing the amount of filler is a common means to improve the wear resistance of the rubber. Increasing the amount of filler will inevitably increase the energy consumption during the mixing process, generate a lot of heat during mixing, and the rubber molecules are subjected to strong shear at high temperatures, which makes them easy to be plasticized, affecting the tensile and tearing properties of the rubber. In order to ensure the puncture resistance and wear resistance of agricultural tires, the number of fillers used in agricultural tire tread rubber is generally high. Highly filled rubbers usually have increased hysteresis loss factors and heat generation, and poor filler dispersion and flexural resistance. In order to avoid poor filler dispersion due to increased filler dosage, the filler particle size is usually increased, such as semi-reinforced 2-series or 3-series carbon black. The flexural resistance, puncture resistance, wear resistance and heat generation of rubber restrict each other, and conventional technical solutions are difficult to meet them all at the same time.

[0004] In recent decades, wet mixing (liquid phase mixing) technology has developed rapidly, which can reduce the number of mixing stages, reduce energy consumption, avoid dust pollution, and solve the problem that high specific surface area fillers are difficult to disperse in conventional mixing. However, most wet mixing technologies use latex and filler slurry, and then produce masterbatch by chemical coagulation. CN106750389A discloses a method for preparing white carbon black / solution polymerized styrene butadiene rubber masterbatch by wet method, firstly dispersing white carbon black in an organic solvent, adding a silane coupling agent to modify white carbon black, and then mixing it with solution polymerized styrene butadiene rubber glue liquid, and removing the organic solvent by the method of co-evaporation of water vapor and solvent to obtain white carbon black / solution polymerized styrene butadiene rubber masterbatch. However, the dehydration time is long, and it is only applied to white carbon black and solution polymerized styrene butadiene rubber system. "Application of Liquid-phase Mixed NR / Carbon Black Composites in Tread Rubber" (Tire Industry, 2005, 25(2):4) discloses the application of carbon black composites (CEC). The carbon black composites are prepared by Cabot Corporation of the United States using natural rubber latex and carbon black slurry in a liquid phase continuous process for manufacturing natural rubber carbon black masterbatch. This method of preparing rubber filler masterbatch by liquid phase continuous mixing simplifies the mixing process and mixing time, reduces energy consumption and labor, but the types and contents of rubber and fillers used in the preparation of the 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 in tire debris enters the water circulation system and has been proven to cause environmental water pollution. The European Commission Directive 2400 / 73 / EC and the SB1260 bill proposed by California in 2016 both recommend limiting the use of zinc or zinc oxide in tires. Companies in the rubber tire industry are facing pressure to transform to a green environment and are committed to reducing the impact of the production process on the environment. Summary of the invention

[0006] The main purpose of the present invention is to provide a tread rubber and a preparation method thereof, and an agricultural tire, so as to solve the problem that the rubber in the prior art is difficult to have good flexural resistance, wear resistance and heat generation and is difficult to meet the needs of agricultural tires and has zinc pollution.

[0007] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for preparing tread rubber is provided, wherein the raw materials of 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-reacting an antioxidant and a vulcanization system chemical; the preparation method comprises: step S1, mixing the vulcanizing aid 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, performing banbury mixing on the masterbatch, and performing a first dry mixing on the obtained rubber with the second rubber, the protective wax and the anti-tear resin to obtain a masterbatch; step S3, performing a second dry mixing on the masterbatch, the first vulcanizing agent and the first vulcanization accelerator, and performing a 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 under the action of a catalyst, and the catalyst includes stearic acid;

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

[0013] Preferably, the preliminary reaction is carried out in the second organic solvent, the catalyst further comprises 1 to 10 parts by weight of zinc oxide, and after the preliminary reaction is completed, the zinc oxide is filtered out.

[0014] Furthermore, the first filler and the second filler are independently any one or more of a reinforcing agent or a filler;

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

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

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

[0018] 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;

[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 white carbon black, and the second filler is carbon black;

[0021] Preferably, the synthetic rubber is 30 to 80 parts by weight, the natural rubber is 20 to 70 parts by weight, the white carbon black is 5 to 50 parts by weight, and the carbon black is 20 to 80 parts by weight.

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

[0023] Further, 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] The wet mixing method includes 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;

[0025] The method of solvent separation includes any one or more of 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 masterbatch should be lower than 70.

[0027] According to another aspect of the present application, a tread rubber is provided, and the tread rubber is prepared by any one of the above preparation methods.

[0028] According to yet another aspect of the present application, an agricultural tire is provided, the agricultural tire comprising the above-mentioned tread rubber.

[0029] By applying the technical solution of the present invention, the above-mentioned method for preparing tread rubber can reduce the amount of solvent, reduce energy consumption and the difficulty of solvent removal by wet mixing the first rubber and the filler, and dry mixing the second rubber and a section of wet masterbatch, and can also improve the wear resistance, flex resistance, heat generation and other properties of the tread rubber through the combination of wet mixing and dry mixing. In addition, the tread rubber preparation method of the present application also adds a vulcanization aid generated by the reaction of an antioxidant and a vulcanization system chemical, and the vulcanization aid contains an active intermediate that can promote vulcanization and can replace zinc oxide. In other words, the tread rubber prepared by the method of the present application does not contain zinc element, can achieve zinc-free emissions, and is more environmentally friendly. DETAILED DESCRIPTION

[0030] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0031] As disclosed in the background technology of the present application, the prior art has the problem that the rubber material is difficult to have good flexural resistance, wear resistance and heat generation properties, which makes it difficult to meet the needs of agricultural tires, and there is zinc pollution. In order to solve this problem, the present application provides a tread rubber and a preparation method thereof, and an agricultural tire.

[0032] According to a typical embodiment of the present application, the present application provides a method for preparing tread rubber, wherein the raw materials of 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-reacting stearic acid and a vulcanization system chemical; 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 the first solvent, performing wet mixing, and separating the solvent to obtain a masterbatch; step S2, mixing the masterbatch, and performing a first dry mixing with the obtained rubber material and the second rubber, the protective wax and the anti-tear resin to obtain a masterbatch; step S3, performing a second dry mixing with the first vulcanizing agent and the first vulcanization accelerator, and performing a vulcanization treatment on the second dry mixing product to obtain a vulcanized rubber.

[0033] The above-mentioned method for preparing tread rubber, by wet-mixing the first rubber and the filler, and dry-mixing the second rubber and a section of wet masterbatch, can not only reduce the amount of solvent used, reduce energy consumption and the difficulty of solvent removal, but also improve the wear resistance, flex resistance, heat generation and other properties of the tread rubber through the combination of wet mixing and dry mixing. In addition, the tread rubber preparation method of the present application also adds a vulcanization aid generated by the reaction of an antioxidant and a vulcanization system drug, and the vulcanization aid contains an active intermediate that can promote vulcanization and can replace zinc oxide. In other words, the tread rubber prepared by the method of the present application does not contain zinc element, can achieve zinc-free emissions, and is more environmentally friendly.

[0034] In some embodiments of the present application, in order to further promote the pre-reaction, the pre-reaction is carried out under the action of a catalyst, and the catalyst includes stearic acid. Taking the phenylenediamine antioxidant and 2-thiobenzothiazole vulcanization system chemicals 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 vulcanization reaction.

[0035]

[0036] In some embodiments of the present application, the temperature of the pre-reaction is 100-190°C, and the pre-reaction time is 1min-120min. For example, the temperature of the pre-reaction is 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 temperature of the pre-reaction is 110-170°C, which can generate more active intermediates, and the tread rubber prepared by the pre-reaction has better performance. For example, the pre-reaction time is 3min, 10min, 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, etc. Preferably, the pre-reaction time is 5min-50min.

[0037] In some preferred embodiments of the present application, the above-mentioned vulcanization system chemicals include any one or more of the second vulcanizing agent and the second accelerator. The above-mentioned second vulcanizing agent and the second vulcanization accelerator can be selected from the prior art. 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, sulfonamide 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 the present application, the above-mentioned vulcanization system contains a second vulcanization accelerator, which is easier to react with the antioxidant to generate an active intermediate that can promote vulcanization, thereby further improving the comprehensive performance of the tread rubber.

[0039] In some embodiments of the present application, the antioxidant is a p-phenylenediamine antioxidant; for example, any one or more of 4020, 4010NA and 7PPD. In some preferred embodiments of the present application, the antioxidant is a compound having a structure of formula I. The antioxidant having this structure can not only generate highly active active intermediates with vulcanization system drugs, but also has the characteristics of low toxicity and less impact on the environment.

[0040]

[0041] In Formula I, R 1 Selected from C1-C 18 Chain hydrocarbon groups, C3-C 18 Alicyclic hydrocarbon or C6-C 18 The aromatic hydrocarbon 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 aliphatic rings separately or simultaneously, R 6 Selected from H, C1-C 18 Chain hydrocarbon groups, C3-C 18 Alicyclic hydrocarbon or C6-C 18 x=0 or 1, y=0 or 1, z=0 or 1, w=0 or 1, and at least one of x and w has a value of 1, and at least one of y and z has a value of 1.

[0042] In some embodiments of the present application, the above-mentioned pre-reaction is carried out in a second organic solvent; preferably, the above-mentioned 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 vulcanization system drugs, but also are conducive to the pre-reaction and improve the reaction efficiency. The second solvent can be separated and removed after the pre-reaction is completed, or the vulcanization accelerator solution obtained after the pre-reaction can be directly used in step S1 and removed together with the above-mentioned first solvent in the solvent separation stage. There is no special requirement for the amount of the above-mentioned second solvent, as long as it can dissolve the antioxidant, the vulcanization system drugs and stearic acid.

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

[0044] In some embodiments of the present application, the above-mentioned pre-reaction is carried out in a second organic solvent, and 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, after the pre-reaction, the zinc oxide can be separated by filtration. The prepared vulcanization aid also does not contain zinc oxide, and the zinc-free tread rubber can also be achieved.

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

[0046] In some preferred embodiments of the present application, in order to further improve the flexural and abrasion resistance of the rubber and make it more suitable for the preparation of agricultural tires, the first filler is white carbon black 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, etc., 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 the present application, the specific surface area of ​​white carbon black is 10 to 500 m 2 / g, more preferably 10 to 300 m 2 / g, more preferably 100 to 300 m 2 / g; preferably, the oil absorption value of white carbon black is 20 to 350 mL / 100 g, more preferably 25 to 300 mL / 100 g, and further preferably 30 to 290 mL / 100 g.

[0048] In some embodiments of the present application, the specific surface area of ​​carbon black is 10 to 500 m 2 / g, preferably 10 to 300 m 2 / g, more preferably 100 to 300 m 2 / g.

[0049] The first rubbers may be the same or different, and the specific types may be selected in the prior art. For example, the first rubber and the second rubber are 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 can better balance 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, etc., 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 the present application, 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. That is, the synthetic rubber and white carbon black, carbon black, silane coupling agent, vulcanization aid, etc. are wet-mixed, and the natural rubber, etc. are dry-mixed. This not only makes the above components mixed more evenly, but also enables the above components to better play their roles.

[0052] In some preferred embodiments of the present application, among the raw materials of the above-mentioned tread rubber, 30 to 80 parts by weight, the natural rubber is 20 to 70 parts by weight, the white carbon black is 5 to 50 parts by weight, and the carbon black is 20 to 80 parts by weight, which can better exert their synergistic effect and further improve the flexural resistance and heat generation performance of the prepared rubber.

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

[0054] In the above-mentioned method for preparing tread rubber, step S1 wet-mixes part of the raw materials so that the first filler, the second filler and the first rubber, the vulcanizing agent and the silane coupling agent are mixed more evenly and fully, and combined with subsequent dry mixing, the rubber and the filler are evenly dispersed and the rubber is fully cross-linked.

[0055] In some embodiments of the present 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 gasoline, cycloalkanes and substituted cycloalkanes, normal 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, chloroform, carbon tetrachloride, dichloroethane, chlorobenzene, tetrachloroethylene, chlorotoluene, etc.

[0056] The specific method of the wet mixing can be selected from the prior art. In some embodiments of the present application, the wet mixing method includes but is not limited to at least one of 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. The preferred wet mixing method is rubber solution / filler continuous liquid phase mixing method, which is more conducive to improving the performance of the rubber compound and is easy to implement.

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

[0058] In some embodiments of the present application, solvent separation is performed by evaporation, and the evaporation is performed using an oven or a drying plate. In some embodiments of the present application, solvent separation is performed by spray drying, and the atomization method is centrifugal atomization, pressure atomization or two-fluid atomization. In some embodiments of the present application, solvent separation is performed by expansion drying, wherein the expansion drying method is to first heat and then suddenly release the pressure. In some embodiments of the present application, solvent separation is performed by flash evaporation, which can be at least one of atmospheric flash evaporation or reduced pressure flash evaporation, and the flash evaporation level is 1 to 3. In some embodiments of the present application, solvent separation is performed by low-pressure vacuum drying, specifically, volatilizing the solvent or filtering under vacuum to a pressure lower than one atmosphere, and the pressure can be -0.1MPa to 0, preferably -0.09MPa to 0, and more preferably -0.08MPa to 0. In some embodiments of the present application, the above-mentioned expansion drying is to flash vaporize the solvent through a screw expansion dryer. Preferably, the screw expansion dryer is pushed along the shaft at 0-20MPa, more preferably 1-10MPa, the pitch decreases, friction generates heat, the outlet pressure drops sharply, the rubber strip expands and relaxes, and the solvent in the rubber strip flashes and vaporizes.

[0059] In some embodiments of the present application, when the solid content of the rubber material after the separation of the peptizing agent is less than 98wt%, the rubber material is dried to remove the residual solvent in the solvent separation process. Specifically, the drying process can be heating drying and / or mechanical drying. As an example, mechanical drying is performed using an open mill, a kneading mill, an internal mixer, or a screw extruder, and the operating temperature of the mechanical drying is 20°C-250°C;

[0060] The drying process may be performed by heating drying first and then mechanical drying, or by mechanical drying first and then heating drying. When mechanical drying is selected, heating drying may be performed simultaneously, and the temperature is 10°C to 250°C; when heating drying is selected, heating may be performed in a gas medium, and the gas medium includes at least one of air, nitrogen, water vapor, and CO2.

[0061] During the solvent separation or drying process, the solvent can be recycled and reused. The recycling method can be selected from the prior art, such as recycling by a condenser and a fractionation tower. The solvent recycling method can use any method known in the art, such as recycling the vaporized solvent by surface condensation or direct contact condensation. When the direct condensation contact method is used, the coolant can be water.

[0062] The above steps S2 and S3 are dry-mixed, and the process of the above dry-mixing can refer to the prior art. Among them, the first dry-mixing includes one-stage mixing, two-stage mixing and possible re-mixing, that is, the dry-mixing before the final mixing; the second dry-mixing represents the final mixing, which is distinguished from the first dry-mixing. For example, the device used for dry mixing includes at least one of an open mixer, an internal mixer, a kneading mill, a continuous mixer or a screw mixer, which is not limited in this application.

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

[0064] In some typical embodiments of the present application, in order to better control the performance of the product rubber, the Mooney viscosity ML (1 + 4) @ 125 ° C of the above-mentioned masterbatch needs to be lower than 70; if the above conditions are not met, the rubber compound obtained by the first dry mixing is re-mixed, and the re-mixing process is the same as the initial mixing.

[0065] In some preferred embodiments of the present application, the temperature of the above-mentioned vulcanization treatment is 130-160° C., the vulcanization time is 0.5-3 hours, and the vulcanization effect is better.

[0066] According to another typical embodiment of the present application, a tread rubber is provided, and the tread rubber is prepared by any one of the above-mentioned preparation methods.

[0067] The tread rubber of the present application adopts the above-mentioned preparation method, has good flexural resistance, heat generation and other properties, and has low cost, and is particularly suitable for use in agricultural tires. In addition, the tread rubber of the present application does not contain zinc, can achieve zinc-free emissions, and is more environmentally friendly.

[0068] According to another typical embodiment of the present application, an agricultural tire is provided, which contains the above-mentioned tread rubber. The agricultural tire not only has good flex resistance, heat generation and other properties, but is also environmentally friendly and has broad market application prospects.

[0069] The beneficial effects that can be achieved by the present application will be further illustrated below in combination with embodiments and comparative examples.

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

[0071] Styrene butadiene rubber, ESBR1502, Taiwan Rubber Corporation;

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

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

[0074] White carbon black: 165MP, Quecheng Silicon Chemical Co., Ltd.; specific surface area 179m 2 / g, oil absorption value 245mL / 100g;

[0075] Silane coupling agent Si69, 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 Sinopec Nanjing Chemical Industry Co., Ltd.;

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

[0080] Antioxidant self made;

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

[0082] Vulcanization accelerator CZ, a product of Shandong Shangshun Chemical Co., Ltd.;

[0083] Vulcanization accelerator DPG, 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 an internal mixer, 40 parts (by weight, the same below) of white carbon black 165MP, 20 parts of N134 carbon black and 4 parts of Si69 were 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 were added. The mixture was mixed for 3 minutes and 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 were added to the internal mixer. The mixture was mixed for 2 minutes and discharged at 100°C. After the mixed rubber was stood for 8 hours, it was vulcanized at 150°C for 40 minutes using a flat vulcanizer to obtain a dry vulcanized rubber a.

[0087] Comparative Example 2

[0088] 40 parts of white carbon black 165MP, 20 parts of N134 carbon black and 4 parts of Si69 were added to a n-hexane solution of 70 parts of ESBR1502 and 30 parts of natural rubber, mixed, and continuously injected into a coagulator for coagulation. The solvent was then flash vaporized and desolvated by a screw expansion dryer, and dried to obtain masterbatch A. The masterbatch A was added to the internal mixer and mixed for 1 minute. Then, 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 were added. The mixture was mixed for 3 minutes and discharged at 150°C. After standing for 8 hours, the mixture was added to the internal mixer evenly. Then, 1.8 parts of vulcanization accelerator CZ, 1.3 parts of vulcanization accelerator DPG and 1.3 parts of sulfur were added. The mixture was mixed for 2 minutes and discharged at 100°C. After mixing, the mixture was rolled and sheeted. After standing for 8 hours, the mixed rubber was vulcanized on a flat vulcanizer at 150°C for 40 minutes to obtain a continuously prepared vulcanized rubber aa.

[0089] Example 1

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

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

[0092] 3) After adding the masterbatch A into an internal mixer and mixing for 1 minute, 30 parts of natural rubber, 1 part of protective wax and 2 parts of tear-resistant resin were added, and the mixture was mixed for 3 minutes and discharged at 150° C. to obtain a first-stage mixed rubber, the Mooney viscosity ML (1+4) @ 125° C. of which was lower than 70.

[0093] 4) After the mixed rubber in the first stage was left standing for 8 hours, 1.3 parts of sulfur and 1.3 phr of vulcanization accelerator DPG were added into the internal mixer, mixed for 2 minutes and discharged at 100°C. After the mixed rubber in the first stage was left standing for 8 hours, it was vulcanized at 150°C for 40 minutes using a flat vulcanizer to obtain a continuously prepared vulcanized rubber A.

[0094] Example 2

[0095] The difference from Example 1 is that during the preparation of the vulcanization aid, the antioxidant is replaced by 1.5 parts of antioxidant 4020 and 1.5 parts of antioxidant RD.

[0096] Example 3

[0097] The difference from Example 1 is that the amount of white carbon black added is 10 parts, 1 part of si69, and the amount of carbon black added is 60 parts.

[0098] Example 4

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

[0100] The vulcanized rubbers prepared in the above examples and comparative examples were tested according to the following method. The test results are listed in Table 1.

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

[0102] Determine the hardness of the rubber compound in accordance with GB / T 531.1-2008 Test method for indentation hardness of vulcanized rubber or thermoplastic rubber Part 1: Shore hardness method (Shore hardness)

[0103] Determine the physical properties of the rubber compound (tensile strength, elongation at break) in accordance with GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber;

[0104] Determine the vulcanization characteristics of the rubber compound in accordance with GB / T 16584-1996 Determination of vulcanization characteristics of rubber using a rotorless vulcanizer;

[0105] The elastic modulus of the rubber 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 principles, and the tanδmax of the rubber was determined using a rotational rheometer.

[0106] Table 1

[0107] Test items Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Filler dispersion, grade 8.1 10.0 10.0 10.0 9.2 9.1 Hardness, RT, Shore A 62 60 61 60 62 61 Tensile strength, MPa 19.6 24.6 25.0 24.9 22.8 21.9 Elongation at break, % 505 543 550 548 521 519 tand@60℃ 0.280 0.235 0.229 0.230 0.256 0.247 Compression heat 54 40.9 40.0 40.2 48.2 45.7 DIN wear index 87 105 103 106 94 96

[0108] By comparing the physical and dynamic properties of the tire tread rubber obtained by the continuous preparation process and the dry preparation process in the examples and comparative examples, it can be seen that under the same and similar formula, after the continuous preparation process is applied, the dispersion of the filler in the rubber is improved, the tensile properties of the vulcanized rubber are excellent, the compression heat generation is reduced, and the DIN wear is significantly improved. Furthermore, the present application obtains performance close to that of the rubber compound with zinc oxide added by adding a vulcanization accelerator that does not contain zinc element.

[0109] In addition, extraction experiments were carried out on the tire wear chips of Example 1 and Comparative Example 2, and the extracts were analyzed by HRMS, which confirmed that the self-synthesized environmentally friendly antioxidant did not produce highly toxic quinone compounds. Toxicity testing of the extracts confirmed that the environmentally friendly antioxidant was less toxic to zebrafish and coho salmon than the commercial antioxidant 4020 (6PPD), etc., and was environmentally friendly.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing tread rubber, characterized in that: The raw materials of the tread rubber include a first rubber, a second rubber, a first filler, a second filler, a vulcanization aid, a silane coupling agent, a protective wax, an anti-tear resin, a first vulcanizing agent and a first vulcanization accelerator; the vulcanization aid is obtained by pre-reacting an antioxidant and a vulcanization system chemical; the preparation method includes: Step S1, mixing the vulcanization aid 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, mixing the masterbatch, mixing the obtained rubber with the second rubber, protective wax and tear-resistant resin by a first dry process, and obtaining a masterbatch. Step S3, performing a second dry mixing process on the masterbatch, the first vulcanizing agent, and the first vulcanization accelerator, and performing a vulcanization treatment on the second dry mixing product to obtain a vulcanized rubber.

2. The preparation method according to claim 1, characterized in that: 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; The vulcanization system chemicals include any one or more of the second vulcanizing agent and the second vulcanization accelerator; Preferably, the pre-reaction is carried out in a second organic solvent; Preferably, the pre-reaction is carried out under the action of a catalyst, and the catalyst comprises stearic acid; Preferably, 1 to 10 parts by weight of stearic acid, 0.5 to 15 parts by weight of antioxidant, and 0.5 to 12 parts by weight of vulcanization system chemicals are added to the pre-reaction; Preferably, the preliminary reaction is carried out in a second organic solvent, the catalyst further comprises 1 to 10 parts by weight of zinc oxide, and after the preliminary reaction is completed, the zinc oxide is filtered out.

3. The preparation method according to claim 1, characterized in that: The first filler and the second filler are independently any one or more of a reinforcing agent or a filler; Preferably, the first filler is white carbon black, 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.

4. The preparation method according to claim 1, characterized in that: The first rubber and the second rubber are independently selected from any one or more of natural rubber and synthetic rubber; 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; Preferably, the mass ratio of the first rubber to the second rubber is 95:5 to 50:

50.

5. The preparation method according to claim 4, 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; Preferably, the synthetic rubber is 30 to 80 parts by weight, the natural rubber is 20 to 70 parts by weight, the white carbon black is 5 to 50 parts by weight, and the carbon black is 20 to 80 parts by weight.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The raw materials of the tread rubber include 30 to 80 parts by weight of a first rubber, 20 to 70 parts by weight of a second rubber, 5 to 40 parts by weight of a first filler, 30 to 60 parts by weight of a second filler, 5 to 15 parts by weight of a vulcanization aid, 0.1 to 10 parts by weight of a silane coupling agent, 0.5 to 5 parts by weight of a protective wax, 0.1 to 15 parts by weight of an anti-tear resin, 0.5 to 5 parts by weight of a first vulcanizing agent and 0.5 to 5 parts by weight of a first vulcanization accelerator.

7. The preparation method according to any one of claims 1 to 5, characterized in that: 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 includes 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 includes any one or more of normal pressure evaporation, low pressure vacuum drying, heating, spray drying, expansion drying and flash evaporation.

8. The preparation method according to any one of claims 1 to 5, characterized in that: The Mooney viscosity ML (1+4) @ 125°C of the first stage masterbatch should be lower than 70.

9. A tread rubber, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

10. An agricultural tire, characterized in that: A tread rubber comprising the tread rubber according to claim 9.

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