Rubber for solid tyres, process for its preparation and use

Abstract

This invention provides a solid tire rubber, its preparation method, and its application. The preparation method includes: Step S1, mixing a continuous flow of natural rubber, carbon black slurry, silica slurry, and a vulcanizing agent, followed by coagulation to obtain a wet masterbatch; Step S2, dry-mixing the wet masterbatch with other additives to obtain a masterbatch compound; wherein, the preparation method of the vulcanizing agent includes: reacting the vulcanizing system chemicals and an antioxidant in a first solvent at a temperature of 100-190°C for 1-120 minutes under the action of a catalyst to obtain the vulcanizing agent, the catalyst including stearic acid. This application, by wet-mixing carbon black slurry, silica, and natural rubber, improves the dispersion of various fillers in the rubber, better utilizing the properties of carbon black, silica, and natural rubber, resulting in a rubber compound with better tensile properties and abrasion resistance, and significantly reduced compression heat generation. The prepared rubber is particularly suitable for the preparation of solid tires.

Description

Technical Field

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

[0002] Solid tires offer advantages such as good load-bearing capacity and safety, good puncture resistance, and the ability to be tireless, making them suitable for low-speed, high-load vehicles or machinery. They are characterized by low speeds, short travel distances, high loads, and frequent steering and braking. However, solid tires are prone to wear, chipping, and cracking during use. The thicker tread of solid tires prevents timely heat dissipation, leading to reduced tire support strength, slippage, and increased wear. Strong localized impacts can even cause blowouts, resulting in a shorter tire lifespan. Unlike pneumatic tires, solid tires are not composed of multiple different carcass and skeleton materials; therefore, the carcass materials require high overall performance in terms of tensile / tear resistance, abrasion resistance, and heat generation. Traditional tire rubber compounding processes are energy-intensive, time-consuming, produce significant dust pollution, and have poor filler dispersion. Increasing the amount of filler is a common way to improve the wear resistance of rubber compounds. However, increasing the amount of filler inevitably increases the energy consumption during the mixing process. The mixing process generates a lot of heat, and the rubber molecules are subjected to strong shear at high temperatures, making them easy to plasticize and affecting the tensile and tear properties of the rubber compound. Rubber compounds with high filler content usually have higher hysteresis loss factors and heat generation.

[0003] 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. CN106750389A 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.

[0004] 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

[0005] The main objective of this invention is to provide a solid tire rubber, its preparation method, and its application, in order to solve the problems that the tensile properties and wear resistance of the tread rubber in the prior art are difficult to meet the requirements of solid tires and that there is zinc contamination.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for preparing rubber for solid tires is provided, the method comprising: step S1, mixing a continuous flow of natural rubber, carbon black slurry, silica slurry and vulcanizing agent, and coagulating to obtain a wet masterbatch; step S2, dry mixing the wet masterbatch with other additives to obtain a masterbatch compound; wherein the method for preparing the vulcanizing agent comprises: reacting a vulcanizing system reagent and an antioxidant in a first solvent at a temperature of 100-190°C for 1 min-120 min under the action of a catalyst to obtain the vulcanizing agent, the catalyst comprising stearic acid.

[0007] Furthermore, in the preparation method of solid tire rubber, the amount of natural rubber added is 100 parts by weight, the amount of carbon black added in carbon black slurry is 1 to 100 parts by weight, the amount of vulcanizing agent added is 5 to 15 parts by weight, the amount of silica added in silica slurry is 1 to 100 parts by weight, and the amount of other additives added is 5 to 30 parts by weight.

[0008] Preferably, other additives include any one or more of the following: protective wax, tear-resistant resin, first vulcanizing agent, and first accelerator.

[0009] Further, the silica slurry in step S1 includes silica, a silane coupling agent, and a second solvent; the second solvent is water, or any mixture of water with ethanol, propanol, and butanol.

[0010] Preferably, the content of silica in the silica slurry is 1 wt% to 30 wt%.

[0011] Preferably, in the silica slurry, the mass of the silane coupling agent is 0.1% to 30% of the mass of the silica;

[0012] Preferably, the silica slurry is prepared by the following method: silica and silane coupling agent are mixed, heated to 120-150°C and held for 20-500 min, cooled and mixed with water, and then ground to obtain silica slurry.

[0013] Furthermore, the specific surface area of ​​carbon black is 10–500 m². 2 / g, more preferably 10-300m 2 / g, more preferably 100-300m 2 / g; preferably, the oil absorption value of carbon black is 50-200mL / 100g, more preferably 70-150mL / 100g;

[0014] The specific surface area of ​​silica is 10–500 m². 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.

[0015] Furthermore, the natural rubber continuous flow and carbon black slurry are aqueous media dispersions;

[0016] Preferably, the water content in the aqueous medium is greater than or equal to 50 wt%.

[0017] Furthermore, the vulcanization system reagent includes a second vulcanizing agent and a second accelerator, preferably, the vulcanization system reagent is the second accelerator;

[0018] The antioxidant is a p-phenylenediamine-based antioxidant;

[0019] Preferably, the antioxidant is any one or more of 4020, 4010NA and 7PPD;

[0020] Preferably, the antioxidant is a compound having the structure of Formula I:

[0021]

[0022] 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-C18 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.

[0023] Furthermore, in the preparation method of the vulcanizing aid, the reaction temperature is 110-170℃ and the reaction time is 5min-50min;

[0024] Optionally, the catalyst may also include zinc oxide, which is removed by filtration after the reaction is complete.

[0025] Furthermore, the preparation method of solid tire rubber also includes: step S3, vulcanizing the masterbatch to obtain vulcanized rubber;

[0026] Preferably, the vulcanization temperature is 140–160°C and the vulcanization time is 0.3–2 h.

[0027] To achieve the above objectives, according to one aspect of the present invention, a solid tire rubber is provided, which is prepared by any of the above-described methods for preparing solid tire rubber.

[0028] According to another aspect of the present invention, the application of the above-described solid tire rubber in solid tires is provided.

[0029] By applying the technical solution of this invention, the dispersion of various fillers in the rubber is improved through wet mixing of carbon black slurry, silica, and natural rubber. This allows for better utilization of the properties of carbon black, silica, and natural rubber, resulting in a rubber compound with better tensile properties and abrasion resistance, and significantly reduced heat generation during compression. The prepared rubber is particularly suitable for the preparation of solid tires. Furthermore, the vulcanizing aid used in this application contains antioxidants and active intermediates generated by the action of chemicals in the vulcanization system, which promote vulcanization. This allows the vulcanizing aid to replace the role of zinc oxide. In other words, the preparation method of this application can achieve full cross-linking of the rubber without the addition of zinc, resulting in rubber with excellent properties and zero zinc emissions, making it 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 analyzed in the background section of this application, existing technologies suffer from problems such as insufficient tensile properties and abrasion resistance of tread rubber to meet the requirements of solid tires, as well as zinc contamination. To address these issues, this application provides a rubber for solid tires, its preparation method, and its application.

[0032] According to a typical embodiment of this application, a method for preparing rubber for solid tires is provided. The method includes: step S1, mixing a continuous flow of natural rubber, carbon black slurry, silica slurry, and vulcanizing auxiliaries, and coagulating to obtain a wet masterbatch; step S2, dry mixing the wet masterbatch with other auxiliaries to obtain a masterbatch compound; wherein, the method for preparing the vulcanizing auxiliaries includes: reacting a vulcanizing system reagent and an antioxidant in a first solvent at a temperature of 100-190°C for 1 min-120 min under the action of a catalyst to obtain the vulcanizing auxiliaries, wherein the catalyst includes stearic acid.

[0033] This application improves the dispersion of various fillers in the rubber by wet-mixing carbon black slurry, silica, and natural rubber. This allows for better utilization of the properties of carbon black, silica, and natural rubber, resulting in a rubber compound with better tensile properties and abrasion resistance, and significantly reduced compression heat generation. The prepared rubber is particularly suitable for the production of solid tires. Furthermore, the vulcanizing aid used in this application contains antioxidants and active intermediates generated from the action of chemicals in the vulcanization system, which promote vulcanization. This allows the vulcanizing aid to replace the role of zinc oxide. In other words, the preparation method of this application can achieve full cross-linking of the rubber without the addition of zinc, resulting in rubber with excellent properties and zero zinc emissions, making it environmentally friendly.

[0034] In some embodiments of this application, the silica slurry in step S1 includes silica, a silane coupling agent, and a second solvent; the second solvent is water, or a mixture of any one of ethanol, propanol, and butanol with water; preferably, the silica content in the silica slurry is 1 wt% to 30 wt%, more preferably 3 wt% to 25 wt%. Preferably, the mass of the silane coupling agent in the silica slurry is 0.1% to 30% of the silica mass, specifically it can be 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 28%, 30%, etc., or other values ​​within the above range.

[0035] In some embodiments of this application, the above-mentioned silica slurry is prepared by the following method: silica and silane coupling agent are mixed, heated to 120-150°C (e.g., 120°C, 125°C, 130°C, 140°C, 145°C, etc.) and held for 20-500 min (e.g., 20 min, 50 min, 80 min, 100 min, 200 min, 300 min, 400 min, 500 min, etc.), cooled, mixed with water, and ground to obtain silica slurry.

[0036] In some embodiments of this application, the silane coupling agent is selected from any one or more of bis(triethoxypropylsilane)tetrasulfide and disulfide, 3-thiocyanopropyl-triethoxysilane, γ-mercaptopropyl-trimethoxysilane, 3-octanoylthio-1-propyltriethoxysilane, [2-(4-chloromethylphenyl)ethyl]-triethoxysilane and (3-mercaptopropyl)-bis[tetrazylpolyoxyethylene(5)yl]-ethoxysilane.

[0037] This application utilizes a continuous flow of natural rubber to mix a dispersion of natural rubber with carbon black slurry, silica slurry, and vulcanizing agents. This allows for a more uniform mixing of the natural rubber with the carbon black, silica, and vulcanizing agents, and the continuous process further improves the efficiency of solid tire rubber production. Continuous flow of natural rubber refers to the supply of natural rubber or a natural rubber dispersion at a stable or constant flow rate. For example, mixing a flowable natural rubber dispersion in a storage tank with carbon black slurry, silica slurry, and vulcanizing agents at a stable or constant flow rate. Understandably, brief intervals (e.g., a few minutes or seconds, generally not exceeding 10 minutes) may occur when switching between storage tanks supplying the fluid; such fluids are still considered continuous flow.

[0038] In some embodiments of this application, the natural rubber continuous flow and the carbon black slurry are aqueous dispersions, wherein the aqueous medium contains water or is 100% water for dispersion. Preferably, the water content in the aqueous medium is greater than or equal to 50 wt%. The aqueous medium may contain one or more solvents miscible with water, for example, alcohols include, but are not limited to, ethanol, propanol, and butanol. By using an aqueous medium to disperse natural rubber and carbon black separately to form a slurry, and then performing wet mixing, the vulcanization aid of this application can not only significantly reduce the use of organic solvents, but also improve the overall performance of rubber for solid tires. In some embodiments, the dry rubber content of the natural rubber in the natural rubber continuous flow is 10–70 wt%, and the carbon black content in the carbon black slurry is 1–30 wt%.

[0039] In some embodiments of this application, in the preparation method of solid tire rubber, the amount of natural rubber added is 100 parts by weight, the amount of carbon black added in carbon black slurry is 1 to 100 parts by weight, the amount of vulcanizing agent added is 5 to 15 parts by weight, the amount of silica added in silica slurry is 1 to 100 parts by weight, and the amount of other additives added is 5 to 30 parts by weight. This can better exert the synergistic effect of each component and further improve the performance of the rubber compound.

[0040] The aforementioned carbon black can be selected from existing technologies; preferably, the specific surface area of ​​the carbon black is 10–500 m². 2 / g, more preferably 10-300m 2 / g, more preferably 100-300m 2 / g. Preferably, the oil absorption value of carbon black is 50-200 mL / 100g, more preferably 70-150 mL / 100g.

[0041] The aforementioned silica can also be selected from existing technologies; preferably, the specific surface area of ​​the silica is 10–500 m². 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.

[0042] In some typical embodiments of this application, other additives include any one or more of protective wax, tear-resistant resin, first vulcanizing agent, and first accelerator. The specific types of protective wax, tear-resistant resin, first vulcanizing agent, and first accelerator can be selected from existing technologies, and this application does not impose any particular limitation. For example, the first vulcanizing agent can be sulfur, and the first accelerator includes, but is not limited to, any one or more of sulfonamide vulcanizing accelerators, sulfenamide vulcanizing accelerators, and thiazole vulcanizing accelerators. Preferably, the accelerator is selected from any one or more of CZ, DZ, DM, M, and NS.

[0043] Those skilled in the art can also add other additives according to the process or the application requirements of the rubber to achieve the corresponding functions, and this application does not have any special limitations. As an example, other additives may include any one or more of silane coupling agents, oils, activators, antioxidants, heat stabilizers, light stabilizers, flame retardants, dyes, pigments, plasticizers, softeners, and processing aids. The dosage of other additives is the conventional dosage, or may be adjusted according to the actual requirements.

[0044] The vulcanizing auxiliaries prepared by reacting the aforementioned vulcanizing system pharmaceuticals with antioxidants contain active intermediates that promote vulcanization. In some embodiments of this application, the aforementioned vulcanizing system pharmaceuticals include a second vulcanizing agent and a second accelerator. The specific types of the second vulcanizing agent and the second accelerator can be selected from the prior art, and specific reference can be made to the selection of the first vulcanizing agent and the first accelerator.

[0045] In some preferred embodiments of this application, the vulcanizing agent is a second accelerator. The vulcanizing auxiliaries prepared are applied in the preparation method of solid tire rubber of this application, which can improve the overall performance of the rubber product.

[0046] In some typical embodiments of this application, the antioxidant is a p-phenylenediamine antioxidant; for example, the antioxidant is any one or more of 4020, 4010NA and 7PPD, but is not limited thereto.

[0047] 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 prepare vulcanizing auxiliaries with better performance, but are also more environmentally friendly.

[0048]

[0049] 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.

[0050] Taking an antioxidant as an example of a compound with the structure of Formula I and a 2-thiobenzothiazole-based sulfurization system drug, the reaction between the antioxidant and the sulfurization system drug is shown in the following reaction equation. The generated active intermediate has the effect of promoting sulfurization.

[0051]

[0052] In some typical embodiments of this application, in the preparation method of the vulcanizing aid, the amount of stearic acid added during the reaction is 0.5-15 phr, the amount of antioxidant added is 0.5-15 phr, and the amount of vulcanizing system chemicals added is 0.5-15 phr. The reaction efficiency is high, and it is beneficial to give full play to the vulcanizing promoting effect of the vulcanizing aid formed by the above components in the rubber preparation process.

[0053] In some preferred embodiments of this application, the first 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 sulfurized chemical systems, but also facilitate the pre-reaction and improve reaction efficiency. There are no specific requirements for the amount of the first solvent; it only needs to be sufficient to dissolve the antioxidants, sulfurized chemical systems, and stearic acid.

[0054] In some preferred embodiments of this application, the reaction temperature in the preparation method of the above-mentioned vulcanization aid is 110-170°C and the reaction time is 5 min-50 min, which can further improve the vulcanization promoting effect of the product.

[0055] In some embodiments of this application, the first solvent is an organic solvent, and the catalyst also includes zinc oxide. Since zinc oxide is insoluble in the organic solvent, after the reaction is completed, the zinc oxide can be filtered out, which can also achieve the zinc-free rubber. The addition of zinc oxide can further promote the generation of active intermediates.

[0056] The vulcanizing aid prepared by any of the above methods can be directly mixed with carbon black slurry, natural rubber continuous flow, etc. in solution state, or the solid vulcanizing aid obtained after solvent removal can be mixed with other materials. This application does not limit this, and an appropriate method can be selected according to the actual production situation.

[0057] In step S1 above, the dispersibility of carbon black in natural rubber is improved through wet rubber mixing, and a dry wet masterbatch is obtained through dehydration. In some embodiments of this application, in order to make the natural rubber, carbon black, and vulcanizing aids more uniformly mixed, in step S1, the natural rubber is first dissolved in an aqueous medium to form a uniform natural rubber solution, and then the solution is mixed with carbon black slurry, silica slurry, and vulcanizing aids in a continuous flow. This allows these materials to be mixed more uniformly, thereby improving the performance of the final rubber compound.

[0058] The specific methods for coagulation described above can be selected from existing technologies, and this application does not impose any particular limitations. For example, coagulation can be carried out using an ejector, a stirrer, or a screw mixer.

[0059] In some embodiments of this application, the natural rubber / carbon black / fumed silica mixture is dehydrated after coagulation. Preferably, a screw dehydrator is used for dehydration.

[0060] In some embodiments of this application, to further remove solvents or moisture from the rubber compound, when the solid content of the dehydrated rubber compound is less than 98 wt%, the rubber compound is dried, either by heating or by mechanical drying. For example, the heating drying is oven drying or air drying; mechanical drying is performed using an open mill, kneader, internal mixer, or screw extruder, with a working temperature of 20°C-250°C. Alternatively, heating drying can be performed first, followed by mechanical drying, or vice versa. When mechanical drying is selected, heating drying can be performed simultaneously at a temperature of 10°C to 250°C; when heating drying is selected, heating can be carried out in a gaseous medium, including at least one of air, nitrogen, water vapor, and CO2.

[0061] During the aforementioned coagulation or dehydration drying process, the separated water can be recycled and reused. The recycling method can be selected from existing technologies, such as recycling through condensers and distillation towers.

[0062] In step S2 above, the wet masterbatch containing filler carbon black / fumed silica is dry-mixed with other additives. The specific dry mixing equipment can be selected from existing technologies. For example, the dry mixing can be carried out using at least one of open mill, internal mixer, kneader, continuous mixer or screw mixer.

[0063] In some embodiments of this application, in order to further improve the preparation efficiency of the rubber compound, a portion of the natural rubber can be added during the dry mixing process. Preferably, the mass of the natural rubber added during the dry mixing process accounts for 1 to 5% of the total amount of natural rubber added.

[0064] In some typical embodiments of this application, to further improve the performance of the masterbatch, step S2 includes: step S21, performing a first dry mixing of the wet masterbatch with protective wax and tear-resistant resin to obtain a first-stage masterbatch; step S22, performing a second dry mixing of the first-stage masterbatch with a first vulcanizing agent and a first accelerator to obtain the masterbatch. Preferably, the temperature of the first dry mixing is 130–170°C, and the time is 2–8 min; preferably, the temperature of the second dry mixing is 90–110°C, and the time is 2–5 min.

[0065] In some embodiments of this application, the method for preparing solid tire rubber further includes: step S3, subjecting the masterbatch to vulcanization treatment to obtain vulcanized rubber. Preferably, the vulcanization temperature is 140–160°C and the vulcanization time is 0.3–2 hours, which is beneficial for further improving the performance of the vulcanized rubber.

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

[0067] The solid tire rubber prepared by the above method involves wet mixing of carbon black, silica, and natural rubber, followed by dry mixing of the wet masterbatch with other additives. This improves the dispersion of various fillers in the rubber, allowing for better utilization of the properties of carbon black, silica, and natural rubber. Consequently, the solid tire rubber exhibits good tensile properties and abrasion resistance, while significantly reducing compression heat. Furthermore, since zinc oxide is not required during the preparation process, the solid tire rubber of this application has zero zinc emissions, making it environmentally friendly.

[0068] According to another typical embodiment of this application, the above-mentioned solid tire rubber is provided for use in solid tires. Solid tires made using this solid tire rubber not only have good tensile properties, wear resistance, and low compression heat generation, but also do not contain zinc, making them more environmentally friendly.

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

[0072] Carbon black: N134, Shanghai Cabot Co., Ltd.; specific surface area 143 m² 2 / g, oil absorption value 127mL / 100g;

[0073] Silica: 165MP, manufactured by Quecheng Silicon Chemical Co., Ltd.; specific surface area 179m² 2 / g, oil absorption value 245mL / 100g;

[0074] Silane coupling agent: Si69, Nanjing Shuguang Silane Chemical Co., Ltd.;

[0075] Stearic acid, a product of Tyco Brown Chemical (Zhangjiagang) Co., Ltd.

[0076] Protective wax, a product of Qingdao Jinxian Chemical Co., Ltd.

[0077] Antioxidant RD, a product of Nanjing Chemical Industry Co., Ltd., China Petrochemical Corporation;

[0078] Antioxidant 4020, a product of Jiangsu Shengao Chemical Technology Co., Ltd.

[0079] Anti-aging agents self made

[0080] Tear-resistant resin, Jiangsu Qixiang High-Tech Materials Co., Ltd.;

[0081] Accelerator CZ, a product of Shandong Shangshun Chemical Co., Ltd.

[0082] DPG accelerator, a product of Shandong Shangshun Chemical Co., Ltd.

[0083] Sulfur, a product of Liaoning Chaoyang Tianming Industry and Trade Co., Ltd.

[0084] Comparative Example 1

[0085] In a Banbury mixer, 30 parts of 165MP silica, 3 parts of silane coupling agent, and 20 parts of N134 carbon black were added to 100 parts of natural rubber and mixed for 1 minute. Then, 4 parts of zinc oxide, 1 part 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 and mixed for 3 minutes. The mixture was discharged at 150°C. After the mixture was left to stand for 8 hours, 1.3 parts of accelerator CZ, 0.5 parts of accelerator DPG, and 1.4 parts of sulfur were added to the Banbury mixer and mixed for 2 minutes. The mixture was discharged at 100°C. After the mixture was left to stand for 8 hours, it was vulcanized at 150°C for 40 minutes using a flat vulcanizing machine to obtain dry vulcanized rubber a.

[0086] Comparative Example 2

[0087] 30 parts of 165MP silica, 3 parts of silane coupling agent, and 20 parts of N134 carbon black were added to a hexane solution of 100 parts of natural rubber. After mixing, the mixture was continuously injected into a coagulant for coagulation, followed by solvent removal and drying to obtain masterbatch A. Masterbatch A was added to a mixer and homogenized. Then, 4 parts of zinc oxide, 1 part 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. After mixing for 3 minutes, the mixture was discharged at 150°C and allowed to stand for 8 hours. The mixture was then added back to the mixer, along with 1.3 parts of accelerator CZ, 0.5 parts of accelerator DPG, and 1.4 parts of sulfur. After mixing for 2 minutes, the mixture was discharged at 100°C. After mixing, the mixture was rolled and sheeted. After standing for 8 hours, the mixture was vulcanized at 150°C for 40 minutes using a flat vulcanizing machine to obtain continuously prepared vulcanized rubber aa.

[0088] Example 1

[0089] Preparation of vulcanization aids:

[0090] 1 phr of stearic acid and 3 phr of environmentally friendly anti-aging agent 1.3 phr accelerator CZ is mixed in xylene and pre-reacted at 140℃ for 35 min to obtain a vulcanization aid solution;

[0091] Preparation of silica slurry:

[0092] 165MP silica and silane coupling agent were mixed evenly at room temperature. The mixture was heated to 135°C and held for 40 minutes. After returning to room temperature, water was added and the mixture was ground to prepare silica slurry.

[0093] The above-mentioned vulcanizing aid solution was mixed with 15 wt% N134 carbon black slurry, 15 wt% silica slurry, and natural rubber latex (natural rubber mass concentration of 60%). The mixture was then continuously injected into a coagulant for coagulation, dehydrated, and dried using a heated conveyor belt dryer to obtain masterbatch A containing 20 parts carbon black, 30 parts silica, 100 parts natural rubber, and 3 parts silane coupling agent. Masterbatch A was added to a mixer and mixed for 1 minute, followed by the addition of 1 part protective wax and 2 parts tear-resistant resin. After mixing for 3 minutes, the mixture was discharged at 150°C. After resting for 8 hours, 1.4 parts sulfur and 0.5 phr DPG accelerator were added to the mixer, and after mixing for 2 minutes, the mixture was discharged at 100°C. After resting for 8 hours, it was vulcanized for 40 minutes at 150°C using a flat vulcanizing machine to obtain continuously prepared vulcanized rubber A.

[0094] Example 2

[0095] The only difference from Example 1 is that, in the preparation of the vulcanizing aid, 1.5 phr antioxidant RD and 1.5 phr antioxidant 4020 are used instead of the 3 phr environmentally friendly antioxidant.

[0096] Example 3

[0097] The only difference from Example 1 is that, in the preparation of the vulcanizing aid, 3 phr antioxidant 4020 is used instead of 3 phr environmentally friendly antioxidant.

[0098] Example 4

[0099] The above-mentioned vulcanizing aid solution (which is exactly the same as the vulcanizing aid solution in Example 1) is mixed with N134 carbon black slurry with a concentration of 15 wt% dispersed in water, white carbon black slurry with a solid content of 15 wt% (same as in Example 1), and natural rubber latex (natural rubber mass concentration of 60%). The mixture is continuously injected into a coagulant for coagulation, dehydrated, and dried by a heated conveyor belt dryer to obtain masterbatch A containing 20 parts carbon black, 30 parts white carbon black, 80 parts natural rubber, and 3 parts silane coupling agent. After adding masterbatch A to a mixer and mixing for 1 minute, add 20 parts of natural rubber, 1 part of protective wax, and 2 parts of tear-resistant resin. Mix for 3 minutes and discharge the mixture at 150°C. After letting the mixture stand for 8 hours, add 1.4 parts of sulfur and 0.5 phr accelerator DPG to the mixer and mix for 2 minutes. Discharge the mixture at 100°C and let it stand for 8 hours. Then, vulcanize the mixture at 150°C for 40 minutes using a flat vulcanizing machine to obtain continuously prepared vulcanized rubber A.

[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 vulcanization characteristics of rubber compounds were determined according to GB / T16584-1996 "Determination of vulcanization characteristics using a rotorless vulcanizing apparatus for rubber".

[0102] The physical properties (tensile strength, elongation at break) of the rubber compound were determined in accordance with GB / T528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0103] The hardness of the rubber compound was determined according to GB / T531.1-2008 Test method for indentation hardness of vulcanized rubber or thermoplastic rubber - Part 1: Shore hardness tester method (Shore hardness)

[0104] The elastic modulus of the rubber compound at 60°C was determined according to GB / T9870.1-2006 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.

[0105] The filler dispersion grade was determined according to the "Rapid Comparative Method for Evaluation of Carbon Black and Carbon Black / Silica Dispersion in Rubber" (GB / T6030-2006).

[0106] Table 1

[0107] Test Project Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Packing material dispersion, grade 8.3 10.0 10.0 10.0 10.0 10.0 Hardness, RT, Shore A 60 59 59 59 59 59 Tensile strength, MPa 21.3 26.0 27.2 28.1 27.9 28.0 Elongation at break, % 458 504 541 556 561 534 tand@60℃ 0.125 0.101 0.098 0.099 0.100 0.099 Compression generates heat 25.0 19.8 19.0 19.7 20.0 20.1 DIN Abrasion Index 87 115 118 115 113 117

[0108] The vulcanized rubber A obtained in Examples 1-4 above was used in the tread of solid tires, and tests showed no zinc emissions.

[0109] The test data from Example 2 and Comparative Example 1 show that, except for the absence of zinc oxide in the raw materials of Example 1, the rubber prepared by the method of this application has more uniform filler dispersion, slightly lower hardness, significantly increased tensile strength and elongation at break, significantly reduced heat generation during compression, and significantly improved DIN wear.

[0110] The test data from Example 2 and Comparative Example 2 show that, based on a combination of wet and dry methods, this application, by adding a vulcanizing agent instead of zinc oxide and using an aqueous medium for dispersion, achieved similar results to Comparative Example 2 in preparing the rubber, and its tensile strength, elongation at break, and other properties were even better than those of Comparative Example 2.

[0111] In addition, the tire wear debris from Examples 1 and 2 were subjected to extraction experiments, and the extracts were analyzed by HRMS. This 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 silver salmon than commercial antioxidants such as 4020 (6PPD) and RD, and was therefore environmentally friendly.

[0112] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: This application improves the dispersion of various fillers in the rubber by wet-mixing carbon black and natural rubber, and further dry-mixing the wet masterbatch with silica and other additives. This allows for better utilization of the properties of carbon black, silica, and natural rubber, resulting in a rubber compound with better tensile properties and abrasion resistance, and significantly reduced compression heat generation. The prepared rubber is particularly suitable for the preparation of solid tires. Furthermore, the vulcanizing agent used in this application contains antioxidants and active intermediates generated by the action of chemicals in the vulcanization system, which promote vulcanization. This allows the vulcanizing agent to replace the role of zinc oxide. In other words, the preparation method of this application can achieve full cross-linking of the rubber without adding zinc, resulting in rubber with excellent properties and zero zinc emissions, making it environmentally friendly.

[0113] The above are merely preferred embodiments of the present invention and are not intended to limit the present 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 preparing rubber for solid tires, characterized in that, include: Step S1: Mix natural rubber continuous flow, carbon black slurry, white carbon black slurry and vulcanization aid, coagulate to obtain wet masterbatch; Step S2: The wet masterbatch is dry-mixed with other additives to obtain masterbatch. The preparation method of the vulcanization aid includes: reacting the vulcanization system reagent and the antioxidant in a first solvent at a temperature of 100-190°C for 1 min-120 min under the action of a catalyst to obtain the vulcanization aid, wherein the catalyst includes stearic acid.

2. The preparation method according to claim 1, characterized in that, In the preparation method of the solid tire rubber, the amount of natural rubber added is 100 parts by weight, the amount of carbon black added in the carbon black slurry is 1 to 100 parts by weight, the amount of vulcanizing agent added is 5 to 15 parts by weight, the amount of silica added in the silica slurry is 1 to 100 parts by weight, and the amount of other additives added is 5 to 30 parts by weight. Preferably, the other additives include any one or more of the following: protective wax, tear-resistant resin, first vulcanizing agent, and first accelerator.

3. The preparation method according to claim 1, characterized in that, The silica slurry in step S1 includes silica, a silane coupling agent, and a second solvent; the second solvent is water, or any one of ethanol, propanol, and butanol mixed with water. Preferably, the content of silica in the silica slurry is 1 wt% to 30 wt%. Preferably, in the silica slurry, the mass of the silane coupling agent is 0.1% to 30% of the mass of the silica; Preferably, the silica slurry is prepared by the following method: silica and silane coupling agent are mixed, heated to 120-150°C and held for 20-500 min, cooled and mixed with water, and ground to obtain silica slurry.

4. The preparation method according to claim 2, characterized in that, The specific surface area of ​​the carbon black is 10–500 m². 2 / g, more preferably 10-300m 2 / g, more preferably 100-300m 2 / g; preferably, the oil absorption value of the carbon black is 50-200mL / 100g, more preferably 70-150mL / 100g; The specific surface area of ​​the silica is 10–500 m². 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.

5. The preparation method according to claim 1, characterized in that, The natural rubber continuous flow and the carbon black slurry are aqueous media dispersions; Preferably, the water content in the aqueous medium is greater than or equal to 50 wt%.

6. The preparation method according to claim 1, characterized in that, The vulcanization system includes a second vulcanizing agent and a second accelerator; preferably, the vulcanization system includes a second accelerator. The antioxidant is a p-phenylenediamine-based antioxidant. Preferably, the antioxidant is any one or more of 4020, 4010NA and 7PPD; Preferably, the antioxidant is a compound having the structure of Formula I: 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.

7. The preparation method according to claim 1, characterized in that, In the preparation method of the vulcanization aid, the reaction temperature is 110-170℃ and the reaction time is 5min-50min; Optionally, the catalyst further includes zinc oxide, which is removed by filtration after the reaction is complete.

8. The preparation method according to claim 1, characterized in that, The method for preparing the solid tire rubber further includes: Step S3: The masterbatch is subjected to vulcanization treatment to obtain vulcanized rubber; Preferably, the vulcanization temperature of the vulcanization treatment is 140-160°C, and the vulcanization time is 0.3-2 hours.

9. A type of rubber for solid tires, characterized in that, It is prepared by the method for preparing solid tire rubber according to any one of claims 1 to 8.

10. The application of the solid tire rubber according to claim 9 in solid tires.

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