A rubber composition for tire tread and its preparation method

Abstract

This invention discloses a rubber composition for tire tread and its preparation method, belonging to the field of rubber technology. This product, using a blend of cis-butadiene rubber and natural rubber as the rubber matrix, and incorporating specific types of carbon black and rubber oil as compounding components, achieves excellent performance in low-temperature environments, exhibiting high elasticity, good grip, and good cut resistance.

Description

Technical Field

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

[0002] All-steel radial engineering machinery tires operate primarily in environments such as mines and construction sites, bearing high loads and operating for long periods. Therefore, they require high-performance tire tread compounds with stringent requirements, including cut resistance, abrasion resistance, and low heat generation. Currently, the main materials used in tire tread compounds are raw rubber blends of natural rubber, styrene-butadiene rubber, and trans-butadiene rubber. However, these rubber compounds generally have high glass transition temperatures (typically Tg < -50℃). Therefore, when these products are used in extremely cold regions, tread cracking may occur, leading to significant performance degradation or even failure.

[0003] Therefore, people have tried to prepare tread rubber for use in extremely cold environments by combining high-cis polybutadiene rubber, which has better cold resistance, with natural rubber. However, high-cis polybutadiene rubber will crystallize and freeze its molecular chains at -30℃, resulting in a significant decrease in the elasticity of the product, a decrease in the grip of the tire tread rubber, and even a risk of losing vehicle control. Summary of the Invention

[0004] Based on the deficiencies of the existing technology, the purpose of this invention is to provide a rubber composition. This product uses cis-butadiene rubber and natural rubber as the rubber matrix, and introduces specific types of carbon black and rubber oil as compounding components. It can achieve good performance in low-temperature environments, high elasticity, good grip and good cut resistance.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A rubber composition comprising the following raw materials in parts by weight:

[0007] 40-60 parts of cis-butadiene rubber, 40-60 parts of natural rubber, 45-60 parts of carbon black, and 1-5 parts of rubber oil;

[0008] The glass transition temperature of the cis-butadiene rubber is -90 to -82°C.

[0009] The carbon black has an iodine absorption value of 115–165 g / kg and an oil absorption value of 105–140 × 10⁻⁶ g / kg. -5 m 3 / kg;

[0010] The kinematic viscosity of the rubber oil at 40°C is ≤40 mm. 2 / s, pour point ≤-24℃.

[0011] To ensure ideal cold-resistance after the product is formulated into tire tread compound, the rubber composition of this invention uses cis-butadiene rubber (PPB), which has excellent cold-resistance and a low glass transition temperature, in a specific ratio with natural rubber. This balances the basic performance of the product with the performance retention rate under severe cold conditions. The amount of PPB added should not be excessive, otherwise the product's cut resistance will deteriorate. Furthermore, the inventors discovered that different types of carbon black have varying bonding strengths and effects with the rubber molecular chains within the rubber matrix. Improper selection may lead to a decrease in the product's internal impact and tear resistance, the appearance of cracks within the rubber, a significant reduction in dynamic cut resistance, and also affect the product's cold-resistance. Therefore, it is necessary to select carbon black with specific iodine and oil absorption values ​​as compound fillers in an appropriate ratio. In addition, the viscosity and pour point of the rubber oil in the product also affect the low-temperature performance of the rubber matrix. Selecting rubber oils with low kinematic viscosity and low pour point for compounding can significantly improve the product's cold-resistance.

[0012] Preferably, the glass transition temperature Tg of the cis-butadiene rubber (cis-1,4-butadiene-isoprene copolymer) tested by the DMA method is one or any two of the following values: -90℃, -88℃, -86℃, -85℃, -84℃, and -82℃. Specifically, the DMA test is performed using a dynamic viscoelastic spectrum analyzer with a temperature range of -100℃ to +80℃, a frequency of 10Hz, a dynamic strain of 0.1%, a prestress of 1N, and a heating rate of 3℃ / min.

[0013] Products made with cis-butadiene rubber and natural rubber, compared to those made with traditional cis-polybutadiene rubber or trans-butadiene rubber, not only achieve excellent cold resistance, but also have higher practical application properties such as low-temperature elasticity and cut resistance, resulting in superior overall performance.

[0014] Preferably, the natural rubber has a Mooney viscosity ≥ 70 MU according to ASTM D1646 standard.

[0015] Preferably, the carbon black is in the range of 45 parts, 50 parts, 55 parts, 60 parts by weight, or any two of these values.

[0016] Under specific iodine absorption and oil absorption values, the inventors discovered that the amount of carbon black introduced not only affects some basic properties of the product, such as modulus and toughness, but also affects the product's cold resistance. When too much carbon black is added, the product's cold resistance and dynamic cut resistance will deteriorate significantly, so the addition ratio needs to be strictly controlled.

[0017] Preferably, the kinematic viscosity of the rubber oil at 40°C is 8–36 mm. 2 / s, pour point is -30~-24℃

[0018] More preferably, the rubber oil is a plant-derived rubber oil.

[0019] Preferably, the raw materials for preparing the rubber composition further include 1 to 1.8 parts of an accelerator;

[0020] More preferably, the accelerator includes at least one of thiazole accelerators, sulfenamide accelerators, and thiuram accelerators.

[0021] Preferably, the raw materials for preparing the rubber composition also include processing aids, including but not limited to antioxidants, tackifiers, dispersants, lubricants, catalysts, anti-reversion agents, and anti-scorching agents. Those skilled in the art can appropriately apply the above-mentioned processing aids to improve the processing efficiency and practicality of the product based on the actual application requirements of the product, without affecting the effect of the key raw materials in the product and the performance of the final product.

[0022] More preferably, the raw materials for preparing the rubber composition further include 3 to 8 parts of zinc oxide, 1 to 3 parts of stearic acid, 1 to 4 parts of dispersant, 1 to 4 parts of tackifier, 2 to 5 parts of antioxidant, 0.5 to 2 parts of anti-reversion agent and 0.1 to 0.4 parts of anti-scorching agent.

[0023] More preferably, the antioxidant is a mixture of amine antioxidants, quinoline antioxidants, and wax antioxidants.

[0024] More preferably, the antioxidant is a mixture of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline, and a wax antioxidant, wherein the mass ratio of the two is (1.5-2.5):(1-2):(0.5-1.5).

[0025] Preferably, the raw materials for preparing the rubber composition also include sulfur.

[0026] Another object of the present invention is to provide a method for preparing the rubber composition, comprising the following steps:

[0027] (1) Mix natural rubber, cis-butadiene rubber, stearic acid, zinc oxide, dispersant, tackifier and antioxidant in an internal mixer and press for 10-30s. Then add carbon black and press to 100-115°C. Remove the roller and add rubber oil. Press to 125-135°C. Remove the roller and hold for 10-30s. Then press to 155-165°C again. Extrude and sheet to obtain a compound rubber.

[0028] (2) The first stage of compound rubber is pressed and mixed in an internal mixer to 120-135°C, the mixer is lifted and held for 10-30 seconds, and then pressed and mixed again to 145-155°C. The mixture is then extruded and pressed into sheets to obtain the second stage of compound rubber.

[0029] (3) The two-stage compound rubber, sulfur, accelerator, anti-sulfurization reversion agent and anti-scorching agent are mixed in a mixer and pressed for 30-60s, then lifted and held for 10-30s. Then, the mixture is pressed for 30-60s and lifted for 10-30s. Finally, the mixture is pressed and mixed to 95-115℃, and then extruded and pressed into sheets to obtain the rubber composition.

[0030] Preferably, the interval between each mixing section is 3 to 12 hours.

[0031] The preparation method of the rubber composition of the present invention has simple operation steps, low equipment requirements, and can realize large-scale mass production.

[0032] Another object of the present invention is to provide a tire tread compound comprising the rubber composition described herein.

[0033] The rubber composition of this invention possesses ideal cold-resistant properties, exhibiting high grip and good cut resistance in icy and snowy environments; its cold resistance coefficient can reach 0.502–0.595, with low low-temperature modulus, high elasticity, and a dynamic cutting depth as low as 1.24 cm. 3 The following products have excellent overall performance and are very suitable for tire tread rubber, especially for all-steel radial engineering machinery tire tread rubber in low-temperature environments and with high basic usage requirements.

[0034] The beneficial effects of the present invention are that it provides a rubber composition, which uses cis-butadiene rubber and natural rubber as the rubber matrix, and introduces specific types of carbon black and rubber oil as compounding components, thereby achieving good performance in low-temperature environments, high elasticity, good grip and good cut resistance. Detailed Implementation

[0035] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0036] Example 1

[0037] An embodiment of the rubber composition of the present invention includes a method for preparing the rubber composition comprising the following steps:

[0038] (1) Mix rubber (natural rubber, cis-butadiene rubber) with stearic acid, zinc oxide, dispersant, tackifier and antioxidant in a mixer and press for 20s. Then add carbon black and press to 110°C. Remove the roller and add rubber oil. Press to 130°C and keep for 20s. Then press to 160°C again and extrude to form a sheet to obtain a compound rubber.

[0039] (2) The first stage of compound rubber is pressed and mixed in an internal mixer to 130°C, lifted and held for 20s, and then pressed and mixed again to 150°C. The mixture is then extruded and pressed into sheets to obtain the second stage of compound rubber.

[0040] (3) The two-stage compound rubber, sulfur, accelerator, anti-sulfurization reversion agent and anti-scorching agent are mixed in a mixer and pressed for 45s, then lifted and held for 20s. Then, the mixture is pressed for 45s and lifted for 20s again. Finally, the mixture is pressed and mixed to 110°C, and then extruded and pressed into sheets to obtain the rubber composition.

[0041] The added materials and their weight proportions are shown in Table 1.

[0042] Examples 2-8

[0043] An embodiment of the rubber composition of the present invention differs from Example 1 only in the addition of materials and their weight proportions, as shown in Table 1.

[0044] Comparative Examples 1-14

[0045] A rubber composition differs from Example 1 only in the amount and weight of the added materials, as shown in Table 2.

[0046] The materials used in each embodiment and comparative example are shown below:

[0047] Rubber-1: Natural rubber, STR20, from Sittang Rubber Co., Ltd., Thailand;

[0048] Rubber-2: Styrene-butadiene rubber, glass transition temperature -38℃, SBR1502, Sinopec Qilu Petrochemical Company;

[0049] Rubber-3: Nickel-based cis-butadiene rubber, glass transition temperature -102℃, BR9000, Sinopec Qilu Petrochemical Company;

[0050] Rubber-4: Lithium-based cis-butadiene rubber, glass transition temperature -100℃, KBR820, Kumho Petrochemical Co., Ltd., South Korea;

[0051] Rubber-5: Rare earth butadiene rubber, glass transition temperature -105℃, NdBR40, Kumho Petrochemical Co., Ltd., South Korea;

[0052] Rubber-6: Trans-butadiene rubber, glass transition temperature -71℃, TBIR2249, Shandong Jingbo Petrochemical Co., Ltd.;

[0053] Rubber-7: cis-butadiene rubber, glass transition temperature -92℃, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences;

[0054] Rubber-8: Cis-Butadiene-Venerene rubber, glass transition temperature -90℃, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences;

[0055] Rubber-9: Cis-Butadiene-Venerene rubber, glass transition temperature -82℃, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences;

[0056] Rubber-10: cis-butadiene rubber, glass transition temperature -79℃, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences;

[0057] Carbon Black-1: N134, Cabot Corporation, USA, iodine absorption value 142±5 g / kg, DBP oil absorption value 127±5×10 -5 m 3 / kg;

[0058] Carbon Black-2: N220, Cabot Corporation, USA, iodine absorption value 121±5 g / kg, DBP oil absorption value 114±5×10 -5 m 3 / kg;

[0059] Carbon Black-3: N231, Cabot Corporation, USA, iodine absorption value 121±5 g / kg, DBP oil absorption value 92±5×10 -5 m 3 / kg;

[0060] Carbon Black-4: N347, Cabot Corporation, USA, iodine absorption value 90±5 g / kg, DBP oil absorption value 124±5×10 -5 m 3 / kg;

[0061] Rubber Oil-1: PIONIER TP130B, Hansheng Group, Germany, kinematic viscosity (40℃) is 9 mm. 2 / s, pour point -30℃;

[0062] Rubber Oil-2: VIVATEC 3307, Hansheng Group, Germany, kinematic viscosity (40℃) is 36 mm. 2 / s, pour point -24℃;

[0063] Rubber Oil-3: VIVATEC 4818, Hansheng Group, Germany, kinematic viscosity (40℃) is 224 mm. 2 / s, pour point -24℃;

[0064] Rubber Oil-4: VIVATEC 500, Hansheng Group, Germany, kinematic viscosity (40℃) is 400 mm. 2 / s, pour point 30℃;

[0065] Zinc oxide: Zinc oxide (indirect method), Dalian Zinc Oxide Plant;

[0066] Stearic acid: octadecanoic acid, a natural oil and fat chemical product from Malaysia;

[0067] Tackifier: SL1801, Huachi (China) Chemical Co., Ltd.;

[0068] Dispersant: Atflow L-12, Kunshan Atman New Material Technology Co., Ltd.;

[0069] Antioxidant-1: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), Sheng'ao Chemical Technology Co., Ltd.;

[0070] Antioxidant-2: 2,2,4-trimethyl-1,2-dihydroquinoline, Sheng'ao Chemical Technology Co., Ltd.;

[0071] Anti-aging agent-3: OK2122H protective wax, Bairuimei Special Materials (Suzhou) Co., Ltd.;

[0072] Sulfur: IS60, Weilin New Material Technology Co., Ltd.;

[0073] Accelerator-1: N-cyclohexyl-2-benzothiazole sulfinamide (CBS), Weilin New Material Technology Co., Ltd.;

[0074] Accelerator-2: Dibenzothiazole disulfide (DM), Weilin New Material Technology Co., Ltd.;

[0075] Anti-sulfurization reversion agent: WK-901 (1,3-bis(citronellylimidemethyl)benzene), Wuhan Jinghe Chemical Co., Ltd.;

[0076] Scorching inhibitor: N-cyclohexylthiophthalimide (CTP), Weilin New Material Technology Co., Ltd.

[0077] Table 1

[0078]

[0079]

[0080] Table 2

[0081]

[0082]

[0083]

[0084] Example of effect 1

[0085] To verify the performance of the rubber composition described in this invention, the products obtained in each example and comparative example were vulcanized (150°C, 60 min), and then the following tests were performed:

[0086] (1) -40℃ cold resistance coefficient test: Refer to HG / T 3866-2008, test temperature -40℃, cooling for 5min; compression rate 20%; the larger the cold resistance coefficient, the better the elastic recovery ability of the product at low temperature and the better the cold resistance performance.

[0087] (2) -40℃ E' modulus test: The test shall be conducted in accordance with the method of GB / T40396-2021; the smaller the E' modulus, the better the grip performance of the product in low temperature environment;

[0088] (3) Glass transition temperature Tg test: Refer to GB / T40396-2021 method; the lower the glass transition temperature, the wider the range of applications of the product at low temperatures;

[0089] (4) Dynamic cutting test: Refer to T / CRIA 29003-2023 to test the dynamic cutting amount of the product, with a rotation speed of 720 rpm, a striking speed of 120 times / min, and a striking time of 20 min; the smaller the dynamic cutting amount, the better the cutting resistance of the product.

[0090] The test results are shown in Tables 3 and 4.

[0091] Table 3

[0092]

[0093] Table 4

[0094]

[0095] The results clearly show that the rubber compositions prepared in the various embodiments of the present invention possess ideal cold resistance and performance after vulcanization, with a cold resistance coefficient of 0.502–0.595, an E' modulus as low as 133–215 MPa, a glass transition temperature as low as -60–-55°C, and a dynamic cutting depth as low as 1.04–1.24 cm. 3 .

[0096] The main reason why the products in each embodiment can achieve this effect lies in the combination of the base rubber components and the selection of the types of carbon black and rubber oil used as compounding agents. As shown in Comparative Examples 1 to 5, in Comparative Examples 1 to 3, different systems of cis-butadiene rubber are combined with natural rubber as the base rubber, but the cold resistance coefficients of the three products are all less than 0.5, indicating that cis-butadiene rubber does not have ideal cold resistance. In addition, the E' modulus of these products is too high, making it difficult to achieve high grip at low temperatures, and they are not suitable for tire treads. The dynamic cutting volume of these products is also generally greater than that of the products in the embodiments, and their cut resistance is not high. The compounded rubbers used in Comparative Examples 4 and 5 are trans-butadiene rubber and conventional styrene-butadiene rubber. The cold resistance coefficients of the two products are even lower. In fact, the E' modulus of Comparative Example 5 is nearly 10 times that of the products in the embodiments, and its glass transition temperature is only -44°C. It may completely fail when used in low-temperature environments. However, in the products of this invention, the glass transition temperature of the cis-butadiene rubber needs to be maintained within a specific range. If this value is too high or too low, as shown in Comparative Examples 6 and 7, in addition to the change in the glass transition temperature of the product, the product may not be able to achieve a balance between low-temperature performance and cut resistance. The product of Comparative Example 6 has good cold resistance but excessive dynamic cutting depth, while the product of Comparative Example 7 has a small dynamic cutting depth, good cut resistance, but less than ideal low-temperature performance. In contrast, Examples 1 and 8, with the same system formulation, used suitable cis-butadiene rubber, and the products prepared can achieve a balance between cold resistance and cut resistance.

[0097] Furthermore, the ratio of cis-butadiene rubber to natural rubber in the rubber component also needs to be maintained within a specific range to achieve excellent overall performance. As shown in Comparative Example 9, Example 4, Example 1, Example 3 and Comparative Example 8, it can be seen that when the proportion of natural rubber added is too small, although the product has a high cold resistance coefficient, low E' modulus and good cold resistance, the dynamic cutting amount of the product is too large and it does not have ideal cut resistance. As the content of natural rubber increases, the product can achieve a balance between cold resistance and cut resistance, but if there is too much, the cold resistance of the product will deteriorate significantly.

[0098] On the other hand, the selection of carbon black is also crucial to the product's performance. As can be seen from Examples 1, 5, and Comparative Examples 10-11, only carbon black with appropriate iodine and oil absorption values ​​can achieve good bonding with rubber molecules. If only one of these is met, as shown in Comparative Example 10, the carbon black used in this product has the same iodine absorption value as the type used in Example 1, but a lower oil absorption value. The bonding strength between the carbon black and rubber molecules in the product is insufficient, leading to increased internal cracks caused by periodic impacts and a larger dynamic cutting capacity of the product. The carbon black used in the product of Comparative Example 11 has the same oil absorption value as the type used in Example 5, but a lower iodine absorption value, which does not meet the requirements of this solution. The cutting resistance of the product is also poor.

[0099] On the other hand, there are also certain limitations on the amount of carbon black added. As shown in Examples 1, 6-7 and Comparative Example 12, although the more carbon black added, the lower the production cost of the product, the more the various properties of the product deteriorate significantly. Therefore, it is necessary to strictly control its ratio with the rubber components.

[0100] In addition, the type of rubber oil in the product also needs to be carefully considered. As can be seen from Examples 1, 8 and Comparative Examples 13-14, the cold resistance coefficients of products prepared with rubber oils of different kinematic viscosities and pour points vary greatly. If the type is not selected properly, the cold resistance performance of the product may not reach the expected level.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the present invention.

Claims

1. A rubber composition, characterized in that, The preparation materials include the following parts by weight: 40-60 parts of cis-butadiene rubber, 40-60 parts of natural rubber, 45-60 parts of carbon black, 1-5 parts of rubber oil, and 1-1.8 parts of accelerator; The glass transition temperature of the cis-butadiene rubber is -90~-82℃; The carbon black has an iodine absorption value of 115~165 g / kg and a DBP oil absorption value of 105~140×10⁻⁶ g / kg. -5 m 3 / kg; The kinematic viscosity of the rubber oil at 40°C is ≤40 mm. 2 / s, pour point ≤-24℃.

2. The rubber composition according to claim 1, characterized in that, The kinematic viscosity of the rubber oil at 40°C is 8~36 mm. 2 / s, pour point is -30~-24℃.

3. The rubber composition according to claim 1, characterized in that, The accelerator includes at least one of thiazole accelerators, sulfenamide accelerators, and thiuram accelerators.

4. The rubber composition according to claim 1, characterized in that, The raw materials for preparing the rubber composition also include 3-8 parts zinc oxide, 1-3 parts stearic acid, 1-4 parts dispersant, 1-4 parts tackifier, 2-5 parts antioxidant, 0.5-2 parts anti-reversion agent and 0.1-0.4 parts anti-scorching agent.

5. The rubber composition according to claim 4, characterized in that, The antioxidant is a mixture of amine antioxidants, quinoline antioxidants, and wax antioxidants.

6. The rubber composition according to claim 1, characterized in that, The raw materials for preparing the rubber composition also include sulfur.

7. The method for preparing the rubber composition according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Mix natural rubber, cis-butadiene rubber, stearic acid, zinc oxide, dispersant, tackifier and antioxidant in a mixer and press for 10~30s. Then add carbon black and press to 100~115℃. Remove the roller and add rubber oil. Press to 125~135℃. Remove the roller and hold for 10~30s. Then press to 155~165℃ again. Extrude and press into sheets to obtain a compound rubber. (2) The first stage of compound rubber is pressed and mixed in an internal mixer to 120~135℃, the mixer is lifted and held for 10~30s, and then pressed and mixed again to 145~155℃. The mixture is then extruded and pressed into sheets to obtain the second stage of compound rubber. (3) Mix the two-stage compound rubber with sulfur, accelerator, anti-sulfurization reversion agent and anti-scorching agent in a mixer and press the mixture for 30-60s, then lift it and hold for 10-30s. Then press it for 30-60s again and lift it for 10-30s again. Finally, press the mixture to 95-115℃ and extrude it into sheets to obtain the rubber composition.

8. The method for preparing the rubber composition according to claim 7, characterized in that, The interval between each mixing section is 3 to 12 hours.

9. A tire tread compound, characterized in that, Includes the rubber composition according to any one of claims 1 to 6.

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