A sidewall rubber composition, sidewall rubber and preparation method thereof with low rolling resistance and early wax spraying

Abstract

The invention discloses a sidewall rubber composition with low rolling impedance and early wax spraying, a sidewall rubber and a preparation method, and relates to the technical field of tire rubber preparation. The sidewall rubber composition with low rolling impedance and early wax spraying comprises, by weight: 1-100 parts of natural rubber, 45-55 parts of butadiene rubber, 20-100 parts of white carbon black, 2-10 parts of silane coupling agent, 3.5 parts of antioxidant 4020, 3.5 parts of zinc oxide, 2.5 parts of stearic acid, 1 part of antioxidant RD, 3 parts of tackifying resin, 15-30 parts of carbon black, 2.2 parts of insoluble sulfur, 0.8-1.5 parts of accelerator, and 1.5-2.5 parts of protective wax. The invention adopts masterbatch of white carbon black and natural rubber, rare earth butadiene rubber and low specific surface area carbon black, and the prepared sidewall rubber has low hysteresis, low heat generation and low tire rolling resistance; the rubber does not contain operating oil, and the physical properties and flexural fatigue meet the design requirements, and the anti-blooming performance is improved, the probability of blooming is greatly reduced, the appearance of the tire is improved, and the long-term protective performance is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of tire rubber preparation, and in particular to a low rolling impedance early wax-sprayed sidewall rubber composition, sidewall rubber and a preparation method. Background Art

[0002] The sidewall is the outer part of the tire between the tire bead and the crown, and the sidewall forms a physical connection between the crown and the rim for transmitting power. Its function is to protect the tire body from the external natural environment.

[0003] At present, the sidewall rubber of truck radial tires is generally reinforced with N330 or N375 carbon black, and rubber operating oil is used to improve the dispersion of carbon black. It can also adjust the elongation and hardness of the vulcanized rubber. However, the rubber has high hysteresis and high heat generation, resulting in high tire rolling resistance and high fuel consumption.

[0004] When tires are in daily use, the sidewall rubber on them will come into contact with trace amounts of ozone in the air. Ozone can attack the double bonds in diene rubber, breaking bonds and causing aging and cracking of the rubber, deteriorating rubber performance and causing the tire to lose its use value prematurely.

[0005] In order to avoid ozone damage to the tire sidewall rubber, people usually add a certain amount of protective wax to the sidewall rubber composition, and protect the rubber from static ozone attack by the film or physical barrier formed by the wax migrating to the tire rubber surface. It is well known that wax must migrate to the tire rubber surface to provide protection. If the amount of protective wax migrating is too little, it will not have an ideal protective effect. If the amount migrating is too much, it will easily cause frosting, causing the tire surface to turn white, affecting the appearance of the tire.

[0006] The migration of protective wax is not only related to the type of rubber, but also to the operating oil. When the operating oil is dispersed in the rubber matrix, the protective wax will quickly migrate to the rubber surface with the help of the operating oil path. During the storage and use of tires, due to excessive temperature and humidity (temperature ≥35°C, humidity ≥60%), the protective wax will migrate out early, affecting the appearance of the product (easy to be contaminated). In addition, since the amount of protective wax added to the rubber is fixed, the precipitation and shedding of a large amount of protective wax in the early stage will also cause the anti-aging performance of the finished tire to decrease during later use.

[0007] Therefore, how to control the migration of protective wax in a high-humidity and high-heat environment so that the protective wax can ensure the protective effect without affecting the appearance of the tire is a technical problem that technicians in this field urgently need to solve.

[0008] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0009] In view of the above technical problems, the embodiments of the present invention provide a sidewall rubber composition, a sidewall rubber and a preparation method for early wax spraying with low rolling resistance, so as to solve the problems raised in the above background art.

[0010] The present invention provides the following technical solutions:

[0011] A sidewall rubber composition for early wax spraying with low rolling resistance, by weight, includes: 1-100 parts of natural rubber, 45-55 parts of cis-butadiene rubber, 20-100 parts of silica, 2-10 parts of silane coupling agent, 3.5 parts of antioxidant 4020, 3.5 parts of zinc oxide, 2.5 parts of stearic acid, 1 part of antioxidant RD, 3 parts of tackifying resin, 15-30 parts of carbon black, 2.2 parts of insoluble sulfur, 0.8-1.5 parts of accelerator, and 1.5-2.5 parts of protective wax.

[0012] Preferably, 50 parts of natural rubber, 50 parts of cis-butadiene rubber, 30 parts of silica, 3 parts of silane coupling agent, 3.5 parts of antioxidant 4020, 3.5 parts of zinc oxide, 2.5 parts of stearic acid, 1 part of antioxidant RD, 3 parts of tackifying resin, 15 parts of carbon black, 2.2 parts of insoluble sulfur, 1 part of accelerator, and 2 parts of protective wax.

[0013] Preferably, 40-60 parts of natural rubber are selected. The tensile crystallinity of natural rubber brings high tear resistance and low flex crack growth to the rubber compound.

[0014] Preferably, the cis-butadiene rubber is rare earth cis-butadiene rubber CB24; among them, the rare earth cis-butadiene rubber has low hysteresis loss and can overcome the longitudinal cracks on the sidewall of the radial tire.

[0015] Preferably, the silica is selected as 200MP; the purpose is to ensure both reinforcement and rolling resistance.

[0016] Preferably, the carbon black is selected as N550; the purpose is that the carbon black with low specific surface area has low reinforcement and low hardness for rubber, and the carbon black can improve the ultraviolet aging resistance of the rubber compound and the smoothness of the extruded surface of the rubber compound compared with silica, and at the same time, N550 carbon black can also ensure the rolling resistance.

[0017] Preferably, the accelerator is selected from sulfenamide accelerators; the sulfenamide accelerator is preferably N-tert-butyl-2-benzothiazole sulfenamide NS.

[0018] Among them, accelerator NS has a long scorch time and a fast vulcanization speed, which can improve the vulcanization speed of rubber; the protective wax is selected from the product of Shandong Yanggu Huatai Co., Ltd., with the brand H654; the insoluble sulfur is preferably sulfur OT-20.

[0019] A method for preparing a sidewall rubber from a sidewall rubber composition includes the following steps:

[0020] Component weighing: Weigh each component for preparing the above-mentioned sidewall rubber composition with low rolling resistance and early wax spraying according to the component ratio;

[0021] Masterbatch preparation: Take natural rubber, silica, silane coupling agent, antioxidant 4020, zinc oxide, stearic acid, antioxidant RD and tackifying resin and add them to an internal mixer for wet mixing to prepare a masterbatch;

[0022] First-stage mixed rubber: Add the masterbatch, cis-butadiene rubber, carbon black and protective wax to an internal mixer, press the top plug for mixing for 30 seconds, raise the top plug, press the top plug for mixing for 50 seconds, raise the top plug, press the top plug for mixing for 45 seconds, and open the discharge door to discharge the rubber; Sheet the rubber on a two-roll mill, cool and stack it;

[0023] Final-stage mixed rubber: Add the first-stage masterbatch, insoluble sulfur and accelerator to an internal mixer, press the top plug for mixing for 30 seconds, raise the top plug to clean, press the top plug for mixing for 30 seconds, raise the top plug, press the top plug for mixing for 20 seconds, raise the top plug, press the top plug for mixing for 20 seconds, raise the top plug, and open the discharge door to discharge the rubber; Sheet the rubber on a two-roll mill, cool and stack it.

[0024] It should be noted that wet mixing is a mixing method that has been widely used in the tire manufacturing process in recent years. Wet mixing can mix and disperse highly specific surface area silica, which cannot be dispersed by traditional mixing, very evenly; for example, in the patent with publication number CN102153792B and patent name "Preparation method of wet-mixed natural rubber compound", the preparation method of wet-mixed natural rubber mentioned in the above patent involves adding silica and other inorganic fillers to natural rubber latex and flocculating it into rubber with acetic acid;

[0025] Using the preparation method in the above patent to prepare a masterbatch of highly specific surface area silica, the silica has good dispersion, the vulcanized rubber compound is soft, the modulus at a specified elongation and hardness are low, and it can make up for the shortcoming of the pure natural rubber sidewall formula that the flex cracking forms early; in addition, the compound has small hysteresis loss and good tear resistance, and is a very good raw material for preparing sidewall rubber compounds; it not only meets the performance requirements of sidewall rubber, but also has a short mixing time and low energy consumption.

[0026] Preferably, the discharge temperature during the first-stage mixed rubber process is controlled at 155 - 160 °C; the discharge temperature during the final-stage mixed rubber process is controlled at 95 - 105 °C.

[0027] A sidewall rubber with low rolling resistance and early wax spraying is made of the above-mentioned sidewall rubber composition or is prepared by the above-mentioned sidewall rubber preparation method.

[0028] A sidewall rubber composition with low rolling resistance and early wax spraying provided by an embodiment of the present invention has the following

[0029] Beneficial effects:

[0030] 1. The present invention uses a masterbatch of silica and natural rubber, together with rare-earth cis-polybutadiene rubber and carbon black with a low specific surface area, to prepare a sidewall compound with low hysteresis, low heat build-up, and low rolling resistance of the tire.

[0031] 2. The compound does not contain processing oil, and its physical properties and flex fatigue both meet the design requirements. Moreover, it improves the anti-spraying property, greatly reduces the probability of spraying, improves the appearance of the tire, and at the same time ensures long-term protection performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Appearance photo of the sidewall compound prepared in Formulation Example 1 after 30 days;

[0033] Figure 2 Appearance photo of the sidewall compound prepared in Formulation Comparative Example 1 after 30 days. DETAILED DESCRIPTION OF THE INVENTION

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0035] The design concept of the present invention is as follows:

[0036] 1. At present, the sidewall compound formula of radial truck tires mainly uses natural rubber / cis-polybutadiene rubber. This is mainly to ensure that the compound has good flex resistance, and the compounding ratio design enables the formation and growth of cracks in the compound to reach the best balance. Cis-polybutadiene rubber is used to overcome the problem of longitudinal cracks in the sidewall of radial tires, and the filler system uses carbon black to reinforce the compound.

[0037] 2. At the same time, the above sidewall compound formula needs to use processing oil to reduce the modulus at a given elongation of the compound, improve the elongation at break and deformation ability of the compound, but the prepared compound has high hysteresis, high heat build-up, high rolling resistance of the tire, and high fuel consumption; for the early excessive precipitation of protective wax, modified protective wax HG72 is used. This method can be used as an improvement approach, but modified protective wax HG72 needs to be specially prepared, with high cost and difficult to obtain in the market.

[0038] 3. To solve the above technical problems, the present invention uses a system of natural rubber + cis-polybutadiene rubber + silica + carbon black, and at the same time applies the wet mixing technology. First, natural rubber and silica are mixed evenly to prepare a masterbatch. This masterbatch benefits from silica and the wet mixing process, and has lower hysteresis loss and lower compound hardness than the dry carbon black natural rubber compound with the same number of parts.

[0039] 4. Then mix the masterbatch with butadiene rubber and a small amount of carbon black. The carbon black is low specific surface area N550 or N660 carbon black. The low specific surface area carbon black has lower reinforcing performance on the rubber than the high specific surface area carbon black, so the hardness of the rubber is low. In addition, carbon black can improve the disadvantage of white carbon black rubber that it is not resistant to ultraviolet aging, and at the same time improve the smoothness of the rubber extruded surface;

[0040] 5. The sidewall rubber compound designed above has low hardness and does not need to be added with operating oil, thereby ensuring the flexural performance while reducing the risk of excessive early precipitation of protective wax.

[0041] In view of the problems mentioned in the above background technology, the embodiment of the present invention provides a low rolling resistance early wax sprayed sidewall rubber composition, sidewall rubber and preparation method to solve the above technical problems. The specific implementation method and technical solution are as follows:

[0042] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0043] Example 1: Experimental Grouping

[0044] Table 1 is the formula of each group of experiments

[0045] Serial number Material Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 1 Natural rubber 50 50 50 50 2 Butadiene rubber 50 50 3 Rare earth butadiene rubber 50 50 4 Carbon black N550 15 15 5 Carbon black N330 45 45 6 Silica 30 30 7 Silane coupling agent 3 3 8 Stearic acid 2.5 2.5 2.5 2.5 9 Indirect oxidation 3.5 3.5 3.5 3.5 10 Tert-butyl tackifier 3 3 3 3 11 Environmentally friendly aromatic oil 5 5 12 Antioxidant RD 1 1 1 1 13 Antioxidant 3.5 3.5 3.5 3.5 14 Protective wax 2 2 2 2 15 Sulfur OT-20 2.2 2.2 2.2 2.2 16 Accelerator 1 1 1 1 17 Remarks Masterbatch wet method Masterbatch dry method Masterbatch dry method Masterbatch wet method

[0046] Example 2: Preparation of sidewall rubber from various formulation compositions

[0047] The method for preparing the sidewall rubber of the present invention specifically comprises the following steps:

[0048] (1) Weighing components: Weigh the components for preparing the above-mentioned low rolling resistance early wax spray sidewall rubber composition according to the component ratio;

[0049] (2) preparing a masterbatch: adding natural rubber, white carbon black, silane coupling agent, antioxidant 4020, zinc oxide, stearic acid, antioxidant RD and tackifying resin into an internal mixer for wet mixing to prepare a masterbatch;

[0050] (3) One-stage mixing: add masterbatch, butadiene rubber, carbon black and protective wax into a GK400 internal mixer, adjust the speed of the GK400 internal mixer to 55 rpm; press the top bolt and mix for 30 seconds, raise the top bolt, press the top bolt and mix for 50 seconds, raise the top bolt, press the top bolt and mix for 45 seconds, open the discharge door to discharge the rubber; control the discharge temperature at 155-160°C; open the mixer to unload the sheets, cool and stack;

[0051] (4) Final compound: Add the first-stage masterbatch, insoluble sulfur, and accelerator into the GK255 internal mixer. Adjust the rotation speed of the GK255 internal mixer to 20 revolutions per minute; lower the upper ram for kneading for 30 seconds, raise the upper ram for cleaning, lower the upper ram for kneading for 30 seconds, raise the upper ram, lower the upper ram for kneading for 20 seconds, raise the upper ram, lower the upper ram for kneading for 20 seconds, raise the upper ram, and open the discharge door to discharge the rubber; control the discharge temperature at 95 - 105 °C; roll the rubber on a two-roll mill, cool it, and stack it.

[0052] It should be noted that Comparative Example 1 and Comparative Example 2 were also prepared using the above-mentioned method for preparing the sidewall rubber of the present invention; however, in step (2), conventional dry mixing was used to replace wet mixing, and the mixing time, temperature control, and other experimental conditions in each stage of the dry mixing process were the same as those of the dry mixing experiment.

[0053] Example Three: Performance Test

[0054] The sidewall rubber prepared from the above-mentioned examples and comparative example formulations was tested, and the test results are as follows:

[0055] Table 2 Physical Property Test Results

[0056] Formula Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Hardness / A 53 54 59 49 Tensile strength / Mpa 22.3 21.7 22.5 24.7 Elongation at break / % 592 552 501 663 100% modulus / Mpa 1.7 1.4 2.0 1.2 300% modulus / Mpa 7.2 5.9 7.8 5.6 TanDelta @ 60℃ 0.081 0.129 0.117 0.095 Flexing number 3 million times 3 million times 3 million times 3 million times Crack grade 0 0 3 0 72h static ozone aging, grade 0 0 0 0

[0057] Remarks: The static ozone aging conditions are: concentration 50 pphm, temperature 40 °C, elongation 20%; in the crack grade, "Grade 3" means 0.5 mm < crack width ≤ 1.0 mm.

[0058] Table 3 Blooming Thickness Test Results

[0059] Formula Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Blooming thickness test 15 days 0.6μm 2.1μm 0.7μm 2.3μm 30 days 2.0μm 3.8μm 2.5μm 4.2μm 60 days 2.8μm 5.0μm 3.2μm 5.3μm

[0060] Remarks: The blooming wax film thickness was tested by the dissolution method; the storage environment of the finished tire is at a temperature of 35 - 40 °C and a humidity of 60 - 85%.

[0061] Comparative Example 1 is a normal low rolling resistance sidewall formula, and its physical properties and flex fatigue both meet the design requirements, but TanDelta@60 °C is relatively high, and the wax film thickness is also large; Comparative Example 2 cancels the environmentally friendly aromatic oil on the basis of Comparative Example 1, the wax film thickness decreases, but the hardness increases, and the flex fatigue does not meet the requirements; Comparative Example 3 uses a liquid-phase mixed masterbatch, adds environmentally friendly aromatic oil compared with Example 1, and its physical properties and flex fatigue both meet the design requirements, but the wax film thickness is large.

[0062] Prepare the tires of Example 1 and Comparative Example 1, and compare the appearance observation results of the 30-day finished tires. Figure 1 The appearance of the tire of Example 1 is shown, and no blooming or whitening is seen. Figure 2 The appearance of the tire of Comparative Example 1 is shown, and the blooming and whitening phenomenon of the tire is serious, indicating that Example 1 can significantly improve the blooming and whitening phenomenon of the tire appearance.

[0063] The above are only the preferred embodiments of the present invention and are 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 within the protection scope of the present invention.

Claims

1. A sidewall rubber composition with low rolling resistance and early wax spraying, characterized in that, By weight parts, it consists of the following components: 50 - 100 parts of natural rubber, 50 - 55 parts of cis-butadiene rubber, 30 - 100 parts of white carbon black, 3 - 10 parts of silane coupling agent, 3.5 parts of antioxidant 4020, 3.5 parts of zinc oxide, 2.5 parts of stearic acid, 1 part of antioxidant RD, 3 parts of tackifying resin, 15 - 30 parts of carbon black, 2.2 parts of insoluble sulfur, 0.8 - 1.5 parts of accelerator, 1.5 - 2.5 parts of protective wax; The carbon black is selected from N550 carbon black or N660 carbon black; Among them, the cis-butadiene rubber is rare-earth cis-butadiene rubber CB24; A method for preparing a sidewall rubber using the sidewall rubber composition, comprising the following steps: Component weighing: Weigh each component for preparing the sidewall rubber composition with low rolling resistance and early wax spraying according to the component ratio; Masterbatch preparation: Take natural rubber, white carbon black, silane coupling agent, antioxidant 4020, zinc oxide, stearic acid, antioxidant RD and tackifying resin and add them to an internal mixer for wet mixing to prepare a masterbatch; First-stage mixed rubber: Add the masterbatch, cis-butadiene rubber, carbon black and protective wax to an internal mixer, press the top plug and mix for 30 seconds, raise the top plug, press the top plug and mix for 50 seconds, raise the top plug, press the top plug and mix for 45 seconds, open the discharge door to discharge the rubber; Sheet down on a two-roll mill, cool and stack; Final-stage mixed rubber: Add the first-stage mixed rubber, insoluble sulfur and accelerator to an internal mixer, press the top plug and mix for 30 seconds, raise the top plug to clean, press the top plug and mix for 30 seconds, raise the top plug, press the top plug and mix for 20 seconds, raise the top plug, press the top plug and mix for 20 seconds, raise the top plug, open the discharge door to discharge the rubber; Sheet down on a two-roll mill, cool and stack.

2. The sidewall rubber composition with low rolling resistance and early wax spraying according to claim 1, wherein 50 parts of natural rubber, 50 parts of rare-earth cis-butadiene rubber CB24, 30 parts of white carbon black, 3 parts of silane coupling agent, 3.5 parts of antioxidant 4020, 3.5 parts of zinc oxide, 2.5 parts of stearic acid, 1 part of antioxidant RD, 3 parts of tackifying resin, 15 parts of carbon black, 2.2 parts of insoluble sulfur, 1 part of accelerator, 2 parts of protective wax.

3. The sidewall rubber composition with low rolling resistance and early wax spraying according to claim 1, characterized in that The white carbon black is selected as 200MP.

4. The sidewall rubber composition with low rolling resistance and early wax spraying according to claim 1, characterized in that, The accelerator is selected from sulfenamide accelerators.

5. The sidewall rubber composition with low rolling resistance and early wax spraying according to claim 1, characterized in that, During the first-stage mixed rubber process, the discharge temperature is controlled at 155 - 160 °C; during the final-stage mixed rubber process, the discharge temperature is controlled at 95 - 105 °C.

6. A sidewall rubber compound with low rolling resistance and early wax spraying, characterized in that, It is made of the sidewall rubber composition with low rolling resistance and early wax spraying according to any one of claims 1 - 5.

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