High-ozone-aging-resistance rubber composition for tire sidewall and preparation method of high-ozone-aging-resistance rubber composition

Abstract

The invention relates to the field of rubber, and particularly discloses a rubber composition for a tire sidewall with high ozone aging resistance and a preparation method of the rubber composition, the rubber composition takes natural rubber and butadiene rubber as main raw materials, takes carbon black as a reinforcing agent, and is added with a vulcanizing agent, an accelerant, an anti-aging agent, other auxiliaries and the like. The rubber composition is characterized by being prepared from the following raw materials in parts by weight: 40.0 to 60.0 parts of natural rubber, 40.0 to 60.0 parts of butadiene rubber, 40.0 to 60.0 parts of carbon black, 2.0 to 5.0 parts of zinc oxide, 0.5 to 3.0 parts of stearic acid, 1.0 to 3.0 parts of vulcanizing agent, 0.5 to 2.0 parts of accelerant, 4.0 to 8.0 parts of oil and 1.0 to 3.0 parts of protective wax. The composition is used in the tire sidewall, has the characteristic of good comprehensive performance, and shortens the vulcanization time on the premise of keeping better scorching safety; the flexural performance is improved; particularly, the novel protective wax has excellent ozone aging resistance and good ozone protection effect. The preparation method can be completed by a common rubber processing technology on the basis of synthesizing the novel protective wax, and the processability of the novel protective wax is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of rubber, and particularly relates to a rubber composition for tire sidewalls with high ozone aging resistance and a preparation method thereof. Technical Background

[0002] During the processing, storage, and use of rubber products, especially during dynamic use, they are "attacked" by oxygen and ozone in the air, and are also affected by a combination of factors such as light, heat, radiation, mechanical force, and other chemical factors, resulting in a series of aging phenomena such as stickiness, hardening, embrittlement, or cracking of the rubber products.

[0003] Rubber protective wax is a physical anti-aging agent used in the rubber industry. It is generally used in combination with chemical anti-aging agents and is an important component in the rubber product formula. As a physical anti-aging agent, rubber protective wax can form a dense film on the surface of the product to isolate ozone, prevent rubber products from aging due to contact with ozone, endow rubber products with ozone resistance, thereby protecting rubber products and extending their service life. Rubber protective wax is widely used in rubber products, especially suitable for unsaturated rubbers. The field with the largest application amount is the ozone aging resistance of the tread rubber and sidewall rubber of radial tires.

[0004] Rubber protective wax is usually selected from paraffin wax and microcrystalline wax with a suitable carbon number distribution and blended in a certain ratio. Ordinary paraffin wax is mainly composed of low molecular weight straight-chain alkanes and is prone to spraying at low temperatures; microcrystalline wax is mainly composed of high molecular weight branched-chain alkanes and is prone to spraying at high temperatures. The new type of protective wax is a special rubber protective wax product developed by selecting paraffin wax, microcrystalline wax, and various special additives. The Beijing Rubber Industry Research and Design Institute Co., Ltd. evaluated its performance in rubber practical formulations.

[0005] During the operation of the tire, the deformation and hysteresis loss of the tire sidewall are relatively large, which are important factors affecting the service life and rolling resistance of the tire. At present, most studies only focus on one aspect of improving fatigue resistance, reducing the heat generation of the sidewall, and improving the heat conduction of the sidewall. To improve the service life of the tire, it is necessary to start researching from the ozone resistance of the sidewall rubber.

[0006] This patent uses a newly developed rubber protective wax. Based on the conventional physical property tests of the wax product, it compares with the mainstream products at home and abroad, studies the performance of the rubber protective wax in the application formula of NR / BR tire sidewall rubber, and analyzes the performance characteristics of the new protective wax. Summary of the Invention

[0007] The object of the present invention is to provide a rubber composition for tire sidewalls with high ozone aging resistance. The rubber composition has good comprehensive performance when used in tire sidewalls. It can shorten the vulcanization time on the premise of good scorch safety; improve the flexing performance; especially has excellent ozone aging resistance, indicating that the new protective wax has good ozone protection effect and superior protection performance. Its preparation method is based on the synthesis of the new protective wax and can be completed by ordinary rubber processing techniques, and its processing performance is improved.

[0008] The technical solution adopted by the present invention is: a rubber composition for tire sidewalls with high ozone aging resistance, which is characterized by being made of the following raw materials in parts by weight: 40.0 - 60.0 parts of natural rubber, 40.0 - 60.0 parts of cis-butadiene rubber, 40.0 - 60.0 parts of carbon black, 2.0 - 5.0 parts of zinc oxide, 0.5 - 3.0 parts of stearic acid, 1.0 - 3.0 parts of vulcanizing agent, 0.5 - 2.0 parts of accelerator, 4.0 - 8.0 parts of oil, and 1.0 - 3.0 parts of protective wax.

[0009] Preferably, the high-performance rubber composition for tire sidewalls is characterized by preferably consisting of the following raw materials in parts by weight: 45.0 - 55.0 parts of natural rubber, 45.0 - 55.0 parts of cis-butadiene rubber, 45.0 - 55.0 parts of carbon black, 2.5 - 4.0 parts of zinc oxide, 0.5 - 2.5 parts of stearic acid, 1.0 - 2.0 parts of vulcanizing agent, 0.8 - 1.5 parts of accelerator, 5.0 - 7.0 parts of oil, and 1.0 - 1.5 parts of protective wax.

[0010] Among them, the protective wax is preferably a blended microcrystalline wax. The carbon peak value of the protective wax is at C31 - C33, the mass fraction content of non-normal paraffins is 35% - 40%, the kinematic viscosity (100 °C) is 5.0 mm 2 / s - 8.0 mm 2 / s, and the ash content ≤ 0.1%.

[0011] The beneficial effect of the present invention is that the rubber composition has good comprehensive performance in the sidewall rubber. It can shorten the vulcanization time on the premise of good scorch safety; improve the flexing performance; especially has excellent ozone aging resistance, indicating that the new protective wax has good ozone protection effect and superior protection performance. Its preparation method is based on the synthesis of the new protective wax and can be completed by ordinary rubber processing techniques, and its processing performance is improved. Specific Embodiments

[0012] The present invention will be described in detail below in conjunction with specific embodiments.

[0013] The rubber composition described in the present invention can be prepared according to the existing conventional techniques. The specific steps are as follows:

[0014] The first stage mixing process: It is carried out in a 1.57L internal mixer, with an initial temperature of 80°C and a rotational speed of 80 revolutions per minute.

[0015] Add raw rubber, lower the upper plug, and plasticize the rubber for 1.0 minute;

[0016] Lift the upper plug, add carbon black, stearic acid, zinc oxide, antioxidant, and protective wax, lower the upper plug, and mix for 3.0 minutes;

[0017] Lift the upper plug, load oil, and mix for 2.0 minutes;

[0018] When the temperature of the rubber compound reaches 160°C or the total time reaches 6 minutes, the rubber compound can be unloaded.

[0019] The second stage mixing process: It is carried out on a 6-inch open mill, with a roll gap of 1.5 mm and a roll temperature of 40 ± 5°C.

[0020] The rubber compound from the first stage mixing wraps around the slow roll;

[0021] Add sulfur and accelerator NS, make three 3 / 4 cutters on each side, and then roll up the mixed rubber and take it off the lower roll;

[0022] Adjust the roll gap to 0.8 mm, roll up the mixed rubber, add it alternately from each end, and thin pass it longitudinally six times;

[0023] Take off the sheet and press the rubber compound into a sheet with a thickness of 2 ± 0.5 mm.

[0024] The experimental data involved in the specific embodiments of the present invention are all carried out in accordance with the corresponding national or industrial standards. The following are the main instrument equipment and test conditions:

[0025] (1) Rubber mixing: The initial mixing is carried out in a 1.57L Bambury internal mixer at a temperature of 80°C and a rotor speed of 80 revolutions per minute; the final mixing is carried out on an XK-160 type open mill.

[0026] (2) Mooney viscosity and Mooney relaxation: The Mooney viscosity and Mooney relaxation of the rubber compound are measured using an M200E type Mooney viscometer from Beijing Youshen Electronic Instrument Factory in accordance with GB / T 1232.1-2000. The test temperature is 100°C and the Mooney relaxation time is 120 s.

[0027] (3) Mooney scorch: The Mooney scorch of the rubber compound is measured using an M200E type Mooney viscometer from Beijing Youshen Electronic Instrument Factory in accordance with European standard GB / T 1233-2008. The test temperature is 120°C.

[0028] (4) Vulcanization characteristics: The vulcanization characteristics of the mixed rubber are measured using a C2000E type rotorless vulcanizer from Beijing Youshen Electronic Instrument Factory in accordance with GB / T16584-1996. The test temperature is 160°C and the test time is 60 min.

[0029] (5) High strength performance: The tensile stress-strain performance of the rubber was tested using the T2000E electronic tensile testing machine of Beijing Youshen Electronic Instrument Factory in accordance with GB / T 528-2009, and the tear performance of the rubber compound was tested in accordance with GB / T 529-2008.

[0030] (6) Aging performance: The heat air aging test was carried out on the vulcanized rubber specimens in accordance with GB / T 3512-2001. The aging conditions were heat air aging at 100 °C for 48 h. Then, the tensile strength, elongation at break, and modulus at a specified elongation of the rubber compound after aging were measured according to the aforementioned method.

[0031] (7) Ozone aging performance: Tested using the UA-2074 ozone aging test machine of Youken Technology Co., Ltd. in accordance with GB / T 7762-2014.

[0032] (8) Others: For other tests on the various properties of raw rubber, compounded rubber, and vulcanized rubber in this work, they were all carried out in accordance with the relevant provisions of the corresponding national standards or industry standards.

[0033] The following further illustrates the purpose of the present invention in combination with embodiments, but does not limit the protection scope of the present invention. The scope of the present invention is set forth in the claims. It is shown that the rubber composition for tire sidewalls of the present invention has good comprehensive performance in use, can shorten the vulcanization time on the premise of better scorch safety, improve the flexing performance, and especially has excellent ozone aging resistance, indicating that the new protective wax has good ozone protection effect and superior protection performance. Its preparation method is based on the synthesis of the new protective wax and can be completed by ordinary rubber processing technology, and its processing performance is improved.

[0034] Examples

[0035] To confirm the reliability of the effects of the present invention, the performance indexes of the rubber composition for tire sidewalls involved in the present invention (the present invention) were compared with those of the currently used ordinary tire sidewall rubber (comparative example), and the results are as follows:

[0036] Table 1 Formulation table (unit: parts)

[0037] Raw materials Comparative example The present invention NR 45.0 45.0 BR9000 55.0 55.0 Carbon black N375 50.0 50.0 Microcrystalline wax 2.0 New type of protective wax 2.0 Zinc oxide 3.5 3.5 Stearic acid 2.0 2.0 Oil 5.0 5.0 Sulfur 1.5 1.5 Others 6.0 6.0

[0038] Table 2 Mooney viscosity and Mooney relaxation of compounded rubber

[0039] Item Comparative example The present invention <![CDATA[ML 1+4 , 100 °C]]> 49 47 Mooney relaxation <![CDATA[t 70 / s]]> 7 7 <![CDATA[t 80 / s]]> 10 10 Intercept k 46.9 44.9 Slope α -0.5 -0.6 Area A 800 625

[0040] The test results of the Mooney viscosity and Mooney relaxation of the compounded rubber are shown in Table 2. The relaxation area A of the present invention is lower than that of the comparative example, indicating that the processing performance of the present invention is better than that of the rubber used in the comparative example.

[0041] Table 3 Vulcanization characteristics and Mooney scorch of compounded rubber

[0042]

[0043] The vulcanization characteristics and Mooney scorch results of the rubber compound are shown in Table 3.

[0044] Table 4 Physical and mechanical properties of vulcanizates

[0045]

[0046]

[0047] Note: Vulcanization conditions: 151°C × 30 min.

[0048] The physical and mechanical properties of vulcanizates are shown in Table 4.

[0049] Table 5 Aging properties of vulcanizates

[0050] Item Comparative example The present invention Change rate of elongation at break after aging / % -38 -37 Change rate of tensile strength after aging / % -30 -30

[0051] Note: Vulcanization conditions: 151°C × 30 min, aging conditions: 100°C × 48 h.

[0052] The aging properties of vulcanizates are shown in Table 5. In the sidewall rubber, the levels of tensile strength and elongation at break after aging of the present invention are relatively...

[0053] The ozone aging resistance of vulcanizates is shown in the attached drawing description. Figure 1 After 24 h, 48 h, and 72 h of ozone aging, it can be clearly seen from the pictures that the ozone protection effect of the present invention is good. Attached drawing description

[0054] Figure 1 It is a graph of the ozone aging performance of vulcanizates. Under the ozone aging condition of 20% pre-stretch, adjust for 72 h without light and ozone, then adjust the ozone concentration to 50 pphm, and the test temperature is 50°C.

Claims

1. A rubber composition for tire sidewalls with high ozone aging resistance and its preparation method, characterized in that it is made of the following raw materials in parts by weight: natural rubber 40.0 - 60.0 parts, cis-butadiene rubber 40.0 - 60.0 parts, carbon black 40.0 - 60.0 parts, zinc oxide 2.0 - 5.0 parts, stearic acid 0.5 - 3.0 parts, vulcanizing agent 1.0 - 3.0 parts, accelerator 0.5 - 2.0 parts, oil 4.0 - 8.0 parts, protective wax 1.0 - 3.0 parts.

2. The rubber composition for tire sidewalls with high ozone aging resistance according to claim 1, characterized in that: the protective wax is preferably a blended microcrystalline wax, the carbon peak value of the protective wax is at C31 - C33, the mass fraction content of non-normal paraffins is 35% - 40%, the kinematic viscosity (100 °C) is 5.0 mm2 / s - 8.0 mm2 / s, and the ash content ≤ 0.1%.

3. The rubber composition according to claim 1, characterized in that: the composition has good comprehensive performance when used in tire sidewalls. It can shorten the vulcanization time on the premise of better scorch safety; improve the flexing performance; especially the new protective wax has excellent ozone aging resistance, indicating good ozone protection effect and superior protection performance. Its preparation method is based on the synthesis of the new protective wax and can be completed by ordinary rubber processing techniques, and its processing performance is improved.

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