KR20240000968A - Side wall rubber composition and tire manufactured using the same - Google Patents

Abstract

The present invention relates to a rubber composition for tire sidewalls, and specifically, replaces part or all of natural rubber with hydrogenated styrene-butadiene rubber (Hydrogenated SBR, H-SBR) to provide not only excellent tensile strength, fatigue stiffness, and low fuel efficiency, but also particularly fatigue resistance. This is a technology that provides a rubber composition for tire sidewalls with improved chemical resistance.

Description

Side wall rubber composition and tire manufactured using the same}

The present invention relates to a rubber composition for tire sidewalls, and more specifically, to hydrogenated styrene-butadiene rubber (Hydrogenated), a new synthetic elastomer that can improve aging resistance while maintaining green strength by replacing or adding natural rubber to the sidewall. This is about compound development using SBR).

In the tire industry, styrene-butadiene rubber is used to supplement the characteristics of natural rubber or replace it with superior physical properties. However, the rubber composition used in the tire sidewall has the characteristic of reducing tire deformation by increasing rigidity for lightweight and low fuel consumption while maintaining reinforcement for durability. To this end, the rubber composition is mainly based on natural rubber and butadiene rubber. Do it as In the case of natural rubber, there is some variation in physical properties depending on the place of origin, cultivation climate, etc., and such variation at the raw material stage can ultimately lead to variation in physical properties and quality problems of tires. Additionally, double bonds in natural rubber molecules are vulnerable to oxygen and ozone resistance, so additional chemicals must be added to overcome this, but the elution of wax components causes other problems related to long-term durability and quality. In addition, as the use of natural rubber is gradually decreasing in line with recent sustainable development trends, the need for an elastomer for sidewalls to replace it is increasing, so an invention for this is needed. Recently, research has been actively conducted on replacing natural rubber, such as synthetic cis 1,4-polyisoprene rubber, but additional verification is required before commercialization to replace natural rubber in the side wall portion, and therefore, in order to provide solutions to the problems listed above. In the present invention, hydrogenated styrene-butadiene rubber (hydrogenated SBR, hereinafter referred to as H-SBR), which is hydrogenated at least 90 parts by weight based on 100 parts by weight of butadiene unit of existing SBR rubber, is intended to be applied to a rubber composition for side walls.

H-SBR develops a unique high pattern viscosity during the hydrogenation process, which has the advantage of complementing the green strength of the natural rubber of the side wall. In addition, hydrogenated H-SBR has enhanced oxygen resistance, which strengthens chemical resistance that can be caused by high deformation and/or chain scission in high temperature areas, thereby achieving the high level required for side walls. Aging resistance can be satisfied.

Japanese Patent Publication No. 2015-562972 and Japanese Patent Publication No. 6,627,512 mention that H-SBR can be used in the side wall part, but specifically, due to the wear resistance of H-SBR, it has abrasion resistance and low rolling resistance (LRR). : Low Rolling Resistance) This is different from the purpose of this patent as it concerns the application of H-SBR to overall truck, bus, studless, all-season, and summer tire treads for the purpose of improving performance. U.S. Patent Publication No. 2017-0240731 also mentions sidewall parts, but this is a typical reference in patents on rubber compositions, and the patent also covers the invention of a compound composition for tire treads to improve LRR and wear and tear characteristics. You can confirm that it is about this.

The purpose of the present invention is to provide a sidewall rubber composition using synthetic elastomer with excellent aging resistance and low fuel efficiency. Specifically, H-SBR is applied to the rubber composition for tire sidewall to partially or completely replace natural rubber, thereby providing excellent performance. The purpose is to provide a rubber composition for tire sidewalls with improved tensile strength, fatigue stiffness, low fuel efficiency, and especially improved aging resistance.

The rubber composition for a tire sidewall according to the present invention is characterized by containing hydrogenated styrene-butadiene rubber (H-SBR) as a raw rubber.

The raw rubber may be comprised of 0 to 40 parts by weight of natural rubber, 20 to 70 parts by weight of hydrogenated styrene-butadiene rubber (H-SBR), and 30 to 60 parts by weight of butadiene rubber, based on the total amount of raw rubber.

The hydrogenated styrene-butadiene rubber (H-SBR) may have a vinyl content in butadiene of 1% by weight or less.

The rubber composition for the tire sidewall may contain 30 to 60 parts by weight of at least one type selected from carbon and recycled carbon as a reinforcing filler, based on 100 parts by weight of raw rubber.

The rubber composition for tire sidewall of the present invention replaces natural rubber in part or entirely by applying H-SBR, which has excellent aging resistance and low fuel efficiency, and has excellent tensile strength, fatigue stiffness, and low fuel efficiency, as well as especially improved aging resistance. It can be used as a rubber composition.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement it. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

The rubber composition for a tire sidewall according to the present invention is characterized by containing hydrogenated styrene-butadiene rubber (H-SBR) as a raw rubber.

In the case of hydrogenated styrene-butadiene rubber, polyethylene crystalline is formed during the hydrogenation process, which results in a high raw MV (rubber raw material pattern viscosity), so it can supplement rigidity when used as an alternative to natural rubber in the sidewall composition. In addition, due to the enhanced oxygen resistance, the aging process is reduced by slowing down the elution of wax or resin that may result from high deformation and/or chain scission in high temperature areas, resulting in mechanochemical derived aging. (Mechanochemical-induced aging) may exhibit advantageous properties. In addition, in the case of H-SBR, it participates only in a very small part or does not participate in cross-linking with sulfur and exists in a dispersed form in the rubber composition, showing an improvement in rolling resistance due to an increase in the ratio of rubber in the composition, so it is used in the sidewall. Even when applied, it can have an effective rolling resistance improvement effect.

Specifically, the raw rubber may be comprised of 0 to 40 parts by weight of natural rubber, 20 to 70 parts by weight of hydrogenated styrene-butadiene rubber, and 30 to 60 parts by weight of butadiene rubber, based on the total amount of raw rubber.

In order to solve the problem of reduced ozone resistance that generally occurs when the content of natural rubber is more than 60 parts by weight or the content of butadiene rubber is less than 30 parts by weight, this problem was overcome by partially or entirely replacing H-SBR. In addition, the problems of low fuel efficiency and processability, which decrease in proportion to the content of butadiene rubber, were overcome by using a mixture of H-SBR, and the tensile strength, fatigue stiffness, and aging resistance were all improved. The H-SBR has a double bond content in the rubber chain of 0 to 2% by weight through hydrogenation, which is extremely small compared to general SBR, preferably 1.5% or less, and more preferably 0.3 to 0.7%.

Since the hydrogenation rate of the hydrogenated styrene-butadiene rubber is low, more double bonds can participate in the crosslinking reaction when the number exceeds 2% by weight, which may affect the crosslinking system and cause adverse effects on mechanical and viscoelastic properties. there is.

In addition, the weight average molecular weight (Mw) of the H-SBR may be 100,000 to 500,000 g/mol, preferably 200,000 to 400,000 g/mol. By satisfying this numerical range, excellent processability can be achieved.

Furthermore, the H-SBR has a glass transition temperature of -40 ℃ to -20 ℃, preferably -40 ℃ to -30 ℃, and the glass transition temperature is -70 ℃ to -55 ℃. In contrast, since it has a high glass transition temperature, it can contribute to improving rolling resistance due to the polymer.

In addition, unlike the structural characteristics of general styrene-butadiene rubber, the H-SBR may have a vinyl content of 1% by weight or less, preferably 0.1% by weight to 0.7% by weight. The H-SBR can improve the fatigue rigidity and durability of the tire by reducing the double bond of the vinyl group in styrene-butadiene through hydrogenation. Generally, in styrene-butadiene rubber containing H-SBR, as the vinyl content in butadiene decreases, the pattern viscosity increases, which is disadvantageous in terms of processability. However, when styrene-butadiene rubber with a high vinyl content is hydrogenated, the vinyl content decreases by 1 weight. Even if it is less than %, it has the effect of lowering the pattern viscosity. The hydrogenation reaction for styrene-butadiene rubber can be performed according to generally known techniques, and the vinyl content in butadiene of the styrene-butadiene rubber before the hydrogenation reaction is preferably 30 to 50% by weight. If the vinyl content in butadiene of the styrene-butadiene rubber before the hydrogenation reaction is less than 30% by weight, the pattern viscosity after hydrogenation is not sufficiently lowered, and if it exceeds 50% by weight, the vinyl content after hydrogenation exceeds 1% by weight, resulting in The effect of increasing the fatigue stiffness and durability of the tire is reduced.

The carbon black, which is a reinforcing filler, may have a specific surface area of 100 to 400 m2/g, an iodine adsorption amount of 30 to 41 mg/g, and a DBP oil absorption amount of 85 to 97 cc/100 g measured using BET. It can be used in an amount of 20 to 80 parts by weight, and more preferably 30 to 60 parts by weight, based on 100 parts by weight of the raw rubber. If the carbon black is less than 30 parts by weight, the hardness and modulus are low, resulting in disadvantageous handling performance, reduced fatigue performance, and reduced machinability, and if it exceeds 60 parts by weight, rotational resistance performance may be reduced. Meanwhile, recycled carbon may be used as the carbon black.

Of course, in addition to the compositions mentioned above, the tire sidewall rubber composition may include various additives such as zinc oxide, stearic acid, coupling agents, or processing aids used in conventional sidewall rubber compositions, selected as needed. Therefore, the rubber composition used in the present invention can use commonly added compounding agents, such as vulcanizing agents, vulcanizing accelerators, anti-aging agents, etc., which are described in detail below, but are not limited thereto, according to common knowledge in the field. It is self-evident to those who have.

First, as other additives, sulfur-based vulcanizing agents, organic peroxides, resin vulcanizing agents, and metal oxides such as magnesium oxide can be used. Specifically, the sulfur-based vulcanizing agent includes inorganic vulcanizing agents such as powdered sulfur (S), insoluble sulfur (S), precipitated sulfur (S), and colloidal sulfur, and tetramethylthiuram disulfide (TMTD). Organic curing agents such as tetraethyltriuram disulfide (TETD) and dithiodimorpholine can be used.

The vulcanizing agent is preferably included in an amount of 0.5 to 2.5 parts by weight based on 100 parts by weight of the raw rubber in order to achieve an appropriate vulcanization effect and makes the raw rubber less sensitive to heat and chemically stable.

The organic peroxides include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, and methyl ethyl. Methylethylketone peroxide, Cumene hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (2,5-dimethyl-2,5-di(t) -butylperoxy)hexane), 2,5-dimethyl-2,5-di(benzoylperox)hexane), 1,3-bis(t-butylperoxy) Propyl) benzene (1,3-bis(t-butylperoxypropyl)benzene), di-t-butylperoxy-diisopropyl benzene, t-butylperoxy benzene ), 2,4-dichlorobenzoyl peroxide, 1,1-dibutylperoxy-3,3,5-trimethylsiloxane ), n-butyl-4,4-di-t-butylperoxyvalate (4,4-di-tbutylperoxyvalate), and combinations thereof.

The resin vulcanizing agent may be an alkyl phenol resin, etc., and other materials may be used without particular limitation as long as they are used in the relevant technical field as needed.

The vulcanization accelerator refers to an accelerator that accelerates the vulcanization speed or delays the action in the initial vulcanization stage. In order to maximize productivity and rubber properties by accelerating the vulcanization speed, it is added to 100 parts by weight of the raw material rubber. It may be included in 0.5 to 5 parts by weight.

The vulcanization accelerators include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based, aldehyde-ammonia-based, imidazoline-based, xanthate-based and these. Any one selected from the group consisting of combinations may be used.

The vulcanization accelerator is a compounding agent used in combination with the vulcanization accelerator to completely enhance its accelerating effect. Any one selected from the group consisting of inorganic vulcanization accelerator, organic vulcanization accelerator, and combinations thereof may be used. .

The inorganic vulcanization accelerator may be any one selected from the group consisting of zinc oxide (ZnO), zinc carbonate (ZnCO3), magnesium oxide (MgO), lead oxide (PbO), potassium hydroxide (KOH), and combinations thereof. there is. The organic vulcanization accelerator aids include stearic acid, zinc stearate, palmitic acid, linoleic acid, oleic acid, lauric acid, Any one selected from the group consisting of dibutyl ammonium oleate, their derivatives, and combinations thereof may be used.

In order to function as an appropriate vulcanization accelerator, the vulcanization accelerator may be included in an amount of 1.5 to 8 parts by weight based on 100 parts by weight of the raw rubber, and when the zinc oxide and the stearic acid are used together, the vulcanization accelerator is used in an amount of 1 to 5 parts by weight. parts and 0.5 to 3 parts by weight of stearic acid.

The rubber composition for tire sidewall according to the present invention has excellent processability, so it does not need to contain a softener, but an additional softener can be added as needed.

The softener is an additive added to reduce the hardness of the vulcanized rubber in order to provide plasticity to the rubber and facilitate processing. It is any one selected from the group consisting of process oil, vegetable oil, and combinations thereof. It can be used without any particular restrictions as long as it is used in the relevant technical field.

The processing oil may be any one selected from the group consisting of paraffin-based processing oil, naphthenic processing oil, aromatic processing oil, and combinations thereof.

However, with the recent increase in environmental awareness, it is known that the content of polycyclic aromatic hydrocarbons (PAHs) in the aromatic process oil is more than 3% by weight and is highly likely to cause cancer, so it is used as a softener. The processing oil has a total content of PAHs of 3% by weight or less, a kinematic viscosity of 95°C or more (210°F SUS), an aromatic component in the softener of 15 to 25% by weight, and a naphthenic component of 27 to 27% by weight relative to the entire processed oil. It is preferable to use 37% by weight and 38 to 58% by weight of paraffinic component.

When the rubber composition for tire sidewall according to the present invention contains the above-described processing oil, the low-temperature characteristics and fuel efficiency performance of the tire sidewall manufactured using the same are improved, and it also has advantageous properties against environmental factors such as the cancer-causing potential of PAHs. has

The above vegetable oils include castor oil, cottonseed oil, linseed oil, canola oil, soybean oil, palm oil, palm oil, peanut oil, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, and camellia oil. , jojoba oil, macadamia nut oil, safflower oil, tung oil, and combinations thereof can be used.

In order to improve the processability of the raw rubber, the softener may be included in an amount of 0 to 50 parts by weight, or 20 to 40 parts by weight, based on 100 parts by weight of the raw rubber.

The anti-aging agent is an additive used to stop the chain reaction in which tires are automatically oxidized by oxygen. As the anti-aging agent, any one selected from the group consisting of amine-based, phenol-based, imidazole-based, carbamic acid metal salts, and combinations thereof may be added.

The anti-aging agent includes N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine (N-(1,3-Dimethylbutyl)-N-phenyl-phenyl-phenylenediamine, 6PPD), N-phenyl-n -Isopropyl-p-phenylenediamine (N-phenyl-n-isopropyl-p-phenylenediamine, 3PPD) and poly (2,2,4-trimethyl-1,2-dihydroquinoline (Poly (2,2,4 -trimethyl-1,2-dihydroquinoline (RD) and combinations thereof may be preferably used.

Considering the conditions that the anti-aging agent must have a high solubility in rubber, low volatility, inert to rubber, and not inhibit vulcanization in addition to anti-aging effect, the ratio of the anti-aging agent is 0 per 100 parts by weight of the raw material rubber. It may be included in an amount of from 10 to 10 parts by weight.

The present invention also provides a tire manufactured using the above-described tire sidewall rubber composition.

The tires may be passenger car tires, racing tires, airplane tires, agricultural machinery tires, off-the-road tires, truck tires, or bus tires. Additionally, the tire may be a radial tire or a bias tire.

Hereinafter, the present invention will be explained by the following examples and comparative examples. However, these are examples of the present invention and the scope of the present invention is not limited by these.

[Manufacturing example] Preparation of rubber composition

Rubber compositions for tire sidewalls according to Examples and Comparative Examples were prepared using the compositions shown in Table 1 below. The manufacturing of the rubber composition followed the manufacturing method of a conventional rubber composition for sidewalls.

(Unit: parts by weight) compounding agent Comparative Example 1 Comparative example 2 Example 1 Example 2 Example 3 Example 4 Example 5 natural rubber 40 30 S-SBR ¹⁾ 40 H-SBR ²⁾ 40 50 60 60 40 BR ³⁾ 60 60 60 50 40 40 40 Carbon black ⁴⁾ 50 50 50 45 50 50 50 Resin ⁵⁾ 4 4 4 2 0 0 4 Sulfur ⁶⁾ 5 5 5 5 5 4 5 Accelerator ⁷⁾ 3 3 3 3 3 3 3 Anti-river agent One One One One One One One

1) S-SBR: Solution polymerization styrene-butadiene rubber produced by a batch method with a styrene content of 25 parts by weight, a vinyl content in butadiene of 40 parts by weight, a pattern viscosity of 70, and a Tg of -30°C.

2) H-SBR: Hydrogenated styrene-butadiene rubber synthesized with a molecular weight of approximately 400,000, a vinyl content of 0.4 parts by weight, and a glass transition temperature of -34°C.

3) BR: High cis Nd-BR

4) Carbon black: GPF

5) Resin

6) Sulfur: powdered sulfur

7) Vulcanization accelerator: TBBS

[Experimental Example] Physical properties of the manufactured rubber composition

For the rubber specimens prepared in the above examples and comparative examples, pattern viscosity, hardness, low elongation modulus, viscoelasticity, etc. were measured in accordance with ASTM regulations, and the results are shown in Table 2 below.

division Comparative Example 1 Comparative example 2 Example 1 Example 2 Example 3 Example 4 Example 5 Hardness (Shore A) 75 58 73 65 69 67 68 50% modulus (Mpa) 46 37 44 42 41 39 40 Elongation rate (%) 97 102 110 112 120 124 107 Rebound at 100℃ 48.9% 42.3% 52.3% 54.8% 53.8% 51.2% 47.0% tensile strength 103 108 112 118 118 124 105 Fatigue resistance (Index) 100 78 103 104 94 92 110 tanδ at 100℃ 0.037 0.078 0.034 0.035 0.040 0.042 0.041 Low heat generation (Index) 100 54 102 104 99 94 97

- Hardness was measured according to DIN53505.

- Modulus and elongation/tensile strength were measured according to ISO37 and ASTM D412 standards, and elongation refers to the elongation at break, and was measured by expressing the strain value as a % until the test piece breaks in a tensile tester.

- Viscoelasticity was measured using an ARES tester by performing a temperature sweep from -80 ℃ to 100 ℃ under the conditions of 10 Hz, static strain 5%, and dynamic strain 0.5%.

- Rebound: Zwick, 100℃

- Fatigue resistance was conducted using the ASTM method and measured under 120% extension.

Important physical properties for natural rubber (high cis 1,4-poly butadiene) based tire sidewall rubber compositions are considered herein as rebound (100 °C) and tan delta (100 °C), which are related to rolling resistance. It is a son of man. It can be inferred that the higher the rebound value and the lower the tan delta, the more suitable it is as a sidewall composition. As can be seen in the examples, it can be seen that when hydrogenated styrene-butadiene rubber is used, tan delta performance, which indicates rolling resistance characteristics, and rebound characteristics are improved. In addition to hardness and low elongation modulus. Fatigue resistance and heat resistance were confirmed to have effects similar to those of the comparative example.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims are also possible. falls within the scope of rights.

Claims (4)

As raw rubber,
A rubber composition for a tire sidewall, comprising hydrogenated styrene-butadiene rubber (H-SBR).
According to paragraph 1,
The raw rubber is a tire sidewall rubber, characterized in that it consists of 0 to 40 parts by weight of natural rubber, 20 to 70 parts by weight of hydrogenated styrene-butadiene rubber (H-SBR), and 30 to 60 parts by weight of butadiene rubber, based on the total amount of raw rubber. Composition.
According to paragraph 1,
The hydrogenated styrene-butadiene rubber (H-SBR) is a rubber composition for tire sidewalls, characterized in that the vinyl content in butadiene is 1% by weight or less.
According to paragraph 1,
A rubber composition for a tire sidewall, comprising 30 to 60 parts by weight of at least one selected from carbon and recycled carbon as a reinforcing filler, based on 100 parts by weight of raw rubber.