KR20110072160A - Rubber composition for white sidewall and tire using the same - Google Patents

Abstract

PURPOSE: A rubber composition for white sidewall is provided to improve heat resistance and ozone resistance while avoiding the influence on processability and properties and to maintain high whiteness of a sidewall after aging. CONSTITUTION: A rubber composition for white sidewall comprises a phenolic antiaging agent represented by chemical formula 1 and rutile type titanium dioxide. In chemical formula 1, 2 < n < 50. The phenolic antiaging agent is used in the amount of 0.5-5 parts by weight and the rutile type titanium dioxide is used in the amount of 25-45 parts by weight, based on 100 parts by weight of a base rubber.

Description

Rubber composition for white sidewall and tire using the same

The present invention relates to a white sidewall rubber composition and a tire using the same, and more particularly, to a white side including a phenolic anti-aging agent and a rutile titanium dioxide, which can improve heat resistance and ozone resistance of a tire and improve visibility. A month rubber composition and a tire using the same.

In the case of the pneumatic tire, the tire can be classified into two types based on the sidewall of the tire, that is, a pneumatic tire using a black sidewall rubber composition and a pneumatic tire using a colored sidewall rubber composition. Generally, a black sidewall rubber composition is used.

In the case of colored sidewall rubber compositions, tires in which white is partially used in the sidewall are generalized, but tires in which white is used throughout the sidewall or in other colors are used for occasional events or promotions. Most of this is.

The white sidewall rubber composition generally uses calcium carbonate or clay instead of carbon black, which is used as a reinforcing agent, and uses titanium oxide as a white pigment to represent white color. In addition, butyl rubber with less double bonds, chlorinated isobutylene-isoprene copolymer rubber (Cl-IIR, brominated isobutylene-isoprene copolymer rubber (Br-IIR)), and ethylene propylene diene rubber for improved weatherability and ozone resistance monomer rubber (hereinafter EPDM rubber), butadiene rubber is used, and some natural rubber is used to improve the processability.

Commonly known problems of white sidewall rubber compositions include processability problems, inherent properties of the white sidewall rubber composition (lack of adhesion, low aging and ozone properties, low dispersion) and discoloration of the white sidewall rubber composition that occurs during use of tires. The problem of contamination by this is mentioned.

The main physical property of the white sidewall is the degree of whiteness, and the factor influencing the physical properties is titanium oxide, which is used as a white pigment, and titanium dioxide. Titanium dioxide is classified into three types, namely anatase, rutile and brookite, depending on the crystal structure. Conventionally, tires using the anatase type mainly use the disadvantages in terms of whiteness before and after aging, and thus have poor visual properties.

Other major physical properties include heat resistance and ozone resistance, and these properties are highly dependent on anti-aging agents. The butylated hydroxy toluene (BHT) used as an anti-aging agent has a low molecular weight of about 220, which is highly volatile and has a high volatile diffusion rate to the sidewall surface of the tire, which is very weak in terms of heat resistance and ozone resistance. Therefore, the anti-aging agent is denatured by ultraviolet rays in the air and heat of the tire itself while driving the vehicle, thereby contaminating the surface of the white sidewall and damaging its appearance.

The present invention is to overcome the problems of the prior art described above, one object of the present invention is to include a phenolic anti-aging agent and rutile titanium dioxide to improve the heat resistance and ozone resistance and to improve the white side It is to provide a monthly rubber composition.

Another object of the present invention is to provide a tire using the white sidewall rubber composition of the present invention.

One aspect of the present invention for solving the above problems is a white sidewall rubber composition comprising a lungol-based antioxidant and rutile titanium dioxide represented by the formula (1) below.

[Formula 1]

Wherein 2 <n <50.

Another aspect of the present invention relates to a tire using the composition.

According to the present invention, when the white sidewall rubber composition is applied to a tire including a waste aging antioxidant and rutile titanium dioxide, the white sidewall rubber composition improves the heat resistance and ozone resistance of the tire without affecting the processability and physical properties of the rubber composition. The high whiteness of the sidewalls can be maintained even after aging to improve visibility. As a result, the appearance of white through the side wall is maintained even while the car is driving, thereby providing a continuous aesthetic feeling to the user.

Hereinafter, the present invention will be described in more detail.

The white sidewall rubber composition of the present invention is characterized in that it comprises a phenolic antioxidant and rutile titanium dioxide represented by the following formula (1).

[Formula 1]

Wherein 2 <n <50.

One embodiment of the present invention relates to a white sidewall rubber composition which improves the heat resistance and ozone resistance of a tire and does not contaminate the surface of the sidewall even upon aging by ultraviolet rays or the like. To this end, the present invention adopts a phenolic antioxidant having a higher molecular weight and relatively low volatility than BHT, which is a conventionally used antioxidant, to maintain an anti-aging effect in the long term. The phenolic anti-aging agent contains 0.5 to 5 parts by weight with respect to 100 parts by weight of the raw material rubber, if the content is less than 0.5 parts by weight, the effect of the addition is insignificant, it is difficult to expect the heat resistance and ozone resistance effect, if it exceeds 5 parts by weight There may be a problem of lowering the mechanical properties of the blended rubber.

The phenolic anti-aging agent represented by Chemical Formula 1 is a product (Winstay®-L) commercially available from Eliokem Co., Ltd., for the butylation reaction of p-cresol and dicyclopentadiene. Synthesized by It is used in non-contaminated applications where heat resistance is required due to its high activity and very low volatility. The Winstay®-L has a specific gravity of at least 0.95, an average molecular weight of at least 600, a melting point of at least 100 ° C, and a primary glass transition temperature of at least 84 ° C.

In the present invention, a white pigment is used to maintain the whiteness of the sidewall of the tire and to improve visibility even after aging due to ultraviolet rays. Such a white pigment uses rutile titanium dioxide. Such rutile titanium dioxide includes 25 to 45 parts by weight with respect to 100 parts by weight of the raw material rubber, if the content is less than 25 parts by weight, the whiteness is low, if the content exceeds 45 parts by weight may have a problem of low rubber properties. . Titanium dioxide is roughly classified into rutile type which is relatively stable at high temperature, anatase type which is stable at low temperature, and brookite type which is stable at intermediate temperature, depending on its crystal structure. In the present invention, a rutile type having excellent refractive index and coloring power is used. Other usable white pigments include, but are not limited to, lithopone (ZnS + BaSO ₄ ), lead white (2PbCO ₃ · Pb (OH) ₂ ), and the like.

The raw material rubber usable in the present invention is not particularly limited to that which can be used in a general rubber composition for tires, but a low double bond content is selected in order to improve heat resistance and ozone resistance. Examples of such raw rubber include natural rubber or halogenated butyl rubber, EPDM rubber, butadiene rubber and the like. In the present invention, it may include 10 to 60 parts by weight of natural rubber, 10 to 40 parts by weight of chloro butyl rubber, and 10 to 35 parts by weight of EPDM rubber.

In addition, various reinforcing agents may be added to the white sidewall rubber composition of the present invention in order to improve the physical properties of the vulcanized rubber and the processability of the unvulcanized rubber. In the present invention, calcium carbonate or clay may be used as the white filler (reinforcing agent) for rubber, but is not necessarily limited thereto.

As the vulcanizing active agent usable in the present invention, zinc oxide and stearic acid may be used, and processing aids such as active agents such as waxes and amines to improve fluidity during processing may be included.

The vulcanizing agents usable in the present invention include, but are not limited to, sulfur, organic peroxides, magnesium oxide and the like.

Examples of the vulcanization accelerator usable in the present invention include ammonia, amine, guanidine, thiazole, thiuram, sulfamide, and the like. no. Usually, zincation is used in combination to complete the vulcanization promoting effect.

The white sidewall rubber composition of the present invention may further comprise all or some other components and additives typically used in rubber compositions for tires. For example, such other additives include plasticizers, ozone suppressors, vulcanization accelerators, extended oils, vulcanizers, emollients and the like.

White sidewall rubber compositions of the present invention may be prepared according to techniques known to those skilled in the art. For example, the rubber composition of the present invention is obtained by kneading using a kneader such as an open kneader such as a roll or a closed kneader such as a Banbury mixer, and can be vulcanized after molding to produce various rubber products. Do.

When the white sidewall rubber using the rubber composition is applied to the sidewall of the tire, the whiteness of the tire may be improved and the color of the exterior may be continuously maintained to increase visibility. These tires with improved visibility may be applied to passenger car radial (PCR), light truck radial (LTR), truck bus radial (TBR) and racing tires. The tire of the present invention can withstand aging due to ultraviolet rays while maintaining the properties required for the tire as it is, it is possible to continuously maintain the aesthetics due to its white appearance.

Hereinafter, the present invention will be described in more detail with reference to Examples, but these Examples are for illustrative purposes only and are not intended to limit the protection scope of the present invention.

Example 1

As shown in Table 1 below, by mixing Wingstay®-L, rutile titanium dioxide, calcium carbonate, zincation, stearic acid and wax in the raw material rubber according to the composition based on 100 parts by weight of the raw material rubber, After kneading in a Banbury mixer, further kneading with addition of sulfur and vulcanization accelerators produced a vulcanized rubber, ie a white sidewall rubber composition.

Comparative Example 1

Except for adding BHT in place of Wingstay®-L in the rubber composition of Example 1, and anatase type titanium dioxide instead of rutile titanium dioxide according to the blending composition as shown in Table 1 in the same manner as in Example 1 A white sidewall rubber composition was prepared.

Comparative Example 2

A white sidewall rubber composition was prepared according to the blending composition as described in Table 1 below in the same manner as in Example 1 except for adding anatase type titanium dioxide instead of rutile type titanium dioxide in the rubber composition of Example 1. .

Property evaluation method

Using the white sidewall rubber composition prepared in Example 1 and Comparative Examples 1 and 2 as a rubber specimen, the physical properties were evaluated by lab test as follows, and the results are shown in Table 2 below.

(1) Mooney Viscosity

① Pattern viscosity refers to the degree of viscosity that defines the processing conditions of rubber, and is the viscosity of unvulcanized rubber measured by a pattern viscometer. The viscometer uses a large rotor at 125 ° C., and measures 4 minutes after 1 minute of preheating and denotes ML1 + 4. (2) The phenomenon that processing into a rubber product becomes impossible due to the decrease of plasticity as the compounded rubber is vulcanized before the vulcanization process. It is called scorch or premature vulcanization. The unvulcanized rubber measured by the pattern viscometer The scorch time is called the monetary scorch time. This patterned scouring time records the viscosity at 1 minute intervals after heating to 125 ° C. in a small rotor, usually the time it takes to rise to 5 points per pattern at the lowest viscosity, indicating that the longer the scorch stability is improved.

(2) Vulcanization characteristics

Rheometer is a device that determines vulcanization characteristics by inserting unvulcanized rubber between the upper dies of a flat plate of a prescribed temperature and measuring various torque changes of the rubber by vibration. According to the present invention, the temperature of the plate is 160 ° C. and the cure time is the time until the maximum torque Tmax, the minimum torque Tmin and the torque change reach 90% of the total change Tmax-Tmin. t90) was measured. The smaller the vulcanization time, the faster the crosslinking rate.

(3) hardness and tensile properties

① Hardness represents the magnitude of resistance to deformation of the material, and Shore hardness tester is used to measure the repulsive force when the hammer and the like collide. ② Tensile property refers to 300% modulus (Mod), elongation (enlongation), tensile strength, etc., these properties were measured according to ASTM by using a universal testing machine (Intron). For the evaluation regarding heat resistance, these measurements were performed after aging (after aging) for 1 week at room temperature (before aging) and 100 ° C, respectively.

(4) Oxygen Bomb Test

In order to expedite the evaluation of heat resistance and ozone resistance, the rubber specimen was aging at 300 psi in an ozone concentration at 70 ° C. for 72 hours, and then hardness and tensile properties were measured.

After the test tire was manufactured using the white sidewall rubber composition and subjected to a real vehicle test in the Middle East, the test was performed in the same manner as in the ozone test, and the results are shown in Table 3 below.

When comparing the white sidewall rubber composition prepared in Example 1 with the white sidewall rubber composition prepared in Comparative Examples 1 and 2 as shown in Table 2, there was no significant change in basic physical properties. On the other hand, in comparison with the white sidewall rubber composition prepared in Comparative Example 1 in terms of ozone resistance performance compared to the white sidewall rubber composition prepared in Example 1, the numerical value of 300% modulus and elongation was significantly lower. In addition, elongation and tensile strength were also lower in the actual vehicle test conducted in the Middle East. As a result, when the white sidewall rubber composition contains Wingstay®-L having a high molecular weight as an anti-aging agent, it can be seen that heat resistance and ozone resistance are improved without affecting its basic physical properties.

Whiteness evaluation

The whiteness of the white sidewall rubber compositions prepared in Examples 1 and Comparative Examples 1 and 2 was measured using a Minolta spectrophotometer that satisfies the SCI / SCE standard and the like. At this time, by combining the chromaticity data of the white sidewall rubber composition of Comparative Example 1 containing a conventional anti-aging agent, the whiteness was indexed to 100 and displayed based on the numerical value. If the value is less than 100, the whiteness is poor, and if the whiteness is greater than 100, the whiteness is excellent. In order to confirm the maintenance of whiteness by aging, the whiteness of the white sidewall rubber composition before and after the actual vehicle evaluation in the Middle East was measured, respectively, and the results are shown in Table 4 below.

When comparing Example 1 and Comparative Examples 1 and 2 as shown in Table 4, the white sidewall rubber composition of Example 1 was superior to Comparative Examples 1 and 2 before and after the actual vehicle evaluation in the Middle East. Accordingly, it can be seen that the white sidewall rubber composition containing rutile titanium dioxide as a white pigment has better whiteness before and after aging than when anatase type titanium dioxide is included, thereby improving visibility.

Although the present invention has been described in detail with reference to preferred embodiments of the present invention, it will be apparent to those skilled in the art that the present invention may be variously changed or modified without departing from the spirit and scope of the present invention. Modifications and variations are also to be construed as being included in the protection scope of the present invention.

Claims (6)

A white sidewall rubber composition comprising a phenolic antioxidant and rutile titanium dioxide represented by the formula (1). [Formula 1]

Wherein 2 <n <50. The white sidewall rubber composition according to claim 1, wherein the waste aging antioxidant is 0.5 to 5 parts by weight based on 100 parts by weight of the raw material rubber, and the rutile titanium dioxide is 25 to 45 parts by weight. The white sidewall rubber composition according to claim 1, wherein the number average molecular weight of the phenolic anti-aging agent is 600 or more. The white sidewall rubber composition of claim 1, wherein the composition further comprises one or more additives selected from the group consisting of reinforcing agents, vulcanizing agents, processing aids, vulcanizing agents, and vulcanization accelerators. A tire comprising the white sidewall rubber composition of claim 1. The tire according to claim 5, wherein the tire is a passenger car, a light truck radial (LTR), a truck bus radial (TBR), or a racing tire.