Color rubber composition for tires and tires

Abstract

To suppress iridescence color tone, while maintaining ozone resistance.SOLUTION: A color rubber composition for tires according to the embodiment contains 0.2 to 20 pts.mass of a pigment other than black and white, 0.5 to 15 pts.mass of petroleum wax, and 10 to 150 pts.mass of a white filler with respect to 100 pts.mass of the rubber component, wherein the petroleum wax has a normal / iso (mass ratio) of 70 / 30 to 90 / 10. A carbon number distribution (mass%) of the iso component in the entire petroleum wax is 1.0% or less with 25 or less carbon atoms, 4.0 to 8.0% with 26 to 32 carbon atoms, 5.0 to 15.0% with 33 to 44 carbon atoms, and 1.0% or more with 45 or more carbon atoms. The carbon number distribution (mass%) of the normal components in the entire petroleum wax is 5.0 to 18.0% for 25 or less carbon atoms, 40.0 to 48.0% for 26 to 32 carbon atoms, 15.0 to 27.5% for carbons 33 to 44, and 2.0% or more for carbon number 45 or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a color rubber composition for tires and a tire using the same. [Background technology]

[0002] 2. Description of the Related Art Colored rubber may be provided on a side portion such as a sidewall of a tire for decoration purposes, and various proposals have been made (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-168616 A [Patent Document 2] JP 2002-301904 A [Patent Document 3] Japanese Patent Application Publication No. 7-228727 Summary of the Invention [Problem to be solved by the invention]

[0004] Rubber compositions used in tires exposed to the external environment are generally required to have ozone resistance. Ozone resistance can be improved by blending wax, and the wax can be precipitated on the rubber surface to make it less susceptible to ozone degradation. However, when wax is blended into colored rubber, the wax precipitated on the rubber surface can cause diffuse reflection of light, resulting in whitening.

[0005] In view of the above, an object of an embodiment of the present invention is to provide a color rubber composition for tires that maintains ozone resistance and is less susceptible to color change. [Means for solving the problem]

[0006] The color rubber composition for tires according to the embodiment of the present invention contains 0.2 to 20 parts by mass of a pigment other than black and white, 0.5 to 15 parts by mass of petroleum wax, and 10 to 150 parts by mass of a white filler, per 100 parts by mass of the rubber component. The petroleum wax has a normal / iso ratio of normal alkanes to isoalkanes of 70 / 30 to 90 / 10, and the content of isoalkanes having 25 or less carbon atoms in the entire petroleum wax is 1.0 mass% or less, the content of isoalkanes having 26 to 32 carbon atoms is 4.0 to 8.0 mass%, the content of isoalkanes having 33 to 44 carbon atoms is 5.0 to 15.0 mass%, the content of isoalkanes having 45 or more carbon atoms is 1.0 mass% or more, the content of normal alkanes having 25 or less carbon atoms is 5.0 to 18.0 mass%, the content of normal alkanes having 26 to 32 carbon atoms is 40.0 to 48.0 mass%, the content of normal alkanes having 33 to 44 carbon atoms is 15.0 to 27.5 mass%, and the content of normal alkanes having 45 or more carbon atoms is 2.0 mass% or more.

[0007] A tire according to an embodiment of the present invention contains the above-mentioned color rubber composition for tires. Effect of the Invention

[0008] According to an embodiment of the present invention, by blending the specific wax, it is possible to suppress color change while maintaining ozone resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The color rubber composition for tires according to the embodiment (hereinafter also referred to as the color rubber composition) contains a rubber component, a pigment other than black and white, petroleum wax, and a white filler.

[0010] The rubber component is not particularly limited, and various rubber components that are usually used in rubber compositions for tires can be used, for example, diene rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), and styrene butadiene rubber (SBR), non-diene rubbers such as butyl rubber and ethylene propylene diene rubber (EPDM), etc. Butyl rubber is a concept that includes butyl rubber (IIR) and halogenated butyl rubber (e.g., chlorinated butyl rubber (CIIR), brominated butyl rubber (BIIR), etc.). Any one of these rubbers may be used, or two or more may be used in combination.

[0011] In one embodiment, the rubber component may include a diene rubber and a butyl rubber, or may include a diene rubber, a butyl rubber, and an ethylene propylene diene rubber. The content of these rubbers in the rubber component is not particularly limited, but is preferably 20 to 60 parts by mass, more preferably 30 to 50 parts by mass, more preferably 20 to 60 parts by mass, more preferably 30 to 50 parts by mass, and more preferably 0 to 30 parts by mass, more preferably 5 to 20 parts by mass, of 100 parts by mass of the rubber component.

[0012] In one embodiment, the rubber component preferably contains natural rubber, butyl rubber, and ethylene propylene diene rubber. More preferably, 100 parts by mass of the rubber component contains 20 to 60 parts by mass of natural rubber, 20 to 60 parts by mass of butyl rubber, and 5 to 30 parts by mass of ethylene propylene diene rubber, and even more preferably, 100 parts by mass of the rubber component contains 30 to 50 parts by mass of natural rubber, 30 to 50 parts by mass of butyl rubber, and 10 to 20 parts by mass of ethylene propylene diene rubber. In addition to the natural rubber, butyl rubber, and ethylene propylene diene rubber, other diene rubbers or non-diene rubbers may be contained.

[0013] The pigment is a coloring agent used to make the color rubber composition according to the present embodiment have a color other than black and white, and a colored pigment other than white or black is used. Note that the white pigment is blended as a white filler, but is not included in the colored pigments referred to here. On the other hand, it is preferable not to blend a black pigment such as carbon black into the color rubber composition, since the color of the colored pigment is not displayed when the black pigment is added.

[0014] The colored pigment is not particularly limited, and examples thereof include pigments of various colors such as blue, red, yellow, and green. Specific examples thereof include inorganic pigments such as ultramarine, Prussian blue, red lead, iron oxide red, yellow lead, and zinc yellow, polycyclic pigments (e.g., phthalocyanine, anthraquinone, quinacridone, diketopyrrolopyrrole, perylene, etc.), azo pigments, lake pigments (e.g., basic dye lake, acid dye lake, etc.), and fluorescent pigments. These may be used alone or in combination of two or more.

[0015] When an organic pigment is blended, the pigment may be prepared in advance as a master batch together with the rubber component to improve dispersibility.

[0016] The content of the color pigment is 0.2 to 20 parts by mass, preferably 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass, and may be 2 to 8 parts by mass, based on 100 parts by mass of the rubber component.

[0017] Petroleum wax is a wax made of saturated hydrocarbons and contains normal alkanes (straight-chain paraffins) and isoalkanes (branched-chain paraffins). By blending petroleum wax, it precipitates on the rubber surface, forming a film that protects against ozone in the atmosphere and suppresses ozone degradation.

[0018] In this embodiment, the petroleum wax used satisfies the following conditions (1) to (3). (1) Normal / iso (mass ratio): 70 / 30~90 / 10 (2) Carbon number distribution of iso components in petroleum wax: Carbon number 25 or less: 1.0% by mass or less Carbon number 26~32: 4.0~8.0% by mass Carbon number 33~44: 5.0~15.0% by mass Carbon number 45 or more: 1.0% by mass or more (3) Carbon number distribution of normal components in petroleum wax: Carbon number 25 or less: 5.0~18.0% by mass Carbon number 26~32: 40.0~48.0% by mass Carbon number 33~44: 15.0~27.5% by mass Carbon number 45 or more: 2.0% by mass or more

[0019] Petroleum waxes that satisfy these conditions (1) to (3) can suppress color changes on the rubber surface while maintaining ozone resistance. The reason for this is thought to be that, although it is not intended to be limited thereto, the crystal size of the petroleum waxes when precipitated on the rubber surface is small, so that the rubber surface is less likely to diffusely reflect light and to discolor. In contrast, petroleum waxes that do not satisfy conditions (1) to (3) are likely to crystallize on the rubber surface, resulting in large crystal sizes, which is thought to cause the rubber surface to diffusely reflect light and to discolor.

[0020] The normal / iso ratio in condition (1) is the mass ratio of normal alkanes to isoalkanes contained in the petroleum wax, and is 70 / 30 or more and 90 / 10 or less. The normal / iso ratio is preferably 75 / 25 or more and 85 / 15 or less.

[0021] Conditions (2) and (3) are the mass ratios of each component when the entire petroleum wax is taken as 100 mass%. The content of isoalkanes having 25 or less carbon atoms is 1.0 mass% or less, more preferably 0.5 mass% or less. The content of isoalkanes having 26 to 32 carbon atoms is 4.0 to 8.0 mass%, more preferably 4.0 to 7.0 mass%. The content of isoalkanes having 33 to 44 carbon atoms is 5.0 to 15.0 mass%, more preferably 8.0 to 13.0 mass%. The content of isoalkanes having 45 or more carbon atoms is 1.0 mass% or more, more preferably 1.0 to 4.5 mass%.

[0022] The content of normal alkanes having 25 or less carbon atoms is 5.0 to 18.0% by mass, more preferably 8.0 to 13.0% by mass. The content of normal alkanes having 26 to 32 carbon atoms is 40.0 to 48.0% by mass, more preferably 42.0 to 46.0% by mass. The content of normal alkanes having 33 to 44 carbon atoms is 15.0 to 27.5% by mass, more preferably 17.0 to 25.0% by mass, and even more preferably 18.0 to 23.0% by mass. The content of normal alkanes having 45 or more carbon atoms is 2.0% by mass or more, more preferably 2.0 to 6.0% by mass.

[0023] The method for preparing a petroleum wax satisfying such conditions (1) to (3) is not particularly limited, and for example, the wax can be prepared by combining known methods such as reduced pressure distillation, solvent deoiling, sweating, and press deoiling to obtain fractions in which each component is concentrated, and then mixing the fractions to the above-mentioned blending ratio. For example, a petroleum wax satisfying conditions (1) to (3) may be prepared by separating various commercially available waxes through a column using gas chromatography (GC), separating and collecting wax components having specific carbon numbers, and combining and blending these wax components.

[0024] The normal / iso ratio and carbon number distribution of the petroleum wax can be measured by a known method using gas chromatography.

[0025] The content of the petroleum wax is 0.5 to 15 parts by mass, preferably 1 to 15 parts by mass, more preferably 3 to 12 parts by mass, and further preferably 5 to 10 parts by mass, based on 100 parts by mass of the rubber component.

[0026] The white filler is not particularly limited, and may include, for example, at least one selected from the group consisting of silica, clay, calcium carbonate, manganese oxide, titanium oxide, magnesium oxide, and zinc oxide.

[0027] The content of the white filler is 10 to 150 parts by mass, preferably 30 to 120 parts by mass, and more preferably 50 to 100 parts by mass, based on 100 parts by mass of the rubber component. In one embodiment, the rubber composition may contain 30 to 100 parts by mass (more preferably 50 to 90 parts by mass) of clay and 5 to 30 parts by mass (more preferably 10 to 25 parts by mass) of silica and / or titanium oxide based on 100 parts by mass of the rubber component. In the one embodiment, the rubber composition may further contain 0.1 to 5 parts by mass (more preferably 0.5 to 3 parts by mass) of magnesium oxide and 1 to 10 parts by mass (more preferably 2 to 8 parts by mass) of zinc oxide.

[0028] In addition to the above components, the color rubber composition according to the present embodiment may contain various additives that are generally used in rubber compositions for tires, such as stearic acid, a vulcanizing agent, and a vulcanization accelerator.

[0029] As the vulcanizing agent, sulfur is preferably used. The amount of the vulcanizing agent is not particularly limited, but is preferably 0.1 to 7 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0030] Examples of the vulcanization accelerator include various vulcanization accelerators such as sulfenamide-based, thiuram-based, thiazole-based, guanidine-based, and dithiocarbamate-based, and any one of them can be used alone or in combination of two or more. The amount of the vulcanization accelerator is not particularly limited, but is preferably 0.1 to 7 parts by mass, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the rubber component.

[0031] The color rubber composition according to the present embodiment can be prepared by kneading in a conventional manner using a commonly used mixer such as a Banbury mixer, kneader, or roll. For example, in the first mixing stage (non-pro kneading process), additives other than the vulcanizing agent and vulcanization accelerator are added and mixed with the rubber component along with the colored pigment, petroleum wax, and white filler. Next, in the final mixing stage (pro kneading process), the vulcanizing agent and vulcanization accelerator are added and mixed to the resulting mixture to prepare an unvulcanized rubber composition.

[0032] The color rubber composition according to the present embodiment can be used in pneumatic tires for various applications, such as passenger cars, trucks, and buses for heavy loads. The site of use in the tire is not particularly limited. In one embodiment, the color rubber composition can be used in a side portion such as a sidewall to display, for example, letters, symbols, figures, etc., thereby improving the decorativeness and design of the tire. Therefore, a tire (pneumatic tire) according to a preferred embodiment has a color rubber portion formed from the color rubber composition in a side portion such as a sidewall.

[0033] In addition, the various numerical ranges, including the above-mentioned blend amounts, mass ratios, and mass %, can each be arbitrarily combined with their upper and lower limits, and all such combinations are considered to be preferred numerical ranges and are described in this specification. EXAMPLES

[0034] Examples will be shown below, but the present invention is not limited to these examples.

[0035] The components used in the examples and comparative examples are as follows. Natural rubber: SIR20 Chlorinated butyl rubber: "Chlorobutyl 1066" manufactured by Japan Butyl Co., Ltd. ·EPDM: “EP33” manufactured by JSR Corporation Clay: "Hard Bright" manufactured by Takehara Chemical Co., Ltd. Silica: Evonik "Ultrasil VN3" Titanium oxide: Sakai Chemical Industry Co., Ltd. "A-190" Magnesium oxide: Kyowa Chemical Industry Co., Ltd. "Kyowa Mag 150" Zinc oxide: "Zinc oxide type 2" manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Kao Corporation's "Lunac S-20" Blue pigment MB: A masterbatch made by mixing 50% by mass of blue pigment made of copper phthalocyanine, 30% by mass of SBR (styrene butadiene rubber), and 20% by mass of mineral oil. Red pigment MB: A masterbatch made by mixing 50% by mass of a red pigment made of an azo compound, 30% by mass of SBR (styrene butadiene rubber), and 20% by mass of mineral oil. Vulcanization accelerator 1: "Noccela DM-P" manufactured by Ouchi Shinko Chemical Industry Vulcanization accelerator 2: "Noccelaer D" manufactured by Ouchi Shinko Chemical Industry Vulcanization accelerator 3: ARKEMA "VULTAC5" Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.

[0036] Wax A: Petroleum wax with the following normal / iso ratio and carbon number distribution (1) Normal / iso (mass ratio): 82 / 18 (2) Carbon number distribution of iso components in the entire petroleum wax (mass%): Carbon number 25 or less: 0.3%, Carbon number 26-32: 3.6%, Carbon number 33-44: 13.4%, Carbon number 45 or more: 0.6% (3) Carbon number distribution of normal components in the entire petroleum wax (mass%): Carbon number 25 or less: 11.1%, Carbon number 26-32: 36.6%, Carbon number 33-44: 34.0%, Carbon number 45 or more: 0.3%

[0037] Wax B: Petroleum wax with the following normal / iso ratio and carbon number distribution (1) Normal / iso (mass ratio): 79 / 21 (2) Carbon number distribution of iso components in the entire petroleum wax (mass%): Carbon number 25 or less: 0.3%, Carbon number 26-32: 6.8%, Carbon number 33-44: 11.2%, Carbon number 45 or more: 2.3% (3) Carbon number distribution of normal components in the entire petroleum wax (mass%): Carbon number 25 or less: 10.6%, Carbon number 26-32: 44.9%, Carbon number 33-44: 20.6%, Carbon number 45 or more: 3.4%

[0038] Wax C: Petroleum wax with the following normal / iso ratio and carbon number distribution (1) Normal / iso (mass ratio): 83 / 17 (2) Carbon number distribution of iso components in the entire petroleum wax (mass%): Carbon number 25 or less: 0.2%, Carbon number 26-32: 4.1%, Carbon number 33-44: 11.4%, Carbon number 45 or more: 1.2% (3) Carbon number distribution of normal components in the entire petroleum wax (mass%): Carbon number 25 or less: 9.3%, Carbon number 26-32: 44.2%, Carbon number 33-44: 27.0% Carbon number 45 or more: 2.6%

[0039] The normal / iso ratio and carbon number distribution of waxes A to C were measured using a capillary GC as a measuring device, a polyimide-coated capillary column, a carrier gas of helium, a flow rate of 4 mL / min, and a heating rate of 15°C / min from 180°C to 390°C. The carbon number of isoalkane was calculated by taking all peaks between the carbon numbers (N) and (N-1) of normal alkanes in the obtained gas chromatographic chart as isoalkanes of carbon number (N). The content was calculated by expressing it as a ratio when the total of normal alkanes and isoalkanes was 100 mass%.

[0040] [Examples 1 and 2 and Comparative Examples 1 and 2] Using a Banbury mixer, according to the formulation (parts by mass) shown in Table 1 below, first, in the first mixing stage, compounding ingredients other than sulfur and vulcanization accelerator were added to the rubber component and kneaded (discharge temperature = 160 ° C.). Next, in the final mixing stage, sulfur and vulcanization accelerator were added to the obtained kneaded product and kneaded (discharge temperature = 90 ° C.). In this way, a color rubber composition was prepared.

[0041] Each of the obtained color rubber compositions was vulcanized at 160°C for 30 minutes to prepare test pieces, and the ozone resistance and color change due to outdoor exposure were evaluated.

[0042] -Ozone resistance: In accordance with JIS K6259, test pieces were left for 24 hours under conditions of 10°C temperature, 100pphm ozone concentration, and 50% elongation, after which the rubber surface was visually inspected for cracks. If cracks were present, it was rated as "occurred", and if no cracks were visible to the naked eye, it was rated as "not occurring".

[0043] Color change: The color of the test pieces exposed outdoors for 6 months was measured using a Konica Minolta spectrophotometer "CR-200." The color change was calculated based on ΔE, and the color change was evaluated according to the following criteria. The smaller the ΔE value, the smaller the color change before and after outdoor exposure, and the better the appearance. A: ΔE is less than 5.0 B: ΔE is 5.0 or more and less than 7.5 C: ΔE is 7.5 or more

[0044] [Table 1]

[0045] The results are shown in Table 1. Comparative Example 1, which did not contain petroleum wax, was prone to ozone degradation and had poor ozone resistance. Comparative Example 2 contained petroleum wax, but wax A did not satisfy the above conditions (2) and (3), so the wax turned white after outdoor exposure and showed a large change in color, although the wax was excellent in ozone resistance. In contrast, Examples 1 and 2 contained waxes B and C, which satisfied the above conditions (1) to (3), so the wax was excellent in ozone resistance, the wax turned white after outdoor exposure was suppressed, and the color change was small. In particular, Example 1, which used wax B, was better, with less color change.

[0046] [Examples 3 and 4 and Comparative Examples 3 and 4] Color rubber compositions were prepared according to the formulation (parts by mass) shown in Table 2 below, in the same manner as in Example 1. The ozone resistance and color change of each obtained color rubber composition were evaluated in the same manner as in Example 1.

[0047] [Table 2]

[0048] The results are shown in Table 2, and Comparative Example 3, which did not contain any petroleum wax, had poor ozone resistance. Comparative Example 4 contained wax A, which did not satisfy the above conditions (2) and (3), and therefore had excellent ozone resistance, but suffered a large change in color due to whitening. Examples 3 and 4 contained waxes B and C, which satisfied the above conditions (1) to (3), and therefore had excellent ozone resistance and suffered less color change due to whitening than Comparative Example 4. Example 3, which used wax B, in particular, was better, with less color change.

[0049] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their omissions, substitutions, modifications, etc. are included in the scope and gist of the invention as well as the invention and its equivalents described in the claims.

Claims

1. The rubber composition contains 0.2 to 20 parts by mass of a pigment other than black and white, 0.5 to 15 parts by mass of petroleum wax, and 10 to 150 parts by mass of a white filler, relative to 100 parts by mass of the rubber component; The petroleum wax has a mass ratio of normal alkanes to isoalkanes, normal / iso, of 70 / 30 to 90 / 10; The color rubber composition for tires has a carbon number of 25 or less of 1.0% by mass or less, a carbon number of 26 to 32 of 4.0 to 8.0% by mass, a carbon number of 33 to 44 of 5.0 to 15.0% by mass, a carbon number of 45 or more of 1.0% by mass or more, a normal alkane content of 25 or less of 5.0 to 18.0% by mass, a carbon number of 26 to 32 of 40.0 to 48.0% by mass, a carbon number of 33 to 44 of 15.0 to 27.5% by mass, and a carbon number of 45 or more of 2.0% by mass or more, based on the total petroleum wax.

2. 2. The tire color rubber composition according to claim 1, wherein the rubber component comprises a natural rubber, a butyl rubber, and an ethylene propylene diene rubber.

3. 3. The color rubber composition for tires according to claim 1, wherein the white filler comprises at least one selected from the group consisting of silica, clay, calcium carbonate, manganese oxide, titanium oxide, magnesium oxide, and zinc oxide.

4. A tire comprising the color rubber composition for tires according to any one of claims 1 to 3.

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