Vulcanized rubber for tires and tire

Abstract

The present invention addresses the problem of providing a vulcanized rubber for tires which has excellent grip performance on ice and has improved durability and ozone resistance. The problem is solved by a vulcanized rubber for tires that is characterized by having a plurality of voids and comprising a rubber component (A), a filler (B), an anti-aging agent (C), and a C5-based resin (D), wherein the anti-aging agent (C) comprises a triphenylamine-based anti-aging agent (C1) represented by general formula (1).

Description

Vulcanized rubber for tires and tires

[0001] The present invention relates to a vulcanized rubber for a tire and a tire.

[0002] Studless tires with soft tread rubber have been used to safely run on ice as well as on normal roads, and it is known that softening the tread rubber improves the tire's performance on ice. It is also known that applying a rubber composition containing a resin to the tire's tread rubber improves the tire's performance on ice.

[0003] For example, Patent Document 1 listed below discloses a tire with excellent braking performance on ice, in which the tread uses a rubber composition that contains 50 to 90 parts by mass of a filler containing silica per 100 parts by mass of a rubber component containing natural rubber, polybutadiene rubber, and styrene-butadiene copolymer rubber, and in which 50% by mass or more of silica is contained in a phase containing polybutadiene rubber and styrene-butadiene copolymer rubber; it also discloses that a resin is compounded into the rubber composition.

[0004] In general, various rubber components constituting rubber products such as tires, rubber crawlers, and seismic isolation rubber may deteriorate due to the influence of external environments such as the presence of ozone, and as this deterioration progresses, cracks may occur. To address this problem, rubber compositions containing antioxidants are often applied to the various rubber components constituting rubber products. For example, Patent Document 2 below discloses that cracks and discoloration on the tire surface can be suppressed by applying a rubber composition containing a specific quinoline-based antioxidant and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD) to the rubber constituting the tire surface.

[0005] International Publication No. 2019 / 116701 International Publication No. 2018 / 056384

[0006] However, rubber compositions containing conventional resins have the problem of reduced tire durability. Furthermore, the N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antioxidant 6PPD) used in Patent Document 2 may have an environmental impact. Taking into account the possibility of future European regulations, it is desirable to use an antioxidant with a lower environmental impact. While it may be possible to avoid or minimize the use of antioxidant 6PPD in the rubber that constitutes the surface of rubber products, the inventors' investigations have shown that the ozone resistance of the rubber that constitutes the surface of tires is reduced when antioxidant 6PPD is not used or is barely used. Therefore, in addition to improving grip performance on ice, it is necessary to improve durability and ozone resistance.

[0007] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a vulcanized rubber for a tire that has excellent grip performance on ice and has improved durability and ozone resistance.Another object of the present invention is to provide a tire that has excellent grip performance on ice and has improved durability and ozone resistance.

[0008] The gist and configuration of the present invention to solve the above problems is as follows.

[0009] [1] A rubber component (A), a filler (B), an antioxidant (C), and ５ and a hydroxybenzoate-based resin (D), wherein the antioxidant (C) is a compound represented by the following general formula (1): [In the formula, R １１ and R １２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms; R １３ represents a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２and each independently represent a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.], and the vulcanized rubber for tires has a plurality of voids.

[0010] [2] The tire vulcanizate according to [1], wherein the proportion of natural rubber is 35% by mass or more and the proportion of butadiene rubber is 65% by mass or less, based on 100% by mass of the rubber component (A).

[0011] [3] The tire vulcanizate according to [1] or [2], wherein the content of the filler (B) is 65 parts by mass or more per 100 parts by mass of the rubber component (A).

[0012] [4] The tire vulcanizate according to any one of [1] to [3], wherein the proportion of carbon black is 70% by mass or more and the proportion of silica is 0% by mass or more and 20% by mass or less, in 100% by mass of the filler (B).

[0013] [5] The above C ５ [5] The tire vulcanizate according to any one of [1] to [4], wherein the content of the base resin (D) is 5 parts by mass or more and 18 parts by mass or less per 100 parts by mass of the rubber component (A).

[0014] [6] The tire vulcanizate according to any one of [1] to [5], further comprising a softener, the content of which is 30 parts by mass or less per 100 parts by mass of the rubber component (A).

[0015] [7] The above C ５ [7] The tire vulcanizate according to any one of [1] to [6], wherein the mass ratio (D / C) of the base resin (D) to the antioxidant (C) is 0.5 to 36.

[0016] [8] R in the above general formula (1) １１ and R １２ are each independently an alkyl group selected from the group consisting of an isopropyl group, a 1,3-dimethylbutyl group, and a 1,4-dimethylpentyl group.

[0017] [9] R in the above general formula (1) １１ and R１２ and each independently have 2 to 8 carbon atoms.

[0018]

[10] The tire vulcanizate according to any one of [1] to [9], wherein the content of the antioxidant (C) is 0.5 to 10 parts by mass per 100 parts by mass of the rubber component (A), the antioxidant (C) further contains a quinoline-based antioxidant (C2), and a proportion of the quinoline-based antioxidant (C2) in the antioxidant (C) is 5 to 50% by mass.

[0019]

[11] The antioxidant (C) further comprises a compound represented by the following general formula (2): [In the formula, R ２１ and R ２２ are each independently a monovalent saturated hydrocarbon group.], and a proportion of the amine-based antioxidant (C3) in the antioxidant (C) is 0.1 to 80 mass %.

[0020]

[12] The antioxidant (C) further comprises a compound represented by the following general formula (3): [In the formula, R ３１ and R ３２ represents a phenyl group, and m3 represents an integer of 7 or greater.], and a proportion of the amine-based antioxidant (C4) in the antioxidant (C) is 0.1 to 80 mass%.

[0021]

[13] A tire having a tread rubber including a cap rubber located on the outermost surface of a tread portion and a base rubber located radially inward of the cap rubber, wherein the tire vulcanized rubber according to any one of [1] to

[12] is used for the base rubber.

[0022]

[14] A rubber component (A), a filler (B), an antioxidant (C), and ５and a rubber-based resin (D), wherein, in 100% by mass of the rubber component (A), a proportion of natural rubber is 35% by mass or more and a proportion of butadiene rubber is 65% by mass or less, the content of the filler (B) is 65 parts by mass or more relative to 100 parts by mass of the rubber component (A), and, in 100% by mass of the filler (B), a proportion of carbon black is 70% by mass or more and a proportion of silica is 20% by mass or more, and the antioxidant (C) is a compound represented by the following general formula (1): [In the formula, R １１ and R １２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms; R １３ represents a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.], and a tire vulcanized rubber having a plurality of voids is used as the cap rubber.

[0023]

[15] The tire according to

[13] or

[14] , wherein the rubber component (A) in the base rubber further contains a styrene-butadiene rubber.

[0024]

[16] The tire according to

[15] , wherein the rubber component (A) in the base rubber contains 5 to 50 parts by mass of the styrene-butadiene rubber per 100 parts by mass of the rubber component (A).

[0025] According to the present invention, it is possible to provide a tire vulcanizate having excellent grip performance on ice and improved durability and ozone resistance. Also, according to the present invention, it is possible to provide a tire having excellent grip performance on ice and improved durability and ozone resistance.

[0026] 1 is a cross-sectional view of an embodiment of a tire according to the present invention. 2 is a schematic diagram showing a cross section of an embodiment of a cap rubber of a tire according to the present invention.

[0027] The vulcanized rubber for tires and the tire of the present invention will be described in detail below by way of example based on embodiments thereof.

[0028] <Definitions> The compounds described herein may be derived in whole or in part from fossil resources, from biological resources such as plant resources, from recycled resources such as used tires, or from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0029] In this specification, the weight average molecular weight of a resin is measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent value.

[0030] <Vulcanized rubber for tires> The vulcanized rubber for tires of this embodiment (hereinafter, sometimes simply referred to as "vulcanized rubber") comprises a rubber component (A), a filler (B), an antioxidant (C), and ５ and a hydroxybenzoate-based resin (D), wherein the antioxidant (C) is a compound represented by the following general formula (1): [In the formula, R １１ and R １２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms; R １３ represents a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ and each independently represent a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.], and the composition is characterized by containing a triphenylamine-based antioxidant (C1) represented by the following formula:

[0031] In the tire vulcanizate of this embodiment, by containing a filler (B) of a predetermined composition, the rubbing of the filler (B) increases the overall hysteresis loss, thereby improving the tire's grip performance on ice. Furthermore, by having a plurality of voids in the tire vulcanizate of this embodiment, the tire exhibits appropriate flexibility, and these voids function as drainage channels to remove water that has welled up on the ice, improving the tire's grip performance on ice. In this way, the vulcanized rubber of this embodiment can achieve excellent tire grip performance on ice. Furthermore, by containing the filler (B), durability is improved. Furthermore, by containing the triphenylamine-based antioxidant (C1) represented by the above general formula (1) as the antioxidant (C), the tire vulcanizate of this embodiment can ensure sufficient ozone resistance. Therefore, the tire vulcanizate of this embodiment has excellent grip performance on ice and improved durability and ozone resistance.

[0032] In the vulcanized rubber for tires of this embodiment, multiple voids can be formed by foaming using a foaming agent, and in this case, the foaming rate is usually 1 to 50%, preferably 5 to 40%. With a foaming rate of 50% or less, the voids on the rubber surface do not become too large, ensuring a sufficient contact area for the tread portion, and maintaining an appropriate amount of bubbles (voids) while ensuring the formation of bubbles (voids) that function effectively as drainage channels. Here, the foaming rate of the vulcanized rubber means the average foaming rate Vs, and specifically means the value calculated by the following formula: Vs = (ρ ０ / ρ １ -1)×100(%) In the formula, ρ １ is the density of the vulcanized rubber (g / cm ３ ) and ρ ０ is the density of the solid phase in the vulcanized rubber (g / cm ３ The density of the vulcanized rubber and the density of the solid phase of the vulcanized rubber are calculated from the mass in ethanol and the mass in air. The foaming ratio of the vulcanized rubber can be changed as appropriate by changing the type and amount of the foaming agent and foaming assistant.

[0033] The vulcanized rubber for tires of this embodiment can be obtained by vulcanizing a rubber composition of a predetermined composition. Furthermore, except for components such as a foaming agent that decomposes when heated, the composition of each component of the vulcanized rubber for tires of this embodiment substantially corresponds to the composition of each component of the rubber composition.

[0034] (Rubber Component (A)) The vulcanized rubber of this embodiment contains a rubber component (A). The vulcanized rubber of this embodiment contains at least natural rubber (NR) as the rubber component (A), and the proportion of natural rubber in 100% by mass of the rubber component (A) is preferably 35% by mass or more. From the viewpoint of further improving the compatibility characteristics of the rubber component (A) and further improving grip performance on ice, the proportion of natural rubber in 100% by mass of the rubber component (A) is preferably 50% by mass or more, and more preferably 60% by mass or more. On the other hand, the upper limit of the proportion of natural rubber in 100% by mass of the rubber component (A) is not particularly limited, but is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. The natural rubber may be unmodified or modified.

[0035] The origin of the natural rubber (NR) is not particularly limited, and examples thereof include those derived from Hevea brasiliensis, guayule, and Russian dandelion. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized synthetic isoprene rubber, hydrogenated synthetic isoprene rubber, and grafted synthetic isoprene rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0036] The vulcanized rubber for tires of this embodiment contains at least butadiene rubber (BR) as the rubber component (A), and the proportion of the butadiene rubber in 100% by mass of the rubber component (A) is preferably 65% ​​by mass or less. If the proportion of the butadiene rubber exceeds 65% by mass, grip performance on ice may deteriorate. Furthermore, from the viewpoint of further improving the compatibility characteristics of the rubber component (A) and further improving grip performance on ice, the proportion of the butadiene rubber in 100% by mass of the rubber component (A) is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 38% by mass or less, and even more preferably 35% by mass or less. On the other hand, the lower limit of the proportion of the butadiene rubber in 100% by mass of the rubber component (A) is not particularly limited, but is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. The butadiene rubber may be unmodified or modified.

[0037] In the vulcanized rubber of this embodiment, the proportion of natural rubber is preferably 35% by mass or more and the proportion of butadiene rubber is preferably 65% ​​by mass or less in 100% by mass of the rubber component (A). By having the proportion of natural rubber be 35% by mass or more and the proportion of butadiene rubber be 65% by mass or less in 100% by mass of the rubber component (A), the properties relating to the compatibility of the rubber component (A) become good (particularly, the compatibility of the rubber component (A) with the C ５ The compatibility of the hydroxyl group-based resin (D) with the hydroxyl group-based resin (D) increases, and the hysteresis loss at low temperatures increases.

[0038] The vulcanized rubber of this embodiment may contain rubber components other than natural rubber (NR) and butadiene rubber (BR). Examples of other rubber components include isoprene rubber (IR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), polysulfide rubber, silicone rubber, fluororubber, and urethane rubber. These other rubber components may be modified. These other rubber components may be used alone or in combination of two or more. Alternatively, these other rubber components may not be used (i.e., rubber component (A) may consist only of natural rubber (NR) and butadiene rubber (BR)). In particular, the vulcanized rubber of this embodiment may not contain styrene-butadiene rubber (SBR).

[0039] (Filler (B)) The vulcanized rubber of the present embodiment contains a filler (B). Examples of the filler (B) include carbon black and silica.

[0040] Carbon Black Carbon black reinforces the rubber composition and can improve the abrasion resistance of the rubber composition. As the carbon black, plant-derived carbon black and recycled carbon black (also called "recycled carbon black") are preferred. Examples of plant-derived carbon black include those derived from castor oil and pine oil. Recycled carbon black will be described in detail below.

[0041] From the viewpoint of further improving the abrasion resistance of the rubber composition and a tire using the same, the content of carbon black (total of recycled carbon black and carbon black other than recycled carbon black) in the rubber composition is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of rubber component (A). Also, from the viewpoint of workability of the rubber composition, the content of carbon black in the rubber composition is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less, per 100 parts by mass of rubber component (A).

[0042] --Recycled Carbon Black-- In this specification, "recycled carbon black" refers to carbon black recovered from recycled waste raw materials. Examples of such waste include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only that generated from rubber products but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeled rubber. Buffing powder is fine rubber generated during the buffing process, for example, in tire retreading, where the tread portion remaining on the base tire is scraped off. Peeled rubber is a long piece of rubber, e.g., 1 to 2 cm wide, peeled from the surface of a rubber product such as a tire. Peeled rubber is generated by scraping the surface of a rubber product such as a tire using a U- or V-shaped knife like a peeler. Furthermore, waste rubber is not limited to crosslinked rubber but also includes unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, as well as rubber parts or components during the manufacturing process of final products. Used tires may be tires to be retreaded, or may be tires discarded for some reason, such as tires generated during tire replacement or scrapping, or ELTs (End-of-Life Tires) that have reached the end of their service life. Waste oils are not limited to those generated during the decomposition of plastics and rubber, but also include used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oils that contain no non-organic components, such as those derived from silicone rubber or polyvinyl chloride, are desirable. Furthermore, waste oils containing carbon black or rubber containing carbon black are desirable. "Recycled carbon black" differs from carbon black produced directly from hydrocarbons such as petroleum, natural gas, and coal, i.e., non-recycled carbon black. Note that "used" here refers not only to waste oils discarded after actual use, but also to waste oils that were produced but discarded without actually being used.

[0043] The recycled carbon black is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by pyrolysis of a vulcanized rubber product containing carbon black is readily available because vulcanized rubber products containing carbon black are readily available and can be easily obtained by pyrolysis. Furthermore, the recycled carbon black is preferably obtained from the solid residue produced by the pyrolysis of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and recycled carbon black can be recovered from either of them. When recovering carbon black from the volatile component, the oil component with a specific gravity suitable for producing carbon black can be recovered and used to produce carbon black using existing carbon black production methods (e.g., JP 2015-520259 A). Unlike carbon black recovered from solid residues, this method offers advantages such as no impurities and no mixing of different grades. In addition, in the production of environmentally friendly carbon black, various options are available, including oils obtained by recovering volatile components from rubber pyrolysis, as described above, as well as vegetable oils and oils derived from waste plastics. However, edible resources such as vegetable oils are needed for other uses, such as food, and there are challenges in securing sufficient quantities, as well as the environmental impact of expanding cultivated land. Furthermore, oils derived from waste plastics are also used for other purposes, such as horizontal plastic recycling, so supply issues are also a concern. On the other hand, using volatile components (oils) produced by the pyrolysis of vulcanized rubber products, particularly tires, allows for the continued use of existing materials due to the tire industry's ongoing system of using existing materials, thereby reducing the consumption of new materials in new tire production and contributing to a reduction in the industry's environmental impact. The grade of carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0044] Solid residues obtained by pyrolysis of waste materials such as used rubber and used tires contain ash in addition to carbon black. The ash is derived from non-volatile components contained in the rubber and tires. Therefore, recycled carbon black obtained from the solid residues has a relatively low carbon black content. On the other hand, considering the various physical properties required for tires manufactured using recycled carbon black, the higher the carbon content of the recycled carbon black, the better. The carbon content of the recycled carbon black is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and particularly preferably 89% by mass or more. Furthermore, the carbon content of the recycled carbon black is preferably 97% by mass or less. Note that the carbon content does not include adsorbed moisture.

[0045] Specific examples of the ash include zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, and magnesium oxide. In the case of recycled carbon black produced from solid residue obtained by pyrolysis of waste, a certain amount of ash remains even after various processes for removing the ash. In this embodiment, the recycled carbon black is allowed to contain ash. In one embodiment, the lower limit of the ash content of the recycled carbon black may be 0.5% by mass.

[0046] The recycled carbon black can also be obtained from a pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3,427,975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes that recycled carbon black can be obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (paragraph

[0027] ). Carbon black obtained from such pyrolysis processes typically lacks functional groups on its surface, as mentioned in paragraph

[0004] of Japanese Patent Publication No. 6,856,781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black and Commercially Available Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0047] The recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. The treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, carbon black obtained by a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, in Japanese Patent Publication No. 6,856,781, carbon black obtained by a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black according to this embodiment also includes carbon blacks treated to include functional groups on their surfaces.

[0048] Furthermore, examples of thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0049] The crosslinked rubber products used for the decomposition may be grouped by the type of rubber component previously compounded, and then the decomposition step may be performed for each group. Alternatively, the crosslinked rubber products may be grouped by the type of filler previously compounded (e.g., type of carbon black, type of silica, mixing ratio of carbon black and silica, etc.), and then the decomposition step may be performed for each group. Furthermore, the crosslinked rubber products may be grouped by both type of rubber component and type of filler, and then the decomposition step may be performed for each group. When the decomposition step is performed for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when the recycled carbon black is compounded again into a rubber component, a rubber composition with better performance can be obtained.

[0050] Furthermore, when the crosslinked rubber product used in the degradation is derived from tires, the tires may be grouped in advance by type (e.g., for passenger cars, for trucks and buses, for large vehicles such as off-road vehicles, for aircraft, for agricultural vehicles, etc.), and the degradation step may be carried out for each group. Alternatively, the tires may be grouped in advance by tire component (e.g., tread rubber, sidewall rubber, bead rubber, steel cord-coated rubber, organic fiber-coated rubber, pad rubber, cushion rubber, etc.), and the degradation step may be carried out for each group. Furthermore, the tires may be grouped both by type and by tire component, and the degradation step may be carried out for each group. When the degradation step is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and therefore, when the recycled carbon black is blended again into a rubber component, a rubber composition with better performance can be obtained.

[0051] The recycled carbon black has a nitrogen adsorption specific surface area of ​​40 to 100 m as measured by the BET method. ２ / g, and 50 to 90m ２ / g, and more preferably 55 to 75m ２ In this specification, the nitrogen adsorption specific surface area of ​​recycled carbon black measured by the BET method is a statistical thickness specific surface area (STSA) determined in accordance with ASTM D6556.

[0052] The pH of the recycled carbon black is preferably 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. In this specification, the pH of the recycled carbon black is determined in accordance with ASTM D1512.

[0053] The recycled carbon black preferably has a toluene color transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, the toluene color transmittance of recycled carbon black is determined in accordance with ASTM D1618.

[0054] The recycled carbon black preferably has a heat loss of 3% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less at 125°C. Herein, the heat loss of recycled carbon black at 125°C is determined in accordance with ASTM D1509.

[0055] The recycled carbon black preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0056] The recycled carbon black preferably has a 35 mesh sieve residue of 20 mass ppm or less, more preferably 15 mass ppm or less, and particularly preferably 10 mass ppm or less. Herein, the 35 mesh sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0057] The recycled carbon black preferably has a 325 mesh (44 μm) sieve residue of 1000 mass ppm or less, more preferably 700 mass ppm or less, and particularly preferably 300 mass ppm or less. Herein, the 325 mesh (44 μm) sieve residue of the recycled carbon black is determined in accordance with ASTM D1514.

[0058] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Herein, the pellet hardness of recycled carbon black is determined in accordance with ASTM D5230.

[0059] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. Herein, the pellet fine powder content of recycled carbon black is determined in accordance with ASTM D1508.

[0060] The particle size (D97) of the recycled carbon black is preferably 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Herein, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size distribution analyzer, assuming a refractive index of water of 1.33 and a refractive index of the filler of 1.75.

[0061] The recycled carbon black preferably contains particles of 5 μm or less in a proportion of 50% by volume or more, more preferably 70% by volume or more, and particularly preferably 80% by volume or more.

[0062] The recycled carbon black preferably has an ash content of 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. When the ash content of the recycled carbon black is 25% by mass or less, the physical properties of the rubber product to which the rubber composition is applied can be improved. Herein, the ash content of the recycled carbon black is determined in accordance with ASTM D8474 and D1506.

[0063] The recycled carbon black preferably has a dibutyl phthalate (DBP) absorption of 70 to 120 mL / 100 g, more preferably 75 to 110 mL / 100 g, and particularly preferably 80 to 100 mL / 100 g. Herein, the DBP absorption of recycled carbon black is determined in accordance with ASTM D2414.

[0064] The recycled carbon black preferably has a compressed dibutyl phthalate (24M4DBP) absorption capacity of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Herein, the 24M4DBP absorption capacity of the recycled carbon black is determined in accordance with ASTM D3493.

[0065] Commercially available recycled carbon black can be used. For example, Enrestec's product name "PB365" can be mentioned as such a commercially available product. PB365 is a recycled carbon black produced through the thermal decomposition of used tires, and has a nitrogen adsorption specific surface area of ​​73.6 m2 as measured by the BET method. ２ / g and contains about 17% by mass of ash.

[0066] The content of the recycled carbon black is preferably 1 to 100 parts by mass, more preferably 5 to 80 parts by mass, even more preferably 5 to 50 parts by mass, still more preferably 5 to 30 parts by mass, and particularly preferably 5 to 20 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the recycled carbon black is 5 parts by mass or more per 100 parts by mass of the rubber component (A), the effect of improving the proportion of sustainable materials in rubber products to which the rubber composition is applied is significant, and when the content is 50 parts by mass or less, the fracture resistance of the rubber composition can be more reliably maintained.

[0067] The silica is not particularly limited, and examples thereof include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. The silica may be used alone or in combination of two or more.

[0068] In the vulcanized rubber of this embodiment, the content of the filler (B) is preferably 65 parts by mass or more per 100 parts by mass of the rubber component (A). When the content of the filler (B) is 65 parts by mass or more per 100 parts by mass of the rubber component (A), durability can be improved. Furthermore, from the viewpoint of further improving durability, the content of the filler (B) per 100 parts by mass of the rubber component (A) is preferably 70 parts by mass or more, more preferably 75 parts by mass or more, and even more preferably 80 parts by mass or more. On the other hand, the upper limit of the content of the filler (B) per 100 parts by mass of the rubber component (A) is not particularly limited, but from the viewpoint of low rolling resistance, it is preferably 120 parts by mass or less, more preferably 110 parts by mass or less, and even more preferably 100 parts by mass or less.

[0069] The vulcanized rubber of this embodiment contains at least carbon black as the filler (B), and the proportion of the carbon black in 100% by mass of the filler (B) is preferably 70% by mass or more. This allows for improved wear resistance of the tire. Furthermore, from the viewpoint of further improving the wear resistance of the tire tread, the proportion of carbon black in 100% by mass of the filler (B) is preferably 75% by mass or more, more preferably 80% by mass or more, and may even be 100% by mass (i.e., the filler (B) consists solely of carbon black).

[0070] In the vulcanized rubber of this embodiment, the proportion of silica in 100% by mass of the filler (B) is preferably 0% by mass or more and 20% by mass or less, and from the viewpoint of abrasion resistance, the proportion of silica in 100% by mass of the filler (B) is preferably 5% by mass or more, more preferably 10% by mass or more.

[0071] Examples of fillers other than carbon black and silica include aluminum hydroxide, clay, alumina, talc, mica, kaolin, glass balloons, glass beads, calcium carbonate, magnesium carbonate, magnesium hydroxide, magnesium oxide, titanium oxide, potassium titanate, and barium sulfate. The above-mentioned other fillers may be used alone or in combination of two or more. Furthermore, the above-mentioned other fillers may not be used (i.e., filler (B) may consist only of carbon black and silica).

[0072] (Antiaging Agent (C)) The vulcanized rubber of this embodiment contains an antioxidant (C). The antioxidant (C) has the effect of preventing aging of the vulcanized rubber and a tire using the same. The antioxidant (C) contains a triphenylamine-based antioxidant (C1) represented by the following general formula (1), and may further contain at least one of the following quinoline-based antioxidant (C2), an amine-based antioxidant (C3) represented by the following general formula (2), an amine-based antioxidant (C4) represented by the following general formula (3), and other antioxidants (C5).

[0073] The content of the antioxidant (C) is preferably 0.5 to 10 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1 to 8 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the antioxidant (C) is within the above range, the ozone resistance is more excellent.

[0074] [Triphenylamine-based antioxidant (C1) represented by general formula (1)] The triphenylamine-based antioxidant (C1) is a triphenylamine-based antioxidant represented by the following general formula (1): [In the formula, R １１ and R １２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms; R １３ represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.] The triphenylamine-based antiaging agent represented by the above general formula (1) has the effect of improving ozone resistance. In addition, the triphenylamine-based antiaging agent represented by the above general formula (1) has a small environmental impact.

[0075] R in the above general formula (1) １１ and R １２ R each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. １１ and R １２ As the alkyl group, a linear or branched alkyl group having 2 to 8 carbon atoms and a cycloalkyl group having 5 to 8 carbon atoms are preferred.

[0076] R in the above general formula (1) １３ represents hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ R each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. １３ is hydrogen, a linear or branched alkyl group having 1 to 10 carbon atoms, -NH-R １３１ , and -O-R １３２ is preferable. １３１ As R, a linear or branched alkyl group having 2 to 8 carbon atoms and a cycloalkyl group having 5 to 8 carbon atoms are preferred. １３２ As the alkyl group, a linear or branched alkyl group having 1 to 10 carbon atoms is preferred.

[0077] R １１ , R １２ and R １３１With regard to the above, examples of the linear or branched alkyl group having 2 to 8 carbon atoms include an ethyl group, a propyl group (i.e., an n-propyl group, an isopropyl group), a butyl group (i.e., an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group), a pentyl group, a hexyl group, a heptyl group, and an octyl group (e.g., an n-octyl group, a 2-octyl group).

[0078] R in the above general formula (1) １１ and R １２ are preferably each independently an alkyl group selected from the group consisting of an isopropyl group, a 1,3-dimethylbutyl group, a 1,4-dimethylpentyl group, and a 2-octyl group. １１ and R １２ Preferably, each independently has 2 to 8 carbon atoms.

[0079] R １３ and R １３２ With regard to (1), examples of the linear or branched alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group (i.e., an n-propyl group, an isopropyl group), a butyl group (i.e., an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group), a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. Among these, a methyl group, an ethyl group, and a propyl group (i.e., an n-propyl group, an isopropyl group) are preferred, a methyl group and an ethyl group are more preferred, and a methyl group is particularly preferred.

[0080] Also, R １１ , R １２ , R １３ , R １３１ and R １３２ Regarding the above, examples of the cycloalkyl group having 5 to 8 carbon atoms include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group, and among these, a cyclohexyl group is preferred.

[0081] Specific examples of the triphenylamine-based antioxidants represented by the general formula (1) include 4,4',4''-tris(isopropylamino)triphenylamine, 4,4',4''-tris(1,3-dimethylbutylamino)triphenylamine, 4,4',4''-tris(2-octylamino)triphenylamine, 4,4',4''-tris(1,4-dimethylpentylamino)triphenylamine, 4,4'-bis(isopropylamino)triphenylamine, 4,4'-bis(1,3-dimethylbutylamino)triphenylamine, 4,4'-bis(1,4- Preferred are 4,4'-bis(dimethylpentylamino)triphenylamine, 4,4'-bis(2-octylamino)triphenylamine, 4,4'-bis(isopropylamino)-4''-methoxytriphenylamine, 4,4'-bis(1,3-dimethylbutylamino)-4''-methoxytriphenylamine, 4,4'-bis(2-octylamino)-4''-methoxytriphenylamine, 4,4'-bis(1,4-dimethylpentylamino)-4''-methoxytriphenylamine, and 4,4'-bis(1-methylheptylamino)-4''-methoxytriphenylamine. These triphenylamine-based antioxidants (C1) may be used alone or in combination of two or more.

[0082] The triphenylamine-based antioxidant (C1) is a compound represented by the following general formula (1-1) or (1-2): [In the formula, R １１ , R １２ and R １３１ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.] [In the formula, R １４ and R １５ are each independently a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.] The triphenylamine antioxidants represented by general formula (1-1) or (1-2) have the effect of improving the ozone resistance of vulcanized rubber.

[0083] R in the above general formula (1-1) １１ , R １２ and R １３ and R in the general formula (1-2) １４ and R １５ are each independently a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms, and are preferably a linear or branched alkyl group having 2 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms. Examples of the linear or branched alkyl group having 2 to 8 carbon atoms include an ethyl group, a propyl group (i.e., an n-propyl group, an isopropyl group), a butyl group (i.e., an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group), a pentyl group, a hexyl group, a heptyl group, and an octyl group. Examples of the cycloalkyl group having 5 to 8 carbon atoms include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group, and among these, a cyclohexyl group is preferred.

[0084] The triphenylamine-based antioxidant (C1) is preferably a compound represented by the following general formula (1-1-1) or (1-2-1): In the above general formula (1-1-1), a compound represented by R １１１ , R １１２ , R １２１ , R １２２ , R １３２ and R １３３ are each independently an alkyl group, provided that R １３２ and R １３３ The total number of carbon atoms in R is 2 to 11, preferably 2 to 7. １１１ and R １１２ The total number of carbon atoms in R is 2 to 11, preferably 2 to 7. １２１ and R １２２ The total number of carbon atoms in R is 2 to 11, and preferably 2 to 7. １４１ , R １４２ , R １５１ and R １５２ are each independently an alkyl group, provided that R １４１ and R１４２ The total number of carbon atoms in R is 2 to 11, preferably 2 to 7. １５１ and R １５２ The total number of carbon atoms is 2 to 11, preferably 2 to 7.

[0085] The synthesis method of the triphenylamine-based antioxidant (C1) represented by the above general formula (1-1) or (1-2) is described in French Patent No. 1,354,536 and US Pat. No. 3,277,174.

[0086] R in the above general formula (1-1) １１ , R １２ and R １３１ and R in the general formula (1-2) １４ and R １５ are preferably each independently an alkyl group selected from the group consisting of an isopropyl group, a 1,3-dimethylbutyl group, a 1,4-dimethylpentyl group, and a 2-octyl group. １１ , R １２ and R １３ is an isopropyl group, a 1,3-dimethylbutyl group, a 1,4-dimethylpentyl group, or a 2-octyl group, and a triphenylamine-based antioxidant represented by the general formula (1-2): １４ and R １５ A triphenylamine antioxidant in which R is an isopropyl group, a 1,3-dimethylbutyl group, or a 1,4-dimethylpentyl group can further improve the ozone resistance of vulcanized rubber.

[0087] R in the above general formula (1-1) １１ , R １２ and R １３１ and R in the general formula (1-2) １４ and R １５ Each of R in the general formula (1-1) preferably has 2 to 8 carbon atoms. １１ , R １２ and R １３ and a triphenylamine-based antioxidant having 2 to 8 carbon atoms, １４ and R １５The triphenylamine antioxidant having 2 to 8 carbon atoms can further improve the ozone resistance of the vulcanized rubber.

[0088] The proportion of the triphenylamine-based antioxidant (C1) represented by the general formula (1-1) or (1-2) in the antioxidant (C) is preferably 10 to 100 mass%, more preferably 20 to 100 mass%. When the proportion of the triphenylamine-based antioxidant (C1) represented by the general formula (1-1) or (1-2) in the antioxidant (C) is 10 to 100 mass%, the ozone resistance of the vulcanized rubber can be further improved.

[0089] The triphenylamine-based antioxidant (C1) may be a compound represented by the following general formula (1-3): In the above general formula (1-3), a compound represented by R １１１ , R １１２ , R １２１ and R １２２ are each independently an alkyl group, provided that R １１１ and R １１２ The total number of carbon atoms in R is 2 to 11, preferably 2 to 7. １２１ and R １２２ The total number of carbon atoms in R in the general formula (1-3) is 2 to 11, and preferably 2 to 7. １３ represents R in the general formula (1). １３ and is synonymous with hydrogen, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ are each independently a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. １３ With respect to -NH-R １３１ Examples of the group include —NH—CHR １３１１ R １３１２ is preferred, where R １３１１ and R １３１２ are each independently an alkyl group, provided that R １３１１and R １３１２ The total number of carbon atoms is 2 to 11, preferably 2 to 7.

[0090] [Quinoline-Based Antiaging Agent (C2)] The antioxidant (C) preferably further contains a quinoline-based antioxidant (C2). The quinoline-based antioxidant (C2) is an antioxidant having a quinoline moiety or a derivative thereof (e.g., a dihydroquinoline moiety, a tetrahydroquinoline moiety, etc.). The quinoline-based antioxidant (C2) has the effect of improving the ozone resistance of vulcanized rubber, and a vulcanized rubber containing both the triphenylamine-based antioxidant (C1) represented by the above general formula (1-1) or (1-2) and the quinoline-based antioxidant (C2) can further improve the ozone resistance of tires.

[0091] The quinoline-based antioxidant (C2) preferably has a dihydroquinoline moiety, and more preferably has a 1,2-dihydroquinoline moiety. Specific examples of the quinoline-based antioxidant (C2) include a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ) and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. The quinoline-based antioxidant (C2) preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ). Quinoline-based antioxidants (C2) containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline are highly effective in improving the ozone resistance of vulcanized rubber and also have the advantage of being less likely to discolor the vulcanized rubber. Therefore, vulcanized rubber containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline can improve the ozone resistance of tires and is less susceptible to discoloration. Examples of the polymer of 2,2,4-trimethyl-1,2-dihydroquinoline include a dimer, trimer, and tetramer of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0092] The proportion of the quinoline-based antioxidant (C2) in the antioxidant (C) is preferably 5 to 50 mass%, more preferably 10 to 40 mass%. When the proportion of the quinoline-based antioxidant (C2) in the antioxidant (C) is 5 to 50 mass%, the ozone resistance of the rubber composition can be further improved.

[0093] In one embodiment, the rubber composition of the present embodiment preferably contains the antioxidant (C) in an amount of 0.5 to 10 parts by mass relative to 100 parts by mass of the rubber component (A), the antioxidant (C) further contains a quinoline-based antioxidant (C2), and the proportion of the quinoline-based antioxidant (C2) in the antioxidant (C) is 5 to 50% by mass.

[0094] [Amine-based antioxidant (C3) represented by general formula (2)] In the vulcanized rubber of this embodiment, the antioxidant (C) may further be an amine-based antioxidant represented by the following general formula (2): [In the formula, R ２１ and R ２２ are each independently a monovalent saturated hydrocarbon group. The amine-based antioxidant represented by general formula (2) (hereinafter sometimes simply referred to as "amine-based antioxidant (C3)") is similar to, for example, the conventionally known antioxidant N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD) in that it contains a phenylenediamine moiety, but differs in that it does not contain a double bond other than the phenylenediamine moiety. Furthermore, when blended in a predetermined amount with a rubber composition containing the above-mentioned rubber component (A) and the above-mentioned syndiotactic 1,2-polybutadiene (B), the amine-based antioxidant has the effect of maintaining advantageous durability.

[0095] In the above general formula (2), R ２１ and R ２２ are each independently a monovalent saturated hydrocarbon group. ２１ and R ２２ may be the same or different, but from the viewpoint of synthesis, it is preferable that they are the same.

[0096] The number of carbon atoms in the monovalent saturated hydrocarbon group is preferably 1 to 20, more preferably 3 to 10, and even more preferably 6 or 7. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass increases, resulting in a greater anti-aging effect and further improved durability.

[0097] R in the above general formula (2) ２１ and R ２２ and are preferably each independently a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms, from the viewpoint of further improving the durability of the vulcanized rubber, particularly the durability after thermal aging.

[0098] Examples of the monovalent saturated hydrocarbon group include an alkyl group and a cycloalkyl group. The alkyl group may be linear or branched, and the cycloalkyl group may further have an alkyl group or the like bonded thereto as a substituent. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,3-dimethylbutyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,2-dimethylpentyl group, a 1,3-dimethylpentyl group, a 1,4-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,4-dimethylpentyl group, an n-hexyl group, a 1-methylhexyl group, a 2-methylhexyl group, various octyl groups, various decyl groups, and various dodecyl groups. Of these, a 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include a cyclopentyl group, a methylcyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Of these, a cyclohexyl group is preferred.

[0099] Specific examples of the amine-based antioxidant (C3) represented by the general formula (2) include N,N'-dicyclohexyl-p-phenylenediamine, etc. The amine-based antioxidant (C3) represented by the general formula (2) may be used alone or in combination of two or more.

[0100] The content of the amine-based antioxidant (C3) represented by the general formula (2) is preferably 0.1 parts by mass or more and 11 parts by mass or less per 100 parts by mass of the rubber component (A). When the content of the amine-based antioxidant (C3) represented by the general formula (2) is 0.1 parts by mass or more per 100 parts by mass of the rubber component, sufficient durability can be obtained. On the other hand, when the content of the amine-based antioxidant (C3) represented by the general formula (2) exceeds 11 parts by mass per 100 parts by mass of the rubber component (A), adverse effects on heat buildup, hardness, etc. become significant, making the rubber unsuitable for tire applications. Furthermore, the content of the amine-based antioxidant (C3) represented by the general formula (2) per 100 parts by mass of the rubber component (A) is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of durability. Furthermore, the content is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, from the viewpoint of influence on other rubber physical properties.

[0101] The amine-based antiaging agent (C3) represented by the general formula (2) may be supported on any carrier. For example, the amine-based antiaging agent (C3) represented by the general formula (2) may be supported on a filler such as silica, which will be described later. The amine-based antiaging agent (C3) represented by the general formula (2) may also constitute a masterbatch together with the rubber component (A). The amine-based antiaging agent (C3) represented by the general formula (2) may also be in the form of a salt with an organic acid. The organic acid used to form the salt is not particularly limited, but examples thereof include stearic acid.

[0102] The proportion of the amine-based antioxidant (C3) represented by the general formula (2) in the antioxidant (C) is preferably 0.1 to 80 mass %, more preferably 1 to 70 mass %. When the proportion of the amine-based antioxidant (C3) represented by the general formula (2) is within the above range, the ozone resistance of the vulcanized rubber can be further improved.

[0103] [Amine-based Antiaging Agent (C4) Represented by General Formula (3)] The antiaging agent (C) may further be an amine-based antiaging agent represented by the following general formula (3): [In the formula, R ３１ and R ３２represents a phenyl group, and m3 represents an integer of 7 or more. ] (hereinafter, may be simply referred to as "amine-based antioxidant (C4)"). The amine-based antioxidant (C4) represented by the above general formula (3) has a higher molecular weight than conventional antioxidants, and, as shown in the above general formula (3), has a bridge moiety having a unique and relatively long chain length, i.e., "-NH-CH(CH ３ )-(CH ２ ) ｍ３ -CH(CH ３ )-NH-". It is believed that the high molecular weight and the presence of a specific bridge moiety of the amine-based antioxidant (C4) reduce the diffusion rate in the vulcanized rubber, further suppressing migration to the rubber surface. Furthermore, the amine-based antioxidant (C4) has a moiety composed of "-CH(CH ３ )-(CH ２ ) ｍ３ -CH(CH ３ One hydrogen atom is bonded to each of the two nitrogen atoms present at both ends of "-" (forming a so-called secondary amino group), and the presence of this bond in the structure represented by general formula (3) is thought to contribute to the specific effect of improving ozone resistance (weather resistance).

[0104] In the above general formula (3), R ３１ and R ３２ is a phenyl group. ３１ and R ３２ When is a phenyl group, the ozone resistance of the vulcanized rubber can be further improved, and discoloration of the vulcanized rubber can be more reliably prevented.

[0105] In the above general formula (3), m3 is an integer of 7 or more, and from the viewpoint of improving the ozone resistance of the vulcanized rubber and preventing discoloration, it is preferably an integer of 8 to 16, and more preferably an integer of 10 to 14.

[0106] Examples of the amine-based antioxidant (C4) of the general formula (3) include N,N'-bis(4-anilinophenyl)dodecane-2,11-diamine, N,N'-bis(4-anilinophenyl)tetradecane-2,13-diamine, N,N'-bis(4-anilinophenyl)hexadecane-2,15-diamine, N,N'-bis(4-anilinophenyl)octadecane-2,17-diamine, etc. Among these, N,N'-bis(4-anilinophenyl)tetradecane-2,13-diamine and N,N'-bis(4-anilinophenyl)octadecane-2,17-diamine are particularly preferred.

[0107] The proportion of the amine-based antioxidant (C4) represented by the general formula (3) in the antioxidant (C) is preferably 0.1 to 80 mass%, more preferably 1 to 70 mass%. When the proportion of the amine-based antioxidant (C4) represented by the general formula (3) in the antioxidant (C) is 0.1 to 80 mass%, the ozone resistance of the vulcanized rubber can be further improved.

[0108] [Other Antiaging Agents (C5)] The vulcanized rubber of this embodiment may or may not contain an antioxidant (C5) other than the triphenylamine-based antioxidant (C1) represented by the general formula (1), the quinoline-based antioxidant (C2), the amine-based antioxidant (C3) represented by the general formula (2), and the amine-based antioxidant (C4) represented by the general formula (3). Examples of the other antioxidant (C5) include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and N,N'-diphenyl-p-phenylenediamine (DPPD). Among these, it is preferable not to contain N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD). Commercially available antioxidants can be used as the antioxidants, and examples of commercially available antioxidants that can be used include products from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., Flexis, and the like. These antioxidants (C5) may be used alone or in combination of two or more. The proportion of the other antioxidants (C5) in the antioxidant (C) is preferably 0 to 20% by mass, more preferably 0 to 10% by mass.

[0109] (C ５ Resin (D)) The vulcanized rubber for tires of this embodiment contains C ５ Contains a C-based resin (D). ５ Among resins, the resin (D) has high compatibility with the rubber component of the predetermined composition of this embodiment, so that the vulcanized rubber of this embodiment can be ５ By including the C-based resin (D), grip performance on ice can be improved. ５ The resin (D) may be used alone or in combination of two or more.

[0110] In this specification, "C ５ "C-based resin" refers to ５ It refers to a resin obtained by polymerizing the fraction. ５The fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene.

[0111] C ５ Examples of the resin (D) include aliphatic hydrocarbon resins and alicyclic hydrocarbon resins. ５ Examples of such resins include petroleum resins produced by polymerizing 1,3-pentadiene, a petroleum fraction of the C type, as the main raw material, and examples thereof include the "Quinton 100" series (A100, B170, K100, M100, R100, N295, U190, S100, D100, U185, P195N, etc.) manufactured by Zeon Corporation. ５ Examples of petroleum resins produced by polymerizing petroleum fractions of the above-mentioned series include the "ESCOLETZ" series (product names 1102, 1202(U), 1304, 1310, 1315, 1395, etc.) manufactured by ExxonMobil Corporation and the "HI-LETZ" series (product names G-100X, -T-100X, -C-110X, -R-100X, etc.) manufactured by Mitsui Chemicals, Inc.

[0112] The alicyclic hydrocarbon resins include C ５ Cyclopentadiene-based petroleum resin produced using cyclopentadiene extracted from the distillate as the main raw material, C ５ Examples of dicyclopentadiene-based petroleum resins include those produced using dicyclopentadiene in the fraction as the main raw material. Examples of the cyclopentadiene-based petroleum resins include the "Quinton 1000" series (1325, 1345, etc.) manufactured by Zeon Corporation. Examples of the dicyclopentadiene-based petroleum resins include the "Marukarets M" series (M-890A, M-845A, M-990A, etc.) manufactured by Maruzen Petrochemical Co., Ltd.

[0113] Above C ５ The resin (D) is a hydrogenated C ５ In this case, the hydrogenated C ５The C-type resin has a higher compatibility with rubber components, which can further improve grip performance on ice. ５ Compared to other resins, this improves manufacturing workability.

[0114] The above C in the tire vulcanizate of this embodiment ５ The content of the C-based resin (D) is preferably 5 parts by mass or more and 18 parts by mass or less per 100 parts by mass of the rubber component (A). ５ When the content of the C-based resin (D) is 5 parts by mass or more per 100 parts by mass of the rubber component (A), the effect of further improving the grip performance on ice can be obtained. ５ If the content of the C-based resin (D) is 18 parts by mass or less relative to 100 parts by mass of the rubber component (A), the adhesion of the rubber composition of the vulcanized rubber can be suppressed to a range that does not cause problems in workability. ５ The content of the resin (D) is more preferably 8 parts by mass or more, and even more preferably 12 parts by mass or more.

[0115] In the tire vulcanizate of this embodiment, C ５ It is preferable that the mass ratio (D / C) of the resin (D) to the antioxidant (C) is 0.5 to 36. When the mass ratio is within the above range, an excellent balance of ice grip performance, durability, and ozone resistance is achieved. ５ The mass ratio (D / C) of the resin (D) to the antioxidant (C) is more preferably 0.5 to 20.

[0116] (Softener) The vulcanized rubber of this embodiment preferably further contains a softener. The softener is a compounding agent that has the effect of softening the rubber composition and the vulcanized rubber. By further containing a softener in the vulcanized rubber of this embodiment, grip performance on ice can be further improved. The softener is usually liquid at 25°C (room temperature).

[0117] The softener is not particularly limited, and examples thereof include oils and liquid polymers, among which oils are preferred. These softeners may be used alone or in combination of two or more.

[0118] Examples of the oil include petroleum oils such as aromatic oils, paraffinic oils, and naphthenic oils, and vegetable oils such as palm oil, castor oil, cottonseed oil, and soybean oil. Of these, petroleum oils are preferred.

[0119] Examples of the liquid polymer include liquid polybutadiene, liquid polyisoprene, and liquid polystyrene-butadiene. The liquid polymer preferably has a weight average molecular weight of 5,000 to 100,000. In this specification, the liquid polymer is not included in the rubber component (A).

[0120] The content of the softener in the vulcanized rubber of this embodiment is preferably 30 parts by mass or less per 100 parts by mass of the rubber component (A). If the content of the softener is 30 parts by mass or less per 100 parts by mass of the rubber component (A), the viscosity of the rubber composition, which is reduced by the resin when the resin is added, can be adjusted (improved), thereby improving the workability in producing the rubber composition and the vulcanized rubber. From the same viewpoint, the content of the softener per 100 parts by mass of the rubber component (A) is more preferably 28 parts by mass or less, even more preferably 26 parts by mass or less, even more preferably 24 parts by mass or less, and particularly preferably 22 parts by mass or less. Furthermore, since the effect of improving grip performance on ice is enhanced, the content of the softener is preferably 5 parts by mass or more per 100 parts by mass of the rubber component (A), more preferably 8 parts by mass or more, and even more preferably 10 parts by mass or more.

[0121] (Foaming Agent) The rubber composition of the vulcanized rubber preferably contains a foaming agent. This allows multiple voids to be formed in the resulting vulcanized rubber. Examples of foaming agents include azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), dinitrosopentastyrenetetramine, benzenesulfonyl hydrazide derivatives, p,p'-oxybisbenzenesulfonyl hydrazide (OBSH), ammonium bicarbonate that generates carbon dioxide, sodium bicarbonate, ammonium carbonate, nitrososulfonylazo compounds that generate nitrogen, N,N'-dimethyl-N,N'-dinitrosophthalamide, toluenesulfonyl hydrazide, p-toluenesulfonylsemicarbazide, and p,p'-oxybisbenzenesulfonylsemicarbazide. These foaming agents may be used alone or in combination of two or more.

[0122] The content of the foaming agent in the rubber composition of the vulcanized rubber is preferably 7 parts by mass or more and 12 parts by mass or less per 100 parts by mass of the rubber component (A), from the viewpoint of forming a desired plurality of voids in the vulcanized rubber.

[0123] (Foaming Aid) The rubber composition of the vulcanized rubber preferably contains a foaming aid in addition to the foaming agent. By using a foaming aid in combination, the foaming reaction can be accelerated to increase the degree of completion of the reaction, and unnecessary deterioration over time can be suppressed. Examples of the foaming aid include urea, zinc stearate, zinc benzenesulfinate, and zinc oxide. These foaming aids may be used alone or in combination of two or more.

[0124] (Vulcanizing Agent) The rubber composition of the vulcanized rubber preferably contains a vulcanizing agent. Sulfur is typically used as the vulcanizing agent, and examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur. The content of the vulcanizing agent in the rubber composition of the vulcanized rubber is preferably 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component (A). A vulcanizing agent content of 0.1 parts by mass or more allows for sufficient vulcanization, while a content of 10 parts by mass or less can suppress the aging resistance of the vulcanized rubber. From the same viewpoint, the content of the vulcanizing agent per 100 parts by mass of the rubber component (A) is more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and more preferably 8 parts by mass or less, even more preferably 6 parts by mass or less.

[0125] The vulcanized rubber may contain other components in addition to those described above. Examples of such other components include a silane coupling agent, C ５ Compounding agents commonly used in the rubber industry, such as resins other than the base resin (D), vulcanization accelerators, zinc oxide, stearic acid, etc., can be selected and contained as appropriate within the scope of the present invention. Commercially available products can also be used as these compounding agents.

[0126] (Production of Vulcanized Rubber for Tire) The method for producing the vulcanized rubber for tire of this embodiment is not particularly limited. For example, the vulcanized rubber for tire of this embodiment can be produced by appropriately selecting and blending the above-mentioned components, kneading, heating, extruding, etc. to prepare a rubber composition, and then vulcanizing the rubber composition.

[0127] The preparation of the rubber composition is not particularly limited, and kneading machines such as a Banbury mixer, a roll, or an internal mixer can be used. The kneading may be carried out in one stage or in two or more stages. For example, in the first stage, the vulcanization system, such as a vulcanizing agent and a vulcanization accelerator, and components other than the foaming agent may be blended and kneaded, and in the second stage, the vulcanization system, such as a vulcanizing agent and a vulcanization accelerator, and the foaming agent may be blended and kneaded. In this case, the maximum temperature in the first stage of kneading is preferably 130 to 170°C, and the maximum temperature in the second stage of kneading is preferably 90 to 120°C.

[0128] <Tire> A tire according to the present embodiment will now be described. Fig. 1 is a cross-sectional view of one embodiment of a tire according to the present invention. The tire 1 shown in Fig. 1 has a pair of bead portions 2, a pair of sidewall portions 3, and a tread portion 6 connected to both sidewall portions 3 and having a cap rubber 4 and a base rubber 5, in that order from the outer side in the tire radial direction. The tire also has a carcass 7 extending in a toroidal shape between the pair of bead portions 2 to reinforce these portions 2, 3, and 6, and a belt 8 disposed on the outer side in the tire radial direction of the crown portion of the carcass 7.

[0129] The carcass 7 of the tire shown in FIG. 1 is composed of one carcass ply made of a plurality of parallel-arranged cords covered with a coating rubber, and the carcass 7 is composed of a main body portion extending in a toroidal shape between the bead cores 9 embedded in each of the bead portions 2, and a folded-up portion wound up radially outward from the inner side toward the outer side in the tire width direction around each bead core 9, but the number of plies and the structure of the carcass 7 in the tire of this embodiment are not limited to this.

[0130] 1 is composed of two belt layers, the number of belt layers constituting the belt 8 in the tire of the present embodiment is not limited to this, and the number of belt layers may be three or more. Here, the belt layer is usually composed of a rubberized layer of reinforcing cords (preferably steel cords) extending at an angle with respect to the tire equatorial plane, and the two belt layers are laminated to constitute the belt 8 such that the reinforcing cords constituting the belt layers cross each other with the tire equatorial plane in between.

[0131] The tire of this embodiment is a tire equipped with a tread rubber 10 including a cap rubber 4 located on the outermost surface of a tread portion 6 and a base rubber 5 located radially inward of the cap rubber 4, and is characterized in that the tire vulcanized rubber of this embodiment is used as the base rubber. The tire of this embodiment has excellent grip performance on ice, and has improved durability and ozone resistance.

[0132] <<Base Rubber>> The tire of the present embodiment includes a tread rubber, and the tread rubber includes a base rubber. The base rubber uses the tire vulcanizate of the present embodiment.

[0133] The vulcanized rubber for tires used in the base rubber (hereinafter, sometimes simply referred to as "vulcanized rubber") is as described for the vulcanized rubber for tires of this embodiment, and the components contained or that can be contained in the vulcanized rubber (rubber component (A), filler (B), antioxidant (C), ５ A common explanation for the above resins (A, B, C, D, etc.) will be omitted.

[0134] In the tire of this embodiment, it is preferable that the rubber component (A) in the vulcanized rubber used in the base rubber (hereinafter sometimes referred to as "rubber component (A) in the base rubber") further contains styrene-butadiene rubber (SBR). When the rubber component (A) in the base rubber contains styrene-butadiene rubber in addition to natural rubber, the tire's grip performance on ice is further improved. The styrene-butadiene rubber is not particularly limited, and examples include solution-polymerized styrene-butadiene rubber (S-SBR) and emulsion-polymerized styrene-butadiene rubber (E-SBR). Among these, emulsion-polymerized styrene-butadiene rubber (E-SBR) is preferred. The styrene-butadiene rubber may be modified or unmodified.

[0135] The rubber component (A) in the base rubber preferably contains 5 to 50 parts by mass of the styrene-butadiene rubber per 100 parts by mass of the rubber component (A). By making the content of the styrene-butadiene rubber per 100 parts by mass of the rubber component (A) of the base rubber 5 parts by mass or more, the tire's grip performance on ice can be further improved. From the same viewpoint, the rubber component (A) in the base rubber more preferably contains 10 to 50 parts by mass of the styrene-butadiene rubber per 100 parts by mass of the rubber component (A).

[0136] <<Cap Rubber>> The tire of this embodiment comprises a rubber component (A), a filler (B), an antioxidant (C), and ５ and a rubber-based resin (D), wherein, in 100% by mass of the rubber component (A), a proportion of natural rubber is 35% by mass or more and a proportion of butadiene rubber is 65% by mass or less, the content of the filler (B) is 65 parts by mass or more relative to 100 parts by mass of the rubber component (A), and, in 100% by mass of the filler (B), a proportion of carbon black is 70% by mass or more and a proportion of silica is 20% by mass or more, and the antioxidant (C) is a compound represented by the following general formula (1): [In the formula, R １１ and R １２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms; R １３ represents a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ and each independently represent a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.], and a tire vulcanized rubber having a plurality of voids is preferably used as the cap rubber.

[0137] The rubber component (A), filler (B), antioxidant (C), and C in the cap rubber ５The components contained in the vulcanized rubber, such as the base resin (D), and the components that can be contained in the vulcanized rubber, such as the softener and the foaming agent, are the same as those that are or can be contained in the vulcanized rubber for tires of the present embodiment, and a common description thereof will be omitted.

[0138] The filler (B) of the vulcanized rubber for tires used in the cap rubber (hereinafter sometimes referred to as "vulcanized rubber in the cap rubber") contains silica. The silica content of the filler (B) of the vulcanized rubber in the cap rubber differs from the silica content of the vulcanized rubber for tires of the present embodiment described above. The silica content of the filler (B) of the vulcanized rubber in the cap rubber is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and preferably 70% by mass or less, and more preferably 60% by mass or less. When the silica content of the filler (B) is 20% by mass or more, better grip performance on ice can be obtained. Furthermore, when the silica content of the filler (B) is 70% by mass or less, better abrasion resistance can be obtained.

[0139] (Voids) As shown in Fig. 2, in the tire of this embodiment, the cap rubber 4 has a plurality of voids 11. By having the cap rubber 4 have a plurality of voids 11, the performance of the tire on ice can be improved.

[0140] The voids in the cap rubber preferably have an average diameter of about 1 to 500 μm. Here, the void diameter refers to the largest diameter of the void (if the void is not spherical, the largest distance between any two points on the inner wall of the void).

[0141] The porosity of the cap rubber is preferably 5 to 45%. By making the porosity of the cap rubber 5% or more, it is possible to more reliably improve the tire's performance on ice. From the same viewpoint, the porosity is more preferably 7% or more, and even more preferably 15% or more. Furthermore, by making the porosity of the cap rubber 45% or less, it is possible to more reliably suppress a decrease in the tire's wear resistance. From the same viewpoint, it is more preferably 40% or less, and even more preferably 37% or less. Here, the porosity refers to the ratio (volume %) of the volume of the voids in the cap rubber.

[0142] The method for providing multiple voids in the cap rubber is not particularly limited. For example, as described below, a method for providing voids in the cap rubber can be mentioned, in which a void-introducing agent is compounded into the rubber composition before vulcanization of the vulcanized rubber used for the cap rubber. The void ratio can be controlled by changing the vulcanization conditions of the rubber composition or by the content of the void-introducing agent. Another method for providing the voids is to compound powdered rubber into the rubber composition before vulcanization, so that the powdered rubber falls off from the surface of the rubber composition after vulcanization, forming voids near the surface of the cap rubber. In this case, the size and void ratio of the voids can be adjusted by adjusting the particle size and number of the powdered rubber.

[0143] A preferred method for providing multiple voids in the cap rubber is to compound a void-introducing agent into the rubber composition of the vulcanized rubber used for the cap rubber. By compounding a void-introducing agent into the rubber composition of the vulcanized rubber used for the cap rubber, the cap rubber has voids on the surface or inside, or on the surface and inside, so that a tire using the cap rubber has flexibility and is easily in close contact with icy road surfaces, and water on the road surface is absorbed into the voids on the tire surface, making it easy to remove water from the icy and snowy road surface, thereby improving braking performance on ice.

[0144] Examples of the void-introducing agent include a foaming agent, a metal sulfate, a thermally expandable microcapsule, a porous cellulose particle, a lignin derivative, etc., and one of these may be used alone or two or more may be mixed together. From the viewpoint of the tire performance on ice, it is preferable to use a foaming agent as the void-introducing agent.

[0145] The content of the void-introducing agent in the rubber composition for the cap rubber is not particularly limited, but from the viewpoint of obtaining a desired void ratio and maintaining abrasion resistance, etc., it is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component (A).

[0146] The vulcanized rubber for tires used in the tire cap rubber of this embodiment may further contain the following components. The vulcanized rubber for tires can be obtained by vulcanizing a rubber composition of a predetermined composition. Furthermore, except for components such as a foaming agent that decomposes when heated, the composition of each component of the vulcanized rubber for tires of this embodiment substantially corresponds to the composition of each component of the above-mentioned rubber composition.

[0147] Metal Sulfate—The vulcanized rubber used in the cap rubber may contain a metal sulfate. When the vulcanized rubber contains a metal sulfate as a void-introducing agent, the metal sulfate protrudes from the tire surface obtained by vulcanizing the rubber composition, performing a claw function without the disadvantage of being abrasive. Subsequently, the metal sulfate gradually leaves the rubber matrix, creating cavities that function as storage volumes and passages for discharging the water film on the ice surface. Under these conditions, contact between the tire surface (e.g., the tread surface) and ice is no longer lubricated, and therefore, examples of metal sulfates that improve the coefficient of friction include magnesium sulfate.

[0148] The metal sulfate preferably has micrometer-sized particles. Specifically, the average particle size and median particle size (both expressed by mass) are preferably 1 μm to 1 mm, and the median particle size is more preferably 2 μm to 800 μm. When the average particle size and median particle size are 1 μm or more, the desired technical effect (i.e., the formation of an appropriate micro-roughness) is easily achieved. Furthermore, when the average particle size and median particle size are 1 mm or less, the degradation of the tire aesthetics is suppressed (the appearance of too obvious particles on the cap rubber surface can be suppressed) and the grip performance on melting ice is less likely to be impaired. For all of these reasons, the median particle size of the metal sulfate is preferably 2 μm to 500 μm, and more preferably 5 μm to 200 μm. This particularly preferred particle size range appears to correspond to the optimal compromise between the desired surface roughness on the one hand and good contact between the cap rubber and ice on the other hand.

[0149] The content of the metal sulfate is preferably 5 to 40 parts by mass, and more preferably 10 to 35 parts by mass, based on 100 parts by mass of the rubber component (A).

[0150] Various known methods for analyzing particle size and calculating the median particle size of microparticles (or the average diameter of microparticles assuming a substantially spherical shape), for example by laser diffraction, are applicable (see, for example, standard ISO-8130-13 or standard JIS K5600-9-3). Particle size analysis by mechanical sieving can also be used simply and preferably. The procedure consists of: sieving a defined amount of sample (for example 200 g) for 30 minutes on a vibrating table through various sieve diameters (for example through meshes of 1000, 800, 630, 500, 400, ..., 100, 80 and 63 μm according to a progressive ratio equal to 1.26); weighing the oversize particles collected on each sieve on a precision balance; estimating the percentage of oversize particles at each mesh diameter relative to the total mass of the substance from the weighing; finally, calculating the median particle size (or median diameter) or mean particle size (or mean diameter) in a known manner from a histogram of the particle size distribution.

[0151] -Thermal-Expandable Microcapsules- The vulcanized rubber used in the cap rubber may contain thermally expandable microcapsules. The thermally expandable microcapsules are configured by encapsulating a thermally expandable substance within a shell material formed from a thermoplastic resin. The shell material of the thermally expandable microcapsules can be formed from a nitrile-based polymer. The thermally expandable substance encapsulated within the shell material of the microcapsules has the property of vaporizing or expanding upon heat, and is exemplified by at least one type selected from the group consisting of hydrocarbons such as isoalkanes and normal alkanes. Examples of isoalkanes include isobutane, isopentane, 2-methylpentane, 2-methylhexane, and 2,2,4-trimethylpentane. Examples of normal alkanes include n-butane, n-propane, n-hexane, n-heptane, and n-octane. These hydrocarbons may be used alone or in combination. A preferred form of the thermally expandable substance is one in which a hydrocarbon that is gaseous at room temperature is dissolved in a hydrocarbon that is liquid at room temperature. By using such a hydrocarbon mixture, sufficient expansion force can be obtained from low to high temperature ranges within the vulcanization molding temperature range (150°C to 190°C) of an unvulcanized tire.

[0152] Examples of such thermally expandable microcapsules include those manufactured by Expancel AB in Sweden under the trade names "EXPANCEL 091DU-80" or "EXPANCEL 092DU-120" and those manufactured by Matsumoto Yushi Seiyaku Co., Ltd. under the trade names "Matsumoto Microsphere F-85D" or "Matsumoto Microsphere F-100D".

[0153] The content of the thermally expandable microcapsules is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the rubber component (A).

[0154] -Porous Cellulose Particles- The vulcanized rubber in the cap rubber may contain porous cellulose particles. When the vulcanized rubber in the cap rubber contains porous cellulose particles as a void-introducing agent, if the porous cellulose particles are exposed on the surface of a tire obtained by vulcanizing the rubber composition, water on the icy road surface can be absorbed by the porous cellulose particles, thereby removing water from between the tire and the road surface. Furthermore, the presence of cellulose, which is a polysaccharide, causes an interaction between the tire and water on the icy road surface, and therefore the interaction between the tire and water by the modified polyoxyalkylene glycol can also be further enhanced.

[0155] The porous cellulose particles have a porous structure with a porosity of 75 to 95%, and when blended with vulcanized rubber, they can significantly improve performance on ice. A porosity of 75% or more in the porous cellulose particles provides excellent performance improvement on ice, while a porosity of 95% or less enhances particle strength. The porosity is more preferably 80 to 90%. The porosity of the porous cellulose particles can be calculated by measuring the volume of a given mass of sample (i.e., porous cellulose particles) with a measuring cylinder, determining the bulk density, and then using the following formula: Porosity [%] = {1 - (bulk density of sample [g / ml]) / (true specific gravity of sample [g / ml])} × 100, where the true specific gravity of cellulose is 1.5.

[0156] The particle size of the porous cellulose particles is not particularly limited, but from the viewpoint of abrasion resistance, particles having an average particle size of 1,000 μm or less are preferably used. The lower limit of the average particle size is not particularly limited, but it is preferably 5 μm or more. The average particle size is more preferably 100 to 800 μm, and even more preferably 200 to 800 μm. Spherical particles having a major axis / minor axis ratio of 1 to 2 are preferably used as the porous cellulose particles. The use of particles with such a spherical structure improves dispersibility in vulcanized rubber, contributing to improved grip performance on ice and the maintenance of abrasion resistance. The major axis / minor axis ratio is more preferably 1.0 to 1.5. The average particle size and major axis / minor axis ratio of the porous cellulose particles can be determined as follows. That is, porous cellulose particles are observed under a microscope to obtain an image, and this image is used to measure the long and short diameters of the particles (if the long and short diameters are the same, the length in a certain axial direction and the length in an axial direction perpendicular to it) for 100 particles, and the average particle size is obtained by calculating the average value, and the long diameter / short diameter ratio is obtained by averaging the values ​​obtained by dividing the long diameter by the short diameter.

[0157] The porous cellulose particles are commercially available from Rengo Co., Ltd. under the name "Viscopal" and are also described in JP-A Nos. 2001-323095 and 2004-115284, and can be suitably used.

[0158] The content of the porous cellulose particles is preferably 0.3 to 20 parts by mass per 100 parts by mass of the rubber component (A). By having the content of the porous cellulose particles be 0.3 parts by mass or more per 100 parts by mass of the rubber component (A), the effect of improving grip performance on ice can be enhanced, and by having the content of the porous cellulose particles be 20 parts by mass or less, it is possible to prevent the rubber hardness from becoming too high and to suppress a decrease in abrasion resistance. The content of the porous cellulose particles is more preferably 1 to 15 parts by weight, and even more preferably 3 to 15 parts by mass per 100 parts by mass of the rubber component (A).

[0159] -Lignin Derivative- When the vulcanized rubber used in the cap rubber contains a lignin derivative as a void-introducing agent, the effect of improving performance on ice can be enhanced. Here, lignin sulfonates are preferably used as the lignin derivative. Examples of lignin sulfonates include alkali metal salts, alkaline earth metal salts, ammonium salts, and alcoholamine salts of lignin sulfonic acid, and at least one of these can be used. Preferred are alkali metal salts and / or alkaline earth metal salts of lignin sulfonic acid, such as potassium salt, sodium salt, calcium salt, magnesium salt, lithium salt, and barium salt, and mixed salts of these are also acceptable.

[0160] -Organic Acid- The rubber composition of the vulcanized rubber used for the cap rubber may contain an organic acid, if necessary. In this case, the SP value of the organic acid is 9.15 to 16.0 (cal / cm ３ ) １／２ The organic acid has the effect of improving the foaming rate of the vulcanized rubber by balancing the rate of the decomposition / foaming reaction of the foaming agent and the rate of the vulcanization reaction of the rubber composition during vulcanization of the rubber composition. Therefore, by compounding the organic acid into the rubber composition, the workability of the rubber composition is maintained good, while the decomposition / foaming reaction of the foaming agent is promoted, thereby balancing the rate of the decomposition / foaming reaction and the rate of the vulcanization reaction of the rubber composition, and improving the foaming rate of the vulcanized rubber. By applying this vulcanized rubber to a tire, the tire's performance on ice can be improved. The SP value of the organic acid is 9.15 (cal / cm ３ ) １／２ If the SP value of the organic acid is less than 16.0 (cal / cm), the decomposition of the foaming agent may not be sufficiently promoted. ３ ) １／２ If the content exceeds this range, the adhesiveness of the rubber composition containing the organic acid will be high, and the rubber composition may adhere to manufacturing equipment such as rolls during production of the rubber composition, which may deteriorate the workability of the rubber composition.

[0161] From the same viewpoint, the SP value of the organic acid is 10.5 to 14.3 (cal / cm ３ )１／２ The SP value of the organic acid is preferably 10.5 (cal / cm ３ ) １／２ When the SP value of the organic acid is 14.3 (cal / cm or more), the effect of promoting the decomposition of the foaming agent is further increased. ３ ) １／２ When the SP value is 9.12 (cal / cm), the adhesiveness of the rubber composition containing the organic acid can be further reduced, and the workability of the rubber composition can be further improved. ３ ) １／２ In this specification, the SP value (solubility parameter) of an organic acid is calculated according to the Fedors method.

[0162] The organic acid may be any of monocarboxylic acid, dicarboxylic acid, tricarboxylic acid, etc., and may be aliphatic or aromatic. Furthermore, it may have a functional group other than a carboxyl group, such as a hydroxyl group, a ketone group, or an ethylenically unsaturated group. The organic acid preferably has an aromatic ring (aromatic), and more preferably a monocarboxylic acid. When the organic acid has an aromatic ring, the adhesion of the rubber composition can be further reduced, the workability of the rubber composition is further improved, and the rubber composition is less likely to adhere to manufacturing equipment such as rolls.

[0163] Examples of the aliphatic monocarboxylic acid include palmitic acid. Examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Examples of the aromatic monocarboxylic acid include benzoic acid and salicylic acid. Examples of the aromatic dicarboxylic acid include phthalic acid. Examples of organic acids having a functional group other than a carboxyl group include tartaric acid, malic acid, maleic acid, glycolic acid, and α-ketoglutaric acid. The organic acids may be used alone or in combination of two or more.

[0164] It is particularly preferable to use benzoic acid as the organic acid. When benzoic acid is compounded into the rubber composition, the adhesion of the rubber composition can be further reduced, the workability of the rubber composition is further improved, and the rubber composition becomes even less likely to adhere to manufacturing equipment such as rolls.

[0165] From the viewpoints of workability of the rubber composition, the foaming rate of the vulcanized rubber, and the tire's performance on ice, the content of the organic acid is preferably 0.1 to 7 parts by mass, more preferably 1.5 to 7 parts by mass, and even more preferably 3 to 7 parts by mass, per 100 parts by mass of the rubber component (A). Furthermore, from the viewpoints of the foaming rate of the vulcanized rubber and the tire's performance on ice, the total content of the foaming agent and the organic acid is preferably 3 parts by mass or more and less than 15 parts by mass, more preferably 5 parts by mass or more and less than 15 parts by mass, and even more preferably 7 parts by mass or more and less than 15 parts by mass, per 100 parts by mass of the rubber component (A). Furthermore, from the viewpoints of the foaming rate of the vulcanized rubber and the tire's performance on ice, the mass ratio of the foaming agent to the organic acid (foaming agent:organic acid) is preferably in the range of 1:0.5 to 1:1.5, and more preferably 1:0.7 to 1:1.3.

[0166] - Composite Fiber - The vulcanized rubber used in the cap rubber also preferably contains composite fiber. By containing the composite fiber, it is possible to ensure sufficient affinity with water, and to impart excellent drainage and ice performance to the tire. The composite fiber is preferably made of a hydrophilic resin having a coating layer formed on its surface. This is because providing a coating layer on the surface of the composite fiber improves the dispersibility of the composite fiber in the vulcanized rubber. The hydrophilic resin is preferably insoluble in water, and by using a water-insoluble hydrophilic resin, dissolution of the composite fiber can be suppressed even when the composite fiber is exposed on the surface of a product (e.g., a tire).

[0167] The hydrophilic resin is not particularly limited as long as it is a resin that can exhibit affinity with water, that is, a resin that has a hydrophilic group in the molecule. Specifically, it is preferably a resin that contains an oxygen atom, a nitrogen atom, or a sulfur atom, such as —OH, —C(═O)OH, —OC(═O)R (R is an alkyl group), —NH２ , —NCO, and —SH. Among these groups, the most preferred are resins containing at least one group selected from the group consisting of —OH, —C(═O)OH, —OC(═O)R, —NH ２ , —NCO are preferred. More specific examples of the hydrophilic resin include ethylene-vinyl alcohol copolymers, vinyl alcohol homopolymers, poly(meth)acrylic acid resins or ester resins thereof (hereinafter, copolymers containing structural units derived from (meth)acrylic acid and (co)polymers containing structural units derived from (meth)acrylic acid esters are collectively referred to as (meth)acrylic resins), polyamide resins, polyethylene glycol resins, carboxyvinyl copolymers, styrene-maleic acid copolymers, polyvinylpyrrolidone resins, vinylpyrrolidone-vinyl acetate copolymers, polyester resins, and cellulose-based resins. Among these, ethylene-vinyl alcohol copolymers, vinyl alcohol homopolymers, poly(meth)acrylic acid resins, polyamide resins, aliphatic polyamide-based resins, aromatic polyamide-based resins, polyester resins, polyvinyl alcohol-based resins, cellulose-based resins, and (meth)acrylic resins are preferred, with ethylene-vinyl alcohol copolymers being more preferred.

[0168] The surface of the fiber made of the hydrophilic resin preferably has a coating layer formed thereon, the coating layer being made of a low-melting-point resin (hereinafter also referred to as "low-melting-point resin") that has affinity for the rubber component (A) and preferably has a melting point lower than the maximum vulcanization temperature. The formation of such a coating layer effectively maintains the hydrophilic resin's inherent affinity for water while exhibiting good affinity with the rubber component (A) near the composite fiber. It also captures the hydrophilic resin, which is difficult to melt during vulcanization (foaming), and promotes the formation of voids within the composite fiber. That is, it ensures good dispersion of the composite fiber in the rubber component (A), fully exhibiting the drainage effect due to the hydrophilic resin, while also fully exhibiting the on-ice performance improvement effect due to the voids present within the composite fiber. Furthermore, the low-melting-point resin melts during vulcanization to form a fluid coating layer, contributing to improved adhesion between the rubber component (A) and the composite fiber, thereby imparting good on-ice performance and abrasion resistance. The thickness of the coating layer may vary depending on the amount of the hydrophilic resin blended, the average diameter of the composite fiber, and other factors, but is preferably 0.001 to 10 μm, and more preferably 0.001 to 5 μm. By forming the coating layer with a thickness within the above range, the desired effects can be fully achieved. The coating layer may be formed over the entire surface of the hydrophilic resin, or may be formed on only a portion of the surface of the hydrophilic resin. Specifically, the coating layer is preferably formed so as to occupy at least 50% of the total surface area of ​​the hydrophilic resin.

[0169] Specifically, the low-melting-point resin used in the coating layer is preferably a resin in which the polar component is 50% by mass or less of the total components, and more preferably a polyolefin resin. Resins with polar components within the above range have an appropriate difference in SP value with the rubber component (A) and a melting point that is appropriately lower than the maximum vulcanization temperature. This allows for easy melting during vulcanization and promotes foaming of the vulcanized rubber while ensuring sufficient affinity with the rubber component. This allows for more reliably improved dispersion of the hydrophilic resin fiber in the rubber composition and reliable formation of cavities within the composite fiber.

[0170] The polyolefin-based resin may be branched, linear, or the like. It may also be an ionomer resin in which ethylene-methacrylic acid copolymer molecules are crosslinked with metal ions. Specific examples of the polyolefin-based resin include polyethylene, polypropylene, polybutene, polystyrene, ethylene-propylene copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene-diene terpolymer, ethylene-vinyl acetate copolymer, and ionomer resins thereof. These may be used alone or in combination of two or more. Among these, polyethylene-based resins, polypropylene-based resins, polyolefin ionomers, and maleic anhydride-modified α-polyolefins are preferred as the polyolefin-based resin. When polyolefin ionomers or maleic anhydride-modified α-polyolefins are used, they also adhere to the hydroxyl groups of hydrophilic resins, thereby further improving rubber strength.

[0171] To produce a composite fiber made of a hydrophilic resin with a coating layer made of the low-melting-point resin, the resins can be blended using a mixing mill, melt-spun to form an undrawn yarn, and then hot-drawn the undrawn yarn to form a fiber. Alternatively, the resins can be blended using two twin-screw extruders equipped with dies and then similarly shaped into a fiber. In this case, the hydrophilic resin and the low-melting-point resin are simultaneously extruded from the two die outlets, forming an undrawn yarn. The amount of resins added to the mixing mill or hopper varies depending on the length and diameter of the resulting composite (fiber), but is preferably 5 to 300 parts by mass, more preferably 10 to 150 parts by mass, of the low-melting-point resin per 100 parts by mass of the hydrophilic resin. Adding these resins in amounts within the above ranges effectively forms a coating layer that can exert the desired effects on the surface of the hydrophilic resin composite (fiber) obtained after the drawing process.

[0172] The average length of the resulting composite fiber is preferably 0.1 to 500 mm, more preferably 0.1 to 7 mm, and the average diameter is preferably 0.001 to 2 mm, more preferably 0.005 to 0.5 mm. When the average length and average diameter are within the above ranges, there is no risk of the composite fibers becoming entangled more than necessary, and there is no risk of impairing good dispersibility. The aspect ratio is preferably 10 to 4,000, more preferably 50 to 2,000. The aspect ratio refers to the ratio of the major axis to the minor axis of the composite fiber.

[0173] Furthermore, the ratio (X / Y) of the length X of the cross section in the major axis direction in a cross section perpendicular to the major axis direction to the length Y of the cross section in the minor axis direction perpendicular to the major axis direction is preferably greater than 1, more preferably 1.5 or more, even more preferably 1.8 or more, and particularly preferably 2.0 or more. Furthermore, the ratio X / Y is preferably 20 or less, even more preferably 15 or less, and particularly preferably 10 or less. By keeping it within the above range, grip performance on ice is further improved. Note that, as long as X / Y is greater than 1, the cross-sectional shape is not particularly limited and may be any of elliptical, rectangular, polygonal, irregular, etc.

[0174] The blending amount of the hydrophilic resin composite fiber having the coating layer formed thereon is preferably 0.1 to 100 parts by mass, more preferably 0.3 to 30 parts by mass, even more preferably 0.5 to 10 parts by mass, and even more preferably 1 to 6 parts by mass, per 100 parts by mass of the rubber component (A). When the blending amount of the hydrophilic resin composite fiber having the coating layer formed thereon is within the above range, cavities are formed within the composite fiber, thereby exhibiting good drainage properties and maintaining sufficient durability. Furthermore, the content ratio of the composite fiber and the void-introducing agent is not particularly limited, but from the viewpoint of achieving and improving both durability and performance on ice, the mass ratio of the composite fiber to the void-introducing agent (void-introducing agent / composite fiber) is preferably 0.5 to 10, more preferably 1 to 8, even more preferably 1.5 to 7, and particularly preferably 2 to 6.

[0175] (Tire Manufacturing Method) The tire of this embodiment can be manufactured by a known method depending on the type of tire to be applied. The components of the tire of this embodiment other than the cap rubber and base rubber are not particularly limited, and known components can be used. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire can be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0176] The present disclosure will be explained in more detail below by way of examples, but the present invention is not limited to the following examples in any way.

[0177] <Examples 1-1 to 1-5 and Comparative Example 1-1> For Examples 1-1 to 1-5, rubber compositions were prepared by kneading in a conventional manner according to the formulations shown in Table 1. The rubber compositions were then vulcanized at 145°C for 33 minutes to obtain vulcanized rubber in which multiple voids derived from the foaming agent were formed. For Comparative Example 1-1, a vulcanized rubber was obtained in the same manner as in Examples 1-1 to 1-5 above.

[0178] <Evaluation Method> (Ice Grip Performance and Wet Grip Performance) For Examples 1-1 to 1-5, the loss tangent (tan δ) of the resulting vulcanized rubber was measured at temperatures of -20°C and 0°C using a spectrometer manufactured by Ueshima Seisakusho under conditions of an initial strain of 2%, an initial input of 150 μm, and a frequency of 52 Hz. The evaluation results are normalized for each example, with Comparative Example 1-1 set as the control (index value of 100). The index values ​​were classified according to the following criteria, and the evaluation results for each example are shown in Table 1. For Comparative Example 1-1, measurements were carried out in the same manner as for Examples 1-1 to 1-5, and the results were normalized and classified according to the following criteria. The evaluation results are shown in Table 1. A: Index value greater than 150 B: Index value of 120 or greater but 150 or less C: Index value less than 120

[0179] (Ozone Resistance) For Examples 1-1 to 1-5, a dynamic ozone degradation test (a test in which repeated strain is applied) was conducted in accordance with ISO 1431 (JIS K 6259), and the samples were observed at 20x magnification using a microscope. The observed samples were ranked according to the size and depth of cracks and classified according to the following criteria (1 to 5), with smaller numbers indicating better results. For Comparative Example 1-1, the test was conducted in the same manner as for Examples 1-1 to 1-5, and the samples were observed and evaluated according to the following criteria. (Ranking by Crack Size and Depth) 1: Not visible to the naked eye but visible with a 10x magnifying glass. 2: Visible to the naked eye. 3: Deep and relatively large cracks (less than 1 mm). 4: Deep and large cracks (1 mm or more but less than 3 mm). 5: Cracks of 3 mm or more or likely to cause breakage.

[0180]

[0181] *1 Natural rubber: TSR20 *2 Butadiene rubber: Ube Elastomer Co., Ltd., "UBEPOL BR150L" *3 Carbon black: HS-HAF grade *4 Silica: Tosoh Silica Corporation, "Nipsil AQ" *5 Softener: Oil, ENEOS Corporation, "Super Oil Y22" *6 C ５ Resin: Hydrogenated C ５ * 7 Foaming agent: azodicarbonamide (ADCA) * 8 Antioxidant-1: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), Ouchi Shinko Chemical Industry Co., Ltd.'s "Nocrac (registered trademark) 6C" * 9 Antioxidant-2: 4,4'-bis(2-octylamino)triphenylamine, a triphenylamine-based antioxidant represented by the following formula (a) *10 Antioxidant-3: 4,4'-bis(2-octylamino)-4''-methoxytriphenylamine, a triphenylamine-based antioxidant represented by the following formula (b) *11 Antioxidant-4: 4,4',4''-tris(1,3-dimethylbutylamino)triphenylamine, a triphenylamine-based antioxidant represented by the following formula (c) *12 Vulcanization accelerator: Sanshin Chemical Industry Co., Ltd., "Suncerer CM-G", NOCIL LIMITED, "PILCURE MBTS"

[0182] From Table 1, it can be seen that the vulcanized rubbers of the Examples have excellent grip performance on ice and ozone resistance.

[0183] <Examples 2-1 to 2-5, and Comparative Example 2-1> For Examples 2-1 to 2-5, rubber compositions were prepared by blending and kneading the components according to the formulations shown in Table 2. The resulting rubber compositions were evaluated for fracture properties, viscoelasticity (tan δ), and ozone resistance using the following methods. In addition to the components shown in Table 2, the rubber compositions also contained predetermined amounts of sulfur, vulcanization accelerator, etc. For Comparative Example 2-1, a rubber composition was prepared in the same manner as for Examples 2-1 to 2-5. The resulting rubber compositions were measured for fracture properties and viscoelasticity (tan δ) using the following methods. The resulting rubber compositions were also evaluated for ozone resistance.

[0184] <Evaluation Method> (Fracture Properties) The rubber compositions obtained in Examples 2-1 to 2-5 were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber test pieces. The obtained vulcanized rubber test pieces were subjected to tensile tests in accordance with JIS K 6251 at room temperature (23°C) and 100°C to measure elongation at break (EB), tensile strength (TB), and toughness (TF), with Comparative Example 2-1 designated as the control (index value 100). The index values ​​were classified according to the following criteria, and the evaluation results for each example are shown in Table 2. A higher index value indicates better fracture properties. For the rubber composition of Comparative Example 2-1, vulcanized rubber test pieces were obtained in the same manner as in Examples 2-1 to 2-5, and measurements were performed in the same manner to obtain index values, which were then classified according to the following criteria. The evaluation results are shown in Table 2. (EB at room temperature) A: Index value 140 or more B: Index value more than 100 and less than 140 C: Index value 100 or less (TB at room temperature) A: Index value 140 or more B: Index value more than 100 and less than 140 C: Index value 100 or less (TF at room temperature) A: Index value 160 or more B: Index value more than 100 and less than 160 C: Index value 100 or less (EB at 100°C) A: Index value 160 or more B: Index value more than 100 and less than 160 C: Index value 100 or less (TB at 100°C) A: Index value 160 or more B: Index value more than 100 and less than 160 C: Index value 100 or less (TF at 100°C) A: Index value 250 or more B: Index value more than 100 and less than 250 C: Index value 100 or less

[0185] (Viscoelasticity (tan δ)) For Examples 2-1 to 2-5, the resulting rubber compositions were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber test pieces. The loss tangent (tan δ) at 40°C of the resulting vulcanized rubber test pieces was measured using a viscoelasticity measuring device (manufactured by Rheometrics) under conditions of 1% strain and 52 Hz frequency, with Comparative Example 2-1 being the control (index value 100). The index values ​​were classified according to the following criteria, and the evaluation results for each example are shown in Table 2. For Comparative Example 2-1, a rubber test piece was obtained and measured in the same manner as in Examples 2-1 to 2-5, and the index values ​​were classified according to the following criteria. The evaluation results are shown in Table 2. For the loss tangent (tan δ) at 40°C, the smaller the index value, the more excellent the fuel economy performance. A: Index value 80 or less B: Index value more than 80 and less than 100 C: Index value 100 or more

[0186] (Ozone Resistance) Comparative Example 2-1 is subjected to a dynamic ozone degradation test (a test in which repeated strain is applied) in accordance with ISO 1431 (JIS K 6259), and the sample is observed at 20x magnification using a microscope. Examples 2-1 to 2-5 are subjected to the same test and observation as Comparative Example 2-1. The observed samples are ranked according to the size and depth of cracks and classified according to the following criteria (1 to 5), with smaller numbers indicating better results. (Ranking by crack size and depth) 1: Not visible to the naked eye but visible with a 10x magnifying glass. 2: Visible to the naked eye. 3: Deep and relatively large cracks (less than 1 mm). 4: Deep and large cracks (1 mm or more but less than 3 mm). 5: Cracks of 3 mm or more or likely to cause breakage.

[0187]

[0188] * 21 Natural rubber: TSR20 * 22 S-SBR: Solution polymerization styrene-butadiene rubber, manufactured by Asahi Kasei Corporation, trade name "TUFDEN3835" * 23 E-SBR: Emulsion polymerization styrene-butadiene rubber, manufactured by ENEOS Materials Corporation, trade name "ESBR0122" * 24 Carbon black-1: HAF grade carbon black, manufactured by Tokai Carbon Co., Ltd., trade name "Seat KHA" * 25 Carbon black-2: SAF grade carbon black, manufactured by Tokai Carbon Co., Ltd., trade name "Seat 7HM" * 26 Oil: Manufactured by ENEOS Corporation, trade name "Super Oil Y22"

[0189] From Table 2, it can be seen that the vulcanized rubbers of the examples are excellent in fracture properties and ozone resistance.

[0190] According to the present invention, it is possible to provide a tire vulcanizate having excellent grip performance on ice and improved durability and ozone resistance. Also, according to the present invention, it is possible to provide a tire having excellent grip performance on ice and improved durability and ozone resistance.

[0191] 1: Tire 2: Bead portion 3: Sidewall portion 4: Cap rubber 5: Base rubber 6: Tread portion 7: Carcass 8: Belt 9: Bead core 10: Tread rubber 11: Gap

Claims

1. A rubber component (A), a filler (B), an antioxidant (C), and ５ and a hydroxybenzoate-based resin (D), wherein the antioxidant (C) is a compound represented by the following general formula (1): [In the formula, R １１ and R １２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms; R １３ represents a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ and each independently represent a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.], and the vulcanized rubber for tires has a plurality of voids.

2. The vulcanized rubber for tires according to claim 1, wherein the proportion of natural rubber is 35% by mass or more and the proportion of butadiene rubber is 65% by mass or less, based on 100% by mass of the rubber component (A).

3. The vulcanized rubber for tires according to claim 1, wherein the content of the filler (B) is 65 parts by mass or more per 100 parts by mass of the rubber component (A).

4. The vulcanized rubber for tires according to claim 1, wherein the proportion of carbon black is 70% by mass or more and the proportion of silica is 0% by mass or more and 20% by mass or less, based on 100% by mass of the filler (B). 5.C above ５ 2. The vulcanized rubber for tires according to claim 1, wherein the content of the base resin (D) is 5 parts by mass or more and 18 parts by mass or less per 100 parts by mass of the rubber component (A).

6. The vulcanized rubber for tires according to claim 1, further comprising a softener, the content of which is 30 parts by mass or less per 100 parts by mass of the rubber component (A).

7. Above C ５ 2. The tire vulcanizate according to claim 1, wherein a mass ratio (D / C) of the base resin (D) to the antioxidant (C) is 0.5 to 36.

8. R in the above general formula (1) １１ and R １２ are each independently an alkyl group selected from the group consisting of an isopropyl group, a 1,3-dimethylbutyl group, a 1,4-dimethylpentyl group, and a 2-octyl group.

9. R in the above general formula (1) １１ and R １２ and each independently have 2 to 8 carbon atoms.

10. The tire vulcanizate according to claim 1, wherein the content of the antioxidant (C) is 0.5 to 10 parts by mass per 100 parts by mass of the rubber component (A), the antioxidant (C) further contains a quinoline-based antioxidant (C2), and the proportion of the quinoline-based antioxidant (C2) in the antioxidant (C) is 5 to 50% by mass.

11. The antioxidant (C) further comprises a compound represented by the following general formula (2): [In the formula, R ２１ and R ２２ are each independently a monovalent saturated hydrocarbon group.], and a proportion of the amine-based antioxidant (C3) in the antioxidant (C) is 0.1 to 80 mass %.

12. The antioxidant (C) further comprises a compound represented by the following general formula (3): [In the formula, R ３１ and R ３２ represents a phenyl group, and m3 represents an integer of 7 or greater. ], and a proportion of the amine-based antioxidant (C4) in the antioxidant (C) is 0.1 to 80 mass %.

13. A tire having a tread rubber including a cap rubber located on the outermost surface of the tread portion and a base rubber located radially inward of the cap rubber, wherein the tire vulcanized rubber according to claim 1 is used for the base rubber.

14. A rubber component (A), a filler (B), an antioxidant (C), and C ５ and a rubber-based resin (D), wherein, in 100% by mass of the rubber component (A), a proportion of natural rubber is 35% by mass or more and a proportion of butadiene rubber is 65% by mass or less, the content of the filler (B) is 65 parts by mass or more relative to 100 parts by mass of the rubber component (A), and, in 100% by mass of the filler (B), a proportion of carbon black is 70% by mass or more and a proportion of silica is 20% by mass or more, and the antioxidant (C) is a compound represented by the following general formula (1): [In the formula, R １１ and R １２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms; R １３ represents a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, -NH-R １３１ , or -O-R １３２ where R １３１ and R １３２ and each independently represent a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.], and a tire vulcanized rubber having a plurality of voids is used as the cap rubber.

15. The tire according to claim 13, wherein the rubber component (A) in the base rubber further contains a styrene-butadiene rubber.

16. The tire according to claim 15, wherein the rubber component (A) in the base rubber contains 5 to 50 parts by mass of the styrene-butadiene rubber per 100 parts by mass of the rubber component (A).

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