tire

Abstract

To provide a tire that is light in weight but allows for improved ride comfort.SOLUTION: A tire has a tread and a sidewall. When the thickness of tread rubber constituting the tread at a tire equator is defined as T (mm), the thickness of the sidewall rubber constituting the sidewall at a tire maximum width position as S (mm), the tire weight as G (kg), and the maximum load ability of the tire as WL (kg), T, S, G and WL satisfy the following formulae (1)-(3). The rubber composition constituting the tread rubber contains thermoplastic elastomer of less than 100 pts.mass relative to the rubber component of 100 pts.mass. Formula (1) T≤8.5. Formula (2) S / T<0.50. Formula (3) G / WL≤0.012.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a tire with improved ride comfort performance. [Background technology]

[0002] In pneumatic tires, weight reduction is required from the perspective of improving fuel efficiency. Patent Document 1 describes a certain tire in which the rubber volume has been reduced for weight reduction. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-43281 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, lightweight tires with reduced rubber volume have the drawback of not providing satisfactory ride comfort.

[0005] The present invention aims to provide a tire that is lightweight while improving ride comfort performance. [Means for solving the problem]

[0006] As a result of diligent research, the inventors have found that in a lightweight tire in which the ratio of tire weight to maximum load capacity is less than or equal to a predetermined value, the thickness of the tread rubber is less than or equal to a predetermined value, and in conjunction with this, the thickness of the sidewall rubber is also adjusted so as not to become too thick, and furthermore, a predetermined amount of thermoplastic elastomer is blended into the rubber composition constituting the tread rubber, thereby solving the above problem. Further research has been conducted to complete the present invention.

[0007] In other words, the present invention relates to the following tires.

[0008] A tire comprising a tread portion and a sidewall portion, wherein when the thickness of the tread rubber constituting the tread portion at the tire equator is defined as T (mm), the thickness of the sidewall rubber constituting the sidewall portion at the tire maximum width position is defined as S (mm), the tire weight is defined as G (kg), and the maximum load capacity of the tire is defined as WL (kg), T, S, G and WL satisfy the following formulas (1) to (3), the tire, wherein the rubber composition constituting the tread rubber contains less than 100 parts by mass of a thermoplastic elastomer relative to 100 parts by mass of a rubber component. Formula (1): T≦8.5 Formula (2): S / T<0.50 Formula (3): G / WL≦0.012 [Effects of the Invention]

[0009] The tire of the present invention can improve riding comfort performance while being lightweight. [Brief Description of Drawings]

[0010] [Figure 1] Fig. 1 is an example of a cross-sectional view of a tire, showing T (mm), which is the thickness of the tread rubber at the tire equator, and S (mm), which is the thickness of the sidewall rubber at the tire maximum width position. [Figure 2] Fig. 2 is an example of a cross-sectional view of a tire, showing the tire cross-sectional width Wt, the tire cross-sectional height Ht, and the tire outer diameter Dt. [Mode for Carrying Out the Invention]

[0011] In the present invention, the upper and lower numerical values relating to the terms "at least", "at most" and "~" in the description of numerical ranges are any values that can be arbitrarily combined; in addition, the numerical values in the examples can also be combined with the upper and lower limits. When a numerical range is specified by "~", it means that the values at both ends are also included, unless otherwise specified. Furthermore, in the present invention, unless it is contrary to the gist of the present invention, a numerical range indicated as including the values at both ends shall be construed as simultaneously indicating a numerical range excluding one of the values at both ends, and even a numerical range excluding both values at both ends.

[0012] A tire that is one embodiment of the present invention comprises a tread portion and a sidewall portion. Where, let T (mm) be the thickness at the tire equator of the tread rubber constituting the tread portion, let S (mm) be the thickness at the tire maximum width position of the sidewall rubber constituting the sidewall portion, let G (kg) be the tire weight, and let WL (kg) be the maximum load capacity of the tire, T, S, G and WL satisfy the following formulas (1) to (3), and the rubber composition constituting the tread rubber contains less than 100 parts by mass of thermoplastic elastomer based on 100 parts by mass of the rubber component. Formula (1) T≦8.5 Formula (2) S / T<0.50 Formula (3) G / WL≦0.012

[0013] While not intended to be constrained by theory, the following mechanisms are conceivable for improving ride comfort performance while maintaining lightness in the present invention. Specifically, the tire of the present invention has the following characteristics: (1) The ratio of the tire weight G (kg) to the tire's maximum load capacity WL (kg) (G / WL) is 0.012 or less, and because it is relatively light, it generates little heat, and because the thickness of the tread rubber is thin, heat does not easily accumulate in the tread; (2) Because the thickness of the sidewall rubber is limited to be thin in accordance with the thickness of the tread rubber, heat dissipation also progresses from the sidewall, so heat does not accumulate in the tread even more; (3) Because a thermoplastic elastomer is blended into the rubber composition that makes up the tread rubber, flexible and tough domains are formed by the thermoplastic elastomer, and by these domains, the impact applied to the tread is converted into heat and easily mitigated. Furthermore, it is believed that the combined action of (1) to (3) above allows the tire of the present invention to efficiently convert impact from the tread into heat, while preventing heat from accumulating in the tread, thus ensuring that ride comfort is not compromised even when driving continuously on uneven surfaces.

[0014] The thermoplastic elastomer preferably includes a styrene-based thermoplastic elastomer.

[0015] This is because it makes it easier to achieve the effects of the present invention.

[0016] The thermoplastic elastomer preferably includes a hydrogenated styrene-based thermoplastic elastomer.

[0017] Hydrogenated thermoplastic elastomers have improved wear resistance, which helps to reduce the deterioration of ride comfort due to wear.

[0018] The content of the thermoplastic elastomer is preferably 10 parts by mass or more per 100 parts by mass of the rubber component.

[0019] This is because the proportion of thermoplastic elastomer in the rubber composition constituting the tread rubber increases, making it easier to exhibit the effects of the present invention.

[0020] The above S preferably satisfies the following formula (4). Formula (4) S≦3.0

[0021] This is because it makes it easier to achieve the effects of the present invention.

[0022] The rubber composition preferably contains 80 parts by mass or less of silica.

[0023] The effect of this invention is that it makes it easier to achieve both ride comfort and wet grip performance.

[0024] The rubber composition preferably contains 5 parts by mass or less of carbon black.

[0025] The effect of this invention is that it makes it easier to achieve both ride comfort and wet grip performance.

[0026] The rubber composition preferably contains 85 parts by mass or less of a reinforcing filler.

[0027] The effect of this invention is that it makes it easier to achieve both ride comfort and wet grip performance.

[0028] The rubber composition preferably contains 24 parts by mass or less of oil.

[0029] The effect of this invention is that it makes it easier to achieve both ride comfort and wet grip performance.

[0030] The rubber composition preferably contains 5 parts by mass or less of resin.

[0031] The effect of this invention is that it makes it easier to achieve both ride comfort and wet grip performance.

[0032] The rubber composition preferably contains 29 parts by mass or less of a plasticizer.

[0033] The effect of this invention is that it makes it easier to achieve both ride comfort and wet grip performance.

[0034] The tire of the present invention is preferably for use in passenger cars.

[0035] This is because it is suitable for enjoying the benefits resulting from the effects of the present invention.

[0036] <Definition> A "standard rim" is the rim specified for each tire in the standardization system that the tire is based on. For example, it is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. In the case of tires whose size is not specified in the aforementioned standardization system, it refers to the narrowest rim with the smallest diameter that can be mounted on that tire without causing air leakage between the rim and the tire.

[0037] "Regular internal pressure" refers to the air pressure specified for each tire in the tire standard system, including the standard on which the tire is based. For example, it is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. For tires of sizes not specified in the aforementioned standard system, the regular internal pressure is set at 250 kPa.

[0038] "Normal condition" refers to a tire mounted on a normal rim, filled to the normal internal pressure, and under no load. For tires of sizes not specified in the aforementioned standard system, this refers to a tire mounted on the smallest rim, filled to 250 kPa, and under no load. Unless otherwise specified in this specification, the dimensions and angles of each part of the tire are measured under the normal condition. If there are patterns or letters on the tire sidewall, these are treated as if they were not present during measurement.

[0039] "T (mm) thickness of tread rubber at the tire equator" refers to the thickness (mm) of the tread rubber at the tire equator under normal conditions. For example, in Figure 1, it is the distance from point PT on the tread surface intersecting the tire equator to the belt layer 6.

[0040] "S (mm) thickness of the sidewall rubber at the tire's maximum width position" refers to the thickness (mm) of the sidewall rubber at the tire's maximum width position under normal conditions. For example, in Figure 1, this is the distance from point PS on the sidewall at the tire's maximum width position to the carcass.

[0041] "Tire weight G (kg)" is the weight of the tire alone, excluding the weight of the rim.

[0042] The "maximum load capacity (WL) (kg)" is a value calculated by the following formulas (A) and (B), where Wt (mm) is the tire section width, Ht (mm) is the tire section height, and Dt (mm) is the tire outer diameter, as measured under normal conditions. V is the virtual volume of space occupied by the tire. The tire section width Wt is the maximum width between the outer surfaces of the sidewalls under normal conditions, excluding any patterns or letters on the tire sidewall. The tire section height Ht is the distance from the bottom of the bead to the outermost surface of the tread, and is half the difference between the tire outer diameter and the nominal rim diameter. In this invention, unless otherwise specified, the maximum load capacity refers to the "maximum load capacity (WL) (kg)" described above. V = {(Dt / 2)} 2 -(Dt / 2-Ht)2} × π × Wt ···(A) WL = 0.000011 × V + 100 ... (B)

[0043] "Oil content" includes the amount of oil contained in the oil-applied rubber.

[0044] <Measurement method> "Styrene content" is, 1 This value is calculated by 1H-NMR measurement and is applied, for example, to rubber components having repeating units derived from styrene, such as SBR.

[0045] "Vinyl content (amount of 1,2-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and is applied to rubber components having repeating units derived from butadiene, such as SBR and BR.

[0046] "Cis content (amount of cis-1,4-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and is applied, for example, to rubber components having repeating units derived from butadiene, such as BR.

[0047] The "glass transition temperature (Tg)" is a value measured according to JIS K 7121, using a differential scanning calorimeter (Q200) manufactured by T.A. Instruments Japan Co., Ltd., while increasing the temperature at a rate of 10°C / min. It is applied to rubber components such as SBR.

[0048] The "weight-average molecular weight (Mw)" can be determined by converting the measured value using gel permeation chromatography (GPC) (for example, the GPC-8000 series from Tosoh Corporation, with a differential refractometer as the detector and TSKGEL SUPERMALTIPORE HZ-M column from Tosoh Corporation) to a standard polystyrene equivalent. This method is applicable, for example, to SBR, BR, etc.

[0049] The N2SA rating of carbon black is measured in accordance with JIS K 6217-2:2017.

[0050] The DBP oil absorption capacity of carbon black is measured in accordance with JIS K 6217-4:2017.

[0051] The N2SA content of silica is measured by the BET method in accordance with ASTM D3037-93.

[0052] <Tires> Let me describe a tire, which is one embodiment of this invention.

[0053] The tire of the present invention comprises a tread portion and a sidewall portion, where T (mm) is the thickness of the tread rubber constituting the tread portion at the tire equator, S (mm) is the thickness of the sidewall rubber constituting the sidewall portion at the tire's maximum width position, G (kg) is the tire weight, and WL (kg) is the maximum load capacity of the tire. Then T, S, G, and WL satisfy the predetermined relationships shown in equations (1) to (3).

[0054] (Formula (1)) Formula (1) specifies that the thickness T (mm) of the tread rubber constituting the tread portion of the tire of the present invention at the tire equator is 8.5 mm or less. This is because if the tread rubber is too thick, heat will accumulate in the tread, which is undesirable from the viewpoint of the effects of the present invention. T is preferably 8.0 mm or less, more preferably 7.8 mm or less, even more preferably 7.6 mm or less, even more preferably 7.5 mm or less, and even more preferably 7.2 mm or less. On the other hand, there is no particular limit to the lower limit of T from the viewpoint of the effects of the present invention, but it is usually around 7.0 mm.

[0055] (Formula (2)) Equation (2) specifies that the ratio (S / T) of the thickness S (mm) of the sidewall rubber constituting the sidewall portion of the tire at the tire's maximum width position to T (mm) is less than 0.50. This is because if the sidewall rubber is too thick, heat dissipation from the sidewall will be hindered, and consequently, heat will accumulate in the tread, which is undesirable from the viewpoint of the effects of the present invention. S / T is preferably 0.45 or less, more preferably 0.40 or less, even more preferably 0.35 or less, even more preferably 0.33 or less, and even more preferably 0.30 or less. On the other hand, there are no particular restrictions on the lower limit of S / T from the viewpoint of the effects of the present invention, but it is usually around 0.28.

[0056] (Formula (3)) Equation (3) specifies that the ratio of the tire weight G (kg) of the tire of the present invention to the maximum load capacity WL (kg) (G / WL) is 0.012 or less. This is because the tire of the present invention is intended for relatively lightweight tires in which the tire weight is limited based on the maximum load capacity. G / WL is preferably 0.011 or less, more preferably 0.010 or less, and even more preferably 0.009 or less. On the other hand, there is no particular limit to the lower limit of G / WL from the viewpoint of the effects of the present invention, but it is usually around 0.008. The value of G / WL can be reduced by reducing the value of G relative to the value of WL.

[0057] The value of G can be reduced by decreasing the mass of each component, such as the tread rubber and sidewall rubber. In addition, for components made of a rubber composition, it can also be reduced by reducing the specific gravity of the rubber composition. The specific gravity of the rubber composition can be reduced by reducing the content of components such as silica and carbon black.

[0058] (Formula (4)) In the present invention, it is preferable that the tire S (mm) satisfies the following formula (4). Formula (4) S≦3.0

[0059] If the sidewall rubber is too thick, heat dissipation from the sidewall will be hindered, and consequently, heat will accumulate in the tread, which is undesirable from the viewpoint of the effects of the present invention. S is more preferably 2.9 mm or less, even more preferably 2.8 mm or less, even more preferably 2.7 mm or less, even more preferably 2.6 mm or less, and even more preferably 2.5 mm or less. On the other hand, there are no particular restrictions on the lower limit of S from the viewpoint of the effects of the present invention, but it is usually around 2.0 mm.

[0060] <Rubber composition> The rubber composition constituting the tread rubber of the tire according to the present invention contains less than 100 parts by mass of thermoplastic elastomer per 100 parts by mass of rubber component.

[0061] (Rubber component) In the present invention, any rubber component commonly used in the tire industry can be suitably used. Examples of such rubber components include diene rubbers such as isoprene rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene-butadiene copolymer rubber (SIBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and polynorbornene rubber, as well as non-diene rubbers such as hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, silicone rubber, polyethylene chloride rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. The rubber component may be used alone or in combination of two or more types.

[0062] The rubber component preferably contains diene rubber, and may consist solely of diene rubber. Furthermore, it is preferable that the diene rubber contains at least one selected from the group consisting of isoprene rubber, SBR, and BR. The rubber component is preferably a rubber component containing SBR, more preferably a rubber component containing both SBR and BR, and may consist solely of SBR and BR, or it may be a rubber component with isoprene rubber added to these.

[0063] ≪SBR≫ There are no particular limitations on SBR, and examples include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Modified SBRs include SBRs in which the terminals and / or main chain are modified, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those with branched structures, etc.). Among these, S-SBR and modified SBRs are preferred because they can significantly improve fuel efficiency and wear resistance. Furthermore, hydrogenated versions of these SBRs (hydrogenated SBRs) can also be used. These SBRs may be used individually or in combination of two or more types.

[0064] The styrene content of SBR is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of ensuring damping properties in the tread and wet grip performance. Furthermore, from the viewpoint of the temperature dependence of grip performance and wear resistance, it is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. In this specification, the styrene content of SBR is calculated by the method described above.

[0065] The vinyl content of SBR is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, from the viewpoint of ensuring reactivity with silica, rubber strength, and abrasion resistance. Furthermore, the vinyl content of SBR is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less, from the viewpoint of preventing increased temperature dependence, wet grip performance, elongation at break, and abrasion resistance. In this specification, the vinyl content of SBR (amount of 1,2-bonded butadiene units) is measured by the method described above.

[0066] The glass transition temperature (Tg) of SBR is preferably -90°C or higher, more preferably -70°C or higher, and even more preferably -50°C or higher, from the viewpoint of wet grip performance. Furthermore, from the viewpoint of low fuel consumption, Tg is preferably 0°C or lower, more preferably -10°C or lower, and even more preferably -15°C or lower. Note that Tg can be determined by the method described above.

[0067] The weight-average molecular weight (Mw) of SBR is preferably 150,000 or more, and more preferably 200,000 or more, from the viewpoint of wear resistance. Furthermore, from the viewpoint of crosslinking uniformity, Mw is preferably 2,500,000 or less, more preferably 2,000,000 or less, and even more preferably 1,500,000 or less. Mw can be determined by the method described above.

[0068] For SBR, either oil-expanded SBR or non-oil-expanded SBR can be used. When using oil-expanded SBR, the amount of oil expanded in the SBR, that is, the amount of oil-expanding oil contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of rubber solids in the SBR.

[0069] For example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Ube Industries, Ltd., Asahi Kasei Corporation, Nippon Zeon Co., Ltd., and ZS Elastomer Co., Ltd. can be used.

[0070] When SBR is included, the content in the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, even more preferably 70% by mass or more, even more preferably 90% by mass or more, and may also be 100% by mass, from the viewpoint of ensuring damping properties in the tread and wet grip performance. Furthermore, from the viewpoint of improving durability by suppressing heat generation in the tread, it is preferably 95% by mass or less, and more preferably 90% by mass or less.

[0071] ≪BR≫ BR is not particularly limited, and for example, BR with a cis content of less than 50% (low-cis BR), BR with a cis content of 90% or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. BR may be used alone or in combination of two or more types.

[0072] The cis content of BR is preferably 90 mol% or more, more preferably 93 mol% or more, and even more preferably 95 mol% or more, from the viewpoint of durability and abrasion resistance. The cis content is measured by the measurement method described above.

[0073] Rare earth-based BRs can be those commonly used in the tire industry. Known rare earth element catalysts can be used for the synthesis (polymerization) of rare earth-based BRs, including, for example, lanthanum series rare earth element compounds, organoaluminum compounds, aluminoxanes, halogen-containing compounds, and catalysts containing Lewis bases as needed. Among these, Nd-based catalysts using neodymium (Nd)-containing compounds as the lanthanum series rare earth element compound are preferred from the viewpoint of obtaining BRs with high cis content and low vinyl content.

[0074] SPB-containing BR includes those in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR, but are chemically bonded to BR and then dispersed.

[0075] Modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and further modified BRs in which the ends of the modified BR molecule are linked by a tin-carbon bond (tin-modified BR), and butadiene rubber having a condensed alkoxysilane compound at the active end of the butadiene rubber (modified BR for silica).

[0076] The weight-average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more, from the viewpoint of wear resistance. Furthermore, from the viewpoint of crosslinking uniformity, it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. Mw can be determined by the method described above.

[0077] For example, commercially available BRs from companies such as Ube Industries, Ltd., Sumitomo Chemical Co., Ltd., JSR Corporation, and Lanxess Corporation can be used.

[0078] When BR is included, the content in the rubber component is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of abrasion resistance. Furthermore, from the viewpoint of wet grip performance, it is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0079] Isoprene-based rubber As isoprene-based rubbers, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. Among these, natural rubber includes not only unmodified natural rubber (NR), but also modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. Natural rubber is preferred among these, and for example, NR can be suitably used. These isoprene-based rubbers may be used individually or in combination of two or more types.

[0080] NR is not particularly limited and can be any tire that is common in the tire industry, such as SIR20, RSS#3, and TSR20.

[0081] From the viewpoint of processability and durability, the content of isoprene-based rubber in the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 20% by mass or more, and even more preferably 25% by mass or more. On the other hand, there is no particular upper limit to the content of isoprene-based rubber component, but from the viewpoint of obtaining good ride comfort performance due to damping in the tread portion, it is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, even more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0082] (Thermoplastic elastomer) A "thermoplastic elastomer" refers to a thermoplastic resin material that is an elastic polymer compound, comprising a copolymer having a crystalline, high-melting-point hard segment and an amorphous, low-glass transition-temperature soft segment. In thermoplastic elastomers, the crystalline, high-melting-point hard segment acts as a pseudo-crosslinking point, exhibiting elasticity. Thermoplastic elastomers can be reused because the pseudo-crosslinking points can be regenerated by heating to melt the hard segment and then cooling it. On the other hand, rubber has double bonds in its molecular chains, and elasticity is exhibited by creating a three-dimensional network structure through crosslinking (vulcanization) with sulfur, etc. Therefore, once rubber is crosslinked (vulcanized), it loses its fluidity due to this three-dimensional network structure, making it difficult to reuse even when heated. The thermoplastic elastomer of the present invention does not contain the aforementioned rubber components.

[0083] The thermoplastic elastomers that can be used in the present invention are not particularly limited, but examples include styrene-based thermoplastic elastomers, urethane-based thermoplastic elastomers, olefin-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and among these, styrene-based thermoplastic elastomers or urethane-based thermoplastic elastomers are preferred, and styrene-based thermoplastic elastomers are more preferred. One or more thermoplastic elastomers can be used.

[0084] ≪Styrene-based thermoplastic elastomer≫ The styrene-based thermoplastic elastomer is a copolymer having at least one styrene block (hard segment) and at least one elastomer block (soft segment). The molecular structure of the styrene-based thermoplastic elastomer is not particularly limited, but it is preferable to have a molecular structure in which styrene blocks are present at one or both ends and elastomer blocks elsewhere. Having a styrene block at at least one end tends to result in better grip performance. Furthermore, it is even more preferable for the styrene-based thermoplastic elastomer to have a structure in which styrene blocks are not present in the main chain portion other than the ends. With such a structure, the hardness of the thermoplastic elastomer in the room temperature range does not become too high, resulting in better grip performance, and tends to result in better fracture characteristics and abrasion resistance.

[0085] Examples of elastomer blocks include vinyl-polydienes such as styrene-butadiene (SB), polyisoprene (IP), polybutadiene, polyethylene, polychloroprene, and poly2,3-dimethylbutadiene. Furthermore, hydrogenated versions of the above-mentioned elastomer blocks can also be used.

[0086] Examples of styrene-based thermoplastic elastomers include styrene-isobutylene block copolymer (SIB), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene block copolymer (SEB), styrene-ethylene-propylene block copolymer (SEP), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-butylene-ethylene block copolymer (SEBC), hydrogenated styrene-butadiene copolymer (HSBR), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), and styrene-butadiene-butylene-styrene block copolymer (SBBS).

[0087] From the viewpoint of grip performance, the styrene unit content (styrene content) of the styrene-based thermoplastic elastomer is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. Furthermore, from the viewpoint of suppressing heat generation, it is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0088] ≪Urethane-based thermoplastic elastomer≫ The urethane-based thermoplastic elastomer is not particularly limited, but for example, those prepared from polyols and diisocyanates can be suitably used. Examples of polyols include polyester polyols, polyester ether polyols, polycarbonate polyols, and polyether polyols. Examples of diisocyanates include tolylene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI).

[0089] ≪Olefin-based thermoplastic elastomers≫ Examples of olefin-based thermoplastic elastomers include ethylene-α-olefin copolymers such as ethylene-propylene copolymer (EPR), ethylene-butene copolymer (EBR), ethylene-hexene copolymer (EHR), and ethylene-octene copolymer (EOR); and ethylene-α-olefin-diene ternary copolymers such as ethylene-propylene-ethylidene norbornene copolymer, ethylene-propylene-butadiene copolymer, and ethylene-propylene-isoprene copolymer.

[0090] ≪Hydrogenation≫ Hydrogenation of thermoplastic elastomers enhances their wear resistance. Therefore, from the viewpoint of further suppressing the deterioration of ride comfort due to wear and maintaining the ride comfort of lightweight tires over a long period, hydrogenated thermoplastic elastomers are preferred. Examples of such hydrogenated thermoplastic elastomers include hydrogenated styrene-based thermoplastic elastomers.

[0091] The thermoplastic elastomer preferably includes a hydrogenated thermoplastic elastomer, or preferably consists solely of a hydrogenated thermoplastic elastomer.

[0092] ≪Degeneration≫ Thermoplastic elastomers can also be modified with a modifying agent to introduce a modifying group, if desired. Any of the modifying groups commonly used in this field can be suitably used, such as alkoxysilyl groups (e.g., trimethoxysilyl group, triethoxysilyl group). For example, after synthesizing a styrene-based thermoplastic elastomer having a styrene terminus at least one end, treatment with chlorotriethoxysilane as a modifying agent can yield a modified styrene-based thermoplastic elastomer in which a triethoxysilyl group is introduced at the active end of the styrene-based thermoplastic elastomer.

[0093] As the thermoplastic elastomer, commercially available products or those obtained through synthesis may be used. Examples of commercially available products include those manufactured and sold by JSR Corporation, Asahi Kasei Corporation, Kuraray Co., Ltd., and Nippon Miractran Co., Ltd.

[0094] The content of thermoplastic elastomer per 100 parts by mass of rubber component is less than 100 parts by mass. If the content of thermoplastic elastomer is 100 parts by mass or more, the abrasion resistance deteriorates and is therefore undesirable. From the viewpoint of abrasion resistance, the content of thermoplastic elastomer is preferably 90 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 50 parts by mass or less. On the other hand, the lower limit of the content of thermoplastic elastomer may vary depending on other formulations, but is not particularly limited as long as the effects of the present invention are exhibited. For example, such a content is 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more.

[0095] (Reinforcement filler) The rubber composition according to the present invention preferably contains a reinforcing filler. The reinforcing filler preferably contains carbon black and silica, but may also consist of at least one of carbon black and silica.

[0096] Carbon Black The carbon black used is not particularly limited and can be any that is common in the tire industry, such as GPF, FEF, HAF, ISAF, SAF, etc. Specifically, N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, etc. can be suitably used, as can other proprietary synthetic products. These carbon blacks may be used individually or in combination of two or more types.

[0097] The nitrogen adsorption specific surface area (N2SA) of carbon black is 50m², considering its weather resistance and reinforcing properties. 2 Preferably 80m / g or more. 2 More preferably 100m / g or more, 2 A value of 250m / g or higher is even more preferable. Furthermore, from the viewpoint of dispersibility, low fuel consumption, fracture characteristics, and durability, 250m is preferable. 2 Preferably less than / g, 220m 2 A value of less than / g is more preferable. Note that the N2SA of carbon black in this specification is the value measured by the method described above.

[0098] When carbon black is included, the content per 100 parts by mass of rubber component 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, from the viewpoint of weather resistance and reinforcing properties. Furthermore, from the viewpoint of improving durability by suppressing heat generation in the tread area, it is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and even more preferably 5 parts by mass or less.

[0099] Silica Silica is not particularly limited, and for example, those commonly used in the tire industry can be used, such as silica prepared by a dry process (anhydrous silica), silica prepared by a wet process (hydrous silica), and the like. Among these, hydrous silica prepared by a wet process is preferable because it has a large number of silanol groups. These silicas may be used alone, or two or more kinds thereof may be used in combination.

[0100] The nitrogen adsorption specific surface area (N2SA) of silica is 140 m from the viewpoint of securing reinforcing properties and damping properties in the tread portion 2 / g or more is preferable, 150 m 2 / g or more is more preferable, 160 m 2 / g or more is even more preferable, 170 m 2 / g or more is still more preferable. Further, from the viewpoint of heat build-up and processability, it is 350 m 2 / g or less is preferable, 300 m 2 / g or less is more preferable, 250 m 2 / g or less is even more preferable. Note that N2SA of silica in the present specification is a value measured by the above method.

[0101] When silica is contained, the content relative to 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, from the viewpoint of securing damping properties in the tread portion and wet grip performance. Further, from the viewpoints of reducing the specific gravity of the rubber composition to achieve weight reduction, improving durability by suppressing heat build-up in the tread portion, and securing riding comfort performance due to the softness of rubber, the content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, further preferably 90 parts by mass or less, and still more preferably 80 parts by mass or less.

[0102] <<Other Reinforcing Fillers>> Other reinforcing fillers besides silica and carbon black can include aluminum hydroxide, calcium carbonate, alumina, clay, talc, and other materials commonly used in the tire industry.

[0103] The silica content in the total 100% by mass of silica and carbon black is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and may also be 100% by mass.

[0104] From the viewpoint of the effects of the present invention, the total content of the reinforcing filler per 100 parts by mass of rubber component is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and even more preferably 85 parts by mass or less. Furthermore, from the viewpoint of ensuring reinforcing properties and damping properties in the tread portion, it is preferably 25 parts by mass or more, more preferably 35 parts by mass or more, even more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and even more preferably 55 parts by mass or more.

[0105] Furthermore, if the reinforcing filler consists only of carbon black and silica, the total content of the reinforcing filler and the content of either carbon black or silica are determined according to the above, and the content of the other is automatically determined.

[0106] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent that has conventionally been used in combination with silica in the tire industry can be used, for example, the following silane coupling agents having a mercapto group; silane coupling agents having a sulfide group such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; silane coupling agents having a vinyl group such as vinyltriethoxysilane and vinyltrimethoxysilane; 3-aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane Examples of silane coupling agents include those having an amino group, such as nopropyltrimethoxysilane and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents, such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents, such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents, such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. In particular, it is preferable to contain at least one silane coupling agent having a sulfide group and a silane coupling agent having a mercapto group, and it is preferable to contain a silane coupling agent having a sulfide group. Examples of silane coupling agents include those manufactured and sold by Momentive and Evonik Degussa. These silane coupling agents may be used individually or in combination of two or more.

[0107] The silane coupling agent having a mercapto group is preferably at least one compound represented by the following chemical formula (1), and a compound containing bond unit A represented by the following chemical formula (2) and bond unit B represented by the following chemical formula (3). [ka] (In the formula, R 101 , R 102 , and R 103Each of these is independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or -O-(R 111 -O) z -R 112 (z R 111 Each of these independently represents a divalent hydrocarbon group having 1 to 30 carbon atoms; R 112 R represents an alkyl group with 1 to 30 carbon atoms, an alkenyl group with 2 to 30 carbon atoms, an aryl group with 6 to 30 carbon atoms, or an aralkyl group with 7 to 30 carbon atoms; z represents an integer from 1 to 30. 104 (This represents alkylenes with 1 to 6 carbon atoms.) [ka] [ka] (In the formula, x represents an integer greater than or equal to 0; y represents an integer greater than or equal to 1; R 201 R represents a C1-C30 alkyl, C2-C30 alkenyl, or C2-C30 alkynyl atom which may be substituted with a hydrogen atom, a halogen atom, a hydroxyl or carboxyl atom; 202 R represents alkylene with 1 to 30 carbon atoms, alkenylene with 2 to 30 carbon atoms, or alkynylene with 2 to 30 carbon atoms; where R 201 and R 202 (They may form a ring structure.)

[0108] Examples of compounds represented by chemical formula (1) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and compounds represented by the following chemical formula (4). Examples of these silane coupling agents include those manufactured by Evonik Degussa. These silane coupling agents may be used individually or in combination of two or more. [ka]

[0109] Examples of compounds containing the bonding unit A shown in chemical formula (2) and the bonding unit B shown in chemical formula (3) include those manufactured by Momentive. These may be used individually or in combination of two or more.

[0110] When a silane coupling agent is included, the content per 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more, from the viewpoint of improving silica dispersibility. Furthermore, from the viewpoint of preventing a decrease in wear resistance, the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less.

[0111] (Plasticizer) The rubber composition according to the present invention preferably contains a plasticizer. In this specification, a plasticizer is a material that imparts plasticity to a rubber component, and is a concept that includes liquid plasticizers (plasticizers that are liquid at 25°C) and solid plasticizers (plasticizers that are solid at 25°C). Specifically, it is a component that can be extracted from a rubber composition using acetone. These may be used individually or in combination of two or more.

[0112] Examples of liquid plasticizers include oils, liquid polymers (diene-based, olefin-based, ester-based, etc.), liquid resins, essential oils derived from natural products such as turpentine oil, and ester-based plasticizers, of which oils are preferred. Examples of solid plasticizers include resins commonly used in the tire industry that are solid at 25°C. These may be used individually or in combination of two or more.

[0113] From the viewpoint of the effects of the present invention, the total content of plasticizers (total content of liquid plasticizers and solid plasticizers) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, per 100 parts by mass of rubber components. Furthermore, the total content is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, and even more preferably 29 parts by mass or less.

[0114] ≪Oil≫ Examples of oils include process oils, vegetable oils, and animal oils. Examples of process oils include paraffinic process oils, naphthenic process oils, and aromatic process oils. Furthermore, process oils with a low content of polycyclic aromatic compounds (PCA) are used as an environmental measure. Examples of low-PCA process oils include treated distillate aromatic extract (TDAE) obtained by re-extracting oil-aromatic process oils, aroma substitute oils which are a mixture of asphalt and naphthenic oil, mild extraction solvates (MES), and heavy naphthenic oils.

[0115] When oil is included, the oil content per 100 parts by mass of rubber component is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of low fuel consumption and durability, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and even more preferably 24 parts by mass or less. In this specification, the oil content also includes the amount of oil contained in oil-spread rubber and oil-containing sulfur.

[0116] ≪Resin≫ The resin is not particularly limited, but examples include petroleum resins, terpene resins, rosin resins, and phenolic resins commonly used in the tire industry. These resins may be used individually or in combination of two or more.

[0117] Petroleum resin Examples of petroleum resins include C5-based petroleum resins, aromatic petroleum resins, and C5C9-based petroleum resins. One or more types of petroleum resins can be used.

[0118] C5 petroleum resin In this specification, "C5 petroleum resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions with 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is preferably used as the C5 petroleum resin. One or more types of C5 petroleum resins can be used.

[0119] Aromatic petroleum resin In this specification, "aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, which may be hydrogenated or modified. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of aromatic petroleum resins that are preferably used include coumarone indene resin, coumarone resin, indene resin, and aromatic vinyl resins. As aromatic vinyl resins, homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene are preferred, and copolymers of α-methylstyrene and styrene are more preferred, due to their economical nature, ease of processing, and excellent heat generation properties. Commercially available aromatic vinyl resins, such as those manufactured by Kraton, are preferably used. One or more aromatic petroleum resins can be used.

[0120] C5C9 petroleum resin In this specification, "C5C9 petroleum resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be hydrogenated or modified. Examples of the C5 fraction and C9 fraction include the petroleum fractions mentioned above. Commercially available C5C9 petroleum resins, such as those manufactured by LUHUA, Qilong, and Tosoh Corporation, are preferably used. One or more types of C5C9 petroleum resins can be used.

[0121] Terpene resins Examples of terpene resins include polyterpene resins consisting of at least one terpene compound selected from α-pinene, β-pinene, limonene, dipentene, etc., aromatically modified terpene resins made from terpene compounds and aromatic compounds, terpene phenol resins made from terpene compounds and phenolic compounds (terpene resins that have not been hydrogenated), and these terpene resins that have been hydrogenated (hydrogenated terpene resins). Examples of aromatic compounds used as raw materials for aromatically modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene, and examples of phenolic compounds used as raw materials for terpene phenol resins include phenol, bisphenol A, cresol, and xylenol. One or more types of terpene petroleum resins can be used.

[0122] Rosin-based resin Rosin-based resins are resins whose main component is rosin acid obtained by processing pine resin. Examples of rosin-based resins include naturally occurring rosin resins (polymerized rosin) such as gum rosin, wood rosin, and tall oil rosin, which are mainly composed of resin acids such as abietic acid, neoabietic acid, palastic acid, levopimaric acid, pimaric acid, isopimaric acid, and dehydroabietic acid, as well as modified rosin resins such as hydrogenated rosin resin, unsaturated carboxylic acid-modified rosin resin, and rosin-modified phenolic resin, rosin esters such as rosin glycerin ester and unsaturated carboxylic acid-modified rosin ester, and disproportionated rosin resins obtained by disproportionating rosin resin. One or more types of rosin-based petroleum resins can be used.

[0123] Phenolic resins Phenolic resins are resins that contain a phenol skeleton in their structure, and examples include phenol-formaldehyde resins, alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, and oil-modified phenol-formaldehyde resins. One or more types of phenolic resins can be used.

[0124] As for the resin, petroleum resin is preferred, aromatic petroleum resin is more preferred, and aromatic vinyl resin is even more preferred, from the viewpoint of obtaining a good balance of ride comfort, durability, and wet grip performance.

[0125] When resin is included, the content of the rubber component per 100 parts by mass 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, from the viewpoint of ride comfort and wet grip performance. Furthermore, from the viewpoint of durability performance, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less.

[0126] (Other combination drugs) In addition to the components mentioned above, the tread rubber composition according to the present invention may appropriately contain compounding agents commonly used in the tire industry, such as waxes, processing aids, antioxidants, vulcanizing agents such as zinc oxide, stearic acid, and sulfur, and vulcanization accelerators.

[0127] ≪Wax≫ When wax is included, the amount of wax per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of weather resistance of the rubber. Furthermore, from the viewpoint of preventing whitening of the tire due to bloom, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0128] Processing aids As processing aids, fatty acid metal salts can be used to lower the viscosity of the rubber and ensure mold release properties before vulcanization, and commercially available compatibilizers can be used to suppress microscopic layer separation of rubber components.

[0129] When processing aids are included, the content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of exhibiting an effect of improving processability. Furthermore, from the viewpoint of abrasion resistance and fracture strength, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0130] Anti-aging agent Anti-aging agents are not limited to any specific type, but examples include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as metal carbamate salts.

[0131] When an anti-aging agent is included, the content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of the rubber's resistance to ozone cracking. Furthermore, from the viewpoint of wear resistance and wet grip performance, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0132] ≪Zinc Oxide≫ When zinc oxide is included, its content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of wear resistance, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0133] ≪Stearic Acid≫ When stearic acid is included, its content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0134] ≪Sulfurizing agent≫ Sulfur is preferably used as a vulcanizing agent. Suitable sulfur varieties include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0135] When sulfur is included as a vulcanizing agent, the amount of sulfur per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1.0 part by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, it is preferably 7.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 5.0 parts by mass or less.

[0136] Examples of vulcanizing agents other than sulfur include organic crosslinking agents containing sulfur atoms, such as alkylphenol-sulfur chloride condensates, 1,6-hexamethylene-dithiosulfate sodium dihydrate, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, as well as organic peroxides such as dicumyl peroxide. Examples of these non-sulfur vulcanizing agents include those manufactured by Taoka Chemical Industries, Ltd., Flexis, and Lanxess K.K.

[0137] <<Vulcanization accelerator>> While there are no particular limitations on the vulcanization accelerators, examples include sulfenamide, thiazole, thiram, thiourea, guanidine, dithiocarbamate, aldehyde-amine or aldehyde-ammonia, imidazoline, and xanthate vulcanization accelerators. Among these, sulfenamide and guanidine vulcanization accelerators are preferred because they more favorably produce the desired effects, and it is even more preferable to use these two in combination.

[0138] Examples of sulfenamide-based vulcanization accelerators include N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), Nt-butyl-2-benzothiazolyl sulfenamide (TBBS), N-oxyethylene-2-benzothiazolyl sulfenamide, N,N'-diisopropyl-2-benzothiazolyl sulfenamide, and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide. Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole and dibenzothiazolyl disulfide. Examples of thiuram-based vulcanization accelerators include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, and tetrabenzylthiuram disulfide (TBzTD). Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), diorthototrilguanidine, and orthototrilbiguanidine. These vulcanization accelerators may be used individually or in combination of two or more.

[0139] When a vulcanization accelerator is included, its content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, and more preferably 2 parts by mass or more. Furthermore, the content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less. By keeping the content of the vulcanization accelerator within the above range, it tends to be possible to ensure fracture strength and elongation.

[0140] <Manufacturing method> (Rubber composition) Rubber compositions can be manufactured by known methods. For example, they can be manufactured by mixing each of the above components using rubber mixing equipment such as an open roll or closed-type kneader (Banbury mixer, kneader, etc.).

[0141] The mixing process includes, for example, a base mixing process in which compounding agents and additives other than the vulcanizing agent and vulcanization accelerator are mixed, and a final mixing (F mixing) process in which the vulcanizing agent and vulcanization accelerator are added to the mixture obtained in the base mixing process and mixed. Furthermore, the base mixing process can be divided into multiple processes as desired. The mixing conditions are not particularly limited, but for example, in the base mixing process, mixing is performed at a discharge temperature of 150 to 170°C for 1 to 10 minutes, and in the final mixing process, mixing is performed at 70 to 110°C for 1 to 5 minutes.

[0142] (tire) The tire of the present invention can be manufactured by conventional methods. For example, the unvulcanized rubber composition obtained above can be extruded to match the shape of the tread portion, bonded together with other tire components on a tire molding machine, and molded to form an unvulcanized tire. This unvulcanized tire can then be heated and pressurized in a vulcanizing machine to manufacture the tire. The vulcanization conditions are not particularly limited, and for example, a method of vulcanization at 150 to 200°C for 10 to 30 minutes can be used.

[0143] <Application> The tire according to the present invention has a tread portion made of the above-mentioned rubber composition and can be used for passenger car tires, truck and bus tires, run-flat tires, motorcycle tires, etc. It can also be used for summer tires and all-season tires. Of these, it can be suitably used for passenger cars from the viewpoint of the effects of the present invention. A passenger car tire is a tire intended to be mounted on a four-wheeled vehicle and has a maximum load capacity of 1000 kg or less. Here, the maximum load capacity is the maximum load capacity specified for each tire in the standard system including the standard on which the tire is based. For example, in the case of the JATMA standard (Japan Automobile Tire Manufacturers Association standard), it is the maximum load capacity based on the load index (LI), in the case of TRA it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO it is "LOAD CAPACITY". [Examples]

[0144] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0145] The various chemicals used in the examples and comparative examples are summarized below.

[0146] <Various chemicals> SBR1: HPR850 manufactured by JSR Corporation (S-SBR, styrene content: 27.5% by mass, vinyl content: 59.0 mol%, Tg: -24℃, Mw: 200,000, non-oil-based product) SBR2: NipolNS522 manufactured by ZS Elastomer Co., Ltd. (S-SBR, styrene content: 39.0% by mass, vinyl content: 40.0 mol%, Tg: -25℃, Mw: 1.25 million, contains 37.5 parts by mass of oil-extending agent per 100 parts by mass of solids) BR: UBEPOL BR(registered trademark) 150B manufactured by Ube Industries, Ltd. (Vinyl content: 1.5 mol%, Cis content: 97%, Mw: 440,000) Carbon Black: Mitsubishi Chemical Corporation's Dia Black N220 (N2SA: 115ml) 2 / g) Silica: ULTRASIL(registered trademark) VN3 (N2SA: 175m) manufactured by Evonik Degussa. 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa. Oil: H&R VivaTec400 (TDAE oil) Thermoplastic elastomer 1: Dynalon 4600P manufactured by JSR Corporation (hydrogenated styrene-based thermoplastic elastomer, styrene-ethylene-butylene-ethylene block copolymer (SEBC), styrene content: 20%) Thermoplastic elastomer 2: Hybrar 5125 (unhydrogenated styrene-based thermoplastic elastomer, styrene-isoprene-styrene block copolymer (SIS), styrene content: 20%) manufactured by Kuraray Co., Ltd. Thermoplastic elastomer 3: Miractran P22M (polyurethane-based thermoplastic elastomer) manufactured by Miractran Japan Co., Ltd. Resin: Sylvares SA85 manufactured by Kraton (a copolymer of α-methylstyrene and styrene, softening point: 85°C) Wax: Sunnock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Stearic acid: Beads of stearic acid manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator 1: Noxellar NS-P (N-(tert-butyl)-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noxellar D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0147] <Tire Manufacturing> According to the formulation shown in the table, all chemicals except sulfur and vulcanization accelerator were mixed in a 1.7 L sealed Banbury mixer at a discharge temperature of 150°C for 5 minutes. Next, sulfur and vulcanization accelerator were added to the resulting mixture and kneaded in a twin-screw open roll for 4 minutes until it reached 105°C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into the shape of a tread and bonded together with other tire components to produce an unvulcanized tire. The tire was then press-vulcanized at 170°C for 12 minutes to obtain test tire 1 (195 / 65R15 91V) and test tire 2 (195 / 60R15 88H).

[0148] <Rating> The following tests were conducted on each of the test tires obtained above. The results for test tire 1 are shown in Table 1, and the results for test tire 2 are shown in Table 2. In Table 1, Comparative Example 1 is the standard comparative example, and in Table 2, Comparative Example 10 is the standard comparative example.

[0149] (Wet grip performance) Each test tire was mounted on one of the four wheels of a 1600cc front-wheel-drive passenger car, and the vehicles were driven on a wet asphalt test course. Twenty test drivers evaluated the handling stability at 80 km / h based on their subjective feeling, using an integer score from 1 to 5. The total score was then calculated. The total score for the benchmark and comparison was converted to a baseline value (100), and the evaluation results for each test tire were indexed. A higher numerical value indicates better wet grip performance.

[0150] (Ride comfort performance) Each test tire was mounted on the four wheels of a 1600cc front-wheel-drive passenger car, and the vehicles were driven on an unpaved test course. Twenty test drivers evaluated the ride comfort performance at 80 km / h based on their feelings during straight-line driving, lane changes, and acceleration / deceleration, using an integer score from 1 to 5. The total score was calculated. The total score of the comparison between the standard and comparison tires was converted to a baseline value (100), and the evaluation results of each test tire were indexed. A higher numerical value indicates better ride comfort performance.

[0151] [Table 1]

[0152] [Table 2]

[0153] (Consideration) From the above results, it can be seen that the tire of the present invention has improved ride comfort performance. Furthermore, in a preferred embodiment of the tire of the present invention, a balance with wet grip performance is also achieved.

[0154] <Embodiment> Examples of embodiments of the present invention are shown below.

[0155] [1] comprising a tread section and a sidewall section, When the thickness of the tread rubber constituting the tread portion at the tire equator is T (mm), the thickness of the sidewall rubber constituting the sidewall portion at the tire's maximum width position is S (mm), the tire weight is G (kg), and the tire's maximum load capacity is WL (kg), then T, S, G, and WL satisfy the following equations (1) to (3) (wherein the right-hand side of equation (1) is preferably 8.0, more preferably 7.8, even more preferably 7.6, even more preferably 7.5, and even more preferably 7.2; the right-hand side of equation (2) is preferably 0.45, more preferably 0.40, even more preferably 0.35, even more preferably 0.33, and even more preferably 0.30; and the right-hand side of equation (3) is preferably 0.011, more preferably 0.010, and even more preferably 0.009). A tire in which the rubber composition constituting the tread rubber contains less than 100 parts by mass of thermoplastic elastomer per 100 parts by mass of rubber component. Formula (1) T≦8.5 Equation (2) S / T<0.50 Formula (3) G / WL≦0.012 [2] The tire according to [1] above, wherein the thermoplastic elastomer comprises a styrene-based thermoplastic elastomer. [3] The tire according to [1] above, wherein the thermoplastic elastomer comprises a hydrogenated styrene-based thermoplastic elastomer. [4] The tire according to any one of [1] to [3] above, wherein the content of the thermoplastic elastomer is 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, per 100 parts by mass of the rubber component. [5] A tire according to any of [1] to [4] above, wherein S satisfies the following formula (4) (wherein the right-hand side of formula (4) is preferably 2.9, more preferably 2.8, even more preferably 2.7, even more preferably 2.6, and even more preferably 2.5). Formula (4) S≦3.0 [6] The tire according to any one of [1] to [5] above, wherein the rubber composition contains 200 parts by mass or less of silica, preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and even more preferably 80 parts by mass or less. [7] The tire according to any one of [1] to [6] above, wherein the rubber composition comprises 40 parts by mass or less, preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 5 parts by mass or less of carbon black. [8] The tire according to any one of [1] to [7] above, wherein the rubber composition contains 200 parts by mass or less, preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and even more preferably 85 parts by mass or less of a reinforcing filler. [9] The tire according to any one of [1] to [8] above, wherein the rubber composition contains 50 parts by mass or less of oil, preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 24 parts by mass or less.

[10] The tire according to any one of [1] to [9] above, wherein the rubber composition contains 30 parts by mass or less of resin, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less.

[11] The tire according to any one of [1] to

[10] above, wherein the rubber composition contains 100 parts by mass or less, preferably 90 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, and even more preferably 29 parts by mass or less of a plasticizer.

[12] A tire for passenger cars, as described in any of [1] to

[11] above.

[0156] In a preferred embodiment, the tire of the present invention not only provides excellent ride comfort but also achieves a balance with good wet grip performance. [Explanation of Symbols]

[0157] 1 tire 2 Tread section 21 Tread Rubber 3. Sidewall section 31 Sidewall rubber 4. Bead section 41 Bead core 5 Carcass 6 Belt Layer 61 Belt ply 62 Belt ply R Rim CL Tire Equator In the PT tire cross-section, a point on the tread surface intersects the tire equator. In the PS tire cross-section, a point on the sidewall at the position of the tire's maximum width. T-tire tread rubber thickness at the equator S: Thickness of the sidewall rubber at the tire's widest point. Wt Tire section width Ht Tire section height DT Tire Outer Diameter

Claims

1. It comprises a tread section and a sidewall section. When the thickness of the tread rubber constituting the tread portion at the tire equator is T (mm), the thickness of the sidewall rubber constituting the sidewall portion at the tire's maximum width position is S (mm), the tire weight is G (kg), and the tire's maximum load capacity is WL (kg), then T, S, G, and WL satisfy the following equations (1) to (3): A passenger car tire in which the rubber composition constituting the tread rubber contains less than 100 parts by mass of thermoplastic elastomer per 100 parts by mass of rubber component. Formula (1) T≦8.5 Formula (2) S / T<0.50 Formula (3) G / WL≦0.012

2. The tire according to claim 1, wherein the thermoplastic elastomer includes a styrene-based thermoplastic elastomer.

3. The tire according to claim 1, wherein the thermoplastic elastomer comprises a hydrogenated styrene-based thermoplastic elastomer.

4. The tire according to any one of claims 1 to 3, wherein the content of the thermoplastic elastomer is 10 parts by mass or more per 100 parts by mass of the rubber component.

5. The tire according to any one of claims 1 to 3, wherein S satisfies the following formula (4). Formula (4) S≦3.0

6. The tire according to any one of claims 1 to 3, wherein the rubber composition contains 80 parts by mass or less of silica.

7. The tire according to any one of claims 1 to 3, wherein the rubber composition contains 5 parts by mass or less of carbon black.

8. The tire according to any one of claims 1 to 3, wherein the rubber composition contains 85 parts by mass or less of a reinforcing filler.

9. The tire according to any one of claims 1 to 3, wherein the rubber composition contains 24 parts by mass or less of oil.

10. The tire according to any one of claims 1 to 3, wherein the rubber composition contains 5 parts by mass or less of resin.

11. The tire according to any one of claims 1 to 3, wherein the rubber composition contains 29 parts by mass or less of a plasticizer.

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