tire

Abstract

To provide a tire having improved durability.SOLUTION: A tire comprises an inner liner and a belt layer. The inner liner is composed of a rubber composition comprising a rubber component. In the rubber component, an aromatic vinyl unit content is defined as S (mass%), and a distance from the tire inner plane on the tire equatorial plane to the innermost part of the belt layer in the radial direction of the tire is defined as D (mm), S is 0.70 mass% or more and 8.00 mass% or less, and the product of S and D (S×D) is 2.0 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to tires. [Background technology]

[0002] An inner liner is provided on the inner cavity surface of a tire as an air permeation suppressing layer to maintain a constant tire air pressure. Further improvement in durability is required for the inner liner. Patent Document 1 describes a rubber composition for an inner liner that can improve durability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-66324 Summary of the Invention [Problem to be solved by the invention]

[0004] The inner liner layer not only maintains the internal pressure of the tire but also prevents oxygen, moisture, and the like from the tire cavity from diffusing into the tire interior, thereby suppressing tire deterioration. Meanwhile, as the tire life cycle has been extending in recent years, it is desired to improve the durability of the inner liner layer and further improve the overall durability of the tire.

[0005] The present disclosure aims to provide a tire with improved durability performance. [Means for solving the problem]

[0006] As a result of extensive investigations, it was found that the above-mentioned problems can be solved by ensuring a predetermined relationship between the aromatic vinyl unit content in the rubber component constituting the inner liner and the distance from the tire cavity surface on the tire equatorial plane to the innermost part in the tire radial direction of the belt layer.

[0007] That is, the present disclosure relates to a tire including an inner liner and a belt layer, wherein the inner liner is made of a rubber composition containing a rubber component, and where S (mass%) is an aromatic vinyl unit content in the rubber component and D (mm) is a distance from the tire cavity surface on the tire equatorial plane to the innermost part of the belt layer in the tire radial direction, S is 0.70 mass% or more and 8.00 mass% or less, and the product of S and D (S × D) is 2.0 or more. [Effects of the Invention]

[0008] According to the present disclosure, a tire is provided with improved durability performance. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a portion of a tire according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] A tire according to one embodiment of the present disclosure is a tire including an inner liner and a belt layer, wherein the inner liner is made of a rubber composition containing a rubber component, and where S (mass%) is an aromatic vinyl unit content in the rubber component and D (mm) is a distance from the tire cavity surface on the tire equatorial plane to the innermost part of the belt layer in the tire radial direction, S is 0.70 mass% or more and 8.00 mass% or less, and the product of S and D (S × D) is 2.0 or more.

[0011] When the aromatic vinyl unit content in the rubber component constituting the inner liner and the distance from the tire cavity surface on the tire equatorial plane to the innermost part in the tire radial direction of the belt layer satisfy the above-mentioned requirements, the durability performance of the obtained tire, particularly after wet heat aging, is significantly improved. The reason for this is thought to be as follows, without intending to be bound by theory.

[0012] It is believed that oxygen and water vapor that pass through the inner liner layer affect the deterioration of the adhesive interface between the cord and rubber in the belt layer, resulting in a decrease in tire durability. The tire of the present disclosure forms domains with aromatic vinyl, which has a bulky skeleton, in the rubber component that constitutes the inner liner layer, thereby reducing the mobility of the polymer molecule main chain, and the bulky skeleton can block oxygen and water molecules from passing through the inner liner layer. In addition, aromatic vinyl is highly hydrophobic, so it is believed to easily repel moisture.

[0013] Furthermore, as the distance from the tire cavity surface to the innermost part of the belt layer in the tire radial direction (gauge from the tire cavity surface to the belt layer) becomes thinner, the air permeability resistance of the tire as a whole tends to decrease. Therefore, by setting the product of the gauge and the aromatic vinyl unit content to a certain level or more and increasing the aromatic vinyl unit content in the rubber component constituting the inner liner as the gauge decreases, the inner liner layer becomes in a state where it more effectively blocks the permeation of oxygen and water molecules, which makes it easier to suppress deterioration of the adhesive interface of the belt layer and is thought to achieve a notable effect of significantly improving the durability performance of the tire, particularly after wet heat aging.

[0014] From the viewpoint of air permeation resistance, the rubber component of the present disclosure preferably contains 75% by mass or more of a butyl rubber.

[0015] From the viewpoint of suppressing cracking at low temperatures, the rubber component of the present disclosure preferably contains a styrene-butadiene rubber having a glass transition temperature (Tg) of -75°C or higher and -40°C or lower.

[0016] The rubber component of the present disclosure preferably contains hydrogenated styrene-butadiene rubber from the viewpoint of suppressing the occurrence of cracks due to deterioration.

[0017] The rubber composition of the present disclosure preferably contains an aromatic petroleum resin from the viewpoint of blocking oxygen and moisture in the tire cavity from diffusing into the tire interior.

[0018] In the tire of the present disclosure, when the thickness of the inner liner on the tire equatorial plane is L (mm), it is preferable that L / D is 0.10 or more.

[0019] By setting L / D within the above range, the thickness of the inner liner layer is ensured to be sufficient relative to the distance from the tire cavity to the belt layer, which is thought to make it easier to suppress the diffusion of oxygen and water vapor into the belt layer.

[0020] From the viewpoint of durability after wet heat aging, the rubber composition of the present disclosure preferably contains 10 parts by mass or more and 50 parts by mass or less of the filler per 100 parts by mass of the rubber component.

[0021] <Definition> The term "aromatic vinyl unit" refers to a unit derived from an aromatic vinyl compound in a copolymer. Here, the term "aromatic vinyl compound" refers to an aromatic compound substituted with at least a vinyl group, and does not include the conjugated diene compounds described below. Examples of aromatic vinyl compounds include styrene, α-methylstyrene, p-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, and 2,4,6-trimethylstyrene, with styrene being preferred. These compounds may be used alone or in combination of two or more.

[0022] "Aromatic vinyl unit content in the rubber component" refers to the total content (mass%) of aromatic vinyl units such as styrene moieties contained in 100% by mass of the rubber component, and is calculated by multiplying the aromatic vinyl unit content (mass%) for each rubber component by the mass fraction in the rubber component, and then adding up the values ​​obtained. Specifically, it is calculated by Σ(aromatic vinyl unit content (mass%) of each aromatic vinyl unit-containing rubber × content (mass%) of each aromatic vinyl unit-containing rubber in the rubber component / 100). When the aromatic vinyl unit-containing rubber is a styrene-butadiene rubber, it is the "styrene content."

[0023] A "genuine rim" is a rim that is determined for each tire by the standard system that includes the standard on which the tire is based. For JATMA, it is a "standard rim," for TRA, it is a "design rim," and for ETRTO, it is a "measuring rim."

[0024] "Distance D from the tire cavity surface on the tire equatorial plane to the innermost part in the tire radial direction of the belt layer" refers to the straight-line distance from the tire cavity surface on the tire equatorial plane to the innermost part in the tire radial direction of the belt layer in a cross section of the tire cut along a plane including the tire rotation axis.

[0025] "The thickness L of the inner liner at the tire equatorial plane" refers to the linear distance from the tire cavity surface at the tire equatorial plane to the innermost part of the carcass in the tire radial direction in a cross section of the tire cut along a plane including the tire rotation axis.

[0026] "Oil content" includes the amount of oil contained in oil-extended rubber.

[0027] <Measurement method> The "distance D from the tire cavity surface to the innermost part of the belt layer in the tire radial direction on the tire equatorial plane" and the "thickness L of the inner liner on the tire equatorial plane" are values ​​measured when the tire is cut at a plane including the tire rotation axis and the width of the bead portion is adjusted to the width of the regular rim.

[0028] "Aromatic vinyl unit content" means 1 This value is calculated by H-NMR measurement and is applied to rubber components (aromatic vinyl unit-containing rubbers) having repeating units derived from aromatic vinyl compounds, such as SBR, copolymers of isobutylene and p-alkylstyrene, and halides of such copolymers.

[0029] The glass transition temperature (Tg) of SBR is measured in accordance with JIS K 7121 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan, Inc., while increasing the temperature at a rate of 10°C / min.

[0030] "N2SA of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0031] A manufacturing procedure for a tire according to one embodiment of the present disclosure will be described in detail below. However, the following description is an example for explaining the present disclosure and is not intended to limit the technical scope of the present disclosure to the described range. In this specification, when a numerical range is indicated using "to" it is intended to include both ends of the numerical range.

[0032] [tire] Fig. 1 is an enlarged cross-sectional view showing a portion of the tread of a tire according to the present disclosure, but is not limited to such an embodiment. The tire according to the present disclosure has a tread portion 1 that comes into contact with the ground during running, and a belt layer 8 on the radially inner side of the tread portion 1. A carcass 9 and an inner liner 7 are laminated below the belt layer 8. A band may also be present between the tread portion 1 and the belt layer 8. In Fig. 1, the belt layer 8 is laminated in two layers, and a band 11 having a jointless structure is disposed inside the base rubber layer 4.

[0033] In FIG. 1, "thickness L of the inner liner" refers to the linear distance from the innermost part of the inner liner 7 in the tire radial direction to the innermost part of the carcass 9 in the tire radial direction at the tire equatorial plane CL.

[0034] In FIG. 1, "distance D from the tire cavity surface to the innermost part in the tire radial direction of the belt layer" refers to the linear distance from the innermost part in the tire radial direction of the inner liner 7 to the innermost part in the tire radial direction of the belt layer 8 at the tire equatorial plane CL, and specifically, is the sum of the thicknesses of the inner liner 7 and the carcass 9.

[0035] From the viewpoint of the effects of the present disclosure, the distance D (mm) from the tire cavity surface on the tire equatorial plane to the innermost part in the tire radial direction of the belt layer is preferably 1.0 mm or more, more preferably 1.5 mm or more, even more preferably 2.0 mm or more, and particularly preferably 2.5 mm or more. Also, from the viewpoint of the effects of the present disclosure, D (mm) is preferably 7.0 mm or less, more preferably 6.0 mm or less, even more preferably 5.0 mm or less, and particularly preferably 4.0 mm or less.

[0036] From the viewpoint of the effects of the present disclosure, the thickness L (mm) of the inner liner on the tire equatorial plane is preferably 0.1 mm or more, more preferably 0.2 mm or more, and even more preferably 0.3 mm or more. Also, from the viewpoint of the effects of the present disclosure, L (mm) is preferably 1.0 mm or less, more preferably 0.9 mm or less, even more preferably 0.8 mm or less, and particularly preferably 0.7 mm or less.

[0037] From the viewpoint of the effects of the present disclosure, the aromatic vinyl unit content S in the rubber component constituting the inner liner is 0.70% by mass or more, preferably 0.85% by mass or more, more preferably 1.00% by mass or more, and even more preferably 1.20% by mass or more. Also, from the viewpoint of the effects of the present disclosure, the aromatic vinyl unit content S in the rubber component is 8.00% by mass or less, preferably 7.20% by mass or less, more preferably 6.60% by mass or less, even more preferably 6.00% by mass or less, and particularly preferably 5.00% by mass or less.

[0038] The aromatic vinyl unit content value in the rubber component constituting the inner liner corresponds to the weighted average of the aromatic vinyl unit contents of each rubber component contained in the rubber component. Therefore, for example, the aromatic vinyl unit content value can be increased by using a large amount of rubber components with a large aromatic vinyl unit content value, and conversely, the aromatic vinyl unit content value can be decreased by using a large amount of rubber components with a small aromatic vinyl unit content value.

[0039] The product of S and D (S×D) is 2.0 or more, preferably 2.4 or more, more preferably 2.8 or more, even more preferably 3.0 or more, and particularly preferably 4.0 or more. By setting the product of S and D (S×D) within the above range, the air permeability resistance of the inner liner can be ensured. Furthermore, from the viewpoint of the effects of the present disclosure, the product of S and D (S×D) is preferably 15.0 or less, more preferably 13.0 or less, even more preferably 11.0 or less, and particularly preferably 10.0 or less.

[0040] The ratio (L / D) of the thickness of the inner liner L at the tire equatorial plane to the distance D from the tire cavity surface at the tire equatorial plane to the innermost part of the belt layer in the tire radial direction is preferably 0.05 or more, more preferably 0.07 or more, and even more preferably 0.10 or more. By setting L / D within the above range, the thickness of the inner liner layer is ensured sufficiently relative to the distance from the tire cavity to the belt layer, which is thought to make it easier to suppress the diffusion of oxygen and water vapor into the belt layer. Furthermore, from the viewpoint of the effects of the present disclosure, L / D is preferably 0.90 or less, more preferably 0.70 or less, even more preferably 0.50 or less, even more preferably 0.40 or less, and particularly preferably 0.30 or less.

[0041] [Rubber composition] In the tire of the present disclosure, the aromatic vinyl unit content in the rubber component constituting the inner liner and the distance from the tire cavity surface on the tire equatorial plane to the innermost part in the tire radial direction of the belt layer work together to more effectively improve the overall performance of embrittlement resistance and durability performance after wet heat aging.

[0042] <Rubber component> The rubber composition constituting the inner liner of the present disclosure (hereinafter, unless otherwise specified, referred to as the rubber composition of the present disclosure) preferably contains a butyl-based rubber as a rubber component, more preferably contains a butyl-based rubber and a styrene-butadiene rubber, and may be a rubber component consisting only of a butyl-based rubber and a styrene-butadiene rubber.

[0043] Examples of butyl rubbers include non-halogenated butyl rubber (regular butyl rubber, IIR), halogenated butyl rubber (X-IIR) such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR), and copolymers of isobutylene and p-alkylstyrene. Of these, one or more selected from the group consisting of halogenated butyl rubber (X-IIR) and copolymers of isobutylene and p-alkylstyrene are preferred, with copolymers of isobutylene and p-alkylstyrene being more preferred. These butyl rubbers may be used alone or in combination of two or more.

[0044] Examples of p-alkylstyrenes constituting the copolymer of isobutylene and p-alkylstyrene include p-methylstyrene. The copolymer of isobutylene and p-alkylstyrene may be halogenated. The halogenated site may be either an isobutylene unit or a p-alkylstyrene unit, but is preferably a p-alkylstyrene unit, and more preferably an alkyl group of the p-alkylstyrene unit.

[0045] From the viewpoints of air permeation resistance and heat resistance, the content of the butyl rubber in the rubber component is preferably 60% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, and particularly preferably 75% by mass. The upper limit of the content of the butyl rubber in the rubber component is not particularly limited, but can be, for example, 99% by mass or less, 97% by mass or less, 95% by mass or less, 93% by mass or less, or 90% by mass or less.

[0046] The aromatic vinyl unit content of the copolymer of isobutylene and p-alkylstyrene and the halogenated product of the copolymer can be appropriately selected so that the aromatic vinyl unit content in the rubber component satisfies the above-mentioned range, but is preferably 1.0 mass% or more, more preferably 3.0 mass% or more, even more preferably 5.0 mass% or more, and particularly preferably 7.0 mass% or more. The aromatic vinyl unit content of the copolymer of isobutylene and p-alkylstyrene and the halogenated product of the copolymer is preferably 20 mass% or less, more preferably 18 mass% or less, and even more preferably 15 mass% or less. The aromatic vinyl unit content of the multicomponent polymer is measured by the above-mentioned measurement method.

[0047] (SBR) The SBR is not particularly limited, and examples thereof include emulsion-polymerized SBR (E-SBR) and solution-polymerized SBR (S-SBR). Modified SBRs using modifiers (modified SBRs) and hydrogenated SBRs (hydrogenated SBRs) can also be used. These SBRs may be used alone or in combination. Hydrogenated SBRs are preferred because they contain fewer highly reactive unsaturated bonds than non-hydrogenated SBRs, resulting in less degradation due to heat and aging.

[0048] The hydrogenation rate of hydrogenated SBR is preferably 30 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, and particularly preferably 90 mol% or more. There is no particular upper limit to the hydrogenation rate of the multicomponent polymer, as long as it is less than 100 mol%. The hydrogenation rate can be adjusted by adjusting the reaction conditions, such as the hydrogen gas supply pressure and reaction temperature, in the hydrogenation reaction as described in Production Example 2 below. The hydrogenation rate of SBR refers to the proportion of double bonds on conjugated diene units that have been hydrogenated, 1 It can be calculated from the spectral reduction rate of the unsaturated bond portion of the spectrum obtained by measuring H-NMR.

[0049] The SBR may be either oil-extended or non-oil-extended. When oil-extended SBR is used, the amount of oil extension of the SBR, i.e., the content of the oil-extending oil contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of the rubber solids content of the SBR.

[0050] The glass transition temperature (Tg) of SBR is preferably −75° C. or higher, more preferably −70° C. or higher, and even more preferably −65° C. or higher. The Tg is also preferably −25° C. or lower, more preferably −30° C. or lower, still more preferably −35° C. or lower, still more preferably −40° C. or lower, still more preferably −45° C. or lower, and particularly preferably −50° C. or lower. By setting the Tg of SBR within the above range, the Tg of the rubber composition also decreases, which is thought to improve embrittlement resistance at low temperatures.

[0051] The styrene content of SBR can be appropriately selected so that the aromatic vinyl unit content in the rubber component falls within the aforementioned range, but is preferably 40% by mass or less, more preferably 36% by mass or less, even more preferably 32% by mass or less, and particularly preferably 28% by mass or less. The styrene content of SBR is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. The styrene content of SBR is measured by the above-mentioned method for measuring aromatic vinyl unit content.

[0052] The content of SBR in the rubber component can be appropriately selected so that the aromatic vinyl unit content in the rubber component satisfies the above-mentioned range, but is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 7% by mass or more. On the other hand, the content of SBR in the rubber component is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less.

[0053] (Other rubber components) The rubber component may contain rubber components other than those described above, provided that the effects of the present disclosure are not impaired. Examples of such rubber components include diene rubbers other than SBR, such as isoprene rubber, butadiene rubber (BR), styrene-isoprene rubber (SIR), styrene-isoprene butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR); and non-diene rubbers such as hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. In addition to the rubber components described above, the rubber composition may or may not contain a known thermoplastic elastomer.

[0054] Examples of isoprene-based rubbers that can be used include those commonly used in the tire industry, such as isoprene rubber (IR) and natural rubber. Natural rubber includes unmodified natural rubber (NR) as well as modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), highly purified natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0055] The NR is not particularly limited, and those commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0056] From the viewpoint of the effects of the present disclosure, the content of the isoprene-based rubber in the rubber component is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less. There is no particular lower limit for the content of the isoprene-based rubber in the rubber component.

[0057] <Filler> The rubber composition according to the present disclosure contains carbon black as a filler, and may also contain a filler other than carbon black. The filler may also consist solely of carbon black.

[0058] (carbon black) The carbon black is not particularly limited, and can be, for example, one commonly used in the tire industry, such as GPF, FEF, HAF, ISAF, SAF, etc. These carbon blacks may be used alone or in combination of two or more.

[0059] The nitrogen adsorption specific surface area (N2SA) of carbon black is 10 m because it provides sufficient reinforcing effect. 2 / g or more is preferable, and 20m 2 In addition, the N2SA of carbon black is preferably 80m / g or more from the viewpoint of air permeability resistance and durability. 2 / g or less is preferable, and 60m 2 / g or less is more preferable, and 40m 2 / g or less is more preferable. The N2SA of carbon black is measured by the above-mentioned measurement method.

[0060] When carbon black is contained, the content per 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more, and particularly preferably 30 parts by mass or more, from the viewpoint of embrittlement resistance and reinforcement. Also, from the viewpoint of durability after moist heat aging, the content of carbon black is preferably 70 parts by mass or less, more preferably 65 parts by mass or less, even more preferably 60 parts by mass or less, still more preferably 55 parts by mass or less, and particularly preferably 50 parts by mass or less.

[0061] (Other fillers) Fillers other than carbon black that have been commonly used in the tire industry can be blended, such as silica aluminum hydroxide, calcium carbonate, alumina, clay, talc, etc. Among these, one or more selected from the group consisting of calcium carbonate, clay, and talc are preferred, with calcium carbonate being more preferred.

[0062] The content of the filler other than carbon black per 100 parts by mass of the rubber component is not particularly limited, but from the viewpoint of reinforcement, it 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. Moreover, the content of the filler other than carbon black is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less.

[0063] From the viewpoint of the effects of the present disclosure, the total amount of filler per 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more, and particularly preferably 30 parts by mass or more. Also, from the viewpoint of the effects of the present disclosure, the total amount of filler per 100 parts by mass of the rubber component is preferably 70 parts by mass or less, more preferably 65 parts by mass or less, even more preferably 60 parts by mass or less, still more preferably 55 parts by mass or less, and particularly preferably 50 parts by mass or less.

[0064] From the viewpoint of the effects of the present disclosure, the content of carbon black in 100% by mass of the filler is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more. There is no particular upper limit to the content of carbon black in 100% by mass of the filler.

[0065] <Other compounding agents> In addition to the above components, the rubber composition according to the present disclosure may appropriately contain compounding agents conventionally commonly used in the tire industry, such as softeners, waxes, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0066] (softener) The rubber composition according to the present disclosure preferably contains a softener, such as a resin component, oil, or liquid rubber.

[0067] The resin component is not particularly limited, but examples thereof include hydrocarbon resins commonly used in the tire industry, such as petroleum resins, terpene resins, rosin resins, and phenolic resins, with aromatic petroleum resins being preferred. These resin components may be used alone or in combination of two or more.

[0068] As used herein, "aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified version of the resin. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of aromatic petroleum resins that are suitable for use include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins. Preferred aromatic vinyl resins are homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene, with copolymers of α-methylstyrene and styrene being more preferred, due to their economical efficiency, ease of processing, and excellent heat generation properties. Examples of aromatic vinyl resins that can be used include commercially available products from Kraton, Eastman Chemical Company, and the like.

[0069] When a resin component is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 1.0 part by mass or more. The content of the resin component is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0070] Examples of oils include process oil, vegetable oils, and animal fats. Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil. Furthermore, as an environmental measure, process oil with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of the low-PCA process oil include mild extract solvates (MES), treated distillate aromatic extracts (TDAE), and heavy naphthenic oil.

[0071] When oil is contained, the content per 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more from the viewpoint of processability, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 10 parts by mass or less from the viewpoint of abrasion resistance.

[0072] The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25°C), and examples thereof include liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), liquid farnesene rubber, etc. These liquid rubbers may be used alone or in combination of two or more.

[0073] When the liquid rubber is contained, the content thereof is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 10 parts by mass or less.

[0074] When a softener is contained, the content (total amount when multiple softeners are used) per 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more. The content of the softener is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less.

[0075] When wax is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of weather resistance of the rubber, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of preventing whitening of the tire due to bloom.

[0076] Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. Examples of processing aids that can be used include those commercially available from Schill + Seilacher, Performance Additives, etc. One type of processing aid may be used alone, or two or more types may be used in combination.

[0077] When a processing aid is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of improving processability, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less, from the viewpoint of abrasion resistance and breaking strength.

[0078] The antioxidant is not particularly limited, and those used in the rubber industry can be used, such as quinoline-based, quinone-based, phenol-based, and phenylenediamine-based antioxidants.

[0079] When an antioxidant is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 0.8 parts by mass or more, and from the viewpoints of dispersibility of fillers and the like, elongation at break, and kneading efficiency, the content of the antioxidant is preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, and even more preferably 1.2 parts by mass or less.

[0080] When stearic acid is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of vulcanization rate, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of processability.

[0081] When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of vulcanization rate, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of abrasion resistance.

[0082] As the vulcanizing agent, sulfur is preferably used, and examples of sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0083] When sulfur is contained as a vulcanizing agent, the content per 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, the content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, even more preferably 3.0 parts by mass or less, and particularly preferably 2.5 parts by mass or less. When oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0084] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensate, sodium 1,6-hexamethylene-dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. These vulcanizing agents other than sulfur can be commercially available from Taoka Chemical Co., Ltd., Lanxess K.K., Flexis, etc.

[0085] Examples of vulcanization accelerators include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. Among them, in terms of more suitably obtaining the desired effect, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based, and thiazole-based vulcanization accelerators are preferred, and thiazole-based vulcanization accelerators are more preferred.

[0086] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), etc. Among these, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS) and N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) are preferred.

[0087] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0088] Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, etc. Among these, di-2-benzothiazolyl disulfide is preferred.

[0089] When a vulcanization accelerator is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more. The content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably 8.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, breaking strength and elongation tend to be ensured.

[0090] <Manufacturing> The rubber composition according to the present disclosure can be produced by a known method, for example, by kneading the above-described components using a rubber kneading device such as an open roll or an internal kneader (such as a Banbury mixer or kneader).

[0091] The kneading step includes, for example, a base kneading step in which compounding ingredients and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading step and kneaded. Furthermore, the base kneading step can be divided into multiple steps as desired.

[0092] The kneading conditions are not particularly limited, but examples include a method in which the base kneading step involves kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and a method in which the final kneading step involves kneading for 1 to 5 minutes at 70 to 110°C. The vulcanization conditions are not particularly limited, but examples include a method in which vulcanization is carried out for 10 to 30 minutes at 150 to 200°C.

[0093] The tire of the present disclosure, which includes an inner liner made of the rubber composition, can be manufactured by a conventional method. That is, an unvulcanized rubber composition obtained by blending the above-mentioned components with a rubber component as needed is extruded to fit the shape of the inner liner, and then laminated together with other tire components in a tire building machine and molded by a conventional method to form an unvulcanized tire. The unvulcanized tire is then heated and pressurized in a vulcanizer to manufacture the tire. The vulcanization conditions are not particularly limited, and examples include a method of vulcanizing at 150 to 200°C for 10 to 30 minutes.

[0094] <Application> The tire of the present disclosure can be suitably used as a passenger car tire, a truck / bus tire, a motorcycle tire, or a racing tire, and is particularly preferably used as a passenger car tire. Passenger car tires are tires designed to be mounted on four-wheeled vehicles and have a maximum load capacity of 1000 kg or less. The tire of the present disclosure can also be used as an all-season tire, a summer tire, or a winter tire such as a studless tire. [Example]

[0095] Hereinafter, the present disclosure will be described based on examples, but the present disclosure is not limited to these examples.

[0096] The various chemicals used in the examples and comparative examples are listed below. NR:TSR20 SBR1: SL553 manufactured by JSR Corporation (unmodified SBR, styrene content: 10% by mass, Tg: -61°C, non-oil extended) SBR2: N9541 manufactured by Zeon Corporation (unmodified SBR, styrene content: 46% by mass, Tg: -66°C, contains 37.5 parts by mass of oil per 100 parts by mass of rubber solids) SBR3: HPR355 manufactured by JSR Corporation (modified S-SBR, styrene content: 27% by mass, Tg: -24°C, non-oil extended) SBR4: Hydrogenated SBR produced in Production Example 1 described below (hydrogenation rate: 60%, styrene content: 30% by mass, Tg: -31°C, oil content: 25 parts by mass per 100 parts by mass of rubber solids) Butyl rubber 1: Exxon 2255 (brominated butyl rubber) manufactured by Exxon Mobil Corporation Butyl rubber 2: Exxpro 3563 (halogenated copolymer of isobutylene and p-methylstyrene, aromatic vinyl unit content: 9.0% by mass) manufactured by Exxon Mobil Corporation Carbon black: Seast V (GPF, N660, N2SA: 27m) manufactured by Tokai Carbon Co., Ltd. 2 / g) Calcium carbonate: FP-300 manufactured by Calfine Co., Ltd. Resin component: Kraton Sylvatraxx 4401 (copolymer of α-methylstyrene and styrene) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corporation Sulfur: HK-200-5 (powdered sulfur containing 5% oil by mass) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela DM (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0097] Production Example 1: Production of hydrogenated SBR A heat-resistant reactor thoroughly purged with nitrogen was charged with 2000 mL of n-hexane, 60 g of styrene, 140 g of butadiene, 2.5 g of THF, and 0.45 mmol of n-butyllithium, and the mixture was stirred at 50°C for 5 hours to carry out the polymerization reaction. Next, hydrogen gas was supplied at 0.4 MPa-Gauge pressure while stirring for 20 minutes, reacting with unreacted lithium at the polymer terminals to produce lithium hydride. Hydrogen gas was supplied at a pressure of 0.7 MPa-Gauge, the reaction temperature was set to 90°C, and hydrogenation was carried out using a catalyst mainly composed of titanocene dichloride. When the cumulative amount of hydrogen absorption reached the target hydrogenation rate, the reaction temperature was returned to room temperature, the hydrogen pressure was returned to normal, and the mixture was removed from the reactor. 25 parts by weight of extender oil per 100 parts by weight of polymer was added to this polymer solution and mixed, after which the solvent was removed to obtain the desired hydrogenated SBR.

[0098] Examples and Comparative Examples According to the formulations shown in Tables 1 and 2, a 2.0 L internal Banbury mixer was used to knead the chemicals other than sulfur and the vulcanization accelerator for 4 minutes at a discharge temperature of 150°C to obtain a kneaded mixture. The resulting kneaded mixture was then re-mixed (remilled) for 3 minutes using the same Banbury mixer at a discharge temperature of 130°C. Next, using a two-screw open roll, sulfur and the vulcanization accelerator were added to the resulting kneaded mixture, and the mixture was kneaded for 3 minutes until the temperature reached 95°C to obtain an unvulcanized rubber composition. The resulting unvulcanized rubber composition was extruded into the shape of an inner liner using an extruder equipped with a predetermined die, and then bonded together with other tire components to form an unvulcanized tire. Each test tire was then produced by press-vulcanizing the composition at 170°C for 12 minutes.

[0099] The test tires obtained were evaluated as follows. The evaluation results are shown in Table 1.

[0100] <Durability after humid heat degradation> The resulting tire was mounted on a rim, filled with 400 mL of water and an internal pressure of 250 kPa, and then aged in an oven at 80°C for one week. Thereafter, the tire was run on a drum at a speed of 80 km / h under a load of 80% of the normal load, and the running distance until damage was observed was measured and expressed as an index, with the value for Comparative Example 2 being set at 100. A higher index value indicates better durability after moist heat aging.

[0101] [Table 1]

[0102] [Table 2]

[0103] The results in Tables 1 and 2 show that the tire of the present disclosure, in which the aromatic vinyl unit content in the rubber component constituting the inner liner and the distance from the tire cavity surface on the tire equatorial plane to the innermost part in the tire radial direction of the belt layer have a predetermined relationship, has improved durability performance after wet heat aging.

[0104] <Embodiment> Examples of embodiments of the present disclosure are provided below.

[0105] [1] A tire having an inner liner and a belt layer, wherein the inner liner is made of a rubber composition containing a rubber component, and when the aromatic vinyl unit content in the rubber component is S (mass%) and the distance from the tire cavity surface on the tire equatorial plane to the innermost part of the belt layer in the tire radial direction is D (mm), S is 0.70 mass% or more and 8.00 mass% or less, and the product of S and D (S × D) is 2.0 or more. [2] The tire according to [1] above, wherein the rubber component contains 75% by mass or more of a butyl rubber. [3] The tire according to [1] or [2] above, wherein the rubber component contains styrene-butadiene rubber having a glass transition temperature (Tg) of −75° C. or higher and −40° C. or lower. [4] The tire according to any one of the above [1] to [3], wherein the rubber component contains hydrogenated styrene-butadiene rubber. [5] The tire according to any one of the above [1] to [4], wherein the rubber composition contains an aromatic petroleum resin. [6] The tire according to any one of the above [1] to [5], wherein L / D is 0.10 or more, where L (mm) is the thickness of the inner liner on the tire equatorial plane. [7] The tire according to any one of the above [1] to [6], which contains 10 parts by mass or more and 50 parts by mass or less of a filler per 100 parts by mass of the rubber component. [Explanation of symbols]

[0106] 1 Tread section 2 Cap rubber layer 4 Base rubber layer 7 Inner liner 8 Belt Layers 9. Carcass 11 bands CL Tire equatorial plane

Claims

1. A tire having an inner liner and a belt layer, the inner liner is made of a rubber composition containing a rubber component, the thickness L of the inner liner on the tire equatorial plane is 0.1 to 1.0 mm; The rubber component contains 75% by mass or more of a butyl rubber, The tire has a rubber component having an aromatic vinyl unit content S (mass%) and a distance D (mm) from the tire cavity surface on the tire equatorial plane to the innermost part of the belt layer in the tire radial direction, wherein S is 0.70 mass% or more and 8.00 mass% or less, and the product of S and D (S × D) is 2.0 or more and 15.0 or less.

2. The tire of claim 1 , wherein the rubber component comprises styrene butadiene rubber. tires.

3. The tire according to claim 1 or 2, wherein the rubber component contains a styrene-butadiene rubber having a glass transition temperature (Tg) of −75° C. or higher and −40° C. or lower.

4. The tire according to any one of claims 1 to 3, wherein the rubber component includes a hydrogenated styrene-butadiene rubber.

5. The tire according to any one of claims 1 to 4, wherein the rubber composition contains an aromatic petroleum resin.

6. The tire according to any one of claims 1 to 5, wherein L / D is 0.10 or more, where L (mm) is the thickness of the inner liner on the tire equatorial plane.

7. The tire according to any one of claims 1 to 6, further comprising 10 parts by mass or more and 50 parts by mass or less of a filler per 100 parts by mass of the rubber component.

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