tire

Abstract

To provide a tire having improved crack resistance performance.SOLUTION: A tire includes a tread and an inner liner. The inner liner is formed of a rubber composition containing a polymer component. A distance G from a crown part of the tread to a tire inner cavity surface is 9.0 mm or less. An elongation at break (80°CEB) of the rubber composition measured under a condition of a temperature of 80°C and a tension speed of 3.3 mm / sec, a loss tangent tanδ (70°Ctanδ) of the rubber composition measured under a condition of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ± 2.5%, and G (mm) satisfy the following expressions (1) and (2): 80°CEB / 70°Ctanδ≥2600...(1), 80°CEB / G≥40...(2).SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In order to improve the fuel efficiency of tires, it is also necessary to reduce heat generation in inner liners. Patent Document 1 describes a rubber composition for inner liners that has excellent handling stability, fuel efficiency, and a balance of physical properties while maintaining air permeability resistance and durability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-218147 Summary of the Invention [Problem to be solved by the invention]

[0004] However, from the perspective of increasing tire recyclability, there is a movement to promote retreading, where the tread portion of used tires is replaced and reused, and therefore it is thought that there will be demand for components such as tire inner liners to have an even longer life.On the other hand, if the inner liner is made to have a low heat generation, it will become difficult for the inside of the inner liner to absorb impacts applied to the tire, and there is a concern that cracks will occur inside the tire when it is driven for a long period of time, resulting in a decrease in air retention.

[0005] An object of the present disclosure is to provide a tire with improved crack resistance. [Means for solving the problem]

[0006] As a result of extensive research, it was discovered that the above-mentioned problems can be solved by ensuring a predetermined relationship between the elongation at break and loss tangent of the rubber composition constituting the inner liner and the distance from the crown portion of the tread to the tire cavity surface.

[0007] That is, the present disclosure relates to a tire including a tread and an inner liner, wherein the inner liner is made of a rubber composition containing a polymer component, the distance G from the crown portion of the tread to the tire cavity surface is 9.0 mm or less, and the breaking elongation (80°C EB) of the rubber composition measured under conditions of a temperature of 80°C and a tensile speed of 3.3 mm / sec, the loss tangent tanδ (70°C tanδ) of the rubber composition measured under conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ±2.5%, and G (mm) satisfy the following formulas (1) and (2): 80℃EB / 70℃tanδ≧2600 (1) 80℃EB / G≧40 (2) [Effects of the Invention]

[0008] According to the present disclosure, a tire is provided with improved crack resistance. [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 a tread and an inner liner, wherein the inner liner is made of a rubber composition containing a polymer component, the distance G from the crown portion of the tread to the tire cavity surface is 9.0 mm or less, and the breaking elongation (80°C EB) of the rubber composition measured under conditions of a temperature of 80°C and a tensile speed of 3.3 mm / sec, the loss tangent tanδ (70°C tanδ) of the rubber composition measured under conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ±2.5%, and G (mm) satisfy the following formulas (1) and (2): 80℃EB / 70℃tanδ≧2600 (1) 80℃EB / G≧40 (2)

[0011] When the 80°C EB and 70°C tan δ of the rubber composition constituting the inner liner and the distance from the crown portion of the tread to the tire cavity surface satisfy the above-mentioned requirements, the resulting tire exhibits significantly improved overall performance in terms of fuel economy and crack resistance. The reason for this is thought to be as follows, without intending to be bound by theory.

[0012] When a tire rolls, its temperature rises above room temperature. The tire of the present disclosure is designed to have a breaking elongation at high temperatures higher than a certain level relative to the heat buildup (70°C tan δ) of the inner liner so as to satisfy the above formula (1). This makes it possible to prevent the inner liner layer from increasing in temperature due to self-heating during rolling, which would result in a decrease in breaking strength, while ensuring sufficient breaking elongation at high temperatures, which is thought to prevent cracks from occurring.

[0013] Furthermore, to satisfy the formula (2), the breaking elongation at high temperatures is set to be at least a certain level relative to the distance G from the outermost surface of the crown portion of the tread to the tire cavity surface. As a result, when the inner liner layer deforms in response to the deformation of the tread, it is believed that the larger G is, the greater the strain applied to the inner liner surface, and conversely, the smaller G is, the smaller the strain applied to the inner liner layer can be. Therefore, by reducing the distance from the tread surface to 9.0 mm or less and setting the breaking elongation at high temperatures sufficiently high relative to that distance, it is possible to suppress the strain applied to the inner liner layer while providing sufficient elongation, and it is believed that the occurrence of cracks can be more effectively suppressed.

[0014] As a result of the above, it is possible to prevent the temperature of the inner liner layer from increasing and the breaking elongation from decreasing, while also ensuring sufficient breaking elongation in response to the strain applied to the inner liner layer, thereby making it possible to significantly improve crack resistance.

[0015] From the viewpoint of a balance between crack resistance and fuel economy, the rubber composition of the present disclosure preferably contains 10 to 45 parts by mass of a filler per 100 parts by mass of the polymer component.

[0016] From the viewpoint of air permeability resistance and heat resistance, the polymer component of the present disclosure preferably contains 75% by mass or more of butyl rubber.

[0017] The rubber composition of the present disclosure preferably contains an aromatic petroleum resin from the viewpoints of crack resistance and air permeation resistance.

[0018] From the viewpoint of air permeation resistance, the polymer component of the present disclosure preferably has a total content of isoprene-based rubber and butadiene rubber of 10% by mass or less.

[0019] 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 / G is less than 0.10.

[0020] By setting L / G within the above range, the thickness of the inner liner portion can be reduced, which is thought to make it easier to prevent strain from concentrating within the inner liner layer when it deforms to follow the tread.

[0021] <Definition>

[0022] 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."

[0023] The term "crown portion of the tread" refers to the outermost end of the tread intersecting with the tire equatorial plane when the tire does not have a circumferential groove on the tire equatorial plane, and refers to the portion where the line segment connecting the outermost ends of the tread in the land portions at both ends of the circumferential groove intersects with the tire equatorial plane when the tire has a circumferential groove on the tire equatorial plane.

[0024] "Distance G from the crown of the tread to the tire cavity surface" refers to the linear distance from the crown to the tire cavity surface on the tire equatorial plane 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 G from the crown of the tread to the tire cavity surface" 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 standard rim.

[0028] "80°C EB" is the elongation at break (elongation at break) measured in an 80°C atmosphere at a tensile speed of 3.3 mm / sec in accordance with JIS K 6251:2017. The sample used for EB measurement is a dumbbell-shaped No. 7 vulcanized rubber test piece.

[0029] "70°C tanδ" is the loss tangent measured under the conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and an extension mode. The sample for measuring the loss tangent is a vulcanized rubber composition having a length of 20 mm, a width of 4 mm, and a thickness of 1 mm.

[0030] 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.

[0031] "N2SA of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0032] 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.

[0033] [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.

[0034] From the viewpoint of fuel economy, the 80°C EB (%) of the rubber composition constituting the inner liner is preferably 360% or more, more preferably 400% or more, even more preferably 440% or more, and particularly preferably 480% or more. There is no particular upper limit to the 80°C EB (%) of the rubber composition constituting the inner liner.

[0035] From the viewpoint of fuel economy, the 70°C tan δ of the rubber composition constituting the inner liner is preferably 0.20 or less, more preferably 0.19 or less, even more preferably 0.17 or less, and particularly preferably 0.15 or less. From the viewpoint of the effects of the present disclosure, the 70°C tan δ of the rubber composition constituting the inner liner is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.10 or more.

[0036] The 80° C. EB and 70° C. tan δ of the rubber composition can be adjusted appropriately by the types and amounts of the polymer components, fillers, oils, resin components, etc., which will be described later.

[0037] From the viewpoint of the effects of the present disclosure, the distance G (mm) from the crown portion of the tread to the tire cavity surface is 9.0 mm or less, preferably 8.8 mm or less, more preferably 8.5 mm or less, even more preferably 8.3 mm or less, and particularly preferably 8.0 mm or less. Also, from the viewpoint of the effects of the present disclosure, G (mm) is preferably 3.0 mm or more, more preferably 4.0 mm or more, even more preferably 5.0 mm or more, and particularly preferably 6.0 mm or more.

[0038] 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.

[0039] The 80°C EB / 70°C tan δ is 2600 or more, preferably 2900 or more, more preferably 33200 or more, and even more preferably 3500 or more. By setting the 80°C EB / 70°C tan δ within the above range, it is possible to prevent the inner liner layer from increasing in temperature due to self-heating during rolling and thereby reducing its breaking strength, while ensuring sufficient breaking elongation at high temperatures, which is thought to prevent cracking. Furthermore, from the viewpoint of the effects of the present disclosure, the 80°C EB / 70°C tan δ is preferably 5000 or less, more preferably 4800 or less, and even more preferably 4500 or less.

[0040] The 80°C EB / G is 40 or more, preferably 45 or more, more preferably 50 or more, even more preferably 55 or more, and particularly preferably 60 or more. By setting the 80°C EB / G in the above range, it is possible to suppress the strain applied to the inner liner layer while providing sufficient elongation, and it is thought that the occurrence of cracks can be more effectively suppressed. Furthermore, from the viewpoint of the effects of the present disclosure, the 80°C EB / G is preferably 120 or less, more preferably 110 or less, even more preferably 100 or less, and particularly preferably 95 or less.

[0041] L / G is preferably less than 0.30, more preferably less than 0.25, even more preferably less than 0.20, even more preferably less than 0.15, even more preferably less than 0.14, even more preferably less than 0.12, and particularly preferably less than 0.10. By setting L / G within the above range, it is thought that by reducing the thickness of the inner liner portion, it is possible to more easily prevent strain concentration within the inner liner layer when the tire deforms in accordance with the tread. From the viewpoint of the effects of the present disclosure, L / G is preferably 0.04 or more, more preferably 0.05 or more, even more preferably 0.06 or more, and particularly preferably 0.07 or more.

[0042] [Rubber composition] The tire of the present disclosure can more effectively improve the overall performance of fuel economy and crack resistance by the cooperation of the 80°C EB and 70°C tanδ of the rubber composition constituting the inner liner and the distance from the crown portion of the tread to the tire cavity surface.

[0043] <Polymer component> The polymer components of the present disclosure include the rubber component and thermoplastic elastomer described below, and are components that mainly form the matrix of the composition, and are detected as polymer components in composition analysis such as with a thermogravimetric analyzer (TGA).

[0044] (rubber component) In the present disclosure, the term "rubber component" refers to a component that forms a chemical network with a vulcanizing agent such as sulfur and exhibits rubber elasticity.

[0045] The rubber composition constituting the innerliner of the present disclosure (hereinafter, unless otherwise specified, referred to as the rubber composition of the present disclosure) preferably contains a butyl rubber as a rubber component. In addition to the butyl rubber, a diene rubber such as styrene-butadiene rubber may also be contained.

[0046] 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.

[0047] 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.

[0048] From the viewpoints of air permeability resistance and heat resistance, the content of the butyl rubber in the polymer 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 polymer 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 91% by mass or less.

[0049] The SBR is not particularly limited, and examples thereof include emulsion-polymerized SBR (E-SBR) and solution-polymerized SBR (S-SBR). SBRs modified with a modifier (modified SBR) and hydrogenated SBRs (hydrogenated SBR) can also be used. These SBRs may be used alone or in combination of two or more.

[0050] 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 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the rubber solids content of the SBR.

[0051] From the viewpoint of the effects of the present disclosure, 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. From the viewpoint of the effects of the present disclosure, the Tg is preferably −40° C. or lower, more preferably −45° C. or lower, and even more preferably −50° C. or lower.

[0052] When SBR is contained, the content in the polymer component is not particularly limited, and can be, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 7% by mass or more. On the other hand, from the viewpoint of the effects of the present disclosure, the content of SBR in the polymer 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] 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.

[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] From the viewpoint of the effects of the present disclosure, the total content of the isoprene-based rubber and BR in the polymer component is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, still more preferably 5% by mass or less, and particularly preferably less than 1% by mass; the polymer component may not contain the isoprene-based rubber or the BR.

[0056] The polymer component of the present disclosure preferably contains a rubber component. From the viewpoint of the effects of the present disclosure, the content of the rubber component in the polymer component is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more. On the other hand, the upper limit of the content of the rubber component in the polymer component is not particularly limited as long as the effects of the present disclosure are exhibited, but may be, for example, 100% by mass, 95% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 55% by mass or less.

[0057] (thermoplastic elastomer) The polymer component of the present disclosure may contain a thermoplastic elastomer in addition to the rubber component. In the present disclosure, the term "thermoplastic elastomer" refers to a polymeric compound having elasticity, a thermoplastic resin material composed of a copolymer having a polymer constituting a crystalline hard segment with a high melting point and a polymer constituting an amorphous soft segment with a low glass transition temperature, and which forms a pseudo-network due to van der Waals forces within the rubber composition. The crystalline hard segments of a thermoplastic elastomer act as pseudo-crosslinking points, thereby exhibiting elasticity. Thermoplastic elastomers can be reused by heating the hard segments to melt them and then cooling them, since the pseudo-crosslinking points can be regenerated. On the other hand, rubber contains double bonds in the molecular chain, and by adding sulfur or the like to crosslink (vulcanize) it generates a three-dimensional network structure, thereby exhibiting elasticity. Therefore, once crosslinked (vulcanized), rubber loses its fluidity due to this three-dimensional network structure, making it difficult to reuse, even when heated.

[0058] The thermoplastic elastomer usable in the present disclosure is not particularly limited, but examples thereof include styrene-based thermoplastic elastomers, urethane-based thermoplastic elastomers, olefin-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, etc. Among these, styrene-based thermoplastic elastomers or urethane-based thermoplastic elastomers are preferred, and styrene-based thermoplastic elastomers are more preferred. One or more types of thermoplastic elastomers can be used.

[0059] 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 a molecular structure having a styrene block at one or both ends and an elastomer block elsewhere is preferred. Having a styrene block at at least one end tends to provide better grip performance. Furthermore, it is more preferred that the styrene-based thermoplastic elastomer has a structure that does not have a styrene block in the main chain portion other than the end. This structure tends to prevent the hardness of the thermoplastic elastomer from becoming too high at room temperature, resulting in better grip performance, as well as better fracture properties and abrasion resistance.

[0060] Examples of the elastomer block include vinyl polydienes such as styrene-butadiene (SB), polyisoprene (IP), polybutadiene, polyethylene, polychloroprene, poly-2,3-dimethylbutadiene, etc. Furthermore, the elastomer block may be a hydrogenated product of the above elastomer blocks.

[0061] 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-isobutylene-styrene block copolymer (SIBS), 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), styrene-butadiene-butylene-styrene block copolymer (SBBS), styrene-vinyl-isoprene-styrene block copolymer (vinyl SIS), and styrene-vinyl-ethylene-propylene-styrene block copolymer (vinyl SEPS).

[0062] 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 from the viewpoint of grip performance. Furthermore, from the viewpoint of suppressing heat buildup, it is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0063] The urethane-based thermoplastic elastomer is not particularly limited, but for example, one prepared from a polyol and a diisocyanate can be suitably used. Examples of polyols include polyester-based polyols, polyester ether-based polyols, polycarbonate-based polyols, and polyether-based polyols. Examples of diisocyanates include tolylene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI).

[0064] 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 terpolymers such as ethylene-propylene-ethylidenenorbornene copolymer, ethylene-propylene-butadiene copolymer, and ethylene-propylene-isoprene copolymer.

[0065] From the viewpoint of suppressing deterioration, the thermoplastic elastomer preferably contains a hydrogenated thermoplastic elastomer, more preferably contains a hydrogenated styrene-based thermoplastic elastomer, and preferably consists of only a hydrogenated thermoplastic elastomer.

[0066] If desired, the thermoplastic elastomer can be modified with a modifying agent to introduce a modifying group. Any of the modifying groups commonly used in this field can be used, including alkoxysilyl groups (e.g., trimethoxysilyl and triethoxysilyl groups). For example, a styrene-based thermoplastic elastomer having a styrene terminal at least at one end can be synthesized, and then treated with chlorotriethoxysilane as a modifying agent to obtain a modified styrene-based thermoplastic elastomer in which a triethoxysilyl group has been introduced at the active end of the styrene-based thermoplastic elastomer.

[0067] The thermoplastic elastomer may be a commercially available product or a synthetic product, such as those manufactured and sold by JSR Corporation, Asahi Kasei Corporation, Kuraray Co., Ltd., and Nihon Miractoran Co., Ltd.

[0068] When a thermoplastic elastomer is contained, the content in the polymer component is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less, from the viewpoint of crack resistance. On the other hand, the lower limit of the thermoplastic elastomer content may vary depending on other ingredients and is not particularly limited as long as the effects of the present disclosure are exhibited, but can be, for example, 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 45% by mass or more.

[0069] <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.

[0070] (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.

[0071] 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.

[0072] When carbon black is contained, the content per 100 parts by mass of the polymer 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 65 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 55 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 45 parts by mass or less.

[0073] (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.

[0074] The content of the filler other than carbon black relative to 100 parts by mass of the polymer 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. 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.

[0075] From the viewpoint of the effects of the present disclosure, the total content of the filler per 100 parts by mass of the polymer 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, even 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 content of the filler per 100 parts by mass of the polymer component is preferably 65 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 55 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 45 parts by mass or less.

[0076] 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 75% by mass or more. There is no particular upper limit to the content of carbon black in 100% by mass of the filler.

[0077] <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.

[0078] (softener) The rubber composition according to the present disclosure preferably contains a softener, such as a resin component, oil, or liquid rubber.

[0079] 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.

[0080] 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.

[0081] When a resin component is contained, the content thereof is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1.0 parts by mass or more, and particularly preferably 1.5 parts by mass or more, per 100 parts by mass of the polymer component, and 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 7.0 parts by mass or less.

[0082] 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.

[0083] When oil is contained, the content per 100 parts by mass of the polymer 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, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less from the viewpoint of abrasion resistance.

[0084] 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.

[0085] When a liquid rubber is contained, the content thereof is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, per 100 parts by mass of the polymer 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.

[0086] When a softener is contained, the content (total amount when multiple softeners are used) per 100 parts by mass of the polymer component is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, even more preferably 5.0 parts by mass or more, and particularly preferably 7.0 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.

[0087] When wax is contained, the content per 100 parts by mass of the polymer component is preferably 0.5 parts by mass or more, more preferably 1.0 part 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.

[0088] Examples of processing aids include fatty acid metal salts, fatty acid esters, fatty acid amides, amide esters, mixtures of fatty acid metal salts and fatty acid esters, mixtures of fatty acid metal salts and fatty acid amides, mixtures of fatty acid metal salts and amide esters, silica surfactants, etc. Examples of processing aids that can be used include those commercially available from Schill + Seilacher, Performance Additives, etc. These processing aids may be used alone or in combination of two or more.

[0089] When a processing aid is contained, the content per 100 parts by mass of the polymer 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, from the viewpoint of improving processability, and is preferably 10 parts by mass or less, more preferably 8.0 parts by mass or less, and even more preferably 5.0 parts by mass or less, from the viewpoint of abrasion resistance and breaking strength.

[0090] 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.

[0091] When an antioxidant is contained, the content thereof is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, per 100 parts by mass of the polymer component, 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 still more preferably 1.2 parts by mass or less.

[0092] When stearic acid is contained, the content per 100 parts by mass of the polymer component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, from the viewpoint of vulcanization rate, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, from the viewpoint of processability.

[0093] When zinc oxide is contained, the content per 100 parts by mass of the polymer component is preferably 0.5 parts by mass or more, more preferably 1.0 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.

[0094] 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.

[0095] When sulfur is contained as a vulcanizing agent, the content per 100 parts by mass of the polymer 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.

[0096] 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.

[0097] 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 vulcanization accelerators, guanidine-based vulcanization accelerators, and thiazole-based vulcanization accelerators are preferred, and thiazole-based vulcanization accelerators are more preferred.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] When a vulcanization accelerator is contained, the content thereof per 100 parts by mass of the polymer component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more. The content thereof per 100 parts by mass of the polymer component is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 4.0 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.

[0102] <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).

[0103] 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.

[0104] 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.

[0105] 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 polymer 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.

[0106] <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]

[0107] Hereinafter, the present disclosure will be described based on examples, but the present disclosure is not limited to these examples.

[0108] The various chemicals used in the examples and comparative examples are listed below. 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) manufactured by Exxon Mobil Corporation SBR: JSR Corporation's SL553 (unmodified S-SBR, Tg: -61°C, non-oil extended) Thermoplastic elastomer: SIBSTAR 102T (SIBS, styrene content: 15% by mass) manufactured by Kaneka 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. Oil: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd. Resin component: Kraton Sylvatraxx 4401 (copolymer of α-methylstyrene and styrene) Processing aid: Struktol WB16 (a mixture of fatty acid metal salts and fatty acid esters) manufactured by Schill + Seilacher Antioxidant: Nocrac RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corporation Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. 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.

[0109] Examples and Comparative Examples According to the formulation shown in Table 1, a 2.0 L internal Banbury mixer was used to knead all the chemicals except 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 rolled into a 2 mm thick raw rubber sheet and press-vulcanized at 170°C for 12 minutes to produce a vulcanized rubber composition.

[0110] The unvulcanized rubber composition obtained was extruded into the shape of an inner liner using an extruder equipped with a nozzle of a predetermined shape, and then laminated together with other tire components to form an unvulcanized tire. Each test tire was manufactured by press-vulcanizing the tire at 170°C for 12 minutes.

[0111] <Tensile test> Dumbbell-shaped No. 7 test pieces were prepared from each vulcanized rubber composition. Tensile tests were carried out in accordance with JIS K 6251:2017 under conditions of an 80°C atmosphere and a tensile speed of 3.3 mm / sec, and the elongation at break (EB) (%) was measured.

[0112] <Viscoelasticity test> For rubber test pieces (length 20 mm x width 4 mm x thickness 1 mm) prepared from each vulcanized rubber composition, the loss tangent (tanδ) was measured using an Iplexer series manufactured by GABO under the conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and an extension mode. The thickness direction of the sample was the radial direction of the tire.

[0113] <Crack resistance> Using a drum testing machine, each test tire (size: 205 / 55R16, rim 16x6.5JJ, internal pressure: 230 kPa) was driven 20,000 km under conditions of a load (690 kg) and a speed (80 km / h). After that, the rim was removed, and the interior of the tire was visually inspected to evaluate the degree of cracking. Evaluation was performed using an integer value from 1 to 10, with a higher score indicating better crack resistance. A total score was calculated by 10 expert panelists. The total score of the control tire (Comparative Example 7) was converted to a reference value (100), and the evaluation results of each test tire were indexed and displayed proportional to the total score.

[0114] [Table 1]

[0115] The results in Table 1 show that the tires of the present disclosure have improved crack resistance.

[0116] <Embodiment> Examples of embodiments of the present disclosure are provided below.

[0117] [1] A tire having a tread and an inner liner, wherein the inner liner is made of a rubber composition containing a polymer component, the distance G from the crown portion of the tread to the tire cavity surface is 9.0 mm or less, and the breaking elongation (80°C EB) of the rubber composition measured under conditions of a temperature of 80°C and a tensile speed of 3.3 mm / sec, the loss tangent tanδ (70°C tanδ) of the rubber composition measured under conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ±2.5%, and G (mm) satisfy the following formulas (1) and (2): 80℃EB / 70℃tanδ≧2600 (1) 80℃EB / G≧40 (2) [2] The tire according to [1] above, wherein 80°C EB / 70°C tan δ≧3500. [3] The tire according to the above [1] or [2], which contains 10 to 45 parts by mass of a filler per 100 parts by mass of the polymer component. [4] The tire according to any one of the above [1] to [3], wherein the polymer component contains 75% by mass or more of a butyl 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 the total content of the isoprene-based rubber and the butadiene rubber in the polymer component is 10% by mass or less. [7] The tire according to any one of the above [1] to [6], wherein L / G is less than 0.10, where L (mm) is the thickness of the inner liner on the tire equatorial plane. [Explanation of symbols]

[0118] 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 a tread and an inner liner, the inner liner is made of a rubber composition containing a polymer component, The distance G from the crown portion of the tread to the tire cavity surface is 9.0 mm or less, A tire in which the breaking elongation (80°C EB) of the rubber composition measured under conditions of a temperature of 80°C and a tensile speed of 3.3 mm / sec, the loss tangent tanδ (70°C tanδ) of the rubber composition measured under conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ±2.5%, and G (mm) satisfy the following formulas (1) and (2): 80℃EB / 70℃tanδ≧2600...(1) 80℃EB / G≧40...(2)

2. The tire of claim 1, wherein 80°C EB / 70°C tan δ is ≥ 3500.

3. The tire according to claim 1 or 2, wherein the polymer component contains 75% by mass or more of a butyl rubber.

4. The tire according to any one of claims 1 to 3, wherein the rubber composition contains an aromatic petroleum resin.

5. The tire according to any one of claims 1 to 4, wherein the total content of the isoprene-based rubber and the butadiene rubber in the polymer component is 10% by mass or less.

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

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