Pneumatic tire

Abstract

To provide a pneumatic tire which restricts scattered reflection of light due to a surface protective film at side wall parts, maintains an exterior appearance in a matting state for a long period of time and uses coloring to prevent the fine appearance from being impaired, and further, reduces occurrences of cracking on the surface protective film.SOLUTION: Provided is a pneumatic tire with side wall parts. The side wall part includes a protrusion formation part on which a plurality of micro-protrusions are formed on its external surface. A height of the micro-protrusion is 0.5 mm or less. The protrusion formation part has an area of 10 mm2 or more. In at least one direction, 20 micro-protrusions or more are formed at an interval of 0.5 mm or less. In the pneumatic tire, in a 25°C environment of the side wall parts, M300 / M100 of a stress M100 at a tensile strain 100% and a stress M300 at a tensile strain 300% in a tensile test at a tension speed 500 mm / min is greater than 4.0, and 70°Ctanδ is 0.09 or less.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present disclosure relates to a pneumatic tire, and more particularly to a pneumatic tire provided with a sidewall portion.

Background Art

[0002] In recent years, from the viewpoint of reducing carbon dioxide emissions, there has been a strong demand for improvement in fuel efficiency and life performance of pneumatic tires (hereinafter also simply referred to as "tires") mounted on automobiles.

[0003] In particular, since the same rubber surface is used from the start of tire use to the wear life of the tread portion in the sidewall portion of the tire, it is required to be able to withstand the influence of deterioration factors such as ozone over a long period of time. Deterioration factors such as ozone generate minute cracks in the sidewall portion.

[0004] Therefore, in order to prevent deterioration by ozone or the like, a rubber composition to which a surface protective agent such as wax is added is used for the sidewall portion, and the wax or the like exudes to the surface of the sidewall portion to form a protective film, thereby blocking deterioration factors such as ozone (for example, Patent Document 1).

[0005] However, the surface protective film such as wax increases the diffuse reflection of light, making it impossible to maintain the appearance in a dull state, and may also impair the aesthetics due to coloring. For this reason, some drivers dislike the deterioration of the appearance and may wash away the surface protective film when washing the car.

[0006] In addition, cracks occur in the surface protective film as the driving distance increases, resulting in a decrease in the blocking function of deterioration factors such as ozone, and there is also a problem that the aesthetics are impaired due to the cracks.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In view of the above problems, the present disclosure aims to improve the long-term aesthetic appearance of tires by suppressing light irregular reflection caused by a surface protective film such as wax in the sidewall portion and reducing the occurrence of cracks accompanying an increase in the running distance, and provides a pneumatic tire capable of achieving this.

Means for Solving the Problems

[0009] The present disclosure has conducted intensive studies on solving the above problems, found that the above problems can be solved by the disclosure described below, and has completed the present disclosure.

[0010] The present disclosure is a pneumatic tire having a sidewall portion, wherein the sidewall portion has a raised portion formed with a plurality of minute protrusions on the outer surface, the height of the minute protrusions is 0.5 mm or less, the raised portion has an area of 10 mm 2 or more, and 20 or more of the minute protrusions are formed at intervals of 0.5 mm or less in at least one direction, when the stress at a tensile strain of 100% in a tensile test at 25°C in the sidewall portion at a tensile speed of 500 mm / min is defined as M100 (MPa) and the stress at a tensile strain of 300% is defined as M300 (MPa), M300 / M100 is greater than 4.0, and the loss tangent tanδ measured under the conditions of temperature: 70°C, initial strain: 2.5%, dynamic strain: ±1%, frequency: 10 Hz, and deformation mode: tension is 0.09 or less.

Effects of the Invention

[0011] According to the present disclosure, it is possible to provide a pneumatic tire that can improve the long-term aesthetic appearance of the tire by suppressing irregular reflection of light by a surface protective film such as wax in the sidewall portion and reducing the occurrence of cracks associated with an increase in the running distance.

Brief Description of the Drawings

[0012] [Figure 1A] It is a perspective view schematically showing the shape of the raised portion forming part of the sidewall portion of the pneumatic tire according to one embodiment of the present disclosure. [Figure 1B] It is a view taken along the line X-X of FIG. 1A. [Figure 2A] It is a perspective view schematically showing the shape of the raised portion forming part of the sidewall portion of the pneumatic tire according to another embodiment of the present disclosure. [Figure 2B] It is a view taken along the line X-X of FIG. 2A.

Embodiments for Carrying Out the Invention

[0013] [1] Features of the Tire of the Present Disclosure 1. Overview The pneumatic tire of the present disclosure has the following features.

[0014] First, as a structural feature, the sidewall portion of the pneumatic tire of the present disclosure has a raised portion forming part with a height of 0.5 mm or less and a pitch of 0.5 mm or less in at least one direction on the outer surface, and 20 or more minute raised portions are formed in a 10 mm 2 portion or more.

[0015] And, as a feature of the rubber composition of the sidewall portion, when the stress at a tensile strain of 100% in a tensile test at a tensile speed of 500 mm / min in an environment of 25°C of the sidewall portion is defined as M100 (MPa) and the stress at a tensile strain of 300% is defined as M300 (MPa), M300 / M100 is greater than 4.0. Also, the loss tangent tanδ measured under the conditions of temperature: 70°C, initial strain: 2.5%, dynamic strain: ±1%, frequency: 10 Hz, and deformation mode: tension is 0.09 or less.

[0016] By configuring the sidewall portion as described above, as shown in the next section, the irregular reflection of light by a surface protective film such as wax can be suppressed, and the appearance in a matte state can be maintained for a long time. Further, deterioration of the aesthetic appearance due to coloring of the surface protective film is suppressed. Furthermore, generation of cracks in the surface protective film can be reduced.

[0017] Note that the upper limit of M300 / M100 is not limited, but it is preferably 10.0 or less.

[0018] Also, the height of the minute projections is preferably low, more preferably 0.4 mm or less. However, it is preferably 0.01 mm or more.

[0019] Note that in the above, the shape of the minute projections is not particularly limited, and specifically, columnar, frustum-shaped, rib-shaped (strip-shaped), etc. can be mentioned.

[0020] Also, the "interval" means the minimum linear distance connecting the topmost portions of adjacent minute projections when the minute projections are viewed from a direction perpendicular to the one direction.

[0021] Note that the height and interval size of the minute projections in the projection forming portion are the sizes measured in a state where the pneumatic tire is assembled to a standard rim, a standard internal pressure is applied, and there is no load.

[0022] Here, the "standard rim" refers to the rim defined for each tire in the standard system including the standards on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it refers to the standard rim in the applicable sizes described in the "JATMA YEAR BOOK"; in the case of ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" described in the "STANDARDS MANUAL"; and in the case of TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" described in the "YEAR BOOK". For a tire not defined by the standards, it refers to the rim that can be assembled with the tire and can hold the internal pressure, that is, among the rims that do not cause air leakage between the rim / tire, the one with the smallest rim diameter and then the narrowest rim width.

[0023] And the "standard internal pressure" refers to the air pressure defined for each tire by the above-mentioned standards. In the case of JATMA, it refers to the maximum air pressure; in the case of TRA, it refers to the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it refers to the "INFLATION PRESSURE".

[0024] Also, M100 and M300 are values measured in accordance with the method specified in JIS K6251:2017.

[0025] Also, tanδ can be measured using a viscoelasticity measuring device such as the "Implexer (registered trademark)" manufactured by GABO.

[0026] 2. Mechanism of effect manifestation in the pneumatic tire of the present disclosure Regarding the mechanism of effect manifestation in the pneumatic tire of the present disclosure, that is, suppressing the irregular reflection of light by the surface protective film such as wax in the sidewall portion and reducing the aesthetics due to cracks in the surface protective film accompanying the increase in the driving distance Prevention of The mechanism that can achieve this is speculated as follows.

[0027] In other words, in the pneumatic tire of the present disclosure, a ridge-forming portion having a large number of closely spaced micro-ridges is formed on the outer surface of the sidewall portion over an area equal to or greater than a predetermined value, and therefore, the large number of closely spaced micro-ridges suppresses diffuse reflection of light from the sidewall surface even when a wax surface protection film is formed, allowing the matte appearance to be maintained for a long period of time.

[0028] Regarding the density of the micro-ridges, specifically, the height is 0.5 mm or less, and the ridge formation part where such micro-ridges are formed is 10 mm. 2 The surface area is 20 or more micro-ridges that are densely packed together at intervals of 0.5 mm or less in at least one direction.

[0029] The rubber composition of the sidewall has also been designed to prevent stress concentration on the surface when external stress is applied. Specifically, when the sidewall is subjected to a tensile test at 25°C and a tensile speed of 500 mm / min, the stress at 100% tensile strain is defined as M100 (MPa) and the stress at 300% tensile strain is defined as M300 (MPa). The ratio M300 / M100 is set to a certain value or greater, specifically, greater than 4.0. This allows the sidewall to flexibly deform during rolling, preventing stress concentration on the surface and providing a stress that can withstand large deformation, thereby suppressing cracking.

[0030] Furthermore, because stress concentration on the surface can be prevented, the side wall moves as a whole in response to external forces without localized deformation, preventing cracking of the surface protective film. As a result, the deterioration of the ozone blocking function is suppressed. In addition, diffuse reflection of light caused by cracking of the wax surface protective film is suppressed, allowing the matte appearance to be maintained for a long period of time.

[0031] Incidentally, from the perspective of crack resistance performance, the above-mentioned M300 is preferably 3.0 MPa or more, more preferably 4.0 MPa or more, and even more preferably 5.0 MPa or more. On the other hand, although the upper limit is not particularly limited, it is preferably 20 MPa or less, more preferably 18 MPa or less, and even more preferably 15 MPa or less.

[0032] Also, from the perspective of alleviating stress concentration on the surface of the sidewall portion, the above-mentioned M100 is preferably 5.0 MPa or less, more preferably 4.5 MPa or less, and even more preferably 4.0 MPa or less. On the other hand, although the lower limit is not particularly limited, it is preferably 0.8 MPa or more, more preferably 1.0 MPa or more, and even more preferably 1.2 MPa or more.

[0033] In addition, the above-mentioned M300 and M100 can be appropriately adjusted according to the amount and type of filler, the amount of vulcanizing agent, etc. of the rubber composition forming the sidewall portion. Specifically, by increasing the amount of filler, increasing the particle size of the filler, using carbon as the filler, etc., M300 can be increased, while by reducing the amount of crosslinking agents such as sulfur and vulcanization accelerators, M100 can be reduced. And by combining these, it is easy to improve M300 / M100.

[0034] Furthermore, in the pneumatic tire of the present disclosure, the loss tangent tanδ of the sidewall portion is set to a certain value or less to achieve low heat generation. Specifically, the loss tangent tanδ measured under the conditions of temperature: 70 °C, initial strain: 2.5%, dynamic strain: ±1%, frequency: 10 Hz, and deformation mode: tension is set to 0.09 or less. As a result, low heat generation is achieved, and excessive exudation of wax is prevented by suppressing heat generation during rolling. For this reason, effects such as preventing the wax layer from becoming thick on the surface of the sidewall portion and suppressing diffuse reflection of light from the surface are exerted over a long period.

[0035] The above-mentioned tanδ is not particularly limited as long as it is 0.09 or less, but it is preferably 0.085 or less, and more preferably 0.08 or less. On the other hand, the lower limit is not particularly limited either, but it is preferably 0.04 or more, more preferably 0.045 or more, and even more preferably 0.050 or more.

[0036] In addition, the above-mentioned tanδ can be appropriately adjusted by changing the type of rubber component, the type of filler, the amount of filler, the amount of vulcanizing agent, etc. of the rubber composition forming the sidewall portion. Specifically, by using a rubber component with a low glass transition temperature such as natural rubber or butadiene rubber, increasing the particle size of the filler, reducing the amount of filler, or increasing the amount of vulcanizing agents such as sulfur and vulcanization accelerators, tanδ can be reduced.

[0037] [2] More preferred embodiments in the pneumatic tire of the present disclosure In the pneumatic tire of the present disclosure, it is preferable that M300 / M100 is 4.5 or more. Thereby, it is possible to further prevent stress concentration on the surface of the sidewall portion during running.

[0038] In addition, in the pneumatic tire of the present disclosure, when the tire cross-sectional height is H (mm), it is preferable that H and tanδ satisfy the following (Formula 1). tanδ × H ≦ 8.64 (Formula 1)

[0039] That is, as the tire cross-sectional height H (mm) increases, the cross-sectional height of the sidewall portion increases. And the larger the cross-sectional height of the sidewall portion, the larger the volume of the sidewall portion, and the easier it is to store heat. On the other hand, by making tanδ decrease in inverse proportion to the magnitude of H and suppressing heat generation, heat storage can be suppressed. As a result, by making tanδ × H below a certain value, the temperature rise of the sidewall portion is suppressed, so it is considered possible to easily suppress excessive exudation of wax.

[0040] Specifically, when tanδ and H satisfy (Equation 1), the effects of the present disclosure can be more effectively exerted.

[0041] The tire section height H (mm) can be obtained as half of the value obtained by subtracting the rim diameter R (mm) from the outer diameter dt (mm) of the tire when the tire is mounted on a standard rim and the internal pressure is 250 kPa.

[0042] Further, for the pneumatic tire of the present disclosure, when the tire section width is Wt (mm), it is preferable that Wt, M300, and M100 satisfy the following (Equation 2). Wt × (M300 / M100) ≥ 740 (Equation 2)

[0043] That is, it is considered that as the tire section width becomes smaller, the amount of deformation applied to the sidewall portion increases, and cracks in the surface protective film such as wax are likely to occur. Therefore, when the section width is small, by increasing M300 / M100 so that stress concentration is less likely to occur, it is considered possible to prevent cracks in the surface protective film such as wax and maintain the appearance.

[0044] Specifically, as shown in (Equation 2), by making the product of the tire section width Wt and (M300 / M100) 740 or more, stress concentration is less likely to occur, cracks in the surface protective film can be prevented, and it becomes easier to maintain the appearance.

[0045] In the above, the tire section width Wt is the width obtained by excluding patterns, letters, etc. on the side surface of the tire from the straight-line distance (total width of the tire) between the sidewalls including all patterns, letters, etc. on the side surface of the tire in a state where the tire is mounted on a standard rim, the internal pressure is 250 kPa, and the tire is unloaded.

[0046] Further, for the pneumatic tire of the present disclosure, in order to stably exhibit the function of the micro-protrusions, it is preferable that the micro-protrusions have a longitudinal section in which the width gradually decreases from the bottom surface side toward the top surface side.

[0047] Specific examples include trapezoidal protrusions and rib-like protrusions whose longitudinal cross section in the width direction is trapezoidal.

[0048] In addition, from the viewpoint of flexibility of the sidewall portion and suppression of deformation of the sidewall portion due to rolling, the thickness of the sidewall portion at the cross-sectional width position of the pneumatic tire of the present disclosure is preferably 2 mm or more and 15 mm or less, and more preferably 10 mm or less.

[0049] In the above, the "thickness at the cross-sectional width position" refers to the thickness at a position in the tire radial direction where the tire cross-sectional width Wt is measured in a tire that is mounted on a regular rim, has an internal pressure of 250 kPa, and is in an unloaded state, and is the thickness excluding the patterns, letters, etc. Simply, it can be determined by measuring the thickness of the rubber composition forming the sidewall portion at the cross-sectional width position in the direction perpendicular to the tire surface in a cross section cut out from the tire in a state where the width of the bead portion is fixed to match the regular rim width.

[0050] In addition, in order to more effectively suppress diffuse reflection of light from the sidewall surface, the pneumatic tire of the present disclosure preferably has a surface roughness of 5 μm or more and 30 μm or less in at least 1 / 4 of the area of the micro-ridges.

[0051] The surface roughness is the ten-point average roughness Rz measured in accordance with JIS B 0601 (2001), and is measured using a known measuring instrument such as a stylus-type surface roughness measuring instrument.

[0052] In addition, in the pneumatic tire of the present disclosure, from the viewpoint of stable self-supporting properties and flexibility of the microbumps, the diameter of the bottom surface of the microbumps is preferably 0.03 mm or more and 0.5 mm or less. Furthermore, in the case of rib-shaped microbumps, the width in one direction is preferably 0.03 mm or more and 0.5 mm or less.

[0053] Also, it is desirable that the maximum width of the minute projection is 0.03 mm or more and 0.5 mm or less.

[0054] Also, it is desirable that the interval between adjacent minute projections is 0.2 mm or less.

[0055] Also, the minute projection The rise of formation part preferably has an area of 15 mm 2 or more.

[0056] [3] Embodiment Hereinafter, the present disclosure will be specifically described based on the embodiment.

[0057] <1> Sidewall part 1. Projection formation part In the projection formation part, a plurality of minute projections are formed at intervals of 0.5 mm or less in at least one direction, and 20 or more are formed. FIG. 1A is a perspective view schematically showing the shape of the projection formation part of the sidewall part of the pneumatic tire according to an embodiment of the present disclosure, FIG. 1B is a view taken along the line X-X of FIG. 1A, and is a view of the side surface of the projection formation part seen from a direction perpendicular to the one direction. Further, FIG. 2A is a perspective view schematically showing the shape of the projection formation part of the sidewall part of the pneumatic tire according to another embodiment of the present disclosure, FIG. 2B is a view taken along the line X-X of FIG. 2A, and is a view of the side surface of the projection formation part seen from a direction perpendicular to the one direction.

[0058] In each figure, 1 is the third wall part, 2 is the sidewall, and 21 is the outer surface of the sidewall. Also, 3 is the projection formation part, and 4 and 5 are minute projections. The minute projections 4 and 5 each have a bottom surface 41, 51 and a top surface 42, 52.

[0059] As described above, the minute projections include columnar projections, frustum-shaped projections, rib-shaped projections, etc. whose longitudinal sections are rectangular. The shapes of the cross sections of the columnar projections and the frustum-shaped projections are not particularly limited, and examples thereof include circular, elliptical, and polygonal shapes. Specifically, minute projections such as columnar, prismatic, frustum-shaped, and pyramidal frustum-shaped projections can be mentioned. Further, the shape of the cross section perpendicular to the longitudinal direction of the rib-shaped minute projection is not particularly limited, but a rectangular or trapezoidal shape is preferable.

[0060] In FIGS. 1A and 1B, minute frustum-shaped projections having a circular cross section are shown. Each minute projection 4 has a height h of 0.5 mm and a bottom diameter which is the maximum width w of the minute projection of 0.5 mm. Further, they are formed at intervals d of 0.5 mm or less in one direction.

[0061] In FIGS. 2A and 2B, rib-shaped minute projections are shown. A plurality of rib-shaped minute projections 5 are substantially parallel and are formed in a plurality in one direction. Each minute projection 5 has a height h of 0.5 mm. Further, the width of the bottom which is the maximum width w of the minute projection is 0.5 mm, and the interval d is 0.5 mm or less.

[0062] 2. Sidewall rubber composition The sidewall portion is produced by molding into a predetermined shape using a sidewall rubber composition composed of the compounding materials described below.

[0063] (1) Compounding materials (a) Rubber component In the present embodiment, the rubber component is not particularly limited, and diene rubbers such as isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), and nitrile rubber (NBR), butyl rubbers such as butyl rubber, and other rubbers (polymers) generally used in the production of tires can be used. Among these, from the viewpoint of forming a phase-separated structure and being less likely to generate cracks during deformation, it is preferable to include isoprene rubber and butadiene rubber. Note that, if necessary, SBR and other rubber components may be used in combination.

[0064] (i) Isoprene rubber The content (total content) of isoprene rubber in 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, from the viewpoint of exhibiting good tensile strength and making it difficult to generate damage such as cracks against deformation. On the other hand, from the viewpoint of forming a phase-separated structure with other rubber components and preventing the progress of cracks and fractures inside the rubber, it is preferably 50 parts by mass or less, more preferably 45 parts by mass or less.

[0065] Examples of the isoprene rubber include natural rubber (NR), isoprene rubber (IR), modified NR, denatured NR, denatured IR, etc., and NR is preferred in terms of excellent strength.

[0066] As NR, for example, those commonly used in the tire industry such as SIR20, RSS#3, TSR20, etc. can be used. As IR, it is not particularly limited, and for example, those commonly used in the tire industry such as IR2200, etc. can be used. Examples of the modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., examples of the denatured NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc., and examples of the denatured IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These may be used alone or in combination of two or more.

[0067] (b) BR In the present embodiment, it is preferable to use BR together with the isoprene rubber in the rubber component. The content of BR is preferably 50 parts by mass or more, more preferably 55 parts by mass or more, from the viewpoint of suppressing the progress of cracks and fractures. On the other hand, it is preferably 70 parts by mass or less, more preferably 65 parts by mass or less.

[0068] The weight-average molecular weight of BR is, for example, over 100,000 and less than 2,000,000. The vinyl bond content (1,2-bonded butadiene unit content) of BR is, for example, over 1% by mass and less than 30% by mass. The cis content of BR is, for example, over 1% by mass and 98% by mass or less. The trans content of BR is, for example, over 1% by mass and less than 60% by mass. Note that the cis content can be measured by infrared absorption spectrometry.

[0069] BR is not particularly limited, and BR with a high cis content (cis content of 90% or more), BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. can be used. BR can be either unmodified BR or modified BR. As the modified BR, for example, S-modified BR modified with a compound (modifying agent) represented by the following formula can be used.

[0070] [Chemical formula]

[0071] In the formula, R 1 , R 2 and R 3 are the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH), or a derivative thereof. R 4 and R 5 are the same or different and represent a hydrogen atom or an alkyl group. R 4 and R 5 may combine to form a ring structure together with a nitrogen atom. n represents an integer.

[0072] Examples of the modified BR modified with the compound (modifying agent) represented by the above formula include BR in which the polymerization terminal (active terminal) is modified with the compound represented by the above formula.

[0073] R 1 , R 2 and R 3As the [group], an alkoxy group is preferred (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms). R 4 and R 5 As the [group], an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) is preferred. n is preferably 1 or more and 5 or less, more preferably 2 or more and 4 or less, and still more preferably 3. Also, R 4 and R 5 When they are bonded to form a ring structure together with the nitrogen atom, it is preferably a 4-membered ring or more and an 8-membered ring or less. The alkoxy group includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group and a benzyloxy group).

[0074] Specific examples of the above-mentioned modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, and the like. These may be used alone or in combination of two or more kinds.

[0075] In addition, as the modified BR, modified BR modified with the following compounds (modifying agents) can also be used. Examples of the modifying agent include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine, 4,4'-diglycidyl-dibenzylmethylamine; diglycidylamino compounds such as diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl orthotoluidine, tetraglycidyl metaxylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane, (3-glycidyloxypropyl)-pentamethyldisiloxane;(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide and other sulfide group-containing silane compounds; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; alkoxysilanes such as methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltriethoxysilane; (thio)benzophenone compounds having an amino group and / or a substituted amino group such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, N,N,N',N'-bis-(tetraethylamino)benzophenone; benzaldehyde compounds having an amino group and / or a substituted amino group such as 4-N,N-dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-t-butyl-2-pyrrolidone, N-methyl-5-methyl-2-pyrrolidone; N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, N-phenyl-2-piperidone;N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam, as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), and tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione , N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophen, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. Modification with the above compounds (modifiers) can be carried out by known methods.

[0076] The modified BR may be, for example, a tin-modified BR, which is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and which preferably has a tin-carbon bond at the end of the tin-modified BR molecule.

[0077] Examples of the lithium initiator include lithium compounds such as alkyllithium, aryllithium, vinyllithium, organotinlithium, and organonitrogen lithium compounds, as well as lithium metal. By using the lithium initiator as the initiator for the tin-modified BR, a tin-modified BR with a high vinyl and low cis content can be produced.

[0078] Examples of tin compounds include tin tetrachloride, butyltin trichloride, dibutyltin dichloride, dioctyltin dichloride, tributyltin chloride, triphenyltin chloride, diphenyldibutyltin, triphenyltin ethoxide, diphenyldimethyltin, ditolyltin chloride, diphenyltin dioctanoate, divinyldiethyltin, tetrabenzyltin, dibutyltin distearate, tetraallyltin, and p-tributyltin styrene.

[0079] The tin atom content in the tin-modified BR is preferably 50 ppm or more, more preferably 60 ppm or more, and is preferably 3000 ppm or less, more preferably 2500 ppm or less, and even more preferably 250 ppm or less.

[0080] The molecular weight distribution (Mw / Mn) of the tin-modified BR is preferably 2 or less, and more preferably 1.5 or less.

[0081] The vinyl bond content in the tin-modified BR is preferably 5% by mass or more, more preferably 7% by mass or more, while the vinyl bond content in the tin-modified BR is preferably 50% by mass or less, more preferably 20% by mass or less.

[0082] The above-mentioned S-modified BR and tin-modified BR may be used alone or in combination of two or more kinds.

[0083] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0084] (c) SBR In the present embodiment, if necessary, part of the BR in the rubber component, specifically 25 parts by mass or more and 35 parts by mass or less, may be SBR.

[0085] The weight-average molecular weight of SBR is, for example, more than 100,000 and less than 2,000,000. The styrene content of SBR is, for example, preferably more than 5% by mass, more preferably more than 10% by mass, and even more preferably more than 20% by mass. On the other hand, it is preferably less than 50% by mass, more preferably less than 40% by mass, and even more preferably less than 35% by mass. The vinyl bond content of SBR is, for example, preferably more than 5% by mass and less than 70% by mass. SBR structural identification (measurement of styrene content and vinyl bond content) can be performed using, for example, a JNM-ECA series instrument manufactured by JEOL Ltd.

[0086] The SBR is not particularly limited, and examples thereof include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. The SBR may be either unmodified SBR or modified SBR, and these may be used alone or in combination of two or more types.

[0087] The modified SBR may be any SBR having a functional group that interacts with a filler such as silica, and examples thereof include terminal-modified SBR in which at least one terminal of the SBR has been modified with a compound (modifier) having the above functional group (terminal-modified SBR having the above functional group at the terminal), main-chain-modified SBR in which the main chain has the above functional group, main-chain terminal-modified SBR in which the main chain and terminals have the above functional group (for example, main-chain terminal-modified SBR in which the main chain has the above functional group and at least one terminal has been modified with the above modifier), and terminal-modified SBR in which the SBR has been modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and in which a hydroxyl group or epoxy group has been introduced.

[0088] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. The SBR may be used alone or in combination of two or more types.

[0089] (d) Other rubber components In addition, as other rubber components, rubber (polymers) generally used in the production of tires such as nitrile rubber (NBR) may be included as necessary.

[0090] In the present disclosure, the sidewall rubber composition may be blended with, for example, a composite material containing a functional group having at least one metal coordination ability in its molecular structure. Here, the functional group having a metal coordination ability is not particularly limited as long as it has a metal coordination ability, and examples thereof include functional groups containing metal-coordinating atoms such as oxygen, nitrogen, and sulfur. Specifically, dithiocarbamic acid groups, phosphate groups, carboxylic acid groups, carbamic acid groups, dithio acid groups, aminophosphoric acid groups, thiol groups, etc. are exemplified. The above functional groups may be contained alone or in two or more kinds.

[0091] Examples of the coordination metal for the functional group include Fe, Cu, Ag, Co, Mn, Ni, Ti, V, Zn, Mo, W, Os, Mg, Ca, Sr, Ba, Al, Si, etc. For example, in a polymer material containing a compound having such a metal atom (M1) and a functional group (-COO etc.) having a metal coordination ability, each -COOM1 forms a coordination bond and a large number of -COOM1 overlap, thereby forming a cluster in which metal atoms aggregate. The blending amount of the above metal atom (M1) is preferably 0.01 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the polymer component in the polymer material.

[0092] (b) Blending materials other than the rubber component (i) Filler In the present embodiment, the sidewall rubber composition preferably contains a filler (reinforcing filler). Examples of the filler include carbon black, silica, calcium carbonate, short fiber materials such as cellulose nanofibers, and mM2·xSiO y·zH2O (wherein M2 represents at least one metal selected from the group consisting of aluminum, calcium, magnesium, titanium, and zirconium, or an oxide, hydroxide, hydrate, or carbonate of the metal, m is a numerical value in the range of 1 to 5, x is a numerical value in the range of 0 to 10, y is a numerical value in the range of 2 to 5, and z is a numerical value including both ends in the range of 0 to 10). Examples of the filler represented by this formula include fillers and the like.

[0093] The above mM2·xSiO y Specific examples of the filler represented by ·zH2O include aluminum hydroxide (Al(OH)3), alumina (Al2O3, Al2O3·3H2O (hydrate)), clay (Al2O3·2SiO2), kaolin (Al2O3·2SiO2·2H2O), pyrophyllite (Al2O3·4SiO2·H2O), bentonite (Al2O3·4SiO2·2H2O), aluminum silicate (Al2SiO5, Al4(SiO2)3·5H2O, etc.), calcium aluminum silicate (Al2O3·CaO·2SiO2), calcium hydroxide (Ca(OH)2), calcium oxide (CaO), calcium silicate (Ca2SiO4), calcium magnesium silicate (CaMgSiO4), magnesium hydroxide (Mg(OH)2), magnesium oxide (MgO), talc (MgO·4SiO2·H2O), attapulgite (5MgO·8SiO2·9H2O), magnesium aluminum oxide (MgO·Al2O3), titanium white (TiO2), titanium black (Ti n O 2n-1 ) and the like. In a polymer material containing such a filler, clusters in which the filler aggregates are formed.

[0094] (i) Carbon black The sidewall rubber composition preferably contains carbon black. The content of carbon black is preferably, for example, 10 parts by mass or more and 100 parts by mass or less, more preferably 15 parts by mass or more and 60 parts by mass or less, and even more preferably 25 parts by mass or more and 55 parts by mass or less, based on 100 parts by mass of the rubber component.

[0095] The carbon black is not particularly limited, and examples thereof include furnace black (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal black (thermal carbon black) such as FT and MT; channel black (channel carbon black) such as EPC, MPC, and CC. These may be used alone or in combination of two or more.

[0096] The nitrogen adsorption specific surface area (N2SA) of the carbon black is, for example, more than 30 m 2 / g and less than 250 m 2 / g. The dibutyl phthalate (DBP) absorption amount of the carbon black is, for example, more than 50 ml / 100 g and less than 250 ml / 100 g. The nitrogen adsorption specific surface area of the carbon black is measured according to ASTM D4820-93, and the DBP absorption amount is measured according to ASTM D2414-93.

[0097] Specific carbon blacks are not particularly limited, and examples thereof include N110, N115, N120, N121, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N335, N339, N343, N347, N351, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, etc. As commercially available products, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Chemical Carbon Co., Ltd., Columbian Carbon Company, etc. can be used, but carbon black synthesized independently can also be used. These may be used alone or in combination of two or more.

[0098] (ii) Silica The sidewall rubber composition preferably further contains silica as needed. From the viewpoint of obtaining good durability performance, the BET specific surface area of the silica is preferably more than 140 m 2 / g, more preferably more than 160 m 2 / g. On the other hand, from the viewpoint of obtaining good low rolling resistance, it is preferably less than 250 m 2 / g, more preferably less than 220 m 2 / g.

[0099] Also, when not used in combination with a silane coupling agent, the content of the silica with respect to 100 parts by mass of the rubber component is preferably 3 parts by mass or more, more preferably 5 parts by mass or more. On the other hand, it is preferably 25 parts by mass or less, more preferably 15 parts by mass or less. When used in combination with a silane coupling agent, it is preferably 25 parts by mass or more. On the other hand, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. The above-mentioned BET specific surface area is the value of N2SA measured by the BET method according to ASTM D3037-93.

[0100] Examples of the silica include dry-process silica (anhydrous silica), wet-process silica (hydrous silica), etc. Among them, wet-process silica is preferred because of its large number of silanol groups. Also, silica using hydrated glass or the like as a raw material, or silica using biomass materials such as rice husks as a raw material may be used.

[0101] Examples of the silica that can be used include products of Degussa, Rhodia, Tosoh Silica Corporation, Solvay Japan K.K., Tokuyama Corporation, etc.

[0102] (iii) Silane coupling agent As mentioned above, when using silica, a silane coupling agent can be used in combination. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocathanide, Examples of such compounds include sulfide-based compounds such as rubamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These compounds may be used alone or in combination of two or more.

[0103] As the silane coupling agent, for example, products from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used.

[0104] The content of the silane coupling agent is, for example, more than 3 parts by mass and less than 15 parts by mass relative to 100 parts by mass of silica.

[0105] (iv) Other fillers In addition to the above-mentioned carbon black and silica, the sidewall rubber composition may further contain fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. The content of these fillers is, for example, more than 0.1 part by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0106] (b) Hardening resin component The sidewall rubber composition may contain a curable resin component such as a modified resorcinol resin or a modified phenolic resin, if necessary.

[0107] Specific examples of modified resorcinol resins include Sumikanol 620 (modified resorcinol resin) manufactured by Taoka Chemical Co., Ltd., and examples of modified phenolic resins include PR12686 (cashew oil modified phenolic resin) manufactured by Sumitomo Bakelite Co., Ltd.

[0108] The content of the curable resin component is, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component, from the viewpoint of sufficiently improving the complex modulus and obtaining a large reaction force during deformation, while the content is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, from the viewpoint of maintaining the breaking strength.

[0109] When using the modified resorcinol resin, it is preferable to contain a methylene donor as a curing agent. Examples of the methylene donor include hexamethylenetetramine (HMT), hexamethoxymethylol melamine (HMMM), hexamethylol melamine pentamethyl ether (HMMPME), etc. It is preferably contained in an amount of, for example, 5 parts by mass or more and about 15 parts by mass with respect to 100 parts by mass of the curable resin component. If it is too little, there is a risk that a sufficient complex elastic modulus cannot be obtained. On the other hand, if it is too much, the viscosity of the rubber may increase and the processability may deteriorate.

[0110] As a specific methylene donor, for example, Sumicanol 507 manufactured by Tago Chemical Industry Co., Ltd. can be used.

[0111] (C) Plasticizer component The sidewall rubber composition may contain, as a component for softening the rubber, oil (including extender oil), liquid rubber, and resin as plasticizer components as needed. The plasticizer component is a component that can be extracted from the vulcanized rubber with acetone. The total content of the plasticizer components is preferably more than 5 parts by mass, more preferably more than 10 parts by mass, with respect to 100 parts by mass of the rubber component. On the other hand, it is preferably less than 70 parts by mass, more preferably less than 50 parts by mass, and even more preferably less than 30 parts by mass. The content of the oil also includes the amount of oil contained in the rubber (oil-extended rubber).

[0112] (i) Oil Examples of the oil include mineral oil (generally referred to as process oil), vegetable oil and fat, or a mixture thereof. Examples of the mineral oil (process oil) include paraffinic process oil, aromatic process oil, naphthenic process oil, etc. Examples of the vegetable oil and fat include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, etc. Further, from the viewpoint of life cycle assessment, lubricating oil after being used in a mixer of a rubber mixer or an automobile engine, waste cooking oil used in a cooking shop, etc. may be appropriately refined and used. These may be used alone or in combination of two or more kinds.

[0113] As specific process oil (mineral oil), for example, products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Corporation, Orysoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kogyo Co., Ltd., etc. can be used.

[0114] (ii) Liquid rubber The liquid rubber mentioned as a plasticizer is a polymer in a liquid state at normal temperature (25°C) and is a rubber component that can be extracted from a vulcanized tire by acetone extraction. Examples of the liquid rubber include farnesene-based polymers, liquid diene-based polymers, and hydrogenated products thereof.

[0115] The farnesene-based polymer is a polymer obtained by polymerizing farnesene and has a structural unit based on farnesene. Isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene) exist in farnesene.

[0116] The farnesene-based polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0117] Examples of liquid diene polymers include liquid styrene butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), and liquid styrene isoprene copolymer (liquid SIR).

[0118] The liquid diene polymer has a weight average molecular weight (Mw) of, for example, 1.0 × 10 in terms of polystyrene measured by gel permeation chromatography (GPC). 3 Super, 2.0×10 5 In this specification, the Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0119] The amount of the liquid rubber (total amount of the liquid farnesene polymer, liquid diene polymer, etc.) is, for example, more than 1 part by mass and less than 100 parts by mass per 100 parts by mass of the rubber component.

[0120] As the liquid rubber, for example, products of Kuraray Co., Ltd., Cray Valley Co., Ltd., etc. can be used.

[0121] (iii) Resin component The resin component also functions as a tackifier and may be solid or liquid at room temperature. Specific examples of the resin component include rosin-based resins, styrene-based resins, coumarone-based resins, terpene-based resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins, and two or more of these may be used in combination. The content of the resin component is preferably more than 2 parts by mass and less than 45 parts by mass, more preferably less than 30 parts by mass, per 100 parts by mass of the rubber component. These resin components are distinct from the thermosetting resin component described above, and are components that can be extracted from the vulcanized rubber with a solvent such as acetone.

[0122] Rosin-based resins are resins mainly composed of rosin acids obtained by processing pine resin. These rosin-based resins (rosins) can be classified according to the presence or absence of modification, and can be classified into unmodified rosin (non-modified rosin) and rosin modified products (rosin derivatives). Examples of unmodified rosin include tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. Rosin modified products are modified products of unmodified rosin, and examples include rosin esters, unsaturated carboxylic acid-modified rosins, unsaturated carboxylic acid-modified rosin esters, amide compounds of rosin, and amine salts of rosin.

[0123] Styrene-based resins are polymers using styrene-based monomers as constituent monomers, and examples include polymers polymerized with styrene-based monomers as the main component (50% by mass or more). Specifically, styrene-based monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) are each polymerized alone to form homopolymers, copolymers obtained by copolymerizing two or more styrene-based monomers, and copolymers of styrene-based monomers and other monomers copolymerizable therewith.

[0124] Examples of the other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, acrylates, unsaturated carboxylic acids such as methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene isoprene, olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof.

[0125] Among coumarone resins, coumarone-indene resins are preferred. A coumarone-indene resin is a resin containing coumarone and indene as monomer components constituting the resin skeleton (main chain). Examples of monomer components other than coumarone and indene contained in the skeleton include styrene, α-methylstyrene, methyl indene, vinyltoluene, and the like.

[0126] The content of the coumarone-indene resin is, for example, more than 1.0 part by mass and less than 50.0 parts by mass with respect to 100 parts by mass of the rubber component.

[0127] The hydroxyl value (OH value) of the coumarone-indene resin is, for example, more than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is the amount of potassium hydroxide in milligrams required to neutralize acetic acid bonded to hydroxyl groups when 1 g of the resin is acetylated, and is a value measured by the potentiometric titration method (JIS K 0070:1992).

[0128] The softening point of the coumarone-indene resin is, for example, more than 30°C and less than 160°C. The softening point is the temperature at which the ball drops when measured with a ring and ball softening point measuring device according to the softening point defined in JIS K 6220-1:2001.

[0129] Examples of terpene resins include polyterpene, terpene phenol, and aromatic-modified terpene resins. Polyterpene is a resin obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are hydrocarbons represented by the composition of (C5H8) n and their oxygen-containing derivatives, and include monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32) It is a compound having a terpene as a basic skeleton and classified into, for example, α-pinene, β-pinene, dipentene, limonene, myrcene, allo-ocimene, ocimene, α-farnesene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc.

[0130] As polyterpenes, in addition to terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, β-pinene / limonene resin, etc. which use the above-mentioned terpene compounds as raw materials, hydrogenated terpene resins obtained by hydrogenating the terpene resins are also included. As terpene phenols, resins obtained by copolymerizing the above-mentioned terpene compounds and phenolic compounds, and resins obtained by hydrogenating the resins are included. Specifically, resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds and formalin are included. Examples of phenolic compounds include phenol, bisphenol A, cresol, xylenol, etc. As aromatic-modified terpene resins, resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the resins are included. The aromatic compound is not particularly limited as long as it has an aromatic ring. For example, phenolic compounds such as phenol, alkylphenol, alkoxyphenol, phenol containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, naphthol containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, styrene containing an unsaturated hydrocarbon group; coumarone, indene, etc. are included.

[0131] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of the C5 fraction include petroleum fractions corresponding to 4 to 5 carbon atoms such as cyclopentadiene, pentene, pentadiene, isoprene, etc. As the C5-based petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0132] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified version. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples include coumarone-indene resin, coumarone resin, indene resin, and aromatic vinyl resin. 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. Examples of aromatic vinyl resins that can be used include those commercially available from Kraton, Eastman Chemical, and the like.

[0133] "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of C5 fractions and C9 fractions include the petroleum fractions mentioned above. As the C5C9 resin, for example, commercially available products from Tosoh Corporation, LUHUA, etc. can be used.

[0134] The acrylic resin is not particularly limited, but for example, a solventless acrylic resin can be used.

[0135] Examples of solvent-free acrylic resins include (meth)acrylic resins (polymers) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization) (methods described in U.S. Pat. No. 4,414,370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, U.S. Pat. No. 5,010,166, and Toa Gosei Kenkyusho TREND 2000 Vol. 3, pp. 42-45, etc.), with minimal use of secondary raw materials such as polymerization initiators, chain transfer agents, and organic solvents. In this disclosure, (meth)acrylic refers to both methacrylic and acrylic.

[0136] Examples of the monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (such as alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0137] In addition, as the monomer components constituting the acrylic resin, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or (meth)acrylic acid derivatives.

[0138] The acrylic resin may be a resin composed only of the (meth)acrylic component or a resin having components other than the (meth)acrylic component as constituent elements. Further, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0139] Examples of the resin component include products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Toray Industries, Inc., Rutgers Chemicals, BASF, Arizona Chemical, Nippon Paint Co., Ltd., Nippon Catalyst Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Industries, Ltd., Tago Chemical Industry Co., Ltd., etc.

[0140] (II) Reversion (vulcanization reversion) inhibitor The sidewall rubber composition preferably contains a reversion (vulcanization reversion) inhibitor as needed. Thereby, reversion is suppressed and durability is improved. The content of the reversion inhibitor is preferably 0.1 part by mass or more and 3 parts by mass or less, more preferably 0.2 part by mass or more and 2.5 parts by mass or less, and even more preferably 0.3 part by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the rubber component. Specific examples of the reversion inhibitor include Parkerlink 900 (1,3-bis(citraconimidomethyl)benzene) manufactured by Flexsys.

[0141] (e) Antiaging agents The sidewall rubber composition preferably contains an antioxidant as needed. The content of the antioxidant is, for example, more than 1 part by mass and less than 10 parts by mass per 100 parts by mass of the rubber component.

[0142] Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of antioxidants include p-phenylenediamine antioxidants such as quinolone; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. These antioxidants may be used alone or in combination of two or more.

[0143] As the antioxidant, for example, products available from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc. can be used.

[0144] (f) Stearic acid The sidewall rubber composition may contain stearic acid as needed. The content of stearic acid is, for example, more than 0.5 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component. Conventionally known stearic acids can be used, such as those available from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0145] (g) Zinc oxide The sidewall rubber composition may contain zinc oxide as required. The content of zinc oxide is, for example, more than 0.5 part by mass and less than 15 parts by mass with respect to 100 parts by mass of the rubber component. As the zinc oxide, conventionally known ones can be used, for example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusuitech Co., Ltd., Shoindo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0146] (D) Crosslinking agent and vulcanization accelerator The sidewall rubber composition preferably contains a crosslinking agent such as sulfur. The content of the crosslinking agent is, for example, more than 0.1 part by mass and less than 10.0 parts by mass with respect to 100 parts by mass of the rubber component.

[0147] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc. generally used in the rubber industry. These may be used alone or in combination of two or more.

[0148] As the sulfur, for example, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexsys, Nippon Kankyu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0149] Examples of crosslinking agents other than sulfur include vulcanizing agents containing sulfur atoms such as Tackiol V200 manufactured by Takeoka Chemical Industry Co., Ltd., Duralink HTS (sodium 1,6 - hexamethylene - dithiolsulfate dihydrate) manufactured by Flexsys, KA9188 (1,6 - bis(N,N’ - dibenzylthiocarbamoyldithio)hexane) manufactured by Rancess, etc., and organic peroxides such as dicumyl peroxide.

[0150] The sidewall rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, more than 0.3 part by mass and less than 10.0 parts by mass with respect to 100 parts by mass of the rubber component.

[0151] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more.

[0152] (R) Other In addition to the above components, the sidewall rubber composition may further contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, organic peroxides, etc. The content of these additives is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0153] (2) Preparation of Sidewall Rubber Composition The sidewall rubber composition is produced by a general method, for example, a production method including a base kneading step of kneading a rubber component with a filler such as carbon black, and a finish kneading step of kneading the kneaded product obtained in the base kneading step with a crosslinking agent.

[0154] The kneading can be carried out using a known (internal) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0155] The kneading temperature in the base kneading step is, for example, higher than 50° C. and lower than 200° C., and the kneading time is, for example, higher than 30 seconds and lower than 30 minutes. In the base kneading step, in addition to the above components, compounding agents conventionally used in the rubber industry, for example, plasticizer components such as oil, stearic acid, zinc oxide, antioxidants, waxes, vulcanization accelerators, etc., may be appropriately added and kneaded as needed.

[0156] In the final kneading step, the kneaded product obtained in the base kneading step is kneaded with a crosslinking agent. The kneading temperature in the final kneading step is, for example, higher than room temperature and lower than 80°C, and the kneading time is, for example, longer than 1 minute and shorter than 15 minutes. In the final kneading step, in addition to the above components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added and kneaded as necessary.

[0157] 3. Manufacturing of sidewall components The resulting sidewall rubber composition can be molded into a predetermined shape to produce a sidewall member.

[0158] <2> Pneumatic tire manufacturing The pneumatic tire of this embodiment can be produced as an unvulcanized tire by molding the sidewall member obtained above together with other tire components in a tire building machine using a normal method.

[0159] Specifically, an inner liner as a component for ensuring the airtightness of the tire, a carcass as a component for withstanding the load, impact, and filling air pressure received by the tire, and a belt member as a component for tightly fastening the carcass to increase the rigidity of the tread are wound around a forming drum, and both ends of the carcass are fixed to both side edges, and bead portions as components for fixing the tire to the rim are arranged. After forming into a toroidal shape, a tread is attached to the center of the outer periphery, and sidewall members are attached to the radially outer sides to form sidewall portions, thereby producing an unvulcanized tire.

[0160] Thereafter, the obtained unvulcanized tire is loaded into a vulcanizing mold and heated and pressurized to obtain a tire. The heating and pressurization are carried out by a known method using a mold equipped with a side plate having an engraving for forming minute protrusions engraved on the opposing surface of the protrusion forming portion. The vulcanization temperature is, for example, over 120°C and less than 200°C, and the vulcanization time is, for example, over 5 minutes and less than 60 minutes.

[0161] The applicable range of the tire of the present disclosure is not particularly limited and can be applied to any tire such as passenger car tires, truck / bus tires, motorcycle tires, etc. However, it is particularly preferably applied to pneumatic passenger car tires where aesthetics are highly regarded, that is, tires mounted on four-wheeled automobiles with a maximum load capacity of 1000 Kg or less.

[0162] Note that the above-mentioned maximum load capacity is not particularly limited as long as it is 1000 Kg or less. However, generally, as the maximum load capacity increases, the tire weight tends to increase, and accordingly, the heat generation property of the tire tends to be high. Therefore, it is preferably 900 Kg or less, more preferably 800 Kg or less, and even more preferably 700 Kg or less.

[0163] Also, from the viewpoint of reducing the heat generation property of the tire, the above-mentioned tire weight is preferably 20 Kg or less, more preferably 15 Kg or less, and even more preferably 12 Kg or less, 10 Kg or less, or 8 Kg or less. Note that the tire weight referred to here is the weight of the entire tire, and when the tire inner cavity surface is provided with a sealant, sponge, three-dimensional network structure, electronic components, etc., it includes their weights.

[0164] Among pneumatic passenger car tires, when the present disclosure is applied to tires mounted on high-performance vehicles and assumed to be used severely, specifically, pneumatic passenger car tires with a section height of 96 mm or less and a section width of 185 mm or more, the effects according to the present disclosure can be obtained particularly significantly.

[0165] In recent years, due to the popularization of hybrid cars and electric vehicles, the weight of automobiles has tended to increase. Along with this, the burden on tires, especially the sidewall part, has become larger, and there is concern that damage such as crack generation in the sidewall part may occur. However, by mounting the tire according to the present disclosure, it is possible to reduce the burden on the sidewall part, which is preferable.

Example

[0166] Hereinafter, the present disclosure will be described in more detail with reference to examples.

[0167] In the examples described below, a total of 12 types of test tires of Example 1 to Example 7 and Comparative Example 1 to Comparative Example 5 with a size of 225 / 40R18 (section height: section height is 90 mm), different heights h and maximum widths w of the micro projections, intervals d, and compositions of the rubber compositions constituting the sidewall members were manufactured, and the crack resistance performance and appearance of the sidewall part were evaluated.

[0168] 1. Preparation of sidewall member First, a sidewall member was prepared using a sidewall rubber composition.

[0169] (1) Compounding materials for sidewall rubber composition First, each of the following compounding materials was prepared.

[0170] (a) Rubber component (i) IR: Nipol IR2200 manufactured by Zeon Corporation of Japan (ii) BR: UBEPOL - BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass) (iii) SBR: HPR850 (solution - polymerized SBR) manufactured by JSR Corporation (styrene content: 27.5% by mass, vinyl bond amount: 58.5% by mass)

[0171] (b) Compounding materials other than rubber component (i) CB: Show Black N660 manufactured by Cabot Japan Ltd. (b) Silica: VN3 manufactured by Eponex (c) Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (d) Stearic acid: Stearic acid "Tsubaki" manufactured by NOF Corporation (e) Antioxidant 1: Nocrac 6C (6PPD) manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) (f) Antioxidant 2: Nocrac 224 manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. (2,2,4-trimethyl-1,2-dihydroquinoline polymer) (g) Sulfur: Powder sulfur manufactured by Karuizawa Sulfur Co., Ltd. (h) Vulcanization accelerator: Nocceler CZ manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. (N-cyclohexyl-2-benzothiazolylsulfenamide)

[0172] (2) Production of sidewall rubber composition According to each compounding content shown in Table 1 and Table 2, using a 3L Banbury mixer, materials other than sulfur and vulcanization accelerator were kneaded at 150 °C for 5 minutes to obtain a kneaded product. Each compounding amount is in parts by mass.

[0173] Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and it was kneaded using an open roll at 80 °C for 5 minutes to obtain a sidewall rubber composition.

[0174] Next, using the obtained sidewall rubber composition, a sidewall member having a predetermined shape was produced.

[0175] 2. Tire production The sidewall member obtained above was bonded together with other tire members to form an unvulcanized tire, which was press-vulcanized at 140 °C for 50 minutes to produce each test tire having a cross-sectional width shown in Table 1 and Table 2.

[0176] 3. Measurement of various dimensions, physical properties, and calculation of parameters Each test tire was mounted on a standard rim, and at an internal pressure of 250 kPa and under no load, the cross-sectional width, cross-sectional height of the tire, and the height, maximum width, and interval size of the micro-protrusions within the protrusion formation part were measured. At the same time, the ten-point average roughness Rz in a region that is 1 / 4 of the area of the micro-protrusions was measured in accordance with JIS B 0601 (2001).

[0177] Next, the thickness at the tire cross-sectional width position of the sidewall part was measured. Then, a rubber composition was cut out from the sidewall part to prepare test pieces of a predetermined size, and using an Iplexer manufactured by GABO, the loss tangent tanδ was measured under the conditions of temperature: 70 °C, initial strain: 2.5%, dynamic strain: ±1%, frequency: 10 Hz, and deformation mode: tension.

[0178] Also, using an autograph manufactured by Shimadzu Corporation, in accordance with JIS K6251, the stress M100 (MPa) at a tensile strain of 100% and the stress M300 (MPa) at a tensile strain of 300% in a tensile test at 25 °C and a tensile speed of 500 mm / min were measured.

[0179] Next, "tanδ × H" and "Wt × M300 / M100" were calculated from the above respective measurement results. The above results are summarized and shown in Table 1 and Table 2.

[0180] 4. Performance Evaluation Test (Evaluation of Appearance) The evaluation of appearance was carried out using a drum tester. Specifically, after each test tire was mounted on a standard rim, it was filled with the standard internal pressure (250 kPa), a load of 75% of the standard load was applied, and it was run on the drum for 10,000 km. Regarding the appearance of the side part of the tire after the running was completed, 20 evaluators gave scores on a 5-point scale (the higher the score, the better the appearance), and the obtained scores were totaled to obtain the evaluation results for each test tire.

[0181] Next, taking the evaluation result in Comparative Example 2 as 100, it was indexed based on the following formula to obtain the evaluation of appearance. The larger the numerical value, the better the appearance. Appearance Performance = [(Evaluation Result of Test Tire) / (Evaluation Result of Comparative Example 2)] × 100

[0182] The evaluation results are collectively shown in Tables 1 and 2.

[0183]

Table 1

[0184]

Table 2

[0185] It can be seen from Tables 1 and 2 that Examples 1 to 7 that meet the requirements of the present disclosure are excellent in aesthetics.

[0186] Also, among Examples 1 to 5 where the tire section width Wt, section height H, and sidewall rubber thickness are equal, it can be seen that Examples 1, 3, and 4 with M300 / M100 of 4.5 or more have better crack resistance performance. Further, among the examples, Example 6 with a large sidewall rubber thickness of 15 mm obtained a result that the aesthetic evaluation result was slightly inferior to other examples.

[0187] As described above, the present disclosure has been described based on the embodiments, but the present disclosure is not limited to the above embodiments. Various changes can be made to the above embodiments within the same and equivalent scope as the present disclosure.

[0188] The present disclosure (1) is a pneumatic tire having a sidewall portion, wherein the sidewall portion has a raised portion formed with a plurality of minute protrusions on the outer surface, the minute protrusions have a height of 0.5 mm or less, the raised portion has an area of 10 mm 2 or more, and 20 or more of the minute protrusions are formed at intervals of 0.5 mm or less in at least one direction, When the stress at 100% tensile strain in the tensile test at a tensile speed of 500 mm / min in the 25°C environment of the sidewall part is defined as M100 (MPa) and the stress at 300% tensile strain is defined as M300 (MPa), M300 / M100 is greater than 4.0, It is a pneumatic tire characterized in that the loss tangent tanδ measured under the conditions of temperature: 70°C, initial strain: 2.5%, dynamic strain: ±1%, frequency: 10 Hz, and deformation mode: tension is 0.09 or less.

[0189] This disclosure (2) is It is a pneumatic tire according to disclosure (1), characterized in that the loss tangent tanδ is 0.08 or less.

[0190] This disclosure (3) is It is a pneumatic tire according to disclosure (2), characterized in that the loss tangent tanδ is 0.07 or less.

[0191] This disclosure (4) is It is a pneumatic tire according to any one of disclosures (1) to (3), characterized in that M300 / M100 is 4.5 or more.

[0192] This disclosure (5) is When the tire section height is H (mm), it is a pneumatic tire according to any one of disclosures (1) to (4), characterized in that H and the loss tangent tanδ satisfy the following (Formula 1). tanδ × H ≤ 8.64 (Formula 1)

[0193] This disclosure (6) is When the tire section width is Wt (mm), it is a pneumatic tire according to any one of disclosures (1) to (5), characterized in that Wt and M300 / M100 satisfy the following (Formula 2). Wt × (M300 / M100) ≥ 740 (Formula 2)

[0194] This disclosure (7) is The micro-protrusions are characterized by having a longitudinal cross-section with a width that gradually decreases from the bottom side to the top side, and it is a pneumatic tire in any arbitrary combination with any one of the present disclosures (1) to (6).

[0195] The present disclosure (8) is characterized in that the thickness of the rubber composition of the sidewall portion at the tire cross-sectional width position is 2 mm or more and 15 mm or less, and it is a pneumatic tire in any arbitrary combination with any one of the present disclosures (1) to (7).

[0196] The present disclosure (9) is characterized in that the thickness of the rubber composition of the sidewall portion at the tire cross-sectional width position is 2 mm or more and 10 mm or less, and it is the pneumatic tire described in the present disclosure (8).

[0197] The present disclosure (10) is characterized in that the shape of the micro-protrusions is columnar, frustum-shaped or rib-shaped, and it is a pneumatic tire in any arbitrary combination with any one of the present disclosures (1) to (9).

[0198] The present disclosure (11) is characterized in that the height of the micro-protrusions is 0.4 mm or less, and it is a pneumatic tire in any arbitrary combination with any one of the present disclosures (1) to (10).

[0199] The present disclosure (12) is characterized in that the maximum width of the micro-protrusions is 0.03 mm or more and 0.5 mm or less, and it is a pneumatic tire in any arbitrary combination with any one of the present disclosures (1) to (11).

[0200] The present disclosure (13) is characterized in that the interval between adjacent micro-protrusions is 0.2 mm or less, and it is a pneumatic tire in any arbitrary combination with any one of the present disclosures (1) to (12).

[0201] The present disclosure (14) is The minute projections have a circular cross-section and an average diameter of 0.03 mm or more and 0.5 mm or less, and are pneumatic tires in any combination of any of (1) to (13) of the present disclosure.

[0202] The present disclosure (15) is The minute projections are blade-shaped minute projections having a rectangular cross-section, and an average width of 0.03 mm or more and 0.5 mm or less, and are pneumatic tires in any combination of any of (1) to (13) of the present disclosure.

[0203] The present disclosure (16) is In at least 1 / 4 of the area of the minute projections, it has a surface roughness with a ten-point average roughness Rz measured in accordance with JIS B 0601 (2001) of 5 μm or more and 30 μm or less, and is a pneumatic tire in any combination of any of (1) to (15) of the present disclosure.

[0204] The present disclosure (17) is The front Kiyoshi formation part has an area of 15 mm 2 or more, and is a pneumatic tire in any combination of any of (1) to (16) of the present disclosure.

[0207] The present disclosure ( 18 ) is a pneumatic tire for passenger cars, and is a pneumatic tire in any combination of any of (1) to ( 17 ) of the present disclosure.

[0208] The present disclosure ( 19 ) is a pneumatic tire for passenger cars with a section height of 96 mm or less and a section width of 185 mm or more, and is the pneumatic tire described in the present disclosure ( 18 ).

Explanation of Signs

[0209] 1 Sidewall part 2 Sidewall 3 Protrusion Forming Portion 4, 5 Micro-protrusions 21 Outer Surface of Side Wall 41, 51 Bottom Surface 42, 52 Top Surface h Height of Micro-protrusion d Spacing w Maximum Width of Micro-protrusion

Claims

1. A pneumatic tire having a sidewall portion, wherein the sidewall portion has a raised portion formed with a plurality of minute raised portions on the outer surface, the height of the minute raised portions is 0.5 mm or less, The raised portion has an area of 10 mm ２ or more, and 20 or more of the minute projections are formed at intervals of 0.5 mm or less in at least one direction. when the stress at a tensile strain of 100% in a tensile test at a tensile speed of 500 mm / min in an environment of 25°C of the sidewall portion is defined as M100 (MPa), and the stress at a tensile strain of 300% is defined as M300 (MPa), M300 / M100 is greater than 4.0, a pneumatic tire characterized in that a loss tangent tanδ measured under the conditions of temperature: 70°C, initial strain: 2.5%, dynamic strain: ±1%, frequency: 10 Hz, and deformation mode: tension is 0.09 or less.

2. The pneumatic tire according to claim 1, characterized in that the loss tangent tanδ is 0.08 or less.

3. The pneumatic tire according to claim 2, characterized in that the loss tangent tanδ is 0.07 or less.

4. The pneumatic tire according to any one of claims 1 to 3, characterized in that M300 / M100 is 4.5 or more.

5. The pneumatic tire according to any one of claims 1 to 4, characterized in that when the tire section height is H (mm), H and the loss tangent tanδ satisfy the following (Equation 1). tanδ × H ≤ 8.64 (Equation 1)

6. The pneumatic tire according to any one of claims 1 to 5, characterized in that when the tire section width is Wt (mm), Wt and M300 / M100 satisfy the following (Equation 2). Wt × (M300 / M100) ≥ 740 (Equation 2)

7. The pneumatic tire according to any one of claims 1 to 6, characterized in that the minute raised portions have a longitudinal section in which the width gradually decreases from the bottom surface side to the top surface side.

8. The pneumatic tire according to any one of claims 1 to 7, characterized in that the thickness of the rubber composition of the sidewall portion at the tire section width position is 2 mm or more and 15 mm or less.

9. The pneumatic tire according to claim 8, characterized in that the thickness of the rubber composition of the sidewall portion at the tire section width position is 2 mm or more and 10 mm or less.

10. The pneumatic tire according to any one of claims 1 to 9, characterized in that the shape of the minute raised portions is columnar, frustum-shaped, or rib-shaped.

11. The pneumatic tire according to any one of Claims 1 to 10, wherein the height of the minute projection is 0.4 mm or less.

12. The pneumatic tire according to any one of Claims 1 to 11, wherein the maximum width of the minute projection is 0.03 mm or more and 0.5 mm or less.

13. The pneumatic tire according to any one of Claims 1 to 12, wherein the interval between adjacent minute projections is 0.2 mm or less.

14. The pneumatic tire according to any one of Claims 1 to 13, wherein the minute projection has a circular cross section and an average diameter of 0.03 mm or more and 0.5 mm or less.

15. The pneumatic tire according to any one of Claims 1 to 13, wherein the minute projection is a blade-shaped minute projection having a rectangular cross section and an average width of 0.03 mm or more and 0.5 mm or less.

16. The pneumatic tire according to any one of Claims 1 to 15, wherein in at least 1 / 4 of the area of the minute projection, the surface roughness has a ten-point mean roughness Rz measured in accordance with JIS B 0601 (2001) of 5 μm or more and 30 μm or less.

17. The raised portion forming part has an area of 15 mm ２ or more, and the pneumatic tire according to any one of claims 1 to 16, characterized in that it has an area of 15 mm

18. The pneumatic tire according to any one of Claims 1 to 17, which is a pneumatic tire for a passenger car.

19. The pneumatic tire according to Claim 18, which is a pneumatic tire for a passenger car having a section height of 96 mm or less and a section width of 185 mm or more.

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