tire

Abstract

To provide a tire that inhibits a deterioration in noise performance after wear.SOLUTION: In a tire with a tread part, the tread part comprises four or more rubber layers that have two or more circumferential grooves continuously extended in a circumferential direction of the tire, and a pair of shoulder land parts divided by the circumferential grooves and a center land part positioned between the pair of shoulder land parts, and in which complex elastic moduli at 30°C are different from one another.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] As a method for suppressing vibration sounds (noise) of tires during driving, for example, a method is known in which the tread rubber of a pneumatic tire has a two-layer structure and foam rubber is used for the inner rubber layer (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-156016 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional tires, as the tread wears, the rigidity of the land portion of the tread increases and the vibration noise suppression effect decreases, so noise tends to increase with increased driving.

[0005] An object of the present invention is to provide a tire in which deterioration of noise performance after wear is suppressed. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by laminating four or more rubber layers, each having a different complex modulus, in the tread portion of a tire, and have thus completed the present invention.

[0007] That is, the present invention provides [1] A tire having a tread portion, the tread portion having two or more circumferential grooves extending continuously in the circumferential direction of the tire, a pair of shoulder land portions separated by the circumferential grooves, and a center land portion located between the pair of shoulder land portions, the tire being made up of four or more rubber layers each having a different complex modulus at 30°C; [2] The tire according to the above [1], wherein in the four or more rubber layers, the difference in complex modulus at 30°C between any two adjacent rubber layers is 1.0 MPa or more. [3] The tire according to the above [1], wherein in the four or more rubber layers, the difference in complex modulus at 30°C between any two adjacent rubber layers is 2.0 MPa or more. [4] The tire according to any one of the above [1] to [3], wherein the complex modulus at 30 ° C. of the four or more rubber layers decreases in sequence from the first layer constituting the tread surface toward the inner side in the tire radial direction. [5] The tire according to any one of the above [1] to [4], wherein the first layer constituting the tread surface has a complex modulus of elasticity at 30°C of 5.0 MPa or more. [6] The tire according to any one of the above [1] to [5], wherein the rubber layer located at the innermost position in the tire radial direction among the four or more rubber layers is composed of a rubber composition containing a rubber component and a powdered rubber, and the content of the powdered rubber per 100 parts by mass of the rubber component is 10 to 80 parts by mass. [7] The tire according to any one of the above [1] to [6], further comprising one or more low-density members selected from the group consisting of a sealant layer, a noise-damping body, and a three-dimensional mesh structure on the tire inner circumferential surface of the tread portion. [8] The tire according to any one of the above [1] to [7], wherein the groove area ratio in the shoulder land portion is greater than the groove area ratio in the center land portion. [9] The tire according to any one of the above [1] to [8], wherein the width direction length of at least one of the land portions gradually increases from the outer side toward the inner side in the tire radial direction.

[10] The groove width on the tread surface of the circumferential groove located at the outermost position when mounted on a vehicle is L0, and the groove width at the 95% position of the deepest part of the groove bottom of the circumferential groove located at the outermost position when mounted on a vehicle is GrooveWidth L 95 Then, L 95 The tire according to any one of the above items [1] to [9], wherein / L0 is 0.20 to 0.80. Effect of the Invention

[0008] According to the present invention, a tire is provided in which deterioration of noise performance after wear is suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of an example of a tire according to an embodiment of the present disclosure. [Diagram 2] 1 is a schematic diagram of a tire contact surface when the tread is pressed against a flat surface. [Diagram 3] 1 is an enlarged cross-sectional view showing a schematic view of a portion of a tread of a tire according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A tire that is one embodiment of the present disclosure is a tire with a tread portion, the tread portion having two or more circumferential grooves extending continuously in the circumferential direction of the tire, a pair of shoulder land portions separated by the circumferential grooves, and a center land portion located between the pair of shoulder land portions, and the tire is made of four or more rubber layers, each having a different complex modulus at 30°C.

[0011] Without intending to be bound by theory, the following is believed to be the mechanism by which deterioration of noise performance after tire wear can be suppressed in this disclosure.

[0012] Even when the first layer constituting the tread surface wears and the second layer is exposed, there will be one or more rubber layers with different hardness at the temperature during running between the base material constituting the land blocks (the innermost layer of the tread, which is the fourth layer or a rubber layer radially inward from it in this disclosure) and the ground contact surface, and the vibration energy will be gradually lost when transmitted between these rubber layers, making it possible to maintain the tire's noise performance even in the later stages of running. In addition, as wear progresses, the rubber layer interface in the vertical direction (tire radial direction) to the tread surface will be lost, but at that time, the number of rubber layers through which the vibration transmitted to the rubber layer constituting the tread surface passes when transmitting the vibration to the adjacent block will increase, making it possible to suppress resonance between the blocks and prevent deterioration of noise performance due to running.

[0013] The four or more rubber layers are preferably laminated adjacently in order from the first rubber layer constituting the tread surface toward the inside in the radial direction of the tire.

[0014] The difference in complex modulus between adjacent rubber layers at 30° C. is preferably 1.0 MPa or more, and more preferably 2.0 MPa or more, which is thought to increase the difference in stiffness between the adjacent rubber layers and to increase the likelihood of vibration energy being lost when vibration propagates across the rubber layer interface.

[0015] The complex modulus at 30° C. of the four or more rubber layers preferably decreases in sequence from the first layer constituting the tread surface toward the inner side in the tire radial direction, which is believed to make the innermost layer of the tread the softest, and thus obtain the vibration energy absorbing effect within the innermost layer, and the softest rubber layer remains until the later stage of wear, which is believed to facilitate the sustainment of the vibration suppression effect.

[0016] The first layer constituting the tread surface preferably has a complex modulus at 30° C. of 5.0 MPa or more.

[0017] In the tread portion of the present disclosure, it is preferable that the rubber layer located at the innermost position in the tire radial direction among the four or more rubber layers is composed of a rubber composition containing a rubber component and powdered rubber, and the content of the powdered rubber is 10 to 80 parts by mass per 100 parts by mass of the rubber component. It is believed that the powdered rubber forms an independent domain in the rubber layer, which allows a minute interface to exist in the inner rubber layer, making it easier to obtain the effect of absorbing vibration energy.

[0018] The tread portion of the present disclosure preferably includes, on the inner peripheral surface of the tire, one or more low-density members selected from the group consisting of a sealant layer, a sound-damping body, and a three-dimensional mesh structure. By providing low-density members on the inner peripheral surface of the tire, when vibrations are transmitted from the tread surface, these low-density members vibrate inside the tire, making it possible to offset the vibrations in the tread portion, and it is expected that this effect will be exerted even in the later stages of wear.

[0019] It is preferable that the groove area ratio in the shoulder land portion is greater than the groove area ratio in the center land portion.

[0020] It is preferable that the width direction length of at least one of the land portions gradually increases from the outer side toward the inner side in the tire radial direction, which is considered to facilitate uniform formation of multiple rubber layers on the land portion side surface during tire manufacturing, thereby making it easier to suppress deterioration of noise performance in the later stage of wear.

[0021] The groove width on the tread surface of the circumferential groove located at the outermost position when mounted on a vehicle is L0, and the groove width at the 95% position of the deepest part of the groove bottom of the circumferential groove located at the outermost position when mounted on a vehicle is L1. Groove Width L 95 Then, L 95 / L0 is preferably in the range of 0.20 to 0.70.

[0022] A tire including a rubber layer according to an embodiment of the present disclosure will be described in detail below. However, the following description is merely an example for explaining the present invention, and is not intended to limit the technical scope of the present invention to the described range. In this specification, when a numerical range is indicated using "~", the numerical range includes both ends of the range.

[0023] [Rubber composition for tread] The tread portion of the present disclosure comprises four or more rubber layers each having a different complex modulus at 30°C. The rubber compositions constituting each layer of the tread portion can be produced according to the required complex modulus at 30°C using the raw materials described below.

[0024] <Rubber component> The rubber composition according to the present disclosure preferably contains at least one selected from the group consisting of isoprene-based rubber, styrene butadiene rubber (SBR) and butadiene rubber (BR) as a rubber component. The rubber composition constituting the rubber layer (at least the first to third layers in the present disclosure) that is assumed to come into contact with the road surface during driving preferably contains SBR as a rubber component, more preferably contains SBR and BR, further preferably contains isoprene-based rubber, SBR and BR, and may be a rubber component consisting of only isoprene-based rubber, SBR and BR. In addition, when the tire is a studless tire or winter tire, it is preferable to contain isoprene-based rubber and BR. On the other hand, the rubber composition constituting the rubber layer that is not assumed to come into contact with the road surface during driving preferably contains isoprene-based rubber or BR as a rubber component, more preferably contains isoprene-based rubber and BR, and may be a rubber component consisting of only isoprene-based rubber and BR. The fourth layer of the present disclosure may be a rubber layer that is intended to come into contact with the road surface during running, or may be a rubber layer that is not intended to come into contact with the road surface during running, depending on the application and structure of the tire.

[0025] (Isoprene rubber) As the isoprene-based rubber, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. In addition to unmodified natural rubber (NR), natural rubber also includes modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0026] The NR is not particularly limited, and any NR commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0027] In the case where an isoprene-based rubber is contained in a rubber composition constituting a rubber layer that is assumed to come into contact with a road surface during running, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less, from the viewpoint of wet grip performance. The lower limit of the content 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 10% by mass or more.

[0028] When an isoprene-based rubber is contained in a rubber composition constituting a rubber layer that is not intended to come into contact with the road surface during driving, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, and may be 100% by mass.

[0029] (SBR) There are no particular limitations on the SBR, and examples thereof include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Modified SBRs include SBRs whose ends and / or main chains are modified, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Of these, S-SBR and modified SBR are preferred. Furthermore, hydrogenated products of these SBRs (hydrogenated SBR), etc. can also be used.

[0030] The SBRs listed above may be used alone or in combination of two or more. As the SBRs listed above, for example, those commercially available from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, ZS Elastomers Co., Ltd., etc. may be used.

[0031] From the viewpoints of wet grip performance and abrasion resistance, the styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. From the viewpoints of temperature dependency of grip performance and blow resistance, the styrene content is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. In this specification, the styrene content of SBR is 1 It is calculated by H-NMR measurement.

[0032] The vinyl content of SBR is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, from the viewpoints of ensuring reactivity with silica, wet grip performance, rubber strength, and abrasion resistance. Also, the vinyl content of SBR is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less, from the viewpoints of preventing an increase in temperature dependency, breaking elongation, and abrasion resistance. In this specification, the vinyl content of SBR (amount of 1,2-bonded butadiene units) is measured by infrared absorption spectroscopy.

[0033] From the viewpoint of wet grip performance, the weight average molecular weight (Mw) of SBR is preferably 200,000 or more, more preferably 250,000 or more. From the viewpoint of crosslinking uniformity, the weight average molecular weight is preferably 2,000,000 or less, more preferably 1,800,000 or less, and even more preferably 1,500,000 or less. In this specification, the weight average molecular weight of SBR can be calculated in terms of standard polystyrene based on the measured value obtained by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0034] In the case where SBR is contained in a rubber composition constituting a rubber layer that is assumed to come into contact with a road surface during driving, the content in 100% by mass of the rubber 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, from the viewpoint of wet grip performance. The upper limit of the content of SBR in the rubber component is not particularly limited, but can be, for example, 70% by mass or less, 80% by mass or less, 90% by mass or less, or may be 100% by mass. In addition, in the rubber composition constituting a rubber layer that is not assumed to come into contact with a road surface during driving, the content of SBR in the rubber component is not particularly limited.

[0035] (BR) The BR is not particularly limited, and can be one that is commonly used in the tire industry, such as BR with a cis content of less than 50% by mass (low cis BR), BR with a cis content of 90% by mass or more (high cis BR), rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high cis modified BR, low cis modified BR), etc. These BRs can be used alone or in combination of two or more.

[0036] As the high cis BR, for example, those commercially available from Zeon Corporation, Ube Industries, Ltd., JSR Corporation, etc. can be used. By containing high cis BR, low temperature properties and wear resistance can be improved. The cis content is preferably 95 mass% or more, more preferably 96 mass% or more, further preferably 97 mass% or more, and particularly preferably 98 mass% or more. In this specification, the cis content (cis-1,4-bonded butadiene unit amount) is a value calculated by infrared absorption spectrum analysis.

[0037] As the modified BR, a modified butadiene rubber (modified BR) in which the terminals and / or the main chain are modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen and oxygen is preferably used.

[0038] Other modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and further having the terminals of the modified BR molecule bonded with tin-carbon bonds (tin-modified BR), etc. The modified BR may be either non-hydrogenated or hydrogenated.

[0039] From the viewpoint of wear resistance, the weight average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more. From the viewpoint of crosslinking uniformity, it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. The weight average molecular weight of BR can be determined by standard polystyrene conversion based on the measured value obtained by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0040] In the case where the rubber composition constituting the rubber layer that is assumed to come into contact with the road surface during running contains BR, the content of BR in 100% by mass of the rubber component is preferably 60% by mass or less, more preferably 50% by mass or less, further preferably 45% by mass or less, and particularly preferably 40% by mass or less, from the viewpoint of wet grip performance. The lower limit of the content is not particularly limited, and can be, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, or 15% by mass or more.

[0041] In the case where the rubber composition constituting the rubber layer that is not supposed to come into contact with the road surface during running contains BR, the content of BR in 100% by mass of the rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. The lower limit of the content 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 10% by mass or more.

[0042] (Other rubber components) The rubber component according to the present disclosure may contain rubber components other than the isoprene-based rubber, SBR, and BR. As the other rubber components, crosslinkable rubber components generally used in the tire industry can be used, such as styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. These other rubber components may be used alone or in combination of two or more.

[0043] <Filler> The rubber composition according to the present disclosure preferably uses a filler containing carbon black and / or silica. The rubber composition constituting the rubber layer that is intended to come into contact with the road surface during driving preferably contains silica as a filler, more preferably contains carbon black and silica. The rubber composition constituting the rubber layer that is not intended to come into contact with the road surface during driving preferably contains carbon black as a filler.

[0044] (Carbon Black) The carbon black is not particularly limited, and may 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.

[0045] From the perspective of reinforcement, the nitrogen adsorption specific surface area (N2SA) of carbon black is 10m 2 / g or more is preferable, and 30m 2 / g or more is more preferable, and 50m 2 From the viewpoints of fuel economy and processability, it is more preferable that the tensile strength is 200 m 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 100m 2 / g or less is more preferable, and 80m 2 / g or less is more preferable, and 50m 2 The N2SA of carbon black is a value measured in accordance with JIS K 6217-2 "Basic properties of carbon black for rubber - Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method".

[0046] When the rubber composition constituting the rubber layer that is assumed to come into contact with the road surface during running contains carbon black, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, from the viewpoint of abrasion resistance and wet grip performance. Also, from the viewpoint of fuel efficiency performance, it is preferably 50 parts by mass or less, more preferably 35 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. When the rubber composition constituting the rubber layer that is not assumed to come into contact with the road surface during running contains carbon black, the content relative to 100 parts by mass of the rubber component is preferably 20 to 100 parts by mass, more preferably 25 to 80 parts by mass, and even more preferably 30 to 60 parts by mass.

[0047] (silica) The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrated silica), or other silica commonly used in the tire industry. Among them, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. These silicas can be used alone or in combination of two or more.

[0048] The nitrogen adsorption specific surface area (N2SA) of silica is set at 140m from the viewpoints of fuel efficiency and wear resistance. 2 / g or more is preferable, and 170m 2 / g or more is more preferable, and 200m 2 From the viewpoints of fuel efficiency and processability, it is more preferable that the tensile strength is 350 m / g or more. 2 / g or less is preferable, and 300m 2 / g or less is more preferable, and 250m 2 / g or less is more preferable. In this specification, the N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0049] When the rubber composition constituting the rubber layer that is assumed to come into contact with the road surface during running contains silica, the content per 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 60 parts by mass or more, and particularly preferably 70 parts by mass or more, from the viewpoint of wet grip performance. Also, from the viewpoint of abrasion resistance, it is preferably 130 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 110 parts by mass or less. Note that the content of silica per 100 parts by mass of the rubber component in the rubber composition constituting the rubber layer that is not assumed to come into contact with the road surface during running is not particularly limited.

[0050] The total content of silica and carbon black per 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 60 parts by mass or more, and particularly preferably 70 parts by mass or more, from the viewpoint of abrasion resistance performance, and is preferably 160 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 120 parts by mass or less, from the viewpoint of fuel economy performance and elongation at break.

[0051] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent conventionally used in combination with silica in the tire industry can be used. Examples of the silane coupling agent include the following mercapto-based silane coupling agents; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; vinyl-based silane coupling agents such as vinyl triethoxysilane and vinyl trimethoxysilane; amino-based silane coupling agents such as 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane and 3-(2-aminoethyl) aminopropyl triethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyl triethoxysilane and γ-glycidoxypropyl trimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyl trimethoxysilane and 3-nitropropyl triethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane. Among them, sulfide-based silane coupling agents and / or mercapto-based silane coupling agents are preferred, and mercapto-based silane coupling agents are more preferred. These silane coupling agents may be used alone or in combination of two or more.

[0052] The mercapto-based silane coupling agent is preferably a compound represented by the following formula (1) and / or a compound containing a bonding unit A represented by the following formula (2) and a bonding unit B represented by the following formula (3). [ka] (In the formula, R 101 , R 102 , and R 103 are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or -O-(R 111 -O) z -R 112 (z R 111 each independently represents a divalent hydrocarbon group having 1 to 30 carbon atoms; R112 represents an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms; z represents an integer of 1 to 30; 104 represents an alkylene having 1 to 6 carbon atoms. [ka] [ka] (wherein x represents an integer of 0 or more; y represents an integer of 1 or more; R 201 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or an alkynyl group having 2 to 30 carbon atoms, which may be substituted by a hydroxyl or carboxyl group; R 202 represents an alkylene having 1 to 30 carbon atoms, an alkenylene having 2 to 30 carbon atoms, or an alkynylene having 2 to 30 carbon atoms; 201 and R 202 may form a ring structure.)

[0053] Examples of the compound represented by formula (1) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the compound represented by the following formula (4) (Si363 manufactured by Evonik Degussa), and the compound represented by the following formula (4) can be preferably used. These may be used alone or in combination of two or more kinds. [ka]

[0054] Examples of compounds containing a bond unit A represented by formula (2) and a bond unit B represented by formula (3) include those manufactured and sold by Momentive, Inc. These may be used alone or in combination of two or more.

[0055] When a silane coupling agent is contained, the total content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 2.0 parts by mass or more, and particularly preferably 4.0 parts by mass or more, from the viewpoint of improving the dispersibility of silica, and is preferably 20 parts by mass or less, more preferably 12 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 9.0 parts by mass or less, from the viewpoint of preventing a decrease in abrasion resistance.

[0056] The content of silane coupling agent with respect to 100 parts by mass of silica (when multiple silane coupling agents are used, the total amount of all of them) is preferably 1.0 parts by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more, from the viewpoint of increasing the dispersibility of silica.Furthermore, from the viewpoint of cost and processability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less.

[0057] As the filler, in addition to carbon black and silica, other fillers may be used. Such fillers are not particularly limited, and any fillers generally used in this field, such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, etc., may be used. These fillers may be used alone or in combination of two or more.

[0058] <Softener> The rubber composition according to the present disclosure preferably contains a softener. Examples of the softener include a resin component, oil, and liquid rubber.

[0059] The resin component is not particularly limited, but examples thereof include petroleum resins, terpene resins, rosin resins, phenol resins, etc. These resin components may be used alone or in combination of two or more.

[0060] When a resin component is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. The content of the resin component is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less.

[0061] Examples of the oil include process oil, vegetable oil, and animal oil. Examples of the process oil include paraffin-based process oil, naphthenic process oil, and aromatic process oil. In addition, as an environmental measure, process oil with a low content of polycyclic aromatic compound (PCA) compounds can be used. Examples of the low PCA content process oil include light extract solvate (MES), treated distillate aromatic extract (TDAE), and heavy naphthenic oil.

[0062] When oil is contained, the content per 100 parts by mass of the rubber component is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and particularly preferably 15 parts by mass or more, from the viewpoint of processability. Also, from the viewpoint of abrasion resistance, the content is preferably 120 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 50 parts by mass or less. In this specification, the content of oil includes the amount of oil contained in the oil-extended rubber.

[0063] 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 kinds.

[0064] When the liquid rubber is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. The content of the liquid rubber is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less.

[0065] When the rubber composition constituting the rubber layer that is assumed to come into contact with the road surface during running contains a softener, the content (total amount of all softeners when multiple softeners are used) per 100 parts by mass of the rubber component is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and particularly preferably 15 parts by mass or more. The content of the softener is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 90 parts by mass or less, and particularly preferably 80 parts by mass or less.

[0066] When the rubber composition constituting the rubber layer that is not intended to come into contact with the road surface during driving contains a softener, the content thereof (the total amount of all softeners when multiple softeners are used in combination) per 100 parts by mass of the rubber component is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

[0067] <Other compounding agents> In addition to the above-mentioned components, the rubber composition according to the present disclosure may appropriately contain compounding agents commonly used in the tire industry, such as wax, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0068] When the wax is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of weather resistance of the rubber, and is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, from the viewpoint of preventing whitening of the tire due to bloom.

[0069] Examples of the processing aid include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. These processing aids may be used alone or in combination of two or more. Examples of the processing aids that can be used include those commercially available from Schill+Seilacher, Performance Additives, etc.

[0070] When a processing aid is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of improving processability, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, from the viewpoints of abrasion resistance and breaking strength.

[0071] The antiaging agent is not particularly limited, but examples thereof include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, and carbamic acid metal salts, and the like. Phenylenediamine-based antiaging agents such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and quinoline-based antiaging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These antiaging agents may be used alone or in combination of two or more.

[0072] When an antioxidant is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of ozone crack resistance of the rubber, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of abrasion resistance and wet grip performance.

[0073] When stearic acid is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of vulcanization speed.

[0074] When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of abrasion resistance.

[0075] As the vulcanizing agent, sulfur is preferably used, and examples of the sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0076] When sulfur is contained as a vulcanizing agent, the content per 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of ensuring sufficient vulcanization reaction. Also, 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, and even more preferably 3.0 parts by mass or less. Note that, when oil-containing sulfur is used as a vulcanizing agent, the content of the vulcanizing agent is the total content of the pure sulfur contained in the oil-containing sulfur.

[0077] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, sodium 1,6-hexamethylene-dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. As these vulcanizing agents other than sulfur, commercially available products from Taoka Chemical Co., Ltd., Lanxess Co., Ltd., Flexis, etc. can be used.

[0078] Examples of the vulcanization accelerator 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, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based, and thiazole-based vulcanization accelerators are preferred, and sulfenamide-based vulcanization accelerators are more preferred.

[0079] 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 them, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferred.

[0080] Examples of the guanidine vulcanization accelerator 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 them, 1,3-diphenylguanidine (DPG) is preferable.

[0081] Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, etc. Among these, 2-mercaptobenzothiazole is preferred.

[0082] When a vulcanization accelerator is contained, the content per 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 2.5 parts by mass or more. The content is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, breaking strength and elongation tend to be secured.

[0083] <Powdered rubber> The rubber composition constituting the rubber layer located at the innermost position in the tire radial direction among the four or more rubber layers preferably contains powdered rubber. The powdered rubber is obtained by pulverizing vulcanized rubber.

[0084] Examples of the rubber component of the rubber powder include diene rubbers such as NR, IR, SBR, BR, NBR, EPDM, CR, IIR, etc. These diene rubbers may be used alone or in combination of two or more.

[0085] The powdered rubber may contain, in addition to the rubber component, the above-mentioned filler and compounding ingredients such as stearic acid, zinc oxide, an antioxidant, a vulcanizing agent, and a vulcanization accelerator.

[0086] The vulcanized rubber can be obtained by kneading the rubber component and, if necessary, a filler and compounding ingredients in, for example, a Banbury mixer, kneading the resulting kneaded mixture with a crosslinking agent and a vulcanization accelerator in an open roll, and then vulcanizing the mixture.

[0087] Methods for pulverizing vulcanized rubber include freeze-pulverization using liquid nitrogen, grinding with a stone mill, grinding with a roll or mixer, grinding with an extruder, etc. It is preferable to perform freeze-pulverization after grinding with a cutter mill because this allows the particle size to be reduced.

[0088] From the viewpoints of ride comfort and noise performance, the average particle size of the powdered rubber is preferably 20 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more. From the viewpoint of processability, the average particle size of the powdered rubber is preferably 1000 μm or less, more preferably 800 μm or less, and even more preferably 600 μm or less. The average particle size of the powdered rubber is measured by an electron microscope, a laser type particle size distribution meter, a sieving method using a mesh, or the like.

[0089] When the powdered rubber is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more. The content is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less. By setting the powdered rubber content within the above range, noise performance tends to be further improved.

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

[0091] The kneading step includes, for example, a base kneading step in which compounding ingredients and additives other than the vulcanizing agent and the vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and the 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 a plurality of steps as desired.

[0092] The kneading conditions are not particularly limited, but examples thereof include a method in which in the base kneading step, kneading is performed for 3 to 10 minutes at a discharge temperature of 150 to 170° C., and in the final kneading step, kneading is performed for 1 to 5 minutes at 50 to 110° C. The vulcanization conditions are not particularly limited, but examples thereof include a method in which vulcanization is performed for 5 to 30 minutes at 150 to 200° C.

[0093] [tire] Hereinafter, a tire according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the embodiment described below is merely an example, and the tire according to the present disclosure is not limited to the embodiment described below.

[0094] FIG. 1 is a cross-sectional view of a tire taken along a plane passing through the tire rotation axis, and shows only the right side of the tire divided by the tire center line CL. The tire in FIG. 1 includes a tread portion 1, a sidewall 2, a bead portion 3, a carcass 4, a belt 5, and a band 6. The tread portion 1 is composed of four or more rubber layers including a first layer 32 that constitutes the tread surface. The bead portion 3 includes a bead core 31. The carcass 4 may include a carcass cord (not shown). The belt 5 may include a belt cord (not shown). The band 6 includes an edge band 61 that covers only the edge portion of the belt 5, and a full band 62 that covers the entire area of ​​the belt 5. Both the edge band 61 and the full band 62 may include a band cord (not shown). Note that the illustration of each rubber layer in the tread portion 1 is omitted.

[0095] 2 is a development view of the tread portion 1. A tread pattern, the orientation of which is specified when the tire is mounted on a vehicle, is formed on the tread portion 1. The tread pattern of the tread portion 1 is formed in an asymmetric shape with respect to the tire equator C.

[0096] The tread portion 1 has an outer tread edge To and an inner tread edge Ti. The outer tread edge To is located on the outer side of the vehicle (on the right side in FIG. 2) when the tire is mounted on the vehicle. The inner tread edge Ti is located on the inner side of the vehicle (on the left side in FIG. 2) when the tire is mounted on the vehicle.

[0097] Each tread edge To, Ti is the outermost contact point in the tire width direction W (left and right direction in FIG. 2; hereinafter simply referred to as width direction W) when a tire in a normal state is loaded with a normal load and touches the ground on a flat surface with a camber angle of 0 degrees. The normal state refers to a state in which the tire is mounted on a normal rim, inflated to a normal internal pressure, and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal state.

[0098] A "genuine rim" is a rim that is determined for each tire by the standard system that includes the standards on which the tire is based. In the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "Design Rim," and in the case of ETRTO, it is called a "Measuring Rim."

[0099] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. For JATMA, it is the "maximum air pressure." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "INFLATION PRESSURE."

[0100] "Normal load" is the load that each standard specifies for each tire in the system of standards on which the tire is based. For JATMA, it is the "maximum load capacity." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "LOAD CAPACITY."

[0101] The tread portion 1 has a plurality of circumferential grooves 11, 12, 13 that extend continuously in the circumferential direction C. In FIG. 2, three circumferential grooves 11, 12, 13 are provided. However, the number of circumferential grooves is not particularly limited, and may be, for example, two to five. In addition, in the present disclosure, the circumferential grooves 11, 12, 13 extend linearly along the circumferential direction C, but are not limited to such an embodiment, and may extend, for example, in a wavy, sinusoidal, zigzag, or other shape along the circumferential direction C.

[0102] In this disclosure, the term "shoulder land portion" refers to a pair of land portions formed between the circumferential groove located on the outermost side in the width direction W from the tire equator C and each tread edge To, Ti. In Fig. 1, there are provided an outer shoulder land portion 16 formed between the circumferential groove 12 located on the outermost side when mounted on a vehicle and the outer tread edge To, and an inner shoulder land portion 17 formed between the circumferential groove 11 located on the innermost side when mounted on a vehicle and the inner tread edge Ti.

[0103] In the present disclosure, the "center land portion" refers to all land portions sandwiched between the pair of shoulder land portions. In Fig. 1, there are provided an outer center land portion 18 formed between a circumferential groove 13 provided along the tire equator C and a circumferential groove 12 located on the outermost side when mounted on a vehicle, and an inner center land portion 19 formed between a circumferential groove 13 provided along the tire equator C and a circumferential groove 11 located on the innermost side when mounted on a vehicle, but the number of center land portions is not particularly limited and may be, for example, 1 to 5.

[0104] In the present disclosure, the shoulder land portions 16, 17 and the center land portions 18, 19 are provided with lateral grooves and / or sipes that cross the land portions. In Fig. 2, the shoulder land portions 16, 17 are provided with a plurality of shoulder lateral grooves 21 whose ends open into the circumferential grooves 11, 12 and a plurality of shoulder sipes 22 whose one ends open into the circumferential grooves 11, 12, and the center land portions 18, 19 are provided with a plurality of center sipes 23 whose one ends open into the circumferential grooves 11, 13.

[0105] In this specification, the term "groove", including circumferential grooves and lateral grooves, refers to a recess having a width of at least 2.0 mm, whereas the term "sipe" refers to a thin cut having a width of 2.0 mm or less, preferably 0.5 to 2.0 mm.

[0106] In this disclosure, the groove area ratio in the shoulder land portion refers to the total area of ​​the lateral grooves and / or sipes crossing the land portion relative to the total area of ​​the shoulder land portion, and the groove area ratio in the center land portion refers to the total area of ​​the lateral grooves and / or sipes crossing the land portion relative to the total area of ​​the center land portion.

[0107] From the viewpoint of noise performance, the groove area ratio in the shoulder land portion is preferably larger than that in the center land portion. The groove area ratio in the shoulder land portion is preferably 15 to 50%, more preferably 20 to 45%, and even more preferably 25 to 40%. The groove area ratio in the center land portion is preferably 10 to 45%, more preferably 15 to 40%, and even more preferably 20 to 35%.

[0108] In this specification, the total area of ​​the shoulder land portions, the total area of ​​the center land portion, and the total area of ​​the lateral grooves and / or sipes crossing these land portions are calculated from the ground contact shape when the tread is pressed against a flat surface under normal load. The ground contact shape is obtained by, for example, applying ink to the tread portion 1 after mounting the tire on a normal rim and maintaining normal internal pressure, applying normal load and pressing the tire vertically against cardboard or the like (camber angle is 0°), and transferring the ink applied to the tread portion 1. In addition, from the obtained ground contact shape, the sum of the areas of the shoulder land portions when all the lateral grooves and / or sipes crossing the shoulder land portions are filled is defined as the total area of ​​the shoulder land portions, and the sum of the areas of the center land portions when all the lateral grooves and / or sipes crossing the center land portions are filled is defined as the total area of ​​the center land portions.

[0109] The tread portion 1 of the present disclosure includes at least a first layer constituting a tread surface, a second layer adjacent to the radially inner side of the first layer, a third layer adjacent to the radially inner side of the second layer, and a fourth layer adjacent to the radially inner side of the third layer. The first layer typically corresponds to a cap tread. In addition, one or more rubber layers may be further provided between the fourth layer and the belt layer as long as the object of the present disclosure is achieved.

[0110] In the present disclosure, it is preferable that the width direction length of at least one of the shoulder land portion and the center land portion present in the tread portion 1 gradually increases from the outer side to the inner side in the tire radial direction. This makes it easier to form multiple rubber layers uniformly on the side surface of the land portion during tire manufacturing, which is thought to make it easier to suppress deterioration of noise performance in the later stage of wear. Note that, although the groove wall 7 of the circumferential groove of the present disclosure extends linearly from the outer side to the inner side in the tire radial direction, it is not limited to such an embodiment and may extend, for example, in a curved or stepped shape.

[0111] The groove width L0 of the circumferential groove 12 located at the outermost position on the tread surface when the tire is mounted on a vehicle is 95% of the deepest part of the groove bottom of the circumferential groove 12. Groove Width L 95 Ratio (L 95 In view of the effects of the present disclosure, L is preferably 0.20 or more, more preferably 0.25 or more, even more preferably 0.30 or more, and particularly preferably 0.35 or more. 95 / L0 is preferably equal to or less than 0.80, more preferably equal to or less than 0.70, further preferably equal to or less than 0.65, and particularly preferably equal to or less than 0.60. Note that in Fig. 3, illustration of each rubber layer is omitted.

[0112] <Low density material> The tire of the present disclosure may include a low-density member on the inner circumferential surface of the tire tread portion. The low-density member is not particularly limited as long as it has the effect of canceling vibration transmitted to the inner circumferential surface of the tire through resonance. Examples of such low-density members include a sealant layer used to prevent punctures, a sound-damping body, and a three-dimensional mesh structure.

[0113] The low-density member can exert its effect by being disposed on the inner circumferential surface of the tire in the tread portion. The thickness of the low-density member in the radial direction of the tire, the width in the axial direction of the tire, or the volume, cross-sectional area, and other properties of the low-density member may vary depending on the type of the low-density member, and can be appropriately determined by a person skilled in the art.

[0114] The low-density member may be used alone or in combination with a plurality of low-density members. Examples of combinations include, but are not limited to, first providing a sealant layer on the inner circumferential surface of the tire tread, and then providing a sound-damping body or a three-dimensional mesh structure thereon.

[0115] (Sealant layer) As the sealant layer, a layer generally used on the inner peripheral surface of the tire tread portion for puncture prevention can be suitably used. Specific examples of such a sealant layer include those described in JP 2020-23152 A. The thickness of the sealant layer is usually preferably 1 to 10 mm. The width of the sealant layer is usually preferably 85 to 115% of the maximum width of the belt layer, more preferably 95 to 105%.

[0116] (sound damping body) Any sound-damping body can be suitably used as long as it can exert a sound-damping effect in the tire cavity. Specific examples of such sound-damping bodies include those described in JP 2019-142503 A. The sound-damping body is, for example, made of a porous sponge material. The sponge material is a spongy porous structure, and includes, for example, a so-called sponge having continuous bubbles formed by foaming rubber or synthetic resin, as well as a web-like structure in which animal fibers, plant fibers, synthetic fibers, etc. are intertwined and connected together. In addition, the "porous structure" includes those having not only continuous bubbles but also closed bubbles. An example of the sound-damping body is a sponge material having continuous bubbles made of polyurethane. Suitable sponge materials include synthetic resin sponges such as ether-based polyurethane sponge, ester-based polyurethane sponge and polyethylene sponge, and rubber sponges such as chloroprene rubber sponge (CR sponge), ethylene propylene rubber sponge (EDPM sponge) and nitrile rubber sponge (NBR sponge). In particular, polyurethane-based or polyethylene-based sponges including ether-based polyurethane sponge are preferred from the standpoints of sound-damping properties, light weight, foaming adjustability, durability, and the like.

[0117] The sound-damping body 9 is in the form of a long strip having a bottom surface fixed to the inner cavity surface of the tread portion, and extends in the tire circumferential direction. In this case, the outer ends in the circumferential direction may be butted against each other to form a substantially annular shape, or the outer ends may be spaced apart in the circumferential direction. The sound-damping body 9 has substantially the same cross-sectional shape at each circumferential position except for the outer ends. As this cross-sectional shape, a flat, horizontally elongated shape with a height smaller than the width in the axial direction of the tire is preferable in order to prevent collapse or deformation during running. In particular, if the sound-damping body is provided with a groove 7 extending continuously in the circumferential direction on the radially inner side, the surface area of ​​the sound-damping body can be increased to absorb more resonance energy, and the heat dissipation can be improved to suppress the temperature rise of the sponge material.

[0118] The glass transition temperature (Tg) of the sound damper is preferably −55° C. to −45° C. from the viewpoint of maintaining good durability and flexibility. If the flexibility of the sound damper is maintained at low temperatures, the sound damper effectively converts the vibration energy of the air into heat energy, for example, even when driving in cold weather, and driving noise is sufficiently reduced. In this specification, Tg is a value measured using a differential scanning calorimeter SC Q2000 manufactured by TA Instruments in accordance with ASTM D 6604 (published in 2013).

[0119] The density of the sound-damping body is set to 1.0×10 in order to reduce running noise at around 250 Hz without increasing the weight of the tire. -2 g / cm 3 ~4.0×10 -2 g / cm 3 It is preferable that:

[0120] From the viewpoint of sufficient conversion of air vibration energy, the volume of the noise damper is desirably 0.4 to 30% of the total volume of the tire cavity. The volume of the noise damper means the apparent total volume of the noise damper, which is the volume determined from the outer shape including the air bubbles inside. In this specification, the total volume V of the tire cavity is approximately calculated by the following formula in a normal unloaded state in which the pneumatic tire is mounted on a normal rim and inflated to the normal internal pressure. V=A×{(Di-Dr) / 2+Dr}×π In the above formula, "A" is the cross-sectional area of ​​the tire cavity obtained by CT scanning the tire-rim assembly in the normal state, "Di" is the maximum outer diameter of the tire cavity surface in the normal state, "Dr" is the rim diameter, and "π" is the circular constant.

[0121] The tensile strength of the noise damper is preferably 70 to 115 kPa from the viewpoint of durability of the noise damper.

[0122] (3D mesh structure) Generally, any three-dimensional mesh structure can be suitably used as long as it acts as a sound absorbing material. Specific examples of such sound absorbing materials include those described in JP 2018-90131 A. More specifically, the three-dimensional mesh structure is formed by irregularly entangling a plurality of filaments made of melted resin and welding the entangled portions.

[0123] The three-dimensional mesh structure is preferably fixed to the tire cavity. The method of fixing to the tire cavity is not particularly limited, and may be, for example, by adhering to the tire inner surface with an adhesive or the like, but it may also be fixed by the sealant material constituting the sealant layer, and is preferably fixed in this manner.

[0124] The thickness of the three-dimensional mesh structure is not particularly limited, but is preferably 1.0 to 150 mm, more preferably 30 to 120 mm. The width is not particularly limited, but is preferably 50 to 95% of the width of the sealant layer, more preferably 60 to 90%, because the effect can be more suitably obtained.

[0125] The cross-sectional area ratio of the three-dimensional mesh structure (i.e., (cross-sectional area of ​​the three-dimensional mesh structure / cross-sectional area of ​​the tire cavity)×100) is preferably 2 to 90%, more preferably 5 to 70%, and even more preferably 20 to 70% from the viewpoint of efficient sound absorption performance. Here, the cross-sectional area ratio can be changed, for example, by changing the width and thickness of the three-dimensional mesh structure. The cross-sectional area of ​​the three-dimensional mesh structure is the apparent cross-sectional area of ​​the three-dimensional mesh structure, which is determined from the outer shape of the three-dimensional mesh structure including the internal cavities. The cross-sectional area of ​​the three-dimensional mesh structure is calculated by dividing the volume of the three-dimensional mesh structure by the average thickness (thickness in the tire radial direction) of the three-dimensional mesh structure. Here, the volume of the three-dimensional mesh structure is the apparent total volume of the three-dimensional mesh structure, which is determined from the outer shape of the three-dimensional mesh structure including the internal cavities. The average thickness of the three-dimensional mesh structure also refers to the average thickness determined from the outer shape of the three-dimensional mesh structure including the internal cavities. In this specification, the cross-sectional area of ​​the tire cavity is calculated by dividing the total volume of the tire cavity by the height of the tire cavity in the tire radial direction.

[0126] From the viewpoint of efficient sound absorption performance, the apparent density of the three-dimensional mesh structure is 1.0 to 25.0 × 10 -2 g / cm 3 is preferable, and 2.0 to 20.0 × 10 -2 g / cm 3 More preferably, 3.0 to 10.0 × 10 -2 g / cm 3 is more preferable. In this specification, the apparent density is a density calculated by regarding the cavities present inside the three-dimensional mesh structure as part of the volume of the three-dimensional mesh structure, and is calculated by dividing the mass of the three-dimensional mesh structure by the total apparent volume of the three-dimensional mesh structure (the volume determined from the external shape of the three-dimensional mesh structure including the internal cavities). Specifically, the apparent density can be calculated by preparing a cubic measurement sample roughly 1 m x 1 m x 1 m using the three-dimensional mesh structure and measuring the mass of the measurement sample.

[0127] The 25% compression hardness of the three-dimensional mesh structure is preferably 20 to 250 N, more preferably 60 to 220 N. When the 25% compression hardness is within the above range, good road noise reduction is obtained without adversely affecting the sealing property, and the tire is less susceptible to damage when a nail or the like is stuck into it. In this specification, the 25% compression hardness of the three-dimensional mesh structure is measured in accordance with JIS K 6400-2 using a circular pressure plate having a diameter of 200 mm.

[0128] In the three-dimensional mesh structure, the filaments are preferably hollow fibers. This provides better road noise reduction. The hollow ratio of the filaments is preferably 10 to 90%, more preferably 20 to 80%, because it provides better sealing and road noise reduction. In this specification, the hollow ratio of the filaments refers to a value calculated by photographing a cross section (transverse section) perpendicular to the filament axis (fiber axis) of the filaments, measuring the total area (Sa) of the cross section and the area (Sb) of the hollow section, and using the following formula. However, when there are multiple hollow sections, Sb means the sum of the areas of the respective hollow sections. Hollowness ratio (%)=(Sb / Sa)×100

[0129] The average diameter (average fiber diameter) of the filaments is not particularly limited, but is preferably 0.1 to 5.0 mm, more preferably 0.3 to 2.0 mm. By setting the average diameter of the filaments within the above range, a sufficient noise reduction effect can be obtained, and the tire can be made less susceptible to damage when a nail or the like is stuck into it. The average diameter of the filaments can be measured by image analysis of scanning atomic force micrographs, image analysis of scanning electron micrographs, image analysis of transmission micrographs, analysis of X-ray scattering data, pore electrical resistance method (Coulter principle method), etc. The diameter of the filaments means the apparent diameter (diameter including cavities) of a cross section perpendicular to the filament axis (fiber axis) of the filaments.

[0130] In the present disclosure, the 30° C. ToThe complex modulus (30°C E*) at 30°C is measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, and a frequency of 10 Hz. In the tire of the present disclosure, the four or more rubber layers constituting the tread portion each have a different 30°C E*. The difference in the complex modulus at 30°C between adjacent rubber layers is preferably 1.0 MPa or more, more preferably 1.5 MPa or more, and even more preferably 2.0 MPa or more. By setting the difference in the complex modulus at 30°C between adjacent rubber layers to the above range, resonance between adjacent rubber layers can be more effectively suppressed.

[0131] In the present disclosure, it is preferable that the complex modulus at 30° C. of the four or more rubber layers decreases in sequence from the first layer constituting the tread surface toward the inner side in the tire radial direction. This makes the innermost layer of the tread the softest, and the vibration energy absorption effect is obtained within the innermost layer, and the softest rubber layer remains until the later stage of wear, which is thought to facilitate the sustainment of the vibration suppression effect.

[0132] The 30°C E* of the first layer is preferably 5.0 MPa or more, more preferably 6.0 MPa or more, even more preferably 7.0 MPa or more, and particularly preferably 8.0 MPa or more. The 30°C E* of the first layer is preferably 15.0 MPa or less, more preferably 14.0 MPa or less, even more preferably 13.0 MPa or less, and particularly preferably 12.0 MPa or less.

[0133] The 30°C E* of the fourth layer is preferably 1.5 MPa or more, more preferably 2.0 MPa or more, even more preferably 2.5 MPa or more, and particularly preferably 3.0 MPa or more. The 30°C E* of the fourth layer is preferably 10.0 MPa or less, more preferably 8.0 MPa or less, even more preferably 6.0 MPa or less, and particularly preferably 5.0 MPa or less.

[0134] The 30°C E* of each rubber layer can be appropriately adjusted by changing the types and amounts of the rubber components, fillers, softeners, etc. For example, increasing the amount of softener (especially oil) tends to increase the 30°C E*, while decreasing the amount of softener tends to decrease the 30°C E*.

[0135] The tire according to the present disclosure has a tread including a first layer, a second layer, a third layer, and a fourth layer, and may be a pneumatic tire or a non-pneumatic tire. The tire is suitable for use as a racing tire, a passenger tire, a large passenger tire, a large SUV tire, or a motorcycle tire, and can be used as a summer tire, a winter tire, or a studless tire.

[0136] A tire having a tread including a first layer, a second layer, a third layer, and a fourth layer can be manufactured by a normal method using the above-mentioned tread rubber composition. That is, an unvulcanized rubber composition obtained by blending the above-mentioned components with a rubber component as necessary is extruded into the shape of the first layer, the second layer, the third layer, and the fourth layer using an extruder equipped with a die of a predetermined shape, and is laminated together with other tire components on a tire building machine and molded by a normal method to form an unvulcanized tire, and the unvulcanized tire is heated and pressurized in a vulcanizer to manufacture a tire. EXAMPLES

[0137] The present disclosure will be described based on examples, but the present disclosure is not limited to only the examples.

[0138] <Manufacturing of low-density components> (Low density material 1 (sound damping body)) As the noise-damping body, a polyurethane-based sponge containing an ether-based polyurethane sponge having the shape shown in Fig. 1 was used. The volume of the noise-damping body was 15% of the total volume of the tire cavity, and the density was 2.7 × 10 -2 g / cm 3 , Tg is -50°C.

[0139] (Low density member 2 (sealant layer)) The components in Table 1 were fed into a twin-screw kneading extruder and kneaded at a barrel temperature of 100°C and 200 rpm to prepare a sealant. Details of each component listed in Table 1 are as follows.

[0140] Butyl rubber: Butyl 268 (manufactured by Exxon Mobil, Mooney viscosity (ML1+8 (125°C)) = 32) Liquid polybutene: Nippon Oil Polybutene HV300 (manufactured by JXTG Nippon Oil & Energy Corporation, kinetic viscosity at 40°C 26000 mm 2 / s, kinematic viscosity at 100°C 590mm 2 / s, number average molecular weight 1400) Carbon black: N330 (Cabot Japan, HAF grade, DBP oil absorption 102 mL / 100 g) Crosslinking agent: BPO (dibenzoyl peroxide manufactured by NOF Corporation) Crosslinking agent: Valnoc GM (p-benzoquinone dioxime manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0141] [Table 1]

[0142] The sealant was used to form a sealant layer. The sealant layer was formed on the inner circumferential surface of the tire in the tread portion, with a width approximately equal to that of the belt layer and a thickness of 3.0 mm. This sealant layer was used as the low-density member 2.

[0143] (Low-density member 3 (three-dimensional mesh structure)) A three-dimensional mesh structure (apparent density: 5.1 × 10) was produced according to the manufacturing method described in JP 2018-90131 A using velprene as the resin. -2 g / cm 3 ) was used. Using this three-dimensional mesh structure, a sound absorbing layer with a width of 100 mm, a thickness of 80 mm, and a cross-sectional area ratio of 41% was formed on the inner peripheral surface of the tire in the tread portion, to form a low-density member 3. The hollow ratio of the filaments forming the three-dimensional mesh structure was 50%.

[0144] <Production of Rubber Composition and Tire> The various chemicals used in the examples and comparative examples are listed below. NR:TSR20 SBR: Modified S-SBR produced in Production Example 1 described later (styrene content: 30 mass%, vinyl bond content: 52 mol%, Mw: 250,000, non-oil extended product) BR: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass, Mw: 440,000) Carbon black: Cabot Japan Co., Ltd. Show Black N220 (N2SA: 111m 2 / g) Silica: Ultrasil VN3 (N2SA: 175m) manufactured by Evonik Degussa 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Powdered rubber: W2-A manufactured by Muraoka Rubber Industries Co., Ltd. (rubber powder: 30 mesh, polymer content: 52% by mass, carbon content: 32% by mass, average particle size: 500 μm, specific gravity: 1.14) Oil: VivaTec400 (TDAE oil) manufactured by H&R Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Stearic acid: Beads of stearic acid camellia manufactured by NOF Corporation Wax: Ozoace 0355 by Nippon Seiro Co., Ltd. Sulfur: HK-200-5 (powdered sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0145] Production Example 1: Synthesis of modified S-SBR Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-substituted autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium was added to initiate polymerization. Polymerization was performed under adiabatic conditions, with the maximum temperature reaching 85°C. When the polymerization conversion reached 99%, 1,3-butadiene was added, and polymerization was continued for another 5 minutes, after which N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane was added as a modifier to carry out the reaction. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Next, the solvent was removed by steam stripping, and the mixture was dried with a heated roll adjusted to 110°C to obtain a modified S-SBR.

[0146] Examples and Comparative Examples According to the compounding recipe shown in Table 2, chemicals other than sulfur and vulcanization accelerator were kneaded for 1 to 10 minutes using a 1.7 L closed type Banbury mixer until the discharge temperature reached 150 to 160 ° C., and a kneaded product was obtained. Next, sulfur and vulcanization accelerator were added to the kneaded product obtained using a two-axis open roll, and the mixture was kneaded for 4 minutes until the temperature reached 105 ° C., and an unvulcanized rubber composition was obtained. The unvulcanized rubber composition obtained was molded according to the shapes of the first layer (thickness: 1.5 mm), second layer (thickness: 3.5 mm), third layer (thickness: 3.5 mm), and fourth layer (thickness: 1.5 mm) of the tread, and laminated together with other tire components to prepare an unvulcanized tire, which was vulcanized at 170 ° C. to obtain each test tire (size: 195 / 65R15, rim: 15 × 6.0J, internal pressure: 230 kPa) described in Table 3. The groove depth (deepest part) of the circumferential groove was 8.0 mm.

[0147] <Measurement of complex elastic modulus E*> Each rubber test piece was cut from the inside of the rubber layer of the tread of each test tire to a length of 20 mm, width of 4 mm, and thickness of 1 mm, with the long side in the tire circumferential direction, and the complex modulus of elasticity E* was measured using an Iplexer series manufactured by GABO under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, and a frequency of 10 Hz. The thickness direction of the sample was the tire radial direction.

[0148] <Noise deterioration suppression performance> Each new test tire and each worn test tire were mounted on four wheels of a FF passenger car with an engine displacement of 2000cc, and the actual vehicle was driven on a test course with a dry asphalt surface. The noise felt by the test drivers inside the car when driving at 120km / h was evaluated based on their own feelings. The evaluation was performed using integer values ​​from 1 point to 10 points, and the total score of the 10 test drivers was calculated based on the evaluation criteria that the higher the score, the better the noise performance. For each test tire, the change rate of the noise performance score before and after wear was calculated using the following formula, and the change rate of the control tire (Comparative Example 3) was converted to 100, and the noise deterioration suppression index after wear of each test tire was obtained. The higher the value, the smaller the change in noise performance before and after wear and the better the noise deterioration suppression performance. (Noise change rate of control tire) = (Noise performance rating of control tire after wear) / (Noise performance rating of target tire when new) (Noise change rate of each test tire) = (Noise performance rating of each test tire after wear) / (Noise performance rating of each test tire when new) (Noise deterioration suppression index for each test tire) = (Noise change rate for each test tire) / (Noise change rate for control tire)

[0149] Each test tire after wear was produced by wearing the tread portion along the tread radius so that the depth of the deepest circumferential groove of a new tire was 50% of that of a new tire, and then thermally deteriorating the tire at 80° C. for 7 days. After wear, the second layer of each test tire was exposed, forming a tread surface.

[0150] [Table 2]

[0151] [Table 3]

[0152] The results in Tables 2 and 3 show that the tire of the present disclosure, in which four or more rubber layers each having a different complex modulus are laminated in the tread portion, significantly suppresses the deterioration of noise after tire wear. [Explanation of symbols]

[0153] 1 Tread section 2 Sidewall 3 Bead section 4. Carcass 5 Belt 6 Bands 7 Groove 8 Rims 9 Low density components 10 Tread surface 11, 12, 13 Circumferential groove 15 Circumferential groove wall 16 Outer shoulder land area 17 Inner shoulder land area 18 Outer center land area 19 Inner Center Land Section 21 Shoulder groove 22 Shoulder sipes 23 Center sipe C Tire Equator To outer tread edge Ti inner tread edge W Tire width direction H Circumferential groove bottom 31 Bead core 61 Edge Band 62 Full Band

Claims

1. A tire having a tread portion, The tread portion has two or more circumferential grooves extending continuously in the circumferential direction of the tire, a pair of shoulder land portions separated by the circumferential grooves, and a center land portion located between the pair of shoulder land portions, and The rubber layer is made up of four or more rubber layers each having a different complex modulus at 30°C. Here, the complex modulus at 30°C of each rubber layer constituting the tread portion is measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, and a frequency of 10 Hz, The complex modulus of elasticity at 30° C. of the four or more rubber layers decreases successively from a first layer constituting a tread surface toward the inside in the tire radial direction.

2. A tire having a tread portion, The tread portion has two or more circumferential grooves extending continuously in the circumferential direction of the tire, a pair of shoulder land portions separated by the circumferential grooves, and a center land portion located between the pair of shoulder land portions, and The rubber layer is made up of four or more rubber layers each having a different complex modulus at 30°C. Here, the complex modulus at 30°C of each rubber layer constituting the tread portion is measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, and a frequency of 10 Hz, A tire in which a first layer constituting the tread surface has a complex modulus of elasticity at 30°C of 5.0 MPa or more.

3. A tire having a tread portion, The tread portion has two or more circumferential grooves extending continuously in the circumferential direction of the tire, a pair of shoulder land portions separated by the circumferential grooves, and a center land portion located between the pair of shoulder land portions, and The rubber layer is made up of four or more rubber layers each having a different complex modulus at 30°C. The tread portion includes at least a first layer constituting a tread surface, a second layer adjacent to the first layer on the radially inner side of the tire, a third layer adjacent to the second layer on the radially inner side of the tire, and a fourth layer adjacent to the third layer on the radially inner side of the tire, Here, the complex modulus at 30°C of each rubber layer constituting the tread portion is measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, and a frequency of 10 Hz, The fourth layer has a complex modulus of elasticity at 30° C. of 2.0 MPa or more.

4. A tire having a tread portion, The tread portion has two or more circumferential grooves extending continuously in the circumferential direction of the tire, a pair of shoulder land portions separated by the circumferential grooves, and a center land portion located between the pair of shoulder land portions, and The rubber layer is made up of four or more rubber layers each having a different complex modulus at 30°C. Here, the complex modulus at 30°C of each rubber layer constituting the tread portion is measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, and a frequency of 10 Hz, The groove area ratio in the center land portion is 27 to 45%, and A tire in which a groove area ratio in the shoulder land portion is greater than a groove area ratio in the center land portion.

5. The tire according to any one of claims 1 to 4, wherein in the four or more rubber layers, a difference in complex modulus at 30°C between any two adjacent rubber layers is 1.0 MPa or more.

6. The tire according to any one of claims 1 to 4, wherein in the four or more rubber layers, a difference in complex modulus at 30°C between any two adjacent rubber layers is 2.0 MPa or more.

7. a rubber layer located at an innermost position in a tire radial direction among the four or more rubber layers is made of a rubber composition containing a rubber component and a powdered rubber, The tire according to any one of claims 1 to 6, wherein an amount of the powdered rubber per 100 parts by mass of the rubber component is 10 to 80 parts by mass.

8. The tire according to any one of claims 1 to 7, further comprising at least one low-density member selected from the group consisting of a sealant layer, a noise-damping material, and a three-dimensional mesh structure, on an inner circumferential surface of the tire in the tread portion.

9. The tire according to any one of claims 1 to 8, wherein a width direction length of at least one of the shoulder land portion and the center land portion gradually increases from an outer side toward an inner side in the tire radial direction.

10. The groove width on the tread surface of the circumferential groove located at the outermost side when mounted on a vehicle is L 0 The groove width at 95% of the deepest portion of the bottom of the circumferential groove located at the outermost position when mounted on a vehicle is L 95 When this is done, L 95 / L 0 The tire according to any one of claims 1 to 9, wherein the σ is 0.20 to 0.80.

Images