Tire

Abstract

Provided is a tire having a tread with land portions divided by a plurality of circumferential grooves, and in a tire meridional cross section including a tire rotation axis, a portion in which the length of the land portion closest to a tire equatorial plane in a width direction increases from a tire radial outside toward an inside; the tread has at least one rubber layer, a contact surface of the tread is composed of a first rubber layer, the first rubber layer is composed of a rubber composition including a rubber component including a diene rubber; a contact angle A1 with pure water measured after the rubber composition of the first rubber layer is immersed in water at 23°C under normal pressure for 1 hour and left to dry at 23°C under normal pressure for 24 hours, and a contact angle A2 with pure water measured after the rubber composition of the first rubber layer is immersed in water at 23°C under normal pressure for 1 hour and left to dry at 23°C under normal pressure for 24 hours after the contact angle A1 is measured are each 80° or less.

Description

tire Technical Field

[0001] This disclosure relates to a tire whose wet grip performance remains unchanged over a long period of time. Background Technology

[0002] As a method to improve tire wet grip performance by improving the adhesion of the tire to wet road surfaces, there is a known method, for example, of incorporating plasticizers such as resins into the tread rubber (Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: JP 2007-56137A Summary of the Invention

[0006] The technical problem to be solved by the present invention

[0007] However, as the tire travels, the plasticizers disappear from the tread rubber over time, so the tire's wet grip is believed to deteriorate towards the end of the journey.

[0008] The purpose of this disclosure is to provide a tire whose wet grip performance remains constant over a long period of time.

[0009] Problem-solving methods

[0010] As a result of in-depth research, it has been found that the above problems can be solved by configuring the tire with a preset tread pattern, in which the contact area increases due to wear, thereby setting the contact angle of the rubber component of the tread rubber within a preset range.

[0011] That is, this disclosure relates to a tire including a tread having a land portion divided by a plurality of circumferential grooves, wherein in a radial cross-section of the tire including the tire's axis of rotation, the land portion closest to the tire's equatorial plane has a length that increases from the radially outer side of the tire towards the inner side in the width direction; the tread has at least one rubber layer, the contact surface of which is composed of a first rubber layer, the first rubber layer being composed of a rubber composition comprising a rubber component comprising a diene rubber, the contact angle A1 of the rubber composition of the first rubber layer with pure water after being immersed in water at 23°C and atmospheric pressure for 1 hour and then dried at 23°C and atmospheric pressure for 24 hours, and the contact angle A2 of the rubber composition of the first rubber layer with pure water after measuring the contact angle A1 and then being immersed in water at 23°C and atmospheric pressure for 1 hour and then dried at 23°C and atmospheric pressure for 24 hours, are both below 80°.

[0012] Technical effects of the present invention

[0013] According to this disclosure, a tire with consistently stable wet grip performance over a long period of time can be provided. Attached Figure Description

[0014] Figure 1 is an enlarged cross-sectional view, schematically showing a portion of a tire tread according to an embodiment of the present disclosure.

[0015] Figure 2 is an enlarged cross-sectional view, schematically showing a portion of the tire tread of the comparative example. Detailed Implementation

[0016] Methods of implementing the present invention

[0017] The tire according to one embodiment of this disclosure is a tire including a tread having a land portion divided by a plurality of circumferential grooves. In the radial cross-section of the tire including the tire's axis of rotation, the land portion closest to the tire's equatorial plane has a length that increases from the radially outer side of the tire towards the inner side in the width direction. The tread has at least one rubber layer, and the contact surface of the tread is composed of a first rubber layer. The first rubber layer is composed of a rubber composition containing a rubber component, which contains diene rubber. The contact angle A1 with pure water, measured after the rubber composition of the first rubber layer is immersed in water at 23°C and atmospheric pressure for 1 hour and then dried at 23°C and atmospheric pressure for 24 hours, and the contact angle A2 with pure water, measured after measuring the contact angle A1 and then immersing the rubber composition of the first rubber layer in water at 23°C and atmospheric pressure for 1 hour and then drying at 23°C and atmospheric pressure for 24 hours, are both 80° or less (preferably 75° or less, more preferably 70° or less, and particularly preferably 65° or less).

[0018] While not intended to be bound by theory, this disclosure suggests that a mechanism for maintaining consistent wet grip performance over a long period is possible as follows: By using a highly wettable rubber composition with a tread rubber contact angle of less than 80° in the rubber layers constituting the tread, the affinity between the tread rubber and the wet road surface remains unchanged even after repeated driving on wet surfaces, and the contact area expands due to wear caused by driving. Therefore, it is believed that braking performance on wet surfaces can remain unchanged until the end of driving.

[0019] The rubber composition of the first rubber layer preferably includes a thermoplastic elastomer containing hydrophilic functional groups, and more preferably, it includes 0.5 to 50 parts by weight of thermoplastic elastomer relative to 100 parts by weight of the rubber component, the thermoplastic elastomer containing at least one functional group selected from carboxyl, hydroxyl, ester, ether, carbonyl and amide groups.

[0020] The rubber component in the rubber composition of the first rubber layer preferably includes isoprene-based rubber modified with hydrophilic functional groups, and more preferably includes 10 to 90% by mass of isoprene-based rubber modified with one or more functional groups selected from hydroxyl, amino and ether groups.

[0021] The acetone extraction amount of the rubber composition in the first rubber layer is preferably 5 to 25% by mass.

[0022] The rubber composition of the first rubber layer preferably comprises at least one selected from petroleum resins, terpene resins, and resins obtained by hydrogenation of them.

[0023] The rubber composition of the first rubber layer preferably includes a liquid polymer.

[0024] The rubber composition of the first rubber layer preferably includes a nitrogen adsorption specific surface area of ​​180 m². 2 / g or more of silicon dioxide.

[0025] The length L in the width direction of the land portion closest to the tire equator when the tread is 90% worn. 90 The ratio L to the length L0 in the width direction when the tire is new 90 / L0 is preferably 1.1 or higher.

[0026] The contact angles A1 and A2 of the rubber composition in the first rubber layer are preferably both below 70°.

[0027] The production steps of a tire, as one embodiment of this disclosure, will be described in detail below. However, the following description is for illustrative purposes only and is not intended to limit the technical scope of this disclosure to the scope described herein. Furthermore, in this specification, the numerical range indicated by "to" means including values ​​at both ends.

[0028] Figure 1 is an enlarged cross-sectional view showing a portion of the tire tread. In Figure 1, the vertical direction is the tire radial direction, the horizontal direction is the tire width direction, and the direction perpendicular to the plane of the paper is the tire circumferential direction.

[0029] The tread disclosed herein has a plurality of circumferential grooves 2 extending continuously in the tire circumferential direction. Although the circumferential grooves 2 extend linearly in the circumferential direction, this is not a limitation; they may also extend in the circumferential direction in, for example, a wavy, sinusoidal, or zigzag shape.

[0030] The tread of this disclosure has a land portion 3 divided in the tire width direction by circumferential grooves 2, 2. The land portion 3 is not particularly limited as long as it has a portion in the tire radial direction whose length increases from the outer radial side to the inner side in the width direction, within the tire radial cross-section including the tire's axis of rotation. However, it is preferable that the length of the land portion 3 gradually increases from the outer radial side to the inner side in the width direction. In this document, "land portion closest to the tire equator" refers to the land portion present on the tire equator C, and in the case where no land portion exists on the tire equator C, it refers to the land portion having the groove edge 4 closest to the circumferential groove on the tire equator C. The groove wall 5 of the circumferential groove 2 of this disclosure extends linearly from the outer radial side to the inner side of the tire, but the invention is not limited to this embodiment; the groove wall may extend in, for example, a curved or stepped shape.

[0031] The groove depth H of the circumferential groove 2 is calculated by the distance between the tread surface 1 and the extension line of the deepest part of the bottom of the circumferential groove 2. Furthermore, for example, in the case of multiple circumferential grooves, the groove depth H is the distance between the tread surface 1 and the extension line of the deepest part of the bottom of the deepest circumferential groove 2 among the multiple circumferential grooves 2.

[0032] In the tire disclosed herein, the length L in the width direction of the land portion 3 closest to the tire equatorial plane when the tread wears 90% is... 90 The ratio L to the length L0 in the width direction when the tire is new 90 / L0 is preferably 1.1 or higher, more preferably 1.2 or higher, and even more preferably 1.3 or higher. When L 90 When L0 is within the above range, wet grip performance remains unchanged even after wear. On the other hand, L 90 There is no particular upper limit to / L0, but it can be, for example, below 2.0, below 1.8, or below 1.5. Furthermore, as shown in the figure, the length L in the width direction when the tread is 90% worn is... 90 It is calculated from the length of the land portion 3 in the width direction from the tread surface 1 toward the radial inner side of the tire at 0.90H (90% of the groove depth H of the circumferential groove 2).

[0033] The groove depth H of the circumferential groove 2 is preferably greater than 90% of the total tread thickness, more preferably greater than 92%, and particularly preferably greater than 94%. Furthermore, the groove depth H of the circumferential groove 2 is preferably less than 99% of the total tread thickness, more preferably less than 97%. In this disclosure, the total tread thickness refers to the total thickness of the rubber layers forming the tread, calculated from the shortest distance from the tread surface 1 to the belt layer.

[0034] From the perspective of the effects of this disclosure, the groove depth H of the circumferential groove 2 is preferably 5.0 mm or more, more preferably 6.0 mm or more, and from the perspective of resistance to chipping, it is preferably 10.0 mm or less, more preferably 9.0 mm or less.

[0035] The land section 3 may be provided with transverse grooves and / or sipes that cut across the land section 3. Furthermore, in this specification, the term "groove," including circumferential and lateral grooves, refers to a recess with a width at least greater than 2.0 mm. On the other hand, in this specification, "sipe" refers to a narrow notch with a width of 2.0 mm or less, preferably 0.5 mm to 2.0 mm.

[0036] In this disclosure, the tread has at least one rubber layer. The tread of this disclosure may be a tread consisting of a single rubber layer, or it may be a tread having a first rubber layer forming tread surface 1 on its outer surface and one or more rubber layers present between the first rubber layer and the belt layer.

[0037] The thickness of the first rubber layer may be greater than 70%, 80%, 90%, or 95% relative to the thickness of the entire tread, and the tread may be composed of the first rubber layer.

[0038] In this disclosure, unless otherwise stated, the dimensions and angles of the tire components are measured with the tire mounted on a standard rim and inflated to standard internal pressure. No load is applied to the tire during measurement. Furthermore, in this specification, "standardized rim" refers to a rim defined according to standards within the standard system upon which the tire is based. For example, it is JATMA's "standard rim," TRA's "design rim," and ETRTO's "measuring rim." Additionally, in this specification, "standardized internal pressure" refers to the air pressure defined for each tire according to standards, namely JATMA's "maximum air pressure," the maximum value listed in TRA's table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATIONPRESSURES," or ETRTO's "INFLATIONPRESSURE."

[0039] The “contact angle” in this disclosure is calculated by dropping 2.0 μL of pure water onto the surface of a horizontal rubber composition and measuring the angle formed between the tip of the droplet and the surface of the rubber composition using a commercially available contact angle meter after 180 seconds.

[0040] In the rubber composition of the first rubber layer, the contact angle A1 with pure water, measured after immersing the rubber composition in water at 23°C and atmospheric pressure for 1 hour and then drying it at 23°C and atmospheric pressure for 24 hours, and the contact angle A2, measured after immersing the rubber composition in water at 23°C and atmospheric pressure for 1 hour and then drying it at 23°C and atmospheric pressure for 24 hours, are both 80° or less, preferably 75° or less, more preferably 70° or less, and particularly preferably 65° or less. When the contact angles A1 and A2 are within the above ranges, good wet grip performance can remain unchanged until the end of driving. Furthermore, the lower limit of the contact angle of the rubber composition of this disclosure is not particularly limited, and is generally 30° or more. The contact angle of the rubber composition of the first rubber layer can be appropriately adjusted by the type and content of the plasticizer, which will be described below.

[0041] The "acetone extraction amount" in this disclosure can be calculated according to JIS K 6229:2015 by immersing each vulcanized rubber specimen in acetone for 24 hours to extract the soluble components, and measuring the mass of each vulcanized rubber specimen before and after extraction using the following formula. Furthermore, the acetone extraction amount in this disclosure can be used as an indicator of the concentration of low-molecular-weight organic compounds in the plasticizer contained in the vulcanized rubber composition.

[0042] Acetone extraction amount (mass%) = {(mass of rubber specimen before extraction - mass of rubber specimen after extraction) / (mass of rubber specimen before extraction)} × 100.

[0043] The acetone extraction amount of the rubber composition disclosed herein is preferably 5% by mass or more, more preferably 7% by mass or more, and particularly preferably 9% by mass or more. Furthermore, the acetone extraction amount is preferably 25% by mass or less, more preferably 23% by mass or less, particularly preferably 21% by mass or less, and especially preferably 19% by mass or less. When the acetone extraction amount is within the above range, good wet grip performance can remain unchanged until the end of the driving period.

[0044] <Rubber Composition>

[0045] The rubber component of the first rubber layer includes diene-based rubber as a basic component. From the perspective of the effects of this disclosure, the content of diene-based rubber in the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, particularly preferably 95% by mass or more, and especially preferably 98% by mass or more. Furthermore, the rubber component may consist solely of diene-based rubber.

[0046] Examples of diene-based rubbers include, for example, isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). These rubber components can be used alone or in combination of two or more. Preferably, at least one selected from SBR, BR, and isoprene-based rubbers is included; more preferably, BR is included; and even more preferably, isoprene rubber or a combination of SBR and BR is included.

[0047] (Isoprene-based rubber)

[0048] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), purified NR, modified NR, and modified IR. As NR, commonly used NRs in the tire industry, such as SIR20, RSS#3, and TSR20, can be used. IR has no particular restrictions; commonly used IRs in the tire industry, such as IR2200, can be used. Examples of purified NR include deproteinized natural rubber (DPNR) and ultrapure natural rubber. Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These isoprene-based rubbers can be used alone or in combination of two or more types.

[0049] When isoprene-based rubber is incorporated into a rubber component, its content is preferably 1% by mass or more, more preferably 5% by mass or more, and particularly preferably 10% by mass or more. On the other hand, there is no particular upper limit to the content of isoprene-based rubber, which can be, for example, 90% by mass or less, 85% by mass or less, 80% by mass or less, or 75% by mass or less.

[0050] As the isoprene-based rubber, the rubber component of this disclosure preferably includes an isoprene-based rubber modified with hydrophilic functional groups. Examples of hydrophilic functional groups include, for example, one or more functional groups selected from hydroxyl, amino, and ether groups. Preferably, modified epoxy natural rubber (ENR) or modified epoxy isoprene rubber is obtained by adding a hydrophilic modifying compound having hydroxyl, amino, or ether groups to the epoxy groups of modified ENR or modified epoxy isoprene rubber and further modifying it; modified ENR is more preferred. When an isoprene-based rubber modified with hydrophilic functional groups is incorporated, the contact angle of the rubber composition decreases, and the water film formed between the road surface and the tread rubber during driving becomes easier to remove, thus improving wet grip performance.

[0051] As a modified ENR, an ENR modified with one or more functional groups selected from hydroxyl, amino, and ether groups is preferred, and a modified ENR having polyethylene glycol monoalkyl ether residues on its side chain is more preferred. As a modified epoxidized isoprene rubber, an epoxidized isoprene rubber modified with one or more functional groups selected from hydroxyl, amino, and ether groups is preferred, and a modified epoxidized isoprene rubber having polyethylene glycol monoalkyl ether residues is more preferred.

[0052] The epoxidation rate of the ENR or epoxidized isoprene rubber is preferably 1 to 80 mol%, more preferably 5 to 65 mol%, further preferably 25 to 50 mol%, and particularly preferably 30 to 50 mol%. In this document, the epoxidation rate refers to the ratio of the number of epoxidized carbon-carbon double bonds to the total number of carbon-carbon double bonds in the natural rubber or isoprene rubber before epoxidation, calculated by methods such as titration or nuclear magnetic resonance (NMR) analysis. For example, those commercially available from Kumpulan Guthrie Berhad can be used as the ENR.

[0053] Modified ENR or modified epoxidized isoprene rubber having polyethylene glycol monoalkyl ether residues at the side chains is obtained by reacting ENR or epoxidized isoprene rubber with polyethylene glycol monoalkyl ether, and can be prepared according to methods described, for example, in RSC Adv., 2016, 6, 107021-107028, Advanced Materials Research, 2013, 795, 251-255. The epoxy groups of the ENR or epoxidized isoprene rubber are partially or completely ring-opened by the addition of polyethylene glycol monoalkyl ether. Furthermore, the modification ratio of the epoxy groups (ring-opening) can be adjusted by the charge ratio of the ENR or epoxidized isoprene rubber to the polyethylene glycol monoalkyl ether, preferably 50% or more, more preferably 70% or more, further preferably 90% or more, and particularly preferably 100%.

[0054] The weight-average molecular weight (Mw) of polyethylene glycol monoalkyl ethers is preferably from 100 to 3000, more preferably from 200 to 2000, and even more preferably from 300 to 1000. From the perspective of hydrophilicity, the alkyl ether portion of the polyethylene glycol monoalkyl ether is preferably an alkyl ether having 1 to 4 carbon atoms (e.g., methyl ether, ethyl ether, propyl ether, butyl ether), more preferably methyl ether and ethyl ether, and particularly preferably methyl ether.

[0055] When modified isoprene-based rubber is incorporated into the rubber component, its content 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. Furthermore, the content of modified ENR in the rubber component is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less.

[0056] (SBR)

[0057] There are no particular limitations on SBRs, and examples include solution SBRs (S-SBR), emulsion SBRs (E-SBR), and their modified SBRs (modified S-SBR, modified E-SBR), etc. Examples of modified SBRs include SBRs modified at their ends and / or main chains, modified SBRs coupled with tin, silicon compounds, etc. (modified SBRs that are condensates or modified SBRs with branched structures, etc.). In addition, hydrogenated adducts of the above-mentioned SBRs (hydrogenated SBRs), etc., can also be used. Among these, S-SBR is preferred, and modified S-SBR is more preferred.

[0058] As a modified SBR, a modified SBR with functional groups containing at least one element selected from silicon, nitrogen and oxygen can be used appropriately at its ends and / or on the main chain.

[0059] As SBR, either oil-extended SBR or non-oil-extended SBR can be used. When using oil-extended SBR, the oil content of the SBR, i.e., the content of filler oil contained in the SBR, is preferably 10 to 50 parts by mass relative to the rubber solids content of 100 parts by mass of the SBR.

[0060] The SBRs listed above can be used individually or in combination of two or more. Examples of the SBRs listed above include products available from companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, and ZS Elastomer Co., Ltd.

[0061] The styrene content of the SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, thereby more appropriately obtaining the effects of this disclosure. Furthermore, the styrene content is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 45% by mass or less, and even more preferably 40% by mass. In addition, in this specification, the styrene content of the SBR is determined by… 1 It is calculated by H-NMR measurement.

[0062] The vinyl content of the SBR is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, thereby more appropriately obtaining the effects of this disclosure. Furthermore, the vinyl content is preferably 80 mol% or less, more preferably 75 mol% or less, and even more preferably 70 mol% or less. In addition, in this specification, the vinyl content (amount of 1,2-bonded butadiene units) is measured by infrared absorption spectroscopy.

[0063] The weight-average molecular weight (Mw) of the SBR is preferably 200,000 or more, more preferably 300,000 or more, and even more preferably 400,000 or more, thereby more appropriately obtaining the effects of this disclosure. Furthermore, Mw is preferably 2,000,000 or less, more preferably 1,800,000 or less, and even more preferably 1,500,000 or less. In addition, in this specification, the weight-average molecular weight (Mw) can be calculated from standard polystyrene based on measurements obtained by gel permeation chromatography (GPC) (e.g., GPC-8000 series, manufactured by Tosoh Corporation; detector: differential refractometer; column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

[0064] From the perspective of the effects of this disclosure, the content of SBR in 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. On the other hand, there is no particular upper limit on the content of SBR, for example, it can be 95% by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, or 75% by mass or less, and the rubber component can consist of only SBR. Furthermore, when oil-extended SBR is used as the SBR, the content of SBR itself, which is the rubber solids content contained in the oil-extended SBR, is defined as the content of SBR in the rubber component.

[0065] (BR)

[0066] There are no particular restrictions on BR. Commonly used BRs in the tire industry, such as BRs with a cis content of less than 50 mol% (low-cis BR) and BRs with a cis content of more than 90 mol% (high-cis BR), are all acceptable. Rare-earth-based butadiene rubbers synthesized using rare-earth element-based catalysts (rare-earth-based BR), BRs containing syndiotactic polybutadiene (SPB) crystals (SPB-containing BR), and modified BRs (high-cis modified BR, low-cis modified BR), etc., are also acceptable. Examples of modified BRs include those modified with functional groups similar to those described in the SBR section above. These BRs can be used alone or in combination of two or more.

[0067] As a high-cis BR, commercially available options include those from Zeon Corporation, Ube Industries, Ltd., and JSR Corporation. Incorporating a high-cis BR improves low-temperature performance and abrasion resistance. The cis content is preferably 95 mol% or more, more preferably 96 mol% or more, even more preferably 97 mol% or more, and particularly preferably 98 mol% or more. Furthermore, in this specification, the cis content (the amount of cis-1,4-butadiene units) is a value calculated using infrared absorption spectroscopy.

[0068] As a rare-earth-based BR, a BR synthesized using a rare-earth element catalyst can be used, preferably with a vinyl content of 1.8 mol% or less, more preferably 1.0 mol% or less, even more preferably 0.8 mol% or less, and a cis content of 95 mol% or more, more preferably 96 mol% or more, even more preferably 97 mol% or more, and particularly preferably 98 mol% or more. As a rare-earth-based BR, those available from companies such as LANXESS can be used.

[0069] Examples of SPB-containing BRs include those in which 1,2-meta-isobutadiene crystals are chemically bonded to and dispersed within the BR, but not those in which the crystals are merely dispersed within the BR. SPB-containing BRs can be those available from companies such as Ube Industries, Ltd.

[0070] As a modified BR, a modified BR modified with functional groups containing at least one element selected from silicon, nitrogen and oxygen can be used at its ends and / or main chain.

[0071] Other examples of modified BR include tin-modified BR obtained by adding a tin compound after polymerization of 1,3-butadiene with a lithium initiator, where the ends are further bonded via tin-carbon bonds. Furthermore, modified BR can be either unhydrogenated or hydrogenated.

[0072] The various BRs listed above can be used individually, or in combination of two or more of them.

[0073] From the perspective of abrasion 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. Furthermore, from the perspective of crosslinking uniformity, it is preferably 2,000,000 or less, more preferably 1,000,000 or less. In addition, the weight-average molecular weight of BR can be calculated from standard polystyrene based on measurements obtained by gel permeation chromatography (GPC) (e.g., GPC-8000 series, manufactured by Tosoh Corporation; detector: differential refractometer; column: TSKGEL SUPERMULTIPOREHZ-M, manufactured by Tosoh Corporation).

[0074] From the perspective of the effects of this disclosure, when BR is incorporated into the rubber component, its content is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. On the other hand, when BR is incorporated into the rubber component, its content is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

[0075] (Other rubber components)

[0076] Provided it does not affect the effectiveness of this disclosure, the rubber component may also include rubber components other than diene rubbers. Examples of other rubber components commonly used in the tire industry include butyl rubber (IIR), halogenated butyl rubber, ethylene-propylene rubber, polynorbornene rubber, silicone rubber, polyvinyl chloride rubber, fluororubber (FKM), acrylic rubber (ACM), and chloroprene rubber. These other rubber components may be used alone or in combination of two or more.

[0077] <Thermoplastic Elastomers>

[0078] From the perspective of achieving good wet grip performance, the rubber composition of the first rubber layer preferably comprises a thermoplastic elastomer having hydrophilic functional groups. Examples of hydrophilic functional groups include at least one functional group selected from carboxyl, hydroxyl, ester, ether, carbonyl, and amide groups. Since the thermoplastic elastomer of this disclosure has a large molecular weight similar to that of the rubber component and is entangled with the rubber component, it becomes less likely to detach from the rubber composition over time, and because it partially exhibits hydrophilicity, its wet grip performance is expected to remain stable over a long period.

[0079] In this specification, "thermoplastic elastomer" refers to an elastic polymer compound, specifically a thermoplastic resin material composed of copolymers. These copolymers consist of polymers forming crystalline hard segments with high melting points and polymers forming amorphous soft segments with low glass transition temperatures. In thermoplastic elastomers, the crystalline hard segments with high melting points act as pseudo cross-linking points and exhibit elasticity. On the other hand, rubber molecules contain double bonds, and the addition of sulfur or the like for cross-linking (vulcanization) generates a three-dimensional network structure and exhibits elasticity. Therefore, when a thermoplastic elastomer is heated, the hard segments melt; when cooled, the pseudo cross-linking points regenerate, allowing the thermoplastic elastomer to be reused. Conversely, once rubber is cross-linked (vulcanized), a three-dimensional network structure is formed, and it loses its fluidity, making it difficult to reuse even after heating. Furthermore, the thermoplastic elastomers disclosed herein should not include the aforementioned rubber components.

[0080] Thermoplastic elastomers containing hydrophilic functional groups (preferably thermoplastic elastomers containing at least one functional group selected from carboxyl, hydroxyl, ester, ether, carbonyl, and amide groups) are not particularly limited, and examples include, for instance, polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, and polyamide-based thermoplastic elastomers, with polyurethane-based thermoplastic elastomers being preferred. Furthermore, copolymers of polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, or polyamide-based thermoplastic elastomers with diene elastomers are also suitable for use. Among these, copolymers of polyurethane-based thermoplastic elastomers with diene elastomers are preferred, and copolymers of polyurethane-based thermoplastic elastomers with styrene-based thermoplastic elastomers are more preferred.

[0081] There are no particular limitations on polyurethane-based thermoplastic elastomers, but those prepared from polyols and diisocyanates, for example, can be suitably used. Examples of polyols include polyester polyols, polyester ether polyols, polycarbonate polyols, and polyether polyols. Examples of diisocyanates include, for example, toluene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI).

[0082] There are no particular limitations on polyester-based thermoplastic elastomers, but for example, those using olefin-based elastomers as soft segments and those using polyethylene terephthalate, polybutylene terephthalate, etc., as hard segments are also suitable. Examples of olefin-based elastomers include those obtained by homopolymerization of one or more of linear olefins, branched olefins, and polyvinyl acetate having 1 to 8 carbon atoms, particularly ethylene-vinyl acetate copolymers, ethylene-propylene resins, linear low-density polyethylene, etc.

[0083] Examples of polyamide-based thermoplastic elastomers include, but are not particularly limited to, polyamides (amide 6) obtained by ring-opening polycondensation of ε-caprolactam, polyamides (amide 11) obtained by ring-opening polycondensation of undecylactam, polyamides (amide 12) obtained by ring-opening polycondensation of laurolactam, polyamides (amide 66) obtained by polycondensation of diamines and diacids, and polyamides (amide MX) with m-phenylenediamine as the structural unit.

[0084] In this disclosure, "dien elastomer" refers to any homopolymer obtained by polymerizing conjugated diene monomers, or any copolymer obtained by copolymerizing one or more conjugated dienes with each other or with vinyl aromatic compounds. These copolymers may be hydrogenated, or their ends may be modified with hydroxyl, carboxyl, anhydride, amino, epoxy, or other groups using a modifier. In the case of copolymers, the latter comprises 20% to 99% by mass diene units and 1% to 80% by mass vinyl aromatic units.

[0085] Examples of conjugated diene monomers include butadiene, isoprene, 1,3-pentadiene, etc.

[0086] Examples of aromatic vinyl monomers include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, etc., with styrene usually chosen because of its availability.

[0087] Styrene-based thermoplastic elastomers are copolymers having at least one styrene block (hard segment) and at least one elastomeric block (soft segment). The molecular structure of styrene-based thermoplastic elastomers is not particularly limited, but a structure having styrene blocks at one or both ends and elastomeric blocks in the remaining portions is preferred. Better grip is generally achieved when at least one end has a styrene block. Furthermore, more preferably, the structure of a styrene-based thermoplastic elastomer has no styrene blocks in the main chain portion other than at its ends. Because of this structure, the rubber does not become too hard within the normal temperature range, resulting in better grip and generally better fracture and abrasion resistance.

[0088] Examples of elastomeric blocks include, for example, vinyl-polydiene, polyisoprene, polybutadiene, polyethylene, polychloroprene, poly2,3-dimethylbutadiene, etc. Furthermore, elastomeric blocks obtained by hydrogenating the aforementioned elastomeric blocks can also be used as elastomeric blocks.

[0089] Examples of styrene-based thermoplastic elastomers include, for example, styrene-isobutylene block copolymers (SIB), styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-ethylene-butene block copolymers (SEB), styrene-ethylene / propylene block copolymers (SEP), styrene-ethylene / butene-styrene block copolymers (SEBS), styrene-ethylene / butene-ethylene block copolymers (SEBC), hydrogenated styrene / butadiene copolymers (HSBR), styrene-ethylene / propylene-styrene block copolymers (SEPS), styrene-ethylene / ethylene / propylene-styrene block copolymers (SEEPS), and styrene-butadiene / butene-styrene block copolymers (SBBS).

[0090] From the perspective of wet grip performance, the styrene unit content (styrene content percentage) of the styrene-based thermoplastic elastomer is preferably 5% by mass or more, more preferably 10% by mass or more. Furthermore, from the perspective of suppressing heat generation, it is preferably 30% by mass or less, more preferably 20% by mass or less.

[0091] From the perspective of hydrophilicity with the rubber component, the content of thermoplastic elastomer containing hydrophilic functional groups (preferably a thermoplastic elastomer containing at least one functional group selected from carboxyl, hydroxyl, ester, ether, carbonyl, and amide groups) relative to 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, even more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more. Furthermore, from the perspective of balancing with other properties (such as wet grip, abrasion resistance, and tensile strength), it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass.

[0092] <packing>

[0093] The rubber composition of the first rubber layer preferably includes fillers comprising carbon black and / or silica. Alternatively, the filler may be a filler composed of carbon black and silica.

[0094] (Silicon dioxide)

[0095] There are no particular limitations on silica; any silica commonly used in the tire industry can be used, such as silica prepared by dry methods (anhydrous silica) and silica prepared by wet methods (hydrated silica). Hydrated silica prepared by wet methods is preferred because it contains many silanol groups. Examples of silica that can be used include those produced and sold by companies such as Evonik Degussa GmbH, Solvay, Tosoh Silica Corporation, and Tokuyama Corporation. These silicas can be used alone or in combination of two or more.

[0096] The average primary particle size of silica is preferably 22 nm or less, more preferably 20 nm or less, even more preferably 18 nm or less, and particularly preferably 16 nm or less. There is no particular limitation on the lower limit of the average primary particle size, but it is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. When the average primary particle size of silica is within the above range, the dispersibility of silica can be better improved, and the reinforcing properties, wet grip properties, and abrasion resistance can be further improved. Furthermore, the average primary particle size of silica can be calculated by observing silica with a transmission electron microscope or a scanning electron microscope, measuring more than 400 primary silica particles observed in the field of view, and taking their average value.

[0097] From the perspective of fuel efficiency and wear resistance, the nitrogen adsorption specific surface area (N2SA) of silica is preferably 140 m². 2 / g or more, preferably 160m 2 / g or more, further preferably 180m 2 / g or more, especially preferably 200mg 2 / g or higher. Furthermore, from the perspective of fuel efficiency and processability, 350m is preferred. 2 / g or less, preferably 300m 2 Below / g, 250m is further preferred. 2 / g or less. Furthermore, the N2SA of silica in this specification is the value determined according to the BET method of ASTM D3037-93.

[0098] From the perspective of wet grip performance, the silica content relative to 100 parts by weight of rubber component is preferably 30 parts by weight or more, more preferably 40 parts by weight or more, further preferably 50 parts by weight or more, and particularly preferably 55 parts by weight or more. Furthermore, from the perspective of silica dispersibility and abrasion resistance, it is preferably 150 parts by weight or less, more preferably 130 parts by weight or less, further preferably 110 parts by weight or less, and particularly preferably 95 parts by weight or less.

[0099] (Silane coupling agent)

[0100] Silica is preferably used in combination with a silane coupling agent. There are no particular limitations on the silane coupling agent; any silane coupling agent commonly used in the tire industry in combination with silica can be used. Examples of such silane coupling agents include, for instance, sulfide-based silane coupling agents, such as bis(3-triethoxysilylpropyl)disulfide and bis(3-triethoxysilylpropyl)tetrasulfide; and mercapto-based silane coupling agents, such as 3-mercaptopropyltrimethoxysilane, produced by Momenttive Performance Materials Ltd. Materials) produces NXT-Z100, NXT-Z45, and NXT; thioester-based silane coupling agents, such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane; vinyl-based silane coupling agents, such as vinyltriethoxysilane and vinyltrimethoxysilane; and amino-based silane coupling agents, such as 3-aminopropyltriethoxysilane, 3... -Aminopropyltrimethoxysilane and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidyl ether oxysilane coupling agents, such as γ-glycidyl ether oxypropyltriethoxysilane and γ-glycidyl ether oxypropyltrimethoxysilane; nitro silane coupling agents, such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; chlorinated silane coupling agents, such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane, etc. Preferably, one or more of sulfide-based silane coupling agents, mercapto-based silane coupling agents, and thioester-based silane coupling agents are selected. These silane coupling agents can be used alone or in combination of two or more.

[0101] When a silane coupling agent is incorporated relative to 100 parts by weight of silica, its content is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, even more preferably 3 parts by weight or more, and particularly preferably 5 parts by weight or more. Furthermore, relative to 100 parts by weight of silica, the above-mentioned content is preferably 20 parts by weight or less, more preferably 18 parts by weight or less.

[0102] When the silane coupling agent is incorporated relative to 100 parts by weight of the rubber component, its content is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, even more preferably 2 parts by weight or more, and particularly preferably 3 parts by weight or more. Furthermore, relative to 100 parts by weight of the rubber component, the above-mentioned content is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and even more preferably 12 parts by weight or less.

[0103] (Carbon black)

[0104] There are no particular restrictions on carbon black; any commonly used carbon black in the tire industry can be appropriately used, such as GPF, FEF, HAF, ISAF, and SAF. These carbon blacks can be used alone or in combination of two or more.

[0105] The preferred nitrogen adsorption specific surface area (N2SA) of carbon black is 50 m². 2 / g or more, preferably 80m 2 / g or more, especially 100m 2 / g or higher. When it is above the lower limit, good abrasion resistance and grip performance are often obtained. In addition, N2SA is preferably 200m. 2 / g or less, preferably 160m 2 Below / g, 150m is particularly preferred. 2 Below / g. When it is below the upper limit, good carbon black dispersion is often obtained. The N2SA of carbon black is calculated according to JIS K 6217-2:2017.

[0106] From the perspective of reinforcing performance, the carbon black content 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, relative to 100 parts by mass of the rubber component. Furthermore, from the perspective of processability and fuel efficiency, it is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 9 parts by mass or less.

[0107] From the perspective of wet grip performance, the content of all fillers is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 50 parts by mass or more, and particularly preferably 55 parts by mass or more, relative to 100 parts by mass of rubber component. Furthermore, from the perspective of abrasion resistance, it is preferably 120 parts by mass or less, more preferably 110 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 95 parts by mass or less.

[0108] From the perspective of fuel efficiency, the silica content in the filler is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and especially preferably 85% by mass or more. From the perspective of weather resistance and reinforcing performance, it is preferably 99% by mass or less, more preferably 95% by mass or less.

[0109] (Other reinforcing fillers)

[0110] Besides silica and carbon black, other fillers commonly used in the tire industry can be incorporated, such as aluminum hydroxide, calcium carbonate, alumina, clay, and talc.

[0111] <Plasticizer>

[0112] The rubber composition of the first rubber layer preferably includes a plasticizer. Examples of plasticizers include, for example, resin components, oils, liquid polymers, ester-based plasticizers, etc.

[0113] There are no particular limitations on the resin components; examples include petroleum resins, terpene resins, rosin resins, and phenolic resins commonly used in the tire industry, and these can be products obtained by hydrogenating these resin components. These resin components can be used alone or in combination of two or more.

[0114] In this specification, "C5 series petroleum resin" refers to resin obtained by polymerizing C5 fractions. Examples of C5 fractions include, for example, petroleum fractions equivalent to 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Cyclopentadiene-based resins may suitably be used as C5 series petroleum resins. Examples of cyclopentadiene-based resins include dicyclopentadiene resins (DCPD resins), cyclopentadiene resins, methylcyclopentadiene resins (non-hydrogenated cyclopentadiene resins), and resins obtained by hydrogenating these cyclopentadiene-based resins (hydrogenated cyclopentadiene-based resins). Cyclopentadiene-based resins, for example, those available from companies such as ExxonMobil Chemical, may be used.

[0115] In this specification, "aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, which may be hydrogenated or modified. Examples of C9 fractions include, for example, petroleum fractions equivalent to 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methyl indene. Specific examples of aromatic petroleum resins include, for example, coumarone-indene resin, coumarone resin, indene resin, and aromatic vinyl resins.

[0116] As an aromatic vinyl resin, homopolymers of α-methylstyrene derivatives or styrene derivatives, or copolymers of α-methylstyrene derivatives with styrene derivatives and / or indene, are preferred due to their economic efficiency, ease of processing, and excellent thermal properties. Furthermore, "α-methylstyrene derivative" refers to α-methylstyrene compounds, even if the benzene ring is substituted (preferably α-methylstyrene compounds in which the benzene ring can be substituted by a saturated hydrocarbon group having 1 to 4 carbon atoms), and "styrene derivative" refers to styrene compounds, even if the benzene ring is substituted (preferably styrene compounds in which the benzene ring can be substituted by a saturated hydrocarbon containing 1 to 4 carbon atoms). Commercially available resins from companies such as Mitsui Chemicals, Inc., Kraton Corporation, and Eastman Chemical Company can be used as the aforementioned aromatic vinyl resins.

[0117] In this specification, "C5-C9 series petroleum resin" refers to a resin obtained by copolymerizing C5 and C9 fractions, which may be hydrogenated or modified. Examples of C5 and C9 fractions include the aforementioned petroleum fractions. Commercially available petroleum resins, such as those from Tosoh Corporation and Zibo LuhuaHongjin New Material Group Co., Ltd., may be appropriately used as C5-C9 series petroleum resins.

[0118] Examples of terpene resins include polyterpene resins composed of at least one selected from terpene compounds such as α-pinene, β-pinene, limonene, and dipentene; aromatic modified terpene resins made from terpene compounds and aromatic compounds; terpene phenolic resins made from terpene compounds and phenolic compounds; and hydrogenated terpene resins (hydrogenated terpene resins). Examples of aromatic compounds used as raw materials for aromatic modified terpene resins include, for example, styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds used as raw materials for terpene phenolic resins include, for example, phenol, bisphenol A, cresol, and xylenol. Commercially available resins, such as those from Yasuhara Chemical Co., Ltd., can be used as terpene resins.

[0119] Examples of rosin-based resins include, but are not limited to, natural rosin resins and modified rosin resins. Commercially available rosin resins, such as those from Arakawa Chemical Industries, Ltd. and Harima Chemicals Group, Inc., can be used as rosin resins.

[0120] Examples of phenolic resins include, but are not limited to, phenol-formaldehyde resins, alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, and oil-modified phenol-formaldehyde resins.

[0121] As a resin component, it is preferred to select one or more from petroleum resins and terpene resins, and more preferably to select one or more from cyclopentadiene resins, aromatic vinyl resins and terpene resins.

[0122] From the perspective of wet grip performance, the softening point of the resin component is preferably 80°C or higher, more preferably 85°C or higher, and even more preferably 90°C or higher. Furthermore, from the perspective of processability and improving the dispersibility of the rubber component and filler, it is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower. Additionally, the softening point in this specification can be defined as the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point measuring device.

[0123] From the perspective of wet grip performance, when incorporating resin components relative to 100 parts by weight of rubber components, the content of the resin components is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and even more preferably 5 parts by weight or more. Furthermore, from the perspective of suppressing heat generation, it is preferably 60 parts by weight or less, more preferably 50 parts by weight or less, particularly preferably 40 parts by weight or less, and especially preferably 30 parts by weight or less.

[0124] Examples of oils include processing oils, vegetable fats and oils, animal fats and oils, etc. Examples of processing oils include paraffin-based processing oils, cycloalkane-based processing oils, and aromatic processing oils. Furthermore, as an environmentally friendly measure, processing oils with low levels of polycyclic aromatic hydrocarbons (PCA) can also be used. Examples of processing oils with low PCA content include mild extraction solutions (MES), treated distilled aromatic extracts (TDAE), and heavy cycloalkane oils.

[0125] From the perspective of wet grip performance, when oil is incorporated relative to 100 parts by weight of the rubber component, its content is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and even more preferably 5 parts by weight or more. Furthermore, from the perspective of abrasion resistance, it is preferably 60 parts by weight or less, more preferably 50 parts by weight or less, even more preferably 40 parts by weight or less, and particularly preferably 30 parts by weight or less. In addition, the oil content can be 0 parts by weight. Furthermore, in this specification, the oil content also includes the oil content contained in the oil-extended rubber.

[0126] There are no particular limitations on liquid polymers, as long as they are liquid at room temperature (25°C). Examples include, for instance, 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 can also be hydrogenated products of these liquid rubbers, or modified liquid polymers (preferably end-modified liquid polymers) whose main chain and / or ends are modified with modifying groups. These liquid polymers can be used alone or in combination of two or more.

[0127] Examples of modified liquid polymers include, but are not particularly limited to, liquid butadiene polymers modified at one or both ends (terminated liquid BR), liquid styrene-butadiene polymers modified at one or both ends (terminated liquid SBR), and hydrogenated products of these liquid polymers. Preferably, end-modified liquid BRs are hydrogenatable.

[0128] There are no particular limitations on the modifying group, and examples include, for instance, silyl, trialkoxysilyl, amino, amide, isocyanate, imino, imidazole, urea, ether, carbonyl, oxycarbonyl, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imide, hydrazine, azo, diazo, nitrile, pyridinyl, alkoxy, hydroxy, oxygen, carboxyl, epoxy, acrylic, methacrylic, acryloyl, and methacryl. Preferably, one or more groups selected from hydroxyl, carboxyl, acryloyl, and methacryl are used.

[0129] When the liquid polymer is incorporated relative to 100 parts by weight of the rubber component, its content is preferably 1 part by weight or more, more preferably 2 parts by weight or more, even more preferably 3 parts by weight or more, and particularly preferably 5 parts by weight or more. Furthermore, the content of the liquid rubber is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, and even more preferably 20 parts by weight or less.

[0130] Examples of ester-based plasticizers include, for instance, dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di(2-ethylhexyl) azelaate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl azelaate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymine triphosphate (TTP), tricresyl phosphate (TCP), and tri(xyl) phosphate (TXP). These ester-based plasticizers can be used alone or in combination of two or more.

[0131] From the perspective of wet grip performance, when plasticizer is incorporated relative to 100 parts by weight of rubber component, its content (total when multiple components are used together) is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and even more preferably 5 parts by weight or more. Furthermore, from the perspective of processability, it is preferably 120 parts by weight or less, more preferably 100 parts by weight or less, even more preferably 90 parts by weight or less, and particularly preferably 80 parts by weight or less.

[0132] (Other compounding agents)

[0133] In addition to the components mentioned above, the rubber composition of the first rubber layer may also appropriately include compounding agents commonly used in the tire industry, such as waxes, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, vulcanization accelerators, etc.

[0134] From the perspective of rubber's weather resistance, when wax is incorporated relative to 100 parts by weight of rubber component, its content is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more. Furthermore, from the perspective of preventing tire whitening due to powder bloom, it is preferably 10 parts by weight or less, more preferably 5 parts by weight or less.

[0135] Examples of processing aids include, for instance, fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. These processing aids can be used alone or in combination of two or more. For example, commercially available additives from companies such as Schill+Seilacher GmbH and Performance Additives can be used as processing aids.

[0136] From the perspective of improving processability, when processing aids are incorporated relative to 100 parts by weight of rubber component, their content is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more. Furthermore, from the perspective of abrasion resistance and tensile strength, it is preferably 10 parts by weight or less, more preferably 8 parts by weight or less.

[0137] Examples of antioxidants include, but are not particularly limited to, amine, quinoline, quinone, phenolic, and imidazole compounds, as well as carbamate metal salts, preferably phenylenediamine antioxidants such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-bis-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and quinoline antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. These antioxidants can be used alone or in combination of two or more.

[0138] From the perspective of the rubber's resistance to ozone cracking, when an antioxidant is incorporated relative to 100 parts by weight of the rubber component, its content is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more. Furthermore, from the perspective of abrasion resistance and wet grip performance, it is preferably 10 parts by weight or less, more preferably 5 parts by weight or less.

[0139] From the perspective of processability, when stearic acid is incorporated relative to 100 parts by weight of rubber component, its content is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more. Furthermore, from the perspective of vulcanization rate, it is preferably 10 parts by weight or less, more preferably 5 parts by weight or less.

[0140] From the perspective of processability, when zinc oxide is incorporated into 100 parts by weight of rubber component, its content is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 1.5 parts by weight or more. Furthermore, from the perspective of abrasion resistance, it is preferably 10 parts by weight or less, more preferably 5 parts by weight or less.

[0141] Sulfur can be suitable as a sulfiding agent. Powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersed sulfur can all be used.

[0142] From the perspective of ensuring a sufficient vulcanization reaction, the sulfur content when used as a vulcanizing agent 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, relative to 100 parts by mass of rubber component. Furthermore, from the perspective of preventing deterioration, it 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. In addition, when oil-containing sulfur is used as a vulcanizing agent, the content of the vulcanizing agent should be the total content of pure sulfur contained in the oil-containing sulfur.

[0143] Examples of vulcanizing agents other than sulfur include, for example, alkylphenol / sulfur chloride condensates, disodium salt of 1,6-hexanediol thiosulfate, and 1,6-bis(N,N'-dibenzylthiocarbamoyl dithiohexane). Commercially available vulcanizing agents other than sulfur, such as those from Taoka Chemical Co., Ltd., LANXESS, and Flexsys, can be used.

[0144] Examples of vulcanization accelerators include, for example, sulfonamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamate-based, aldehyde-amine-based or aldehyde-amine-based, imidazoline-based, and xanthate-based vulcanization accelerators. These vulcanization accelerators can be used alone or in combination of two or more. Preferably, one or more vulcanization accelerators selected from sulfonamide-based, guanidine-based, and thiazole-based vulcanization accelerators are used; more preferably, a combination of sulfonamide-based and guanidine-based vulcanization accelerators is used.

[0145] Examples of sulfonamide-based vulcanization accelerators include, for example, N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (DCBS). Among these, N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS) is preferred.

[0146] Examples of guanidine-based vulcanization accelerators include, for example, 1,3-diphenylguanidine (DPG), 1,3-di-o-toluidine, 1-o-toluidine biguanide, di-o-toluidine salts of dicatechin borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0147] Examples of thiazole-based accelerators include, for example, 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and di-2-benzothiazole disulfide. Among these, 2-mercaptobenzothiazole is preferred.

[0148] When a vulcanization accelerator is incorporated relative to 100 parts by weight of the rubber component, its content is preferably 1 part by weight or more, more preferably 2 parts by weight or more. Furthermore, relative to 100 parts by weight of the rubber component, the content of the vulcanization accelerator is preferably 8 parts by weight or less, more preferably 7 parts by weight or less, and even more preferably 6 parts by weight or less. When the content of the vulcanization accelerator is within the above ranges, the breaking strength and elongation tend to stabilize.

[0149] <Rubber Components and Tire Production>

[0150] The rubber composition disclosed herein can be produced by known methods. For example, it can be produced by kneading the above components using rubber kneading equipment (such as open rollers and closed kneaders (Banbury mixers, kneaders, etc.)).

[0151] The kneading step includes, for example, a basic kneading step that kneads compounding agents and additives other than vulcanizing agents and vulcanization accelerators, and a final kneading (F-kneading) step that adds vulcanizing agents and vulcanization accelerators to the kneaded product obtained by the basic kneading step and kneads them together. Furthermore, if necessary, the basic kneading step can be divided into multiple steps.

[0152] There are no particular restrictions on kneading conditions. Examples of kneading include, for instance, kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C in the basic kneading step, and kneading for 1 to 5 minutes at a temperature of 70 to 110°C in the final kneading step. There are no particular restrictions on vulcanization conditions. Examples of vulcanization include, for instance, vulcanizing at 150 to 200°C for 10 to 30 minutes.

[0153] The tire disclosed herein can be produced by conventional methods using the above-described rubber composition. That is, the tire can be produced by: extruding an uncured rubber composition obtained by adding the above-described components to a rubber component as needed into a tread shape using an extruder equipped with an outlet having a predetermined shape; bonding it to other tire components on a tire forming machine; forming it by conventional methods to form an uncured tire; and then heating and pressurizing the uncured tire in a vulcanizing machine.

[0154] The tire disclosed herein can be a pneumatic tire or a non-pneumatic tire. Furthermore, it is suitable for racing tires, passenger car tires, large passenger car tires, large SUV tires, motorcycle tires, etc., and can be used as a summer tire, a winter tire, or a studless tire. Additionally, in this specification, a passenger car tire refers to a tire mounted on a four-wheeled vehicle, specifically a tire with a maximum load capacity of less than 1000 kg. Examples

[0155] This disclosure will be described based on embodiments, but is not limited to the embodiments.

[0156] The following examples illustrate the various chemicals used in the embodiments and comparative examples.

[0157] NR: TSR20

[0158] Hydrophilic ENR50: The modified ENR prepared in Preparation Example 1 described later.

[0159] Hydrophilic ENR25: The modified ENR prepared in Preparation Example 2 described later.

[0160] SBR: Nipol 1502 (E-SBR, styrene content: 23.5% by mass, vinyl content: 18% by mass, Mw: 500,000) manufactured by Zeon Corporation.

[0161] BR: Ubepol BR (registered trademark) 150B (cis content: 97 mol%, Mw: 440000) manufactured by Ube Industries, Ltd.

[0162] Carbon black: Show black N220 (N2SA: 111m) manufactured by Cabot Japan KK Co., Ltd. 2 / g)

[0163] Silica 1: Ultrasil VN3 (N2SA: 175m) manufactured by Evonik Degussa GmbH. 2 / g, average primary particle size: 18nm)

[0164] Silica 2: Ultrasil 9100GR (N2SA: 230m) manufactured by Evonik Degussa GmbH. 2 / g, average primary particle size: 15nm)

[0165] Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl)disulfide) manufactured by Evonik Degussa GmbH.

[0166] Surfactant: EMULGEN 306P (polyoxyethylene stearate ether, nonionic surfactant) manufactured by Kao Corporation.

[0167] Thermoplastic elastomer: KURAMIRON TU-S5265 (a copolymer of polyurethane-based thermoplastic elastomer and styrene-based thermoplastic elastomer) manufactured by Kuraray Co., Ltd.

[0168] Oil: Diana Process NH-70S manufactured by Idemitsu Kosan Co., Ltd.

[0169] Resin component 1: Sylvares SA85 (α-methylstyrene / styrene resin, softening point: 85℃) manufactured by Kraton Corporation.

[0170] Resin component 2: Oppera PR-140 (hydrogenated dicyclopentadiene resin, softening point: 100°C) manufactured by ExxonMobil Chemical.

[0171] Liquid BR: "NISSO-PB GI-3000" (hydrogenated polybutadiene with hydroxyl groups at both ends) manufactured by Nippon Soda Co., Ltd.

[0172] Stearic acid: Beaded stearic acid "CAMELLIA" manufactured by NOF CORPORATION.

[0173] Zinc oxide: "Ginrei R" manufactured by Toho Zinc Co., Ltd.

[0174] Wax: OZOACE 355 manufactured by Nippon Seiro Co., Ltd.

[0175] Antioxidant 1: Antigen6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.

[0176] Antioxidant 2: AntigenRD (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Sumitomo Chemical Co., Ltd.

[0177] Sulfur: HK-200-5 (powdered sulfur containing 5% oil), manufactured by Hosoi Chemical Industry Co., Ltd.

[0178] Vulcanization accelerator 1: Nocceler D (N,N'-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0179] Vulcanization accelerator 2: Nocceller CZ-G (N-cyclohexyl-2-benzothiazole sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0180] Preparation Example 1: Synthesis of Hydrophilic ENR50

[0181] A tetrahydrofuran solution of ENR50 (manufactured by Kumpulan Guthrie Berhad, epoxidation rate: 50 mol%) was poured into methanol, washed with alcohol, and then dried. The purified ENR50 was dissolved in dimethylformamide, and polyethylene glycol monomethyl ether (Mw: 400) was added. The mixture was then heated and stirred in an oil bath at 140°C for 8 hours under a nitrogen atmosphere. The solvent was then removed from the mixture using an evaporator, and the mixture was dried under vacuum at 80°C for 12 hours. Further, the mixture was Soxhlet extracted with methanol for 24 hours, and the purified product was dried under vacuum in an oven at 25°C for 3 days to obtain hydrophilic ENR50. Polyethylene glycol monomethyl ether was added to all the epoxy groups of the obtained hydrophilic ENR50 to perform ring-opening (ring-opening rate: 100%).

[0182] Preparation Example 2: Synthesis of Hydrophilic ENR25

[0183] Hydrophilic ENR25 was obtained using the same method as in Example 1, except that ENR25 (manufactured by Kumpulan Guthrie Berhad, epoxidation rate: 25 mol%) was used. Polyethylene glycol monomethyl ether was added to all the epoxy groups of the resulting hydrophilic ENR25 to perform ring-opening (ring-opening rate: 100%).

[0184] (Example and Comparative Examples)

[0185] According to the formulations shown in Tables 1 to 4, all chemicals except sulfur and vulcanization accelerators were kneaded for 4 minutes at a discharge temperature of 160°C using a 1.7L closed Banbury mixer to obtain a kneaded product. Next, sulfur and vulcanization accelerators were added to the obtained kneaded product using an open roller mill, and the mixture was kneaded for 4 minutes until the temperature reached 105°C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was then vulcanized under pressure at 170°C for 12 minutes to obtain a test vulcanized rubber sheet. The obtained unvulcanized rubber composition was molded into a tread shape and bonded to other tire components to form an unvulcanized tire, which was then vulcanized at 170°C to obtain test tires (size: 205 / 65R15, rim: 15×6JJ, internal pressure: 230kPa). Furthermore, as shown in Figure 2, the tires of Comparative Examples 1, 3, 5, 7-11 and 14-17 have a consistent length in the width direction of the land portion closest to the tire equator, which extends radially from the outer side of the tire to the inner side.

[0186] <Measuring Acetone Extraction Volume>

[0187] After vulcanization, each rubber specimen was immersed in acetone for 24 hours to extract soluble components. The mass of each specimen before and after extraction was measured. The amount of acetone extracted was determined according to the following formula:

[0188] Acetone extraction yield (%) = {(mass of rubber specimen before extraction - mass of rubber specimen after extraction) / (mass of rubber specimen before extraction)} × 100.

[0189] <Measuring contact angle>

[0190] Each vulcanized rubber specimen, 20 mm long × 30 mm wide × 2 mm thick, was cut from the first rubber layer of the tread of each test tire, with the tire circumference as the long side. Then, the contact angles of each rubber specimen after the following treatment were measured using a DMs-401 contact angle measuring instrument manufactured by Kyowa Interface Science Co., Ltd. Specifically, firstly, each rubber specimen cut from the first rubber layer was immersed in water at 23°C under normal pressure for 1 hour, and then left to stand at 23°C under normal pressure for 24 hours to air dry. Then, 2.0 μL of pure water was dropped onto the surface of each horizontally placed rubber specimen, and the angle formed between the tip of the droplet and the surface of the rubber composition (contact angle A1) was measured 180 seconds after the droplet was dropped. After measuring the contact angle A1, each rubber specimen was immersed in water at 23°C under normal pressure for 1 hour, and then left to stand at 23°C under normal pressure for 24 hours to air dry. Then, 2.0 μL of pure water was dropped onto the surface of each horizontally placed rubber specimen, and the angle (contact angle A2) formed between the tip of the droplet and the surface of the rubber composition was measured 180 seconds after the drop was dropped.

[0191] <Wet grip performance of tires when new and after wear>

[0192] Each test tire was mounted on all wheels of a vehicle (Japanese-made FF2000cc), and braking was performed at 100 km / h on a wet asphalt track. The braking distance from that point was measured. Next, after the tires were heat-treated at 80°C for 7 days, each test tire with worn tread along its radius to 10% of its original thickness was mounted on all wheels of the vehicle. The vehicle was driven for 10 laps on a wet asphalt track. Braking was then performed at 100 km / h, and the braking distance from the braking point was measured. The wet grip performance of each tire, both when new and after wear, was expressed as an index using the following formula, with the braking distance of the reference comparison tires (Comparative Example 1 in Tables 1 and 2, and Comparative Example 13 in Tables 3 and 4) when the tires were new defined as 100. The results show that a higher index indicates better wet grip performance.

[0193] (Wet grip performance index) = (Breaking distance of the reference tire (when the tire is new) / (Breaking distance of each test tire (when the tire is new and after wear)) × 100.

[0194] Table 1

[0195]

[0196]

[0197] Table 2

[0198]

[0199] Table 3

[0200]

[0201] Table 4

[0202]

[0203] The results from Tables 1 to 4 show that in the tires disclosed herein, the contact area increases due to wear when configured with a predetermined tread pattern. Therefore, by setting the contact angle of the rubber composition of the tread rubber within a predetermined range, the tire exhibits excellent wet grip performance when it is new, and the deterioration of wet grip performance after wear is significantly suppressed.

[0204] <Implementation Method>

[0205] Examples of embodiments of the present invention are shown below.

[0206] (1) A tire having a tread, wherein the tread has a land portion divided by a plurality of circumferential grooves, and in the radial cross section of the tire including the tire's axis of rotation, the land portion closest to the tire's equatorial plane has a portion whose length in the width direction increases from the radially outer side of the tire towards the inner side, the tread having at least one rubber layer, the contact surface of the tread being formed by a first rubber layer, the first rubber layer being composed of a rubber composition, the rubber composition comprising a rubber component comprising a diene rubber, wherein the contact angle A1 with pure water measured after the rubber composition of the first rubber layer is immersed in water at 23°C and atmospheric pressure for 1 hour and then dried at 23°C and atmospheric pressure for 24 hours, and the contact angle A2 with pure water measured after the rubber composition of the first rubber layer is immersed in water at 23°C and atmospheric pressure for 1 hour and then dried at 23°C and atmospheric pressure for 24 hours, are both 80° or less (preferably 75° or less).

[0207] (2) The tire according to (1), wherein the rubber component in the rubber composition of the first rubber layer comprises isoprene rubber modified with hydrophilic functional groups, and / or the rubber composition of the first rubber layer comprises a thermoplastic elastomer containing hydrophilic functional groups.

[0208] (3) The tire according to (1) or (2), wherein, relative to 100 parts by weight of the rubber component, the rubber composition of the first rubber layer comprises 0.5 to 50 parts by weight of a thermoplastic elastomer, said thermoplastic elastomer comprising at least one functional group selected from carboxyl, hydroxyl, ester, ether, carbonyl and amide groups.

[0209] (4) The tire according to any one of (1) to (3), wherein the rubber component in the rubber composition of the first rubber layer comprises 10% by mass to 90% by mass of isoprene rubber, said isoprene rubber being modified with one or more functional groups selected from hydroxyl, amino and ether groups.

[0210] (5) The tire according to any one of (1) to (4), wherein the acetone extraction amount of the rubber composition of the first rubber layer is 5% to 25% by mass (preferably 7% to 23% by mass, more preferably 9% to 21% by mass).

[0211] (6) The tire according to any one of (1) to (5), wherein the rubber composition of the first rubber layer comprises at least one selected from petroleum resins, terpene resins and resins obtained by hydrogenation therefrom.

[0212] (7) The tire according to any one of (1) to (6), wherein the rubber composition of the first rubber layer comprises a liquid polymer.

[0213] (8) The tire according to any one of (1) to (7), wherein the rubber composition of the first rubber layer comprises a nitrogen adsorption specific surface area of ​​180 m². 2 / g or more (preferably 200mg) 2 Silicon dioxide (at least / g).

[0214] (9) The tire according to any one of (1) to (8), wherein the length L in the width direction of the land portion closest to the tire equatorial plane when the tread is 90% worn. 90 The ratio L to the length L0 in the width direction when the tire is new 90 / L0 is 1.1 or higher (preferably 1.2 or higher, more preferably 1.3 or higher).

[0215] (10) The tire according to any one of (1) to (9), wherein the contact angle A1 and contact angle A2 of the rubber composition of the first rubber layer are both 70° or less (preferably 65° or less).

[0216] Reference tag list

[0217] 1. Tread

[0218] 2. Circumferential groove

[0219] 3. Land Department

[0220] 4. Groove edge

[0221] 5. Tank wall

[0222] C. Tire equatorial plane

[0223] H. Trench depth of the circumferential groove

[0224] L0. Length of the tire in the width direction when the tire is new.

[0225] L 90 Length in the width direction when the tread wears 90%

Claims

1. A tire having a tread, characterized in that, The tread has a land portion divided by multiple circumferential grooves. In the radial cross-section of the tire including the tire's axis of rotation, the portion of the land portion closest to the tire's equatorial plane has a length that increases from the radially outer side of the tire towards the inner side. The tread has at least one rubber layer. The contact surface of the tread is composed of a first rubber layer, which is composed of a rubber composition containing a rubber component, the rubber component containing a diene rubber. The contact angle A1 with pure water, measured after the rubber composition of the first rubber layer is immersed in water at 23°C and atmospheric pressure for 1 hour and then dried at 23°C and atmospheric pressure for 24 hours, and the contact angle A2 with pure water, measured after measuring contact angle A1 and then immersing the rubber composition of the first rubber layer in water at 23°C and atmospheric pressure for 1 hour and then drying at 23°C and atmospheric pressure for 24 hours, are both below 80°.

2. The tire according to claim 1, characterized in that, The rubber component in the rubber composition of the first rubber layer comprises isoprene-based rubber modified with hydrophilic functional groups, and / or the rubber composition of the first rubber layer comprises a thermoplastic elastomer having hydrophilic functional groups.

3. The tire according to claim 1 or 2, characterized in that, The rubber composition of the first rubber layer comprises, relative to 100 parts by weight of the rubber component, 0.5 to 50 parts by weight of a thermoplastic elastomer, said thermoplastic elastomer comprising at least one functional group selected from carboxyl, hydroxyl, ester, ether, carbonyl and amide groups.

4. The tire according to claim 1 or 2, characterized in that, The rubber component in the rubber composition of the first rubber layer comprises 10% to 90% by mass of isoprene rubber, wherein the isoprene rubber is modified with one or more functional groups selected from hydroxyl, amino and ether groups.

5. The tire according to claim 1 or 2, characterized in that, The acetone extraction amount of the rubber composition in the first rubber layer is from 5% to 25% by mass.

6. The tire according to claim 1 or 2, characterized in that, The rubber composition of the first rubber layer comprises at least one selected from petroleum resins, terpene resins, and resins obtained by hydrogenation of the same.

7. The tire according to claim 1 or 2, characterized in that, The rubber composition of the first rubber layer comprises a liquid polymer.

8. The tire according to claim 1 or 2, characterized in that, The rubber composition of the first rubber layer contains a nitrogen adsorption specific surface area of ​​180 m². 2 / g or more of silicon dioxide.

9. The tire according to claim 1 or 2, characterized in that, The length L in the width direction of the land portion closest to the tire equator when the tread wears 90% is... 90 The ratio L to the length L0 in the width direction when the tire is new 90 / L0 is 1.1 or higher.

10. The tire according to claim 1 or 2, characterized in that, The contact angles A1 and A2 of the rubber composition in the first rubber layer are both below 70°.

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