Pneumatic tires

Abstract

To provide a pneumatic tire achieving both low rolling resistance and improvement in noise performance during high-speed travelling satisfactorily.SOLUTION: A pneumatic tire comprises a belt layer and a tread part. The tread part is arranged outside the belt layer in a tire radial direction. Reinforcement cords in the belt layer are configured so that 50 / 5 cm or more cords made of mono-filaments are arranged in a tire width direction, on a cross section in the tire radial direction of the belt layer. A maximum load capacity WL (Kg) of the tire and weight WT (Kg) of the tire satisfy a following formula (1): 0.0145≤(WT / WL).....( formula 1).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having a belt layer. [Background technology]

[0002] In recent years, there has been a growing demand for more fuel-efficient automobiles due to growing concerns about environmental issues and economic reasons, and there is also a strong demand for improved fuel efficiency in pneumatic tires (hereinafter simply referred to as "tires") that are fitted to automobiles.

[0003] The fuel efficiency of a tire can be evaluated by its rolling resistance, and it is known that the smaller the rolling resistance, the more fuel efficient the tire.

[0004] Therefore, it has been proposed to reduce the rolling resistance by modifying the compounding of the rubber composition constituting the tread portion of the tire (for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-178034 A [Patent Document 2] JP 2018-178034 A [Patent Document 3] WO2018 / 186367 publication [Patent Document 4] JP 2019-206643 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned conventional technologies are aimed at rolling resistance during normal driving, and in recent years, with the development of expressways and high-speed driving becoming commonplace, users are increasingly demanding reduced rolling resistance during high-speed driving as well.In addition, a new problem has arisen: the need to improve noise performance during high-speed driving.

[0007] Therefore, an object of the present invention is to provide a pneumatic tire in which both low rolling resistance during high-speed running and noise performance during high-speed running are sufficiently improved. [Means for solving the problem]

[0008] The present inventors have conducted extensive research into solving the above problems, and have found that the above problems can be solved by the invention described below, thereby completing the present invention.

[0009] The invention described in claim 1 is A pneumatic tire having a belt layer and a tread portion, The tread portion is disposed on the outer side of the belt layer in the tire radial direction, The reinforcing cords in the belt layer are monofilament cords, and are arranged at 50 cords / 5 cm or more in the tire width direction in the tire radial cross section of the belt layer. , at a specified interval It is arranged and configured, The pneumatic tire is characterized in that the maximum load capacity WL (kg) and the tire weight WT (kg) of the tire satisfy the following (Equation 1). 0.0145≦(WT / WL) (Formula 1) The "maximum load capacity WL of the tire" is a value calculated using the following two formulas based on the tire section width Wt (mm), tire section height Ht (mm), and tire outer diameter Dt (mm) when the tire is mounted on a regular rim, the internal pressure is set to 250 kPa, and there is no load. V(mm 3 )={(Dt / 2) 2 -(Dt / 2-Ht) 2 }×π×Wt WL(kg)=0.000011×V+100

[0010] The invention described in claim 2 is The pneumatic tire according to claim 1, characterized in that the following (Formula 2) is satisfied. 0.015≦(WT / WL) (Formula 2)

[0011] The invention described in claim 3 is 3. The pneumatic tire according to claim 1 or 2, characterized in that the cord made of the monofilament has an outer diameter of 0.1 mm or more and 0.5 mm or less.

[0013] Claim 4 The invention described in The tread portion has a plurality of circumferential grooves extending continuously in a circumferential direction of the tire, 2. The tire according to claim 1, wherein the total cross-sectional area of ​​the plurality of circumferential grooves is 10% or more and 30% or less of the cross-sectional area of ​​the tread portion. 3 13. The pneumatic tire according to claim 12,

[0014] Claim 5 The invention described in The tread portion has a plurality of lateral grooves extending in an axial direction of the tire, 2. A tire according to claim 1, wherein the total volume of the plurality of lateral grooves is 2.0% or more and 5.0% or less of the volume of the tread portion. 4 13. The pneumatic tire according to claim 12,

[0015] Claim 6 The invention described in At least two belt layers are provided, In at least one pair of the belt layers adjacent in the tire radial direction, 10. The tire according to claim 1, wherein the average distance D (mm) between the belt layers in the tread portion is 0.6 mm or less. 5 13. The pneumatic tire according to claim 12,

[0016] Claim7 The invention described in At least two belt layers are provided, In at least one pair of the belt layers adjacent in the tire radial direction, 2. The tire circumferential angle between the belt layers in the tread portion is 65 degrees or less. 6 13. The pneumatic tire according to claim 12,

[0017] Claim 8 The invention described in The tread portion has a circumferential groove extending continuously in the tire circumferential direction, 2. The tire according to claim 1, wherein a ratio (L80 / L0) of a groove width L80 at a depth of 80% of the maximum depth of the circumferential groove to a groove width L0 of the circumferential groove in the ground contact surface of the tread portion is 0.3 or more and 0.7 or less. 7 13. The pneumatic tire according to claim 12,

[0018] Claim 9 The invention described in Claims 1 to 5, characterized in that the tire cross-sectional width Wt (mm) is less than 200 mm. 8 13. The pneumatic tire according to claim 12, Effect of the Invention

[0020] According to the present invention, it is possible to provide a pneumatic tire in which both low rolling resistance during high-speed running and noise performance during high-speed running are sufficiently improved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] [1] Characteristics of the tire according to the present invention First, the features of the pneumatic tire according to the present invention will be described.

[0022] 1. Overview The tire according to the present invention is a tire including a belt layer and a tread portion. The tread portion is disposed radially outward of the belt layer. The reinforcing cords in the belt layer are configured by arranging 50 cords / 5 cm or more in the tire width direction in the radial cross section of the belt layer.

[0023] Furthermore, in the tire according to the present invention, the maximum load capacity WL (kg) and the tire weight WT (kg) of the tire further satisfy the following (Equation 1). 0.0145≦(WT / WL) (Formula 1)

[0024] By having these characteristics, it is possible to provide a tire that is sufficiently improved in both low rolling resistance during high-speed running and noise performance during high-speed running, as will be described later.

[0025] In the above description, the "maximum load capacity WL" is a value calculated using the following two formulas based on the tire section width Wt (mm), tire section height Ht (mm), and tire outer diameter Dt (mm) when the tire is mounted on a regular rim, the internal pressure is set to 250 kPa, and there is no load. be Here, V is the volume of the space occupied by the tire (virtual volume), and (Dt / 2-Ht) is the rim diameter (mm). V(mm 3 )={(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt WL(kg)=0.000011×V+100

[0026] Here, "genuine rim" refers to a rim that is determined for each tire by a standard system that includes the standard on which the tire is based, such as the standard rim for the applicable size described in the "JATMA YEAR BOOK" for the above-mentioned JATMA, the "Measuring Rim" described in the "STANDARDS MANUAL" for the ETRTO (The European Tire and Rim Technical Organisation), and the "Design Rim" described in the "YEAR BOOK" for the TRA (The Tire and Rim Association, Inc.). In the case of a tire not specified by a standard, it refers to a rim that can be assembled to a rim and can hold internal pressure, that is, a rim that does not leak air from between the rim and tire, with the smallest rim diameter and the next narrowest rim width.

[0027] The tire cross-sectional width Wt can be calculated as the width obtained by excluding the patterns, letters, etc. on the tire side from the linear distance between the sidewalls (total tire width), including all patterns, letters, etc. on the tire side. The tire cross-sectional height Ht can be calculated as half the difference between the tire outer diameter and the nominal rim diameter.

[0028] 2. Mechanism of effect manifestation in the tire according to the present invention The mechanism by which the effect of the tire according to the present invention is manifested, that is, the mechanism by which both the low rolling resistance during high-speed running and the noise performance during high-speed running are sufficiently improved, is presumed to be as follows.

[0029] Since deformation of the tread portion of a tire may lead to a deterioration in rolling resistance, it is preferable to suppress deformation of the tread portion from the viewpoint of improving low rolling resistance.

[0030] One possible solution is to use monofilament cords (single wire) rather than twisted cords (twisted cords) to form the belt layer reinforcing the tread. Monofilament cords are less likely to stretch, so by arranging 50 or more cords per 5 cm, i.e., by arranging them closely with an interval of 1 mm or less per cord, it is believed that the tread portion can be sufficiently restrained and its deformation can be sufficiently suppressed.

[0031] However, in such tires, there is a concern that the rigidity of the tread portion generates stress concentration in other members, which may result in a deterioration of rolling resistance.

[0032] Therefore, in the present invention, attention is focused on the relationship between the maximum load capacity WL (kg) of the tire and the tire weight WT (kg), and the relationship is set to 0.0145≦(WT / WL) (Formula 1). In this way, by appropriately controlling (WT / WL), the distortion of each member can be made uniform and stress concentration on other members can be suppressed, and therefore, coupled with the restraint of the tread portion by the belt layer using the monofilament cords arranged in a dense state as described above, it is believed that low rolling resistance during high-speed driving can be improved.

[0033] In addition, by appropriately controlling (WT / WL), the natural frequency of the tire can be shifted to the lower frequency side, which, together with suppressing deformation of the tread, is believed to improve noise performance during high-speed driving.

[0034] It is more preferable that (WT / WL) is 0.015 or more. The outer diameter of the monofilament cord is preferably 0.1 to 0.5 mm. If the cord is too thin, there is a risk that sufficient binding force cannot be exerted even if the cord is arranged closely. On the other hand, if the cord is too thick, the interval between the monofilament cords becomes narrow, and the resonance frequency between the monofilament cords becomes high, which is thought to reduce the effect of improving noise performance during high-speed driving.

[0035] [2] More preferred embodiments of the tire according to the present invention The tire according to the present invention can achieve even greater effects by adopting the following aspects.

[0036] 1. Loss tangent of tread rubber and distance from tread to belt layer In the tire according to the present invention, it is preferable that the loss tangent (tan δ) of the tread rubber composition forming the contact surface in the outermost layer of the tread portion, measured under the conditions of temperature: 0°C, initial strain: 5%, dynamic strain: ±0.25%, frequency: 10 Hz, and deformation mode: tension, and the distance T (mm) from the outermost surface of the tread portion to the outermost surface of the belt layer satisfy (tan δ × T) ≧ 5.5 (Equation 3).

[0037] The loss tangent tanδ is a parameter that indicates energy absorption performance. The larger the value, the greater the energy absorption and the less heat generation in the tread portion can be achieved. This is believed to result in improvements in both low rolling resistance during high-speed driving and noise performance during high-speed driving.

[0038] On the other hand, it is considered that the larger the distance from the outermost surface of the tread portion to the outermost surface of the belt layer, the more the deformation of the tread portion is suppressed and the more sufficient the constraint by the belt layer is secured, thereby enabling improvements in both low rolling resistance during high-speed driving and noise performance during high-speed driving to be achieved.

[0039] Based on this idea, experiments were conducted to determine the preferable relationship between the loss tangent tan δ and the distance T from the outermost surface of the tread portion to the outermost surface of the belt layer. It was found that if the above-mentioned relationship (tan δ × T) ≧ 5.5 is satisfied, the constraint by the belt layer can be sufficiently ensured, and both low rolling resistance during high-speed driving and noise performance during high-speed driving can be improved.

[0040] In the above description, the loss tangent (tan δ) can be measured using a viscoelasticity measuring device such as "IPLEXER (registered trademark)" manufactured by GABO Co., Ltd. And, (tan δ×T) is more preferably 6.0 or more, and even more preferably 6.5 or more.

[0041] In the present invention, specifically, tan δ is preferably 0.5 or more, and more preferably 0.7 or more.

[0042] In addition, the specific distance T (mm) is preferably 12.0 mm or less, more preferably 10.0 mm or less, and even more preferably 7.5 mm or less. If it exceeds 12.0 mm, the distance from the tread surface to the belt layer becomes too long, and there is a concern that it is difficult to obtain a sufficient improvement effect in noise performance during high-speed driving. In addition, the lower limit is preferably 6.0 mm or more, and more preferably 7.0 mm or more. If it is less than 6.0 mm, the impact from the tread portion is easily transmitted to the belt layer, so there is a concern that it is difficult to obtain a sufficient improvement effect in noise performance during high-speed driving.

[0043] In the above description, the distance T is the linear distance from the tread surface on the tire equatorial plane to the surface of the monofilament cord of the outermost belt layer in the tire radial cross section when the tire is mounted on a regular rim, the internal pressure is 250 kPa, and there is no load. When a groove is formed on the tread equatorial plane, the linear distance from the intersection point of the line obtained by connecting the tire ground contact surface ends of the groove and the tire equatorial plane to the outermost belt layer is taken as the distance T. When the monofilament cord of the outermost belt layer does not exist on the tire equatorial plane, the intersection point of the line connecting two points on the tire radial outermost side of a pair of monofilament cords closest to the equatorial plane and the equatorial plane is regarded as the position of the outermost belt layer, and the linear distance to the tread surface is taken as the distance T. For simplicity, the measurement can be performed in a state where the bead portion of a section cut out in the tire width direction with a thickness of 2 to 4 mm is pressed down to match the corresponding rim width.

[0044] 2. Tread grooves In the tire according to the present invention, the tread portion has a plurality of circumferential grooves, and the total cross-sectional area of ​​the plurality of circumferential grooves is preferably 10% or more and 30% or less of the cross-sectional area of ​​the tread portion. This is believed to suppress the movement of the tread portion, and to further improve both the low rolling resistance during high-speed driving and the noise performance during high-speed driving. It is more preferable that it is 15% or more, even more preferable that it is 18% or more, and particularly preferable that it is 21% or more. On the other hand, it is more preferable that it is 27% or less, even more preferable that it is 25% or less, and particularly preferable that it is 23% or less.

[0045] The cross-sectional area of ​​the circumferential grooves mentioned above refers to the total area defined by the straight line connecting the ends of the tread circumferential grooves and the groove walls in a tire mounted on a regular rim, with an internal pressure of 250 kPa and no load applied. Simply put, this area can be determined by cutting the tire in a radial direction with a width of 2 to 4 cm and pressing the space between the bead portions of the cut section against the rim width.

[0046] The cross-sectional area of ​​the tread portion refers to the area radially outward of the belt layer in a region bounded by a straight line connecting the ends of the circumferential grooves of the tread portion and two straight lines parallel to the equatorial plane, passing through both ends of the widest one of the tread surface profile and belt layers formed by the tread surface, in a radial cross section of a tire mounted on a regular rim, with an internal pressure of 250 kPa and no load. Note that, in the case where a belt reinforcing layer using organic fibers and / or steel cords is present radially outward of the belt layer, the cross-sectional area refers to the area radially outward of the belt reinforcing layer.

[0047] It is also preferable that the tread portion has a plurality of lateral grooves extending in the tire axial direction, and the total volume of the plurality of lateral grooves is 2.0% or more and 5.0% or less of the volume of the tread portion. This is believed to suppress the movement of the tread portion, and to further improve both the low rolling resistance during high-speed driving and the noise performance during high-speed driving. It is possible to sufficiently suppress uneven wear of the tread portion and improve durability. It is more preferable that it is 2.2% or more and 4.0% or less, even more preferable that it is 2.5% or more and 3.5% or less, and particularly preferable that it is 2.7% or more and 3.0% or less.

[0048] The volume of the lateral grooves mentioned above refers to the total volume formed by the surface connecting the ends of the lateral grooves and the groove walls in a tire mounted on a standard rim, with an internal pressure of 250 kPa and no load, and can be calculated by determining the volume of each individual lateral groove.

[0049] Furthermore, the groove width L at a depth of 80% of the maximum depth of the circumferential groove with respect to the groove width L0 of the circumferential groove on the contact surface of the tread portion 80 Ratio (L 80 / L0) is preferably 0.3 or more and 0.7 or less. This is believed to suppress the movement of the entire land portion at the bottom surface of the land portion of the tread portion, thereby further improving both low rolling resistance during high-speed driving and noise performance during high-speed driving. It is more preferably 0.35 or more and 0.65 or less, even more preferably 0.40 or more and 0.60 or less, and particularly preferably 0.45 or more and 0.55 or less.

[0050] The above L0 and L 80 The straight-line distance (L0) between the ends of the circumferential grooves on the tread surface of a tire mounted on a standard rim, with an internal pressure of 250 kPa and no load applied, and the minimum distance (L) between the groove walls at a position of 80% of the groove depth 80 ) and can be calculated simply by cutting a section of the tire in the radial direction with a width of 2 to 4 cm and pressing the space between the beads to match the width of the rim.

[0051] 3.Multi-layered belt In the present invention, the belt layer is multi-layered by providing at least two layers, and it is preferable that in at least one pair of belt layers adjacent to each other in the radial direction of the tire, the average distance D (mm) between the belt layers in the tread portion is 0.6 mm or less.

[0052] This allows a pair of belt layers to work together to appropriately restrain the tread portion and reduce the amount of deformation of the tread portion during rolling, thereby further improving both low rolling resistance during high-speed driving and noise performance during high-speed driving.

[0053] The average distance D between the belt layers referred to here is the average distance between the monofilaments (cords) of the belt layers, and is the distance between the inner surface of the monofilament of the belt layer on the surface side and the outer surface of the monofilament of the inner belt layer on the equator plane of two overlapping belt layers.

[0054] In the case of a multi-layered belt layer, in at least one pair of belt layers adjacent in the radial direction of the tire, the angle formed by the belt layers in the tread portion in the tire circumferential direction is preferably 65° or less, more preferably 60° or less, and even more preferably 58° or less.

[0055] By arranging the belt layers inclined to each other at an appropriate angle, a hoop effect can be obtained, and almost the entire width of the tread portion can be firmly restrained, thereby suppressing the amount of deformation of the tread portion during rolling, thereby further improving both low rolling resistance during high-speed driving and noise performance during high-speed driving.

[0056] 4. Tire shape In the tire according to the present invention, when the tire is mounted on a regular rim and the internal pressure is set to 250 kPa, the specific tire outer diameter Dt (mm) is, for example, preferably 515 mm or more, more preferably 558 mm or more, even more preferably 585 mm or more, particularly preferably 658 mm or more, and most preferably 673 mm or more. On the other hand, it is preferably less than 843 mm, more preferably less than 725 mm, even more preferably less than 707 mm, particularly preferably less than 685 mm, and most preferably less than 655 mm.

[0057] A specific tire cross-sectional width Wt (mm) is, for example, preferably 115 mm or more, more preferably 130 mm or more, even more preferably 150 mm or more, even more preferably 170 mm or more, particularly preferably 185 mm or more, and most preferably 193 mm or more. On the other hand, it is preferably less than 305 mm, more preferably less than 245 mm, even more preferably less than 210 mm, particularly preferably less than 205 mm, and most preferably less than 200 mm.

[0058] In this case, it is preferable that the tire cross-sectional width Wt (mm) and the loss tangent (tan δ) of the tread portion satisfy (tan δ×Wt)≧95 (Formula 4). This is believed to further reduce heat generation in the tread portion. It is more preferable that (tan δ×Wt) is 98 or more, even more preferable that it is 100 or more, and particularly preferable that it is 110 or more. On the other hand, it is preferable that it is 200 or less, more preferably 180 or less, and even more preferably 170 or less.

[0059] A specific tire section height Ht (mm) is, for example, preferably 37 mm or more, more preferably 87 mm or more, and even more preferably 95 mm or more, while it is preferably less than 180 mm, more preferably less than 112 mm, and even more preferably less than 101 mm.

[0060] A specific value of the above-mentioned V (virtual volume) is, for example, 13,000,000 mm 3 It is preferable that the length is 29,000,000 mm or more. 3 More preferably, it is 36,000,000 mm or more. 3 More preferably, the thickness is 66,000,000 mm or more. 3 Preferably less than 44,000,000 mm 3 Preferably less than 38,800,000 mm 3 It is even more preferable that it is less than 1000 .mu.m.

[0061] In the present invention, in consideration of the stability of the ride comfort during running, (Dt-2×Ht) is preferably 450 (mm) or more, more preferably 470 (mm) or more, and even more preferably 480 (mm) or more. On the other hand, in consideration of the deformation of the tread portion, it is preferably less than 560 (mm), more preferably less than 530 (mm), and even more preferably less than 510 (mm).

[0062] [3] Implementation form Hereinafter, the present invention will be described in detail based on the embodiments.

[0063] 1. Rubber composition constituting the outermost layer of the tread (1) Compounding materials The rubber composition constituting the outermost layer of the tread portion of the tire according to the present invention (hereinafter also referred to as "tread rubber composition") can be obtained from the rubber components and other compounded materials described below.

[0064] (a) Rubber component In the present embodiment, the rubber component is not particularly limited, and rubbers (polymers) generally used in tire production can be used, such as diene rubbers such as isoprene-based rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), and nitrile rubber (NBR), and butyl-based rubbers such as butyl rubber. These may be used alone or in combination, but it is preferable to include any one of isoprene-based rubber, BR, and SBR, and it may include isoprene-based rubber and BR, BR and SBR, isoprene-based rubber and SBR, or it may include isoprene-based rubber, BR, and SBR.

[0065] (a) SBR The content of SBR in 100 parts by mass of the rubber component is, for example, preferably more than 10 parts by mass, more preferably more than 30 parts by mass, even more preferably more than 50 parts by mass, and particularly preferably more than 60 parts by mass from the viewpoint of noise performance during high-speed driving. On the other hand, from the viewpoint of heat buildup (related to low rolling resistance during high-speed driving), the content is preferably less than 100 parts by mass, more preferably less than 90 parts by mass, even more preferably less than 80 parts by mass, and particularly preferably less than 75 parts by mass.

[0066] The weight average molecular weight of SBR is, for example, more than 100,000 and less than 2,000,000. The styrene content of SBR is, for example, preferably more than 5% by mass, more preferably more than 10% by mass, and even more preferably more than 20% by mass, from the viewpoint of noise performance during high-speed driving. On the other hand, from the viewpoint of low rolling resistance during high-speed driving, it is preferably less than 50% by mass, more preferably less than 40% by mass, and even more preferably less than 35% by mass. The vinyl bond amount (1,2-bonded butadiene unit amount) of SBR is, for example, more than 5% by mass and less than 70% by mass. The structure identification of SBR (measurement of styrene content and vinyl bond amount) can be performed, for example, using a JNM-ECA series device manufactured by JEOL Ltd.

[0067] There are no particular limitations on the SBR, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. may be used. The SBR may be either unmodified SBR or modified SBR.

[0068] The modified SBR may be any SBR having a functional group that interacts with a filler such as silica, and examples thereof include terminal-modified SBR in which at least one end of SBR has been modified with a compound (modifying agent) having the above-mentioned functional group (terminal-modified SBR having the above-mentioned functional group at the end), main-chain-modified SBR in which the main chain has the above-mentioned functional group, main-chain-terminal-modified SBR in which the main chain and at least one end are modified with the above-mentioned modifier, and terminal-modified SBR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or epoxy group introduced therein.

[0069] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, etc. These functional groups may have a substituent.

[0070] Furthermore, as the modified SBR, for example, SBR modified with a compound (modifying agent) represented by the following formula can be used.

[0071] [ka]

[0072] In the formula, R 1 , R 2 and R 3R may be the same or different and represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH), or a derivative thereof. 4 and R 5 R may be the same or different and represents a hydrogen atom or an alkyl group. 4 and R 5 may bond to form a ring structure together with the nitrogen atom, and n represents an integer.

[0073] As the modified SBR modified with a compound (modifier) ​​represented by the above formula, SBR in which the polymerization terminals (active terminals) of solution-polymerized styrene-butadiene rubber (S-SBR) have been modified with a compound represented by the above formula (such as the modified SBR described in JP 2010-111753 A).

[0074] R 1 , R 2 and R 3 R is preferably an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). 4 and R 5 is preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and further preferably 3. In addition, R 4 and R 5 When the nitrogen atom and the nitrogen atom are bonded to each other to form a ring structure, the ring is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group and a benzyloxy group).

[0075] Specific examples of the modifying agent include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0076] In addition, modified SBR modified with the following compounds (modifiers) can also be used as the modified SBR. Examples of the modifiers include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, Diglycidyl amino compounds such as diglycidyl orthotoluidine, tetraglycidyl meta-xylylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxy sulfide group-containing silane compounds such as (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, Alkoxysilanes such as thyltriethoxysilane; (thio)benzophenone compounds having amino groups and / or substituted amino groups, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, and N,N,N',N'-bis-(tetraethylamino)benzophenone; Benzaldehyde compounds having an amino group and / or a substituted amino group, such as dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, 4-N,N-divinylaminobenzaldehyde, etc.; N-substituted pyrrolidones, such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, N-methyl-5-methyl-2-pyrrolidone, etc.; N-substituted piperidones, such as N-methyl-2-piperidone, N-vinyl-2-piperidone, N-phenyl-2-piperidone, etc.;N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam, as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), and tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione , N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophene, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. Modification with the above compounds (modifiers) can be carried out by known methods.

[0077] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, Versalis Inc., etc. may be used. The SBR may be used alone or in combination of two or more kinds.

[0078] (b) BR The tread rubber composition may further contain BR as necessary. In this case, the content of BR in 100 parts by mass of the rubber component is, for example, preferably more than 5 parts by mass, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more. On the other hand, it is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, even more preferably less than 35 parts by mass, and particularly preferably less than 30 parts by mass.

[0079] The weight average molecular weight of the BR is, for example, more than 100,000 and less than 2,000,000. The vinyl bond amount of the BR is, for example, more than 1 mass% and less than 30 mass%. The cis amount of the BR is, for example, more than 1 mass% and less than 98 mass%. The trans amount of the BR is, for example, more than 1 mass% and less than 60 mass%.

[0080] The BR is not particularly limited, and BR with a high cis content (cis content of 90% or more), BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. can be used. The BR may be either unmodified BR or modified BR, and the modified BR may be modified BR into which the above-mentioned functional groups have been introduced. These may be used alone or in combination of two or more. The cis content can be measured by infrared absorption spectroscopy.

[0081] As the modified BR, for example, tin-modified BR can be used. The tin-modified BR is preferably obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and the terminals of the tin-modified BR molecule are preferably bonded with a tin-carbon bond.

[0082] Examples of the lithium initiator include lithium-based compounds such as alkyl lithium, aryl lithium, vinyl lithium, organotin lithium, and organonitrogen lithium compounds, as well as lithium metal, etc. By using the lithium initiator as the initiator of the tin-modified BR, it is possible to prepare a tin-modified BR having a high vinyl and low cis content.

[0083] Examples of tin compounds include tin tetrachloride, butyltin trichloride, dibutyltin dichloride, dioctyltin dichloride, tributyltin chloride, triphenyltin chloride, diphenyldibutyltin, triphenyltin ethoxide, diphenyldimethyltin, ditolyltin chloride, diphenyltin dioctanoate, divinyldiethyltin, tetrabenzyltin, dibutyltin distearate, tetraallyltin, and p-tributyltin styrene.

[0084] The content of tin atoms in the tin-modified BR is preferably 50 ppm or more, more preferably 60 ppm or more, while it is preferably 3000 ppm or less, more preferably 2500 ppm or less, and even more preferably 250 ppm or less.

[0085] The molecular weight distribution (Mw / Mn) of the tin-modified BR is preferably 2 or less, and more preferably 1.5 or less.

[0086] The vinyl bond content in the tin-modified BR is preferably 5% by mass or more, more preferably 7% by mass or more, while the vinyl bond content in the tin-modified BR is preferably 50% by mass or less, more preferably 20% by mass or less.

[0087] The above-mentioned S-modified BR and tin-modified BR may be used alone or in combination of two or more kinds.

[0088] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, etc. can be used.

[0089] (c) Isoprene rubber The tread rubber composition may further contain an isoprene-based rubber as required. In this case, the content of the isoprene-based rubber in 100 parts by mass of the rubber component is, for example, preferably more than 3 parts by mass, more preferably 5 parts by mass or more. On the other hand, it is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, and even more preferably less than 30 parts by mass.

[0090] Examples of isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR, with NR being preferred from the standpoint of excellent strength.

[0091] As the NR, for example, SIR20, RSS♯3, TSR20, etc., which are common in the tire industry, can be used. As the IR, there is no particular limitation, and for example, IR2200, etc., which are common in the tire industry can be used. As the modified NR, deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), etc. can be used. As the modified NR, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. can be used. As the modified IR, epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. can be used. These may be used alone or in combination of two or more kinds.

[0092] (D) Other rubber components Furthermore, as other rubber components, rubber (polymer) that is generally used in the manufacture of tires, such as nitrile rubber (NBR), may be included as necessary.

[0093] (b) Compounding materials other than rubber components (a) Filler In this embodiment, the tread rubber composition preferably contains a filler. Specific examples of the filler include carbon black, silica, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. Among these, silica is preferably used as a reinforcing agent, and in this case, it is preferable to use it in combination with a silane coupling agent. It is also preferable to use carbon black as a reinforcing agent as necessary.

[0094] (i) Silica The tread rubber composition preferably contains silica. From the viewpoint of obtaining good durability, the BET specific surface area of ​​the silica is 140 m 2 / g, and preferably more than 160m 2 On the other hand, from the viewpoint of obtaining a good low rolling resistance, it is more preferable that the rolling resistance is more than 250 m 2 / g, and preferably less than 220m 2It is more preferable that the BET specific surface area is less than N2SA / g. The BET specific surface area is the value of N2SA measured by the BET method in accordance with ASTM D3037-93.

[0095] The amount of silica per 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, while it is preferably 100 parts by mass or less, more preferably 85 parts by mass or less, and even more preferably 70 parts by mass or less.

[0096] Examples of silica include dry silica (anhydrous silica) and wet silica (hydrated silica). Among them, wet silica is preferred because it has a large number of silanol groups. The silica is not particularly limited, and may be made from silicon tetrachloride, sodium silicate, or rice husk ash.

[0097] Commercially available products that can be used include those manufactured by Degussa, Rhodia, Tosoh Silica, Solvay Japan, and Tokuyama.

[0098] (ii) Silane coupling agent As described above, when using silica, it is preferable to use a silane coupling agent in combination. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl silane, and the like. Examples of the silane include sulfide-based silanes such as rubamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide, mercapto-based silanes such as 3-mercaptopropyl trimethoxysilane, 2-mercaptoethyl triethoxysilane, and NXT and NXT-Z manufactured by Momentive, vinyl-based silanes such as vinyl triethoxysilane and vinyl trimethoxysilane, amino-based silanes such as 3-aminopropyl triethoxysilane and 3-aminopropyl trimethoxysilane, glycidoxy-based silanes such as γ-glycidoxypropyl triethoxysilane and γ-glycidoxypropyl trimethoxysilane, nitro-based silanes such as 3-nitropropyl trimethoxysilane and 3-nitropropyl triethoxysilane, and chloro-based silanes such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane. These may be used alone or in combination of two or more.

[0099] As the silane coupling agent, for example, products available from Degussa, Momentive, Shin-Etsu Silicones, Tokyo Chemical Industry, Azumax, Dow Corning Toray, etc. can be used.

[0100] The content of the silane coupling agent is, for example, preferably more than 3 parts by mass, more preferably more than 5 parts by mass, and even more preferably more than 7 parts by mass, relative to 100 parts by mass of silica, while it is preferably less than 17 parts by mass, more preferably less than 15 parts by mass, and even more preferably less than 13 parts by mass.

[0101] (iii) Carbon black The tread rubber composition preferably contains carbon black as necessary. The content of carbon black is, for example, preferably 3 parts by mass or more, more preferably 4 parts by mass or more, based on 100 parts by mass of the rubber component. On the other hand, it is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 15 parts by mass or less.

[0102] The carbon black is not particularly limited, and examples thereof include furnace blacks (furnace carbon blacks) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene blacks (acetylene carbon blacks); thermal blacks (thermal carbon blacks) such as FT and MT; channel blacks (channel carbon blacks) such as EPC, MPC, and CC. These may be used alone or in combination of two or more.

[0103] The nitrogen adsorption specific surface area (N2SA) of carbon black is, for example, 30m 2 / g, 250m 2 The carbon black has a dibutyl phthalate (DBP) absorption of, for example, more than 50 ml / 100 g and less than 250 ml / 100 g. The nitrogen adsorption specific surface area of ​​the carbon black is measured according to ASTM D4820-93, and the DBP absorption is measured according to ASTM D2414-93.

[0104] Specific carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone or in combination of two or more kinds.

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

[0106] (b) Hardening resin component The tread rubber composition may contain a curable resin component such as a modified resorcinol resin or a modified phenolic resin, as necessary. This is believed to increase the rigidity of the tread rubber composition and improve the low rolling resistance during high-speed driving.

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

[0108] The content of the curable resin component is, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, based on 100 parts by mass of the rubber component, from the viewpoint of sufficiently improving the complex modulus of elasticity, while it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, from the viewpoint of maintaining the breaking strength.

[0109] When using the modified resorcinol resin, it is preferable to contain a methylene donor as a curing agent. Examples of methylene donors include hexamethylenetetramine (HMT), hexamethoxymethylolmelamine (HMMM), and hexamethylolmelamine pentamethylether (HMMPME), and the like are preferably contained in an amount of, for example, 5 parts by mass or more, and about 15 parts by mass, per 100 parts by mass of the curable resin component. If the amount is too small, there is a risk that a sufficient complex modulus cannot be obtained. On the other hand, if the amount is too large, there is a risk that the viscosity of the rubber increases and the processability deteriorates.

[0110] As a specific example of the methylene donor, Sumikanol 507 manufactured by Taoka Chemical Co., Ltd. can be used.

[0111] (C) Plasticizer components The tread rubber composition may contain oil (including extender oil), liquid rubber, and a resin component as a plasticizer component to soften the rubber. The total content of the plasticizer components is preferably more than 2 parts by mass, and more preferably more than 10 parts by mass, relative to 100 parts by mass of the rubber component. On the other hand, it is preferably less than 40 parts by mass, and more preferably less than 30 parts by mass. The oil content includes the amount of oil contained in the rubber (oil-extended rubber). The resin component is different from the above-mentioned curable resin component and refers to a component that can be extracted from the vulcanized rubber with acetone.

[0112] (i) Oil Examples of oils include mineral oils (generally called process oils), vegetable oils, and mixtures thereof. Examples of mineral oils (process oils) that can be used include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more.

[0113] Specific examples of process oils (mineral oils) that can be used include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and the like.

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

[0115] Farnesene polymers are polymers obtained by polymerizing farnesene and contain structural units based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene).

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

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

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

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

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

[0121] (iii) Resin component The resin component also functions as a tackifier and may be solid or liquid at room temperature, and specific examples of the resin component include rosin resin, styrene resin, coumarone resin, terpene resin, C5 resin, C9 resin, C5C9 resin, acrylic resin, etc., and two or more of them may be used in combination. The content of the resin component is preferably more than 2 parts by mass and less than 45 parts by mass, and more preferably less than 30 parts by mass, based on 100 parts by mass of the rubber component.

[0122] Rosin-based resins are resins whose main component is rosin acid obtained by processing rosin. These rosin-based resins (rosins) can be classified according to whether they have been modified or not, and can be classified into unmodified rosin (unmodified rosin) and modified rosin (rosin derivatives). Examples of unmodified rosins include tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. Modified rosin is a modification of unmodified rosin, and examples of such modified rosin include rosin esters, unsaturated carboxylic acid modified rosin esters, unsaturated carboxylic acid modified rosin esters, rosin amide compounds, and rosin amine salts.

[0123] The styrene resin is a polymer using a styrene monomer as a constituent monomer, and examples thereof include polymers polymerized with a styrene monomer as the main component (50% by mass or more).Specific examples thereof include homopolymers obtained by polymerizing each of the styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more kinds of styrene monomers, and copolymers of a styrene monomer and another monomer that can be copolymerized therewith.

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

[0125] Among the coumarone resins, coumarone-indene resins are preferred. Coumarone-indene resins are resins that contain coumarone and indene as monomer components that constitute the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

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

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

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

[0129] Terpene resins include polyterpene, terpene phenol, and aromatic modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are (C5H8) n The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: Monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ), and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0130] Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin, which are made from the above-mentioned terpene compounds, as well as hydrogenated terpene resins obtained by hydrogenating the terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds, and resins obtained by hydrogenating the above-mentioned resins, and specifically include resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. Examples of phenolic compounds include, for example, phenol, bisphenol A, cresol, and xylenol. Examples of aromatic modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the above-mentioned resins. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenolic compounds such as phenol, alkylphenols, alkoxyphenols, and phenols containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthols, alkoxynaphthols, and naphthols containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrenes, alkoxystyrenes, and styrenes containing an unsaturated hydrocarbon group; coumarone, indene, and the like.

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

[0132] The term "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a resin obtained by hydrogenating or modifying the resin. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of suitable resins include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins. As aromatic vinyl resins, homopolymers of α-methylstyrene or styrene or copolymers of α-methylstyrene and styrene are preferred, and copolymers of α-methylstyrene and styrene are more preferred, because they are economical, easy to process, and have excellent heat generation properties. As aromatic vinyl resins, for example, those commercially available from Kraton, Eastman Chemical, etc. can be used.

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

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

[0135] Examples of the solvent-free acrylic resin include (meth)acrylic resins (polymers) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization) (methods described in U.S. Pat. No. 4,414,370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, U.S. Pat. No. 5,010,166, and Toa Gosei Kenkyuu Nenpo TREND 2000 Vol. 3, p. 42-45, etc.) using as little secondary raw material as possible, such as polymerization initiators, chain transfer agents, and organic solvents. In the present invention, (meth)acrylic means methacryl and acrylic.

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

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

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

[0139] Examples of the resin component that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JX Energy Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Co., Ltd.

[0140] (D) Anti-aging agents The tread rubber composition preferably contains an antioxidant. The content of the antioxidant is, for example, more than 1 part by mass and less than 10 parts by mass per 100 parts by mass of the rubber component.

[0141] Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. p-phenylenediamine-based antioxidants such as quinolinone, quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline, monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol, and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. These may be used alone or in combination of two or more.

[0142] As the antioxidant, for example, products available from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc. can be used.

[0143] (e) Stearic acid The tread rubber composition may contain stearic acid. The content of stearic acid is, for example, more than 0.5 parts by mass and less than 10.0 parts by mass with respect to 100 parts by mass of the rubber component. As the stearic acid, a conventionally known product can be used, for example, a product of NOF Corporation, NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. can be used.

[0144] (F) Zinc oxide The tread rubber composition may contain zinc oxide. The content of zinc oxide is, for example, more than 0.5 parts by mass and less than 15 parts by mass with respect to 100 parts by mass of the rubber component. As the zinc oxide, a conventionally known product can be used, for example, a product of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0145] (G) Crosslinking agents and vulcanization accelerators The tread rubber composition preferably contains a crosslinking agent such as sulfur, etc. The content of the crosslinking agent is, for example, more than 0.1 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0146] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. These may be used alone or in combination of two or more kinds.

[0147] As sulfur, for example, products from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanritsu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0148] Examples of crosslinking agents other than sulfur include vulcanizing agents containing sulfur atoms, such as Tackirol V200 manufactured by Taoka Chemical Co., Ltd., Duralink HTS (sodium 1,6-hexamethylenedithiosulfate dihydrate) manufactured by Flexsys, and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by LANXESS, as well as organic peroxides such as dicumyl peroxide.

[0149] The tread rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, more than 0.3 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0150] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more kinds.

[0151] (H) Others In addition to the above components, the tread rubber composition may further contain additives commonly used in the tire industry, such as processing aids such as fatty acid metal salts, carboxylate metal salts, organic peroxides, reversion (reversion) inhibitors, etc. The content of these additives is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0152] (2) Preparation of tread rubber composition The tread rubber composition is produced by a general method, for example, a manufacturing method including a base kneading step of kneading a rubber component with a filler such as silica or carbon black, and a finish kneading step of kneading the kneaded product obtained in the base kneading step with a crosslinking agent.

[0153] The kneading can be carried out using a known (internal) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0154] The kneading temperature in the base kneading step is, for example, more than 50° C. and less than 200° C., and the kneading time is, for example, more than 30 seconds and less than 30 minutes. In the base kneading step, in addition to the above-mentioned components, compounding agents conventionally used in the rubber industry, for example, softeners such as oil, stearic acid, zinc oxide, antioxidants, waxes, vulcanization accelerators, etc., may be appropriately added and kneaded as necessary.

[0155] In the final kneading step, the kneaded product obtained in the base kneading step is kneaded with a crosslinking agent. The kneading temperature in the final kneading step is, for example, higher than room temperature and lower than 80° C., and the kneading time is, for example, longer than 1 minute and shorter than 15 minutes. In the final kneading step, in addition to the above components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added and kneaded as necessary.

[0156] (3) Manufacturing of tread The tread portion can be manufactured by molding the tread rubber composition obtained above into a predetermined shape. In the case of a multi-layer tread having a cap layer, a base layer, etc., the tread rubber composition is made to be the outermost layer.

[0157] 2. Manufacturing of belt components The belt member can be produced by topping both sides of reinforcing cords (monofilament cords such as steel cords) arranged in parallel at a predetermined interval (50 cords / 5 cm or more) with a known coating rubber composition.

[0158] 3. Tire manufacturing The tire according to the present embodiment can be produced as an unvulcanized tire by molding the tread portion and belt member obtained above together with other tire components in a tire building machine by a normal method.

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

[0160] In this embodiment, as described above, it is preferable that at least two belt layers are provided from the viewpoint of increasing the binding force on the tread during running and making it easier to suppress the growth of the outer diameter. In this case, it is preferable that the average distance D (mm) between each belt layer in the tread portion of the vulcanized tire is 0.6 mm or less. It is also preferable that the angle formed by the reinforcing cords of each belt layer in the tread portion in the tire circumferential direction is 65° or less.

[0161] The angle of the reinforcing cord is the angle of the reinforcing cord with respect to the circumferential direction of the tire when the tire is not filled with air, and can be confirmed by peeling off the tread portion from the radially outer side of the tire.

[0162] The unvulcanized tire thus produced is then heated and pressurized in a vulcanizer to obtain a tire. The vulcanization step can be carried out by applying a known vulcanization method. The vulcanization temperature is, for example, more than 120°C and less than 200°C, and the vulcanization time is, for example, more than 5 minutes and less than 15 minutes.

[0163] A tire is preferable because it has excellent low rolling resistance during high-speed running when mounted on a regular rim and the tire cross-sectional width Wt (mm) and tire outer diameter Dt (mm) satisfy the following formula when the internal pressure is set to 250 kPa. 1600≦(Dt 2 ×π / 4) / Wt≦2827.4

[0164] Specific examples of tires to which the present invention is preferably applied include tires with size notations such as 145 / 60R18, 145 / 60R19, 155 / 55R18, 155 / 55R19, 155 / 70R17, 155 / 70R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 185 / 55R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, 205 / 55R16, and 215 / 55R17.

[0165] In this embodiment, among tires classified into passenger car tires, truck and bus tires, motorcycle tires, etc., it is preferable to apply the present invention to passenger car tires, i.e., tires that are mounted on automobiles that run on four wheels and have a maximum load capacity of 1000 kg or less, and by satisfying (Equation 1), it can more appropriately contribute to solving the problem in the present invention of providing a pneumatic tire that has excellent handling stability and durability during high-speed driving.

[0166] The above-mentioned maximum load capacity is not particularly limited as long as it is 1000 kg or less. However, since an increase in the maximum load capacity generally leads to an increase in tire weight and a larger impact transmitted to the tire, it is preferable that the maximum load capacity be 900 kg or less, more preferably 800 kg or less, and even more preferably 700 kg or less.

[0167] Here, from the viewpoint of mitigating the impact transmitted to the tire, the tire weight is preferably 20 kg or less, more preferably 15 kg or less, and even more preferably 12 kg or less, 10 kg or less, or 8 kg or less. If a sponge, sealant, or the like is provided inside the tire, the weight of the entire tire including the weight of these is the tire weight WT. EXAMPLES

[0168] The present invention will now be described more specifically with reference to examples.

[0169] [Experiment 1] In this experiment, tires having a tire size of 185 / 65R16 were manufactured and evaluated.

[0170] 1. Production of tread rubber composition First, a tread rubber composition was produced.

[0171] (1) Compounding materials First, the following blended materials were prepared.

[0172] (a) Rubber component (a) NR:TSR20 (b) SBR: Versalis C2525 (solution polymerization SBR) (styrene content: 26% by mass, vinyl bond content: 24% by mass) (c) BR: UBEPOL BR150B manufactured by Ube Industries, Ltd. (Cis content: 97% by mass, Trans content: 2% by mass)

[0173] (b) Compounding materials other than rubber components (a) Carbon black: Show Black N220 manufactured by Cabot Japan Co., Ltd. (N2SA:111m 2 / g) (b) Silica: Ultrasil VN3 manufactured by Evonik (BET specific surface area: 165m 2 / g) (c) Silane coupling agent: Degussa Si69 (Bis(3-triethoxysilylpropyl)tetrasulfide) (d) Oil: H&R VIVATEC NC500 (aromatic process oil) (E) Resin: Terpene styrene resin TO125 manufactured by Yasuhara Chemical Co., Ltd. (Aromatic modified terpene resin) (f) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (G) Anti-aging agent-1: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) (H) Anti-aging agent-2: Antage RD manufactured by Kawaguchi Chemical Industry Co., Ltd. (2,2,4-trimethyl-1,2-dihydroquinoline) (R) Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. (J) Stearic acid: NOF Corp.'s "Tsubaki" stearic acid (K) Crosslinking agents and vulcanization accelerators Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator-1: Noccela CZ-G (CZ) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-cyclohexyl-2-benzothiazolyl sulfenamide) Vulcanization accelerator-2: Noccela D (DPG) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (1,3-Diphenylguanidine)

[0174] (2) Manufacturing of tread rubber composition According to the composition shown in Tables 1 and 2, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using a Banbury mixer to obtain a kneaded mixture. Each compounding amount is in parts by mass.

[0175] Next, sulfur and a vulcanization accelerator were added to the obtained kneaded mixture, and the mixture was kneaded for 5 minutes at 80° C. using an open roll to obtain a tread rubber composition.

[0176] (3) Preparation of the tread Next, the obtained tread rubber composition was molded into a predetermined shape to prepare a tread portion.

[0177] 2. Manufacturing of belt components A belt member was manufactured separately from the preparation of the tread portion. Specifically, steel cords having the configuration and outer diameter shown in Tables 1 and 2 were arranged in the ends (pieces / 5 cm) shown in Tables 1 and 2, and then a known belt layer rubber composition was coated on both sides of the arrangement so that the average distance D between the steel cords of the two belt layers was the distance shown in Tables 1 and 2, to prepare a two-layer belt member.

[0178] 3. Tire manufacturing Thereafter, two layers were laminated together to form a belt layer so that the steel cords in the belt member crossed each other at the angles shown in Tables 1 and 2, and this was laminated together with other tire components including the tread portion to form an unvulcanized tire. The tire was press-vulcanized for 10 minutes under a condition of 170°C to produce each test tire shown in Tables 1 and 2.

[0179] In addition, for each test tire, the above-mentioned (L 80 / L0) was 0.5, the total cross-sectional area of ​​the circumferential grooves was 22% of the cross-sectional area of ​​the tread, and the total volume of the lateral grooves, including those with a groove width / groove depth ratio of 0.65, was 3.5% of the volume of the tread.

[0180] 4. Calculation of parameters Then, the outer diameter Dt (mm), section width Wt (mm), and distance T (mm) from the outermost surface of the tread to the outermost surface of the belt layer of each test tire were measured, and the tire weight WT (kg) was also measured. From the measured outer diameter Dt and section width Wt, the virtual volume V (mm 3 ) was calculated, and further, the maximum load capacity WL (kg) was calculated from the calculated virtual volume V, and the ratio of WT to WL (WT / WL) was calculated. In addition, rubber was cut out from between the belt layers of each test tire to prepare a rubber test piece for viscoelasticity measurement with a length of 40 mm and a width of 4 mm. Using a GABO Iplexer series, tan δ was measured under the following conditions: temperature: 0°C, initial strain: 5%, dynamic strain rate ±0.25%, frequency: 10 Hz, deformation mode: tension, and (tan δ × T) and (tan δ × Wt) were calculated. The results are shown in Tables 1 and 2.

[0181] 5.Performance evaluation test (1) Evaluation of low rolling resistance during high-speed driving Each test tire was fitted to all wheels of a vehicle (a domestically produced FF vehicle with an engine displacement of 2000cc) and filled with air so that the internal pressure was 250kPa. The vehicle was then driven around a test course on a dry surface for 10km at a speed of 80km / h, after which the accelerator was released and the distance from when the accelerator was turned off until the vehicle came to a stop was measured.

[0182] Next, the results of Comparative Examples 1-8 were set as 100 and indexed according to the following formula to relatively evaluate low rolling resistance during high-speed driving. The larger the value, the longer the distance from when the accelerator was released until the vehicle stopped, the smaller the rolling resistance in the steady state, and the better the low rolling resistance during high-speed driving, which indicates excellent fuel economy. Low rolling resistance at high speeds = [(Test tire results) / (Comparative example 1-8 results)] x 100

[0183] (2) Evaluation of noise performance during high-speed driving Each test tire was fitted to all wheels of a vehicle (a domestically produced FF vehicle with an engine displacement of 2000cc) and air was inflated so that the internal pressure in the front wheels was 230kPa and the internal pressure in the rear wheels was 220kPa. The vehicle was then driven on a test course with a dry surface at a speed of 60km / h while the driver sat by the window and performed a sensory test on noise on a 5-point scale.

[0184] The evaluation was carried out by adding up the scores of the 20 drivers, indexing the total score of Comparative Examples 1 to 10 as 100, and then using the reciprocal of that index to evaluate the results. A larger value indicates that noise is reduced more, and that the noise performance during high-speed driving is excellent. Noise performance at high speeds = [(Evaluation score of Comparative Examples 1-10) / (Evaluation score of test tire)]×100

[0185] (3) Overall evaluation The results of the evaluations (1) and (2) above were summed up to determine the overall evaluation.

[0186] (4) Evaluation results The results of each evaluation are shown in Tables 1 and 2. In the tables, "1x1" indicates that the cord is a monofilament, and "1x2" indicates that it is a twisted wire made of two filaments twisted together.

[0187] [Table 1]

[0188] [Table 2]

[0189] [Experiment 2] In this experiment, tires having a tire size of 205 / 55R16 were manufactured and evaluated.

[0190] In the same manner as in Experiment 1, each test tire shown in Tables 3 and 4 was manufactured, and each parameter was determined in the same manner. Then, a performance evaluation test was conducted and evaluated in the same manner. The low rolling resistance during high-speed driving was evaluated by setting the result of Comparative Example 2-8 to 100, and the noise performance during high-speed driving was evaluated by setting the result of Comparative Example 2-10 to 100. The results of each evaluation are shown in Tables 3 and 4.

[0191] [Table 3]

[0192] [Table 4]

[0193] [Experiment 3] In this experiment, tires having a tire size of 215 / 55R17 were manufactured and evaluated.

[0194] In the same manner as in Experiment 1, each test tire shown in Tables 5 and 6 was manufactured, and each parameter was determined in the same manner. Then, a performance evaluation test was conducted and evaluated in the same manner. The low rolling resistance during high-speed driving was evaluated by setting the result of Comparative Example 3-8 to 100, and the noise performance during high-speed driving was evaluated by setting the result of Comparative Example 3-10 to 100. The results of each evaluation are shown in Tables 5 and 6.

[0195] [Table 5]

[0196] [Table 6]

[0197] The results of Experiments 1 to 3 (Tables 1 to 6) show that, regardless of the size of tires, when the reinforcing cords in the belt layer are configured with monofilament cords arranged at 50 cords / 5 cm or more and the above-mentioned (Equation 1) is satisfied, a pneumatic tire can be obtained that has sufficiently improved both low rolling resistance during high-speed driving and noise performance during high-speed driving.

[0198] Furthermore, it can be seen that by controlling the above-mentioned (Equation 2) and (Equation 3) and by appropriately controlling the outer diameter of the cord, it is possible to provide a pneumatic tire that has improved both low rolling resistance during high-speed driving and noise performance during high-speed driving.

[0199] Although the present invention has been described above based on the embodiment, the present invention is not limited to the above embodiment. Various modifications can be made to the above embodiment within the same and equivalent scope of the present invention.

Claims

1. A pneumatic tire having a belt layer and a tread portion, The tread portion is disposed on the outer side of the belt layer in the tire radial direction, The reinforcing cords in the belt layer are configured by arranging, in a radial cross section of the belt layer, 50 cords / 5 cm or more in the tire width direction at predetermined intervals, and A pneumatic tire characterized in that the maximum load capacity WL (kg) and the weight WT (kg) of the tire satisfy the following (Equation 1). 0.0145≦(WT / WL) (Formula 1) The "maximum load capacity WL of the tire" is a value calculated using the following two formulas based on the tire section width Wt (mm), tire section height Ht (mm), and tire outer diameter Dt (mm) when the tire is mounted on a regular rim, the internal pressure is set to 250 kPa, and there is no load. V (mm 3 ) = {(Dt / 2) 2 - (Dt / 2-Ht) 2}×π×Wt WL (kg) = 0.000011 x V + 100

2. 2. The pneumatic tire according to claim 1, wherein the following formula 2 is satisfied: 0.015≦(WT / WL)...(Formula 2)

3. 3. The pneumatic tire according to claim 1, wherein the cord made of the monofilament has an outer diameter of 0.1 mm or more and 0.5 mm or less.

4. The tread portion has a plurality of circumferential grooves extending continuously in a circumferential direction of the tire, 4. The pneumatic tire according to claim 1, wherein a total cross-sectional area of ​​the plurality of circumferential grooves is 10% or more and 30% or less of a cross-sectional area of ​​the tread portion.

5. The tread portion has a plurality of lateral grooves extending in an axial direction of the tire, 5. The pneumatic tire according to claim 1, wherein a total volume of the plurality of lateral grooves is 2.0% or more and 5.0% or less of a volume of the tread portion.

6. At least two belt layers are provided, In at least one pair of the belt layers adjacent in the tire radial direction, 6. The pneumatic tire according to claim 1, wherein an average distance D (mm) between the belt layers in the tread portion is 0.6 mm or less.

7. At least two belt layers are provided, In at least one pair of the belt layers adjacent in the tire radial direction, 7. The pneumatic tire according to claim 1, wherein an angle between the belt layers in the tread portion in the tire circumferential direction is 65 degrees or less.

8. The tread portion has a circumferential groove extending continuously in the tire circumferential direction, A groove width L of the circumferential groove at the ground contact surface of the tread portion ０ The groove width L at a depth of 80% of the maximum depth of the circumferential groove ８０ The ratio (L ８０ / L ０ 8. The pneumatic tire according to claim 1, wherein the ratio of the axial length of the tyre to the axial length of the tire is 0.3 or more and 0.7 or less.

9. 9. The pneumatic tire according to claim 1, wherein a tire cross-sectional width Wt (mm) is less than 200 mm.

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