Tire

Abstract

To provide a tire achieving both riding comfort and steering stability at the time of high-speed travelling.SOLUTION: A tire includes a cord-rubber composite. Tire weight (WT) of the tire is 20 kg or less. The cord-rubber composite includes an organic fiber cord, a topping rubber coating the organic fiber cord, and a short-fiber filler, where dispersion V of the short-fiber filler which is defined by a predetermined formula is 0.6 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a tire.

Background Art

[0002] Conventionally, in order to increase the strength of cellulose fibers used as carcass cords, by using cellulose fiber cords reinforced with carbon nanotubes (CNT), it has been proposed to achieve high durability of the carcass cords without increasing the carcass cord diameter or the number of cords driven in, and to improve the handling stability during high-speed driving (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when using a short fiber filler such as cellulose fiber together with an organic fiber cord, a method for quantitatively evaluating the orientation (degree) of the short fiber filler has not been established. For this reason, the influence exerted by the orientation of the short fiber filler has not been fully understood.

[0005] The present disclosure aims to provide a tire that achieves both ride comfort and handling stability during high-speed driving.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the inventors have found that in a tire having a cord-rubber composite and a weight of a predetermined value or less, when the cord-rubber composite includes an organic fiber cord, a topping rubber covering the organic fiber cord, and a short fiber filler, by setting the dispersion V of the short fiber filler defined by a predetermined formula to 0.6 or less, it is possible to achieve both ride comfort and handling stability during high-speed driving. Through further studies, the present disclosure has been completed.

[0007] That is, the present disclosure relates to the following tire.

[0008] A tire provided with a cord-rubber composite, wherein the tire has a tire weight (WT) of 20 kg or less, the cord-rubber composite includes an organic fiber cord, a topping rubber covering the organic fiber cord, and a short fiber filler, and the short fiber filler has a dispersion V defined below of 0.6 or less. V = 1 - R

Number

Advantages of the Invention

[0009] According to the present disclosure, it is possible to provide a tire that achieves both ride comfort and handling stability during high-speed driving.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0011] <Definition> "Tire weight" is represented by WT (kg). However, WT is the weight of the tire alone, excluding the weight of the rim. On the other hand, when the inner cavity of the tire is provided with a member made of sponge or sealant or a sensor member, etc., it is the weight including them.

[0012] "Regular rim" means the rim determined for each tire in the standard system including the standard on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it is the standard rim in the applicable size described in the "JATMA YEAR BOOK", in the case of ETRTO (The European Tyre and Rim Technical Organisation), it is the "Measuring Rim" described in the "STANDARDS MANUAL", and in the case of TRA (The Tire and Rim Association, Inc.), it is the "Design Rim" described in the "YEAR BOOK". And in the case of a tire not specified in the standard, it means the rim that can be assembled with the tire and can hold the internal pressure, that is, among the rims that do not cause air leakage between the rim / tire, the one with the smallest rim diameter and then the narrowest rim width.

[0013] "Normal internal pressure" refers to the air pressure defined for each tire in the standard system including the standards on which the tire is based. For JATMA, it is the "maximum air pressure"; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; for ETRTO, it is the "INFLATION PRESSURE". For tires not specified in the standards, the normal internal pressure is 250 kPa.

[0014] "Normal state" means that the tire is mounted on the normal rim and filled with the normal internal pressure, and moreover, it is in a no-load state. In this specification, unless otherwise specified, the dimensions of each part of the tire (such as the tire section width W, etc.) are measured in the above normal state.

[0015] "Maximum load capacity (W L )(kg)" is defined as follows when the tire section width measured in the normal state is W (mm), the tire outer diameter is Dt (mm), and the tire inner diameter is r (mm). However, the tire section width W is the maximum width between the outer surfaces of the sidewalls excluding patterns or characters etc. on the tire sidewall. W L =0.000011×VT + 100 [Here, VT is the virtual volume (mm 3 ) of the tire when a load of 250 kPa internal pressure is applied and is calculated by the following formula. VT ={(Dt 2 -r 2 ) / 4×π}×W Dt: Tire outer diameter (mm) r: Tire inner diameter (mm) π: Pi W: Tire section width (mm)]

[0016] "Tread ends Ti, To" refer to the outermost grounding positions when a normal load is applied to the tire in the normal state and it is grounded on a plane at a camber angle of 0 degrees. Tread end Ti represents the tread end that becomes the inner side of the vehicle when mounted on the vehicle, and tread end To represents the tread end that becomes the outer side of the vehicle.

[0017] The "tread width TW" is the distance in the tire width direction X (the left - right direction in FIGS. 2 to 4) between the tread edge To and the tread edge Ti.

[0018] The "land area" in the tread portion refers to the area partitioned by circumferential grooves that continuously extend in the tire circumferential direction between the tread edge To and the tread edge Ti. For example, when there are two circumferential grooves, the land area is divided into a pair of shoulder land areas and the center land area sandwiched therebetween. When there are three circumferential grooves, the center land area is further divided into the land area on the inner side of the vehicle and the land area on the outer side of the vehicle when the tire is mounted on the vehicle.

[0019] The "oil content" includes the amount of oil contained in the oil - extended rubber.

[0020] In this specification, when indicating a numerical range using "~", unless otherwise specified, the numerical values at both ends are included.

[0021] <Measurement method> The "styrene content" 1 is calculated by 1H - NMR measurement. For example, it is applicable to styrene - containing rubbers such as SBR.

[0022] The "vinyl content (amount of 1,2 - bonded butadiene units)" is measured by infrared absorption spectroscopy. For example, it is applicable to SBR.

[0023] The "cis 1,4 - bond content ratio" is a value calculated by infrared absorption spectroscopy analysis. For example, it is applicable to BR.

[0024] The "N2SA of carbon black" is measured in accordance with JIS K 6217 - 2 "Basic properties of carbon black for rubber - Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single - point method".

[0025] The "N2SA of silica" is measured by the BET method in accordance with ASTM D3037 - 93.

[0026] <Tire> The tire of the present disclosure will be described below.

[0027] The tire of the present disclosure is a tire provided with a cord-rubber composite, wherein the tire has a tire weight (WT) of 20 kg or less, and the cord-rubber composite includes an organic fiber cord, a topping rubber covering the organic fiber cord, and a short fiber filler, and the short fiber filler has a dispersion V defined by the above formula of 0.6 or less.

[0028] Although not intending to be bound by theory, the following may be considered as the mechanism by which the tire of the present disclosure can achieve both ride comfort and handling stability during high-speed driving.

[0029] That is, the tire according to the present disclosure is provided with a cord-rubber composite. Since the cord-rubber composite has the short fiber filler oriented, anisotropy in the stress distribution occurs in the material during deformation, and further anisotropy also occurs in the elastic modulus. Therefore, such a cord-rubber composite can exhibit a stronger tagging effect on the tire than in the past, and thus it is considered that excellent handling stability can be achieved even during high-speed driving with a large input. On the other hand, since the cord-rubber composite can move flexibly in the direction perpendicular to the orientation direction of the short fiber filler (tire radial direction), it is easy to obtain followability to the road surface. Therefore, it is considered that excellent ride comfort can also be exhibited.

[0030] However, if the compression of the tire on the ground contact surface becomes too large, the short fiber filler will partially receive strong tensile deformation, and good ride comfort and handling stability during high-speed driving cannot be obtained. Therefore, the tire weight is suppressed to 20 kg or less to reduce the influence of the weight of the tire itself. As a result, it is considered that the anisotropy of the stress distribution of the short fiber filler in the ground contact surface does not become excessive, and good ride comfort and handling stability during high-speed driving are not impaired.

[0031] As described above, the effects of the orientation of the short fiber filler in the cord-rubber composite and the effect of suppressing the tire weight combine to make it possible to achieve both handling stability and ride comfort during high-speed driving.

[0032] Conventionally, regarding a cord-rubber composite containing a short fiber filler, various factors such as the fiber diameter and fiber length of the short fiber filler, the length and size of the short fiber filler agglomerate, the blending amount of the short fiber filler, and the degree of orientation of the short fiber filler are considered to be related to the anisotropy of the elastic modulus and the strength, and a quantitative evaluation method has not been established. In the present disclosure, attention is paid to a short fiber filler agglomerate in which a plurality of short fiber fillers are aggregated, and in a cross section obtained by cutting the cord-rubber composite on a predetermined plane, the degree of orientation of the short fiber filler agglomerate is evaluated by a dispersion V obtained from a predetermined mathematical formula, and by controlling this, it has been found that the ride comfort and the handling stability during high-speed driving can be improved.

[0033] The tire preferably has a ratio (WT / W L ) of the tire weight (WT) to the maximum load capacity (W L ) defined below of 0.027 or less. W L =0.000011×VT + 100 [Here, VT is the virtual volume (mm 3 ) of the tire when a tire internal pressure of 250 kPa is applied and is calculated by the following formula. VT={(Dt 2 -r 2 ) / 4×π}×W Dt: Tire outer diameter (mm) r: Tire inner diameter (mm) π: Pi W: Tire cross-sectional width (mm)]

[0034] Generally, the higher the maximum load capacity, the heavier the tire tends to be, and it is considered that impact is more likely to be transmitted thereby. However, by making the tire weight with respect to the maximum load capacity satisfy the above relationship, the transmission of impact can be suppressed, and good ride comfort can be easily obtained. Further, by reducing the tire weight, the contribution of the short fiber-containing rubber cord composite in the tire increases, so it is considered that good handling stability during high-speed driving can also be easily obtained.

[0035] Regarding the short fiber filler mass, it is preferable that the average aspect ratio defined below is 3.0 or more for the tire. Average aspect ratio = (average value of the major axis of the short fiber filler mass) / (average value of the minor axis of the short fiber filler mass)

[0036] With such a configuration and by orienting, it is considered that anisotropy of the elastic modulus in the cord-rubber composite is likely to occur.

[0037] For the tire, it is preferable that the average of the angle (radian) formed by the length direction of the organic fiber cord and the orientation direction of each short fiber filler mass is π / 4 or less.

[0038] With such a configuration, as a result, the deviation of the angle between the orientation direction of the short fiber filler mass and the length direction of the organic fiber cord is suppressed, and it is considered that the effects of the present disclosure are likely to be exhibited.

[0039] It is preferable that the short fiber filler of the tire is at least one selected from the group consisting of cellulose nanofiber (CNF) and carbon nanotube (CNT).

[0040] It is considered that CNF and CNT are likely to exhibit the effects of the present disclosure as short fiber fillers.

[0041] It is preferable that the tire has a cross-sectional width W of 150 mm to 290 mm.

[0042] With such a configuration, it is considered that the effects of the present disclosure can be easily exhibited.

[0043] It is preferable that the tire uses the cord-rubber composite for the carcass.

[0044] With such a configuration, it is considered that the effects of the present disclosure can be easily exhibited.

[0045] It is preferable that the tire satisfies the following formula (1) for the tire outer diameter Dt and the tire cross-sectional width W. 1963.4 ≦ (Dt 2 × π / 4) / W ≦ 2827.4 (1)

[0046] By increasing the outer shape with respect to the cross-sectional width of the tire, it is considered that the inertia during rolling can be increased and the handling stability can be improved. At the same time, it is considered that the transmission of the impact from the tread portion can be reduced. And, by the cooperation of these and the reaction force in the orientation direction and the flexibility in the reverse orientation direction of the cord-rubber composite containing the short fiber filler, it is considered that good handling stability and riding comfort during high-speed driving can be easily obtained.

[0047] The tire includes a tread portion, the tread portion has a tread end To on the outer side of the vehicle and a tread end Ti on the inner side of the vehicle when mounted on the vehicle, and between the tread end To and the tread end Ti, two or more circumferential grooves continuously extending in the tire circumferential direction, a pair of shoulder land portions partitioned by a pair of outermost circumferential grooves located at the outermost ends in the tire width direction of the circumferential grooves, and one or more center land portions located between the pair of shoulder land portions. The pair of shoulder land portions and the one or more center land portions have a plurality of lateral grooves extending in the tire width direction. It is preferable that the lateral grooves of at least one of the pair of shoulder land portions reach the tread grounding end at one end and remain within the land portion without reaching the outermost circumferential groove at the other end.

[0048] Since one end of the lateral groove reaches the tread grounding end, shear deformation at the grounding end is likely to occur. Also, since the other end of the lateral groove stays within the land portion, reaction force is likely to be obtained, so it is considered that handling stability is likely to be obtained. And it is considered that by the cooperation of these and the reaction force in the orientation direction and the flexibility in the anti-orientation direction of the cord-rubber composite containing the short fiber filler, good handling stability and riding comfort during high-speed driving are likely to be obtained.

[0049] In the tire, among the one or more center land portions, it is preferable that the lateral groove of at least one center land portion has one end communicating with one of the two circumferential grooves defining the center land portion and the other end not reaching the other circumferential groove and staying within the land portion.

[0050] By adopting such a configuration, the pattern rigidity of the center land portion can be increased.

[0051] In the tire, the two circumferential grooves defining the center land portion are composed of a circumferential groove with a large distance from the tire center line and a circumferential groove with a small distance from the tire center line, and it is preferable that the circumferential groove with which the lateral groove communicates is the circumferential groove with a large distance from the tire center line.

[0052] It is considered that when the lateral groove communicates with the circumferential groove with a large distance from the tire center line, it is easier to generate a reaction force from the grounding center of the tire.

[0053] The tire is preferably a run-flat tire.

[0054] By adopting such a configuration, it is considered that the effects of the present disclosure are likely to be exhibited.

[0055] (Tire provided with a cord-rubber composite) The tire of the present disclosure is a tire provided with a cord-rubber composite. The cord-rubber composite includes an organic fiber cord, a topping rubber that coats the organic fiber cord, and a short fiber filler. Here, in the cord-rubber composite, the organic fiber cords are arranged in a certain direction. Also, a plurality of the short fiber fillers aggregate with each other to form a short fiber filler mass.

[0056] FIG. 1 is a cross-sectional view showing an embodiment of the tire of the present disclosure. In FIG. 1, the tire 1 of the present disclosure is a run-flat tire and includes a tread portion 2, a sidewall portion 3, a breaker 4, a carcass 5, an inner liner 6, a side reinforcing rubber 7, a bead portion 8, and a clinch 9.

[0057] In the tire of the present disclosure, the use of the cord-rubber composite can be used as a member including an organic fiber cord and a topping rubber that coats the cord without being particularly limited. More specifically, for example, it can be used for a breaker or a carcass, and among these, it is preferably used for a carcass.

[0058] (Tire weight) The weight WT (kg) of the tire of the present disclosure is 20 kg or less. When the tire weight exceeds 20 kg, the volume of the tire increases, and the compression of the tire on the ground surface tends to become too large, and the short fiber filler is partially subjected to strong tensile deformation. For this reason, good ride comfort and handling stability during high-speed driving cannot be obtained. The tire weight is preferably 19 kg or less, more preferably 18 kg or less, still more preferably 17 kg or less, and still more preferably 16 kg or less. There is no particular limitation on the lower limit of the tire weight WT, but for example, a tire of about 8 kg may be used.

[0059] (Organic fiber cord) The organic fiber cord used for the cord-rubber composite of the present disclosure refers to one obtained by twisting one or more filament yarns. For example, a cord commonly used as a reinforcing material in the tire industry can be used.

[0060] Organic fiber cord d Examples of the types of organic fibers used include, for example, polyester fibers such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); nylon fibers; rayon fibers; vinylon fibers; aramid fibers; and polyurethane fibers. One or more types of organic fibers can be used.

[0061] Among these organic fibers, from the perspective of the effects of the present disclosure, it is preferable to use polyester fibers such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and rayon fibers. Among them, it is particularly preferable to use rayon fibers.

[0062] Examples of cords made of polyester fibers (polyester cords) include, for example, i) combining two or three 1100 dtex multifilaments each (in other words, 1100 / 2 dtex or 1100 / 3 dtex), applying a twist of 10 to 60 turns / 10 cm, and then combining two of these lower-twisted cords and applying the same number of upper twists in the opposite direction to the lower twist, or ii) combining two 1670 dtex multifilaments each (in other words, 1670 / 2 dtex), applying a twist of 20 to 50 turns / 10 cm, and then combining two of these lower-twisted cords and applying the same number of upper twists in the opposite direction to the lower twist, which can be used.

[0063] Examples of cords made of nylon fibers (nylon cords) include, for example, i) combining two 940 dtex multifilaments each (in other words, 940 / 2 dtex), applying a twist of 31 to 48 turns / 10 cm, and then combining two of these lower-twisted cords and applying the same number of upper twists in the opposite direction to the lower twist (with an intermediate elongation of 8.80% when a constant load of 44 N is applied), or ii) combining two 1400 dtex multifilaments each (in other words, 1400 / 2 dtex), applying a twist of 30 to 51 turns / 10 cm, and then combining two of these lower-twisted cords and applying the same number of upper twists in the opposite direction to the lower twist (with an intermediate elongation of 8.80% when a constant load of 66 N is applied), which can be used.

[0064] As the rayon cord (rayon cord) made of rayon fiber, for example, multifilaments of 1840 decitex are combined in two (in other words, 1840 / 2 decitex), after applying a twist of 20 to 50 times / 10 cm, two of these lower-twist cords are combined and the same number of upper twists are applied in the opposite direction to the lower twist (intermediate elongation of 4.80% when applying a constant load of 44 N) can be used.

[0065] As the aramid cord (aramid cord) made of aramid fiber, for example, aromatic polyamide multifilaments of 1670 decitex (Kevlar manufactured by DuPont) are combined in two or three (in other words, 1670 / 2 decitex, or 1670 / 3 decitex), after applying a twist of 30 to 78 times / 10 cm, two of these lower-twist cords are combined and the same number of upper twists are applied in the opposite direction to the lower twist (intermediate elongation of 0.7 to 1.5% when applying a constant load of 44 N) can be used.

[0066] As the cord made of polyester fiber and nylon fiber (polyester-nylon hybrid cord), for example, polyester multifilaments of 1440 decitex and nylon multifilaments of 1440 decitex are combined in two (in other words, 1440-P / 1400-N decitex), after applying a twist of 30 to 38 times / 10 cm, two of these lower-twist cords are combined and the same number of upper twists are applied in the opposite direction to the lower twist (intermediate elongation of 4.40% when applying a constant load of 44 N, intermediate elongation of 6.30% when applying a constant load of 66 N) can be used.

[0067] As the cord made of aramid fiber and nylon fiber (aramid-nylon hybrid cord), for example, aramid multifilaments of 1100 decitex and nylon multifilaments of 940 decitex are combined in two (in other words, 1100-K / 940-N decitex), after applying a twist of 42 times / 10 cm, two of these lower-twist cords are combined and the same number of upper twists are applied in the opposite direction to the lower twist (intermediate elongation of 3.60% when applying a constant load of 44 N) can be used.

[0068] (Topping rubber) In the cord-rubber composite of the present disclosure, the rubber composition used for the topping rubber that coats the organic fiber cord (rubber composition for topping rubber) is not particularly limited as long as it is commonly used in the rubber industry.

[0069] ≪Rubber component≫ As the rubber component, isoprene rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), etc. can be used. Among these, SBR and isoprene rubber are preferable because of their excellent mechanical strength, anti-reversion property, heat resistance, and crack growth resistance. One or more rubber components can be used.

[0070] As the isoprene rubber, for example, those commonly used in the tire industry such as isoprene rubber (IR) and natural rubber can be used. Natural rubber includes, in addition to non-modified natural rubber (NR), modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene rubbers may be used alone or in combination of two or more. NR is not particularly limited, and those commonly used in the tire industry can be used, for example, SIR20, RSS#3, TSR20, etc.

[0071] From the viewpoint of the present disclosure, the content of the isoprene rubber in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and may be 100% by mass.

[0072] The SBR is not particularly limited, and examples thereof include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Examples of the modified SBR include SBRs with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Among them, S-SBR and modified SBR are preferred. Furthermore, hydrogenated products of these SBRs (hydrogenated SBR) can also be used. These SBRs may be used alone or in combination of two or more. Examples of the S-SBR that can be used in the present disclosure include S-SBRs manufactured and sold by JSR Corporation, Sumitomo Chemical Company, Limited, Ube Industries, Ltd., Asahi Kasei Corporation, ZS Elastomer Co., Ltd., etc.

[0073] From the viewpoints of wet grip performance and abrasion resistance performance, the styrene content of the SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more. Also, from the viewpoints of the temperature dependence of the grip performance and the blow resistance performance, it is preferably 60% by mass or less, and from the viewpoint of the effects of the present disclosure, it is preferably 35% by mass or less, and more preferably 30% by mass or less. The styrene content of the SBR is measured by the above measurement method.

[0074] From the viewpoints of ensuring reactivity with silica, wet grip performance, rubber strength, and abrasion resistance performance, the vinyl content of the SBR is preferably 10 mol% or more, more preferably 15 mol% or more, and still more preferably 20 mol% or more. Also, from the viewpoints of preventing an increase in temperature dependence, elongation at break, and abrasion resistance performance, the vinyl content of the SBR is preferably 70 mol% or less, more preferably 65 mol% or less, and still more preferably 60 mol% or less. The vinyl content of the SBR is measured by the above measurement method.

[0075] From the viewpoint of the effects of the present disclosure, the content in 100% by mass of the rubber component when containing SBR is preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably 50% by mass or more. Also, the content of SBR is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass or less.

[0076] The BR is not particularly limited. For example, BR with a cis-1,4 bond content (cis content) of less than 50% (low-cis BR), BR with a cis-1,4 bond content of 90% or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element-based catalyst (rare-earth-based BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. These BRs may be used alone or in combination of two or more. The cis-1,4 bond content of BR is measured by the above-mentioned measurement method. As the modified BR, it can be obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and furthermore, the terminal of the modified BR molecule is bonded by a tin-carbon bond (tin-modified BR), or a butadiene rubber having a condensed alkoxysilane compound at the active terminal of the butadiene rubber (modified BR for silica), etc. Examples of such modified BRs include tin-modified BR and modified BR for silica manufactured and sold by, for example, ZS Elastomer Co., Ltd.

[0077] From the viewpoint of the effects of the present disclosure, the content of BR in 100% by mass of the rubber component when containing BR is preferably 3% by mass or more, more preferably 5% by mass or more, and still more preferably 10% by mass or more. Also, the content of BR is preferably 40% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less.

[0078] As the rubber component according to the present disclosure, a rubber component other than the above-mentioned isoprene rubber, SBR, and BR may be contained. As other rubber components, crosslinkable rubber components generally used in the tire industry can be used. For example, styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. can be mentioned. These other rubber components may be used alone or in combination of two or more. The content of other rubber components in the rubber component may be 0% by mass.

[0079] ≪Filler≫ The rubber composition according to the present disclosure can contain a filler. Examples of the filler include carbon black, silica, etc. One or more fillers can be used.

[0080] As carbon black, those common in the tire industry can be appropriately used. For example, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. can be mentioned. These carbon blacks may be used alone or in combination of two or more.

[0081] From the viewpoint of reinforcing property, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 80 m 2 / g or more, more preferably 90 m 2 / g or more, and even more preferably 100 m 2 / g or more. Also, from the viewpoints of low fuel consumption performance and processability, N2SA is preferably 200 m 2 / g or less, more preferably 170 m 2 / g or less, and even more preferably 155 m 2 / g or less. The N2SA of carbon black is measured by the above measurement method.

[0082] When containing carbon black, the content relative to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more from the viewpoints of wear resistance performance and wet grip performance. Further, from the viewpoint of low fuel consumption performance, it is preferably 60 parts by mass or less, more preferably 55 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 10 parts by mass or less.

[0083] The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. Among them, hydrous silica prepared by a wet method is preferable because of having many silanol groups. These silicas may be used alone or in combination of two or more.

[0084] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 140 m 2 / g or more, and more preferably 170 m 2 / g or more from the viewpoints of low fuel consumption performance and wear resistance performance. Further, from the viewpoints of low fuel consumption performance and processability, it is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, and still more preferably 250 m 2 / g or less. The N2SA of the silica is measured by the above measurement method.

[0085] When containing silica, the content relative to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more from the viewpoint of wet grip performance. Further, from the viewpoint of wear resistance performance, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 40 parts by mass or less.

[0086] As the filler, in addition to carbon black and silica, other fillers may be further used. Such fillers are not particularly limited, and for example, any fillers generally used in this field such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, etc. can be used. These fillers may be used alone or in combination of two or more.

[0087] ≪Silane coupling agent≫ Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and in the tire industry, any silane coupling agent conventionally used in combination with silica can be used. For example, mercapto-based silane coupling agents; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane, etc. Among them, sulfide-based silane coupling agents and mercapto-based silane coupling agents are preferred. These silane coupling agents may be used alone or in combination of two or more.

[0088] The content of the silane coupling agent relative to 100 parts by mass of silica (when a plurality of silane coupling agents are used in combination, the total amount of all) is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more from the viewpoint of enhancing the dispersibility of silica. Further, from the viewpoints of cost and processability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less.

[0089] ≪Other compounding agents≫ In addition to the above components, the rubber composition according to the present disclosure may appropriately contain compounding agents generally used in the conventional tire industry, such as softeners, waxes, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, vulcanization accelerators, and the like.

[0090] Examples of the softener include oils, liquid rubbers, ester plasticizers, resins, and the like. The softener may be used alone or in combination of two or more.

[0091] Examples of the oil include process oils, vegetable oils, animal oils, and the like. Examples of the process oil include paraffinic process oils, naphthenic process oils, aromatic process oils, and the like. Further, a process oil having a low content of polycyclic aromatic compounds (PCA) can also be used for environmental measures. Examples of the low-PCA-content process oil include mildly extracted solvent naphthenes (MES), treated distillate aromatic extracts (TDAE), heavy naphthenic oils, and the like. The oil may be used alone or in combination of two or more.

[0092] When the oil is contained, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more from the viewpoint of processability. Further, from the viewpoint of wear resistance performance, it is preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less.

[0093] The liquid rubber is not particularly limited as long as it is a polymer in a liquid state at normal temperature (25°C). For example, 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. may be mentioned. The liquid rubber may be used alone or in combination of two or more.

[0094] When containing the liquid rubber, the content based on 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more. Also, the content of the liquid rubber is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 10 parts by mass or less.

[0095] Examples of the ester plasticizer include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), bis(2-ethylhexyl) azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), etc. The ester plasticizer may be used alone or in combination of two or more.

[0096] When containing the ester plasticizer, the content based on 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more. Also, the content of the ester plasticizer is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 10 parts by mass or less.

[0097] The resin is not particularly limited, and examples thereof include C9-based petroleum resins, C5C9-based petroleum resins, alkylphenol resins, coumarone resins, terpene resins, rosin resins, etc., which are commonly used in the tire industry. The resin may be used alone or in combination of two or more kinds.

[0098] The content of the softener with respect to 100 parts by mass of the rubber component (when a plurality of softeners are used in combination, the total amount of all) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 parts by mass or more from the viewpoint of wet grip performance. Also, from the viewpoint of processability, it is more preferably 100 parts by mass or less, further preferably 50 parts by mass or less, and still further preferably 25 parts by mass or less.

[0099] When wax is contained, the content with respect 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 from the viewpoint of the weather resistance of the rubber. Also, from the viewpoint of preventing the whitening of the tire due to blooming, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0100] Examples of the processing aid include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. These processing aids may be used alone or in combination of two or more kinds. As the processing aid, for example, those commercially available from Schill+Seilacher, Performance Additives, etc. can be used.

[0101] When the processing aid is contained, the content with respect 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 from the viewpoint of exerting the effect of improving processability. Also, from the viewpoints of abrasion resistance and breaking strength, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less.

[0102] Although the anti-aging agent is not particularly limited, examples thereof include anti-aging agents such as amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, and metal carbamates. Phenylenediamine-based anti-aging agents such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and quinoline-based anti-aging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These anti-aging agents may be used alone or in combination of two or more.

[0103] From the viewpoint of ozone crack resistance of the rubber, the content of the anti-aging agent relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, and more preferably 1 part by mass or more when contained. From the viewpoints of abrasion resistance and wet grip performance, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0104] From the viewpoint of processability, the content of stearic acid relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, and more preferably 1 part by mass or more when contained. From the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0105] From the viewpoint of processability, the content of zinc oxide relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, and more preferably 1 part by mass or more when contained. From the viewpoint of abrasion resistance, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0106] Sulfur is preferably used as the vulcanizing agent. As sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. can be used.

[0107] When sulfur is contained as a vulcanizing agent, the content relative to 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and still more preferably 0.5 part by mass or more from the viewpoint of ensuring a sufficient vulcanization reaction. Further, from the viewpoint of deterioration prevention, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and still more preferably 3.0 parts by mass or less. In addition, when oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is the total content of the pure sulfur component contained in the oil-containing sulfur.

[0108] Examples of vulcanizing agents other than sulfur include alkylphenol sulfur chloride condensates, sodium 1,6-hexamethylene-dithiolsulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, and the like. As these vulcanizing agents other than sulfur, those commercially available from companies such as Taoka Chemical Industry Co., Ltd., Rhenus Co., Ltd., and Flexsys can be used.

[0109] Examples of vulcanization accelerators include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, or xanthate-based vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. Among them, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based, and thiazole-based vulcanization accelerators are preferable.

[0110] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), and the like. Among them, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferable.

[0111] Examples of the guanidine-based vulcanization accelerator include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, and the like. Among them, 1,3-diphenylguanidine (DPG) is preferred.

[0112] Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, and the like. Among them, 2-mercaptobenzothiazole is preferred.

[0113] When the vulcanization accelerator is contained, the content with respect to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more. Also, the content of the vulcanization accelerator with respect to 100 parts by mass of the rubber component is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, the breaking strength and elongation tend to be ensured.

[0114] (Short fiber filler) The cord-rubber composite of the present disclosure contains a short fiber filler. The short fiber filler may be contained in a form that can contribute to the anisotropy and strength of the cord-rubber composite. For example, the short fiber filler may be contained in the rubber composition that forms the topping rubber, or may be contained in a form of covering the organic fiber cord.

[0115] Any of the short fiber fillers commonly used in the tire industry can be used. Examples of such short fiber fillers include cellulose fibers such as nylon fibers, rayon fibers, aramid fibers, polyethylene naphthalate fibers, polyester fibers, and cellulose nanofibers, and nanocarbon materials such as carbon nanotubes. One or more short fiber fillers can be used. Among these, cellulose fibers and nanocarbon materials are preferred, and cellulose nanofibers (CNF) and carbon nanotubes (CNT) are particularly preferred.

[0116] From the viewpoint of the strength of the cord-rubber composite, the average length of the short fiber filler is preferably 0.2 μm or more, more preferably 0.5 μm or more, still more preferably 1.0 μm or more, and even more preferably 2.0 μm or more. On the other hand, from the viewpoint of dispersibility in the matrix, the average length of the short fiber filler is preferably 20.0 μm or less, more preferably 15.0 μm or less, still more preferably 10.0 μm or less. From the viewpoint of the strength of the cord-rubber composite, the average diameter (width) of the short fiber filler is preferably 1 nm or more, more preferably 2 nm or more, still more preferably 3 nm or more, and even more preferably 5 nm or more. On the other hand, from the viewpoint of dispersibility in the matrix, the average diameter (width) of the short fiber filler is preferably 300 nm or less, more preferably 270 nm or less, still more preferably 240 nm or less, and even more preferably 210 nm or less. The average length and average diameter of the short fiber filler can be determined as the average value of any 100.

[0117] From the viewpoint of the strength of the cord-rubber composite, the aspect ratio of the short fiber filler is preferably 3 or more, more preferably 5 or more, still more preferably 10 or more. On the other hand, from the viewpoint of dispersibility in the matrix, the aspect ratio of the short fiber filler is preferably 2000 or less, more preferably 1700 or less, still more preferably 1500 or less, and even more preferably 1300 or less. The aspect ratio of the short fiber filler is a value obtained as the ratio of the average length to the average diameter.

[0118] From the viewpoint of the strength of the cord-rubber composite, the content of the short fiber filler is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more with respect to 100 parts by mass of the topping rubber. On the other hand, from the viewpoint of the adhesiveness between the organic fiber cord and the topping rubber, the content of the short fiber filler is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 40 parts by mass or less.

[0119] (Short fiber filler mass) In the cord-rubber composite, a plurality of short fiber fillers aggregate with each other to form short fiber filler masses. From the viewpoint of the effects of the present disclosure, the average value of the major axis lengths of the short fiber filler masses is preferably 1.0 μm or more, more preferably 3.0 μm or more, and still more preferably 5.0 μm or more. On the other hand, from the viewpoint of the effects of the present disclosure, the average value of the major axis lengths of the short fiber filler masses is preferably 100.0 μm or less, more preferably 50.0 μm or less, and still more preferably 20.0 μm or less. Also, from the viewpoint of the effects of the present disclosure, the average value of the minor axis lengths of the short fiber filler masses is preferably 0.1 μm or more, more preferably 1.0 μm or more, and still more preferably 2.0 μm or more. On the other hand, from the viewpoint of the effects of the present disclosure, the average value of the minor axis lengths of the short fiber filler masses is preferably 50.0 μm or less, more preferably 30.0 μm or less, and still more preferably 10.0 μm or less. Here, for each short fiber filler mass, the "major axis" refers to the diameter with the maximum diameter in the electron microscope image of the observation surface cut out from the cord-rubber composite, and the average value is the arithmetic mean of them. On the other hand, the "minor axis" refers to the maximum diameter in the direction perpendicular to the major axis, and the average value is the arithmetic mean of them. The cutting out of the observation surface is performed on a plane parallel to either the length direction of the cord for the organic fiber cord or the width direction of the cord arrangement. The average value of the major axis and the average value of the minor axis of the short fiber filler masses can be obtained as the average values of N short fiber filler masses included in the range of the following "reference area".

[0120] From the perspective of the effects of the present disclosure, the average aspect ratio of the short fiber filler agglomerates defined below is preferably 1.5 or more, more preferably 1.8 or more, and even more preferably 2.0 or more. From the perspective of the effects of the present disclosure, the average aspect ratio is preferably 20.0 or less, more preferably 10.0 or less, and even more preferably 5.0 or less. Average aspect ratio = (average value of the major axis of the short fiber filler agglomerates) / (average value of the minor axis of the short fiber filler agglomerates)

[0121] The direction of the major axis of the short fiber filler agglomerate is referred to as the "orientation direction" of the short fiber filler agglomerate. The angle (θ, a value in the range of 0 to π (radians)) formed by the orientation direction of each short fiber filler agglomerate and the length direction of the organic fiber cord is preferably such that its average is π / 4 or less, more preferably π / 5 or less, and even more preferably π / 6 or less, from the perspective of the effects of the present disclosure. The smaller the θ, the more preferable it is, and it is more preferable that the short fiber filler agglomerate is oriented in the length direction of the organic fiber cord (θ = 0).

[0122] (Dispersion V of the short fiber filler agglomerates) The dispersion V of the short fiber filler agglomerates is a value defined by the following formula based on the θ. In the present disclosure, from the perspective of its effects, the dispersion V is 0.6 or less. The dispersion V is preferably 0.5 or less, more preferably 0.4 or less, even more preferably 0.3 or less, and even more preferably 0.25 or less. V = 1 - R

Number

[0123] The "range of the reference area" is not particularly limited as long as the value of N is sufficient for calculating the dispersion V of the short fiber filler agglomerates. Such a range may vary depending on the formulation of the rubber composition for topping and the type of short fiber filler used, etc. For example, a rectangular or square range with a side length within the range of 200 μm to 400 μm can be mentioned.

[0124] By focusing on the angle (θ) formed by the orientation direction of the short fiber filler agglomerates and the length direction of the organic fiber cord in the cross-section obtained by cutting out the cord-rubber composite containing the short fiber filler in a plane parallel to both the length direction of the organic fiber cord and the width direction of the cord array, and calculating the dispersion V obtained by the predetermined formula, an index useful for evaluating the effects of the present disclosure can be obtained.

[0125] (WT / W L ) In the tire of the present disclosure, from the viewpoint of suppressing the weight of the tire and facilitating the exertion of the effects of the present disclosure, the ratio (WT / W L ) of the tire weight (WT) to the maximum load capacity (W L ) defined below is preferably 0.027 or less, more preferably 0.025 or less, still more preferably 0.024 or less, still more preferably 0.020 or less, and still more preferably 0.019 or less. W L =0.000011×VT + 100 [Here, VT is the virtual volume (mm 3 ) of the tire when a tire internal pressure of 250 kPa is applied and is calculated by the following formula. VT={(Dt2 -r 2 ) / 4×π}×W Dt: Tire outer diameter (mm) r: Tire inner diameter (mm) π: Pi W: Tire cross-sectional width (mm)]

[0126] Generally, as the maximum load capacity increases, the weight of the tire also increases. However, by suppressing the tire weight to a certain ratio with respect to the maximum load capacity as described above, it is considered possible to obtain good ride comfort and handling stability during high-speed driving.

[0127] (Tire cross-sectional width) From the viewpoint of the effects of the present disclosure, the cross-sectional width W (mm) of the tire of the present disclosure is preferably 150 to 290 mm. The cross-sectional width of the tire is preferably 160 mm or more, more preferably 170 mm or more. On the other hand, the cross-sectional width of the tire is preferably 280 mm or less, more preferably 270 mm or less.

[0128] (Relationship formula (1) between Dt and W) The tire outer diameter Dt and the tire cross-sectional width W preferably satisfy the following formula (1). 1963.4 ≦ (Dt 2 ×π / 4) / W ≦ 2827.4 (1)

[0129] By increasing the outer shape with respect to the cross-sectional width so as to satisfy formula (1), the deformation transmitted from the tread portion during rolling is minimized, and the reinforcing effect by the short fibers is exerted, so that good ride comfort and handling stability during high-speed driving can be improved.

[0130] Tires that satisfy formula (1) can be classified as so-called narrow and large-diameter tires, and it is expected that they will have excellent noise performance during high-speed driving. The left side of the above formula (1) is preferably 1970, more preferably 2070. On the other hand, the right side of the above formula (1) is preferably 2800, more preferably 2700.

[0131] (Tread portion) In the tire of the present disclosure, the tread portion has a tread end To on the outer side of the vehicle and a tread end Ti on the inner side of the vehicle when mounted on the vehicle, and between the tread end To and the tread end Ti, there are two or more circumferential grooves continuously extending in the tire circumferential direction and a pair of outermost circumferential grooves located at the outermost ends in the tire width direction among the circumferential grooves, partitioning a pair of shoulder land portions and one or more center land portions located between the pair of shoulder land portions. It is preferable that the pair of shoulder land portions and the one or more center land portions have a plurality of lateral grooves extending in the tire width direction.

[0132] ≪Circumferential groove, land portion≫ The circumferential groove may extend linearly or may extend in a zigzag shape. Also, the number of circumferential grooves may be two or more, but when there are three or more, the center land portion can be further divided into a land portion on the inner side of the vehicle and a land portion on the outer side of the vehicle when mounted on the vehicle. For this reason, the tread patterns of the respective land portions can be made different, which is preferable because the degree of freedom in designing the tread pattern is improved. The number of circumferential grooves may be four or more, or may be five or more.

[0133] When the number of circumferential grooves is three or more, a pair of circumferential grooves located at the outermost ends in the tire width direction among them are referred to as outermost circumferential grooves, and the circumferential grooves other than the outermost circumferential grooves are referred to as central circumferential grooves. Among the pair of outermost circumferential grooves, it is preferable that the groove width of at least one outermost circumferential groove is narrower than the groove width of at least one central circumferential groove. More preferably, the groove widths of both of the pair of outermost circumferential grooves are narrower than the groove width of the central circumferential groove.

[0134] When the number of circumferential grooves is 5 or more, among three or more central circumferential grooves, it is preferable that the groove width of the middle central circumferential groove is wider than the groove widths of a pair of central circumferential grooves on both sides thereof. By adopting such a configuration, in the tread portion of the tire during turning, the pressure on the outer side in the tire width direction inevitably tends to be high. Therefore, by adjusting the groove width as described above, the reaction force at the shoulder land portion can be increased, and the steering stability on a snow-covered road surface tends to be easily improved.

[0135] ≪Transverse grooves in the land portion≫ The land portion has a plurality of transverse grooves extending in the tire width direction. The width of the transverse grooves is not particularly limited, but is usually 8 mm or less. Among the transverse grooves, those with a width of 2 mm or less are particularly called sipes. The direction of the transverse grooves may have a predetermined angle with respect to the tire width direction W. The range of the angle is, for example, 0° to ±80°. For one transverse groove, the angle may be constant at any position in the tire width direction, or the angle may change according to the displacement of the position in the tire width direction.

[0136] It is preferable from the viewpoint of increasing the pattern rigidity that the transverse grooves have one end that does not communicate with the circumferential grooves. For example, in at least one of the pair of shoulder land portions, preferably in both shoulder land portions, one end of the transverse groove reaches the tread contact end, and the other end preferably stays within the land portion without reaching the outermost circumferential groove. Also, in at least one center land portion, one end of the transverse groove preferably communicates with one of the two circumferential grooves defining the center land portion, and the other end stays within the land portion without reaching the other circumferential groove. Further, when the two circumferential grooves defining the center land portion consist of a circumferential groove with a large distance from the tire center line and a circumferential groove with a small distance from the tire center line, the circumferential groove with which the transverse groove communicates is preferably the circumferential groove with a large distance from the tire center line.

[0137] All the lateral grooves may communicate with all the circumferential grooves adjacent thereto, but it is preferable that some of the lateral grooves are the lateral grooves having one end that does not communicate with the adjacent circumferential grooves, and it is more preferable that all the lateral grooves are the lateral grooves having one end that does not communicate with the adjacent circumferential grooves.

[0138] ≪Tread Pattern≫ The tread pattern of the tire of the present disclosure is not particularly limited as long as it conforms to the above description. Hereinafter, the tread pattern of the tire of the present disclosure will be described with reference to the drawings. However, the drawings are merely for explaining the embodiments, and the content of the present disclosure is not limited by these drawings.

[0139] FIG. 2 is a developed view of a tread portion showing an embodiment of the present disclosure. X represents the tire width direction. TW represents the distance in the tire width direction X between the inner tread end Ti and the outer tread end To. The tread portion has five linear circumferential grooves 10 (three central circumferential grooves 11 and two outermost circumferential grooves 12). The widest central circumferential groove 11 passes above the tire center line C, and a pair of central circumferential grooves 11 with a slightly narrower width passes outside thereof, and a pair of outermost circumferential grooves 12 with a narrower width passes further outside thereof. In the shoulder land portion 30, the lateral groove 20 has one end reaching the tread ground contact end Ti or To and the other end reaching the outermost circumferential groove. In a pair of center land portions 40 in contact with the central circumferential groove 11 passing through the tire center line C, the lateral groove (sipes) 21 has both ends communicating with the two central circumferential grooves 11 that define the center land portion. No lateral grooves are formed in a pair of center land portions 41 located further outside the center land portion.

[0140] FIG. 3 is a developed view of a tread portion showing an embodiment of the present disclosure. FIG. 3 is different from FIG. 2 in that in a pair of shoulder land portions 30, the lateral groove 20 has one end reaching the tread ground contact end but the other end does not reach the outermost circumferential groove.

[0141] FIG. 4 is a developed view of a tread portion showing an embodiment of the present disclosure. FIG. 4 is different from FIG. 2 in that in a pair of shoulder land portions 30, although the lateral groove 20 reaches one end up to the tread grounding end, the other end does not reach the outermost circumferential direction groove, and further, in a pair of center land portions 40 partitioned by the central circumferential groove 11, the lateral groove (sipes) 21 reaches one end up to the central circumferential groove 11 having a larger distance from the tire center line C among the two central circumferential grooves 11 that define each center land portion, but the other end does not reach the central circumferential groove 11 passing through the tire center line and remains within the land portion.

[0142] <Manufacture> (Manufacture of Topping Rubber Composition) The topping rubber composition according to the present disclosure can be manufactured by a known method. For example, it can be manufactured by kneading each of the above components using a rubber kneading device such as an open roll, a closed kneader (Banbury mixer, kneader, etc.).

[0143] The kneading process includes, for example, a base kneading process of kneading compounding agents and additives other than the vulcanizing agent and the vulcanization accelerator, and a final kneading (F kneading) process of adding the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the base kneading process and kneading them. Further, the base kneading process can be divided into a plurality of processes if desired.

[0144] The kneading conditions are not particularly limited, but for example, in the base kneading process, kneading is performed at a discharge temperature of 150 to 170°C for 3 to 10 minutes, and in the final kneading process, kneading is performed at 70 to 110°C for 1 to 5 minutes.

[0145] The rubber composition for topping obtained by the above kneading is molded for use in coating an organic fiber cord. The molding is not particularly limited as long as it can align the orientation directions of the short fiber fillers contained in the rubber composition for topping, and as a result, the dispersion V is 0.6 or less. Such a method includes, for example, extrusion-molding the rubber composition obtained by the above kneading into a desired sheet-like shape. By adjusting the degree of rolling during the extrusion molding, the value of the dispersion V of the short fiber fillers contained in the rubber composition for topping can be adjusted. That is, the dispersion V tends to decrease when rolling is performed more highly, and the dispersion V tends to increase when rolling is not performed much. Therefore, those skilled in the art can adjust the dispersion V to a desired value through limited trial and error.

[0146] ≪Method of containing short fiber fillers≫ In the present disclosure, the short fiber fillers can be incorporated into the rubber composition by kneading them in the above kneading step in the same manner as other additives. Alternatively, as described below, they can be incorporated into the rubber composition by mixing them with the rubber component in advance as a wet masterbatch and then performing the above kneading using the wet masterbatch. Or, the short fiber fillers may be incorporated into the cord-rubber composite by preliminarily coating the organic fiber cord.

[0147] ≪Wet masterbatch≫ The method for producing the wet masterbatch is not particularly limited. For example, it can be prepared by mixing a rubber latex and a dispersion liquid of the above short fiber fillers, and then coagulating and drying them.

[0148] The rubber latex is not particularly limited, and examples thereof include isoprene-based rubber latexes such as natural rubber latex, and synthetic diene-based rubber latexes (latexes such as BR, SBR, styrene isoprene butadiene rubber, acrylonitrile butadiene rubber, ethylene vinyl acetate rubber, chloroprene rubber, vinyl pyridine rubber, and butyl rubber). These may be used alone or in combination of two or more. Among them, latexes of isoprene-based rubbers such as SBR latex, NR, epoxidized natural rubber (ENR), and isoprene rubber (IR) are preferred because they are excellent in terms of fracture performance, low heat generation, and adhesion to cords.

[0149] The above rubber latex can be prepared by a conventionally known production method, and various commercially available products can also be used. As the above rubber latex, it is preferable to use one having a rubber solid content (solid content concentration) of 5 to 80% by mass. More preferably 7% by mass or more, and still more preferably 10% by mass or more. Further, from the viewpoint of the dispersibility of the short fiber-like filler, more preferably 70% by mass or less, and still more preferably 60% by mass or less.

[0150] The short fiber filler dispersion is obtained by dispersing the short fiber filler in a solvent. As the solvent, water is usually preferably used, and in addition, for example, alcohols, ethers, ketones, etc. that are soluble in water can also be used. The short fiber filler dispersion can be produced by a known method, and the production method is not particularly limited. For example, it can be prepared by dispersing the short fiber filler in the solvent using a high-speed homogenizer, ultrasonic homogenizer, high-pressure homogenizer, colloid mill, blender mill, etc. The temperature and time during the preparation can also be appropriately set within the range usually carried out so that the short fiber filler is sufficiently dispersed in the solvent.

[0151] The content (solid content, solid concentration) of the short fiber filler in the above short fiber filler dispersion is not particularly limited. However, from the perspective of the dispersibility of the short fiber filler in the dispersion, it is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.4% by mass or more, and even more preferably 0.5% by mass or more in 100% by mass of the short fiber filler dispersion. On the other hand, the content is preferably 20% by mass or less, and more preferably 10% by mass or less.

[0152] The mixing of the rubber latex and the short fiber filler dispersion is not particularly limited as long as the rubber latex and the short fiber filler dispersion are mixed, and other compounding agents such as binders other than the rubber latex and the short fiber filler dispersion may be further added. The method of this mixing is not particularly limited, and for example, it can be carried out using known stirring devices such as a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, and a blender mill.

[0153] After the above mixing, it is usually coagulated. The coagulation step is usually carried out by adding acidic compounds such as formic acid and sulfuric acid, and coagulants such as sodium chloride. In addition, it may be coagulated by the above mixing, and in this case, a coagulant may not be used.

[0154] After coagulation, usually, the obtained coagulated product is recovered, dehydrated by centrifugation, etc., and further washed and dried to obtain a wet masterbatch. Examples of the dryer that can be used for drying include a vacuum dryer, an air dryer, a drum dryer, a band dryer, a hot air dryer, and a kiln dryer.

[0155] The wet masterbatch thus obtained can be used in the above kneading step in the same manner as other raw materials.

[0156] (Manufacture of cord-rubber composite) The cord-rubber composite can be formed by coating both sides of a strip-shaped woven fabric having parallel side edges woven with a warp composed of organic fiber cords and a weft, for example, with a sheet obtained by molding the rubber composition for topping according to a conventional method. In this case, it is preferable that the rubber composition for topping covers the organic fiber cords with the extrusion direction when formed into a sheet being parallel to the length direction of the organic fiber cords. When the rubber composition for topping does not contain a short fiber filler, the short fiber filler can be incorporated by previously sprinkling it on the organic fiber cords. In this case, the dispersion V can be adjusted by the extrusion speed.

[0157] As the organic fiber cord which is the warp, those in the range of usually 940 decitex / 2 to 6600 decitex / 2 can be used. As the weft, a yarn made of a heat-resistant material having substantially no melting point such as cotton or flat rayon can be used, but a low-melting point material having a melting point of 110 to 150°C can also be used. In this case, the weft can be melted under the action of heat and tension during tire vulcanization, and the phenomenon of the warp undulating like a tatami mat can be prevented. That is, under the heat and pressure under the tire vulcanization temperature (about 150°C) conditions, when the melting point of the weft is 110 to 150°C, the restraining force of the warp during vulcanization can be reduced. Examples of the material for the weft having the low melting point include high-density polyethylene, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, terpolymer polyamide, quaternary copolymer polyamide, multi-copolymer polyamide, etc. And those usually in the range of 180 denier to 270 denier can be used. Here, the weft is woven so as to maintain the warp at regular intervals and prevent them from spreading apart from each other.

[0158] The array density of the organic fiber cords, which are the warp threads in the curtain fabric, is set according to the required ply strength and the like. For example, in the case of carcass ply, the range of 40 to 70 cords per 5 cm is common. The thickness of the cord-rubber composite is preferably 0.8 mm or less. By setting the thickness to 0.8 mm or less, the heat generation during running can be reduced. Also, the weight reduction of the pneumatic tire using the cord-rubber composite can be achieved.

[0159] The curtain fabric may be subjected to an adhesion treatment prior to being embedded in the topping rubber composition. The adhesion treatment includes an immersion step of immersing the curtain fabric in an adhesion treatment liquid, and a heating (baking) step of heating the curtain fabric under a certain tension applied to the warp threads after this immersion step. Thereby, the rubber adhesion of the tire reinforcing curtain fabric is improved.

[0160] (Manufacture of Tires) The tire of the present disclosure can be manufactured by a normal method using the cord-rubber composite. That is, on a tire molding machine, the cord-rubber composite is bonded together with other tire members and molded by a normal method to form an unvulcanized tire, and the tire can be manufactured by heating and pressurizing this unvulcanized tire in a vulcanizer. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200 °C for 10 to 30 minutes can be mentioned.

[0161] <Uses> The tire of the present disclosure can be suitably used for passenger car tires, truck and bus tires, motorcycle tires, and racing tires, and among them, it is preferably used for passenger car tires. Note that a passenger car tire is a tire assumed to be mounted on a four-wheeled automobile, and refers to a tire having a maximum load capacity of 1000 kg or less. Also, the tire of the present disclosure can be used for all-season tires, summer tires, and winter tires such as studless tires. The tire of the present disclosure is preferably used for run-flat tires.

[0162] <Evaluation Method> The evaluation method of the present disclosure is a method for evaluating the degree of orientation of short fiber fillers in a molded body of a rubber composition containing short fiber fillers, and includes the following steps. (1) A step of cutting the rubber composition in a direction that is horizontal in the extrusion direction when the rubber composition is molded and in a direction in which the cross-section of the molded body is maximized to cut out an observation cross-section. (2) A step of imaging the observation cross-section with an electron microscope to obtain an electron microscope image. (3) A step of extracting only the images of the short fiber filler agglomerates from the electron microscope image. (4) A step of measuring the angle θ formed by the orientation direction of each short fiber filler agglomerate with respect to an arbitrarily determined reference direction in the image of the short fiber filler agglomerate. (5) A step of obtaining the variance V of the angle formed by the reference direction and the orientation direction of each short fiber filler agglomerate according to the following formula based on the angle. V = 1 - R

Number

[0163] According to the evaluation method of the present disclosure, regarding a molded body of a rubber composition containing short fiber fillers, paying attention to the short fiber filler agglomerates in which a plurality of short fiber fillers are aggregated in a cross-section obtained by cutting this with a predetermined surface, and obtaining the variance V of the angle obtained from a predetermined mathematical formula regarding the orientation direction, the degree of orientation of the short fiber filler agglomerates can be evaluated.

[0164] (Step (1)) Step (1) is a step of cutting the rubber composition in a direction horizontal to the extrusion direction when the rubber composition is molded and in a direction in which the cross-section of the molded body obtained by extrusion is maximized to cut out a cross-section for observation. By cutting out the cross-section for observation in this way, useful information regarding the degree of orientation of the short fiber filler can be obtained. The cutting out of the cross-section for observation can be carried out by a conventional method. When the rubber composition is used as a cord-rubber composite, for example, in a tire carcass, etc., the cutting out of the cross-section for observation can be carried out on a plane parallel to both the length direction of the cord with respect to the organic fiber cord and the width direction of the cord arrangement.

[0165] (Step (2)) Step (2) is a step of imaging the cross-section for observation with an electron microscope to obtain an electron microscope image. Imaging with an electron microscope can be carried out by a conventional method. The electron microscope is not particularly limited, and a scanning electron microscope (SEM), a transmission electron microscope (TEM), etc. can be used.

[0166] (Step (3)) Step (3) is a step of extracting only the image of the short fiber filler mass from the electron microscope image. The extraction of such an image can be carried out, for example, by performing processing such as polarizing using software such as Image J, setting a threshold value, and extracting only the image portion of the short fiber filler (CNF) mass.

[0167] (Step (4)) Step (4) is a step of measuring the angle θ formed by the orientation direction of each short fiber filler mass with respect to an arbitrarily determined one reference direction in the image of the short fiber filler mass. That is, in the obtained image of the short fiber filler mass, each short fiber filler mass is approximated by an ellipse, and the major axis direction thereof is taken as the orientation direction of the short fiber filler mass, and the angle (θ) formed by the orientation direction and the reference direction is measured. When the rubber composition is used as a cord-rubber composite, for example, in a tire carcass, etc., the length direction of the organic fiber cord can be used as the reference direction, and the angle (θ) formed with the reference direction can be measured.

[0168] (Step (5)) Step (5) is a step of obtaining the variance V of the angle (θ) formed between the reference direction and the orientation direction of each short fiber filler mass based on the angle (θ) by the following formula. V = 1 - R [Number] {θ j | j = 1, 2, ···, N} [Here, i represents the imaginary unit, N is the number of short fiber filler masses that can be confirmed from the range of the reference area of the electron microscope image of the observation cross-section, and θ represents the angle (in radians) formed between the orientation direction of each short fiber filler mass and the reference direction in the observation cross-section.]

[0169] Note that the "range of the reference area" is as described above.

[0170] (Step (6)) Step (6) is a step of evaluating the degree of orientation of the short fiber filler from the variance V. As a result of evaluating the degree of orientation, it becomes possible to evaluate the useful functions of the molded body of the rubber composition. For example, when the molded body of the rubber composition is combined as an organic fiber cord and used in the carcass of a tire, the degree of orientation can serve as one of the indices for evaluating the riding comfort of the tire and the handling stability at high speeds.

[0171] This evaluation method can, as long as there is no particular contradiction, incorporate the descriptions of "tire", "manufacture", and "use" in this specification as the description of the "evaluation method". Similarly, the description regarding the "evaluation method" can also, as long as there is no particular contradiction, be incorporated as the description of "tire", "manufacture", and "use".

Examples

[0172] Hereinafter, the present disclosure will be specifically described based on examples, but the present disclosure is not limited thereto.

[0173] [Various Chemicals] Summarize the various chemicals used in the examples and comparative examples. NR: Natural rubber (RSS#3 grade) Carbon black: Diablack N220 manufactured by Mitsubishi Chemical Corporation (average particle size: 23 nm, CTAB: 110 m 2 / g, N2SA: 114 m 2 / g) Oil: VIVATEC 500 (TDAE oil) manufactured by H&R Stearic acid: Bead stearic acid camellia manufactured by NOF Corporation Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator: Nocceler NS (TBBS, N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Short fiber filler 1: Carbon nanotube (CNT) (average fiber diameter: 5 nm, average fiber length: 6 μm, aspect ratio: 1200) Short fiber filler 2: Cellulose nanofiber (CNF) (The average fiber diameter, average fiber length and aspect ratio after being prepared as a wet masterbatch are as described below.) Organic fiber cord A: Rayon fiber (1840 decitex / 2)

[0174] Production Example 1: Production of Wet Masterbatch (WMB) 1 10 kg of pure water was added to 100 g of cellulose nanofiber (CNF) to prepare a 1.0 mass% (solid content concentration) suspension of CNF. The mixture was stirred for about 5 minutes with a high-speed homogenizer ("T50" manufactured by IKA Japan Co., Ltd., rotation speed: 8000 rpm) to prepare a uniform aqueous dispersion. After adjusting the dry rubber content (DRC) of natural rubber latex to 10 mass%, the above-prepared aqueous dispersion was added to 100 parts by mass of the rubber solids of natural rubber latex so that the dry weight (solid content) of CNF was 20 parts by mass. The mixture was stirred and mixed at 25°C for 5 minutes using a high-speed homogenizer ("T50" manufactured by IKA Japan Co., Ltd., rotation speed: 8000 rpm) to prepare a rubber latex dispersion (compounded latex). Next, sulfuric acid was added while slowly stirring at 25°C for 5 minutes (Eurostar [electrically controlled stirrer] manufactured by IKA Japan Co., Ltd., rotation speed: 100 rpm) to adjust the pH to 3 - 4, and coagulation occurred. The obtained solid was filtered and dried to obtain Wet Masterbatch 1.

[0175] (Calculation of fiber diameter and fiber length) A 0.001 mass% aqueous dispersion of Wet Masterbatch 1 was prepared. This diluted dispersion was thinly spread on a mica sample stage and heated and dried at 50°C to prepare a sample for observation. The sample was observed with an atomic force microscope (AFM, "Scanning Probe Microscope SPI3800N" manufactured by Hitachi High-Technologies Corporation), and the fiber diameter and fiber length were calculated by measuring the cross-sectional height of the shape image. The average fiber diameter was 200 nm, the average fiber length was 4 μm, and the aspect ratio [fiber length / fiber diameter] was 20.

[0176] <Manufacture of unvulcanized rubber composition> According to each formulation content shown in Table 1, using a 1.7L closed Banbury mixer, chemicals other than sulfur and vulcanization accelerators were kneaded at a discharge temperature of 160°C for 4 minutes to obtain a kneaded product. Next, using an open roll, sulfur and vulcanization accelerators were added to the obtained kneaded product and kneaded for 4 minutes to obtain an unvulcanized rubber composition. Rubber composition A and rubber composition B are those with a matrix of short fiber fillers as the rubber composition. On the other hand, since rubber composition C does not contain short fiber fillers, when manufacturing a test tire, as described below, the short fiber fillers were incorporated into the organic fiber cord.

[0177] The unvulcanized rubber composition obtained above was formed into a sheet by extrusion molding. The degree of rolling during this extrusion was adjusted so that the value of the angular dispersion V would be a predetermined value of 0.6 or less. On the other hand, in the comparative example, the angular dispersion V was adjusted by extruding multiple times while changing the extrusion direction.

[0178]

Table 1

[0179] <Manufacture of Test Tires in Table 2> According to the description in Table 2, tires were manufactured. That is, using the unvulcanized rubber composition A or rubber composition B extruded into a sheet as described above, 50 organic fiber cords A were embedded at an array density of 50 cords / 5 cm to produce a carcass with a thickness of 2.0 mm, and it was bonded to other tire members to produce a green tire. The green tire thus obtained was press-vulcanized at 170°C for 20 minutes to produce a test tire (255 / 45RF18) that is a run-flat tire. The tire weight was adjusted by changing the rubber gauge of the tread part.

[0180] <Manufacture of Test Tires in Table 3> According to the description in Table 3, tires were manufactured. First, the short fiber filler 1 (CNT) was incorporated by previously coating the organic fiber cord A. That is, the matrix of the short fiber filler was the organic fiber cord. At this time, the angular dispersion V of the short fiber filler agglomerates was adjusted by adjusting the extrusion speed. The content of the short fiber filler 1 was adjusted to be the same as that in the test tire of Table 2 above.

[0181] Except for using the thus obtained CNT-containing organic fiber cord A and the unvulcanized rubber composition of formulation C obtained above, a test tire (255 / 45RF18) was obtained in the same manner as the manufacture of the test tire of Table 2 above.

[0182] <Manufacture of the test tire of Table 4> According to the description in Table 4, tires were manufactured. That is, a test tire (255 / 45R18) was obtained in the same manner as the manufacture of the test tire of Table 2 above, except that the test tire was made as a non-run-flat tire.

[0183] <Evaluation> The measurement method and evaluation method are shown below. The overall performance is evaluated by the total value of the ride comfort index and the handling stability index during high-speed driving.

[0184] (Ride comfort) Each test tire was mounted on all four wheels of a domestic FF car with a displacement of 2000 cc, and the ride comfort when driving on a dry paved road was evaluated by the sensory evaluation of a test driver from the viewpoints of roughness, jolting, and damping. The evaluation was performed with integer values from 1 to 5 points. Based on the evaluation criteria that the higher the score, the better the ride comfort, the total score of 10 test drivers was calculated. The total score of the reference comparative example was converted to a reference value (100), and the evaluation results of each test tire were indexed and displayed to be proportional to the total score.

[0185] (Handling stability during high-speed driving) Each test tire was mounted on all wheels of a domestic FF car with a displacement of 2000 cc, and a test drive was conducted on a test course with a dry asphalt surface. Based on the feelings of straight running, lane changing, acceleration and deceleration during driving at 120 km / h by the test driver, the handling characteristics were evaluated. The evaluation was performed with integer values from 1 to 5 points, and the total score of 10 test drivers was calculated based on the evaluation criteria that the higher the score, the better the handling characteristics. The total score of the reference comparison example was converted to a reference value (100), and the evaluation results of each test tire were indexed and displayed in proportion to the total score.

[0186] (Dispersion V of short fiber filler) The measurement method of the dispersion V of the short fiber filler is as follows. (1) Regarding the carcass of the test tire, a rubber composition was cut in a plane parallel to both the length direction of the cord for the organic fiber cord and the width direction of the cord arrangement to cut out an observation cross-section. (2) The obtained observation cross-section was imaged at an acceleration voltage of 15 kV using a scanning electron microscope (XL30 manufactured by FEI Company, Japan) to obtain an electron microscope image. The image obtained for the test tire of Example 5 is shown in FIG. 5 (magnification: 500 times). (3) The obtained electron microscope image was polarized using Image J, a threshold value was set, and only the image portion of the short fiber filler (CNF) mass was extracted. The image obtained for the test tire of Example 5 is shown in FIG. 6 (magnification: 500 times). (4) In the range of 320 μm × 240 μm of the obtained image of the short fiber filler mass, each short fiber filler mass was approximated by an ellipse, and the major axis direction was taken as the orientation direction of the short fiber filler mass. The angle (θ) formed by the orientation direction and the length direction (reference direction) of the organic fiber cord was measured. (5) Based on the obtained angle (θ), the dispersion V was determined for the angle formed by the reference direction and the orientation direction of each short fiber filler mass according to the above formula.

[0187] For each test tire, the dispersion V of the short fiber filler was determined according to the above (1) to (5).

[0188]

Table 2

[0189]

Table 3

[0190]

Table 4

[0191] From the results of Tables 2 to 4, it can be seen that in the case of evaluating the degree of orientation of the short fiber filler mass by dispersion V, for the tires of the examples where the dispersion V is 0.6 or less and the tire weight WT is 20 kg or less, excellent ride comfort and handling stability performance at high speeds are achieved compared to the tires of the comparative examples.

[0192] <Embodiment> Examples of the embodiments of the present disclosure are shown below.

[0193] [1] A tire provided with a cord-rubber composite, wherein the tire has a tire weight (WT) of 20 kg or less, preferably 19 kg or less, more preferably 18 kg or less, still more preferably 17 kg or less, and still more preferably 16 kg or less, the cord-rubber composite includes an organic fiber cord, a topping rubber covering the organic fiber cord, and a short fiber filler, the short fiber filler is a tire having a dispersion V defined below of 0.6 or less, preferably 0.5 or less, more preferably 0.4 or less. V = 1 - R

Equation

[10] The tire according to [9] above, wherein in at least one of the one or more center land portions, one end of the transverse groove of the center land portion communicates with one of the two circumferential grooves defining the center land portion, and the other end does not reach the other circumferential groove and remains within the land portion.

[11] The two circumferential grooves that define the center land portion consist of a circumferential groove with a large distance from the tire center line and a circumferential groove with a small distance from the tire center line, and the circumferential groove through which the lateral groove communicates is the circumferential groove with a large distance from the tire center line. The tire according to

[10] above.

[12] The tire according to any one of [1] to

[11] above, wherein the tire is a run-flat tire.

[13] A method for evaluating the degree of orientation of a short fiber filler in a molded body of a rubber composition containing a short fiber filler, An evaluation method including the following steps. (1) A step of cutting the rubber composition in a direction that is horizontal in the extrusion direction when the rubber composition is molded and in a direction where the cross-section of the molded body is maximized to cut out an observation cross-section. (2) A step of imaging the observation cross-section with an electron microscope to obtain an electron microscope image. (3) A step of extracting only the images of the short fiber filler agglomerates from the electron microscope image. (4) A step of measuring, for each short fiber filler agglomerate, the angle θ formed by the orientation direction of the short fiber filler agglomerate with respect to an arbitrarily defined reference direction in the image of the short fiber filler agglomerate. (5) A step of obtaining the variance V of the angle formed by the reference direction and the orientation direction of each short fiber filler agglomerate according to the following formula based on the angle. V = 1 - R

Number

Explanation of Signs

[0194] 1 Tire 2 Tread portion 3 Sidewall portion 4 Breaker 5 carcass 6 inner liner 7 side reinforcement rubber 8 bead part 9 clinch C tire center line J rim 10 circumferential groove 11 center circumferential groove 12 outermost circumferential groove 20 lateral groove 21 lateral groove (siping) 30 shoulder land 40 center land 41 center land Ti inner tread end To outer tread end TW tread width X tire width direction

Claims

1. A tire comprising a cord-rubber composite, wherein the tire has a tire weight (WT) of 20 kg or less, the cord-rubber composite includes an organic fiber cord, a topping rubber covering the organic fiber cord, and a short fiber filler, the short fiber filler has a dispersion V defined below of 0.6 or less, and for the short fiber filler agglomerates, the average aspect ratio defined below is 3.0 or more. V = 1 - R 【Number 1】 {θ j | j = 1, 2, ···, N} [where i represents the imaginary unit, N is the number of short fiber filler agglomerates that can be confirmed from the range of the reference area of the electron microscope image in the cross-section of the topping rubber cut out in a plane parallel to both the length direction of the cord and the width direction of the cord arrangement for the organic fiber cord, and θ represents the angle (radian) formed by the orientation direction of each short fiber filler agglomerate and the length direction of the organic fiber cord in the cross-section of the topping rubber.] Average aspect ratio = (average value of the major axis of the short fiber filler agglomerates) / (average value of the minor axis of the short fiber filler agglomerates)

2. A tire comprising a cord-rubber composite, wherein the tire has a tire weight (WT) of 20 kg or less, the cord-rubber composite includes an organic fiber cord, a topping rubber covering the organic fiber cord, and a short fiber filler, the short fiber filler has a dispersion V defined below of 0.6 or less, and the outer diameter Dt of the tire and the cross-sectional width W of the tire satisfy the following formula (1). V = 1 - R 【Number 2】 {θ j | j = 1, 2, ···, N} [where i represents the imaginary unit, N is the number of short fiber filler agglomerates that can be confirmed from the range of the reference area of the electron microscope image in the cross-section of the topping rubber cut out in a plane parallel to both the length direction of the cord and the width direction of the cord arrangement for the organic fiber cord, and θ represents the angle (radian) formed by the orientation direction of each short fiber filler agglomerate and the length direction of the organic fiber cord in the cross-section of the topping rubber.] 1963.4 ≤ (Dt 2 × π / 4) / W ≤ 2827.4 (1)

3. The ratio (WT / W L ), of the tire weight (WT) to the maximum load capacity (W L ) defined below, is 0.027 or less. The tire according to claim 1 or 2. W L = 0.000011 × VT + 100 Here, VT is the virtual volume (mm 3 ) of the tire when a 250 kPa internal pressure is applied, and is calculated by the following formula. VT = { (Dt 2 - r 2 ) / 4 × π} × W Dt: Tire outer diameter (mm) r: Tire inner diameter (mm) π: Pi W: Tire cross-sectional width (mm) ]

4. The tire according to any one of claims 1 to 3, wherein the average of the angles (radians) formed by the length direction of the organic fiber cord and the orientation direction of each short fiber filler agglomerate is π / 4 or less.

5. The tire according to any one of claims 1 to 4, wherein the short fiber filler is at least one selected from the group consisting of cellulose nanofibers and carbon nanotubes.

6. The tire according to any one of claims 1 to 5, wherein in the tire, the section width W is 150 mm to 290 mm.

7. The tire according to any one of claims 1 to 6, wherein the cord-rubber composite is used for the carcass.

8. Comprising a tread portion, The tread portion has a tread edge To on the outer side of the vehicle and a tread edge Ti on the inner side of the vehicle when the tire is mounted on the vehicle, and between the tread edge To and the tread edge Ti, two or more circumferential grooves continuously extending in the tire circumferential direction, and a pair of shoulder land portions partitioned by a pair of outermost circumferential grooves located at the outermost ends in the tire width direction of the circumferential grooves, and one or more center land portions located between the pair of shoulder land portions, The pair of shoulder land portions and the one or more center land portions have a plurality of lateral grooves extending in the tire width direction, The tire according to any one of claims 1 to 7, wherein in at least one of the pair of shoulder land portions, one end of the lateral groove of the shoulder land portion reaches the tread grounding end, and the other end does not reach the outermost circumferential groove and remains within the land portion.

9. The tire according to claim 8, wherein in at least one of the one or more center land portions, one end of the lateral groove of the center land portion communicates with one of the two circumferential grooves defining the center land portion, and the other end does not reach the other circumferential groove and remains within the land portion.

10. The tire according to claim 9, wherein the two circumferential grooves defining the center land portion consist of a circumferential groove with a large distance from the tire center line and a circumferential groove with a small distance from the tire center line, and the circumferential groove with which the lateral groove communicates is the circumferential groove with a large distance from the tire center line.

11. The tire according to any one of claims 1 to 10, wherein the tire is a run-flat tire.

12. A method for evaluating the degree of orientation of a short fiber filler in a molded body of a rubber composition containing the short fiber filler, comprising: An evaluation method including the following steps. (1) A step of cutting the rubber composition in a direction horizontal to the extrusion direction when the rubber composition is molded and in a direction in which the cross section of the molded body is maximized to cut out an observation cross section. (2) A step of imaging the observation cross section with an electron microscope to obtain an electron microscope image. (3) A step of extracting only the images of the short fiber filler agglomerates from the electron microscope image. (4) A step of measuring, in the image of the short fiber filler agglomerates, the angle θ formed by the orientation direction of each short fiber filler agglomerate with respect to an arbitrarily determined reference direction. Step of obtaining dispersion V of the angle formed by the reference direction and the orientation direction of each short fiber filler mass based on the angle by the following formula V = 1 - R 【Number 3】 {θ j | j = 1, 2, ···, N} [where i represents the imaginary unit, N is the number of short fiber filler masses that can be confirmed from the range of the reference area of the electron microscope image of the observation cross-section, and θ represents the angle (in radians) formed by the orientation direction of each short fiber filler mass and the reference direction in the observation cross-section.] Step of evaluating the degree of orientation of the short fiber filler from the dispersion V

13. The method according to claim 12, wherein the average aspect ratio defined below for the short fiber filler mass is 3.0 or more. Average aspect ratio = (average value of the major axis of the short fiber filler mass) / (average value of the minor axis of the short fiber filler mass)

14. The molded body of the rubber composition containing the short fiber filler is a cord-rubber composite containing an organic fiber cord, The method according to claim 12 or 13, wherein the average of the angles (in radians) formed by the length direction of the organic fiber cord and the orientation direction of each short fiber filler mass is π / 4 or less.

15. The method according to any one of claims 12 to 14, wherein the short fiber filler is at least one selected from the group consisting of cellulose nanofibers and carbon nanotubes.

Images