JP2020006871A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire achieving both abrasion resistance and wet grip performance at a higher level.SOLUTION: A pneumatic tire has a tread including a block having a periphery surrounded by a groove. The pneumatic tire is such that: a ratio (L/S) of a land area (L) as a sum total of a grounding part surface area of the block to a sea area (S) as an area of a whole groove bottom surface is 68-78%; a ground plate shape index (FSF80) shown by a ratio of a grounding length SL0 in the tire circumferential direction on a tire equator to a grounding length SL80 in the tire circumferential direction in a position separated for a tire axial direction distance of 80% of a tread grounding half-width from the tire equator is 1.00-1.15; an average number of sipes is 2-4 sipes/1 block; and the tread has rubber physical property in which a product E@30°C×EB of a dynamic modulus E@30°C(MPa) and a breaking elongation EB(%) is 7,000-20,000, and a loss tangent tanδ at 0°C is 0.55-0.90.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having both abrasion resistance and wet grip properties.

  2. Description of the Related Art Pneumatic tires for automobiles (hereinafter, also simply referred to as “tires”) have long been valued for durability and are required to have excellent wear resistance. In recent years, safety has been increasingly considered, and further improvement in wet grip performance has been demanded. Above all, for a sports utility vehicle (SUV), it is desired to realize a pneumatic tire in which these two performances are compatible at a high level.

  However, since the wear resistance and the wet grip performance have a trade-off relationship, it is not easy to make these two types of performance compatible. Therefore, in order to improve the wear resistance and the wet grip property while improving the balance, examination of the compounding material of the rubber composition constituting the tread (Patent Documents 1 and 2) and examination of the tread pattern (Patent Documents 3 and 4) And so on.

JP 2012-229285 A JP 2013-107989 A JP 2014-177238 A JP-A-2015-147543

  However, at present, the wear resistance and the wet grip performance have not yet been achieved at a high level desired by the SUV.

  Therefore, an object of the present invention is to provide a pneumatic tire in which wear resistance and wet grip performance are compatible at a higher level.

  The present inventors have conducted intensive studies and found that the above-described problems can be solved by the invention described below, and have completed the present invention.

The invention according to claim 1 is
A pneumatic tire having a tread including a block surrounded by grooves on a tread surface,
A land sea ratio (L / S), which is a ratio of a land area (L), which is the total surface area of the ground contact portion of the block on the tread surface, and a sea area (S), which is the area of the entire groove bottom, is 68 to 78%. And
In a normal state with no load loaded into the normal rim and filled with the normal internal pressure, a ground contact length in the tire circumferential direction on the tire equator formed when a normal load is applied and the tread surface is pressed against a flat surface. The contact surface shape index (FSF80) represented by the ratio (SL0 / SL80) of the tire SL0 to the contact length SL80 in the tire circumferential direction at a position separated by 80% of the tread contact half width from the tire equator in the tire axial direction. , 1.00 to 1.15;
The average number of sipes in the block is 2 to 4 / block,
Said tread,
Dynamic elastic modulus E ^* ＠ 30 ° C. (MPa) measured at a frequency of 10 Hz, initial strain 1%, and dynamic strain rate 5% (30 ° C.), and breaking elongation EB (%) measured according to JIS K6301 The product E ^{* ＊} 30 ° C. × EB is 7000 to 20,000,
A pneumatic tire having rubber physical properties having a loss tangent tan δ at 0 ° C of 0.55 to 0.90.

The invention described in claim 2 is
The pneumatic tire according to claim 1, wherein the land sea ratio (L / S) is 70 to 76%.

The invention according to claim 3 is:
The pneumatic tire according to claim 2, wherein the land sea ratio (L / S) is 72 to 74%.

The invention described in claim 4 is
The pneumatic tire according to any one of claims 1 to 3, wherein the ground contact surface shape index (FSF80) is 1.05 to 1.15.

The invention according to claim 5 is
The pneumatic tire according to claim 4, wherein the ground contact surface shape index (FSF80) is 1.10 to 1.15.

The invention according to claim 6 is
The pneumatic tire according to any one of claims 1 to 5, wherein the loss tangent tan δ at 0 ° C is 0.57 to 0.90.

The invention according to claim 7 is
The pneumatic tire according to claim 6, wherein the loss tangent tan δ at 0 ° C is 0.60 to 0.90.

The invention according to claim 8 is
8. The pneumatic tire according to claim 1, wherein the E ^* ℃ 30 ° C. × EB is 8500 to 18000. 9.

The invention according to claim 9 is
The pneumatic tire according to claim 8, wherein the E ^* ＠ 30 ° C. × EB is 10,000 to 16,000.

The invention according to claim 10 is
The said tread WHEREIN: 50-90 mass parts of styrene butadiene rubber (SBR) whose glass transition point (Tg) is -50 degreeC or more is mix | blended with 100 mass parts of rubber components. The pneumatic tire according to claim 9.

The invention according to claim 11 is
In the tread, 10 to 50 parts by mass of a butadiene rubber (BR) having a mass average molecular weight (Mw) of 550,000 or more is blended in 100 parts by mass of the rubber component. The pneumatic tire according to claim 10.

The invention according to claim 12 is
The pneumatic tire according to any one of claims 1 to 11, wherein, in the tread, 20 to 200 parts by mass of silica is blended with respect to 100 parts by mass of the rubber component. is there.

The invention according to claim 13 is:
13. The tread according to claim 1, wherein 5 to 100 parts by mass of carbon black composed of hard carbon is blended with respect to 100 parts by mass of the rubber component. It is a pneumatic tire.

The invention according to claim 14 is
14. The tread according to any one of claims 1 to 13, wherein 5 to 50 parts by mass of α-methylstyrene resin is blended with respect to 100 parts by mass of the rubber component. It is a pneumatic tire.

The invention according to claim 15 is
The pneumatic tire according to any one of claims 1 to 14, wherein the pneumatic tire is an SUV tire.

  According to the present invention, it is possible to provide a pneumatic tire in which abrasion resistance and wet grip performance are compatible at a higher level.

It is a figure showing a tread pattern of a tire tread concerning one embodiment of the present invention. It is a schematic diagram which shows the tread shape which pressed the tread on the plane.

  Hereinafter, the present invention will be described based on embodiments.

[1] Features of the present invention First, features of the present invention will be described.

The pneumatic tire according to the present invention,
A pneumatic tire having a tread including a block surrounded by grooves on a tread surface,
A land sea ratio (L / S), which is a ratio of a land area (L), which is the total surface area of the ground contact portion of the block on the tread surface, and a sea area (S), which is the area of the entire groove bottom, is 68 to 78%. And
In a normal state with no load loaded into the normal rim and filled with the normal internal pressure, a ground contact length in the tire circumferential direction on the tire equator formed when a normal load is applied and the tread surface is pressed against a flat surface. The contact surface shape index (FSF80) represented by the ratio (SL0 / SL80) of the tire SL0 to the contact length SL80 in the tire circumferential direction at a position separated by 80% of the tread contact half width from the tire equator in the tire axial direction. , 1.00 to 1.15;
The average number of sipes in the block is 2 to 4 / block,
Said tread,
Dynamic elastic modulus E ^* ＠ 30 ° C. (MPa) measured at a frequency of 10 Hz, initial strain 1%, and dynamic strain rate 5% (30 ° C.), and breaking elongation EB (%) measured according to JIS K6301 The product E ^{* ＊} 30 ° C. × EB is 7000 to 20,000,
It is characterized by having rubber physical properties having a loss tangent tan δ at 0 ° C. of 0.55 to 0.90.

The present inventor does not individually examine each of the tread pattern and the rubber composition, but examines them as being related to each other. As a result, the tread pattern of the tread is adjusted and the “land sea ratio (L / S)” is adjusted. In addition to adjusting the “ground contact surface shape index (FSF80)” within a specific range, the rubber composition of the tread is adjusted, and the rubber properties are adjusted under the conditions of a frequency of 10 Hz, an initial strain of 1%, and a dynamic strain rate of 5% (30 ° C.). Product of the dynamic elastic modulus E ^* ＠ 30 ° C. (MPa) measured in the above and the elongation at break EB (%) measured in accordance with JIS K6301 E ^* ＠ 30 ° C. × EB ”and“ loss tangent tan δ at 0 ° C. By providing two types within a specific range, we provide a pneumatic tire that balances abrasion resistance and wet grip performance that are in conflict with each other at a higher level in a well-balanced manner. It was found that the kill.

That is, regarding the wear resistance, excellent wear resistance can be exhibited by setting the above-mentioned FSF80, the number of sipes, the loss tangent tan δ, and E ^* (＠ 30 ° C.) × EB within appropriate ranges. As for the wet grip performance, the land sea ratio, FSF80, sipe number, loss tangent tan δ, and dynamic elastic modulus E ^* (＠ 30 ° C.) are within appropriate ranges, so that excellent wet grip performance can be obtained. Can be demonstrated.

  Furthermore, in the present invention, when all of these requirements are in an appropriate range, a synergistic effect is exerted in cooperation with each other. It is possible to provide tires that are compatible at the same level.

[2] Embodiments of the Present Invention Hereinafter, the present invention will be specifically described based on embodiments.

1. Tread (1) Tread Pattern As described above, in the present embodiment, the tread surface of the tire has the land sea ratio (L / S) and the ground contact surface shape index (FSF80: Foot Print Shape Factor 80) within specific ranges. Is characterized in that:

(A) Land sea ratio (L / S)
In the present invention, a land area ratio (L / S), which is a ratio of a land area (L), which is the total surface area of the ground contact portion of the block on the tread surface, and a sea area (S), which is the area of the entire groove bottom, is 68. It is preferably about 78%. By setting the land sea ratio (L / S) within the above range, good wet grip performance can be secured.

  The land sea ratio (L / S) will be specifically described with reference to FIG. 1 showing a tread pattern of a tire tread according to one embodiment of the present invention. In FIG. 1, 1 is a tread contact surface, C is a tire equator, Te is a contact end, and TW is a tread contact width. 2 is a block, 3 is a vertical groove, 4 is a horizontal groove, and 5 is a sipe. The thick arrow indicates the tire rotation direction.

In FIG. 1, when the total of the surface area of the ground contact portion of the block 2 on the tread surface between the ground tread ends Te and Te is the land area (L) and the entire area of the groove bottom is the sea area (S), the land sea ratio ( L / S) is represented by the following equation.
Land sea ratio (L / S) = land area (L) / sea area (S)

  At the above-mentioned land sea ratio (L / S), in order to secure a sufficient contact area and exhibit wet grip performance, and to secure a sufficient drainage path and exhibit sufficient wet grip performance, L / S Is preferably set to 68 to 78%. It is more preferably from 70 to 76%, and further preferably from 72 to 74%.

(B) Tread shape index (FSF80)
In the present invention, the pneumatic tire is rim assembled to a regular rim, and in a normal state of no load filled with a regular internal pressure, a regular load is applied to the pneumatic tire, and a tread is pressed against a flat surface. Is preferably 1.00 to 1.15. By setting the ground contact surface shape index (FSF80) within the above range, good wear resistance and wet grip performance can be ensured.

  The ground contact surface shape index (FSF80) will be specifically described with reference to FIG. 2, which is a schematic diagram showing the contact surface shape when the tread is pressed against a flat surface.

FIG. 2 shows a ground contact surface shape (FP: footprint) in which the tread is pressed against a flat surface. The contact length in the tire circumferential direction (tire rotation direction) on the tire equator is SL0, and the tread contact from the tire equator is tread. Assuming that the contact length in the tire circumferential direction at a position separated by a tire axial distance (0.8a) of 80% of the half width (a) is SL80, the contact surface shape index (FSF80) is represented by the following equation. The “tread contact half width” means half the distance in the tire axial direction between the outermost contact points in the tire axial direction on the contact surface.
Landing surface shape index (FSF80) = SL0 / SL80

  In the above-mentioned ground contact surface shape index (FSF80), in order to secure sufficient wear resistance and wet grip performance, it is preferable that the FSF80 is 1.00 to 1.15. It is more preferably from 1.05 to 1.15, and further preferably from 1.10 to 1.15.

  In the above description, the “regular rim” is a rim defined for each tire in a standard system including the standard on which the tire is based. For example, a standard rim for JATMA and a “Design” for TRA Rim ”, or“ Measuring Rim ”for ETRTO.

  "Normal internal pressure" is the air pressure specified for each tire in the above standard, and is the maximum air pressure for JATMA, and the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURESURE" for TRA, and ETRTO for TRA. If there is, “INFLATION PRESSURE” is set.

  The "regular load" is a load defined for each tire according to the standard, and is a maximum load capacity in the case of JATMA, and a maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURESURE" in the case of TRA, ETRTO. If so, "LOAD CAPACITY" is set.

  The above-mentioned contact surface shape can be obtained by appropriately adjusting the methods such as the mold profile, the gauge distribution, and the structure, but the method is not particularly limited as long as the above-mentioned contact surface shape is achieved. For example, by adjusting the thickness of the tread central portion and / or the tread shoulder portion and adjusting the tread gauge distribution, the ground contact surface shape index can be adjusted.

(C) Sipe As described above, FIG. 1 is a diagram showing a tread pattern of a tire tread according to one embodiment of the present invention, where 1 is a tread contact surface, C is a tire equator, Te is a contact end, and TW is The tread contact width. 2 is a block, 3 is a vertical groove, 4 is a horizontal groove, and 5 is a sipe.

  The contact surface 1 is provided with a plurality of blocks 2 whose periphery is surrounded by a vertical groove 3 and a horizontal groove 4. The block 2 is provided with a plurality of, more specifically, 2 to 4 sipes 5 (narrow grooves) per block.

  By forming the block 2 surrounded by the grooves 3 and 4 in this way, even when traveling on a wet road surface, water can be smoothly drained from the grooves, so that sufficient wet grip performance can be obtained. Can be demonstrated.

  By providing the sipe 5 in the block 2, the water accumulated on the block 2 can be smoothly drained, so that the wet grip performance can be further improved. Further, when the sipe 5 is provided, the contact area with the road surface is reduced, so that the amount of wear can be reduced.

  In consideration of the wet grip performance and the amount of wear, the number of sipes per block in the present embodiment is preferably 2 to 4. The direction of the sipe 5 is not particularly limited, but is preferably provided in the width direction in consideration of drainage of water from the block.

(2) Rubber Physical Properties of Tread In this embodiment, the rubber physical properties of the tread are, as described above, the dynamic properties measured at 30 ° C. under the conditions of a frequency of 10 Hz, an initial strain of 1%, and a dynamic strain rate of 5%. The product E ^* ＠ 30 ° C. × EB of the elastic modulus E ^* Ｅ30 ° C. (MPa) and the elongation at break EB (%) measured in accordance with JIS K6301 is 7000 to 20000, and the “loss tangent tan δ at 0 ° C.” Have rubber properties of 0.55 to 0.90.

(A) Dynamic elastic modulus and elongation at break The dynamic elastic modulus E ^* is an index indicating the rigidity of rubber. By having an appropriate rigidity, that is, the dynamic elastic modulus E ^* , the maneuverability and wet grip performance are improved. Can be both favorable. On the other hand, the elongation at break EB is an index indicating the followability to deformation generated due to the force applied to the rubber, and by having a large elongation at break, following the deformation, excellent durability can be obtained, The wear resistance is improved.

Therefore, the product of E ^* and EB can be used as an index for evaluating the wear characteristics. That is, usually, when E ^* increases, EB decreases. However, if E ^* of the rubber is set to be high and EB is set to be high, even if the rubber is deformed by receiving a force, the EB is reduced by elongation. Since it is possible to follow the deformation, a large contact area between the road surface and the rubber is ensured, the spring force applied per unit area thereof is absorbed, the wear of the tire can be suppressed, and the wear resistance is improved.

Since E ^* and EB can be represented by absolute values, E ^* × EB is preferable as an index for evaluating abrasion resistance.

Specifically, for example, the dynamic elastic modulus E ^{* ＊} 30 measured at a frequency of 10 Hz, an initial strain of 1%, and a dynamic strain rate of 5% (30 ° C.) using a viscoelasticity measuring device manufactured by Rheometrics Co., Ltd. ° C, the product E ^{* ＊} 30 ° C × EB of the elongation at break measured in accordance with JIS K6301 is preferably 7000 to 20,000, more preferably 8500 to 18,000, and more preferably 10,000 to 16,000. More preferred.

(B) Loss tangent at 0 ° C. (tan δ ＠ 0 ° C.)
The loss tangent at 0 ° C. (tan δ ＠ 0 ° C.) can be measured, for example, using a viscoelasticity measuring device manufactured by Rheometrics. The specific measurement is performed at 0 ° C. on the vulcanized rubber composition under the conditions of a frequency of 10 Hz, an initial strain of 1%, and a dynamic strain rate of 5%.

  In the present embodiment, tan δ is preferably 0.55 to 0.90 in order to secure the wear resistance and the wet grip performance. It is more preferably from 0.57 to 0.90, and further preferably from 0.60 to 0.90.

(3) Rubber Composition for Manufacturing Tread Next, a rubber composition for manufacturing the tread of the present embodiment will be described. The tread of the present embodiment is manufactured using a rubber composition in which the following rubber component (polymer) and a compounding material are compounded.

(A) Rubber Component In the present embodiment, the rubber component used in the rubber composition is not particularly limited. For example, natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), butyl rubber (IIR) ) And diene rubbers such as halogenated butyl rubber (X-IIR).

  Above all, it is preferable to use SBR as a main rubber component because wet grip performance and wear resistance can be obtained in a well-balanced manner.

In the present embodiment, the styrene content in the SBR is preferably from 10 to 60 wt%, and preferably from 20 to 50 wt%, in consideration of securing wet grip performance and securing rolling resistance characteristics and breaking strength at low temperatures. Is more preferable, and it is more preferable that it is 20 to 40 wt%. In addition, this styrene content is calculated by H ¹ -NMR measurement.

  At this time, the glass transition point (Tg) of the SBR is preferably -50 ° C or higher, more preferably -40 ° C or higher, and still more preferably -30 ° C or higher. By using such a high Tg SBR, wet grip performance can be further improved. This Tg is a value measured according to JIS K7121 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Co., Ltd. while heating at a heating rate of 10 ° C./min. (Middle point glass transition temperature).

  In the rubber composition of the present embodiment, the amount of SBR is 50 to 90 parts by mass in 100 parts by mass of the rubber component in consideration of securing wet grip performance and securing wear resistance. Is preferably 55 to 85 parts by mass, and more preferably 60 to 80 parts by mass.

  As the rubber component other than SBR, BR is preferably used, but is not limited.

  In consideration of ensuring abrasion resistance and ensuring wet grip performance and workability, the blending amount of BR is preferably BR in the remaining 100 parts by mass of the rubber component excluding SBR. That is, the amount is preferably 10 to 50 parts by mass. It is more preferably 15 to 45 parts by mass, and still more preferably 20 to 40 parts by mass.

  At this time, the mass average molecular weight (Mw) of BR is preferably 550,000 or more. By blending such a high molecular weight BR, the abrasion resistance can be further improved. In consideration of an improvement in workability, Mw is more preferably 550,000 to 1,500,000, further preferably 550,000 to 1,000,000. The Mw is measured by a gel permeation chromatograph (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation). Can be.

  An example of a specific high molecular weight BR is a high molecular weight BR having a high cis content of 96% or more of cis-1,4 butadiene units and synthesized by solution polymerization.

(B) Silica In the present embodiment, it is preferable to mix silica in the rubber composition. By incorporating silica, the reinforcing property is improved and the wet grip performance can be further improved. Examples of usable silica include silica produced by a wet method and silica produced by a dry method, but are not particularly limited. In addition, one kind of silica may be used alone, or two or more kinds may be used in combination.

The nitrogen adsorption specific surface area _(N 2 SA) of silica is, in view of ensuring the dispersibility and securing the reinforcing property, preferably 80~250m ² / g, more preferable to be 100~220m ² / g, 120~ More preferably, it is 200 m ² / g. This N ₂ SA is a value measured by the BET method according to ASTM D3037-81.

  The amount of the silica is preferably 20 to 200 parts by mass with respect to 100 parts by mass of the rubber component in consideration of securing of reinforcement and securing of dispersibility (kneading processability). It is more preferably from 30 to 150 parts by mass, and still more preferably from 40 to 100 parts by mass.

  In the present embodiment, a silane coupling agent may be used together with silica. Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, and bis (3-triethoxysilylpropyl) disulfide. Among them, bis (3-triethoxysilylpropyl) disulfide is preferred from the viewpoint that the reinforcing effect is high. These silane coupling agents may be used alone or in combination of two or more.

  Considering the saturation of the reinforcing effect and the viscosity (processability) of the rubber composition, the content of the silane coupling agent is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass with respect to 100 parts by mass of the silica. preferable.

(C) Carbon Black From the viewpoint of abrasion resistance, it is preferable to mix carbon black with the rubber composition of the present embodiment. Examples of the carbon black include carbon black produced by an oil furnace method, and two or more types having different colloidal properties may be used in combination. Specific examples include HAF, ISAF, SAF, and EPC. Among them, hard carbon-based carbon blacks such as SAF, ISAF, and HAF are preferable because of particularly high wear resistance.

The nitrogen adsorption specific surface area _(N 2 SA) of carbon black, in view to ensure the security and wear resistance of the wet grip performance, preferably 70 to 250 ² / g, preferably more When it is 110~200m ² / g . The dibutyl phthalate oil absorption (DBP) of the carbon black is preferably 50 to 250 ml / 100 g for the same reason. Incidentally, _N 2 SA of carbon black, JIS K 6217-2: 2001, DBP is, JIS K6217-4: a value measured according to the 2001.

  The amount of the hard carbon-based carbon black in the rubber composition is preferably 5 to 100 parts by mass with respect to 100 parts by mass of the rubber component in consideration of ensuring wet grip performance and ensuring abrasion resistance. Preferably, it is more preferably 20 to 90 parts by mass, and still more preferably 30 to 80 parts by mass.

(D) Resin In addition, in the present embodiment, the rubber composition includes styrene resin such as α-methylstyrene resin, coumarone indene resin, terpene resin, acrylic resin, rosin resin, vinyl toluene resin, polyisopentane resin, etc. It is preferable to mix two or more of these resins.

  Among these resins, an α-methylstyrene resin is particularly preferred from the viewpoint of improving wet grip performance. The compounding amount is preferably 5 to 50 parts by mass from the viewpoint of improving wet grip performance and ensuring abrasion resistance. The amount is more preferably 5 to 40 parts by mass, and further preferably 5 to 30 parts by mass.

(E) Other compounding agents In addition to the above compounding, the rubber composition of the present embodiment is generally used in the production of rubber such as a softener, an antioxidant, a vulcanizing agent, and a vulcanizing aid. Publicly known compounding agents can be compounded. The amount of the compounding agent can be appropriately selected.

  Oils can be mentioned as the softener. The oil is not limited, and for example, process oils, vegetable fats and oils, and mixtures thereof can be used. Examples of the process oil include a paraffin-based process oil, a naphthenic-based process oil, and an aromatic-based process oil. Also, as vegetable oils, castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, bean oil oil, Examples include sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, safflower oil, tung oil and the like. Among these oils, aromatic process oils are preferred.

  Examples of the anti-aging agent include diphenylamine (p- (p-toluenesulfonylamide) -diphenylamine, octylated diphenylamine, etc.) and p-phenylenediamine (N- (1,3-dimethylbutyl) -N′-phenyl-p). -Phenylenediamine (6PPD), N-phenyl-N'-isopropyl-p-phenylenediamine (IPPD), N, N'-di-2-naphthyl-p-phenylenediamine and the like can be used.

  As the vulcanizing agent, sulfur as a vulcanizing agent and a vulcanization accelerator can be appropriately used.

  Powdered sulfur may be used as sulfur, but oil-treated powdered sulfur is preferably used in consideration of dispersibility in rubber.

  As the vulcanization accelerator, a vulcanization accelerator generally used in combination with powdered sulfur in the rubber industry can be used. Specific examples of the vulcanization accelerator include, for example, sulfenamides, thiazoles, and thiurams. Thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, or xanthate-based vulcanization accelerators, and can be used alone, but two or more of them can be used. May be used in combination.

  Zinc oxide, stearic acid, and the like can also be used as a vulcanization accelerating aid.

2. Pneumatic Tire A tire manufactured using the above-described tread has a higher level of both abrasion resistance and wet grip performance, and thus can be used as a tire suitable for SUV.

  Hereinafter, the present invention will be described more specifically with reference to examples.

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

(1) Compounding materials First, each compounding material shown below was prepared based on each compounding prescription shown in Table 1.

(A) Rubber component (a) SBR-1 (high TgSBR): JSR0122 (manufactured by JSR)
・ Aromatic advanced oil (25.4wt%) oil-extended emulsion polymerization SBR
・ Styrene content (bound styrene content) 37% by mass
・ Tg -40 ℃

(B) SBR-2: JSR1502 (manufactured by JSR)
・ Non-oil-extended emulsion polymerization SBR
・ Styrene content (bound styrene content) 23.5% by mass
・ Tg -51 ° C

(C) SBR-3: Nipol-NS540 (manufactured by Zeon Corporation)
・ Development oil 25wt% oil extended solution polymerization SBR
・ Styrene content (bound styrene content) 42.0% by mass
・ Tg -27 ° C

(D) BR-1: UBEPOL-BR150B (manufactured by Ube Industries)
-Mass average molecular weight (Mw) 500,000
・ Cis-1,4 butadiene unit amount 97%

(E) BR-2 (high molecular weight BR): UBEPOL-BR360B (manufactured by Ube Industries)
-Weight average molecular weight (Mw) 570,000
・ Cis-1,4 butadiene unit amount 98%

(B) Silica and silane coupling agent (a) Silica (wet silica): ULTRASIL VN3 (manufactured by Evonik Japan)
・ Nitrogen adsorption specific surface area 175m ² / g

(B) Silane coupling agent: Si69 (manufactured by Evonik Japan)
-Type: Bis (3-triethoxysilylpropyl) disulfide

(C) Carbon black (a) CB-1 (hard carbon): N134 (manufactured by Tokai Carbon Co., Ltd.)
・ SAF-HS type ・ Nitrogen adsorption specific surface area (N ₂ SA) 142m ² / g
・ Dibutyl phthalate oil absorption (DBP) 130ml / 100g

(B) CB-2 (hard carbon): N220 (manufactured by Tokai Carbon Co., Ltd.)
・ ISAF type ・ Nitrogen adsorption specific surface area (N ₂ SA) 119 m ² / g
・ Dibutyl phthalate oil absorption (DBP) 114ml / 100g

(D) Resin: SYLVATRAXX 4401
・ Α-methylstyrene resin (manufactured by Arizona Chemical)

(E) Others-Softener: Diana Process NH-70S (aroma oil manufactured by Idemitsu Kosan Co., Ltd.)
・ Wax: Sunnock N (Ouchi Shinko Chemical Co., Ltd.), Tsubaki (NOF stearic acid)
Anti-aging agent: Antigen 6C and Antigen RD (Sumitomo Chemical Co., Ltd.)
・ Sulfur: powdered sulfur (made by Karuizawa sulfur)
・ Vulcanization aid: Jincock Super F-2 (Zinc oxide manufactured by Hakusui Tech Co., Ltd.)
・ Vulcanization accelerator: Noxeller DM and Noxeller TOT-N (Ouchi Shinko Chemical Co., Ltd.)

(2) Production of rubber composition for tread Using a Banbury mixer, materials other than the sulfur and the vulcanization accelerator are kneaded at 150 ° C. for 5 minutes from each of the compounding formulations shown in Table 1, and the rubber composition for the tread is prepared. Was manufactured.

2. Manufacture of Tire (1) Manufacture of Tread Next, sulfur and a vulcanization accelerator are added to the obtained rubber composition for a tread, and the mixture is kneaded with an open roll at 80 ° C. for 5 minutes to obtain an unvulcanized rubber. A composition was obtained. The obtained unvulcanized rubber composition was molded into a tread shape shown below to obtain a tread rubber.

・ L / S: 73%
-FSF80: 1.10
・ Average number of sipes: 3/1 block

(2) Production of test tires Using a tire molding machine, each tread rubber is bonded together with other tire members to form a low cover, and then vulcanized at 170 ° C. for 12 minutes to test for size 275 / 55R20. Tires were manufactured.

3. Performance Evaluation Test (1) Rubber Properties The following rubber properties were measured and evaluated for each of the test tires obtained. As the rubber properties other than below in Comparative Example 1, a type A hardness was measured in accordance with JIS K6253 is 66, _{M 100,} as measured in accordance (No. 3 dumbbell-shaped) in JIS K6301 is 2.8MPa , _{M 200} is 7.0 _{MPa, M 300} is 12.3MPa, TB was 19.0 MPa.

(A) Dynamic elastic modulus (E ^* )
Using a rheometrics viscoelasticity measuring device, the dynamic elastic modulus E ^* (E ^* Ｅ30 ° C.) (MPa) at 30 ° C. under the conditions of a frequency of 10 Hz, an initial strain of 1%, and a dynamic strain rate of 5% was measured. It was measured.

(B) Elongation at break (EB)
No. 3 dumbbell-shaped samples were prepared from each tire, and a tensile test was performed using a tensile tester manufactured by Toyo Seiki Co., Ltd. in accordance with JIS K6301, and the elongation at break (EB) (%) was measured.

(C) Loss tangent (tan δ)
Using a viscoelasticity measuring device manufactured by Rheometrics, the loss tangent tan δ (tan δ メ ト リ ッ ク 0 ° C.) at 0 ° C. was measured at a frequency of 10 Hz, an initial strain of 1%, and a dynamic strain rate of 5%.

(2) Abrasion performance evaluation test (a) Evaluation of actual vehicle wear performance Each test tire was mounted on all wheels of the vehicle (RAM1500), and on a dry asphalt road test course, at a speed of 80 km / h for 96 hours, the actual vehicle was used. The remaining groove amount after traveling is measured (15 mm when new), and a relative value when the remaining groove amount in Example 1 is set to 100 is obtained by the following equation (actual vehicle wear performance index). It can be evaluated that the larger the numerical value is, the more excellent the abrasion resistance is.
Actual vehicle wear performance index = (remaining groove amount of Example 1 / remaining groove amount of test tire) × 100

(B) Wet brake performance (WET performance) evaluation test Each test tire was mounted on all wheels of a vehicle (RAM 1500), and the braking distance from a speed of 100 km / h on a wet asphalt road surface was determined. As a result, a relative value when the braking distance in Example 1 is set to 100 is obtained by the following equation (wet brake performance index). The larger the value, the better the wet grip performance.
Wet brake performance index
= (Braking distance of Example 1 / braking distance of test tire) x 100

(3) Results of evaluation test Table 1 shows the results of the evaluation test.

From Table 1, in Examples 1 to 3, a tread rubber having a rubber property of tan δ of 0.55 to 0.90 and E ^* ＠ 30 ° C. × EB of 7000 to 20,000 is produced. It can be seen that by manufacturing a tire using such a tread rubber, a tire excellent in both actual vehicle wear performance and wet brake performance was manufactured.

  And each tread rubber in Examples 1-3 has 50-90 mass parts of SBR whose Tg is -50 degreeC or more, 10-50 mass parts of BR whose Mw is 550,000 or more, and 20-200 mass parts of silica. By mixing 5 to 100 parts by mass of carbon black composed of hard carbon and 5 to 50 parts by mass of α-methylstyrene resin.

On the other hand, in Comparative Examples 1 to 5, at least one of E ^* Ｅ30 ° C. × EB, wet brake performance, and actual vehicle wear performance was inferior to each of the examples, and wear resistance and wet grip performance were improved. It can be seen that is not fully compatible with the.

[2] Experiment 2
In Experiment 1, by using a tread rubber having a rubber property of tan δ of 0.55 to 0.90 and E ^* × 30 ° C. × EB of 7000 to 20,000, any of the actual vehicle wear performance and the wet brake performance was achieved. Then, it was found that an excellent tire could be obtained. Next, the effects of L / S and FSF80 were tested.

  Specifically, a test tire was manufactured in the same manner as in Example 1 in Experiment 1, except that L / S (5 levels) and FSF80 (5 levels) were changed as shown in Table 2. Similarly, an actual vehicle wear performance evaluation test and a wet grip performance evaluation test were performed.

  Table 2 shows the results. In Table 2, the wet grip performance index is shown on the left and the actual vehicle wear performance index is shown on the right.

  Table 2 shows that when L / S is 68 to 78% and FSF is 1.00 to 1.15, a tire excellent in both wet grip performance and actual vehicle wear performance can be obtained.

[3] Experiment 3
In Experiments 1 and 2, a tread rubber having tan δ of 0.55 to 0.90 and rubber properties of E ^* ＠ 30 ° C. × EB of 7000 to 20,000 was used, and L / S was 68 to 78% and By manufacturing the tread rubber so that the FSF is 1.00 to 1.15, it was found that a tire excellent in both actual vehicle wear performance and wet brake performance was obtained. The effect was tested.

  Specifically, a test tire was manufactured in the same manner as in Example 1 in Experiment 1, except that the average number of sipes in the block of the tread rubber was changed to 1 to 5 per block. An actual vehicle wear performance evaluation test and a wet grip performance evaluation test were performed.

  Table 3 shows the results. In Table 3, the wet grip performance index is shown on the left and the actual vehicle wear performance index is shown on the right.

  From Table 3, it can be seen that when the average number of sipes is 2 to 4 / block, a tire excellent in both wet grip performance and actual vehicle wear performance can be obtained.

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

DESCRIPTION OF SYMBOLS 1 Tread surface 2 Block 3 Vertical groove 4 Lateral groove 5 Sipe C Tire equator Te Tread end TW Tread tread width

Claims (15)

A pneumatic tire having a tread including a block surrounded by grooves on a tread surface,
A land sea ratio (L / S), which is a ratio of a land area (L), which is the total surface area of the ground contact portion of the block on the tread surface, and a sea area (S), which is the area of the entire groove bottom, is 68 to 78%. And
In a normal state with no load loaded into the normal rim and filled with the normal internal pressure, a ground contact length in the tire circumferential direction on the tire equator formed when a normal load is applied and the tread surface is pressed against a flat surface. The contact surface shape index (FSF80) represented by the ratio (SL0 / SL80) of the tire SL0 to the contact length SL80 in the tire circumferential direction at a position separated by 80% of the tread contact half width from the tire equator in the tire axial direction. , 1.00 to 1.15;
The average number of sipes in the block is 2 to 4 / block,
Said tread,
Dynamic elastic modulus E ^* ＠ 30 ° C. (MPa) measured at a frequency of 10 Hz, initial strain 1%, and dynamic strain rate 5% (30 ° C.), and breaking elongation EB (%) measured according to JIS K6301 The product E ^{* ＊} 30 ° C. × EB is 7000 to 20,000,
A pneumatic tire having a rubber property having a loss tangent tan δ at 0 ° C of 0.55 to 0.90.   The pneumatic tire according to claim 1, wherein the land sea ratio (L / S) is 70 to 76%.   The pneumatic tire according to claim 2, wherein the land sea ratio (L / S) is 72 to 74%.   The pneumatic tire according to any one of claims 1 to 3, wherein the ground contact surface shape index (FSF80) is 1.05 to 1.15.   The pneumatic tire according to claim 4, wherein the ground contact surface shape index (FSF80) is 1.10 to 1.15.   The pneumatic tire according to any one of claims 1 to 5, wherein the loss tangent tan δ at 0 ° C is from 0.57 to 0.90.   The pneumatic tire according to claim 6, wherein the loss tangent tan δ at 0 ° C is 0.60 to 0.90. 8. The pneumatic tire according to claim 1, wherein the E ^* ℃ 30 ° C. × EB is 8500 to 18000. 9. The pneumatic tire according to claim 8, wherein the E ^* ＠ 30 ° C. × EB is 10,000 to 16,000.   The said tread WHEREIN: 50-90 mass parts of styrene butadiene rubber (SBR) whose glass transition point (Tg) is -50 degreeC or more is mix | blended with 100 mass parts of rubber components. The pneumatic tire according to claim 9.   In the tread, 10 to 50 parts by mass of a butadiene rubber (BR) having a mass average molecular weight (Mw) of 550,000 or more is blended in 100 parts by mass of the rubber component. The pneumatic tire according to claim 10.   The pneumatic tire according to any one of claims 1 to 11, wherein the tread contains 20 to 200 parts by mass of silica with respect to 100 parts by mass of the rubber component.   13. The tread according to claim 1, wherein 5 to 100 parts by mass of carbon black composed of hard carbon is blended with respect to 100 parts by mass of the rubber component. Pneumatic tires.   14. The tread according to any one of claims 1 to 13, wherein 5 to 50 parts by mass of α-methylstyrene resin is blended with respect to 100 parts by mass of the rubber component. Pneumatic tire.   The pneumatic tire according to any one of claims 1 to 14, wherein the tire is an SUV tire.

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