JP2019093830A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire of which both of wear resistance and wet grip performance are achieved at a higher level.SOLUTION: A pneumatic tire has a tread which comprises a block, of which a circumference is surrounded by a groove, on a tread surface, in which a land-sea ratio (L/S) of a land area (L), which is a sum total of a ground part surface area of the block on the tread surface, to a sea area (S) which is an area of the whole of a groove bottom surface, is 68 to 78%, and a grounding surface shape index (FSF80) represented by a ratio (SL0/SL80) of a grounding length SL0 in a tire circumferential direction on a tire equator to a grounding length SL80 in the tire circumferential length at a position separated from the tire equator by a tire axial direction distance which is 80% of a grounding half-width is 1.00 to 1.15. An average siping number in the block is 2 to 4/one block, and the tread has a rubber physical property such that a loss tangent tanδ of the tread at an LAT abrasion index of 195 to 300, 0°C is 0.55 to 0.90.SELECTED DRAWING: None

Description

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

  2. Description of the Related Art A pneumatic tire for an automobile (hereinafter, also simply referred to as a "tire") has conventionally been emphasized on durability, and excellent abrasion resistance is required. Further, in recent years, safety considerations have been further increased, and further improvement of wet grip performance is required. Above all, for sport utility vehicles (SUVs), it is desirable to realize a pneumatic tire having both of these performances at a high level.

  However, since abrasion resistance and wet grip performance are in a contradictory relationship, it is not easy to make these two types of performance compatible. Therefore, in order to improve the abrasion resistance and the wet grip while keeping balance, the examination of the compounding material of the rubber composition constituting the tread (patent documents 1 and 2) and the examination of tread pattern (patent documents 3 and 4) And so on.

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

  However, under the present circumstances, it has not yet been achieved until the abrasion resistance and the wet grip performance can be compatible at the high level as desired in the above-mentioned SUV.

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

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

The invention according to claim 1 is
What is claimed is: 1. A pneumatic tire having a tread provided with a grooved block on the tread surface.
The land area ratio (L / S), which is the ratio of the land area (L), which is the sum of the ground surface area of the block on the tread surface, and the sea area (S), which is the area of the entire groove bottom, is 68 to 78%. As well as
In the unloaded normal condition with the normal rim filled with the normal internal pressure, the contact length in the tire circumferential direction on the tire equator formed when the 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 contact length SL80 in the tire circumferential direction at a position separating the tire axial distance of 80% of the tread contact half width from the tire equator , 1.00 to 1.15,
The average number of sipes in the block is 2 to 4 per block,
The tread is
LAT wear index 195-300,
It is a pneumatic tire characterized by having a rubber physical property whose loss tangent tan δ at 0 ° C. is 0.55 to 0.90.

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

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

The invention according to claim 4 is
The pneumatic tire according to any one of claims 1 to 3, wherein the contact surface shape index (FSF 80) is 1.05 to 1.15.

The invention according to claim 5 is
The pneumatic tire according to claim 4, wherein the contact surface shape index (FSF 80) 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 LAT wear index is 210 to 300.

The invention according to claim 7 is
The pneumatic tire according to claim 6, wherein the LAT wear index is 230 to 300.

The invention according to claim 8 is
The pneumatic tire according to any one of claims 1 to 7, wherein the loss tangent tan δ at 0 ° C is 0.57 to 0.90.

The invention according to claim 9 is
The pneumatic tire according to claim 8, wherein the loss tangent tan δ at 0 ° C is 0.60 to 0.90.

The invention according to claim 10 is
The tread of the present invention is characterized in that 50 to 90 parts by mass of styrene butadiene rubber (SBR) having a glass transition point (Tg) of -50 ° C or higher is blended in 100 parts by mass of the rubber component. It is a pneumatic tire according to any one of claims 9.

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

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

The invention according to claim 13 is
The tread according to any one of claims 1 to 12, wherein 5 to 100 parts by mass of carbon black made of hard carbon is blended with 100 parts by mass of the rubber component. Pneumatic tire.

The invention according to claim 14 is
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 100 parts by mass of the rubber component. It is a pneumatic tire.

The invention according to claim 15 is
It is a SUV tire, It is a pneumatic tire of any one of the Claims 1-14 characterized by the above-mentioned.

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

It is a figure showing the tread pattern of the tire tread concerning the 1 embodiment of the present invention. It is a schematic diagram which shows the ground-contacting surface shape which pressed the tread on the plane.

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

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

The pneumatic tire according to the present invention is
What is claimed is: 1. A pneumatic tire having a tread provided with a grooved block on the tread surface.
The land area ratio (L / S), which is the ratio of the land area (L), which is the sum of the ground surface area of the block on the tread surface, and the sea area (S), which is the area of the entire groove bottom, is 68 to 78%. As well as
In the unloaded normal condition with the normal rim filled with the normal internal pressure, the contact length in the tire circumferential direction on the tire equator formed when the 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 contact length SL80 in the tire circumferential direction at a position separating the tire axial distance of 80% of the tread contact half width from the tire equator , 1.00 to 1.15,
The average number of sipes in the block is 2 to 4 per block,
The tread is
LAT wear index 195-300,
It is characterized in that it has rubber physical properties such that the loss tangent tan δ at 0 ° C. is 0.55 to 0.90.

  The inventor does not examine each of the tread pattern and the rubber composition individually, but considers them as being related to each other, and as a result, adjusts the tread pattern of the tread to adjust the "land ratio (L / S)". And "ground surface shape index (FSF 80)" within a specific range, and adjusting the rubber composition of the tread to specify two kinds of "LAT wear index" and "loss tangent tan δ at 0 ° C" It has been found that by setting the value within the range, it is possible to provide a pneumatic tire in which the abrasion resistance and the wet grip performance, which are in a contradictory relationship, are well balanced at an advanced level.

[2] Embodiments of the Present Invention Hereinafter, the present invention will be specifically described based on the embodiments.
1. Tread (1) Tread pattern As described above, in the present embodiment, the tread surface of the tire has a land area ratio (L / S) and a contact surface shape index (FSF 80: Foot Print Shape Factor 80) within a specific range. It is characterized by being.

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

  The landsea ratio (L / S) will be specifically described with reference to FIG. 1 showing a tread pattern of a tire tread according to an embodiment of the present invention. In FIG. 1, 1 is a tread contact surface, C is a tire equator, Te is a tread edge, and TW is a tread contact width. Further, 2 is a block, 3 is a longitudinal groove, 4 is a lateral groove, and 5 is a sipe. The thick arrows indicate the tire rotation direction.

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

  In the above-mentioned land seal ratio (L / S), in order to secure a sufficient contact area and exert wet grip performance, and to sufficiently secure a drainage path and exhibit sufficient wet grip performance, L / S Is preferably 68 to 78%. It is more preferable that it is 70 to 76%, and it is further preferable that it is 72 to 74%.

(B) Grounding area shape index (FSF 80)
In the present invention, in a non-loaded normal state in which the pneumatic tire is rim-assembled to a normal rim and filled with a normal internal pressure, the pneumatic tire is loaded with a normal load to press the tread into a flat contact surface shape The ground contact area shape index (FSF 80) derived from the above is preferably 1.00 to 1.15. By setting the ground contact area shape index (FSF 80) within the above range, it is possible to ensure good wear resistance and wet grip performance.

  The contact area shape index (FSF 80) will be specifically described with reference to FIG. 2 which is a schematic view showing the contact surface shape in which the tread is pressed against a flat surface.

FIG. 2 shows a contact surface shape (FP: footprint) in which the tread is pressed against a flat surface, and the contact length of the tire circumferential direction (tire rotating direction) on the tire equator is SL0, and the tread is grounded from the tire equator When the contact length in the circumferential direction of the tire at a position separating the axial distance (0.8a) of the half width (a) is 80%, the contact area shape index (FSF 80) is expressed by the following equation. The term “tread contact half width” means half of the axial distance between the outermost tread ends in the tire axial direction on the tread surface.
Grounding area shape index (FSF80) = SL0 / SL80

  In the contact area shape index (FSF 80), in order to ensure sufficient wear resistance and wet grip performance, it is preferable to set FSF 80 to 1.00 to 1.15. It is more preferably 1.05 to 1.15, and still more preferably 1.10 to 1.15.

  In the above, the “regular rim” is a rim that defines the standard for each tire in the standard system including the standard on which the tire is based. In the case of "Rim", in the case of ETRTO "Measuring Rim".

  The “normal internal pressure” is the air pressure specified for each tire in the above standard, the maximum air pressure in the case of JATMA, and the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFlation PRESSURES” in the case of TRA by ETRTO. If there is, it will be "INFLATION PRESSURE".

  The “normal load” is the load specified for each tire in the above standard, and in the case of JATMA, the maximum load capacity, and in the case of TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFlation PRESSURES”, ETRTO In this case, "LOAD CAPACITY" is set.

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

(C) Sipe As described above, FIG. 1 is a view showing a tread pattern of a tire tread according to an embodiment of the present invention, 1 is a tread contact surface, C is a tire equator, Te is a contact end, TW is a tread It is a tread contact width. Further, 2 is a block, 3 is a longitudinal groove, 4 is a lateral groove, and 5 is a sipe.

  The contact surface 1 is provided with a plurality of blocks 2 whose circumference is surrounded by the longitudinal grooves 3 and the lateral grooves 4. In addition, the block 2 is provided with a plurality of sipes 5 (thin grooves), specifically 2 to 4 per block.

  As described above, by forming the block 2 surrounded by the grooves 3 and 4 around, even when traveling on a wet road surface, water can be smoothly drained from the grooves, so sufficient wet grip performance can be achieved. It can be demonstrated.

  And, by providing the sipes 5 in the block 2, the water accumulated on the block 2 can be smoothly drained, so the wet grip performance can be further improved. Further, when the sipes 5 are 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 two to four. The direction of the sipe 5 is not particularly limited, but in consideration of drainage of water from the block, it is preferable to provide in the width direction.

(2) Rubber physical properties of the tread In the present embodiment, the rubber physical properties of the tread are, as described above, the loss tangent at LAT wear index of 195 to 300, 0 ° C. (tan δ @ 0 ° C.) (hereinafter simply referred to as “tan δ (Also referred to as “0.5” to “0.90”).

(A) LAT Wear Index The LAT wear index is an index for evaluating wear resistance, and is measured using a friction tester, for example, a LAT tester (Laboratory Abration and Skid Teste) such as LAT 100 (manufactured by VMI). Be done. The measurement is carried out by vulcanizing the unvulcanized rubber composition at 170 ° C. for 20 minutes with a 0.5 mm mold, and using the vulcanized rubber composition, conditions of load 50 N, speed 20 km / h, slip angle 5 ° Measure the volume loss of the vulcanized rubber composition (volume loss to be evaluated), and use it as the standard composition, for example, the volume loss in the vulcanized rubber composition of the basic formulation of the conventional tread rubber (standard volume The relative value when the loss amount) is 100 is determined by the following equation. It can be evaluated that the larger the numerical value is, the better the wear resistance is.
LAT wear index = (reference volume loss / volume loss to be evaluated) × 100

  In the present embodiment, the LAT wear index is preferably 195 to 300 as described above in order to secure sufficient wear resistance. It is more preferable that it is 210-300, and it is further more preferable that it is 230-300.

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

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

(3) Rubber composition for producing tread Next, a rubber composition for producing 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 compounding material are blended.

(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) can be used.

  Among them, SBR is preferably used 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 SBR is preferably 10 to 60 wt%, 20 to 50 wt%, in consideration of securing wet grip performance, rolling resistance characteristics, and securing breaking strength at low temperature. Is more preferably 20 to 40 wt%. The styrene content is calculated by H ¹ -NMR measurement.

  At this time, the glass transition point (Tg) of 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, the wet grip performance can be further improved. The Tg is a value measured while raising the temperature at a temperature rising rate of 10 ° C./min using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Ltd. in accordance with JIS K7121. (Mid-point glass transition temperature).

  And, in the rubber composition of the present embodiment, the blending amount of SBR is 50 to 90 parts by mass in 100 parts by mass of the rubber component, in consideration of securing of wet grip performance and securing of abrasion resistance. Is preferable, and it is more preferable that it is 55-85 mass parts, and it is further more preferable that it is 60-80 mass parts.

  And although it is preferable to use BR as rubber components other than SBR, it is not limited.

  As the compounding amount of BR, it is preferable that the remaining part excluding SBR is 100 parts by mass of the rubber component in consideration of securing of wear resistance and securing of wet grip performance and processability. That is, it is preferable that it is 10-50 mass parts. It is more preferable that it is 15-45 mass parts, and it is further more preferable that it is 20-40 mass parts.

  At this time, the mass average molecular weight (Mw) of BR is preferably 550,000 or more. Wear resistance can be further improved by blending such high molecular weight BR. In addition, in consideration of improvement in processability, Mw is more preferably 550,000 to 1,500,000, and further preferably 550,000 to 1,000,000. In addition, this Mw should be measured by gel permeation chromatograph (GPC) (Tosoh Corp. GPC-8000 series, detector: Differential refractometer, column: TSKEL SUPERMALTPORE HZ-M manufactured by Tosoh Corp.) Can.

  As an example of a specific high molecular weight BR, a high molecular weight BR which is high-cis having a cis-1,4 butadiene unit content of 96% or more and is synthesized by solution polymerization can be mentioned.

(B) Silica In the present embodiment, it is preferable to blend silica in the rubber composition. By blending silica, the reinforcing property can be improved and the wet grip performance can be further improved. Examples of the silica that can be used include silica manufactured by a wet method, silica manufactured by a dry method, and the like, but there is no particular limitation. In addition, a silica may be used individually by 1 type and may be used in combination of 2 or more type.

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. Incidentally, the _N 2 SA is a value measured by the BET method in accordance with ASTM D3037-81.

  As a compounding quantity of silica, it is preferable that it is 20-200 mass parts with respect to 100 mass parts of rubber components, when ensuring of reinforcement property and ensuring of dispersibility (kneading processability) are considered. The amount is more preferably 30 to 150 parts by mass, and further preferably 40 to 100 parts by mass.

  In the present embodiment, a silane coupling agent may be used in combination with silica. Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide and the like. Among these, bis (3-triethoxysilylpropyl) disulfide is preferable in that it has a high reinforcing property improvement effect. These silane coupling agents may be used alone or in combination of two or more.

  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 silica, in consideration of saturation of reinforcing effect and viscosity (processability) of the rubber composition. preferable.

(C) Carbon Black From the viewpoint of wear resistance, it is preferable to blend carbon black into 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 different types of colloidal characteristics may be used in combination. Specific examples thereof include HAF, ISAF, SAF, and EPC. Among these, hard carbon-based carbon blacks such as SAF, ISAF, and HAF are particularly preferable because they have high abrasion 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 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 compounding amount of the hard carbon carbon black in the rubber composition is 5 to 100 parts by mass with respect to 100 parts by mass of the rubber component, in consideration of securing of wet grip performance and of 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 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. These resins are preferably blended, and two or more of these resins may be used in combination.

  Among these resins, α-methylstyrene resin is particularly preferable in terms of the improvement of the wet grip performance. The compounding amount is preferably 5 to 50 parts by mass from the viewpoint of the improvement of the wet grip performance and the securing of the abrasion resistance. It is more preferable that it is 5-40 mass parts, and it is further more preferable that it is 5-30 mass parts.

(E) Other compounding agents In addition to the above compounding, the rubber composition of the present embodiment is generally used for the production of rubbers such as a softener, an antiaging agent, a vulcanizing agent, a vulcanizing aid and the like. Can be blended. The addition amount of the compounding agent can be appropriately selected.

  An oil can be mentioned as a softening agent. The oil is not limited, and, for example, process oil, vegetable oil, and mixtures thereof can be used. Examples of process oils include paraffinic process oils, naphthenic process oils, and aromatic process oils. In addition, as vegetable oil, castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine oil, pine tar, tall oil, corn oil, rice oil, vegetable oil, Examples include sesame oil, olive oil, sunflower oil, palm kernel oil, soy sauce, jojoba oil, macadamia nut oil, safflower oil, soy sauce and the like. Among these oils, aromatic process oils are preferred.

  As an antiaging agent, diphenylamines (p- (p-toluenesulfonylamide) -diphenylamine, octylated diphenylamine, etc.), p-phenylenediamines (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 a vulcanizing agent, sulfur which is a vulcanizing agent and a vulcanization accelerator can be suitably used.

  As sulfur, although powdered sulfur may be used, it is preferable to use oil-treated powdered sulfur in consideration of dispersibility in rubber.

  As a vulcanization accelerator, a vulcanization accelerator generally used in combination with powdered sulfur in the rubber industry can be used, and as a specific vulcanization accelerator, for example, sulfenamide type, thiazole type, thiuram type And thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerators may be used alone or in combination. You may use together.

  Moreover, zinc oxide, stearic acid, etc. can also be used as a vulcanization acceleration adjuvant.

2. Pneumatic Tire The tire manufactured using the above-described tread can be used as a tire suitable for SUV because the wear resistance and the wet grip performance are compatible at a higher level.

  Hereinafter, the present invention will be more specifically described by way of examples.

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

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

(A) Rubber component (i) SBR-1 (high Tg SBR): JSR0122 (manufactured by JSR Corporation)
・ Aromatic-based developed oil (25.4 wt%) oil extended emulsion polymerization SBR
-Styrene content (bound styrene amount) 37% by mass
・ Tg -40 ° C

(B) SBR-2: JSR 1502 (manufactured by JSR Corporation)
・ Non-oil spread emulsion polymerization SBR
-Styrene content (bound styrene amount) 23.5 mass%
· Tg-51 ° C

(C) BR-1: UBEPOL-BR150B (manufactured by Ube Industries, Ltd.)
・ Mass average molecular weight (Mw) 500,000
· 97% of cis-1,4 butadiene unit

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

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

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

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

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

(D) Resin: SYLVATRAXX 4401
· Α-Methylstyrene resin (Arizona Chemical)

(E) Others-Softener: Diana Process NH-70S (Aroma oil manufactured by Idemitsu Kosan Co., Ltd.)
・ Wax: Sannock N (made by Ouchi New Chemical Co., Ltd.), 椿 (made by NOF Corporation stearic acid)
・ Anti-aging agent: Antigen 6C and Antigen RD (manufactured by Sumitomo Chemical Co., Ltd.)
Sulfur: Powdered sulfur (made by Karuizawa Sulfur Co., Ltd.)
Vulcanization assistant: Jincock Super F-2 (Haxuitec Zinc Oxide)
Vulcanization accelerator: Noxceler DM and Noxceler TOT-N (made by Ouchi New Chemical Co., Ltd.)

(2) Production of rubber composition for tread Using a Banbury mixer, materials other than sulfur and a vulcanization accelerator are kneaded at 150 ° C. for 5 minutes out of the respective formulation shown in Table 1 to obtain a rubber composition for tread Made things.

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

・ L / S: 73%
FSF 80: 1.10
・ Average sipe number: 3 per 1 block

(2) Production of test tire Each tread rubber is bonded together with other tire members using a tire molding machine, and then a low cover is molded, and then molded by vulcanization at 170 ° C. for 12 minutes, test of size 275 / 55R20 A tire was manufactured.

3. Performance evaluation test The following rubber physical properties were measured and evaluated about each obtained tire for a test. In addition, as rubber physical properties other than the following in the comparative example 1, Type A hardness measured based on JIS K6253 is 66, frequency 10Hz, initial strain 1%, dynamic distortion rate 5% conditions (30 ° C.) Measured E ^* @ 30 ° C. is 12.0 MPa, tan δ @ 30 ° C. is 0.28, and measured according to JIS K 6301 (No. 3 dumbbell shape) M ₁₀₀ is 2.8 MPa, M ₂₀₀ is 7.0 MPa , M ₃₀₀ was 12.3 MPa, TB was 19.0 MPa, and EB was 430%.

(1) Loss tangent (tan δ)
Using a rheometrics visco-elasticity measuring device, tan δ (tan δ @ 0 ° C.) at 0 ° C. was measured under the conditions of a frequency of 10 Hz, an initial strain of 1%, and a dynamic strain rate of 5%.

(2) Wear resistance performance evaluation test (a) Measurement of LAT wear index According to the method described above, the LAT wear index was calculated from the following equation using a LAT tester. In addition, as a reference | standard volume loss amount, the volume loss amount of the comparative example 1 (basic composition of the conventional tread rubber) was used. It can be evaluated that the larger the numerical value is, the better the wear resistance is.
LAT wear index = (reference volume loss / volume loss to be evaluated) × 100

(B) Evaluation of Wear Performance of Vehicles Remaining grooves after running on a test road of dry asphalt road surface for 96 hours at a speed of 80 km / h with each test tire mounted on all wheels of a vehicle (RAM 1500) The amount is measured (15 mm when new), and the relative value when the residual groove amount of Example 1 is 100 is determined by the following equation (actual vehicle wear performance index). It can be evaluated that the larger the numerical value is, the better the wear resistance is.
Actual wheel wear performance index = (remaining groove amount of Example 1 / remaining groove amount of test tire) × 100

(3) Wet brake performance (WET performance) evaluation test Each test tire was mounted on all wheels of a vehicle (RAM 1500), and a braking distance from a speed of 100 km / h was determined on a wet asphalt road surface. As a result, the relative value when the braking distance in Example 1 is 100 is determined 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

(4) Results of evaluation test The results of the evaluation test are shown in Table 1.

  From Table 1, in Examples 1 to 4, a tread rubber having a rubber physical property having a tan δ of 0.55 to 0.90 and a LAT wear index of 195 to 300 is manufactured, and such a tread rubber It can be seen that by manufacturing a tire using the tire, a tire excellent in both the real car wear performance and the wet brake performance was manufactured.

  And each tread rubber in Examples 1-4 has 50-90 mass parts of SBR whose Tg is -50 ° C or more, 10-50 mass parts of BR whose Mw is 550,000 or more, and 20-200 mass parts of silica. And 5 to 100 parts by mass of a carbon black composed of hard carbon and 5 to 50 parts by mass of an α-methylstyrene resin.

  On the other hand, in Comparative Examples 2 to 5, at least one physical property of the LAT wear index, the wet brake performance, and the in-vehicle wear performance is inferior to each example, and the wear resistance and the wet grip performance are sufficient. It turns out that we can not achieve both.

[2] Experiment 2
In Experiment 1, by using a tread rubber having a physical property of tan δ of 0.55 to 0.90 and a LAT wear index of 195 to 300, both the actual vehicle wear performance and the wet brake performance were excellent. Since it turned out that a tire was obtained, next, it experimented about the influence of L / S and FSF80.

  Specifically, a test tire was manufactured in the same manner as Example 1 in Experiment 1, except that L / S (five levels) and FSF 80 (five levels) were changed as shown in Table 2. Similarly, a vehicle wear performance evaluation test and a wet grip performance evaluation test were conducted.

  The results are shown in Table 2. In Table 2, the wet grip performance index is described on the left, and the actual wear performance index is described on the right.

  It can be seen from Table 2 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 in-vehicle wear performance can be obtained.

[3] Experiment 3
In experiments 1 and 2, a tread rubber having a rubber physical property having tan δ of 0.55 to 0.90 and a LAT wear index of 195 to 300 is used, L / S is 68 to 78%, and FSF is 1. It was found that by manufacturing the tread rubber so as to be 00 to 1.15, it was found that a tire excellent in both the real car wear performance and the wet brake performance can be obtained. .

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

  The results are shown in Table 3. In Table 3, the wet grip performance index is shown on the left, and the actual wear performance index is on the right.

  It can be seen from Table 3 that when the average sipe number is 2 to 4 per 1 block, a tire excellent in both wet grip performance and actual vehicle wear performance can be obtained.

  As mentioned above, although the present invention was explained based on an embodiment, the present invention is not limited to the above-mentioned embodiment. Various modifications can be made to the above embodiment within the same and equivalent scope of the present invention.

1 contact surface 2 block 3 longitudinal groove 4 lateral groove 5 sipe C tire equator Te contact end TW tread contact width

Claims (15)

What is claimed is: 1. A pneumatic tire having a tread provided with a grooved block on the tread surface.
The land area ratio (L / S), which is the ratio of the land area (L), which is the sum of the ground surface area of the block on the tread surface, and the sea area (S), which is the area of the entire groove bottom, is 68 to 78%. As well as
In the unloaded normal condition with the normal rim filled with the normal internal pressure, the contact length in the tire circumferential direction on the tire equator formed when the 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 contact length SL80 in the tire circumferential direction at a position separating the tire axial distance of 80% of the tread contact half width from the tire equator , 1.00 to 1.15,
The average number of sipes in the block is 2 to 4 per block,
The tread is
LAT wear index 195-300,
A pneumatic tire characterized by having a rubber physical property having a loss tangent tan δ at 0.5 ° C of 0.55 to 0.90.   The pneumatic tire according to claim 1, wherein the landsea ratio (L / S) is 70 to 76%.   The pneumatic tire according to claim 2, wherein the landsea ratio (L / S) is 72 to 74%.   The pneumatic tire according to any one of claims 1 to 3, wherein the contact surface shape index (FSF 80) is 1.05 to 1.15.   The pneumatic tire according to claim 4, wherein the contact surface shape index (FSF 80) is 1.10 to 1.15.   The pneumatic tire according to any one of claims 1 to 5, wherein the LAT wear index is 210 to 300.   The pneumatic tire according to claim 6, wherein the LAT wear index is 230 to 300.   The pneumatic tire according to any one of claims 1 to 7, wherein the loss tangent tan δ at 0 ° C is 0.57 to 0.90.   The pneumatic tire according to claim 8, wherein the loss tangent tan δ at 0 ° C is 0.60 to 0.90.   The tread of the present invention is characterized in that 50 to 90 parts by mass of styrene butadiene rubber (SBR) having a glass transition point (Tg) of -50 ° C or higher is blended in 100 parts by mass of the rubber component. The pneumatic tire according to any one of claims 9.   In the tread, 100 parts by mass of the rubber component is mixed with 10 to 50 parts by mass of butadiene rubber (BR) having a mass average molecular weight (Mw) of 550,000 or more. The pneumatic tire according to any one of claims 10.   The pneumatic tire according to any one of claims 1 to 11, wherein 20 to 200 parts by mass of silica is compounded with respect to 100 parts by mass of the rubber component in the tread.   The tread according to any one of claims 1 to 12, wherein 5 to 100 parts by mass of carbon black made of hard carbon is blended with 100 parts by mass of the rubber component. Pneumatic tire.   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 100 parts by mass of the rubber component. Pneumatic tire.   The pneumatic tire according to any one of claims 1 to 14, wherein the pneumatic tire is an SUV tire.

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