WO2019155799A1 - Rubber composition and pneumatic tire - Google Patents

Abstract

The present invention provides a rubber composition and a pneumatic tire which ensure excellent grip performance (wet grip performance, dry grip performance, etc.). The present invention relates to a rubber composition having a maximum temperature of 30°C or lower when subjected to friction under predetermined frictional conditions.

Description

Rubber composition and pneumatic tire

The present invention relates to a rubber composition and a pneumatic tire.

Rubber compositions used for tire treads and the like are required to have grip performance (wet grip performance, dry grip performance, etc.) from the viewpoint of safety and the like, and various devices have been conventionally made.

For example, a rubber composition having improved silica dispersibility by adding a silica compound for improving wet grip performance or the like and further adding a silane coupling agent such as bis (3-triethoxysilylpropyl) tetrasulfide has been proposed ( Patent Document 1).

However, demands for improving grip performance such as wet grip performance are severe, and further improvements are required.

JP 2011-57797 A

An object of the present invention is to solve the above problems and provide a rubber composition excellent in grip performance (wet grip performance, dry grip performance, etc.) and a pneumatic tire.

The present invention relates to a rubber composition having a maximum temperature during friction of 30 ° C. or less under the following friction conditions.
[Friction conditions]
(1) Size and shape of rubber composition: 2 mm thick sheet (width 16 mm)
(2) Measuring plate: A flat plate made of Al ₂ O ₃

The maximum temperature is preferably 25 ° C. or lower.
The maximum temperature is preferably 23 ° C. or lower.

The present invention also relates to a pneumatic tire using the rubber composition in a tread.

Since the present invention is a rubber composition in which the maximum temperature during friction under a predetermined friction condition is 30 ° C. or less, a pneumatic tire excellent in grip performance (wet grip performance, dry grip performance, etc.) can be provided.

FIG. 1 is a cross-sectional view showing a situation in which the temperature of a sample surface during friction under a predetermined friction condition is measured. FIG. 2 is a perspective view showing some devices used in the temperature measurement of FIG. FIG. 2 is a relationship diagram between the number of friction tests and the dynamic friction coefficient μ in Table 1. FIG. 2 is a relationship diagram between the number of friction tests and the dynamic friction coefficient μ in Table 1.

The rubber composition of the present invention has a maximum temperature during friction under a predetermined friction condition of 30 ° C. or less.

Japanese Patent Application Laid-Open No. 2016-70880 describes that the temperature of a rubber composition at a portion where a frictional force is actually applied can be measured by a method of measuring the maximum temperature at the time of friction.
In the present invention, it has been found that the maximum temperature (instantaneous calorific value, flash temperature) varies depending on the rubber composition, and further, when the rubber composition has the maximum temperature of 30 ° C. or less, the grip performance is improved. This finding has been completed.
The reason why the grip performance is improved is not necessarily clear, but if the calorific value is low, the grip performance will decrease during driving because the influence of thermal sag is less and the viscoelastic region used does not shift to the high temperature side. Therefore, it is presumed that the grip performance is improved as a whole during traveling.
Both wet grip performance and dry grip performance show the same tendency. When the maximum temperature is 30 ° C. or less, a tire excellent in wet grip performance and dry grip performance can be provided.

The rubber composition is a rubber composition having a maximum temperature of 30 ° C. or less during friction under the following friction conditions, preferably 27 ° C. or less, more preferably 25 ° C. or less, and even more preferably 23 ° C. or less. Grip performance improves that it is 30 degrees C or less. Moreover, the minimum of the said maximum temperature is although it does not specifically limit, Preferably it is 20 degreeC or more.
[Friction conditions]
(1) Size and shape of rubber composition: 2 mm thick sheet (width 16 mm)
(2) Measuring plate: A flat plate made of Al ₂ O ₃

The maximum temperature can be measured by the method described in Japanese Patent Application Laid-Open No. 2016-70880. Specifically, the maximum temperature can be measured by the method described in the examples described later (measurement of the maximum temperature).

The maximum temperature is the temperature of the hottest part of the surface temperature of the rubber composition (sample) during the friction test. Specifically, the temperature distribution of the surface of each part of the sample (rubber composition) is measured using the method described in JP-A-2016-70880, and from 7 km / hour to 0 km / hour after the start of the test. (The highest surface temperature of the part (location) where the highest surface temperature is detected) is adopted.

A rubber composition having a maximum temperature at the time of friction of 30 ° C. or less under the friction conditions can be produced by appropriately selecting the blending and manufacturing method.
Specifically, carbon fiber, a resin crosslinking agent, addition of a compound represented by the formula (I), adjustment of the blending amount thereof, and the like can be given.

The rubber components usable in the rubber composition include isoprene-based rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene- Examples include diene rubbers such as isoprene-butadiene copolymer rubber (SIBR), ethylene propylene diene rubber (EPDM), butyl rubber (IIR), and halogenated butyl rubber (X-IIR). These diene rubbers may be used alone or in combination of two or more. Among these, SBR, isoprene-based rubber, and BR are preferable from the viewpoint that the effects of the present invention can be obtained better, and SBR is more preferable from the viewpoint of grip performance.

The SBR is not particularly limited, and for example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR), and the like can be used. These may be used alone or in combination of two or more.

The SBR may be non-modified SBR or modified SBR.
The modified SBR may be any SBR having a functional group that interacts with a filler such as silica. For example, at least one terminal of SBR is modified with a compound having a functional group (modifier). SBR (terminal-modified SBR having the above-mentioned functional group at the terminal), main-chain-modified SBR having the above-mentioned functional group at the main chain, and main-chain end-modified SBR having the above-mentioned functional group at the main chain and the terminal (for example, in the main chain) A hydroxyl group modified (coupled) with a polyfunctional compound having the above functional group and having at least one terminal modified with the above modifier with a main chain terminal modified SBR) or a polyfunctional compound having two or more epoxy groups in the molecule. And terminal-modified SBR into which an epoxy group has been introduced. These may be used alone or in combination of two or more.

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

As SBR, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used, for example.

The vinyl content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more. The vinyl content is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 35% by mass or less. There exists a tendency for favorable grip performance to be acquired by making it more than a minimum. By setting it to the upper limit or less, good durability tends to be obtained.
In the present specification, the vinyl content can be measured by infrared absorption spectrum analysis.

The styrene content of SBR is preferably 20% by mass, more preferably 25% by mass or more. Moreover, this styrene content becomes like this. Preferably it is 60 mass% or less, More preferably, it is 50 mass% or less, More preferably, it is 45 mass% or less. There exists a tendency for favorable grip performance to be acquired by making it more than a minimum. By setting it to the upper limit or less, good durability can be obtained, and there is a tendency that the temperature dependency is reduced and the performance change with respect to the temperature change can be suppressed.
In the present specification, the styrene content of SBR can be calculated by H ¹ -NMR measurement.

The content of SBR is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, particularly preferably 90% by mass, and 100% by mass in 100% by mass of the rubber component. May be. When it is 50% by mass or more, better grip performance can be obtained.

Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. As the NR, for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20 and the like can be used. As IR, it is not specifically limited, For example, IR2200 etc. can use what is common in tire industry. As modified NR, deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., modified NR, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B, BR150B and other high cis content BR, Ube Industries, Ltd. VCR412, VCR617, etc. BR containing tactic polybutadiene crystals can be used. These may be used alone or in combination of two or more. Among them, the BR cis content is preferably 95% by mass or more because the wear resistance performance is improved.

BR may be non-modified BR or modified BR. These may be used alone or in combination of two or more.
Examples of the modified BR include a modified BR in which the same functional group as that of the above-described modified SBR is introduced.

As BR, for example, products such as Ube Industries, JSR, Asahi Kasei, Nippon Zeon, and the like can be used.

The rubber composition preferably contains carbon black. Although it does not specifically limit as carbon black, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762 etc. are mentioned. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 5 m ² / g or more, more preferably 50 m ² / g or more, and still more preferably 100 m ² / g or more. There exists a tendency for favorable grip performance to be acquired by making it more than a minimum. Further, the _N 2 SA is preferably 200 meters ² / g or less, more preferably 150 meters ² / g, more preferably not more than 130m ² / g. By making it below the upper limit, good dispersion of carbon black tends to be obtained.
Incidentally, the nitrogen adsorption specific surface area of carbon black can be determined according to JIS K6217-2: 2001.

Examples of carbon black include products such as Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Shin-Nikka Carbon Co., Ltd., Columbia Carbon Co., etc. Can be used.

When the rubber composition contains silica, the content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 10 parts by mass or less, more preferably 8 parts by mass or less. There exists a tendency for favorable grip performance to be acquired by making it in the said range.

When the rubber composition does not contain silica, the carbon black content is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and still more preferably 70 parts by mass or more with respect to 100 parts by mass of the rubber component. is there. The content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and still more preferably 100 parts by mass or less. There exists a tendency for favorable grip performance to be acquired by making it in the said range.

The rubber composition preferably contains pitch-based carbon fibers.

As the pitch-based carbon fiber, a coal pitch-based carbon fiber is preferable because the effects of the present invention can be obtained more favorably.

The thermal conductivity (in the fiber axis direction) of the pitch-based carbon fiber is preferably 100 W / m · K or more, more preferably 120 W / m · K or more, still more preferably 130 W / m · K or more, and particularly preferably 135 W / m. -K or more. The upper limit of the thermal conductivity is not particularly limited, but is preferably 1500 W / m · K or less, more preferably 1000 W / m · K or less, and still more preferably 500 W / m · K or less. Within the above range, the effects of the present invention can be obtained better.
In the present specification, the thermal conductivity of the pitch-based carbon fiber is obtained from the value of the electrical resistivity by the following formula using a very good correlation between the thermal conductivity of the carbon fiber and the electrical resistivity. Calculated.
K = 1272.4 / ER-49.4
(K represents the thermal conductivity (W / m · K) of the carbon fiber, and ER represents the electrical resistivity (μΩm) of the carbon fiber.)

The pitch-based carbon fiber preferably has an average fiber diameter of 1 to 80 μm from the viewpoint of dispersion in rubber and improvement of thermal conductivity. The lower limit of the average fiber diameter is more preferably 3 μm or more, and further preferably 5 μm or more. Further, the upper limit of the average fiber diameter is more preferably 30 μm or less, and still more preferably 20 μm or less.

The pitch-based carbon fiber preferably has an average fiber length of 0.1 to 30 mm from the viewpoint of dispersion in rubber and improvement of thermal conductivity. The lower limit of the average fiber length is more preferably 1 mm or more, and further preferably 4 mm or more. Moreover, the upper limit of average fiber length becomes like this. More preferably, it is 15 mm or less, More preferably, it is 10 mm or less.
In addition, the said average fiber diameter and average fiber length can be measured by electron microscope observation, for example.

The pitch-based carbon fiber in the present invention is not particularly limited. For example, a coal pitch-based carbon fiber obtained by a production method described in JP-A-7-331536 is preferably used. Specifically, the pitch fiber is infusible according to a conventional method, and carbonized and / or graphitized at a desired temperature to obtain “carbon fiber as a raw material”. A coal pitch-based carbon fiber can be produced by placing it in a graphite crucible together with the graphitized packing coke and performing a graphitization treatment.

In addition, as pitch fiber (spinning pitch) used by the said manufacturing method, carbonaceous raw materials (40% or more, preferably 70% or more, more preferably 90%) such as coal-based coal tar, coal tar pitch, and coal liquefaction. And those obtained by spinning using an optically anisotropic structure of at least%). Moreover, a sizing agent (such as an epoxy compound or a water-soluble polyamide compound) may be attached to the “carbon fiber as a raw material”.

By the manufacturing method, the thermal conductivity in the fiber axis direction is 100-1500 W / m · K, the tensile elastic modulus is 85 ton / mm ² or more, the compressive strength is 35 kg / mm ² or more, the graphite crystal lamination thickness Lc is 30-50 nm, Coal pitch-based carbon fibers having a ratio (La / Lc) with a spread La in the layer surface direction of the graphite crystal of 1.5 times or more and a domain size in a cross section in the fiber axis direction of 500 nm or less can be produced. Can be suitably used. The tensile elastic modulus, compressive strength, Lc, La, domain size, and optical anisotropic structure ratio can be measured by the method described in the above publication.

The coal pitch-based carbon fiber produced by the above production method uses a liquid crystal (mesophase) whose molecular orientation is regulated in one direction as a raw material, and therefore has a very high degree of crystallinity, a high elastic modulus and a high thermal conductivity.
The coal pitch-based carbon fiber in the present invention preferably has a structure in which polycyclic aromatic molecular skeletons are stacked in layers. As a commercial product of coal pitch-based carbon fiber, “K6331T” manufactured by Mitsubishi Plastics, Inc., and the like can be given.

The content of the pitch-based carbon fiber is preferably 3 parts by mass or more, more preferably 8 parts by mass or more, and further preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. The effect of this invention is acquired more favorably as it is 3 mass parts or more. The content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less. Better durability performance is obtained as it is 50 parts by mass or less.

The rubber composition preferably contains a resin crosslinking agent.
The resin crosslinking agent is not particularly limited, and examples thereof include phenol resins, melamine / formaldehyde resins, triazine / formaldehyde condensates, hexamethoxymethyl / melamine resins, and alkylphenol / sulfur chloride condensates. Of these, alkylphenol / sulfur chloride condensates are preferred from the viewpoint of the effects of the present invention.

The alkylphenol / sulfur chloride condensate is not particularly limited, but a compound represented by the following formula (II) is preferable from the viewpoint that low exothermic property, hardness and the like can be obtained well and reversion can be suppressed.

(In the formula, R ¹⁰¹ , R ¹⁰² and R ¹⁰³ are the same or different and each represents an alkyl group having 5 to 12 carbon atoms. X and y are the same or different and each represents an integer of 1 to 3. k is Represents an integer of 0 to 250.)

k is preferably an integer of 0 to 250, more preferably an integer of 0 to 100, from the viewpoint of good dispersibility of the alkylphenol / sulfur chloride condensate in the rubber component. x and y are both preferably 2 because high hardness can be efficiently expressed. R ¹⁰¹ to R ¹⁰³ are preferably alkyl groups having 6 to 9 carbon atoms from the viewpoint of good dispersibility of the alkylphenol / sulfur chloride condensate in the rubber component.

The alkylphenol / sulfur chloride condensate can be prepared by a known method, and examples thereof include a method in which alkylphenol and sulfur chloride are reacted at a molar ratio of 1: 0.9 to 1.25. Specific examples of the alkylphenol-sulfur chloride condensate include Takkol V200 (formula (II-1) below) manufactured by Taoka Chemical Co., Ltd.

(In the formula, k represents an integer of 0 to 100.)

The content of the resin crosslinking agent is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, with respect to 100 parts by mass of the rubber component. By setting the lower limit or more, there is a tendency that the effect of improving the grip performance can be sufficiently obtained. The content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less. By making it below the upper limit, the vulcanization speed tends to be at an appropriate level.

The rubber composition preferably contains a compound represented by the following formula (I).

(Wherein R ¹ and R ² are the same or different and each represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, or an alkynyl group having 1 to 20 carbon atoms. M ^{r +} Represents a metal ion, and r represents its valence.)

Examples of the alkyl group for R ¹ and R ² include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group.
Examples of the alkenyl group for R ¹ and R ² include a vinyl group, an allyl group, a 1-propenyl group, and a 1-methylethenyl group.
Examples of the alkynyl group for R ¹ and R ² include an ethynyl group and a propargyl group.

R ¹ and R ² are preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom or a methyl group, and still more preferably a hydrogen atom. That is, the compound represented by the above formula (I) is preferably a compound represented by the following formula (I-1), (I-2) or (I-3). It is more preferable that it is a compound represented by.

In the above formulas (I), (I-1), (I-2), and (I-3), examples of the metal ions include sodium ions, potassium ions, and lithium ions, and sodium ions are preferable.

The content of the compound represented by the formula (I) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and particularly preferably 8 parts by mass or more with respect to 100 parts by mass of carbon black. There exists a tendency for favorable grip performance to be acquired as it is 1 mass part or more. Moreover, this content becomes like this. Preferably it is 20 mass parts or less, More preferably, it is 15 mass parts or less. When the amount is 20 parts by mass or less, the steering stability performance, the thermal sag performance, and the fracture characteristics tend to be improved in a balanced manner.

The rubber composition preferably contains silica. Examples of the silica include dry process silica (anhydrous silica), wet process silica (hydrous silica), and wet process silica is preferred because it has many silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 100 m ² / g or more, more preferably 150 m ² / g or more, and further preferably 200 m ² / g or more. The N ₂ SA is preferably 500 m ² / g or less, more preferably 300 m ² / g or less. There exists a tendency for favorable grip performance to be acquired by making it in the said range.
Note that the nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

Examples of silica that can be used include products such as Degussa, Rhodia, Tosoh Silica, Solvay Japan, and Tokuyama.

When the rubber composition contains silica, the content of silica is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 40 parts by mass or more, particularly 100 parts by mass of the rubber component. Preferably it is 60 mass parts or more. There exists a tendency for favorable grip performance to be acquired by making it more than a minimum. The content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 80 parts by mass or less. By setting it to the upper limit or less, good silica dispersibility tends to be obtained.

In the rubber composition, the total content of silica and carbon black is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and still more preferably 70 parts by mass or more with respect to 100 parts by mass of the rubber component. The total content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and still more preferably 100 parts by mass or less. There exists a tendency for favorable grip performance to be acquired by making it in the said range.

When silica is contained, it is preferable that both contain a silane coupling agent. Thereby, the effect of this invention is acquired more suitably.
The silane coupling agent is not particularly limited. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis ( 3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilyl ester) 3) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3 -Sulphides such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, NXT and NXT-Z manufactured by Momentive, vinyltriethoxysilane, vinyl Vinyl type such as trimethoxysilane, amino type such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycid Glycidoxy such as cyclopropyltrimethoxysilane, nitro such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, chloro such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane Etc. Of these, sulfide and mercapto are preferable, and mercapto is more preferable.

As the mercapto-based silane coupling agent, a silane coupling agent containing a binding unit A represented by the following formula (1) and a binding unit B represented by the following formula (2) can be preferably used.

(Wherein x is an integer of 0 or more, y is an integer of 1 or more. R ¹ is hydrogen, halogen, branched or unbranched alkyl group having 1 to 30 carbon atoms, branched or unbranched carbon atoms of 2 to 30 alkenyl groups, branched or unbranched alkynyl groups having 2 to 30 carbon atoms, or a group in which the hydrogen at the terminal of the alkyl group is substituted with a hydroxyl group or a carboxyl group, R ² is a branched or unbranched carbon number 1 represents an alkylene group having 1 to 30 carbon atoms, a branched or unbranched alkenylene group having 2 to 30 carbon atoms, or a branched or unbranched alkynylene group having 2 to 30 carbon atoms, wherein R ¹ and R ² form a ring structure. May be.)

The content of the binding unit A is preferably 30 mol% or more, more preferably 50 mol% or more, preferably 99 mol% or less, more preferably 90 mol% or less. Further, the content of the binding unit B is preferably 1 mol% or more, more preferably 5 mol% or more, still more preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less, More preferably, it is 55 mol% or less. Further, the total content of the binding units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably 100 mol%.
The content of the bond units A and B is an amount including the case where the bond units A and B are located at the terminal of the silane coupling agent. The form in which the bonding units A and B are located at the end of the silane coupling agent is not particularly limited, as long as the units corresponding to the formulas (1) and (2) indicating the bonding units A and B are formed. .

Regarding R ¹ , examples of the halogen include chlorine, bromine, and fluorine. Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms include a methyl group and an ethyl group. Examples of the branched or unbranched alkenyl group having 2 to 30 carbon atoms include vinyl group and 1-propenyl group. Examples of the branched or unbranched alkynyl group having 2 to 30 carbon atoms include ethynyl group and propynyl group.

Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms for R ² include an ethylene group and a propylene group. Examples of the branched or unbranched alkenylene group having 2 to 30 carbon atoms include vinylene group and 1-propenylene group. Examples of the branched or unbranched alkynylene group having 2 to 30 carbon atoms include an ethynylene group and a propynylene group.

In the silane coupling agent containing the bonding unit A represented by the formula (I) and the coupling unit B represented by the formula (II), the number of repeating units (x) of the bonding unit A and the number of repeating units (y) of the bonding unit B The total number of repetitions (x + y) is preferably in the range of 3 to 300.

Examples of the silane coupling agent that can be used include Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Amax Co., Ltd., and Toray Dow Corning Co., Ltd.

The content of the silane coupling agent is preferably 3 parts by mass or more and more preferably 5 parts by mass or more with respect to 100 parts by mass of the inorganic filler (preferably the total content of silica and aluminum hydroxide is 100 parts by mass). If it is at least the lower limit, the effect of blending the silane coupling agent tends to be sufficiently obtained. The content is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less. When it is 20 parts by mass or less, an effect commensurate with the blending amount is sufficiently obtained, and good workability during kneading tends to be obtained.

In addition to silica, the rubber composition may contain an inorganic filler such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. In this specification, aluminum hydroxide means Al (OH) ₃ or Al ₂ O ₃ .3H ₂ O. These fillers may be used individually by 1 type, and may use 2 or more types together.

You may mix | blend solid resin, oil, etc. with the said rubber composition.
Examples of the solid resin include aromatic vinyl polymers such as α-methylstyrene and / or α-methylstyrene resins obtained by polymerizing styrene. The solid resin preferably has a softening point of 60 to 120 ° C. The softening point of the solid resin is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1: 2001 is measured with a ring and ball softening point measuring device.

As the α-methylstyrene-based resin, α-methylstyrene or a homopolymer of styrene or a copolymer of α-methylstyrene and styrene is preferable because of excellent wet grip performance and the like. A copolymer with styrene is more preferred.

The content of the solid resin is preferably 3 to 30 parts by mass, more preferably 5 to 20 parts by mass with respect to 100 parts by mass of the rubber component. By blending a predetermined amount of solid resin, grip performance and the like tend to be improved.

Examples of the solid resin include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yashara Chemical Co., Ltd., Tosoh Co., Ltd., Rutgers Chemicals Co., Ltd., BASF Co., Arizona Chemical Co., Ltd., Nikko Chemical Co., Ltd. ) Products such as Nippon Shokubai, JX Energy Co., Ltd., Arakawa Chemical Co., Ltd., Taoka Chemical Co., Ltd. can be used.

Examples of the oil include process oil, vegetable oil and fat, or a mixture thereof. As the process oil, for example, a paraffin process oil, an aroma process oil, a naphthenic process oil, or the like can be used. As vegetable oils and fats, castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut hot water, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more.

Examples of the oil include Idemitsu Kosan Co., Ltd., Sankyo Oil Chemical Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H & R Co., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu Co., Ltd., Fuji Kosan Co., Ltd. Etc. can be used.

The oil content is preferably 1 part by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. If it is within the above numerical range, the effect of the present invention tends to be obtained better.
The oil content includes the amount of oil contained in rubber (oil-extended rubber).

You may mix | blend a wax with the said rubber composition.
The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant waxes and animal waxes; synthetic waxes such as polymers such as ethylene and propylene. These may be used alone or in combination of two or more. Of these, petroleum wax is preferable, and paraffin wax is more preferable.

The content of the wax is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

As the wax, for example, products such as Ouchi Shinsei Chemical Co., Ltd., Nippon Seiwa Co., Ltd., Seiko Chemical Co., Ltd. can be used.

The rubber composition preferably contains an anti-aging agent.
Examples of the antiaging agent include naphthylamine type antiaging agents such as phenyl-α-naphthylamine; diphenylamine type antiaging agents such as octylated diphenylamine and 4,4′-bis (α, α′-dimethylbenzyl) diphenylamine; N -Isopropyl-N'-phenyl-p-phenylenediamine, N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, N, N'-di-2-naphthyl-p-phenylenediamine, etc. P-phenylenediamine-based anti-aging agent; quinoline-based anti-aging agent such as a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methylphenol; Monophenolic anti-aging agents such as styrenated phenol; tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydride Kishifeniru) propionate] bis methane, tris, and the like polyphenolic antioxidants. These may be used alone or in combination of two or more. Of these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferable, and N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1 More preferred is a polymer of 1,2-dihydroquinoline.

The content of the anti-aging agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

As the anti-aging agent, for example, products such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Co., Ltd., and Flexis Co. can be used.

The rubber composition preferably contains stearic acid.
A conventionally well-known thing can be used as a stearic acid, For example, products, such as NOF Corporation, NOF company, Kao Corporation, FUJIFILM Wako Pure Chemicals Co., Ltd., and Chiba fatty acid company, can be used.

The content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

The rubber composition preferably contains zinc oxide.
Conventionally known zinc oxide can be used, for example, Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd. Can be used.

The content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. If it is within the above numerical range, the effect of the present invention tends to be obtained better.

The rubber composition preferably contains sulfur.
Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur that are generally used in the rubber industry. These may be used alone or in combination of two or more.

The sulfur content is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, with respect to 100 parts by mass of the rubber component. The content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 3 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

As the sulfur, for example, products such as Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Nihon Kiboshi Kogyo Co., Ltd., Hosoi Chemical Co., Ltd. can be used.

The rubber composition preferably contains a vulcanization accelerator.
Examples of vulcanization accelerators include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram disulfide (TMTD ), Tetrabenzylthiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N), and other thiuram vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl- 2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N, N′-diisopropyl-2-benzothiazolesulfenamide, etc. The sulfenami And guanidine vulcanization accelerators such as diphenyl guanidine, diortolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more. Of these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred because the effects of the present invention can be obtained more suitably.

The content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component with respect to 100 parts by mass of the rubber component. Further, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained satisfactorily.

In addition to the above components, additives generally used in the tire industry can be added to the rubber composition, and examples include organic peroxides; processing aids such as plasticizers and lubricants, and the like. .

As a method for producing the rubber composition, known methods can be used. For example, the above components can be produced by kneading each component using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing. .

Regarding the kneading conditions, in the base kneading step in which additives other than the crosslinking agent (vulcanizing agent) and the vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180 ° C., preferably 120 to 170 ° C. In the final kneading step of kneading the vulcanizing agent and vulcanization accelerator, the kneading temperature is usually 120 ° C. or lower, preferably 85 to 110 ° C. Further, a composition obtained by kneading a vulcanizing agent and a vulcanization accelerator is usually subjected to vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190 ° C, preferably 150 to 185 ° C.

The rubber composition can be suitably used as a tire rubber composition. Although the said rubber composition can be used for each member of a tire, it can be used conveniently for a tread especially.

The pneumatic tire of the present invention can be produced by a usual method using the rubber composition.
That is, the rubber composition blended with the above components is extruded in accordance with the shape of the tire member such as tread, sidewall, clinch, wing, etc. in the unvulcanized stage, and put on the tire molding machine together with other tire members. Thus, an unvulcanized tire can be formed by molding by a usual method. A tire is obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

The pneumatic tire of the present invention is a tire for passenger cars, a tire for large passenger cars, a tire for large SUVs, a tire for trucks and buses, a tire for competition, a studless tire (winter tire), a tire for motorcycles, a run flat tire, an aircraft. It can be suitably used for tyres, mining tires and the like.

FIG. 1 is a cross-sectional view showing a state of temperature measurement in a method for measuring the maximum temperature during friction. In FIG. 1, the direction indicated by the arrow X is the upward direction, and the opposite is the downward direction. The apparatus 2 for this temperature measuring method includes a measuring plate 4, a temperature measuring device 6, a measuring table 8, and a friction characteristic measuring device 10. Also shown in FIG. 1 is a rubber 12 to be measured. FIG. 2 is a perspective view showing the measuring plate 4, the temperature measuring device 6, and the measuring table 8 among them.

The measurement plate 4 is plate-shaped. The measurement plate 4 is placed on the measurement table 8. As shown in the figure, the measurement plate 4 includes a recess 14 on the lower surface side. The thickness between the bottom of the recess 14 and the upper surface 16 of the measurement plate 4 is thinner than the thickness between the upper surface 16 and the lower surface 18 of the measurement plate 4 at a portion where the recess 14 is not present. The portion where the thickness is reduced is referred to as a measurement window 20 of the measurement plate 4. In the figure, the shape of the measurement window 20 is circular in plan view. The shape of the measurement window 20 may not be circular.

The measurement window 20 of the measurement plate 4 transmits the electromagnetic wave 22 radiated from the rubber 12 by heat radiation. The transmittance of the electromagnetic wave 22 with respect to the measurement plate 4 varies depending on the wavelength of the electromagnetic wave 22. The transmittance of the electromagnetic wave 22 with respect to the measurement plate 4 also varies depending on the material of the measurement plate 4 and the thickness of the measurement window 20. The measurement window 20 of the transmission plate transmits the electromagnetic wave 22 from the rubber 12 to such an extent that the temperature measuring device 6 can measure the temperature of the rubber 12.

The measurement table 8 is a table on which the measurement plate 4 is placed. A measurement plate 4 is placed on the upper surface of the measurement table 8. The measurement table 8 fixes the measurement plate 4. The center of the upper surface of the measuring plate 4 is open. When the measurement plate 4 is placed on the measurement table 8, the measurement window 20 can be seen from the lower side of the measurement table 8.

The temperature measuring device 6 measures the temperature of the substance by measuring the intensity of the electromagnetic wave radiated from the substance by thermal radiation. The temperature measuring device 6 is located under the measuring plate 4 placed on the measuring table 8. The temperature measuring device 6 is located under the measuring window 20 of the measuring plate 4. The temperature measuring device 6 measures the intensity of the electromagnetic wave 22 radiated from the rubber 12 and transmitted through the measurement window 20 of the measurement plate 4. Thereby, the temperature measuring device 6 measures the temperature of the rubber 12.

The friction characteristic measuring instrument 10 includes a rotating plate 24 and a main body 26. The rotating plate 24 is circular. On the lower surface of the rotating plate 24, the rubber 12 to be measured is set. The main body 26 is located above the rotating plate 24. The main body 26 rotates the rotating plate 24. The main body 26 can rotate the rotating plate 24 at a desired speed. The main body 26 can apply a load to the rubber 12 from above the rotating plate 24. The rubber plate 12 is brought into contact with the measurement plate 4, and the rotating plate 24 is rotated in a state where a load is applied to the rubber 12. As a result, the rubber 12 slides with respect to the measurement plate 4. The main body 26 measures the slip resistance between the rubber 12 and the measuring plate 4. The friction characteristic measuring instrument 10 is a dynamic friction tester.

In the temperature measurement method using this apparatus 2, first, the measurement plate 4 is fixed to the measurement table 8. Under the measurement window 20 of the measurement plate 4, the temperature measuring device 6 is arranged. The rubber 12 to be tested is set on the rotating plate 24 of the friction characteristic measuring instrument 10. This friction characteristic measuring instrument 10 is arranged on the upper surface 16 side of the measuring plate 4. This rubber 12 is brought into contact with the upper surface 16 of the measuring plate 4. The rubber 12 is brought into contact with the measurement window 20 of the measurement plate 4. The rubber 12 is pressed against the measuring plate 4 by the main body 26. A load is applied to the rubber 12 in the direction of the measurement plate 4. The rotating plate 24 is rotated by the main body 26. The rubber 12 rotates. Thereby, the rubber 12 slides with respect to the measurement plate 4. The main body 26 measures the slip resistance at this time. At the same time, the temperature measuring device 6 measures the electromagnetic wave 22 transmitted from the measurement window 20. The temperature measuring device 6 measures the temperature of the rubber 12 in the part in contact with the measuring plate 4. The temperature measuring device 6 measures the temperature of the rubber 12 in the portion where the frictional force is working.

The material of the measurement plate 4 is Al ₂ O ₃ (sapphire). The measuring plate 4 made of Al ₂ O ₃ has high strength. Furthermore, the measuring plate 4 having sufficient strength against thermal changes and physical impacts can be formed.

In FIG. 1, a double arrow T is the thickness of the measurement window 20. The thickness T is preferably 4.0 mm or less. By setting the thickness T to 4.0 mm or less, the measurement plate 4 has good transmittance. When the material of the measurement plate 4 is Al ₂ O ₃ , the measurement plate 4 including the 70% transmission wavelength band including the wavelength band (2 μm-4 μm) can be formed by setting the thickness T to 4.0 mm or less. .

The upper surface 16 of the measurement plate 4 is preferably roughened. An enlarged view of the upper surface 16 of the measuring plate 4 is shown in FIG. This enlarged view shows a state in which the upper surface 16 has been roughened. By roughing the upper surface 16 of the measuring plate 4, the friction coefficient can be increased. The coefficient of friction depends on the rough surface roughness of the measuring plate 4. By preparing the measuring plate 4 having different rough surface roughnesses, it is possible to measure the temperature of the rubber 12 where friction occurs under various friction coefficients.

Shot blasting and sand blasting are suitable for roughing the measurement plate 4. By performing shot blasting or sand blasting on the upper surface 16 of the measuring plate 4, the measuring plate 4 having a desired rough surface roughness can be easily formed. When the material of the measurement plate 4 is Al ₂ O ₃ , silicon carbide grains are preferable as the blast material to be sprayed onto the upper surface 16 of the measurement plate 4 by shot blasting. The silicon carbide grains can form a rough surface even on the measuring plate 4 made of Al ₂ O ₃ . By changing the particle size of silicon carbide, the roughness of the rough surface can be changed.

The lower surface 18 of the measuring plate 4 is preferably mirror-finished. The transmittance of the electromagnetic wave 22 can be improved by mirror-treating the lower surface 18 of the measurement plate 4.

Most of the electromagnetic waves 22 emitted from the rubber 12 by thermal radiation have a wavelength of 0.1 μm or more and 1.0 mm or less. The wavelength band of the electromagnetic wave 22 whose intensity can be measured by the temperature measuring device 6 is preferably included in the wavelength band (0.2 μm-1.0 mm).

The wavelength band of the electromagnetic wave 22 that can be measured by the temperature measuring device 6 preferably includes the 70% wavelength band of the measurement plate 4. By using Al ₂ O ₃ as the material of the measurement plate 4, it is possible to form the measurement plate 4 in which the 70% transmission wavelength band includes the wavelength band (2 μm-4 μm).

The temperature measuring device 6 is preferably a thermography equipped with a camera. The temperature distribution on the surface of the rubber 12 can be measured within the range photographed by this camera. The camera preferably has a magnifying lens. By using this lens, the temperature distribution on the surface of the rubber 12 can be measured in smaller area units. By changing the magnification of the camera, the temperature distribution can be measured with a desired fineness of area.

The temperature measuring device 6 preferably has a function capable of continuous photographing. By continuously photographing the surface of the rubber 12, when the rubber 12 is slid on the measuring plate 4, a change in the surface temperature of the rubber 12 with time can be measured. By changing the frame rate (the number of images taken per second), it is possible to measure the change in surface temperature according to the speed at which the rubber 12 slides.

In order to bring the rubber 12 into contact with the upper surface 16 of the measuring plate 4 and to slide the rubber 12 against the measuring plate 4, it is preferable to use a dynamic friction tester. Thereby, the slip resistance can be measured according to the desired load and the desired slip speed. By changing the rough surface roughness of the measuring plate 4, the slip resistance can be measured under different friction coefficients. By dampening the measurement plate 4, it is possible to measure the slip resistance when the measurement plate 4 is wet. By using the dynamic friction tester, it is possible to measure the temperature of the rubber 12 in the portion where the frictional force is working while measuring these friction characteristics.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
SBR: Toughden 3830 manufactured by Asahi Kasei Corporation (vinyl content: 35% by mass, styrene content: 33% by mass)
Modified SBR: Solution polymerization modified SBR synthesized in Production Example 1 below (styrene content 35% by mass, vinyl content 50% by mass, Mw 700,000)
BR: BR360L manufactured by Ube Industries, Ltd. (cis 1,4 bond amount 98%)
NR: TSR
Carbon Black: Show Black N220 (N ₂ SA: 111 m ² / g, DBP: 115 ml / 100 g) manufactured by Cabot Japan
Silica 1: Ultrasil 9000GR manufactured by Evonik (N ₂ SA: 240 m ² / g)
Silica 2: Ultrasil VN3 manufactured by Evonik (N ₂ SA: 175 m ² / g)
Carbon fiber: Coal pitch-based carbon fiber “K6331T” manufactured by Mitsubishi Plastics Co., Ltd. (chopped fiber, average fiber diameter: 11 μm, average fiber length: 6.3 mm, thermal conductivity: 140 W / m · K)
Resin cross-linking agent: TAKIROLL V200 (alkylphenol / sulfur chloride condensate, alkylphenol / sulfur chloride condensate represented by the above formula (I-1), Taoka Chemical Industries, Ltd., sulfur content: 24% by mass, weight average Molecular weight: 9000)
Compound A: (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoic acid sodium salt (compound represented by the following formula) manufactured by Sumitomo Chemical Co., Ltd.

Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Zinc flower type 2 anti-aging agent manufactured by Mitsui Mining & Smelting Co., Ltd. 6C: Nocrack 6C (N- (1,3-dimethylbutyl) -N'-phenyl-p manufactured by Ouchi Shinsei Chemical Co., Ltd.) -Phenylenediamine)
Anti-aging agent RD: NOCRACK 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Oil: Diana Process NH-70S manufactured by Idemitsu Kosan Co., Ltd.
Silane coupling agent 1: NXT-Z45 manufactured by Degussa (copolymer of bonding unit A and bonding unit B (bonding unit A: 55 mol%, bonding unit B: 45 mol%))
Silane coupling agent 2: Si266 (bis (3-triethoxysilylpropyl disulfide)) manufactured by Degussa
Sulfur: HK-200-5 manufactured by Hosoi Chemical Co., Ltd. (vulcanizing agent, oil content 5% by mass)
Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazylsulfenamide Vulcanization accelerator DPG: Diphenylguanidine

(Production Example 1: Synthesis of modified SBR)
Using a reactor equipped with a stirrer and a jacket, under a nitrogen atmosphere, cyclohexane, 1,3-butadiene, tetrahydrofuran and styrene were charged, adjusted to 30 ° C., and then n-butyllithium was added to initiate polymerization. After raising the temperature to 70 ° C., polymerization was performed for 2 hours, and after reaching a polymerization conversion rate of 100%, a small amount of tin tetrachloride was added, and a coupling reaction was performed at 70 ° C. Thereafter, 3-diethylaminopropyltrimethoxysilane was added and a denaturation reaction was performed at 60 ° C. 2,6-di-tert-butyl-p-cresol is added to the obtained copolymer solution, and then the solvent is removed by steam stripping, followed by drying with a hot roll at 110 ° C. to obtain a modified SBR. It was.

<Examples and Comparative Examples>
In accordance with the formulation shown in Table 1, various chemicals except sulfur and a vulcanization accelerator were kneaded at 150 ° C. for 5 minutes using a Banbury mixer. Sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded at 80 ° C. for 5 minutes using an open roll to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 20 minutes to obtain a vulcanized rubber sheet.

The following evaluation was performed using the obtained vulcanized rubber sheet (sample). The results are shown in Table 1 and FIGS.

[Maximum temperature measurement]
The temperature of the sample was measured using the temperature measuring device shown in FIGS. In this measurement, a measurement plate made of Al ₂ O ₃ was prepared. The thickness T of the measurement window of this measurement plate is 2 mm. The thickness of the measurement plate at a portion other than the measurement window is 10 mm. The upper surface of the measurement plate is roughened. The rough surface was formed by shot blasting. Silicon carbide (trade name “Shinano Random GC F16” manufactured by Shinano Denki Co., Ltd.) was used as a blast material.
A dynamic friction tester “DF Tester S type” manufactured by Nihon Sangyo Co., Ltd. was used as a friction characteristic measuring instrument. A sample was set in this tester. At the time of measurement, the measurement plate was moistened with 20 ° C. water. On this wet measuring plate, the sample was slid at a speed of 7 km / h. The temperature of the sample at this time was measured from the measurement window with a temperature measuring device. The environmental temperature at the time of measurement is 20 ° C. A thermography “InfReC H8000” manufactured by Nippon Avionics Co., Ltd. was used as a temperature measuring device. During the measurement, a 15 μm microscope lens was attached. This temperature measuring instrument measures the intensity of electromagnetic waves having a wavelength of 2 μm or more and 5 μm or less.
The temperature distribution on the rubber surface was confirmed from the result of the thermography. Table 1 shows the temperature (maximum temperature) at the place where the temperature is the highest among the rubber surfaces.
[Friction conditions]
Equipment used: Dynamic friction tester “DF Tester S type” manufactured by Nihon Sangyo Co., Ltd.
(1) Size and shape of rubber composition (sample):
Thickness: 2mm thick sheet, surface slicing treatment (similar to PFT)
(Measured within 48 hours after slicing due to the influence of surface bloom)
Width: 16mm
Ground contact length: Depends on rubber rigidity (uses DF tester S type fixture)
Sample: 2 pieces (DF tester S type)
(2) Measuring plate (sliding the sample with respect to the measuring plate):
A flat plate made of Al ₂ O ₃ (a flat plate moistened with water at 20 ° C.)
(3) Measurement window thickness T: 2 mm
(4) Speed at which the rubber composition (sample) slides against the measuring plate: Fluctuation 15 km / hour to 0 km / hour deceleration test After the start of the test, the maximum temperature between 7 km / hour and 0 km / hour is set. adopt.
(5) Initial speed for sliding the rubber composition (sample) against the measurement plate: 15 km / hour (6) Acceleration for sliding the rubber composition (sample) against the measurement plate:
Deceleration test from 15 km / hour to 0 km / hour, because of the deceleration test pressed with a constant load (DF tester S type), fluctuates depending on the composition. (7) The sliding distance of the rubber composition (sample) with respect to the measurement plate Constant load (8) Time to slide the rubber composition (sample) against the measurement plate for the deceleration test pressed with (DF tester S type) For the deceleration test pressed with a constant load (DF tester S type) Depends on the formulation

[Friction test by linear wear tester (PFT)]
A friction test was conducted under the following test conditions using a linear friction tester “Portable friction tester (Model No. 380.02)” manufactured by HENTSCHEL (number of continuous tests: 10 times).
The test sample used was a surface treated (sliced) sample surface, and the influence of the surface condition at the start was reset (“NP-120” manufactured by Nippi Machinery Co., Ltd. was used for slicing).
For each friction test, the road surface condition was managed and the change in the road surface condition was reset.
For the management of the road surface condition, the reference tread formulation was used, and in this test, μ _s 0.800 was used as the reference value of the reference sample, and a correction value was obtained (for example, in the second friction test of the formulation A, Measured value, that is, μ _s2 0.815 (measured value) of the reference sample and 0.745 (measured value) of sample A, μ _A2 (corrected value) is 0.745+ (0.800− 0.815) = 0.73.
In the continuous (repetitive) friction test, it is shown that the grip performance is not lowered during traveling and the grip performance is improved as a whole during traveling as the decrease in μ value is suppressed.

(Test conditions)
Constant load sliding speed without weight: 2000mm / s
Acceleration: 15m / s
Ground pressure: 0.2Mpa
Water temperature: 20 ° C
Road surface temperature: 20 ° C
Road surface: Test course model road surface (tire labeling μ-S evaluation standard road surface)
TD = 0.7 ± 0.3, BPN = 42-60
* Reference for BNP, managed with μ of the reference sample

3 and 4 showing the results of Table 1 and Table 1, in Formulation A in which the maximum temperature at the time of friction under a predetermined friction condition is 35 ° C., μ greatly decreases according to the number of tests. On the other hand, in Formulations B to F where the maximum temperature is 30 ° C. or less, the decrease in μ according to the number of tests is small, and it is clear that the grip performance such as wet grip performance and dry grip performance is improved. It was.

2 Temperature measuring device 4 Measuring plate 6 Temperature measuring device 8 Measuring table 10 Friction characteristic measuring device 12 Rubber 14 Dimple 16 Upper surface 18 Lower surface 20 Measuring window 22 Electromagnetic wave 24 Rotating plate 26 Main body

Claims (4)

1. A rubber composition having a maximum temperature of 30 ° C. or less during friction under the following friction conditions.
   [Friction conditions]
   (1) Size and shape of rubber composition: 2 mm thick sheet (width 16 mm)
   (2) Measuring plate: A flat plate made of Al ₂ O ₃
2. The rubber composition according to claim 1, wherein the maximum temperature is 25 ° C. or less.
3. The rubber composition according to claim 1, wherein the maximum temperature is 23 ° C. or lower.
4. A pneumatic tire using the rubber composition according to any one of claims 1 to 3 in a tread.

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