JP7259744B2 - Rubber composition and pneumatic tire - Google Patents

Description

The present invention relates to rubber compositions and pneumatic tires.

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

For example, a rubber composition has been proposed in which silica is compounded to improve wet grip performance, etc., and a silane coupling agent such as bis(3-triethoxysilylpropyl) tetrasulfide is added to improve silica dispersibility ( See Patent Document 1).

However, demands for improvement of grip performance such as wet grip performance are severe, and further improvement is required.

JP 2011-57797 A

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

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

It is preferable that the maximum temperature is 25° C. or less.
It is preferable that the maximum temperature is 23° C. or less.

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

INDUSTRIAL APPLICABILITY The present invention is a rubber composition having a maximum friction temperature of 30° C. or less under predetermined friction conditions, and therefore can provide a pneumatic tire having excellent grip performance (wet grip performance, dry grip performance, etc.).

FIG. 1 is a cross-sectional view showing the measurement of the temperature of the sample surface during friction under predetermined friction conditions. FIG. 2 is a perspective view showing a part of the device used for temperature measurement in FIG. 2 is a relational diagram between the number of friction tests in Table 1 and the coefficient of dynamic friction μ. FIG. 2 is a relational diagram between the number of friction tests in Table 1 and the coefficient of dynamic friction μ. FIG.

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

Japanese Patent Application Laid-Open No. 2016-70880 describes that the temperature of the rubber composition at the portion where the frictional force is actually acting can be measured by a method of measuring the maximum temperature at the time of friction for the rubber composition.
In the present invention, we have found that the maximum temperature (instantaneous heat generation amount, flash temperature) varies depending on the rubber compounding, and furthermore, if the maximum temperature is 30 ° C. or less, the rubber composition improves the grip performance. It was completed by discovering the knowledge that.
The reason why grip performance improves is not necessarily clear, but when the amount of heat generated is low, the effect of heat sagging is small and the viscoelastic region used does not shift to the high temperature side, so grip performance decreases during driving. It is assumed that the grip performance is improved as a whole during running.
Both wet grip performance and dry grip performance show similar tendencies, and 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 has a maximum friction temperature of 30° C. or less, preferably 27° C. or less, more preferably 25° C. or less, and still more preferably 23° C. or less under the following friction conditions. Grip performance improves as it is 30 degrees C or less. Although the lower limit of the maximum temperature is not particularly limited, it is preferably 20°C or higher.
[Friction condition]
(1) Size and shape of rubber composition: 2 mm thick sheet (width 16 mm)
(2) Measurement plate: flat plate made of Al ₂ O ₃

The maximum temperature can be measured by the method described in JP-A-2016-70880, and specifically by the method described in Examples below (measurement of maximum temperature).

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

A rubber composition having a maximum friction temperature of 30° C. or less under the friction conditions can be produced by appropriately selecting the formulation and production method.
Specifically, addition of carbon fibers, a resin cross-linking agent, and the compound represented by the formula (I), adjustment of the blending amount of these, and the like can be mentioned.

Examples of rubber components that can be used 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- Diene rubbers such as isoprene-butadiene copolymer rubber (SIBR), ethylene propylene diene rubber (EPDM), butyl rubber (IIR), and halogenated butyl rubber (X-IIR) can be mentioned. These diene rubbers may be used alone or in combination of two or more. Among these, SBR, isoprene-based rubber, and BR are preferred from the viewpoint that the effects of the present invention can be obtained more favorably, and SBR is more preferred from the viewpoint of grip performance.

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

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

Examples of the functional groups include amino group, amido group, silyl group, alkoxysilyl group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide 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 and the like. . In addition, these functional groups may have a substituent.

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

The vinyl content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more. Also, the vinyl content is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 35% by mass or less. By making it more than the lower limit, there is a tendency that good grip performance can be obtained. By making it below the upper limit, there is a tendency for good durability to be obtained.
In this specification, the vinyl content can be measured by infrared absorption spectrometry.

The styrene content of SBR is preferably 20% by mass, more preferably 25% by mass or more. Also, the styrene content is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. By making it more than the lower limit, there is a tendency that good grip performance can be obtained. By setting the content to the upper limit or less, good durability can be obtained, and there is a tendency that the temperature dependence can be reduced to suppress performance changes due to temperature changes.
In this specification, the styrene content of SBR can be calculated by H ¹ -NMR measurement.

The SBR content in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or 100% by mass. may A more favorable grip performance is obtained as it is 50 mass % or more.

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

The BR is not particularly limited, and examples thereof include BR1220 manufactured by Nippon Zeon Co., Ltd.; BR or the like containing tactic polybutadiene crystals can be used. These may be used alone or in combination of two or more. Above all, the cis content of BR is preferably 95% by mass or more because it improves the wear resistance performance.

BR may be unmodified BR or modified BR. These may be used alone or in combination of two or more.
Examples of modified BR include modified BR into which functional groups similar to those of the above-described modified SBR are introduced.

As BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

The rubber composition preferably contains carbon black. Examples of carbon black include, but are not limited to, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. 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 even more preferably 100 m ² /g or more. By making it more than the lower limit, there is a tendency that good grip performance can be obtained. The N ₂ SA is preferably 200 m ² /g or less, more preferably 150 m ² /g or less, and even more preferably 130 m ² /g or less. By making it below the upper limit, there is a tendency for good dispersion of carbon black to be obtained.
The nitrogen adsorption specific surface area of carbon black is determined according to JIS K6217-2:2001.

As carbon black, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, 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, relative to 100 parts by mass of the rubber component. The above content is preferably 10 parts by mass or less, more preferably 8 parts by mass or less. By setting it within the above range, there is a tendency to obtain good grip performance.

When the rubber composition does not contain silica, the content of 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. be. The content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 100 parts by mass or less. By setting it within the above range, there is a tendency to obtain good grip performance.

The rubber composition preferably contains pitch-based carbon fibers.

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

The thermal conductivity (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. Although the upper limit of the thermal conductivity is not particularly limited, it 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 more satisfactorily.
In this specification, the thermal conductivity of the pitch-based carbon fiber is calculated from the value of the electrical resistivity by using the very good correlation between the thermal conductivity of the carbon fiber and the electrical resistivity, according to the following formula: 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, still more preferably 5 μm or more. Also, the upper limit of the average fiber diameter is more preferably 30 μm or less, and still more preferably 20 μm or less.

Further, 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 longer, still more preferably 4 mm or longer. Also, the upper limit of the average fiber length is more preferably 15 mm or less, still more preferably 10 mm or less.
The average fiber diameter and average fiber length can be measured, for example, by electron microscope observation.

Although the pitch-based carbon fiber in the present invention is not particularly limited, for example, coal pitch-based carbon fiber obtained by the method described in JP-A-7-331536 is preferably used. Specifically, pitch fibers are infusible according to a conventional method, carbonized and/or graphitized at a desired temperature to obtain "raw material carbon fibers", and then the raw material carbon fibers are prepared in advance. Coal pitch-based carbon fibers can be produced by putting the carbon fibers together with graphitized packing coke into a graphite crucible and subjecting them to graphitization.

In addition, the pitch fiber (spun pitch) used in the above production method includes carbonaceous raw materials such as coal tar, coal tar pitch, and liquefied coal (40% or more, preferably 70% or more, more preferably 90% % or more optically anisotropic structure is preferred). In addition, a sizing agent (an epoxy compound, a water-soluble polyamide compound, etc.) may be attached to the "raw carbon fiber".

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

The coal pitch-based carbon fiber produced by the above method is made from liquid crystal (mesophase) or the like in which the orientation of molecules is regulated in one direction.
The coal pitch-based carbon fiber in the present invention preferably has a structure in which polycyclic aromatic molecular skeletons are stacked in layers. Commercial products of coal pitch-based carbon fibers include "K6371T" manufactured by Mitsubishi Plastics, Inc., and the like.

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 still more preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. When it is 3 parts by mass or more, the effects of the present invention can be obtained more favorably. Also, the content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. When the content is 50 parts by mass or less, better durability performance can be obtained.

The rubber composition preferably contains a resin crosslinking agent.
The resin crosslinking agent is not particularly limited, and includes phenolic resins, melamine/formaldehyde resins, triazine/formaldehyde condensates, hexamethoxymethyl/melamine resins, alkylphenol/sulfur chloride condensates, and the like. Among them, the alkylphenol/sulfur chloride condensate is preferable 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 heat build-up, good hardness, etc. can be obtained and reversion can be suppressed.

（式中、Ｒ^１０１、Ｒ^１０２及びＲ^１０３は、同一若しくは異なって、炭素数５～１２のアルキル基を表す。ｘ及びｙは、同一若しくは異なって、１～３の整数を表す。ｋは０～２５０の整数を表す。）

(wherein R ¹⁰¹ , R ¹⁰² and R ¹⁰³ are the same or different and represent an alkyl group having 5 to 12 carbon atoms; x and y are the same or different and represent an integer of 1 to 3; k is represents an integer from 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. Both x and y are preferably 2 from the viewpoint that 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.

（式中、ｋは０～１００の整数を表す。）The alkylphenol/sulfur chloride condensate can be prepared by a known method, for example, a method of reacting alkylphenol and sulfur chloride at a molar ratio of 1:0.9 to 1.25. Specific examples of the alkylphenol/sulfur chloride condensate include Takkiroru V200 (formula (II-1) below) manufactured by Taoka Kagaku Kogyo Co., Ltd. and the like.

(In the formula, k represents an integer from 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, relative to 100 parts by mass of the rubber component. By making it more than the lower limit, there is a tendency that a sufficient effect of improving the grip performance can be 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 rate tends to be at an appropriate level.

（式中、Ｒ^１、Ｒ^２は、同一又は異なって、水素原子、炭素数１～２０のアルキル基、炭素数１～２０のアルケニル基又は炭素数１～２０のアルキニル基である。Ｍ^ｒ＋は金属イオンを示し、ｒはその価数を表す。）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 represent 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+ indicates a metal ion, and r indicates its valence.)

Examples of alkyl groups for R ¹ and R ² include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group and tert-butyl group.
Examples of alkenyl groups for R ¹ and R ² include vinyl group, allyl group, 1-propenyl group, 1-methylethenyl group and the like.
Examples of alkynyl groups 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, 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), and the following formula (I-1 ) is more preferred.

In the above formulas (I), (I-1), (I-2) and (I-3), the metal ion includes sodium ion, potassium ion and lithium ion, preferably sodium ion.

The content of the compound represented by 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. When it is 1 part by mass or more, there is a tendency that good grip performance is obtained. Also, the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. When the amount is 20 parts by mass or less, there is a tendency that steering stability performance, heat sagging performance, and breaking properties can be improved in a well-balanced manner.

The rubber composition preferably contains silica. Examples of silica include dry-process silica (anhydrous silica) and wet-process silica (hydrous silica), but wet-process silica is preferable because it contains 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, still more 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. By setting it within the above range, there is a tendency to obtain good grip performance.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

As silica, for example, products of Degussa, Rhodia, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used.

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, with respect to 100 parts by mass of the rubber component. Preferably, it is 60 parts by mass or more. By making it more than the lower limit, there is a tendency that good grip performance can be obtained. Also, the content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 80 parts by mass or less. By making it below the upper limit, there is a tendency that good silica dispersibility can 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 even more preferably 100 parts by mass or less. By setting it within the above range, there is a tendency to obtain good grip performance.

When silica is included, both preferably include a silane coupling agent. Thereby, the effect of the present invention can be obtained more preferably.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis ( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3- sulfides such as triethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyl-based such as methoxysilane; amino-based such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among them, sulfide-based and mercapto-based are preferred, and mercapto-based are more preferred.

（式中、ｘは０以上の整数、ｙは１以上の整数である。Ｒ^１は水素、ハロゲン、分岐若しくは非分岐の炭素数１～３０のアルキル基、分岐若しくは非分岐の炭素数２～３０のアルケニル基、分岐若しくは非分岐の炭素数２～３０のアルキニル基、又は該アルキル基の末端の水素が水酸基若しくはカルボキシル基で置換されたものを示す。Ｒ^２は分岐若しくは非分岐の炭素数１～３０のアルキレン基、分岐若しくは非分岐の炭素数２～３０のアルケニレン基、又は分岐若しくは非分岐の炭素数２～３０のアルキニレン基を示す。Ｒ^１とＲ^２とで環構造を形成してもよい。）As the mercapto-based silane coupling agent, a silane coupling agent containing a bonding unit A represented by the following formula (1) and a bonding 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, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched C 2 to A 30 alkenyl group, a branched or unbranched alkynyl group having 2 to 30 carbon atoms, or an alkyl group in which the terminal hydrogen is substituted with a hydroxyl group or a carboxyl group, where R ² is a branched or unbranched carbon number. represents an alkylene group of 1 to 30, a branched or unbranched alkenylene group of 2 to 30 carbon atoms, or a branched or unbranched alkynylene group of 2 to 30 carbon atoms, wherein R ¹ and R ² form a ring structure; may be used.)

The content of the binding unit A is preferably 30 mol % or more, more preferably 50 mol % or more, and preferably 99 mol % or less, more preferably 90 mol % or less. 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. Also, 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 %.
In addition, the content of the bonding units A and B is the amount including the case where the bonding units A and B are positioned at the terminal of the silane coupling agent. When the bonding units A and B are located at the ends of the silane coupling agent, the form is not particularly limited as long as they form units corresponding to the formulas (1) and (2) representing the bonding units A and B. .

Halogen for R ¹ includes chlorine, bromine, fluorine and the like. 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 a vinyl group and a 1-propenyl group. Branched or unbranched alkynyl groups having 2 to 30 carbon atoms include ethynyl and propynyl groups.

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 a vinylene group and a 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 a silane coupling agent containing a bonding unit A represented by formula (I) and a bonding unit B represented by formula (II), the number of repetitions (x) of bonding unit A and the repetition number (y) of bonding unit B The total number of repetitions (x+y) is preferably in the range of 3-300.

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

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, relative to 100 parts by mass of the inorganic filler (preferably 100 parts by mass of the total content of silica and aluminum hydroxide). If it is at least the lower limit, there is a tendency that the effect of blending the silane coupling agent is sufficiently obtained. Moreover, 20 mass parts or less are preferable, and, as for the said content, 15 mass parts or less are more preferable. When the content is 20 parts by mass or less, there is a tendency that sufficient effects commensurate with the blending amount can be obtained, and good workability during kneading can be obtained.

In addition to silica, the rubber composition may contain inorganic fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide and mica. In addition _, in this specification, aluminum hydroxide means Al(OH) ₃ or _{Al2O3.3H2O .} One of these fillers may be used alone, or two or more thereof may be used in combination.

A solid resin, an oil, or the like may be added to the rubber composition.
Examples of solid resins include α-methylstyrene and/or aromatic vinyl polymers such as 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 ball descends when the softening point specified in JIS K 6220-1:2001 is measured with a ring and ball type softening point measuring device.

As the α-methylstyrene resin, α-methylstyrene, homopolymers of styrene, or copolymers of α-methylstyrene and styrene are preferable because of their excellent wet grip performance. 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, per 100 parts by mass of the rubber component. Blending a predetermined amount of solid resin tends to improve grip performance and the like.

Examples of solid resins include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nichinuri Chemical Co., Ltd. ) Nippon Shokubai Co., JX Energy Co., Ltd., Arakawa Chemical Industries Co., Ltd., Taoka Chemical Co., Ltd., and other products can be used.

Oils include, for example, process oils, vegetable oils, or mixtures thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, etc. can be used. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, Olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil and the like. These may be used alone or in combination of two or more.

As oil, for example, Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H & R, Toyokuni Oil Mills Co., Ltd., Showa Shell Oil Co., Ltd., Fuji Kosan Co., Ltd. etc. products can be used.

The content of the oil 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. Also, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be obtained more satisfactorily.
The content of oil also includes the amount of oil contained in the rubber (oil-extended rubber).

Wax may be blended in the rubber composition.
The wax is not particularly limited, and includes petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant waxes and animal waxes; synthetic waxes such as polymers of ethylene and propylene. These may be used alone or in combination of two or more. Among them, petroleum waxes are preferred, and paraffin waxes are more preferred.

The wax content is preferably 1.0 parts by mass or more, more preferably 1.5 parts by mass or more, relative to 100 parts by mass of the rubber component. Moreover, 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 favorably obtained.

As the wax, for example, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used.

The rubber composition preferably contains an antioxidant.
Antiaging agents include, for example, naphthylamine antiaging agents such as phenyl-α-naphthylamine; diphenylamine antiaging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; -isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, etc. p-phenylenediamine-based antioxidants; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methylphenol, monophenolic antioxidants such as styrenated phenol; bis, tris, polyphenolic antioxidants such as tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane inhibitors and the like. These may be used alone or in combination of two or more. Among them, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferable, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1 , 2-dihydroquinoline polymers are more preferred.

The content of the antioxidant is preferably 1 part by mass or more, more preferably 2 parts by mass or more, relative to 100 parts by mass of the rubber component. Moreover, 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 favorably obtained.

As the anti-aging agent, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis, etc. can be used, for example.

The rubber composition preferably contains stearic acid.
Conventionally known stearic acid can be used, for example, products of NOF Corporation, NOF, Kao Corporation, Fuji Film Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd. can be used.

The stearic acid content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the rubber component. Moreover, 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 favorably obtained.

The rubber composition preferably contains zinc oxide.
As the zinc oxide, conventionally known ones can be used, for example, products of Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. 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, relative to 100 parts by mass of the rubber component. Moreover, 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 more satisfactorily.

The rubber composition preferably contains sulfur.
Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur and the like commonly 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, relative to 100 parts by mass of the rubber component. The above content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be favorably obtained.

As sulfur, for example, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Io Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Ltd., Nippon Kantan Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

The rubber composition preferably contains a vulcanization accelerator.
Vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram disulfide (TMTD ), tetrabenzyl thiuram 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. and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred because the effects of the present invention can be obtained more favorably.

The content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of the rubber component. Moreover, 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 favorably obtained.

In addition to the above components, the rubber composition may contain additives commonly used in the tire industry, such as organic peroxides; processing aids such as plasticizers and lubricants; .

As a method for producing the rubber composition, a known method can be used. For example, the above components can be kneaded using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanized. .

As for the kneading conditions, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C in the base kneading step for kneading additives other than the cross-linking agent (vulcanizing agent) and the vulcanization accelerator. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. 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 generally 140-190°C, preferably 150-185°C.

The rubber composition can be suitably used as a rubber composition for tires. The rubber composition can be used for each member of a tire, and is particularly suitable for a tread.

The pneumatic tire of the present invention can be produced by a normal method using the above rubber composition.
That is, the rubber composition blended with the above components is extruded in an unvulcanized stage according to the shape of tire components such as treads, sidewalls, clinches, wings, etc., and placed on a tire building machine together with other tire components. An unvulcanized tire can be formed by molding in a conventional manner. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

The pneumatic tire of the present invention includes tires for passenger cars, tires for large passenger cars, tires for large SUVs, tires for trucks and buses, tires for racing, studless tires (winter tires), tires for motorcycles, run-flat tires, and aircraft. It can be suitably used for tractor tires, mining tires, and the like.

FIG. 1 is a sectional view showing the state of temperature measurement in the method of measuring the maximum temperature during friction. In FIG. 1, the direction indicated by the arrow X is the upward direction, and the opposite direction is the downward direction. The device 2 for this temperature measuring method comprises a measuring plate 4 , a temperature measuring device 6 , a measuring table 8 and a friction property measuring device 10 . Also shown in FIG. 1 is the 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 these.

The measuring plate 4 is plate-shaped. The measuring plate 4 is placed on a measuring table 8 . As shown in the figure, the measuring plate 4 has a recess 14 on its underside. The thickness between the bottom of the recess 14 and the top surface 16 of the measuring plate 4 is less than the thickness between the top surface 16 and the bottom surface 18 of the measuring plate 4 where the recess 14 is absent. This thinned portion is referred to as the measurement window 20 of the measurement plate 4 . In the drawing, the shape of the measurement window 20 is circular in plan view. The shape of the measurement window 20 may not be circular.

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

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

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

The frictional property measuring instrument 10 has a rotating plate 24 and a main body 26 . Rotating plate 24 is circular. A piece of rubber 12 whose temperature is to be measured is set on the lower surface of the rotating plate 24 . A body 26 is positioned above the rotating plate 24 . Body 26 rotates rotating plate 24 . Body 26 can rotate 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 12 is brought into contact with the measurement plate 4 and the rotating plate 24 is rotated while a load is applied to the rubber 12 . This causes the rubber 12 to slide against the measuring plate 4 . The main body 26 measures the slip resistance between the rubber 12 and the measuring plate 4 . This friction characteristic measuring instrument 10 is a dynamic friction tester.

In the temperature measurement method using this device 2, the measurement plate 4 is fixed to the measurement table 8 first. A temperature measuring device 6 is arranged under the measuring window 20 of the measuring plate 4 . The rubber 12 to be tested is set on the rotating plate 24 of the frictional characteristic measuring instrument 10 . This friction characteristic measuring device 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 . Rubber 12 is brought into contact with measuring window 20 of measuring plate 4 . The main body 26 presses the rubber 12 against the measuring plate 4 . A load is applied to the rubber 12 in the direction of the measuring plate 4 . The rotating plate 24 is rotated by the main body 26 . The rubber 12 rotates. Thereby, the rubber 12 slides on the measuring plate 4 . The main body 26 measures the slip resistance force at this time. At the same time, the temperature measuring device 6 measures the electromagnetic waves 22 transmitted through the measurement window 20 . A temperature measuring device 6 measures the temperature of the rubber 12 in contact with the measuring plate 4 . A temperature measuring device 6 measures the temperature of the rubber 12 at the portion where the frictional force is acting.

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 measurement plate 4 can be formed to have sufficient strength against thermal changes and physical impacts.

In FIG. 1, a double arrow T indicates the thickness of the measurement window 20. As shown in FIG. The thickness T is preferably 4.0 mm or less. By setting the thickness T to 4.0 mm or less, this measurement plate 4 has good transmittance. When the material of the measurement plate 4 is Al ₂ O ₃ , the thickness T is set to 4.0 mm or less, so that the measurement plate 4 can be formed in which the 70% transmission wavelength band includes the wavelength band (2 μm to 4 μm). .

The upper surface 16 of the measuring 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 the top surface 16 having been roughened. By roughening the upper surface 16 of the measuring plate 4, the coefficient of friction can be increased. The coefficient of friction depends on the roughness of the measuring plate 4 . By preparing measurement plates 4 having different surface roughnesses, it is possible to measure the temperature of the rubber 12 in the area where friction occurs under various friction coefficients.

Shot blasting and sand blasting are suitable for roughening the measuring plate 4 . By subjecting the top surface 16 of the measuring plate 4 to shot blasting or sandblasting, the measuring plate 4 having a desired surface roughness can be easily formed. When the material of the measurement plate 4 is Al ₂ O ₃ , grains of silicon carbide are preferable as the blasting material to be shot-blasted onto the upper surface 16 of the measurement plate 4 . The grains of silicon carbide can form a rough surface even for a measuring plate 4 made of Al ₂ O ₃ . By changing the grain size of silicon carbide, the surface roughness can be changed.

The lower surface 18 of the measurement plate 4 is preferably mirror-finished. By mirror-finishing the lower surface 18 of the measurement plate 4, the transmittance of the electromagnetic wave 22 can be improved.

Most of the electromagnetic waves 22 emitted by thermal radiation from the rubber 12 have wavelengths 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 measurable 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 for the measurement plate 4, the measurement plate 4 can be formed in which the 70% transmission wavelength band includes the wavelength band (2 μm to 4 μm).

The temperature measuring device 6 is preferably a thermograph equipped with a camera. The temperature distribution on the surface of the rubber 12 can be measured within the range photographed by this camera. This camera preferably has a magnifying lens. By using this lens, the temperature distribution on the surface of the rubber 12 can be measured in finer 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 of continuous photographing. By continuously photographing the surface of the rubber 12, when the rubber 12 is slid on the measuring plate 4, changes in the surface temperature of the rubber 12 over 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.

A dynamic friction tester is preferably used to bring the rubber 12 into contact with the upper surface 16 of the measuring plate 4 and slide the rubber 12 against the measuring plate 4 . This allows measurement of the slip resistance according to the desired load and the desired slip velocity. By changing the roughness of the measuring plate 4, slip resistance can be measured under different friction coefficients. By wetting the measuring plate 4, it is possible to measure the slip resistance while the measuring plate 4 is wet. By using a dynamic friction tester, it is possible to measure the temperature of the rubber 12 at the portion where the frictional force acts while measuring these frictional characteristics.

ステアリン酸：日油（株）製のステアリン酸「椿」
酸化亜鉛：三井金属鉱業（株）製の亜鉛華２種
老化防止剤６Ｃ：大内新興化学工業（株）製のノクラック６Ｃ（Ｎ－（１，３－ジメチルブチル）－Ｎ’－フェニル－ｐ－フェニレンジアミン）
老化防止剤ＲＤ：大内新興化学工業（株）製のノクラック２２４（２，２，４－トリメチル－１，２－ジヒドロキノリン重合体）
オイル：出光興産（株）製のダイアナプロセスＮＨ－７０Ｓ
シランカップリング剤１：デグッサ社製のＮＸＴ－Ｚ４５（結合単位Ａと結合単位Ｂとの共重合体（結合単位Ａ：５５モル％、結合単位Ｂ：４５モル％））
シランカップリング剤２：デグッサ社製のＳｉ２６６（ビス（３－トリエトキシシリルプロピルジスルフィド））
硫黄：細井化学工業（株）製のＨＫ－２００－５（加硫剤、オイル分５質量％）
加硫促進剤ＣＺ：Ｎ－シクロヘキシル－２－ベンゾチアジルスルフェンアミド
加硫促進剤ＤＰＧ：ジフェニルグアニジンVarious chemicals used in Examples and Comparative Examples are collectively described below.
SBR: Tafden 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 (cis 1,4 bond amount 98%) manufactured by Ube Industries, Ltd.
NR: TSR
Carbon black: Show Black N220 (N ₂ SA: 111 m ² /g, DBP: 115 ml/100 g) manufactured by Cabot Japan Co., Ltd.
Silica 1: Ultrasil 9000GR from Evonik (N ₂ SA: 240 m ² /g)
Silica 2: Ultrasil VN3 from Evonik (N ₂ SA: 175 m ² /g)
Carbon fiber: Coal pitch-based carbon fiber “K6371T” manufactured by Mitsubishi Plastics, Inc. (chopped fiber, average fiber diameter: 11 μm, average fiber length: 6.3 mm, thermal conductivity: 140 W / m K)
Resin crosslinking agent: Takkiroru V200 manufactured by Taoka Chemical Co., Ltd. (alkylphenol/sulfur chloride condensate, alkylphenol/sulfur chloride condensate represented by the above formula (I-1), sulfur content: 24% by mass, weight average molecular weight: 9000)
Compound A: Sodium (2Z)-4-[(4-aminophenyl)amino]-4-oxo-2-butenoate manufactured by Sumitomo Chemical Co., Ltd. (compound represented by the following formula)

Stearic acid: stearic acid "Tsubaki" manufactured by NOF Corporation
Zinc oxide: Mitsui Kinzoku Mining Co., Ltd. Zinc white type 2 anti-aging agent 6C: Ouchi Shinko Kagaku Kogyo Co., Ltd. Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p - phenylenediamine)
Antiaging agent RD: Nocrack 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinko Kagaku Kogyo 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 manufactured by Degussa (bis (3-triethoxysilylpropyl disulfide))
Sulfur: HK-200-5 (vulcanizing agent, oil content 5% by mass) manufactured by Hosoi Chemical Industry Co., Ltd.
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, cyclohexane, 1,3-butadiene, tetrahydrofuran and styrene were charged under a nitrogen atmosphere, and after adjusting the temperature to 30° C., n-butyllithium was added to initiate polymerization. After the temperature was raised to 70°C, polymerization was carried out for 2 hours. After reaching a polymerization conversion of 100%, a small amount of tin tetrachloride was added and a coupling reaction was carried out at 70°C. After that, 3-diethylaminopropyltrimethoxysilane was added and a modification reaction was carried out at 60°C. After adding 2,6-di-tert-butyl-p-cresol to the obtained copolymer solution, the solvent was removed by steam stripping, and further dried with hot rolls at 110° C. to obtain modified SBR. rice field.

<Examples and Comparative Examples>
According to the composition shown in Table 1, various chemicals except sulfur and vulcanization accelerator were kneaded at 150° C. for 5 minutes in a Banbury mixer. Sulfur and a vulcanization accelerator were added to the resulting kneaded material, 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.

Using the obtained vulcanized rubber sheet (sample), the following evaluations were carried out. The results are shown in Table 1, Figures 3 and 4.

[Measurement of maximum temperature]
The temperature of the sample was measured using the temperature measuring device shown in FIGS. For this measurement, a measuring 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 the 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 (manufactured by Shinano Electric Refining Co., Ltd. under the trade name of "Shinano-random GC F16") was used as the blasting material.
A dynamic friction tester "DF tester S type" manufactured by Nibbo Sangyo Co., Ltd. was used as a friction characteristic measuring instrument. A sample was set in this tester. During the measurement, the measuring plate was moistened with water at 20°C. The sample was slid over this wet measuring plate at a speed of 7 km/h. The temperature of the sample at this time was measured through the measurement window with a thermometer. The environmental temperature at the time of measurement is 20°C. A thermograph "InfReC H8000" manufactured by Nippon Avionics Co., Ltd. was used as a temperature measuring instrument. A 15 μm microscope lens was attached during the measurement. This temperature measuring instrument measures the intensity of electromagnetic waves with a wavelength of 2 μm or more and 5 μm or less.
From the results of the above thermography, the temperature distribution on the rubber surface was confirmed. Table 1 shows the temperature (maximum temperature) at the hottest point on the surface of the rubber.
[Friction condition]
Device 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 slice processing (similar to PFT)
(Measuring within 48 hours after slicing as it is affected by surface bloom)
Width: 16mm
Contact length: Varies depending on rubber rigidity (use the attached jig for DF tester S type)
Sample: 2 installed (DF tester S type)
(2) Measuring plate (sliding the sample against the measuring plate):
Plates made of Al ₂ O ₃ (plates moistened with water at 20° C.)
(3) Thickness of measurement window T: 2 mm
(4) Speed of sliding the rubber composition (sample) against the measuring plate: Deceleration test from 15 km / hour to 0 km / hour After the start of the test, the maximum temperature from 7 km / hour to 0 km / hour adopt.
(5) Initial speed of sliding the rubber composition (sample) on the measuring plate: 15 km / hour (6) Acceleration of sliding the rubber composition (sample) on the measuring plate:
Deceleration test from 15 km/hour to 0 km/hour Variable due to the deceleration test pressed with a constant load (DF tester S type) (7) Distance to slide the rubber composition (sample) against the measurement plate Constant load (DF Tester S type) for deceleration test pressed with a constant load (DF Tester S type) for deceleration test pressed with a constant load (DF Tester S type). , varies with formulation

[Friction test by linear wear tester (PFT)]
Using a HENTSCHEL linear friction tester "Portable friction tester (model number 380.02)", a friction test was performed under the following test conditions (number of continuous tests: 10 times).
For the test samples, the surface of the samples was subjected to surface treatment (slicing), and the influence of the surface conditions at the start was reset (for the slicing, "NP-120" manufactured by Nippi Machinery Co., Ltd. was used).
After each friction test, the road surface condition was controlled and the change in the condition of the road surface was reset.
A reference tread formulation was used to control the road surface condition, and in this test, μ _s 0.800 was used as the reference value of the reference sample to obtain the correction value (for example, in the second friction test of formulation A, the From the actual measured values, that is, μ _s2 0.815 (measured value) of the reference sample and 0.745 (measured value) of sample A, μ _A2 (correction value) is 0.745 + (0.800- 0.815)=0.73.
In a continuous (repeated) friction test, it shows that the grip performance does not deteriorate during running and the grip performance improves as a whole when the decrease in μ value is suppressed.

(Test condition)
Weightless constant load sliding speed: 2000mm/s
Acceleration: 15m/s
Ground pressure: 0.2Mpa
Water temperature: 20℃
Road surface temperature: 20℃
Road surface: Test course model road surface (tire labeling μ-S evaluation standard road surface)
TD=0.7±0.3, BPN=42-60
*For BNP, it is managed by μ of reference sample.

From Table 1 and FIGS. 3 and 4, which show the results of Table 1, it can be seen that the maximum temperature at the time of friction under the predetermined friction conditions is 35° C., and that μ drops significantly depending on 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. rice field.

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

Claims (5)

At least one selected from the group consisting of a rubber component, silica, carbon black, oil, carbon fiber, a resin cross-linking agent, and a compound represented by the following formula (I),

(wherein R ¹ and R ² are the same or different and represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms or an alkynyl group having 2 to 20 carbon atoms. M ^r+ indicates a metal ion, and r indicates its valence.)
With respect to 100 parts by mass of the rubber component, the silica content is 60 to 150 parts by mass, the carbon black content is 1 to 10 parts by mass, and the oil content is 5 to 20 parts by mass,
A vulcanized rubber composition having a maximum friction temperature of 20 to 30° C. under the following friction conditions.
[Friction condition]
Apparatus used: Dynamic friction tester (1) Size and shape of vulcanized rubber composition:
Thickness: 2mm thick sheet Width: 16mm
(2) Measuring plate (sliding the vulcanized rubber composition on the measuring plate):
Plates made of Al ₂ O ₃ (plates moistened with water at 20° C.)
(3) Thickness of measurement window T: 2 mm
(4) Speed at which the vulcanized rubber composition is slid against the measurement plate: Deceleration test from 15 km/h to 0 km/h after the start of the test. do.
(5) Initial speed of sliding the vulcanized rubber composition on the measuring plate: 15 km/hour (6) Acceleration of sliding the vulcanized rubber composition on the measuring plate:
Deceleration test from 15 km/h to 0 km/h Because it is a deceleration test pressed with a constant load, it varies depending on the compounding (7) Distance of sliding the vulcanized rubber composition against the measurement plate , Varies depending on compounding (8) Time for sliding the vulcanized rubber composition against the measuring plate Because it was a deceleration test in which a constant load was pressed, it varies depending on the compounding At least one selected from the group consisting of a rubber component, carbon black, oil, carbon fiber, a resin cross-linking agent, and a compound represented by the following formula (I),

(wherein R ¹ and R ² are the same or different and represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms or an alkynyl group having 2 to 20 carbon atoms. M ^r+ indicates a metal ion, and r indicates its valence.)
and does not contain silica,
The content of carbon black is 50 to 150 parts by mass and the content of oil is 5 to 20 parts by mass with respect to 100 parts by mass of the rubber component,
A vulcanized rubber composition having a maximum friction temperature of 20 to 30° C. under the following friction conditions.
[Friction condition]
Apparatus used: Dynamic friction tester (1) Size and shape of vulcanized rubber composition:
Thickness: 2mm thick sheet Width: 16mm
(2) Measuring plate (sliding the vulcanized rubber composition on the measuring plate):
Plates made of Al ₂ O ₃ (plates moistened with water at 20° C.)
(3) Thickness of measurement window T: 2 mm
(4) Speed at which the vulcanized rubber composition is slid against the measurement plate: Deceleration test from 15 km/h to 0 km/h after the start of the test. do.
(5) Initial speed of sliding the vulcanized rubber composition on the measuring plate: 15 km/hour (6) Acceleration of sliding the vulcanized rubber composition on the measuring plate:
Deceleration test from 15 km/h to 0 km/h Because it is a deceleration test pressed with a constant load, it varies depending on the compounding (7) Distance of sliding the vulcanized rubber composition against the measurement plate , Varies depending on compounding (8) Time for sliding the vulcanized rubber composition against the measuring plate Because it was a deceleration test in which a constant load was pressed, it varies depending on the compounding The vulcanized rubber composition according to claim 1 or 2, wherein said maximum temperature is 20 to 25°C. The vulcanized rubber composition according to claim 1 or 2, wherein said maximum temperature is 20 to 23°C. A pneumatic tire using the vulcanized rubber composition according to any one of claims 1 to 4 for a tread.

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