Rubber composition and tires

Abstract

To provide a rubber composition and a tire which are excellent in steering stability during high-speed traveling.SOLUTION: The present invention relates to the rubber composition containing a rubber component and silica. A coefficient of variation (CV value) of the maximum diameter of each particle of the silica observed with an electron microscope satisfies the following inequality (1): CV value≤75%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a rubber composition and a tire using the same. [Background technology]

[0002] While various tires have been proposed that use silica-based rubber compositions to impart different performance characteristics, in recent years, with the increase in high-speed driving, there has been a growing demand for improved handling stability at high speeds. [Overview of the project] [Problems that the invention aims to solve]

[0003] This disclosure aims to solve the aforementioned problems and provide a rubber composition and tire with excellent handling stability during high-speed driving. [Means for solving the problem]

[0004] This disclosure relates to a rubber composition comprising a rubber component and silica, The present invention relates to a rubber composition in which the coefficient of variation (CV value) of the maximum diameter of each silica particle observed by an electron microscope satisfies the following formula (1). (1) CV value ≤ 75% [Effects of the Invention]

[0005] This disclosure provides a rubber composition containing a rubber component and silica, wherein the coefficient of variation (CV value) of the maximum diameter of each silica particle observed by an electron microscope satisfies formula (1), thereby providing a rubber composition and tire with excellent handling stability during high-speed driving. [Brief explanation of the drawing]

[0006] [Figure 1] This is a cross-sectional view showing a portion of a pneumatic tire. [Figure 2] This is a magnified view of the area around tread 4 in Figure 1. [Modes for carrying out the invention]

[0007] <Rubber composition> The present disclosure relates to a rubber composition containing a rubber component and silica, wherein the coefficient of variation (CV value) of the maximum diameter of each particle of the silica observed by an electron microscope satisfies the following formula (1).

[0008] Although the reason for obtaining the above-described effects is not necessarily clear, it is presumed that the effects are achieved by the following mechanism. The rubber component can be reinforced by silica in the rubber composition to obtain rigidity, and at the same time, a network in which the polymer is reinforced by silica is formed, so that it is considered that a reaction force can be generated. During high-speed driving, it is considered necessary to efficiently generate a reaction force while ensuring rigidity. In the present disclosure, the CV value of the maximum diameter of the silica particles in the rubber composition is set to 75% or less. As a result, the distance and amount of the polymer reinforced by silica in the rubber composition are likely to be made uniform, and force transmission in the rubber is likely to occur. Therefore, it is considered that the handling stability at high speeds can be improved more than before. Therefore, it is presumed that the handling stability during high-speed driving is improved.

[0009] In this way, by configuring the rubber composition such that the coefficient of variation (CV value) of the maximum diameter of each particle of the silica observed by an electron microscope satisfies the formula (1) "CV value ≦ 75%", the problem (objective) of improving the handling stability during high-speed driving is solved. That is, the parameter of the formula (1) "CV value ≦ 75%" does not define the problem (objective). The problem of the present application is to improve the handling stability during high-speed driving, and as a solution means therefor, the configuration is such that the parameter is satisfied.

[0010] For the rubber composition, the coefficient of variation (CV value) of the maximum diameter of each particle of the silica observed by an electron microscope satisfies the following formula (1). (1) CV value ≦ 75% The CV value is preferably 71% or less, more preferably 60% or less, even more preferably 55% or less, and particularly preferably 52% or less. A smaller CV value is desirable because it is thought that the distance and amount of silica-reinforced polymer within the rubber composition become more uniform, and force transmission within the rubber becomes easier, thereby improving handling stability at high speeds. The lower limit is not particularly limited.

[0011] For rubber compositions, it is desirable that the average D of the maximum diameter of each silica particle observed with an electron microscope satisfies the following formula. D ≤ 0.100 μm D is preferably 0.092 μm or less, more preferably 0.070 μm or less, even more preferably 0.064 μm or less, and particularly preferably 0.061 μm or less. The lower limit is preferably 0.030 μm or more, more preferably 0.040 μm or more, and even more preferably 0.050 μm or more. Within the above range, the effect is suitably obtained.

[0012] The coefficient of variation (CV value) is calculated using the mean and standard deviation of the maximum diameter of each silica particle present in the rubber composition, using the following formula. Coefficient of variation (%) = [Standard deviation of the maximum diameter of each silica particle (μm)] / [Average of the maximum diameter of each silica particle (μm)] × 100

[0013] The maximum diameter of each silica particle present in the rubber composition is measured by observation using an electron microscope. Specifically, the rubber composition can be observed using an electron microscope such as SEM or TEM, and then the obtained image can be binarized using image analysis software such as ImageJ to calculate the maximum diameter of each silica particle. Specifically, this can be measured by the method described in the examples below.

[0014] In this disclosure, the coefficient of variation (CV value) is the coefficient of variation of the maximum diameter of each silica particle present in the rubber composition after vulcanization.

[0015] The coefficient of variation (CV value) can be reduced by using various methods that improve the dispersibility of silica in the rubber (reducing the variation in average particle size). For example, the coefficient of variation (CV) can be reduced by using a mixture (masterbatch) of water, silica, and a dispersant such as a fatty acid amide compound.

[0016] The maximum diameter D of each silica particle can be reduced by using various methods that improve the dispersibility of silica in the rubber (reducing the variation in average particle diameter). For example, the maximum diameter D can be reduced by using a method that includes a dispersant (masterbatch) such as silica or a fatty acid amide compound.

[0017] (Rubber component) The rubber composition contains rubber components. In a rubber composition, the rubber component is a component that contributes to crosslinking, and generally, it is a polymer with a weight-average molecular weight (Mw) of 10,000 or more that is not extracted by acetone. The rubber component is in a solid state at room temperature (25°C).

[0018] The weight-average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and also preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Within this range, a better effect tends to be obtained.

[0019] In this specification, the weight-average molecular weight (Mw) can be determined by converting the measured values ​​obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation) to standard polystyrene equivalents.

[0020] Examples of rubber components that can be used in rubber compositions include diene rubbers. Examples of diene rubbers include isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). Butyl rubbers and fluororubbers can also be used. These may be used individually or in combination of two or more. Among these, isoprene rubber, BR, and SBR are preferred from the viewpoint of obtaining better effects, and isoprene rubber is more preferred. Furthermore, these rubber components may undergo modification treatments and hydrogenation treatments as described later, and stretched rubbers that have been stretched with oil, resin, liquid rubber components, etc., may also be used.

[0021] The reason why the aforementioned effects are significantly achieved by using isoprene-based rubber is not entirely clear, but it is thought that because isoprene-based rubber has a high molecular weight, it is easier to form a network and generate and transmit reaction forces. Therefore, it is presumed that handling stability at high speeds is significantly improved.

[0022] The above diene rubber may be either unmodified diene rubber or modified diene rubber. Modified diene rubbers can be any diene rubber having a functional group that interacts with a filler such as silica. Examples include end-modified diene rubbers (end-modified diene rubbers having the functional group at the end) in which at least one end of the diene rubber is modified with a compound (modifier) ​​having the functional group, main-chain modified diene rubbers having the functional group in the main chain, main-chain end-modified diene rubbers having the functional group in both the main chain and the end (for example, main-chain end-modified diene rubbers having the functional group in the main chain and at least one end modified with the modifier), and end-modified diene rubbers that are modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and in which hydroxyl groups or epoxy groups are introduced.

[0023] Examples of the above 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, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, and the like. These functional groups may have substituents. Among these, amino groups (preferably amino groups in which the hydrogen atoms of the amino group are substituted with C1-C6 alkyl groups), alkoxy groups (preferably alkoxy groups having C1-C6), and alkoxysilyl groups (preferably alkoxysilyl groups having C1-C6) are preferred.

[0024] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. For NR, common types used in the rubber industry can be used, such as SIR20, RSS#3, and TSR20. For IR, there are no particular limitations; common types used in the rubber industry can be used, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used individually or in combination of two or more types.

[0025] In the rubber composition, the isoprene-based rubber content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 50% by mass or more, even more preferably 75% by mass or more, and particularly preferably 85% by mass or more, and may be 100% by mass. Within the above range, better effects tend to be obtained. The same range is desirable for tread rubber compositions and belt layer rubber compositions.

[0026] BR is not particularly limited, and for example, high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using a rare-earth catalyst (rare-earth BR) can be used. These may be used individually or in combination of two or more. In particular, it is preferable that the BR contains high-cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more. The cis content can be measured by infrared absorption spectroscopy.

[0027] Furthermore, both unmodified and modified BR can be used. Modified BR includes BR in which functional groups similar to those of modified diene rubber have been introduced. Hydrogenated butadiene polymers (hydrogenated BR) can also be used.

[0028] For example, products from companies such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation can be used as BRs.

[0029] When the rubber composition contains BR, the BR content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. Within the above range, better effects tend to be obtained. The same range is desirable for tread rubber compositions and belt layer rubber compositions.

[0030] The SBR is not particularly limited; for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc., can be used. These may be used individually or in combination of two or more types.

[0031] The styrene content of SBR is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. The styrene content is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. Keeping it within the above range tends to improve handling stability during high-speed driving. In this specification, the styrene content is defined as follows: 1 It can be measured by 1H-NMR.

[0032] The vinyl bonding amount of SBR is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more. The vinyl bonding amount is preferably 25% by mass or less, more preferably 15% by mass or less, and even more preferably 13% by mass or less. Keeping it within the above range tends to improve handling stability during high-speed driving. In this specification, the amount of vinyl bond (amount of 1,2-bonded butadiene units) can be measured by infrared absorption spectroscopy.

[0033] Both unmodified and modified SBR can be used. Modified SBR includes SBR with functional groups similar to those introduced in modified diene rubber. Hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can also be used as SBR.

[0034] For example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Co., Ltd. can be used.

[0035] When the rubber composition contains SBR, the SBR content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. Within the above range, better effects tend to be obtained. The same range is desirable for tread rubber compositions and belt layer rubber compositions.

[0036] (Filler) The rubber composition contains silica. Examples of usable silica include dry-process silica (anhydrous silica), wet-process silica (hydrous silica), etc. Among them, wet-process silica is preferred because of its large number of silanol groups. As commercial products, products of Degussa, Rhodia, Tosoh Silica Corporation, Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used. These may be used alone or in combination of two or more. In addition to these silicas, silica made from biomass materials such as rice husks may also be used.

[0037] The nitrogen adsorption specific surface area (N2SA) of silica is preferably 50 m 2 / g or more, more preferably 100 m 2 / g or more, still more preferably 150 m 2 / g or more, particularly preferably 180 m 2 / g or more, most preferably 190 m 2 / g or more. Also, the upper limit of the N2SA of silica is not particularly limited, but is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, still more preferably 250 m 2 / g or less. When within the above range, the effect tends to be obtained more favorably. Note that the N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0038] In the rubber composition, the content of silica is preferably 5 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, particularly preferably 50 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less, particularly preferably 80 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. Note that the same range is desirable for the tread rubber composition and the belt layer rubber composition.

[0039] The reason why incorporating a large amount of silica, especially 30 parts by mass or more, significantly enhances the aforementioned effects is not entirely clear. However, it is thought that the reinforcing effect of silica improves rigidity, while the reaction force generated by the network formed by silica and polymer becomes greater. Therefore, it is presumed that handling stability at high speeds is significantly improved.

[0040] If the rubber composition contains silica, it is preferable that it further contains a silane coupling agent. The silane coupling agent is not particularly limited and any known in the rubber field can be used, 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-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, Examples include sulfide-based compounds such as N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products from companies such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd. can be used. These can be used individually or in combination of two or more types.

[0041] In the rubber composition, the content of the silane coupling agent is preferably 0.1 parts by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, per 100 parts by mass of silica. The upper limit of the content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0042] The rubber composition may contain fillers other than silica. In the rubber composition, the total filler content (total amount of fillers such as silica and carbon black) is preferably 10 parts by mass or more, more preferably 35 parts by mass or more, even more preferably 45 parts by mass or more, and particularly preferably 55 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of this content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 80 parts by mass or less. When the content is within the above range, a better effect tends to be obtained. The same range is desirable for tread rubber compositions and belt layer rubber compositions.

[0043] Other fillers that can be used besides silica are not particularly limited, and materials known in the rubber field can be used, such as inorganic fillers such as carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica; and poorly dispersible fillers. Among these, carbon-derived fillers (carbon-containing fillers) such as carbon black are preferred.

[0044] While not particularly limited, carbon blacks usable in rubber compositions include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nippon Chemical Carbon Co., Ltd., and Columbia Carbon Corporation can be used. These may be used individually or in combination of two or more. In addition to conventional carbon black made from mineral oil, carbon black made from biomass materials such as lignin may also be used.

[0045] The nitrogen adsorption specific surface area (N2SA) of carbon black is 30 m². 2 Preferably 50m / g or more. 2 More preferably 70m 2 More preferably, the amount of N2SA is 200m 2 Preferably less than / g, 150m 2 More preferably less than / g, 130m 2 More preferably less than / g, and 120m 2 A value of less than / g is even more preferable. Within the above range, there is a tendency to obtain better effects.

[0046] In the rubber composition, the carbon black content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less. When the content is within the above range, a better effect tends to be obtained. The same range is desirable for tread rubber compositions and belt layer rubber compositions.

[0047] Examples of poorly dispersible fillers include microfibrillated plant fibers, short fibrous cellulose, and gel-like compounds. Among these, microfibrillated plant fibers are preferred.

[0048] As the above-mentioned microfibrillated plant fiber, cellulose microfibrils are preferred in that they provide good reinforcing properties. The cellulose microfibrils are not particularly limited as long as they are derived from natural products, and examples include resource biomass such as fruits, grains, and root vegetables; wood, bamboo, hemp, jute, and kenaf, as well as waste biomass such as pulp, paper, cloth, agricultural residues, food waste, and sewage sludge obtained from these raw materials, unused biomass such as rice straw, wheat straw, and thinned wood, and cellulose produced by sea squirts, acetic acid bacteria, etc. One type of these microfibrillated plant fiber may be used, or two or more types may be used in combination.

[0049] In this specification, cellulose microfibrils typically refer to cellulose fibers having an average fiber diameter of 10 μm or less, and more typically, cellulose fibers having a microstructure with an average fiber diameter of 500 nm or less, formed by an aggregate of cellulose molecules. Typical cellulose microfibrils are formed, for example, as aggregates of cellulose fibers having the average fiber diameter described above.

[0050] In the rubber composition, the content of the poorly dispersible filler is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. When the content is within the above range, the effect tends to be better obtained.

[0051] (Dispersant) From the viewpoint of obtaining better effects, it is desirable for the rubber composition to include a dispersant. Any dispersant that has the property of dispersing silica can be used, but fatty acid amide compounds are particularly preferred.

[0052] The reason why the aforementioned effects are significantly achieved by using dispersants, particularly fatty acid amide compounds, is not entirely clear. However, it is thought that the inclusion of fatty acid amide compounds makes it easier to reduce the average particle size of silica. Therefore, it is presumed that handling stability at high speeds is significantly improved.

[0053] In the rubber composition, the dispersant content is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and particularly preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less. When the content is within the above range, a better effect tends to be obtained. The same range is desirable for tread rubber compositions and belt layer rubber compositions. The content of fatty acid amide compounds is also preferably within the same range.

[0054] In rubber compositions, the silica-to-dispersant ratio [silica content (parts by mass) / dispersant content (parts by mass)] is preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 80 / 20, even more preferably 30 / 70 to 70 / 30, and particularly preferably 40 / 60 to 60 / 40. Within this range, better performance tends to be achieved. The same range is desirable for tread rubber compositions and belt layer rubber compositions. Furthermore, the fatty acid amide compound content is also preferably within the same range.

[0055] The aliphatic hydrocarbon groups constituting the fatty acid amide compound include saturated or unsaturated aliphatic hydrocarbon groups having linear, branched, or cyclic structures, such as alkyl groups, alkenyl groups, alkenediyl groups, and cycloalkyl groups. The number of carbon atoms in the aliphatic hydrocarbon group is preferably 10 to 25.

[0056] Examples of fatty acid amide compounds include monoamides, substituted amides, bisamides, methylolamides, and esteramides.

[0057] Examples of monoamides include compounds represented by the following formula. R 1 -CONH2 (In the formula, R 1 (This represents an aliphatic hydrocarbon group with 10 to 25 carbon atoms.)

[0058] Specific examples of monoamides include, for example, lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, oleic acid amide, and erucic acid amide.

[0059] Examples of substituted amides include compounds represented by the following formula. R 2 -CONH-R 3 (In the formula, R 2 and R 3 (This represents an aliphatic hydrocarbon group with 10 to 25 carbon atoms, and these groups may be the same or different.)

[0060] Specific examples of substituted amides include, for example, N-oleyl palmitate amide, N-stearyl stearate amide, N-stearyl oleate amide, N-oleyl stearate amide, and N-stearyl erucate amide.

[0061] Examples of bisamides include compounds represented by the following two formulas. R 4 -CONH-R 5 -HNCO-R 6 R 7 -NHCO-R 8 -CONH-R 9 (In the formula, R 4 , R 6 , R 7 , and R 9 R represents an aliphatic hydrocarbon group having 10 to 25 carbon atoms, and may be the same or different. 5 and R 8 (This represents an alkylene group or an arylene group.)

[0062] Specific examples of bisamides include, for example, methylenebisstearate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenehydroxystearate, ethylenebisoleamide, ethylenebiserucamide, hexamethylenebisoleamide, N,N'-distearyladipamide, N,N'-distearylsebacinamide, N,N'-dioleyladipamide, and N,N'-dioleylsebacinamide.

[0063] Specific examples of the aforementioned fatty acid amide compounds include diethanololeamide, palmitoylethanolamide, and oleylethanolamide. These may be used individually or in combination of two or more.

[0064] (Plasticizer) Plasticizers may be added to the rubber composition. Plasticizers are materials that impart plasticity to rubber components. Examples include liquid plasticizers (plasticizers that are liquid at room temperature (25°C)) and resins (resins that are solid at room temperature (25°C)).

[0065] In the rubber composition, the plasticizer content (total amount of plasticizer) is preferably 100 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, per 100 parts by mass of the rubber component, and may be 0 parts by mass. Within the above range, a better effect tends to be obtained. Note that when the aforementioned stretchable rubber is used, the amount of stretchable component used in that stretchable rubber is included in the plasticizer content.

[0066] The liquid plasticizers (plasticizers that are in a liquid state at room temperature (25°C)) that can be used in rubber compositions are not particularly limited and include oils, liquid polymers (liquid resins, liquid diene polymers, etc.). These may be used alone or in combination of two or more.

[0067] In the rubber composition, the liquid plasticizer content is preferably 100 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, per 100 parts by mass of the rubber component, and may be 0 parts by mass. Within the above range, a better effect tends to be obtained. The oil content is also preferably within a similar range.

[0068] Examples of oils include process oils, vegetable oils, or mixtures thereof. Examples of process oils include paraffinic process oils such as MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), and RAE (Residual Aromatic Extract), as well as aromatic process oils and naphthenic process oils. Examples of 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, and tung oil. Commercially available products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and Nisshin Oillio Group, Ltd. are suitable. Process oils (paraffinic process oils, aromatic process oils, naphthenic process oils, etc.) and vegetable oils are particularly preferred. Furthermore, from a life cycle assessment perspective, lubricating oils used in rubber mixers and engines, or refined waste cooking oils used in restaurants, may also be used as the oils mentioned above.

[0069] Examples of liquid resins include terpene resins (including terpene phenol resins and aromatically modified terpene resins), rosin resins, styrene resins, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, coumarone-indene resins (including coumarone and indene-only resins), phenolic resins, olefin resins, polyurethane resins, and acrylic resins. Hydrogenated versions of these resins can also be used.

[0070] Examples of liquid diene polymers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid farnesene polymer, and liquid farnesene-butadiene copolymer. These polymers may have polar groups attached to their ends or main chains. Hydrogenated versions of these polymers can also be used.

[0071] Examples of the above-mentioned resins (resins that are solid at room temperature (25°C)) that can be used in rubber compositions include aromatic vinyl polymers, coumarone indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins, all of which are solid at room temperature (25°C). The resins may also be hydrogenated. These may be used individually or in combination of two or more. Among these, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred.

[0072] When the rubber composition contains the above resin, the amount of the resin is preferably 100 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, per 100 parts by mass of the rubber component, and may even be 0 parts by mass. Within the above range, a better effect tends to be obtained.

[0073] The softening point of the above resin is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher. The upper limit is preferably 160°C or lower, more preferably 130°C or lower, and even more preferably 115°C or lower. Keeping it within the above range tends to improve handling stability during high-speed driving. The softening point of the above resin is determined by measuring the softening point as specified in JIS K6220-1:2001 using a ring-type softening point measuring device, and it is the temperature at which the sphere descends. The softening point of the above resin is usually 50°C ± 5°C higher than the glass transition temperature of the resin.

[0074] The above-mentioned aromatic vinyl polymer is a polymer containing aromatic vinyl monomers as constituent units. Examples include resins obtained by polymerizing α-methylstyrene and / or styrene, specifically, homopolymers of styrene (styrene resin), homopolymers of α-methylstyrene (α-methylstyrene resin), copolymers of α-methylstyrene and styrene, copolymers of styrene and other monomers.

[0075] The above-mentioned coumarone-indene resin is a resin that contains coumarone and indene as the main monomer components that constitute the resin's backbone (main chain). Other monomer components that may be included in the backbone besides coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0076] The coumarone resin described above is a resin that contains coumarone as the main monomer component that constitutes the resin's backbone (main chain).

[0077] The above-mentioned indene resin is a resin that contains indene as the main monomer component that constitutes the resin's backbone (main chain).

[0078] As the phenolic resin mentioned above, known polymers such as those obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural using an acid or alkali catalyst can be used. Among these, those obtained by reaction with an acid catalyst (such as novolac-type phenolic resins) are preferred.

[0079] Examples of the rosin resins mentioned above include natural rosin, polymerized rosin, modified rosin, their ester compounds, and rosin-based resins represented by their hydrogenated products.

[0080] Examples of the above petroleum resins include C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, and hydrogenated versions thereof. Among these, DCPD resins and hydrogenated DCPD resins are preferred.

[0081] The above-mentioned terpene resins are polymers containing terpenes as constituent units. Examples include polyterpene resins obtained by polymerizing terpene compounds, and aromatically modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. Hydrogenated versions of these can also be used.

[0082] The above polyterpene resin is a resin obtained by polymerizing a terpene compound. The terpene compound is (C5H8) n A hydrocarbon and its oxygen-containing derivative represented by the following composition, monoterpene (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpene (C 20 H 32 These are compounds with a terpene as their basic skeleton, classified as such, and examples include α-pinene, β-pinene, dipentene, limonene, myrcene, allocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0083] Examples of the polyterpene resins mentioned above include pinene resin, limonene resin, dipentene resin, and pinene / limonene resin, which are made from the terpene compounds described above. Among these, pinene resin is preferred. Pinene resin usually contains both α-pinene and β-pinene, which are isomers of each other, but depending on the difference in the components it contains, it is classified into β-pinene resin, which has β-pinene as the main component, and α-pinene resin, which has α-pinene as the main component.

[0084] Examples of the above-mentioned aromatically modified terpene resins include terpene-phenol resins made from the above-mentioned terpene compounds and phenolic compounds, and terpene-styrene resins made from the above-mentioned terpene compounds and styreneic compounds. In addition, terpene-phenol-styrene resins made from the above-mentioned terpene compounds, phenolic compounds, and styreneic compounds can also be used. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of styreneic compounds include styrene and α-methylstyrene.

[0085] The above-mentioned acrylic resin is a polymer containing acrylic monomers as constituent units. Examples include styrene-acrylic resins such as styrene-acrylic resin, which have carboxyl groups and are obtained by copolymerizing an aromatic vinyl monomer component with an acrylic monomer component. Among these, solvent-free carboxyl group-containing styrene-acrylic resins can be suitably used.

[0086] The above-mentioned solvent-free carboxyl group-containing styrene-acrylic resin is a (meth)acrylic resin (polymer) synthesized by high-temperature continuous polymerization (high-temperature continuous mass polymerization) (as described in U.S. Patent No. 4,414,370, Japanese Patent Publication No. 59-6207, Japanese Patent Publication No. 5-58005, Japanese Patent Publication No. 1-313522, U.S. Patent No. 5,010,166, Toa Gosei Research Annual Report TREND2000 No. 3, pp. 42-45, etc.) with minimal use of polymerization initiators, chain transfer agents, organic solvents, etc. as auxiliary raw materials. In this specification, (meth)acrylic means methacrylic and acrylic.

[0087] Examples of acrylic monomer components constituting the above-mentioned acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters such as 2-ethylhexyl acrylate, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives. Note that (meth)acrylic acid is a general term for acrylic acid and methacrylic acid.

[0088] Examples of aromatic vinyl monomer components that constitute the above-mentioned acrylic resin include aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene.

[0089] In addition, other monomer components may be used as monomer components constituting the above-mentioned acrylic resin, along with (meth)acrylic acid, (meth)acrylic acid derivatives, and aromatic vinyl.

[0090] Examples of plasticizers that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Industries, Ltd., and others.

[0091] (Other materials) The aforementioned rubber composition preferably contains an anti-aging agent from the viewpoint of crack resistance, ozone resistance, etc.

[0092] While not particularly limited, the following are examples of anti-aging agents: naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging 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, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of anti-aging agents include p-phenylenediamine-based anti-aging agents such as amines; quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis, tris, and polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercial products such as those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Co., Ltd. can be used.

[0093] In the rubber composition, the content of the anti-aging agent is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, and more preferably 4.0 parts by mass or less.

[0094] The rubber composition preferably contains stearic acid. In the rubber composition, the stearic acid content is preferably 0.5 to 10 parts by mass, more preferably 0.5 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0095] In addition, conventionally known stearic acid can be used, such as products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Corporation, Chiba Fatty Acid Co., Ltd.

[0096] The rubber composition preferably contains zinc oxide. In the rubber composition, the zinc oxide content is preferably 0.5 to 10 parts by mass, more preferably 1 to 3 parts by mass, per 100 parts by mass of the rubber component.

[0097] In addition, conventionally known zinc oxides can be used, such as products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd.

[0098] The rubber composition may contain wax. In the rubber composition, the wax content is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0099] The type of wax used is not particularly limited and includes petroleum-based waxes, natural waxes, and synthetic waxes obtained by refining or chemically processing multiple waxes. These waxes may be used individually or in combination of two or more types.

[0100] Examples of petroleum-based waxes include paraffin wax and microcrystalline wax. Examples of natural waxes are not limited to those derived from non-petroleum resources, and include plant-based waxes such as candelilla wax, carnauba wax, wood wax, rice wax, and jojoba wax; animal-based waxes such as beeswax, lanolin, and whale wax; mineral waxes such as ozokerite, ceresin, and petrolactam; and refined products thereof. Commercially available products include those from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd.

[0101] It is preferable to incorporate sulfur into the rubber composition in order to form appropriate cross-linked chains in the polymer chains, thereby imparting good performance.

[0102] In the rubber composition, the sulfur content is preferably 0.1 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.7 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.0 parts by mass or less.

[0103] Examples of sulfur commonly used in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. Commercially available products include those from Tsurumi Chemical Industries, Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Co., Ltd., Flexis Co., Ltd., Nippon Dry Distillation Co., Ltd., and Hosoi Chemical Industry Co., Ltd. These can be used individually or in combination of two or more types.

[0104] The rubber composition preferably contains a vulcanization accelerator. In the rubber composition, there are no particular restrictions on the content of the vulcanization accelerator, and it can be freely determined according to the desired vulcanization rate and crosslinking density. However, it is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 2.7 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 5.0 parts by mass or less.

[0105] There are no particular restrictions on the type of vulcanization accelerator; commonly used ones can be used. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diortotrilguanidine, and orthotrilbiguanidine. These may be used individually or in combination of two or more. Among them, sulfenamide, guanidine, and benzothiazole vulcanization accelerators are preferred.

[0106] In addition to the above-mentioned components, the rubber composition may also contain other compounding agents commonly used in the tire industry, such as mold release agents.

[0107] As for the method of producing the rubber composition, known methods can be used. For example, the rubber composition can be produced by kneading each of the components using a rubber kneading device such as an open roll or Banbury mixer, and then vulcanizing them.

[0108] In particular, from the viewpoint of obtaining better effects, it is desirable to manufacture the rubber composition by a manufacturing method comprising the steps of (1) preparing a silica dispersion containing the silica and the dispersant (preferably the fatty acid amide compound) and (2) preparing a silica-rubber mixture (compound latex) containing the silica dispersion and rubber latex.

[0109] (Process (1)) The silica dispersion prepared in step (1) is a dispersion (slurry) in which silica and a dispersant are dispersed in a solvent. The solvent is not particularly limited and can be an organic solvent such as water or alcohol, with water being preferred.

[0110] The silica content (solid content) in the above silica dispersion is not particularly limited, but is preferably 0.2 to 20.0% by mass, more preferably 0.5 to 10.0% by mass, and even more preferably 0.5 to 7.0% by mass.

[0111] In step (1) above, a method for preparing a silica dispersion by mixing silica, a dispersant, and a solvent includes, for example, a method of mixing silica, a dispersant, and a solvent using a known stirring device such as a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, or a blender mill, and by stirring thoroughly until the silica and dispersant are sufficiently dispersed, a silica dispersion containing silica and a dispersant can be obtained. The temperature and time when preparing the silica dispersion can be appropriately set within the range that is normally used until the silica and dispersant are sufficiently dispersed, for example, 10 to 40°C for 3 to 120 minutes is preferred, and 15 to 30°C for 5 to 90 minutes is more preferred.

[0112] In step (1), the mixing ratio of silica to dispersant [amount of silica (parts by mass) / amount of dispersant (parts by mass)] is preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 80 / 20, even more preferably 30 / 70 to 70 / 30, and particularly preferably 40 / 60 to 60 / 40. Within this range, a better effect tends to be obtained. The content ratio of silica to fatty acid amide compound should also be within a similar range.

[0113] Furthermore, in step (1), when preparing a silica dispersion containing the silica and the dispersant, it is desirable to further prepare a silica dispersion containing the aforementioned microfibrillated plant fibers. In this case, the microfibrillated plant fibers typically function as an anti-sedimentation agent for silica. By adding the microfibrillated plant fibers, it becomes possible to prevent the silica from settling and agglomerating, allowing for uniform solidification when mixed with the rubber latex and allowed to solidify.

[0114] In step (1), when a silica dispersion containing the microfibrillated plant fibers is further prepared, the content (solids) of the microfibrillated plant fibers in the silica dispersion is preferably 0.1 to 10.0% by mass, more preferably 0.5 to 5.0% by mass, and even more preferably 1.0 to 3.0% by mass. Furthermore, in the silica dispersion, the content (solids) of the microfibrillated plant fibers is preferably 0.01 to 1.00% by mass, more preferably 0.05 to 0.50% by mass, and even more preferably 0.10 to 0.30% by mass, based on 100 parts by mass of silica contained in the silica dispersion.

[0115] (Process (2)) Next, step (2) is performed to produce a silica-rubber mixture (compounded latex) containing the silica dispersion obtained in step (1) and rubber latex.

[0116] Suitable rubber latexes include, for example, natural rubber latex, modified natural rubber latex (saponified natural rubber latex, epoxidized natural rubber latex, etc.), and synthetic diene rubber latex (butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), isoprene rubber, acrylonitrile-butadiene rubber, ethylene vinyl acetate rubber, chloroprene rubber, vinylpyridine rubber, butyl rubber, etc.). These rubber latexes may be used individually or in combination of two or more. Among these, natural rubber latex, isoprene rubber latex such as isoprene rubber latex, SBR latex, and BR latex are preferred, with isoprene rubber latex being more preferred.

[0117] Natural rubber latex is collected as the sap of natural rubber trees such as the Hevea tree, and contains rubber components as well as water, proteins, lipids, inorganic salts, etc., and the gel content in the rubber is thought to be due to the complex presence of various impurities. In this disclosure, as natural rubber latex, raw latex (field latex) obtained by tapping the Hevea tree, concentrated latex obtained by centrifugal separation or creaming (purified latex, high ammonia latex obtained by adding ammonia by conventional methods, LATZ latex stabilized with zinc oxide, TMTD and ammonia, etc.) can be used.

[0118] The pH of the rubber latex is preferably 8.5 or higher, more preferably 9.5 or higher. When the pH is 8.5 or higher, the rubber latex tends to be less unstable and less likely to solidify. The pH of the rubber latex is preferably 12.0 or lower, more preferably 11.0 or lower. When the pH is 12.0 or lower, the rubber latex tends to be less likely to deteriorate.

[0119] Rubber latex can be prepared by conventionally known manufacturing methods, and various commercially available products can also be used. Preferably, the rubber latex used has a rubber solids content of 10 to 80% by mass. More preferably, it is 20% or more and 65% or less by mass.

[0120] In step (2) above, methods for mixing the silica dispersion obtained in step (1) with the rubber latex include, for example, placing the rubber in a known stirring device such as a high-speed homogenizer, ultrasonic homogenizer, colloid mill, or blender mill and dropping the silica dispersion obtained in step (1) while stirring, or dropping the rubber latex into the silica dispersion obtained in step (1) while stirring. By stirring thoroughly until the mixture is sufficiently dispersed, a mixture of the silica dispersion obtained in step (1) and rubber (silica-rubber mixture, compounded latex) can be obtained. The temperature and time for preparing the mixture can be set appropriately within the range usually used until the silica dispersion obtained in step (1) and the rubber are sufficiently dispersed, but for example, 10 to 40°C for 3 to 120 minutes is preferred, and 15 to 30°C for 5 to 90 minutes is more preferred.

[0121] The pH of the silica-rubber mixture (compounded latex) obtained in step (2) above is preferably 9.0 or higher, more preferably 9.5 or higher. It is also preferably 12.0 or lower, and more preferably 11.5 or lower. When the pH of the mixture of silica dispersion obtained in step (1) and rubber latex (compounded latex) is within this range, degradation is suppressed and the mixture can be made stable.

[0122] The silica-rubber mixture (compounded latex) obtained in step (2) above is solidified as needed, and the solidified product (aggregate containing aggregated rubber and filler) is filtered and dried by a known method. After further drying, the rubber is mixed using a twin-screw roller, Banbury, etc., to obtain a composite (rubber-silica composite) in which silica is sufficiently dispersed in the rubber matrix. The rubber-silica composite (wet masterbatch) may contain other components to the extent that they do not inhibit the effect.

[0123] The above solidification is usually carried out by adding an acid to the silica-rubber mixture (compound latex) obtained in step (2) above. Examples of acids used for solidification include sulfuric acid, hydrochloric acid, formic acid, and acetic acid. The preferred temperature for solidification is 10 to 40°C.

[0124] During the above solidification process, it is preferable to adjust the pH of the silica-rubber mixture (compounded latex) obtained in step (2) above to 3-5, and more preferably to 3-4.

[0125] Furthermore, a flocculant may be added to control the state of coagulation (the size of the coagulated aggregated particles). Cationic polymers can be used as flocculants.

[0126] A rubber-silica composite (masterbatch) is prepared by the aforementioned manufacturing method, and a rubber composition can be produced by, for example, kneading the rubber-silica composite and other components using a rubber kneading device such as an open roll or Banbury mixer, and then vulcanizing it.

[0127] Regarding the mixing conditions, in the base mixing step where additives other than the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is usually 50 to 200°C, preferably 80 to 190°C, and the mixing time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes. In the finish mixing step where the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is usually 100°C or lower, preferably room temperature to 80°C. Furthermore, the composition mixed with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200°C, preferably 140 to 180°C.

[0128] The above rubber composition can be used, for example, in tire components (as a rubber composition for tires). The tire components are not particularly limited and include any tire components such as the tread (cap tread, base tread), belt layer, sidewall, bead apex, clinch apex, inner liner, undertread, breaker topping, and pry topping. Among these, it is preferable to use it in the tread and belt layer.

[0129] Tires to which the above rubber composition is applied include pneumatic tires and non-pneumatic tires, but pneumatic tires are preferred. In particular, it can be suitably used as summer tires and winter tires (studless tires, snow tires, studless tires, etc.). The tires can be used for passenger cars, large passenger cars, large SUVs, heavy-duty tires for trucks and buses, light trucks, motorcycles, and racing tires (high-performance tires).

[0130] Tires are manufactured using rubber compositions by conventional methods. For example, a rubber composition containing various materials is extruded to match the shape of the tread and belt layers at the unvulcanized stage, and then molded together with other tire components on a tire molding machine in a conventional manner to form an unvulcanized tire. A tire is then obtained by heating and pressurizing this unvulcanized tire in a vulcanizing machine.

[0131] <Tires> From the viewpoint of obtaining better performance, the tire of this disclosure has a tread made of the rubber composition (after vulcanization), and it is desirable that the average D1 (μm) of the maximum diameter of each silica particle in the tread as observed by an electron microscope (the average D1 of the maximum diameter of each silica particle contained in the rubber composition constituting the tread) and the thickness L1 (mm) of the tread satisfy the following formula. D1 × L1 ≤ 2.5 D1 × L1 is preferably 2.3 or less, more preferably 1.6 or less, even more preferably 1.5 or less, and particularly preferably 1.4 or less. The lower limit is preferably 1.0 or more, more preferably 1.1 or more, and even more preferably 1.2 or more. Within the above range, the effect is suitably obtained.

[0132] The reasons for the aforementioned effects are not entirely clear, but it is presumed that they are achieved through the following mechanism. In addition to reducing the CV value of the silica particle diameter, it is believed that further reducing the average of the maximum diameters of each silica particle will make the network finer, making it easier to transmit force and generate reaction forces in the middle of the rubber. Furthermore, it is thought that a thinner tread layer makes it easier to transmit reaction forces internally, thus improving handling stability. Therefore, by keeping the product of these factors below a predetermined value, the network and force transmission within the rubber are ensured, and it is presumed that handling stability at high speeds will be significantly improved.

[0133] From the viewpoint of obtaining a suitable effect, it is desirable that the tread thickness L1 satisfies the following formula. L1 ≤ 35mm L1 is preferably 30 mm or less, more preferably 27 mm or less, and even more preferably 25 mm or less. The lower limit is preferably 10 mm or more, more preferably 13 mm or more, and even more preferably 15 mm or more. Within the above range, the effect is suitably obtained.

[0134] From the viewpoint of obtaining better performance, the tire of this disclosure has a belt layer made of the rubber composition (after vulcanization), and it is desirable that the average D2 (μm) of the maximum diameter of each silica particle in the belt layer as observed by an electron microscope (the average D2 of the maximum diameter of each silica particle contained in the rubber composition constituting the belt layer) and the distance L2 (mm) from the radially outer surface of the belt layer to the tread surface satisfy the following formula. D2 × L2 ≤ 2.7 D2 × L2 is preferably 2.5 or less, more preferably 1.7 or less, even more preferably 1.6 or less, and particularly preferably 1.5 or less. The lower limit is preferably 1.0 or more, more preferably 1.1 or more, and even more preferably 1.2 or more. Within the above range, the effect is suitably obtained.

[0135] The reasons for the aforementioned effects are not entirely clear, but it is presumed that they are achieved through the following mechanism. In addition to reducing the CV value of the silica particle diameter, further reducing the average of the maximum diameters of each silica particle is thought to make the network finer, making it easier to transmit force and generate reaction forces in the middle of the rubber. Also, by reducing the distance to the tread surface, it is thought that reaction forces can be generated instantaneously, improving handling stability. By keeping the product of these factors below a predetermined value, it is inferred that handling stability at high speeds will be significantly improved.

[0136] From the viewpoint of obtaining a suitable effect, it is desirable that the distance L2 from the radially outer surface of the belt layer to the tread surface satisfies the following formula. L2 ≤ 42mm L2 is preferably 32 mm or less, more preferably 29 mm or less, and even more preferably 27 mm or less. The lower limit is preferably 12 mm or more, more preferably 15 mm or more, and even more preferably 17 mm or more. Within the above range, the effect is suitably obtained.

[0137] The tread thickness L1 refers to the thickness of the tread on the tire's equatorial plane in the tire's radial cross-section. The tread thickness L1 is a value measured along the normal to the tread surface at the tire's equatorial plane point, and is the distance from the tread surface to the interface on the outermost side of the tire with the reinforcing layer, which includes steel, textiles, and other fibrous materials such as belt layers, carcass layers, and belt reinforcement layers. If the tire has grooves on its equatorial plane, the tread thickness L1 is the straight-line distance from the plane formed by the straight line connecting the outermost radial ends of the grooves.

[0138] The distance L2 from the radially outer surface of the belt layer to the tread surface refers to the distance from the radially outer surface of the belt layer to the tread surface on the tire's equatorial plane in the tire's radial cross-section. This distance is measured along the normal to the radially outer surface of the belt layer on the tire's equatorial plane. If the tire has grooves on its equatorial plane, it is the straight-line distance to the plane formed by the straight line connecting the outermost radial ends of the grooves.

[0139] In this specification, unless otherwise specified, the dimensions of the tire (such as the tread thickness L1 and the distance L2 from the radially outer surface of the belt layer to the tread surface) and angles are measured in a cross-sectional section cut radially from the tire, with the width between the bead portions of the tire fixed to match the normal rim width. When measuring the angles that the cords in the belt layer make with the circumferential direction of the tire, as described later, it is possible to confirm these angles by peeling off the tread portion of the cross-sectional section and observing it from the radial direction of the tire.

[0140] A genuine rim refers to a rim defined in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are all considered genuine rims.

[0141] An example of a tire using the aforementioned rubber composition will be explained with reference to Figure 1. In Figure 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the plane of the paper is the circumferential direction of the tire 2. The tread 4 comprises a cap layer 30 and a base layer 28.

[0142] Although Figure 1 shows an example of a two-layer tread 4 consisting of a cap layer 30 and a base layer 28, a single-layer tread or a tread with three or more layers may also be used.

[0143] In tire 2, each sidewall 6 extends radially inward from the edge of the tread 4. The radially outer portion of this sidewall 6 is joined to the tread 4. The radially inner portion of this sidewall 6 is joined to the clinch 10. This sidewall 6 can prevent damage to the carcass 14.

[0144] Each wing 8 in Figure 1 is located between the tread 4 and the sidewall 6. The wing 8 is joined to both the tread 4 and the sidewall 6, respectively.

[0145] Each clinch 10 is located approximately radially inward of the sidewall 6. In the axial direction, the clinch 10 is located outward from the bead 12 and the carcass 14.

[0146] Each bead 12 is located axially inward of the clinch 10. The bead 12 comprises a core 32 and an apex 34 extending radially outward from the core 32. The core 32 is preferably ring-shaped and contains a wound non-stretchable wire. The apex 34 tapers radially outward.

[0147] The carcass 14 is provided with a carcass ply 36. In this tire 2, the carcass 14 consists of one carcass ply 36, but it may be composed of two or more.

[0148] In this tire 2, the carcass ply 36 spans between the beads 12 on both sides and runs along the tread 4 and sidewall 6. The carcass ply 36 is folded axially from the inside to the outside around each core 32. This folding gives the carcass ply 36 a main portion 36a and a pair of folded portions 36b. In other words, the carcass ply 36 comprises a main portion 36a and a pair of folded portions 36b.

[0149] Although not shown in the diagram, the carcass ply 36 preferably consists of a number of parallel cords and topping rubber. The absolute value of the angle that each cord makes with respect to the equatorial plane is preferably between 75° and 90°. In other words, it is preferable that the carcass 14 has a radial structure.

[0150] The belt layer 16 in Figure 1 is located radially inward of the tread 4. The belt layer 16 is laminated with the carcass 14. The belt layer 16 reinforces the carcass 14. The belt layer 16 consists of an inner layer 38 and an outer layer 40. As is clear from Figure 1, in the axial direction, it is desirable that the width of the inner layer 38 is slightly larger than the width of the outer layer 40. In this tire 2, the axial width of the belt layer 16 is preferably 0.6 times or more, and preferably 0.9 times or less, the cross-sectional width of the tire 2 (see JATMA).

[0151] Although not shown in the diagram, it is desirable that each of the inner layer 38 and the outer layer 40 consists of a number of parallel cords and topping rubber. In other words, the belt layer 16 contains a number of parallel cords. Each cord is inclined with respect to the equatorial plane. The general absolute value of the inclination angle is between 10° and 35°. The inclination direction of the cords of the inner layer 38 with respect to the equatorial plane is opposite to the inclination direction of the cords of the outer layer 40 with respect to the equatorial plane.

[0152] The tire 2 has a tread 4 and / or belt layer 16 made of the rubber composition that satisfies formula (1) "CV value ≤ 75%". Furthermore, it is desirable that the rubber composition satisfies formula "D ≤ 0.100 μm", and the tire 2 using the rubber composition is preferably satisfied with "D1 × L1 ≤ 1.5", "D2 × L2 ≤ 1.6", "L1 ≤ 35 mm", and "L2 ≤ 42 mm".

[0153] In Figure 1, band 18 is located radially outside the belt layer 16. In the axial direction, band 18 has a width equal to the width of the belt layer 16. Band 18 may have a width greater than the width of the belt layer 16.

[0154] Although not shown in the diagram, the band 18 preferably consists of a cord and a topping rubber. The cord is wound in a spiral shape. This band 18 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is preferably 5° or less, and more preferably 2° or less. Since the belt layer 16 is restrained by this cord, lifting of the belt layer 16 is suppressed.

[0155] The belt layer 16 and band 18 in Figure 1 constitute the reinforcing layer. The reinforcing layer may also be composed of the belt layer 16 alone.

[0156] Figure 2 is a magnified view of the area around tread 4 in Figure 1. In Figure 2, L1 represents the thickness of the tread on the tire's equatorial plane in the radial cross-section of the tire on the tread surface 24. This value is measured along the normal to the tread surface 24 on the tire's equatorial plane and represents the distance from the tread surface 24 to the outermost surface interface of the band 18.

[0157] In Figure 2, L2 represents the distance from the radially outer surface of the outer layer 40 of the belt layer 16 to the tread surface 24. This distance is measured along the normal to the radially outer surface of the outer layer 40 on the tire equatorial plane in the radial cross-section of the tire.

[0158] The inner liner 20 is located inside the carcass 14. The inner liner 20 is bonded to the inner surface of the carcass 14. Typical base rubbers for the inner liner 20 are butyl rubber or halogenated butyl rubber. The inner liner 20 maintains the internal pressure of the tire 2.

[0159] Each chafer 22 is located near the bead 12. In this embodiment, it is preferable that the chafer 22 consists of cloth and rubber impregnated into the cloth. The chafer 22 may be integrated with the clinch 10.

[0160] In this tire 2, the tread 4 is provided with main grooves 42 as grooves 26. As shown in Figure 1, this tread 4 has multiple main grooves 42, specifically three. These main grooves 42 are spaced apart in the axial direction. The three main grooves 42 in this tread 4 form four ribs 44 that extend in the circumferential direction. In other words, the space between the ribs 44 is the main groove 42.

[0161] Each main groove 42 extends in the circumferential direction. The main grooves 42 are continuous and uninterrupted in the circumferential direction. The main grooves 42 promote the drainage of water present between the road surface and the tire 2, for example, in rainy weather. As a result, the tire 2 can maintain sufficient contact with the road surface even when it is wet.

[0162] The following examples (implementations) are considered preferable for implementation, but the scope of this disclosure is not limited to these examples.

[0163] The various chemicals used in the examples and comparative examples are described below. NR:TSR20 Natural rubber latex: We use field latex obtained from Muhibbah Latex. SBR latex: LX110 (E-SBR, vinyl content 18% by mass, styrene content 37.5% by mass, rubber component concentration in rubber latex 40.5% by mass) manufactured by Nippon Zeon Co., Ltd. Modified SBR: HPR355 (3-aminopropyltrimethoxysilane modified, styrene content: 27% by mass) manufactured by JSR Corporation. BR: BR150B manufactured by Ube Industries, Ltd. (cis content 97% by mass) Silica 1: Solvay Premium SW (N2SA275m) 2 / g) Silica 2: Rhodia Zeosil 1165MP (N2SA 160m2 / g) Silica 3: Rhodia Zeosil Premium 200MP (N2SA220m) 2 / g) Silica 4: Rhodia Zeosil 1115MP (N2SA115m 2 / g) Fatty acid amide compound 1: Diethanololeamide (manufactured by Fujifilm Wako Pure Chemical Corporation) Fatty acid amide compound 2: Palmitoylethanolamide (manufactured by Tokyo Chemical Industry Co., Ltd.) Fatty acid amide compound 3: Oleylethanolamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Microfibrillated plant fiber: Biomass nanofiber manufactured by Sugino Machine Co., Ltd. (product name "BiNFi-s Cellulose", solid content 2% by mass, moisture content 98% by mass, average fiber diameter 20 nm, average fiber length 2000 nm) Anti-aging agent: Nocrack 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) (6PPD) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Camellia oil manufactured by NOF Corporation Carbon black: Mitsubishi Chemical N220 (N2SA114m 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik DeGussa. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industries Co., Ltd. Vulcanization accelerator 1: Noxellar NS (N-tert-butyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noxellar D (N,N'-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0164] (Preparation of silica dispersion) According to the formulation shown in Table 1, each silica, each fatty acid amide compound, microfibrillated plant fiber, and water are added, and the mixture is stirred at room temperature (20-30°C) for 5 minutes using a high-speed homogenizer to prepare a silica dispersion containing silica and fatty acid amide compounds.

[0165] [Table 1]

[0166] (Preparation of rubber-silica composite (wet masterbatch (WMB))) Each rubber-filler composite (each WMB) was manufactured according to the formulation shown in Table 2. Specifically, the prepared silica dispersion is added to natural rubber latex or SBR latex, and stirred at room temperature for 5 minutes using a high-speed homogenizer to obtain a latex compound with a pH of 10.2. Next, a 2% by mass aqueous solution of formic acid is added at room temperature to adjust the pH to 3-4 and obtain a solidified product. The resulting solidified material is filtered and dried to produce a rubber-silica composite (WMB).

[0167] [Table 2]

[0168] (Preparation of rubber-silica composite (dry masterbatch (DMB))) Each rubber-filler composite (each DMB) was manufactured according to the formulation shown in Table 3. Specifically, silica and rubber are mixed using a 1.7L Banbury mixer to produce a rubber-silica composite (DMB). do.

[0169] [Table 3]

[0170] <Preparation of test tires> According to the formulations in Tables 4-19, the chemicals other than sulfur and vulcanization accelerators are mixed using a 1.7L Banbury mixer. Next, using rollers, sulfur and a vulcanization accelerator are added to the resulting mixture and kneaded to obtain an unvulcanized rubber composition. The resulting unvulcanized rubber composition is molded into the shape of a tread or belt layer, bonded together with other tire components on a tire molding machine to form an unvulcanized tire, and then vulcanized at 170°C for 12 minutes to produce a test tire (size: 195 / 65R15, specifications: see table).

[0171] The results calculated based on the evaluation method below are shown in each table, assuming test tires obtained from compositions with varying formulations according to each table. While the formulations in Tables 4-19 do not include microfibrillated plant fibers due to their trace amounts, as shown in Tables 1 and 2, each formulation containing a wet masterbatch (WMB) has 1 part by mass of microfibrillated plant fibers per 100 parts by mass of silica during WMB preparation. The reference comparison examples are as follows: Table 4: Comparative example 1-1b Table 5: Comparative Examples 1-2 Table 6: Comparative Examples 1-3 Table 7: Comparative Examples 1-4 Table 8: Comparative Examples 1-5 Table 9: Comparative Examples 1-6 Table 10: Comparative example 2-1b Table 11: Comparative Example 2-2 Table 12: Comparative Example 2-3 Table 13: Comparative Example 2-4 Table 14: Comparative Examples 2-5 Table 15: Comparative Example 2-6 Table 16: Comparative Example 3-1 Table 17: Comparative Example 3-2 Table 18: Comparative Example 4-1 Table 19: Comparative Example 4-2

[0172] (Measurement of the average D of the maximum diameter of each silica particle, standard deviation, and calculation of the CV value) The individual silica particles in the vulcanized rubber sampled from the tread or belt layer of a test tire will be observed using a FIB-SEM (Focused Ion Beam Scanning Electron Microscope, FEI "Helios"). The resulting 40,000x magnified image is then binarized using imageJ's Fiji-"Trainable Weka Segmentation" function. The mean and standard deviation are calculated from the numerical data of the "maximum value (Major)" of the silica particle size. Calculate the CV value from the mean and standard deviation. (CV value (%) = [Standard deviation of the maximum diameter of each silica particle (μm)] / [Average of the maximum diameter of each silica particle (μm)] × 100) In measurements using FIB-SEM, the observation field size is 3 × 2 μm, and particle size values ​​are determined from the results of measurements taken at five different locations with varying fields of view.

[0173] (Handling stability at high speeds) Test tires are fitted to all wheels of a domestically produced FF 2000cc vehicle, and the vehicle is driven on a test course at 100 km / h. The handling stability is evaluated based on the driver's subjective evaluation during swerving maneuvers. Based on the feelings of 10 drivers, each will be rated on a 10-point scale. The sum of these evaluations is calculated as a score, and the benchmark comparison is set to 100, and the score is then indexed. A higher index indicates better handling stability at high speeds.

[0174] [Table 4]

[0175] [Table 5]

[0176] [Table 6]

[0177] [Table 7]

[0178] [Table 8]

[0179] Table 9

[0180] Table 10

[0181] Table 11

[0182] Table 12

[0183] Table 13

[0184] Table 14

[0185] Table 15

[0186] Table 16

[0187] Table 17

[0188] Table 18

[0189] Table 19

[0190] This disclosure (1) is a rubber composition comprising a rubber component and silica, The rubber composition satisfies the coefficient of variation (CV value) of the maximum diameter of each silica particle observed by an electron microscope, as shown in the following formula (1). (1) CV value ≤ 75%

[0191] Disclosure (2) is the rubber composition according to Disclosure (1) wherein the rubber component comprises isoprene rubber.

[0192] Disclosure (3) is a rubber composition according to Disclosure (1) or (2) comprising a fatty acid amide compound.

[0193] Disclosure (4) is a rubber composition according to any one of Disclosures (1) to (3), wherein the silica content is 30 parts by mass or more per 100 parts by mass of rubber component.

[0194] Disclosure (5) is a rubber composition according to any of Disclosures (1) to (4) in which the maximum diameter D of each silica particle observed by electron microscope satisfies the following formula. D≦0.070μm or less

[0195] Disclosure (6) is a tire using a rubber composition described in any of Disclosures (1) to (5).

[0196] Disclosure (7) relates to a tire having a tread and / or belt layer composed of any of the rubber compositions described in Disclosure (1) to (5).

[0197] Disclosure (8) relates to a tire having a tread made of a rubber composition described in any of Disclosures (1) to (5), The tire is one in which the average maximum diameter D1 (μm) of each silica particle in the tread, as observed by an electron microscope, and the thickness L1 (mm) of the tread satisfy the following formula. D1 × L1 ≤ 1.5

[0198] This disclosure (9) is the tire described in this disclosure (8) in which the tread thickness L1 satisfies the following formula. L1≦25mm

[0199] Disclosure (10) is a tire having a belt layer composed of a rubber composition as described in any of Disclosures (1) to (5), A tire is one in which the average maximum diameter D2 (μm) of each silica particle in the belt layer, as observed by an electron microscope, and the distance L2 (mm) from the radially outer surface of the belt layer to the tread surface satisfy the following formula. D2 × L2 ≤ 1.6

[0200] The present disclosure (11) is a tire according to the present disclosure (10) in which the distance L2 from the radially outer surface of the belt layer to the tread surface satisfies the following formula. L2 ≤ 27mm or less [Explanation of Symbols]

[0201] 2 tires 4 tread 6 Sidewall 8 Wing 10. Clinch 12 beads 14 Carcass 16 Belt Layer 18 bands 20 Inner Liner 22 Chafer 24 Tread surface 26 Groove 28 Base Layer 30 cap layers 32 cores 34 Apex 36 Carcass ply 36a Main section 36b Folded section 38 Inner layer 40 outer layer 42 Main groove 44 Ribs CL Tire 2 equatorial plane L1 Thickness of the tread at a predetermined point on the tread surface 24 L2 Distance from a predetermined point on the outer surface of the outer layer 40 of the belt layer 16 to the tread surface 24

Claims

1. A rubber composition comprising rubber components, silica, and fatty acid amide compounds, A rubber composition in which the coefficient of variation (CV value) of the maximum diameter of each silica particle observed by an electron microscope satisfies the following formula (1). (1) CV value ≤ 75% The CV value is calculated by observing each silica particle in the vulcanized rubber obtained by vulcanizing the rubber composition using a FIB-SEM (Focused Ion Beam, "Helios" manufactured by FEI), binarizing the resulting 40,000x magnified image using imageJ's Fiji-"Trainable Weka Segmentation", and using the following formula, where the average value calculated from the numerical data of the "Maximum Major" of the silica particle size is the average of the maximum diameter of each silica particle, and the standard deviation is the standard deviation of the maximum diameter of each silica particle. CV value (%) = [Standard deviation of the maximum diameter of each silica particle (μm)] / [Average of the maximum diameter of each silica particle (μm)] × 100

2. The rubber composition according to claim 1, wherein the rubber component comprises isoprene-based rubber.

3. The rubber composition according to claim 1, wherein the silica content is 30 parts by mass or more per 100 parts by mass of rubber component.

4. The rubber composition according to claim 1, wherein the average D of the maximum diameter of each silica particle observed by an electron microscope is 0.070 μm or less.

5. A tire using the rubber composition described in claim 1.

6. A tire having a tread and / or belt layer made of the rubber composition described in claim 1.

7. A tire having a tread made of the rubber composition described in claim 1, A tire in which the average maximum diameter D1 (μm) of each silica particle in the tread, as observed by an electron microscope, and the thickness L1 (mm) of the tread satisfy the following formula. D1 × L1 ≤ 1.5

8. The tire according to claim 7, wherein the tread thickness L1 satisfies the following formula. L1 ≤ 25 mm

9. A tire having a belt layer made of the rubber composition described in claim 1, A tire in which the average maximum diameter D2 (μm) of each silica particle in the belt layer observed by an electron microscope and the distance L2 (mm) from the radially outer surface of the belt layer to the tread surface satisfy the following formula. D2 × L2 ≤ 1.6

10. The tire according to claim 9, wherein the distance L2 from the radially outer surface of the belt layer to the tread surface is 27 mm or less.

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