Rubber compositions and tires

Abstract

The present application provides a rubber composition containing: 10 to 90 parts by mass of a rubbery polymer having an iodine value of 10 to 200 (g / 100g), a content of ethylene structure of 3% by mass or more, a content of aromatic vinyl monomer block of less than 10% by mass, and a content of conjugated diene monomer unit of 2% by mass or more; and 10 to 90 parts by mass of a natural rubber, relative to 100 parts by mass of the total amount of rubber components including the above rubbery polymer and the above natural rubber, containing 20 to 80 parts by mass of a silica-based inorganic filler and carbon black, the content of the above silica-based inorganic filler being 60 parts by mass or less, and the content of the above carbon black being 60 parts by mass or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a rubber composition and a tire. BACKGROUND

[0002] In recent years, in pneumatic tires used in heavy load vehicles such as trucks and buses, there is a demand for improving fuel efficiency and improving tire wear resistance in response to social demands for reducing the load on the earth's environment. In addition, from the aspect of protecting human life, there is an increasing demand for maintaining safety and comfort during driving by suppressing performance degradation in the later stage of tire use.

[0003] Conventionally, in order to improve the fuel efficiency of a tire, a technique of compounding silica in the crown rubber has been studied. The fuel efficiency can be improved by this technique, but if the dispersibility of the silica is poor, sufficient wear resistance cannot be obtained, and there is a problem in that it is difficult to balance the fuel efficiency and the wear resistance at a high level.

[0004] In addition, the tire undergoes changes in performance in the later stage of use, for example, there is a problem that ride comfort deteriorates as the hardness increases.

[0005] In recent years, in the field of tire treads, sheets, membranes, and rubber materials for modifying asphalt, a rubber composition containing a rubbery polymer having an ethylene structure and an introduced cross-linkable unsaturated group has been proposed for the purpose of improving mechanical strength and compression set. By containing such a rubbery polymer in a tire rubber composition, it is possible to achieve an improvement in the wear resistance of the tire (for example, refer to Patent Documents 1 to 4).

[0006] In a rubber composition containing a rubbery polymer having an ethylene structure and an introduced cross-linkable unsaturated group, the number of unsaturated bonds is reduced, and deterioration over the years is suppressed, so it is also possible to expect suppression of deterioration in ride comfort in the later stage of tire use.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT DOCUMENTS

[0009] Patent Document 1: International Publication No. 2003 / 085010

[0010] Patent Document 2: International Publication No. 2019 / 151126

[0011] Patent Document 3: International Publication No. 2019 / 151127

[0012] Patent Document 4: International Publication No. 2019 / 078083 SUMMARY

[0013] PROBLEMS TO BE SOLVED BY THE INVENTION

[0014] However, if the hydrogenation rate of the rubbery polymer having an ethylene structure and into which a crosslinkable unsaturated group is introduced is too high, the Mooney viscosity increases, and there is a problem in that processability tends to deteriorate.

[0015] In addition, according to the research by the present inventors, if the hydrogenation rate of the rubbery polymer is too high, sufficient dispersibility of silica in the rubber composition is not obtained, and there is a problem in that processability and wear resistance tend to deteriorate.

[0016] Therefore, in view of the problems of the above-described prior art, an object of the present application is to provide a rubber composition which is excellent in processability, low fuel consumption, and wear resistance, and in which a change in performance in the later stage of use of a tire is also suppressed.

[0017] Means for solving the problem

[0018] The present inventors have conducted intensive research in order to solve the problems of the above-described prior art, and as a result, have found that the problems of the above-described prior art can be solved by a rubber composition containing a rubbery polymer (in which the iodine value, the content of ethylene structure, the content of aromatic vinyl monomer block, and the content of conjugated diene monomer unit are defined), natural rubber, and a silica-based inorganic filler and carbon black as a reinforcing material, in prescribed amounts, thereby completing the present application.

[0019] That is, the present application is as described below. [1]

[0021] A rubber composition containing:

[0022] 10 parts by mass or more and 90 parts by mass or less of a rubbery polymer having an iodine value of 10 to 200 (g / 100 g), a content of ethylene structure of 3% by mass or more, a content of aromatic vinyl monomer block of less than 10% by mass, and a content of conjugated diene monomer unit of 2% by mass or more; and

[0023] 10 parts by mass or more and 90 parts by mass or less of a natural rubber,

[0024] with respect to 100 parts by mass of the total amount of a rubber component including the above-described rubbery polymer and the above-described natural rubber,

[0025] 20 parts by mass or more and 80 parts by mass or less of a silica-based inorganic filler and carbon black,

[0026] the content of the above-described silica-based inorganic filler is 60 parts by mass or less, and the content of the above-described carbon black is 60 parts by mass or less. [2]

[0028] The rubber composition described in the above [1], wherein the glass transition temperature (Tg) of the rubbery polymer is -35°C or lower. [3]

[0030] The rubber composition described in the above [1] or [2], wherein the rubbery polymer is a conjugated diene polymer and contains 5 mass% or more and 40 mass% or less of aromatic vinyl monomer units, and the amount of 1,2-vinyl bonds in the conjugated diene monomer units is 10 mol% or more and 60 mol% or less. [4]

[0032] The rubber composition described in any one of the above [1] to [3], wherein the rubbery polymer contains a nitrogen atom. [5]

[0034] The rubber composition described in the above [4], wherein the modification rate of the rubbery polymer is 40 mass% or more. [6]

[0036] The rubber composition described in any one of the above [1] to [5], wherein,

[0037] the iodine value (A) of the rubbery polymer,

[0038] the content (mass parts) of the silica-based inorganic filler (B) and the content (mass parts) of the carbon black (C) with respect to 100 mass parts of the total amount of the rubber component,

[0039] the BET specific surface area (D) of the silica-based inorganic filler, and

[0040] the BET specific surface area (E) of the carbon black

[0041] has the following formula (1).

[0042] (Formula (1)):

[0043] 0 < (0.029 x ((B) x (D)) + ((C) x (E))) - (A) < 250 [7]

[0045] The rubber composition described in any one of the above [1] to [6], wherein further contains less than 35 mass parts of an oil and / or a ring-containing resin with respect to 100 mass parts of the total amount of the rubber component. [8]

[0047] The rubber composition described in any one of the above [1] to [7], wherein further contains less than 10 mass parts of an oil with respect to 100 mass parts of the total amount of the rubber component. [9]

[0049] The rubber composition according to any one of the above [1] to [8], wherein the iodine value of the rubbery polymer is 80 to 200 (g / 100 g), and the content of the aromatic vinyl monomer unit is 13 mass% or less.

[10]

[0051] The rubber composition according to any one of the above [1] to [9], wherein the 1,2-vinyl bond content in the conjugated diene monomer unit of the rubbery polymer is 50 mol% or more and 60 mol% or less.

[11]

[0053] The rubber composition according to any one of the above [1] to

[10] , wherein,

[0054] the iodine value (A) of the rubbery polymer,

[0055] the content (mass parts) of the silica-based inorganic filler (B) and the content (mass parts) of the carbon black (C) with respect to 100 mass parts of the total amount of the rubber component,

[0056] the BET specific surface area (D) of the silica-based inorganic filler, and

[0057] the BET specific surface area (E) of the carbon black

[0058] has the following formula (2).

[0059] (Formula (2)):

[0060] 0 < (0.029 x ((B) x (D)) + ((C) x (E))) - (A) < 136

[12]

[0062] A tire comprising the rubber composition according to any one of the above [1] to

[11] .

[13]

[0064] A pneumatic tire having a crown comprising the rubber composition according to any one of the above [1] to

[11] , and a load index of 100 or more and 170 or less.

[0065] Effects of the Invention

[0066] According to the present application, a rubber composition having excellent processability, low fuel consumption, and wear resistance, and capable of suppressing changes in performance in the later stages of tire use can be provided, and an excellent tire can be obtained. DETAILED DESCRIPTION

[0067] The following describes a specific embodiment of the present application (hereinafter referred to as "the present embodiment").

[0068] Note that the following present embodiment is for illustrating an example of the present application, and the present application is not limited to the following embodiment. The present application can be suitably modified and implemented within the scope of its gist.

[0069] [Rubber composition]

[0070] The rubber composition of the present embodiment contains: 10 to 90 parts by mass of a rubbery polymer (hereinafter sometimes simply referred to as a rubbery polymer) having an iodine value of 10 to 200 (g / 100 g), a content of ethylene structure of 3 mass% or more, a content of aromatic vinyl monomer block of less than 10 mass%, and a content of conjugated diene monomer unit of 2 mass% or more; and 10 to 90 parts by mass of natural rubber.

[0071] In addition, with respect to 100 parts by mass of the total amount of the rubber components including the above-described rubbery polymer and the above-described natural rubber, 20 to 80 parts by mass of a silica-based inorganic filler and carbon black are contained, the content of the above-described silica-based inorganic filler is 60 parts by mass or less, and the content of the above-described carbon black is 60 parts by mass or less.

[0072] By the above-described constitution, a rubber composition having excellent processability, low fuel consumption, and wear resistance, and capable of suppressing changes in performance in the later stage of tire use, and excellent tires can be obtained.

[0073] The rubber composition of the present embodiment is suitably used in the form of a vulcanizate. The vulcanizate can be obtained, for example, by mixing the rubbery polymer with the above-described fillers such as silica, carbon black, and rubber components other than the above-described rubbery polymer, a silane coupling agent, a rubber softener, a wax, a vulcanizing agent, a vulcanization accelerator, and a vulcanization aid, preparing a rubber composition, and heating and vulcanizing the rubber composition.

[0074] The following describes each component in detail.

[0075] (Rubbery polymer)

[0076] The rubbery polymer used in the rubber composition of the present embodiment is obtained, for example, by at least copolymerizing a conjugated diene monomer and then hydrogenating a part of the conjugated diene monomer unit, or at least copolymerizing ethylene and a conjugated diene monomer.

[0077] Thereby, a rubbery polymer containing an ethylene structure and a conjugated diene monomer unit can be obtained.

[0078] In addition, the rubbery polymer can include an aromatic vinyl monomer unit as needed. In this case, the rubbery polymer can be obtained by at least copolymerizing a conjugated diene monomer with an aromatic vinyl monomer and then hydrogenating a part of the conjugated diene monomer units, or by at least copolymerizing ethylene with a conjugated diene monomer and an aromatic vinyl monomer. In addition, the rubbery polymer can further include other monomer units.

[0079] Note that the "monomer" in the present embodiment refers to a compound before polymerization, and the "monomer unit" refers to a structural unit constituting a polymer. In addition, the "ethylene structure" includes both a structure generated by hydrogenating a part of the double bond portion of the conjugated diene monomer unit and an ethylene monomer unit when ethylene is used as a monomer.

[0080] As a method of polymerizing a conjugated diene monomer and then hydrogenating it, for example, as described in International Publication No. 96 / 05250, Japanese Patent Application Publication No. 2000-053706, International Publication No. 2003 / 085010, International Publication No. 2019 / 151126, International Publication No. 2019 / 151127, International Publication No. 2002 / 002663, and International Publication No. 2015 / 006179, a method of polymerizing a conjugated diene monomer by anionic polymerization under various additives and conditions, and further hydrogenating it as needed after copolymerizing it with other monomers is preferable.

[0081] As the conjugated diene monomer, for example, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene can be given, but are not limited thereto.

[0082] Among these, from the aspect of ease of industrial availability, 1,3-butadiene and isoprene are preferable, and 1,3-butadiene is more preferable. They can be used alone or in combination of two or more.

[0083] In addition, as the aromatic vinyl monomer, for example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-dimethylstyrene, p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, α-methylstyrene, vinyl toluene, vinyl xylene, vinyl naphthalene, and diphenyl ethylene can be given, but are not limited thereto.

[0084] Among these, from the aspect of ease of industrial availability, styrene is preferable. They can be used alone or in combination of two or more.

[0085] By including a structural unit based on such an aromatic vinyl monomer in the rubbery polymer, there is a tendency to further improve the balance of the breaking strength, fuel efficiency, wet skid resistance, and wear resistance of a tire made from the rubber composition of the present embodiment.

[0086] In addition, as other monomers, non-conjugated polyene compound monomers such as ethylidene norbornene, dicyclopentadiene, vinyl norbornene, divinylbenzene, and the like can be given, but are not limited thereto; cyclic non-conjugated polyene compound monomers such as dicyclopentadiene, vinyl norbornene, ethylidene norbornene, and the like can be given, but are not limited thereto.

[0087] By using such other monomers, there is a tendency to further improve the balance of the breaking strength, fuel efficiency, wet skid resistance, and wear resistance of a tire made from the rubber composition of the present embodiment.

[0088] These monomers can be used singly or in combination of two or more.

[0089] As a method of copolymerizing at least ethylene and a conjugated diene monomer, for example, the methods described in International Publication No. 2019 / 078083, International Publication No. 2019 / 171679, and International Publication No. 2019 / 142501 can be given as preferred methods.

[0090] In particular, a method of copolymerizing ethylene, a conjugated diene monomer, and, if necessary, other monomers by coordination polymerization under various additives and conditions can be given as a preferred method.

[0091] <Iodine Value>

[0092] The iodine value of the rubbery polymer is 10 (g / 100 g) or more, preferably 15 (g / 100 g) or more, more preferably 30 (g / 100 g) or more, further preferably 50 (g / 100 g) or more, and further preferably 80 (g / 100 g) or more. By making the iodine value 10 (g / 100 g) or more, there is a tendency to further improve the processability, crosslinking easiness, and low fuel consumption of the rubber composition after being made into a tire. In particular, by making the iodine value 80 (g / 100 g) or more, there is a tendency to further improve the processability, dispersion of the reinforcing material, and resistance to static fatigue after being made into a tire.

[0093] On the other hand, the iodine value of the rubbery polymer is 200 (g / 100 g) or less, preferably 170 (g / 100 g) or less, more preferably 140 (g / 100 g) or less, further preferably 110 (g / 100 g) or less, and still further preferably 80 (g / 100 g) or less. By making the iodine value 200 (g / 100 g) or less, the wear resistance of the rubber composition after the rubber composition is made into a tire is further improved, and the tendency of the performance of the tire to change in the later stage of use can be suppressed.

[0094] The iodine value can be measured according to the method described in "JIS K 0070: 1992". The iodine value is a value expressed by converting the amount of halogen that reacts with 100 g of the subject substance into grams of iodine, and thus the unit of the iodine value is "g / 100 g".

[0095] The iodine value of the rubbery polymer can be controlled by adjusting the amount of double bonds included in the conjugated diene monomer unit.

[0096] In the manufacturing method of the rubbery polymer described later, for example, in the case of copolymerizing a conjugated diene monomer and an aromatic vinyl monomer, when the content of the conjugated diene monomer is low, the iodine value decreases; in addition, in the case of hydrogenating the conjugated diene monomer, when the hydrogenation rate is high, the iodine value tends to decrease.

[0097] <ethene structure>

[0098] The content of the ethene structure included in the rubbery polymer is 3% by mass or more, preferably 5% by mass or more, and more preferably 20% by mass or more. By making the ethene structure 3% by mass or more, the tendency of the rubber composition to have excellent wear resistance is exhibited. In addition, the content of the ethene structure of the rubbery polymer is preferably 90% by mass or less, 80% by mass or less, and more preferably 70% by mass or more. By making the content of the ethene structure 90% by mass or less, the tendency of the rubber composition to have further improved rubber elasticity is exhibited.

[0099] The rubbery polymer used in the rubber composition of the present embodiment can be manufactured by performing a hydrogenation reaction on a conjugated diene-based copolymer having an aromatic portion and a conjugated diene portion so as to make a part of the double bond portion in the conjugated diene portion into an ethene structure, or can be manufactured by randomly copolymerizing an aromatic vinyl monomer, a conjugated diene monomer, and ethene.

[0100] Among them, from the aspect of manufacturing cost, the rubbery polymer is preferably obtained by performing a hydrogenation reaction on a conjugated diene-based copolymer.

[0101] Regarding the content of the ethene structure, it can be controlled to be 3% by mass or more by adjusting the added amount of ethene, the amount of the conjugated diene monomer unit, and the hydrogenation rate thereof.

[0102] Note that, in the present specification, a structural unit based on an aromatic vinyl monomer is sometimes referred to as an "aromatic portion", and a structural unit based on a conjugated diene monomer is sometimes referred to as a "conjugated diene portion".

[0103] <Content of aromatic vinyl monomer block>

[0104] The content of the aromatic vinyl monomer block contained in the rubbery polymer is less than 10% by mass, preferably 7% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less. By making the content of the aromatic vinyl monomer block less than 10% by mass, the fuel efficiency when the rubber composition of the present embodiment is used in a tire tends to be further improved. The lower limit of the content of the aromatic vinyl monomer block is not limited, and can be 1% by mass or more.

[0105] Note that, the "aromatic vinyl monomer block" described above refers to a structure in which the aromatic vinyl monomer units are linked in 8 or more.

[0106] From the aspect of the fuel efficiency after the rubber composition of the present embodiment is used in a tire, it is preferable that the number of the aromatic vinyl monomer blocks be small or absent in the rubbery polymer used in the rubber composition of the present embodiment.

[0107] The method for measuring the content of the aromatic vinyl monomer block in the rubbery polymer is not particularly limited, and, for example, in the case where the rubbery polymer is a butadiene-styrene copolymer, the following method can be mentioned: the butadiene-styrene copolymer is decomposed by the method of Kolthoff (I. M. Kolthoff, et al., J. Polym. Sci. 1, 429 (1946)), and the amount of polystyrene that is insoluble in methanol is analyzed, whereby the measurement is performed. As other methods, well-known methods such as the measurement of the chain of styrene units using NMR as described in International Publication No. 2014-133097 can be mentioned.

[0108] The content of the aromatic vinyl monomer block in the rubbery polymer can be controlled to be less than 10% by mass by adjusting the amount of addition, timing of addition, and the like of the aromatic vinyl monomer in the polymerization step.

[0109] <Content of conjugated diene monomer unit>

[0110] The content of the conjugated diene monomer unit in the rubbery polymer is 2% by mass or more, preferably 3% by mass or more, and more preferably 6% by mass or more. The double bond possessed by the conjugated diene monomer unit constitutes an unsaturated group that can be crosslinked.

[0111] The content of the conjugated diene monomer unit in the rubbery polymer is closely related to the iodine value. By having the content of the conjugated diene monomer unit be 2% by mass or more, the rubber composition of the present embodiment has a tendency to be excellent in processability, ease of crosslinking, and fuel efficiency after the tire is manufactured. In addition, the content of the conjugated diene monomer unit in the rubbery polymer is preferably 50% by mass or less, more preferably 30% by mass or less, and further preferably 20% by mass or less. By having the content of the conjugated diene monomer unit be 50% by mass or less, the rubber composition of the present embodiment has a tendency to be excellent in wear resistance after the tire is manufactured, and also capable of suppressing changes in performance in the later stage of tire use.

[0112] The content of the conjugated diene monomer unit in the rubbery polymer can be controlled within the above numerical range by adjusting the amount of the conjugated diene monomer added in the polymerization step.

[0113] <Content of aromatic vinyl monomer unit>

[0114] The rubbery polymer preferably contains an aromatic vinyl monomer unit. The content of the aromatic vinyl monomer unit in the rubbery polymer is preferably 5% by mass or more, more preferably 7% by mass or more, and further preferably 9% by mass or more. By having the content of the aromatic vinyl monomer unit be 5% by mass or more, the rubber composition of the present embodiment has a tendency to be excellent in steering stability when used for a tire.

[0115] In addition, the content of the aromatic vinyl monomer unit is preferably 40% by mass or less, more preferably 35% by mass or less, and further preferably 30% by mass or less. By having the content of the aromatic vinyl monomer unit be 40% by mass or less, the rubber composition of the present embodiment has a tendency to further improve in fuel efficiency when used for a tire.

[0116] Furthermore, by having the content of the aromatic vinyl monomer unit in the rubbery polymer be 13% by mass or less, the rubber composition of the present embodiment has a tendency to further improve in fuel efficiency and wear resistance when used for a tire.

[0117] The content of the aromatic vinyl monomer unit in the rubbery polymer can be controlled within the above numerical range by adjusting the amount of the aromatic vinyl monomer added in the polymerization step.

[0118] <1,2-vinyl bond content in conjugated diene monomer unit>

[0119] From the aspect of excellent braking performance when the rubber composition of the present embodiment is used for a tire, the 1,2-vinyl bond content in the conjugated diene monomer unit in the above rubbery polymer is preferably 10 mol% or more, more preferably 20 mol% or more, and further preferably 30 mol% or more.

[0120] In addition, from the viewpoint of excellent fuel efficiency when the rubber composition of the present embodiment is used for a tire, the amount of 1,2-vinyl bonding in the conjugated diene monomer unit is preferably 60 mol% or less, more preferably 50 mol% or less, and further preferably 40 mol% or less.

[0121] In addition, from the viewpoint of excellent endurance to permanent set when the rubber composition of the present embodiment is used for a tire, the amount of 1,2-vinyl bonding in the conjugated diene monomer unit in the rubbery polymer is preferably 50 mol% or more and 60 mol% or less.

[0122] The amount of 1,2-vinyl bonding in the conjugated diene monomer unit in the rubbery polymer can be controlled within the above numerical range by adjusting the amount of addition of the conjugated diene monomer in the polymerization step, the amount of hydrogenation in the hydrogenation step, and the reaction time.

[0123] <Content of Rubbery Polymer>

[0124] In the rubber composition of the present embodiment, when the total amount of the rubber component including the rubbery polymer and the natural rubber is set to 100 parts by mass, the content of the rubbery polymer is 10 parts by mass or more, preferably 20 parts by mass or more, and more preferably 30 parts by mass or more.

[0125] By having the content of the rubbery polymer be 10 parts by mass or more, the tendency of the rubber composition of the present embodiment to have excellent fuel efficiency and excellent wear resistance when used for a tire is exhibited. In addition, from the viewpoint of ensuring excellent processability, the content of the rubbery polymer is 90 parts by mass or less, preferably 70 parts by mass or less, more preferably 50 parts by mass or less, and further preferably 40 parts by mass or less.

[0126] Hereinafter, with respect to the value indicated by “parts by mass”, unless otherwise specified, it is the value when the total amount of the rubber component including the rubbery polymer and the natural rubber is set to 100 parts by mass.

[0127] The method for identifying the kind and the content ratio of the specific rubber component included in the rubber composition of the present embodiment is not particularly limited, and a method using NMR can be cited.

[0128] For example, in the report (JSR TECHNICAL REVIEW No. 126 / 2019), by using a solid 13 C-C-NMR, the ratio of the styrene unit, 1,2-vinyl bonding, 1,4-vinyl bonding, 1,4-cis bonding, and isoprene unit included in the rubber component composed of two or more different components can be quantitatively calculated.

[0129] The two or more different components are not particularly limited, and examples of the conjugated diene monomer unit, the aromatic vinyl monomer unit, and the monomer unit other than these, which are introduced in the combination of unhydrogenated 1,2-vinyl combination, hydrogenated 1,2-vinyl combination, unhydrogenated 3,4-vinyl combination, hydrogenated 3,4-vinyl combination, unhydrogenated 1,4-vinyl combination, and hydrogenated 1,4-vinyl combination, can be given. Note that the amount of each of the conjugated diene monomer units introduced in each combination can be determined by NMR or the like.

[0130] The molar volume, the molar cohesive energy of the conjugated diene monomer unit, the aromatic vinyl monomer unit, and the monomer unit other than these, which are introduced in the combination of unhydrogenated 1,2-vinyl combination, hydrogenated 1,2-vinyl combination, unhydrogenated 3,4-vinyl combination, hydrogenated 3,4-vinyl combination, unhydrogenated 1,4-vinyl combination, and hydrogenated 1,4-vinyl combination, can be calculated according to the method described in J. Bicerano, Prediction of Polymer Properties, 3rd Ed. Marcel Dekker, 2002 (Bicerano method).

[0131] As described above, by determining them, the kind of the specific rubber component included in the rubber composition of the present embodiment, and the content ratio thereof, can be determined.

[0132] <Glass transition temperature of rubbery polymer>

[0133] The glass transition temperature of the rubbery polymer used in the rubber composition of the present embodiment is preferably -35°C or lower, more preferably -45°C or lower, and further preferably -50°C or lower.

[0134] When the rubber composition of the present embodiment is used for a tire, the tendency of excellent wear resistance is exhibited when the glass transition temperature of the rubbery polymer is in the above range.

[0135] The glass transition temperature of the rubbery polymer can be controlled in the above numerical range by adjusting the 1,2-vinyl combination amount of the conjugated diene monomer unit, the amount of the aromatic vinyl monomer unit, the hydrogenation rate, and the like.

[0136] Specifically, by reducing the amount of the aromatic vinyl monomer unit, and reducing the 1,2-vinyl combination amount, the glass transition temperature of the rubbery polymer can be reduced.

[0137] As a method of making the glass transition temperature -35°C or lower, for example, a method of making the content of the aromatic vinyl monomer unit 5 to 30 mass%, and making the 1,2-vinyl combination amount of the conjugated diene monomer unit 20 to 50 mass% can be given.

[0138] The hydrogenation rate also affects the glass transition temperature, but less than the 1,2-vinyl bond amount and the content of the aromatic vinyl monomer unit. Therefore, in the control of the glass transition temperature, it is preferable to adjust the increase or decrease of the 1,2-vinyl bond amount and / or the content of the aromatic vinyl monomer unit.

[0139] The glass transition temperature of the rubbery polymer can be measured by determining the peak top (inflection point) of the DSC differential curve, in accordance with ISO 22768:2006, by recording the DSC curve while increasing the temperature in a prescribed temperature range. Specifically, it can be measured by the method described in the Examples described later.

[0140] The lower limit value of the glass transition temperature of the rubbery polymer is not particularly limited, and is preferably -90°C or higher, more preferably -80°C or higher, and further preferably -70°C or higher.

[0141] By setting the glass transition temperature of the rubbery polymer to be -90°C or higher, the rubber composition of the present embodiment has a tendency to have excellent wet grip performance.

[0142] By setting the rubbery polymer described above to not contain the aromatic vinyl monomer unit, and adjusting the 1,2-vinyl bond amount to be 20% or more, it is possible to set the glass transition temperature of the rubbery polymer to be around -90°C.

[0143] <Content of Nitrogen Atom>

[0144] From the aspect of improving the fuel efficiency when the rubber composition of the present embodiment is used for a tire, the rubbery polymer preferably contains a nitrogen atom.

[0145] The nitrogen atom can be introduced into the rubbery polymer using a modifier. By reducing the hydrogenation rate of the rubbery polymer, it is also possible to improve the dispersibility of the silica-based inorganic filler, which is a reinforcing material, in the rubber composition, but by modifying the rubbery polymer using a modifier containing a nitrogen atom, there is a tendency for the dispersibility of the silica-based inorganic filler in the rubber composition to be further improved.

[0146] <Modification Rate>

[0147] From the viewpoint of dispersibility of the silica-based inorganic filler as a reinforcing material when the rubber composition of the present embodiment is used for a tire, the modification rate of the rubbery polymer is preferably 40% by mass or greater. The modification rate is more preferably 60% by mass or greater, and further preferably 70% by mass or greater. The upper limit of the modification rate of the rubbery polymer is not particularly limited, and from the viewpoint of lowering the viscosity of the compounded material after mixing the rubber composition of the present embodiment, and good processability, it is preferably 98% by mass or less, more preferably 95% by mass or less, and further preferably 90% by mass or less.

[0148] In the present specification, the "modification rate" indicates the mass ratio of the polymer having a nitrogen atom-containing functional group with respect to the total amount of the rubbery polymer.

[0149] The introduction position of the nitrogen atom into the rubbery polymer can be any of the polymerization start end, the molecular chain (including grafting), and the polymerization end of the rubbery polymer.

[0150] In the case where the rubbery polymer is produced by polymerizing a conjugated diene monomer and then hydrogenating, from the viewpoints of polymer production rate, high modification rate, and fuel consumption saving when the rubber composition of the present embodiment is used for a tire, it is preferable to use a method in which a nitrogen atom-containing functional group is introduced into the rubbery polymer using a coupling agent containing a nitrogen atom.

[0151] As the coupling agent containing a nitrogen atom, from the viewpoints of polymer production rate and high modification rate, it is preferable to use an isocyanate compound, an isothiocyanate compound, an isocyanuric acid derivative, a nitrogen atom-containing carbonyl compound, a nitrogen atom-containing vinyl compound, a nitrogen atom-containing epoxy compound, and a nitrogen atom-containing alkoxysilane compound.

[0152] From the viewpoint of improving the processability when the rubber composition of the present embodiment is used for a tire, it is preferable that the above coupling agent have a high number of branches.

[0153] The number of branches of the coupling agent is not particularly limited, and from the viewpoint of improving the processability of the rubber composition of the present embodiment, it is preferably 3 branches or greater, and more preferably 4 branches or greater. The upper limit of the number of branches is not particularly limited, and from the viewpoint of production rate, it is preferably 30 branches or less.

[0154] As the above coupling agent containing a nitrogen atom, from the viewpoints of polymer production rate, high modification rate, and tensile strength when the rubber composition of the present embodiment is used for a tire, a nitrogen atom-containing alkoxysilane compound is more preferable.

[0155] As the alkoxysilane compound containing a nitrogen group, there can be mentioned, but not limited to, for example, 2,2-dimethoxy-l-(3-trimethoxysilylpropyl)-l-aza-2-silacyclopentane, 2,2-diethoxy-l-(3-triethoxysilylpropyl)-l-aza-2-silacyclopentane, 2,2-dimethoxy-l-(4-trimethoxysilylbutyl)-l-aza-2-silacyclohexane, 2,2-dimethoxy-l-(5-trimethoxysilylpentyl)-l-aza-2-silacycloheptane, 2,2-dimethoxy-l-(3-dimethoxymethylsilylpropyl)-l-aza-2-silacyclopentane, 2,2-diethoxy-l-(3-diethoxyethylsilylpropyl)-l-aza-2-silacyclopentane, 2-methoxy-2-methyl-l-(3-trimethoxysilylpropyl)-l-aza-2-silacyclopentane, 2-ethoxy-2-ethyl-l-(3-triethoxysilylpropyl)-l-aza-2-silacyclopentane, 2-methoxy-2-methyl-l-(3-dimethoxymethylsilylpropyl)-l-aza-2-silacyclopentane, 2-ethoxy-2-ethyl-l-(3-diethoxyethylsilylpropyl)-l-aza-2-silacyclopentane, tris(3-trimethoxysilylpropyl)amine, tris(3-methyldimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-methyldiethoxysilylpropyl)amine, tris(trimethoxysilylmethyl)amine, tris(2-trimethoxysilyl ethyl)amine, tris(4-trimethoxysilylbutyl)amine, tetra[3-(2,2-dimethoxy-l-aza-2-silacyclopentane)propyl]-l,3-propanediamine, tetra(3-trimethoxysilylpropyl)-l,3-propanediamine, tetra(3-trimethoxysilylpropyl)-l,3-bisaminomethylcyclohexane, and N1-(3-(bis(3-(trimethoxysilyl)propyl)amino)propyl)-N1-methyl-N3-(3-(methyl(3-(trimethoxysilyl)propyl)amino)propyl)-N3-(3-(trimethoxysilyl)propyl)-l,3-propanediamine.

[0156] In the case where ethylene is copolymerized with a conjugated diene monomer to produce a rubbery polymer, from the viewpoint of fuel efficiency, wear resistance, and softness when the rubber composition of the present embodiment is used for a tire, the rubbery polymer preferably contains a tin atom, a nitrogen atom, or a silicon atom.

[0157] As a method of introducing these atoms into the rubbery polymer, from the viewpoint of manufacturability, a method of using a coupling agent containing a tin atom, a nitrogen atom, or a silicon atom at the time when the polymerization reaction reaches 100% is preferably applied.

[0158] As the coupling agent containing a tin atom, a nitrogen atom, or a silicon atom, there can be mentioned, but not limited to, for example, tin-containing compounds such as bis(maleic acid- 1-octadecyl) dioctyl tin, isocyanate compounds such as 4,4-diphenylmethane diisocyanate, alkoxysilane compounds such as glycidylpropyltrimethoxysilane, and the like.

[0159] <MOLECULAR WEIGHT>

[0160] From the viewpoint of the shape stability of the molded body of the rubber composition of the present embodiment, the tensile strength, and the abrasion resistance of the crosslinked body using the rubber composition, the weight average molecular weight of the rubbery polymer is preferably 150,000 or more, more preferably 200,000 or more. On the other hand, from the viewpoint of the processability when the rubber composition of the present embodiment is made into a crosslinking rubber composition, the weight average molecular weight is preferably 1,000,000 or less, more preferably 500,000 or less, further preferably 400,000 or less.

[0161] From the viewpoint of the fuel consumption saving when the rubber composition of the present embodiment is used for a tire, the molecular weight distribution (= weight average molecular weight / number average molecular weight) of the rubbery polymer is preferably 2.0 or less, more preferably 1.8 or less, further preferably 1.6 or less.

[0162] On the other hand, from the viewpoint of the processability when the rubber composition of the present embodiment is made into a crosslinking rubber composition, the molecular weight distribution of the rubbery polymer is preferably 1.05 or more, more preferably 1.2 or more, further preferably 1.4 or more.

[0163] The weight average molecular weight and the molecular weight distribution can be calculated from the polystyrene conversion molecular weight determined by GPC (gel permeation chromatography).

[0164] <DEACTIVATOR, NEUTRALIZER, STABILIZER, RUBBER SOFTENING AGENT>

[0165] A deactivator, a neutralizer, and the like can be added as needed at the final stage of the polymerization process of the rubbery polymer.

[0166] As the deactivator, there can be mentioned, but not limited to, for example, water; alcohols such as methanol, ethanol, isopropanol, and the like.

[0167] Note that the final stage of the polymerization process of the rubbery polymer described above means a state in which 95% or more of the added monomer is consumed in the polymerization.

[0168] As the neutralizer, there can be mentioned, but not limited to, for example, carboxylic acids such as stearic acid, oleic acid, neodecanoic acid (i.e., a mixture of carboxylic acids having 9 to 11 carbon atoms, centered on 10), and the like; aqueous solutions of inorganic acids, carbon dioxide.

[0169] From the viewpoint of preventing gel generation and processing stability, it is preferable to add a rubber stabilizer at the final stage of the polymerization process of the rubbery polymer.

[0170] As the rubber stabilizer, known substances such as antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (hereinafter also referred to as "BHT"), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate, 2-methyl-4,6-bis[(octylthio)methyl]phenol, and the like can be used, but are not limited thereto.

[0171] At the final stage of the polymerization process of the rubbery polymer, and the like, from the viewpoint of improving the productivity of the rubbery polymer, and the processability at the time of compounding an inorganic filler or the like when manufacturing a tire using the rubber composition of the present embodiment, it is preferable to add a rubber softener as necessary.

[0172] As the rubber softener, for example, extender oils, liquid rubbers, cyclic resin-containing resins, and the like can be given, but are not limited thereto.

[0173] As the method of adding the rubber softener to the rubbery polymer, for example, a method in which the rubber softener is added to a solution of the rubbery polymer, mixed, and a rubbery polymer solution containing the rubber softener is produced, and then desolvated, can be given, but is not limited thereto.

[0174] As the extender oil, for example, aromatic oils, naphthenic oils, paraffinic oils, and the like can be given. Among these, from the viewpoint of environmental safety, and the prevention of oil bleeding and wet grip properties, an alternative aromatic oil in which the polycyclic aromatic (PCA) component based on the IP346 method is 3% by mass or less is preferable. As the alternative aromatic oil, for example, TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), RAE (Residual Aromatic Extracts), and the like shown in Kautschuk Gummi Kunststoffe 52(12) 799 (1999) can be given.

[0175] From the viewpoint of suppressing the deterioration over time when the rubber composition is used in a tire, the content of the extender oil in the rubber composition of the present embodiment is preferably 10% by mass or less, more preferably 7% by mass or less, and further preferably 5% by mass or less.

[0176] As the softening agent for rubber, examples of the cyclic hydrocarbon resin include, but are not limited to, aromatic petroleum cyclic hydrocarbon resin, benzofuran-indene cyclic hydrocarbon resin, terpene cyclic hydrocarbon resin, rosin derivative (including tung oil cyclic hydrocarbon resin), tall oil, derivative of tall oil, rosin ester cyclic hydrocarbon resin, natural and synthetic terpene cyclic hydrocarbon resin, aliphatic hydrocarbon cyclic hydrocarbon resin, aromatic hydrocarbon cyclic hydrocarbon resin, mixed aliphatic-aromatic hydrocarbon cyclic hydrocarbon resin, coumarin-indene cyclic hydrocarbon resin, phenol cyclic hydrocarbon resin, p-t-butylphenol-acetylene cyclic hydrocarbon resin, phenol-formaldehyde cyclic hydrocarbon resin, xylene-formaldehyde cyclic hydrocarbon resin, oligomer of mono-olefin, oligomer of di-olefin, aromatic petroleum cyclic hydrocarbon resin, hydrogenated aromatic hydrocarbon cyclic hydrocarbon resin, cyclic aliphatic hydrocarbon cyclic hydrocarbon resin, hydrogenated hydrocarbon cyclic hydrocarbon resin, hydrocarbon cyclic hydrocarbon resin, hydrogenated tung oil cyclic hydrocarbon resin, hydrogenated oil cyclic hydrocarbon resin, ester of hydrogenated oil cyclic hydrocarbon resin and monofunctional or polyfunctional alcohol, and the like.

[0177] These cyclic hydrocarbon resins can be used singly or in combination of two or more.

[0178] In the case of the cyclic hydrocarbon resin being a hydrogenated product, the unsaturated group can be completely hydrogenated or a part of the unsaturated group can remain.

[0179] By adding the cyclic hydrocarbon resin to the rubber-like polymer, the processability of the rubber composition of the present embodiment can be improved, and the tendency to increase the breaking strength after the rubber composition is made into a vulcanizate is exhibited.

[0180] The amount of the filling oil, liquid rubber, or cyclic hydrocarbon resin as the softening agent for rubber to be added is preferably 35 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 10 parts by mass or less, relative to 100 parts by mass of the total amount of the rubber components including the rubber-like polymer and the natural rubber. By setting the amount of the filling oil, liquid rubber, or cyclic hydrocarbon resin to be added within this range, the rubber composition of the present embodiment has the tendency to exhibit excellent wear resistance and fuel efficiency.

[0181] In addition, the content of the oil such as the filling oil and / or the cyclic hydrocarbon resin in the rubber composition of the present embodiment is preferably less than 35 parts by mass, more preferably 20 parts by mass or less, and further preferably 10 parts by mass or less, relative to 100 parts by mass of the rubber components including the rubber-like polymer and the natural rubber.

[0182] Furthermore, the content of the oil such as the filling oil is preferably less than 10 parts by mass, more preferably 7 parts by mass or less, and further preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber components including the rubber-like polymer and the natural rubber.

[0183] By setting the amount of the filling oil, liquid rubber, or cyclic hydrocarbon resin to be added within this range, the rubber composition of the present embodiment has the tendency to exhibit excellent wear resistance and fuel efficiency.

[0184] The rubbery polymer constituting the rubber composition of the present embodiment is obtained by polymerizing a prescribed monomer in a solution, and removing the solvent from the polymer solution to obtain the rubbery polymer.

[0185] As a method for removing the solvent from the polymer solution to obtain the rubbery polymer, a publicly known method can be used. For example, a method in which the solvent is separated by stripping or the like, and then the polymer is filtered out, and further dehydrated and dried to obtain the rubbery polymer; a method in which concentration is performed using a flash tank, and further devolatilization is performed using an air-venting extruder or the like; a method in which devolatilization is directly performed using a rotary drum dryer or the like; and the like can be cited.

[0186] (Natural Rubber)

[0187] The rubber composition of the present embodiment contains natural rubber.

[0188] In the rubber composition of the present embodiment, when the total amount of the rubber component containing the rubbery polymer and the natural rubber is set to 100 parts by mass, the content of the natural rubber is 10 parts by mass or more, preferably 30 parts by mass or more from the viewpoint of abrasion resistance and processability, and the content of the natural rubber is more preferably 50 parts by mass or more, further preferably 60 parts by mass or more from the viewpoint of improving mechanical strength in addition to abrasion resistance and processability.

[0189] In addition, the content of the natural rubber is 90 parts by mass or less, preferably 80 parts by mass or less, more preferably 70 parts by mass or less from the viewpoint of fuel consumption when the rubber composition of the present embodiment is used for a tire, and the viewpoint of suppressing changes in performance in the later stage of tire use.

[0190] The natural rubber is not particularly limited, and for example, RSS No. 3 to 5 as smoked sheet rubber, SMR (Standard Malaysian Rubber), and epoxidized natural rubber can be cited from the viewpoint of having a high content of high molecular weight components and excellent breaking strength.

[0191] The rubber component constituting the rubber composition of the present embodiment can also contain other rubber in addition to the above-described rubbery polymer and natural rubber.

[0192] The other rubber is not particularly limited, and can be appropriately selected according to the purpose, and for example, styrene-butadiene rubber (emulsion polymerization type, solution polymerization type), polyisoprene, butadiene rubber (high-cis polybutadiene, low-cis polybutadiene, syndiotactic 1,2-polybutadiene), nitrile rubber (NBR), chloroprene rubber, ethylene-propylene rubber, ethylene-butene rubber, ethylene-a-olefin copolymer rubber such as ethylene-octene, ethylene-propylene-diene rubber (EPDM), butyl rubber, polysulfide rubber, silicone rubber, fluororubber, and urethane rubber, and the like can be cited.

[0193] These components can be used singly or in combination of two or more.

[0194] As to the mixing of other rubber, the other rubber in a dry state can be mixed after the polymerization of the rubbery polymer, or the other rubber in a solution state can be mixed during the polymerization of the rubbery polymer.

[0195] From the aspect of the breaking strength of the rubber composition of the present embodiment, when the total of the rubbery polymer and the natural rubber is 100 parts by mass, the content of the "other rubber" is preferably 40 parts by mass or less. For example, in the case where the wear resistance is insufficient when only the rubbery polymer and the natural rubber are used, it is conceivable to blend polybutadiene, in which case, the addition amount of the polybutadiene is preferably 40 parts by mass or less relative to the total amount of the rubbery polymer and the natural rubber, which is 100 parts by mass.

[0196] (Silica-based inorganic filler, and carbon black)

[0197] In the rubber composition of the present embodiment, relative to the total amount of 100 parts by mass of the rubber components including the rubbery polymer and the natural rubber, and the other rubber when necessary, 20 parts by mass or more and 80 parts by mass or less of the silica-based inorganic filler and the carbon black are contained. The content is preferably 30 parts by mass or more and 70 parts by mass or more, and more preferably 40 parts by mass or more and 60 parts by mass or less.

[0198] (Silica-based inorganic filler)

[0199] From the aspect of the improvement in the grip performance and the steering stability when the rubber composition of the present embodiment is used for a tire, the content of the silica-based inorganic filler in the rubber composition of the present embodiment is 60 parts by mass or less, preferably 58 parts by mass or less, and more preferably 56 parts by mass or less, relative to the total amount of 100 parts by mass of the rubber components including the rubbery polymer and the natural rubber, and the other rubber when necessary.

[0200] The silica-based inorganic filler is not particularly limited, and a publicly known substance can be used, and a solid particle including SiO2 or Si3Al as a structural unit is preferable, and a solid particle in which SiO2 or Si3Al is a main component of the structural unit is more preferable.

[0201] Here, the main component means a component that is contained in the silica-based inorganic filler at 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more.

[0202] As the silica-based inorganic filler, inorganic fibrous substances such as silica, clay, talc, mica, diatomite, wollastonite, montmorillonite, zeolite, and glass fibers can be given, but are not limited thereto.

[0203] As a commercially available product of the silica-based inorganic filler, for example, "Ultrasil 7000GR" manufactured by Evonik Degussa Co. can be given.

[0204] In addition, a silica-based inorganic filler whose surface is hydrophobized, or a mixture of a silica-based inorganic filler and an inorganic filler other than the silica-based inorganic filler can also be used.

[0205] Among these, from the aspects of the strength and the wear resistance of the rubber composition of the present embodiment, silica and glass fiber are preferred, and silica is more preferred. As the silica, for example, dry silica, wet silica, and synthetic silicate silica can be given. Among these, from the aspects of the improvement effect on the breaking properties and the balance of the wet skid resistance of the rubber composition of the present embodiment, wet silica is preferred.

[0206] In the rubber composition of the present embodiment, from the aspects of obtaining a practically good wear resistance and breaking properties, the nitrogen adsorption specific surface area (BET specific surface area) of the silica-based inorganic filler, which is obtained by the BET adsorption method, is preferably 100 m 2 / g or more and 300 m 2 / g or less, and more preferably 170 m 2 / g or more and 250 m 2 / g or less. In addition, a filler having a relatively small specific surface area (for example, a silica-based inorganic filler having a specific surface area of less than 200 m 2 / g) can be used in combination with a filler having a relatively large specific surface area (for example, a silica-based inorganic filler having a specific surface area of 200 m 2 / g or more). Thereby, the good wear resistance and breaking properties and the low hysteresis loss of the rubber composition of the present embodiment can be highly balanced.

[0207] Note that the nitrogen adsorption specific surface area is obtained according to JIS K 6217-2:2001.

[0208] (Carbon Black)

[0209] In the rubber composition of the present embodiment, in addition to the silica-based inorganic filler, carbon black is further contained.

[0210] From the aspect of the improvement of the wear resistance of the rubber composition of the present embodiment, the content of the carbon black is 60 parts by mass or less, preferably 58 parts by mass or less, and more preferably 56 parts by mass or less, relative to 100 parts by mass of the total amount of the above rubber component.

[0211] The nitrogen adsorption specific surface area (BET specific surface area) of the carbon black used in the rubber composition of the present embodiment is preferably 5 m 2 / g or more, more preferably 15 m 2 / g or more, further preferably 35 m 2 / g or more, more further preferably 55 m 2 / g or more.

[0212] By making the BET specific surface area of the carbon black 5 m 2 / g or more, sufficient reinforcing effect can be obtained in the rubber composition of the present embodiment, and sufficient rubber breaking strength and handling stability are obtained.

[0213] The BET specific surface area of the carbon black is preferably 200 m 2 / g or less, more preferably 180 m 2 / g or less, further preferably 140 m 2 / g or less. By making it 200 m 2 / g or less, good low fuel consumption can be obtained in the rubber composition of the present embodiment.

[0214] In addition, the dibutyl phthalate oil absorption (DBP) of the carbon black used in the rubber composition of the present embodiment is preferably 50 mL / 100 g or more, more preferably 70 mL / 100 g or more, further preferably 90 mL / 100 g or more.

[0215] By making the DBP of the carbon black 50 mL / 100 g or more, sufficient reinforcing effect can be obtained in the rubber composition of the present embodiment, and sufficient rubber breaking strength and handling stability are obtained.

[0216] In addition, the DBP of the carbon black is preferably 200 mL / 100 g or less, more preferably 150 mL / 100 g or less, further preferably 110 mL / 100 g or less.

[0217] By making the DBP of the carbon black 200 mL / 100 g or less, there is a tendency that excellent low fuel consumption can be obtained in the rubber composition of the present embodiment.

[0218] Note that the DBP of the carbon black can be measured according to JIS K 6217-4:2001.

[0219] In the case where the rubber composition of the present embodiment is used for the bead of a tire, it is preferable to contain carbon black having a nitrogen adsorption specific surface area (BET specific surface area) of 5 to 200 m 2 / g. The lower limit value is more preferably 15 m 2 / g or more, further preferably 50 m 2 / g or more. In addition, the upper limit value is more preferably 180 m2 / g, further preferably 130 m 2 / g, further more preferably 100 m 2 / g. By making the BET specific surface area of the carbon black 5 m 2 / g or more, a sufficient reinforcing effect can be obtained; by making it 200 m 2 / g or less, there is a tendency that an excellent low fuel consumption can be obtained.

[0220] In the case where the rubber composition of the present embodiment is used for a tire bead, the content of the carbon black is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, with respect to 100 parts by mass of the total amount of the above rubber component. The content is 60 parts by mass or less, more preferably 55 parts by mass or less, further preferably 50 parts by mass or less.

[0221] When the content is within the above range, a good low fuel consumption, chip resistance, and resistance to growth of permanent set cracks can be obtained.

[0222] With respect to the total content of the silica-based inorganic filler and the carbon black in the rubber composition of the present embodiment, 20 parts by mass or more, preferably 30 parts by mass or more, more preferably 40 parts by mass or more, with respect to 100 parts by mass of the total amount of the above rubber component, is preferable from the viewpoint of obtaining a practically good wear resistance and breaking properties. In addition, 80 parts by mass or less, preferably 75 parts by mass or less, more preferably 70 parts by mass or less, further preferably 60 parts by mass or less, is preferable from the viewpoint of low fuel consumption.

[0223] With respect to the ratio of the silica-based inorganic filler to the carbon black, in the case where low fuel consumption is emphasized, the ratio of the silica-based inorganic filler in the total amount of the silica-based inorganic filler and the carbon black is preferably 60 mass% or more, more preferably 70 mass% or more, further preferably 80 mass% or more. In the case where wear resistance is emphasized, the ratio of the carbon black in the total amount of the silica-based inorganic filler and the carbon black is preferably 30 mass% or more, more preferably 40 mass% or more, further preferably 50 mass% or more.

[0224] (metal oxide, metal hydroxide)

[0225] In the rubber composition of the present embodiment, in addition to the silica-based inorganic filler and the carbon black, a metal oxide and a metal hydroxide can be contained.

[0226] The metal oxide refers to a solid particle of which a chemical formula MxOy (M represents a metal atom, and x and y each independently represent an integer of 1 to 6) is a structural unit of a main component, and examples thereof include aluminum oxide, titanium oxide, magnesium oxide, zinc oxide, and the like.

[0227] In addition, a mixture of a metal oxide and an inorganic filler other than a metal oxide can also be used.

[0228] The metal hydroxide is not particularly limited, and examples thereof include aluminum hydroxide, magnesium hydroxide, and zirconium hydroxide.

[0229] (Silane Coupling Agent)

[0230] The rubber composition of the present embodiment can contain a silane coupling agent.

[0231] The silane coupling agent has a group having affinity or binding property for each of a rubber component containing a rubber-like polymer and a silica-based inorganic filler, and has a function of making the interaction between the rubber component and the silica-based inorganic filler close.

[0232] As the silane coupling agent, for example, a compound having a sulfur-binding moiety, an alkoxysilyl group, and a silanol group moiety in one molecule is used.

[0233] silane coupling agents containing a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxaoctadec-1-yloxy)silane [manufactured by Evonik Degussa: Si363], NXT-Z30, NXT-Z45, NXTZ60, NXT silane manufactured by Momentive, and the like; bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilyl ethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilyl ethyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyltetrasulfide, 3-triethoxysilylpropylbenzoyltetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, dimethoxymethylsilylpropylbenzothiazolyltetrasulfide, and the like.

[0234] Among the above-mentioned silane coupling agents, from the viewpoint of the high reinforcing effect of the rubber composition of the present embodiment, bis-[3-(triethoxysilyl)-propyl]-disulfide; ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxaoctadec-1-yloxy)silane [manufactured by Evonik Degussa: Si363], NXT-Z30, NXT-Z45, NXTZ60, NXT silane manufactured by Momentive, and the like silane coupling agents containing a mercapto group; bis-[3-(triethoxysilyl)-propyl]-tetrasulfide are preferable.

[0235] These silane coupling agents can be used alone or in combination of two or more.

[0236] The amount of the silane coupling agent to be blended in the rubber composition of the present embodiment is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 1 part by mass or more, relative to 100 parts by mass of the total amount of the rubber component including the rubbery polymer and the natural rubber, from the viewpoint of making the interaction between the rubber component and the silica-based inorganic filler more significant. In addition, the amount of the silane coupling agent to be blended is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 15 parts by mass or less, from the viewpoint of making the processability of the rubber composition of the present embodiment good.

[0237] (Rubber softening agent)

[0238] The rubber composition of the present embodiment can contain a rubber softening agent from the viewpoint of improving processability.

[0239] As the rubber softening agent, for example, a mineral oil-based rubber softening agent and a liquid or low-molecular-weight synthetic softening agent are suitable.

[0240] The mineral oil-based rubber softening agent described above is also referred to as an operation oil or an extender oil, and is used for the purpose of achieving softening, compatibilization, and improvement of processability of rubber. In addition, the mineral oil-based rubber softening agent described above is a mixture of an aromatic ring, a naphthenic ring, and a paraffin chain, and a substance in which the number of carbon atoms of the paraffin chain accounts for 50% or more of the total carbon is referred to as a paraffin-based substance, a substance in which the number of carbon atoms of the naphthenic ring is 30 to 45% is referred to as a naphthenic-based substance, and a substance in which the number of carbon atoms of the aromatic ring exceeds 30% is referred to as an aromatic-based substance. As the rubber softening agent, when the number of carbon atoms of the aromatic ring is moderate, the affinity with the rubbery polymer tends to be good, and thus it is preferable.

[0241] The amount of the rubber softening agent to be blended is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and further preferably 5 parts by mass or less, relative to 100 parts by mass of the total amount of the rubber component including the rubbery polymer and the natural rubber, from the viewpoint of suppressing bleeding and preventing the rubber composition from being cured over time.

[0242] [Method for producing rubber composition]

[0243] The rubber composition of the present embodiment can be produced by mixing constituent materials including a rubber component including a rubbery polymer and a natural rubber, a silica-based inorganic filler, carbon black, other fillers as necessary, a silane coupling agent, a rubber softening agent, and other additives.

[0244] As the mixing method, there can be mentioned, but not limited to, for example, a melt kneading method using a common mixer such as an open mill, a Banbury mixer, a kneader, a single screw extruder, a twin screw extruder, a multi screw extruder, etc.; a method of dissolving and mixing each component and then removing a solvent by heating.

[0245] Among these, from the viewpoint of productivity and good kneading properties, a melt kneading method using an open mill, a Banbury mixer, a kneader, or an extruder is preferred. In addition, either of a method of kneading the constituent materials of the rubber composition of the present embodiment at one time, and a method of mixing in several times can be applied.

[0246] The rubber composition of the present embodiment can be made into a vulcanized composition by subjecting to a vulcanization treatment using a vulcanizing agent.

[0247] As the vulcanizing agent, there can be mentioned, but not limited to, for example, a radical initiator such as an organic peroxide and an azo compound, an oxime compound, a nitroso compound, a polyamine compound, sulfur, a sulfur-containing compound.

[0248] The sulfur-containing compound includes sulfur monochloride, sulfur dichloride, a disulfide compound, a high molecular polysulfide compound, etc.

[0249] From the viewpoint of improving the breaking strength by utilizing the reinforcing effect, the content of the vulcanizing agent is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and further preferably 1 part by mass or more, relative to 100 parts by mass of the total amount of the rubber component including the rubbery polymer and the natural rubber. In addition, from the viewpoint of having softness and improving the breaking elongation, the content of the vulcanizing agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 10 parts by mass or less.

[0250] As the vulcanization method, a publicly known method can be applied, and the vulcanization temperature is not particularly limited. From the viewpoint of being able to shorten the vulcanization time and improve the production efficiency, the temperature is preferably 120°C or higher, more preferably 135°C or higher, and further preferably 140°C or higher. In addition, from the viewpoint of suppressing thermal degradation at the time of vulcanization, the temperature is preferably 200°C or lower, more preferably 160°C or lower, and further preferably 150°C or lower.

[0251] At the time of vulcanization, a vulcanization accelerator can be used as needed.

[0252] As the vulcanization accelerator, a publicly known material can be used, and there can be mentioned, but not limited to, for example, a sulfenamide-based compound, a guanidine-based compound, a thiuram-based compound, an aldehyde-amine-based compound, an aldehyde-ammonia-based compound, a thiazole-based compound, a thiourea-based compound, a dithiocarbamate-based compound, and the like.

[0253] In addition, as the vulcanization aid, zinc white, stearic acid, and the like can be mentioned, but are not limited thereto.

[0254] The content of the vulcanization accelerator is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the total amount of the rubber component including the rubbery polymer and the natural rubber.

[0255] In the rubber composition of the present embodiment, various additives other than the above-described constituting components, such as other softening agents, fillers, heat-resistant stabilizers, antistatic agents, weather-resistant stabilizers, anti-aging agents, coloring agents, and lubricants, can be used within a range not impairing the object of the present application.

[0256] As the other softening agent, a publicly known softening agent can be used. As the other filler, for example, calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate can be mentioned.

[0257] As the heat-resistant stabilizer, antistatic agent, weather-resistant stabilizer, anti-aging agent, coloring agent, and lubricant, a publicly known material can be used, respectively.

[0258] [Preferred physical properties of the rubber composition]

[0259] In the rubber composition of the present embodiment, the iodine value (A) of the rubbery polymer,

[0260] The content (parts by mass) of the above-described silica-based inorganic filler relative to 100 parts by mass of the total amount of the above-described rubber component (B) and the content (parts by mass) of the above-described carbon black (C),

[0261] The BET specific surface area (D) of the above-described silica-based inorganic filler and the BET specific surface area (E) of the above-described carbon black preferably have the following relation of formula (1).

[0262] (Formula (1))

[0263] 0 < (0.029 x ((B) x (D)) + ((C) x (E))) - (A) < 250

[0264] The above-described formula (1) represents the balance between the wear resistance due to the reinforcing effect of the filler and the processability of the rubber composition in the rubber composition of the present embodiment, and by making it greater than 0 and less than 250, a rubber composition excellent in both the wear resistance and the processability can be obtained.

[0265] The above-described numerical range is more preferably 10 or more and 200 or less, and further preferably 50 or more and 150 or less.

[0266] In the rubber composition of the present embodiment, the iodine value (A) of the rubbery polymer,

[0267] the content (mass parts) of the above-mentioned silica-based inorganic filler (B) and the content (mass parts) of the above-mentioned carbon black (C) relative to 100 mass parts of the total amount of the above-mentioned rubber component,

[0268] The BET specific surface area (D) of the above-mentioned silica-based inorganic filler and the BET specific surface area (E) of the above-mentioned carbon black preferably have the following relation of formula (2).

[0269] (Formula (2)):

[0270] 0 < (0.029 x ((B) x (D)) + ((C) x (E))) - (A) < 136

[0271] By making the above-mentioned formula (2) greater than 0 and less than 136, a rubber composition having excellent wear resistance, processability, and resistance to static elongation fatigue can be obtained.

[0272] The above-mentioned numerical range is more preferably 10 or greater and 126 or less, and further preferably 50 or greater and 100 or less.

[0273] [Tire]

[0274] The rubber composition of the present embodiment is suitable for use as a rubber composition for a tire for a heavy load vehicle.

[0275] That is, the crown portion of the tire of the present embodiment is composed of the rubber composition of the present embodiment.

[0276] From the aspect of load resistance, the JATMA standard load index, which indicates the load resistance of a tire for a heavy load vehicle, is preferably 100 or greater, more preferably 110 or greater, and further preferably 120 or greater.

[0277] A tire for a heavy load vehicle is used under conditions in which wear is severe, and thus excellent wear resistance is required.

[0278] In addition, in view of environmental load and operating costs, a tire is required to have low fuel consumption. Thus, from the aspects of wear resistance and low fuel consumption, the rubber composition of the present embodiment preferably contains a natural rubber having a low glass transition temperature, and further a polybutadiene having a low glass transition point, a styrene butadiene block copolymer are used as a rubbery polymer. In addition, from the aspect of wear resistance, it is preferable that the rubber composition of the present embodiment has a small amount of extender oil mixed therein.

[0279] As described above, by using the present embodiment, a rubber composition can be provided, which can obtain a tire having excellent wear resistance, excellent processability and low fuel consumption, and further can suppress changes in performance of the tire in the later stage of use.

[0280] The rubber composition of the present embodiment can be applied to, but is not limited to, for example, various tire portions such as a tire tread, a tire carcass, a tire bead, a tire shoulder portion, and the like of a fuel-efficient tire, an all-season tire, a studless tire, and the like.

[0281] In particular, the rubber composition of the present embodiment is excellent in low fuel consumption and wear resistance after vulcanization, and further can suppress changes in performance in the later stage of tire use, and thus is more suitable for use in a tire tread for a fuel-efficient tire, an all-season tire, and a snow tire for a heavy load vehicle.

[0282] Examples

[0283] The present embodiment will be described in more detail below by citing specific examples and comparative examples, but the present embodiment is not limited in any way by the examples and comparative examples below.

[0284] Various physical properties in the examples and comparative examples were measured by the following methods.

[0285] Weight-average molecular weight (Mw) of rubbery polymer

[0286] A GPC measuring device in which three columns using polystyrene-based gels as fillers were connected was used to measure a chromatogram, and the weight-average molecular weight (Mw) of the rubbery polymer was calculated based on a calibration curve obtained using standard polystyrene.

[0287] Specific measurement conditions are shown below.

[0288] The following measurement liquid 20 μL was injected into the GPC measuring device to perform measurement.

[0289] <Measurement conditions>

[0290] Device: "HLC-8320 GPC" manufactured by Tosoh Corporation

[0291] Eluent: tetrahydrofuran (THF) to which 5 mmol / L of triethylamine was added

[0292] Guard column: "TSK guard column Super H-H" manufactured by Tosoh Corporation,

[0293] Separation column: "TSKgel Super H5000", "TSKgel Super H6000", and "TSKgel Super H7000" manufactured by Tosoh Corporation were sequentially connected.

[0294] Oven temperature: 40°C

[0295] Flow rate: 0.6 mL / minute

[0296] Detector: RI detector (trade name "HLC8020" manufactured by Tosoh Corporation)

[0297] Measurement solution: A measurement solution prepared by dissolving 10 mg of the measurement sample in 20 mL of THF

[0298] (Mooney viscosity of rubbery polymer and rubber composition)

[0299] The Mooney viscosity of the rubbery polymer and the rubber composition was measured using a Mooney viscometer (trade name "VR1132" manufactured by Shimazu Seisakusho Co., Ltd.) in accordance with ISO 289 using an L-shaped rotor.

[0300] First, the sample was preheated at 100°C for 1 minute, and then the rotor was rotated at 2 rpm, and the torque after 4 minutes was measured as the Mooney viscosity at 100°C (ML (1+4) ).

[0301] (Modification rate of rubbery polymer)

[0302] The modification rate of the rubbery polymer was measured by column adsorption GPC method as follows using the property that the modified rubbery polymer is adsorbed by a column.

[0303] The adsorption amount on the silica-based column was measured from the difference between the chromatogram obtained by measurement using a polystyrene-based column filled with a polystyrene-based gel and the chromatogram obtained by measurement using a silica-based column filled with a silica-based gel, and the modification rate was calculated.

[0304] The GPC measurement conditions using a polystyrene-based column are shown below.

[0305] The measurement solution 20 μL described below was injected into the GPC measurement device, and measurement was performed.

[0306] <GPC measurement conditions using a polystyrene-based column>

[0307] Device: "HLC-8320 GPC" manufactured by Tosoh Corporation

[0308] Eluent: THF to which 5 mmol / L of triethylamine was added

[0309] Guard column: "TSK guard column Super H-H" manufactured by Tosoh Corporation

[0310] Column: "TSKgel Super H5000", "TSKgel Super H6000", and "TSKgel Super H7000" manufactured by Tosoh Corporation were sequentially connected

[0311] Oven temperature: 40°C

[0312] Flow rate: 0.6 mL / min

[0313] Detector: RI detector (HLC8020 manufactured by Tosoh Corporation)

[0314] Sample solution: 10 mg of the sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a sample solution.

[0315] The GPC measurement conditions using a silica-based column are shown below.

[0316] 50 μL of the following sample solution was injected into the GPC measurement device to perform the measurement.

[0317] <GPC measurement conditions using a silica-based column>

[0318] Device: Trade name "HLC-8320 GPC" manufactured by Tosoh Corporation

[0319] Eluent: THF

[0320] Guard column: Trade name "DIOL 4.6 x 12.5 mm 5 micron" manufactured by GL Sciences

[0321] Separation column: Trade name "Zorbax PSM-1000S", "PSM-300S", "PSM-60S" manufactured by Agilent Technologies were sequentially connected

[0322] Oven temperature: 40°C,

[0323] Flow rate: 0.5 mL / min

[0324] Detector: RI detector (HLC8020 manufactured by Tosoh Corporation)

[0325] Method for calculating the modification rate:

[0326] The peak area of the chromatogram obtained using a polystyrene-based column was set to 100, the peak area of the sample was set to Pl, the peak area of the standard polystyrene was set to P2, the peak area of the chromatogram obtained using a silica-based column was set to 100, the peak area of the sample was set to P3, and the peak area of the standard polystyrene was set to P4. The modification rate (%) was calculated by the following formula.

[0327] Modification rate (%) = [1 - (P2 x P3) / (Pl x P4)] x 100

[0328] (where, Pl + P2 = P3 + P4 = 100)

[0329] (Binding styrene amount of the rubber-like polymer)

[0330] A sample 100 mg was dissolved in chloroform to 100 mL as a measurement sample.

[0331] The bound styrene amount (mass %) relative to 100 mass % of the rubbery polymer as a sample was measured by the amount of absorption at the ultraviolet absorption wavelength (around 254 nm) based on the styrene-based phenyl group.

[0332] As a measurement device, a spectrophotometer "UV-2450" manufactured by Shimadzu Corporation was used.

[0333] (Microstructure of butadiene portion of rubbery polymer (1,2-vinyl bond amount))

[0334] A sample 50 mg was dissolved in carbon disulfide 10 mL as a measurement sample.

[0335] Using a solution cell, an infrared spectrum was measured in the range of 600 to 1000 cm -1 The microstructure of butadiene portion, i.e., 1,2-vinyl bond amount (mol %) was calculated from the absorbance at a prescribed wave number according to the calculation formula of the Hampton method (a method described in R.R. Hampton, Analytical Chemistry 21, 923 (1949)).

[0336] As a measurement device, a Fourier transform infrared spectrophotometer "FT-IR230" manufactured by Japan Spectroscopic Co., Ltd. was used.

[0337] (Hydrogenation rate, ethylene structure, conjugated diene monomer unit of rubbery polymer)

[0338] The integral value of the unsaturated bonding portion of the polymer before hydrogenation was obtained by 1 H-NMR measurement.

[0339] Next, a large amount of methanol was added to the reaction solution after the hydrogenation reaction, whereby the hydrogenated conjugated diene polymer (rubbery polymer) was precipitated to be recovered.

[0340] Subsequently, the hydrogenated conjugated diene polymer was extracted with acetone, and the hydrogenated conjugated diene polymer was vacuum-dried.

[0341] This was used as 1 a sample for H-NMR measurement, and the hydrogenation rate, ethylene structure, and conjugated diene monomer unit were measured. 1 The conditions for H-NMR measurement were as follows.

[0342] (Measurement conditions)

[0343] Measurement device: JNM-LA400 (manufactured by JEOL)

[0344] Solvent: Deuterated chloroform

[0345] Test samples: Extracts of the polymer before and after hydrogenation.

[0346] Sample concentration: 50 mg / mL

[0347] Observation frequency: 400MHz

[0348] Chemical shift reference: TMS (tetramethylsilane)

[0349] Pulse delay: 2.904 seconds

[0350] Number of scans: 64

[0351] Pulse width: 45°

[0352] Measurement temperature: 26℃

[0353] (Amount of styrene blocks in rubber-like polymers)

[0354] A chain consisting of eight or more styrene structural units is considered a styrene block. The amount of this styrene block is calculated as follows.

[0355] Based on measurements at 400 MHz using deuterated chloroform as a solvent 1 Using H-NMR spectra, determine the integral ratio of each chemical shift range of (X) below, and determine the content of styrene blocks contained in the rubber-like block polymer.

[0356] (X) Aromatic vinyl compounds with chains of 8 or more: 6.00 ≤ X < 6.68

[0357] (Iodine value of rubber-like polymers)

[0358] The iodine value of the rubbery polymer was calculated according to the method described in "JIS K 0070:1992".

[0359] (Glass transition temperature (Tg) of rubber-like polymers)

[0360] Using a rubbery polymer as a sample, and in accordance with ISO 22768:2006, a differential scanning calorimeter "DSC3200S" manufactured by Mac Science was used to heat the sample from -100°C at a rate of 20°C / min with a flow of 50 mL / min of helium. The DSC curve was recorded, and the peak (inflection point) of the DSC differential curve was taken as the glass transition temperature.

[0361] [Manufacturing of rubber-like polymers]

[0362] ((Manufacture Example 1) Rubber-like polymer (A) before hydrogenation)

[0363] A high-pressure vessel with a content volume of 40 L, provided with a stirrer and a jacket, which can be temperature-controlled, was used as a reactor. To the reactor, 1,3-butadiene 2,160 g, from which impurities had been removed in advance, styrene 300 g, cyclohexane 21,000 g, tetrahydrofuran (THF) 30 mmol as a polar substance, and 2,2-bis(2-tetrahydrofuryl)propane 4.9 mmol were added, and the temperature inside the reactor was maintained at 42°C. To the above reactor, n-butyllithium 33.2 mmol as a polymerization initiator was supplied.

[0364] After the start of the polymerization reaction, the temperature inside the reactor started to rise due to the heat of polymerization, and after the monomer conversion rate in the reactor reached 98%, 1,3-butadiene 540 g was added, and the reaction was performed.

[0365] The final temperature inside the reactor reached 76°C. After 2 minutes from reaching this reaction temperature peak, 2,2-dimethoxy-l-(3-trimethoxysilylpropyl)-l-aza-2-silacyclopentane (Compound 1) 6.6 mmol was added to the reactor, and a coupling reaction was performed for 20 minutes, and a polymer solution was obtained. To this polymer solution, methanol 6.0 mmol as a reaction terminator was added, and a rubber-like polymer solution (A-l) was obtained.

[0366] A part of the conjugated diene-based polymer solution was drawn out, and solvent was removed using a drier, and a rubber-like polymer (A) before hydrogenation was obtained.

[0367] The analysis results are shown in Table 1.

[0368] ((Manufacture Example 2) Rubber-like polymer (B) before hydrogenation)

[0369] A high-pressure vessel with a content volume of 40 L, provided with a stirrer and a jacket, which can be temperature-controlled, was used as a reactor. To the reactor, 1,3-butadiene 2,160 g, from which impurities had been removed in advance, styrene 300 g, cyclohexane 21,000 g, tetrahydrofuran (THF) 30 mmol as a polar substance, and 2,2-bis(2-tetrahydrofuryl)propane 4.9 mmol were added, and the temperature inside the reactor was maintained at 42°C. To the above reactor, n-butyllithium 33.2 mmol as a polymerization initiator was supplied.

[0370] After the start of the polymerization reaction, the temperature inside the reactor started to rise due to the heat of polymerization, and after the monomer conversion rate in the reactor reached 98%, 1,3-butadiene 540 g was added, and the reaction was performed.

[0371] The final temperature in the reactor reached 78°C. Two minutes after reaching this reaction temperature peak, 2,2-dimethoxy-l-(3-trimethoxysilylpropyl)-l-aza-2-silacyclopentane (Compound 1) 5.2 mmol was added to the reactor, and a coupling reaction was carried out for 20 minutes. Methanol 4.7 mmol was added to the polymer solution as a reaction terminator, and a rubbery polymer solution (B-1) was obtained. A portion of the conjugated diene-based polymer solution was drawn off, and solvent was removed using a drier to obtain a rubbery polymer (B) before hydrogenation.

[0372] ((Production Example 3) Rubbery Polymer (C) Before Hydrogenation)

[0373] A rubbery polymer solution (C-1) was obtained in the same manner as in the above (Production Example 1), except that 2,2-dimethoxy-l-(3-trimethoxysilylpropyl)-l-aza-2-silacyclopentane (Compound 1) was changed to tetraglycidyl-l,3-bisaminomethylcyclohexane (Compound 2). A portion of the conjugated diene-based polymer solution was drawn off, and solvent was removed using a drier to obtain a rubbery polymer (C) before hydrogenation.

[0374] ((Production Example 4) Rubbery Polymer (D) Before Hydrogenation)

[0375] A rubbery polymer solution (D-1) was obtained in the same manner as in the above (Production Example 1), except that the amount of 2,2-dimethoxy-l-(3-trimethoxysilylpropyl)-l-aza-2-silacyclopentane (Compound 1) added was changed to 3.9 mmol. A portion of the conjugated diene-based polymer solution was drawn off, and solvent was removed using a drier to obtain a rubbery polymer (D) before hydrogenation.

[0376] ((Production Example 5) Rubbery Polymer (E) Before Hydrogenation)

[0377] A high-pressure vessel with a content volume of 40 L, equipped with a stirrer and a jacket for temperature control, was used as a reactor, and 1,3-butadiene 1,680 g, styrene 780 g, cyclohexane 21,000 g, tetrahydrofuran (THF) 50 mmol as a polar substance, and 2,2-bis(2-tetrahydrofuryl)propane 8.2 mmol, from which impurities had been previously removed, were added to the reactor, and the temperature in the reactor was maintained at 42°C. To the above reactor, n-butyllithium 33.2 mmol was supplied as a polymerization initiator.

[0378] After the start of the polymerization reaction, the temperature in the reactor began to rise due to the heat of polymerization, and after the monomer conversion in the reactor reached 98%, 1,3-butadiene 540 g was added, and the reaction was carried out.

[0379] The final temperature in the reactor reached 76°C. Two minutes after reaching this peak reaction temperature, 2,2-dimethoxy-l-(3-trimethyloxysilylpropyl)-l-aza-2- silacyclopentane (Compound 1) 6.6 mmol was added to the reactor, and a 20 minute coupling reaction was performed. Methanol 6.0 mmol was added to the polymer solution as a reaction terminator, and a rubbery polymer solution (E-1) was obtained. A portion of the conjugated diene-based polymer solution was drawn off, and solvent was removed using a drier to obtain a rubbery polymer (E) before hydrogenation.

[0380] ((Production Example 6) Rubbery Polymer (F) Before Hydrogenation)

[0381] A high-pressure vessel with a capacity of 40 L, equipped with a stirrer and a jacket for temperature control, was used as the reactor, and 1,3-butadiene 3,000 g, from which impurities had been previously removed, cyclohexane 21,000 g, tetrahydrofuran (THF) 50 mmol as a polar substance, and 2,2-bis(2-tetrahydrofuryl)propane 6.7 mmol were added to the reactor, and the temperature in the reactor was maintained at 40°C. To the above reactor, n-butyllithium 45.0 mmol was supplied as a polymerization initiator.

[0382] After the start of the polymerization reaction, the temperature in the reactor began to rise due to the heat of polymerization, and the final temperature in the reactor reached 79°C. Two minutes after reaching this peak reaction temperature, 2,2-dimethoxy-l-(3-trimethyloxysilylpropyl)-l-aza-2- silacyclopentane (Compound 1) 8.0 mmol was added to the reactor, and a 20 minute coupling reaction was performed. Methanol 12.6 mmol was added to the polymer solution as a reaction terminator, and a rubbery polymer solution (F-1) was obtained. A portion of the conjugated diene-based polymer solution was drawn off, and solvent was removed using a drier to obtain a rubbery polymer (F) before hydrogenation.

[0383] ((Production Example 6) Rubbery Polymer (F) Before Hydrogenation)

[0384] A high-pressure vessel with a capacity of 40 L, equipped with a stirrer and a jacket for temperature control, was used as the reactor, and 1,3-butadiene 3,000 g, from which impurities had been previously removed, cyclohexane 21,000 g, tetrahydrofuran (THF) 50 mmol as a polar substance, and 2,2-bis(2-tetrahydrofuryl)propane 6.7 mmol were added to the reactor, and the temperature in the reactor was maintained at 40°C. To the above reactor, n-butyllithium 45.0 mmol was supplied as a polymerization initiator.

[0385] After the start of the polymerization, the temperature in the reactor began to rise due to the heat of polymerization, and after the monomer conversion in the reactor reached 98%, 540 g of 1,3-butadiene was added and the reaction was carried out.

[0386] The final temperature in the reactor reached 79°C. After 2 minutes from reaching the peak of the reaction temperature, 6.4 mmol of 2,2-dimethoxy-l-(3-trimethyloxysilylpropyl)-l-aza-2-silacyclopentane (Compound 1) was added to the reactor and a coupling reaction was carried out for 20 minutes. Methanol 6.1 mmol was added to the polymer solution as a reaction terminator, and a rubbery polymer solution (G-1) was obtained. A portion of the conjugated diene-based polymer solution was drawn out and desolvated using a desiccator to obtain a rubbery polymer before hydrogenation (G).

[0387] ((Manufacturing Example 8) Rubbery Polymer Before Hydrogenation (H))

[0388] A high-pressure vessel having a temperature-controllable agitator and jacket with a content volume of 40 L was used as the reactor, and 2,100 g of 1,3-butadiene, 360 g of styrene, 21,000 g of cyclohexane, 50 mmol of tetrahydrofuran (THF) as a polar substance, and 29.5 mmol of 2,2-bis(2-tetrahydrofuryl)propane were added to the reactor, and the temperature in the reactor was maintained at 40°C. To the above reactor, 34.7 mmol of n-butyllithium as a polymerization initiator was supplied.

[0389] After the start of the polymerization, the temperature in the reactor began to rise due to the heat of polymerization, and after the monomer conversion in the reactor reached 98%, 540 g of 1,3-butadiene was added and the reaction was carried out.

[0390] The final temperature in the reactor reached 76°C. After 2 minutes from reaching the peak of the reaction temperature, 6.9 mmol of 2,2-dimethoxy-l-(3-trimethyloxysilylpropyl)-l-aza-2-silacyclopentane (Compound 1) was added to the reactor and a coupling reaction was carried out for 20 minutes. Methanol 6.6 mmol was added to the polymer solution as a reaction terminator, and a rubbery polymer solution (H-1) was obtained. A portion of the conjugated diene-based polymer solution was drawn out and desolvated using a desiccator to obtain a rubbery polymer before hydrogenation (H).

[0391] (Preparation of Hydrogenation Catalyst (TC1))

[0392] To the reaction solution subjected to nitrogen substitution, dry and refined cyclohexane 1 L was charged, and bis(η5-cyclopentadienyl) titanium dichloride 100 mmol was added, and a solution containing trimethylaluminum 200 mmol in n-hexane was added while stirring was sufficiently performed, and the reaction was performed at room temperature for about 3 days to obtain a hydrogenation catalyst (TC1).

[0393] ((Manufacturing Example 9) Rubber-like Polymer (AH1))

[0394] To the rubber-like polymer solution (A-1) obtained in the above (Manufacturing Example 1), the above hydrogenation catalyst (TC1) was added at 60 ppm based on Ti per 100 parts by mass of the rubber-like polymer before hydrogenation, and a hydrogenation reaction was performed under a hydrogen pressure of 0.8 MPa at an average temperature of 85°C for 50 minutes. To the obtained rubber-like polymer solution, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid n-octadecyl ester 12.6 g as an antioxidant and 4,6-bis(octylthiomethyl) o-cresol 3.0 g were added, and then the rubber-like polymer solution was dropped into warm water, the solvent was removed, and drying treatment was performed using a drier to obtain a rubber-like polymer (AH1).

[0395] ((Manufacturing Example 10) Rubber-like Polymer (AH2))

[0396] Except that the amount of addition of the above hydrogenation catalyst (TC1) was changed to 70 ppm based on Ti per 100 parts by mass of the rubber-like polymer before hydrogenation, a rubber-like polymer (AH2) was obtained in the same manner as in the above (Manufacturing Example 9).

[0397] ((Manufacturing Example 11) Rubber-like Polymer (AH3))

[0398] Except that the amount of addition of the above hydrogenation catalyst (TC1) was changed to 74 ppm based on Ti per 100 parts by mass of the rubber-like polymer before hydrogenation, a rubber-like polymer (AH3) was obtained in the same manner as in the above (Manufacturing Example 9).

[0399] ((Manufacturing Example 12) Rubber-like Polymer (AH4))

[0400] Except that the amount of addition of the above hydrogenation catalyst (TC1) was changed to 80 ppm based on Ti per 100 parts by mass of the rubber-like polymer before hydrogenation, a rubber-like polymer (AH3) was obtained in the same manner as in the above (Manufacturing Example 9).

[0401] ((Manufacturing Example 13) Rubber-like Polymer (BH1))

[0402] To the rubbery polymer solution (B-1) obtained in the above (Production Example 2) was added the hydrogenation catalyst (TC1) at 85 ppm based on Ti per 100 parts by mass of the rubbery polymer before hydrogenation, and hydrogenation reaction was performed under hydrogen pressure of 0.8 MPa and average temperature of 85°C for 50 minutes. To the obtained solution of the rubbery polymer were added 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid n-octadecyl ester 12.6 g and 4,6-bis(octylthiomethyl) o-cresol 3.0 g as antioxidants, and then the rubbery polymer solution was added dropwise to warm water, the solvent was removed, and drying treatment was performed using a drier to obtain a rubbery polymer (BH1).

[0403] ((Production Example 14) Rubbery Polymer (CH1))

[0404] To the rubbery polymer solution (C-1) obtained in the above (Production Example 3) was added the hydrogenation catalyst (TC1) at 70 ppm based on Ti per 100 parts by mass of the rubbery polymer before hydrogenation, and hydrogenation reaction was performed under hydrogen pressure of 0.8 MPa and average temperature of 85°C for 50 minutes. To the obtained solution of the rubbery polymer were added 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid n-octadecyl ester 12.6 g and 4,6-bis(octylthiomethyl) o-cresol 3.0 g as antioxidants, and then the rubbery polymer solution was added dropwise to warm water, the solvent was removed, and drying treatment was performed using a drier to obtain a rubbery polymer (CH1).

[0405] ((Production Example 15) Rubbery Polymer (DH1))

[0406] To the rubbery polymer solution (D-1) obtained in the above (Production Example 4) was added the hydrogenation catalyst (TC1) at 60 ppm based on Ti per 100 parts by mass of the rubbery polymer before hydrogenation, and hydrogenation reaction was performed under hydrogen pressure of 0.8 MPa and average temperature of 85°C for 50 minutes. To the obtained solution of the rubbery polymer were added 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid n-octadecyl ester 12.6 g and 4,6-bis(octylthiomethyl) o-cresol 3.0 g as antioxidants, and then the rubbery polymer solution was added dropwise to warm water, the solvent was removed, and drying treatment was performed using a drier to obtain a rubbery polymer (DH1).

[0407] ((Production Example 16) Rubbery Polymer (EH1))

[0408] To the rubbery polymer solution (E-1) obtained in the above (Production Example 5) was added the hydrogenation catalyst (TC1) at 60 ppm based on Ti per 100 parts by mass of the rubbery polymer before hydrogenation, and hydrogenation reaction was performed at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C for 50 minutes. To the obtained rubbery polymer solution were added 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-n-octadecyl propionate 12.6 g and 4,6-bis(octylthiomethyl) o-cresol 3.0 g as antioxidants, and then the rubbery polymer solution was added dropwise to warm water, the solvent was removed, and drying treatment was performed using a drier to obtain a rubbery polymer (EH1).

[0409] ((Production Example 17) Rubbery Polymer (FH1))

[0410] To the rubbery polymer solution (F-1) obtained in the above (Production Example 6) was added the hydrogenation catalyst (TC1) at 60 ppm based on Ti per 100 parts by mass of the rubbery polymer before hydrogenation, and hydrogenation reaction was performed at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C for 60 minutes. To the obtained rubbery polymer solution were added 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-n-octadecyl propionate 12.6 g and 4,6-bis(octylthiomethyl) o-cresol 3.0 g as antioxidants, and then the rubbery polymer solution was added dropwise to warm water, the solvent was removed, and drying treatment was performed using a drier to obtain a rubbery polymer (FH1).

[0411] ((Production Example 18) Rubbery Polymer (GH1))

[0412] To the rubbery polymer solution (G-1) obtained in the above (Production Example 7) was added the hydrogenation catalyst (TC1) at 60 ppm based on Ti per 100 parts by mass of the rubbery polymer before hydrogenation, and hydrogenation reaction was performed at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C for 80 minutes. To the obtained rubbery polymer solution were added 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-n-octadecyl propionate 12.6 g and 4,6-bis(octylthiomethyl) o-cresol 3.0 g as antioxidants, and then the rubbery polymer solution was added dropwise to warm water, the solvent was removed, and drying treatment was performed using a drier to obtain a rubbery polymer (GH1).

[0413] ((Production Example 19) Rubbery Polymer (HH1))

[0414] To the rubbery polymer solution before hydrogenation (H-1) obtained in the above (Production Example 8), the above hydrogenation catalyst (TC1) was added at 60 ppm based on Ti per 100 parts by mass of the rubbery polymer before hydrogenation, and hydrogenation reaction was performed under a hydrogen pressure of 0.8 MPa at an average temperature of 90°C for 60 minutes. To the obtained rubbery polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol as antioxidants were added, and then the rubber composition solution was dropped into warm water, the solvent was removed, and drying treatment was performed using a drier to obtain a rubbery polymer (HH1).

[0415]

[0416] [Examples 1 to 35, Examples 36 to 41, Comparative Examples 1 to 11]

[0417] As the raw rubber components, the rubbery polymers shown in Table 1, high-cis polybutadiene (BR, "UBEPOL U150" manufactured by Ube Industries, Ltd.), and natural rubber (NR) were used, and rubber compositions containing each raw rubber were obtained in the proportions shown in Tables 2 to 9 below and the following.

[0418] Note that the amounts (parts by mass) of each raw rubber when the total amount of the (A) rubber component is set to 100 parts by mass are shown in the table.

[0419]

[0420]

[0421]

[0422] [Table 5]

[0423]

[0424]

[0425]

[0426] [Table 8]

[0427]

[0428] [Table 9]

[0429]

[0430] Regarding each component in Tables 2 to 9, the product names used are as described below.

[0431] • Silica 1 (trade name "Ultrasil 7000GR" manufactured by Evonik Degussa, nitrogen adsorption specific surface area 165 m2 / g) 2 / g)

[0432] • Silica 2 (trade name "Ultrasil 9100GR" manufactured by Evonik Degussa, nitrogen adsorption specific surface area 235 m2 / g) 2 / g)

[0433] • Carbon black (trade name "N234" manufactured by Cabot Japan)

[0434] • S-RAE oil (trade name "Process NC140" manufactured by JX Nippon Oil & Energy)

[0435] • Hydrogenated terpene (manufactured by Yasuhara Chemical, product name Clearon M125)

[0436] • Coupling agent (trade name "Si69" manufactured by Evonik Degussa, bis(triethoxysilylpropyl)tetrasulfide)

[0437] • Anti-aging agent (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine)

[0438] • Vulcanization accelerator 1 (CBS) (N-cyclohexyl-2-benzothiazylsulfenamide)

[0439] • Vulcanization accelerator 2 (DPG) (diphenyl guanidine)

[0440] • Wax (paraffin wax)

[0441] The above-described materials were kneaded by the following method to obtain a rubber composition.

[0442] Using a closed kneader (content volume 0.3 L) equipped with a temperature control device, as a first-stage kneading, the raw rubber (rubbery polymer, natural rubber, high-cis polybutadiene), filler (silica, carbon black), silane coupling agent, process oil, zinc white, and stearic acid were kneaded under conditions of a filling rate of 65% and a rotor rotation speed of 30 to 50 rpm.

[0443] At this time, the temperature of the closed mixer was controlled, and each rubber composition (compound) was obtained at a discharge temperature of 155 to 160°C.

[0444] Next, as a second-stage kneading, the compound obtained above was cooled to room temperature, and an anti-aging agent was added, and the kneading was performed again in order to improve the dispersibility of the silica-based inorganic filler.

[0445] In this case, the discharge temperature of the compound was adjusted to 145 to 150°C by temperature control of the mixer.

[0446] After cooling, as the third stage mixing, the rubber composition was mixed using an open mill set to 70°C with sulfur and vulcanization accelerator 1,2. Thereafter, molding was performed and vulcanization was performed for 25 minutes at 150°C using a vulcanization press. The properties of the rubber composition before vulcanization and the rubber composition after vulcanization were evaluated.

[0447] Specifically, the evaluation was performed by the following method. The results are shown in Tables 2 to 9.

[0448] [Evaluation of Properties]

[0449] (Evaluation 1) Processability: Compound Mooney Viscosity

[0450] The compound obtained after the second stage mixing and before the third stage mixing was used as a sample, and using a Mooney viscometer, after preheating for 1 minute at 130°C in accordance with JIS K6300-1, the rotor was rotated at 2 rotations per minute for 4 minutes, and then the viscosity was measured.

[0451] In Tables 2 to 5, the results of Comparative Example 1 were indexed to 100; in Tables 6 to 9, the results of Comparative Example 7 were indexed to 100. The larger the index, the better the processability.

[0452] In all of the indices, in Tables 2 to 5, the test results obtained using a tire using the rubber composition of Comparative Example 1 were taken as Δ, and in Tables 6 to 9, the results of Comparative Example 7 were taken as Δ, and cases in which optimization was performed in a range of 5% or more and less than 15% were taken as O, cases in which optimization was performed in a range of 15% or more and less than 20% were taken as, and cases in which optimization was performed in a range of 20% or more were taken as.

[0453] (Evaluation 2) Low Fuel Consumption: Viscoelasticity Parameter

[0454] A viscoelasticity tester "ARES" manufactured by Rheometric Scientific was used to measure the viscoelasticity parameter in a torsion mode.

[0455] For each measured value, in Tables 2 to 5, the results for the rubber composition of Comparative Example 1 were indexed to 100; in Tables 6 to 9, the results of Comparative Example 7 were indexed to 100.

[0456] The tan δ measured at 50°C at a frequency of 10 Hz and a strain of 3% was taken as an index of fuel consumption. The larger the index, the better the fuel consumption.

[0457] In all of the indices, the test results obtained from the tire using the rubber composition of Comparative Example 1 are taken as Δ in Tables 2 to 5, and the results of Comparative Example 7 are taken as Δ in Tables 6 to 9, and cases in which optimization is performed in a range in which the effect is 5% or more and less than 15% are marked as O, cases in which optimization is performed in a range in which the effect is 15% or more and less than 20% are marked as, and cases in which optimization is performed in a range in which the effect is 20% or more are marked as.

[0458] (3) Abrasion resistance

[0459] The abrasion amount at a load of 44.4 N and 1000 rotations was measured using an Akron abrasion tester (manufactured by Seishin Enterprise Co., Ltd.) in accordance with JIS K6264-2, and the results of Comparative Example 1 were indexed by taking 100 as the index in Tables 2 to 5; the results of Comparative Example 7 were indexed by taking 100 as the index in Tables 6 to 9. The larger the index, the better the abrasion resistance.

[0460] In all of the indices, the test results obtained from the tire using the rubber composition of Comparative Example 1 are taken as Δ in Tables 2 to 5, and the results of Comparative Example 7 are taken as Δ in Tables 6 to 9, and cases in which optimization is performed in a range in which the effect is 5% or more and less than 15% are marked as O, cases in which optimization is performed in a range in which the effect is 15% or more and less than 20% are marked as, and cases in which optimization is performed in a range in which the effect is 20% or more are marked as.

[0461] (4) Fatigue resistance under constant elongation

[0462] The number of times of elongation until the breakage under the conditions of a strain of 80% and a speed of 300 cpm when elongation was repeatedly performed was measured using a constant elongation fatigue tester (manufactured by MYS Co., Ltd.) in accordance with JIS K6260, and the results of Comparative Example 1 were indexed by taking 100 as the index in Tables 2 to 5, and the results of Comparative Example 7 were indexed by taking 100 as the index in Tables 6 to 9. The larger the index, the more the number of times of elongation until the breakage, and the better the fatigue resistance under constant elongation.

[0463] In all of the indices, the test results obtained from the tire using the rubber composition of Comparative Example 1 are taken as Δ in Tables 2 to 5, and the results of Comparative Example 7 are taken as Δ in Tables 6 to 9, and cases in which optimization is performed in a range in which the effect is 5% or more and less than 15% are marked as O, cases in which optimization is performed in a range in which the effect is 15% or more and less than 20% are marked as, and cases in which optimization is performed in a range in which the effect is 20% or more are marked as.

[0464] (5) Ride comfort when driving a truck after aging of the tire

[0465] A method of evaluating changes in performance in the later stages of use of the tire is shown.

[0466] Tires of 275 / 80R22.5 load index 151 in which each of the rubber compositions was used for the tread were produced, and after aging in a constant temperature chamber at 80°C for 72 hours, the tires were mounted on a vehicle loaded with 20 tons, and after traveling a distance of about 100 km including general roads and expressways, the ride comfort was evaluated.

[0467] If the tire is aged, the hardness increases or other physical properties change, thereby deteriorating the ride comfort.

[0468] In Tables 2 to 5, the results of Comparative Example 1 were indexed with 100, and in Tables 6 to 9, the results of Comparative Example 7 were indexed with 100.

[0469] In all of the indices, in Tables 2 to 5, the test results obtained with the tire using the rubber composition of Comparative Example 1 were taken as Δ, and in Tables 6 to 9, the results of Comparative Example 7 were taken as Δ, and cases in which optimization was performed in a range of 5% or more and less than 15% of the effect were marked as O, cases in which optimization was performed in a range of 15% or more and less than 20% were marked as, and cases in which optimization was performed in a range of 20% or more were marked as.

[0470] As shown in Tables 2 to 9, it was confirmed that the balance of processability, low fuel consumption, and wear resistance of the rubber compositions in Examples 1 to 41 was excellent compared to Comparative Examples 1 to 11, and furthermore, it was possible to suppress changes in performance of the tire in the later stage of use.

[0471] This application is based on Japanese Patent Application (Japanese Patent Application No. 2020-182774) filed in Japan Patent Office on October 30, 2020, the content of which is incorporated herein by reference in its entirety.

[0472] Industrial Applicability

[0473] The rubber composition of the present application has industrial applicability in the fields of treads of pneumatic tires for heavy load vehicles, interior and exterior materials for automobiles, shock absorbing rubbers, belts, footwear, foams, various industrial products, and the like.

Claims

1. A rubber composition comprising: 10 parts by mass or more and 90 parts by mass or less of a rubbery polymer, the rubbery polymer having an iodine value of 10 to 200, a content of ethylene structure of 3 mass% or more, a content of aromatic vinyl monomer block of less than 10 mass%, and a content of conjugated diene monomer unit of 2 mass% or more, the iodine value being a value expressed by converting the amount of halogen that reacts with 100 g of a subject substance into grams of iodine, as measured according to the method described in JIS K 0070:1992; and 10 parts by mass or more and 90 parts by mass or less of a natural rubber, 10 parts by mass or more and 90 parts by mass or less of a natural rubber, with respect to 100 parts by mass of the total amount of a rubber component including the rubbery polymer and the natural rubber, containing 20 parts by mass or more and 80 parts by mass or less of a silica-based inorganic filler and carbon black, the content of the silica-based inorganic filler being 60 parts by mass or less and the content of the carbon black being 60 parts by mass or less, the rubbery polymer including an aromatic vinyl monomer unit, the aromatic vinyl monomer being one or more selected from the group consisting of styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, a-methylstyrene, vinyl ethylbenzene, vinyl xylene, vinyl naphthalene, and diphenyl ethylene, a modification rate of the rubbery polymer being 40 mass% or more, the modification rate representing the mass proportion of a polymer having a functional group containing a nitrogen atom with respect to the total amount of the rubbery polymer.

2. The rubber composition of claim 1, wherein, a glass transition temperature (Tg) of the rubbery polymer being -35°C or lower.

3. The rubber composition of claim 1 or 2, wherein, the rubbery polymer being a conjugated diene-based polymer and including 5 mass% or more and 40 mass% or less of an aromatic vinyl monomer unit, and a 1,2-vinyl bond content in a conjugated diene monomer unit being 10 mol% or more and 60 mol% or less.

4. The rubber composition according to claim 1 or 2, wherein the iodine value (A) of the rubbery polymer, the content (B) of the silica-based inorganic filler and the content (C) of the carbon black in parts by mass with respect to 100 parts by mass of the total amount of the rubber component, the BET specific surface area (D) of the silica-based inorganic filler, and the BET specific surface area (E) of the carbon black have the following relationship of formula (1), Formula (1): 0 < (0.029 x ((B) x (D)) + ((C) x (E))) - (A) < 250.

5. The rubber composition of claim 1 or 2, wherein, further comprising less than 35 parts by mass of an oil and / or a ring-containing resin with respect to 100 parts by mass of the total amount of the rubber component.

6. The rubber composition of claim 1 or 2, wherein, further comprising less than 10 parts by mass of an oil with respect to 100 parts by mass of the total amount of the rubber component.

7. The rubber composition of claim 1 or 2, wherein, the iodine value of the rubbery polymer is 80 to 200, and the content of the aromatic vinyl monomer unit is 13 mass% or less.

8. The rubber composition of claim 1 or 2, wherein, the 1,2-vinyl bond content in the conjugated diene monomer unit of the rubbery polymer is 50 mol% or more and 60 mol% or less.

9. The rubber composition according to claim 1 or 2, wherein the iodine value (A) of the rubbery polymer, a content (B) of the silica-based inorganic filler and a content (C) of the carbon black, both in terms of mass parts per 100 mass parts of the total amount of the rubber component, a BET specific surface area (D) of the silica-based inorganic filler, and a BET specific surface area (E) of the carbon black has a relationship of the following formula (2), Formula (2): 0 < (0.029 x ((B) x (D)) + ((C) x (E))) - (A) < 136.

10. The rubber composition of claim 1 or 2, wherein, The content of the ethylene structure in the rubbery polymer is 5 mass% or more.

11. The rubber composition of claim 1 or 2, wherein, The content of the aromatic vinyl monomer block in the rubbery polymer is 5 mass% or less.

12. The rubber composition of claim 1 or 2, wherein, The content of the conjugated diene monomer unit in the rubbery polymer is 2 mass% or more and 50 mass% or less.

13. The rubber composition of claim 1 or 2, wherein, The modification rate of the rubbery polymer is 60 mass% or more.

14. The rubber composition of claim 1 or 2, wherein, The weight average molecular weight of the rubbery polymer is 200,000 or more and 500,000 or less.

15. The rubber composition of claim 1 or 2, wherein, The content of the silica-based inorganic filler is 56 mass parts or less per 100 mass parts of the total amount of the rubber component including the rubbery polymer and the natural rubber.

16. The rubber composition of claim 1 or 2, wherein, The silicon oxide-based inorganic filler has a nitrogen adsorption specific surface area, i.e., a BET specific surface area, of 100 m 2 / g or more and 300 m 2 / g or less, as determined by a BET adsorption method.

17. The rubber composition of claim 1 or 2, wherein, The content of the carbon black is 56 mass parts or less per 100 mass parts of the total amount of the rubber component including the rubbery polymer and the natural rubber.

18. The rubber composition of claim 1 or 2, wherein, The carbon black has a nitrogen adsorption specific surface area, i.e. BET specific surface area, of 5 m 2 / g or more and 200 m 2 / g or less, as determined by the BET adsorption method.

19. The rubber composition of claim 1 or 2, wherein, The total content of the silica-based inorganic filler and the carbon black is 30 mass parts or more and 60 mass parts or less per 100 mass parts of the total amount of the rubber component including the rubbery polymer and the natural rubber.

20. A tire comprising the rubber composition according to any one of claims 1 to 19.

21. A pneumatic tire having a crown comprising the rubber composition according to any one of claims 1 to 19, and having a load index of 100 or more and 170 or less.

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