Rubber composition

Abstract

To provide a rubber composition having high friction characteristics.SOLUTION: There is provided a rubber composition comprising a rubbery polymer containing a conjugated diene-based polymer and a silica-based filler, wherein the conjugated diene-based polymer has a glass transition temperature of -65°C or more and 0°C or less and a vulcanized molded body of the rubber composition satisfies the following <Condition (i)> and <Condition (ii)>. <Condition (i)> In dynamic viscoelasticity measurement, the storage modulus E' measured at 4.58% strain and 1.52 Hz frequency is 3.5 MPa or more and 5.5 MPa or less and E'-1 / 3 tanδ is 0.075 MPa-1 / 3 or more and 0.25 MPa-1 / 3 or less. <Condition (ii)> In dynamic viscoelasticity measurement, the storage modulus E' measured at 4.58% strain and 15.2 Hz frequency is 4.0 MPa or more and 7.0 MPa or less and E'-1 / 3 tanδ is 0.085 MPa-1 / 3 or more and 0.40 MPa-1 / 3 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition. [Background technology]

[0002] In recent years, slipping has accounted for a large proportion of falls in the workplace, which has led to a demand for shoe soles with high slip resistance on oily or wet floors. On the other hand, there are far more traffic accidents in rainy weather than in sunny weather, so tires are required to have high wet grip. In view of the above, there is a need for rubber materials with high friction properties. In conventionally known rubber compositions, viscoelastic properties are used to evaluate frictional properties, but the relationship between viscoelastic properties and frictional properties has not been fully clarified, and there is a problem in that rubber materials with high wear properties have not been sufficiently provided.

[0003] In order to solve the above-mentioned problems, Patent Document 1 proposes a rubber composition containing a solution-polymerized styrene-butadiene rubber and hydrous silica, which has a loss modulus (tan δ) peak in the temperature range of −10°C to −30°C in dynamic viscoelasticity measurement under specific conditions.

[0004] However, even in Patent Document 1, the relationship between viscoelasticity and frictional properties is still unclear, and further improvement is required. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-17717 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, although high frictional properties have been required of rubber compositions, there is a problem in that the relationship between the frictional properties and the viscoelastic properties used as an index of the frictional properties has not yet been clarified.

[0007] Therefore, in order to solve the above-mentioned problems of the conventional techniques, an object of the present invention is to provide a rubber composition with high friction characteristics by specifying the viscoelastic characteristics under specific conditions. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems of the prior art, the present inventors have conducted extensive research and have found that, in viscoelasticity measurements carried out under specific conditions, the storage modulus E' and E' -1 / 3 The inventors have found that a rubber composition with high friction characteristics can be obtained by specifying tan δ, and have thus completed the present invention. That is, the present invention is as follows.

[0009] [1] a rubbery polymer containing a conjugated diene-based polymer; a silica-based filler; A rubber composition comprising: the glass transition temperature of the conjugated diene polymer is −65° C. or higher and 0° C. or lower, The vulcanized molded article of the rubber composition satisfies the following <condition (i)> and <condition (ii)>: , Rubber composition. <Condition (i)> In dynamic viscoelasticity measurement, the storage modulus E' measured at a strain of 4.58% and a frequency of 1.52 Hz is 3.5 MPa or more and 5.5 MPa or less, and E' -1 / 3 tanδ is 0.075MPa -1 / 3 More than 0.25MPa -1 / 3 The following is the result. <Condition (ii)> In dynamic viscoelasticity measurement, the storage modulus E' measured at a strain of 4.58% and a frequency of 15.2 Hz is 4.0 MPa or more and 7.0 MPa or less, and E' -1 / 3tanδ is 0.085MPa -1 / 3 More than 0.40MPa -1 / 3 The following is the result. [2] The vulcanized molded article of the rubber composition satisfies the following <condition (iii)>: The rubber composition according to [1] above. <Condition (iii)> In dynamic viscoelasticity measurement, the storage modulus E' measured at a strain of 4.58% and a frequency of 152 Hz is 5.0 MPa or more and 10.0 MPa or less, and E' -1 / 3 tanδ is 0.090MPa -1 / 3 More than 0.50MPa -1 / 3 The following is the result. [3] The conjugated diene polymer is a modified conjugated diene polymer. The rubber composition according to [1] or [2] above. [4] The content of the silica-based filler is 20 parts by mass or more relative to 100 parts by mass of the conjugated diene polymer, The rubber composition according to any one of [1] to [3]. [5] The rubber composition is a rubber composition for shoes. The rubber composition according to any one of [1] to [4]. [Effects of the Invention]

[0010] According to the present invention, a rubber composition having high friction characteristics can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The following embodiments are merely examples for explaining the present invention, and the present invention is not limited to the following embodiments. The present invention can be practiced with appropriate modifications within the scope of its gist.

[0012] [Rubber composition] The rubber composition of the present embodiment is a rubbery polymer containing a conjugated diene-based polymer; a silica-based filler; Including, The vulcanized molded article of the rubber composition satisfies the following <condition (i)> and <condition (ii)>: . <Condition (i)> In dynamic viscoelasticity measurement, the storage modulus E' measured at a strain of 4.58% and a frequency of 1.52 Hz is 3.5 MPa or more and 5.5 MPa or less, and E' -1 / 3 tanδ is 0.075MPa -1 / 3 More than 0.25MPa -1 / 3 The following is the result. <Condition (ii)> In dynamic viscoelasticity measurement, the storage modulus E' measured at a strain of 4.58% and a frequency of 15.2 Hz is 4.0 MPa or more and 7.0 MPa or less, and E' -1 / 3 tanδ is 0.085MPa -1 / 3 More than 0.40MPa -1 / 3 The following is the result.

[0013] The friction of rubber compounds is largely determined by the adhesion term (μ adh ) and the hysteresis term (μ hys ) and the coefficient of friction (μ) can be expressed as their sum, then the coefficient of friction (μ) is expressed by the following formula. μ=μ adh +μ hys

[0014] In the above equation, the adhesion term (μ adh ) is thought to correlate with the adhesive area, i.e., the storage modulus E'. When the storage modulus E' becomes smaller, the adhesive area becomes larger, and the adhesion term (μ adh ) is expected to become larger. Hysteresis term (μ hys According to Amino et al. (Journal of the Japan Rubber Association, 74(3), 110(2001)), E' -1 / 3 It is proportional to tan δ. Adhesion term (μ adh ) and the hysteresis term (μ hysIn order to increase the coefficient of friction (μ), which is the sum of the adhesion term (μ adh ) and the hysteresis term (μ hys ) balance is important.

[0015] The friction coefficient (μ Gly ) was measured, the adhesion term (μ adh )<<hysteresis term (μ hys ) Furthermore, the fluid friction term (μ fluid ) in consideration of μ hys =μ Gly -μ fluid Assume that: At this time, the fluid friction term (μ fluid ) is calculated by the following formula (1) according to J. de Vicente et al. (Tribology Letters Vol. 20, (2005), pp. 273-286):

[0016]

number

[0017] In the above formula (1), SSR is the slip ratio, W is the normal load [N], v is the sliding speed [m / s], R is the typical curvature radius of the asphalt surface protrusion [m], η is the viscosity of the lubricant [Pa s], and E * : Complex elastic modulus [Pa], ν: Poisson's ratio. From this, the coefficient of friction without lubrication is μ Dry Then, μ adh =μ Dry -μ hys It can be calculated as follows. Specific μ Dry , μ Gly The measurement method is described in the Examples.

[0018] In the rubber composition of the present embodiment, for example, a direct-acting friction tester, model name "μV-1000" manufactured by Trinity Lab Co., Ltd., is used to measure the friction coefficient. Dry , μ Gly Specifically, a SUS304 ball (diameter 16.0 mm) is brought into contact with the surface under a normal load of 0.098 N, and the sliding speed v is set to 1.0 mm / s, 10.0 mm / s, and 100.0 mm / s. Dry , μ Gly The specific measurement method will be described in the Examples below. Also, μ fluid , μ hys , μ adh The calculated values ​​are also described in the Examples.

[0019] Based on the Hertz contact theory, the maximum strain and the radius of the strain region (1.5 times the contact radius) expected when the rubber composition of this embodiment comes into contact with a SUS304 ball were calculated to be 4.58% and 0.657 mm, respectively. The strain frequencies calculated from the time it takes for the SUS304 ball to pass through the strain region at v = 1.0 mm / s, 10.0 mm / s, and 100.0 mm / s were found to be 1.52 Hz, 15.2 Hz, and 152 Hz, respectively.

[0020] E' and tanδ were measured using a dynamic viscoelasticity measuring device (Metravib DMA+1000) at frequencies of 1 to 100 Hz and strains of 0.1 to 10%, respectively, and E' and tanδ were estimated at strains of 4.58% and frequencies of 1.52 Hz, 15.2 Hz, and 152 Hz. -1 / 3 Calculate tan δ.

[0021] In the dynamic viscoelasticity measurement of the rubber composition of this embodiment, E' is 3.5 MPa or more and 5.5 MPa or less when measured at a strain of 4.58% and a frequency of 1.52 Hz (condition (i)), and E' tan δ -1 / 3 is 0.075 MPa -1 / 3 More than 0.25MPa -1 / 3 or less (condition (i)). Preferably, E' is 3.5 MPa or more and 5.0 MPa or less, and E' tan δ -1 / 3is 0.080MPa -1 / 3 More than 0.20MPa -1 / 3 More preferably, E' is 4.0 MPa or more and 4.8 MPa or less, and E' tan δ -1 / 3 is 0.085 MPa -1 / 3 More than 0.20MPa -1 / 3 The following is the result. Furthermore, the rubber composition of this embodiment has E' of 4.0 MPa or more and 7.0 MPa or less when measured at a strain of 4.58% and a frequency of 15.2 Hz (condition (ii)), and E' tan δ -1 / 3 is 0.085 MPa -1 / 3 More than 0.40MPa -1 / 3 or less (condition (ii)). Preferably, E' is 4.0 MPa or more and 6.5 MPa or less, and E' tan δ -1 / 3 is 0.085 MPa -1 / 3 More than 0.38MPa -1 / 3 More preferably, E' is 4.5 MPa or more and 6.5 MPa or less, and E' tan δ -1 / 3 is 0.090 MPa -1 / 3 More than 0.35MPa -1 / 3 The following is the result. E' and E' -1 / 3 When tanδ is in the above-mentioned range, the adhesion term (μ adh ) and the hysteresis term (μ hys ) and has a high coefficient of friction μ, and tends to provide a rubber composition with high friction characteristics.

[0022] Furthermore, the rubber composition of the present embodiment preferably has E' of 5.0 MPa or more and 10.0 MPa or less when measured at a strain of 4.58% and a frequency of 152 Hz (condition (iii)), and E' tan δ -1 / 3 is 0.090 MPa -1 / 3 More than 0.50MPa -1 / 3 More preferably, E' is 5.5 MPa or more and 9.5 MPa or less, and E' tan δ -1 / 3 is 0.090 MPa -1 / 3 More than 0.38MPa -1 / 3 More preferably, E' is 5.5 MPa or more and 9.0 MPa or less, and E' tan δ -1 / 3is 0.095 MPa -1 / 3 More than 0.35MPa -1 / 3 The following is the result. E' and E' -1 / 3 When tanδ is in the above-mentioned range, the adhesion term (μ adh ) and the hysteresis term (μ hys ) and has a high coefficient of friction μ, and tends to provide a rubber composition with high friction characteristics.

[0023] In the rubber composition of this embodiment, E' and E' -1 / 3 Tan δ tends to be controllable within the above-mentioned range by adjusting the vinyl bond amount, aromatic vinyl monomer unit content, and glass transition temperature ranges of the conjugated diene polymer used in the rubber composition.

[0024] (Conjugated diene polymer) The rubber composition of the present embodiment contains a conjugated diene polymer. The conjugated diene polymer refers to a polymer obtained by polymerizing at least a conjugated diene compound, and also includes a copolymer obtained by copolymerizing a conjugated diene compound and an aromatic vinyl compound. In this specification, the term "compound" refers to a compound before polymerization, and the term "monomer unit" refers to a structural unit that constitutes a polymer.

[0025] <1,2-vinyl bond content> The conjugated diene polymer used in the rubber composition of this embodiment preferably has a 1,2-vinyl bond content of 15 mol% or more and 58 mol% or less. The 1,2-vinyl bond content of the conjugated diene polymer is more preferably 20 mol% or more and 58 mol% or less, and even more preferably 30 mol% or more and 58 mol% or less. When the 1,2-vinyl bond content is in the above range, E' and E' in the above-mentioned numerical ranges can be achieved. -1 / 3 Therefore, a rubber composition having a tan δ tends to be obtained. The 1,2-vinyl bond content of the conjugated diene polymer can be controlled within the above-mentioned numerical range by adjusting the amount of polar substance added to the polymerization initiator in the polymerization step, and the 1,2-vinyl bond content tends to increase by increasing the amount of polar substance added.

[0026] <Aromatic vinyl monomer unit content> The conjugated diene polymer used in the rubber composition of this embodiment preferably has an aromatic vinyl monomer unit content of 15% by mass or more and 45% by mass or less. The aromatic vinyl monomer unit content of the conjugated diene polymer is more preferably 20% by mass or more and 45% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less. When the aromatic vinyl monomer unit content is in the above range, E' and E' in the above-mentioned numerical ranges can be achieved. -1 / 3 This tends to result in a rubber composition with high friction characteristics having a tan δ. The content of the aromatic vinyl monomer unit in the conjugated diene polymer can be controlled within the above-mentioned range by adjusting the amount of monomer added in the polymerization step, the polymerization temperature and the polymerization time.

[0027] <Degeneration rate> The conjugated diene polymer of the present embodiment may be a modified conjugated diene polymer. The modification rate is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 65% ​​by mass or more. When the modification rate is within the above range, the interaction with the silica-based filler that is the reinforcing material of the outsole becomes stronger, and a rubber composition with high friction properties tends to be obtained while increasing dispersibility and improving processability. The upper limit of the modification rate is not particularly limited, but is, for example, 100% by mass. The modification rate of the modified conjugated diene polymer can be measured by a column adsorption GPC method, more specifically, by the method described in the examples. The modification rate can be controlled within the above range by adjusting the type and amount of the polymerization initiator and the amount of the modifying agent.

[0028] In this specification, the term "modification ratio" refers to the mass ratio of a polymer having a nitrogen atom-containing functional group to the total amount of the modified conjugated diene polymer. The position at which the nitrogen atom is introduced into the modified conjugated diene polymer may be the polymerization initiation terminal, in the molecular chain (including grafting), or at the polymerization terminal of the modified conjugated diene polymer. An example of a method for introducing a nitrogen atom into the polymerization initiation terminal is a method described in International Publication No. 2016 / 133202, which uses an organolithium compound containing a nitrogen atom as a polymerization initiator.

[0029] <Mooney viscosity> The conjugated diene polymer used in the rubber composition of the present embodiment preferably has a Mooney viscosity of 30 or more and 90 or less, more preferably 50 or more and 90 or less, and even more preferably 55 or more and 88 or less. When the conjugated diene polymer has a Mooney viscosity within the above range, the processability when made into a rubber composition tends to be excellent. If the Mooney viscosity is 30 or more, sufficient tensile strength tends to be obtained, and if it is 90 or less, excellent processability tends to be obtained. The Mooney viscosity can be measured using, for example, a Mooney viscometer (trade name "VR1132" manufactured by Ueshima Seisakusho Co., Ltd.) with an L-shaped rotor in accordance with JIS K6300 (ISO 289-1). Specifically, the sample is first preheated at 100°C for 1 minute, and then the rotor is rotated at 2 rpm. The torque after 4 minutes is measured to determine the Mooney viscosity at 100°C.

[0030] <Glass transition temperature> The conjugated diene polymer used in the rubber composition of the present embodiment has a glass transition temperature (Tg) of -65°C or higher and 0°C or lower, preferably -50°C or higher and 0°C or lower, and more preferably -35°C or higher and 0°C or lower. By having a glass transition temperature in the above range, E' and E' -1 / 3 This tends to result in a rubber composition with high friction characteristics having a tan δ. When the conjugated diene polymer used in the rubber composition of the present embodiment has a glass transition temperature (Tg) of -50°C or higher, the rubber composition tends to have excellent gripping properties, and when the glass transition temperature (Tg) is 0°C or lower, the rubber composition tends to have excellent wear resistance. The glass transition temperature (Tg) of the conjugated diene polymer used in the rubber composition of this embodiment tends to decrease by decreasing the aromatic vinyl / conjugated diene ratio, and by decreasing the amount of polar substance added relative to the amount of polymerization initiator added, the amount of 1,2-vinyl bonds decreases, and the glass transition temperature (Tg) tends to decrease. The glass transition temperature tends to decrease by about 1°C by decreasing the content of aromatic vinyl monomer units by 1 mass%, and by about 1.5°C by decreasing the amount of 1,2-vinyl bonds by 2 mol%. The amount of 1,2-vinyl bonds in conjugated diene polymers can be controlled by adjusting the amount of polar substance added to the polymerization initiator, and the amount of 1,2-vinyl bonds tends to increase by increasing the amount of polar substance added, which allows the glass transition temperature (Tg) to be controlled.

[0031] (Method of producing conjugated diene polymer) The conjugated diene polymer used in the rubber composition of this embodiment can be produced, for example, by carrying out a polymerization step in which a conjugated diene compound and an aromatic vinyl compound are polymerized using an organolithium compound as a polymerization initiator. In the case of a modified conjugated diene polymer, the polymer can be produced by carrying out a modification step in which a coupling agent containing a modifying group (hereinafter referred to as "modifier") is reacted with the active terminal of the conjugated diene polymer. As the modifier, one that can react with the active terminal of the conjugated diene polymer to produce a modified conjugated diene polymer having four or more branches is preferred from the viewpoint of processability of the modified conjugated diene polymer. From the viewpoint of polymerization productivity and obtaining a stable modification rate, preferred modifiers include, for example, isocyanate compounds, isothiocyanate compounds, isocyanuric acid derivatives, nitrogen-containing carbonyl compounds, nitrogen-containing vinyl compounds, nitrogen-containing epoxy compounds, and nitrogen-containing alkoxysilane compounds.

[0032] Examples of organolithium compounds as polymerization initiators include, but are not limited to, n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium. In particular, n-butyllithium and sec-butyllithium are preferred from the viewpoints of industrial availability and ease of control of the polymerization reaction.

[0033] As the polymerization initiator, an organolithium compound having no active hydrogen or a substituted amino group with a structure in which the active hydrogen is protected may be used. Examples of organolithium compounds having a substituted amino group with a structure that does not have active hydrogen include, but are not limited to, 3-dimethylaminopropyllithium, 3-diethylaminopropyllithium, 4-(methylpropylamino)butyllithium, and 4-hexamethyleneiminobutyllithium. Examples of alkyllithium compounds having an amino group with a structure in which an active hydrogen is protected include, but are not limited to, 3-bistrimethylsilylaminopropyllithium and 4-trimethylsilylmethylaminobutyllithium.

[0034] The organolithium compound having a substituted amino group can also be used as a solubilized oligomeric organolithium compound by reacting it with a small amount of a polymerizable monomer, such as 1,3-butadiene, isoprene, or styrene.

[0035] These organolithium compounds may be used alone or in combination of two or more, or may be used in combination with other organometallic compounds.

[0036] The Mooney viscosity of the conjugated diene polymer can be controlled by adjusting the amount of organolithium added in the polymerization step. That is, the Mooney viscosity decreases when the amount of organolithium added increases, and increases when the amount of organolithium added decreases. By utilizing this, the Mooney viscosity can be controlled to a desired value.

[0037] Conjugated diene compounds that are polymerization monomers used in the polymerization step include, but are not limited to, 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. Among these, from the viewpoint of ease of industrial availability, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred. These may be used alone or in combination of two or more.

[0038] Examples of aromatic vinyl compounds that are polymerization monomers used in the polymerization step include, but are not limited to, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene. Among these, styrene is preferred from the viewpoint of industrial availability. These may be used alone or in combination of two or more. By including such a structural unit based on an aromatic vinyl compound, the hardness of the conjugated diene polymer used in the rubber composition of this embodiment can be controlled when used as a material for the outsole of a shoe.

[0039] In the polymerization step, in addition to the above-mentioned polymerizable monomers, other monomers may also be used. Examples of other monomers include, but are not limited to, non-conjugated polyene compound monomers such as ethylidene norbornene, dicyclopentadiene, vinyl norbornene, and divinylbenzene; and cyclic non-conjugated polyene compound monomers such as dicyclopentadiene, vinyl norbornene, and ethylidene norbornene. By using such other monomers, when the conjugated diene-based polymer used in the rubber composition of the present embodiment is used as a material for the outsole of a shoe, the balance of breaking strength, friction properties, and abrasion resistance tends to be further improved. These may be used alone or in combination of two or more.

[0040] The polymerization reaction of the conjugated diene polymer is preferably carried out in a solvent. Examples of the solvent include, but are not limited to, hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific examples of the hydrocarbon solvent include, but are not limited to, aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; and hydrocarbons consisting of mixtures thereof.

[0041] In the polymerization step, a polar compound may be added. This allows the aromatic vinyl compound and the conjugated diene compound to be randomly copolymerized. Polar compounds tend to be usable as vinylating agents for controlling the microstructure of the conjugated diene moiety. They also tend to be effective in accelerating the polymerization reaction.

[0042] Examples of polar compounds include, but are not limited to, ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium tert-butylate, and sodium amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used alone or in combination of two or more.

[0043] The amount of polar compound used is not particularly limited and can be selected depending on the purpose, but is preferably 0.01 mol or more and 100 mol or less per mol of the polymerization initiator. Such polar compounds (vinylating agents) can be used in an appropriate amount depending on the desired vinyl bond amount as an agent for adjusting the microstructure of the conjugated diene portion in the polymer. Many polar compounds also have an effective randomizing effect in the copolymerization of a conjugated diene compound and an aromatic vinyl compound, and tend to be used as agents for adjusting the distribution of the aromatic vinyl compound or the amount of styrene blocks. As a method for randomizing a conjugated diene compound and an aromatic vinyl compound, for example, as described in JP-A-59-140211, a method may be used in which a copolymerization reaction is initiated with the entire amount of styrene and a portion of 1,3-butadiene, and the remaining 1,3-butadiene is intermittently added during the copolymerization reaction.

[0044] In the polymerization step, polymerization may be carried out by either a batch polymerization method or a continuous polymerization method, but from the viewpoint of stably producing a conjugated diene polymer with controlled high and low molecular weight components and branching, continuous polymerization is preferred, and polymerization in one reactor or a reactor in which two or more reactors are connected is more preferred. In order to make the conjugated diene polymer into a modified conjugated diene polymer with a modification rate of 30% by mass or more, the polymerization temperature in the polymerization step is preferably 50°C or higher and 100°C or lower, and the conjugated diene polymer is preferably polymerized at a solid content of 16.0% by mass or lower.

[0045] The modification step is not particularly limited, and can be carried out using a reactor equipped with a stirrer and capable of temperature control with a jacket, and an in-line mixer, static mixer, or the like may also be used. As the modifying agent used in the modification step, from the viewpoints of polymerization productivity and a high modification rate, a nitrogen-containing modifying agent is preferred, and examples thereof include isocyanate compounds, isothiocyanate compounds, isocyanuric acid derivatives, nitrogen-group-containing carbonyl compounds, nitrogen-group-containing vinyl compounds, nitrogen-group-containing epoxy compounds, and nitrogen-group-containing alkoxysilane compounds. Furthermore, from the viewpoint of processability when the rubber composition of the present embodiment is used as a material for an outsole, the number of branches of the modifier is preferably high. The number of branches is not particularly limited, but from the viewpoint of processability, 3 branches or more is preferred, and 4 branches or more is more preferred. The upper limit of the number of branches is not particularly limited, but from the viewpoint of processability, 30 branches or less is preferred.

[0046] The nitrogen-containing modifier may be a nitrogen-containing epoxy compound. Examples of the nitrogen-containing epoxy compound include, but are not limited to, N,N-diglycidyl-4-glycidoxyaniline, 1-N,N-diglycidylaminomethyl-4-glycidoxycyclohexane, 4-(4-glycidoxyphenyl)-(N,N-diglycidyl)aniline, 4-(4-glycidoxyphenoxy)-(N,N-diglycidyl)aniline, 4-(4-glycidoxybenzyl)-(N,N-diglycidyl)aniline, 4-(N,N'-diglycidyl-2-piperazinyl)-glycidoxybenzene, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-m-xylenediamine. , 4,4-methylene-bis(N,N-diglycidylaniline), 1,4-bis(N,N-diglycidylamino)cyclohexane, N,N,N',N'-tetraglycidyl-p-phenylenediamine, 4,4'-bis(diglycidylamino)benzophenone, 4-(4-glycidylpiperazinyl)-(N,N-diglycidyl)aniline, 2-[2-(N,N-diglycidylamino)ethyl]-1-glycidylpyrrolidine, N,N-diglycidylaniline, 4,4'-diglycidyl-dibenzylmethylamine, N,N-diglycidylaniline, N,N-diglycidylorthotoluidine, and N,N-diglycidylaminomethylcyclohexane. Of these, N,N-diglycidyl-4-glycidoxyaniline and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane are more preferred.

[0047] As these nitrogen-containing modifiers, nitrogen group-containing alkoxysilane compounds are more preferred from the viewpoint of polymerization productivity and a high modification rate of the conjugated diene polymer used in the rubber composition of the present embodiment.

[0048] Examples of the nitrogen group-containing alkoxysilane compound include, but are not limited to, 3-(4-methylpiperazin-1-yl)propyltriethoxysilane, 3-(4-methylpiperazin-1-yl)propyltrimethoxysilane, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(4-trimethoxy ... 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy-2-methyl-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-Ethoxy-2-ethyl-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy-2-methyl-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, 2-ethoxy-2-ethyl-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, tris(3-trimethoxysilylpropyl)amine, tris(3-methyldimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine tris(trimethoxysilylpropyl)amine, tris(3-methyldiethoxysilylpropyl)amine, tris(trimethoxysilylmethyl)amine, tris(2-trimethoxysilylethyl)amine, tris(4-trimethoxysilylbutyl)amine, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, and N1-(3-(bis(3-(trimethoxysilyl)propyl)amino)propyl)-N1-methyl-N3-(3-(methyl(3-(trimethoxysilyl)propyl)amino)propyl)-N3-(3-(trimethoxysilyl)propyl)-1,3-propanediamine.

[0049] In the method for producing the conjugated diene polymer used in the rubber composition of the present embodiment, a deactivator, a neutralizer, etc. may be added at the end of the polymerization step, if necessary. Examples of the deactivator include, but are not limited to, water; alcohols such as methanol, ethanol, and isopropanol; etc. The term "final stage of the polymerization process" used herein refers to a state in which 95% or more of the added monomers have been consumed in the polymerization. Examples of neutralizing agents include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, mainly 10 carbon atoms); aqueous solutions of inorganic acids; and carbon dioxide gas.

[0050] In the method for producing the conjugated diene polymer used in the rubber composition of the present embodiment, it is preferable to add a rubber stabilizer towards the end of the polymerization step from the viewpoint of preventing gel formation and improving processing stability. The rubber stabilizer is not limited to the following and known stabilizers can be used, but preferred are 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-butylphenol) propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol.

[0051] In the method for producing the conjugated diene-based polymer used in the rubber composition of the present embodiment, a rubber softener may be added as needed, for example, at the end of the polymerization step, from the viewpoint of improving polymer productivity and processability when a filler or the like is blended in the rubber composition when an outsole is produced using the rubber composition. Examples of rubber softeners include, but are not limited to, extender oils, liquid rubbers, resins, etc. From the viewpoints of processability, productivity, and economy, extender oils are preferred. The method for adding a rubber softener to a conjugated diene polymer is not limited to the following, but a preferred method is to add the rubber softener to a polymer solution, mix, and then remove the solvent from the resulting polymer solution containing the rubber softener.

[0052] Examples of extender oils include naphthenic oil and paraffin oil. The content of the extender oil in the rubber composition of the present embodiment is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of suppressing deterioration over time when used as an outsole material.

[0053] Examples of resins include, but are not limited to, aromatic petroleum resins, coumarone-indene resins, terpene resins, rosin derivatives (including tung oil resins), tall oil, tall oil derivatives, rosin ester resins, natural and synthetic terpene resins, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, mixed aliphatic-aromatic hydrocarbon resins, coumarin-indene resins, phenolic resins, p-tert-butylphenol-acetylene resins, phenol-formaldehyde resins, xylene-formaldehyde resins, monoolefin oligomers, diolefin oligomers, hydrogenated aromatic hydrocarbon resins, cyclic aliphatic hydrocarbon resins, hydrogenated hydrocarbon resins, hydrocarbon resins, hydrogenated tung oil resins, hydrogenated oil resins, and esters of hydrogenated oil resins with monofunctional or polyfunctional alcohols. These resins may be used alone or in combination of two or more. When hydrogenating, all of the unsaturated groups may be hydrogenated, or some may remain.

[0054] The effect of adding the resin is to improve the processability of a rubber composition containing the conjugated diene polymer and a filler, etc., and also tends to improve the breaking strength of a vulcanized product.

[0055] The conjugated diene polymer used in the rubber composition of the present embodiment can be obtained by removing the solvent from a polymer solution. As a method for obtaining the conjugated diene polymer, a known method can be used, such as a method of separating the solvent by steam stripping or the like, filtering the polymer, and then dehydrating and drying it to obtain the polymer, a method of concentrating the polymer in a flashing tank and then devolatilizing it with a vent extruder or the like, or a method of directly degassing it with a drum dryer or the like.

[0056] (Rubber polymer other than conjugated diene polymer in rubber component) The rubber composition of the present embodiment may contain, as a rubber component, a rubbery polymer other than the above-described conjugated diene-based polymer. Examples of the rubber-like polymer include diene rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), acrylonitrile-chloroprene rubber, acrylonitrile-isoprene rubber, styrene-chloroprene rubber, and styrene-isoprene rubber. These may be used alone or in combination. Preferred are rubber-like polymers selected from natural rubber, isoprene rubber, butadiene rubber, butyl rubber, acrylonitrile-butadiene rubber, and styrene-butadiene rubber, and more preferred are butadiene rubber (BR) and isoprene rubber (IR).

[0057] The above-mentioned conjugated diene polymer can be used alone as the rubber component constituting the rubber composition of this embodiment, but when a rubbery polymer other than the above-mentioned conjugated diene polymer is contained, the content of the rubbery polymer is preferably 10 mass % or more, more preferably 30 mass % or more, even more preferably 50 mass % or more, and still more preferably 60 mass % or more, based on the total amount of the rubber component. When the rubber composition of the present embodiment is used as an outsole material, the rubber polymer content within the above range tends to further improve abrasion resistance and breaking strength. Also, from the viewpoint of improving friction characteristics when the rubber composition of the present embodiment is used as an outsole material, the rubber polymer content is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

[0058] (filler) The rubber composition of the present embodiment contains a filler, and has a silica-based filler as an essential component. From the viewpoint of improving gripping properties and abrasion resistance when the rubber composition of the present embodiment is used as a material for an outsole, the content of the filler is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 35 parts by mass or more, per 100 parts by mass of the total amount of the rubber components. Furthermore, from the viewpoint of reducing weight when the rubber composition of the present embodiment is used as a material for an outsole, the content of the filler is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less, per 100 parts by mass of the total amount of the rubber component. From the viewpoint of reinforcement, the content of the silica-based filler is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 35 parts by mass or more, relative to 100 parts by mass of the conjugated diene-based polymer. Furthermore, from the viewpoint of weight reduction, the content is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, relative to 100 parts by mass of the conjugated diene-based polymer.

[0059] The filler used in the rubber composition of the present embodiment is preferably an inorganic filler. As the inorganic filler, in addition to silica-based fillers, known inorganic fillers can be used, and examples thereof include, but are not limited to, silica-based fillers such as clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, and glass fiber, light calcium carbonate, heavy calcium carbonate, various surface-treated calcium carbonates, magnesium carbonate, magnesium hydroxide, aluminum hydroxide, barium sulfate, magnesium sulfate, calcium sulfate, titanium oxide, magnesium oxide, alumina, and carbon.

[0060] The inorganic filler is an essential component of the rubber composition. Examples of the silica filler include dry silica, wet silica, and synthetic silicate silica. From the viewpoint of improving the interaction between the rubber component and the silica filler, the modifying group of the modifying agent is preferably an amino group.

[0061] (Silane coupling agent) The rubber composition of the present embodiment may contain a silane coupling agent. Silane coupling agents have groups that have affinity or bonding properties for both the rubber component and the silica-based filler, and function to strengthen the interaction between them. Generally, compounds that have a sulfur bond moiety, an alkoxysilyl group, and a silanol group moiety in one molecule are preferably used.

[0062] Examples of silane coupling agents include, but are not limited to, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silane [Si363 manufactured by Evonik Degussa], and NXT-Z30, NXT-Z45, NXT-Z60, and NXT silane manufactured by Momentive. Silane coupling agents containing mercapto groups, 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-trimethoxysilylethyl)tetrasulfide silane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide tetrasulfide, 3-triethoxysilylpropyl benzoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, and the like.

[0063] Among the silane coupling agents, mercapto group-containing silane coupling agents such as bis-[3-(triethoxysilyl)-propyl]-disulfide, ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silane [Si363 manufactured by Evonik Degussa], and NXT-Z30, NXT-Z45, NXT-Z60, and NXT silane manufactured by Momentive, and bis-[3-(triethoxysilyl)-propyl]-tetrasulfide are preferred from the viewpoint of high reinforcing effect. These silane coupling agents may be used alone or in combination of two or more.

[0064] The amount of the silane coupling agent is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of the rubber component, from the viewpoint of further enhancing the effect of intensifying the interaction between the rubber component and the silica-based filler. Also, from the viewpoint of improving processability, the amount of the silane coupling agent is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of the rubber component.

[0065] (rubber softener) The rubber composition of the present embodiment may contain a rubber softener in order to improve processability. Suitable rubber softeners include, for example, mineral oil-based rubber softeners and liquid or low-molecular weight synthetic softeners. The mineral oil-based rubber softeners are also called process oils or extender oils and are used to soften rubber, increase its volume, and improve its processability. Furthermore, the mineral oil-based rubber softeners are mixtures of aromatic rings, naphthenic rings, and paraffin chains. Softeners in which the carbon number of the paraffin chains accounts for 50% or more of the total carbons are called paraffinic, those in which the carbon number of the naphthenic rings is 30 to 45% are naphthenic, and those in which the aromatic carbon number is more than 30% are called aromatic. As the rubber softener used together with the conjugated diene polymer used in the rubber composition of this embodiment, one having an appropriate aromatic content is preferred because it tends to have good affinity with the conjugated diene polymer.

[0066] [Method for producing rubber composition] The rubber composition of the present embodiment can be produced by mixing a rubber component containing the above-described conjugated diene polymer and, if necessary, other rubbery polymers, a silica-based filler, if necessary other fillers, and, if necessary, additives such as a silane coupling agent and a rubber softener. The mixing method is not limited to the following, but examples thereof include a melt-kneading method using a general mixer such as an open roll, a Banbury mixer, a kneader, a single-screw extruder, a twin-screw extruder, or a multi-screw extruder, and a method in which the components are dissolved and mixed and then the solvent is removed by heating.

[0067] Among these, melt-kneading methods using a roll, a Banbury mixer, a kneader, or an extruder are preferred from the viewpoints of productivity and good kneading ability. In addition, either a method of kneading the constituent materials of the rubber composition of the present embodiment all at once or a method of mixing them in several batches can be applied.

[0068] The rubber composition of the present embodiment may be vulcanized using a vulcanizing agent to form a vulcanized composition. Examples of the vulcanizing agent include, but are not limited to, radical generators such as organic peroxides and azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. The sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, polymeric polysulfur compounds, and the like.

[0069] From the viewpoint of improving breaking strength through a reinforcing effect, the content of the vulcanizing agent is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of the total amount of the rubber component consisting of the conjugated diene polymer and the rubbery polymer. From the viewpoint of improving flexibility and elongation at break, the content of the vulcanizing agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

[0070] As the vulcanization method, a conventionally known method can be applied, and the vulcanization temperature is not particularly limited, but from the viewpoint of shortening the vulcanization time and increasing production efficiency, it is preferably 120°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. Also, from the viewpoint of suppressing thermal degradation during vulcanization, it is preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower.

[0071] In vulcanization, a vulcanization accelerator may be used as needed. As the vulcanization accelerator, a conventionally known material can be used, and examples thereof include, but are not limited to, sulfenamide compounds, guanidine compounds, thiuram compounds, aldehyde-amine compounds, aldehyde-ammonia compounds, thiazole compounds, thiourea compounds, and dithiocarbamate compounds.

[0072] Furthermore, examples of the vulcanization accelerator include, but are not limited to, zinc oxide and stearic acid.

[0073] 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, per 100 parts by mass of the total amount of the rubber components.

[0074] To the rubber composition of the present embodiment, various additives other than those described above, such as softeners, fillers, heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, and lubricants, may be added within a range that does not impair the object of the present embodiment. Known materials can be used for the heat stabilizer, antistatic agent, weather stabilizer, antioxidant, colorant, and lubricant.

[0075] [Rubber composition for shoes] The rubber composition of this embodiment is suitable as a rubber composition for shoes. The rubber composition for shoes of this embodiment is particularly suitable for use as a rubber composition for shoe soles. That is, by using the rubber composition for shoe soles of this embodiment, an outsole having excellent abrasion resistance and gripping properties can be obtained. The rubber composition for shoes of this embodiment can be used as a sole material for all types of footwear, including, but not limited to, sports shoes, running shoes, trekking shoes, and casual shoes. [Example]

[0076] Hereinafter, the present embodiment will be described in detail with reference to specific production examples, examples, and comparative examples, but the present invention is not limited to the following examples and comparative examples. Hereinafter, "parts" means "parts by mass" unless otherwise specified. Various physical properties in the Production Examples, Examples and Comparative Examples were measured by the methods shown below.

[0077] [Physical Properties of Conjugated Diene Polymers] (Mooney viscosity) The Mooney viscosity was measured using a Mooney viscometer (trade name "VR1132" manufactured by Ueshima Seisakusho Co., Ltd.) in accordance with JIS K6300 (ISO 289-1) using an L-shaped rotor. First, the sample was preheated at 100°C for 1 minute, and then the rotor was rotated at 2 rpm. The torque was measured after 4 minutes to determine the Mooney viscosity at 100°C.

[0078] (denaturation rate) The modification rate is calculated by utilizing the adsorption characteristics of a modified conjugated diene polymer in a specific column. Furthermore, a column with this characteristic adsorbs nitrogen. In other words, the modification rate is the proportion of nitrogen-containing conjugated diene polymers. The modification rate of the modified conjugated diene polymer was measured by a column adsorption GPC method as follows, utilizing the property of the modified conjugated diene polymer to be adsorbed onto a column. The amount of adsorption onto the silica-based column was measured by subtracting the chromatogram of a sample solution containing the sample and low-molecular-weight internal standard polystyrene measured using a column packed with polystyrene-based gel from the chromatogram measured using a column packed with silica-based gel, and the modification rate was calculated. The GPC measurement conditions using a polystyrene column are as follows: 20 μL of the measurement solution below was injected into the GPC measurement device and the measurement was carried out. <GPC measurement conditions using a polystyrene column> Device: Tosoh Corporation, product name "HLC-8320GPC" Eluent: THF containing 5mmol / L triethylamine Guard column: Tosoh Corporation's product name "TSKguardcolumn SuperH-H" Column: Tosoh Corporation product names "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" connected in this order Oven temperature: 40°C Flow rate: 0.6mL / min Detector: RI detector (Tosoh HLC8020) Measurement solution: 10 mg of sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a sample solution. The conditions for GPC measurement using a silica column are as follows: 50 μL of the measurement solution below was injected into the GPC measurement device and measurement was carried out. <GPC measurement conditions using a silica column> Device: Tosoh Corporation, product name "HLC-8320GPC" Eluent:THF Guard column: GL Sciences product name "DIOL 4.6 x 12.5 mm 5 micron" Separation column: Agilent Technologies' Zorbax PSM-1000S, PSM-300S, and PSM-60S columns connected in this order Oven temperature: 40℃, Flow rate: 0.5mL / min Detector: RI detector (Tosoh HLC8020) <Calculation method of denaturation rate>: The total peak area of ​​the chromatogram using the polystyrene-based column was set to 100, the peak area of ​​the sample was set to P1, the peak area of ​​the standard polystyrene was set to P2, and the total peak area of ​​the chromatogram using the 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 (% by mass) was calculated using the following formula. Modification rate (mass%) = [1-(P2 x P3) / (P1 x P4)] x 100 (However, P1+P2=P3+P4=100)

[0079] (Aromatic vinyl monomer unit content) 100 mg of the sample was dissolved in 100 mL of chloroform to prepare a measurement sample. The content (mass%) of the aromatic vinyl monomer unit relative to 100 mass% of the sample conjugated diene polymer was measured based on the amount of absorption at the ultraviolet absorption wavelength (around 254 nm in the case of styrene) by the aromatic group of the aromatic vinyl monomer unit. The measurement device used was a spectrophotometer "UV-2450" manufactured by Shimadzu Corporation.

[0080] (1,2-vinyl bond content) 50 mg of sample was dissolved in 10 mL of carbon disulfide to prepare a measurement sample. Using a solution cell, the infrared spectrum was measured from 600 to 1000 cm -1The absorbance at a predetermined wave number was measured in the range of 100 Hz to 100 Hz, and the microstructure of the butadiene moiety, i.e., the 1,2-vinyl bond content (mol%) was determined according to the calculation formula of Hampton's method (method described in R.R. Hampton, Analytical Chemistry 21, 923 (1949)). The measuring device used was a Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation.

[0081] (glass transition temperature (Tg)) In accordance with ISO 22768:2006, a differential scanning calorimeter "DSC3200S" manufactured by Mac Science was used to record a DSC curve while raising the temperature from -100°C at 20°C / min under a helium flow of 50 mL / min, and the peak top (inflection point) of the DSC differential curve was taken as the glass transition temperature.

[0082] [Production of Conjugated Diene Polymer] (Production Example 1) Conjugated Diene Polymer A One autoclave with an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom, an outlet at the top, and a stirrer and a jacket for temperature control was used. Furthermore, a static mixer was connected just before the raw material inlet of the reactor. 1,3-butadiene, from which impurities such as water had been removed, was mixed at 18.7 g / min, styrene at 11.0 g / min, and n-hexane at 185.6 g / min to obtain a mixed solution. Just before this mixed solution entered the first reactor, n-butyllithium for impurity inactivation treatment was fed at 0.020 phm, mixed in the static mixer, and then continuously fed to the bottom of the first reactor. Furthermore, 0.291 phm of 2,2-bis(2-oxolanyl)propane as a polar substance and 0.075 phm of NBL (normal butyl lithium) as a polymerization initiator were continuously fed to the bottom of the reactor, and the temperature inside the reactor was maintained at 82°C to obtain a rubber solution. The rubber solution produced in the reactor was supplied to a static mixer from the top of the reactor, and a reaction was carried out before the static mixer by continuously supplying M1 (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) as a modifier at a ratio of 1.0 equivalent (however, the amount added was calculated assuming that 4 moles of NBL react with 1 mole of M1) to the lithium of NBL supplied as a polymerization initiator, thereby obtaining a conjugated diene polymer A. The physical properties of the conjugated diene polymer A are shown in Table 1.

[0083] (Production Examples 2 to 4) Conjugated Diene Polymers B to D (Comparative Production Example 1) Conjugated Diene Polymer E Conjugated diene polymers B to E were obtained under the conditions shown in Table 1 below using the same procedure as for conjugated diene polymer A.

[0084] [Table 1]

[0085] [Production of Rubber Composition] (Examples 1 to 4), (Comparative Example 1) The conjugated diene polymers A to E prepared as described above were kneaded in the formulations shown in Table 2 below by the following method to obtain first-stage rubber compositions. In Table 2, the one using the conjugated diene polymer A is indicated as "blending A." Similarly, the compositions using conjugated diene polymers B to E are denoted as "compounds B to E," respectively. In the first stage of mixing, raw rubber (conjugated diene polymer and specified rubber), inorganic filler (silica), silane coupling agent, zinc oxide, stearic acid, and antioxidant were mixed at a filling rate of 65% and a rotor rotation speed of 30 rpm using an internal mixer (capacity 0.6 L) equipped with a temperature control device. At this time, the temperature of the internal mixer was controlled, and the discharge temperature was 125 to 135°C to obtain a first-stage rubber composition. Thereafter, in the second stage of kneading, the rubber composition discharged in the first stage was passed through an open roll set at 73° C. seven times to obtain a second stage rubber compound. After cooling, in the third stage of kneading, sulfur and vulcanization accelerators 1 and 2 were added to the second stage compound in the parts by mass shown in Table 3 below and kneaded using an open roll set at 73°C. Thereafter, the rubber was molded and vulcanized at 160°C in a vulcanizing press to obtain vulcanized rubber sheets A to E. Vulcanized rubber sheets corresponding to the conjugated diene polymers A to E are designated A to E, respectively. The properties of the vulcanized rubber sheets were evaluated. Specifically, the evaluation was carried out by the method described below. The evaluation results are shown in Table 4 below.

[0086] The materials used for each component in Tables 2 and 3 are as follows: Conjugated diene polymers: Conjugated diene polymers of Production Examples 1 to 4 and Comparative Production Example 1 in Table 1 (The conjugated diene polymers A to E used are referred to as Blends A to E, respectively.) BR (Ube Industries' "UBEPOL U150") Silica (trade name "Ultrasil VN3" manufactured by Evonik Degussa) Silane coupling agent (Evonik Degussa brand name "Si69", bis(triethoxysilylpropyl)tetrasulfide) Antioxidant (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) Vulcanization accelerator 1 (2-mercaptobenzothiazole: MBT) Vulcanization accelerator 2 (N-(tert-butyl)-2-benzothiazole sulfenamide: TBBS)

[0087] [Evaluation of Rubber Composition] (Rating 1:μ Dry , μ Gly , μ fluid ) Measurements were carried out using a direct acting friction tester manufactured by Trinity Lab, model name "μV-1000". A petri dish and a vulcanized rubber sheet (20mm x 100mm x 2mm) were fixed on the stage, and a SUS304 ball (diameter 16.0mm) was brought into contact with the plate under a normal load of 0.098N without wetting. The frictional force was measured when the plate was slid at sliding speeds of v = 1.0mm / s, 10.0mm / s, and 100.0mm / s over a sliding distance of d = 50mm. The measurement was repeated five times, and the average value of the friction coefficient without lubrication at d = 20.0 mm to 40.0 mm was calculated as μ Dry It was decided. Using the same measurement procedure, the average friction coefficient when lubricated with glycerin was measured. Gly It was decided. μ fluid When calculating μ, the following three values ​​are calculated according to the proviso of the above formula (1), and these values ​​are used to calculate μ as described below. fluid was calculated.

[0088]

number

[0089] According to the above formula (1), μ fluid was calculated. The conditions are shown below. Slip ratio SSR = 2, normal load W = 0.098 [N], representative radius of curvature of asphalt surface protrusion R = 0.008 [m], lubricant viscosity η = 1.35 [Pa·s] (for vulcanized rubber sheet A), 1.21 [Pa·s] (for vulcanized rubber sheet B), 1.25 [Pa·s] (for vulcanized rubber sheet C), 1.30 [Pa·s] (for vulcanized rubber sheet D), 1.29 [Pa·s] (for vulcanized rubber sheet E), Poisson's ratio ν = 0.49

[0090] (Rating 2: E', E * , tanδ) Storage modulus E' and complex modulus E *The tan δ was measured using a dynamic viscoelasticity measuring device (DMA+1000 manufactured by Metravib) with a frequency of 1 to 100 Hz and a strain of 0.1 to 10%, respectively, on a vulcanized rubber sheet (5 mm × 50 mm × 2 mm) as the measurement sample, using a film shear jig. Storage modulus E' and complex modulus E * Since tanδ changes depending on the strain and frequency, by mapping the measurement results, the storage modulus E' and complex modulus E were calculated at a strain of 4.58% (corresponding to the strain of the SUS304 ball (diameter 16.0 mm) when measuring the friction coefficient described above) and frequencies of 1.52 Hz, 15.2 Hz, and 152 Hz (corresponding to the frequencies of sliding velocities v = 1.0 mm / s, 10.0 mm / s, and 100.0 mm / s, respectively, when measuring the friction coefficient described above). * , tanδ is estimated, and E' -1 / 3 The tan δ was calculated.

[0091] [Table 2]

[0092] [Table 3]

[0093] [Table 4]

[0094] As shown in Table 4, E' and E' measured under specific conditions -1 / 3 It was found that the rubber compositions with specified tan δ, that is, the Examples, were rubber compositions with higher friction characteristics than the Comparative Examples. As shown in Table 4, by satisfying the above-mentioned <Condition (i)> and <Condition (ii)>, it was found that high friction characteristics could be obtained, especially at low sliding speeds of around 1 mm / s and 10 mm / s. At high speeds of about 100 mm / s, improvement in frictional characteristics was confirmed even in Comparative Example 1, which does not satisfy the above-mentioned <Condition (iii)>. However, a comparison of Examples 2 and 4 with Example 3 made it clear that satisfaction of <Condition (iii)> ensures a more reliable improvement in frictional characteristics. For example, when applied to shoes, the conditions during normal walking are closer to low speeds of 1 mm / s or 10 mm / s than to high speeds of 100 mm / s, so improvement at low speeds is more desirable. [Industrial Applicability]

[0095] The rubber composition of the present invention is useful in the field of shoe soles, particularly as a sole material for general footwear such as sports shoes, running shoes, trekking shoes, and casual shoes, and further has industrial applicability as a material for various components such as tires, rubber compositions for housing, and industrial products including vibration-isolating rubber.

Claims

1. a rubbery polymer containing a conjugated diene-based polymer; a silica-based filler; A rubber composition comprising: the glass transition temperature of the conjugated diene polymer is −65° C. or higher and 0° C. or lower, The vulcanized molded article of the rubber composition satisfies the following <Condition (i)> and <Condition (ii)>: 、 Rubber composition. <Condition (i)> In dynamic viscoelasticity measurement, the storage modulus E' measured at a strain of 4.58% and a frequency of 1.52 Hz is 3.5 MPa or more and 5.5 MPa or less, and E' -1 / 3 tanδ is 0.075 MPa -1 / 3 0.25MPa or more -1 / 3 The following is the result. <Condition (ii)> In dynamic viscoelasticity measurement, the storage modulus E' measured at a strain of 4.58% and a frequency of 15.2 Hz is 4.0 MPa or more and 7.0 MPa or less, and E' -1 / 3 tanδ is 0.085 MPa -1 / 3 More than 0.40 MPa -1 / 3 The following is the result.

2. The vulcanized molded article of the rubber composition satisfies the following <Condition (iii)>: The rubber composition according to claim 1. <Condition (iii)> In dynamic viscoelasticity measurement, the storage modulus E' measured at a strain of 4.58% and a frequency of 152 Hz is 5.0 MPa or more and 10.0 MPa or less, and E' -1 / 3 tan δ is 0.090 MPa -1 / 3 More than 0.50 MPa -1 / 3 The following is the result.

3. The conjugated diene polymer is a modified conjugated diene polymer. The rubber composition according to claim 1.

4. The content of the silica-based filler is 20 parts by mass or more relative to 100 parts by mass of the conjugated diene polymer, The rubber composition according to claim 1.

5. The rubber composition is a rubber composition for shoes. The rubber composition according to any one of claims 1 to 4.

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