Modified conjugated diene-based polymer, rubber composition for shoes and outsole

Abstract

To provide a modified conjugated diene-based polymer which is excellent in tensile strength, has a good balance of grip performance and wear resistance, in particular is excellent in grip performance and can obtain a light-weight rubber composition for shoes because an inorganic filler can be reduced.SOLUTION: There is provided a modified conjugated diene-based polymer having a glass transition temperature (Tg) of -40°C or more, wherein based on the total area 100% of the molecular weight distribution curve obtained by GPC (gel permeation chromatography), the area of the molecular weight distribution curve of a component having a bound aromatic vinyl content of 30 mass% or less is 20% or more, the area of the molecular weight distribution curve of a component having a bound aromatic vinyl content of 40 mass% or more is 20% or more and in the molecular weight distribution curve, the area region of a component having a bound aromatic vinyl content of 40 mass% or more is present on the higher molecular weight side than the area region of a component having a bound aromatic vinyl content of 30 mass% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a modified conjugated diene-based polymer, a rubber composition for shoes, and an outsole. [Background technology]

[0002] Conventionally, rubber compositions for shoes (e.g., rubber compositions for shoe soles, such as materials for manufacturing outsoles) have been required to have grip performance to enhance safety, strength to withstand loads and impact forces associated with the wearer's exercise, and abrasion resistance. From the perspective of reducing the weight of shoes, it has been proposed to use foams as shoe sole materials. However, foams have the problem of being inferior in abrasion resistance to non-foamed materials (see, for example, Patent Document 1).

[0003] A common method for improving the abrasion resistance of rubber compositions is to compound inorganic fillers such as carbon black, calcium carbonate, and silica. White inorganic fillers such as silica and calcium carbonate are generally used because they allow for coloring of shoe soles and enhance design. However, inorganic fillers such as silica have a lower affinity with rubber materials than carbon black, and therefore the dispersibility of silica in rubber materials is not necessarily good. This poor dispersibility leads to problems such as reduced processability, abrasion resistance, and mechanical strength of the rubber composition.

[0004] In response to the above-mentioned problems, Patent Document 2 proposes a rubber composition for shoe soles whose main component is a conjugated diene rubber having a structure in which a specific functional group is bonded to a conjugated diene polymer chain. However, the technology disclosed in Patent Document 2 has the problem that although it improves the processability of the rubber composition, it still does not sufficiently improve the grip and abrasion resistance of the rubber composition as a shoe sole material.

[0005] Furthermore, Patent Document 3 discloses a foam composition containing 1,2-polybutadiene, vinyl-cis-butadiene rubber, a thermoplastic polymer, a foaming agent, and a crosslinking agent, and describes that the foam composition is useful as a shoe sole composition. However, the foam composition disclosed in Patent Document 3 has problems in that strength, abrasion resistance, etc. are still insufficient and there is room for improvement. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-236905 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-162777 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-16518 Summary of the Invention [Problem to be solved by the invention]

[0007] In the technical field of shoe rubber compositions used for outsoles and the like, there is a demand for high levels of both grip and abrasion resistance, and in addition to these properties, there is also a demand for tensile strength and light weight when used as a shoe rubber composition, but these have not yet been achieved with the above-mentioned conventional technologies.

[0008] In view of the above-mentioned problems of the prior art, the present invention aims to provide a modified conjugated diene-based polymer that has excellent tensile strength and an excellent balance between gripping property and abrasion resistance, which are contradictory properties, and that is particularly excellent in gripping property, and that can provide a lightweight rubber composition for shoes by reducing the amount of inorganic filler added; a rubber composition for shoes containing the modified conjugated diene-based polymer; and an outsole. [Means for solving the problem]

[0009] As a result of extensive research into solving the problems of the prior art described above, the present inventors have found that the problems of the prior art described above can be solved by controlling the amount of bound aromatic vinyl at each molecular weight of a modified conjugated diene-based polymer and specifying the glass transition temperature, and have thus completed the present invention. That is, the present invention is as follows.

[0010] [1] The area of the molecular weight distribution curve obtained by GPC (gel permeation chromatography) measurement is 100%, and the area of the molecular weight distribution curve of the component having a bound aromatic vinyl content of 30% by mass or less is 20% or more, the area of the molecular weight distribution curve of the component having a bound aromatic vinyl content of 40% by mass or more is 20% or more; In the molecular weight distribution curve, an area region of components in which the amount of bound aromatic vinyl is 40% by mass or more is located on the higher molecular weight side than an area region of components in which the amount of bound aromatic vinyl is 30% by mass or less, Glass transition temperature (Tg) is higher than -40°C. Modified conjugated diene polymer. [2] For a total area of 100% of the molecular weight distribution curve, The area ratio of components with molecular weights of 100,000 or less is 5% or more, The area ratio of components with a molecular weight of 1,000,000 or more is 5% or more, The modified conjugated diene polymer according to [1] above. [3] The following conditions (1) and (2) are met: The modified conjugated diene polymer according to [1] or [2] above. <Condition (1)> The Mooney viscosity measured under the conditions of JIS K6300 (ISO 289-1) is 30 to 100. <Condition (2)> The modification rate is 30% by mass or more. [4] the modified conjugated diene polymer contains a polymer having a conjugated diene monomer unit and an aromatic vinyl monomer unit and having a nitrogen atom-containing functional group; The modified conjugated diene polymer according to any one of [1] to [3] above. [5] 100 parts by mass of a rubber component containing the modified conjugated diene polymer according to any one of [1] to [4] above; 20 parts by mass or more of an inorganic filler (B); A rubber composition for shoes comprising: [6] the rubber component contains a rubbery polymer (C) other than the modified conjugated diene-based polymer, the content of the modified conjugated diene polymer in the rubber component is 90% by mass or less, The content of the rubber-like polymer (C) in the rubber component is 10% by mass or more. The rubber composition for shoes described in [5] above. [7] An outsole comprising the rubber composition for shoes according to [5] or [6]. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a modified conjugated diene-based polymer which has excellent tensile strength, an excellent balance between gripping property and abrasion resistance, and in particular excellent gripping property, and which enables a reduction in the amount of inorganic filler, thereby obtaining a lightweight rubber composition for shoes; a rubber composition for shoes containing the modified conjugated diene-based polymer; and an outsole. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing an example of the relationship between molecular weight and the amount (mass %) of bound aromatic vinyl in a molecular weight distribution curve. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. Note that the following present embodiment is an example for explaining the present invention, and the present invention is not limited to the following embodiment. The present invention can be carried out with appropriate modifications within the scope of its gist. In this specification, for example, when a numerical range is expressed as "1 to 100," it is intended to include both the lower limit value "1" and the upper limit value "100." The same applies to other numerical ranges.

[0014] [Modified conjugated diene polymer] In the modified conjugated diene polymer of the present embodiment, the area of the molecular weight distribution curve of components having a bound aromatic vinyl content of 30% by mass or less is 20% or more relative to the total area of the molecular weight distribution curve (100%) obtained by GPC (gel permeation chromatography), The modified conjugated diene polymer has an area of 20% or more in a molecular weight distribution curve for components having a bound aromatic vinyl content of 40% by mass or more, and the area region of the components having a bound aromatic vinyl content of 40% by mass or more in the molecular weight distribution curve is located on the higher molecular weight side than the area region of components having a bound aromatic vinyl content of 30% by mass or less, and has a glass transition temperature (Tg) of higher than -40°C. According to the present embodiment, it is possible to provide a modified conjugated diene-based polymer from which a rubber composition for shoes can be obtained which has excellent tensile strength, an excellent balance between gripping property and abrasion resistance, and a good balance of mechanical strengths such as tensile strength even when the amount of inorganic filler added is reduced.

[0015] The modified conjugated diene polymer of the present embodiment is suitably used as a vulcanizate. The vulcanizate can be obtained, for example, by mixing the modified conjugated diene polymer of the present embodiment with an inorganic filler such as silica or carbon black, a rubbery polymer (C) component other than the modified conjugated diene polymer of the present embodiment, a silane coupling agent, a vulcanizing agent, a vulcanization accelerator, and a vulcanization aid to form a rubber composition, and then heating and vulcanizing the composition. The modified conjugated diene polymer of this embodiment will be described in detail below.

[0016] (Amount of bound aromatic vinyl) In the modified conjugated diene polymer of this embodiment, the area of the molecular weight distribution curve of components having a bound aromatic vinyl of 30% by mass or less is 20% or more, preferably 23% or more, and more preferably 26% or more, relative to the total area (100%) of the molecular weight distribution curve obtained by GPC. Also, in the modified conjugated diene polymer of this embodiment, the area of the molecular weight distribution curve of components having a bound aromatic vinyl of 40% by mass or more is 20% or more, preferably 23% or more, and more preferably 26% or more. Furthermore, in the modified conjugated diene-based polymer of this embodiment, the area region of the component having a bound aromatic vinyl content of 40% by mass or more is located on the polymer side relative to the area region of the component having a bound aromatic vinyl content of 30% by mass or less, and the glass transition temperature (Tg) is higher than −40° C. By adjusting the amount of bound aromatic vinyl and the area thereof in the molecular weight distribution curve obtained by GPC to the above-mentioned ranges, the modified conjugated diene-based polymer of the present embodiment tends to have a good balance between gripping properties and abrasion resistance, and also tends to have good mechanical strength such as tensile strength even when the amount of inorganic filler added is reduced, making it an advantageous rubber composition for shoes. When the area of the molecular weight distribution curve of the component having a bound aromatic vinyl of 30% by mass or less is present relative to 100% of the total area obtained by GPC of the modified conjugated diene polymer of this embodiment, the rubber composition for shoes of this embodiment tends to have good abrasion resistance, and when the area of the molecular weight distribution curve is 20% or more, the rubber composition for shoes of this embodiment tends to have good gripping properties. Furthermore, when the rubber composition for shoes of this embodiment contains a component having a bound aromatic vinyl of 40% by mass or more, the rubber composition for shoes of this embodiment tends to have good gripping properties, and when the area of the molecular weight distribution curve of the component having a bound aromatic vinyl of 40% by mass or more is 20% or more, the rubber composition for shoes of this embodiment tends to have even better gripping properties.

[0017] In the modified conjugated diene polymer of this embodiment, the area of the molecular weight distribution curve obtained by GPC, of components having a bound aromatic vinyl content of 30% by mass or less, is 20% or more, and the area of the molecular weight distribution curve, of components having a bound aromatic vinyl content of 40% by mass or more, is 20% or more, relative to the total area (100%) of the molecular weight distribution curve, and components having a high bound aromatic vinyl content are present on the polymer side, and the glass transition temperature (Tg) is higher than -40°C. In the shoe rubber composition using the modified conjugated diene polymer of this embodiment, when high-cis butadiene with a high cis bond content is used as the rubbery polymer (C) other than the modified conjugated diene polymer of this embodiment, if the bonded aromatic vinyl content of the modified conjugated diene polymer of this embodiment is 30% by mass or less, compatibility with the high-cis butadiene tends to be improved, and the processability and gripping properties of the shoe rubber composition of this embodiment tend to be improved. If the bonded aromatic vinyl content of the modified conjugated diene polymer is 40% by mass or more, compatibility with the high-cis butadiene tends to be poor, and the wear resistance and tensile strength of the shoe rubber composition using the modified conjugated diene polymer of this embodiment tend to be improved.

[0018] The area region of the molecular weight distribution curve for the component with a bound aromatic vinyl content of 40% by mass or more is located on the higher molecular weight side than the area region of the molecular weight distribution curve for the component with a bound aromatic vinyl content of 30% by mass or less. In other words, the presence of components with a high bound aromatic vinyl content on the higher molecular weight side tends to increase the hardness of the resulting shoe rubber composition. Using the modified conjugated diene polymer of this embodiment makes it possible to reduce the amount of inorganic filler, such as silica, used in the production of shoe rubber compositions. Furthermore, the area region of the molecular weight distribution curve for the component with a bound aromatic vinyl content of 40% by mass or more is located on the higher molecular weight side than the area region of the molecular weight distribution curve for components with a bound aromatic vinyl content of 30% by mass or less. This tends to increase the mechanical strength, such as tensile strength, of the resulting shoe rubber composition. Inorganic fillers, such as silica, are used as reinforcing materials in shoe rubber compositions, but their high specific gravity tends to increase the overall mass and hardness. Therefore, since the area region of the molecular weight distribution curve for the component having a bound aromatic vinyl content of 40% by mass or more is located on the higher molecular weight side than the area region of the molecular weight distribution curve for the component having a bound aromatic vinyl content of 30% by mass or less, it becomes possible to reduce the amount of inorganic filler such as silica to be compounded when the shoe rubber composition is prepared, and there is a tendency for the shoe rubber composition to have a good balance between weight reduction and hardness, as well as mechanical strength such as tensile strength.

[0019] The modified conjugated diene-based polymer of the present embodiment, in which the area of the molecular weight distribution curve of components having a bound aromatic vinyl content of 30% by mass or less is 20% or more, the area of the molecular weight distribution curve of components having a bound aromatic vinyl content of 40% by mass or more is 20% or more, and the area region of the molecular weight distribution curve of components having a bound aromatic vinyl content of 40% by mass or more is located on the higher molecular weight side than the area region of the molecular weight distribution curve of components having a bound aromatic vinyl content of 30% by mass or less, can be produced by the method shown in the method for producing a modified conjugated diene-based polymer described below. The amount of bound aromatic vinyl and the area in the molecular weight distribution curve can be measured by the method described in the Examples below.

[0020] (glass transition temperature) The modified conjugated diene polymer of this embodiment has a glass transition temperature of higher than -40°C. By having a glass transition temperature within this range, the rubber composition for shoes of this embodiment tends to have a good balance between gripping property and abrasion resistance, and tends to have particularly good gripping property. When the modified conjugated diene polymer of this embodiment has a lower glass transition temperature, the rubber composition for shoes tends to have improved gripping property while maintaining abrasion resistance. The modified conjugated diene polymer of this embodiment preferably has a glass transition temperature of higher than -40°C and 0°C or lower, more preferably from -30°C to -10°C, and even more preferably from -20°C to -10°C. The glass transition temperature of the modified conjugated diene polymer of this embodiment tends to decrease by decreasing the mass ratio of aromatic vinyl to conjugated diene, 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 tends to decrease. In other words, by adjusting these amounts, the glass transition temperature can be controlled within the above-mentioned numerical range. The glass transition temperature tends to be lowered by about 1°C by reducing the amount of aromatic vinyl by 1 mass%, and by about 1.5°C by reducing the amount of 1,2-vinyl bonds by 2 mol%.

[0021] (1,2-vinyl bond content) In the rubber composition for shoes of this embodiment, when high-cis butadiene with a high cis bond content is used as the rubbery polymer (C) other than the modified conjugated diene polymer of this embodiment, the compatibility with high-cis butadiene tends to improve as the 1,2-vinyl bond content of the modified conjugated diene polymer of this embodiment increases, and the processability and gripping properties of the rubber composition for shoes of this embodiment tend to improve. The compatibility with high-cis butadiene tends to decrease as the 1,2-vinyl bond content of the modified conjugated diene polymer of this embodiment decreases, and the abrasion resistance and tensile strength of the rubber composition for shoes of this embodiment tend to improve. From this viewpoint, the 1,2-vinyl bond content of the modified conjugated diene polymer of the present embodiment is preferably from 20 to 60 mol %, more preferably from 25 to 60 mol %, and even more preferably from 30 to 55 mol %. The vinyl bond content of the modified conjugated diene polymer can be measured by the method described in the Examples below, and can be controlled to fall within the above-mentioned numerical range by adjusting the amount of polar substance added to the polymerization initiator in the polymerization step. The 1,2-vinyl bond content tends to increase by increasing the amount of polar substance added.

[0022] The modified conjugated diene polymer of the present embodiment preferably satisfies the following conditions from the viewpoint of obtaining a modified conjugated diene polymer that can further improve the balance between gripping property and abrasion resistance of the shoe rubber composition of the present embodiment and further improve the balance of mechanical strength such as tensile strength while reducing the blending amount of inorganic filler.

[0023] (area ratio of molecular weights below 100,000) In the modified conjugated diene polymer of this embodiment, the area ratio of the molecular weight distribution curve of components having a molecular weight of 100,000 or less is preferably 5% or more relative to the total area (100%) of the molecular weight distribution curve obtained by GPC. By making the area ratio of the molecular weight distribution curve of components having a molecular weight of 100,000 or less 5% or more, the gripping properties of the rubber composition for shoes of this embodiment tend to be further improved. The area ratio of the molecular weight distribution curve of components having a molecular weight of 100,000 or less is more preferably 6% or more, even more preferably 7% or more, and still more preferably 8% or more. There is no particular upper limit to the area ratio of the molecular weight distribution curve of components having a molecular weight of 100,000 or less, but it may be, for example, 30% or less. The area ratio of the molecular weight distribution curve of the component having a molecular weight of 100,000 or less can be controlled, for example, by adjusting the amount of polymerization initiator added in the polymerization step. If the amount of polymerization initiator is small, the molecular weight distribution curve of the resulting modified conjugated diene polymer obtained by GPC will be shifted overall to the high molecular weight side, and the area ratio of the molecular weight of 100,000 or less will tend to be small. If the amount of polymerization initiator is large, the molecular weight distribution curve of the resulting modified conjugated diene polymer obtained by GPC will be shifted overall to the low molecular weight side, and the area ratio of the molecular weight of 100,000 or less will tend to be large. Furthermore, the area ratio of the molecular weight distribution curve of the component having a molecular weight of 100,000 or less can be controlled to 5% or more by the method described below in the production method for the modified conjugated diene polymer.

[0024] (area ratio of molecular weights of 1,000,000 or more) The area ratio of the molecular weight distribution curve of components with a molecular weight of 1,000,000 or more is preferably 5% or more relative to the total area (100%) of the molecular weight distribution curve obtained by GPC of the modified conjugated diene polymer of this embodiment. By setting the area ratio of components with a molecular weight of 1,000,000 or more to 5% or more, the durability of the rubber composition for shoes of this embodiment tends to be further improved. The area ratio of components with a molecular weight of 1,000,000 or more is more preferably 6% or more, even more preferably 7% or more, and even more preferably 8% or more. The upper limit of the area ratio of components with a molecular weight of 1,000,000 or more is not particularly limited, but may be, for example, 30% or less. The area ratio of components with a molecular weight of 1,000,000 or less can be controlled by adjusting the amount of polymerization initiator added, similar to the area ratio of components with a molecular weight of 100,000 or less.

[0025] (Mooney viscosity) The modified conjugated diene polymer of this embodiment preferably has a Mooney viscosity of 30 to 100. By setting the Mooney viscosity within this range, a rubber composition for shoes that exhibits excellent gripping properties and high abrasion resistance tends to be obtained. The Mooney viscosity is more preferably 40 to 100, even more preferably 50 to 100, and even more preferably 60 to 100. The Mooney viscosity of the modified conjugated diene polymer of this embodiment can be measured using 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 is measured after 4 minutes, and the Mooney viscosity at 100°C can be measured. The Mooney viscosity tends to increase when the modified conjugated diene polymer has a high molecular weight, a high modification rate, and a multi-branched structure, and can be controlled by adjusting the amount of polymerization initiator and the amount of modifier added to the active terminal of the conjugated diene polymer. The Mooney viscosity can also be controlled by the method described later in the production method of the modified conjugated diene polymer.

[0026] (denaturation rate) In this specification, the "modification ratio" represents the mass ratio of the 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 of this embodiment may be any of the polymerization initiation terminal, the molecular chain (including graft), and the polymerization terminal. Examples of a method for introducing a nitrogen atom into the polymerization initiation terminal include a method using an organolithium compound containing a nitrogen atom as a polymerization initiator, as described in WO2016 / 133202. The modified conjugated diene polymer of the present embodiment preferably has a modification rate of 30% by mass or more. A modification rate of 30% by mass or more allows a rubber composition for shoes to be obtained that exhibits excellent gripping properties and high abrasion resistance, and also improves the dispersibility of the silica-based inorganic filler, resulting in excellent processability and enabling the polymer to exhibit excellent properties when used as an outsole material. The modified conjugated diene polymer of the present embodiment has a modification rate of more preferably 50% by mass or more, even more preferably 60% by mass or more, and even more preferably 68% by mass or more. 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, and more specifically, by the method described in the examples. The modification rate can be controlled within the above-mentioned range by adjusting the amount of the modifying agent used or by adjusting the polymerization temperature as described below.

[0027] (Molecular weight distribution (Mw / Mn)) The molecular weight distribution (Mw / Mn) of the modified conjugated diene polymer of the present embodiment is not particularly limited, but is preferably, for example, 1.5 to 3.5. When the molecular weight distribution is in this range, a rubber composition for shoes tends to be obtained that has excellent processability when vulcanized and exhibits excellent gripping properties and abrasion resistance. Furthermore, from the viewpoints of improving productivity when vulcanized and safety and durability when used as an outsole material, the modified conjugated diene polymer of this embodiment preferably has a molecular weight distribution (Mw / Mn) of 1.5 or more and 3.5 or less, more preferably 1.7 or more and 3.0 or less, and even more preferably 1.8 or more and 2.6 or less, although this does not apply when the modified conjugated diene polymer of this embodiment is used as a mixture with another conjugated diene polymer. The molecular weight distribution can be controlled by adjusting the residence time distribution and the amount of modifier added in the polymerization step. The modified conjugated diene polymer of this embodiment may be a single modified conjugated diene polymer, or a mixture of a single modified conjugated diene polymer and at least one other polymer. The molecular weight distribution may be a unimodal molecular weight distribution without peaks, valleys, and peaks, or a multimodal molecular weight distribution with peaks, valleys, and peaks, and therefore the molecular weight distribution (Mw / Mn) is not limited to 1.5 to 3.5.

[0028] (Weight average molecular weight (Mw)) The weight-average molecular weight (Mw) of the modified conjugated diene polymer of this embodiment is preferably 200,000 or more, more preferably 300,000 or more, from the viewpoint of the shape stability of a molded article of the shoe rubber composition of this embodiment and the tensile strength and abrasion resistance of a crosslinked article using the shoe rubber composition. On the other hand, from the viewpoint of the processability when the shoe rubber composition is made into a crosslinkable composition, the weight-average molecular weight (Mw) is preferably 1,500,000 or less, more preferably 1,000,000 or less, and even more preferably 500,000 or less. The weight-average molecular weight can be controlled by adjusting the amount of polymerization initiator and modifier added. The weight-average molecular weight can be increased by reducing the amount of polymerization initiator added. The weight-average molecular weight increases when the amount of modifier added is increased relative to the lithium at the active end of the conjugated diene polymer. The weight-average molecular weight is maximized when one equivalent is added relative to the lithium at the active end. Adding more than one equivalent of modifier tends to decrease the weight-average molecular weight.

[0029] The weight average molecular weight and molecular weight distribution can be calculated from the polystyrene-equivalent molecular weight measured by GPC, and specifically, can be determined by the method described in the Examples below.

[0030] (Polymer structure) The modified conjugated diene polymer of this embodiment is preferably a polymer obtained by copolymerizing at least a conjugated diene compound and an aromatic vinyl compound, followed by reaction with a nitrogen-containing modifying agent. That is, the modified conjugated diene polymer of this embodiment preferably contains conjugated diene monomer units and aromatic vinyl monomer units, and also contains a nitrogen-atom-containing functional group. When a modifying agent having multiple functional groups is used, coupling proceeds simultaneously with modification, resulting in a modified polymer having branches. Branched polymers are preferred because they tend to be more easily mixed with fillers and the like than linear polymers of the same molecular weight. For example, a modified conjugated diene polymer having a multibranched structure with four or more branches can be obtained by reacting a low-molecular-weight compound having four or more nitrogen-atom-containing modifying groups with the active terminal of a conjugated diene polymer.

[0031] By modifying the active terminals of a conjugated diene polymer using a nitrogen atom-containing low molecular weight compound as a modifier, the interaction with inorganic fillers such as silica and carbon black improves, the dispersibility of the inorganic filler compounded improves, the processability when vulcanized improves, and the gripping properties and abrasion resistance tend to improve.

[0032] In this embodiment, the term "compound" refers to a compound before polymerization, and the term "monomer unit" refers to a structural unit that constitutes a polymer.

[0033] Conjugated diene compounds 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, 1,3-butadiene and isoprene are preferred from the viewpoint of industrial availability. 1,3-butadiene is more preferred. These compounds may be used alone or in combination of two or more.

[0034] Examples of aromatic vinyl compounds 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 compounds may be used alone or in combination of two or more. By including a structural unit based on such an aromatic vinyl compound, the hardness of the modified conjugated diene polymer of this embodiment when used as an outsole material can be adjusted.

[0035] The modified conjugated diene polymer of the present embodiment may also have monomer units derived from other compounds other than the conjugated diene monomer units and aromatic vinyl monomer units. Examples of other compounds include, but are not limited to, non-conjugated polyene compounds such as ethylidene norbornene, dicyclopentadiene, vinyl norbornene, and divinylbenzene; and cyclic non-conjugated polyene compounds such as dicyclopentadiene, vinyl norbornene, and ethylidene norbornene. The use of such other compounds tends to improve the balance of breaking strength, gripping properties, and abrasion resistance when the modified conjugated diene polymer of the present embodiment is used as an outsole material. These compounds may be used alone or in combination of two or more.

[0036] [Method for producing modified conjugated diene polymer] The method for producing the modified conjugated diene polymer of the present embodiment can include, for example, a step of polymerizing a conjugated diene compound and an aromatic vinyl compound using an organolithium compound as a polymerization initiator to obtain a conjugated diene polymer, and a step of reacting an active terminal of the conjugated diene polymer with a modifying agent containing a modifying group to obtain a modified conjugated diene polymer. The modifier is preferably one that can react with the active terminal of a conjugated diene polymer to produce a modified conjugated diene polymer having four or more branches, and the modified conjugated diene polymer is preferable from the viewpoint of processability. As such a modifier, from the viewpoint of polymerization productivity and obtaining a stable modification rate, an isocyanate compound, an isothiocyanate compound, an isocyanuric acid derivative, a nitrogen-containing carbonyl compound, a nitrogen-containing vinyl compound, a nitrogen-containing epoxy compound, a nitrogen-containing alkoxysilane compound, etc. are preferable.

[0037] In the method for producing a modified conjugated diene polymer of the present embodiment, polymerization may be carried out by either a batch polymerization method or a continuous polymerization method. However, from the viewpoint of stably producing a conjugated diene polymer having controlled high-molecular-weight components, low-molecular-weight components, and branching, polymerization is preferably carried out by a continuous polymerization method, and polymerization is more preferably carried out in one reactor or in a reactor in which two or more reactors are connected together. To achieve a modification rate of 30% by mass or more, the polymerization temperature is preferably 50° C. or more and 100° C. or less, and the conjugated diene polymer is preferably polymerized with a solid content of 16.0% by mass or less.

[0038] The modification step in which the modifying agent is reacted is not particularly limited, but is preferably carried out using, for example, a reactor equipped with a stirrer and capable of controlling the temperature with a jacket, an in-line mixer, a static mixer, or the like.

[0039] The polymerization reaction of the conjugated diene polymer is preferably carried out in a solvent. Examples of the solvent include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific hydrocarbon solvents 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.

[0040] In order to adjust the Mooney viscosity of the modified conjugated diene polymer of the present embodiment to 30 to 100, when a modifier that reacts with the active terminals of the conjugated diene polymer to form four branches is added, the weight average molecular weight of the conjugated diene polymer before the modification reaction is preferably 400,000 or less, more preferably 350,000 or less, and even more preferably 300,000 or less. The lower limit is preferably 200,000 or more. When a modifier that gives three branches is added, the weight average molecular weight of the conjugated diene polymer before the modification reaction is preferably 250,000 or more and 350,000 or less.

[0041] When a modifier for tri- or tetra- or more branches is reacted with the active terminals of a conjugated diene polymer having a molecular weight of 200,000 to 300,000 before modification, the amount of modifier added is preferably 0.4 to 1.0 equivalent relative to the active terminals. The modification rate of the modified conjugated diene polymer is adjusted to 30% by mass or more, and the weight-average molecular weight is preferably adjusted to 250,000 or more, more preferably 300,000 or more. The upper limit of the weight-average molecular weight is preferably 500,000 or less, more preferably 450,000 or less, and even more preferably 400,000 or less.

[0042] By adjusting the weight average molecular weight of the conjugated diene polymer before the modification reaction and the modification rate and weight average molecular weight of the modified conjugated diene polymer after the modification reaction within the above ranges, the Mooney viscosity of the modified conjugated diene polymer of this embodiment can be controlled to 30 to 100.

[0043] The modification rate of the modified conjugated diene polymer of this embodiment is preferably 30% by mass or more as described above, and the modification rate can be controlled by adjusting the amount of modifier added relative to the active terminals of the conjugated diene polymer before modification. The modification rate can be increased by increasing the amount of modifier added relative to the active terminals of the conjugated diene polymer. Furthermore, the area of components having a molecular weight of 100,000 or less in the molecular weight distribution curve of the modified conjugated diene polymer of this embodiment can be increased because the amount of unmodified conjugated diene polymer can be increased by increasing the amount of polymerization initiator added, decreasing the molecular weight, and decreasing the modification rate.

[0044] In order to control the area of components having a molecular weight of 100,000 or less in the molecular weight distribution curve of the modified conjugated diene polymer of this embodiment to 5% or more, it is effective to adjust the weight average molecular weight of the conjugated diene polymer to 300,000 or less and the modification rate to 70% by mass or less. However, the control method is not limited to this, since the area varies depending on the selected values of the weight average molecular weight and the modification rate.

[0045] The weight average molecular weight of the modified conjugated diene polymer of the present embodiment can be controlled by adjusting the weight average molecular weight before the modification reaction and the modification rate. For example, to adjust the weight average molecular weight of a modified conjugated diene polymer to 500,000, the weight average molecular weight of the conjugated diene polymer before modification is adjusted to 320,000, and a modifier that imparts four branches to the active terminals of the conjugated diene polymer is added to obtain a modified conjugated diene polymer with a modification rate of 45% by mass.

[0046] In the molecular weight distribution curve of the modified conjugated diene polymer of this embodiment, productivity tends to improve by making the area of components with a molecular weight of 100,000 or less 5% or more. By making the area of components having a molecular weight of 1,000,000 or more in the molecular weight distribution curve of the modified conjugated diene polymer of this embodiment 5% or more, the durability of the modified conjugated diene polymer of this embodiment when used as an outsole material is improved and tends to be economically advantageous.

[0047] As described above, from the viewpoints of improving productivity when vulcanized and safety and durability when used as an outsole material, the modified conjugated diene polymer of this embodiment preferably has a molecular weight distribution (Mw / Mn) of 1.5 or more and 3.5 or less, more preferably 1.7 or more and 3.0 or less, and even more preferably 1.8 or more and 2.6 or less, except when the modified conjugated diene polymer of this embodiment is mixed with another conjugated diene polymer.

[0048] The molecular weight distribution can be controlled by selecting a polymerization method such as batch polymerization or continuous polymerization. Continuous polymerization tends to produce a modified conjugated diene polymer with a broad molecular weight distribution. The molecular weight distribution also tends to be broadened by adding an excessive amount or a small amount of modifier to the active terminal of the conjugated diene polymer.

[0049] The modified conjugated diene polymer of this embodiment is a modified conjugated diene polymer in which, relative to the total area of the molecular weight distribution curve (100%), the area of the molecular weight distribution curve for components having a bound aromatic vinyl content of 30% by mass or less is 20% or more, and the area of the molecular weight distribution curve for components having a bound aromatic vinyl content of 40% by mass or more is 20% or more, the area region of the components having a bound aromatic vinyl content of 40% by mass or more is located on the higher molecular weight side than the area region of the components having a bound aromatic vinyl content of 30% by mass or less, and the polymer has a glass transition temperature (Tg) higher than −40° C. The modified conjugated diene polymer of this embodiment may be a single type of modified conjugated diene polymer, or may be a mixture of a single type of modified conjugated diene polymer and at least one other polymer. The molecular weight distribution may be a unimodal molecular weight distribution without peaks and valleys, or a multimodal molecular weight distribution with peaks, valleys, and peaks.

[0050] The one or more other polymers may be a modified conjugated diene polymer, or may be a conjugated diene polymer, or may be a mixture of a modified conjugated diene polymer and a conjugated diene polymer.

[0051] In order to obtain a modified conjugated diene-based polymer having a glass transition temperature (Tg) of higher than −40° C., in which the area of components having a bound aromatic vinyl content of 30% by mass or less is 20% or more and the area of components having a bound aromatic vinyl content of 40% by mass or more is 20% or more relative to the total area (100%) of the molecular weight distribution curve, and the area region of components having a bound aromatic vinyl content of 40% by mass or more is located on the higher molecular weight side than the area region of components having a bound aromatic vinyl content of 30% by mass or less, it is effective to control the amount of bound aromatic vinyl. The amount of bound aromatic vinyl in the modified conjugated diene polymer of this embodiment is preferably 25% by mass to 50% by mass, more preferably 25% by mass to 45% by mass, and even more preferably 30% by mass to 40% by mass.

[0052] In order to obtain a modified conjugated diene polymer having a glass transition temperature (Tg) higher than −40° C., in which the area of components having a bound aromatic vinyl content of 30% by mass or less is 20% or more and the area of components having a bound aromatic vinyl content of 40% by mass or more is 20% or more, relative to 100% of the total area of the molecular weight distribution curve, and the area region of components having a bound aromatic vinyl content of 40% by mass or more is located on the higher molecular weight side than the area region of components having a bound aromatic vinyl content of 30% by mass or less, it is effective to control the vinyl bond content (1,2-bond content). The vinyl bond content (1,2-bond content) is preferably 20 mol % to 60 mol %, more preferably 25 mol % to 60 mol %, and even more preferably 30 mol % to 55 mol %. The vinyl bond content of the modified conjugated diene polymer can be measured by the method described in the Examples below, and can be controlled within the above-mentioned range by adjusting the amount of polar substance added to the polymerization initiator in the polymerization step. The 1,2-vinyl bond content tends to increase by increasing the amount of polar substance added. It can also be controlled by adjusting the polymerization temperature. The 1,2-vinyl bond content tends to increase by lowering the polymerization temperature.

[0053] In order to obtain a modified conjugated diene polymer having a glass transition temperature (Tg) higher than −40° C., in which the area of components having a bound aromatic vinyl content of 30% by mass or less accounts for 20% or more of the total area (100%) of the molecular weight distribution curve, and the area of components having a bound aromatic vinyl content of 40% by mass or more accounts for 20% or more of the total area (100%), and the area region of components having a bound aromatic vinyl content of 40% by mass or more is located on the higher molecular weight side than the area region of components having a bound aromatic vinyl content of 30% by mass or less, it is effective to control the phm ratio of polar substance / n-butyllithium addition amount. The polar substance / n-butyllithium addition amount ratio (phm ratio) is preferably 0.5 to 3.5, and when the addition ratio is high, a lower polymerization temperature is preferred.

[0054] Controlling the polymerization temperature is effective in obtaining a modified conjugated diene-based polymer in which the area of components having a bound aromatic vinyl content of 30% by mass or less is 20% or more, the area of components having a bound aromatic vinyl content of 40% by mass or more is 20% or more, and the area region having the bound aromatic vinyl content of 40% by mass or more is located on the higher molecular weight side than the area region having the bound aromatic vinyl content of 30% by mass or less, relative to the total area (100%) of the molecular weight distribution curve, and the glass transition temperature (Tg) is higher than −40° C. The polymerization temperature is preferably 50 to 95°C, more preferably 60 to 95°C, and even more preferably 70 to 90°C. The control of the polymerization temperature differs depending on the selected values of the bonded aromatic vinyl amount and the vinyl bond amount (1,2-bond amount), and is not limited to the above.

[0055] By blending one type of modified conjugated diene polymer with at least one other polymer, the area of components having a bound aromatic vinyl content of 30% by mass or less and the area of components having a bound aromatic vinyl content of 40% by mass or more are 20% or more of the total area (100%) of the molecular weight distribution curve, the area of components having a bound aromatic vinyl content of 40% by mass or more is 20% or more, the area region of components having a bound aromatic vinyl content of 40% by mass or more is located on the higher molecular weight side than the area region of components having a bound aromatic vinyl content of 30% by mass or less, and a modified conjugated diene polymer having a glass transition temperature (Tg) higher than −40° C. can be obtained by blending one type of modified conjugated diene polymer with a low molecular weight polymer. The molecular weight of the low molecular weight polymer is preferably 100,000 or less, more preferably 70,000 or less, even more preferably 50,000 or less, and even more preferably 30,000 or less.

[0056] As described above, methods for obtaining a mixture of one type of modified conjugated diene polymer and at least one other type of polymer include a method in which each polymer is polymerized in each reactor and then mixed in a polymerization solution, and the solvent is degassed in a finishing step to obtain a mixed polymer, a method in which each polymer is kneaded in an extruder, a method in which each polymer is mixed with a roll, etc. The polymers may be mixed in the step of obtaining a rubber composition for shoes.

[0057] To obtain a molecular weight distribution curve in which the area ratio of components with molecular weights of 100,000 or less is 5% or more and the area ratio of components with molecular weights of 1,000,000 or more is 5% or more relative to the total area (100%) of the molecular weight distribution curve, a single modified conjugated diene polymer may be used, or a mixture of a single modified conjugated diene polymer and at least one other polymer. Furthermore, the molecular weight distribution may be a unimodal molecular weight distribution without peaks and valleys, or a multimodal molecular weight distribution with peaks, valleys, and peaks.

[0058] The one or more other polymers may be a modified conjugated diene polymer, or may be a conjugated diene polymer, or may be a mixture of a modified conjugated diene polymer and a conjugated diene polymer.

[0059] Methods for obtaining a mixture of one type of modified conjugated diene polymer and at least one other polymer include a method in which each polymer is polymerized in a reactor and then mixed in a polymerization solution, and the solvent is degassed in a finishing step to obtain a mixed polymer, a method in which each polymer is kneaded in an extruder, a method in which each polymer is mixed with a roll, etc. The polymers may be mixed in the step of obtaining a rubber composition for shoes.

[0060] A method for obtaining a mixture of the one type of modified conjugated diene polymer and at least one other polymer in which the area ratio of components having a molecular weight of 100,000 or less is 5% or more relative to the total area of 100% of the molecular weight distribution curve can be achieved by mixing one type of modified conjugated diene polymer with a polymer having a low molecular weight. The molecular weight of the low molecular weight polymer is preferably 100,000 or less, more preferably 70,000 or less, even more preferably 50,000 or less, and even more preferably 30,000 or less.

[0061] The modified conjugated diene polymer of the present embodiment preferably has a modification rate of 30% by mass or more. As the nitrogen atom-containing modifier for adjusting the modification rate, from the viewpoints of polymerization productivity and a high modification rate, an isocyanate compound, an isothiocyanate compound, an isocyanuric acid derivative, a nitrogen group-containing carbonyl compound, a nitrogen group-containing vinyl compound, a nitrogen group-containing epoxy compound, a nitrogen group-containing alkoxysilane compound, and the like are preferred.

[0062] Furthermore, from the viewpoint of improving productivity when the modified conjugated diene polymer of this 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 improving productivity, 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 productivity, 30 branches or less is preferred.

[0063] As these nitrogen atom-containing modifiers, nitrogen group-containing alkoxysilane compounds are more preferred from the viewpoints of productivity, a high modification rate, weight reduction when used as an outsole material, and an improved balance between tensile strength, gripping properties, and abrasion resistance.

[0064] Examples of the nitrogen group-containing alkoxysilane compound include, but are not limited to, 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-trimethoxysilylbutyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacycloheptane, 2,2-dimethoxy-1-(3- 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-Methoxy-2-methyl-1-(3-dimethoxymethylsilylpropyl)-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 Tris(3-trimethoxysilylpropyl)amine, Tris(3-methyldimethoxysilylpropyl)amine, Tris(3-triethoxysilylpropyl)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.

[0065] In the method for producing a modified conjugated diene polymer of this 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 final stage of the polymerization process refers to a state in which 95% or more of the added monomers have been consumed in the polymerization.

[0066] 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.

[0067] In the method for producing a modified conjugated diene polymer, it is preferable to add a rubber stabilizer at the end of the polymerization step from the viewpoint of preventing gel formation and improving processing stability.

[0068] The rubber stabilizer is not limited to the following, and known stabilizers can be used. Preferred examples include 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.

[0069] In the method for producing the modified conjugated diene-based polymer 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 the productivity of the polymer and the processability when an inorganic filler or the like is blended during the production of an outsole.

[0070] 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.

[0071] The method of adding a rubber softener to the conjugated diene polymer obtained in the polymerization step is not limited to the following, but a preferred method is to add the rubber softener to a polymer solution, mix them, and then remove the solvent from the resulting polymer solution containing the rubber softener.

[0072] Examples of extender oils include naphthenic oil and paraffin oil. The content of the extender oil in the rubber composition for shoes of the present embodiment described below 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.

[0073] Liquid rubber is a low molecular weight rubber-like polymer, and includes liquid diene rubbers such as liquid styrene butadiene rubber (liquid SBR) and liquid butadiene rubber (liquid BR).

[0074] The liquid rubber is not particularly limited as long as it is liquid, but it is preferable that the peak top molecular weight measured by GPC measurement be in the range of 1,000 to 50,000. The peak top molecular weight of the liquid rubber measured by GPC measurement is preferably 4,000 to 35,000, more preferably 7,000 to 30,000. When the peak top molecular weight of the liquid rubber is within the above range, the processability and strength of the crosslinked rubber composition are further improved. Note that when a liquid rubber with a low molecular weight is used, the processability is further improved, but the strength tends to decrease. The above liquid rubbers may be used alone or in combination of two or more.

[0075] The content of the liquid rubber in the crosslinked rubber composition is not particularly limited and may be, for example, 0.00 to 15 parts by mass relative to 100 parts by mass of the total of the styrene-butadiene copolymer rubber and the diene rubber. The content of the liquid rubber is preferably 0.10 to 10.0 parts by mass, more preferably 0.20 to 7.0 parts by mass, and even more preferably 0.30 to 4.0 parts by mass. When the content of the liquid rubber is within the above range, the processability and strength of the crosslinked rubber composition tend to be further improved.

[0076] 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, aromatic petroleum resins, hydrogenated aromatic hydrocarbon resins, cyclic aliphatic hydrocarbon resins, hydrogenated hydrocarbon resins, hydrogenated tung oil resins, hydrogenated oil resins, esters of hydrogenated oil resins with monofunctional or polyfunctional alcohols, and other hydrocarbon resins.

[0077] The resins may be used alone or in combination of two or more. When the resins are hydrogenated, all of the unsaturated groups may be hydrogenated, or some of the unsaturated groups may remain.

[0078] By adding a resin to the conjugated diene polymer obtained by the polymerization step, the processability of the rubber composition for shoes containing the conjugated diene polymer and a filler or the like is improved, and there is a tendency for the effect of improving the breaking strength of the vulcanized product to be obtained.

[0079] The modified conjugated diene polymer of the present embodiment can be obtained by removing the solvent from the polymer solution using any known method, including, for example, a method in which the solvent is separated by steam stripping or the like, the modified conjugated diene polymer is then filtered, and the resulting polymer is then dehydrated and dried to obtain a modified conjugated diene polymer, a method in which the polymer is concentrated in a flashing tank and then devolatilized using a vent extruder or the like, and a method in which the polymer is directly degassed using a drum dryer or the like.

[0080] [Rubber composition for shoes] The rubber composition for shoes of this embodiment contains 100 parts by mass of a rubber component containing the modified conjugated diene polymer (A) of this embodiment and 20 parts by mass or more of the inorganic filler (B). The rubber composition for shoes of this embodiment has excellent processability when made into a vulcanizate, and the vulcanizate has excellent abrasion resistance and gripping properties.

[0081] The content of the modified conjugated diene polymer (A) in the shoe rubber composition of this embodiment may be 100% by mass relative to the total amount of the rubber components, but from the viewpoint of improving abrasion resistance and breaking strength when used as an outsole material, it is preferably 90% by mass or less, more preferably 70% by mass or less, even more preferably 50% by mass or less, and still more preferably 40% by mass or less. From the viewpoint of improving gripping properties when made into an outsole, the content of the modified conjugated diene polymer (A) of this embodiment is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more relative to the total amount of the rubber components.

[0082] (Rubber polymer (C) other than modified conjugated diene polymer (A)) The rubber composition for shoes of this embodiment preferably contains, as a rubber component, a rubbery polymer (C) other than the modified conjugated diene-based polymer of this embodiment. Examples of the rubbery polymer (C) include, but are not limited to, 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 components 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).

[0083] In the rubber composition for shoes of this embodiment, the modified conjugated diene polymer of this embodiment can be used alone as the rubber component, but when the rubbery polymer (C) is blended, the blending amount thereof is preferably 30 mass % or less, more preferably 25 mass % or less, even more preferably 20 mass % or more, and still more preferably 15 mass % or less, based on the total amount of the rubber component including the modified conjugated diene polymer and the rubbery polymer (C). When the content of the rubbery polymer (C) is within the above range, the balance between grip performance and abrasion resistance when made into an outsole is improved. On the other hand, from the viewpoint of achieving a good balance between gripping properties and abrasion resistance when made into an outsole, the content of the rubber polymer (C) relative to the total amount of the rubber component is preferably 10% by mass or more, more preferably 25% by mass or more, and even more preferably 35% by mass or more.

[0084] (inorganic filler) The rubber composition for shoes of the present embodiment contains an inorganic filler. From the viewpoint of improving grip performance and abrasion resistance when the rubber composition for shoes of this embodiment is used as an outsole material, the content of the inorganic filler is 20 parts by mass or more, preferably 30 parts by mass or more, and more preferably 35 parts by mass or more, per 100 parts by mass of the total rubber component. Also, from the viewpoint of weight reduction when used as an outsole material, the content of the inorganic 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 rubber component.

[0085] The inorganic filler (B) used in the shoe rubber composition of this embodiment can be a known inorganic filler, and examples thereof include, but are not limited to, silica-based inorganic fillers such as silica, 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.

[0086] The inorganic filler (B) is preferably silica, and examples thereof include dry silica, wet silica, and synthetic silicate silica. When the inorganic filler (B) is silica, from the viewpoint of improving the interaction between the rubber and the silica, the modifying group of the modifying agent used in producing the modified conjugated diene-based polymer of this embodiment is preferably an amino group.

[0087] (Silane coupling agent) The rubber composition for shoes 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 inorganic filler, and function to strengthen the interaction between them. Generally, compounds that have a sulfur bond, an alkoxysilyl group, and a silanol group in one molecule are used.

[0088] 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.

[0089] Among these, from the viewpoint of high reinforcing effect, silane coupling agents containing a mercapto group, 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, NXTZ60, and NXT silane manufactured by Momentive, and bis-[3-(triethoxysilyl)-propyl]-tetrasulfide are preferred. The silane coupling agents may be used alone or in combination of two or more.

[0090] 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 enhancing the effect of intensifying the interaction between the rubber component and the silica-based inorganic 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.

[0091] (rubber softener) The rubber composition for shoes of this embodiment may contain a rubber softener from the viewpoint of improving processability. Suitable rubber softeners include, for example, mineral oil-based rubber softeners and liquid or low-molecular weight synthetic softeners. Mineral oil-based rubber softeners, also known as process oils or extender oils, are used to soften rubber, increase its volume, and improve its processability. These mineral oil-based rubber softeners are mixtures of aromatic rings, naphthenic rings, and paraffin chains. Softeners in which the carbon number of paraffin chains accounts for 50% or more of the total carbons are called paraffinic, those in which the carbon number of naphthenic rings is 30-45% are naphthenic, and those in which the aromatic carbon number is more than 30% are called aromatic. As the rubber softener to be used together with the modified conjugated diene polymer of this embodiment, one having an appropriate aromatic content is preferred because it tends to have good affinity with the polymer.

[0092] [Method for producing rubber composition for shoes] The rubber composition for shoes of this embodiment can be produced by mixing the modified conjugated diene polymer (A) of this embodiment and the inorganic filler (B) described above, and, if necessary, additives such as a rubbery polymer (C), a silane coupling agent, a rubber softener, etc. 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.

[0093] 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 for shoes of the present embodiment all at once or a method of mixing them in several batches can be applied.

[0094] The shoe rubber composition of this embodiment may be a vulcanized composition that has been subjected to vulcanization treatment with a vulcanizing agent. Examples of vulcanizing agents 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.

[0095] The sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, polymeric polysulfur compounds, and the like.

[0096] From the viewpoint of improving breaking strength through a 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 even more preferably 1 part by mass or more, relative to 100 parts by mass of the total amount of the rubber component containing the modified conjugated diene polymer of the present embodiment and other rubbery polymers. 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.

[0097] As the vulcanization method, a conventionally known method can be applied. The vulcanization temperature is not particularly limited, but from the viewpoint of shortening the vulcanization time and improving production efficiency, it is preferably 120°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. Furthermore, 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.

[0098] In vulcanization, a vulcanization accelerator or a vulcanization aid may be used as necessary. 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.

[0099] Furthermore, examples of the vulcanization aid include, but are not limited to, zinc oxide and stearic acid.

[0100] The content of the vulcanization accelerator in the rubber composition for shoes of this embodiment is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, per 100 parts by mass of the total rubber component.

[0101] The shoe rubber composition of this embodiment may contain various additives other than those mentioned above, such as softeners, fillers, heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, and lubricants, within the scope that does not impair the object of this embodiment. Known materials can be used for the heat stabilizer, antistatic agent, weather stabilizer, antioxidant, colorant, and lubricant.

[0102] [Outsole] The outsole of this embodiment contains the rubber composition for shoes of this embodiment described above. The rubber composition for shoes for outsoles 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]

[0103] Hereinafter, the present embodiment will be described in detail with reference to specific examples and comparative examples, but the present invention is not limited to the following examples and comparative examples in any way. Hereinafter, "parts" means "parts by mass" unless otherwise specified. Various physical properties in the examples and comparative examples were measured by the methods shown below.

[0104] (Area ratio (%) of molecular weight distribution curves of components with bound aromatic vinyl of 30% by mass or less and components with bound aromatic vinyl of 40% by mass or more) The chromatogram was measured using a gel permeation chromatography (hereinafter also referred to as "GPC") measuring device consisting of three connected columns packed with polystyrene gel, and the weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution curve (RI) were determined based on a calibration curve using standard polystyrene. At the same time as measuring the molecular weight distribution curve (RI), the detection wavelength of the ultraviolet absorption (UV) detector was fixed at 254 nm, the UV intensity at each molecular weight was measured to obtain a UV distribution curve, and the amount of bound aromatic vinyl at each molecular weight in the molecular weight distribution curve of the modified conjugated diene polymer was determined. The characteristic absorption due to the aromatic ring of the bound aromatic vinyl was detected by setting the detection wavelength of the ultraviolet (UV) detector to 254 nm. The amount of bound aromatic vinyl at each molecular weight in the molecular weight distribution curve (RI) was calculated as follows. <When the amount of bound aromatic vinyl in the modified conjugated diene polymer is 30.0% by mass> The ratio of the RI intensity at each molecular weight was calculated when the total RI intensity detected by the RI detector was taken as 100%, and an RI distribution curve was created. The proportion of UV intensity at each molecular weight was calculated when the total UV intensity detected by the UV detector was taken as 100%, and a UV distribution curve was created. The UV distribution curve was adjusted so that the ratio of the total area of the RI distribution curve to the total area of the UV distribution curve was 1:1. The amount of bound aromatic vinyl having a molecular weight such that the ratio of UV intensity to RI intensity (UV intensity / RI intensity) after adjustment is 1.00 was set to 30.0% by mass, and the amount of bound aromatic vinyl was calculated from the UV intensity / RI intensity for each molecular weight (for example, the amount of bound aromatic vinyl having a molecular weight such that UV intensity / RI intensity = 0.80 is 30.0% by mass × 0.80 = 24.0% by mass).

[0105] The area ratios on the molecular weight distribution curve for components with a bound aromatic vinyl content of 30% by mass or less and 40% by mass or more refer to the area of the portion enclosed by the molecular weight distribution curve, a line drawn perpendicularly to the horizontal axis from point A, and the horizontal axis, and similarly refer to the area of the portion enclosed by the line drawn perpendicularly to the horizontal axis from point B, and the horizontal axis, and were calculated as follows. With regard to the area ratio of components with a bound aromatic vinyl content of 30% by mass or less, at the joining point with the line showing the bound aromatic vinyl content at each molecular weight of 2,000,000 or less in the molecular weight distribution, the molecular weight at which the bound aromatic vinyl content first reaches 30% by mass from the high molecular weight side was defined as Point A, and the area of the molecular weight distribution curve for molecular weights at or below Point A was defined as the area of the molecular weight distribution curve for components with a bound aromatic vinyl content of 30% by mass or less. With regard to the area ratio of components with a bound aromatic vinyl content of 40% by mass or more, at the joining point with the line showing the bound aromatic vinyl content at each molecular weight of 100,000 or more in the molecular weight distribution, the molecular weight at which the bound aromatic vinyl content first reaches 40% by mass as viewed from the low molecular weight side was defined as point B, and the area of the molecular weight distribution curve for molecular weights at point B or more was defined as the area of the molecular weight distribution curve for components with a bound aromatic vinyl content of 40% by mass or more. FIG. 1 shows a schematic diagram of an example of the amount of bound aromatic vinyl (mass %) in the molecular weight distribution.

[0106] The specific measurement conditions are shown below. 20 μL of the following measurement solution was injected into the GPC measurement device and the measurement was carried out. <Measurement conditions> Device: Tosoh Corporation, product name "HLC-8320GPC" Eluent: 5mmol / L triethylamine in tetrahydrofuran (THF) Guard column: Tosoh Corporation's product name "TSKguardcolumn SuperH-H" Separation 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 Corporation, product name "HLC8020") UV detector (Tosoh Corporation, product name "HLC8320") Measurement solution: 10 mg of sample dissolved in 20 mL of THF

[0107] (Weight average molecular weight (Mw), number average molecular weight (Mn), area ratio of molecular weights of 100,000 or less, and area ratio of molecular weights of 1,000,000 or more) The chromatogram was measured using a gel permeation chromatography (hereinafter also referred to as "GPC") measuring device with three columns connected together, each packed with a polystyrene gel, and the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were determined based on a calibration curve using standard polystyrene. Furthermore, from the obtained molecular weight distribution curve, the area ratio of components with a molecular weight of 100,000 or less and the area ratio of components with a molecular weight of 1,000,000 or more were calculated. The specific measurement conditions are shown below. 20 μL of the following measurement solution was injected into the GPC measurement device and the measurement was carried out. <Measurement conditions> Device: Tosoh Corporation, product name "HLC-8320GPC" Eluent: 5mmol / L triethylamine in tetrahydrofuran (THF) Guard column: Tosoh Corporation's product name "TSKguardcolumn SuperH-H" Separation 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 Corporation, product name "HLC8020") UV detector (Tosoh Corporation, product name "HLC8320") Measurement solution: 10 mg of sample dissolved in 20 mL of THF

[0108] (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. Specifically, the sample was first preheated at 100°C for 1 minute, and then the rotor was rotated at 2 rpm. After 4 minutes, the torque was measured to determine the Mooney viscosity at 100°C.

[0109] (denaturation rate) 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 for modification rate: The total peak area of the chromatogram using a polystyrene 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 a silica 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 (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)

[0110] (Amount of bound aromatic vinyl) 100 mg of the sample was dissolved in 100 mL of chloroform to prepare a measurement sample. The amount of bound aromatic vinyl (mass %) relative to 100 mass % of the modified conjugated diene polymer sample 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. The measurement device used was a spectrophotometer "UV-2450" manufactured by Shimadzu Corporation.

[0111] (1,2-vinyl bond content) 50 mg of the sample was dissolved in 10 mL of carbon disulfide to prepare a measurement sample. Using a solution cell, infrared spectra were recorded from 600 to 1000 cm -1 The 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.

[0112] (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.

[0113] [Production of modified conjugated diene polymer] (Example A1) Sample No. A One autoclave was used, 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. 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 16.9 g / min, styrene at 6.5 g / min, and n-hexane at 131.1 g / min. Just before this mixture entered the first reactor, n-butyllithium for impurity inactivation treatment was supplied at 0.020 phm and mixed in the static mixer. The mixture was then continuously supplied to the bottom of the first reactor. Furthermore, 0.142 phm of 2,2-bis(2-oxolanyl)propane as a polar substance and 0.082 phm of NBL (normal butyl lithium) as a polymerization initiator were continuously supplied to the bottom of the reactor, and from a position 3 / 4 of the way up from the bottom inside the reactor, 2.8 g / min of styrene and 6.5 g / min of n-hexane were continuously supplied, and the temperature inside the reactor was maintained at 85°C to obtain a rubber solution. The rubber solution produced in the reactor was fed from the top of the reactor to a static mixer, and a reaction was carried out before the static mixer by continuously feeding (AS-2):(1,3-bis-(N,N'-diglycidylaminomethyl)cyclohexane) as a modifier in a ratio of 1.0 equivalent to the lithium of NBL fed as a polymerization initiator, thereby obtaining Sample No. A.

[0114] (Example A2) Sample No. B The modifying agent was changed to (AS-1): (2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane. Other conditions were the same as in Example A1 to obtain Sample No. B.

[0115] (Example A3) Sample No. C The amount of the modifier added was changed to 0.4 equivalents. Other conditions were the same as in Example A1, and sample No. C was obtained.

[0116] (Example A4) Sample No. D The amount of polar substance added was changed to 0.350 phm, and the polymerization temperature was changed to 82° C. Other conditions were the same as in Example A1, and Sample No. D was obtained.

[0117] (Example A5) Sample No. E The amount of the polymerization initiator added was changed to 0.112 phm, and the amount of the polar substance added was changed to 0.119 phm. Other conditions were the same as in Example A1, and sample No. E was obtained.

[0118] (Example A6) Sample No. F 1,3-butadiene was added at a rate of 17.8 g / min, styrene at a rate of 5.9 g / min, and n-hexane at a rate of 131.8 g / min. A polymerization initiator was added at a rate of 0.106 phm, and a polar substance was added at a rate of 0.084 phm from the bottom of the reactor. From a position three-quarters of the height from the bottom inside the reactor, styrene was continuously added at a rate of 2.5 g / min and n-hexane at a rate of 5.8 g / min. Sample No. F was obtained under the same conditions as in Example A1.

[0119] (Example A7) Sample No. G 1,3-butadiene was added at a rate of 16.2 g / min, styrene at a rate of 7.0 g / min, and n-hexane at a rate of 130.6 g / min. A polymerization initiator was continuously fed from the bottom of the reactor at a rate of 0.103 phm. Styrene and n-hexane were continuously fed from a position three-quarters of the way up from the bottom of the reactor at a rate of 3.0 g / min and 7.0 g / min, respectively. The polymerization temperature was changed to 75° C. Sample No. G was obtained under the same conditions as in Example A4.

[0120] (Comparative Example A1) Sample No. H The amount of polar substance added was changed to 0.228 phm, and the polymerization temperature was changed to 98° C. Other conditions were the same as in Example A1, and sample No. H was obtained.

[0121] (Comparative Example A2) Sample No. I The amount of polar substance added was changed to 0.095 phm and the polymerization temperature was changed to 98° C. Other conditions were the same as in Example A6, and Sample No. I was obtained.

[0122] (Comparative Example A3) Sample No. J 1,3-butadiene was mixed at 19.3 g / min, styrene at 4.8 g / min, and n-hexane at 132.7 g / min. A polymerization initiator was added at 0.069 phm, and a polar substance was added at 0.228 phm. These were continuously fed to the bottom of the first reactor. From a position three-quarters of the way up from the bottom of the reactor, styrene was continuously fed at 2.1 g / min and n-hexane at 4.9 g / min. Sample No. J was obtained under the same conditions as in Example A1.

[0123] (Comparative Example A4) Sample No. K 1,3-butadiene was mixed at 15.2 g / min, styrene at 7.7 g / min, and n-hexane at 129.9 g / min, and the mixture was continuously fed into the bottom of the first reactor. From a position three-quarters of the way up from the bottom of the reactor, styrene was continuously fed at 3.3 g / min and n-hexane at 7.7 g / min. Sample No. K was obtained under the same conditions as in Example A7.

[0124] (Comparative Example A5) Sample No. L The amount of polymerization initiator added was changed to 0.070 phm, the amount of polar substance added was changed to 0.025 phm, and the polymerization temperature was changed to 98° C. Other conditions were the same as in Example A1, and sample No. L was obtained.

[0125] (Comparative Example A6) Sample No. M Sample No. M was obtained in the same manner as in Example A1, except that 1,3-butadiene, styrene, and n-hexane were mixed at rates of 16.9 g / min, 9.3 g / min, and 137.6 g / min, and this mixed liquid was continuously supplied to the bottom of the first reactor, and styrene and n-hexane were not supplied from a position three-quarters of the way up from the bottom of the reactor.

[0126] The polymerization conditions and physical properties of the modified conjugated diene polymers (sample Nos. A to M) of Examples A1 to A7 and Comparative Examples A1 to A6 are shown in Table 1 below.

[0127] [Table 1]

[0128] [Production and Evaluation of Rubber Composition] (Materials used) Rubber compositions were prepared as described below. The product names used were as follows: Polybutadiene rubber (UBEPOL U150 manufactured by Ube Industries) Polyisoprene rubber (manufactured by Nippon Zeon Co., Ltd., product name "Nipol IR2200") 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)

[0129] (Method of evaluating characteristics) <(Evaluation 1) Tear strength> Trouser-shaped test specimens were prepared as test pieces, and a tear test was carried out in accordance with JIS K-6252 to measure the maximum tear strength (unit: NK / m) until the test piece broke. In the following Table 3, the evaluation of Comparative Example B6 is set to 100 and the evaluation of Examples B1 to B7 and Comparative Examples B1 to B5 is indexed. The larger the index, the better the tear strength. In the following Table 5, the evaluation of Comparative Example C6 is set to 100 and the evaluation of Examples C1 to C7 and Comparative Examples C1 to C5 is indexed. The larger the index, the better the tear strength. In the following Table 7, the evaluation of Comparative Example B3 is set to 100 and the evaluation of Examples D1 to D7 and Comparative Examples D1 to D6 is indexed. The larger the index, the better the tear strength.

[0130] <(Evaluation 2) Tensile strength> The breaking strength (unit: MPa) and breaking elongation (unit: %) were measured in accordance with the tensile test method of JIS K6251. In the following Table 3, the evaluation of Comparative Example B6 is set to 100, and Examples B1 to B7 and Comparative Examples B1 to B5 are indexed. The larger the index, the better the tensile strength. In the following Table 5, the evaluation of Comparative Example C6 is set to 100, and Examples C1 to C7 and Comparative Examples C1 to C5 are indexed. The larger the index, the better the tensile strength. In the following Table 7, the evaluation of Comparative Example B3 is set to 100 and the evaluation of Examples D1 to D7 and Comparative Examples D1 to D6 is indexed. The larger the index, the better the tensile strength.

[0131] <(Rating 3) Grip: Dynamic friction coefficient> The dynamic friction coefficient was measured using a dynamic friction tester (Heidon Tribogear Type 40) manufactured by Shinto Scientific Co., Ltd. The higher the dynamic friction coefficient, the better the grip. The sliding surface was a ceramic tile, lubricated with water, and a vulcanized sheet 3 mm thick, 30 mm wide, and 30 mm deep was placed on the sliding surface. The grip was evaluated as the average value of the dynamic friction coefficient under a load of 500 gf, a sliding speed of 25 mm / min, and a sliding distance of 80 mm. In the following Table 3, the evaluation of Comparative Example B6 is set to 100 and Examples B1 to B7 and Comparative Examples B1 to B5 are indexed. The higher the index, the better the gripping ability. In the following Table 5, the evaluation of Comparative Example C6 is set to 100 and Examples C1 to C7 and Comparative Examples C1 to C5 are indexed. The higher the index, the better the gripping ability. In the following Table 7, the evaluation of Comparative Example B3 is set to 100 and Examples D1 to D7 and Comparative Examples D1 to D6 are indexed. The higher the index, the better the gripping ability.

[0132] <(Rating 4) Abrasion resistance> The specific wear volume (unit: mm3) was measured using a DIN abrasion tester (manufactured by Ueshima Seisakusho) in accordance with JIS K6264. In the following Table 3, the evaluation of Comparative Example B6 is set to 100 and the evaluation of Examples B1 to B7 and Comparative Examples B1 to B5 is indexed. The larger the index, the more excellent the abrasion resistance. In the following Table 5, the evaluation of Comparative Example C6 is set to 100 and the evaluation of Examples C1 to C7 and Comparative Examples C1 to C5 is indexed. The larger the index, the more excellent the abrasion resistance. In the following Table 7, the evaluation of Comparative Example B3 is set to 100 and the evaluation of Examples D1 to D7 and Comparative Examples D1 to D6 is indexed. The larger the index, the more excellent the abrasion resistance.

[0133] [Production of Rubber Composition] (Examples B1 to B7 and Comparative Examples B1 to B6) As shown in Table 2 below, 100 parts of modified conjugated diene polymer as the rubber component was blended with an inorganic filler and the like to obtain rubber compositions containing the respective raw rubbers. More specifically, the materials in Table 2 were kneaded by the following method to obtain a rubber composition. In the first stage of mixing, a closed mixer (0.6 L capacity) equipped with a temperature control device was used to mix the raw rubber (modified conjugated diene polymer), filler (silica), silane coupling agent, zinc oxide, stearic acid, and antioxidant at a filling rate of 65% and a rotor rotation speed of 30 rpm. At this time, the temperature of the closed mixer was controlled, and each rubber composition (compound) was obtained at a discharge temperature of 125 to 135°C. 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. After cooling, the mixture was mixed in the third stage using an open roll set at 73°C, adding sulfur and vulcanization accelerators 1 and 2. The mixture was then vulcanized and molded in a vulcanization press at 160°C, and the properties of the vulcanized rubber composition were evaluated. Specifically, the evaluations were performed using the methods described below. The evaluation results are shown in Table 3.

[0134] [Table 2]

[0135] [Table 3]

[0136] (Examples C1 to C7 and Comparative Examples C1 to C6) As shown in Table 4 below, rubber compositions containing each raw rubber were obtained by blending 60 parts of polybutadiene rubber, 10 parts of polyisoprene rubber, 30 parts of modified conjugated diene polymer, and inorganic fillers as raw rubber components. More specifically, the materials in Table 4 below were kneaded by the following method to obtain rubber compositions. In the first stage of mixing, raw rubber (polybutadiene rubber, polyisoprene rubber, modified conjugated diene polymer), 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. During this process, the temperature of the internal mixer was controlled, and each rubber composition (compound) was obtained at a discharge temperature of 125 to 135°C. 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. After cooling, the mixture was kneaded in the third stage using an open roll set at 73°C, after which sulfur and vulcanization accelerators 1 and 2 were added and kneaded. Thereafter, the rubber composition was vulcanized in a vulcanizing press at 160°C, and the properties of the vulcanized rubber composition were evaluated. Specifically, the evaluation was carried out by the following methods, and the evaluation results are shown in Table 5.

[0137] [Table 4]

[0138] [Table 5]

[0139] (Examples D1 to D7, Comparative Examples D1 to D6, and Comparative Example B3) The properties of the rubber composition were evaluated when the weight of the rubber composition after vulcanization was reduced by reducing the compounding amount of silica (Ultrasil VN3) (30 parts compounded). For comparison, Comparative Example B3 in Table 3 was added, in which the blending amount of silica (Ultrasil VN3) was 40 parts. As shown in Table 6 below, rubber compositions containing each raw rubber were obtained by reducing the blending amount of modified conjugated diene polymer (100 parts) and silica (Ultrasil VN3) to 30 parts as the rubber component. More specifically, the materials in Table 6 below were kneaded in the following manner to obtain the rubber compositions. Using an internal mixer (0.6 L capacity) equipped with a temperature control device, the raw rubber (modified conjugated diene polymer), filler (silica), silane coupling agent, zinc oxide, stearic acid, and antioxidant were kneaded in the first stage at a filling rate of 65% and a rotor rotation speed of 30 rpm. The temperature of the internal mixer was controlled, and each rubber composition (compound) was obtained at a discharge temperature of 125 to 135°C. 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. After cooling, the mixture was mixed in the third stage using an open roll set at 73°C, adding sulfur and vulcanization accelerators 1 and 2. The mixture was then vulcanized and molded in a vulcanization press at 160°C, and the properties of the vulcanized rubber composition were evaluated. Specifically, the evaluations were performed using the methods described below. The evaluation results are shown in Table 7 below.

[0140] [Table 6]

[0141] [Table 7]

[0142] As shown in Table 3 below, it was found that Examples B1 to B7 had superior tear strength and tensile strength of the rubber composition compared to Comparative Examples B1 to B6, and also had an excellent balance between grip performance and abrasion resistance, which are in a trade-off relationship. As shown in Table 5 below, it was found that Examples C1 to C7 had superior tear strength and tensile strength of the rubber composition compared to Comparative Examples C1 to C6, and also had an excellent balance between grip performance and abrasion resistance, which are in a trade-off relationship. As shown in Table 7 below, it was found that Examples D1 to D7 had superior tear strength and tensile strength of the rubber composition compared to Comparative Examples D1 to D6 and Comparative Example B3, and also had an excellent balance between grip performance and abrasion resistance, which are in a trade-off relationship. In particular, even when compared with Comparative Example B3, which contains 40 parts of silica (Ultrasil VN3), Examples D1 to D7, which contain 30 parts of silica (Ultrasil VN3) to reduce the weight of the rubber composition, have rubber compositions with equivalent tear strength, tensile strength, and abrasion resistance, excellent grip properties, and an excellent balance between grip properties and abrasion resistance, which are trade-offs. [Industrial Applicability]

[0143] The modified conjugated diene-based polymer and shoe rubber composition according to the present invention have industrial applicability in the field of shoe soles, particularly as sole materials for all types of footwear such as sports shoes, running shoes, trekking shoes, and casual shoes.

Claims

1. the area of the molecular weight distribution curve obtained by GPC (gel permeation chromatography) measurement, of which the area of the molecular weight distribution curve of components having a bound aromatic vinyl content of 30% by mass or less is 20% or more, is 100% of the total area of the molecular weight distribution curve, the area of the molecular weight distribution curve of the component having a bound aromatic vinyl content of 40% by mass or more is 20% or more; In the molecular weight distribution curve, an area region of components in which the amount of bound aromatic vinyl is 40% by mass or more is located on the higher molecular weight side than an area region of components in which the amount of bound aromatic vinyl is 30% by mass or less, A glass transition temperature (Tg) of greater than -40°C; Modified conjugated diene polymer.

2. With respect to the total area of the molecular weight distribution curve (100%), The area ratio of components having a molecular weight of 100,000 or less is 5% or more, The area ratio of components having a molecular weight of 1,000,000 or more is 5% or more, The modified conjugated diene polymer according to claim 1 .

3. The following conditions (1) and (2) are met: The modified conjugated diene polymer according to claim 1 . <Condition (1)> The Mooney viscosity measured under the conditions of JIS K6300 (ISO 289-1) is 30 to 100. <Condition (2)> The modification rate is 30% by mass or more.

4. the modified conjugated diene polymer contains a polymer having a conjugated diene monomer unit and an aromatic vinyl monomer unit and having a nitrogen atom-containing functional group; The modified conjugated diene polymer according to claim 1 .

5. 100 parts by mass of a rubber component containing the modified conjugated diene-based polymer according to claim 1; 20 parts by mass or more of an inorganic filler (B); A rubber composition for shoes comprising:

6. the rubber component contains a rubber-like polymer (C) other than the modified conjugated diene-based polymer, the content of the modified conjugated diene polymer in the rubber component is 90% by mass or less, The content of the rubber-like polymer (C) in the rubber component is 10% by mass or more. The rubber composition for shoes according to claim 5.

7. An outsole comprising the rubber composition for shoes according to claim 5 or 6.

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