Modified polybutadiene for outsoles, and rubber composition for outsoles

Abstract

An objective of the present invention is to provide a modified polybutadiene suitable for outsoles or for a rubber composition for outsoles, and a rubber composition for outsoles with improved abrasion resistance and tear strength while suppressing a decrease in adhesive strength. The modified polybutadiene for outsoles of the present invention has a silicon atom content of 60-150 ppm, and a nitrogen atom content of 80-280 ppm.

Description

Modified polybutadiene for outsoles, and rubber composition for outsoles 【0001】 This invention relates to modified polybutadiene for outsoles and rubber compositions for outsoles. 【0002】 Traditionally, abrasion resistance and tear strength have been cited as important properties for shoe outsoles, but there is a need for further improvement in these physical properties. Therefore, technologies related to outsoles that attempt to improve abrasion resistance and tear strength have been disclosed to date. 【0003】 For example, Patent Document 1 discloses a technology relating to a rubber composition and outsole in which abrasion resistance and tear strength are improved by containing a specified amount of vulcanizable rubber and syndiotactic-1,2-polybutadiene with a specified reduction viscosity. Patent Document 2 also discloses a technology relating to a rubber composition and outsole in which abrasion resistance is improved by using a specified amount of high-cis-butadiene rubber and an oil having a specified molecular weight. 【0004】 In addition to the above issues, there is another problem: if too much time is required between the outsole fabrication and the bonding of the outsole and midsole, the bonding strength decreases. A widely known solution to this problem is to buff the bonding surface of the outsole to increase the bonding strength. 【0005】 Japanese Patent Publication No. 2003-082165, International Publication No. 2016 / 098257 【0006】 However, the rubber compositions described in Patent Documents 1 and 2 have room for improvement when applied to outsoles of sports shoes and the like, where superior abrasion resistance and tear strength are required. Furthermore, if too much time is needed for the outsole and midsole to bond after the outsole is manufactured, the bonding strength decreases. While this problem can be solved by buffing, buffing has drawbacks, such as decreased productivity and increased manpower due to the addition of a buffing process, and deterioration of the working environment due to the scattering of abrasion dust into the air during buffing. 【0007】Therefore, in view of the problems of the prior art described above, the present invention aims to provide a rubber composition for outsoles or a modified polybutadiene suitable for outsoles, and a rubber composition for outsoles that improves abrasion resistance and tear strength while suppressing a decrease in adhesive strength. 【0008】 The present inventors conducted diligent studies to solve the problems of the prior art described above, and found that a specific modified polybutadiene is suitable for outsole rubber compositions or outsoles, and that a rubber composition containing a specific modified polybutadiene and an inorganic filler, wherein the specific modified polybutadiene is contained in a specific amount in the rubber component and the inorganic filler is contained in a specific amount in the rubber composition, can improve abrasion resistance and tear strength, and further suppress changes in adhesive strength over time, thus completing the present invention. 【0009】 In other words, the present invention is as follows: 【0010】 [1] Modified polybutadiene for outsoles, having a silicon atom content of 60 ppm to 150 ppm and a nitrogen atom content of 80 ppm to 280 ppm. 【0011】 [2] Mooney viscosity at 100°C (ML （１＋４） A modified polybutadiene for outsoles as described in [1], wherein the ratio is 40 or more and 100 or less. 【0012】 [3] Modified polybutadiene for outsoles according to [1] or [2], wherein the Mooney relaxation rate (MSR) at 100°C is 0.30 or more and 0.80 or less. 【0013】 [4] Modified polybutadiene for outsoles according to any one of [1] to [3], wherein the lithium atom content is 2 ppm or more and 130 ppm or less. 【0014】 [5] Modified polybutadiene for outsoles according to any one of [1] to [4], wherein the molecular weight distribution (Mw / Mn), expressed as the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) on a standard polystyrene basis, measured by gel permeation chromatography (GPC), is 1.05 or more and 3.00 or less. 【0015】 [6] Modified polybutadiene for outsoles according to any one of [1] to [5], wherein the nitrogen atom content is 90 ppm or more and 180 ppm or less. 【0016】 A rubber composition for outsoles comprising a modified polybutadiene described in any one of [7] [1] to [6] and an inorganic filler, wherein the content of the modified polybutadiene is 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition, and the content of the inorganic filler is 20 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. 【0017】 [7-1] A rubber composition for outsoles comprising modified polybutadiene and an inorganic filler, wherein the content of the modified polybutadiene is 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition, the content of silicon atoms in the modified polybutadiene is 60 ppm or more and 150 ppm or less, the content of nitrogen atoms in the modified polybutadiene is 80 ppm or more and 180 ppm or less, and the content of the inorganic filler is 20 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. 【0018】 [8] The rubber composition for outsoles according to [7] or [7-1], wherein the difference (ΔG') between the storage modulus at a strain of 0.1% and the storage modulus at a strain of 10%, measured in rotation mode at a frequency of 10 Hz and a test temperature of 50°C based on JIS K6394:2007 for rubber composition test specimens, is 0.80 or less. 【0019】 [9] The rubber composition for outsoles according to any one of [7], [7-1], and [8], wherein the total area of ​​the differential molecular weight distribution curve obtained by gel permeation chromatography (GPC) measurement of the modified polybutadiene is taken as 100%, and there are two or more peaks with an area of ​​10% or more, and the area of ​​the lowest molecular weight peak among the peaks with an area of ​​10% or more is 15% or more and 70% or less. 【0020】

[10] The outsole rubber composition according to any one of [7], [7-1], [8], and [9], wherein the modified polybutadiene has a modified group derived from a compound having one or more amino groups and two or more alkoxysilyl groups. 【0021】

[11] Mooney viscosity (ML) of the modified polybutadiene at 100°C （１＋４） An outsole rubber composition according to any one of [7], [7-1], and [8] to

[10] , wherein ) is 50 or more and 80 or less. 【0022】

[12] The rubber composition for outsoles according to any one of [7], [7-1], and [8] to

[11] , wherein the amount of 1,2-vinyl bond in the modified polybutadiene is 9 mol% or more and 40 mol% or less based on 100 mol% of the content of structural units derived from 1,3-butadiene. 【0023】

[13] An outsole rubber composition according to any one of [7], [7-1], and [8] to

[12] , further comprising a polybutadiene rubber other than the modified polybutadiene and a polyisoprene rubber, wherein the content of the polybutadiene rubber other than the modified polybutadiene is 30 parts by mass or more and 85 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition, and the content of the polyisoprene rubber is 5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. 【0024】

[14] A method for producing an outsole rubber composition according to any one of [7], [7-1], and [8] to

[13] , comprising a kneading step of kneading raw materials containing the total rubber components and the inorganic filler. 【0025】 An outsole obtained by vulcanizing a rubber composition for outsoles described in any one of

[15] , [7], [7-1], and [8] to

[14] . 【0026】

[16] The outsole described in

[15] , wherein the force required to make the outsole bend at a 45° angle, as measured in accordance with ISO 17707-2005, is between 1N and 40N. 【0027】

[17] The coefficient of kinetic friction (μ DRY ) in the dry state and the coefficient of kinetic friction (μ WET ) in the wet state, and the difference therebetween (μ DRY - μ WET ) is 0.05 or more and 0.70 or less, and the outsole according to

[15] or

[16] . 【0028】

[18] The outsole according to any one of

[15] to

[17] , wherein the rubber composition further contains a polybutadiene rubber other than the modified polybutadiene and a styrene-butadiene rubber. 【0029】

[19] The outsole according to any one of

[15] to

[18] , wherein the rubber composition further contains a polybutadiene rubber other than the modified polybutadiene, and the total content of the modified polybutadiene and the polybutadiene rubber other than the modified polybutadiene is 70 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of all rubber components in the rubber composition. 【0030】

[20] The outsole according to any one of

[15] to

[19] , wherein the rubber composition further contains a modified polybutadiene other than the modified polybutadiene and an acrylonitrile-butadiene rubber, the content of the polybutadiene rubber other than the modified polybutadiene is 30 parts by mass or more and 85 parts by mass or less with respect to 100 parts by mass of all rubber components in the rubber composition, and the content of the acrylonitrile-butadiene rubber is 1 part by mass or more and 30 parts by mass with respect to 100 parts by mass of all rubber components in the rubber composition. 【0031】 According to the present invention, a modified polybutadiene suitable for a rubber composition for an outsole or an outsole can be provided. According to the present invention, a rubber composition for an outsole having improved abrasion resistance and tear strength and suppressing a decrease in adhesion strength can be provided. 【0032】 Hereinafter, embodiments 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 exemplification for explaining the present invention, and the present invention is not limited to the following embodiments. The present invention can be appropriately modified and implemented within the scope of its gist. 【0033】 In this specification, when expressing by sandwiching numerical values or physical property values before and after with "~", it is used including the values before and after. In the numerical ranges described stepwise in this specification, the upper limit value or lower limit value described in one numerical range may be replaced with the upper limit value or lower limit value of the numerical range of other stepwise descriptions. Also, in the numerical ranges described in this specification, the upper limit value or lower limit value of the numerical range may be replaced with the value shown in the examples. 【0034】 [Rubber Composition for Outsole] The rubber composition for outsole of the present embodiment (hereinafter, also simply referred to as "rubber composition") contains modified polybutadiene and an inorganic filler, and the content of the modified polybutadiene is 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of all rubber components in the rubber composition. The content of silicon atoms in the modified polybutadiene is 60 ppm or more and 150 ppm or less, the content of nitrogen atoms in the modified polybutadiene is 80 ppm or more and 180 ppm or less, and the content of the inorganic filler is 20 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of all rubber components in the rubber composition. 【0035】 (Modified Polybutadiene) The rubber composition for outsole of the present embodiment contains modified polybutadiene (also referred to as "modified polybutadiene rubber") as a rubber component. The modified polybutadiene may be used alone or in an appropriate combination of two or more kinds having different physical properties and configurations. 【0036】 The content of the modified polybutadiene is 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of all rubber components in the rubber composition. From the point that abrasion resistance and tear strength are further improved and the decrease in adhesion strength can be further suppressed, the content of the modified polybutadiene is preferably 16 parts by mass or more and 44 parts by mass or less, more preferably 20 parts by mass or more and 40 parts by mass or less, and still more preferably 22 parts by mass or more and 38 parts by mass or less with respect to 100 parts by mass of all rubber components in the rubber composition. 【0037】In this specification, suppressing the decrease in adhesive strength means suppressing the decrease in adhesive strength that occurs as time elapses between the manufacturing of the outsole and the bonding of the outsole and midsole. 【0038】 The inclusion of modified polybutadiene in the rubber composition effectively suppresses blooming over time after the preparation of the outsole rubber composition of this embodiment. This effectively suppresses a decrease in the adhesive strength between the outsole and the midsole. 【0039】 Modified polybutadiene contains structural units derived from 1,3-butadiene. Modified polybutadiene may contain styrene due to impurities or other reasons. The styrene content is usually 0.5% by mass or less per 100% by mass of modified polybutadiene. The lower limit of the styrene content is not particularly limited, but for example, it is usually 0% by mass or more per 100% by mass of modified polybutadiene. 【0040】 <Silicon atoms, nitrogen atoms, and lithium atoms in modified polybutadiene> The modified polybutadiene of this embodiment contains silicon atoms and nitrogen atoms after modification. The modified polybutadiene of this embodiment may also contain lithium atoms. Modification methods are not limited to the following, but include, for example, a method in which a nitrogen-containing compound is reacted with a modifying agent to the ends of the polybutadiene as needed, a method in which a nitrogen-containing compound is reacted to modify the double bonds of the polymerized polybutadiene, and a method in which a polymerization initiator containing a nitrogen-containing compound is used. 【0041】The denaturing agents are not limited to the following, but include, for example, 3-(4-methylpiperazine-1-yl)propyltriethoxysilane, 1-[3-(diethoxyethylsilyl)propyl]-4-methylpiperazine, 1-[3-(trimethoxysilyl)propyl]-3-methylimidazolidine, 1-[3-(diethoxysilyl)propyl]-3-ethylimidazolidine, 1-[3-(triethoxysilyl)propyl]-3-methylhexahydropyrimidine, 1-[3-(dimethoxymethylsilyl)propyl]-3-methylhexahydropyrimidine, 3-[3-(tributoxysilyl)propyl]-1-methyl-1,2,3,4-tetrahydropyrimidine, 3-[3-(dimethoxymethylsilyl)propyl]-1-ethyl-1,2,3,4-tetrahydropyrimidine, 1-(2-ethoxyethyl)-3-[3-(trimethoxysilyl)propyl]imidazolidine, (2-{3-[3-(trimethylsilyl)propyl [Tetrahydropyrimidine-ylethyl)dimethylamine, 1-[3-(triethoxysilyl)propyl]-4-(trimethylsilyl)piperazine, 1-[3-(dimethoxymethylsilyl)propyl]-4-(trimethylsilyl)piperazine, 1-[3-(tributoxysilyl)propyl]-4-(trimethylsilyl)piperazine, 1-[3-(diethoxyethylsilyl)propyl]-3-(triethylsilyl)imidazolidine, 2-(trimethoxy) Examples include silanyl)-1,3-dimethylimidazolidine, 1-[3-(triethoxysilyl)propyl]-3-(trimethylsilyl)imidazolidine, 1-[3-(dimethoxymethylsilyl)propyl]-3-(trimethylsilyl)hexahydropyrimidine, 1-[3-(triethoxysilyl)propyl]-3-(trimethylsilyl)hexahydropyrimidine, and 1-[4-(triethoxysilyl)propyl]-4-(trimethylsilyl)piperazine. 【0042】Furthermore, the denaturing agents are not limited to the following, but include, for example, 2-[3-(trimethoxysilyl)propyl]-1,3-dimethylimidazolidine, 2-[3-(trimethoxysilyl)propyl]-1,3-(bistrimethylsilyl)imidazolidine, 2-(diethoxydiethylsilyl)-1,3-diethylimidazolidine, 2-(triethoxysilyl)-1,4-diethylpiperazine, 2-(dimethoxymethylsilyl)-1,4-dimethylpiperazine, 5-(triethoxysilyl)-1,3-dipropylhexahydropyrimidine, 5 -(diethoxyethylsilyl)-1,3-diethylhexahydropyrimidine, {2-[3-(2-dimethylaminoethyl)-2-(ethyldimethoxysilyl)-imidazolidine-1-yl]-ethyl}dimethylamine, 5-(trimethoxysilyl)-1,3-bis-(2-methoxyethyl)-hexahydropyrimidine, 5-(ethyldimethoxysilyl)-1,3-bis-(2-trimethylsilylethyl)-hexahydropyrimidine, 1,3-dimethylimidazolidine, 2-(3-diethoxyethylsilyl-propyl)-1,3-diethyl Midazolidine, 2-(3-triethoxysilyl-propyl)-1,4-diethylpiperazine, 2-(3-dimethoxymethylsilyl-propyl)-1,4-dimethylpiperazine, 5-(3-triethoxysilyl-propyl)-1,3-dipropylhexahydropyrimidine, 5-(3-diethoxyethylsilyl-propyl)-1,3-diethylhexahydropyrimidine, {2-[3-(2-dimethylaminoethyl)-2-(3-ethyldimethoxysilyl-propyl)-imidazolidined-1-yl]-ethyl}dimethylamine, 5-(3-tri Methoxysilyl-propyl)-1,3-bis-(2-methoxyethyl)-hexahydropyrimidine, 5-(3-ethyldimethoxysilyl-propyl)-1,3-bis-(2-trimethylsilylethyl)-hexahydropyrimidine, 2-[3-(trimethoxysilyl)propyl]-1,3-bis(trimethylsilyl)imidazolidine, 2-(diethoxyethylsilyl)-1,3-bis(triethylsilyl)imidazolidine, 2-(triethoxysilyl)-1,4-bis(trimethylsilyl)piperazine, 2-(dimethoxymethylsilyl)-1,Examples include 4-bis(trimethylsilyl)piperazine and 5-(triethoxysilyl)-1,3-bis(tripropylsilyl)hexahydropyrimidine. 【0043】 Furthermore, the denaturing agents are not limited to the following, but include, for example, [3-(1-hexamethyleneimino)propyl]triethoxysilane, [3-(1-hexamethyleneimino)propyl]trimethoxysilane, [2-(1-hexamethyleneimino)ethyl]triethoxysilane, [2-(1-hexamethyleneimino)ethyl]trimethoxysilane, [3-(1-pyrrolidinyl)propyl]triethoxysilane, [3-(1-pyrrolidinyl)propyl]trimethoxysilane, [3-(1-heptamethyleneimino)propyl]triethoxysilane, [3 Examples include [1-dodecamethyleneimino]propyl]triethoxysilane, [3-(1-hexamethyleneimino)propyl]diethoxymethylsilane, [3-(1-hexamethyleneimino)propyl]diethoxyethylsilane, N-[3-(triethoxysilyl)-propyl]-N,N'-diethyl-N'-trimethylsilyl-ethane-1,2-diamine, N-[2-(trimethoxysilanyl)-ethyl]-N,N',N'-trimethylethane-1,2-diamine, and N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane. 【0044】Furthermore, the denaturing agents are not limited to the following, but include, for example, [3-(dimethylamino)propyl]triethoxysilane, [3-(dimethylamino)propyl]trimethoxysilane, [3-(diethylamino)propyl]triethoxysilane, [3-(diethylamino)propyl]trimethoxysilane, [2-(dimethylamino)ethyl]triethoxysilane, [2-(dimethylamino)ethyl]trimethoxysilane, [3-(dimethylamino)propyl]diethoxymethylsilane, and [3-dibutylaminopropyl]triethoxysilane. Examples include N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltriethoxysilane, and N,N-bis(trimethylsilyl)aminoethylmethyldiethoxysilane. 【0045】 Furthermore, the denaturing agents are not limited to the following, but include, for example, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, and N,N-bis(trimethylsilyl)aminoethyl Examples include riethoxysilane, N,N-bis(trimethylsilyl)aminoethylmethyldimethoxysilane, N,N-bis(trimethylsilyl)aminoethylmethyldiethoxysilane, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, N,N-diethyl-3-aminopropyltrimethoxysilane, N,N-diethyl-3-aminopropyltriethoxysilane, 2-(triethoxysilylethyl)pyridine, and γ-isocyanatetopropyltriethoxysilane. 【0046】Furthermore, the denaturing agents are not limited to the following, but examples include N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N-(1-methylethylidene)-3-(triethoxysilyl)-1-propanamine, N-ethylidene-3-(triethoxysilyl)-1-propanamine, N-(1-methylpropyridene)-3-(triethoxysilyl)-1-propanamine, N-(4-N,N-dimethylaminobenzylidene)-3- Examples include (triethoxysilyl)-1-propanamine, N-(cyclohexylidene)-3-(triethoxysilyl)-1-propanamine, 1-[3-(triethoxysilyl)propyl]-4,5-dihydroimidazole, 1-[3-(trimethoxysilyl)propyl]-4,5-dihydroimidazole, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, and N-(3-methyldiethoxypropyl)-4,5-dihydroimidazole. 【0047】 Furthermore, examples of denaturing agents, though not limited to those listed below, include 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-isocyanatopropylmethyldiethoxysilane, 3-isocyanatopropyltriisopropoxysilane, and tris(3-trimethoxysilylpropyl)isocyanurate. 【0048】 Furthermore, examples of denaturing agents, though not limited to those listed below, include N-n-butyl-aza-2,2-dimethoxysilacyclopentane, N-ethyl-aza-2,2-diethoxy-4-methylsilacyclopentane, N-allyl-aza-2,2-dimethoxysilacyclopentane, and 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane. 【0049】Among the modifiers mentioned above, compounds having one or more nitrogen atoms and two or more alkoxysilyl groups are preferred because they can more effectively suppress the decrease in the adhesive strength of the rubber composition. Examples of such compounds include 3-(4-methylpiperazine-1-yl)propyltriethoxysilane, 1-[3-(trimethoxysilyl)propyl]-3-methylimidazolidine, 1-[3-(triethoxysilyl)propyl]-3-methylhexahydropyrimidine, 1-[3-(triethoxysilyl)propyl]-4-(trimethylsilyl)piperazine, 1-[3-(triethoxysilyl)propyl]-3-(trimethylsilyl)imidazolidine, 1-[3-(triethoxysilyl)propyl]-3-(trimethylsilyl)hexahydropyrimidine, 2-[3-(trimethoxysilyl)propyl]-1,3-dimethylimidazolidine, and 2-[3-(trimethoxysilyl)propyl]-1,3-(bistrimethylsilyl)imidazolidine. Among these, 3-(4-methylpiperazine-1-yl)propyltriethoxysilane is preferred. These denaturing agents may be used individually or in combination of two or more. 【0050】 Examples of nitrogen-containing compounds include, but are not limited to, dimethylamine, diethylamine, dibutylamine, dipropylamine, diheptylamine, dihexylamine, dioctylamine, di(2-ethylhexyl)amine, didecylamine, ethylpropylamine, ethylbutylamine, ethylbenzylamine, methylphenethylamine, piperidine, hexamethyleneimine, azacyclooctane, 1,3,3-trimethyl-6-azabicyclo[3.2.1]octane, 1,2,3,6-tetrahydropyridine, and 3,5-dimethylpiperidine. Among these, piperidine is preferred. These nitrogen-containing compounds may be used individually or in combination of two or more. 【0051】 Examples of polymerization initiators include, but are not limited to, organolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, n-propyllithium, and i-propyllithium. 【0052】 Furthermore, as a polymerization initiator, for example, a reaction product of the nitrogen-containing compound and the organolithium compound may be used. These polymerization initiators may be used individually or in combination of two or more. 【0053】 As nitrogen-containing compounds, for example, coupling-type nitrogen-containing compounds and non-coupling-type nitrogen-containing compounds may be used. These compounds may be used individually or in combination of two or more. 【0054】 Examples of coupling nitrogen-containing compounds include, but are not limited to, tetraglycidyl-1,3-bisaminomethylcyclohexane. 【0055】 Examples of non-coupling nitrogen-containing compounds include, but are not limited to, 1,3-diethyl-2-imidazolinone, 1,3-dimethyl-2-imidazolinone, 1,3-dipropyl-2-imidazolinone, 1-methyl-3-ethyl-2-imidazolinone, 1-methyl-3-propyl-2-imidazolinone, 1-methyl-3-butyl-2-imidazolinone, and 1,3-dihydro-1,3-dimethyl-2H-imidazole-2-one. These non-coupling nitrogen-containing compounds may be used individually or in combination of two or more. 【0056】 <Silicon content in modified polybutadiene> The silicon content in modified polybutadiene is between 60 ppm and 150 ppm. 【0057】 From the standpoint of further improving wear resistance and more effectively suppressing the decrease in adhesive strength, the silicon atom content is preferably 70 ppm or more, more preferably 75 ppm or more, and even more preferably 80 ppm or more. 【0058】 From the standpoint of further improving tear strength, the silicon atom content is preferably 140 ppm or less, more preferably 135 ppm or less, and even more preferably 130 ppm or less. 【0059】The silicon atom content in modified polybutadiene can be controlled by the type and amount of the modifying agent used. In this specification, the silicon atom content, the nitrogen atom content (described later), and the lithium atom content (described later) can be measured, for example, using ICP emission spectrometry (inductively coupled plasma emission spectrometry). Specific measurement methods should be referred to in the examples. 【0060】 <Nitrogen atom content in modified polybutadiene> The nitrogen atom content in modified polybutadiene is between 80 ppm and 280 ppm. 【0061】 From the standpoint of further improving wear resistance and more effectively suppressing the decrease in adhesive strength, the nitrogen atom content is preferably 90 ppm or more, more preferably 95 ppm or more, and even more preferably 100 ppm or more. 【0062】 From the standpoint of further improving tear strength, the nitrogen atom content is preferably 180 ppm or less, more preferably 170 ppm or less, even more preferably 160 ppm or less, even more preferably 150 ppm or less, and even more preferably 140 ppm or less. 【0063】 The nitrogen atom content in modified polybutadiene can be controlled by the nitrogen-containing compound and its amount used, the type and amount of the non-coupling nitrogen-containing compound, and the type and amount of the modifying agent. 【0064】 <Lithium atom content in modified polybutadiene> The lithium atom content in modified polybutadiene may be 2 ppm or more and 130 ppm or less. 【0065】 The lithium atom content may be 20 ppm to 110 ppm, or 40 ppm to 90 ppm, in order to suppress the hydrolysis of the adhesive that bonds the midsole and outsole. 【0066】 The lithium atom content in modified polybutadiene can be controlled by the polymerization initiator and its amount used. 【0067】<Amount of 1,2-vinyl binding in modified polybutadiene> The amount of 1,2-vinyl binding in modified polybutadiene is the molar ratio of the amount of 1,2-vinyl binding when based on the content of structural units derived from 1,3-butadiene. From the viewpoint of obtaining better grip, the amount of 1,2-vinyl binding in modified polybutadiene is preferably 9 mol% or more, more preferably 10 mol% or more, even more preferably 11 mol% or more, and even more preferably 12 mol% or more, based on the content of structural units derived from 1,3-butadiene (100 mol%). 【0068】 From the viewpoint of further improving abrasion resistance, the amount of 1,2-vinyl bonded material in modified polybutadiene is preferably 40 mol% or less, more preferably 35 mol% or less, even more preferably 32 mol% or less, and even more preferably 30 mol% or less, based on 100 mol% of the structural unit content derived from 1,3-butadiene. 【0069】 The amount of 1,2-vinyl bond can be controlled within the above numerical range by adjusting the reaction start and end temperatures during polymerization of the conjugated diene polymer, as well as the type and amount of polar compound added. 【0070】 In this specification, the amount of 1,2-vinyl bonds in modified polybutadiene and the amount of styrene bonds in modified polybutadiene are, for example, １ Each can be measured using H-NMR. For specific measurement methods, please refer to the examples. 【0071】 <Molecular weight and molecular weight distribution of modified polybutadiene> In order for the outsole rubber composition of this embodiment to have better dimensional stability and improved abrasion resistance and tear strength, the weight-average molecular weight (Mw) of modified polybutadiene is preferably 150,000 or more, more preferably 200,000 or more, and even more preferably 350,000 or more. 【0072】 From the viewpoint of the rubber composition having better processability, the weight-average molecular weight (Mw) of the modified polybutadiene is preferably 1 million or less, more preferably 800,000 or less, and even more preferably 650,000 or less. 【0073】From the standpoint of further improving tear strength, the molecular weight distribution (= weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of the modified polybutadiene is preferably 3.00 or less, more preferably 2.00 or less, even more preferably 1.80 or less, and even more preferably 1.60 or less. 【0074】 From the viewpoint of having better processability in the rubber composition, the molecular weight distribution (Mw / Mn) of the modified polybutadiene is preferably 1.05 or higher, more preferably 1.10 or higher, and even more preferably 1.20 or higher. 【0075】 In this specification, the weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn), as well as the peak-top molecular weight (Mp) and differential molecular weight distribution curve described later, can be calculated from the molecular weight on a standard polystyrene basis, measured by GPC (gel permeation chromatography). Specific measurement methods should be referred to in the examples. 【0076】 <Differential Molecular Weight Distribution Curve of Modified Polybutadiene> When the total area of ​​the differential molecular weight distribution curve obtained by GPC measurement is set to 100%, it is preferable that modified polybutadiene has two or more peaks with an area of ​​10% or more, and among those peaks with an area of ​​10% or more, the area of ​​the lowest molecular weight peak is between 15% and 70%. 【0077】 If the rubber composition has two or more peaks with an area of ​​10% or more, it tends to have better elongation. Since it tends to have even better elongation, it is preferable that the number of peaks with an area of ​​10% or more be three or more. The upper limit of the number of peaks with an area of ​​10% or more is not limited to the following, but is usually six or less. 【0078】 From the viewpoint of having superior elongation, the area of ​​the lowest molecular weight peak among the peaks with an area of ​​10% or more is more preferably 20% or more, and even more preferably 25% or more. From the viewpoint of further improving tear strength, the area of ​​the lowest molecular weight peak among the peaks with an area of ​​10% or more is more preferably 65% ​​or less, and even more preferably 60% or less. 【0079】<Mooney viscosity of modified polybutadiene> From the viewpoint of further improving the tear strength, the Mooney viscosity (ML （１＋４） ) at 100 ° C of the modified polybutadiene is preferably 40 or more, more preferably 50 or more, still more preferably 55 or more, and even more preferably 57 or more. 【0080】 From the viewpoint of obtaining better grip properties, the Mooney viscosity (ML （１＋４） ) at 100 ° C of the modified polybutadiene is preferably 100 or less, more preferably 80 or less, still more preferably 70 or less, and even more preferably 65 or less. 【0081】 In this specification, the Mooney viscosity (ML （１＋４） ) at 100 ° C of the modified polybutadiene is measured at a temperature of 100 ° C in accordance with JIS K6300-1: 2013 (ISO 289-1: 2005) using a Mooney viscometer. For a specific measurement method, refer to the examples. 【0082】 <Mooney relaxation rate of modified polybutadiene> From the viewpoint of processability, the Mooney relaxation rate (MSR) at 100 ° C of the modified polybutadiene is preferably 0.30 or more, more preferably 0.40 or more, and still more preferably 0.50 or more. 【0083】 From the viewpoint of tensile strength, the Mooney relaxation rate (MSR) at 100 ° C of the modified polybutadiene is preferably 0.80 or less, more preferably 0.75 or less, and still more preferably 0.70 or less. 【0084】 The Mooney viscosity and the Mooney relaxation rate can be controlled by the content of silicon atoms and nitrogen atoms in the modified polybutadiene, and the molecular weight of the modified polybutadiene. 【0085】 In this specification, the Mooney relaxation rate (MSR) at 100 ° C of the modified polybutadiene can be measured as follows. That is, in accordance with JIS K6300-1: 2013 (ISO 289-1: 2005), first preheat the sample at 100 ° C for 1 minute. Subsequently, rotate the rotor at 2 rpm, and from the torque after 4 minutes, the Mooney viscosity (ML (1+4)The torque is measured. Then, the rotor rotation is immediately stopped, and the torque is recorded in Mooney units at 0.1-second intervals for 1.6 to 5 seconds after stopping, and the torque and time (seconds) are plotted on a log-log scale. The slope of the resulting line is determined, and its absolute value is defined as the Mooney relaxation rate (MSR). The Mooney relaxation rate (MSR) is measured at a temperature of 100°C. For specific measurement methods, please refer to the examples. 【0086】 <Reformation Rate> In this specification, "reformation rate" refers to the rate of deformation due to nitrogen atom-containing functional groups, and represents the mass ratio of modified polybutadiene having nitrogen atom-containing functional groups to the total amount of modified polybutadiene. 【0087】 For example, when a modifying agent or a nitrogen atom-containing compound is reacted with the ends of a polymer, the mass ratio of the polymer having nitrogen atom-containing functional groups due to the modifying agent or nitrogen atom-containing compound to the total amount of the polymer is expressed as the modification rate. 【0088】 Furthermore, if the modifying agent or nitrogen atom-containing compound is a branching agent containing nitrogen atoms, and the polymer is branched by that branching agent, the resulting polymer will also have nitrogen atom-containing functional groups. Therefore, this branched polymer will also be counted when calculating the modification rate. 【0089】 Furthermore, when polymers containing nitrogen atom-containing functional groups are formed by the aforementioned coupling-positive or non-coupling-positive nitrogen-containing compounds, these are also counted when calculating the modification rate. 【0090】 In other words, in this specification, a polymer having a nitrogen atom-containing functional group refers to a polymer having a nitrogen atom-containing functional group due to a modifying agent or a nitrogen atom-containing modifying agent, a branched polymer due to a branching agent, and a polymer having a nitrogen atom-containing functional group due to a coupling nitrogen-containing compound or a non-coupling nitrogen-containing compound, and the total mass ratio of these is the "modification rate". 【0091】The modified polybutadiene used in the outsole rubber composition of this embodiment has improved stability in performance and quality due to improved processability and filler dispersibility. Therefore, when all of the polybutadiene polymers constituting the modified polybutadiene contain nitrogen atom-containing functional groups, the modification rate by nitrogen atom-containing functional groups is preferably 30% to 90%, more preferably 40% to 85%, and even more preferably 60% to 80%, relative to 100% of the modified polybutadiene. 【0092】 The denaturation rate can be measured, for example, by chromatography, which can separate denatured components containing functional groups from undenatured components. 【0093】 One method using this chromatography is to use a gel permeation chromatography column packed with a polar compound such as silica that adsorbs nitrogen atom-containing functional groups, and quantify the non-adsorbed components using an internal standard for comparison (column adsorption GPC method). 【0094】 More specifically, the denaturation rate can be determined by measuring the amount adsorbed onto the silica column from the difference between the chromatogram measured on a polystyrene gel column and the chromatogram measured on a silica column, for a sample solution containing the sample and a low molecular weight internal standard polystyrene. 【0095】 In the modified polybutadiene used in the outsole rubber composition of this embodiment, the modification rate can be controlled, for example, by adjusting the amount of the modifying agent added and the reaction method. 【0096】 <Modifying groups in modified polybutadiene> Modified polybutadiene preferably has a modifying group derived from a compound having one or more amino groups and two or more alkoxysilyl groups. In modified polybutadiene, there are usually 12 or fewer amino groups and 16 or fewer alkoxysilyl groups. 【0097】<Additives> Modified polybutadiene may contain additives such as antioxidants, anti-aging agents, UV inhibitors, antistatic agents, and color inhibitors, as needed. Additives may be used individually or in combination of two or more. 【0098】 Examples of antioxidants include n-octadecyl-3-(3,5-di-t-butyl-4-hydrooxyphenyl)propionate and 4,6-bis(octylthiomethyl)-o-cresol. The antioxidant may be used alone or in combination of two or more. 【0099】 The additive content is typically between 0.1 parts by mass and 10.0 parts by mass per 100 parts by mass of modified polybutadiene. 【0100】 <Method for producing modified polybutadiene> The method for producing modified polybutadiene according to this embodiment includes, for example, a polymerization step in which a polymerization reaction is carried out using 1,3-polybutadiene as a monomer, and a modification step in which modification is carried out after the polymerization step with a modifying agent together with a nitrogen-containing compound as necessary. 【0101】 <<Polymerization Process>> In the polymerization process of the modified polybutadiene of this embodiment, it is preferable to polymerize the polybutadiene having active ends obtained by a growth reaction by an anionic polymerization reaction using, for example, a polymerization solvent, a polar compound, and a polymerization initiator. It is even more preferable to polymerize the polybutadiene having active ends by a growth reaction by living anionic polymerization. This makes it possible to obtain polybutadiene with a high degree of modification. 【0102】The polymerization method is not particularly limited, but examples include batch polymerization and continuous polymerization. In continuous polymerization, one or more connected reactors can be used. Reactors such as tank-type and tubular reactors with stirrers can be used. When polymerization is carried out by batch polymerization, it tends to produce modified polybutadiene with a more stable and suitable molecular weight distribution compared to continuous polymerization. Using such modified polybutadiene tends to improve the processability when vulcanizing. 【0103】 The polymerization temperature is not particularly limited as long as it is the temperature at which living anionic polymerization proceeds, but from the viewpoint of productivity, it is preferably 0°C or higher. From the viewpoint of ensuring a sufficient reaction amount of the modifying agent or nitrogen-containing compound to the active ends after polymerization is complete, the polymerization temperature is preferably 120°C or lower. Furthermore, from the viewpoint of preventing cold flow of modified polybutadiene, a polyfunctional aromatic vinyl compound such as divinylbenzene may be used to control branching. 【0104】 (Polymerization Solvent) The polymerization process is preferably carried out in a solvent. Examples of solvents include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specifically, these include 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. The solvent may be used alone or in combination of two or more. 【0105】 (Polymerization Initiator) The polymerization initiator may be an organolithium compound, or a reaction product of a nitrogen-containing compound and organolithium. Refer to the above for information on organolithium compounds and reaction products. 【0106】(Polar Compounds) Polar compounds may be added before or after the polymerization initiator is added during the polymerization process. In anionic polymerization, polar compounds may be used to adjust the microstructure of modified polybutadiene (adjust the amount of vinyl bonds) or to accelerate the polymerization rate. Examples of polar compounds include ether compounds, tertiary amine compounds, and alkali metal alkoxide compounds. 【0107】 Examples of polar compounds include, but are not limited to, ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium-t-amylate, potassium-t-butyrate, sodium-t-butyrate, and sodium amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used individually or in combination of two or more. 【0108】 The amount of polar compound used is not particularly limited and can be selected according to the purpose. Typically, it is 0.001 mol to 100 mol per 1 mol of the polymerization initiator mentioned above. 【0109】 <<Modification Process>> The modification process involves reacting the polybutadiene with the aforementioned modifying agent or nitrogen-containing compound after the polymerization process to modify it. Refer to the above for the modifying agent or nitrogen-containing compound to be used. 【0110】 (Other Rubbers) The rubber composition for the outsole of this embodiment preferably further contains other rubbers other than modified polybutadiene as rubber components. 【0111】Other types of rubber include, for example, natural rubber and synthetic rubber. These other types of rubber may be used individually or in combination of two or more types. 【0112】 Examples of natural rubber include, but are not limited to, smoke-dried RSS (Ribbed Smoked Sheet) No. 3 to 5, mechanically dried TSR (Technically Specified Rubber) such as SIR (Standard Indonesian Rubber) (from Indonesia), STR (Standard Thai Rubber) (from Thailand), SMR (Standard Malaysian Rubber) (from Malaysia), etc., and epoxidized natural rubber. Natural rubber may be used alone or in combination of two or more types. 【0113】 Examples of synthetic rubbers include, but are not limited to, polybutadiene rubber other than modified polybutadiene (BR), polyisoprene rubber (IR), styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber (HSBR), acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile rubber (HNBR), chloroprene rubber, butyl rubber (IIR), brominated butyl rubber (BIIR), chlorinated butyl rubber (CIIR), ethylene-propylene-diene rubber (EPDM), epichlorohydrin rubber (ECO), urethane rubber (U), chlorosulfonated polyethylene rubber (CSM), acrylic rubber (ACM), silicone rubber (Q), and fluororubber (FKM). Synthetic rubbers also include thermoplastic elastomers and thermosetting elastomers. Synthetic rubbers may be used individually or in combination of two or more types. 【0114】 The rubber component included in the rubber composition preferably contains two or more other types of rubber in addition to modified polybutadiene. 【0115】As for other rubbers, at least one selected from the group consisting of polybutadiene rubber other than modified polybutadiene (BR), polyisoprene rubber (IR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber, butyl rubber (IIR), butyl rubber brominated (BIIR), butyl rubber chlorinated (CIIR), and ethylene-propylene-diene rubber (EPDM) is preferred because it offers a better balance of abrasion resistance and grip, as well as superior cost and supply stability. 【0116】 The content of other rubbers is 50 parts by mass or more and 90 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. The content of modified polybutadiene is 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. 【0117】 From the standpoint of further improving abrasion resistance and tear strength and further suppressing the decrease in adhesive strength, the total content of other rubbers is preferably 56 parts by mass or more and 84 parts by mass or less, more preferably 60 parts by mass or more and 80 parts by mass or less, and even more preferably 62 parts by mass or more and 78 parts by mass or less, per 100 parts by mass of the total rubber components in the rubber composition. The content of modified polybutadiene is preferably 16 parts by mass or more and 44 parts by mass or less, more preferably 20 parts by mass or more and even more preferably 22 parts by mass or more and 38 parts by mass or less, per 100 parts by mass of the total rubber components in the rubber composition. In this specification, the total rubber components refer to the total rubber components of modified polybutadiene and other rubbers contained in the rubber composition, and the total rubber components do not include the liquid rubber and other components described later. 【0118】 - It is preferable that the other rubber further includes polybutadiene rubber other than modified polybutadiene, as it offers a better balance of abrasion resistance and grip, as well as superior cost and supply stability. 【0119】From the standpoint of providing a better balance of abrasion resistance and grip, as well as superior cost and supply stability, the total content of modified polybutadiene and polybutadiene rubber other than modified polybutadiene is preferably 70 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. 【0120】 The rubber composition preferably contains at least one selected from the group consisting of polybutadiene rubber other than modified polybutadiene and polyisoprene rubber, and more preferably further contains polybutadiene rubber other than modified polybutadiene and polyisoprene rubber. 【0121】 From the standpoint of further improving abrasion resistance and tear strength and further suppressing the decrease in adhesive strength, the content of modified polybutadiene is preferably 10 parts by mass or more and 50 parts by mass or less, more preferably 16 parts by mass or more and 43 parts by mass or less, even more preferably 21 parts by mass or more and 40 parts by mass or less, and even more preferably 25 parts by mass or more and 37 parts by mass or less, based on 100 parts by mass of the total rubber components in the rubber composition. 【0122】 In order to further suppress the decrease in adhesive strength, the polyisoprene rubber content is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, even more preferably 9 parts by mass or more, and even more preferably 10 parts by mass or more, based on 100 parts by mass of the total rubber components in the rubber composition. 【0123】 From the standpoint of obtaining superior oil resistance, the polyisoprene rubber content is preferably 20 parts by mass or less, more preferably 17 parts by mass or less, even more preferably 15 parts by mass or less, and even more preferably 13 parts by mass or less, based on 100 parts by mass of the total rubber components in the rubber composition. 【0124】 In order to more favorably have a 300% modulus, the content of polybutadiene rubber other than modified polybutadiene is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and even more preferably 50 parts by mass or more, based on 100 parts by mass of the total rubber components in the rubber composition. 【0125】From the standpoint of obtaining better grip, the content of polybutadiene rubber other than modified polybutadiene is preferably 85 parts by mass or less, more preferably 77 parts by mass or less, even more preferably 70 parts by mass or less, and even more preferably 65 parts by mass or less, based on 100 parts by mass of the total rubber components in the rubber composition. 【0126】 - For use as an outsole, a polybutadiene rubber other than modified polybutadiene and styrene-butadiene rubber preferably contains at least one selected from the group consisting of polybutadiene rubber other than modified polybutadiene and styrene-butadiene rubber, in order to obtain more suitable tear strength. It is more preferable that the rubber composition further contains polybutadiene rubber other than modified polybutadiene and styrene-butadiene rubber. 【0127】 From the standpoint of further improving abrasion resistance and tear strength, and further suppressing the decrease in adhesive strength, the content of modified polybutadiene is preferably 10 parts by mass or more and 45 parts by mass or less, and more preferably 13 parts by mass or more and 40 parts by mass or less, per 100 parts by mass of the total rubber components in the rubber composition. 【0128】 For use as an outsole, the content of polybutadiene rubber other than modified polybutadiene is preferably 30 parts by mass or more and 85 parts by mass or less, and more preferably 40 parts by mass or more and 72 parts by mass or less, per 100 parts by mass of the total rubber components in the rubber composition, in order to further improve abrasion resistance and tear strength and to further suppress the decrease in adhesive strength. 【0129】 For outsoles, the styrene-butadiene rubber content is preferably 5 parts by mass or more, and more preferably 15 parts by mass or more, per 100 parts by mass of the total rubber components in the rubber composition, in order to obtain more favorable tear strength. For abrasion resistance, it is preferably 25 parts by mass or less, and more preferably 20 parts by mass or less. 【0130】- For use as an outsole, polybutadiene rubber other than modified polybutadiene, styrene-butadiene rubber, and acrylonitrile-butadiene rubber preferably contains at least one selected from the group consisting of polybutadiene rubber other than modified polybutadiene, styrene-butadiene rubber, and acrylonitrile-butadiene rubber, in order to obtain more favorable oil resistance. 【0131】 From the standpoint of further improving abrasion resistance and tear strength and further suppressing the decrease in adhesive strength, the content of modified polybutadiene is preferably 10 parts by mass or more and 50 parts by mass or less, more preferably 12 parts by mass or more and 45 parts by mass or less, and more preferably 14 parts by mass or more and 35 parts by mass or less, per 100 parts by mass of the total rubber components in the rubber composition. 【0132】 For use as an outsole, the content of polybutadiene rubber other than modified polybutadiene is preferably 20 parts by mass or more and 89 parts by mass or less, more preferably 35 parts by mass or more and 81 parts by mass or less, and more preferably 50 parts by mass or more and 74 parts by mass or less, based on 100 parts by mass of the total rubber components in the rubber composition. 【0133】 For use as an outsole, the amount of acrylonitrile-butadiene rubber is preferably 1 to 30 parts by mass, more preferably 7 to 20 parts by mass, and even more preferably 12 to 15 parts by mass, based on 100 parts by mass of the total rubber components in the rubber composition. 【0134】For use as an outsole, to obtain more favorable oil resistance, the total content of styrene-butadiene rubber and acrylonitrile-butadiene rubber is preferably 1 to 30 parts by mass, more preferably 7 to 20 parts by mass, and even more preferably 12 to 15 parts by mass, per 100 parts by mass of the total rubber components in the rubber composition. 【0135】 Furthermore, other rubbers may be hydrogenated. The method of hydrogenating the rubber is not particularly limited, but for example, the method described in International Publication No. 2021 / 206068 can be used. 【0136】 In this embodiment, the outsole rubber composition has better processability than other rubbers, and therefore the Mooney viscosity (ML) at 100°C is greater than that of other rubbers. （１＋４） The Mooney viscosity (ML) at 100°C is preferably 120 or less, more preferably 90 or less, and even more preferably 60 or less. From the viewpoint of further improving the tear strength of the outsole rubber composition, the Mooney viscosity (ML) at 100°C of other rubbers is preferable. （１＋４） ) is preferably 25 or more, more preferably 35 or more, and even more preferably 45 or more. 【0137】 (Liquid Rubber) The rubber composition for the outsole of this embodiment may contain liquid rubber in order to further improve processability and flexibility. Liquid rubber is different from modified polybutadiene and other rubbers. 【0138】 Examples of liquid rubber include low molecular weight rubbery polymers. Examples of such liquid rubbers include liquid styrene-butadiene rubber (liquid SBR), liquid butadiene rubber (liquid BR), and liquid isoprene rubber (liquid IR). Liquid rubber may be used alone or in combination of two or more types. 【0139】 Furthermore, "liquid rubber" is any component that can be distinguished from the modified polybutadiene and other rubbers contained in the outsole rubber composition of this embodiment by its form (solid or liquid). 【0140】The cis content of the liquid BR is not particularly limited and may include at least one selected from the group consisting of high-cis (cis) liquid butadiene rubber, medium-cis (cis) liquid butadiene rubber, and low-cis (cis) liquid butadiene rubber. 【0141】 Liquid rubber is not particularly limited as long as it is in liquid form, but it is preferable that its peak-top molecular weight (Mp), measured by GPC, is in the range of 1,000 to 50,000. Preferably, the peak-top molecular weight of the liquid rubber measured by GPC is 4,000 to 35,000, and 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 flexibility of the rubber composition tend to be further improved. Note that if liquid rubber with a relatively low peak-top molecular weight is used, the processability will be further improved, but the strength will tend to be further reduced. 【0142】 The liquid rubber content is not particularly limited and can be, for example, 0% to 15.0% by mass relative to 100% by mass of the total rubber components in the rubber composition. Preferably, the liquid rubber content is 0.10% to 10.0% by mass, more preferably 0.20% to 7.0% by mass, and even more preferably 0.30% to 4.0% by mass, relative to 100% by mass of the total rubber components in the rubber composition. 【0143】 The liquid rubber content is not particularly limited and can be, for example, 0 to 15.0 parts by mass per 100 parts by mass of the total rubber components in the rubber composition. Preferably, the liquid rubber content is 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 per 100 parts by mass of the total rubber components in the rubber composition. When the liquid rubber content is within the above range, the processability and flexibility of the rubber composition tend to improve further. 【0144】(Inorganic Filler) The rubber composition for the outsole of this embodiment contains an inorganic filler. The amount of inorganic filler is 20 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. 【0145】 From the viewpoint of further improving abrasion resistance and tear strength, the inorganic filler content is preferably 28 parts by mass or more and 55 parts by mass or less, more preferably 32 parts by mass or more and 50 parts by mass or less, and even more preferably 35 parts by mass or more and 48 parts by mass or less, based on 100 parts by mass of the total rubber components in the rubber composition. 【0146】 The type of inorganic filler is not particularly limited, as long as it is commonly used as a material for rubber compositions for outsoles. Examples of such inorganic fillers include silica (dry silica, wet silica, colloidal silica), synthetic silicate-based white carbon, calcium carbonate, titanium dioxide, and talc. Inorganic fillers may be used individually or in combination of two or more types. 【0147】 Silica is preferred as the inorganic filler, and wet-processed silica is more preferred. 【0148】 When silica is used as an inorganic filler, it is preferable to add substances that improve the affinity between the inorganic filler and the rubber component, such as silane coupling agents, in order to further improve the dispersibility of silica and enhance performance stability and reproducibility. Details of silane coupling agents will be described later. 【0149】 Inorganic fillers may be obtained by purchasing commercially available products, or they may be manufactured by conventionally known methods. 【0150】 Furthermore, the silica content relative to the total mass (100% by mass) of the inorganic filler is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, from the viewpoint of further improving rigidity. There is no particular upper limit, but for example, it is 100% by mass or less. 【0151】(Crosslinking agent) The rubber composition for outsoles of this embodiment may contain a crosslinking agent. Preferably, the rubber composition for outsoles of this embodiment is a crosslinked body of a composition containing a predetermined crosslinking agent. In this specification, the crosslinking agent also includes a vulcanizing agent. 【0152】 The crosslinking agent is not particularly limited, and conventionally known crosslinking agents used for crosslinking rubber compositions can be used. Examples of crosslinking agents include sulfur, sulfur compounds, organic peroxides, and radical crosslinking agents. The crosslinking agent may be used alone or in combination of two or more types. 【0153】Examples of organic peroxides include, but are not limited to, dicumyl peroxide, benzoyl peroxide, di-t-hexyl peroxide, t-butylcumyl peroxide, diisobutyryl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, di(2-t-butylperoxyisopropyl)benzene, cumyl peroxyneodecanoate, and di-n-propyl peroxydicarbonate. , diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, di(4-t-butylcyclohexyl) peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di(3,5,5-tri Methylhexanoyl peroxide, dilauroyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, disuccinate peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, t-butyl peroxy-2-ethylhexanoate, di(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide Dibenzoyl peroxide, 1,1-di(t-butylperoxy)-2-methylcyclohexane, 1,1-di(t-hexylperoxy)-3,5,5-trimethylcyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5Examples include 5-trimethylhexanoate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy 2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butyl peroxyacetate, 2,2-di-(t-butylperoxy)butane, t-butyl peroxybenzoate, n-butyl-4,4-di-(t-butylperoxy)valerate, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide. Organic peroxides may be used individually or in combination of two or more. 【0154】 Examples of radical crosslinking agents include, but are not limited to, ethylene glycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate, triallyl isocyanurate, triallyl cyanurate, diethylene glycol diacrylate, and neopentyl glycol diacrylate. Radical crosslinking agents may be used individually or in combination of two or more. 【0155】 When minimizing contamination of the product, as well as transparency, colorability, and heat resistance, are important, organic peroxides are preferred as crosslinking agents. From the viewpoint of minimizing odor and residue, the crosslinking agent is more preferably at least one selected from the group consisting of dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, di(2-t-butylperoxyisopropyl)benzene, and 1,1-di(t-butylperoxy)cyclohexane. 【0156】 Furthermore, when using rubber with few double bonds, such as butyl rubber, silicone rubber, and fluororubber, it is preferable to select an organic peroxide as the crosslinking agent. 【0157】When cost, tear properties, and ease of processing are important considerations, it is preferable to perform crosslinking by using at least one selected from the group consisting of sulfur and sulfur compounds, and, if necessary, a vulcanization accelerator. 【0158】 Examples of sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, and high-molecular-weight polysulfur compounds. Sulfur compounds may be used individually or in combination of two or more. 【0159】 The crosslinking agent may be used alone or in combination of two or more types. 【0160】 In the manufacturing process of the outsole, the amount of crosslinking agent contained in the rubber composition before molding is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the total rubber components in the rubber composition. Conventional known methods can be applied as the vulcanization method. The vulcanization temperature is preferably 120°C or more and 200°C or less, and more preferably 140°C or more and 180°C or less. 【0161】 When using at least one substance selected from the group consisting of sulfur and sulfur compounds, at least one substance selected from the group consisting of vulcanization accelerators and vulcanization aids may be used as needed. 【0162】 Conventional known materials can be used as vulcanization accelerators, and are not limited to the following, but examples include sulfenamide, guanidine, thiuram, aldehyde-amine, aldehyde-ammonia, thiazole, thiourea, and dithiocarbamate vulcanization accelerators. Specifically, examples of vulcanization accelerators include 2-mercaptobenzothiazole and N-(tert-butyl)-2-benzothiazole sulfenamide. The vulcanization accelerator may be used alone or in combination of two or more types. 【0163】 The amount of vulcanization accelerator is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the total rubber components in the rubber composition. 【0164】Sulfurization aids are not limited to the following, but examples include zinc oxide, stearic acid, and triallyl isocyanurate. Sulfurization aids may be used individually or in combination of two or more. 【0165】 The amount of vulcanization aid is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the total rubber components in the rubber composition. 【0166】 (Other components) When silica is used as an inorganic filler in the rubber composition, it is preferable that the rubber composition contains a silane coupling agent. 【0167】 Examples of silane coupling agents include, but are not limited to, tetraethoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-aminopropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, bis[3-(triethoxysilyl)propyl]tetrasulfide, bis[3-(triethoxysilyl)propyl]disulfide, and alkoxysilane compounds such as triethoxysilylpropyl-methacrylate-monosulfide. The silane coupling agent may be used alone or in combination of two or more. 【0168】 Among these, it is preferable that the silane coupling agent contains bis[3-(triethoxysilyl)propyl]tetrasulfide. 【0169】 The content of the silane coupling agent is not particularly limited, but is, for example, 0 parts by mass or more and 10 parts by mass or less, based on 100 parts by mass of the total rubber components in the rubber composition. 【0170】 From the standpoint of further improving wear resistance, the content of the silane coupling agent is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, based on 100 parts by mass of the total rubber components in the rubber composition. 【0171】From the viewpoint of further improving tear strength, the content of the silane coupling agent is preferably 9.0 parts by mass or less, more preferably 8.0 parts by mass or less, and even more preferably 7.0 parts by mass or less, per 100 parts by mass of the total rubber components in the rubber composition. 【0172】 The rubber composition may further contain other components in addition to those listed above. Such other components include antioxidants, colorants, modifiers, reducing agents, processing agents (fatty acids, etc.), oxygen absorbers, light stabilizers, pH stabilizers, surface treatment agents, heat stabilizers, colorants, fillers (talc, calcium carbonate, etc.), surfactants, gelling agents, UV absorbers (salicylic acid, benzophenone, benzotriazole, cyanoacrylate, hindered amines, etc.), dusting agents (polyolefins such as polyethylene, talc, calcium carbonate powder, etc.), and polyphosphates. These other components may be used individually or in combination of two or more. 【0173】 The content of other components is not particularly limited, but is approximately 0.1 parts by mass to 15 parts by mass per 100 parts by mass of the total rubber components in the rubber composition. 【0174】 Examples of antioxidants include, but are not limited to, monophenol, bisphenol, polyphenol, sulfur, and phosphorus compounds. Specifically, examples of antioxidants include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. Specifically, examples include Nocrac® 6C, Nocrac® SP (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), Irganox® 1076 (manufactured by BASF), Irgaphos® 168 (manufactured by BASF), and Irganox® 1520 (manufactured by BASF). Antioxidants may be used individually or in combination of two or more. 【0175】 Colorants may be used if you want to color the outsole. 【0176】Such colorants may be any known colorants, such as coloring pigments, extender pigments, rust-preventive pigments, and functional pigments (e.g., phthalocyanine green, titanium dioxide, Prussian blue, iron oxide, lead oxide, and zinc sulfide). The colorants may be used individually or in combination of two or more. 【0177】 Other components are present in a total amount of 0.1 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. When these components are included, the total amount of these components is preferably 0.2 parts by mass or more and 10 parts by mass or less, more preferably 0.20 parts by mass or more and 5.0 parts by mass or less, and even more preferably 0.25 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. 【0178】 In rubber compositions, the difference (ΔG') between the storage modulus at 0.1% strain and the storage modulus at 10% strain, measured in rotation mode at a frequency of 10 Hz and a test temperature of 50°C according to JIS K6394:2007 for rubber composition test specimens, is preferably 0.80 or less, more preferably 0.70 or less, and even more preferably 0.65 or less, from the viewpoint of further improving mechanical strength such as flexibility. The lower limit of the difference (ΔG') is not particularly limited, but for example, it is 0.05 or more. For a specific method of calculating ΔG', please refer to the examples. 【0179】 [Method for producing the rubber composition for outsoles] The rubber composition for outsoles of this embodiment preferably contains a specified amount of the above-mentioned modified polybutadiene and inorganic filler, and is crosslinked using a crosslinking agent. Furthermore, it is preferable to produce it by optionally adding other components in appropriate mixing ratios and kneading them together. 【0180】 More specifically, for example, the following methods may be used. 【0181】The method for producing the outsole rubber composition of this embodiment includes, for example, a kneading step of kneading raw materials containing a total rubber component and an inorganic filler. One example includes a step of kneading modified polybutadiene and other rubbers as rubber components, silica, a silane coupling agent, an antioxidant, a vulcanization aid, sulfur as a vulcanizing agent, and a vulcanization accelerator as fillers, and a step of molding the resulting kneaded product. 【0182】 The above mixing process may include, as a first stage of mixing, a step of obtaining a first stage formulation by mixing modified polybutadiene and other rubber as rubber components, silica as a filler, a silane coupling agent, an antioxidant, and a vulcanization aid, and as a second stage of mixing, a step of obtaining a second stage formulation by mixing the first stage formulation with sulfur as a vulcanizing agent and a vulcanization accelerator. 【0183】 The first stage of mixing can be done in any way, such as mixing all the materials at once or preparing a masterbatch. Mixing all materials at once means that the mixture is not discharged from the mixer after the materials are added, and the mixing of all the materials for the first stage is completed in one go. Mixing with a masterbatch means that the modified polybutadiene and the inorganic filler are mixed first, the masterbatch is discharged from the mixer, and then the masterbatch and the other materials are put back into the mixer and mixed. 【0184】 Mixing in a single step reduces the number of steps in the outsole production process, thereby improving productivity. Furthermore, from the viewpoint of the colorability of the outsole in this embodiment, mixing in a single step is preferable. 【0185】 The above mixing process can be carried out using, for example, an open roll, a Banbury mixer, a kneader, a twin-screw extruder, and / or a Laboplast mill. 【0186】 The mixing of the rubber component, filler, and optionally the silane coupling agent and antioxidant may be carried out at a temperature of, for example, 120°C to 160°C, from the viewpoint of uniformly mixing each component. 【0187】The kneading after adding the crosslinking agent may be carried out at a temperature of, for example, 120°C or lower, from the viewpoint of suppressing side reactions. The temperature during kneading after adding the crosslinking agent is preferably 110°C or lower, more preferably 105°C or lower, and even more preferably 0°C to 100°C. 【0188】 In the above kneading process, other components may be added as appropriate. 【0189】 A cross-linked rubber composition of a desired shape can be obtained by a molding process in which the kneaded material is shaped. The molding process may, for example, involve placing the kneaded material obtained in the kneading process into a press die of a suitable shape and heating it. Alternatively, it may involve press molding the kneaded material obtained in the kneading process and punching it out into any desired shape using a punching die. 【0190】 The molding temperature in the molding process is not particularly limited, but is preferably 140°C to 180°C, and more preferably 150°C to 170°C. 【0191】 [Outsole] The outsole of this embodiment may be obtained by vulcanizing and molding an outsole rubber composition. 【0192】 The outsole may be made from a cross-linked rubber composition after molding. Alternatively, the outsole may be made from a cross-linked rubber composition with grooves carved into it to create an uneven surface. 【0193】 The outsole of this embodiment is used as an outsole for shoes. 【0194】 Shoes using the outsole of this embodiment are typically manufactured as follows: The outsole is bonded to the midsole using an adhesive, and then pressed against the midsole. The resulting outsole is then bonded to the upper part of the shoe using an adhesive, and the shoe is manufactured by pressing them together. 【0195】In this embodiment, the force (N) required to bend the outsole to a bending angle of 45°, as measured in accordance with ISO 17707-2005, is preferably 1N to 40N, more preferably 1N to 32N, even more preferably 1N to 26N, and even more preferably 1N to 20N, from the viewpoint of improving the adhesive strength after repeated bending tests. 【0196】 The outsole of this embodiment reduces the number of tripping incidents, and therefore has a low coefficient of dynamic friction (μ) in a dry state. DRY ) and the coefficient of kinetic friction in wet conditions (μ WET The difference (μ) DRY -μ WET The ratio is preferably 0.05 to 0.70, more preferably 0.10 to 0.66, even more preferably 0.15 to 0.62, and even more preferably 0.20 to 0.57. 【0197】 The present invention will be described below with reference to specific polymerization examples, embodiments, and comparative examples, but the present invention is not limited in any way by the following polymerization examples, embodiments, and comparative examples. That is, those skilled in the art can implement the present invention by making various modifications to the embodiments shown below. The various physical properties in the polymerization examples, embodiments, and comparative examples were measured by the methods shown below. Also, unless otherwise specified below, "parts" are based on mass. 【0198】 [Method for measuring physical properties] [GPC measurement] Modified polybutadiene was measured using a GPC measuring device with three columns connected together and packed with polystyrene gel. Based on the obtained chromatogram and a calibration curve using standard polystyrene, the weight-average molecular weight (Mw), number-average molecular weight (Mn), molecular weight distribution (Mw / Mn), and differential molecular weight distribution curve of modified polybutadiene were determined. Furthermore, with the total area of ​​the obtained differential molecular weight distribution curve set to 100%, the number of peaks with an area of ​​10% or more and the area (%) of the lowest molecular weight peak among those peaks with an area of ​​10% or more were determined. 【0199】The specific measurement conditions are shown below. Measurement was performed by injecting 20 μL of the measurement solution into the GPC measuring instrument. (Measurement conditions) Instrument: "HLC-8320GPC" manufactured by Tosoh Corporation Eluent: 5 mmol / L tetrahydrofuran (THF) containing triethylamine Guard column: "TSKguardcolumn SuperH-H" manufactured by Tosoh Corporation Separation column: "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" manufactured by Tosoh Corporation linked in this order. Oven temperature: 40℃ Flow rate: 0.6 mL / min Detector: RI detector ("HLC8020" manufactured by Tosoh Corporation) Measurement solution: Measurement solution obtained by dissolving 10 mg of the sample in 20 mL of THF 【0200】 [Mooney Viscosity] The Mooney viscosity of modified polybutadiene was measured using a Mooney viscometer (product name "VR1132" manufactured by Ueshima Seisakusho Co., Ltd.) in accordance with JIS K6300-1:2013 (ISO 289-1:2005). The measurement temperature was 100°C. Here, the sample was preheated for 1 minute, the rotor was rotated at 2 rpm, and the torque after 4 minutes was measured to determine the Mooney viscosity (ML). （１＋４） ) 【0201】 [Mooney Relaxation Rate] Following the measurement method described above, the Mooney viscosity was measured, and then the Mooney relaxation rate of the modified polybutadiene was measured. Specifically, after measuring the Mooney viscosity, the rotor rotation was immediately stopped, and the torque was recorded in Mooney units at 0.1-second intervals for 1.6 to 5 seconds after stopping. The torque and time (seconds) were then plotted on a log-log scale. The slope of the resulting line was determined, and its absolute value was defined as the Mooney relaxation rate (MSR). The measurement temperature was 100°C. 【0202】 [Amount of 1,2-vinyl bond] Modified polybutadiene was used as the sample. １The amount of 1,2-vinyl bond in the butadiene portion (mol%) was measured by 1H-NMR. <Measurement conditions> Measuring instrument: JNM-LA400 (manufactured by JEOL) Solvent: Deuterated chloroform Sample: Conjugated diene polymer Sample concentration: 50 mg / mL Observation frequency: 400 MHz Chemical shift reference: 5% by weight of TMS (tetramethylsilane) added to deuterated chloroform Pulse delay: 2.904 seconds Number of scans: 64 Pulse width: 45° Measurement temperature: 26°C 【0203】 [Measurement of silicon, nitrogen, and lithium atom content] The content (ppm) of silicon, nitrogen, and lithium atoms in modified polybutadiene was determined using an ICP emission spectrometer (ICPS-8100, manufactured by Shimadzu Corporation). 【0204】 [Synthesis of Modified Polybutadiene] ((Synthesis Example 1) Modified Polybutadiene 1) Using a temperature-controlled autoclave with an internal volume of 10 L, equipped with a stirrer and jacket, 800 g of 1,3-butadiene from which impurities had been removed beforehand, 7000 g of cyclohexane, and 7.81 mmol of tetrahydrofuran (THF) as a polar compound were placed in the reactor, and the reactor temperature was maintained at 55.4°C. 【0205】 6.70 mmol of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction started, the temperature inside the reactor rose due to the heat generated by polymerization, and the reaction peak temperature was 80.2°C. One minute after reaching the reaction peak temperature, 0.586 mmol of tetraglycidyl-1,3-bisaminomethylcyclohexane was added and stirred for 30 seconds, then 2.78 mmol of 3-(4-methylpiperazine-1-yl)propyltriethoxysilane was added and stirred for 5 minutes. 6.70 mmol of ethanol was added to this polymer solution as a reaction stopper. 【0206】To the solution of the obtained polymer, 4.8 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 1.6 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. Then, the modified polybutadiene solution was removed by dropping it into warm water, and the solution was dried in a drying oven to obtain modified polybutadiene 1. The obtained modified polybutadiene 1 was analyzed by the method described above. The results are shown in Table 1. 【0207】 ((Synthesis Example 2) Modified Polybutadiene 2) Using a temperature-controlled autoclave with an internal volume of 10 L, equipped with a stirrer and jacket, 800 g of 1,3-butadiene from which impurities had been removed beforehand, 7000 g of cyclohexane, and 7.31 mmol of tetrahydrofuran (THF) as a polar compound were placed in the reactor, and the reactor temperature was maintained at 57.1°C. 【0208】 5.66 mmol of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction started, the temperature inside the reactor rose due to the heat generated by polymerization, and the reaction peak temperature was 79.3°C. One minute after reaching the reaction peak temperature, 2.83 mmol of 3-(4-methylpiperazine-1-yl)propyltriethoxysilane was added and the mixture was stirred for 5 minutes. 5.66 mmol of ethanol was added to this polymer solution as a reaction stopper. 【0209】 To the obtained polymer solution, 4.8 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 1.6 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. Subsequently, the modified polybutadiene solution was removed by dropping it into warm water, and the solution was dried in a drying oven to obtain modified polybutadiene 2. The obtained modified polybutadiene 2 was analyzed by the method described above. The results are shown in Table 1. 【0210】((Synthesis Example 3) Modified Polybutadiene 3) Using a temperature-controlled autoclave with an internal volume of 10 L, equipped with a stirrer and jacket, 800 g of 1,3-butadiene from which impurities had been removed beforehand, 7000 g of cyclohexane, and 7.85 mmol of tetrahydrofuran (THF) as a polar compound were placed in the reactor, and the reactor temperature was maintained at 56.7°C. 【0211】 As a polymerization initiator, 6.14 mmol of n-butyllithium was supplied to the reactor. After the polymerization reaction started, the temperature inside the reactor rose due to the heat generated by polymerization, and the reaction peak temperature was 82.7°C. One minute after reaching the reaction peak temperature, 0.384 mmol of tetraglycidyl-1,3-bisaminomethylcyclohexane was added and stirred for 30 seconds, then 3.65 mmol of 3-(4-methylpiperazine-1-yl)propyltriethoxysilane was added and stirred for 5 minutes. To this polymer solution, 6.14 mmol of ethanol was added as a reaction stopper. 【0212】 To the obtained polymer solution, 4.8 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 1.6 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. Subsequently, the modified polybutadiene solution was removed by dropping it into warm water, and the solution was dried in a drying oven to obtain modified polybutadiene 3. The obtained modified polybutadiene 3 was analyzed by the method described above. The results are shown in Table 1. 【0213】 ((Synthesis Example 4) Modified Polybutadiene 4) Using a temperature-controlled autoclave with an internal volume of 10 L, equipped with a stirrer and jacket, 800 g of 1,3-butadiene from which impurities had been removed beforehand, 7000 g of cyclohexane, and 7.72 mmol of tetrahydrofuran (THF) as a polar compound were placed in the reactor, and the reactor temperature was maintained at 55.9°C. 【0214】As a polymerization initiator, 6.41 mmol of n-butyllithium was supplied to the reactor. After the polymerization reaction started, the temperature inside the reactor rose due to the heat generated by polymerization, and the reaction peak temperature was 78.6°C. One minute after reaching the reaction peak temperature, 0.561 mmol of tetraglycidyl-1,3-bisaminomethylcyclohexane was added and stirred for 30 seconds, then 1.87 mmol of 3-(4-methylpiperazine-1-yl)propyltriethoxysilane was added and stirred for 5 minutes. To this polymer solution, 6.41 mmol of ethanol was added as a reaction stopper. 【0215】 To the solution of the obtained polymer, 4.8 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 1.6 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. Then, the modified polybutadiene solution was removed by dropping it into warm water, and the solution was dried in a drying oven to obtain modified polybutadiene 4. The obtained modified polybutadiene 4 was analyzed by the method described above. The results are shown in Table 1. 【0216】 ((Synthesis Example 5) Modified Polybutadiene 5) Using a temperature-controlled autoclave with an internal volume of 10 L, equipped with a stirrer and jacket, 800 g of 1,3-butadiene from which impurities had been removed beforehand, 7000 g of cyclohexane, 7.81 mmol of tetrahydrofuran (THF) as a polar compound, and 6.70 mmol of piperidine were added to the reactor, and the reactor temperature was maintained at 52.9°C. 【0217】 6.70 mmol of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction started, the temperature inside the reactor rose due to the heat generated by polymerization, and the reaction peak temperature reached 79.1°C. One minute after reaching the reaction peak temperature, 0.586 mmol of tetraglycidyl-1,3-bisaminomethylcyclohexane was added and stirred for 30 seconds, then 2.78 mmol of 3-(4-methylpiperazine-1-yl)propyltriethoxysilane was added and stirred for 5 minutes. 6.70 mmol of ethanol was added to this polymer solution as a reaction stopper. 【0218】To the obtained polymer solution, 4.8 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 1.6 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. Subsequently, the modified polybutadiene solution was removed by dropping it into warm water, and the solution was dried in a drying oven to obtain modified polybutadiene 5. The obtained modified polybutadiene 5 was analyzed by the method described above. The results are shown in Table 1. 【0219】 【0220】 The modified polybutadienes obtained in Synthesis Examples 1 to 4 were modified with 3-(4-methylpiperazine-1-yl)propyltriethoxysilane, a compound having two amino groups and three alkoxysilyl groups. Therefore, the modified polybutadienes obtained in Synthesis Examples 1 to 4 each had a modifying group derived from the above compound. 【0221】 The modified polybutadiene obtained in Synthesis Example 5 was modified with piperidine, a compound having one amino group, and with 3-(4-methylpiperazine-1-yl)propyltriethoxysilane, a compound having two amino groups and three alkoxysilyl groups. Therefore, the modified polybutadiene obtained in Synthesis Example 5 had modifying groups derived from the above compounds. 【0222】[Production of rubber composition for outsoles and outsoles] (Example 1) A rubber composition for outsoles was obtained according to the following compounding materials and amounts. <Composition of rubber composition for outsoles> ・Rubber component 1 (modified polybutadiene 1 obtained in the synthesis example): 15.0 parts by mass ・Rubber component 2 (polybutadiene rubber, UBEPOL® Highsys BR150 (product name), manufactured by UBE Elastomer Co., Ltd.): 75.0 parts by mass ・Rubber component 3 (polyisoprene rubber, Nipol® IR2200 (product name), manufactured by Nippon Zeon Co., Ltd.): 10.0 parts by mass ・Filler (wet silica, Ultrasil® VN3 (product name), manufactured by Evonik): 40.0 parts by mass ・Silane coupling agent (bis[3-(triethoxysilyl)propyl]tetrasulfide, S i69 (trade name), manufactured by Evonik: 2.0 parts by mass; Antioxidant (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, Nocrack® 6C (trade name), manufactured by Ouchi Shinko Chemical Industry Co., Ltd.): 1.0 part by mass; Sulfurization aid (zinc oxide): 3.0 parts by mass; Sulfurization aid (stearic acid): 2.0 parts by mass; Sulfurizing agent (sulfur): 1.4 parts by mass; Sulfurization accelerator (2-mercaptobenzothiazole, MBT): 1.0 part by mass; Sulfurization accelerator (N-(tert-butyl)-2-benzothiazole sulfenamide, TBBS): 1.0 part by mass; Total: 151.4 parts by mass 【0223】 The above materials were kneaded by the following method to obtain a rubber composition for outsoles. Using a Banbury mixer with a capacity of 0.6 L (Laboplastmill® 10C100 model B600 (product name) manufactured by Toyo Seiki Seisakusho Co., Ltd.), the first stage of kneading was performed under the conditions of a filling rate of 65%, a rotor rotation speed of 35 rpm, and an initial temperature of 75°C. Rubber component 1, rubber component 2, rubber component 3, filler, silane coupling agent, antioxidant, vulcanization aid (zinc oxide), and vulcanization aid (stearic acid) were kneaded for 7 minutes in the above proportions to obtain the first stage compound (outsole rubber composition without vulcanizing agent). The temperature of the first stage compound after 7 minutes of kneading was 139.4°C. 【0224】Next, after cooling, the second stage of mixing was performed by adding the vulcanizing agent, vulcanization accelerator (MBT), and vulcanization accelerator (TBBS) to the first stage compound in the above proportions using an open roll set to 80°C, and mixing to obtain the second stage compound (outsole rubber composition containing the vulcanizing agent). Finally, the second stage compound was vulcanized and molded using a heated press at 160°C and a pressure of approximately 15 MPa for approximately 20 minutes to obtain the vulcanized outsole rubber composition. The physical properties of the vulcanized outsole rubber composition were measured by the following method. The results, along with the compound materials and proportions of the vulcanized outsole rubber composition, are shown in Tables 2 and 3. 【0225】 Furthermore, using the "outsole rubber composition containing a vulcanizing agent" obtained above, an outsole was manufactured by the following method. First, using a heated press, the "outsole rubber composition containing a vulcanizing agent" was heated and pressed at 160°C and a pressure of approximately 15 MPa using a mold designed with an uneven pattern and shape to obtain outsole (1). Outsole (2) was then manufactured by bonding outsole (1) with a foamed EVA (ethylene vinyl acetate) midsole (P-60EVA (product name), manufactured by Fuji Koatsu Co., Ltd.). The physical properties of outsole (2) were measured by the following method. The results, along with the compounding materials and amounts of outsole (2), are shown in Tables 2 and 3. 【0226】(Examples 2-20 and Comparative Examples 1-4) Except for changing the compounding materials and amounts of the rubber composition for the outsole as shown in Table 2 or 3 below, the vulcanized rubber compositions for the outsole and the outsoles (2) for Examples 2-20 and Comparative Examples 1-4 were obtained in the same manner as in Example 1. The following rubber components 4-7 were used. - Rubber component 4 (natural rubber, RSS No. 3 (product name, smoke-dried type), manufactured by UNIMAC RUBBER CO., LTD.) - Rubber component 5 (styrene-butadiene rubber, ASAPRENE 1205 (product name), manufactured by Asahi Kasei Corporation) - Rubber component 6 (butyl rubber brominated, BIIR 2244 (product name), manufactured by ENEOS Material Corporation) - Rubber component 7 (acrylonitrile-butadiene rubber (NBR), Nipol 4050 (product name), manufactured by Nippon Zeon Corporation) The results, along with the compounding materials and their amounts, are shown in Tables 2 and 3. 【0227】 [Evaluation of the physical properties of the outsole rubber composition and outsole (2) after vulcanization] [(1) ΔG'] ΔG' was measured in torsion mode using the "ARES" viscoelasticity tester (product name) manufactured by Rheometrics Scientific. Specifically, using test pieces of the vulcanized outsole rubber compositions of the examples and comparative examples, ΔG' was calculated as the difference G' ([G' at 0.1% strain] - [G' at 10% strain]) between the storage modulus at 0.1% strain and the storage modulus at 10% strain, measured in rotation mode at a frequency of 10 Hz and a test temperature of 50°C, based on JIS K6394:2007. A smaller ΔG' value indicates better silica dispersibility. 【0228】(2) Abrasion Resistance (Amount of Abrasion) Abrasion resistance (amount of abrasion) was measured using a DIN abrasion tester (QC-618A (product name), manufactured by M&K Co., Ltd.) in accordance with JIS K 6264-2:2005, and evaluated by an index value. A higher index value indicates better abrasion resistance. Specifically, in the DIN abrasion test, the abrasion volume of the vulcanized outsole rubber compositions of the examples and comparative examples was measured at a temperature of 23°C, and the index calculated by the following formula was determined as an indicator of abrasion resistance. A standard sample (BAM-E001 (product name), manufactured by BAM) was used. Index = [(Abrasion loss of sample) / (Abrasion loss of standard sample)] × 100 【0229】 (3) Tear Strength: In accordance with JIS K6251:2017, the tear strength of the vulcanized outsole rubber compositions of the examples and comparative examples was measured and evaluated using an index value. A higher index value indicates higher tear strength. 【0230】 (4) Adhesion strength when bonded 21 days after outsole fabrication) Using the outsoles (2) of the examples and comparative examples, peel strength tests were conducted in accordance with ASTM D903-98:2017. For bonding, an aqueous primer (AQUACE® PR-503 (product name) manufactured by Henkel) and an aqueous adhesive (AQUACE® W-06 (product name) manufactured by Henkel) were used. The above tests were conducted 1 day and 21 days after outsole fabrication. A greater force required for peeling indicates greater adhesive strength, and the adhesive strength was evaluated using an index value. The difference in adhesive strength between 1 day and 21 days ((adhesion strength after 1 day) - (adhesion strength after 21 days)) was calculated. In addition, in Tables 2 and 3, the adhesive strength after 21 days is also shown as an index value. 【0231】(5) Flexibility The outsoles (2) of the examples and comparative examples were used to measure the flexibility of the outsoles by an outsole flexion test in accordance with ISO 17707-2005, and the flexibility was evaluated according to the following criteria. Note that a shorter length of laceration growth indicates better flexibility. [Criteria] AA: Laceration growth length was less than 1 mm. A: Laceration growth length was 1 mm or more and less than 2 mm. B: Laceration growth length was 2 mm or more and less than 3 mm. C: Laceration growth length was 3 mm or more. 【0232】 (6) Force required for 45° flexion Using the outsole (2) of the examples and comparative examples, the force required to bend the outsole to a 45° angle was measured in accordance with ISO 17707-2005. In Tables 2 and 3, the required force is listed as an index value. 【0233】 (7) Adhesion strength after repeated bending test The adhesion strength after repeated bending test was performed using the outsoles (2) of the examples and comparative examples. Specifically, in order to reproduce the decrease in adhesion strength due to repeated use of shoes, the adhesive bond between the outsole and the midsole (P-60EVA manufactured by Fuji Koatsu Co., Ltd.) was repeatedly bent in a bending test in accordance with ISO 17707-2005. After that, a peel strength test was performed in accordance with ASTM D903-98:2017. The greater the force required for peeling, the greater the adhesion strength, and the adhesion strength was evaluated by an index value. 【0234】 ((8)μ DRY -μ WET Using the vulcanized outsole rubber compositions of the Examples and Comparative Examples, the coefficient of dynamic friction in a dry state (μ) DRY ) and the coefficient of kinetic friction in wet conditions (μ WET The difference (μ) DRY -μ WETThe coefficient of dynamic friction (μ) was calculated. Specifically, the coefficient of dynamic friction was measured using a friction and wear testing machine (Heidon Tribogear Type 40) manufactured by Shinto Kagaku Co., Ltd. The sliding surface was a ceramic tile, lubricated with water, and an outsole sheet with a thickness of 3 mm, a width of 30 mm, and a depth of 30 mm was brought into contact with the sliding surface. The sample was moved back and forth 10 times with a load of 500 gf, a sliding speed of 10 mm / min, and a sliding distance of 80 mm. The coefficient of dynamic friction for the outward journey of the 6th to 10th return journeys was averaged to calculate the coefficient of dynamic friction (μ) in a wet state. WET The coefficient of dynamic friction was calculated as follows: In addition, in the measurement of the coefficient of dynamic friction described above, the coefficient of dynamic friction when the ceramic tile on the sliding surface was measured without lubrication with water was used as the coefficient of dynamic friction in a dry state (μ). DRY ) was calculated as follows. From the above results, the difference (μ DRY -μ WET The difference (μ) was calculated. DRY -μ WET The outsole's physical properties were defined as follows. 【0235】 (9) Tripping Test: Shoes were made using the outsoles (2) of the examples and comparative examples. Specifically, they were made using the cement method. After that, each of the resulting shoes was worn, and participants walked 20m on a road that had been thoroughly wet with water, and then walked another 40m on a dry road. The number of trips on the dry road was measured. This test was conducted with 20 people, and the average number of trips for each shoe was calculated. 【0236】(10) Oil Resistance Test Using the vulcanized outsole rubber compositions of the Examples and Comparative Examples, test specimens measuring 40 mm in length, 40 mm in width, and 2 mm in thickness were prepared. The test specimens were then immersed in 2,2,4-trimethylpentane in a volume approximately 15 times that of the test specimen at 23°C for 20 hours. After immersion, the test specimens were removed. Using a caliper (manufactured by Takagi Co., Ltd.), the volume before and after immersion in 2,2,4-trimethylpentane was calculated, the volume expansion rate was measured, and the oil resistance was evaluated according to the following criteria. A lower volume expansion rate indicates better oil resistance. [Criteria] AA: Judged to be the best (volume expansion rate was 15% or less). A: Judged to be good (volume expansion rate was greater than 15% and 25% or less). B: Judged to be practically acceptable (volume expansion rate was greater than 25% and 35% or less). C: Judged to be inferior (volume expansion rate was between 35% and 50%). D: Judged to be the worst (volume expansion rate was above 50%). 【0237】 【0238】 【0239】 As shown in Tables 2 and 3, the rubber compositions for outsoles of Examples 1 to 20 were found to have superior dispersibility of inorganic fillers and superior suppression of the decrease in abrasion resistance, tear strength, and adhesive strength compared to the rubber compositions for outsoles of Comparative Examples 1 to 4. 【0240】 The rubber composition for outsoles of this embodiment has industrial applicability as a material for sports shoes, walking shoes, trekking shoes, and the like.

Claims

Modified polybutadiene for outsoles, having a silicon atom content of 60 ppm to 150 ppm and a nitrogen atom content of 80 ppm to 280 ppm. 　 Mooney viscosity at 100°C (ML) （１＋４） The modified polybutadiene for outsoles according to claim 1, wherein the ratio is 40 or more and 100 or less. 　 The modified polybutadiene for outsoles according to claim 1, wherein the Mooney relaxation rate (MSR) at 100°C is 0.30 or more and 0.80 or less. 　 The modified polybutadiene for outsoles according to claim 1, wherein the lithium atom content is 2 ppm or more and 130 ppm or less. The modified polybutadiene for outsoles according to claim 1, wherein the molecular weight distribution (Mw / Mn), expressed as the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) in terms of standard polystyrene, as measured by gel permeation chromatography (GPC), is 1.05 or more and 3.00 or less. 　 The nitrogen atom content is 90 ppm or more and 180 ppm or less. Modified polybutadiene for outsoles according to claim 1. 　 A rubber composition comprising a modified polybutadiene according to any one of claims 1 to 6 and an inorganic filler, The content of the modified polybutadiene is 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. The amount of the inorganic filler is 20 parts by mass or more and 60 parts by mass or less, based on 100 parts by mass of the total rubber components in the rubber composition. Rubber composition for outsoles. The rubber composition for outsoles according to claim 7, wherein the difference (ΔG') between the storage modulus at a strain of 0.1% and the storage modulus at a strain of 10%, measured in rotation mode at a frequency of 10 Hz and a test temperature of 50°C, based on JIS K6394:2007 for rubber composition test specimens, is 0.80 or less. 　 The rubber composition for outsoles according to claim 7, wherein the total area of ​​the differential molecular weight distribution curve obtained by gel permeation chromatography (GPC) measurement of the modified polybutadiene is set to 100%, and there are two or more peaks with an area of ​​10% or more, and among the peaks with an area of ​​10% or more, the area of ​​the lowest molecular weight peak is 15% or more and 70% or less. 　 The outsole rubber composition according to claim 7, wherein the modified polybutadiene has a modified group derived from a compound having one or more amino groups and two or more alkoxysilyl groups. 　 The Mooney viscosity (ML) of the modified polybutadiene at 100°C （１＋４） The rubber composition for outsoles according to claim 7, wherein the ratio is 50 or more and 80 or less. 　 The rubber composition for outsoles according to claim 7, wherein the amount of 1,2-vinyl bonds in the modified polybutadiene is 9 mol% or more and 40 mol% or less based on 100 mol% of the content of structural units derived from 1,3-butadiene. 　 The present invention further comprises polybutadiene rubber other than the modified polybutadiene and polyisoprene rubber, The content of the polybutadiene rubber other than the modified polybutadiene is 30 parts by mass or more and 85 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. The amount of polyisoprene rubber is 5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. The rubber composition for outsoles according to claim 7. 　 A method for producing a rubber composition for an outsole according to claim 7, comprising a kneading step of kneading raw materials containing the aforementioned total rubber components and the aforementioned inorganic filler. 　 An outsole obtained by vulcanizing the rubber composition for outsoles described in claim 7. The outsole according to claim 15, wherein the force required to make the bending angle of the outsole 45°, as measured in accordance with ISO 17707-2005, is 1N or more and 40N or less. 　 Coefficient of dynamic friction in dry conditions (μ DRY ) and the coefficient of kinetic friction in wet conditions (μ WET The difference (μ) DRY -μ WET The outsole according to claim 15, wherein the coefficient of force is 0.05 or more and 0.70 or less. 　 The outsole according to claim 15, wherein the rubber composition further comprises a polybutadiene rubber other than the modified polybutadiene and styrene-butadiene rubber. 　 The rubber composition further comprises a polybutadiene rubber other than the modified polybutadiene, The total content of the modified polybutadiene and the polybutadiene rubber other than the modified polybutadiene is 70 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. The outsole according to claim 15. 　 The rubber composition further comprises a modified polybutadiene other than the modified polybutadiene and acrylonitrile-butadiene rubber. The content of the polybutadiene rubber other than the modified polybutadiene is 30 parts by mass or more and 85 parts by mass or less per 100 parts by mass of the total rubber components in the rubber composition. The content of the acrylonitrile-butadiene rubber is 1 part by mass or more and 30 parts by mass per 100 parts by mass of the total rubber components in the rubber composition. The outsole according to claim 15.

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