Rubber composition for heavy duty tires

Abstract

Provided is a rubber composition which is for a heavy-load tire, has a glass transition temperature (Tg) of at most -50ºC, and contains silica and an aromatic vinyl-conjugated diene copolymer having a functional group that can interact with silica.

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for heavy load tires, which can give a cross-linked rubber product having low heat buildup, excellent abrasion resistance, and high chipping resistance, and which can be suitably used for heavy load tires. [Background technology]

[0002] For heavy-duty tires used for trucks, buses, etc., it is important that they have excellent wear resistance, thereby ensuring a long tire life. Meanwhile, in recent years, there has been an increasing demand for low heat buildup (low fuel consumption) due to environmental and resource issues. In order to impart low heat buildup to heavy-duty tires, the incorporation of silica into rubber compositions for heavy-duty tires has been considered, but this has the problem of reducing wear resistance.

[0003] For example, Patent Document 1 proposes a rubber composition for heavy-duty tires, which contains 35 to 60 parts by weight of carbon black and 0 to 25 parts by weight of silica per 100 parts by weight of a rubber component containing 50 parts by weight or more of a diene rubber produced using a lithium amide-based polymerization initiator, and is characterized in that the ratio of the dibutyl phthalate (DBP) oil absorption of the carbon black to the 24M4DBP oil absorption (DBP oil absorption / 24M4DBP oil absorption) is 1.20 or more, and the ratio of the DBP oil absorption to the nitrogen adsorption specific surface area (N2SA) (DBP oil absorption / N2SA) is 0.8 or more.

[0004] However, although tires obtained using the rubber composition for heavy-duty tires disclosed in Patent Document 1 have sufficient chipping resistance, they do not have sufficient low heat buildup and wear resistance. Therefore, from the perspective of suitable use in heavy-duty tire applications, there has been a demand for further improvements in low heat buildup and wear resistance while maintaining sufficient chipping resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-239444 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a rubber composition for heavy-duty tires that is excellent in low heat buildup and abrasion resistance and can give a cross-linked rubber product that has high chipping resistance. [Means for solving the problem]

[0007] As a result of intensive research to achieve the above object, the present inventors have found that the above object can be achieved by using an aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of −50° C. or less and having a functional group capable of interacting with silica, and by compounding silica into this to form a rubber composition, thereby completing the present invention.

[0008] That is, according to the present invention, there is provided a rubber composition for heavy load tires, which contains an aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of −50° C. or lower and having a functional group capable of interacting with silica, and silica.

[0009] In the rubber composition for heavy-duty tires of the present invention, the glass transition temperature (Tg) of the aromatic vinyl-conjugated diene copolymer is preferably −70° C. or lower. In the rubber composition for a heavy-duty tire of the present invention, the nitrogen adsorption specific surface area of ​​the silica measured by the BET method is 30 to 500 m 2 / g is preferred. In the rubber composition for heavy-duty tires of the present invention, the content of the silica is preferably 10 to 200 parts by weight based on 100 parts by weight of the rubber component containing the aromatic vinyl-conjugated diene copolymer. The rubber composition for a heavy-duty tire of the present invention preferably further contains carbon black. In the rubber composition for a heavy-duty tire of the present invention, the nitrogen adsorption specific surface area of ​​the carbon black measured by the BET method is 30 m 2 / g or more is preferable. In the rubber composition for heavy-duty tires of the present invention, the content of the carbon black is preferably 10 to 200 parts by weight based on 100 parts by weight of the rubber component containing the aromatic vinyl-conjugated diene copolymer.

[0010] In the rubber composition for heavy-duty tires of the present invention, the content of the aromatic vinyl-conjugated diene copolymer is preferably 10 to 80% by weight in 100% by weight of the total rubber component. The rubber composition for heavy-duty tires of the present invention further contains natural rubber, and the content of the natural rubber is preferably 10 to 80% by weight in 100% by weight of the total rubber component. The rubber composition for a heavy-duty tire of the present invention further contains polybutadiene rubber, and the content of the polybutadiene rubber is preferably 10 to 80% by weight in 100% by weight of the total rubber component. In the rubber composition for a heavy-duty tire of the present invention, the functional group capable of interacting with silica in the aromatic vinyl-conjugated diene copolymer is Si—OR a (R a is a hydrogen atom or a hydrocarbyl group which may have a substituent).

[0011] According to the present invention, there is also provided a cross-linked rubber product obtained by cross-linking the rubber composition for heavy load tires of the present invention. Furthermore, according to the present invention, there is provided a heavy-duty tire comprising the above-mentioned cross-linked rubber of the present invention. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a rubber composition for heavy load tires that can give a cross-linked rubber product having low heat buildup, excellent abrasion resistance, and high chipping resistance, as well as a cross-linked rubber product obtained using such a rubber composition for heavy load tires and having low heat buildup, excellent abrasion resistance, and high chipping resistance, and a heavy load tire. DETAILED DESCRIPTION OF THE INVENTION

[0013] The rubber composition for heavy-duty tires of the present invention is a rubber composition containing silica and an aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of −50° C. or lower and having a functional group capable of interacting with silica.

[0014] <Aromatic vinyl-conjugated diene copolymer> The aromatic vinyl-conjugated diene copolymer used in the present invention is a polymer having a glass transition temperature (Tg) of −50° C. or lower and having a functional group capable of interacting with silica.

[0015] The aromatic vinyl-conjugated diene copolymer used in the present invention, which has a glass transition temperature (Tg) of −50° C. or lower and is provided with a functional group capable of interacting with silica (hereinafter referred to as “aromatic vinyl-conjugated diene copolymer” where appropriate), contains conjugated diene monomer units and aromatic vinyl monomer units.

[0016] The conjugated diene compound for forming the conjugated diene monomer unit is not particularly limited, but examples thereof include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, and 3-butyl-1,3-octadiene. Among these, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred. These conjugated diene compounds may be used alone or in combination of two or more.

[0017] The content of conjugated diene monomer units in all monomer units constituting the aromatic vinyl-conjugated diene copolymer used in the present invention is preferably 50 to 99% by weight, more preferably 70 to 99% by weight, even more preferably 80 to 99% by weight, and even more preferably 83 to 97% by weight. By setting the content of conjugated diene monomer units within the above range, the low heat buildup and abrasion resistance of the obtained cross-linked rubber can be further improved.

[0018] The aromatic vinyl compound for forming the aromatic vinyl monomer unit is not particularly limited, but includes styrene, methylstyrene, ethylstyrene, t-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, chlorostyrene, bromostyrene, methoxystyrene, dimethylaminomethylstyrene, dimethylaminoethylstyrene, diethylaminomethylstyrene, diethylaminoethylstyrene, cyanoethylstyrene, vinylnaphthalene, etc. Among these, styrene is preferred. These aromatic vinyl compounds may be used alone or in combination of two or more.

[0019] The content of aromatic vinyl monomer units in all monomer units constituting the aromatic vinyl-conjugated diene copolymer used in the present invention is preferably 1 to 50% by weight, more preferably 1 to 30% by weight, even more preferably 1 to 20% by weight, and even more preferably 3 to 17% by weight. By setting the content of aromatic vinyl monomer units within the above range, the low heat buildup and abrasion resistance of the obtained cross-linked rubber can be further improved.

[0020] The aromatic vinyl-conjugated diene copolymer used in the present invention may contain other monomer units in addition to the conjugated diene monomer units and aromatic vinyl monomer units. Examples of other monomers constituting such other monomer units include linear olefin compounds such as ethylene, propylene, and 1-butene; cyclic olefin compounds such as cyclopentene and 2-norbornene; and non-conjugated diene compounds such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene. The content of other monomer units in the total monomer units constituting the aromatic vinyl-conjugated diene copolymer used in the present invention is preferably 10% by weight or less, more preferably 5% by weight or less.

[0021] The aromatic vinyl-conjugated diene copolymer used in the present invention has a glass transition temperature (Tg) of -50°C or lower, preferably -70°C or lower, and more preferably -80°C or lower. The lower limit of the glass transition temperature (Tg) is not particularly limited, but is preferably -100°C or higher. In the present invention, an aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of -50°C or lower and having a functional group capable of interacting with silica (described below) is used. By combining this with silica, the resulting cross-linked rubber product can be made to have excellent low heat buildup, abrasion resistance, and chipping resistance. Methods for adjusting the glass transition temperature (Tg) of the aromatic vinyl-conjugated diene copolymer within the above range are not particularly limited, but include adjusting the proportion of aromatic vinyl monomer units in all monomer units constituting the aromatic vinyl-conjugated diene copolymer, and adjusting the vinyl bond content in the conjugated diene monomer units.

[0022] The vinyl bond content in the conjugated diene monomer units in the aromatic vinyl-conjugated diene copolymer used in the present invention is preferably 50% by weight or less, more preferably 35% by weight or less, even more preferably 25% by weight or less, still more preferably 20% by weight or less, and particularly preferably 17% by weight or less, from the viewpoint of setting the glass transition temperature (Tg) of the aromatic vinyl-conjugated diene copolymer in the above range. There is no particular restriction on the lower limit of the vinyl bond content, but it is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 12% by weight or more.

[0023] The aromatic vinyl-conjugated diene copolymer used in the present invention has a functional group capable of interacting with silica in the polymer. The functional group capable of interacting with silica is a functional group capable of forming a covalent bond between the functional group and the silica surface, or a functional group capable of forming an intermolecular force weaker than a covalent bond (e.g., ion-dipole interaction, dipole-dipole interaction, hydrogen bond, van der Waals force, etc.). Such functional groups capable of interacting with silica are not particularly limited, but include nitrogen atom-containing functional groups, silicon atom-containing functional groups, and oxygen atom-containing functional groups. Among these, silicon atom-containing functional groups are preferred from the viewpoint of their strong interaction with silica, and Si-OR a (R a is a hydrogen atom or a hydrocarbyl group which may have a substituent).

[0024] R aExamples of the hydrocarbyl group forming the formula (I) include an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, and an aralkyl group, with an alkyl group having 1 to 6 carbon atoms being preferred. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group, a pentyl group, and a hexyl group, with a methyl group and an ethyl group being more preferred, and a methyl group being particularly preferred. When the hydrocarbyl group has a substituent, examples thereof include a hydrocarbyl group having a hydrocarbyloxy group as the substituent, and examples of the hydrocarbyl group having a hydrocarbyloxy group as the substituent include alkoxyalkyl groups such as a methoxymethyl group, an ethoxymethyl group, and a methoxyethyl group; and an aryloxyalkyl group such as a phenoxymethyl group.

[0025] The method for introducing a functional group capable of interacting with silica into the aromatic vinyl-conjugated diene copolymer used in the present invention is not particularly limited, but examples include a method in which, when producing the aromatic vinyl-conjugated diene copolymer, monomers containing a conjugated diene compound and an aromatic vinyl compound are polymerized to obtain an aromatic vinyl-conjugated diene copolymer chain having an active end, and then the aromatic vinyl-conjugated diene copolymer chain having an active end is reacted with a modifier having a functional group capable of interacting with silica.

[0026] <Method of producing aromatic vinyl-conjugated diene copolymer> The method for producing the aromatic vinyl-conjugated diene copolymer used in the present invention is not particularly limited, but may be a polymerization step of polymerizing monomers including a conjugated diene compound and an aromatic vinyl compound in an inert solvent using a polymerization initiator to obtain an aromatic vinyl-conjugated diene copolymer chain having an active terminal; A method for producing an aromatic vinyl-conjugated diene copolymer is preferably provided, which comprises a modification step of reacting the aromatic vinyl-conjugated diene copolymer chain having an active end obtained in the polymerization step with a modifier having a functional group capable of interacting with silica.

[0027] <Polymerization process> The conjugated diene compound and aromatic vinyl compound constituting the monomers used in the polymerization step can be those described above, and the amounts used can be determined according to the monomer composition of the aromatic vinyl-conjugated diene copolymer to be obtained. Furthermore, when the aromatic vinyl-conjugated diene copolymer contains other monomer units other than the conjugated diene monomer units and the aromatic vinyl monomer units, the monomer used in the polymerization step can contain other monomers for forming the other monomer units described above.

[0028] The inert solvent used in the polymerization is not particularly limited as long as it is one commonly used in solution polymerization and does not inhibit the polymerization reaction. Specific examples of the inert solvent include chain aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; and ether compounds such as tetrahydrofuran and diethyl ether. These inert solvents may be used alone or in combination of two or more. The amount of the inert solvent used is not particularly limited, but is, for example, an amount that results in a monomer concentration of 1 to 50% by weight, preferably 10 to 40% by weight.

[0029] The polymerization initiator used in the polymerization is not particularly limited as long as it can polymerize monomers containing a conjugated diene compound and an aromatic vinyl compound to produce an aromatic vinyl-conjugated diene copolymer chain having an active terminal. Specific examples include polymerization initiators using organic alkali metal compounds, organic alkaline earth metal compounds, and lanthanum series metal compounds as the main catalyst. Examples of organic alkali metal compounds include organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; organic polyvalent lithium compounds such as dilithiomethane, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-tris(lithiomethyl)benzene; organic sodium compounds such as sodium naphthalene; and organic potassium compounds such as potassium naphthalene. Examples of organic alkaline earth metal compounds include di-n-butylmagnesium, di-n-hexylmagnesium, diethoxycalcium, calcium distearate, di-t-butoxystrontium, diethoxybarium, diisopropoxybarium, diethylmercaptobarium, di-t-butoxybarium, diphenoxybarium, diethylaminobarium, barium distearate, diketylbarium, etc. Examples of polymerization initiators using a lanthanum series metal compound as the main catalyst include polymerization initiators using a lanthanum series metal salt, such as lanthanum, cerium, praseodymium, neodymium, samarium, or gadolinium, as the main catalyst, which is composed of a lanthanum series metal salt formed from a carboxylic acid and a phosphorus-containing organic acid, etc., together with a co-catalyst such as an alkylaluminum compound, an organoaluminum hydride compound, or an organoaluminum halide compound. Among these polymerization initiators, organic monolithium compounds and organic polyvalent lithium compounds are preferably used, organic monolithium compounds are more preferably used, and n-butyllithium is particularly preferably used.

[0030] The organic alkali metal compound may be used as an organic alkali metal amide compound by reacting it in advance with a secondary amine compound such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, piperidine, hexamethyleneimine, or heptamethyleneimine. By using the organic alkali metal amide compound as a polymerization initiator, the resulting cross-linked rubber product can have excellent low heat buildup and abrasion resistance. These polymerization initiators may be used alone or in combination of two or more.

[0031] The amount of the polymerization initiator used may be determined depending on the molecular weight of the desired aromatic vinyl-conjugated diene copolymer chain, but is usually in the range of 1 to 50 mmol, preferably 1.5 to 20 mmol, and more preferably 2 to 15 mmol per 1000 g of monomer.

[0032] The polymerization temperature is usually in the range of −80 to +150° C., preferably 0 to 100° C., and more preferably 30 to 90° C. As the polymerization mode, any mode such as a batch mode or a continuous mode can be adopted, but a batch mode is preferred in that it is easy to control the randomness of bonding between the conjugated diene monomer units and the aromatic vinyl monomer units.

[0033] The aromatic vinyl-conjugated diene copolymer of the present invention preferably has an aromatic vinyl compound block ratio of 10.0% or less, more preferably 5.0% or less, further preferably 3.0% or less, and particularly preferably 2.0% or less. 1 The obtained compound was measured by H-NMR. 1The peak at 6.1 to 7.7 ppm in the H-NMR spectrum is considered to be the peak attributable to the aromatic vinyl compound, and of that, the peak at 6.1 to 6.88 ppm is considered to be the peak attributable to the aromatic vinyl compound block. The ratio of the peak area attributable to the aromatic vinyl compound block to the peak area attributable to the aromatic vinyl compound is calculated, and this value is multiplied by 2.5 to express it as a percentage, which is the aromatic vinyl compound block ratio. When the aromatic vinyl compound is styrene, the styrene block ratio is preferably within the above range. By controlling the aromatic vinyl compound block ratio within the above range, the obtained cross-linked rubber product can be made to have a higher balance between low heat buildup and abrasion resistance. The aromatic vinyl compound block ratio can be controlled by controlling the proportions of the conjugated diene compound and the aromatic vinyl compound at the start of polymerization when polymerizing the monomers containing the compound; controlling the proportion of the aromatic vinyl compound in the monomer to be added and the timing of the addition when adding the monomer; adjusting the amount of inert solvent relative to the amount of the aromatic vinyl compound; adjusting the type and amount of polar compound; controlling the polymerization temperature; or a combination of these methods.

[0034] In the polymerization step, when polymerizing monomers including a conjugated diene compound and an aromatic vinyl compound, it is preferable to carry out the polymerization in the presence of a polar compound. Specifically, by using preferably 0.01 to 1.2 mol, more preferably 0.1 to 1.1 mol, and even more preferably 0.1 to 1.0 mol of the polar compound per mol of the polymerization initiator and carrying out the polymerization in the presence of such a polar compound, the vinyl bond content in the conjugated diene monomer unit portion contained in the aromatic vinyl-conjugated diene copolymer chain obtained in the polymerization step can be suitably adjusted to the above-mentioned range.

[0035] The method of polymerization in the presence of a polar compound is not particularly limited, but may include, for example, a method of adding a polar compound to an inert solvent used for polymerization and then carrying out polymerization. Specific examples of polar compounds include ether compounds such as dibutyl ether, tetrahydrofuran, and 2,2-di(tetrahydrofuryl)propane; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; and phosphine compounds. Among these, ether compounds and tertiary amines are preferred, with tertiary amines being more preferred, and tetramethylethylenediamine being particularly preferred. These polar compounds may be used alone or in combination of two or more.

[0036] The weight-average molecular weight (Mw) of the aromatic vinyl-conjugated diene copolymer chain having an active end obtained in the polymerization step is not particularly limited, but is preferably 150,000 to 3,000,000, more preferably 170,000 to 2,000,000, even more preferably 200,000 to 1,500,000, particularly preferably 350,000 to 650,000, and most preferably 380,000 to 520,000, as measured by gel permeation chromatography in terms of polystyrene. By setting the weight-average molecular weight (Mw) of the aromatic vinyl-conjugated diene copolymer chain having an active end within the above range, the obtained cross-linked rubber product can be made to have a highly balanced low heat buildup and abrasion resistance.

[0037] Furthermore, the molecular weight distribution, which is expressed as the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the aromatic vinyl-conjugated diene copolymer chain having an active end obtained in the polymerization step, is not particularly limited, but is preferably 1.1 to 3.5, more preferably 1.2 to 3.0, and even more preferably 1.3 to 2.5. When the molecular weight distribution (Mw / Mn) of the aromatic vinyl-conjugated diene copolymer chain having an active end is within the above range, the production of the aromatic vinyl-conjugated diene copolymer becomes easy.

[0038] In the present invention, in order to make the obtained cross-linked rubber product have even lower heat buildup and better abrasion resistance, the polymerization step may be the following step. That is, a step of polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound in an inert solvent using a polymerization initiator to form a polymer block (A) having an active terminal containing 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units; and a step of mixing the polymer block (A) having an active end obtained above with a monomer containing 1,3-butadiene and an aromatic vinyl compound, and continuing the polymerization reaction to form a polymer block (B) containing 1,3-butadiene monomer units and aromatic vinyl monomer units in a continuous state with the polymer block (A), thereby obtaining an aromatic vinyl-conjugated diene copolymer chain having an active end.

[0039] By employing such a process, the aromatic vinyl-conjugated diene copolymer chain having an active end obtained by the polymerization process can be one that includes a polymer block (A) containing 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units and a polymer block (B) containing 1,3-butadiene monomer units and aromatic vinyl monomer units, formed in a continuous manner. Such an embodiment will be described below.

[0040] [Polymer block (A)] The polymer block (A) in the aromatic vinyl-conjugated diene copolymer chain according to one embodiment of the present invention may contain 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units, preferably 85 to 97% by weight of isoprene monomer units and 3 to 15% by weight of aromatic vinyl monomer units, and more preferably 89 to 95% by weight of isoprene monomer units and 5 to 11% by weight of aromatic vinyl monomer units. When the content ratio of isoprene monomer units to aromatic vinyl monomer units is within the above range, the affinity between the aromatic vinyl-conjugated diene copolymer and silica can be further increased, thereby enabling the resulting cross-linked rubber to have improved low heat buildup and wear resistance.

[0041] The aromatic vinyl compounds used to form the aromatic vinyl monomer units contained in the polymer block (A) may be the same as the aromatic vinyl compounds described above, and among these, styrene is preferred. These aromatic vinyl compounds may be used alone or in combination of two or more.

[0042] The polymer block (A) preferably consists of only isoprene monomer units, or isoprene monomer units and aromatic vinyl monomer units, but may contain other monomer units in addition to the isoprene monomer units or isoprene monomer units and aromatic vinyl monomer units, as desired. Other compounds that can be used to form the other monomer units include conjugated diene compounds other than isoprene, such as 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene; α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids or anhydrides such as acrylic acid, methacrylic acid, and maleic anhydride; unsaturated carboxylic acid esters such as methyl methacrylate, ethyl acrylate, and butyl acrylate; and non-conjugated dienes such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene. Among these, 1,3-butadiene is preferred. These other monomers can be used alone or in combination of two or more. The content of other monomer units in the polymer block (A) is preferably 20% by weight or less, more preferably 10% by weight or less, and even more preferably 6% by weight or less.

[0043] In the present invention, the polymer block (A) in the aromatic vinyl-conjugated diene copolymer chain is formed by polymerizing a monomer containing isoprene or a monomer containing isoprene and an aromatic vinyl compound with a polymerization initiator in an inert solvent. The formed polymer block (A) has an active terminal.

[0044] The inert solvent used in the polymerization of isoprene or a monomer containing isoprene and an aromatic vinyl compound to form polymer block (A) may be the same as the inert solvent described above. The amount of the inert solvent used is such that the monomer concentration is preferably 1 to 80% by weight, more preferably 10 to 50% by weight.

[0045] The polymerization initiator used to form the polymer block (A) is not particularly limited as long as it can polymerize isoprene or a monomer containing isoprene and an aromatic vinyl compound to give a polymer chain having an active terminal. Specific examples of the polymerization initiator include those described above.

[0046] The amount of the polymerization initiator used may be determined depending on the target molecular weight, but is preferably in the range of 4 to 250 mmol, more preferably 6 to 200 mmol, and particularly preferably 10 to 70 mmol, per 100 g of isoprene or a monomer containing isoprene and an aromatic vinyl compound.

[0047] The polymerization temperature when polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound is preferably in the range of −80 to +150° C., more preferably 0 to 100° C., and even more preferably 20 to 90° C. The polymerization method may be any method, such as a batch method or a continuous method. Various bonding methods may be used, such as a block type, a tapered type, or a random type.

[0048] Furthermore, when forming the polymer block (A), it is preferable to polymerize isoprene or a monomer containing isoprene and an aromatic vinyl compound in the presence of a polar compound. Specifically, the polar compound is preferably used in an amount of 0.01 to 100 mol, more preferably 0.03 to 30 mol, and even more preferably 0.05 to 1 mol per mol of the polymerization initiator, and polymerization is carried out in the presence of such a polar compound, thereby making it possible to suitably adjust the vinyl bond content of the isoprene monomer unit moiety in the polymer block (A). The vinyl bond in the isoprene monomer unit moiety may be either a 1,2-vinyl bond or a 3,4-vinyl bond.

[0049] The method for polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound in the presence of a polar compound is not particularly limited, but examples thereof include a method in which a polar compound is added to an inert solvent used for polymerization, and the like. The polar compound may be the same as the polar compounds described above.

[0050] The weight average molecular weight (Mw) of the polymer block (A), expressed as a polystyrene equivalent value measured by gel permeation chromatography, is preferably 500 to 15,000, more preferably 1,000 to 12,000, and particularly preferably 1,500 to 10,000. When the weight average molecular weight of the polymer block (A) is within the above range, the low heat buildup and abrasion resistance of the resulting cross-linked rubber can be further improved.

[0051] The molecular weight distribution of the polymer block (A), which is expressed as the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 1.0 to 1.5, and more preferably 1.0 to 1.3. When the molecular weight distribution value (Mw / Mn) of the polymer block (A) is within the above range, the production of the aromatic vinyl-conjugated diene copolymer becomes easier.

[0052] [Polymer block (B)] The polymer block (B) in the aromatic vinyl-conjugated diene copolymer chain according to one embodiment of the present invention may contain 1,3-butadiene monomer units and aromatic vinyl monomer units, but preferably contains 45 to 98% by weight of 1,3-butadiene monomer units and 2 to 55% by weight of aromatic vinyl monomer units, and more preferably contains 60 to 97% by weight of 1,3-butadiene monomer units and 3 to 40% by weight of aromatic vinyl monomer units. By setting the contents of 1,3-butadiene monomer units and aromatic vinyl monomer units within the above ranges, the obtained cross-linked rubber product can have improved low heat buildup and wear resistance.

[0053] The aromatic vinyl compound used to form the aromatic vinyl monomer units contained in the polymer block (B) can be the same as the aromatic vinyl compounds described above, and among these, styrene is preferred.

[0054] The polymer block (B) preferably comprises 1,3-butadiene monomer units and aromatic vinyl monomer units. However, if desired, other monomer units may be included in addition to the 1,3-butadiene monomer units and aromatic vinyl monomer units, as long as the essential properties of the present invention are not impaired. The other monomers used to form the other monomer units can be the same as the compounds exemplified for the polymer block (A) described above (except for 1,3-butadiene). Isoprene can also be used as the other monomer. The content of the other monomer units in the polymer block (B) is preferably 10% by weight or less, more preferably 5% by weight or less.

[0055] In one embodiment of the present invention, polymer block (B) in the aromatic vinyl-conjugated diene copolymer chain is formed continuously with polymer block (A) by mixing polymer block (A) having the above-mentioned active terminal with monomers including 1,3-butadiene and an aromatic vinyl compound and continuing the polymerization reaction. The formed polymer block (B) has an active terminal. Meanwhile, the active terminal disappears from polymer block (A).

[0056] The inert solvent used in the polymerization of the polymer block (A) with the monomer containing 1,3-butadiene and an aromatic vinyl compound to form the polymer block (B) is not particularly limited, and the same inert solvents as those described above can be used.

[0057] The amount of polymer block (A) having an active end used in forming polymer block (B) may be determined depending on the target molecular weight, but is preferably in the range of 0.1 to 5 mmol, more preferably 0.15 to 2 mmol, and even more preferably 0.2 to 1.5 mmol per 100 g of monomers containing 1,3-butadiene and an aromatic vinyl compound.

[0058] The method for mixing the polymer block (A) with the monomer containing 1,3-butadiene and an aromatic vinyl compound is not particularly limited, and the polymer block (A) having an active end may be added to a solution of the monomer containing 1,3-butadiene and an aromatic vinyl compound, or the monomer containing 1,3-butadiene and an aromatic vinyl compound may be added to a solution of the polymer block (A) having an active end. From the viewpoint of controlling the polymerization, the method of adding the polymer block (A) having an active end to a solution of the monomer containing 1,3-butadiene and an aromatic vinyl compound is preferred.

[0059] The polymerization temperature when polymerizing the monomers containing 1,3-butadiene and an aromatic vinyl compound is preferably in the range of −80 to +150° C., more preferably 0 to 100° C., and even more preferably 20 to 90° C. As the polymerization method, any method such as a batch method or a continuous method can be adopted, but a batch method is preferred in that it is easy to control the randomness of bonding.

[0060] The bonding pattern of each monomer in the polymer block (B) can be various, such as block, tapered, or random. Among these, the random pattern is preferred. By using a random pattern, the resulting cross-linked rubber product can have a higher balance of low heat buildup and abrasion resistance. When the bonding pattern of 1,3-butadiene and the aromatic vinyl compound is random, it is preferable to polymerize 1,3-butadiene or 1,3-butadiene and the aromatic vinyl compound by continuously or intermittently supplying them to the polymerization system so that the ratio of the aromatic vinyl compound to the total amount of 1,3-butadiene and the aromatic vinyl compound in the polymerization system does not become too high.

[0061] In one embodiment of the present invention, similar to the formation of polymer block (A), when forming polymer block (B), it is preferable to polymerize monomers containing 1,3-butadiene and an aromatic vinyl compound in the presence of a polar compound. Specifically, by using preferably 0.01 to 0.50 mol, more preferably 0.05 to 0.40 mol, and even more preferably 0.08 to 0.35 mol of the polar compound per mol of the polymerization initiator and conducting the polymerization in the presence of such a polar compound, the vinyl bond content of the 1,3-butadiene monomer unit moiety in polymer block (B) can be suitably adjusted, and as a result, the vinyl bond content of the conjugated diene monomer unit moiety contained in the finally obtained aromatic vinyl-conjugated diene copolymer can be suitably adjusted to the above-mentioned range.

[0062] The method for polymerizing a monomer containing 1,3-butadiene and an aromatic vinyl compound in the presence of a polar compound is not particularly limited, but examples include a method in which the polar compound is added to an inert solvent used for polymerization and then polymerized. In this case, the polar compound is added so that the sum of the amount of polar compound added during the formation of polymer block (A) and the amount of polar compound newly added falls within the above-mentioned range. Therefore, if a polar compound is added during the formation of polymer block (A) in an amount sufficient to adjust the vinyl bond content of the 1,3-butadiene monomer unit portion in polymer block (B), it is not necessary to add a new polar compound. Furthermore, the same polar compounds as those described above can be used as the polar compound.

[0063] In this manner, an aromatic vinyl-conjugated diene copolymer chain having an active end, which has polymer block (A) and polymer block (B), can be obtained. In one embodiment of the present invention, from the viewpoint of productivity, the aromatic vinyl-conjugated diene copolymer chain having an active end is preferably composed of polymer block (A)-polymer block (B), and the terminal of polymer block (B) is the active terminal. However, it may have multiple polymer blocks (A) or may have other polymer blocks. For example, an aromatic vinyl-conjugated diene copolymer chain having an active end may be polymer block (A)-polymer block (B)-polymer block (A). In this case, the active terminal is formed at the terminal of polymer block (A) formed subsequent to polymer block (B). When forming the polymer block (A) at the active terminal side of the aromatic vinyl-conjugated diene copolymer chain, the amount of isoprene used is preferably 10 to 100 mol, more preferably 15 to 70 mol, and particularly preferably 20 to 35 mol, per mol of the polymerization initiator used in the initial polymerization reaction (polymerization reaction to form the first polymer block (A)).

[0064] In one embodiment of the present invention, the weight ratio of polymer block (A) to polymer block (B) in the aromatic vinyl-conjugated diene copolymer chain having an active end (when a plurality of polymer blocks (A) and polymer blocks (B) are present, the weight ratio is based on the total weight of the respective polymer blocks) is (weight of polymer block (A)) / (weight of polymer block (B)), and is preferably 0.001 to 0.2, more preferably 0.005 to 0.1, and particularly preferably 0.01 to 0.05. By setting the weight ratio of polymer block (A) to polymer block (B) within the above range, the obtained cross-linked rubber product can have a highly balanced low heat buildup and abrasion resistance.

[0065] <Denaturation process> Next, in the modification step, the aromatic vinyl-conjugated diene copolymer chain having an active end obtained in the polymerization step is reacted with a modifier having a functional group capable of interacting with silica.

[0066] The modifying agent having a functional group capable of interacting with silica, used in the modification step, is not particularly limited, and may be any compound capable of reacting with the aromatic vinyl-conjugated diene copolymer chain having an active end obtained in the polymerization step described above, and having a functional group capable of interacting with silica. The functional group capable of interacting with silica is not particularly limited, and examples thereof include nitrogen atom-containing functional groups, silicon atom-containing functional groups, and oxygen atom-containing functional groups. Among these, silicon atom-containing functional groups are preferred from the viewpoint of high interaction with silica, and Si-OR a (R a is a hydrogen atom or a hydrocarbyl group which may have a substituent).

[0067] In the present invention, siloxane compound can be suitably used as the modifier having functional group that can interact with silica.As this siloxane compound, it is sufficient to have the structure represented by (-Si-O-Si-), and there is no particular limitation, but the organosiloxane that has the structure represented by (-Si-O-Si-) and organic group is preferred, and the polyorganosiloxane represented by the following general formula (1) is more preferred. [ka] In general formula (1), R 1 ~R 8 is an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, which may be the same or different. X 1 and X 4 is any group selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and an epoxy group-containing group having 4 to 12 carbon atoms, and these may be the same or different. X 2is an alkoxy group having 1 to 5 carbon atoms or a group having 4 to 12 carbon atoms containing an epoxy group, and 2 They may be the same or different. X 3 is a group containing 2 to 20 repeating units of alkylene glycol, and X 3 When there are a plurality of m, they may be the same or different. m is an integer of 1 to 200, n is an integer of 0 to 200, k is an integer of 0 to 200, and m+n+k is 1 or more.

[0068] In the polyorganosiloxane represented by general formula (1), R 1 ~R 8 , X 1 and X 4 Examples of alkyl groups having 1 to 6 carbon atoms that can constitute the above include methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and cyclohexyl groups. Examples of aryl groups having 6 to 12 carbon atoms include phenyl and methylphenyl groups. Among these, methyl and ethyl groups are preferred from the viewpoint of ease of production of the polyorganosiloxane itself.

[0069] In addition, in the polyorganosiloxane represented by the general formula (1), X 1 , X 2 and X 4 Examples of the alkoxy group having 1 to 5 carbon atoms that can constitute the above include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, and a butoxy group. Among these, from the viewpoint of ease of production of the polyorganosiloxane itself, a methoxy group and an ethoxy group are preferred.

[0070] Furthermore, in the polyorganosiloxane represented by the general formula (1), X 1 , X 2 and X 4 Examples of the epoxy group-containing group having 4 to 12 carbon atoms that can constitute the above include groups represented by the following general formula (2). -Z 3 -Z4 -E 2 (2) In general formula (2), Z 3 is an alkylene group or alkylarylene group having 1 to 10 carbon atoms, and Z 4 is a methylene group, a sulfur atom, or an oxygen atom, and E 2 is a hydrocarbon group having 2 to 10 carbon atoms and an epoxy group.

[0071] The group represented by formula (2) includes Z 4 is preferably an oxygen atom, and Z 4 is an oxygen atom, and E 2 is more preferably a glycidyl group, and Z 3 is an alkylene group having 1 to 3 carbon atoms, and Z 4 is an oxygen atom, and E 2 is a glycidyl group is particularly preferred.

[0072] In addition, in the polyorganosiloxane represented by the general formula (1), X 1 and X 4 Among the above, X is preferably a group containing an epoxy group and having 4 to 12 carbon atoms, or an alkyl group having 1 to 6 carbon atoms. 2 Among the above, an epoxy group-containing group having 4 to 12 carbon atoms is preferred as X. 1 and X 4 is an alkyl group having 1 to 6 carbon atoms, and X 2 is more preferably a group containing an epoxy group and having 4 to 12 carbon atoms.

[0073] In addition, in the polyorganosiloxane represented by the general formula (1), X 3 That is, the group containing 2 to 20 repeating units of alkylene glycol is preferably a group represented by the following general formula (3). [ka] In the general formula (3), t is an integer of 2 to 20, and X 5 is an alkylene group or alkylarylene group having 2 to 10 carbon atoms, and R9 is a hydrogen atom or a methyl group, and X 6 is an alkoxy group or an aryloxy group having 1 to 10 carbon atoms. Among these, t is an integer of 2 to 8, and X 5 is an alkylene group having 3 carbon atoms, and R 9 is a hydrogen atom and X 6 is preferably a methoxy group.

[0074] In the polyorganosiloxane represented by general formula (1), m is an integer of 1 to 200, preferably an integer of 20 to 150, and more preferably an integer of 30 to 120. When m is 1 or more, the coupling rate of the resulting aromatic vinyl-conjugated diene copolymer is high, resulting in better low heat buildup and abrasion resistance. Furthermore, when m is 200 or less, the polyorganosiloxane represented by general formula (1) itself is easier to produce, and its viscosity does not become too high, making it easier to handle.

[0075] In the polyorganosiloxane represented by general formula (1), n ​​is an integer of 0 to 200, preferably an integer of 0 to 150, and more preferably an integer of 0 to 120. k is an integer of 0 to 200, preferably an integer of 0 to 150, and more preferably an integer of 0 to 130. The total number of m, n, and k is 1 or more, preferably 3 to 400, more preferably 20 to 300, and particularly preferably 30 to 250. When the total number of m, n, and k is 1 or more, the reaction between the polyorganosiloxane represented by general formula (1) and the aromatic vinyl-conjugated diene copolymer chain having an active terminal proceeds easily. Furthermore, when the total number of m, n, and k is 400 or less, the polyorganosiloxane represented by general formula (1) itself is easily produced, and its viscosity does not become too high, making it easy to handle.

[0076] The amount of the siloxane compound used in the modification step, calculated as the number of repeating units of (-Si-O-) in the siloxane compound, relative to 1 mole of the polymerization initiator used in the polymerization step described above, is preferably 0.1 moles or more, more preferably 0.2 moles or more, even more preferably 0.5 moles or more, particularly preferably 1.0 moles or more, more preferably 1.1 moles or more, and is preferably 10 moles or less, more preferably 5 moles or less, even more preferably 2.5 moles or less, and particularly preferably 2 moles or less. When the amount of the siloxane compound used is within the above range, the low heat buildup property of the obtained cross-linked rubber product can be further improved.

[0077] In particular, it is particularly preferable to use 1 mole or more of the siloxane compound in terms of the number of repeating units of (-Si-O-) per mole of the polymerization initiator, since substantially all of the active ends of the aromatic vinyl-conjugated diene copolymer chains having active ends obtained by the polymerization step can be reacted with the siloxane compound. That is, the alkyl metal groups, i.e., -R - M + (R is a hydrocarbon group forming a polymer chain terminal, and M is an alkali metal atom, alkaline earth metal atom, or lanthanide metal atom) can be made to substantially not remain.

[0078] The method for reacting a siloxane compound with an aromatic vinyl-conjugated diene copolymer chain having an active terminal is not particularly limited, but examples include mixing them in a solvent in which each of them is soluble. Examples of the solvent used in this reaction include those exemplified as inert solvents used in the polymerization step described above. In this reaction, a simple and preferred method is to add the siloxane compound to the polymerization solution used in the polymerization to obtain the aromatic vinyl-conjugated diene copolymer chain having an active terminal. In this reaction, the siloxane compound is preferably dissolved in an inert solvent and added to the polymerization system, with the solution concentration preferably in the range of 1 to 50% by weight. The reaction temperature is not particularly limited, but is typically 0 to 120°C. The reaction time is also not particularly limited, but is typically 1 minute to 1 hour.

[0079] The timing of adding the siloxane compound to the solution containing the aromatic vinyl-conjugated diene copolymer chains having active terminals is not particularly limited, but it is desirable to add the siloxane compound to the solution when the polymerization reaction is not complete and the solution containing the aromatic vinyl-conjugated diene copolymer chains having active terminals also contains monomers, more specifically, when the solution containing the aromatic vinyl-conjugated diene copolymer chains having active terminals contains 100 ppm or more, more preferably 300 to 50,000 ppm of monomers. By adding the siloxane compound in this manner, it is possible to suppress side reactions between the aromatic vinyl-conjugated diene copolymer chains having active terminals and impurities contained in the polymerization system, thereby making it possible to effectively control the reaction.

[0080] In the modification step, a siloxane compound as a modifier is reacted with the active terminal of the aromatic vinyl-conjugated diene copolymer chain having an active terminal obtained in the polymerization step described above, and the active terminal of the aromatic vinyl-conjugated diene copolymer chain reacts with the silicon atom in the siloxane structure. Alternatively, a part of the active terminal of the aromatic vinyl-conjugated diene copolymer chain is converted into an alkoxy group or epoxy group (X essentially contained in the general formula (1)) in the side chain of the polyorganosiloxane represented by the general formula (1).2 In the modification step, a siloxane-modified structure is introduced into the aromatic vinyl-conjugated diene copolymer chain by such a reaction, and thereby a functional group capable of interacting with silica can be introduced into the aromatic vinyl-conjugated diene copolymer.

[0081] Specifically, the active end of the aromatic vinyl-conjugated diene copolymer chain reacts with the silicon atom in the siloxane structure, and a new bond is formed between the silicon atom in the siloxane structure and the active end of the aromatic vinyl-conjugated diene copolymer chain, and a modified structure by siloxane is introduced at the end of the aromatic vinyl-conjugated diene copolymer chain. At the same time, a reaction residue, -O, is formed between the oxygen atom in the siloxane structure and the metal atom that formed the active end of the aromatic vinyl-conjugated diene copolymer chain. - M + (M is an alkali metal atom, an alkaline earth metal atom, or a lanthanide metal atom) is thought to be formed.

[0082] Alternatively, when a polyorganosiloxane represented by the above general formula (1) is used as the siloxane compound, the active end of the aromatic vinyl-conjugated diene copolymer chain reacts with the epoxy group on the side chain of the polyorganosiloxane, causing the ring-opening of the epoxy group, forming a new bond between the carbon atom at the ring-opened portion of the epoxy group and the active end of the aromatic vinyl-conjugated diene copolymer chain, and a siloxane structure is introduced at the end of the aromatic vinyl-conjugated diene copolymer chain. At the same time, a reaction residue, -O, is formed between the oxygen atom in the epoxy group and the metal atom that formed the active end of the aromatic vinyl-conjugated diene copolymer chain. - M +Alternatively, the active end of the aromatic vinyl-conjugated diene copolymer chain reacts with an alkoxy group on the side chain of the polyorganosiloxane, resulting in the elimination of the alkoxy group, and the aromatic vinyl-conjugated diene copolymer chain forms a new bond between the silicon atom in the siloxane structure and the active end of the aromatic vinyl-conjugated diene copolymer chain, thereby introducing a siloxane structure into the end of the aromatic vinyl-conjugated diene copolymer chain.

[0083] In particular, by using 1 mole or more of the siloxane compound in terms of the number of repeating units of (-Si-O-) per mole of the polymerization initiator in the modification step, it is possible to introduce a modified structure by siloxane into almost all of the aromatic vinyl-conjugated diene copolymer chains having active ends obtained by the polymerization step. Therefore, the alkyl metal group, i.e., -R - M + It is possible to make the reaction state such that almost all of the -O - M + Thus, a group represented by the following formula is formed.

[0084] In the present invention, before reacting the aromatic vinyl-conjugated diene copolymer chain having an active end with a modifier having a functional group capable of interacting with silica, such as a siloxane compound, a part of the active ends of the aromatic vinyl-conjugated diene copolymer chain having an active end may be coupled or modified by adding a conventionally used coupling agent or modifier to the polymerization system within a range that does not impair the effects of the present invention.

[0085] In the present invention, compounds having a protected primary amino group and an alkoxysilyl group can be used as a modifying agent having a functional group capable of interacting with silica, such as N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, 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, N,N-bis(trimethylsilyl)aminoethylmethyldimethoxysilane, and N,N-bis(trimethylsilyl)aminoethylmethyldiethoxysilane.

[0086] Furthermore, in the present invention, a polyfunctional compound having two or more epoxy groups and one or more nitrogen-containing groups in the molecule can be used as a modifier having a functional group capable of interacting with silica. More preferably, a polyfunctional compound represented by the following general formula (4) is used. [ka] In the above general formula (4), R 10 and R 11 is a hydrocarbon group having 1 to 10 carbon atoms or a hydrocarbon group having 1 to 10 carbon atoms and an ether structure and / or a tertiary amine; R 12 and R 13 is hydrogen, a hydrocarbon group having 1 to 20 carbon atoms or a hydrocarbon group having 1 to 20 carbon atoms and an ether and / or a tertiary amine; R 14 is a hydrocarbon group having 1 to 20 carbon atoms or a hydrocarbon group having 1 to 20 carbon atoms and having at least one group selected from an ether structure, a tertiary amine, an epoxy, a carbonyl, and a halogen; and s is 1 to 6.

[0087] In the present invention, a compound having a silyl group substituted with two or more alkoxy groups and one or more nitrogen atoms can be used as a modifying agent having a functional group capable of interacting with silica. Examples of such compounds include a compound represented by the following general formula (5), or a hydrocarbyloxysilane having a cyclic amino group containing two or more nitrogen atoms represented by the following general formula (6), as well as other hydrocarbyloxysilanes and cyclic azasilanes containing functional groups such as cyclic amines, acyclic amines, imines, and isocyanates. [ka] (In the above general formula (5), R 15 , R 16 are each independently an alkyl group or an aryl group having 1 to 20 carbon atoms, and R 17 is an alkylene group having 1 to 20 carbon atoms, and R 18 , R 19 are hydrocarbon groups having 1 to 6 carbon atoms, which may be the same or different, and together with two adjacent Ns form a 5- or greater-membered ring structure; R 20 is a hydrocarbon group having 1 to 20 carbon atoms or a tri-substituted silyl group, and u is an integer of 2 or 3. [ka] (In the above general formula (6), R 15 ~R 20 , u is the same as in the general formula (5), and R 21 is a hydrocarbon group having 1 to 20 carbon atoms or an organic substituted silyl group.

[0088] Furthermore, in the present invention, a silane-sulfide compound represented by the following general formula (7) can be used as a modifying agent having a functional group capable of interacting with silica. (R 22 O) x (R 23 ) y Si-R 24 -S-SiR 25 (7) (In the above general formula (7), Si is silicon, S is sulfur, O is oxygen, x is an integer selected from 1, 2, and 3, y is an integer selected from 0, 1, and 2, and x+y=3. R 22 , R 23 , R 25 are the same or different alkyl groups having 1 to 16 carbon atoms, and R 24 is an aryl group, an alkylaryl group, or an alkyl group having 1 to 16 carbon atoms.

[0089] In the present invention, a reactive polysiloxane compound represented by the following general formula (8) can be used as the siloxane compound having a functional group capable of interacting with silica. Y 1 -CH2CH2-Si(R 26 )(R 27 )-{O-Si(R 26 )(R 27 )} z -CH2CH2-Y 1 (8) In the above general formula (8), Y 1 is (X 7 ) a (R 28 ) b Si-, where X 7 is a halogen and R 28 is a lower alkyl group having 20 or less carbon atoms. 26 , R 27 is a lower alkyl group having 20 or less carbon atoms, a is 2 or 3, b is 0 or 1, a+b=3, and z is 1 to 50,000.

[0090] In the present invention, an amide compound may be used as a terminal modifying agent. For example, N-substituted cyclic amides such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, and N-methyl-ε-caprolactam; N-substituted cyclic ureas such as 1,3-dimethylethyleneurea and 1,3-diethyl-2-imidazolidinone; N-substituted aminoketones such as 4,4′-bis(dimethylamino)benzophenone and 4,4′-bis(diethylamino)benzophenone; diphenylmethane diisocyanate and 2,4-tolylene Examples of suitable vinyl compounds include aromatic isocyanates such as diisocyanates; N,N-disubstituted aminoalkyl methacrylamides such as N,N-dimethylaminopropyl methacrylamide; N-substituted aminoaldehydes such as 4-N,N-dimethylaminobenzaldehyde; N-substituted carbodiimides such as dicyclohexylcarbodiimide; Schiff bases such as N-ethylethylideneimine and N-methylbenzylideneimine; and pyridyl group-containing vinyl compounds such as 4-vinylpyridine.

[0091] Furthermore, when the modification is carried out using a siloxane compound as a modifying agent having a functional group capable of interacting with silica, it is preferable to further react the aromatic vinyl-conjugated diene copolymer chain that has been reacted with the siloxane compound with a compound represented by the following general formula (9): [ka] In general formula (9), R 29 is a hydrocarbyl group, and A 1 is a group capable of reacting with an alkyl metal group as the active terminal of an aromatic vinyl-conjugated diene copolymer chain having an active terminal, or with a reaction residue produced by the reaction of an aromatic vinyl-conjugated diene copolymer chain having an active terminal with a siloxane compound, and A 2 is a group containing a nitrogen atom, p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, and p+q+r=4.

[0092] Here, the compound represented by the general formula (9) has an alkyl metal group, i.e., -R - M + , or -O as a reactive residue by reaction with a siloxane compound - M + (-O - M + The amount of the siloxane compound used is 1 mole or more in terms of the number of repeating units of (-Si-O-) per mole of the polymerization initiator, and the amount of the siloxane compound used is 1 mole or more in terms of the number of repeating units of (-Si-O-) per mole of the polymerization initiator. - M + When the compound represented by the general formula (9) is made into a state in which substantially no groups represented by the formula remain, almost all of the compound represented by the general formula (9) is converted into a reaction residue represented by the formula -O - M + This allows a modified structure by the compound represented by general formula (9) to be appropriately introduced into the aromatic vinyl-conjugated diene copolymer chain via a structure derived from a siloxane compound. In addition, when the obtained aromatic vinyl-conjugated diene copolymer is used to obtain a cross-linked rubber product, it can have excellent low heat buildup and abrasion resistance.

[0093] In the compound represented by general formula (9), R 29 is a hydrocarbyl group, and examples thereof include alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, and aralkyl groups, with an alkyl group having 1 to 6 carbon atoms being preferred. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, pentyl group, and hexyl group, with a methyl group and an ethyl group being more preferred, and a methyl group being particularly preferred.

[0094] In the compound represented by general formula (9), A in general formula (9) 1represents an alkyl metal group (i.e., -R - M + ), or a reaction residue (typically, -O) formed by the reaction of an aromatic vinyl-conjugated diene copolymer chain having an active end with a siloxane compound. - M + is a group capable of reacting with a group represented by -OR 30 (R 30 is preferably a group represented by a hydrogen atom or a hydrocarbyl group. 30 Examples of hydrocarbyl groups that can constitute the above include alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, and aralkyl groups, but from the viewpoint of reactivity with the alkyl metal group or reaction residue, alkyl groups having 1 to 6 carbon atoms are preferred. Examples of alkyl groups having 1 to 6 carbon atoms include methyl groups, ethyl groups, n-propyl groups, isopropyl groups, butyl groups, pentyl groups, and hexyl groups, and of these, methyl groups and ethyl groups are more preferred.

[0095] In the compound represented by general formula (9), A in general formula (9) 2is a group containing a nitrogen atom, and is not particularly limited as long as it is a group containing a nitrogen atom, but is preferably an organic group having a nitrogen atom, such as a 3-aminopropyl group, a 4-aminobutyl group, a 3-(2-aminoethylamino)propyl group, a 2-dimethylaminoethyl group, a 3-dimethylaminopropyl group, a 3-diethylaminopropyl group, a 3-dipropylaminopropyl group, a 3-dibutylaminopropyl group, a 3-phenylmethylaminopropyl group, a 3-(4-methylpiperazinyl)propyl group, an N,N-bis(trimethylsilyl)aminopropyl group, an N,N-bis(triethylsilyl)aminopropyl group, or an N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyl group. Among these, a group containing a primary amino group having an active hydrogen atom and / or a secondary amino group having an active hydrogen atom, such as a 3-aminopropyl group, a 4-aminobutyl group, or a 3-(2-aminoethylamino)propyl group, is preferred, as it can further improve the low heat buildup and abrasion resistance of the resulting cross-linked rubber product. The term "active hydrogen atom" refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably has a bond energy lower than that of the carbon-hydrogen bond of a polymethylene chain.

[0096] In the compound represented by general formula (9), p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, and p+q+r=4. From the viewpoint of reactivity with the alkyl metal group as the active terminal of the aromatic vinyl-conjugated diene copolymer chain having an active terminal, or with the reaction residue generated by the reaction of the aromatic vinyl-conjugated diene copolymer chain having an active terminal with the siloxane compound, preferably, p is an integer of 0 to 1, q is an integer of 2 to 3, and r is an integer of 1 to 2, and more preferably, p=0, q=3, and r=1. When p is 2, two R groups are contained in one molecule of the compound represented by general formula (9). 29 Similarly, when q is 2 or 3, a plurality of A groups contained in one molecule of the compound represented by general formula (9) may be the same or different from each other. 1The groups represented by may be the same or different from each other, and when r is 2 or 3, a plurality of A 2 The groups represented by the formula (I) may be the same or different from each other.

[0097] Specific examples of the compound represented by general formula (9) are not particularly limited, but include, for example, A 2 is a group containing a primary amino group having an active hydrogen atom and / or a secondary amino group having an active hydrogen atom, such as 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, and 3-aminopropyltriethoxysilane. 2 compounds having a 3-aminopropyl group; A such as 4-aminobutyldimethylmethoxysilane, 4-aminobutylmethyldimethoxysilane, 4-aminobutyltrimethoxysilane, 4-aminobutyldimethylethoxysilane, 4-aminobutylmethyldiethoxysilane, and 4-aminobutyltriethoxysilane; 2 compounds having a 4-aminobutyl group; 3-(2-aminoethylamino)propyldimethylmethoxysilane, 3-(2-aminoethylamino)propylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propyldimethylethoxysilane, 3-(2-aminoethylamino)propylmethyldiethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, etc. 2 Examples of the arylamino group include compounds having a 3-(2-aminoethylamino)propyl group;

[0098] In addition, A in general formula (9) 2is a group other than a group containing a primary amino group having an active hydrogen atom and / or a secondary amino group having an active hydrogen atom, such as 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropylmethyldimethoxysilane, 3-dimethylaminopropyldimethylmethoxysilane, 3-dimethylaminopropyltriethoxysilane, 3-dimethylaminopropylmethyldiethoxysilane, and 3-dimethylaminopropyldimethylethoxysilane. 2 Compounds having a 3-dimethylaminopropyl group; such as 3-diethylaminopropyltrimethoxysilane, 3-diethylaminopropylmethyldimethoxysilane, 3-diethylaminopropyldimethylmethoxysilane, 3-diethylaminopropyltriethoxysilane, 3-diethylaminopropylmethyldiethoxysilane, and 3-diethylaminopropyldimethylethoxysilane. 2 compounds having a 3-diethylaminopropyl group; 3-dipropylaminopropyltrimethoxysilane, 3-dipropylaminopropylmethyldimethoxysilane, 3-dipropylaminopropyldimethylmethoxysilane, 3-dipropylaminopropyltriethoxysilane, 3-dipropylaminopropylmethyldiethoxysilane, 3-dipropylaminopropyldimethylethoxysilane, etc. 2 as the A, compounds having a 3-dipropylaminopropyl group; 3-dibutylaminopropyltrimethoxysilane, 3-dibutylaminopropylmethyldimethoxysilane, 3-dibutylaminopropyldimethylmethoxysilane, 3-dibutylaminopropyltriethoxysilane, 3-dibutylaminopropylmethyldiethoxysilane, 3-dibutylaminopropyldimethylethoxysilane, etc. 2 Compounds having a 3-dibutylaminopropyl group; 3-phenylmethylaminopropyltrimethoxysilane, 3-phenylmethylaminopropylmethyldimethoxysilane, 3-phenylmethylaminopropyldimethylmethoxysilane, 3-phenylmethylaminopropyltriethoxysilane, 3-phenylmethylaminopropylmethyldiethoxysilane, 3-phenylmethylaminopropyldimethylethoxysilane, etc. 2as the methyl group, a compound having a 3-phenylmethylaminopropyl group; 3-(4-methylpiperazinyl)propyltrimethoxysilane, 3-(4-methylpiperazinyl)propylmethyldimethoxysilane, 3-(4-methylpiperazinyl)propyldimethylmethoxysilane, 3-(4-methylpiperazinyl)propyltriethoxysilane, 3-(4-methylpiperazinyl)propylmethyldiethoxysilane, 3-(4-methylpiperazinyl)propyldimethylethoxysilane, etc. 2 as a compound having a 3-(4-methylpiperazinyl)propyl group;

[0099] A such as N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, and N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane 2 compounds having an N,N-bis(trimethylsilyl)aminopropyl group; N,N-bis(triethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(triethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(triethylsilyl)aminopropylmethyldiethoxysilane, etc. 2 Examples of the A include compounds having an N,N-bis(triethylsilyl)aminopropyl group; N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane. 2 Examples thereof include compounds having an N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyl group; and the like.

[0100] The amount of the compound represented by general formula (9) used is not particularly limited, but is preferably 0.1 to 5 mol, more preferably 0.2 to 2 mol, and even more preferably 0.4 to 1.5 mol, relative to 1 mol of the polymerization initiator used in the polymerization step. By using the compound represented by general formula (9) in the above range, the obtained cross-linked rubber product can be made to have excellent low heat buildup and wear resistance.

[0101] The timing of adding the compound represented by general formula (9) to a solution containing an aromatic vinyl-conjugated diene copolymer chain is not particularly limited, as long as it is after the addition of the siloxane compound. For example, the compound represented by general formula (9) can be added to a solution in which the polymerization reaction is not yet complete and the solution containing the aromatic vinyl-conjugated diene copolymer chain also contains a monomer, more specifically, when the solution containing the aromatic vinyl-conjugated diene copolymer chain contains 100 ppm or more, preferably 300 to 50,000 ppm of monomer. Adding the compound represented by general formula (9) at this timing can suppress side reactions between the aromatic vinyl-conjugated diene copolymer chain and impurities contained in the polymerization system, thereby enabling good reaction control. Alternatively, adding water or an alcohol such as methanol to the solution containing the aromatic vinyl-conjugated diene copolymer chain before or after adding the compound represented by general formula (9) can prevent the formation of -O as a reaction residue formed by the reaction with the siloxane compound. - M + The modification reaction may be carried out in a state in which the group represented by formula (9) is hydrolyzed and converted into a hydroxyl group. When the compound represented by formula (9) is added to a solution containing an aromatic vinyl-conjugated diene copolymer chain, the compound represented by formula (9) may be added after being dissolved in an inert solvent, or may be added directly without being dissolved in an inert solvent. The reaction temperature and reaction time may be the same as those in the case of carrying out a reaction using a siloxane compound.

[0102] After reacting the compound represented by general formula (9), a known polymerization terminator or the like is added as needed to inactivate the reaction system, and then, if desired, an antioxidant such as a phenolic stabilizer, a phosphorus-based stabilizer, or a sulfur-based stabilizer, a crumb-forming agent, or a scale inhibitor is added to the reaction solution, and the polymerization solvent is then separated from the reaction solution by direct drying or steam stripping, to recover the aromatic vinyl-conjugated diene copolymer. Note that, before separating the polymerization solvent from the reaction solution, an extender oil may be mixed with the polymerization solution, and the aromatic vinyl-conjugated diene copolymer may be recovered as an oil-extended rubber.

[0103] Examples of extender oils used when recovering an aromatic vinyl-conjugated diene copolymer as an oil-extended rubber include paraffinic, aromatic, and naphthenic petroleum-based softeners, vegetable-based softeners, and fatty acids. When a petroleum-based softener is used, it is preferable that the polycyclic aromatic content extracted by the IP346 method (a testing method of The Institute of Petroleum in the UK) is less than 3%. When an extender oil is used, the amount used is preferably 1 to 100 parts by weight, more preferably 2 to 60 parts by weight, and even more preferably 3 to 50 parts by weight per 100 parts by weight of the aromatic vinyl-conjugated diene copolymer.

[0104] In the above, the cases where a siloxane compound and a compound represented by general formula (9) are used as examples of a modifying agent having a functional group capable of interacting with silica are mainly shown, but the modifying agent having a functional group capable of interacting with silica is not particularly limited as long as it is a compound capable of reacting with the active end of the aromatic vinyl-conjugated diene copolymer chain having an active end obtained in the polymerization step described above and has a functional group capable of interacting with silica.

[0105] As a method for introducing a functional group capable of interacting with silica into an aromatic vinyl-conjugated diene copolymer, instead of or in addition to the method of reacting a modifier having a functional group capable of interacting with silica with an aromatic vinyl-conjugated diene copolymer chain having an active end obtained in the polymerization step, it is also possible to select a method of introducing a functional group capable of interacting with silica in the polymerization step. Specifically, in the polymerization step, a compound capable of reacting with the monomer used in the polymerization step and having a functional group capable of interacting with silica is copolymerized to introduce the functional group capable of interacting with silica. The functional group capable of interacting with silica is not particularly limited, but examples include nitrogen-containing functional groups, silicon-containing functional groups, and oxygen-containing functional groups. Among these, silicon-containing functional groups are preferred from the viewpoint of their high interaction with silica.

[0106] Examples of the silicon atom-containing modifier used in the polymerization step include (dimethylamino)dimethylvinylsilane, (ethylmethylamino)dimethylvinylsilane, (diethylamino)dimethylvinylsilane, (ethyl-n-propylamino)dimethylvinylsilane, (ethylisopropylamino)dimethylvinylsilane, (di-n-propylamino)dimethylvinylsilane, (diisopropylamino)dimethylvinylsilane, (n-butyl-n-propylamino)dimethylvinylsilane, (di-n-butylamino)dimethylvinylsilane, (dimethylamino)diethylvinylsilane, (ethylmethylamino)diethylvinylsilane, (diethylamino)diethylvinylsilane, (ethyl-n-propylamino)diethylvinylsilane, (ethylisopropylamino)diethylvinylsilane, (di-n-propylamino)diethylvinylsilane, (diisopropylamino)diethylvinylsilane, (n-butyl-n-propylamino)diethylvinylsilane, (di-n-butylamino)diethylvinylsilane, (dimethylamino)dipropylvinylsilane, (ethylmethylamino)dipropylvinylsilane, (diethylamino)dipropylvinylsilane, (ethyl-n-propylamino)dipropylvinylsilane, (ethylisopropylamino)dipropylvinylsilane, (di-n-propylamino)dipropylvinylsilane, (diisopropylamino)dipropylvinylsilane, (n-butyl-n-propylamino)dipropylvinylsilane, (di-n-butylamino)dipropylvinylsilane, (dimethylamino)dibutylvinylsilane, (ethylmethylamino)dibutylvinylsilane, (diethylamino)dibutylvinylsilane, (ethyl-n-propylamino)dibutylvinylsilane, (ethylisopropylamino)dibutylvinylsilane, (di-n-propylamino)dibutylvinylsilane, (diisopropylamino)dibutylvinylsilane, (n-butyl-n-propylamino)dibutylvinylsilane, (di-n-butylamino)dibutylvinylsilane, {di(trimethylsilyl)amino}dimethylvinylsilane, di{(t-butyldimethylsilyl)amino}dimethylvinylsilane, {di(trimethylsilyl)amino}diethylvinylsilane, di{(t-butyldimethylsilyl)amino}diethylvinylsilane, bis(dimethylamino)methylvinylsilane, bis(ethylmethylamino)methylvinylsilane, bis(diethylamino)methylvinylsilane, bis(ethyl-n-propylamino)methylvinylsilane, bis(ethylisopropylamino)methylvinylsilane, bis(di-n-propylamino)methylvinylsilane, bis(diisopropylamino)methylvinylsilane, bis(n-butyl-n-propylamino)methylvinylsilane, bis(di-n-butylamino)methylvinylsilane, Bis(dimethylamino)ethylvinylsilane, bis(ethylmethylamino)ethylvinylsilane, bis(diethylamino)ethylvinylsilane, bis(ethyl-n-propylamino)ethylvinylsilane, bis(ethylisopropylamino)ethylvinylsilane, bis(di-n-propylamino)ethylvinylsilane, bis(diisopropylamino)ethylvinylsilane, bis(n-butyl-n-propylamino)ethylvinylsilane, bis(di-n-butylamino)ethylvinylsilane, Bis(dimethylamino)propyl vinylsilane, bis(ethylmethylamino)propyl vinylsilane, bis(diethylamino)propyl vinylsilane, bis(ethyl-n-propylamino)propyl vinylsilane, bis(ethylisopropylamino)propyl vinylsilane, bis(di-n-propylamino)propyl vinylsilane, bis(diisopropylamino)propyl vinylsilane, bis(n-butyl-n-propylamino)propyl vinylsilane, bis(di-n-butylamino)propyl vinylsilane, bis(dimethylamino)butylvinylsilane, bis(ethylmethylamino)butylvinylsilane, bis(diethylamino)butylvinylsilane, bis(ethyl-n-propylamino)butylvinylsilane, bis(ethylisopropylamino)butylvinylsilane, bis(di-n-propylamino)butylvinylsilane, bis(diisopropylamino)butylvinylsilane, bis(n-butyl-n-propylamino)butylvinylsilane, bis(di-n-butylamino)butylvinylsilane, Examples include bis{di(trimethylsilyl)amino}methylvinylsilane, bis{(t-butyldimethylsilyl)amino}methylvinylsilane, bis{di(trimethylsilyl)amino}ethylvinylsilane, bis{(t-butyldimethylsilyl)amino}ethylvinylsilane, tri(dimethylamino)vinylsilane, tri(ethylmethylamino)vinylsilane, tri(diethylamino)vinylsilane, tri(ethylpropylamino)vinylsilane, tri(dipropylamino)vinylsilane, and tri(butylpropylamino)vinylsilane.

[0107] The compound having a functional group capable of interacting with silica used in the polymerization step may be at least one selected from the group consisting of 4,4'-vinylidenebis(n,n-dimethylaniline), 3-(2-pyrrolidinoethyl)styrene, 4-(2-pyrrolidinoethyl)styrene, and (3-(2-pyrrolidino-1-methylethyl)-alpha-methylstyrene.

[0108] The coupling ratio of the aromatic vinyl-conjugated diene copolymer used in the present invention is not particularly limited, but is preferably 10 to 90% by weight, more preferably 20 to 80% by weight, and particularly preferably 30 to 70% by weight. When the coupling ratio is within the above range, the cross-linked rubber obtained using the aromatic vinyl-conjugated diene copolymer can have excellent low heat buildup and abrasion resistance. The coupling ratio is the weight fraction of polymer molecules having a molecular weight 1.8 times or more the peak top molecular weight of the aromatic vinyl-conjugated diene copolymer chain having an active end before reaction with a modifier having a functional group capable of interacting with silica, such as a siloxane compound or a compound represented by general formula (9), and optionally a coupling agent or other modifier, relative to the total weight of the aromatic vinyl-conjugated diene copolymer finally obtained. The molecular weight is measured as a polystyrene-equivalent molecular weight by gel permeation chromatography.

[0109] The coupling agent used as needed in the present invention is not particularly limited, but for example, a metal halide compound can be used.Specific examples include silicon tetrachloride, hexachlorodisilane, bis(trichlorosilyl)methane, 1,2-bis(trichlorosilyl)ethane, 1,3-bis(trichlorosilyl)propane, 1,4-bis(trichlorosilyl)butane, 1,5-bis(trichlorosilyl)pentane, and 1,6-bis(trichlorosilyl)hexane, and among these, hexachlorodisilane, 1,2-bis(trichlorosilyl)ethane, and 1,6-bis(trichlorosilyl)hexane can be mentioned.In addition, tin tetrachloride can also be used.

[0110] The weight-average molecular weight (Mw) of the aromatic vinyl-conjugated diene copolymer used in the present invention, as measured by gel permeation chromatography in terms of polystyrene, is preferably 150,000 to 3,000,000, more preferably 170,000 to 2,000,000, even more preferably 200,000 to 1,500,000, still more preferably 250,000 to 1,000,000, particularly preferably 350,000 to 650,000, and most preferably 380,000 to 520,000. By setting the weight-average molecular weight of the aromatic vinyl-conjugated diene copolymer within the above range, it becomes easier to compound silica into the aromatic vinyl-conjugated diene copolymer, which can further improve the processability of the rubber composition and further improve the low heat buildup and wear resistance of the resulting cross-linked rubber.

[0111] The molecular weight distribution of the aromatic vinyl-conjugated diene copolymer used in the present invention, expressed as the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 1.1 to 3.5, more preferably 1.2 to 3.0, even more preferably 1.3 to 2.5, and particularly preferably 1.3 to 2.0. By adjusting the molecular weight distribution (Mw / Mn) of the aromatic vinyl-conjugated diene copolymer to fall within the above range, the low heat buildup and abrasion resistance of the resulting cross-linked rubber can be further improved.

[0112] The aromatic vinyl-conjugated diene copolymer used in the present invention preferably has a Mooney viscosity (ML1+4, 100°C) of 20 to 100, more preferably 30 to 90, even more preferably 35 to 80, particularly preferably 40 to 70, and most preferably 45 to 65. When the aromatic vinyl-conjugated diene copolymer is used as an oil-extended rubber, it is preferable that the Mooney viscosity of the oil-extended rubber be in the above range.

[0113] <Silica> The rubber composition for heavy-duty tires of the present invention contains silica in addition to the above-mentioned aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of −50° C. or lower and having a functional group capable of interacting with silica.

[0114] The silica used in the present invention is not particularly limited, but examples thereof include dry-process white carbon, wet-process white carbon, colloidal silica, and precipitated silica. Carbon-silica dual-phase fillers, in which silica is supported on the surface of carbon black, may also be used. Among these, wet-process white carbon, primarily composed of hydrated silicic acid, is preferred. These may be used alone or in combination.

[0115] The silica preferably has a nitrogen adsorption specific surface area measured by the BET method of 50 to 400 m 2 / g, more preferably 140 to 250m 2 / g, more preferably 180 to 240m 2 / g. When the specific surface area is within this range, the chipping resistance, abrasion resistance, and low heat buildup of the obtained cross-linked rubber can be further improved. The pH of the silica is preferably less than 7, and more preferably 5 to 6.9. The nitrogen adsorption specific surface area can be measured by the BET method in accordance with ASTM D3037-81.

[0116] The amount of silica compounded in the rubber composition for heavy load tires of the present invention is preferably 10 to 200 parts by weight, more preferably 13 to 150 parts by weight, and even more preferably 15 to 100 parts by weight, per 100 parts by weight of the rubber component in the rubber composition for heavy load tires. By setting the amount of silica compounded within the above range, it is possible to improve the dispersion of silica during production, while more appropriately improving the low heat buildup, abrasion resistance, and chipping resistance of the obtained cross-linked rubber product.

[0117] <Carbon black> Furthermore, the rubber composition for heavy-duty tires of the present invention preferably further contains carbon black in addition to the above-mentioned aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of −50° C. or lower and having a functional group capable of interacting with silica, and silica. By further containing carbon black, the obtained cross-linked rubber product can be made even more excellent in abrasion resistance.

[0118] Examples of carbon black include furnace black, acetylene black, thermal black, channel black, graphite, etc. Among these, it is preferable to use furnace black, and specific examples thereof include SAF, ISAF, ISAF-HS, ISAF-LS, IISAF-HS, HAF, HAF-HS, HAF-LS, etc. These can be used alone or in combination of two or more.

[0119] The carbon black preferably has a nitrogen adsorption specific surface area measured by the BET method of 30 to 170 m 2 / g, more preferably 70 to 160m 2 / g, more preferably 110 to 150m 2 / g. When the specific surface area is in this range, the abrasion resistance of the obtained cross-linked rubber product can be further improved. The nitrogen adsorption specific surface area can be measured by the BET method in accordance with JIS K-6217.

[0120] The carbon black preferably has a DBP absorption of 60 to 160 cm as measured by Method A. 3 / 100g, more preferably 85 to 150cm 3 / 100g, more preferably 110-145cm 3 / 100g. When the DBP absorption amount is within this range, the abrasion resistance of the obtained cross-linked rubber product can be further improved. The DBP absorption amount can be measured by Method A in accordance with JIS Z-8091.

[0121] The carbon black preferably has an iodine adsorption capacity of 25 to 170 mg / g, more preferably 70 to 160 mg / g, and even more preferably 110 to 150 mg / g. When the iodine adsorption capacity is within this range, the abrasion resistance of the obtained cross-linked rubber product can be further improved. The iodine adsorption capacity can be measured in accordance with JIS Z-8091.

[0122] The amount of carbon black blended in the rubber composition for heavy load tires of the present invention is preferably 10 to 200 parts by weight, more preferably 15 to 150 parts by weight, even more preferably 20 to 100 parts by weight, and still more preferably 22 to 40 parts by weight, per 100 parts by weight of the rubber component in the rubber composition for heavy load tires. By setting the blending amount of carbon black within the above range, the abrasion resistance of the obtained cross-linked rubber product can be more appropriately improved.

[0123] <Natural rubber> Furthermore, the rubber composition for heavy-duty tires of the present invention preferably further contains natural rubber as a rubber component in addition to the aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of -50°C or lower and having a functional group capable of interacting with silica. In addition to ordinary natural rubber, modified natural rubbers such as epoxidized natural rubber having epoxy groups introduced therein and hydrogenated natural rubber can be used as the natural rubber, and these may be used in combination. The inclusion of natural rubber can further improve the chipping resistance of the resulting cross-linked rubber.

[0124] The content of natural rubber in the rubber composition for heavy load tires of the present invention is preferably 10 to 80% by weight, more preferably 30 to 70% by weight, even more preferably 40 to 60% by weight, and particularly preferably 45 to 55% by weight, based on 100% by weight of all rubber components contained in the rubber composition for heavy load tires of the present invention. By blending natural rubber in the above-mentioned proportions, the chipping resistance of the obtained cross-linked rubber can be more appropriately improved.

[0125] <Polybutadiene rubber> Furthermore, the rubber composition for heavy-duty tires of the present invention preferably further contains polybutadiene rubber as a rubber component in addition to the aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of −50°C or lower and having a functional group capable of interacting with silica. The inclusion of polybutadiene rubber can further enhance the low heat buildup of the resulting cross-linked rubber. The polybutadiene rubber may be low-cis BR (polybutadiene rubber), high-cis BR, or high-trans BR (trans bond content of the butadiene portion: 70 to 95%), or these may be used in combination. The polybutadiene rubber may also be modified polybutadiene rubber into which a nitrogen-containing functional group, a silicon-containing functional group, an oxygen-containing functional group, or the like has been introduced.

[0126] The content of polybutadiene rubber in the rubber composition for heavy load tires of the present invention is preferably 10 to 80% by weight, more preferably 10 to 50% by weight, even more preferably 10 to 30% by weight, and particularly preferably 15 to 25% by weight, based on 100% by weight of all rubber components contained in the rubber composition for heavy load tires of the present invention. By blending the polybutadiene rubber in the above-mentioned proportion, the low heat buildup property of the obtained cross-linked rubber can be more appropriately improved.

[0127] When the rubber composition for heavy load tires of the present invention further contains natural rubber and / or polybutadiene rubber as a rubber component, the content of the aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of −50° C. or lower and having a functional group capable of interacting with silica in 100% by weight of all rubber components contained in the rubber composition for heavy load tires of the present invention is preferably 10 to 80% by weight, more preferably 20 to 60% by weight, even more preferably 20 to 40% by weight, and particularly preferably 25 to 35% by weight.

[0128] <Other ingredients> Furthermore, the rubber composition for heavy-duty tires of the present invention may contain, as a rubber component, in addition to the aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of −50°C or lower and having a functional group capable of interacting with silica, and natural rubber and / or polybutadiene rubber, which are used as needed. Examples of rubbers other than natural rubber and / or polybutadiene rubber include polyisoprene rubber, emulsion-polymerized styrene-butadiene copolymer rubber, solution-polymerized styrene-butadiene copolymer rubber, styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, acrylonitrile-styrene-butadiene copolymer rubber, cyclic olefin ring-opening polymers, and hydrogenated conjugated diene polymers, other than the aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of −50°C or lower and having a functional group capable of interacting with silica. These rubbers may be used alone or in combination of two or more.

[0129] When these other rubbers are compounded, the content thereof is preferably 50% by weight or less, more preferably 35% by weight or less, and even more preferably 20% by weight or less, in terms of the content ratio of all rubber components contained in the rubber composition for heavy load tires of the present invention.

[0130] Furthermore, a silane coupling agent may be further blended into the rubber composition for heavy-duty tires of the present invention from the viewpoint of further improving low heat buildup. The silane coupling agent is not particularly limited, and various silane coupling agents can be used, but in the present invention, sulfide-based, mercapto-based, protected mercapto-based (e.g., those having a carbonylthio group), thiocyanate-based, vinyl-based, amino-based, methacrylate-based, glycidoxy-based, nitro-based, epoxy-based, or chloro-based silane coupling agents can be suitably used. Specific examples of silane coupling agents include bis(3-(triethoxysilyl)propyl)disulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-(triethoxysilyl)propyl)tetrasulfide, γ-mercaptopropyltriethoxysilane, 3-[ Examples of suitable silanes include ethoxybis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silyl)-1-propanethiol, 3-octanoylthio-1-propyl-triethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, γ-trimethoxysilylpropylbenzothiazyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-thiocyanatepropyltriethoxysilane, vinyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 3-trimethoxysilylpropyl methacrylate monosulfide, γ-glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-chloropropyltrimethoxysilane. Other examples of silane coupling agents that can be used include NXT-Z100, NXT-Z30, NXT-Z45, NXT-Z60, NXT-Z45, and NXT manufactured by Momentive Performance Materials, and Si69, Si75, and VP Si363 manufactured by Evonik. These silane coupling agents can be used alone or in combination of two or more. Alternatively, one or more of these silane coupling agents can be oligomerized in advance and used in the oligomerized state.The amount of the silane coupling agent to be added is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight, based on 100 parts by weight of silica.

[0131] The rubber composition for heavy-duty tires of the present invention preferably further contains a crosslinking agent. Examples of crosslinking agents include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, and alkylphenol resins having methylol groups. Among these, sulfur is preferably used. The amount of crosslinking agent blended is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 4 parts by weight, per 100 parts by weight of the rubber component in the rubber composition for heavy-duty tires.

[0132] Furthermore, in addition to the above-mentioned components, the rubber composition for heavy load tires of the present invention may contain, according to a conventional method, necessary amounts of compounding agents such as a crosslinking accelerator, a crosslinking activator, an antioxidant, a filler (excluding the above-mentioned silica and carbon black), an activator, a process oil, a plasticizer, a lubricant, a tackifier, a compatibilizer, and a surfactant.

[0133] When sulfur or a sulfur-containing compound is used as the crosslinking agent, it is preferable to use a crosslinking accelerator and a crosslinking activator in combination. Examples of crosslinking accelerators include sulfenamide-based crosslinking accelerators, guanidine-based crosslinking accelerators, thiourea-based crosslinking accelerators, thiazole-based crosslinking accelerators, thiuram-based crosslinking accelerators, dithiocarbamic acid-based crosslinking accelerators, and xanthogenic acid-based crosslinking accelerators. Among these, those containing sulfenamide-based crosslinking accelerators are preferred. These crosslinking accelerators may be used alone or in combination of two or more. The amount of crosslinking accelerator blended is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 4 parts by weight, per 100 parts by weight of the rubber component in the rubber composition for heavy-duty tires.

[0134] Examples of crosslinking activators include higher fatty acids such as stearic acid, zinc oxide, etc. These crosslinking activators may be used alone or in combination of two or more. The amount of crosslinking activator added is preferably 0.05 to 20 parts by weight, and particularly preferably 0.5 to 15 parts by weight, per 100 parts by weight of the rubber component in the rubber composition for heavy load tires.

[0135] In addition, the rubber composition for heavy-duty tires of the present invention may contain a resin in addition to the rubber component. The incorporation of a resin can impart tack to the rubber composition for heavy-duty tires and improve the dispersibility of silica in the rubber composition for heavy-duty tires. As a result, an improved balance of chipping resistance, low heat buildup, and abrasion resistance can be expected for the resulting cross-linked rubber. Furthermore, similar to the effect of a plasticizer, the resin can also improve the processability of the rubber composition for heavy-duty tires. Examples of resins include C5 petroleum resins, C5 / C9 petroleum resins, C9 petroleum resins, dicyclopentadiene resins, terpene resins, terpene phenol resins, aromatic-modified terpene resins, alkylphenol-acetylene resins, rosin resins, rosin ester resins, indene resins, C9 resins containing indene, α-methylstyrene-indene copolymer resins, coumarone-indene resins, farnesene resins, and polylimonene resins. These resins may be modified or hydrogenated. These resins may be used alone or in combination of two or more. The amount of the resin to be compounded is preferably 25 parts by weight or less per 100 parts by weight of the rubber component in the rubber composition for heavy load tires.

[0136] To obtain the rubber composition for heavy-duty tires of the present invention, the components can be kneaded according to a conventional method. For example, the components excluding thermally unstable components such as crosslinking agents and crosslinking accelerators are kneaded with an aromatic vinyl-conjugated diene copolymer, and then the resulting mixture is mixed with thermally unstable components such as crosslinking agents and crosslinking accelerators to obtain the desired composition. The kneading temperature for the components excluding thermally unstable components and the aromatic vinyl-conjugated diene copolymer is preferably 80 to 200°C, more preferably 120 to 180°C, and the kneading time is preferably 30 seconds to 30 minutes. The kneaded mixture is then mixed with the thermally unstable components after cooling to typically 100°C or below, preferably 80°C or below.

[0137] <Rubber cross-linked products> The cross-linked rubber product of the present invention can be obtained by cross-linking the above-mentioned rubber composition for heavy load tires of the present invention.

[0138] The crosslinking method for crosslinking the rubber composition for heavy load tires of the present invention is not particularly limited, and may be selected depending on the shape, size, etc. of the crosslinked rubber. The rubber composition for heavy load tires may be filled into a mold and heated to crosslink simultaneously with molding, or a rubber composition for heavy load tires that has been molded in advance may be heated and crosslinked. The crosslinking temperature is preferably 100 to 200°C, more preferably 130 to 190°C, and the crosslinking time is preferably 1 minute to 24 hours, more preferably 2 minutes to 12 hours, and even more preferably 3 minutes to 6 hours.

[0139] Depending on the shape, size, etc. of the cross-linked rubber product, even if the surface is cross-linked, the inside may not be sufficiently cross-linked, so secondary cross-linking may be carried out by further heating.

[0140] The heating method may be appropriately selected from common methods used for crosslinking rubber, such as press heating, steam heating, oven heating, and hot air heating.

[0141] The cross-linked rubber product of the present invention is obtained using the rubber composition for heavy-duty tires of the present invention described above, and therefore has excellent low heat buildup and abrasion resistance, and high chipping resistance. Therefore, the cross-linked rubber product of the present invention is suitable for various tire applications, particularly for heavy-duty tires to be mounted on trucks (including tractors and trailers), buses, construction vehicles (for example, dump trucks and graders), and the like. Furthermore, the cross-linked rubber product of the present invention can be used in various tire portions such as the tread portion, carcass portion, sidewall portion, and bead portion of such tires, but is particularly suitable for use in the tread portion. Furthermore, it is also suitable for use in the tread portion of retread tires in which worn or deteriorated tread portions are replaced. [Example]

[0142] The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. In the following, "parts" are by weight unless otherwise specified. Various tests and evaluations were carried out according to the following methods.

[0143] [Weight average molecular weight, molecular weight distribution, coupling ratio] The weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), and coupling ratio were determined based on a chart obtained by gel permeation chromatography (GPC) based on the molecular weight converted to polystyrene. The specific measurement conditions for gel permeation chromatography were as follows: Measuring instrument: High-performance liquid chromatograph (Tosoh Corporation, product name "HLC-8320") Column: Two polystyrene columns manufactured by Tosoh Corporation, trade name "GMH-HR-H", were connected in series. Detector: differential refractometer Eluent: tetrahydrofuran Column temperature: 40℃ The coupling rate of the aromatic vinyl-conjugated diene copolymer chain was determined as the ratio of the area of ​​the peak having a peak top molecular weight 1.8 times or more of the peak top molecular weight of the smallest peak to the total elution area in the elution curve obtained by gel permeation chromatography under the above conditions.

[0144] [Styrene unit content, vinyl bond content] The styrene unit content and vinyl bond content are 1 1H-NMR was used to measure the

[0145] [Styrene block ratio] The styrene block ratio as an aromatic vinyl compound block ratio was calculated by using deuterated chloroform as a solvent with reference to the following literature. 1 The obtained compound was measured by H-NMR. 1 The peaks at 6.1 to 7.7 ppm in the H-NMR spectrum were determined to be those derived from styrene, and of these, the peaks at 6.1 to 6.88 ppm were determined to be those derived from styrene blocks. The ratio of the peak area derived from styrene blocks to the peak area derived from styrene was calculated, and the value was multiplied by 2.5 to express it as a percentage, which was taken as the styrene block ratio. Reference: Sardelis, K. Michels, HJ Allen, G. Polymer, 1984, 25, 1011

[0146] [Mooney viscosity (ML(1+4)100℃)] Measurement was carried out using a Mooney viscometer (Shimadzu Corporation) in accordance with JIS K6300-1 (2013).

[0147] [Glass transition temperature (Tg)] Measurements were carried out in a helium atmosphere (gas flow rate: 20.0 mL / min) using a differential scanning calorimeter (PerkinElmer, product name "DSC8500") according to JIS K6240 (2011). The peak top temperature of the differential curve of the obtained DSC curve was determined as the glass transition temperature (Tg).

[0148] [Low heat buildup of cross-linked rubber] The low heat buildup properties of the cross-linked rubber were evaluated by measuring the tan δ value at 60°C under conditions of a dynamic strain of 2.5% and 10 Hz using an ARES-G2 manufactured by TA Instruments, using a test piece 50 mm long, 12.7 mm wide, and 2 mm thick. The low heat buildup properties were calculated as an index, with the measured value of Comparative Example 1 being set at 100. The higher this index, the better the low heat buildup properties.

[0149] [Abrasion resistance of cross-linked rubber] The abrasion resistance of the cross-linked rubber product was evaluated by measuring test pieces with an outer diameter of 50 mm, an inner diameter of 15 mm, and a thickness of 10 mm using an FPS abrasion tester (manufactured by Ueshima Seisakusho Co., Ltd.) under a load of 10 N and a slip ratio of 15%. The abrasion resistance was calculated as an index, with the measured value of Comparative Example 1 being set at 100. The higher this index, the better the abrasion resistance.

[0150] [Chipping resistance] Regarding the low heat buildup property of the cross-linked rubber, a tensile test was carried out in accordance with JIS K6301 using a test piece having a length of 50 mm, a width of 12.7 mm, and a thickness of 2 mm, and the elongation at break was measured. The chipping resistance was calculated as an index, with the measured value of Comparative Example 1 being set at 100. The higher this index, the better the chipping resistance.

[0151] [Production Example 1] (Production of polymer block (A)) A nitrogen-purged vessel was charged with 218.1 parts of cyclohexane, 7.5 parts of styrene, and 0.3 parts of tetramethylethylenediamine, and the internal temperature of the vessel was raised to 50°C. Next, 1.64 parts of n-butyllithium was added, followed by 92.5 parts of isoprene over 80 minutes. The reaction was then allowed to proceed for 15 minutes, yielding a polymer block (A) having an active terminal. This polymer block (A) had a weight-average molecular weight (Mw) of 6,500, a molecular weight distribution (Mw / Mn) of 1.10, a styrene unit content of 7.5%, an isoprene unit content of 92.5%, and a vinyl bond content of 7.0%.

[0152] (Production of Terminally Modified Styrene-Butadiene Copolymer (P1)) An autoclave equipped with a stirrer was charged with 525 parts of cyclohexane, 11.7 parts of styrene, 48.3 parts of 1,3-butadiene, and 0.029 parts of tetramethylethylenediamine under a nitrogen atmosphere. Then, 8.8 parts of the resulting solution containing polymer block (A) with active terminals (2.6 parts of polymer block (A)) was added, and polymerization was initiated at 50°C. Ten minutes after the start of polymerization, 3.3 parts of styrene and 33.7 parts of 1,3-butadiene were added continuously over 60 minutes. Then, 3.0 parts of 1,3-butadiene were added continuously over 10 minutes, followed by stirring for another 10 minutes. The maximum temperature during the polymerization reaction was 75°C. After confirming that the polymerization conversion rate was between 95% and 100%, 0.005 parts of 1,6-bis(trichlorosilyl)hexane was added, and the reaction was allowed to proceed for 10 minutes. Then, 0.15 parts of a polyorganosiloxane represented by the following formula (10) in the form of a 40% xylene solution was added and allowed to react for 10 minutes. Then, 0.15 parts of a polyorganosiloxane represented by the following formula (10) in the form of a 40% xylene solution was added and stirred for 20 minutes. Next, 0.16 parts of 3-(2-aminoethylamino)propyltrimethoxysilane in the form of a 50% xylene solution was added and allowed to react for 15 minutes. Then, as a polymerization terminator, methanol was added in an amount equivalent to twice the molar amount of n-butyllithium used to obtain a polymer solution. Then, 0.25 parts of Irganox 1520L (manufactured by BASF) was added to this polymer solution as an antioxidant per 100 parts of the copolymer contained in the polymer solution. Next, the solvent was removed by steam stripping, and a solid terminally modified styrene butadiene copolymer (P1) was obtained by hot air drying. The weight average molecular weight, coupling ratio, styrene unit content, vinyl bond content, Mooney viscosity, and glass transition temperature of the obtained terminally modified styrene butadiene copolymer (P1) were measured. The results are shown in Table 1. The obtained terminally modified styrene-butadiene copolymer (P1) had, at the polymer chain end, a modified structure (a modified structure containing a Si-OH group, a Si-OCH3 group, etc.) with polyorganosiloxane represented by the following formula (10) and 3-(2-aminoethylamino)propyltrimethoxysilane as a functional group capable of interacting with silica (the same applies to Production Example 2 described later). [ka]

[0153] [Production Example 2] (Production of Terminally Modified Styrene Butadiene Copolymer (P2)) In the production of terminal-modified styrene-butadiene copolymer (P1) of Production Example 1, the amount of styrene added before the start of polymerization was 10.0 parts, and 1,3-butadiene was 50.0 parts. The amount of styrene added 10 minutes after the start of polymerization was 0.0 parts (i.e., no additional styrene was added), and 1,3-butadiene was 37.0 parts. Instead of adding 0.005 parts of 1,6-bis(trichlorosilyl)hexane and reacting for 10 minutes, 0.005 parts of tin tetrachloride was added and reacted for 20 minutes. In addition, 3-(2-aminoethylamino)propyltrimethoxysilane was used instead of 50% concentration xylene solution. A terminal-modified styrene-butadiene copolymer (P2) was obtained in the same manner as in Production Example 1.

[0154] [Production Example 3] (Production of Terminally Modified Styrene Butadiene Copolymer (P3)) An autoclave equipped with a stirrer was charged with 500.4 parts of cyclohexane, 15.0 parts of styrene, 37.1 parts of 1,3-butadiene, and 0.016 parts of tetramethylethylenediamine under a nitrogen atmosphere. Then, 8.8 parts of a solution containing polymer block (A) having active terminals, obtained in the same manner as in Production Example 1, was added, and polymerization was initiated at 55°C. Twelve minutes after the start of polymerization, 3.3 parts of 1,3-butadiene were continuously added over 4 minutes. One minute later, 17.8 parts of 1,3-butadiene were continuously added over 17 minutes. Furthermore, 13.4 parts of 1,3-butadiene were continuously added over 18 minutes. After this, 13.4 parts of 1,3-butadiene were continuously added over 35 minutes. The maximum temperature during the polymerization reaction was 80°C. After a series of continuous additions, the mixture was stirred for 30 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.15 parts of the polyorganosiloxane represented by the formula (10) in a 40% xylene solution was added and allowed to react for 10 minutes. Then, 0.15 parts of the polyorganosiloxane represented by the formula (10) in a 40% xylene solution was added and allowed to react for 20 minutes. Next, 0.16 parts of 3-(2-aminoethylamino)propyltrimethoxysilane diluted with 0.38 parts of cyclohexane was added and allowed to react for 15 minutes. Then, methanol was added as a polymerization terminator in an amount equivalent to twice the molar amount of n-butyllithium used to obtain a polymer solution. Then, 0.20 parts of Irganox 1520L (BASF) was added as an antioxidant to this polymer solution per 100 parts of copolymer contained in the polymer solution. The solvent was then removed by steam stripping, and the resulting mixture was dried with hot air to obtain a solid terminal-modified styrene-butadiene copolymer (P3). The weight-average molecular weight, coupling ratio, styrene unit content, vinyl bond content, Mooney viscosity, and glass transition temperature of the resulting terminal-modified styrene-butadiene copolymer (P3) were measured. The results are shown in Table 1. The obtained terminally modified styrene-butadiene copolymer (P3) had, at the polymer chain end, a modified structure (a modified structure containing a Si-OH group, a Si-OCH3 group, etc.) by polyorganosiloxane represented by the above formula (10) and 3-(2-aminoethylamino)propyltrimethoxysilane as a functional group capable of interacting with silica (the same applies to Production Examples 4, 5, and 7 described later (the structure of the modifier is partially different in Production Examples 4 and 5)).

[0155] [Production Example 4] (Production of Terminally Modified Styrene Butadiene Copolymer (P4)) A terminal-modified styrene-butadiene copolymer (P4) was obtained in the same manner as in Production Example 3, except that in Production Example 3, the amount of styrene added before the start of polymerization was 10 parts, 1,3-butadiene was 42.1 parts, and N,N-bis(triethylsilyl)aminopropyltrimethoxysilane was used instead of 3-(2-aminoethylamino)propyltrimethoxysilane.

[0156] [Production Example 5] (Production of Terminally Modified Styrene Butadiene Copolymer (P5)) A terminal-modified styrene-butadiene copolymer (P5) was obtained in the same manner as in Production Example 3, except that the amount of styrene added was changed to 5 parts and 3-diethylaminopropyltrimethoxysilane was used instead of 3-(2-aminoethylamino)propyltrimethoxysilane.

[0157] [Production Example 6] (Production of Terminally Modified Styrene-Butadiene Copolymer (P6)) An autoclave equipped with a stirrer was charged with 498.8 parts of cyclohexane, 5.0 parts of styrene, and 47.1 parts of 1,3-butadiene under a nitrogen atmosphere, and then 8.8 parts of the solution containing the polymer block (A) having active terminals obtained above (2.6 parts of polymer block (A) used) was added, and polymerization was initiated at 55°C. Twelve minutes after the start of polymerization, 3.3 parts of 1,3-butadiene were continuously added over 4 minutes. One minute later, 17.8 parts of 1,3-butadiene were continuously added over 17 minutes. Furthermore, 13.4 parts of 1,3-butadiene were continuously added over 18 minutes. After this, 13.4 parts of 1,3-butadiene were continuously added over 35 minutes. The maximum temperature during the polymerization reaction was 80°C. After the series of continuous additions, the mixture was stirred for 30 minutes, and after confirming that the polymerization conversion rate had reached 95% to 100%, 0.31 parts of the polyorganosiloxane represented by the formula (10) in a 40% xylene solution diluted with 0.12 parts of cyclohexane was continuously added over 28 minutes. Ten minutes later, 0.16 parts of 3-(2-aminoethylamino)propyltrimethoxysilane diluted with 0.38 parts of cyclohexane was added and allowed to react for 15 minutes. Then, as a polymerization terminator, methanol was added in an amount equivalent to twice the molar amount of n-butyllithium used to obtain a polymer solution. Then, 0.20 parts of Irganox 1520L (manufactured by BASF) was added to this polymer solution as an antioxidant, per 100 parts of copolymer. The solvent was then removed by steam stripping, and a solid terminally modified styrene-butadiene copolymer (P6) was obtained by hot air drying. The weight average molecular weight, coupling ratio, styrene unit content, vinyl bond content, Mooney viscosity, and glass transition temperature of the obtained terminally modified styrene butadiene copolymer (P6) were measured. The results are shown in Table 1. The obtained terminally modified styrene-butadiene copolymer (P6) had, at the polymer chain end, a modified structure (a modified structure containing a Si-OH group, a Si-OCH3 group, etc.) with polyorganosiloxane represented by the above formula (10) and 3-(2-aminoethylamino)propyltrimethoxysilane as a functional group capable of interacting with silica (the same applies to Production Example 8 described later).

[0158] [Production Example 7] (Production of Terminally Modified Styrene-Butadiene Copolymer (P7)) In Production Example 3, the amount of cyclohexane was changed to 784 parts, and after confirming that the polymerization conversion was in the range of 95% to 100%, 0.0026 parts of 1,6-bis(trichlorosilyl)hexane was added before adding the 40% xylene solution of formula (10), and the reaction was continued for 10 minutes. A terminal-modified styrene-butadiene copolymer (P7) was obtained in the same manner as in Production Example 3. The weight-average molecular weight, coupling ratio, styrene unit content, vinyl bond content, Mooney viscosity, and glass transition temperature of the resulting terminal-modified styrene-butadiene copolymer (P7) were measured. The results are shown in Table 1.

[0159] [Production Example 8] (Production of Terminally Modified Styrene Butadiene Copolymer (P8)) In Production Example 6, the amount of cyclohexane was changed to 645 parts, and after confirming that the polymerization conversion was in the range of 95% to 100%, 0.0026 parts of tin tetrachloride was added before adding the 40% xylene solution of formula (10), and the reaction was allowed to proceed for 20 minutes. A terminal-modified styrene-butadiene copolymer (P9) was obtained in the same manner as in Production Example 6. The weight-average molecular weight, coupling ratio, styrene unit content, vinyl bond content, Mooney viscosity, and glass transition temperature of the resulting terminal-modified styrene-butadiene copolymer (P8) were measured. The results are shown in Table 1.

[0160] [Production Example 9] (Production of tin-coupled polybutadiene rubber (P9)) An autoclave equipped with a stirrer was charged with 525 parts of cyclohexane and 48.3 parts of 1,3-butadiene under a nitrogen atmosphere, and then 2.6 parts of n-butyllithium was added to initiate polymerization at 50°C. Ten minutes after the start of polymerization, 33.7 parts of 1,3-butadiene were continuously added over 60 minutes. Then, 3.0 parts of 1,3-butadiene were continuously added over 10 minutes, followed by stirring for another 10 minutes. The maximum temperature during the polymerization reaction was 75°C. After confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.008 parts of tin tetrachloride was added and the reaction was allowed to proceed for 20 minutes. Then, methanol was added as a polymerization terminator in an amount equivalent to twice the molar amount of n-butyllithium used to obtain a polymer solution. Then, 0.25 parts of Irganox 1520L (BASF) was added as an antioxidant to this polymer solution per 100 parts of copolymer contained in the polymer solution. The solvent was then removed by steam stripping, and the solid tin-coupled polybutadiene rubber (P9) was obtained by hot air drying. The weight-average molecular weight, coupling ratio, styrene unit content, vinyl bond content, Mooney viscosity, and glass transition temperature of the obtained tin-coupled polybutadiene rubber (P9) were measured. The results are shown in Table 1.

[0161] [Production Example 10] (Production of tin-coupled styrene-butadiene copolymer (P10)) An autoclave equipped with a stirrer was charged with 525 parts cyclohexane, 20.0 parts styrene, 48.3 parts 1,3-butadiene, and 0.032 parts tetramethylethylenediamine under a nitrogen atmosphere, followed by the addition of 2.6 parts n-butyllithium to initiate polymerization at 50°C. Ten minutes after the start of polymerization, 4.0 parts styrene and 27.7 parts 1,3-butadiene were continuously added over 30 minutes. The mixture was then stirred for another 30 minutes. The maximum temperature during the polymerization reaction was 70°C. After confirming that the polymerization conversion rate was between 95% and 100%, 0.005 parts tin tetrachloride was added and the reaction was allowed to proceed for 15 minutes. Subsequently, methanol was added as a polymerization terminator in an amount equivalent to twice the molar amount of n-butyllithium used to obtain a polymer solution. To this polymer solution, 0.25 parts of Irganox 1520L (BASF) was added as an antioxidant per 100 parts of copolymer contained in the polymer solution. The solvent was then removed by steam stripping, and the solid terminally modified styrene-butadiene copolymer (P10) was obtained by hot air drying. The weight average molecular weight, coupling ratio, styrene unit content, vinyl bond content, Mooney viscosity, and glass transition temperature of the resulting tin-coupled styrene-butadiene copolymer (P10) were measured. The results are shown in Table 1.

[0162] [Table 1] In Table 1, Production Example 9 is a tin-coupled polybutadiene rubber (P9).

[0163] Example 1 In a 250 ml Banbury mixer, 50 parts of natural rubber, 30 parts of the terminal-modified styrene-butadiene copolymer (P1) obtained in Production Example 1, and 20 parts of butadiene rubber (manufactured by Nippon Zeon Co., Ltd., trade name "Nipol BR1220") were masticated for 30 seconds. Next, 25 parts of silica (manufactured by Solvay, trade name "Zeosil 1165MP"), 25 parts of carbon black (manufactured by Tokai Carbon Co., Ltd., trade name "Seast 9H"), and 2.0 parts of a silane coupling agent, bis(3-(triethoxysilyl)propyl)tetrasulfide (manufactured by Evonik, trade name "Si69"), were added and mixed for 1.5 minutes at a starting temperature of 110°C. After that, 3 parts of zinc oxide, 2 parts of stearic acid, and 2 parts of an antioxidant, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac 6C"), were added and mixed for an additional 2.5 minutes. The mixture was then discharged from the mixer. The temperature of the mixture at the end of mixing was 150°C. The mixture was cooled to room temperature and then mixed again in the Banbury mixer at a starting temperature of 110°C for 3 minutes, after which the mixture was discharged from the mixer. The resulting mixture was then kneaded using an open roll at 50°C with a mixture of 1.75 parts sulfur, 1.0 part crosslinking accelerator: N-(tert-butyl)-2-benzothiazole sulfenamide (manufactured by Sanshin Chemical Industry Co., Ltd., trade name "Suncerer NS-G"), and 0.53 parts crosslinking accelerator: 1,3-diphenylguanidine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noccelaer D"), and then a sheet-like rubber composition was removed. The resulting rubber composition was press-crosslinked at 160°C for 7 minutes to prepare test specimens of the crosslinked rubber. These test specimens were then evaluated for low heat buildup, abrasion resistance, and chipping resistance. The results are shown in Table 2.

[0164] Examples 2 to 6 Rubber compositions were obtained, and test pieces of cross-linked rubber were prepared and evaluated in the same manner as in Example 1, except that 30 parts of the terminal-modified styrene-butadiene copolymers (P2) to (P6) obtained in Production Examples 2 to 6 were used instead of 30 parts of the terminal-modified styrene-butadiene copolymer (P1) obtained in Production Example 1. The results are shown in Table 2.

[0165] Example 7 A rubber composition was obtained, and test pieces of the cross-linked rubber were prepared and evaluated in the same manner as in Example 6, except that the silica was changed to "Ultrasil 9100GR" manufactured by Evonik Corporation and the carbon black was changed to "SEAST 7HM" manufactured by Tokai Carbon Co., Ltd. The results are shown in Table 2.

[0166] Example 8 A rubber composition was obtained, and a test piece of the cross-linked rubber was prepared and evaluated in the same manner as in Example 1, except that 30 parts of the terminal-modified styrene-butadiene copolymer (P7) obtained in Production Example 7 was used instead of 30 parts of the terminal-modified styrene-butadiene copolymer (P1) obtained in Production Example 1. The results are shown in Table 2.

[0167] Example 9 A rubber composition was obtained, and a test piece of the cross-linked rubber was prepared and evaluated in the same manner as in Example 1, except that 30 parts of the terminal-modified styrene-butadiene copolymer (P8) obtained in Production Example 8 was used instead of 30 parts of the terminal-modified styrene-butadiene copolymer (P1) obtained in Production Example 1. The results are shown in Table 2.

[0168] Comparative Example 1 A rubber composition was obtained, and a test piece of the cross-linked rubber was prepared and evaluated in the same manner as in Example 1, except that 30 parts of the tin-coupled polybutadiene rubber (P9) obtained in Production Example 9 was used instead of 30 parts of the terminal-modified styrene-butadiene copolymer (P1) obtained in Production Example 1. The results are shown in Table 2.

[0169] Comparative Example 2 A rubber composition was obtained, and a test piece of the cross-linked rubber was prepared and evaluated in the same manner as in Example 1, except that 30 parts of the tin-coupled styrene-butadiene copolymer (P10) obtained in Production Example 10 was used instead of 30 parts of the terminal-modified styrene-butadiene copolymer (P1) obtained in Production Example 1. The results are shown in Table 2.

[0170] [Table 2]

[0171] As shown in Tables 1 and 2, the cross-linked rubber products obtained using the rubber compositions containing silica and an aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of -50°C or lower and having a functional group capable of interacting with silica, were excellent in low heat buildup and abrasion resistance, and had high chipping resistance (Examples 1 to 9). On the other hand, a cross-linked rubber obtained using a polybutadiene rubber having no functional group capable of interacting with silica, even though the polybutadiene rubber had a glass transition temperature (Tg) of -50°C or lower, was insufficient in low heat buildup, abrasion resistance, and chipping resistance (Comparative Example 1). Furthermore, a cross-linked rubber product obtained using an aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) higher than -50°C and no functional group capable of interacting with silica was insufficient in low heat buildup, abrasion resistance, and chipping resistance (Comparative Example 2).

Claims

1. A rubber composition for a heavy-duty tire, comprising: an aromatic vinyl-conjugated diene copolymer having a glass transition temperature (Tg) of −70° C. or lower and having a functional group capable of interacting with silica; and silica, the aromatic vinyl-conjugated diene copolymer comprises an aromatic vinyl-conjugated diene copolymer chain having a polymer block (A) and a polymer block (B); the polymer block (A) contains 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units, The rubber composition for heavy-duty tires, wherein the polymer block (B) contains 1,3-butadiene monomer units and aromatic vinyl monomer units.

2. The nitrogen adsorption specific surface area of ​​the silica measured by the BET method is 30 to 500 m ２ 2. The rubber composition for a heavy load tire according to claim 1, wherein the tensile strength is 1 / g.

3. 3. The rubber composition for a heavy-duty tire according to claim 1, wherein the content of said silica is 10 to 200 parts by weight based on 100 parts by weight of the rubber component containing said aromatic vinyl-conjugated diene copolymer.

4. 4. The rubber composition for a heavy load tire according to claim 1, further comprising carbon black.

5. The carbon black has a nitrogen adsorption specific surface area of ​​30 m as measured by the BET method. ２ The rubber composition for a heavy load tire according to claim 4, wherein the modulus of elasticity is 1 / g or more.

6. 6. The rubber composition for a heavy-duty tire according to claim 4, wherein the content of the carbon black is 10 to 200 parts by weight based on 100 parts by weight of the rubber component containing the aromatic vinyl-conjugated diene copolymer.

7. 7. The rubber composition for a heavy-duty tire according to claim 1, wherein the content of the aromatic vinyl-conjugated diene copolymer is 10 to 80% by weight based on 100% by weight of the total rubber component.

8. Further containing natural rubber, 8. The rubber composition for a heavy-duty tire according to claim 1, wherein the content of the natural rubber is 10 to 80% by weight based on 100% by weight of the total rubber components.

9. Further containing polybutadiene rubber, 9. The rubber composition for a heavy-duty tire according to claim 1, wherein the content of the polybutadiene rubber is 10 to 80% by weight based on 100% by weight of the total rubber component.

10. The functional group capable of interacting with silica in the aromatic vinyl-conjugated diene copolymer is Si—OR ａ (R ａ The rubber composition for a tire for heavy loads according to any one of claims 1 to 9, wherein R is a group having a structure represented by the following formula:

11. A cross-linked rubber product obtained by cross-linking the rubber composition for heavy load tires according to any one of claims 1 to 10.

12. A heavy-duty tire comprising the cross-linked rubber according to claim 11.

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