Rubber composition for heavy load tire and heavy load tire

Abstract

To provide a rubber composition for heavy load tire and a heavy load tire, exhibiting excellent on-snow performance, low rolling resistance, chipping resistance, and abrasion resistance.SOLUTION: A rubber composition for heavy load tire, comprising a rubber component and a filler, wherein the rubber component includes an isoprene-based rubber and a modified conjugated diene-based rubber, the content of the isoprene-based rubber being 50 mass% or more; the modified conjugated diene-based rubber satisfies the formula (1) and has a modifying group including a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto; the filler includes carbon black having an N2SA of 70 m2 / g or more and silica, with the silica content being 10 to 70 mass%; and the filler content is 80 pts.mass or less per 100 pts.mass of the rubber component. IVw10%≤3.1×10-6×Mw10%-2.77 (1). Mw10% is the weight-average molecular weight of the high-molecular-weight-side 10% measured by a differential refractive index detector, and IVw10% is the weight-average intrinsic viscosity of the high-molecular-weight-side 10% measured by a viscosity detector.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for a heavy load tire and a heavy load tire. [Background technology]

[0002] BACKGROUND ART Conventionally, rubber compositions for tires that contain carbon black or silica in order to improve performance have been known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-28902 Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, from the viewpoint of safety, etc., there has been a demand for further improvements in performance such as snow performance, chipping resistance, and wear resistance for tires (particularly heavy-duty tires used for trucks, buses, etc.). In addition, from the viewpoint of environmental issues, etc., there has also been a demand for further improvements in fuel efficiency. Under these circumstances, the present inventors have studied the rubber composition for tires described in Patent Document 1 and the like, and have found that further improvements are desirable in view of the expected increasing demands in the future.

[0005] In view of the above circumstances, the present invention aims to provide a rubber composition for heavy-duty tires that, when made into a tire, exhibits excellent on-snow performance, fuel efficiency, chipping resistance, and abrasion resistance, as well as a heavy-duty tire manufactured using the rubber composition for heavy-duty tires. [Means for solving the problem]

[0006] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using an isoprene-based rubber, a specific modified conjugated diene-based rubber, and a specific filler as rubber components, and optimizing the contents of several components, thereby arriving at the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0007] (1) Contains a rubber component and a filler, the rubber component contains an isoprene-based rubber and a modified conjugated diene-based rubber, The modified conjugated diene rubber satisfies the formula (1) described below and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, The proportion of the isoprene-based rubber in the rubber component is 50% by mass or more, The above packing material has a nitrogen adsorption specific surface area of ​​70m 2 / g or more of carbon black and silica, The proportion of the silica in the filler is 10 to 70 mass %, The rubber composition for heavy-duty tires has a content of the filler of 80 parts by mass or less per 100 parts by mass of the rubber component. (2) The rubber composition for a heavy-duty tire according to (1) above, wherein the glass transition temperature of the modified conjugated diene rubber is −51° C. or lower. (3) The rubber composition for a heavy-duty tire according to (1) or (2) above, wherein the total content of the oil, resin, and plasticizer per 100 parts by mass of the rubber component is 10 parts by mass or less. (4) A heavy-duty tire manufactured using the rubber composition for heavy-duty tires according to any one of (1) to (3) above. [Effects of the Invention]

[0008] As will be described below, according to the present invention, it is possible to provide a rubber composition for heavy load tires that, when made into a tire, exhibits excellent on-snow performance, fuel efficiency, chipping resistance, and abrasion resistance, as well as a heavy load tire manufactured using the rubber composition for heavy load tires. [Brief explanation of the drawings]

[0009] [Figure 1] This is an example of a GPC chromatogram. [Figure 2] 1 is a partial cross-sectional schematic view showing an example of an embodiment of a tire of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The rubber composition for a heavy-duty tire of the present invention will be described below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. Each component may be used alone or in combination of two or more. When two or more components are used in combination, the content of the components refers to the total content unless otherwise specified. Furthermore, with regard to a rubber composition for heavy-duty tires, the on-snow performance, fuel economy, chipping resistance, and wear resistance when made into a tire are also simply referred to as "on-snow performance," "fuel economy," "chipping resistance," and "wear resistance," respectively. Furthermore, excellent on-snow performance, fuel economy, chipping resistance, and abrasion resistance are also referred to as "excellent effects of the present invention." Furthermore, in this specification, a power of 10 may be represented by E. For example, E+5 represents 10 to the fifth power.

[0011] [I] Rubber composition for heavy duty tires The rubber composition for a heavy-duty tire of the present invention (hereinafter also referred to as "the composition of the present invention") is Contains a rubber component and a filler, the rubber component contains an isoprene-based rubber and a modified conjugated diene-based rubber, The modified conjugated diene rubber satisfies the formula (1) described below and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, The proportion of the isoprene-based rubber in the rubber component is 50% by mass or more, The above packing material has a nitrogen adsorption specific surface area of ​​70m 2 / g or more of carbon black and silica, The proportion of the silica in the filler is 10 to 70 mass %, In the rubber composition for heavy-duty tires, the content of the filler per 100 parts by mass of the rubber component is 80 parts by mass or less.

[0012] It is believed that the composition of the present invention can solve the above-mentioned problems because of its structure. The reason for this is not clear, but is presumed to be as follows. The composition of the present invention contains, as rubber components, an isoprene-based rubber and a conjugated diene-based rubber (hereinafter also referred to as a "specific conjugated diene-based rubber") that satisfies the following formula (1) and has a modifying group (hereinafter also referred to as a "specific modifying group") containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. Formula (1) defines the relationship between the weight-average intrinsic viscosity on the high molecular weight side and the weight-average molecular weight on the high molecular weight side. The inventors' studies have revealed that rubbers that satisfy formula (1) have excellent compatibility with isoprene-based rubber and result in highly uniform compositions. Furthermore, the carbon black used in the composition of the present invention has a high nitrogen adsorption specific surface area and high reinforcing properties. Therefore, the composition of the present invention is believed to exhibit excellent chipping resistance and abrasion resistance. Furthermore, in the composition of the present invention, the specific modifying group of the specific conjugated diene-based rubber strongly interacts with silica, resulting in extremely high silica dispersibility. This is believed to contribute to the excellent on-snow performance and fuel economy.

[0013] Each component contained in the composition of the present invention will be described below.

[0014] [1] Rubber component The composition of the present invention contains a rubber component. The rubber component contains an isoprene-based rubber and a specific conjugated diene-based rubber. The rubber component may contain a rubber component other than the isoprene-based rubber and the specific conjugated diene-based rubber.

[0015] [Isoprene rubber] Examples of isoprene-based rubber include natural rubber (NR) and isoprene rubber (synthetic isoprene rubber) (IR). The isoprene-based rubber is preferably natural rubber, since this provides a better effect of the present invention. The isoprene-based rubber preferably does not have a specific modifying group, and more preferably does not have a modifying group (is unmodified), for the reason that the effects of the present invention are more excellent.

[0016] [Content] The proportion of the isoprene-based rubber in the rubber component is 50% by mass or more. The above proportion is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, for reasons of superior effects of the present invention.

[0017] [Specific conjugated diene rubber] The specific conjugated diene rubber is a conjugated diene rubber that satisfies the formula (1) described below and has a modifying group (specific modifying group) that contains a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto.

[0018] [Skeleton] The skeleton of the specific conjugated diene rubber is a polymer having repeating units derived from a conjugated diene. The skeleton is preferably a polymer other than an isoprene-based rubber.

[0019] <Conjugated diene> Specific examples of the conjugated diene include butadiene (particularly 1,3-butadiene), chloroprene, etc. The diene is preferably butadiene (particularly 1,3-butadiene) because the effects of the present invention are more excellent.

[0020] <Other Monomers> The skeleton of the specific conjugated diene rubber may have repeating units other than repeating units derived from conjugated dienes. Examples of monomers that form such repeating units (other monomers) include vinyl monomers and alkenes (e.g., ethylene, propylene, butene). Examples of vinyl monomers include aromatic vinyls (e.g., styrene), acrylonitrile, and the specific branching agents described below.

[0021] <Example> Specific examples of the skeleton include butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), etc. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, etc. The conjugated diene rubber is preferably SBR, since this provides better effects of the present invention.

[0022] [Specific modifying group] As described above, the specific conjugated diene rubber has a modifying group (specific modifying group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent to the silicon atom. The specific modifying group may be present at any of the terminal, main chain, or side chain of the conjugated diene rubber. The specific modifying group preferably contains a silicon atom and an oxygen atom adjacent thereto as an alkoxysilyl group, because this provides a more excellent effect of the present invention. n (R2) 3-n (wherein R1 is an alkyl group, R2 is a hydrogen atom or an alkyl group, and n is an integer of 1 to 3). The specific modifying group preferably contains a nitrogen atom as an amino group (primary to tertiary amino group) because this provides better effects of the present invention. The specific modifying group is preferably a group derived from a specific modifying agent described below, because this provides better effects of the present invention.

[0023] [Formula (1)] The specific conjugated diene rubber satisfies the following formula (1). Formula (1) defines the relationship between the weight-average intrinsic viscosity on the high molecular weight side and the weight-average molecular weight on the high molecular weight side, and polymers with small molecular size relative to their molecular weight, such as those with branches, tend to satisfy formula (1). The reason for limiting the formula to the high molecular weight side is that it has a large impact on the physical properties of the entire polymer.

[0024] IVw 10% ≦3.1×10 -6 ×Mw 10% -2.77 (1)

[0025] Mw in formula (1) 10% and IVw 10% is calculated as follows: The modified conjugated diene rubber is subjected to gel permeation chromatography measurement using a differential refractive index detector (RI detector) and a viscosity detector. The weight average molecular weight (Mw) is calculated using the high molecular weight portion of the chromatogram peak obtained by the differential refractive index detector, which accounts for 10% of the total peak area. 10% However, Mw 10% is 200 x 10 4 The weight average intrinsic viscosity determined using the high molecular weight portion of the peak in the chromatogram obtained by the viscosity detector, which is 10% of the total peak area, is defined as IVw 10% However, the unit of weight average intrinsic viscosity is dL / g.

[0026] Hereinafter, Mw in formula (1) 10% and IVw 10% This will be explained in more detail.

[0027] As described above, the modified conjugated diene rubber is subjected to gel permeation chromatography (GPC) measurement using a differential refractive index detector and a viscosity detector as detectors. The specific method of GPC measurement is as follows.

[0028] The eluent used was toluene containing 5 mmol / L triethylamine. Three columns packed with polystyrene gel (manufactured by Tosoh Corporation under the trade names "TSKgel G4000HXL," "TSKgel G5000HXL," and "TSKgel G6000HXL") were connected together. The sample to be measured was dissolved in toluene to a concentration of 1 mg / mL to prepare the measurement solution. 100 μL of the measurement solution was injected into the GPC measurement device and measured at an oven temperature of 40°C and a toluene flow rate of 1 mL / min.

[0029] The weight average molecular weight is determined by using the high molecular weight side (the side with a shorter elution time) which accounts for 10% of the total area of ​​the peaks (peaks derived from modified conjugated diene rubber) in the chromatogram (horizontal axis: elution time, vertical axis: signal intensity) obtained by the differential refractive index detector. The weight average molecular weight obtained is Mw 10% Let's say.

[0030] In addition, among the peaks (peaks derived from modified conjugated diene rubber) in the chromatogram (horizontal axis: elution time, vertical axis: signal intensity) obtained by the viscosity detector, the weight-average intrinsic viscosity is determined using the portion of the high molecular weight side (shorter elution time) that accounts for 10% of the total peak area. The weight-average intrinsic viscosity thus obtained is referred to as IVw 10% Let's say. The weight average intrinsic viscosity is defined as (Σ(ηi×Mi×Ni)) / (Σ(Mi×Ni)), where Ni is the number of molecules and ηi is the intrinsic viscosity at molecular weight Mi.

[0031] An example of a GPC chromatogram (horizontal axis: elution time, vertical axis: signal intensity) is shown in Figure 1. The Mw peak was calculated using P1, which is the high molecular weight portion (shorter elution time) that accounts for 10% of the area of ​​the entire peak, P0. 10% and IVw 10% Ask for.

[0032] Examples of a method for making the modified conjugated diene rubber satisfy formula (1) include a method of changing the type and amount of the specific modifier and the type and amount of the specific branching agent in the production method of the present invention described below.

[0033] As mentioned above, Mw 10% is 200 x 10 4 That's all. Mw 10% Although there is no particular upper limit to the molecular weight, it is preferably 10,000,000 or less, and more preferably 5,000,000 or less, because the effects of the present invention are more excellent.

[0034] IVw 10% In order to obtain a more excellent effect of the present invention, IVw is preferably 2 to 8, and more preferably 4 to 6. 10% is preferably 4.7 or more because the effects of the present invention are more excellent.

[0035] [Formula (2)] The specific conjugated diene rubber preferably satisfies the following formula (2) for the reason that the effects of the present invention are more excellent.

[0036] St+Vn≦50 (2)

[0037] In formula (2), St represents the proportion (mass%) of repeating units derived from styrene relative to the entire specific conjugated diene rubber (hereinafter also referred to as the "styrene amount"), and Vn represents the proportion (mass%) of repeating units of 1,2-vinyl structure derived from a conjugated diene (e.g., butadiene) relative to the entire specific conjugated diene rubber (hereinafter also referred to as the "vinyl amount").

[0038] St+Vn is preferably 10 to 45, and more preferably 25 to 45, because the effects of the present invention are more excellent.

[0039] St is preferably 5 to 40, more preferably 10 to 35, and even more preferably 15 to 30, because the effects of the present invention are more excellent.

[0040] Vn is preferably 5 to 30, and more preferably 10 to 20, because the effects of the present invention are more excellent.

[0041] [Molecular weight] The weight average molecular weight (Mw) of the specific conjugated diene rubber is preferably 100,000 to 2,000,000, and more preferably 200,000 to 1,300,000, for reasons of better effects of the present invention. The weight average molecular weight (Mw) of the specific conjugated diene rubber is measured in the same manner as described above except that the entire peak is used. 10% is the same as

[0042] [Glass transition temperature] The glass transition temperature (Tg) of the specific conjugated diene rubber is not particularly limited, but in order to obtain better effects of the present invention, it is preferably from −100° C. to −30° C., and more preferably from −80° C. to −45° C. Among them, in order to obtain better effects of the present invention, it is preferably −51° C. or lower. The glass transition temperature can be adjusted by, for example, the amount of styrene or vinyl. In this specification, the glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) at a temperature rise rate of 10° C. / min and calculated by the midpoint method.

[0043] [Preferred embodiment 1] The specific conjugated diene rubber preferably has a star structure with three or more branches, more preferably a star structure with three or more branches in which the specific modifying group is a branch point, for reasons of better effects of the present invention, and even more preferably is a conjugated diene rubber represented by the following formula (A):

[0044] [ka]

[0045] In formula (A), X represents an n-valent group (specific modifying group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, P represents a conjugated diene polymer chain, and n represents an integer of 3 or more.

[0046] As described above, X represents an n-valent group (specific modifying group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. X preferably contains a silicon atom and an oxygen atom adjacent thereto as an alkoxysilyl group, because this provides a better effect of the present invention. X preferably contains a nitrogen atom as an amino group, because this provides a better effect of the present invention.

[0047] As described above, P represents a conjugated diene polymer chain. Multiple Ps may be the same or different. The definition, specific examples and preferred embodiments of the conjugated diene polymer chain are the same as those of the skeleton of the specific conjugated diene rubber described above.

[0048] As described above, n represents an integer of 3 or greater. There is no particular upper limit to n, but it is preferably 30 or less in order to obtain better effects of the present invention.

[0049] [Preferred embodiment 2] When the specific conjugated diene rubber has a star structure with three or more branches, at least one branched chain (conjugated diene polymer chain) of the star structure preferably has a portion derived from a specific branching agent described later, and the portion preferably has a further main chain branched structure, for reasons of better effects of the present invention. The main chain branched structure refers to a structure in which a branched chain (conjugated diene polymer chain) forms a branch point at a portion derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group, and a polymer chain (e.g., another conjugated diene polymer chain) extends from the branch point.

[0050] [Content] The proportion of the specific conjugated diene rubber in the rubber component is preferably 10 to 50% by mass, and more preferably 20 to 40% by mass, for reasons of better effects of the present invention.

[0051] [Method of manufacturing specific conjugated diene rubber] The method for producing the specific conjugated diene rubber is not particularly limited, but a method including the following steps (1) and (2) (hereinafter also referred to as the "production method of the present invention") is preferred because it provides better effects of the present invention. (1) A polymerization step in which a conjugated diene-containing monomer is polymerized by anionic polymerization to obtain a conjugated diene-based polymer. (2) A modification step in which the conjugated diene polymer obtained in the polymerization step is reacted with a compound containing a nitrogen atom and an alkoxysilyl group (hereinafter also referred to as a "specific modifier") to obtain a conjugated diene rubber having a specific modifying group.

[0052] [Polymerization process] The polymerization step is a step of obtaining a conjugated diene-based polymer by polymerizing a monomer containing a conjugated diene through anionic polymerization.

[0053] <Anionic polymerization> The anionic polymerization is not particularly limited, but anionic polymerization using an organolithium compound as an initiator is preferred because it provides better effects of the present invention.

[0054] The organolithium compound is not particularly limited, and specific examples thereof include monoorganolithium compounds such as n-butyllithium (n-BuLi), sec-butyllithium, tert-butyllithium, n-propyllithium, isopropyllithium, and benzyllithium; and polyfunctional organolithium compounds such as 1,4-dilithiobutane, 1,5-dilithiopentane, 1,6-dilithiohexane, 1,10-dilithiodecane, 1,1-dilithiodiphenylene, dilithiopolybutadiene, dilithiopolyisoprene, 1,4-dilithiobenzene, 1,2-dilithio-1,2-diphenylethane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-tirithiobenzene, and 1,3,5-tirithio-2,4,6-triethylbenzene. Among these, the monoorganolithium compounds n-butyllithium, sec-butyllithium, and tert-butyllithium are preferred, and n-butyllithium is more preferred, due to the superior effects of the present invention.

[0055] The amount of the organolithium compound used is not particularly limited, but is preferably 0.001 to 10 mol % relative to the monomer, because this provides a better effect of the present invention.

[0056] <Monomer> Specific examples and preferred embodiments of the conjugated diene-containing monomer used in the polymerization step are the same as those of the conjugated diene and other monomers in the skeleton of the specific conjugated diene-based rubber described above.

[0057] (Specific branching agent) The monomer preferably contains a vinyl monomer containing an alkoxysilyl group or a halosilyl group (hereinafter also referred to as a "specific branching agent"), because this provides a better effect of the present invention. The specific branching agent is preferably an aromatic vinyl (particularly styrene) containing an alkoxysilyl group or a halosilyl group, more preferably an aromatic vinyl containing an alkoxysilyl group, and even more preferably an aromatic vinyl containing a trialkoxysilyl group, for reasons that the effects of the present invention are more excellent.

[0058] (1) Specific examples Specific examples of aromatic vinyls containing an alkoxysilyl group include 1-(trimethoxysilyl)-4-vinylbenzene and 1,1-bis(4-trimethoxysilylphenyl)ethylene. Examples of aromatic vinyls containing a halosilyl group include trichloro(4-vinylphenyl)silane and 1,1-bis(4-trichlorosilylphenyl)ethylene.

[0059] (2) Usage amount The amount of the specific branching agent used is preferably 0.001 to 0.1% by mass, and more preferably 0.005 to 0.05% by mass, based on the conjugated diene, because this provides a better effect of the present invention.

[0060] <Polar compounds> In the polymerization step, a polar compound may be added. This allows the monomers to be copolymerized randomly. Polar compounds also tend to be useful as vinylating agents for controlling the microstructure of conjugated dienes. They also tend to be effective in accelerating the polymerization reaction.

[0061] Examples of polar compounds that can be used include ethers such as tetrahydrofuran, diethyl ether, dioxane, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate and sodium tert-butylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used alone or in combination of two or more.

[0062] (Amount used) The amount of polar compound used is preferably 0.01 moles or more and 100 moles or less per mole of the initiator, because this provides a better effect of the present invention.

[0063] [Modification step] The modification step is a step of obtaining a conjugated diene rubber having a specific modifying group by reacting the conjugated diene polymer obtained in the polymerization step with a modifier (specific modifier) ​​containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto.

[0064] In the modification step, it is considered that the active terminal of the conjugated diene polymer obtained in the polymerization step is bonded to the silicon atom of the specific modifying agent. For example, when the specific modifying agent contains an alkoxysilyl group, it is considered that the active terminal is bonded to the silicon atom of the alkoxysilyl group, and the alkoxy group is released. Furthermore, when the conjugated diene polymer obtained in the polymerization step has a portion derived from the specific branching agent, in addition to the above-mentioned active terminal, the alkoxysilyl group or halosilyl group in the above portion is also thought to react with the specific modifying agent (for example, an alkoxysilyl group). Furthermore, the alkoxysilyl group or halosilyl group in the above portion is also thought to react with the active terminal of another conjugated diene polymer. As a result, the conjugated diene polymer having a portion derived from the specific branching agent will have a main chain branched structure (another conjugated diene polymer chain) in the above portion.

[0065] <Specific denaturant> The specific modifier is a compound containing a nitrogen atom, a silicon atom and an oxygen atom adjacent thereto. For the reason that the effects of the present invention are more excellent, the specific modifier preferably contains a silicon atom and an oxygen atom adjacent thereto as an alkoxysilyl group (particularly, a trialkoxysilyl group) or a group containing a silazane structure (particularly, a cyclic silazane structure) in which an alkoxy group is bonded to the silicon atom of the silazane structure. Here, the silazane structure refers to a structure in which a silicon atom and a nitrogen atom are directly bonded (a structure having an Si-N bond). The specific modifying agent preferably contains a nitrogen atom as a group containing an amino group (primary to tertiary amino group) or a silazane structure (particularly a cyclic silazane structure) because this provides a better effect of the present invention. The specific modifying agent preferably has two or more (preferably three or more) sites capable of reacting with an active terminal such as an alkoxysilyl group. When the specific modifying agent has a plurality of such sites, the specific modifying agent functions as a coupling agent that connects conjugated diene polymers together.

[0066] (Example) Specific examples of the specific modifying agent include tertiary amines having an alkoxysilyl group, such as tris(3-trimethoxysilylpropyl)amine and tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine; cyclic silazanes having an alkoxysilyl group, such as 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane; tertiary amines having a group containing an alkoxysilyl group-containing cyclic silazane structure, such as tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine and tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine; bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine; bis[3 and tertiary amines having an alkoxysilyl group and a group containing a cyclic silazane structure, such as -(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)amine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, and bis(2-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-methyl-1,3-propanediamine.

[0067] (Amount used) The amount of the specific modifier used is preferably 0.01 to 1% by mass, more preferably 0.02 to 0.2% by mass, based on the conjugated diene, because this provides a better effect of the present invention.

[0068] [Other steps] The manufacturing method of the present invention may include steps (other steps) other than the steps described above. Other steps include a polymerization terminating step in which a polymerization terminator (for example, methanol) is added, and a solvent removal step in which the solvent is removed by steam stripping.

[0069] [Other rubber components] The rubber component may contain rubber components (other rubber components) other than isoprene-based rubber and specific conjugated diene-based rubber. Such other rubber components include butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), etc. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR) and styrene-isoprene copolymer rubber. The other rubber components preferably do not have a specific modifying group, and more preferably do not have a modifying group (are unmodified), for the reason that the effects of the present invention are more excellent.

[0070] [Preferred embodiment] The rubber component preferably contains BR because the effects of the present invention are more excellent. When the rubber component contains BR, the proportion of BR in the rubber component is preferably 1 to 30 mass%, more preferably 5 to 15 mass%, because the effects of the present invention are more excellent.

[0071] [Content] The proportion of other rubber components in the rubber component is preferably 30% by mass or less, more preferably 20% by mass or less, for the reason that the effects of the present invention are more excellent. The lower limit is not particularly limited, and is 0% by mass.

[0072] [Molecular weight] The preferred embodiment of the weight average molecular weight (Mw) of the rubber component is the same as that of the specific conjugated diene rubber described above.

[0073] [2] Filler The compositions of the present invention contain a filler. The above packing material has a nitrogen adsorption specific surface area of ​​70m 2 / g or more of carbon black (hereinafter also referred to as "specific carbon black") and silica. The content of silica in the filler is 10 to 70 mass %.

[0074] [Specific carbon black] The specific carbon black has a nitrogen adsorption specific surface area of ​​70m 2 / g or more of carbon black.

[0075] [Nitrogen adsorption specific surface area] The nitrogen adsorption specific surface area (N2SA) of a specific carbon black is 70m 2 / g or more. The nitrogen adsorption specific surface area (N2SA) is 80m because the effect of the present invention is more excellent. 2 / g or more is preferable, and 90m 2 / g or more is more preferable, and 100m 2 It is more preferable that the saturation coefficient is 1 / g or more. The upper limit of the nitrogen adsorption specific surface area (NSA) is not particularly limited, but in order to improve the effects of the present invention, it is preferable to set the upper limit to 200 m 2 / g or less, and 150m 2 It is more preferable that the saturation coefficient is 1 / g or less. In this specification, the nitrogen adsorption specific surface area (N2SA) of carbon black is the amount of nitrogen adsorbed to the surface of carbon black measured in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0076] 〔grade〕 Examples of the grade of the specific carbon black include SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, and HAF.

[0077] [Content] The proportion of the specific carbon black in the filler is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 50 to 70% by mass, because this provides a better effect of the present invention.

[0078] In the composition of the present invention, the content of the specific carbon black is preferably 1 to 70 parts by mass, more preferably 5 to 50 parts by mass, even more preferably 10 to 40 parts by mass, particularly preferably 15 to 35 parts by mass, and most preferably 20 to 25 parts by mass, per 100 parts by mass of the rubber component, because this provides better effects of the present invention.

[0079] [silica] The silica is not particularly limited, and any conventionally known silica can be used. Examples of silica include wet silica, dry silica, fumed silica, diatomaceous earth, etc. The silica may be used alone or in combination of two or more types.

[0080] [CTAB] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​silica (hereinafter, "CTAB adsorption specific surface area" may be simply referred to as "CTAB") is not particularly limited, but for the reason that the effect of the present invention is superior, it is preferred that the specific surface area be 100 to 300 m 2 / g, and 150 to 200m 2 / g is more preferred. Here, the CTAB adsorption specific surface area is a value obtained by measuring the amount of CTAB adsorbed onto the silica surface in accordance with JIS K6217-3:2001 "Part 3: Determination of specific surface area - CTAB adsorption method."

[0081] [Content] The proportion of silica in the filler (hereinafter also referred to as "silica ratio") is 10 to 70 mass %. The silica ratio is preferably 20 to 60 mass %, and more preferably 30 to 50 mass %, because this provides better effects of the present invention.

[0082] In the composition of the present invention, the content of silica is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, even more preferably 10 to 30 parts by mass, and particularly preferably 17 to 25 parts by mass, per 100 parts by mass of the rubber component, because this provides better effects of the present invention.

[0083] [Other fillers] The filler may include fillers other than the specific carbon black and silica. Examples of such other fillers include carbon black other than the specific carbon black (with a nitrogen adsorption specific surface area of ​​70 m 2 / g or less of carbon black).

[0084] [Content] The proportion of other fillers in the above filler is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, for reasons of better effects of the present invention. The lower limit is not particularly limited, and is 0% by mass.

[0085] In the composition of the present invention, the content of the other filler is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component, for reasons of better effects of the present invention. The lower limit is not particularly limited, and is 0 part by mass.

[0086] [Content] In the composition of the present invention, the content of the filler is 80 parts by mass or less per 100 parts by mass of the rubber component, preferably 10 to 70 parts by mass, more preferably 30 to 60 parts by mass, for reasons of better effects of the present invention.

[0087] [3] Optional component The composition of the present invention may contain components (optional components) other than the above-mentioned components, if necessary. Examples of such components include various additives commonly used in rubber compositions, such as silane coupling agents, thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, waxes, processing aids, liquid polymers, resins (thermoplastic resins, thermosetting resins, etc.), oils, plasticizers, vulcanizing agents (e.g., sulfur), vulcanization accelerators (accelerators), and vulcanization activators.

[0088] [Preferred embodiment] In the composition of the present invention, the total content of the oil, resin, and plasticizer per 100 parts by mass of the rubber component is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, for the reason that the effects of the present invention are more excellent. The lower limit is not particularly limited, and is 0 parts by mass.

[0089] [4] Method for preparing rubber composition for tires The method for producing the composition of the present invention is not particularly limited, and specific examples thereof include a method of kneading the above-mentioned components using a known method or apparatus (e.g., a Banbury mixer, a kneader, a roll, etc.) When the composition of the present invention contains sulfur or a vulcanization accelerator, it is preferable to first mix the components other than the sulfur and the vulcanization accelerator at a high temperature (preferably 100 to 160°C), cool the mixture, and then mix the sulfur or the vulcanization accelerator. The composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0090] [II] Tires The tire of the present invention is a tire (particularly a heavy-duty tire) manufactured using the above-mentioned composition of the present invention. In particular, it is preferable that the tire has the composition of the present invention disposed in the tire tread (cap tread). The tire of the present invention is preferably a pneumatic tire, which can be filled with air, an inert gas such as nitrogen, or other gases.

[0091] 2 is a partial cross-sectional schematic view showing one example of an embodiment of the tire of the present invention, although the tire of the present invention is not limited to the embodiment shown in FIG.

[0092] In Figure 2, the tire (pneumatic tire) comprises a pair of left and right bead portions 1 and sidewall portions 2, and a tire tread portion 3 connected to both sidewall portions 2. A carcass layer 4 with steel cords embedded therein is mounted between the pair of left and right bead portions 1, and the ends of the carcass layer 4 are folded back and wound up around bead cores 5 and bead fillers 6 from the inside to the outside of the tire. In the tire tread portion 3, a belt layer 7 is disposed around the entire circumference of the tire on the outside of the carcass layer 4. Belt cushions 8 are disposed on both ends of the belt layer 7. An inner liner 9 is provided on the inner surface of the tire to prevent air filled inside the tire from leaking to the outside of the tire, and tie rubber 10 for bonding the inner liner 9 is laminated between the carcass layer 4 and the inner liner 9. At least the tire tread portion 3 is formed from the above-mentioned composition of the present invention.

[0093] The tire of the present invention can be manufactured, for example, by a conventionally known method. The gas to be filled into the tire can be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. [Example]

[0094] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0095] [Synthesis of specific conjugated diene rubber]

[0096] [Modified SBR2]

[0097] <Polymerization process> An autoclave equipped with a stirrer was charged under a nitrogen atmosphere with cyclohexane at 1000 g / h (hour), tetramethylethylenediamine at 0.023 g / h, 1,3-butadiene at 176.4 g / h, 1-butene at 0.406 g / h, and styrene at 23.6 g / h, and then n-butyllithium was continuously added at 1.43 mmol / h to initiate polymerization at 70 °C. When the polymerization was sufficiently stable, 1-(trimethoxysilyl)-4-vinylbenzene (branching agent) was added at 0.02 g / h and the mixture was stirred to allow the reaction to proceed. The branching agent corresponds to the specific branching agent described above.

[0098] <Denaturation process> To the solution flowing out from the reactor outlet, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine (modifier) ​​was added at 0.08 g / h and stirred to react. Note that this modifier corresponds to the specific modifier described above.

[0099] Thereafter, methanol was added as a polymerization terminator to obtain a solution containing a conjugated diene rubber.

[0100] To the resulting solution, 1.14 parts by mass of Irganox 1520L (manufactured by BASF) was added as an antioxidant per 100 parts by mass of the conjugated diene rubber, and the solvent was then removed by steam stripping. The resulting mixture was vacuum dried at 60°C for 24 hours to obtain a solid conjugated diene rubber. The resulting conjugated diene rubber is also called modified SBR2.

[0101] Modified SBR2 is a reaction product of a conjugated diene polymer, which is a copolymer of butadiene, styrene, and a branching agent, with a modifier, and is a modified conjugated diene rubber having a modifying group (specific modifying group) derived from the modifier, which includes a nitrogen atom, a silicon atom, and an oxygen atom adjacent to the nitrogen atom, and the silicon atom and the silicon atom are adjacent to the modified group. The modified SBR2 has a star structure with three or more branches, with the modifying group as the branching point, and the branched chain bonded to the modifying group has a portion derived from a branching agent, and the portion derived from the branching agent has a further main chain branched structure (conjugated diene-based polymer chain).

[0102] [Modified SBR3] A solid conjugated diene rubber was obtained in the same manner as for modified SBR2, except that the amounts of each component were changed as shown in Table 1. The obtained conjugated diene rubber is also referred to as modified SBR3.

[0103] Modified SBR3 is a reaction product of a conjugated diene polymer, which is a copolymer of butadiene, styrene, and a branching agent, with a modifier, and is a modified conjugated diene rubber having a modifying group (specific modifying group) derived from the modifier, which includes a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. Modified SBR3 has a star structure with three or more branches, with the modifying group as the branching point, and the branched chain bonded to the modifying group has a portion derived from a branching agent, and the portion derived from the branching agent has a further main chain branched structure (conjugated diene-based polymer chain).

[0104] [Table 1]

[0105] [Weight average molecular weight, weight average intrinsic viscosity, styrene content, vinyl content, glass transition temperature] The conjugated diene rubber (modified SBR2-3) synthesized as described above was measured for Mw, Mw 10% , IVw, IVw 10% The values ​​of St, Vn, and glass transition temperature (Tg) are shown in Table 2. Table 2 also shows the values ​​of general-purpose SBR (E581) and modified SBR1 (NS612) described later. In Table 2, the "right side" of Equation (1) refers to the right side of Equation (1), "3.1 x 10 -6 ×Mw 10% represents the value "-2.77". In addition, in Table 2, "Suitable / Inapplicable" for formula (1) indicates whether formula (1) is satisfied or not. Specifically, "A" indicates that formula (1) is satisfied, and "B" indicates that formula (1) is not satisfied. In addition, in Table 2, "St+Vn" in formula (2) represents the above-mentioned St+Vn.

[0106] [Table 2]

[0107] As shown in Table 2, all of modified SBR2 to 3 satisfy formula (1). As described above, all of modified SBR2 to 3 are modified conjugated diene rubbers having a specific modifying group. Therefore, all of modified SBR2 to 3 fall under the category of the above-mentioned specific conjugated diene rubber. On the other hand, as shown in Table 2, neither the general-purpose SBR (E581) nor the modified SBR1 (NS612) satisfies formula (1), and therefore does not fall under the category of the above-mentioned specific conjugated diene rubber.

[0108] [Preparation of Rubber Composition for Tires] The components in Tables 3 and 4 below were mixed in the compositions (parts by mass) shown in the tables. Specifically, first, the components in Tables 3 and 4 other than sulfur and the vulcanization accelerator were mixed in a 1.8 L internal mixer at 160°C or lower for 5 minutes, and a masterbatch was discharged. Thereafter, sulfur and the vulcanization accelerator were added to the masterbatch, and the mixture was mixed using an open roll at 100°C or lower to produce each rubber composition for tires.

[0109] [evaluation] The following evaluations were carried out on each of the obtained rubber compositions for tires.

[0110] [Snow performance] Using each of the obtained rubber compositions for tires, test tires with a tire size of 245 / 40R19 were manufactured and subjected to a snow braking test. Specifically, four test tires were mounted on a passenger car with an engine displacement of 2300cc, and the braking distance from an initial speed of 40km / h on a packed snow road was measured. The reciprocal of the braking distance was then indexed, with the reference example being set at 100. The results are shown in Tables 3 and 4. A higher index indicates better performance on snow. In practice, an index of 101 or higher is preferable.

[0111] [Low fuel consumption performance] Each tire rubber composition was used in a mold of a predetermined shape (inner dimensions: length 150 mm, width 150 mm, thickness 2 mm) and vulcanized at 160°C for 20 minutes to prepare vulcanized rubber test pieces. Using the obtained evaluation samples, tan δ(60°C) was measured in accordance with JIS K6394:2007 using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) under conditions of an elongation deformation strain rate of 10%±2%, a frequency of 20 Hz, and a temperature of 60°C, and the reciprocal of tan δ(60°C) was calculated. The results are shown in Tables 3 and 4. The results are expressed as an index where the reciprocal of tan δ (60°C) of the reference example is set to 100. A larger index means better fuel economy. In practice, an index of 101 or more is preferable.

[0112] [Chipping resistance] Each tire rubber composition was used in a mold of a predetermined shape (inner dimensions: length 150 mm, width 150 mm, thickness 2 mm) and vulcanized at 160°C for 20 minutes to prepare a vulcanized rubber test piece. Using this vulcanized rubber test piece, a dumbbell-shaped JIS No. 3 test piece was prepared in accordance with JIS K6251. Using this test piece, a tensile test was performed at 100°C at a tensile speed of 500 mm / min to measure the elongation at break. The results are shown in Tables 3 and 4. The results are expressed as an index with the reference example being 100. A larger index means better chipping resistance. In practice, an index of 101 or more is preferable.

[0113] [Wear resistance] Each tire rubber composition was used and vulcanized in a mold of a predetermined shape (inner dimensions: length 150 mm, width 150 mm, thickness 2 mm) at 160°C for 20 minutes to prepare each vulcanized rubber test piece. The obtained vulcanized rubber sheet was subjected to a Lambourn abrasion test using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) under an applied load of 4.0 kg / cm in accordance with JIS K 6264-2:2005. 3 The abrasion test was carried out under the conditions of a load of 39N, a slip ratio of 30%, a wear test time of 4 minutes, and a test temperature of room temperature, and the abrasion mass was measured. The index was then calculated as follows: The results are shown in Tables 3 and 4. A larger index indicates a smaller amount of wear and better wear resistance. In practice, an index of 100 or more is preferred. Index = (Wear mass of reference example / Wear mass of each example) x 100

[0114] [Table 3]

[0115] [Table 4]

[0116] Details of each component in Tables 3 and 4 are as follows. NR: Natural rubber TSR20 BR: Nipol BR1220 (butadiene rubber, Tg: -106°C) manufactured by Nippon Zeon Co., Ltd. (does not fall under the category of the specific conjugated diene rubbers mentioned above because it does not have a specific modifying group) General-purpose SBR: Asahi Kasei E581 (terminally modified solution polymerized SBR with hydroxyl groups at the terminals, Tg: -27°C) (does not satisfy formula (1) and therefore does not fall under the category of the specific conjugated diene rubber described above) Modified SBR1: NS612 manufactured by Zeon Corporation (solution polymerization SBR, Tg: -60°C) (does not satisfy formula (1) and therefore does not fall under the category of the specific conjugated diene rubber described above) Modified SBR3: Modified SBR3 synthesized as described above Modified SBR2: Modified SBR2 synthesized as described above CB (ISAF): Cabot Japan Showblack N220 (ISAF grade carbon black, nitrogen adsorption specific surface area (N2SA): 111 m 2 / g) CB (HAF): Tokai Carbon Co., Ltd. SEAT 3 (HAF grade carbon black, nitrogen adsorption specific surface area (N2SA): 79m 2 / g) CB (GPF): Tokai Carbon Co., Ltd., SEAT V (GPF grade carbon black), nitrogen adsorption specific surface area (N2SA): 27m 2 / g) ·Silica: Solvay ZEOSIL 1165MP (CTAB adsorption specific surface area: 160m 2 / g) Zinc oxide: Three types of zinc oxide (manufactured by Seido Chemical Industry Co., Ltd.) Plasticizer: Showa Shell Sekiyu Extract No. 4S Wax: Sunnock (Ouchi Shinko Chemical Industry Co., Ltd.) Stearic acid: Beads Stearic Acid YR (manufactured by NOF Corporation) Anti-aging agent: Nocrac 6C (Ouchi Shinko Chemical Industry Co., Ltd.) Vulcanization accelerator: Noccela NS-P (Ouchi Shinko Chemical Co., Ltd.) Sulfur: Shikoku Chemical Industry Co., Ltd. Myucron OT-20

[0117] In Tables 3 and 4, "total filler amount" represents the parts by mass of the filler, and "silica ratio in total filler" represents the silica ratio described above.

[0118] As can be seen from Tables 3 and 4, all of Examples 1 to 8, which contain predetermined amounts of isoprene-based rubber, specific conjugated diene-based rubber, and predetermined amounts of specific filler and have a silica ratio within a specific range, exhibited excellent snow performance, fuel efficiency, chipping resistance, and abrasion resistance. Comparing Example 1 and Example 2 (comparison between embodiments in which only the type of specific conjugated diene rubber is different), Example 2, in which the glass transition temperature of the specific conjugated diene rubber was -51°C or lower, showed better fuel economy and chipping resistance. Furthermore, comparing Example 2, Example 3, and Example 4 (comparison of embodiments differing only in filler), Examples 2 and 4, which have silica ratios of 30% by mass or more, exhibited better on-snow performance, fuel economy, chipping resistance, and abrasion resistance. Among them, Example 4, which has a silica ratio of 50% by mass or more, exhibited even better on-snow performance, fuel economy, chipping resistance, and abrasion resistance. Furthermore, comparing Example 2 with Example 5 (comparison between embodiments differing only in the proportion of the specific conjugated diene rubber in the rubber component), Example 2, in which the proportion of the specific conjugated diene rubber in the rubber component was 25% by mass or more, showed better on-snow performance. Furthermore, comparing Example 2 with Example 5 (comparison between embodiments differing only in the proportion of the specific conjugated diene rubber in the rubber component), Example 5, in which the proportion of the specific conjugated diene rubber in the rubber component was 25% by mass or less, showed better fuel economy, chipping resistance, and abrasion resistance. Furthermore, a comparison between Example 2 and Example 6 (comparison between embodiments with different proportions of isoprene-based rubber in the rubber component) shows that Example 2, in which the proportion of isoprene-based rubber in the rubber component is 65% by mass or less, exhibits better fuel economy and abrasion resistance. Furthermore, a comparison between Example 2 and Example 6 (comparison between embodiments with different proportions of isoprene-based rubber in the rubber component) shows that Example 6, in which the proportion of isoprene-based rubber in the rubber component is 65% by mass or more, exhibits better on-snow performance and chipping resistance. Furthermore, comparing Example 2 with Example 7, Example 2, in which the total content of oil, resin, and plasticizer was 3 parts by mass or less per 100 parts by mass of the rubber component, exhibited better abrasion resistance. Furthermore, comparing Example 2 with Example 7, in which at least one selected from the group consisting of oil, resin, and plasticizer was included, exhibited better on-snow performance, fuel economy, and chipping resistance. In addition, a comparison between Example 2 and Example 8 (comparison between embodiments in which only the type of specific carbon black is different) shows that the N2SA of the specific carbon black is 100 m 2 / g or more, Example 2 exhibited better snow performance, chipping resistance, and abrasion resistance. In addition, a comparison between Example 2 and Example 8 (a comparison between examples in which only the type of specific carbon black differs) showed that the N2SA of the specific carbon black was 90m 2 / g or less, Example 8 showed even better fuel economy performance.

[0119] On the other hand, the reference example, Comparative Example 1 and Comparative Example 4, which contain a rubber component other than the specific conjugated diene rubber instead of the specific conjugated diene rubber, Comparative Examples 2 to 3, in which the proportion of isoprene-based rubber in the rubber component is less than 50 mass%, Comparative Example 5, in which the silica ratio exceeds 70 mass%, Comparative Example 6, in which the filler content exceeds 80 mass parts per 100 mass parts of the rubber component, and Comparative Example 7, which does not contain the specific carbon black, were insufficient in at least one of snow performance, fuel efficiency, chipping resistance, and abrasion resistance. [Explanation of symbols]

[0120] 1 Bead section 2 Sidewall 3 Tire tread 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 8 Belt cushion 9 Inner liner 10 Thai Rubber

Claims

1. Contains a rubber component and a filler, the rubber component contains an isoprene-based rubber and a modified conjugated diene-based rubber, The modified conjugated diene rubber satisfies the following formula (1) and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, The proportion of the isoprene-based rubber in the rubber component is 50% by mass or more, The filler has a nitrogen adsorption specific surface area of ​​70 m ２ / g or more of carbon black and silica, The proportion of the silica in the filler is 10 to 70 mass %, The rubber composition for a heavy-duty tire, wherein the content of the filler per 100 parts by mass of the rubber component is 80 parts by mass or less. [Vw １０％ ≦3.1×10 －６ ×Mw １０％ -2.77 (1) Mw in formula (1) １０％ and IVw １０％ The details are as follows: The modified conjugated diene rubber is subjected to gel permeation chromatography measurement using a differential refractive index detector and a viscosity detector as detectors. The weight average molecular weight (Mw) was determined using the high molecular weight portion of the peak in the chromatogram obtained by the differential refractive index detector, which accounts for 10% of the total area of ​​the peak. １０％ However, Mw １０％ is 200 x 10 ４ The weight average intrinsic viscosity determined using the high molecular weight portion of the peak in the chromatogram obtained by the viscosity detector, which is 10% of the total peak area, is defined as IVw. １０％ However, the unit of the weight average intrinsic viscosity is dL / g.

2. 2. The rubber composition for a heavy load tire according to claim 1, wherein the glass transition temperature of the modified conjugated diene rubber is −51° C. or lower.

3. 2. The rubber composition for a heavy-duty tire according to claim 1, wherein a total content of the oil, resin, and plasticizer per 100 parts by mass of the rubber component is 10 parts by mass or less.

4. A heavy-duty tire manufactured using the rubber composition for heavy-duty tires according to any one of claims 1 to 3.

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