Modified conjugated diene polymer, method for producing modified conjugated diene polymer, and rubber composition

Abstract

To provide: a modified conjugated diene polymer in which, when blended in a rubber composition including a reinforcing filler, the reinforcing filler show excellent dispersibility, and a rubber composition obtained shows excellent low pyrogenicity and excellent rigidity; a production method thereof; and a rubber composition comprising the modified conjugated diene polymer.SOLUTION: Provided is a modified conjugated diene polymer which is a conjugated diene polymer having in the main chain a functional group(s) which comprise(s) a nitrogen atom and a silicon atom.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a modified conjugated diene polymer, a method for producing a modified conjugated diene polymer, and a rubber composition. [Background technology]

[0002] Generally, reinforcing fillers such as carbon black and silica are compounded in rubber compositions used in tires, etc. However, interactions between the reinforcing fillers can cause the reinforcing fillers to aggregate in the rubber composition, resulting in insufficient properties.

[0003] In this context, for example, Patent Document 1 discloses a modified liquid diene rubber (modified conjugated diene polymer) as a compounding agent for a rubber composition containing a reinforcing filler. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 044892 Summary of the Invention [Problem to be solved by the invention]

[0005] Under these circumstances, the present inventors have investigated the modified conjugated diene polymer described in Patent Document 1 and have found that when the polymer is compounded in a rubber composition containing a reinforcing filler, the dispersibility of the reinforcing filler does not necessarily meet the level currently required. Furthermore, it has also become clear that the low heat buildup and rigidity of the resulting rubber composition may be insufficient.

[0006] In view of the above circumstances, the present invention aims to provide a modified conjugated diene polymer which, when blended into a rubber composition containing a reinforcing filler, exhibits excellent dispersibility of the reinforcing filler and the resulting rubber composition exhibits excellent low heat buildup and rigidity, a method for producing the same, and a rubber composition containing the modified conjugated diene polymer. [Means for solving the problem]

[0007] As a result of intensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a modified conjugated diene polymer, which is a conjugated diene polymer having a functional group containing a nitrogen atom and a silicon atom in the main chain, and have arrived at the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0008] (1) A modified conjugated diene polymer, which is a conjugated diene polymer having a functional group containing a nitrogen atom and a silicon atom in the main chain. (2) The modified conjugated diene polymer according to (1) above, wherein the conjugated diene polymer is an isoprene polymer. (3) The modified conjugated diene polymer according to (1) or (2) above, wherein the modification rate is 0.3 to 3.0 mol %. Here, the modification rate represents the ratio of repeating units having the above functional group to all repeating units of the modified conjugated diene polymer. (4) a branched alkyllithium addition step of mixing a conjugated diene polymer with a branched alkyllithium to generate carbon atom anions in the main chain of the conjugated diene polymer; The method for producing a modified conjugated diene polymer further comprises a modification step of mixing a compound containing a nitrogen atom and a silicon atom to obtain the modified conjugated diene polymer described in any one of (1) to (3) above. (5) A rubber composition comprising a rubber component, the modified conjugated diene polymer described in any one of (1) to (3) above, and a reinforcing filler, The rubber composition, wherein the reinforcing filler comprises at least one selected from the group consisting of silica and carbon black. (6) The rubber composition according to (5) above, wherein the content of the reinforcing filler is 30 to 100 parts by mass per 100 parts by mass of the rubber component. (7) Further, a silane coupling agent is contained, the reinforcing filler comprises silica; The rubber composition according to (5) or (6) above, wherein the content of the silane coupling agent is 1 to 20 mass % relative to the content of the silica. (8) The rubber composition according to any one of (5) to (7) above, wherein the rubber component contains natural rubber. [Effects of the Invention]

[0009] As will be described below, the present invention can provide a modified conjugated diene polymer that, when blended into a rubber composition containing a reinforcing filler, exhibits excellent dispersibility of the reinforcing filler and the resulting rubber composition exhibits excellent low heat buildup and rigidity, a method for producing the same, and a rubber composition containing the modified conjugated diene polymer. DETAILED DESCRIPTION OF THE INVENTION

[0010] The modified conjugated diene polymer of the present invention, the method for producing the same, and the rubber composition 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, "dispersibility of reinforcing filler" is also simply referred to as "dispersibility." Furthermore, with regard to the modified conjugated diene polymer of the present invention, "when blended into a rubber composition containing a reinforcing filler, the reinforcing filler exhibits excellent dispersibility, and the resulting rubber composition exhibits excellent low heat buildup, rigidity, and abrasion resistance" is also referred to as "excellent effects, etc. of the present invention." Furthermore, with regard to a rubber composition containing the modified conjugated diene polymer of the present invention, "the reinforcing filler exhibits excellent dispersibility, and also exhibits low heat buildup, rigidity, and abrasion resistance" is also referred to as "having excellent effects, etc. of the present invention." In addition, in this specification, "solid" means being solid at 25°C and 1 atm, and "liquid" means being liquid at 25°C and 1 atm.

[0011] [1] Modified conjugated diene polymer The modified conjugated diene polymer of the present invention (hereinafter also simply referred to as "the polymer of the present invention") is The modified conjugated diene polymer is a conjugated diene polymer having a functional group containing a nitrogen atom and a silicon atom in the main chain.

[0012] The polymer of the present invention has such a structure, and is therefore believed to be able to solve the above-mentioned problems of the present invention. The reason for this is believed to be that when the polymer of the present invention is blended into a rubber composition containing a reinforcing filler, the skeleton of the polymer of the present invention interacts with the rubber component, and the functional groups containing nitrogen atoms and silicon atoms of the polymer of the present invention interact very strongly with the reinforcing filler, resulting in extremely good dispersibility of the reinforcing filler in the rubber composition.

[0013] The polymer of the present invention will be described in detail below.

[0014] [Skeleton] The polymer of the present invention is a polymer having a conjugated diene skeleton (conjugated diene polymer). The conjugated diene of the conjugated diene polymer is not particularly limited, but specific examples thereof include isoprene, butadiene, farnesene, and chloroprene. The conjugated diene is preferably isoprene because the effects of the present invention are more excellent. That is, the skeleton of the polymer of the present invention is preferably an isoprene polymer because the effects of the present invention are more excellent.

[0015] [Specific functional group] As described above, the polymer of the present invention has a functional group containing a nitrogen atom and a silicon atom (hereinafter also referred to as a "specific functional group") in the main chain.

[0016] [Preferred embodiment] The specific functional group is not particularly limited as long as it is a functional group containing a nitrogen atom and a silicon atom. However, for reasons such as better effects of the present invention, it is preferable that the specific functional group contains a nitrogen atom as an amino group (-NR2: R is a hydrogen atom or a substituent) and that the specific functional group contains a silicon atom as a hydrocarbyloxysilyl group (≡SiOR: R is a hydrocarbon group).

[0017] The specific functional group is preferably a group represented by the following formula (M) because the effects of the present invention are more excellent.

[0018] [ka]

[0019] In the above formula (M), R1 and R2 each independently represent a hydrogen atom or a substituent. In the above formula (M), L represents a single bond or a divalent organic group.

[0020] The above-mentioned substituent is not particularly limited as long as it is a monovalent substituent, and examples thereof include a halogen atom, a hydroxy group, a nitro group, a carboxy group, an alkoxy group, an amino group, a mercapto group, an acyl group, an imido group, a phosphino group, a phosphinyl group, a silyl group (particularly an alkylsilyl group), and a hydrocarbon group which may have a heteroatom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the heteroatom of the hydrocarbon group which may have a heteroatom include an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom. Examples of the hydrocarbon group which may have a hetero atom include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group formed by combining these groups. The aliphatic hydrocarbon group may be linear, branched, or cyclic. Specific examples of the aliphatic hydrocarbon group include linear or branched alkyl groups (particularly having 1 to 30 carbon atoms), linear or branched alkenyl groups (particularly having 2 to 30 carbon atoms), and linear or branched alkynyl groups (particularly having 2 to 30 carbon atoms). Examples of the aromatic hydrocarbon group include aromatic hydrocarbon groups having 6 to 18 carbon atoms, such as a phenyl group, a tolyl group, a xylyl group, and a naphthyl group.

[0021] In the above formula (M), R1 is preferably a hydrogen atom, an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (particularly a trialkylsilyl group) (preferably having 1 to 10 carbon atoms), or an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), for reasons such as better effects of the present invention, and more preferably a hydrogen atom or an alkylsilyl group (particularly a trialkylsilyl group) (preferably having 1 to 10 carbon atoms). Multiple R1's may be the same or different. When the multiple R1s are different, the combination of the multiple R1s is preferably a combination of a hydrogen atom and an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (particularly a trialkylsilyl group) (preferably having 1 to 10 carbon atoms), or an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), for reasons such as better effects of the present invention, more preferably a combination of a hydrogen atom and an alkylsilyl group (particularly a trialkylsilyl group) (preferably having 1 to 10 carbon atoms), and even more preferably a combination of a hydrogen atom and a trialkylsilyl group (preferably having 1 to 10 carbon atoms).

[0022] R2 is preferably a hydrocarbyloxy group (-OR group: R is a hydrocarbon group) and more preferably an alkoxy group (preferably having 1 to 10 carbon atoms) for reasons such as better effects of the present invention.

[0023] As described above, in the above formula (M), L represents a single bond or a divalent organic group. Examples of the divalent organic group include an aliphatic hydrocarbon group (e.g., an alkylene group, preferably having 1 to 10 carbon atoms), an aromatic hydrocarbon group (e.g., an arylene group, preferably having 6 to 18 carbon atoms), -O-, -S-, -SO2-, -N(R)- (R: alkyl group), -CO-, -NH-, -COO-, -CONH-, or a group combining these (e.g., an alkyleneoxy group (-C m H 2m O-: m is a positive integer), an alkyleneoxycarbonyl group, an alkylenecarbonyloxy group, etc. L is preferably an alkylene group (preferably having 1 to 10 carbon atoms) because this will result in better effects of the present invention.

[0024] In the above formula (M), n represents an integer of 0 to 2. n is preferably 2 because the effects of the present invention are more excellent.

[0025] In the above formula (M), m represents an integer of 1 to 3. It is preferable that m is 1, since this will result in better effects of the present invention.

[0026] In the above formula (M), n and m satisfy the relational expression n+m=3.

[0027] In the above formula (M), * represents a bonding position.

[0028] [Modification rate] The modification rate of the polymer of the present invention is not particularly limited, but is preferably 0.1 to 10.0 mol%, more preferably 0.2 to 5.0 mol%, even more preferably 0.3 to 3.0 mol%, and particularly preferably 0.5 to 2.0 mol%, because this provides better effects of the present invention. The modification rate herein refers to the ratio of repeating units having a specific functional group in the main chain to all repeating units of the polymer of the present invention.

[0029] [End] The structure of the terminal of the polymer of the present invention is not particularly limited, and may be modified or unmodified. The polymer of the present invention may have the above-mentioned specific functional group at the terminal.

[0030] [Molecular weight]

[0031] [Weight average molecular weight] The weight average molecular weight (Mw) of the polymer of the present invention is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 1,000 to 1,000,000, more preferably 2,000 to 500,000, and even more preferably 10,000 or more but less than 100,000.

[0032] [Number average molecular weight] The number average molecular weight (Mn) of the polymer of the present invention is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 1,000 to 1,000,000, more preferably 2,000 to 500,000, and even more preferably 10,000 or more and less than 100,000.

[0033] [Molecular weight distribution] The molecular weight distribution (Mw / Mn) of the polymer of the present invention is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 2.0 or less, more preferably 1.7 or less, even more preferably 1.5 or less, and particularly preferably 1.3 or less. There is no particular lower limit, but it is usually 1.0 or more.

[0034] [Measurement method] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated as standard polystyrene obtained by gel permeation chromatography (GPC) measurement under the following conditions. Solvent: Tetrahydrofuran Detector: RI detector

[0035] [Properties] The polymer of the present invention is preferably in a liquid state, since this will result in better effects of the present invention.

[0036] [Manufacturing method] The method for producing the polymer of the present invention is not particularly limited, but is preferably a method comprising the following steps (1) to (2) (hereinafter also referred to as the "production method of the present invention"), because it provides better effects of the present invention.

[0037] (1) Branched alkyllithium addition step a step of mixing a conjugated diene polymer with a branched alkyl lithium to generate carbon atom anions in the main chain of the conjugated diene polymer; (2) Denaturation process Further, a step of obtaining the polymer of the present invention by mixing a compound containing a nitrogen atom and a silicon atom.

[0038] Each step will be described below.

[0039] [Branched alkyllithium addition step] The branched alkyllithium addition step is a step of mixing a conjugated diene polymer with a branched alkyllithium to generate carbon atom anions in the main chain of the conjugated diene polymer.

[0040] <Conjugated diene polymer> The conjugated diene polymer used in the branched alkyllithium addition step is not particularly limited, and specific examples and preferred embodiments of its skeleton, terminals, molecular weight, properties are the same as those of the polymer of the present invention.

[0041] <Branched alkyl lithium> The branched alkyllithium used in the branched alkyllithium addition step is a compound in which a branched alkyl group and a lithium atom are bonded together. The number of carbon atoms in the branched alkyl group is preferably 3 to 10, because this will result in better effects of the present invention. Specific examples of branched alkyllithium include iso-propyllithium, sec-butyllithium (BuLi), and tert-butyllithium (BuLi). Among these, sec-butyllithium (BuLi) is preferred because it provides superior effects of the present invention.

[0042] [Modification step] The modification step is a step in which a compound containing a nitrogen atom and a silicon atom is further mixed to obtain the polymer of the present invention. In the modification step, the carbon atom anion in the main chain of the conjugated diene polymer produced in the branched alkyllithium addition step reacts with a compound containing a nitrogen atom and a silicon atom to obtain a conjugated diene polymer (the polymer of the present invention) having a functional group (specific functional group) containing a nitrogen atom and a silicon atom in the main chain.

[0043] <Specific compound> The compound containing a nitrogen atom and a silicon atom (hereinafter also referred to as "specific compound") used in the modification step is not particularly limited, but is preferably one having electrophilicity. For reasons of superior effects of the present invention, the specific compound preferably contains a nitrogen atom as an amino group (-NR2: R is a hydrogen atom or a substituent) and a silicon atom as a hydrocarbyloxysilyl group (≡SiOR: R is a hydrocarbon group). Note that the hydrocarbyloxysilyl group is considered to have electrophilicity.

[0044] The specific compound is preferably a silazane, and more preferably a cyclic silazane, for reasons of superior effects of the present invention, etc. Here, silazane refers to a compound having a structure in which a silicon atom and a nitrogen atom are directly bonded (a compound having a Si-N bond).

[0045] The cyclic silazane is preferably a compound represented by the following formula (S) because it provides better effects of the present invention.

[0046] [ka]

[0047] In the above formula (S), R1 to R3 each independently represent a hydrogen atom or a substituent. Specific examples and preferred embodiments of the substituent are the same as those of R1 and R2 in the above formula (M). In the above formula (S), L represents a divalent organic group. Specific examples and preferred embodiments of the divalent organic group are the same as those of L in the above formula (M).

[0048] In the above formula (S), R1 is preferably an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (particularly a trialkylsilyl group) (preferably having 1 to 10 carbon atoms), or an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), and more preferably an alkylsilyl group (particularly a trialkylsilyl group), because this will result in better effects of the present invention.

[0049] In the above formula (S), R2 and R3 are each preferably independently a hydrocarbyloxy group (-OR group: R is a hydrocarbon group), and more preferably an alkoxy group (preferably having 1 to 10 carbon atoms), for reasons such as better effects of the present invention.

[0050] In the above formula (S), L is preferably an alkylene group (preferably having 1 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, and even more preferably 3 to 5 carbon atoms) because this provides better effects of the present invention.

[0051] Examples of the compound represented by the above formula (S) include Nn-butyl-1,1-dimethoxy-2-azasilacyclopentane, N-phenyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane, and N-trimethylsilyl-1,1-diethoxy-2-azasilacyclopentane. The silicon atom of the cyclic silazane is believed to have electrophilicity.

[0052] [2] Rubber composition The rubber composition of the present invention (hereinafter also referred to as "the composition of the present invention") is A rubber composition comprising a rubber component, the polymer of the present invention, and a reinforcing filler, In the rubber composition, the reinforcing filler contains at least one selected from the group consisting of silica and carbon black.

[0053] [Rubber component] As mentioned above, the composition of the present invention contains a rubber component. The rubber component is not particularly limited, provided that the rubber component does not include the polymer of the present invention.

[0054] The rubber component is preferably a diene rubber because the effects of the present invention are more excellent. Specific examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), etc. Among these, natural rubber is preferred because it provides better effects of the present invention. When the rubber component contains natural rubber, the content of natural rubber in the rubber component is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, for reasons of better effects of the present invention, etc. The upper limit of the content of natural rubber in the rubber component is not particularly limited, and is 100% by mass.

[0055] [Molecular weight]

[0056] <Weight average molecular weight> The weight average molecular weight (Mw) of the rubber component is not particularly limited, but is preferably 100,000 or more, more preferably 200,000 to 10,000,000, and even more preferably 250,000 to 2,000,000, for reasons such as better effects of the present invention.

[0057] <Number average molecular weight> The weight average molecular weight (Mn) of the rubber component is not particularly limited, but is preferably 100,000 to 5,000,000, and more preferably 120,000 to 1,000,000, for reasons such as better effects of the present invention.

[0058] [Reinforcing filler] As described above, the composition of the present invention contains a reinforcing filler containing at least one selected from the group consisting of carbon black and silica. The reinforcing filler preferably contains both carbon black and silica, as this provides better effects of the present invention.

[0059] [Carbon black] The composition of the present invention preferably contains carbon black as a reinforcing filler because it provides better effects of the present invention, etc. One type of carbon black may be used alone, or two or more types of carbon black may be used in combination. The carbon black is not particularly limited, and various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, and SRF can be used. The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited, but is preferably 50 to 200 m for reasons such as the superior effects of the present invention. 2 / g, and 70 to 150m 2 / g is more preferred. Here, the nitrogen adsorption specific surface area (N2SA) is the amount of nitrogen adsorbed onto the surface of carbon black measured according to JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0060] In the composition of the present invention, the content of carbon black is not particularly limited. However, in order to obtain better effects of the present invention, the content is preferably 1 to 100 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of the rubber component.

[0061] 〔silica〕 The composition of the present invention preferably contains silica as a reinforcing filler, because this provides better effects of the present invention. The silica is not particularly limited, and any conventionally known silica can be used. Examples of the 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.

[0062] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​the silica (hereinafter, "CTAB adsorption specific surface area" may be simply referred to as "CTAB") is not particularly limited, but for the reasons of the superior effects of the present invention, it is preferred that the specific surface area be 100 to 300 m 2 / g, and 185m 2 / g or more is more preferable. 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."

[0063] The nitrogen adsorption specific surface area (N2SA) of the silica is not particularly limited, but is preferably 100 to 300 m for reasons such as the superior effects of the present invention. 2 / g, and 194m 2 / g or more is more preferable. Here, N2SA is a substitute property for the surface area of ​​silica available for adsorption of rubber molecules, and is the value obtained by measuring the amount of nitrogen adsorption on the silica surface in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0064] The ratio of the silica nitrogen adsorption specific surface area to the silica CTAB adsorption specific surface area (N2SA / CTAB) is not particularly limited, but is preferably 0.9 to 1.4 for reasons such as better effects of the present invention.

[0065] In the composition of the present invention, the content of silica is not particularly limited, but in order to obtain better effects of the present invention, the content is preferably 10 to 150 parts by mass, and more preferably 30 to 100 parts by mass, per 100 parts by mass of the rubber component.

[0066] [Content] In the composition of the present invention, the content of the reinforcing filler is not particularly limited, but in order to obtain better effects of the present invention, the content is preferably 5 to 150 parts by mass, and more preferably 30 to 100 parts by mass, per 100 parts by mass of the rubber component described above. When the composition of the present invention contains two or more types of reinforcing fillers, the content of the reinforcing fillers means the total content.

[0067] [Modified conjugated diene polymer] As described above, the composition of the present invention contains the modified conjugated diene polymer of the present invention (the polymer of the present invention). The polymer of the present invention is as described above.

[0068] [Content] In the composition of the present invention, the content of the polymer of the present invention is not particularly limited, but in order to obtain better effects of the present invention, the content is preferably 1 to 50 parts by mass, more preferably 2 to 30 parts by mass, and even more preferably 3 to 20 parts by mass, per 100 parts by mass of the rubber component described above.

[0069] Furthermore, in the composition of the present invention, the content of the polymer of the present invention is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 1 to 50 mass % relative to the content of the above-mentioned reinforcing filler (particularly silica), more preferably 5 to 30 mass %, and even more preferably 15 to 25 mass %.

[0070] [Optional ingredients] 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, terpene resins (preferably aromatic modified terpene resins), thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, waxes, processing aids, process oils, liquid polymers, thermosetting resins, vulcanizing agents (e.g., sulfur), vulcanization accelerators (accelerators), and vulcanization activators.

[0071] [Silane coupling agent] The composition of the present invention preferably contains a silane coupling agent because the effects of the present invention are more excellent. In particular, when the reinforcing filler contains at least silica, the composition of the present invention preferably contains a silane coupling agent because the effects of the present invention are more excellent.

[0072] The silane coupling agent is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group. The hydrolyzable group is not particularly limited, and examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Of these, an alkoxy group is preferred because it provides better effects of the present invention. When the hydrolyzable group is an alkoxy group, the number of carbon atoms in the alkoxy group is preferably 1 to 16, and more preferably 1 to 4, because it provides better effects of the present invention. Examples of alkoxy groups having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, and a propoxy group.

[0073] The organic functional group is not particularly limited, but is preferably a group capable of forming a chemical bond with an organic compound, and examples thereof include an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, a sulfide group, a mercapto group, and a blocked mercapto group (protected mercapto group) (for example, an octanoylthio group). Of these, a sulfide group (particularly a disulfide group or a tetrasulfide group), a mercapto group, and a blocked mercapto group are preferred because they provide better effects of the present invention. The silane coupling agents may be used alone or in combination of two or more.

[0074] The silane coupling agent is preferably a sulfur-containing silane coupling agent because it provides better effects of the present invention.

[0075] Specific examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, 3-octanoylthio-1-propyltriethoxysilane, and the like. One of these may be used alone, or two or more may be used in combination.

[0076] <Content> In the composition of the present invention, the content of the silane coupling agent is not particularly limited, but in order to obtain better effects of the present invention, the content is preferably 1 to 20 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of the rubber component described above.

[0077] Furthermore, in the composition of the present invention, the content of the silane coupling agent is preferably 1 to 20 mass % relative to the content of the silica described above, and more preferably 5 to 15 mass %, because this provides better effects of the present invention.

[0078] [Application] The composition of the present invention is suitably used for, for example, tires, conveyor belts, hoses, vibration-proof materials, rubber rolls, outer covers of railway vehicles, etc. It is particularly suitable for use in tires (particularly treads). [Example]

[0079] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Synthesis Example] A modified conjugated diene polymer was synthesized as follows. Here, the modified conjugated diene polymers 1 and 2 are conjugated diene polymers having a functional group (a functional group containing a nitrogen atom and a silicon atom) represented by the formula (m1) described later in the main chain, and therefore correspond to the polymers of the present invention described above. On the other hand, the comparative modified conjugated diene polymer is a conjugated diene polymer having a triethoxysilyl group-containing group (a functional group containing a silicon atom but not a nitrogen atom) in the main chain, and therefore does not fall under the polymer of the present invention described above.

[0080] <Synthesis Example 1> sec-BuLi (Kanto Chemical: 1.2 mol / L (cyclohexane / hexane solution), 25 mL, 30 mmol) and N,N,N',N'-tetramethylethylenediamine (Kanto Chemical: 10 mL, 67.1 mmol) were added to a mixed solution of LIR-50 (liquid isoprene polymer, Mn: 54,000) (Kuraray Co., Ltd.) (100 g, 1.47 mol) in cyclohexane (500 mL), and the mixture was stirred at room temperature for 1 hour (branched alkyllithium addition step). After the reaction, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane (structure below) (20 mL, 82 mmol) was added and reacted (modification step). The resulting solution was taken out and concentrated under reduced pressure, and the concentrated solution was poured into methanol (1 L) to separate the methanol-insoluble components. As a result, a modified isoprene polymer (liquid) (modification rate: 0.8 mol%), which is an isoprene polymer having a functional group represented by the following formula (m1) (where * represents a bonding position) in its main chain, was obtained in a yield of 99%. The obtained modified isoprene polymer is also referred to as "modified conjugated diene polymer 1".

[0081] [ka]

[0082] [ka]

[0083] <Synthesis Example 2> A modified isoprene polymer was obtained in 99% yield by following the same procedure as in Synthesis Example 1, except that the amount of N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane was changed from "20 mL, 82 mmol" to "40 mL, 164 mmol." The resulting modified isoprene polymer was a modified isoprene polymer (liquid) (modification rate: 1.5 mol%), which is an isoprene polymer having a functional group represented by the above formula (m1) in its main chain. The resulting modified isoprene polymer is also referred to as "modified conjugated diene polymer 2."

[0084] <Synthesis Example 3> A thoroughly dried 5 L autoclave was purged with nitrogen, and 1280 g of cyclohexane and 66 g of sec-butyllithium (10.5 mass % cyclohexane solution) were charged. The temperature was raised to 50°C, and then 1350 g of butadiene was gradually added while stirring and controlling the polymerization temperature to 50°C, and polymerization was carried out for 1 hour. Methanol was then added to terminate the polymerization reaction, yielding a polymer solution. Water was added to the resulting polymer solution, followed by stirring, and the polymer solution was washed with water. After stirring was stopped, separation of the polymer solution phase and the aqueous phase was confirmed, and the water was then separated. The washed polymer solution was vacuum dried at 70°C for 24 hours to yield a butadiene polymer. The resulting butadiene polymer was a butadiene polymer (liquid) (Tg: -90°C) with an Mw of 38,000. Next, 700 g of the resulting butadiene polymer was placed in a 1 L autoclave and degassed with nitrogen while stirring at 60°C for 3 hours. 1.0 g of 1,1-bis(t-hexylperoxy)cyclohexane and 50 g of (3-mercaptopropyl)triethoxysilane were added, and the mixture was allowed to react at 105°C for 8 hours to obtain a modified butadiene polymer. The resulting modified butadiene polymer had an Mw of 38,000 and an average of four triethoxysilyl-containing groups in the main chain. This was a modified butadiene polymer (liquid) (modification rate: approximately 0.8 mol%) (Tg: -90°C). The resulting modified butadiene polymer is also referred to as a comparatively modified conjugated diene polymer.

[0085] [Preparation of Rubber Composition] The components shown in Table 1 below were blended in the proportions (parts by mass) shown in the same table. Specifically, first, the components shown in Table 1 below, excluding sulfur and the accelerator, were mixed for 5 minutes in a Banbury mixer at 80° C. Next, the sulfur and the accelerator were mixed using a roll to obtain a rubber composition.

[0086] 〔evaluation〕 Each of the rubber compositions obtained was evaluated as follows.

[0087] <Dispersibility> Each of the resulting rubber compositions (unvulcanized) was press-vulcanized in a mold (15 cm×15 cm×0.2 cm) at 160° C. for 15 minutes to prepare a vulcanized rubber sheet. The shear strain modulus G' at 0.28% strain and the shear strain modulus G' at 30.0% strain were measured for the obtained vulcanized rubber sheet using a shear strain measuring device (RPA2000, manufactured by α-Technology), and the difference G'0.28 (MPa) - G'30.0 (MPa) was calculated as the Payne effect. The results are shown in Table 1. The results are expressed as an index, with Comparative Example 1 being 100. The smaller the index, the better the dispersibility of the reinforcing filler. An index of 80 or less is preferred.

[0088] <Low heat generation> The loss tangent tanδ(60°C) of the vulcanized rubber sheet prepared as described above was measured at a temperature of 60°C using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho, Ltd.) under conditions of an initial strain of 10%, an amplitude of ±2%, and a frequency of 20 Hz. The results are shown in Table 1. The results are expressed as an index, with Comparative Example 1 being 100. The smaller the index, the better the low heat buildup property. An index of 95 or less is preferred.

[0089] <300% modulus> From the vulcanized rubber sheets prepared as described above, JIS No. 3 dumbbell-shaped test pieces (thickness: 2 mm) were punched out in accordance with JIS K6251:2010, and the 300% modulus (stress at 300% deformation) was measured at a temperature of 20°C and a tensile speed of 500 mm / min. The results are shown in Table 1. The results are expressed as an index, with Comparative Example 1 being 100. A larger index means better rigidity. An index of 101 or more is preferred.

[0090] <Wear resistance> The abrasion loss of the vulcanized rubber sheets prepared as described above was measured at a temperature of 20°C and a slip ratio of 50% using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho) in accordance with JIS K6264-1, 2:2005. The abrasion resistance index was calculated using the following formula. The results are shown in Table 1. A larger index indicates a smaller amount of wear and better wear resistance. Abrasion resistance index = (abrasion amount of Comparative Example 1 / abrasion amount of each vulcanized rubber sheet) × 100

[0091] [Table 1]

[0092] Details of each component in Table 1 are as follows: NR is a solid with an Mn of 100,000 or more, while Modified Conjugated Diene Polymers 1 and 2 and Comparative Modified Conjugated Diene Polymers are liquid with an Mn of less than 100,000. NR: VON BUNDIT TSR20 (weight average molecular weight: 1,890,000) Silica: Zeosil Premium 200MP (silica, N2SA = 200m 2 / g, CTAB=200m 2 / g, N2SA / CTAB=1.0, manufactured by Rhodia) CB: Cabot Japan Show Black N220 (carbon black) Stearic acid: Stearic acid manufactured by NOF CORPORATION Zinc oxide: Three types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd. Silane coupling agent: Evonik Degussa Si69 Conjugated diene polymer: Kuraray LIR-50 (liquid isoprene polymer, Mn: 54,000) Modified conjugated diene polymers 1-2: Modified conjugated diene polymers 1-2 synthesized as described above Comparative modified conjugated diene polymer: Comparative modified conjugated diene polymer synthesized as described above Sulfur: Tsurumi Chemical Industry Co., Ltd. Kinka brand oil-filled fine sulfur Accelerator: Noccela NS-P manufactured by Ouchi Shinko Chemical Co., Ltd.

[0093] As can be seen from Table 1, Examples 1 to 4 containing the polymer of the present invention exhibited excellent dispersibility, low heat buildup and rigidity. Furthermore, a comparison between Example 1 and Example 3 (comparison between embodiments differing only in the content of the polymer of the present invention) shows that Example 3, in which the content of the polymer of the present invention is 7 parts by mass or more per 100 parts by mass of the rubber component, exhibits better dispersibility and low heat buildup. Similarly, a comparison between Example 2 and Example 4 (comparison between embodiments differing only in the content of the polymer of the present invention), shows that Example 4, in which the content of the polymer of the present invention is 7 parts by mass or more per 100 parts by mass of the rubber component, exhibits better dispersibility and low heat buildup. Furthermore, a comparison between Example 1 and Example 2 (comparison between embodiments in which only the modification rate of the polymer of the present invention differs) shows that Example 2, in which the modification rate of the polymer of the present invention is 1.0 mol% or more, exhibited superior dispersibility and low heat buildup. Similarly, a comparison between Example 3 and Example 4 (comparison between embodiments in which only the modification rate of the polymer of the present invention differs), shows that Example 4, in which the modification rate of the polymer of the present invention is 1.0 mol% or more, exhibited superior dispersibility and low heat buildup.

[0094] On the other hand, Comparative Examples 1 to 4, which did not contain the polymer of the present invention, were insufficient in at least one of dispersibility, low heat buildup, and rigidity.

Claims

1. a rubber component having a number average molecular weight of 100,000 or more; a modified conjugated diene polymer having a number average molecular weight of less than 100,000 and a functional group containing a nitrogen atom and a silicon atom in the main chain; and a reinforcing filler, the modification rate of the modified conjugated diene polymer is 0.3 to 3.0 mol %, the reinforcing filler comprises at least one selected from the group consisting of silica and carbon black, The rubber composition has a content of the modified conjugated diene polymer of 1 to 50 parts by mass per 100 parts by mass of the rubber component. Here, the modification rate represents the ratio of the repeating units having the functional group to the total repeating units of the modified conjugated diene polymer.

2. The rubber composition according to claim 1, wherein the conjugated diene polymer is an isoprene polymer.

3. A method for producing a rubber composition to obtain the rubber composition according to claim 1 or 2, comprising: a branched alkyllithium addition step of mixing a conjugated diene polymer with a branched alkyllithium to generate carbon atom anions in the main chain of the conjugated diene polymer; 3. A method for producing a rubber composition, comprising: a modification step of mixing a compound containing a nitrogen atom and a silicon atom to obtain the modified conjugated diene polymer according to claim 1 or 2.

4. The rubber composition according to claim 1 or 2, wherein the modified conjugated diene polymer has a modification rate of 1.0 mol % or more and 3.0 mol % or less. Here, the modification rate represents the ratio of the repeating units having the functional group to the total repeating units of the modified conjugated diene polymer.

5. 5. The rubber composition according to claim 1, wherein the content of the reinforcing filler is 30 to 100 parts by mass per 100 parts by mass of the rubber component.

6. Further, a silane coupling agent is contained, the reinforcing filler comprises silica; The rubber composition according to any one of claims 1 to 2 and 4 to 5, wherein the content of the silane coupling agent is 1 to 20 mass % relative to the content of the silica.

7. The rubber composition according to any one of claims 1 to 2 and 4 to 6, wherein the rubber component comprises natural rubber.

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