Rubber composition and tires

Abstract

To provide a rubber composition excellent in wet performance and wear resistance, and a tire.SOLUTION: A rubber composition contains: a diene rubber; silica; and a modified liquid diene polymer having a specific functional group in the main chain and having a weight average molecular weight of 1,000-100,000. The diene rubber has an average glass transition temperature higher than -50°C. The content of the silica is 50-200 pts.mass based on 100 pts.mass of the diene rubber. The content of the modified liquid diene polymer is 1-25 mass% of the content of the silica. A tire uses the rubber composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to rubber compositions and tires. [Background technology]

[0002] Traditionally, silica has been widely used in rubber compositions for tires to reduce rolling resistance. However, because silica particles tend to aggregate, dispersing silica in rubber is generally difficult. On the other hand, rubber compositions containing modified liquid diene rubber or the like have been proposed to improve the dispersibility of fillers such as silica (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-172859 [Overview of the project] [Problems that the invention aims to solve]

[0004] In this context, the present inventors prepared a rubber composition containing a modified liquid diene rubber with reference to Patent Document 1 and evaluated it. It became clear that such a rubber composition may have poor wet performance or abrasion resistance.

[0005] Therefore, the present invention aims to provide a rubber composition and a tire that have excellent wet performance and abrasion resistance. [Means for solving the problem]

[0006] As a result of diligent research to solve the above problems, the present inventors discovered that the desired effect can be obtained by including a modified liquid diene polymer having a specific functional group in the rubber composition, leading to the present invention. The present invention is based on the above findings, and specifically solves the above problems with the following configuration.

[0007] [1] Diene rubber and Silica and, A modified liquid diene polymer having a main chain containing a specific functional group selected from the group consisting of a functional group represented by the following formula (1) and a functional group represented by the following formula (2), and having a weight-average molecular weight of 1,000 to 100,000, The average glass transition temperature of the above diene rubber is higher than -50°C. The silica content is 50 to 200 parts by mass per 100 parts by mass of the diene rubber. A rubber composition in which the content of the above-mentioned modified liquid diene polymer is 1 to 25% by mass of the content of the above-mentioned silica. [ka] [ka] In equations (1) and (2), R1 and R2 each independently represent an alkylene group having 1 to 6 carbon atoms. X1 represents a carboxyl group, X2 and X3 each independently represent a hydrogen atom or a carboxyl group. * indicates the connection position. However, at least one of X2 and X3 is a carboxyl group. [2] The rubber composition according to [1], wherein the modified liquid diene polymer has an average number of the specified functional groups on the main chain per molecule (number of main chain functional groups) of 1 to 6. [3] The rubber composition according to [1] or [2], wherein the skeleton of the modified liquid diene polymer is a diene polymer or an aromatic vinyl-diene copolymer. [4] The skeleton of the above-mentioned modified liquid diene polymer is at least one polymer selected from the group consisting of butadiene and isoprene, or The rubber composition according to any one of [1] to [3], which is a copolymer of at least one selected from the group consisting of butadiene and isoprene and styrene. [5] The CTAB specific surface area of the silica is 100 to 300 m 2 / g, and the rubber composition according to any one of [1] to [4]. [6] Further, it contains a silane coupling agent, The rubber composition according to any one of [1] to [5], wherein the content of the silane coupling agent is 1 to 20% by mass of the content of the silica. [7] A tire formed using the rubber composition according to any one of [1] to [6]. [8] The tire according to [7], which has a cap tread formed using the rubber composition. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a rubber composition excellent in wet performance and abrasion resistance, and a tire using the rubber composition. [Brief Description of the Drawings]

[0009] [Figure 1] It is a schematic partial cross-sectional view showing an example of an embodiment of the tire of the present invention. [Modes for Carrying Out the Invention]

[0010] The present invention will be described in detail below. In this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In this specification, unless otherwise specified, each component can be used alone or in combination of two or more of the substances corresponding to the component. When the component contains two or more substances, the content of the component means the total content of the two or more substances. In this specification, a superior effect of the present invention means that at least one of the wet performance and abrasion resistance is superior. Furthermore, in this specification, "liquid" means that it is in a liquid state at 20°C and 1 atmosphere.

[0011] [Rubber composition] The rubber composition of the present invention, Diene-based rubber and Silica and, It contains a modified liquid diene polymer having a main chain containing a specific functional group selected from the group consisting of a functional group represented by formula (1) described later and a functional group represented by formula (2) described later, and having a weight-average molecular weight of 1,000 to 100,000. The average glass transition temperature of the above diene rubber is higher than -50°C. The silica content is 50 to 200 parts by mass per 100 parts by mass of the diene rubber. The rubber composition is characterized in that the content of the above-mentioned modified liquid diene polymer is 1 to 25% by mass of the content of the above-mentioned silica. The following describes in detail each component contained in the rubber composition of the present invention. In this specification, the above-mentioned modified liquid diene polymer is also referred to as a "specific polymer."

[0012] [Diene-based rubber] The rubber composition of the present invention contains a diene rubber. In this invention, the diene rubber does not contain a specific polymer. A preferred embodiment is that the diene rubber is solid (solid at 20°C and 1 atm). Furthermore, a preferred embodiment is that the diene rubber is a conjugated diene rubber.

[0013] Examples of diene rubbers include natural rubber, isoprene rubber (IR), butadiene rubber (BR), aromatic vinyl-conjugated diene rubbers such as styrene-butadiene rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), and chloroprene rubber (CR). SBR and / or BR are preferred, and SBR and BR are more preferred, because they provide superior effects in the present invention.

[0014] (degeneration) The diene rubber is preferably modified with functional groups that interact with silica, more preferably contains a modified aromatic vinyl-diene copolymer, and even more preferably contains modified SBR, for better effects of the present invention.

[0015] (modified group) The modifying groups that diene rubbers (e.g., SBR) may have are preferably functional groups that interact with silica, for the sake of superior effects of the present invention. Examples of functional groups that interact with silica include hydrocarbyloxysilyl groups, silanol groups, hydroxyl groups (excluding silanol groups), aldehyde groups, carboxyl groups, amino groups, imino groups, epoxy groups, amide groups, thiol groups, siloxane bonds, and ether bonds. In diene rubbers, the modifying group can be bonded directly or via a linking group to the end and / or side chains of the diene rubber. The linking group is not particularly limited.

[0016] • SBR and BR filtrates When the diene rubber contains SBR and BR, the SBR content is preferably 50 to 95 parts by mass, and more preferably 70 to 90 parts by mass, per 100 parts by mass of the diene rubber, for the reasons that the effects of the present invention are superior. Regarding the above SBR content, the SBR may be either modified SBR or unmodified SBR. When the diene rubber contains SBR and BR, the BR content is preferably 5 to 50 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of the diene rubber, for the reason that the effects of the present invention are superior.

[0017] [Average glass transition temperature of diene rubbers] In the rubber composition of the present invention, the average glass transition temperature (average Tg) of the diene rubber is higher than -50°C. The average Tg of the above diene rubber is preferably -45 to 0°C because the effects of the present invention are superior in this temperature range.

[0018] Here, the average glass transition temperature of diene rubber refers to the glass transition temperature of a single rubber component if the diene rubber contains only one type of rubber component, or, if the diene rubber contains two or more types of rubber components, it is the sum of the values ​​obtained by multiplying the glass transition temperature of each rubber component by the content ratio (by mass) of each rubber component in the diene rubber. The glass transition temperature of each rubber component was measured using a differential thermal analyzer (DSC) manufactured by DuPont, in accordance with ASTM D3418-82, at a heating rate of 10°C / min.

[0019] [silica] The silica contained in the rubber composition of the present invention is not particularly limited, and any conventionally known silica can be used. Specific examples of the above silica include wet silica, dry silica, fumed silica, and diatomaceous earth.

[0020] (CTAB specific surface area of ​​silica) The specific surface area of ​​silica with CTAB (cetyltrimethylammonium bromide) is 100-300 m², as this yields superior results in the present invention. 2 It is preferable that it be / g. The specific surface area for CTAB adsorption can be measured by the amount of CTAB adsorbed onto the silica surface according to JIS K6217-3:2001 "Part 3: Method for determining specific surface area - CTAB adsorption method".

[0021] Silica is preferred because it provides superior effects in this invention, and CTAB is 100-200m 2 Silica and / or CTAB in a quantity of 200m / g 2 / g over 300m 2 It is preferable that the silica content be less than or equal to / g.

[0022] [Silica content] In the rubber composition of the present invention, the silica content is 50 to 200 parts by mass per 100 parts by mass of the diene-based rubber. The silica content is preferably 60 to 150 parts by mass per 100 parts by mass of the diene rubber, for the reason that the effects of the present invention are superior.

[0023] Silica, CTAB 100~200m 2 If silica is present at / g, then CTAB is 100-200m 2 The silica content per gram is preferably 50 to 100% by mass of the total silica.

[0024] [Modified liquid diene polymer] The rubber composition of the present invention contains a modified liquid diene polymer (specific polymer). In the present invention, the specific polymer can function as a plasticizer and a silica dispersant. In the present invention, the modified liquid diene polymer (specific polymer) has a specific functional group in its main chain, which is at least one functional group selected from the group consisting of the functional group represented by the following formula (1) and the functional group represented by the following formula (2). Furthermore, the weight-average molecular weight of the modified liquid diene polymer (specific polymer) is 1,000 to 100,000. [ka] [ka] In equations (1) and (2), R1 and R2 each independently represent an alkylene group having 1 to 6 carbon atoms. X1 represents a carboxyl group, X2 and X3 each independently represent a hydrogen atom or a carboxyl group. * indicates the connection position. However, at least one of X2 and X3 is a carboxyl group.

[0025] (Skeleton) Examples of the backbone (main chain structure) of a specific polymer include diene polymers or aromatic vinyl-diene copolymers. The above-mentioned skeleton is preferably a diene polymer because it provides superior effects for the present invention. A diene polymer is a polymer of a diene (especially a conjugated diene). The diene polymer may be a homopolymer of a diene (especially a conjugated diene) or a copolymer of a diene (especially a conjugated diene), but for the sake of superior effects of the present invention, a homopolymer of a diene (especially a conjugated diene) is preferred. Aromatic vinyl-diene copolymers are copolymers of aromatic vinyl and dienes (especially conjugated dienes). The copolymer described above may be a random copolymer or a block copolymer.

[0026] Specific examples of the diene in the above-mentioned diene polymer include butadiene, isoprene, and chloroprene. The above-mentioned diene is preferably butadiene or isoprene, and more preferably butadiene, for the reasons that the effects of the present invention are superior. A specific example of the aromatic vinyl in the above aromatic vinyl-diene copolymer is styrene. Specific examples and preferred embodiments of the diene in the above aromatic vinyl-diene copolymer are the same as those for the above-mentioned diene polymer.

[0027] Specific examples of the backbone (main chain structure) of specific polymers include butadiene polymers (BR), isoprene polymers (IR), chloroprene polymers (CR), isoprene-butadiene copolymers (IBR), styrene-butadiene copolymers (SBR), and isoprene-styrene copolymers.

[0028] <Suitable configuration> The backbone (main chain structure) of the specific polymer is preferably at least one polymer selected from the group consisting of butadiene and isoprene, or a copolymer of at least one polymer selected from the group consisting of butadiene and isoprene with styrene, more preferably at least one polymer selected from the group consisting of butadiene and isoprene, and even more preferably a polymer of butadiene, for reasons that the effects of the present invention are superior.

[0029] [Specific functional group] The specific polymer has a specific functional group in its main chain, which is at least one functional group selected from the group consisting of the functional group represented by the following formula (1) and the functional group represented by the following formula (2). The above-mentioned specific functional group is preferably a functional group represented by formula (1) for the reason that the effects of the present invention are superior.

[0030] [ka]

[0031] [ka]

[0032] In equations (1) and (2), R1 and R2 each independently represent an alkylene group having 1 to 6 carbon atoms. X1 represents a carboxyl group, X2 and X3 each independently represent a hydrogen atom or a carboxyl group. * indicates the connection position. However, at least one of X2 and X3 is a carboxyl group.

[0033] R1 and R2 are preferably alkylene groups having 1 to 3 carbon atoms, and more preferably alkylene groups having 1 to 2 carbon atoms, for better effects of the present invention. Specifically, R1 could be an alkylene group with one carbon atom.

[0034] When the specific functional group is a functional group represented by formula (2), it is preferable that both X2 and X3 are carboxyl groups for the reason that the effects of the present invention are superior.

[0035] <Number of main chain functional groups> The number of functional groups in the main chain of the specific polymer is preferably 1 to 10 (units are individual units; units are omitted; the same applies hereinafter), more preferably 1 to 6, and even more preferably 3 to 6, for the reasons that the effects of the present invention are superior. Here, the number of main chain functional groups refers to the number of specific functional groups (average number per molecule) that a particular polymer (modified liquid diene polymer) has in its main chain per molecule.

[0036] When a specific polymer has a functional group represented by formula (1), the number of main chain functional groups is preferably 1 to 10, more preferably 1 to 6, and even more preferably 3 to 6, for reasons that the effects of the present invention are superior.

[0037] The number of carboxyl groups derived from a specific functional group that a specific polymer has on average per molecule is preferably 1 to 10, more preferably 1 to 6, and even more preferably 3 to 6, for reasons that the effects of the present invention are superior.

[0038] <Degeneration Rate> The denaturation rate of the specific polymer is preferably 1.0 to 10.0 mol%, and more preferably 2.0 to 5.0 mol%, for the sake of superior effects of the present invention. Here, the denaturation rate represents the ratio of the number of specific functional groups (average number per molecule) that the specific polymer has in its main chain to the degree of polymerization of the specific polymer. The degree of polymerization is calculated from the weight-average molecular weight (Mw) of the specific polymer and the molecular weight of the repeating units that constitute the specific polymer.

[0039] [Molecular weight] In the rubber composition of the present invention, the weight-average molecular weight (Mw) of the specific polymer is 1,000 to 100,000. The weight-average molecular weight (Mw) of the specific polymer is preferably 5,000 to 50,000, and more preferably 8,000 to 20,000, for the reasons that the effects of the present invention are superior. The number-average molecular weight (Mn) of the specific polymer is preferably 1,000 to 100,000, more preferably 5,000 to 50,000, and even more preferably 8,000 to 20,000, for reasons that the effects of the present invention are superior. In this specification, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) are standard polystyrene equivalent values ​​obtained by gel permeation chromatography (GPC) measurement under the following conditions. • Solvent: tetrahydrofuran • Detector: RI detector

[0040] [Liquid] The specific polymer is liquid at 20°C and 1 atmosphere.

[0041] [Content of modified liquid diene polymer] In the rubber composition of the present invention, the content of the specific polymer (modified liquid diene polymer) is 1 to 25% by mass of the silica content. The content of the specific polymer is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, and even more preferably 8 to 15% by mass, based on the silica content, for which the effects of the present invention are superior.

[0042] If the rubber composition of the present invention further contains plasticizers other than the specified polymer, the total content of the specified polymer and the plasticizers other than the specified polymer is preferably 1 to 60 parts by mass per 100 parts by mass of diene rubber, for the reason that the effects of the present invention are superior. If the rubber composition of the present invention further contains plasticizers other than the specified polymer, the proportion of the specified polymer in the total content of the specified polymer and other plasticizers is preferably 10 to 50% by mass.

[0043] [Method for producing specific polymers] The method for producing the specific polymer is not particularly limited, but for reasons that the effects of the present invention are superior, A liquid diene polymer, or a liquid aromatic vinyl-diene copolymer (liquid diene polymer), Radical initiators and A preferred method for obtaining a specific polymer is to react a specific compound, which is at least one compound selected from the group consisting of a compound represented by formula (1A) described later and a compound represented by formula (2A) described later (hereinafter also referred to as "production method 1"). In this specification, liquid diene polymers and liquid aromatic vinyl-diene copolymers are collectively referred to as "liquid diene polymers," but the above-mentioned liquid diene polymers refer to the raw materials for specific polymers (modified liquid diene polymers). In the above manufacturing method 1, a radical initiator removes a hydrogen atom from the α carbon atom of the double bond of the liquid diene polymer, and a specific compound reacts with it to introduce the aforementioned specific functional group into the main chain of the liquid diene polymer. The reaction in the above manufacturing method 1 is preferably carried out in bulk or in an organic solvent because it provides superior effects for the present invention.

[0044] The following describes each component used in manufacturing method 1.

[0045] [Liquid diene polymer] Liquid diene polymers refer to diene polymers in a liquid state. The definitions, specific examples, and preferred embodiments of the diene polymer in liquid diene polymers, the diene polymer in liquid diene polymers, and the aromatic vinyl-diene copolymer in liquid aromatic vinyl-diene copolymers are the same as the skeleton of the specific polymer described above. Furthermore, liquid diene polymers are liquid at 20°C and 1 atmosphere.

[0046] [Radical initiator] The above radical initiators are not particularly limited, and specific examples include benzoyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butyl peroxyhexane, 2,5-dimethyl-2,5-di-t-butyl peroxy-3-hexine, 2,4-dichloro-benzoyl peroxide, di-t-butyl peroxy-diisopropylbenzene, 1,1-bis(t-butyl peroxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(t-butyl Examples of radical generators include organic peroxides such as 2,2'-(t-butylperoxy)butane, azodicarbonamide, azobisisobutyronitrile (AIBN), 2,2'-azobis-(2-amidinopropane)dihydrochloride, dimethyl-2,2'-azobis(isobutyrate), azobis-cyanvaleric acid, 1,1'-azobis-(cyclohexane-1-carbonitride), 2,2'-azobis-(2,4-dimethylvaleronitrile), azobismethylbutyronitrile, and 2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile). The radical initiator described above is preferably azobisisobutyronitrile (AIBN) because it provides superior effects for the present invention.

[0047] <Amount added> The amount of the radical initiator added is not particularly limited, but for better effects of the present invention, it is preferably 0.1 to 10% by mass, and more preferably 1 to 5% by mass, relative to the liquid diene polymer described above.

[0048] [Specific compound] As described above, in manufacturing method 1, it is preferable to use a specific compound which is at least one compound selected from the group consisting of the compound represented by formula (1A) and the compound represented by formula (2A), and it is more preferable to use the compound represented by formula (1A).

[0049] [ka]

[0050] [ka]

[0051] In equations (1A) and (2A), R1 and R2 each independently represent an alkylene group having 1 to 6 carbon atoms. X1 represents a carboxyl group, X2 and X3 each independently represent either a hydrogen atom or a carboxyl group. However, at least one of X2 and X3 is a carboxyl group.

[0052] The specific examples and preferred embodiments of each symbol in formulas (1A) and (2A) are the same as those described above for formulas (1) and (2).

[0053] <Specific example> Specific examples of compounds represented by formula (1A) include mercaptoacetic acid and mercaptopropionic acid. Among these, mercaptoacetic acid is preferred because it exhibits superior effects compared to the present invention. Specific examples of compounds represented by formula (2A) include mercaptosuccinic acid, 2-mercaptoglutaric acid, and 2-mercaptoadipic acid. Among these, mercaptosuccinic acid is preferred because it exhibits superior effects compared to the present invention.

[0054] <Amount added> The amount of specific compound added is not particularly limited, but for better effects of the present invention, it is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 15 to 30% by mass relative to the liquid diene polymer described above.

[0055] [Preferred Embodiment] The above manufacturing method 1 is preferably a method comprising the following steps (1) to (2) (hereinafter also referred to as "manufacturing method 2") for the reason that the effects of the present invention are superior.

[0056] (1) Monomer polymerization process A process to obtain a liquid diene polymer by polymerizing a diene-containing monomer using an organolithium compound. (2) Main chain modification process The process of obtaining a specific polymer by reacting the above-mentioned liquid diene polymer with a radical initiator and the above-mentioned specific compound.

[0057] The following describes each step of manufacturing method 2.

[0058] <Monomer polymerization process> The monomer polymerization process involves polymerizing a diene-containing monomer using an organolithium compound to obtain a liquid diene polymer.

[0059] (Monomers containing dienes) Regarding the monomer containing the above-mentioned diene, specific examples and preferred embodiments of the diene (particularly conjugated diene) are the same as those of the diene that can constitute the backbone of the specific polymer described above. Furthermore, the above monomer may contain aromatic vinyl as a monomer other than the diene. Specific examples and preferred embodiments of the above aromatic vinyl are the same as those aromatic vinyl that can constitute the backbone of the specific polymer described above.

[0060] (Organolithium compounds) The above organolithium compounds are not particularly limited, but specific examples include monoorganolithium compounds such as n-butyllithium, sec-butyllithium, tert-butyllithium, n-propyllithium, iso-propyllithium, 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-trilithiobenzene, and 1,3,5-trilithio-2,4,6-triethylbenzene. Among these, monoorganolithium compounds of n-butyllithium, sec-butyllithium, and tert-butyllithium are preferred, and n-butyllithium is more preferred, for the reason that the effects of the present invention are superior.

[0061] The amount of organolithium compound used is not particularly limited, but for better results in the present invention, it is preferably 0.001 to 10 mol% relative to the above monomer.

[0062] <Main Chain Modification Process> The main chain modification step involves reacting the liquid diene polymer with a radical initiator and the specified compound described above to introduce the specified functional group described above into the main chain of the liquid diene polymer, thereby obtaining the specified polymer. The main chain modification step described above is the same as that of manufacturing method 1 described above.

[0063] (Silane coupling agent) From the viewpoint of achieving superior effects of the present invention, it is preferable that the rubber composition of the present invention further contains a silane coupling agent. The silane coupling agent that may further be contained in the rubber composition of the present invention is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group. In the silane compound, the hydrolyzable group can be bonded to a silicon atom. The above hydrolyzable group is not particularly limited, but examples include alkoxy groups, phenoxy groups, carboxyl groups, and alkenyloxy groups. Among these, alkoxy groups are preferred because they provide superior 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, for superior effects of the present invention. Examples of alkoxy groups with 1 to 4 carbon atoms include methoxy groups, ethoxy groups, and propoxy groups.

[0064] The above organic functional groups are not particularly limited, but groups that can form chemical bonds with organic compounds are preferred. Examples include epoxy groups, vinyl groups, acryloyl groups, methacryloyl groups, amino groups, sulfide groups, mercapto groups, and blocked mercapto groups (protected mercapto groups) (e.g., octanoylthio groups). Among these, sulfide groups (especially disulfide groups and tetrasulfide groups), mercapto groups, and blocked mercapto groups are preferred because they provide superior effects for the present invention.

[0065] In silane coupling agents, a hydrolyzable group and an organic functional group can be bonded via a linking group. The linking group is not particularly limited.

[0066] Specific examples of silane coupling agents include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazoletetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, and 3-octanoylthio-1-propyltriethoxysilane. One of these may be used alone, or two or more may be used in combination.

[0067] (Content of silane coupling agent) When the rubber composition of the present invention further contains a silane coupling agent, the content of the silane coupling agent is preferably 1 to 20% by mass of the silica content because the effects of the present invention are more excellent.

[0068] (Optional components) The rubber composition of the present invention can contain components other than the above-described components (optional components) as necessary. Examples of such components include fillers other than silica (e.g., carbon black), terpene resins (preferably aromatic-modified terpene resins), thermally expandable microcapsules, foaming components, zinc oxide (zinc white), stearic acid, anti-aging agents, waxes, processing aids, plasticizers (excluding specific polymers), thermosetting resins, vulcanizing agents (e.g., sulfur), vulcanization accelerators, and various other additives generally used in rubber compositions.

[0069] · Plasticizer (excluding specific polymers) Examples of the above plasticizer (excluding specific polymers) include process oil and aroma oil.

[0070] · Carbon black The rubber composition of the present invention preferably contains carbon black because the effects of the present invention are more excellent. The carbon black is not particularly limited, and for example, various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, SRF can be used. The nitrogen adsorption specific surface area (N2SA) of the above carbon black is not particularly limited, but is preferably 50 to 200 m 2 / g because the effects of the present invention are more excellent, and more preferably 70 to 150 m 2 / g. Here, the nitrogen adsorption specific surface area (N2SA) is the value obtained by measuring the amount of nitrogen adsorbed onto the carbon black surface according to JIS K6217-2:2001 "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method".

[0071] In the rubber composition of the present invention, the carbon black content is not particularly limited, but for reasons that the effects of the present invention are superior, 1 to 100 parts by mass and 2 to 10 parts by mass are preferred per 100 parts by mass of diene rubber.

[0072] (Method for manufacturing rubber composition) The method for producing the rubber composition of the present invention is not particularly limited, and specific examples include, for example, a method of mixing each of the above-mentioned components using known methods and apparatus (e.g., Banbury mixer, kneader, roll, etc.). If the rubber composition of the present invention contains sulfur or a vulcanization accelerator, it is preferable to first mix the components other than sulfur and the vulcanization accelerator at a high temperature (preferably 100 to 160°C), cool them, and then add the sulfur or vulcanization accelerator and mix further. The rubber composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0073] One example of an application for the rubber composition of the present invention is tires. Furthermore, when applying the rubber composition of the present invention to a tire, there are no particular restrictions on which of the tire's components is formed with the rubber composition of the present invention. However, one preferred embodiment is, for example, applying the rubber composition of the present invention to the tread portion of the tire.

[0074] [tire] The tire of the present invention is a tire formed using the rubber composition of the present invention. The tire of the present invention is preferably a pneumatic tire, and can be filled with air, an inert gas such as nitrogen, and other gases. In particular, it is preferable that the rubber composition of the present invention is used (placed) in the tire tread (cap tread) of the pneumatic tire.

[0075] Figure 1 shows a schematic partial cross-sectional view of a tire representing an example of an embodiment of the tire of the present invention. However, the tire of the present invention is not limited to the embodiment shown in Figure 1.

[0076] In Figure 1, reference numeral 1 represents the bead portion, reference numeral 2 represents the sidewall portion, and reference numeral 3 represents the tire tread portion. Furthermore, a carcass layer 4 with embedded fiber cords is installed between the pair of left and right bead sections 1, and the ends of the carcass layer 4 are folded back and wrapped around the bead core 5 and bead filler 6 from the inside to the outside of the tire. In the tire tread section 3, a belt layer 7 is arranged around the entire circumference of the tire, on the outside of the carcass layer 4. In the bead portion 1, a rim cushion 8 is positioned at the part that contacts the rim. The tire tread portion 3 is preferably formed from the rubber composition of the present invention as described above.

[0077] The tire of the present invention can be manufactured, for example, by conventionally known methods. In addition to ordinary air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used as the gas that can be filled into the tire. [Examples]

[0078] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples.

[0079] [Production of modified liquid diene polymers] The modified liquid diene polymer was prepared as follows. Furthermore, the modified liquid diene polymers of Production Examples 1 to 5 are liquid diene polymers having specific functional groups in their main chain, and therefore fall under the category of specific polymers in the present invention.

[0080] <Manufacturing Example 1> Modified liquid diene polymer 1 was prepared as described below.

[0081] (Monomer polymerization process) 4.2 kg of cyclohexane was mixed with 1200 mL of 1,3-butadiene, 30 mL of n-butyllithium, and 0.1 mL of 2,2-di(2-tetrahydrofuryl)propane, and heated and stirred (60°C, 24 hours) to polymerize 1,3-butadiene. Subsequently, 40 mL of methanol was added and stirred (room temperature, 2.0 hours) to stop the polymerization. The polymerization solution was then purified by adding it to a large amount of methanol, and vacuum-dried at 50°C for 24 hours to obtain a liquid butadiene polymer with an Mw of 10,000.

[0082] (Main chain modification process) 200 g of the obtained liquid butadiene polymer, 24 g of mercaptoacetic acid (corresponding to the compound represented by formula (1A) above), and 2.5 g of AIBN (azobisisobutyronitrile) were added to 200 mL of MEK (methyl ethyl ketone), and the mixture was heated and stirred (80°C, 24 hours). The reaction solution was added to a large amount of methanol for purification, and then vacuum-dried at 50°C for 24 hours to obtain a modified liquid butadiene polymer (Mw: 10,000), which is a liquid butadiene polymer having the functional group represented by formula (1) above (wherein formula (1) is a methylene group) in its main chain. In the obtained modified liquid butadiene polymer, the number of the above functional groups in the main chain (average number per molecule) was 3. The obtained modified liquid butadiene polymer is referred to as modified liquid butadiene polymer 1.

[0083] <Production Example 2> Modified Liquid Diene Polymer 2 A modified liquid butadiene polymer was obtained by following the same procedure as in Production Example 1, except that 47 g of mercaptosuccinic acid (corresponding to the compound represented by formula (2A) above) was used instead of mercaptoacetic acid in the main chain modification step. The obtained modified liquid butadiene polymer was a modified liquid butadiene polymer (Mw: 10,000) having the functional group represented by formula (2) above (wherein formula (2) is a methylene group, and both X2 and X3 are carboxyl groups) in the main chain. In the obtained modified liquid butadiene polymer, the number of the above functional groups in the main chain (average number per molecule) was 3. The obtained modified liquid butadiene polymer is referred to as Modified Liquid Butadiene Polymer 2.

[0084] <Manufacturing Example 3> Modified Liquid Diene Polymer 3 A modified liquid butadiene polymer was obtained by following the same procedure as in Production Example 1, except that the amount of mercaptoacetic acid used in the main chain modification step was changed to 48 g. The obtained modified liquid butadiene polymer was a modified liquid butadiene polymer (Mw: 10,000) having the functional group represented by formula (1) above (wherein formula (1) is a methylene group) in the main chain. In the obtained modified liquid butadiene polymer, the number of the above functional groups in the main chain (average number per molecule) was 6. The obtained modified liquid butadiene polymer is referred to as modified liquid butadiene polymer 3.

[0085] <Manufacturing Example 4> Modified Liquid Diene Polymer 4 A modified liquid butadiene polymer was obtained by following the same procedure as in Production Example 1, except that the amount of mercaptoacetic acid used in the main chain modification step was changed to 79 g. The obtained modified liquid butadiene polymer was a modified liquid butadiene polymer (Mw: 10,000) having the functional group represented by formula (1) above (wherein formula (1) is a methylene group) in the main chain. In the obtained modified liquid butadiene polymer, the number of the above functional groups in the main chain (average number per molecule) was 10. The obtained modified liquid butadiene polymer is referred to as modified liquid butadiene polymer 4.

[0086] <Manufacturing Example 5> Modified Liquid Diene Polymer 5 A modified liquid butadiene polymer was obtained by following the same procedure as in Production Example 1, except that 78 g of mercaptosuccinic acid (corresponding to the compound represented by formula (2A) above) was used instead of mercaptoacetic acid in the main chain modification step. The obtained modified liquid butadiene polymer was a modified liquid butadiene polymer (Mw: 10,000) having the functional group represented by formula (2) above (wherein formula (2) is a methylene group, and both X2 and X3 are carboxyl groups) in the main chain. The number of the above functional groups in the main chain of the obtained modified liquid butadiene polymer (average number per molecule) was 5. The obtained modified liquid butadiene polymer is referred to as modified liquid butadiene polymer 5.

[0087] [Manufacturing of rubber compositions] Using each component from Table 1 below in the composition (parts by mass) shown in the table, the components excluding sulfur and vulcanization accelerator were first kneaded in a 1.7 L Banbury mixer for 5 minutes until the temperature reached 145°C, at which point it was released to obtain a masterbatch. Sulfur and vulcanization accelerator were added to the obtained masterbatch and kneaded in an open roll at 70°C to produce each rubber composition.

[0088] [evaluation] The following evaluations were performed using each rubber composition manufactured as described above. The results are shown in Table 1.

[0089] <Wet performance> Each rubber composition manufactured as described above was press-vulcanized in a predetermined mold at 160°C for 20 minutes to obtain vulcanized rubber test pieces. Next, the dynamic viscoelasticity of the vulcanized rubber sheets obtained from the rubber compositions above was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., with an initial strain of 10%, amplitude of ±2%, and frequency of 20Hz, and tanδ at 0°C was determined. The results were expressed as an exponent, with the standard value set to 100.

[0090] • Evaluation criteria In this invention, when the above index exceeds 100, it is evaluated as having excellent wet performance. The greater the above index is than 100, the better the wet performance. On the other hand, if the above index was 100 or less, it was evaluated as having poor wet performance.

[0091] <Abrasion Resistance> Each rubber composition manufactured as described above was press-vulcanized in a predetermined mold at 160°C for 20 minutes to obtain vulcanized rubber test pieces (thickness 0.2 cm). Next, the amount of wear of the vulcanized rubber sheets obtained from the rubber compositions above was measured using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho) in accordance with JIS K6264-1, 2:2005, under conditions of a temperature of 20°C and a slip ratio of 50%. The results were expressed as an exponent, with the reciprocal of the standard example value set to 100.

[0092] • Evaluation criteria In this invention, when the above index exceeds 100, it is evaluated as having excellent wear resistance. The greater the above index is than 100, the better the wear resistance. On the other hand, if the above index was 100 or less, it was evaluated as having poor wear resistance.

[0093] [Table 1]

[0094] The details of each component shown in Table 1 are as follows: (Diene-based rubber) • Diene rubber 1 (modified aromatic vinyl-diene copolymer): Styrene-butadiene rubber modified with hydroxyl groups. Asahi Kasei Corporation Tuffden E581 (oil-extracted product). Tg of the rubber itself -27℃. The amount of extracting oil per 100 parts by mass of the above rubber is 37.5 parts by mass. • Diene rubber 2 (butadiene rubber): Nipol 1220 manufactured by Nippon Zeon Corporation. Tg -105℃

[0095] (Specific polymers) Modified liquid diene polymers 1-5: Modified liquid diene polymers 1-5 produced as described above.

[0096] • Comparatively modified liquid diene polymer 1: LIR-410 manufactured by Kuraray Co., Ltd. Liquid isoprene rubber having functional groups containing carboxyl groups. Does not contain specific functional groups. The number of functional groups containing carboxyl groups is 10 per molecule of comparatively modified liquid diene polymer 1. • Comparatively Modified Co-Liquid Diene Polymer 2: LIR-403 manufactured by Kuraray Co., Ltd. Liquid isoprene rubber having functional groups containing carboxyl groups. Does not contain specific functional groups. The number of functional groups containing carboxyl groups is 3 per molecule of Comparatively Modified Liquid Diene Polymer 2.

[0097] • Silica 1: Solvay Zeosil 1165MP. CTAB159m 2 / g • Silica 2: Solvay Zeosil 115GR. CTAB103m 2 / g • Silica 3: Solvay ZEOSIL PREMIUM 200MP. CTAB204m 2 / g

[0098] • Silane coupling agent: Evonik Si69

[0099] • Carbon Black: Manufactured by Tokai Carbon Co., Ltd. Seast KH

[0100] • Process oil: Showa Shell Sekiyu Extract No. 4S • Anti-aging agent: 6 PPD, manufactured by Korea Kumho Petrochemical Co., Ltd. • Zinc oxide: Three types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd. • Stearic acid: Beads-type stearic acid manufactured by NOF Corporation

[0101] • Vulcanization accelerator (DPG): Sumitomo Chemical Co., Ltd.'s Soccinol DG • Vulcanization accelerator (CZ): Noxellar CZ-G, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. • Sulfur: Tsurumi Chemical Industry Co., Ltd. Kinka Inoil-containing finely powdered sulfur.

[0102] As shown in Table 1, Comparative Example 1, which contained less of the specified polymer than required, exhibited poor abrasion resistance. Comparative Example 2, which contained a higher-than-specified amount of the specific polymer, exhibited poor wet performance. Comparative Example 3, which had a silica content lower than the specified amount, exhibited poor wet performance and abrasion resistance. Comparative Example 4, which had a silica content higher than specified, exhibited poor abrasion resistance. Comparative Example 5, which did not contain the specific polymer and instead contained a comparatively modified liquid diene polymer 1 having functional groups other than the specific functional group, exhibited poor wet performance and abrasion resistance. Comparative Example 6, which did not contain the specific polymer and instead contained a comparatively modified liquid diene polymer 2 having functional groups other than the specific functional group, exhibited poor wet performance and abrasion resistance.

[0103] In contrast, the rubber composition of the present invention exhibits excellent performance on icy and snowy roads and low fuel consumption. [Explanation of Symbols]

[0104] 1. Bead section 2 Sidewall section 3. Tire tread section 4. Carcass layer 5 Bead core 6. Bead Filler 7 Belt layer

Claims

1. A diene rubber that is solid at 20°C and 1 atmosphere, Silica and, A modified liquid diene polymer is contained, which is liquid at 20°C and 1 atm, has a main chain containing a specific functional group selected from the group consisting of a functional group represented by the following formula (1) and a functional group represented by the following formula (2), and has a weight-average molecular weight of 1,000 to 100,000. The average glass transition temperature of the aforementioned diene rubber is higher than -50°C. The silica content is 50 to 200 parts by mass per 100 parts by mass of the diene rubber. A rubber composition in which the content of the modified liquid diene polymer is 1 to 25% by mass of the silica content. 【Chemistry 1】 【Chemistry 2】 In equations (1) and (2), R １ and R ２ Each of these independently represents an alkylene group having 1 to 6 carbon atoms. X １ This represents a carboxyl group, X ２ and X ３ Each of these independently represents either a hydrogen atom or a carboxyl group. * indicates the joining position. However, X ２ and X ３ At least one of them is a carboxyl group.

2. The rubber composition according to claim 1, wherein the modified liquid diene polymer has an average of 1 to 6 specific functional groups in its main chain per molecule.

3. The rubber composition according to claim 1 or 2, wherein the skeleton of the modified liquid diene polymer is a diene polymer or an aromatic vinyl-diene copolymer.

4. The skeleton of the modified liquid diene polymer is at least one polymer selected from the group consisting of butadiene and isoprene, or The rubber composition according to any one of claims 1 to 3, wherein it is a copolymer of at least one selected from the group consisting of butadiene and isoprene with styrene.

5. The CTAB specific surface area of ​​the silica is 100 to 300 m². 2 The rubber composition according to any one of claims 1 to 4, wherein the weight is / g.

6. Furthermore, it contains a silane coupling agent, The rubber composition according to any one of claims 1 to 5, wherein the content of the silane coupling agent is 1 to 20% by mass of the silica content.

7. A tire formed using the rubber composition described in any one of claims 1 to 6.

8. The tire according to claim 7, having a cap tread formed using the rubber composition.

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