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

Abstract

To provide a diene rubber that shows excellent wear resistance when used as a rubber component of a rubber composition containing a filler for reinforcement, a method for producing the same, and a rubber composition containing the diene polymer.SOLUTION: A diene rubber has a polycyclic hydrocarbon ring having an electron-attracting structure. Relative to the total of a repeat unit having the polycyclic hydrocarbon ring and a repeat unit having a carbon-carbon double bond in the main chain, the ratio of the repeat unit having the polycyclic hydrocarbon ring is 0.05-5 mol%.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] 2. Description of the Related Art Conventionally, rubber compositions containing diene rubber and a reinforcing filler (carbon black, silica, etc.) have been known as rubber compositions used for tires and the like (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-111688 A Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, with the increasing demand for higher safety levels, further improvements in abrasion resistance are required. In this situation, the present inventors have studied the rubber composition described in Patent Document 1 and have found that further improvements are desirable in consideration of demands that are likely to increase in the future.

[0005] In view of the above circumstances, the present invention aims to provide a diene rubber that exhibits excellent abrasion resistance when used as a rubber component in a rubber composition containing a reinforcing filler, a method for producing the same, and a rubber composition containing the diene polymer. [Means for solving the problem]

[0006] 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 diene-based rubber having a specific ratio of polycyclic hydrocarbon rings containing an electron-withdrawing structure, 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.

[0007] (1) A diene rubber having a polycyclic hydrocarbon ring containing an electron-withdrawing structure, The proportion of the repeating unit having the polycyclic hydrocarbon ring to the total of the repeating unit having the polycyclic hydrocarbon ring and the repeating unit having a carbon-carbon double bond in the main chain is 0.05 to 5 mol %. (2) The modified diene rubber according to (1) above, wherein the polycyclic hydrocarbon ring contains the electron-withdrawing structure in the skeleton. (3) The modified diene rubber according to (1) above, wherein the polycyclic hydrocarbon ring contains the electron-withdrawing structure as a substituent. (4) The modified diene rubber according to (1) above, wherein the polycyclic hydrocarbon ring contains the electron-withdrawing structure in the skeleton and also contains the electron-withdrawing structure as a substituent. (5) The modified diene rubber according to the above (1), which is a polymer represented by the formula (A) described below. (6) The modified diene rubber according to any one of the above (1) to (5), wherein the diene rubber has at least one unit selected from the group consisting of an isoprene unit and a butadiene unit. (7) A method for producing a modified diene rubber, comprising mixing 100 parts by mass of a diene rubber with 0.1 to 5 parts by mass of a conjugated diene having an electron-withdrawing structure to obtain the modified diene rubber described in any one of (1) to (6) above. (8) Contains 100 parts by mass of a rubber component and 10 to 150 parts by mass of carbon black, A rubber composition, wherein the rubber component contains 20 parts by mass or more of the modified diene rubber according to any one of (1) to (6) above. (9) Contains 100 parts by mass of a rubber component and 10 to 150 parts by mass of silica, A rubber composition, wherein the rubber component contains 20 parts by mass or more of the modified diene rubber according to any one of (1) to (6) above. Effect of the Invention

[0008] As described below, according to the present invention, it is possible to provide a diene-based rubber that exhibits excellent abrasion resistance when used as a rubber component in a rubber composition containing a reinforcing filler, a production method thereof, and a rubber composition containing the diene polymer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The modified diene rubber of the present invention, the production method thereof, 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. In addition, 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. In addition, with regard to the modified diene rubber of the present invention, "exhibiting excellent abrasion resistance and heat aging resistance when used in a rubber composition containing a reinforcing filler" is also referred to as "having excellent effects, etc. of the present invention."

[0010] [1] Modified diene rubber The modified diene rubber of the present invention is A diene rubber having a polycyclic hydrocarbon ring containing an electron-withdrawing structure (hereinafter also referred to as a "specific hydrocarbon ring"), The modified diene rubber has a proportion of the repeating unit having the polycyclic hydrocarbon ring of 0.05 to 5 mol % relative to the total of the repeating unit having the polycyclic hydrocarbon ring and the repeating unit having a carbon-carbon double bond in the main chain.

[0011] The modified diene rubber of the present invention has such a structure, and therefore is believed to be able to solve the above-mentioned problems of the present invention. The reasons for this are believed to be as follows. When the modified diene rubber of the present invention is used as a rubber component of a rubber composition containing a reinforcing filler, the electron-withdrawing structure of the specific hydrocarbon ring of the modified diene rubber of the present invention interacts with the reinforcing filler, preventing the reinforcing filler from agglomerating in the rubber composition and enhancing the dispersibility of the reinforcing filler. Here, since the electron-withdrawing structure is contained in a polycyclic hydrocarbon ring, the interface portion where the reinforcing filler and the modified diene rubber of the present invention interact becomes an extremely tough structure. As a result, it is presumed that the reinforcing effect of the reinforcing filler is increased and extremely excellent wear resistance is exhibited.

[0012] The modified diene rubber of the present invention will be described in detail below.

[0013] [Diene rubber] The modified diene rubber of the present invention is a modified diene rubber. The diene rubber (skeleton of diene rubber) before modification is not particularly limited, and specific examples thereof include natural rubber (NR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), etc. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, etc. The diene rubber preferably contains at least one unit selected from the group consisting of an isoprene unit and a butadiene unit, and more preferably contains an isoprene unit, because the effects of the present invention are more excellent. The diene rubber is preferably an isoprene rubber because the effects of the present invention are more excellent.

[0014] [Specific hydrocarbon ring] As described above, the modified diene rubber of the present invention is a diene rubber having a polycyclic hydrocarbon ring (specific hydrocarbon ring) containing an electron-withdrawing structure. The specific hydrocarbon ring may contain an electron-withdrawing structure in its skeleton, may contain an electron-withdrawing structure as a substituent, or may contain an electron-withdrawing structure in its skeleton and also as a substituent. For reasons such as better effects of the present invention, the specific hydrocarbon ring preferably contains an electron-withdrawing structure as a substituent, and more preferably contains an electron-withdrawing structure in the skeleton and also as a substituent.

[0015] [Electron attraction structure] The electron-withdrawing structure is an electron-withdrawing structure (group). In this specification, the electron-withdrawing group is defined as a group having a Hammett's substituent constant σ p Refers to a group with a value greater than zero. Here, Hammett's substituent constant σ p The Hammett rule is an empirical rule proposed by LP Hammett in 1935 to quantitatively discuss the effect of substituents on the reaction or equilibrium of benzene derivatives, and is widely accepted as valid today. The substituent constants obtained by the Hammett rule include σ p Value and σ m These values ​​can be found in many general textbooks, for example, "Lange's and book of Chemistry" edited by JADean, 12th edition, 1979 (McGraw-Hill) and "Chemical Domain" special edition, No. 122, pp. 96-103, 1979 (Nankodo). When the structure (group) is a polyvalent group, it is judged whether it is an electron-withdrawing group as a monovalent group (one in which a hydrogen atom is bonded to the other bonding position).

[0016] <Electron-withdrawing structure in the skeleton> When the specific hydrocarbon ring contains an electron-withdrawing structure in the skeleton, the electron-withdrawing structure is preferably a divalent electron-withdrawing structure, more preferably a carbonyl group (-CO-), an oxy group (-O-), or a carbonyloxy group (-CO-O- group), and even more preferably a carbonyloxy group (-CO-O- group), for reasons such as better effects of the present invention.

[0017] <Electron-withdrawing structure as a substituent> When the specific hydrocarbon ring contains an electron-withdrawing structure as a substituent, the electron-withdrawing structure (electron-withdrawing group) is preferably an acid group (particularly a carboxy group), a carboxylate group (RO-CO-: R is a hydrocarbon group), a cyano group, an amide group (-CO-NR2: R is a hydrogen atom or a hydrocarbon group), a hydroxyl group, an alkoxysilyl group, or an amino group, more preferably an acid group, and even more preferably a carboxy group, for reasons such as better effects of the present invention. The hydrocarbon group may be an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof. 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), linear or branched alkynyl groups (particularly having 2 to 30 carbon atoms), etc. 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.

[0018] [Polycyclic hydrocarbon ring] The polycyclic hydrocarbon ring is a polycyclic hydrocarbon ring (bridged hydrocarbon). The hydrocarbon ring may be an aromatic hydrocarbon ring or an aliphatic hydrocarbon ring (alicyclic), but is preferably an aliphatic hydrocarbon ring because the effects of the present invention are more excellent. The aliphatic hydrocarbon ring may be a saturated aliphatic hydrocarbon ring or an unsaturated aliphatic hydrocarbon ring, but is preferably an unsaturated aliphatic hydrocarbon ring because the effects of the present invention are more excellent. That is, the aliphatic hydrocarbon ring preferably has a carbon-carbon double bond. The polycyclic hydrocarbon ring preferably contains a heteroatom because the effects of the present invention are more excellent. The number of hydrocarbon rings constituting the polycyclic hydrocarbon ring is not particularly limited, but is preferably 2 to 10, and more preferably 2 to 3, for reasons such as better effects of the present invention. Specific examples of the polycyclic hydrocarbon ring include a bicyclopentane ring, a bicyclooctane ring, a bicyclohept-2-ene ring, a tricyclooctane ring, a norbornene ring, a norbornadiene ring, an adamantane ring, a naphthalene ring, and an anthracene ring. As described above, the specific hydrocarbon ring may contain an electron-withdrawing structure in the skeleton. In this case, the skeleton of the polycyclic hydrocarbon ring contains an electron-withdrawing structure.

[0019] [Degeneration rate] In the modified diene rubber of the present invention, the ratio of the repeating unit X to the total of the repeating unit having the specific hydrocarbon ring (hereinafter also referred to as "repeating unit X") and the repeating unit having a carbon-carbon double bond (C=C) in the main chain (hereinafter also referred to as "repeating unit Y") (hereinafter also referred to as "modification rate") is 0.05 to 5 mol%. The modification rate is more preferably 0.1 to 3 mol %, and even more preferably 0.2 to 1 mol %, because the effects of the present invention are more excellent.

[0020] [Preferred embodiment] The modified diene rubber of the present invention is preferably a polymer represented by the following formula (A) because the effects of the present invention are more excellent. The polymer represented by the following formula (A) is a polymer composed of a repeating unit with m (corresponding to the repeating unit X described above) and a repeating unit with n (corresponding to the repeating unit Y described above).

[0021] [ka]

[0022] In the formula (A), R1 to R4 each independently represent a hydrogen atom or a hydrocarbon group. Z represents a polycyclic hydrocarbon ring containing an electron-withdrawing structure. m and n represent the proportion (mol%) of each repeating unit, where m is 0.05 to 5 mol%, and m+n is 100 mol%.

[0023] As described above, in the above formula (A), R1 to R4 each independently represent a hydrogen atom or a hydrocarbon group. Specific examples of the hydrocarbon group are as described above. The above R1 to R4 are preferably a hydrogen atom or a methyl group because the effects of the present invention are superior. It is preferable that one of R1 and R2 is a hydrogen atom and the other is a methyl group because the effects of the present invention are more excellent. It is preferable that one of R3 and R4 is a hydrogen atom and the other is a methyl group because the effects of the present invention are more excellent.

[0024] As described above, in the above formula (A), Z represents a polycyclic hydrocarbon ring containing an electron-withdrawing structure, and corresponds to the above-mentioned specific hydrocarbon ring. Z forms a ring together with the carbon atom to which R1 is bonded and the carbon atom to which R2 is bonded. Specific examples and preferred embodiments of Z are the same as those of the above-mentioned specific hydrocarbon ring.

[0025] As described above, in the above formula (A), m and n represent the proportion (mol %) of each repeating unit. As described above, in the above formula (A), m is 0.05 to 5 mol %, and m+n is 100 mol %. The above m corresponds to the above-mentioned modification rate, and its preferred range is the same as the above-mentioned modification rate.

[0026] [Molecular weight]

[0027] [Weight average molecular weight] The weight average molecular weight (Mw) of the modified diene rubber of the present invention is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 100,000 or more, more preferably 200,000 to 10,000,000, even more preferably 250,000 to 2,000,000, particularly preferably 1,000,000 or less, and most preferably 500,000 or less.

[0028] [Number average molecular weight] The weight average molecular weight (Mn) of the modified diene rubber of the present invention is not particularly limited, but in order to obtain better effects of the present invention, it is preferably from 100,000 to 5,000,000, and more preferably from 120,000 to 1,000,000. [Measurement method] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated as standard polystyrene by gel permeation chromatography (GPC) measurement under the following conditions. Solvent: Tetrahydrofuran Detector: RI detector

[0029] [Manufacturing method] The method for producing the modified diene rubber of the present invention is not particularly limited, but a method of mixing 100 parts by mass of diene rubber with 0.1 to 5 parts by mass of a conjugated diene having an electron-withdrawing structure (hereinafter also referred to as "specific conjugated diene") (hereinafter also referred to as "production method of the present invention") is preferred because the modified diene rubber obtained has better effects of the present invention. By mixing the diene rubber with the specific conjugated diene, the carbon-carbon double bond in the main chain of the diene rubber reacts with the specific conjugated diene by Diels-Alder reaction to obtain a diene rubber having a polycyclic hydrocarbon ring containing an electron-withdrawing structure. Hereinafter, "the effects of the present invention are more excellent with respect to the obtained modified diene rubber" will also be simply referred to as "the effects of the present invention are more excellent."

[0030] [Diene rubber] Specific examples and preferred embodiments of the diene rubber used in the production method of the present invention are the same as those of the diene rubber (skeleton of the diene rubber) before modification of the above-mentioned modified diene rubber.

[0031] [Specific conjugated diene] The specific conjugated diene used in the production method of the present invention is a conjugated diene containing an electron-withdrawing structure. The specific conjugated diene may contain an electron-withdrawing structure in the skeleton, may contain an electron-withdrawing structure as a substituent, or may contain an electron-withdrawing structure in the skeleton and also as a substituent. For reasons such as better effects of the present invention, the specific hydrocarbon ring preferably contains an electron-withdrawing structure as a substituent, and more preferably contains an electron-withdrawing structure in the skeleton and also as a substituent.

[0032] <Electronic attraction structure> The definition, specific examples and preferred embodiments of the electron-withdrawing structure contained in the specific conjugated diene are the same as those of the specific hydrocarbon ring described above.

[0033] <Preferred embodiment> The specific conjugated diene is preferably pyrone or a derivative thereof, and more preferably coumaric acid or a coumaric acid ester (particularly methyl coumarate), because the effects of the present invention are more excellent. It is a conjugated diene containing a carboxyl group (-COOH) in the linking structure.

[0034] [Mixing ratio] As described above, in the production method of the present invention, 100 parts by mass of diene rubber and 0.1 to 5 parts by mass of specific conjugated diene are mixed. The ratio (mixing ratio) of the specific conjugated diene to 100 parts by mass of diene rubber is preferably 0.2 to 3 parts by mass, more preferably 0.3 to 2 parts by mass, and further preferably 0.5 to 1 part by mass, for reasons such as better effects of the present invention.

[0035] [2] Rubber composition The rubber composition of the present invention (hereinafter also referred to as "the composition of the present invention") is Contains a rubber component and a reinforcing filler, 100 parts by mass of the rubber component contains 20 parts by mass or more of the modified diene rubber of the present invention described above, In the rubber composition, the reinforcing filler contains at least one selected from the group consisting of silica and carbon black.

[0036] [Rubber component] As mentioned above, the composition of the present invention contains a rubber component. Further, 100 parts by mass of the rubber component contains 20 parts by mass or more of the modified diene rubber of the present invention described above.

[0037] [Modified diene rubber] The modified diene rubber of the present invention is as described above.

[0038] <Content> In the composition of the present invention, the content of the modified diene rubber of the present invention is 20 parts by mass or more per 100 parts by mass of the rubber component. The content of the modified diene rubber of the present invention is preferably 50 parts by mass or more per 100 parts by mass of the rubber component, more preferably 70 parts by mass or more, and even more preferably 90 parts by mass or more, because the effects of the present invention are more excellent. The upper limit of the content of the modified diene rubber of the present invention per 100 parts by mass of the rubber component is not particularly limited, and is 100 parts by mass.

[0039] [Other rubber components] The rubber component may contain a rubber component (other rubber component) other than the modified diene rubber of the present invention. Specific examples of such a rubber component are the same as those of the diene rubber used in the above-mentioned production method of the present invention.

[0040] [Molecular weight] The preferred range of the molecular weight of the rubber component is the same as that of the modified diene rubber described above.

[0041] [Reinforcing filler] As described above, the composition of the present invention contains a reinforcing filler that includes at least one selected from the group consisting of carbon black and silica. The reinforcing filler preferably contains both carbon black and silica because the effects of the present invention are more excellent.

[0042] [Carbon Black] The composition of the present invention preferably contains carbon black as a reinforcing filler because the effects of the present invention are more excellent. The carbon black may be used alone or in combination of two or more kinds. 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 the reason that the effects of the present invention are more excellent. 2 / g, and 70 to 150m 2 It is more preferable that the molecular weight is / g. Here, the nitrogen adsorption specific surface area (N2SA) is the amount of nitrogen adsorbed on 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."

[0043] In the composition of the present invention, the content of carbon black is not particularly limited. However, because the effects of the present invention are more excellent, the content of carbon black is preferably 10 to 150 parts by mass, and more preferably 20 to 100 parts by mass, per 100 parts by mass of the above-mentioned rubber component (particularly the above-mentioned modified diene rubber of the present invention).

[0044] 〔silica〕 The composition of the present invention preferably contains silica as a reinforcing filler because the effects of the present invention are more excellent. 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 kinds.

[0045] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​the silica (hereinafter, the "CTAB adsorption specific surface area" may be simply referred to as "CTAB") is not particularly limited. However, in order to improve the effects of the present invention, it is preferred to use a silica having a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​100 to 300 m. 2 / g, and 185m 2 It is more preferable that the molecular weight is 1 / g or more. Here, the CTAB adsorption specific surface area is a value obtained by measuring the amount of CTAB adsorbed on the silica surface in accordance with JIS K6217-3:2001 "Part 3: Determination of specific surface area - CTAB adsorption method."

[0046] The nitrogen adsorption specific surface area (N2SA) of the silica is not particularly limited, but is preferably 100 to 300 m for the reason that the effects of the present invention are more excellent. 2 / g, and 194m 2 It is more preferable that the molecular weight is 1 / g or more. Here, N2SA is a substitute characteristic for the surface area that silica can use to adsorb rubber molecules, and is the value obtained by measuring the amount of nitrogen adsorption onto the silica surface in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0047] 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 because the effects of the present invention are more excellent.

[0048] In the composition of the present invention, the content of silica is not particularly limited. However, for reasons of better effects of the present invention, the content of silica is preferably 10 to 150 parts by mass, and more preferably 20 to 100 parts by mass, per 100 parts by mass of the above-mentioned rubber component (particularly the above-mentioned modified diene rubber of the present invention).

[0049] [Content] In the composition of the present invention, the content of the reinforcing filler is not particularly limited. However, for reasons of superior effects of the present invention, the content is preferably 10 to 300 parts by mass, and more preferably 20 to 200 parts by mass, per 100 parts by mass of the above-mentioned rubber component (particularly the above-mentioned modified diene rubber of the present invention). When the composition of the present invention contains two or more kinds of reinforcing fillers, the content of the reinforcing fillers means the total content.

[0050] [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.

[0051] [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 above-mentioned 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.

[0052] 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. Among them, an alkoxy group is preferable because the effects of the present invention are more excellent. When the hydrolyzable group is an alkoxy group, the number of carbon atoms of the alkoxy group is preferably 1 to 16, and more preferably 1 to 4, because the effects of the present invention are more excellent. Examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, and a propoxy group.

[0053] The organic functional group is not particularly limited, but is preferably a group capable of forming a chemical bond with an organic compound. Examples of the organic functional group 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) (e.g., an octanoylthio group). Among 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 kinds.

[0054] The silane coupling agent is preferably a sulfur-containing silane coupling agent because the effects of the present invention are more excellent.

[0055] 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.

[0056] <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.

[0057] In addition, in the composition of the present invention, the content of the silane coupling agent is preferably 1 to 20 mass % relative to the above-mentioned silica content, and more preferably 5 to 15 mass %, because this provides better effects of the present invention.

[0058] [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 cars, etc. In particular, it is suitably used for tires (particularly treads). EXAMPLES

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0060] [Production of modified diene rubber] Modified diene rubbers 1 and 2 were produced as follows.

[0061] <Modified diene rubber 1> 100 parts by mass of isoprene rubber (Mw: 120000) and 1.03 parts by mass of coumaric acid (structure shown below) were mixed using a mixer (lab kneader) (140°C, 10 minutes). Note that coumaric acid is a conjugated diene that contains a carbonyloxy group (-CO-O-) that is an electron-withdrawing structure in the skeleton and a carboxy group (-COOH) that is also an electron-withdrawing structure as a substituent, and therefore corresponds to the above-mentioned specific conjugated diene. In this way, a modified isoprene rubber was obtained. The obtained modified isoprene rubber is represented by the following formula (a1). Here, one of R1 and R2 represents a hydrogen atom, and the other represents a methyl group. Also, one of R3 and R4 represents a hydrogen atom, and the other represents a methyl group. Also, m is 0.36 mol%, and m+n is 100 mol%. The obtained modified isoprene rubber is also called modified diene rubber 1.

[0062] (Coumaric acid) [ka]

[0063] [ka]

[0064] The modified diene rubber 1 is an isoprene rubber having a polycyclic hydrocarbon ring (corresponding to the above-mentioned specific hydrocarbon ring) containing a carbonyloxy group (-CO-O)-, which is an electron-withdrawing structure, in the skeleton and a carboxyl group (-COOH), which is an electron-withdrawing structure, as a substituent. The modified diene rubber 1 is composed of a repeating unit having the suffix m in formula (a1) (corresponding to the above-mentioned repeating unit X), which is a repeating unit having the above-mentioned polycyclic hydrocarbon ring, and a repeating unit having the suffix n in formula (a1) (corresponding to the above-mentioned repeating unit Y), which is a repeating unit having a carbon-carbon double bond in the main chain, and the ratio (modification rate) of the repeating unit having the suffix m to the total of the repeating unit having the suffix m and the repeating unit having the suffix n is 0.36 mol%. Therefore, the modified diene rubber 1 corresponds to the above-mentioned modified diene rubber of the present invention.

[0065] <Modified diene rubber 2> A modified isoprene rubber was obtained in the same manner as in modified diene rubber 1, except that 1.13 parts by mass of methyl coumarate (hereinafter, structure) was used instead of coumaric acid. Note that methyl coumarate is a conjugated diene that contains a carbonyloxy group (-CO-O-), which is an electron-withdrawing structure, in the skeleton and also contains a carboxylic acid methyl ester group (-COOCH3), which is an electron-withdrawing structure, as a substituent, and therefore corresponds to the specific conjugated diene described above. The obtained modified isoprene rubber is represented by the following formula (a2). Here, one of R1 and R2 represents a hydrogen atom, and the other represents a methyl group. Also, one of R3 and R4 represents a hydrogen atom, and the other represents a methyl group. Also, m is 0.30 mol%, and m+n is 100 mol%. The obtained modified isoprene rubber is also called modified diene rubber 2.

[0066] (Methyl coumarate) [ka]

[0067] [ka]

[0068] The modified diene rubber 2 is an isoprene rubber having a polycyclic hydrocarbon ring (corresponding to the above-mentioned specific hydrocarbon ring) containing a carbonyloxy group (-CO-O-) which is an electron-withdrawing structure in the skeleton and a carboxylic acid methyl ester group (-COOCH3) which is also an electron-withdrawing structure as a substituent. The modified diene rubber 2 is composed of a repeating unit having the suffix m in formula (a2) (corresponding to the above-mentioned repeating unit X) which is a repeating unit having the above-mentioned polycyclic hydrocarbon ring, and a repeating unit having the suffix n in formula (a2) (corresponding to the above-mentioned repeating unit Y) which is a repeating unit having a carbon-carbon double bond in the main chain, and the ratio (modification rate) of the repeating unit having the suffix m to the total of the repeating unit having the suffix m and the repeating unit having the suffix n is 0.30 mol%. Therefore, the modified diene rubber 2 corresponds to the above-mentioned modified diene rubber of the present invention.

[0069] [Production of rubber composition] The components in Tables 1 and 2 below were mixed in the compositions (parts by mass) shown in the tables. Specifically, first, the components other than sulfur and the accelerator were mixed in a 1.8 L internal mixer at 130°C for 5 minutes, and the master batch was discharged. Then, sulfur and the accelerator were added to the master batch, and the mixture was mixed at 80°C using an open roll to produce each rubber composition.

[0070] 〔evaluation〕 The resulting rubber compositions (unvulcanized) were evaluated as follows.

[0071] <Hardness> Each of the resulting rubber compositions (unvulcanized) was press-vulcanized in a mold (15 cm×15 cm×0.2 cm) at 160° C. for 20 minutes to prepare a vulcanized rubber sheet. The hardness (type A durometer hardness) of the obtained vulcanized rubber sheet was evaluated at 60°C in accordance with JIS K6253-3. The results are shown in Tables 1 and 2. The results are expressed as an index with the value of Comparative Example 1 set to 100 in Table 1, and the results are expressed as an index with the value of Comparative Example 2 set to 100 in Table 2. A larger index means a higher hardness.

[0072] <Wear resistance> The abrasion loss of the vulcanized rubber sheet obtained as described above was measured at a temperature of 20°C and a slip rate 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 from the following formula. The results are shown in Tables 1 and 2. A larger index indicates a smaller amount of wear and better wear resistance. (Table 1) Abrasion resistance index = (amount of abrasion in Comparative Example 1 / amount of abrasion in each vulcanized rubber sheet) x 100 (Table 2) Abrasion resistance index = (amount of abrasion in Comparative Example 2 / amount of abrasion in each vulcanized rubber sheet) x 100

[0073] <Relaxation time T2> 0.3 g of each of the obtained rubber compositions (unvulcanized) was cut and immersed in toluene solvent for 48 hours to extract the rubber that was not adsorbed to the filler or gelled, to prepare a gel. Table 1 shows the amount of rubber (bound rubber amount) in the gel. Bound rubber amount = [(mass of sample after immersion in toluene and drying) - (mass of carbon black or silica)] / (mass of rubber component) The relaxation time T2 of the rubber molecules in the obtained gel was measured by pulsed NMR (nuclear magnetic resonance). The rubber composition was poured into an NMR tube with a diameter of 9 mm, and the spin-spin relaxation time (T2) at 25°C was measured by the solid echo method and the Hahn echo method using a pulse NMR spectrometer MU-25 (manufactured by JEOL Ltd.). The condition for measuring T2 is that if the amount of rubber is 0.3 g or more, a sufficient proton signal is obtained and measurement accuracy is guaranteed. When the decay curve of the solid echo method is separated into two components, the short component (shown in Table 1) with a relaxation time T2 fitted with a Weibull coefficient of 2 has a T2 of several tens of μs, which is close to a glass state, and represents the relaxation time of rubber strongly bound by the filler. In addition, when the decay curve is separated into two components by the Hahn echo method, the Weibull coefficient of the long component was 1, and the Weibull coefficient of the short component was 1 to 2. At this time, the long component (shown in Table 1) is a terminal chain with relatively high molecular motion or a molecular chain far from entanglement, and the short component represents a network chain.

[0074] [Table 1]

[0075] [Table 2]

[0076] Details of each component in Tables 1 and 2 are as follows. Isoprene rubber: The same isoprene rubber used in the production of modified diene rubbers 1 and 2 (Nipol IR2200 manufactured by Nippon Zeon Co., Ltd.) (Mw: 120,000) Modified diene rubbers 1 to 2: Modified diene rubbers 1 to 2 produced as described above Carbon black: HAF grade carbon black, Cabot Japan's Show Black N330, nitrogen adsorption specific surface area 75m 2 / g Silica: Zeosil 1165MP (Rhodia) CTAB adsorption specific surface area 152m 2 / g Silane coupling agents: Silane coupling agents Zinc oxide: 3 types of zinc oxide (manufactured by Seido Chemical Industry Co., Ltd.) Stearic acid: Beads Stearic Acid YR (manufactured by NOF Corporation) Sulfur: Oil-treated sulfur (Karuizawa Refinery Co., Ltd.) Accelerator NS: Sancerer NS-G (manufactured by Sanshin Chemical Industry Co., Ltd.) Accelerator CZ: N-cyclohexyl-2-benzothiazolylsulfenamide (Noccela CZ-G, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Accelerator DPG: 1,3-diphenylguanidine (Noccela DPG, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0077] As can be seen from Table 1, Examples 1 and 2 containing the modified diene rubber of the present invention showed excellent wear resistance compared to Comparative Example 1 not containing the modified diene rubber of the present invention. Among them, Example 1 in which the electron-withdrawing structure is a carboxy group showed better wear resistance. Similarly, as can be seen from Table 2, Examples 3 and 4 containing the modified diene rubber of the present invention showed better wear resistance compared to Comparative Example 2 not containing the modified diene rubber of the present invention. Among them, Example 3 in which the electron-withdrawing structure is a carboxy group showed better wear resistance.

[0078] As shown in Table 1, the relaxation time T2 measured by pulse NMR showed that Examples 1 and 2 containing the modified diene rubber of the present invention had a short relaxation time T2 (short component) in the Solid Echo method compared to Comparative Example 1 not containing the modified diene rubber of the present invention, indicating that the rubber component was strongly adsorbed to the filler. On the other hand, Examples 1 and 2 containing the modified diene rubber of the present invention had a long relaxation time T2 (long component) in the Hahn Echo method compared to Comparative Example 1 not containing the modified diene rubber of the present invention, indicating that the network chain mobility of the rubber component was high. Similarly, as shown in Table 2, in Examples 3 and 4 containing the modified diene rubber of the present invention, the relaxation time T2 (short component) in the Solid Echo method was short compared to Comparative Example 2 not containing the modified diene rubber of the present invention, indicating that the rubber component was strongly adsorbed to the filler. On the other hand, in Examples 3 and 4 containing the modified diene rubber of the present invention, the relaxation time T2 (long component) in the Hahn Echo method was long compared to Comparative Example 2 not containing the modified diene rubber of the present invention, indicating that the mobility of the network chain of the rubber component was high.

Claims

1. A diene rubber having a partial structure in which a portion of the hydrocarbon groups and / or hydrogen atoms of a polycyclic hydrocarbon ring are replaced with an electron-withdrawing structure, A modified diene rubber, wherein a ratio of the repeating unit having the polycyclic hydrocarbon ring to a total of the repeating unit having the polycyclic hydrocarbon ring and the repeating unit having a carbon-carbon double bond in the main chain is 0.05 to 5 mol %, A modified diene rubber which is a polymer represented by the following formula (A): 【Chemistry 1】 In formula (A), R 1 to R 4 each independently represent a hydrogen atom or a hydrocarbon group. Z represents a partial structure in which a portion of the hydrocarbon groups and / or hydrogen atoms of a polycyclic hydrocarbon ring are substituted with an electron-withdrawing structure. m and n represent the proportion (mol %) of each repeating unit, m is 0.05 to 5 mol %, and m+n is 100 mol %.

2. The modified diene rubber according to claim 1 , wherein the partial structure contains the electron-withdrawing structure in the skeleton.

3. The modified diene rubber according to claim 1 , wherein the partial structure contains the electron-withdrawing structure as a substituent.

4. The modified diene rubber according to claim 1 , wherein the partial structure contains the electron-withdrawing structure in the skeleton and also contains the electron-withdrawing structure as a substituent.

5. The modified diene rubber according to any one of claims 1 to 4, wherein the diene rubber has at least one unit selected from the group consisting of an isoprene unit and a butadiene unit.

6. A method for producing a modified diene rubber, comprising mixing 100 parts by mass of a diene rubber with 0.1 to 5 parts by mass of a conjugated diene having an electron-withdrawing structure to obtain the modified diene rubber according to any one of claims 1 to 5.

7. Contains 100 parts by mass of a rubber component and 10 to 150 parts by mass of carbon black, A rubber composition, wherein the rubber component comprises 20 parts by mass or more of the modified diene rubber according to any one of claims 1 to 5.

8. Contains 100 parts by mass of a rubber component and 10 to 150 parts by mass of silica, A rubber composition, wherein the rubber component comprises 20 parts by mass or more of the modified diene rubber according to any one of claims 1 to 5.

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