Compound, rubber composition, vulcanized rubber, tire, and rubber additive

Abstract

To provide a compound which, when applied to a rubber composition, can impart excellent low heat buildup properties without significantly impairing the physical properties of the rubber.SOLUTION: The compound is represented by formula (I), where: R1, R2, R6 and R7 each represent H or formula (A); R3 represents H, formula (A), or formula (B); and R4 and R5 each represent H or the like.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a compound, a rubber composition, a vulcanizate, a tire, and a rubber additive. [Background technology]

[0002] In recent years, land transportation using vehicles such as large trucks and express buses has become increasingly popular, leading to advances in vehicle performance (higher speeds, higher horsepower, larger size, etc.) and the shift to electric vehicles (increased weight). Under these circumstances, tires for vehicles are used under high heat buildup conditions, and active development has been underway to improve the low heat buildup (fuel economy) of rubber used in tires while maintaining durability (hardness). For example, Patent Documents 1 and 2 disclose rubber compositions containing resorcinol or a resorcinol derivative for the purpose of improving low heat buildup, breaking strength, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-232895 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-179299 Summary of the Invention [Problem to be solved by the invention]

[0004] However, tires (vulcanized rubber) and the like obtained from conventional rubber compositions are not sufficient in terms of low heat buildup, and there is still room for improvement.

[0005] The main object of the present invention is to provide a compound that can impart excellent low heat buildup without significantly impairing the physical properties of rubber when applied to a rubber composition, and to provide a rubber composition that has excellent low heat buildup while maintaining the physical properties of rubber. [Means for solving the problem]

[0006] In view of the above problems, the present inventors have conducted extensive research and have found that by applying a resorcinol derivative having a predetermined structure to a rubber composition, it is possible to impart excellent low heat buildup without significantly impairing the physical properties of the rubber, and have thus completed the present invention.

[0007] The present invention provides a compound described in [1] below, a rubber composition described in [2] and [3], a vulcanized rubber described in [4], a tire described in [5], and a rubber additive described in [6] and [7]. [1] A compound represented by formula (I). [ka] [In formula (I), R 1 and R 2 each independently represents a hydrogen atom or a group represented by formula (A). R 3 represents a hydrogen atom, a group represented by formula (A), or a group represented by formula (B). R 4 and R 5 each independently represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkanoyl group having 1 to 18 carbon atoms, or a benzoyl group. However, R 1 , R 2 , and R 3 at least one of R is a group represented by formula (A), 3 is a group represented by formula (B), R 1 , R 2 , R 6 , and R 7 At least one of the groups is a group represented by formula (A). [ka] (In formula (A), * represents a bonding position.) [ka] (In formula (B), R 6 and R 7 each independently represents a hydrogen atom or a group represented by formula (A). R 8 and R 9 each independently represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkanoyl group having 1 to 18 carbon atoms, or a benzoyl group. R 10 and R 11 each independently represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a phenyl group. * indicates the bond position.) [2] A rubber composition containing the compound according to [1], a diene rubber, and a filler. [3] The rubber composition according to [2], further containing a vulcanizing agent. [4] A vulcanized rubber obtained by vulcanizing the rubber composition according to [2] or [3]. [5] A tire having a rubber member containing the vulcanized rubber according to [4]. [6] A rubber additive comprising the compound according to [1]. [7] The rubber additive according to [6], which is a low heat buildup agent. [Effects of the Invention]

[0008] According to the present invention, there are provided a compound that can impart excellent low heat buildup without significantly impairing the rubber physical properties when applied to a rubber composition, and a rubber composition that has excellent low heat buildup while maintaining the rubber physical properties. The present invention also provides a vulcanized rubber using such a rubber composition. The present invention also provides a tire using such a vulcanized rubber. Furthermore, the present invention also provides a rubber additive using such a compound. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0010] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in numerical ranges described in this specification, the upper or lower limit value of that numerical range may be replaced with a value shown in an example.

[0011] In this specification, unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more within the range that meets the conditions. When multiple substances corresponding to each component are present, the content of each component means the total amount of the multiple substances unless otherwise specified.

[0012] [Compound] The compound of one embodiment is a compound represented by formula (I). When the compound of this embodiment is applied to a rubber composition, it becomes possible to impart excellent low heat buildup without significantly impairing the physical properties of the rubber.

[0013] [ka]

[0014] In formula (I), R 1 and R 2 each independently represents a hydrogen atom or a group represented by formula (A). R 3 represents a hydrogen atom, a group represented by formula (A), or a group represented by formula (B). R 4 and R 5 each independently represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkanoyl group having 1 to 18 carbon atoms, or a benzoyl group. However, R 1 , R 2 , and R 3 at least one of R is a group represented by formula (A), 3is a group represented by formula (B), R 1 , R 2 , R 6 , and R 7 At least one of the groups is a group represented by formula (A).

[0015] [ka]

[0016] In formula (A), * represents a bonding position.

[0017] [ka]

[0018] In formula (B), R 6 and R 7 each independently represents a hydrogen atom or a group represented by formula (A). R 8 and R 9 each independently represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkanoyl group having 1 to 18 carbon atoms, or a benzoyl group. R 10 and R 11 each independently represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a phenyl group. * indicates the bond position.

[0019] R 1 and R 2 is preferably a hydrogen atom.

[0020] R 3 is preferably a hydrogen atom or a group represented by formula (A), more preferably a group represented by formula (A).

[0021] R 4 and R 5Examples of the alkyl group in include linear alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, hexadecyl, and icosyl; branched alkyl groups such as isopropyl, isobutyl, isopentyl, neopentyl, and 2-ethylhexyl; and cyclic alkyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and tricyclodecyl. The alkyl group has 1 to 18 carbon atoms, preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 4.

[0022] R 4 and R 5 The alkanoyl group in the formula is a group represented by the formula: R-(CO)-, where R represents a hydrogen atom or an alkyl group having 1 to 17 carbon atoms. Examples of the alkyl group include R 4 and R 5 The number of carbon atoms in the alkanoyl group, including the carbon atoms in (CO), is 1 to 18, preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 4.

[0023] Specific examples of the alkanoyl group include a formyl group, an acetyl group, a propanoyl group, a butanoyl group, a pentanoyl group, and a hexanoyl group.

[0024] R 4 and R 5 is preferably a hydrogen atom.

[0025] R 8 and R 9 Examples of the alkyl group in 4 and R 5 Examples include the same alkyl groups as those in the above. The alkyl group has 1 to 18 carbon atoms, preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 4 carbon atoms.

[0026] R8 and R 9 Examples of the alkanoyl group in 4 and R 5 Examples of the alkanoyl group include those similar to the alkanoyl group in the formula (I). The alkanoyl group has 1 to 18 carbon atoms, preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 4 carbon atoms.

[0027] R 10 and R 11 Examples of the alkyl group in 4 and R 5 The alkyl group has 1 to 18 carbon atoms, preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 4 carbon atoms.

[0028] The number of groups represented by formula (A) in the compound represented by formula (I) is preferably 1 to 4, more preferably 1 to 3, even more preferably 1 or 2, and particularly preferably 1.

[0029] The compound represented by formula (I) is preferably a compound represented by formula (IA).

[0030] [ka]

[0031] In formula (IA), R 1 , R 2 , R 4 , and R 5 is synonymous with the above.

[0032] Examples of the compound represented by formula (I) include compounds represented by formulas (I-1) to (I-2).

[0033] [ka]

[0034] The compound represented by formula (I) can be obtained, for example, by appropriately combining known methods capable of linking a compound that can become a group represented by formula (A) to a predetermined position of a compound represented by formula (Ia).

[0035] [ka]

[0036] In formula (Ia), R 3a represents a hydrogen atom or a group represented by formula (Ba). R 4a and R 5a is R 4 and R 5 is synonymous with.

[0037] [ka]

[0038] In formula (Ba), R 8a and R 9a is R 8 and R 9 is synonymous with. R 10a and R 11a is R 10 and R 11 is synonymous with. * indicates the bond position.

[0039] For example, the compound represented by formula (I-1) can be obtained by reacting resorcinol with 2-mercaptobenzothiazole in the presence of iodine in an organic solvent (dimethyl sulfoxide, etc.).

[0040] [ka]

[0041] [Rubber composition] A rubber composition according to one embodiment contains a compound represented by formula (I), a diene rubber, and a filler. The rubber composition may further contain a vulcanizing agent. Because the rubber composition according to this embodiment contains the compound represented by formula (I), it can have excellent low heat buildup while maintaining rubber physical properties.

[0042] (Compound represented by formula (I)) From the viewpoint of fuel economy, the content of the compound represented by formula (I) may be 0.01 to 5 parts by mass relative to 100 parts by mass of the total amount of the diene rubber described below. The content of the compound represented by formula (I) is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, particularly preferably 0.3 parts by mass or more, relative to 100 parts by mass of the total amount of the diene rubber, and is preferably 3 parts by mass or less, more preferably 2.5 parts by mass or less, even more preferably 2 parts by mass or less, particularly preferably 1.5 parts by mass or less.

[0043] (Diene rubber) Diene rubber refers to rubber made from a diene monomer containing a conjugated double bond. Examples of diene rubber include styrene-butadiene copolymer rubber (SBR), natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), nitrile rubber (NBR), chloroprene rubber (CR), isoprene-isobutylene copolymer rubber (IIR), ethylene-propylene-diene copolymer rubber (EPDM), and halogenated butyl rubber (HR). Diene rubber is preferably a highly unsaturated rubber such as styrene-butadiene copolymer rubber (SBR), natural rubber (NR), or butadiene rubber (BR), and more preferably natural rubber (NR).

[0044] Examples of natural rubber (NR) include grades of natural rubber such as RSS#1, RSS#3, TSR20, and SIR20. Other examples of natural rubber (NR) include epoxidized natural rubber, deproteinized natural rubber, and modified natural rubber.

[0045] The diene rubber may be a modified diene rubber having units based on various modifiers in the molecular chain or at the terminals thereof, which can be produced by reacting a modifier with a monomer containing a conjugated diene compound during solution polymerization.

[0046] The modifier is not particularly limited as long as it is a compound that can be used when preparing a modified diene rubber by solution polymerization. Using a diene rubber modified with a compound having a heteroatom tends to facilitate the dispersion of a filler in the rubber composition. Examples of heteroatoms include oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms. Examples of compounds having a heteroatom include amine compounds, acrylamide compounds, vinylsilane compounds, alkoxysilane compounds, polysiloxane compounds, silane sulfide compounds, sulfanylsilane compounds, cyanate compounds, and polyimine compounds.

[0047] The content of the diene rubber may be 30 to 90% by mass based on the total amount of the rubber composition, and is preferably 35% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, particularly preferably 50% by mass or more, and is preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, particularly preferably 70% by mass or less, based on the total amount of the rubber composition.

[0048] (filler) The filler may include carbon black, may include silica, or may include both carbon black and silica.

[0049] Examples of carbon black include furnace carbon black, acetylene black, thermal black, channel black, graphite, etc. Examples of channel black include EPC, MPC, CC, etc. Examples of furnace carbon black include SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, ECF, etc. Examples of thermal black include FT, MT, etc. The BET specific surface area of ​​the carbon black is preferably 10 to 130 m 2 / g, more preferably 20 to 130m 2 / g, more preferably 40 to 130m 2 / g. Here, the BET specific surface area refers to a value measured by the BET method in accordance with ASTM D3037-93.

[0050] From the viewpoints of fuel economy and abrasion resistance, the carbon black content may be 10 to 70 parts by mass relative to 100 parts by mass of the total amount of diene rubbers. The carbon black content is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 35 parts by mass or more, relative to 100 parts by mass of the total amount of diene rubbers, and is preferably 65 parts by mass or less, more preferably 60 parts by mass or less.

[0051] Examples of silica include dry silica (silicic anhydride), wet silica (hydrated silicic acid), colloidal silica, precipitated silica, etc. The BET specific surface area of ​​the silica is preferably 20 to 400 m 2 / g, more preferably 50 to 350m 2 / g, more preferably 100 to 300m 2 / g. Here, the BET specific surface area refers to a value measured by the BET method in accordance with ASTM D1993-03.

[0052] From the viewpoints of fuel economy and abrasion resistance, the content of silica may be 1 to 50 parts by mass relative to 100 parts by mass of the total amount of diene rubbers. The content of silica is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 7 parts by mass or more, relative to 100 parts by mass of the total amount of diene rubbers, and is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less.

[0053] The filler may contain fillers other than silica and carbon black, such as calcium silicate, aluminum silicate, aluminum hydroxide, ground bituminous coal, talc, clay (particularly, calcined clay), and titanium oxide.

[0054] From the viewpoints of fuel economy and abrasion resistance, the content of the filler may be 10 to 80 parts by mass relative to 100 parts by mass of the total amount of the diene rubber. The content of the filler is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, relative to 100 parts by mass of the total amount of the diene rubber, and is preferably 70 parts by mass or less, more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less.

[0055] (vulcanizing agent) Examples of the vulcanizing agent include sulfur and sulfur-based compounds, such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and surface-treated sulfur.

[0056] The content of the vulcanizing agent may be 0.1 to 5 parts by mass relative to 100 parts by mass of the total amount of the diene rubber, and is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 4 parts by mass or less, more preferably 3 parts by mass or less, relative to 100 parts by mass of the total amount of the diene rubber.

[0057] (Other ingredients) The rubber composition may further contain other components (other components A). Examples of other components A include vulcanization accelerators, vulcanization aids, processing aids, antioxidants, curing agents, extender oils, and silane coupling agents.

[0058] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and dibenzothiazyl disulfide; thiuram-based vulcanization accelerators such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolylsulfenamide and N,N'-diisopropyl-2-benzothiazolylsulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine and orthotolylbiguanidine. The vulcanization accelerator preferably includes a sulfenamide-based vulcanization accelerator.

[0059] The content of the vulcanization accelerator may be 0.1 to 8 parts by mass, 0.5 to 5 parts by mass, or 1 to 3 parts by mass relative to 100 parts by mass of the total amount of the diene rubber.

[0060] Examples of the vulcanization aid include triallyl isocyanurate, N,N'-m-phenylene bismaleimide, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, 2-ethoxyethyl methacrylate, tetrahydrofurfuryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, acrylate, methacryloxyethyl phosphate, 1,4-butanediol diacrylate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, allyl glycidyl ether, N-methylol methacrylamide, 2,2-bis(4-methacryloxypolyethoxyphenyl)propane, aluminum methacrylate, zinc methacrylate, calcium methacrylate, magnesium methacrylate, 3-chloro-2-hydroxypropyl methacrylate, zinc oxide, magnesium oxide, and the like.

[0061] The content of the vulcanization aid may be 0.1 to 15 parts by mass, 0.5 to 10 parts by mass, or 1 to 7 parts by mass relative to 100 parts by mass of the total amount of the diene rubber.

[0062] Examples of processing aids include fatty acids such as oleic acid, palmitic acid, and stearic acid; fatty acid metal salts such as zinc laurate, zinc stearate, barium stearate, and calcium stearate; fatty acid esters; and glycols such as ethylene glycol and polyethylene glycol.

[0063] The content of the processing aid may be 0.1 to 10 parts by mass, 0.5 to 7 parts by mass, or 1 to 5 parts by mass relative to 100 parts by mass of the total amount of the diene rubber.

[0064] Examples of the antioxidant include amine-based antioxidants and sulfur-based antioxidants.

[0065] Examples of the amine-based antioxidants include naphthylamine-based antioxidants such as phenyl-α-naphthylamine and phenyl-β-naphthylamine; N,N'-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine. and p-phenylenediamine antioxidants such as N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine, N-hexyl-N'-phenyl-p-phenylenediamine, and N-octyl-N'-phenyl-p-phenylenediamine.

[0066] Examples of sulfur-based antiaging agents include imidazole-based antiaging agents such as 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, zinc salt of 2-mercaptomethylbenzimidazole, and zinc salt of 2-mercaptomethylimidazole; and aliphatic thioether-based antiaging agents such as dimyristyl thiodipropionate, dilauryl thiodipropionate, distearyl thiodipropionate, ditridecyl thiodipropionate, and pentaerythritol-tetrakis(β-lauryl-thiopropionate).

[0067] The content of the antioxidant may be 0.1 to 10 parts by mass, 0.3 to 5 parts by mass, or 0.5 to 3 parts by mass relative to 100 parts by mass of the total amount of the diene rubber.

[0068] Examples of the curing agent include hexamethylenetetramine, hexamethoxymethylolmelamine, pentamethoxymethylolmelamine, hexamethoxymethylmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, hexakis-(methoxymethyl)melamine, N,N',N"-trimethyl-N,N',N"-trimethylolmelamine, N,N',N"-trimethylolmelamine, N-methylolmelamine, N,N'-(methoxymethyl)melamine, N,N',N"-tributyl-N,N',N"-trimethylolmelamine, and paraformaldehyde.

[0069] The content of the curing agent may be 0.1 to 10 parts by mass, 0.3 to 5 parts by mass, or 0.5 to 3 parts by mass relative to 100 parts by mass of the total amount of the diene rubber.

[0070] Examples of extender oils include aromatic mineral oils (viscosity specific gravity constant (VGC value): 0.900 to 1.049), naphthenic mineral oils (VGC value: 0.850 to 0.899), and paraffinic mineral oils (VGC value: 0.790 to 0.849).

[0071] Examples of silane coupling agents include vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, [γ-(triethoxysilyl)propyl]tetrasulfide, and bis[γ-(triethoxysilyl)propyl]disulfide.

[0072] The rubber composition can be prepared by kneading (mixing) each component with a known kneader (mixer) such as a roll or a mixer.

[0073] The rubber composition may be prepared, for example, by kneading in the following order: first kneading and second kneading. In the first kneading, components other than the vulcanizing agent and vulcanization accelerator are kneaded using a kneader to obtain a kneaded mixture. The kneading temperature in the first kneading is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 to 30 minutes. Subsequently, in the second kneading, the kneaded mixture obtained in the first kneading is kneaded with the vulcanizing agent and vulcanization accelerator to obtain a rubber composition. The kneading temperature in the second kneading is usually 100°C or lower, preferably room temperature (25°C) to 80°C.

[0074] [Vulcanized rubber] The vulcanized rubber of one embodiment is obtained by vulcanizing the above rubber composition.

[0075] The vulcanized rubber can be obtained, for example, by subjecting the rubber composition (the rubber composition obtained in the second kneading) to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200° C., and preferably 140 to 180° C. The vulcanization time is usually 1 to 60 minutes, and preferably 10 to 50 minutes.

[0076] Vulcanized rubber is useful for producing tires and rubber components for tires.

[0077] In addition to tires, vulcanized rubber can be used for vibration-proof rubber, rubber belts, vibration dampers, seismic isolation rubber, etc. Examples of vibration-proof rubber applications include automotive vibration-proof rubber such as engine mounts, strut mounts, bushings, and exhaust hangers. Examples of rubber belt applications include power transmission belts, conveyor belts, and V-belts.

[0078] [tire] A tire of one embodiment includes a rubber member containing the vulcanized rubber.

[0079] The rubber member may be a member coated on a steel cord or a carcass fiber cord, or may be a tread. Examples of the rubber member include a tire belt member including vulcanized rubber and a steel cord, a tire carcass member including vulcanized rubber and a carcass fiber cord, a tire sidewall member, a tire inner liner member, a tire cap tread member, and a tire undertread member.

[0080] [Rubber additives] A rubber additive in one embodiment includes a compound represented by formula (I) above. When used as a rubber additive, the compound represented by formula (I) can impart excellent low heat buildup to a rubber composition. The rubber additive is preferably a low heat buildup agent.

[0081] The rubber additive may be an embodiment consisting solely of the compound represented by formula (I), or may contain other components (other components B) within a range that does not impair the effects of the compound. Examples of other components B include the components exemplified above, such as diene rubber, filler, vulcanizing agent, vulcanization accelerator, vulcanization aid, processing aid, antioxidant, curing agent, extender oil, and silane coupling agent. [Example]

[0082] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is possible to carry out the present invention by making appropriate modifications within the scope of the above and below spirit, and all such modifications are included in the technical scope of the present invention.

[0083] In the following examples, the structures of the compounds were confirmed by nuclear magnetic resonance spectroscopy (VARIAN: 400-MR).

[0084] In the following examples, the melting points (mp) of the compounds were determined by simultaneous thermogravimetry and differential thermal analysis (TG-DTA) (TG-DTA2020SA, manufactured by Bruker AXS).

[0085] Example 1-1 <Synthesis of 2-(2,4-dihydroxyphenyl)mercaptobenzothiazole (compound represented by formula (I-1))> [ka]

[0086] Under a nitrogen atmosphere, 2-mercaptobenzothiazole (75.0 g, 448 mmol, 1.0 equiv.), resorcinol (49.4 g, 449 mmol, 1.0 equiv.), DMSO (dimethyl sulfoxide, 95.6 mL, 1.35 mol, 3.0 equiv.), and iodine (11.4 g, 44.9 mmol, 0.1 equiv.) were mixed and stirred at 80 °C for 3.5 h. The reaction mixture was cooled, ethyl acetate (EtOAc) was added, and the mixture was washed with aqueous sodium thiosulfate (NaSO 3 aq.) and aqueous sodium hydroxide (NaCl aq.), respectively. The mixture was then dried over sodium sulfate (NaSO 4 ). The NaSO 4 was removed by filtration, and the filtrate was concentrated. The concentrated residue was washed by suspending it in CH2Cl2 (dichloromethane) three times and in a CH2Cl2 (dichloromethane) / MeOH (methanol) system twice to obtain 50.2 g of the compound represented by formula (I-1) as a colorless solid.

[0087] <Identification of the compound represented by formula (I-1)> 1 H-NMR(400MHz,DMSO-d6)δ:6.39(d,1H),6.52(s,1H),7.28(t,1H),7.41(m,2H),7.77(d,1H),7.87(d,1H),10.01(s,1H),10.23(s,1H) 13 C-NMR(100MHz,DMSO-d6)δ:103.6,103.7,108.8,121.2,121.7,124.1,126.3,135.1,139.0,154.3,160.6,162.3,173.2 mp:212.9℃

[0088] Example 2-1 <Preparation of Rubber Composition and Production of Vulcanized Rubber> (First mixing: Mixing by Labo Plastomill) Using a Labo Plastomill (Toyo Seiki Co., Ltd., capacity: 600 mL), 100 parts by mass of natural rubber (RSS#1) as a diene rubber, 45 parts by mass of HAF carbon black (Tokai Carbon Co., Ltd., trade name "Seat 3") as a filler, 10 parts by mass of silica (Tosoh Silica Corporation, trade name "Nipsil VN3") as a filler, 3 parts by mass of stearic acid as a processing aid, 5 parts by mass of zinc oxide as a vulcanization aid, 1 part by mass of N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine (6PPD) (Kawaguchi Chemical Industry Co., Ltd., trade name "ANTAGE6C") as an antioxidant, and 0.5 parts by mass of the compound represented by formula (I-1) of Example 1-1 were kneaded to obtain a kneaded mixture. The kneading time was 5 minutes after adding each component, and the mixer rotation speed was 50 rpm. The temperature of the kneaded mixture in the Labo Plastomill was 150-180°C.

[0089] (Second kneading: kneading by an open roll machine) The kneaded product obtained in the first kneading, containing 100 parts by mass of natural rubber, 2 parts by mass of powdered sulfur (manufactured by Hosoi Chemical Industry Co., Ltd., product name "Fine Powdered Sulfur 200 Mesh") as a vulcanizing agent, 1.5 parts by mass of N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) (manufactured by Kawaguchi Chemical Industry Co., Ltd., product name "ACCEL CZ") as a vulcanization accelerator, and hexamethoxymethylmelamine (HMMM) (manufactured by Tokyo Chemical Industry Co., Ltd.) as a curing agent, were kneaded in an open roll machine with the roll temperature set to 40°C to obtain a sheet-like rubber composition of Example 2-1.

[0090] (Vulcanization treatment) The rubber composition obtained in the second kneading was heat-treated at 145°C for 20 to 40 minutes to obtain the vulcanized rubber of Example 2-1.

[0091] Comparative Example 2-1 The rubber composition and vulcanized rubber of Comparative Example 2-1 were obtained in the same manner as in Example 2-1, except that the compound represented by formula (I-1) in Example 1-1 was changed to resorcinol and used in the amounts (parts by mass) shown in Table 1.

[0092] Reference example 2-1 A rubber composition and vulcanized rubber of Reference Example 2-1 were obtained in the same manner as in Example 2-1, except that the compound represented by formula (I-1) and HMMM of Example 1-1 were not used.

[0093] Example 2-2 The rubber composition and vulcanized rubber of Example 2-2 were obtained in the same manner as in Example 2-1, except that the amount (parts by mass) of the compound represented by formula (I-1) in Example 1-1 was changed to the amount (parts by mass) shown in Table 2.

[0094] Comparative Example 2-2 The rubber composition and vulcanized rubber of Comparative Example 2-2 were obtained in the same manner as in Example 2-1, except that the compound represented by formula (I-1) in Example 1-1 was changed to resorcinol and used in the amounts (parts by mass) shown in Table 2.

[0095] <Evaluation of vulcanized rubber>

[0096] The vulcanized rubbers of Example 2-1, Comparative Example 2-1, Reference Example 2-1, Example 2-2, and Comparative Example 2-2 were evaluated as follows.

[0097] (Hardness evaluation) The hardness of the vulcanized rubber of Example 2-1 was measured using a Type A durometer in accordance with JIS K6253-3:2012. The results are shown in Tables 1 and 2.

[0098] (Evaluation of tensile properties) The tensile strength (TS) and elongation at break (EB) of the vulcanized rubber of Example 2-1 were determined according to JIS K6251:2017. The results are shown in Tables 1 and 2.

[0099] (Evaluation of viscoelastic properties) In accordance with JIS K6394:2007, the tan δ of the vulcanized rubber of Example 2-1 at 60°C was measured under the following conditions using a viscoelasticity analyzer manufactured by Ueshima Seisakusho Co., Ltd. The results are shown in Tables 1 and 2. Table 1 shows the relative values ​​of tan δ of the vulcanized rubbers of Example 2-1 and Reference Example 2-1 when the tan δ of the vulcanized rubber of Comparative Example 2-1 is set to 100. Table 2 shows the relative values ​​of tan δ of the vulcanized rubber of Example 2-2 when the tan δ of the vulcanized rubber of Comparative Example 2-2 is set to 100. The smaller the tan δ value, the more improved the viscoelastic properties and the more excellent the low heat buildup (fuel economy).

[0100] [Table 1]

[0101] [Table 2]

[0102] As shown in Table 1, the vulcanized rubber of Example 2-1, which used the compound represented by formula (I), had similar rubber physical properties (hardness and tensile properties) to the vulcanized rubber of Comparative Example 2-1, and was superior in low heat buildup (viscoelastic properties) compared to the vulcanized rubber of Comparative Example 2-1. Similarly, as shown in Table 2, the vulcanized rubber of Example 2-2, which used the compound represented by formula (I), had similar rubber physical properties (hardness and tensile properties) to the vulcanized rubber of Comparative Example 2-2, and was superior in low heat buildup (viscoelastic properties) compared to the vulcanized rubber of Comparative Example 2-2. These results confirm that the compound of the present invention, when applied to a rubber composition, can impart excellent low heat buildup without significantly impairing the rubber's physical properties, and that the rubber composition of the present invention exhibits excellent low heat buildup while maintaining its rubber physical properties.

Claims

1. A compound represented by formula (I): 【Chemical 1】 [In formula (I), R １ and R ２ each independently represents a hydrogen atom or a group represented by formula (A). R ３ represents a hydrogen atom, a group represented by formula (A), or a group represented by formula (B). R ４ and R ５ each independently represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkanoyl group having 1 to 18 carbon atoms, or a benzoyl group. However, R １ , R ２ , and R ３ At least one of R is a group represented by formula (A), ３ is a group represented by formula (B), R １ , R ２ , R ６ , and R ７ At least one of the groups is a group represented by formula (A). 【Chemistry 2】 (In formula (A), * represents a bonding position.) 【Chemistry 3】 (In formula (B), R ６ and R ７ each independently represents a hydrogen atom or a group represented by formula (A). R ８ and R ９ each independently represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkanoyl group having 1 to 18 carbon atoms, or a benzoyl group. R １０ and R １１ each independently represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a phenyl group. * indicates the bond position.)

2. A rubber composition comprising the compound according to claim 1, a diene rubber, and a filler.

3. The rubber composition of claim 2 further comprising a vulcanizing agent.

4. A vulcanized rubber obtained by vulcanizing the rubber composition according to claim 2 or 3.

5. A tire comprising a rubber component comprising the vulcanized rubber according to claim 4.

6. A rubber additive comprising the compound of claim 1.

7. The rubber additive according to claim 6, which is a heat-reducing agent.

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