Steel cord-rubber composite and tire

Abstract

To provide a steel cord-rubber composite excellent in adhesion between rubber and steel cord.SOLUTION: A rubber composition includes a rubber component, and an antioxidant represented by the general formula (1) in the figure, where the solid-and-dashed double line is a single bond or a double bond, R11 and R12 each independently represent hydrogen, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a phenyl group, and R13, R14, R15, R16, R17, R18, and R19 each independently represent hydrogen or an alkyl group having 1 to 12 carbon atoms.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a steel cord-rubber composite and a tire. [Background technology]

[0002] In rubber articles that require particular strength, such as automobile tires and hoses, steel cord-rubber composites, in which a metal reinforcing material such as a steel cord is coated with a coating rubber, are used to reinforce the rubber and improve its strength and durability. Here, in order for such steel cord-rubber composites to exert a high reinforcing effect and ensure reliability, stable and strong adhesion between the coating rubber and the metal reinforcing material is required.

[0003] To obtain a steel cord-rubber composite that exhibits such high adhesion between the coated rubber and the metal reinforcing material, a method known as direct vulcanization adhesion is widely used, in which a metal reinforcing material such as a steel cord plated with zinc, brass, or the like is embedded in a coated rubber containing sulfur, and the two are bonded together during heat vulcanization. Various studies have been conducted on direct vulcanization adhesion to further improve the adhesion between the coated rubber and the metal reinforcing material achieved by this direct vulcanization adhesion.

[0004] For example, Patent Document 1 discloses a method for producing a steel cord for reinforcing a steel cord-rubber composite, which is formed by twisting together a plurality of filaments produced by wet drawing a brass-plated steel wire. The method includes adding resorcinol to a wet lubricant used during steel wire drawing as an adhesion improver between the steel cord and the coating rubber, thereby causing the resorcinol to adhere to the surface of the filaments. Furthermore, Patent Document 2 discloses a technology for improving adhesion to the coating rubber by washing the surfaces of the steel wires and steel cords used with an acidic or alkaline solution to remove phosphorus compounds (derived from the lubricant used in the production of the steel cords), which act as adhesion reaction inhibitors.

[0005] However, with the technology of Patent Document 1, the resorcinol may be altered due to heat generated during steel filament drawing. In such cases, the resorcinol cannot be expected to have a sufficient effect as an adhesion improver between the steel cord and the coating rubber, and therefore further improvement was necessary. Furthermore, the technology of Patent Document 2 does not specifically disclose the amount of phosphorus compounds reduced on the surface of the steel cord after cleaning treatment, the ratio of copper to zinc, or other compositions, and more detailed studies from these perspectives have been desired.

[0006] Furthermore, in order to improve the initial adhesion between the coated rubber and the metal reinforcing material in the direct vulcanization adhesion generally used in tires and the like, a rubber composition is employed in which a cobalt salt, which acts as an adhesion promoter, is compounded in the coated rubber. However, from the viewpoint of improving the durability of the coated rubber against deterioration and crack growth, it is desirable to reduce the amount of such cobalt salt as much as possible. Therefore, Patent Document 3 discloses a steel cord in which specific metals (phosphorus, zinc, and metals with an ionization tendency lower than zinc and higher than copper) are controlled to be present at specific ratios on the outermost surface of the plating layer, with the aim of improving the initial adhesion and heat-resistant adhesion between the steel cord and rubber. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-66298 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-234371 [Patent Document 3] International Publication No. 2011 / 30547 Summary of the Invention [Problem to be solved by the invention]

[0008] According to the technology of Patent Document 2, good adhesion between rubber and steel cord can be obtained even when the amount of adhesion promoter such as cobalt is reduced or not added at all. However, with the advancement of performance in rubber articles such as tires, it is believed that the requirements for the adhesion between rubber and steel cords will become increasingly strict. For example, the performance required for adhesion between steel cords and coated rubber must not only be initial adhesion, but also satisfy various conditions, such as preventing failures due to deterioration of the adhesive interface when the tire is exposed to a deteriorating environment during actual use, preventing problems in the tire manufacturing process, and reducing compounding costs. Furthermore, from the viewpoint of the burden on the environment, it is desirable to reduce the amount of cobalt contained in the rubber and the steel cord as much as possible, and there has been a demand for the development of a technology that provides excellent adhesion between the rubber and the steel cord even when no cobalt is used or when the amount of cobalt used is small.

[0009] Therefore, an object of the present invention is to provide a steel cord-rubber composite that has excellent adhesion between the rubber and the steel cord even when the amount of cobalt used is small. Another object of the present invention is to provide a tire in which the durability of the components using the steel cord is excellent. [Means for solving the problem]

[0010] The gist and configuration of the present invention to solve the above problems is as follows. The steel cord-rubber composite of the present invention is a steel cord-rubber composite obtained by coating a steel cord having one or more steel wires with a rubber composition, The rubber composition comprises a rubber component and a compound represented by the following general formula (1): [ka] is a single or double bond, and R 11 and R 12 are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a phenyl group, and R13 , R 14 , R 15 , R 16 , R 17 , R 18 and R 19 are each independently hydrogen or an alkyl group having 1 to 12 carbon atoms.], and an aminoquinoline antioxidant represented by the following formula: With the above-mentioned structure, even when the amount of cobalt used is small, excellent adhesion between the rubber and the steel cord can be achieved.

[0011] In the steel cord-rubber composite of the present invention, the steel wire has, on its outermost surface, a brass plating layer containing 0.3 to 1.7 atomic % of phosphorus, 2.5 to 14 atomic % of zinc, and 0.01 to 2.0 atomic % of a metal having an ionization tendency smaller than that of zinc and larger than that of copper, as measured by XPS (X-ray photoelectron spectroscopy), It is preferable that the following formulas (I) and (II) are satisfied. 0.3≦A / (A+B)≦0.6 (I) 0.06≦(A / (A+B)) / C≦6 (II) A: The zinc content (atomic %) of the outermost surface of the brass plating layer measured by the XPS method B: The copper content (atomic %) at the outermost surface of the brass plating layer measured by the XPS method C: Content of the aminoquinoline-based inhibitor in the rubber composition (parts by mass per 100 parts by mass of the rubber component) This allows for better adhesion between the rubber and the steel cord.

[0012] In the steel cord-rubber composite of the present invention, the rubber component preferably contains at least one rubber selected from the group consisting of isoprene skeleton rubber, styrene-butadiene rubber, butadiene rubber, and chloroprene rubber, because this makes it possible to further improve the adhesion between the rubber and the steel cord while maintaining good durability.

[0013] Furthermore, in the steel cord-rubber composite of the present invention, the aminoquinoline-based antioxidant is represented by the following general formula (1-1): [ka] The compound represented by the formula (I) is preferred because it can further improve the adhesion between the rubber and the steel cord.

[0014] Furthermore, in the steel cord-rubber composite of the present invention, the content of the aminoquinoline antioxidant in the rubber composition is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component, because this can further improve the adhesion between the rubber and the steel cord while maintaining good durability.

[0015] In the steel cord-rubber composite of the present invention, it is preferable that the rubber composition does not contain a cobalt compound, because this can further reduce the burden on the environment.

[0016] In the steel cord-rubber composite of the present invention, it is preferable that the steel cord has one or more steel filaments on which a plating layer containing copper, zinc, and cobalt is formed, and satisfies the following formulas (L) and (M): A≧40 (L) 8≦A / B≦700 (M) A: The rubber and the plating layer are bonded together, and the layer of the plating layer in which a copper and sulfur compound is present is defined as the adhesive layer. The sulfur content of the adhesive layer is analyzed from the plating layer toward the rubber in a direction perpendicular to the longitudinal direction of the steel filament. The position of the inflection point where the sulfur content increases is defined as the bottom of the adhesive layer. The atomic % of cobalt is analyzed at six equally spaced points in the longitudinal direction of the steel filament, 100 nm inward from the bottom of the adhesive layer in a direction perpendicular to the longitudinal direction of the steel filament. The portion where the atomic % of cobalt is higher than the atomic % of cobalt in the entire plating layer is defined as the cobalt-rich region (nm), and the ratio (%) of the total atomic % of the cobalt-rich regions (nm) at the six points to the total analysis range (600 nm) of the six points B: Content of the aminoquinoline antioxidant in the rubber composition (parts by mass per 100 parts by mass of the rubber component) This is because the adhesiveness between the rubber and the steel cord can be further improved.

[0017] Furthermore, in the steel cord-rubber composite of the present invention, the steel cord has one or more steel wires on which a plating layer is formed, the steel wire has a phosphorus content of 1.5 atomic % or less contained as an oxide in a wire surface layer region extending from the surface of the plating layer to a depth of 5 nm inward in the radial direction of the wire, The ratio (A / B) of the content of phosphorus (A (atomic %)) contained as an oxide in the wire surface region of the steel wire from the surface of the plating layer to a depth of 5 nm inward in the wire radial direction to the content (B (parts by mass)) of the aminoquinoline antioxidant in the rubber composition per 100 parts by mass of the rubber component is preferably 0.02 to 15. This is because the adhesion between the rubber and the steel cord can be further improved.

[0018] Furthermore, in the steel cord-rubber composite of the present invention, the rubber composition contains N-cyclohexyl-2-benzothiazolyl sulfenamide, a ratio (a / b) of a modulus (a) at 50% elongation of the rubber composition after vulcanization to a modulus (b) at 50% elongation of the vulcanized rubber covering the reinforcing material at the tire width direction end portions of the reinforcing layer is 0.94 or more and 1.06 or less, The steel cord is preferably ternary plated with copper, zinc, and iron, because this can further improve the adhesion between the rubber and the steel cord.

[0019] The rubber composition further comprises 0.01 parts by mass or more, per 100 parts by mass of the rubber component, of a rubber-metal adhesion promoter containing at least one selected from the group consisting of a carboxylic acid metal salt having 2 to 25 carbon atoms and a metal species selected from the group consisting of bismuth, copper, antimony, silver, niobium, and zirconium, and a compound represented by the following formula (A): and 4,4'-diphenylmethane bismaleimide. [ka] [In formula (A), Z is a structure selected from formulas (z-1) to (z-4). M is bismuth, copper, antimony, silver, niobium, or zirconium. (RCOO) is a residue of an aliphatic carboxylic acid having 2 to 25 carbon atoms. x is an integer equal to (the valence of M - 1).] This is because it can improve the durability of vulcanized rubber and the heat-degradation adhesion between rubber and metal.

[0020] Furthermore, in the steel cord-rubber composite of the present invention, the rubber composition comprises a nitrogen-containing cyclic compound that does not contain a benzene ring or a mercapto group, and The following general formula (1): [ka] [In the formula, R 1 and R 2 each independently represents a monovalent saturated hydrocarbon group; and The mass ratio (A / B) of the content (A) of the nitrogen-containing cyclic compound that does not contain a benzene ring or a mercapto group to the content (B) of the amine-based antiaging agent is preferably 0.004 to 100. This is because excellent adhesion can be achieved even when exposed to a deteriorating environment.

[0021] The tire of the present invention is characterized by comprising the above-mentioned steel cord-rubber composite of the present invention. With the above-mentioned configuration, excellent durability of the steel cord member can be achieved. [Effects of the Invention]

[0022] According to the present invention, even when the amount of cobalt used is small, a steel cord-rubber composite having excellent adhesion between the rubber and the steel cord can be provided. Furthermore, according to the present invention, a tire having excellent durability of components using the steel cord can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0023] The steel cord-rubber composite and tire of the present invention will be described in detail below based on embodiments thereof.

[0024] <Definition> The compounds described herein may be derived in part or in whole from fossil sources, biological sources such as plant sources, recycled sources such as used tires, or a mixture of two or more of fossil, biological, and recycled sources.

[0025] In this specification, the "proportion of sustainable materials" refers to the total mass proportion of materials derived from biological resources (biomass resources) and materials derived from renewable resources (recycled resources) in the rubber composition, steel cord-rubber composite, and tire in question.

[0026] In this specification, the term "biological resources (biomass resources)" refers to carbon-neutral organic resources derived from living organisms, and includes, for example, materials stored in the form of starch or cellulose, the bodies of animals that grow by eating plants, and products obtained by processing plants or animals, and is a resource excluding fossil resources (petroleum, coal, natural gas, etc.). Such biological resources may be edible or non-edible, but are preferably non-edible from the viewpoint of not competing with food and of effective resource utilization.

[0027] Specific examples of the biological resources include cellulosic crops (pulp, kenaf, wheat straw, rice straw, waste paper, papermaking residues, etc.), wood, charcoal, compost, food waste, vegetable oil residues, fishery residues, livestock excrement, food waste, wastewater sludge, natural rubber, cotton, oils and fats (palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, etc.), and the like. Examples of biological resources include: corn oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, coconut oil, etc.), carbohydrate crops (corn, wheat, rice, rice husks, rice bran, used rice, potatoes, buckwheat, cassava, sago palm, sugarcane, etc.), bagasse (i.e., the residue left after sugarcane juicing), soybeans, soybean pulp refuse, essential oils (pine oil, orange oil, eucalyptus oil, etc.), pulp black liquor, and algae. The biological resources may also be processed (i.e., biological resource-derived substances). Examples of processing methods include biological processing methods utilizing the activity of microorganisms, plants, animals, and their tissue cultures; chemical processing methods utilizing acids, alkalis, catalysts, thermal energy, light energy, etc.; and physical processing methods such as pulverization, compression, microwave treatment, and electromagnetic wave treatment. Furthermore, the biological resources may also be extracted and purified from the biological resources or biological resources that have undergone the above-described processing (i.e., biological resource-derived substances). For example, sugars, proteins, amino acids, fatty acids, fatty acid esters, etc., purified from the above-mentioned biological resources can also be used. Examples of the sugars include sucrose, glucose, trehalose, fructose, lactose, galactose, xylose, allose, talose, gulose, altrose, mannose, idose, arabinose, apiose, maltose, cellulose, starch, chitin, etc., derived from biological resources. Examples of the proteins include compounds derived from biological resources and formed by linking amino acids (preferably L-amino acids), including oligopeptides such as dipeptides. Examples of the amino acids include valine, leucine, isoleucine, arginine, lysine, asparagine, glutamine, phenylalanine, etc., derived from biological resources, with valine, leucine, isoleucine, arginine, and phenylalanine being preferred.The amino acids may be either L-amino acids or D-amino acids, but L-amino acids are preferred from the viewpoints of abundance in nature and ease of availability. Examples of the fatty acids include butyric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc., which are derived from biological resources. Examples of the fatty acid esters include modified products of vegetable oils, animal oils, and fats and oils derived from biological resources. These biological resources may contain various materials and impurities.

[0028] In this specification, the term "recycled resources" refers to resources obtained by regenerating (recycling) products that have been used once, or that have been collected without being used, or that have been discarded. For example, recycled resources include resources obtained by regenerating (recycling) used rubber products such as used tires.

[0029] <Steel cord-rubber composite> The steel cord-rubber composite of the present invention is a steel cord-rubber composite obtained by coating a steel cord having one or more steel wires (steel filaments) on which a plating layer is formed with a rubber composition.

[0030] (Steel cord) Brass-plated steel cord The steel wires constituting the steel cord preferably have a brass plating layer on the outermost surface, which contains 0.3 to 1.7 atomic % of phosphorus, 2.5 to 14 atomic % of zinc, and 0.01 to 2.0 atomic % of a metal whose ionization tendency is smaller than that of zinc and larger than that of copper, as measured by XPS (X-ray photoelectron spectroscopy).

[0031] Here, the outermost surface of the steel wire means a region whose depth from the surface of the steel wire is measured by XPS (X-ray photoelectron spectroscopy), and more specifically, means a thickness of about several nm corresponding to the depth of photoelectrons emitted when X-rays are irradiated onto the surface of a steel wire having a brass plating layer.

[0032] When the outermost surface of the steel wire is measured by the XPS method, it is preferable that the outermost surface contains phosphorus in an amount of 0.3 to 1.7 atomic %, preferably 0.4 to 1.6 atomic %, and more preferably 0.5 to 1.5 atomic %. If the phosphorus content is less than 0.3 atomic %, the activity of the steel cord may be high, making it more susceptible to improper handling, such as storage, and the conditions for compounding with rubber may become narrower. If the phosphorus content exceeds 1.7 atomic %, the initial adhesion rate between the brass-plated steel cord and the coated rubber may decrease.

[0033] The outermost surface of the steel wire preferably contains zinc in an amount of 2.5 to 14 atomic %, more preferably 4.95 to 13.5 atomic %, and even more preferably 5.0 to 13 atomic %. If the zinc content is less than 2.5 atomic %, the adhesive durability of the resulting steel cord-rubber composite may be insufficient, and if it exceeds 14 atomic %, the initial adhesive speed between the steel cord and the coating rubber may decrease.

[0034] Furthermore, the outermost surface of the steel wire preferably contains a metal having an ionization tendency lower than that of zinc and higher than that of copper in an amount of 0.01 to 2.0 atomic %, preferably 0.02 to 1.5 atomic %, and more preferably 0.05 to 1.0 atomic %. If the metal content is less than 0.01 atomic %, there is a risk that the adhesion to the coating rubber will decrease, and if it exceeds 2.0 atomic %, there is a similar risk. Examples of metals with an ionization tendency lower than that of zinc but higher than that of copper include chromium (Cr), iron (Fe), cadmium (Cd), cobalt (Co), nickel (Ni), tin (Sn), and lead (Pb). Cobalt is particularly preferred. Cobalt is typically incorporated into many coating rubbers as an adhesion promoter to further improve adhesion. However, depending on the amount of cobalt contained in the coating rubber, this can potentially reduce the durability of the coating rubber against heat, moisture, and oxidation. However, the inclusion of cobalt in brass-plated steel cords can reduce the cobalt content in the coating rubber, effectively preventing deterioration in rubber properties and reducing costs.

[0035] In the steel cord-rubber composite of the present invention, it is preferable that the steel wires satisfy the following formula (I). 0.3≦A / (A+B)≦0.6 (I) Here, "A" indicates the zinc content (atomic %) at the outermost surface of the brass plating layer as measured by the XPS method, and "B" indicates the copper content (atomic %) at the outermost surface of the brass plating layer as measured by the XPS method. When the ratio (A / (A+B)) of the zinc content to the total content of the zinc and copper on the outermost surface (the brass-plated surface) of the steel wire satisfies the above range, the adhesion between the rubber and the steel cord can be improved. From the same viewpoint, the ratio (A / (A+B)) is more preferably 0.35 to 0.6.

[0036] The steel cord can be produced, for example, by the following method. The peripheral surface of the steel wire is brass-plated and then drawn. The plating composition is usually 70% by mass or less, preferably 60 to 65% by mass, of copper, and 30% by mass or more, preferably 35 to 40% by mass, of zinc. The surface of the obtained steel wire may be immersed in an aqueous solution containing, as a metal salt, a metal with an ionization tendency smaller than that of zinc and larger than that of copper, and then multiple steel wires may be twisted together. Alternatively, multiple steel wires may be twisted together to form a steel cord, and the surface of the steel cord may be immersed in an aqueous solution containing the metal salt.

[0037] Such metal salts are not particularly limited as long as they exhibit high solubility in water, and examples thereof include metal chlorides, metal carbonates, metal nitrates, metal sulfates, metal acetates, metal citrates, metal gluconates, metal acetylacetonates, etc. Among these, metal acetates are preferred in order to achieve a suitable pH value in an aqueous solution containing the metal salt, as described below.

[0038] The aqueous solution containing the metal salt has a concentration of typically 0.001 to 1 mol / L, preferably 0.005 to 0.5 mol / L, and more preferably 0.01 to 0.2 mol / L, and a pH of typically 5.7 to 7.6, preferably 5.9 to 7.1. An aqueous solution containing a metal salt with a concentration and pH value within the above ranges does not adversely affect the brass plating, and allows phosphorus, zinc, and metals with an ionization tendency lower than that of zinc but higher than that of copper to be present in predetermined amounts on the outermost surface of the steel cord. Furthermore, such a pH value is also suitable from the viewpoints of environmental considerations and safety during production.

[0039] The time for immersing the steel cord in the aqueous solution containing the metal salt may be set appropriately, but is usually 0.05 to 30 seconds, preferably 0.1 to 20 seconds.

[0040] Such an immersion treatment cleans the surface of the steel wire or steel cord, and adequately removes components (ZnO, phosphorus compounds, etc.) that are said to inhibit adhesion to the coating rubber formed from the rubber composition for coating a steel cord of the present invention, thereby further improving the initial adhesion between the steel cord and the coating rubber.

[0041] The average thickness of the brass plating layer is not particularly limited, but is preferably 0.13 to 0.30 μm. If the average thickness of the brass plating layer is less than 0.13 μm, the exposed iron base increases, hindering initial adhesion. On the other hand, if the average thickness exceeds 0.30 μm, the heat generated during use of the rubber article may cause the adhesion reaction to proceed excessively, resulting in weak adhesion.

[0042] It is also preferable that the steel cord has one or more steel filaments on which a plating layer containing copper, zinc, and cobalt is formed, and satisfies the following formulas (L) and (M). A≧40 (L) 8≦A / B≦700 (M) L: The rubber and the plating layer are bonded together, and the layer of the plating layer in which a copper and sulfur compound is present is defined as the adhesive layer. The sulfur content of the adhesive layer is analyzed from the plating layer toward the rubber in a direction perpendicular to the longitudinal direction of the steel filament. The position of the inflection point where the sulfur content increases is defined as the bottom of the adhesive layer. The atomic % of cobalt is analyzed at six equally spaced points in the longitudinal direction of the steel filament, 100 nm inward from the bottom of the adhesive layer in a direction perpendicular to the longitudinal direction of the steel filament. The portion where the atomic % of cobalt is higher than the atomic % of cobalt in the entire plating layer is defined as the cobalt-rich region (nm), and the ratio (%) of the total atomic % of the cobalt-rich regions (nm) at the six points to the total analysis range (600 nm) of the six points B: Content of aminoquinoline antioxidant in the rubber composition described below (parts by mass per 100 parts by mass of the rubber component)

[0043] The sulfur content of the adhesive layer is analyzed in a direction perpendicular to the longitudinal direction of the steel filament 2, from the inside of the plating layer 3 toward the rubber 1. The position of the inflection point where the sulfur content increases is designated as the bottommost part 4 of the adhesive layer, and the atomic % of cobalt is analyzed at six equally spaced points in the longitudinal direction of the steel filament 2, extending 100 nm from the bottommost part 4 of the adhesive layer inward in a direction perpendicular to the longitudinal direction of the steel filament 2. Here, when the portion with a higher atomic % of cobalt than the atomic % of cobalt in the entire plating layer is designated as the cobalt-rich region (nm), in the steel cord-rubber composite of the present invention, the total size (nm) of the six cobalt-rich regions is 40% or more of the total size (nm) of the six analysis ranges. That is, it is preferable that the total distance of the cobalt-rich region is 240 nm or more relative to the total distance of 600 nm over which the atomic percentage of cobalt is measured.

[0044] In this way, since the steel cord-rubber composite of the present invention satisfies the above formula (I), it can be said that a cobalt-rich region is formed in the adhesive layer between the rubber 1 and the steel filament 2, and therefore the adhesion between the rubber and the steel cord can be favorably improved. To obtain these effects effectively, the cobalt-rich region is preferably 60% or more (A≧60). Furthermore, in the steel cord-rubber composite of the present invention, a small amount of organic cobalt salt can be added to the rubber as a cobalt atom source, but addition is not necessary. This prevents rubber deterioration and reduces the burden on the environment, and also eliminates the need to extend the rubber mixing time, preventing a deterioration in productivity. Furthermore, from the viewpoint of reducing the amount of cobalt used, the cobalt-rich region is preferably 70% or less (A≦70).

[0045] The cobalt-rich region can be formed by severely deforming only the extreme surface of the ternary plating layer of a steel filament having the ternary plating layer. The extreme surface of the ternary plating layer can be severely deformed, for example, by wiredrawing using a die. When lubricity is reduced by wiredrawing, if the steel filament material comes into contact with the die directly or through an incomplete coating, the extreme surface of the ternary plating layer is disturbed, resulting in finer crystals and a change in the distribution of cobalt in the ternary plating layer. As a result, a cobalt-rich region is formed on the surface of the ternary plating layer.

[0046] For example, to perform wiredrawing under conditions of reduced lubricity by wet wiredrawing using a liquid lubricant, the lubricating component concentration in the lubricant is reduced below that used for normal wiredrawing, or the lubricant temperature is reduced below the recommended lubricant temperature. The degree to which the lubricant is reduced during wiredrawing depends on the strength and diameter of the steel filament being produced. For example, to reduce the lubricating component concentration, the lubricant concentration should be 80% to 20% of the lubricant concentration normally used in steel filament wiredrawing. Reducing the lubricant concentration too much can result in the ternary plating layer shedding, deterioration of the steel filament quality, or wire breakage and die wear. Conversely, if the lubricity is not reduced enough, the proportion of cobalt-rich regions will decrease, preventing sufficient improvement in adhesion between the rubber and the steel cord.

[0047] Furthermore, if the heat generation during the wiredrawing process is too large, the lattice defect density of the ternary plating layer may decrease due to the temperature rise, and the ductility of the steel filament may deteriorate. Therefore, it is preferable to set wiredrawing conditions that reduce heat generation, such as those in the following (1) to (5), and to set the wire drawing temperature from the die to 150°C or less when measured with a contact thermometer. (1) Set the reduction rate per die to a low value. (2) Set the wire drawing speed to a low level. (3) Cool the die to prevent temperature rise. (4) Steel filament material entering the die and / or steel filament material exiting the die Cool the filament. (5) In the continuous wire drawing process using multiple dies, the three dies located at the most downstream At least one of the dies must have a coefficient of friction of 0.18 or higher.

[0048] In this case, in order to form the cobalt-rich region, it is better to make the thickness of the ternary plating layer thicker. Furthermore, when manufacturing by wet continuous wiredrawing, if wiredrawing in the finishing die or in several dies downstream of the wiredrawing including the finishing die is performed under conditions of somewhat reduced lubrication as described above, and other dies are performed under good lubrication conditions, it is possible to reliably manufacture a ternary plating layer that is crystalline inside and has a cobalt-rich region formed on the surface.

[0049] The ternary plating layer formed on the surface of the steel filaments constituting the steel cord is not particularly limited and can be formed by known methods. For example, the steel filament material before wire drawing can be plated with copper, cobalt, and zinc in this order, or with copper, zinc, and cobalt in this order, or with an alloy of copper and zinc and cobalt in this order, and then the ternary plating layer can be formed by thermal diffusion, for example, by heat treatment at a temperature of 500 to 650°C for 5 to 25 seconds. In the steel cord-rubber composite of the present invention, the composition of the ternary plating layer as a whole is not particularly limited, but the copper content may be, for example, 64 to 69 atomic % and the cobalt content may be 1 to 10 atomic %.

[0050] The average thickness of the ternary plating layer is preferably 0.13 to 0.35 μm, more preferably 0.13 to 0.32 μm, and particularly preferably 0.13 to 0.30 μm. If the average thickness of the ternary plating layer is 0.13 μm or more, the exposed iron base is reduced, improving the initial adhesion, while if it is 0.35 μm or less, excessive progress of the adhesion reaction due to heat during use of the rubber article is suppressed, resulting in stronger adhesion.

[0051] Furthermore, it is also preferable that the steel cord has one or more steel wires on which a plating layer is formed, and that the steel wire has a phosphorus content of 1.5 atomic % or less in a wire surface region extending from the surface of the plating layer to a depth of 5 nm inward in the wire radial direction, as an oxide, and that the ratio (A / B) of the phosphorus content (A (atomic %)) in the steel wire in a wire surface region extending from the surface of the plating layer to a depth of 5 nm inward in the wire radial direction to the content (B (parts by mass)) of an aminoquinoline antioxidant represented by general formula (1) described below in the rubber composition per 100 parts by mass of the rubber component is 0.02 to 15. In this case, examples of the types of plating include zinc (Zn) plating, copper (Cu) plating, tin (Sn) plating, brass (copper-zinc (Cu-Zn)) plating, bronze (copper-tin (Cu-Sn)) plating, and ternary plating containing copper, zinc, and cobalt. Among these, brass and ternary plating containing copper, zinc, and cobalt are preferred.

[0052] By setting the phosphorus content at 1.5 atomic % or less, it becomes possible to stably obtain excellent adhesion between the rubber and the steel cord regardless of the moisture content in the rubber. If the phosphorus content in the wire surface layer region increases beyond 1.5 atomic %, the adhesion speed with the rubber will decrease accordingly, and sufficient adhesion may not be obtained. The lower limit of the phosphorus content in the wire surface region is not particularly limited, but can be set to 0.1 atomic % or more.

[0053] Here, the quantitative determination of phosphorus in the wire surface region of the plating layer was carried out using X-ray photoelectron spectroscopy by measuring the number of atoms present in the wire surface region of the plating layer, i.e., C, Cu, Zn, O, P, and N atoms, in an analysis area of ​​20 to 30 μmφ so as not to be affected by the curvature of the wire, and the phosphorus content was calculated as the ratio of the number of P atoms when the total number of C, Cu, Zn, O, P, and N atoms was taken as 100. The number of atoms of each atom was C:C 1S , O:O 1S , P:P2P , Cu:Cu 2p3 / 2 , Zn:Zn 2p3 / 2 and N:N 1S The number of photoelectrons counted was calculated by correcting the number with the respective sensitivity coefficients. For example, the number of detected phosphorus atoms [P] can be calculated using the following formula: [P]=Fp(P 2p Sensitivity coefficient) × (P per certain time 2p Photoelectron counts)

[0054] The number of detected atoms for other atoms can be calculated in the same way, and the results can be calculated using the following formula: P (atomic %) = {[P] / ([Cu] + [Zn] + [C] + [O] + [N] + [P])} × 100 The relative atomic percentage of phosphorus can be determined according to the above formula. Furthermore, the element distribution in the depth direction from the peripheral surface to the inside in the radial direction of the wire can also be measured in detail by performing argon etching or the like.

[0055] If the surface of the wire before the analysis is covered with oil or contaminated with organic matter, the wire surface is washed with an appropriate solvent to ensure accurate analysis.

[0056] In order to keep the amount of phosphorus contained as oxide in the wire surface region to 1.5 atomic % or less, the amount of phosphorus is appropriately adjusted by adjusting, either alone or in appropriate combination, the wiredrawing pass schedule, the shape and angle of the die entrance and approach, the die material, and the lubricant composition, etc. In particular, it is extremely effective to use a lubricant containing an extreme-pressure additive in the final wiredrawing step as usual, and to apply dies made of a material that combines excellent self-lubricating properties and machinability, such as sintered diamond dies, in the final pass or several subsequent passes including the final pass out of the approximately 20 passes in the final wiredrawing step.

[0057] Furthermore, the average thickness of the plating layer is not particularly limited, but is preferably 0.13 to 0.30 μm. If the average thickness of the plating layer is less than 0.13 μm, the exposed iron base increases, hindering initial adhesion, while if it exceeds 0.30 μm, the heat generated during use of the rubber article may cause the adhesion reaction to proceed excessively, resulting in weak adhesion.

[0058] Furthermore, when the plating layer is a ternary plating layer containing copper, zinc, and cobalt, it is preferable that the ratio of copper to the total amount of copper and zinc in the entire plating layer is 60 to 70 wt %, and that the ratio of copper to the total amount of copper and zinc in the wire surface layer region is 15 to 45 atomic %. If the ratio of copper to the total amount of copper and zinc in the entire plating layer is less than 60 wt %, wire drawability will deteriorate, wire breakage will occur, productivity will be hindered, and mass production will become difficult. In addition, it will be difficult to control the copper content in the wire surface layer region to 15 atomic % or more, as described below. On the other hand, if the ratio exceeds 70 wt %, heat-resistant adhesion and moisture-resistant adhesion will decrease, making it impossible to maintain sufficient durability in the environment to which the tire will be exposed, and it will be difficult to control the copper content in the wire surface layer region to 45 atomic % or less, as described below. Furthermore, if the ratio of copper to the total amount of copper and zinc in the wire surface layer region is less than 15 atomic %, the adhesive reaction with rubber will be poor, making it difficult to ensure better rubber adhesion, even if the amount of phosphorus in the wire surface layer region is limited to the above-mentioned 1.5 atomic % or less. On the other hand, if it exceeds 45 atomic %, there is a risk of suffering from the disadvantage of reduced heat-resistant adhesion and moisture-resistant adhesion.

[0059] The diameter of the steel wire is preferably 0.40 mm or less. If the diameter exceeds 0.40 mm, the surface strain increases when the rubber article used therein is repeatedly subjected to strain under bending deformation, which may easily cause buckling.

[0060] (Rubber composition) The steel cord-rubber composite of the present invention further includes a rubber composition that coats the steel cord, and the rubber composition includes a rubber component and an aminoquinoline-based antioxidant.

[0061] Anti-aging agent The aminoquinoline antioxidant contained in the rubber composition is represented by the following general formula (1). [ka] is a single or double bond, and R 11 and R 12 are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a phenyl group, and R 13 , R 14 , R 15 , R 16 , R 17 , R 18 and R 19 are each independently hydrogen or an alkyl group having 1 to 12 carbon atoms. By containing an aminoquinoline antioxidant represented by the following formula, deterioration of the adhesive surface between the rubber and the steel cord can be suppressed, and excellent adhesiveness can be maintained for a long period of time.

[0062] The aminoquinoline antioxidant represented by the above general formula (1) is effective in that it does not contain a phenylenediamine moiety, unlike N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD), and therefore has a low environmental impact. In addition, the aminoquinoline antioxidant represented by general formula (1) also has the effect of improving the ozone resistance of the rubber composition and suppressing a decrease in the retention rate of elongation at break (EB) and tensile strength (TB) after aging.

[0063] In the above general formula (1), TIFF2025169652000006.tif13165 is a single bond or a double bond, preferably a double bond; R 11 and R 12 are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a phenyl group, and are preferably a hydrogen atom or a phenyl group; R 13 , R14 , R 15 , R 16 , R 17 , R 18 and R 19 are each independently hydrogen or an alkyl group having 1 to 12 carbon atoms, and are preferably hydrogen or a methyl group. R in the above general formula (1) 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 and R 19 With regard to the above, the alkyl group having 1 to 12 carbon atoms may be linear or branched. Examples of the alkyl group having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, and various decyl groups. The number of carbon atoms in the alkyl group is preferably in the range of 1 to 8, more preferably 1 to 6, even more preferably 1 to 4, and particularly preferably 1 to 3. R in the above general formula (1) 11 and R 12 With regard to the above, examples of the cycloalkyl group having 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a 1-methylcyclopentyl group, a 2-methylcyclopentyl group, and a 3-methylcyclopentyl group.

[0064] In the above general formula (1), R' is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aromatic group. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,3-dimethylbutyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, various hexyl groups, and the like. Of these, an isopropyl group is preferred. The aromatic group preferably has 3 to 10 carbon atoms, more preferably 3 to 6. Examples of the aromatic group as a substituent on the alkyl group include aromatic hydrocarbon groups such as phenyl, tolyl, xylyl, mesityl, duryl, biphenyl, terphenyl, and naphthyl groups, and aromatic heterocyclic groups such as furyl, thienyl, pyridyl, pyrrolyl, quinolyl, benzofuranyl, and benzothienyl groups, and among these, phenyl and furyl groups (for example, 2-furyl groups) are preferred.

[0065] Specific examples of the aminoquinoline antioxidant represented by the general formula (1) include compounds represented by the following structural formulas (1-1) to (1-47). [ka] [ka]

[0066] Furthermore, among the compounds represented by general formulas (1-1) to (1-47), it is preferable to use the compound represented by general formula (1-1) as the aminoquinoline antioxidant, since this allows for better adhesion to be maintained for a long period of time.

[0067] The method for producing the aminoquinoline antioxidant represented by the general formula (1) is not particularly limited. For example, when an aromatic amine compound is used as a starting material, (i) reacting an aromatic amine compound with sodium nitrite in the presence of an acid to produce an aromatic amine compound having a nitroso group; (ii) reducing the generated nitroso group with sodium borohydride or the like to generate an aromatic diamine compound; (iii) The resulting aromatic diamine compound is reacted with a ketone compound such as acetone to form a condensed ring, A compound having a 6-amino-1,2-dihydroquinoline skeleton, that is, a compound represented by the above general formula (1), Compounds can be prepared in which TIFF2025169652000009.tif11154 is a double bond. Also, if desired, (iv) The compound having a 6-amino-1,2-dihydroquinoline skeleton thus produced is reduced with hydrogen in the presence of a palladium-supported carbon catalyst to produce a compound having a 6-amino-1,2,3,4-tetrahydroquinoline skeleton, i.e., a compound represented by the above general formula (1), It is also possible to prepare compounds in which TIFF2025169652000010.tif10154 is a single bond.

[0068] The content of the aminoquinoline antioxidant in the rubber composition is not particularly limited, but is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component. When the content of the aminoquinoline antioxidant is 0.1 part by mass or more per 100 parts by mass of the rubber component, the ozone resistance of the rubber composition and the adhesion between the rubber and the steel cord can be sufficiently ensured, and decreases in the elongation at break (EB) and tensile strength (TB) of the rubber composition after aging can be sufficiently suppressed. On the other hand, when the content of the aminoquinoline antioxidant is 5 parts by mass or less per 100 parts by mass of the rubber component, adverse effects on rubber physical properties such as heat buildup can be more reliably suppressed, making the rubber suitable for tire applications. Furthermore, from the viewpoint of adhesion between the rubber and the steel cord, the content of the aminoquinoline antioxidant is more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and particularly preferably 3 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of suppressing adverse effects on other rubber physical properties, the content of the aminoquinoline antioxidant is more preferably 4 parts by mass or less, per 100 parts by mass of the rubber component.

[0069] In the steel cord-rubber composite of the present invention, it is preferable that the ratio (A / (A+B)) of the zinc content to the total content of zinc and copper on the outermost surface (the brass-plated surface) of the steel wire and the content (B (parts by mass per 100 parts by mass of the rubber component)) of the aminoquinoline-based antioxidant in the rubber composition satisfy the following formula (II): 0.06≦(A / (A+B)) / C≦6 (II)

[0070] A synergistic effect is obtained between the adhesive strength improving effect achieved by controlling the zinc content ratio relative to the total content of zinc and copper at the outermost surface (the brass-plated surface) of the steel wire, and the effect of the aminoquinoline antioxidant represented by general formula (1) in maintaining adhesive strength for a long period of time, making it possible to improve the adhesion between rubber and steel cord for a long period of time. In other words, the steel cord-rubber composite of the present invention can stably achieve excellent adhesion between the rubber and the steel cord even when the cobalt content is low by satisfying 0.06≦(A / (A+B)) / C≦6. From the same viewpoint, it is more preferable that the (A / (A+B)) / C is 0.12 to 3.

[0071] The rubber composition may contain a quinoline-based antioxidant other than the aminoquinoline-based antioxidant represented by the general formula (1) (hereinafter, sometimes simply referred to as "other quinoline-based antioxidants"). The other quinoline-based antioxidants are antioxidants having a quinoline moiety or a derivative thereof (dihydroquinoline moiety, tetrahydroquinoline moiety, etc.). The other quinoline-based antioxidant, when contained in the rubber composition, has the effect of suppressing a decrease in the retention rate of elongation at break (EB) and tensile strength (TB) after aging.

[0072] The other quinoline antioxidant preferably has a dihydroquinoline moiety, more preferably a 1,2-dihydroquinoline moiety. Specific examples of the other quinoline antioxidants include a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. The other quinoline antioxidant preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ). The other quinoline antioxidant containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline is highly effective in improving the ozone resistance of the rubber composition, and also has the advantage of being less likely to discolor the rubber composition. Examples of the polymer of 2,2,4-trimethyl-1,2-dihydroquinoline include a dimer, trimer, and tetramer of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0073] The content of the other quinoline antioxidant in the rubber composition is preferably in the range of 0.27 to 0.7 in terms of the mass ratio of the content of the other quinoline antioxidant to the content of the aminoquinoline antioxidant. For example, from the viewpoint of ensuring sufficient ozone resistance while suppressing adverse effects on rubber physical properties and sufficiently suppressing decreases in adhesion after aging and the elongation at break (EB) and tensile strength (TB) of the rubber composition, the content of the other quinoline-based antioxidant is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component. When the content of the other quinoline-based antioxidant is 0.1 part by mass or more per 100 parts by mass of the rubber component, the ozone resistance of the rubber composition can be sufficiently ensured and decreases in adhesion after aging and the elongation at break (EB) and tensile strength (TB) of the rubber composition can be sufficiently suppressed. On the other hand, when the content of the other quinoline-based antioxidant is 5 parts by mass or less per 100 parts by mass of the rubber component, adverse effects on rubber physical properties (heat buildup, etc.) can be suppressed, making the rubber suitable for tire applications. From the viewpoint of further improving ozone resistance and adhesion, the content of the other quinoline antioxidant in the rubber composition is more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of more reliably suppressing adverse effects on other rubber physical properties, the content is more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of the rubber component.

[0074] The rubber composition may contain an antioxidant other than the aminoquinoline antioxidant and other quinoline antioxidants. Examples of such antioxidants include N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine. Commercially available antioxidants are available from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., Flexis, and other companies. These antioxidants may be used alone or in combination.

[0075] The content of the other antioxidant is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the target performance, etc. For example, the content of the other antioxidant is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, and is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component.

[0076] Rubber components The rubber component in the rubber composition is not particularly limited and can be appropriately selected depending on the required performance. For example, from the viewpoint of increasing the sustainability rate, the rubber component preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. Here, the "sustainability rate" of the rubber component refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources (recycled resources) in the rubber component.

[0077] The rubber component is preferably the rubber derived from biological resources or the rubber derived from recycled resources. Here, the proportion of the monomer components derived from biological resources in 100 mol% of the monomer components constituting the rubber derived from biological resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%. Furthermore, the proportion of the monomer components derived from recycled resources in 100 mol% of the monomer components constituting the rubber derived from recycled resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%.

[0078] The rubber component is a component that contributes to crosslinking, and typically has a weight average molecular weight (Mw) of 10,000 or more, preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 5,000,000 or less, more preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,300,000 or less. In this specification, the weight average molecular weight (Mw) of the rubber component can be determined, for example, by converting it into standard polystyrene based on a measurement value obtained by gel permeation chromatography (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

[0079] The rubber component is preferably a diene rubber, and the diene rubber is preferably an isoprene rubber or a butadiene rubber. Here, the isoprene rubber refers to a rubber containing units derived from isoprene as a monomer unit, and the butadiene rubber refers to a rubber containing units derived from butadiene as a monomer unit.

[0080] Examples of the isoprene-based rubber include natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), and modified synthetic isoprene rubber (modified IR). Examples of natural rubber (NR) that can be used include those commonly used in the tire industry, such as RSS#3 and TSR20 (e.g., SIR20 and STR20). The origin of the natural rubber (NR) is not particularly limited, and examples include those derived from Hevea brasiliensis, guayule, and Russian dandelion. Examples of synthetic isoprene rubber (IR) are not particularly limited, and examples include those commonly used in the tire industry, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized synthetic isoprene rubber, hydrogenated synthetic isoprene rubber, and grafted synthetic isoprene rubber. These isoprene-based rubbers may be used alone or in combination of two or more. Among these, NR is preferred as the isoprene-based rubber.

[0081] The isoprene-based rubber preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. To achieve a sustainability ratio of the isoprene-based rubber within the above range, it is preferable to use natural rubber (NR) or a polymer synthesized using isoprene derived from biological resources or isoprene derived from recycled resources as a monomer component. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from recycled resources, a copolymer of a monomer derived from biological resources and a monomer derived from recycled resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from recycled resources and a monomer derived from fossil resources (petroleum, etc.).

[0082] Examples of the butadiene rubber include butadiene rubber (BR), aromatic vinyl compound-butadiene copolymer rubber (for example, styrene-butadiene rubber (SBR)), etc. Here, butadiene, which is a raw material for butadiene rubber, is preferably derived from biological resources or recycled resources.

[0083] Examples of the butadiene rubber (BR) include high-cis butadiene rubber, low-cis butadiene rubber, and butadiene rubber containing syndiotactic polybutadiene crystals. Commercially available butadiene rubbers can be used as the butadiene rubber (BR), and examples of commercially available butadiene rubbers include products from UBE Elastomers Co., Ltd., ENEOS Materials Corporation, Asahi Kasei Corporation, and Zeon Corporation. These butadiene rubbers may be used alone or in combination of two or more.

[0084] Examples of the aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR) include emulsion-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., emulsion-polymerized styrene-butadiene rubber (E-SBR)) and solution-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., solution-polymerized styrene-butadiene rubber (S-SBR)). In the aromatic vinyl compound-butadiene copolymer rubber, examples of the aromatic vinyl compound (aromatic vinyl monomer) include styrene, vinylnaphthalene, and divinylnaphthalene. These aromatic vinyl compounds may be used alone or in combination of two or more. Among these, styrene is preferred, and styrene derived from biological resources and styrene derived from recycled resources are particularly preferred. That is, SBR is preferred as the aromatic vinyl compound-butadiene copolymer rubber. The styrene may have a substituent. Commercially available products can be used as the aromatic vinyl compound-butadiene copolymer rubber, and examples of such commercially available products include products from Asahi Kasei Corporation, ENEOS Materials Corporation, Nippon Zeon Corporation, Sumitomo Chemical Co., Ltd., etc. These aromatic vinyl compound-butadiene copolymer rubbers may be used singly or in combination of two or more.

[0085] The butadiene-based rubber preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. To achieve the sustainability rate of the butadiene-based rubber within the above range, for example, a polymer synthesized using biological resource-derived butadiene, recycled resource-derived butadiene, biological resource-derived aromatic vinyl compounds (e.g., biological resource-derived styrene), or recycled resource-derived aromatic vinyl compounds (e.g., recycled resource-derived styrene) as monomer components may be used. In this case, the synthesized polymer may be a homopolymer of a biological resource-derived monomer, a homopolymer of a recycled resource-derived monomer, a copolymer of a biological resource-derived monomer and a recycled resource-derived monomer, or a copolymer of a biological resource-derived monomer and / or a recycled resource-derived monomer and a fossil resource (e.g., petroleum)-derived monomer. Biological resource (biomass resource)-derived butadiene rubber (B-BR) and biological resource-derived aromatic vinyl compound-butadiene copolymer rubber (e.g., biological resource (biomass resource)-derived styrene-butadiene rubber (B-SBR)) include not only rubber obtained by polymerizing butadiene or the like according to conventional methods, but also rubber obtained by reactions involving microorganisms, plants, animals, and tissue cultures thereof (hereinafter also referred to as "microorganisms, etc.") or enzymatic reactions.

[0086] In addition, in order to set the sustainability rate of the entire rubber component within the above range, it is preferable to use natural rubber (NR) as the rubber component or a polymer synthesized using monomer components derived from biological resources or monomer components derived from recycled resources as monomer components.

[0087] Generally, the raw materials for rubber compositions for tires (rubber and its monomers, fillers, resins, etc.) require large-scale manufacturing equipment and are therefore typically produced in large factories in specific regions, requiring significant amounts of energy for the storage and transportation of raw materials and finished products. In contrast, materials derived from biological resources (biomass resources) are derived from local agricultural products, forests, etc., and can be produced on a small scale through microbial fermentation and catalytic reactions. By utilizing local products and waste, the energy required for transporting and storing raw materials can be reduced, and the energy required for transporting and storing the produced materials to tire factories can also be reduced, making them environmentally friendly. Materials derived from recycled resources can be obtained, for example, by dismantling and pyrolyzing used tires to extract the rubber, fillers, steel cords, and other tire-constituting materials. In addition, sulfur can be obtained from biological resources or processed products of biological resources by a method including a desulfurization step of desulfurizing biological resources or processed products of biological resources to remove sulfur-containing substances from the biological resources or processed products of biological resources, a recovery step of recovering sulfur from the desulfurization residue generated in the desulfurization step, and a processing step of processing the recovered sulfur into sulfur for vulcanization (e.g., the method described in WO 2024 / 048141), and raw materials for tire rubber compositions can be obtained from various wastes and used items. In this way, the use of sustainable materials (materials derived from biological resources or recycled resources) can reduce the overall environmental impact of tire manufacturing by reducing carbon dioxide emissions over the entire life cycle (LCCO2), reducing energy consumption over the entire life cycle (LCE), reducing life cycle costs (LCC), and reducing the use of fossil resources.

[0088] Furthermore, when producing the rubber composition, the ratios of monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources can be appropriately selected depending on the supply situation of biological resources, recycled resources, and fossil resources (e.g., monomer components derived from fossil resources) and / or market demand (e.g., demand for biological resources as food). By polymerizing the monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources, rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be obtained that has performance equivalent to that of conventional synthetic rubber. When using monomer components derived from recycled resources, it may be difficult to separate them from monomer components derived from fossil resources due to the manufacturing process of the monomers. In such cases, the environmental impact can be evaluated by adopting the mass balance approach.

[0089] The ratio of each monomer unit (e.g., units derived from isoprene, units derived from butadiene, and units derived from aromatic vinyl compounds) in the entire rubber component can be adjusted appropriately depending on the components to which the rubber is applied. The ratio of each monomer unit in the entire rubber component can be adjusted, for example, by appropriately combining the above-mentioned isoprene-based rubber and butadiene-based rubber. Furthermore, the ratio of cis-bond units in the butadiene-derived units can also be adjusted appropriately depending on the components to which the rubber is applied. In this specification, the term "monomer unit" refers to a structural unit of a polymer, the term "unit derived from isoprene" refers to a structural unit in a polymer constituted based on the monomer isoprene (including the isoprene unit in natural rubber), the term "unit derived from butadiene" refers to a structural unit in a polymer constituted based on the monomer butadiene, and the term "unit derived from an aromatic vinyl compound" refers to a structural unit in a polymer constituted based on the monomer aromatic vinyl compound. In this specification, the ratio of each monomer unit is measured by NMR.

[0090] The rubber component may contain diene rubbers such as acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR), etc., in addition to the above-mentioned isoprene-based rubber, butadiene rubber (BR), and aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR). These rubber components may be used singly or in combination of two or more.

[0091] The rubber component may be modified to introduce functional groups that interact with fillers such as carbon black and silica. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups. These functional groups may also have a substituent. These functional groups may be introduced into the rubber component either individually or in combination. Among these, amino groups, alkoxy groups, and alkoxysilyl groups are preferred, and substituted amino groups in which the hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and alkoxysilyl groups having 1 to 6 carbon atoms are more preferred.

[0092] The functional group can be introduced, for example, by reacting a compound (modifier) ​​having the functional group with the rubber component. The functional group is a modifying functional group that interacts with fillers such as silica and carbon black, and examples thereof include a nitrogen-containing functional group, a silicon-containing functional group, and an oxygen-containing functional group. Examples of compounds (modifiers) having a nitrogen-containing functional group include amino group-containing compounds. Examples of compounds (modifiers) having a silicon-containing functional group include silicon halides and hydrocarbyloxysilane compounds. Examples of compounds (modifiers) having an oxygen-containing functional group include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples of the compounds described in WO 2016 / 194316 and WO 2019 / 117256 include the compounds described in WO 2016 / 194316 and WO 2019 / 117256. These modifiers may be used alone or in combination of two or more.

[0093] The rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be produced in the same manner as conventional methods for producing synthetic rubber derived from fossil resources, for example, by using monomer components derived from biological resources or monomer components derived from recycled resources, and, if necessary, monomer components derived from fossil resources. Furthermore, the rubber derived from sustainable materials (particularly rubber derived from biological resources) can also be obtained by reactions using microorganisms or enzyme reactions.

[0094] Regarding the method for preparing bioresource-derived rubber from the above-mentioned bioresources, for example, the method described in JP 2022-179158 A can be used. For example, by using butadiene obtained from a bioresource as a monomer component, a bioresource (biomass resource)-derived butadiene rubber (B-BR) can be obtained. Furthermore, by using styrene obtained from a bioresource and butadiene obtained from a bioresource as monomer components, a bioresource (biomass resource)-derived styrene-butadiene rubber (B-SBR) can be obtained. Here, methods for obtaining B-BR and B-SBR from bioresources include artificial polymerization methods, in vivo polymerization methods, and polymerization methods using biological enzymes. The molecular weight, branching, microstructure, etc. of the obtained B-BR and B-SBR can be appropriately adjusted by changing the polymerization conditions according to known methods depending on the desired tire performance.

[0095] Suitable butadienes obtained from biological resources include butadienes derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadienes derived from alkenes (preferably ethylene), and butadienes derived from unsaturated carboxylic acids (preferably tiglic acid). Two or more of these butadienes may also be used in combination. As the styrene obtained from the biological resources, styrene obtained from plants (preferably plants belonging to the Hamamelidaceae, Styraxaceae, and Apocynaceae families, more preferably plants belonging to the genus Liquidambar, Styrax rostrata, and Catharanthus roseus, and even more preferably Sweetgum, Styrax rostrata, and Catharanthus roseus), and styrene obtained from microorganisms (preferably microorganisms belonging to the genus Penicillium or Escherichia, more preferably P. citrinum or transformed E. coli) can be suitably used. Two or more of these styrenes may also be used in combination.

[0096] Recently, biomass industrial complexes focused on bioethanol, bioethylene, and the like have been planned. However, bioethanol and bioethylene are produced primarily from sugars and / or cellulose as biological resources, and do not effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of monomer components derived from biological resources, or to combine monomer components derived from biological resources, monomer components derived from renewable resources, and monomer components derived from fossil resources, and to use these monomer components in appropriate ratios. This allows for the effective use of a wide range of biological resources, such as sugars, proteins, and lipids, as well as renewable resources, without relying on a single type of biological resource. It also allows for a stable supply of rubber derived from sustainable materials and further contributes to environmental considerations depending on the production conditions.

[0097] When multiple types of monomer components derived from biological resources are used, it is preferable to use monomer components derived from different biological resources, i.e., monomer components obtained from different biological resources. Specifically, it is preferable to use a mixture of butadienes derived from multiple types of biological resources with different origins as the biological resource-derived butadiene, and / or to use a mixture of styrenes derived from multiple types of biological resources with different origins as the biological resource-derived styrene. This allows for effective use of multiple types of biological resources.

[0098] Furthermore, modified reclaimed rubber can also be used as the rubber component. This "modified reclaimed rubber" is a rubber material obtained by pulverizing a portion of used rubber products (waste rubber products) such as tires, followed by devulcanization, and then functionalizing the resulting material with a thiuram sulfide compound. The use of modified reclaimed rubber functionalized with a thiuram sulfide compound tends to produce better effects. Furthermore, the modified reclaimed rubber is advantageous for improving problems such as reduced reinforcement that can occur when using reclaimed materials, because the crosslinked structures in the rubber are partially cleaved by devulcanization and functionalization, increasing its reactivity. For example, it can be produced by functionalizing reclaimed rubber or vulcanized rubber powder (powdered rubber) that has functional groups that can react with unvulcanized diene rubber with a modifying compound (introducing a modifying compound). The reclaimed rubber is not particularly limited, and examples include ground rubber that is mechanically ground at room temperature or in a frozen state, devulcanized rubber that has been further devulcanized, recycled rubber from used automobile tires, tubes, and other rubber products specified in JIS K6313, and reclaimed rubber with equivalent properties.

[0099] From the viewpoint of improving durability without reducing the low loss properties, the rubber component preferably contains, as the diene rubber, at least one rubber selected from the group consisting of isoprene-skeleton rubber (rubber having an isoprene unit as the main skeleton, such as natural rubber or synthetic isoprene rubber), styrene-butadiene rubber, butadiene rubber, and chloroprene rubber.

[0100] ·sulfur The rubber composition preferably contains sulfur, which makes the rubber composition vulcanizable and improves durability of the rubber composition. Various types of sulfur can be used as the sulfur, but ordinary sulfur (soluble sulfur (powdered sulfur) and the like) is preferable to insoluble sulfur, and oil treat sulfur and the like are also preferred. Here, insoluble sulfur is sulfur insoluble in carbon disulfide (amorphous polymeric sulfur), and soluble sulfur (powdered sulfur) is sulfur soluble in carbon disulfide. The amount of sulfur is preferably in the range of 0.1 to 10 parts by mass, more preferably in the range of 1 to 10 parts by mass, and further preferably in the range of 1 to 5 parts by mass, based on 100 parts by mass of the rubber component.

[0101] Carbon black Furthermore, the rubber composition may contain a filler as needed. Examples of the filler include carbon black. As the carbon black, for example, high-, medium-, or low-structure SAF, ISAF, IISAF, N339, HAF, FEF, GPF, or SRF grade carbon black is preferably used, and particularly, SAF, ISAF, IISAF, N339, HAF, or FEF grade carbon black is preferably used.

[0102] Furthermore, the carbon black is particularly preferably plant-derived carbon black or recycled carbon black. Examples of plant-derived carbon black include those derived from castor oil and pine oil. Examples of recycled carbon black include carbon black obtained by pyrolysis of used tires and carbon black obtained from waste oil. The grade of the carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available carbon black products can be used, including those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Birla Carbon. These carbon blacks may be used alone or in combination.

[0103] Furthermore, the nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the nitrogen adsorption specific surface area (N2SA) of carbon black is 20 m 2 / g or more is preferable, and 50m 2 / g or more is more preferable, and 70m 2 / g or more is more preferable, and 90m 2 / g or more is more preferable, and 200m 2 / g or less is preferable, and 150m2 / g or less is more preferable, and 130m 2 / g or less is more preferable. In this specification, the nitrogen adsorption specific surface area (N2SA) of carbon black is determined according to JIS K 6217-2:2017 (ISO 4652:2012).

[0104] The content of the carbon black is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component.

[0105] ·silica The rubber composition may also contain silica as the filler. When silica is used, the BET specific surface area of ​​the silica (measured in accordance with ISO 5794 / 1) is 40 to 350 m 2 / g. Silica with a BET surface area in this range has the advantage of being able to provide both rubber reinforcement and dispersibility in the rubber component. From this perspective, it is preferable that the BET surface area is 80 to 350 m 2 / g, and a BET surface area of ​​120 to 350 m 2 Silica in the range of 1 / g is particularly preferred. The amount of silica is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 1 part by mass or more and 10 parts by mass or less, based on 100 parts by mass of the rubber component. Furthermore, the total compounding amount of the carbon black and the silica is preferably 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the rubber component.

[0106] The type of silica is not particularly limited, and examples thereof include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred because it contains a large number of silanol groups. These silicas may be used alone or in combination of two or more. Commercially available silicas can be used, including those from Tosoh Silica Corporation, Evonik, Solvay, Solvay Japan, and Tokuyama Corporation. The silica may also be a commercially available product, for example, Zeosil Premium 200MP (trade name) from Rhodia. The silica may be used alone or in combination of two or more.

[0107] From the viewpoint of reducing environmental impact, silica derived from siliceous plants is preferred. Examples of siliceous plants include mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Gramineae. Among these plants, grasses are preferred. Examples of grasses include rice, bamboo, and sugarcane, with rice being preferred. Rice is widely cultivated for food and therefore can be procured locally over a wide area. Furthermore, rice husks are generated in large quantities as industrial waste, making them easy to secure. Therefore, from the viewpoint of availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred. The use of rice husk silica allows for the effective use of rice husks, which are industrial waste. Furthermore, since the raw material can be procured locally near tire manufacturing plants, the energy and costs for transportation and storage can be reduced, which is environmentally preferable from various viewpoints. The rice husk silica may be a powder of rice husk charcoal obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet process using an alkali silicate aqueous solution, which is prepared by extracting rice husk ash generated when rice husks are burned as fuel in a biomass boiler with an alkali. The method for producing the rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husk charcoal can be obtained by pyrolyzing rice husks by steaming them in a kiln. The rice husk charcoal obtained in this manner can be pulverized using a known pulverizer (e.g., a ball mill), sorted, and classified into a predetermined particle size range to obtain rice husk charcoal powder. The rice husk-derived precipitated silica can be produced by a method such as that described in JP 2019-38728 A.

[0108] Furthermore, the silica has a nitrogen adsorption specific surface area (N2SA) of 50 m 2 / g or more, and 100m 2 / g or more is more preferable, and 150m 2 / g or more is more preferable, and 2 / g or less, and 250m 2 / g or less is more preferable, and 2 / g or less is more preferable, and 2It is even more preferable that the saturation coefficient is 1 / g or less. In this specification, the nitrogen adsorption specific surface area (N2SA) of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0109] The content of silica can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of silica, relative to 100 parts by mass of the rubber component, is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 30 parts by mass or more, more preferably 50 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, still more preferably 100 parts by mass or more, particularly preferably 110 parts by mass or more, and is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, still more preferably 180 parts by mass or less, and particularly preferably 150 parts by mass or less.

[0110] Silane coupling agents When the rubber composition of this embodiment contains silica, it is preferable that the rubber composition contains a silane coupling agent to improve the effect of the silica. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, and 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide. Examples of the silane coupling agent include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide. Commercially available silane coupling agents can be used, and examples of commercially available silane coupling agents that can be used include products from Evonik, Momentive, Shin-Etsu Silicones, Dow Corning Toray Co., Ltd., Tokyo Chemical Industry Co., Ltd., and AZMAX Corporation. These silane coupling agents may be used alone or in combination of two or more.

[0111] Bioethanol can also be used as a raw material for the silane coupling agent. Bioethanol is produced primarily from sugars and / or cellulose as biological resources, and does not effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of monomer components derived from biological resources as the biological resource-derived monomer component, or to use a combination of monomer components derived from biological resources, monomer components derived from renewable resources, and monomer components derived from fossil resources. This allows for the effective use of a wide range of biological resources and renewable resources, such as sugars, proteins, and lipids, without relying on a single type of biological resource, and also allows for environmental considerations depending on the production conditions.

[0112] Furthermore, in terms of the effect as a coupling agent and prevention of gelation, the amount of silane coupling agent blended is preferably a mass ratio (silane coupling agent / silica) of 1 / 100 to 20 / 100. If it is 1 / 100 or more, the effect of improving the low heat buildup of the rubber is more suitably exhibited, and if it is 20 / 100 or less, the cost of the tire rubber is reduced, improving economy. A mass ratio of 3 / 100 to 20 / 100 is even more preferable, and a mass ratio of 4 / 100 to 10 / 100 is particularly preferable.

[0113] Boron compounds The rubber composition may further contain a boron-containing compound from the viewpoint of further improving the adhesive durability between the steel cord and the coating rubber and from the viewpoint of fully exhibiting the rust prevention effect. Specifically, the boron-containing compound is preferably contained in an amount of 0.005 to 0.08 parts by mass, preferably 0.01 to 0.06 parts by mass, and more preferably 0.02 to 0.055 parts by mass, calculated as boron, per 100 parts by mass of the rubber component. If the amount of the boron-containing compound calculated as boron is less than 0.005 parts by mass, it may not be possible to sufficiently improve the adhesion durability between the steel cord and the coating rubber. If it exceeds 0.08 parts by mass, the initial vulcanization rate of the rubber may decrease, which may be a factor in reducing the initial adhesion rate between the steel cord and the coating rubber.

[0114] The boron-containing compound is not particularly limited as long as it contains boron, and examples thereof include boric acid, ammonium borate, zinc borate, and tetrafluoroboric acid. Among these, boric acid is preferred from the viewpoints of availability and low cost. These compounds may be used alone or in combination of two or more.

[0115] ·resin The rubber composition may further contain a resin. Examples of such resins include terpene resins, rosin resins, C5 resins, C5-C9 resins, C9 resins, cyclopentadiene resins, aromatic resins, coumarone resins, indene resins, coumarone-indene resins, olefin resins, polyurethane resins, and acrylic resins. These resins may be used alone or in combination of two or more. Among these resins, terpene resins, rosin resins, C5 resins, C5-C9 resins, C9 resins, cyclopentadiene resins, and aromatic resins are preferred, with terpene resins and rosin resins being particularly preferred. Terpene resins and rosin resins are naturally derived, sustainable resins that can further reduce environmental impact and further improve tire performance. C5 resins, C9 resins, C5-C9 resins, and cyclopentadiene resins can improve reinforcement and fuel economy in a well-balanced manner. Furthermore, aromatic resins can improve the rubber strength and the like.

[0116] Furthermore, the resin may be a temperature-responsive resin whose hydrophilicity changes with temperature. An example of the temperature-responsive resin is the temperature-responsive resin described in JP 2022-077145 A.

[0117] The resin may be hydrogenated, i.e., may be a hydrogenated resin (hydrogenated resin). Furthermore, the resin may be modified to introduce a functional group that interacts with fillers such as carbon black and silica. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups.

[0118] The terpene resin is a solid resin obtained by polymerizing turpentine, which is obtained simultaneously with the extraction of rosin from pine trees, or a polymerization component separated from the turpentine, using a Friedel-Crafts catalyst. Examples of such resins include β-pinene resin and α-pinene resin. Terpene resins also include terpene-aromatic compound resins, representative examples of which include terpene-phenol resin and styrene-terpene resin. Terpene-phenol resins can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst or by further condensing the terpene with formalin. Styrene-terpene resins can be obtained by reacting styrene with terpenes using a Friedel-Crafts catalyst. The terpenes used as raw materials are not particularly limited; monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred.

[0119] Examples of the rosin-based resin include natural resin rosins such as gum rosin, tall oil rosin, and wood rosin contained in raw pine resin and tall oil, and examples of modified rosins, rosin derivatives, and modified rosin derivatives include polymerized rosin and partially hydrogenated rosin thereof; glycerin ester rosin and partially hydrogenated rosin thereof and fully hydrogenated rosin thereof; pentaerythritol ester rosin and partially hydrogenated rosin thereof and polymerized rosin; and the like.

[0120] Furthermore, maleic acid-modified rosin resins can also be used as the rosin-based resin. The maleic acid-modified rosin resin is not particularly limited as long as it is one typically used in rubber compositions for tires. Preferably, the resin contains a maleic acid-modified rosin resin having an acid value of 50 KOH mg / g or less. Alternatively, the resin may be a mixture of a maleic acid-modified rosin resin having an acid value of 50 KOH mg / g or less and a maleic acid-modified rosin resin having an acid value of more than 50 KOH mg / g. By including a maleic acid-modified rosin resin having an acid value of 50 KOH mg / g or less, both fracture resistance and low heat buildup can be achieved, with fracture resistance being particularly improved. The acid value of the maleic acid-modified rosin resin can be adjusted by the degree of modification with maleic acid. In this specification, the acid value of the maleic acid-modified rosin resin is the amount of potassium hydroxide required to neutralize the acid contained in 1 g of resin, expressed in milligrams, and can be measured by potentiometric titration (JIS K0070:1992).

[0121] The softening point of the maleic acid-modified rosin resin is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher. If the softening point is lower than 80°C, the resin may melt and aggregate due to the influence of ambient temperature, which may adversely affect handleability. The softening point of the maleic acid-modified rosin resin is preferably 160°C or lower, more preferably 150°C or lower. If the softening point exceeds 160°C, the resin component may not dissolve sufficiently in the rubber component, forming fracture nuclei, which is undesirable. The softening point of the maleic acid resin can be measured using a ring and ball softening point analyzer as defined in JIS K 6220-1:2001.

[0122] The maleic acid-modified rosin resin preferably has a glass transition temperature of 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. If the glass transition temperature is lower than 40°C, the dynamic modulus of elasticity and tensile elongation at break decrease, resulting in poor fracture resistance. Furthermore, the glass transition temperature is preferably 180°C or lower, more preferably 150°C or lower, and even more preferably 120°C or lower. If the temperature exceeds 180°C, heat generation deteriorates. The glass transition temperature can be determined by measuring a thermogram by differential scanning calorimetry (DSC) at a heating rate of 20°C / min, and determining it as the midpoint of the transition region.

[0123] The weight-average molecular weight of the maleic acid-modified rosin resin is preferably 500 to 5000, more preferably 1000 to 4000. By setting the weight-average molecular weight within this range, the target performance can be obtained. The weight-average molecular weight can be determined by gel permeation chromatography (GPC) using standard polystyrene as the standard.

[0124] Examples of the maleic acid-modified rosin resin include Marquid Nos. 1, 2, 5, 6, 8, 31, 32, 33, 34, 382, ​​and 3002 manufactured by Arakawa Chemical Industries, Ltd., and Harimac R-80, T-80, R-100, M-453, M-130A, 135GN, 145P, and R-120AH manufactured by Harima Chemicals Co., Ltd. Among these, Marquid No. 1 (acid value: 25 KOH mg / g) and No. 8 (acid value: 37 KOH mg / g), manufactured by Arakawa Chemical Industries, Ltd., are preferred.

[0125] Examples of the C5 resin include aliphatic petroleum resins obtained by (co)polymerizing C5 fractions obtained by thermal cracking of naphtha in the petrochemical industry. C5 fractions typically include olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene.

[0126] The C5-C9 resin refers to a C5-C9 synthetic petroleum resin, and examples of the C5-C9 resin include petroleum-derived C5-C 11 Examples of suitable C5-C9 resins include solid polymers obtained by polymerizing the fraction using a Friedel-Crafts catalyst such as AlCl3 or BF3. More specifically, examples include copolymers primarily composed of styrene, vinyltoluene, α-methylstyrene, indene, etc. As the C5-C9 resin, a resin with a low content of C9 or higher components is preferred from the viewpoint of compatibility with the rubber component. Here, "low content of C9 or higher components" means that the content of C9 or higher components in the total resin is less than 50 mass%, preferably 40 mass% or less.

[0127] The C9 resin refers to a C9 synthetic petroleum resin, such as a solid polymer obtained by polymerizing a C9 fraction using a Friedel-Crafts catalyst such as AlCl3 or BF3. Examples of the C9 resin include copolymers containing indene, α-methylstyrene, vinyltoluene, etc. as main components.

[0128] The cyclopentadiene-based resin refers to a resin containing a unit derived from a cyclopentadiene-based monomer as a monomer unit. Examples of the cyclopentadiene-based resin include a homopolymer of a cyclopentadiene-based monomer, a copolymer of two or more cyclopentadiene-based monomers, and a copolymer of a cyclopentadiene-based monomer with another monomer. Examples of the cyclopentadiene-based monomer include cyclopentadiene, dicyclopentadiene, and tricyclopentadiene. Among these, dicyclopentadiene is preferred. That is, the cyclopentadiene-based resin is preferably a dicyclopentadiene-based resin. The dicyclopentadiene-based resin refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as AlCl3 or BF3. Examples of dicyclopentadiene resins include homopolymers of dicyclopentadiene, copolymers of dicyclopentadiene and aromatic monomers, and copolymers of dicyclopentadiene and C9 fractions (vinyltoluene, indene, etc.).

[0129] The aromatic resin refers to a resin containing a unit derived from an aromatic monomer as a monomer unit. Examples of the aromatic resin include a homopolymer of an aromatic monomer, a copolymer of two or more aromatic monomers, and a copolymer of an aromatic monomer with another monomer. Examples of the aromatic monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-phenylstyrene; phenolic monomers such as phenol, alkylphenol, and alkoxyphenol; and naphthol monomers such as naphthol, alkylnaphthol, and alkoxynaphthol.

[0130] The resin may also be a mixture (mixed resin) of a hydrogenated styrene resin and an aromatic modified terpene resin.The rosin resin may also be a maleic acid modified rosin resin. The hydrogenated styrene resin is a resin obtained by hydrogenating a styrene resin made from a styrene monomer. Hydrogenating the styrene resin reduces the number of aromatic rings derived from styrene, improving dispersibility in diene rubber and accelerating crosslinking of the diene rubber, thereby uniforming the crosslinking positions between rubber polymers and increasing the modulus of the rubber composition after vulcanization. The uniform and tight crosslinking of the rubber also improves durability.

[0131] The styrene resin that serves as the base of the hydrogenated styrene resin can be obtained by addition polymerization of styrene. The addition polymerization reaction can be carried out according to a known method, such as a solution polymerization method using a living anionic polymerization catalyst, a method using a cationic polymerization catalyst, or a method using a radical polymerization initiator.

[0132] The hydrogenated styrene resin is obtained by hydrogenating the aromatic rings in the styrene resin. The hydrogenation method is a conventionally known method and is not particularly limited. The hydrogenation rate of the aromatic rings is not particularly limited, but is 0.1 to 100%, preferably 1 to 95%, more preferably 40 to 90%, and even more preferably 50 to 80%. If the hydrogenation rate of the aromatic rings is less than 0.1%, the properties due to the hydrogenation are not fully exhibited. Here, the hydrogenation rate of the aromatic rings (hydrogenation rate) is a value calculated from the peak height of the absorbance derived from styrene by IR (infrared spectrophotometer) using the following formula: Hydrogenation rate (%)={(CD) / C}×100 C: Absorbance peak height due to aromatic ring before hydrogenation D: Absorbance peak height due to aromatic ring after hydrogenation The hydrogenated styrene resins may be used alone or in combination of two or more.

[0133] The molecular weight of the hydrogenated styrene resin is, in terms of polystyrene, a weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 500 to 10,000, preferably 1,000 to 7,000, and more preferably 1,500 to 5,000. If the weight average molecular weight is less than 500, the durability of the rubber composition may be poor, and if the weight average molecular weight exceeds 10,000, the effect of improving the grip of the rubber composition may be poor.

[0134] The aromatic modified terpene resin is a copolymer of a terpene and an aromatic compound. Examples of terpenes include α-pinene, β-pinene, dipentene, and limonene. Examples of aromatic compounds include styrene, α-methylstyrene, vinyltoluene, and indene. The content of the aromatic compound in the aromatic modified terpene resin is preferably 10 to 50% by mass, and more preferably 12 to 45% by mass. By compounding the aromatic modified terpene resin with a diene rubber, the dynamic viscoelasticity of the rubber composition can be modified, and the wet grip performance and heat buildup can be improved.

[0135] The softening point of the aromatic modified terpene resin is not particularly limited, but is preferably 60°C to 150°C, more preferably 80°C to 130°C. If the softening point of the aromatic modified terpene resin is less than 60°C, the wet grip performance may be reduced. If the softening point of the aromatic modified terpene resin is more than 150°C, the low rolling resistance may be deteriorated. In this specification, the softening point of the aromatic modified terpene resin is measured based on JIS K6220-1 (ring and ball method).

[0136] The softening point of the resin is preferably 30° C. or higher, more preferably 60° C. or higher, more preferably 80° C. or higher, more preferably higher than 110° C., more preferably 116° C. or higher, more preferably 120° C. or higher, more preferably 123° C. or higher, and even more preferably 127° C. or higher. From the viewpoint of processability, the softening point of the resin is preferably 160° C. or lower, more preferably 150° C. or lower, more preferably 145° C. or lower, more preferably 141° C. or lower, and even more preferably 136° C. or lower. In this specification, the softening point of a resin is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2015 (ISO 28641:2010) is measured using a ring and ball softening point tester.

[0137] Commercially available resins can be used, and examples of commercially available resins include those from ENEOS Corporation, Arakawa Chemical Industries, Ltd., ExxonMobil Corporation, Clayton Corporation, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Clayton Polymers, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., and Taoka Chemical Co., Ltd.

[0138] The content of the resin is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the resin is preferably in the range of 5 to 100 parts by mass, and more preferably in the range of 10 to 60 parts by mass, per 100 parts by mass of the rubber component.

[0139] Rubber powder The rubber composition may also contain rubber crumb. The rubber crumb may be obtained by crushing used rubber products such as used tires and, if desired, removing reinforcing materials such as steel and fibers, dust, glass, sand, stones, etc., or by preparing a new vulcanized rubber composition for the purpose of producing rubber crumb and crushing the resulting product. For example, rubber crumb can be obtained from vulcanized rubber by the method described in "Rubber Chemistry and Technology." Mechanical treatment or low-temperature treatment may be used in the process of crushing vulcanized rubber to obtain rubber crumb. For example, in mechanical treatment, various crushing devices such as a cracker mill or a granulator can be used to mechanically crush the vulcanized rubber into fine particles. In low-temperature treatment, the finely chopped vulcanized rubber is frozen at a cryogenic temperature and then crushed into fine particles. A magnetic separator or the like can be used to remove steel, and an air separator or the like can be used to remove fibers. Commercially available rubber crumbs can also be used. Examples of commercially available rubber crumbs include those from Global Corporation or Nantong Huili Rubber Corporation. From the viewpoint of reducing the environmental load, it is preferable to use rubber powder obtained by crushing used rubber products such as used tires. The rubber powder may be used alone or in combination of two or more types.

[0140] The composition of the rubber crumb is not particularly limited and depends on the composition of the vulcanized rubber from used rubber products (used tires) or the like that serve as the raw material. In one embodiment, the rubber crumb contains a rubber component, carbon black, silica, etc. The rubber component, carbon black, silica, etc. contained in the rubber crumb may be the same as or different from the rubber component, carbon black, silica, etc. contained in the rubber composition of this embodiment described above.

[0141] The rubber powder has a volume average particle size of preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 200 μm or less, and even more preferably 100 μm or less. The smaller the volume average particle size of the rubber powder, the better, and there is no particular lower limit. In this specification, the volume average particle size is measured by a laser diffraction particle size distribution measuring device, for example, "CAPA500" manufactured by Horiba, Ltd.

[0142] The rubber powder preferably has an acetone extractable content of 12% by mass or less, more preferably 11% by mass or less, and even more preferably 10% by mass or less, and preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. In this specification, the acetone extractables in the rubber crumb refers to the acetone extractables (%) determined by the acetone extraction method in accordance with JIS K6350.

[0143] The content of the rubber crumb is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the tire is applied, the tire components, the target performance, etc. For example, the content of the rubber crumb is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, and is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, more preferably 100 parts by mass or less, more preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, per 100 parts by mass of the rubber component.

[0144] Liquid softener The rubber composition may contain a liquid softener. Here, the "liquid softener" refers to a compounding agent that is liquid at 25°C (room temperature) and has the effect of softening the rubber composition. The liquid softener is not particularly limited, and examples thereof include oil and liquid polymer, among which oil is preferred. These liquid softeners may be used alone or in combination of two or more.

[0145] The oil is a general term for extender oils contained in rubber components and liquid oils added as compounding agents to rubber compositions. Examples include vegetable oils, process oils, oils obtained by recycling vegetable oils or process oils, and mixtures thereof. From the perspective of reducing environmental impact, vegetable oils and recycled oils are preferred. Examples of vegetable oils include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, coconut oil, peanut oil, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, coconut oil, seed oils, grain oils, potato oils, bean oils, and vegetable oils. Examples of process oils include paraffinic process oils, aromatic process oils, and naphthenic process oils. The oil may be a commercially available product, such as products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., and Nisshin Oillio Group Co., Ltd. These oils may be used alone or in combination of two or more.

[0146] The liquid polymer is preferably a liquid diene-based polymer. Examples of the liquid diene-based polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid polybutadiene (liquid BR), liquid polyisoprene (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid polyfarnesene, and liquid farnesene-butadiene copolymer. These liquid polymers may be hydrogenated, or their terminals or main chains may be modified with functional groups (polar groups). These liquid polymers may be used alone or in combination of two or more.

[0147] The content of the liquid softener is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the content of the liquid softener is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and still more preferably 30 parts by mass or less, per 100 parts by mass of the rubber component.

[0148] Rubber-metal adhesion promoter The rubber composition preferably contains a rubber-metal adhesion promoter containing at least one selected from the group consisting of a metal carboxylate (1) having 2 to 25 carbon atoms and containing a metal selected from the group consisting of bismuth, copper, antimony, silver, niobium, and zirconium; and a compound (2) represented by the following formula (A): [ka] [In formula (A), Z is a structure selected from formulas (z-1) to (z-4). M is bismuth, copper, antimony, silver, niobium, or zirconium. (RCOO) is a residue of an aliphatic carboxylic acid having 2 to 25 carbon atoms. x is an integer equal to (the valence of M - 1).] It can improve the durability of vulcanized rubber and the heat-degradation adhesion of rubber to metal.

[0149] The carboxylic acid metal salt (1) is a metal salt of an aliphatic carboxylic acid having 2 to 25 carbon atoms. The metal species is bismuth, copper, antimony, silver, niobium, or zirconium. Among the metal species, bismuth, copper, antimony, or silver is preferred, and bismuth or copper is more preferred, as they act as an adhesion promoter that promotes good adhesion between steel cord and rubber even under hot and humid conditions. If the carbon number of the carboxylic acid metal salt (1) is less than 2, the compatibility of the carboxylic acid metal salt (1) with the rubber component is low, and high adhesive strength between the vulcanized rubber and the metal cannot be obtained. In addition, it is difficult to synthesize the carboxylic acid metal salt (1) having more than 25 carbon atoms.

[0150] Examples of aliphatic carboxylic acids having 2 to 25 carbon atoms include aliphatic monocarboxylic acids, aliphatic dicarboxylic acids, etc. The number of carbon atoms in an aliphatic carboxylic acid includes the number of carbon atoms in the carboxy group. Examples of the aliphatic carboxylic acid having 2 to 25 carbon atoms include saturated aliphatic monocarboxylic acids and unsaturated aliphatic monocarboxylic acids.

[0151] Examples of the saturated aliphatic monocarboxylic acid include ethanoic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, 2-ethylhexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, isononanoic acid, decanoic acid, neodecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, eicosanoic acid, docosanoic acid, tetracosanoic acid, and naphthenic acid. Examples of the unsaturated aliphatic monocarboxylic acid include 9-hexadecenoic acid, cis-9-octadecenoic acid, 11-octadecenoic acid, cis,cis-9,12-octadecadienoic acid, 9,12,15-octadecatrienoic acid, 6,9,12-octadecatrienoic acid, 9,11,13-octadecatrienoic acid, eicosanoic acid, 8,11-eicosadienoic acid, 5,8,11-eicosatrienoic acid, 5,8,11,14-eicosatetraenoic acid, tung oil acid, linseed oil acid, soybean oil acid, resin acid, tall oil fatty acid, rosin acid, abietic acid, neoabietic acid, palustric acid, pimaric acid, and dehydroabietic acid. Examples of the aliphatic dicarboxylic acid having 2 to 25 carbon atoms include saturated aliphatic dicarboxylic acids and unsaturated aliphatic dicarboxylic acids. Examples of the saturated aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid. Examples of the unsaturated aliphatic dicarboxylic acid include fumaric acid and maleic acid.

[0152] The aliphatic carboxylic acid having 2 to 25 carbon atoms is preferably an aliphatic monocarboxylic acid or an aliphatic dicarboxylic acid, more preferably an aliphatic monocarboxylic acid, and even more preferably a saturated aliphatic monocarboxylic acid. Use of a saturated aliphatic monocarboxylic acid is less likely to affect the sulfur crosslinking of the rubber, and can prevent deterioration of the rubber properties of the vulcanized rubber. Among the saturated fatty acids, saturated aliphatic monocarboxylic acids having 2 to 20 carbon atoms are preferred, and 2-ethylhexanoic acid, neodecanoic acid, hexadecanoic acid, or octadecanoic acid are more preferred.

[0153] The carboxylic acid metal salt (1) can be obtained, for example, by the following method. Production method 1: A production method (direct method) in which an aliphatic carboxylic acid (a) having 2 to 25 carbon atoms is directly reacted with one or more selected from oxides (b-1) of metals (bismuth, copper, antimony, silver, niobium, zirconium), hydroxides (b-2) of metals (bismuth, copper, antimony, silver, niobium, zirconium), and carbonates (b-3) of metals (bismuth, copper, antimony, silver, niobium, zirconium). Production method 2: A method (metathesis method) in which an aliphatic carboxylic acid (a) having 2 to 25 carbon atoms is reacted with sodium hydroxide in the presence of water to obtain a sodium salt of an aliphatic carboxylic acid, and then the sodium salt of the aliphatic carboxylic acid is reacted with one or more selected from the group consisting of sulfates (c-1) of metals (metal salts of bismuth, copper, antimony, silver, niobium, and zirconium), chlorides (c-2) of metals (bismuth, copper, antimony, silver, niobium, and zirconium), and nitrates (c-3) of metals (bismuth, copper, antimony, silver, niobium, and zirconium).

[0154] Examples of the oxides (b-1) of metals (bismuth, copper, antimony, silver, niobium, zirconium) include bismuth(III) oxide, copper(I) oxide, copper(II) oxide, antimony(III) oxide, antimony(V) oxide, silver(I) oxide, silver(II) oxide, silver(III) oxide, niobium(IV) oxide, niobium(V) oxide, and zirconium oxide. Examples of the hydroxides (b-2) of metals (bismuth, copper, antimony, silver, niobium, zirconium) include copper hydroxide (II) and zirconium hydroxide. Examples of the carbonates (b-3) of metals (bismuth, copper, antimony, silver, niobium, zirconium) include bismuth(III) carbonate, bismuth(III) oxide carbonate, and copper(II) carbonate. Examples of the sulfates (c-1) of metals (bismuth, copper, antimony, silver, niobium, zirconium) include copper (II) sulfate and zirconium sulfate. Examples of chlorides (c-2) of metals (bismuth, copper, antimony, silver, niobium, zirconium) include bismuth chloride oxide (III), copper chloride (I), copper chloride (II), antimony chloride (III), antimony chloride (V), silver chloride (I), and niobium chloride (V). Examples of the nitrates (c-3) of metals (bismuth, copper, antimony, silver, niobium, zirconium) include bismuth(III) nitrate, bismuth(III) subnitrate, and silver(I) nitrate.

[0155] In Production Method 1, the reaction temperature when reacting the aliphatic carboxylic acid (a) having 2 to 25 carbon atoms with the compounds (b-1) to (b-3) is usually 50 to 150° C. The reaction time is usually 1 to 20 hours.

[0156] In Production Method 2, when the aliphatic carboxylic acid (a) having 2 to 25 carbon atoms is reacted with sodium hydroxide in the presence of an organic solvent, the reaction temperature is usually 20 to 100° C. The reaction time is usually 1 to 5 hours. In Production Method 2, the reaction temperature when reacting the sodium salt of an aliphatic carboxylic acid with the compounds (c-1) to (c-3) is usually 20 to 100° C. The reaction time is usually 1 to 5 hours. In Production Method 2, after reacting the sodium salt of an aliphatic carboxylic acid with the compounds (c-1) to (c-3), the aqueous layer in the reaction system is separated, and the solvent present in the oil layer is then removed by vacuum distillation to obtain the carboxylate metal salt (1).

[0157] (RCOO) in the compound (2) is a residue of an aliphatic carboxylic acid having 2 to 25 carbon atoms. If the carbon number of the aliphatic carboxylic acid residue is less than 2, the compatibility between the rubber component and compound (2) is poor, resulting in a decrease in adhesive strength between the vulcanized rubber and metal. If the carbon number of the aliphatic carboxylic acid residue is greater than 25, compound (2) is difficult to synthesize. Furthermore, compound (2) is difficult to disperse in the rubber component, or the vulcanized rubber is difficult to adsorb to the surface of the steel cord, resulting in a decrease in adhesive strength between the vulcanized rubber and metal.

[0158] Examples of the residue of an aliphatic monocarboxylic acid having 2 to 25 carbon atoms include residues of aliphatic monocarboxylic acids, and preferred examples include residues derived from aliphatic monocarboxylic acids described in the carboxylic acid metal salt (1). Among the residues of aliphatic carboxylic acids, residues of saturated aliphatic monocarboxylic acids are preferred. By using a residue of saturated aliphatic monocarboxylic acid, compound (2) becomes more easily dispersed in the vicinity of the steel cord, or the vulcanized rubber becomes more easily adsorbed onto the surface of the steel cord. Among the residues of saturated aliphatic monocarboxylic acids, residues of saturated aliphatic monocarboxylic acids having 2 to 20 carbon atoms are preferred, and residues of 2-ethylhexanoic acid, neodecanoic acid, hexadecanoic acid, and octadecanoic acid are more preferred.

[0159] M in the compound represented by formula (A) is a metal species, specifically bismuth, copper, antimony, silver, niobium, or zirconium. Among the metal species, bismuth, copper, antimony, or silver is preferred, and bismuth or copper is more preferred, as it acts as an adhesion promoter that promotes good adhesion between steel cord and rubber even under moist and hot conditions.

[0160] Furthermore, x in the compound (2) represented by formula (A) is an integer of (the valence of M - 1).

[0161] Z in the compound (2) represented by formula (A) is a structure selected from the above-mentioned formulas (z-1) to (z-4). Among these, the structure represented by formula (z-1) is preferred because it is easy to obtain an adhesion promoter that exhibits high adhesive strength between vulcanized rubber and metal.

[0162] The compound (2) represented by the formula (A) can be produced, for example, by mixing an aliphatic carboxylic acid (a) having 2 to 25 carbon atoms, an inorganic acid ester (d), an acid (e), and a metal compound M (f), heating the mixture, and removing the resulting volatile ester (g).

[0163] Examples of the aliphatic carboxylic acid (a) having 2 to 25 carbon atoms include the above-mentioned aliphatic monocarboxylic acids having 2 to 25 carbon atoms.

[0164] Examples of the inorganic acid ester (d) include borate esters (d-1) of lower alcohols having 1 to 5 carbon atoms, metaborate esters (d-2) of lower alcohols having 1 to 5 carbon atoms, phosphate esters (d-3) of lower alcohols having 1 to 5 carbon atoms, and phosphite esters (d-4) of lower alcohols having 1 to 5 carbon atoms. Examples of the borate ester of a lower alcohol (d-1) include trimethyl borate, triethyl borate, tripropyl borate, and tributyl borate. Examples of metaborate esters of lower alcohols (d-2) include trimethyl metaborate, triethyl metaborate, tripropyl metaborate, and tributyl metaborate. Examples of the lower alcohol phosphate ester (d-3) include methyl phosphate, ethyl phosphate, propyl phosphate, and butyl phosphate. Examples of the lower alcohol phosphite (d-4) include methyl phosphite, ethyl phosphite, propyl phosphite, and butyl phosphite. Among these, metaborate esters of lower alcohols (d-2) are preferred from the viewpoint of inhibiting metal corrosion after treatment and standing.

[0165] The acid (e) is an acid capable of forming a volatile ester (g) together with a lower alcohol residue having 1 to 5 carbon atoms present in the inorganic acid ester (d). Specific examples include ethanoic acid, propanoic acid, and butanoic acid.

[0166] The metal compound M(f) is a metal source for compound (2), and for example, the oxide (b-1), hydroxide (b-2), carbonate (b-3), etc., which have already been described in the production method for metal carboxylate (1), can be used. The proportion of the metal compound M(f) used as the metal source is, for example, 20 to 100 parts by mass per 100 parts by mass of the aliphatic carboxylic acid (a) having 2 to 25 carbon atoms.

[0167] The inorganic acid ester (d) is used in an amount of, for example, 10 to 50 parts by mass per 100 parts by mass of the aliphatic carboxylic acid (a) having 2 to 25 carbon atoms. The proportion of the acid (e) used is, for example, 10 to 50 parts by mass per 100 parts by mass of the aliphatic carboxylic acid (a) having 2 to 25 carbon atoms.

[0168] The aliphatic carboxylic acid (a) having 2 to 25 carbon atoms, the inorganic acid ester (d), the acid (e), and the metal compound M (f) may be mixed in one step or in multiple steps.

[0169] An example of a method for mixing various components in multiple steps is a production method including the following first and second steps. The first step is a step of mixing an aliphatic carboxylic acid (a) having 2 to 25 carbon atoms, an acid (e), and a metal compound M (f) and heating the mixture to obtain a reaction product (h). The second step is a step of removing water from the reaction system containing the reactant (h) obtained in the first step, and then adding the inorganic acid ester (d) to the reaction system from which the water has been removed, thereby reacting the reactant (h) with the inorganic acid ester (d). By producing compound (2) through the above two steps, it is possible to prevent the inorganic acid ester (d) from being hydrolyzed by water generated in the first step, and compound (2) can be produced efficiently.

[0170] In the above two-step production method, the temperature at which the aliphatic carboxylic acid (a) having 2 to 25 carbon atoms, the inorganic acid ester (d), the acid (e), and the metal compound M (f) are reacted is, for example, 100 to 250° C., and preferably 150 to 220° C. The reaction time is, for example, 1 to 20 hours, and preferably 1 to 5 hours.

[0171] In addition, the content of the rubber-metal adhesion promoter in the rubber composition is preferably 0.01 part by mass or more per 100 parts by mass of the rubber component, from the viewpoint of improving the adhesion between the vulcanized rubber and the metal and improving the durability of the metal-rubber composite and the tire. If the content is less than 0.01 mass, sufficient adhesion between the vulcanized rubber and the metal may not be obtained. Furthermore, the rubber-metal adhesion promoter is preferably contained in an amount of less than 1.0 part by mass per 100 parts by mass of the rubber component. Therefore, the content of the rubber-metal adhesion promoter in the rubber composition is more preferably 0.01 to 0.9 parts by mass, even more preferably 0.02 to 0.8 parts by mass, and particularly preferably 0.02 to 0.7 parts by mass.

[0172] Nitrogen-containing cyclic compounds and amine-based antioxidants The rubber composition comprises a nitrogen-containing cyclic compound that does not contain a benzene ring or a mercapto group, The following general formula (1): [ka] [In the formula, R 1 and R 2 and each independently represents a monovalent saturated hydrocarbon group. Excellent adhesion can be achieved even when exposed to degrading environments.

[0173] From the viewpoint of obtaining even better adhesion under a deterioration environment, it is more preferable that the mass ratio (A / B) of the content (A) of the nitrogen-containing cyclic compound that does not contain a benzene ring or a mercapto group to the content (B) of the amine-based antiaging agent is 0.004 to 100 (0.004≦A / B≦100).

[0174] The inclusion of the nitrogen-containing cyclic compound that does not contain a benzene ring or a mercapto group provides an effect of improving the initial adhesion and the adhesion when exposed to a deterioration environment, while the inclusion of the amine-based antioxidant represented by general formula (1) provides an effect of maintaining the adhesion for a long period of time, thereby achieving a synergistic effect, making it possible to improve the adhesion between the rubber and the metal cord over a long period of time when exposed to a deterioration environment. That is, the metal cord-rubber composite of the present invention can stably achieve adhesion when exposed to the environment by satisfying 0.004≦A / B≦100. From the same viewpoint, the A / B is preferably 0.04 to 10, and more preferably 0.2 to 2.

[0175] The nitrogen-containing cyclic compound is not limited as long as it is a nitrogen-containing cyclic compound that does not have a benzene ring or a mercapto group. From the viewpoints of cost and the effectiveness of the present invention, at least one selected from the group consisting of triazole, triazole derivatives, imidazole, and imidazole derivatives is preferred. Here, the triazole derivatives and imidazole derivatives preferably have an alkyl group having 1 to 3 carbon atoms (methyl group, ethyl group, propyl group), an aminoalkyl group having 1 to 3 carbon atoms (aminomethyl group, aminoethyl group, aminopropyl group), or an amino group in the side chain.

[0176] Specific examples of usable triazoles and triazole derivatives include 1,2,3-triazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, 1-methyl-1,2,3-triazole, 2-methyl-1,2,3-triazole, 4-methyl-1,2,3-triazole, 4,5-dimethyl-1,2,3-triazole, 1-methyl-1,2,4-triazole, 3-methyl-1,2,4-triazole, 3,5-dimethyl-1,2,4-triazole, and 3,5-diethyl-1,2,4-triazole. These may be used alone or in combination of two or more.

[0177] Specific examples of imidazole and imidazole derivatives that can be used include imidazole, 2-aminoimidazole, 4-aminoimidazole, 5-aminoimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-methyl-4-ethylimidazole. These may be used alone or in combination of two or more.

[0178] Among these, triazole and triazole derivatives are preferred in terms of further enhancing the effects of the present invention, and it is particularly preferred to use those selected from 1,2,3-triazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, and imidazole. The nitrogen-containing cyclic compounds specifically exemplified above are known, and if commercially available (including reagents), the commercially available products may be used, or the compounds may be synthesized by oneself. The method for synthesizing the nitrogen-containing cyclic compounds by oneself is obvious to a person skilled in the art in consideration of the common general technical knowledge at the time of filing of this application.

[0179] In the present invention, by using the above-mentioned nitrogen-containing cyclic compound that does not have a benzene ring or a mercapto group in the rubber composition, the nitrogen-containing cyclic compound blended into the rubber can favorably control the formation of a rubber-metal adhesive layer, etc., and by protecting the surface of the metal material, the formation of an excessively large rubber-metal adhesive layer can be prevented, and the adhesive strength with the metal can be greatly increased, without adversely affecting vulcanization, and the initial adhesion with the target metal and the adhesion when exposed to a deteriorating environment can be excellent, resulting in a coated rubber with excellent durability. Nitrogen-containing cyclic compounds having a benzene ring that are outside the scope of the present invention, such as benzotriazoles, are highly compatible with rubber and cannot adequately protect the surface of metal materials. Furthermore, if the compound has a mercapto group (-SH), for example, a triazole derivative such as 3-mercapto-1,2-triazole having a mercapto group (-SH), adverse effects will occur during vulcanization, making it impossible to ensure initial adhesion. Furthermore, if the compound has a long-chain alkyl group, for example, a compound with a carbon chain length of 8 or more, it will have high compatibility with rubber and will not adequately protect the surface of metal materials.

[0180] The content of the nitrogen-containing cyclic compound is preferably 0.02 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the rubber component. The effect of the present invention can be sufficiently obtained when the content of this nitrogen-containing cyclic compound is 0.02 parts by mass or more per 100 parts by mass of the rubber component, and if it is less than 0.02 parts by mass, adhesion may not be ensured when exposed to a deterioration environment. On the other hand, if it is 10 parts by mass or less, initial adhesion is good, and if it exceeds 10 parts by mass, initial adhesion may deteriorate.

[0181] Furthermore, the amine-based antiaging agent represented by the above general formula (1) contains a phenylenediamine moiety, similar to N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD) and the like, but differs from the antiaging agent 6PPD in that it does not have a double bond other than the phenylenediamine moiety, and therefore has a lower environmental impact. Furthermore, the amine-based antioxidant represented by general formula (1) also has the effect of improving the ozone resistance of the rubber composition and suppressing a decrease in the retention rate of elongation at break (EB) and tensile strength (TB) after aging.

[0182] Here, in the general formula (1), R 1 and R 2 R is independently a monovalent saturated hydrocarbon group. 1 and R 2may be the same or different, but from the viewpoint of synthesis, they are preferably the same.

[0183] The monovalent saturated hydrocarbon group preferably has 1 to 20 carbon atoms, more preferably 3 to 10, and particularly preferably 6 or 7. When the saturated hydrocarbon group has 20 or less carbon atoms, the number of moles per unit mass increases, which enhances the anti-aging effect, further suppresses the decrease in adhesive strength between the rubber and the metal cord, and improves the ozone resistance of the rubber composition. From the same viewpoint, R in the above general formula (1) 1 and R 2 are preferably each independently a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms.

[0184] Here, examples of the monovalent saturated hydrocarbon group include an alkyl group and a cycloalkyl group, and the alkyl group may be linear or branched. Furthermore, the cycloalkyl group may further have an alkyl group or the like bonded thereto as a substituent. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a neopentyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,2-dimethylpentyl group, a 1,3-dimethylpentyl group, a 1,4-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,4-dimethylpentyl group, an n-hexyl group, a 1-methylhexyl group, a 2-methylhexyl group, various octyl groups, various decyl groups, and various dodecyl groups. Of these, a 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include a cyclopentyl group, a methylcyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Of these, a cyclohexyl group is preferred.

[0185] Specific examples of the amine-based antioxidant represented by the general formula (1) include N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antiaging agent 77PD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, and N,N'-dicyclohexyl-p-phenylenediamine (antiaging agent CCPD). Among these, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antiaging agent 77PD) and N,N'-dicyclohexyl-p-phenylenediamine (CCPD) are preferred, with N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antiaging agent 77PD) being particularly preferred. The amine-based antioxidants may be used alone or in combination of two or more.

[0186] The content of the amine-based antioxidant in the rubber composition is not particularly limited, but is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component. When the content of the amine-based antioxidant is 0.1 part by mass or more per 100 parts by mass of the rubber component, the ozone resistance of the rubber composition and the adhesion between the rubber and the metal cord can be sufficiently ensured, and decreases in the elongation at break (EB) and tensile strength (TB) of the rubber composition after aging can be sufficiently suppressed. On the other hand, when the content of the amine-based antioxidant is 5 parts by mass or less per 100 parts by mass of the rubber component, adverse effects on rubber physical properties such as heat buildup can be more reliably suppressed, making the rubber suitable for tire applications. Furthermore, from the viewpoints of the ozone resistance of the rubber composition and the adhesion between the rubber and the metal cord, the content of the amine-based antiaging agent is more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and particularly preferably 3 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of suppressing adverse effects on other rubber physical properties, the content of the amine-based antiaging agent is more preferably 4 parts by mass or less, per 100 parts by mass of the rubber component.

[0187] Other ingredients The rubber composition may optionally contain various chemicals commonly used in the rubber industry, such as vulcanization accelerators, hydrazide compounds, waxes, bismaleimide compounds, stearic acid, zinc oxide, and other additives commonly used in the rubber industry, within a range that does not impair the effects of the present invention.

[0188] Among the other components, the rubber composition preferably further contains a vulcanization accelerator. By including the vulcanization accelerator, vulcanization can be accelerated, and the strength of the rubber composition after vulcanization can be further increased.

[0189] The type of the vulcanization accelerator is not particularly limited, and examples thereof include guanidine-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, sulfenamide-based, thiourea-based, dithiocarbamate-based, xanthate-based vulcanization accelerators, etc. These vulcanization accelerators may be used singly or in combination of two or more. Among the vulcanization accelerators mentioned above, it is preferable to use a sulfenamide-based vulcanization accelerator from the viewpoint of further increasing the strength of the rubber composition after vulcanization. Examples of the sulfenamide vulcanization accelerator include N-cyclohexyl-2-benzothiazolylsulfenamide, N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide, N-ethyl-2-benzothiazolylsulfenamide, N-propyl-2-benzothiazolylsulfenamide, N-butyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N-heptyl-2-benzothiazolylsulfenamide, N-octyl-2-benzothiazolylsulfenamide, N-2-ethylhexyl-2-benzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide, N-Dodecyl-2-benzothiazolylsulfenamide, N-Stearyl-2-benzothiazolylsulfenamide, N,N-Dimethyl-2-benzothiazolylsulfenamide, N,N-Diethyl-2-benzothiazolylsulfenamide, N,N-Dipropyl-2-benzothiazolylsulfenamide, N,N-Dibutyl-2-benzothiazolylsulfenamide, N,N-Dipentyl-2-benzothiazolylsulfenamide, N,N-Dihexyl 2-benzothiazolylsulfenamide, N,N-diheptyl-2-benzothiazolylsulfenamide, N,N-dioctyl-2-benzothiazolylsulfenamide, N,N-di-2-ethylhexylbenzothiazolylsulfenamide, N,N-didecyl-2-benzothiazolylsulfenamide, N,N-didodecyl-2-benzothiazolylsulfenamide, and N,N-distearyl-2-benzothiazolylsulfenamide. Among these, it is more preferable that the vulcanization accelerator contains at least N-cyclohexyl-2-benzothiazolylsulfenamide.

[0190] When at least N-cyclohexyl-2-benzothiazolylsulfenamide is contained as the vulcanization accelerator, the physical properties of the vulcanized rubber are uniform, thereby suppressing reversion due to over-vulcanization, and therefore high-temperature vulcanization in a short time is possible, resulting in excellent productivity. In addition, when the surface of the above-mentioned steel cord is coated with a ternary plating of copper, zinc, and iron, a synergistic effect with adhesion can be obtained.

[0191] Furthermore, from the viewpoint of further improving the low heat buildup and crack resistance of the rubber composition after vulcanization, the content of the vulcanization accelerator is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and is preferably 2.0 parts by mass or less, more preferably 1.8 parts by mass or less, and even more preferably 1.6 parts by mass or less, per 100 parts by mass of the rubber component.

[0192] Among the other components, the hydrazide compound may be a hydrazide compound represented by the following general formula: [ka] (In the formula, R 1 , R 2 are each independently an alkyl group having 1 to 18 carbon atoms.)

[0193] In the above general formula, R 1 , R 2 are each independently an alkyl group having 1 to 18 carbon atoms, and examples thereof include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl. 1 , R 2 One of the groups may be methyl.

[0194] Examples of the hydrazide compound represented by the above general formula include 1-hydroxy-N'-(1-methylethylidene)-2-naphthoic acid hydrazide, 1-hydroxy-N'-(1-methylpropylidene)-2-naphthoic acid hydrazide, 1-hydroxy-N'-(1-methylbutylidene)-2-naphthoic acid hydrazide, 1-hydroxy-N'-(1,3-dimethylbutylidene)-2-naphthoic acid hydrazide, 1-hydroxy-N'-(1,3-dimethylbutylidene)-2-naphthoic acid hydrazide, 3-Hydroxy-N'-(2-furylmethylene)-2-naphthoic acid hydrazide, 3-Hydroxy-N'-(1-methylethylidene)-2-naphthoic acid hydrazide, 3-Hydroxy-N'-(1-methylpropylidene)-2-naphthoic acid hydrazide, 3-Hydroxy-N'-(1-methylbutylidene)-2-naphthoic acid hydrazide, 3-Hydroxy-N'-(1,3-dimethylbutylidene)-2-naphthoic acid hydrazide hydrazide, 3-hydroxy-N'-(2-furylmethylene)-2-naphthoic acid hydrazide, and the like can be mentioned, and preferred are 1-hydroxy-N'-(1-methylethylidene)-2-naphthoic acid hydrazide, 1-hydroxy-N'-(1-methylpropylidene)-2-naphthoic acid hydrazide, 1-hydroxy-N'-(1,3-dimethylbutylidene)-2-naphthoic acid hydrazide, 1-hydroxy-N'- Examples include (2-furylmethylene)-2-naphthoic acid hydrazide, 3-hydroxy-N'-(1-methylethylidene)-2-naphthoic acid hydrazide, 3-hydroxy-N'-(1-methylpropylidene)-2-naphthoic acid hydrazide, 3-hydroxy-N'-(1,3-dimethylbutylidene)-2-naphthoic acid hydrazide, and 3-hydroxy-N'-(2-furylmethylene)-2-naphthoic acid hydrazide.

[0195] Among the other components, examples of waxes include natural waxes such as vegetable waxes and animal waxes; petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as ethylene polymers and propylene polymers. Commercially available waxes can be used, and examples of commercially available waxes include products from Seiko Chemical Co., Ltd., Nippon Seiro Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and the like. These waxes may be used alone or in combination of two or more.

[0196] The wax may also be a hydrolyzed product of a plant-derived wax. Examples of such plant-derived wax hydrolyzates include those obtained by partially or completely hydrolyzing plant waxes such as carnauba wax, candelilla wax, Japan wax, sunflower wax, and rice wax using any method. Among these, rice wax extracted from grasses is particularly suitable because it efficiently produces primary alcohols having the carbon number distribution and component composition described below. Plant-derived wax hydrolyzates typically contain a linear monohydric primary alcohol as an active ingredient, and other components include alkanes, alkenes, alkynes, carboxylic acids, ketones, aldehydes, non-linear and / or unsaturated primary alcohols, secondary alcohols, tertiary alcohols, dihydric or higher polyhydric alcohols, resins, wax esters, etc., although these other components do not necessarily need to be removed. Among these other components, higher fatty acids obtained by hydrolyzing plant waxes function as vulcanization aids in rubber compositions, so their removal is less necessary. Of course, any of these components may be removed using any method. As a specific example, in the case of a hydrolysate of vegetable wax, the fatty acids contained therein may be esterified with a lower alcohol, and then the higher fatty acid esters may be removed and the higher alcohol may be concentrated by utilizing the difference in solubility between the higher alcohol and the ester in a low-polarity solvent.

[0197] The content of the wax is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component.

[0198] Among the other components, zinc oxide (ZnO) is used as a vulcanization accelerator. When the rubber composition further contains zinc oxide, vulcanization can be accelerated, and the strength of the rubber composition after vulcanization can be further increased. The zinc oxide is preferably zinc oxide obtained by recycling. Commercially available zinc oxide products can be used, including those from Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., Mitsui Mining & Smelting Co., Ltd., and Toho Zinc Co., Ltd. These commercially available zinc oxide products may be used alone or in combination of two or more.

[0199] Here, the content of the zinc oxide is not particularly limited, but from the viewpoint of further improving the low heat buildup and crack resistance of the rubber composition, it is preferably 5 to 13 parts by mass, and more preferably 7 to 10 parts by mass, per 100 parts by mass of the rubber component.

[0200] Among the other components, commercially available stearic acid can be used, and examples of commercially available stearic acid include products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. These commercially available stearic acid products may be used alone or in combination of two or more.

[0201] The content of stearic acid is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component.

[0202] The rubber composition may also contain a cobalt compound from the viewpoint of improving adhesion between the rubber and the cord. The type of cobalt compound is not particularly limited and can be appropriately selected depending on the required performance. However, from the viewpoint of environmental load, the rubber composition is preferably a cobalt-free rubber composition. Note that "not containing cobalt in the rubber composition" means that cobalt is not intentionally blended into the rubber composition, and does not include cases where cobalt is unavoidably contained or cobalt that has migrated from the steel cord to the rubber.

[0203] The method for producing the rubber composition is not particularly limited. For example, the composition can be produced by blending the above-mentioned components and kneading them using a kneading machine such as a Banbury mixer, a roll, or an internal mixer. The components of the rubber composition may be kneaded in one stage or in two or more stages.

[0204] The method for covering the steel cord with the rubber composition is not particularly limited, but the following method can be used, for example. A predetermined number of the plated steel cords are arranged in parallel at predetermined intervals, and these steel cords are coated from above and below with unvulcanized rubber sheets of the rubber composition having a thickness of about 0.5 mm, and then vulcanized at a temperature of about 160°C for about 20 minutes. The steel cord-rubber composite obtained in this way has excellent adhesion between the rubber and cord.

[0205] The steel cord-rubber composite of the present invention can be used for various purposes, including as a reinforcing material for rubber articles that require particular strength, such as various automobile tires, hoses, and rubber crawlers. It can be particularly suitable for use as a reinforcing member for belts, carcass plies, wire chafers, and the like in various automobile radial tires.

[0206] <Tires> The tire of the present invention is characterized by comprising the above-mentioned steel cord-rubber composite of the present invention. By using the steel cord-rubber composite of the present invention as a component constituting a tire, the adhesion between the rubber and the steel cord can be improved, and therefore the durability of the component using the steel cord-rubber composite can be improved.

[0207] Furthermore, the tire of the present invention is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. The method for producing the tire of the present invention is not particularly limited, and the tire can be produced by a conventional method. Generally, a rubber composition containing various components is processed into each component in the unvulcanized stage, and the components are attached and molded in a tire building machine by a conventional method to form a green tire. The green tire is then heated and pressurized in a vulcanizer to produce a tire. For example, the rubber composition is kneaded, and steel cords are rubber-coated with the resulting rubber composition. An unvulcanized belt, an unvulcanized carcass, and other unvulcanized components are laminated together, and the unvulcanized laminate is vulcanized to obtain a tire. [Example]

[0208] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0209] <Examples 1 and 2, Comparative Example 1> Rubber composition samples were prepared according to Table 1.

[0210] <Evaluation> The obtained rubber composition samples were evaluated for adhesion between the rubber and the steel cord by the following method. The evaluation results are shown in Table 1.

[0211] (1) Adhesion parameters The vulcanization rate of each sample was measured by a rotorless rheometer. For the evaluation, a relative value was calculated when the vulcanization speed of Comparative Example 1 was set to 100, and is shown in Table 1. The larger the relative value, the better the adhesion parameter, indicating superior adhesion between the rubber and the steel cord.

[0212] [Table 1]

[0213] *1 NR: Natural rubber *2 BR: Butadiene rubber, cis-1,4 bond content 96% or more *3 Carbon black: Asahi Carbon Co., Ltd., product name "Asahi #65" *4 Antioxidant A: Other quinoline-based antioxidant, polymer of 2,2,4-trimethyl-1,2-dihydroquinoline, manufactured by Seiko Chemical Co., Ltd., product name "Nonflex RD" *5 Antioxidant B: An aminoquinoline-based antioxidant represented by the following formula (1-1) [ka] *6 Other chemicals: Total amount including at least oil, zinc oxide, stearic acid and vulcanization accelerator

[0214] The results in Table 1 show that the samples of the examples exhibit superior effects on adhesion parameters compared to the samples of the comparative examples.

[0215] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is thought to be a technology that can contribute to the achievement of goals such as "No. 7 - Affordable and clean energy for all," "No. 12 - Responsible consumption and production," and "No. 13 - Take urgent action against climate change." [Industrial Applicability]

[0216] According to the present invention, even when the amount of cobalt used is small, a steel cord-rubber composite having excellent adhesion between the rubber and the steel cord can be provided. Furthermore, according to the present invention, a tire having excellent durability of components using the steel cord can be provided.

Claims

1. A steel cord-rubber composite obtained by coating a steel cord having one or more steel wires with a rubber composition, The rubber composition comprises a rubber component and a compound represented by the following general formula (1): 【Chemistry 1】 is a single or double bond, and R １１ and R １２ are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a phenyl group; R １３ , R １４ , R １５ , R １６ , R １７ , R １８ and R １９ and an aminoquinoline antioxidant represented by the following formula (I):

2. The steel wire has, on its outermost surface, a brass plating layer containing 0.3 to 1.7 atomic % of phosphorus, 2.5 to 14 atomic % of zinc, and 0.01 to 2.0 atomic % of a metal having an ionization tendency smaller than that of zinc and larger than that of copper, as measured by XPS (X-ray photoelectron spectroscopy); 2. The steel cord-rubber composite according to claim 1, which satisfies the following formulas (I) and (II): 0.3≦A / (A+B)≦0.6...(I) 0.06≦(A / (A+B)) / C≦6...(II) A: The zinc content (atomic %) at the outermost surface of the brass plating layer measured by XPS. B: The copper content (atomic %) at the outermost surface of the brass plating layer measured by XPS. C: Content of the minoquinoline-based inhibitor in the rubber composition (parts by mass per 100 parts by mass of the rubber component)

3. 3. The steel cord-rubber composite according to claim 1, wherein the rubber component comprises at least one rubber selected from the group consisting of an isoprene skeleton rubber, a styrene-butadiene rubber, a butadiene rubber, and a chloroprene rubber.

4. The aminoquinoline antioxidant is represented by the following general formula (1-1): 【Chemistry 2】 3. The steel cord-rubber composite according to claim 1, wherein the compound is a compound represented by the formula:

5. 3. The steel cord-rubber composite according to claim 1, wherein a content of the aminoquinoline-based antioxidant in the rubber composition is 0.1 to 5 parts by mass per 100 parts by mass of the rubber component.

6. 3. The steel cord-rubber composite body according to claim 1, wherein the rubber composition does not contain a cobalt compound.

7. The steel cord has one or more steel filaments on which a plating layer containing copper, zinc, and cobalt is formed, 3. The steel cord-rubber composite according to claim 1, wherein the following formulas (L) and (M) are satisfied: A≧40...(L) 8≦A / B≦700...(M) A: The rubber and the plating layer are bonded together, and the layer of the plating layer in which a copper and sulfur compound is present is defined as the adhesive layer. The sulfur content of the adhesive layer is analyzed from the plating layer toward the rubber in a direction perpendicular to the longitudinal direction of the steel filament. The position of the inflection point where the sulfur content increases is defined as the bottom of the adhesive layer. The atomic % of cobalt is analyzed at six equally spaced points in the longitudinal direction of the steel filament, extending 100 nm from the bottom of the adhesive layer inward in the direction perpendicular to the longitudinal direction of the steel filament. The portion where the atomic % of cobalt is higher than the atomic % of cobalt in the entire plating layer is defined as a cobalt-rich region (nm), and the ratio (%) of the total atomic % of the cobalt-rich regions (nm) at the six points to the total analysis range (600 nm) of the six points B: Content of the aminoquinoline antioxidant in the rubber composition (parts by mass per 100 parts by mass of the rubber component)

8. The steel cord has one or more steel wires on which a plating layer is formed, the steel wire has a phosphorus content of 1.5 atomic % or less contained as an oxide in a wire surface layer region extending from the surface of the plating layer to a depth of 5 nm inward in the wire radial direction, 3. The steel cord-rubber composite according to claim 1, wherein a ratio (A / B) of a content (A (atomic %)) of phosphorus contained as an oxide in a wire surface layer region of the steel wire from the surface of the plating layer to a depth of 5 nm inward in the wire radial direction to a content (B (parts by mass)) of the aminoquinoline-based antioxidant in the rubber composition per 100 parts by mass of the rubber component is 0.02 to 15.

9. the rubber composition contains N-cyclohexyl-2-benzothiazolylsulfenamide, a ratio (a / b) of a modulus (a) at 50% elongation of the rubber composition after vulcanization to a modulus (b) at 50% elongation of a vulcanized rubber covering the reinforcing material at an end portion in the tire width direction of the reinforcing layer is 0.94 or more and 1.06 or less, 3. The steel cord-rubber composite according to claim 1, wherein the steel cord is ternary plated with copper, zinc, and iron.

10. The rubber composition contains 0.01 parts by mass or more of a rubber-metal adhesion promoter containing a metal carboxylate having 2 to 25 carbon atoms and the metal species being any one selected from the group consisting of bismuth, copper, antimony, silver, niobium, and zirconium, and at least one selected from the group consisting of compounds represented by the following formula (A), relative to 100 parts by mass of the rubber component:

3. The steel cord-rubber composite material according to claim 1, further comprising 4,4'-diphenylmethane bismaleimide. 【Transformation 3】 [In formula (A), Z is a structure selected from formulas (z-1) to (z-4). M is bismuth, copper, antimony, silver, niobium, or zirconium. (RCOO) is a residue of an aliphatic carboxylic acid having 2 to 25 carbon atoms. x is an integer equal to (the valence of M - 1).]

11. The rubber composition comprises a nitrogen-containing cyclic compound that does not contain a benzene ring or a mercapto group, The following general formula (1): 【Chemistry 4】 [In the formula, R １ and R ２ and each independently represents a monovalent saturated hydrocarbon group; 3. The steel cord-rubber composite according to claim 1, wherein a mass ratio (A / B) of a content (A) of the nitrogen-containing cyclic compound not containing a benzene ring and a mercapto group to a content (B) of the amine-based antiaging agent is 0.004 to 100.

12. A tire comprising the steel cord-rubber composite according to claim 1 or 2.

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