Steel cord-rubber composite, and tire

Abstract

The purpose of the present invention is to provide a steel cord-rubber composite having excellent adhesiveness between rubber and steel cords and excellent ozone resistance even when the amount of cobalt used is small.　The present invention is a steel cord-rubber composite obtained by coating steel cords having one or a plurality of steel wires with a rubber composition, said steel cord-rubber composite characterized in that the rubber composition includes a rubber component and an anti-aging agent, and the anti-aging agent contains at least one from among aminoquinoline-based anti-aging agents represented by general formula (1) and phenylenediamine-based anti-aging agents represented by general formula (2).

Description

Steel cord-rubber composite and tire

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

[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 by this direct vulcanization adhesion.

[0004] For example, Patent Document 1 discloses a method for manufacturing a steel cord for reinforcing a steel cord-rubber composite, which is made by twisting together a plurality of filaments manufactured by wet drawing a brass-plated steel wire, in which resorcinol is added 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 filament surface. Also, Patent Document 2 discloses a technology for improving adhesion with the coating rubber by washing the surfaces of the steel wire and steel cord used with an acidic or alkaline solution to remove phosphorus compounds (derived from the lubricant used during steel cord manufacturing) that 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, and in such cases, a sufficient effect as an adhesion improver between the steel cord and the coating rubber cannot be expected, so further improvement was necessary. Furthermore, the technology of Patent Document 2 does not specifically disclose the amount of phosphorus compounds reduced on the steel cord surface after cleaning treatment, the ratio of copper to zinc, or other compositions, and more detailed consideration from these perspectives has been desired.

[0006] Furthermore, in order to improve the initial adhesion between coated rubber and metal reinforcing materials in direct vulcanization bonding generally used in tires, etc., rubber compositions are used in which cobalt salts, which act as adhesion promoters, are blended into the coated rubber, but from the viewpoint of improving the durability of the coated rubber against deterioration and crack growth, etc., it is desirable to reduce the amount of such cobalt salts as much as possible. Therefore, Patent Document 3 discloses a steel cord in which the presence of specific metals (phosphorus, zinc, and metals with an ionization tendency lower than zinc and higher than copper) is controlled to be present in specific proportions 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.

[0007] The various rubber components that make up tires can deteriorate due to the influence of external environments, such as in the presence of ozone, and as this deterioration progresses, cracks and other defects can occur. To address this problem, rubber compositions containing antioxidants are often used in various rubber components. For example, Patent Document 4 below discloses that cracks and discoloration on the tire surface can be suppressed by applying a rubber composition containing a selected blend of a specific quinoline-based antioxidant and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD) to the rubber that makes up the tire surface.

[0008] JP 2004-66298 A JP 2001-234371 A International Publication No. 2011 / 30547 International Publication No. 2018 / 056384

[0009] According to the techniques of Patent Documents 2 and 3, 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, as rubber articles such as tires become more and more sophisticated, it is believed that the requirements for adhesion between rubber and steel cord will become increasingly stringent. For example, the performance required for adhesion between steel cord and coated rubber must not only be initial adhesion, but also satisfy various conditions, such as preventing failure 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 perspective of environmental impact, it is desirable to reduce the amount of cobalt contained in rubber and steel cord as much as possible. Therefore, there has been a need for the development of a technology that provides excellent adhesion between rubber and steel cord even when no cobalt is used or when the amount of cobalt used is small.

[0010] Furthermore, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antioxidant 6PPD) used in the above Patent Document 4 may have an impact on the environment, and in consideration of the possibility of future restrictions under European regulations, it has been desired to use an antioxidant that has a lower environmental impact and excellent ozone resistance.

[0011] 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 and also has excellent ozone resistance, even when the amount of cobalt used is small. Another object of the present invention is to provide a tire that has excellent durability of components using the steel cord and also has excellent ozone resistance.

[0012] The gist of the present invention for solving the above problems is as follows: [1] A steel cord-rubber composite obtained by coating a steel cord having one or more steel wires with a rubber composition, wherein the rubber composition comprises a rubber component and a rubber compound represented by the following general formula (1): [In the formula, is a single bond or a double bond, R １１ and R １２are 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 , R １９ and R １１０ are each independently hydrogen or an alkyl group having 1 to 12 carbon atoms, and an aminoquinoline antioxidant represented by the following general formula (2): [In the formula, R ２１ and R ２２ are each independently an alkyl group or an aryl group having 7 or more carbon atoms, and R ２１ and R ２２ and an antioxidant containing one of the phenylenediamine-based antioxidants represented by the formula (I) above, wherein at least one of the phenylenediamine-based antioxidants is an alkyl group having 7 or more carbon atoms. By having the above-mentioned configuration, even when the amount of cobalt used is small, it is possible to achieve excellent adhesion between the rubber and the steel cord and also improve ozone resistance.

[0013] [2] A tire according to the present invention is characterized by including the steel cord-rubber composite of the present invention. The above-mentioned configuration makes it possible to realize excellent durability of the steel cord-containing components, and further, excellent ozone resistance.

[0014] 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 and excellent ozone resistance can be provided.Furthermore, according to the present invention, a tire having excellent durability of components using the steel cord and excellent ozone resistance can be provided.

[0015] The steel cord-rubber composite and tire of the present invention will be described in detail below based on embodiments thereof.

[0016] <Definitions> The compounds described herein may be derived in whole or in part from fossil resources, from biological resources such as plant resources, from recycled resources such as used tires, or from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0017] 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.

[0018] 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.). The biological resources may be edible or non-edible, but are preferably non-edible in order not to compete with food and from the viewpoint of effective resource utilization.

[0019] 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, old 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. 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.

[0020] 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.

[0021] <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.

[0022] <<Steel Cord>> (Brass-Plated Steel Cord) The steel wire constituting the steel cord preferably has, on its outermost surface, a brass-plated 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).

[0023] 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 emission of photoelectrons generated when X-rays are irradiated onto the surface of the steel wire having a brass plating layer.

[0024] When the outermost surface of the steel wire is measured by the XPS method, the outermost surface preferably 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, which may lead to problems in handling such as storage, or may narrow the conditions for compounding with rubber. If the phosphorus content exceeds 1.7 atomic %, the initial adhesion rate between the brass-plated steel cord and the coated rubber may decrease.

[0025] The outermost surface of the steel wire preferably contains zinc in an amount of 2.5 to 14 atomic %, preferably 4.95 to 13.5 atomic %, and more preferably 5.0 to 13 atomic %. If the zinc content is less than 2.5 atomic %, the resulting steel cord-rubber composite may have insufficient adhesion durability, while if it exceeds 14 atomic %, the initial adhesion rate between the steel cord and the coating rubber may decrease.

[0026] Furthermore, the outermost surface of the steel wire preferably contains a metal having an ionization tendency lower than that of zinc but 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 amount of such a metal is less than 0.01 atomic %, adhesion to the coating rubber may be reduced, and if the amount exceeds 2.0 atomic %, the same risk may occur. Examples of metals having 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 compounded 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 may reduce the durability of the coating rubber itself against heat, moisture, and oxidation. However, by making such cobalt present in the brass-plated steel cord, the cobalt content in the coating rubber can be reduced, and it is also possible to reduce costs while effectively suppressing deterioration in the physical properties of the rubber.

[0027] Furthermore, in the steel cord-rubber composite of the present invention, it is preferable that the steel wire satisfy the following formula (I): 0.3≦A / (A+B)≦0.6 (I), where "A" represents the zinc content (atomic %) at the outermost surface of the brass plating layer, as measured by XPS, and "B" represents the copper content (atomic %) at the outermost surface of the brass plating layer, as measured by XPS. When the zinc content ratio (A / (A+B)) relative to the total content of zinc and copper at the outermost surface of the steel wire (the brass plating surface) satisfies the above range, adhesion between the rubber and the steel cord can be improved. From the same viewpoint, it is more preferable that the ratio (A / (A+B)) is 0.35 to 0.6.

[0028] The steel cord can be produced, for example, by the following method: The peripheral surface of a steel wire is plated with brass, and then the steel wire is drawn. The plating composition is typically 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 resulting steel wire may be immersed in an aqueous solution containing, as a metal salt, a metal whose ionization tendency is smaller than that of zinc and larger than that of copper, and then a plurality of these steel wires may be twisted together. Alternatively, a plurality of these 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.

[0029] 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 enable an aqueous solution containing the metal salt to achieve a suitable pH value, which will be described later.

[0030] The aqueous solution containing the metal salt typically has a concentration of 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 is unlikely to 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 standpoint of environmental considerations and safety during production.

[0031] The time for immersing the steel cord in the aqueous solution containing the metal salt may be set as appropriate, but is usually 0.05 to 30 seconds, preferably 0.1 to 20 seconds.

[0032] 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.

[0033] 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 adhesive reaction to proceed excessively, resulting in weak adhesion.

[0034] (Steel cord having a plating layer containing copper, zinc, and cobalt formed thereon) The steel cord preferably has one or more steel filaments having a plating layer containing copper, zinc, and cobalt formed thereon, and satisfies the following formulas (L) and (M): A≧40 (L) 8≦A / B≦700 (M) L: 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, and 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. Then, the atomic % of cobalt is analyzed at six equally spaced points in the longitudinal direction of the steel filament, over 100 nm from the bottom of the adhesive layer inward in the direction perpendicular to the longitudinal direction of the steel filament, and 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 analytical range (600 nm) of the six points B: the content (parts by mass per 100 parts by mass of the rubber component) of an aminoquinoline-based antioxidant in a rubber composition described later

[0035] The sulfur content of the adhesive layer is analyzed from the inside of the plating layer 3 toward the rubber 1 in a direction perpendicular to the longitudinal direction of the steel filament 2. The position of the inflection point where the sulfur content increases is designated as the bottommost part 4 of the adhesive layer. The atomic % of cobalt is analyzed at six equally spaced points in the longitudinal direction of the steel filament 2, extending 100 nm inward from the bottommost part 4 of the adhesive layer in a direction perpendicular to the longitudinal direction of the steel filament 2. Here, when a portion where the atomic % of cobalt is higher than the atomic % of cobalt in the entire plating layer is designated as a cobalt-rich region (nm), in the steel cord-rubber composite of the present invention, the total length (nm) of the cobalt-rich region at the six points is 40% or more of the total length (nm) of the analysis range at the six points. In other words, 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 % of cobalt is measured.

[0036] Thus, by satisfying the above formulas (L) and (M), the steel cord-rubber composite of the present invention can be said to have a cobalt-rich region formed in the adhesive layer between the rubber 1 and the steel filament 2, thereby improving the adhesion between the rubber and the steel cord. To achieve this effect, 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 degradation and reduces the environmental load. Furthermore, it is not necessary to extend the rubber mixing time, which does not adversely affect productivity. Furthermore, from the perspective of reducing the amount of cobalt used, the cobalt-rich region is preferably 70% or less (A≦70).

[0037] 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 via 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.

[0038] For example, to perform wiredrawing with reduced lubricity to a certain extent by wet wiredrawing using a liquid lubricant, the concentration of the lubricating component in the lubricant is reduced below the concentration used in normal wiredrawing, or the temperature of the lubricant 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, when reducing the concentration of the lubricating component, the concentration should be 80% to 20% of the concentration of the lubricant normally used in steel filament wiredrawing. Reducing the lubricant too much can result in the detachment of the ternary plating layer, deterioration of the steel filament quality, or wire breakage and die wear. Conversely, if the lubricity is not reduced enough, the proportion of the cobalt-rich region decreases, preventing sufficient improvement in adhesion between the rubber and the steel cord.

[0039] Furthermore, if the heat generation during the wiredrawing process is too great, the lattice defect density of the ternary plating layer may decrease due to the temperature rise, and the ductility of the steel filaments may deteriorate. Therefore, it is preferable to set wiredrawing conditions that reduce heat generation, such as those in (1) to (5) below, and to set the temperature of the wire coming out of the die to 150°C or less when measured with a contact thermometer. (1) Set the area reduction rate per die low. (2) Set the wiredrawing speed low. (3) Cool the die to suppress the temperature rise. (4) Cool the steel filament material entering the die and / or the steel filament coming out of the die. (5) In a continuous wiredrawing process using multiple dies, set the coefficient of friction of at least one of the three dies located most downstream to 0.18 or more.

[0040] 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 lowered lubrication to a certain extent 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.

[0041] 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 for example, the copper content may be 64 to 69 atomic % and the cobalt content may be 1 to 10 atomic %.

[0042] 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 initial adhesion. On the other hand, if the average thickness 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.

[0043] 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 layer 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 wire surface layer region extending from the surface of the plating layer to a depth of 5 nm inward in the wire radial direction of the steel wire to the content (B (parts by mass)) of an aminoquinoline-based 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.

[0044] By setting the phosphorus content to 1.5 atomic % or less, it is 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 region increases beyond 1.5 atomic %, the adhesion speed with the rubber will decrease accordingly, and sufficient adhesion may not be obtained. Note that the lower limit of the phosphorus content in the wire surface region is not particularly limited, but it can be set to 0.1 atomic % or more.

[0045] Here, the quantitative determination of phosphorus in the wire surface region of the plating layer was carried out by using X-ray photoelectron spectroscopy to measure 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:P ２Ｐ , Cu:Cu ２ｐ３／２ , Zn:Zn ２ｐ３／２and N:N １Ｓ The number of photoelectrons counted was calculated by correcting the number of photoelectrons counted by the respective sensitivity coefficients. For example, the number of detected phosphorus atoms [P] can be calculated by the following formula: [P] = Fp(P ２ｐ Sensitivity coefficient of (P per certain time) × ( ２ｐ Photoelectron counts)

[0046] If the number of detected atoms of other atoms is determined in the same manner, the relative atomic % of phosphorus can be calculated from these results according to the following formula: P (atomic %) = {[P] / ([Cu] + [Zn] + [C] + [O] + [N] + [P])} × 100. Furthermore, the distribution of elements in the depth direction from the peripheral surface toward the inside in the radial direction of the wire can also be measured in detail by performing argon etching or the like.

[0047] 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.

[0048] 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 perform the wiredrawing using dies made of a material that combines excellent self-lubrication 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.

[0049] 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.

[0050] 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 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 become 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 become 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 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 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 incurring the disadvantage of reduced heat-resistant adhesion and moisture-resistant adhesion.

[0051] The diameter of the steel wire is preferably 0.40 mm or less. If the diameter exceeds 0.40 mm, the surface strain may become large when the rubber article used therein is repeatedly subjected to strain under bending deformation, which may easily cause buckling.

[0052] <<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 antioxidant.

[0053] (Rubber Component) 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 sustainability rate of the rubber component is preferably 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, still 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.

[0054] The rubber component is preferably the rubber derived from biological resources and the rubber derived from recycled resources. Here, the proportion of the monomer component 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, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%. Furthermore, the proportion of the monomer component 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, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%.

[0055] 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 in terms of standard polystyrene based on measurements obtained using, for example, a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

[0056] 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.

[0057] 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.

[0058] The isoprene-based rubber preferably has a sustainability ratio 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. To achieve a sustainability ratio 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.).

[0059] Examples of the butadiene-based 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-based rubber, is preferably derived from biological resources or recycled resources.

[0060] 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.

[0061] 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. As the aromatic vinyl compound-butadiene copolymer rubber, commercially available products can be used, and examples of such commercially available products include products from Asahi Kasei Corporation, ENEOS Materials Corporation, Zeon Corporation, Sumitomo Chemical Co., Ltd. These aromatic vinyl compound-butadiene copolymer rubbers may be used alone or in combination of two or more.

[0062] The butadiene-based rubber 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. To achieve a sustainability rate within the above range, for example, a polymer synthesized using a bioresource-derived butadiene, a recycled resource-derived butadiene, a bioresource-derived aromatic vinyl compound (e.g., bioresource-derived styrene), or a recycled resource-derived aromatic vinyl compound (e.g., recycled resource-derived styrene) as a monomer component may be used. In this case, the synthesized polymer may be a homopolymer of a bioresource-derived monomer, a homopolymer of a recycled resource-derived monomer, a copolymer of a bioresource-derived monomer and a recycled resource-derived monomer, or a copolymer of a bioresource-derived monomer and / or a recycled resource-derived monomer and a fossil resource (e.g., petroleum)-derived monomer. Note that the butadiene rubber (B-BR) derived from biological resources (biomass resources) and aromatic vinyl compound-butadiene copolymer rubber derived from biological resources (for example, styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources)) 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.

[0063] 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.

[0064] Generally, the production of rubber composition materials for tires (e.g., rubber and its monomers, fillers, resins, etc.) requires large-scale production equipment, and therefore is typically produced in large factories in specific regions, requiring significant energy for the storage and transportation of raw materials and 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. Therefore, by utilizing local products and waste, the energy required for transporting and storing raw materials can be reduced, and furthermore, 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 tire-constituting materials, such as rubber, fillers, and steel cords. 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 materials derived from recycled resources) can reduce the overall environmental impact in tire manufacturing, such as reducing carbon dioxide emissions (LCCO2) over the entire life cycle, reducing energy consumption (LCE) over the entire life cycle, reducing costs incurred over the entire life cycle (LCC), and reducing the use of fossil resources.

[0065] 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.

[0066] The ratio of each monomer unit (e.g., isoprene-derived units, butadiene-derived units, and aromatic vinyl compound-derived units) 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. 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 "isoprene-derived unit" refers to a structural unit in a polymer based on the isoprene monomer (including isoprene units in natural rubber), the term "butadiene-derived unit" refers to a structural unit in a polymer based on the butadiene monomer, and the term "aromatic vinyl compound-derived unit" refers to a structural unit in a polymer based on the aromatic vinyl compound monomer. In this specification, the ratio of each monomer unit is measured by NMR.

[0067] 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 alone or in combination of two or more.

[0068] The rubber component 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. These functional groups may have a substituent. These functional groups may be introduced into the rubber component either individually or in combination. Among these, an amino group, an alkoxy group, and an alkoxysilyl group are preferred, and a substituted amino group in which a hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an alkoxysilyl group having 1 to 6 carbon atoms are more preferred.

[0069] 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 modified functional group that has interactivity with fillers such as silica and carbon black, and examples thereof include a nitrogen-containing functional group, a silicon-containing functional group, or an oxygen-containing functional group. Examples of compounds (modifiers) having a nitrogen-containing functional group include amino group-containing compounds, and 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.

[0070] 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.

[0071] 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 the monomer component, it is possible to obtain a bioresource (biomass resource)-derived butadiene rubber (B-BR). Furthermore, by using styrene obtained from a bioresource and butadiene obtained from a bioresource as the monomer components, it is possible to obtain a bioresource (biomass resource)-derived styrene-butadiene rubber (B-SBR). 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.

[0072] 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 be used in combination. Suitable styrenes obtained from biological resources include styrenes obtained from plants (preferably plants belonging to the Hamamelidaceae, Styraxaceae, and Apocynaceae families, more preferably plants belonging to the Liquidambar, Styrax, and Catharanthus roseus, and even more preferably sweetgum, Styrax rostrata, and Catharanthus roseus), and styrenes obtained from microorganisms (preferably microorganisms belonging to the Penicillium and Escherichia genera, more preferably P. citrinum, and transformed E. coli). Suitable styrenes may be used in combination.

[0073] Recently, biomass industrial complexes centered on bioethanol, bioethylene, and the like have been planned. However, bioethanol and bioethylene are produced primarily using 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 biological resource-derived monomer components as the biological resource-derived monomer components, or to use a combination of biological resource-derived monomer components, renewable resource-derived monomer components, and fossil resource-derived monomer components, and further adjust the ratios of these monomer components appropriately. This allows for the effective utilization 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.

[0074] 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.

[0075] 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, devulcanizing the resulting material, 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 results. Furthermore, since the crosslinked structure in the rubber is partially cleaved by devulcanization and functionalization, increasing its reactivity, the modified reclaimed rubber is advantageous for overcoming problems such as reduced reinforcing properties that can occur when using recycled materials. For example, reclaimed rubber or vulcanized rubber powder (rubber powder) that has functional groups capable of reacting with unvulcanized diene rubber is functionalized with a modifying compound (introducing a modifying compound). Here, the reclaimed rubber is not particularly limited, and examples thereof include crushed rubber that has been mechanically crushed at room temperature or in a frozen state, devulcanized rubber that has been further desulfurized, recycled rubber from used rubber such as automobile tires, tubes, and other rubber products specified in JIS K6313, and reclaimed rubber with properties equivalent thereto.

[0076] 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.

[0077] (Antiaging Agent) The antioxidant contained in the rubber composition has the effect of preventing aging of the rubber composition and rubber products using the same. Here, the content of the antioxidant is preferably 0.5 to 10 parts by mass per 100 parts by mass of the rubber component. When the content of the antioxidant is 0.5 parts by mass or more per 100 parts by mass of the rubber component, better ozone resistance is obtained and decreases in the elongation at break (EB) and tensile strength (TB) of the rubber composition after aging can be sufficiently suppressed. When the content of the antioxidant is 10 parts by mass or less per 100 parts by mass of the rubber component, adverse effects on rubber physical properties other than ozone resistance (heat buildup, etc.) can be suppressed. From the same viewpoint, the content of the antioxidant is preferably 1 to 8 parts by mass per 100 parts by mass of the rubber component.

[0078] The rubber composition contains an antioxidant selected from the group consisting of an aminoquinoline-based antioxidant represented by the general formula (1) and a phenylenediamine-based antioxidant represented by the general formula (2), which will be described later. This allows for improved ozone resistance while reducing the environmental impact.

[0079] The aminoquinoline antioxidant represented by the general formula (1) is represented by the following general formula (1): [In the formula, is a single bond or 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; R １３ , R １４ , R １５ , R １６ , R １７ , R １８ , R １９ and R １１０ are each independently hydrogen or an alkyl group having 1 to 12 carbon atoms.] The aminoquinoline antioxidant represented by the above general formula (1) has the effect of improving ozone resistance and can suppress cracking in the radially outer cap tread layer and the radially inner cap tread layer. In addition, the aminoquinoline antioxidant represented by the above general formula (1) has a small environmental impact.

[0080] In the above general formula (1), is a single bond or a double bond, preferably a double bond; R １１ and R １２ are each independently hydrogen, 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 hydrogen or a phenyl group; １３ , R １４ , R １５ , R １６ , R １７ , R １８ , R １９ and R １１０ are each independently hydrogen or an alkyl group having 1 to 12 carbon atoms, and are preferably hydrogen or a methyl group. １１ , R １２ , R １３ , R １４ , R １５ , R １６ , R １７ , R １８ , R １９ and R １１０ 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 in the range of 1 to 6, even more preferably in the range of 1 to 4, and particularly preferably in the range of 1 to 3. R in the above general formula (1) １１ and R １２ Regarding 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.

[0081] Specific examples of the aminoquinoline antioxidants represented by the general formula (1) include those represented by the following structural formulas (1-1) to (1-94): Among these, from the viewpoint of suppressing cracking, the compound represented by structural formula (1-1) is particularly preferred. A rubber composition containing the compound represented by structural formula (1-1) has excellent ozone resistance.

[0082] There are no particular limitations on the method for producing the aminoquinoline antioxidant represented by the above general formula (1). For example, when an aromatic amine compound is used as a starting material, the method comprises the steps of: (i) reacting the 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 produced nitroso group with sodium borohydride or the like to produce an aromatic diamine compound; and (iii) reacting the produced aromatic diamine compound with a ketone compound such as acetone to form a condensed ring, thereby producing a compound having a 6-amino-1,2-dihydroquinoline skeleton, i.e., the compound represented by the above general formula (1), In addition, if desired, (iv) the compound having a 6-amino-1,2-dihydroquinoline skeleton thus produced can be 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), Compounds can be prepared in which is a single bond.

[0083] The proportion of the aminoquinoline antioxidant represented by the general formula (1) in the antioxidant (more specifically, in the total amount of antioxidant in each of the radially outer cap tread layer and the radially inner cap tread layer) is preferably 10 to 100 mass%, more preferably 20 to 100 mass%, and even more preferably 30 to 100 mass%. When the proportion of the aminoquinoline antioxidant represented by the general formula (1) in the antioxidant is 10 to 100 mass%, ozone resistance can be further improved.

[0084] Phenylenediamine-based antioxidant represented by general formula (2) In the rubber composition, the antioxidant is a phenylenediamine-based antioxidant represented by the following general formula (2): [In the formula, R ２１ and R ２２ are each independently an alkyl group or an aryl group having 7 or more carbon atoms, and R ２１ and R ２２ wherein at least one of the groups is an alkyl group having 7 or more carbon atoms. By including the phenylenediamine-based antioxidant represented by the general formula (2), the rubber composition can improve ozone resistance while reducing the burden on the environment.

[0085] In the above general formula (2), R ２１ and R ２２ are each independently an alkyl group or an aryl group having 7 or more carbon atoms, and R ２１ and R ２２At least one of the groups is an alkyl group having 7 or more carbon atoms. Examples of the alkyl group having 7 or more carbon atoms include 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, a 1-methylhexyl group, a 2-methylhexyl group, an n-heptyl group, a 1,2-dimethylhexyl group, a 1,3-dimethylhexyl group, a 1,4-dimethylhexyl group, a 1,5-dimethylhexyl group, a 2,3-dimethylhexyl group, a 2,4-dimethylhexyl group, a 2,5-dimethylhexyl group, a 3,4-dimethylhexyl group, a 3,5-dimethylhexyl group, a 1-methylheptyl group, a 2-methylheptyl group, an n-octyl group, various decyl groups, and various dodecyl groups. Of these, a 1,4-dimethylpentyl group and a 1-methylheptyl group are preferred. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesyl group, an α-naphthyl group, a β-naphthyl group, an ethylphenyl group, an n-propylphenyl group, an isopropylphenyl group, an n-butylphenyl group, a t-butylphenyl group, various dimethylphenyl groups, various diethylphenyl groups, various methylethylphenyl groups, various trimethylphenyl groups, various dimethylethylphenyl groups, various methyldiethylphenyl groups, and various triethylphenyl groups, and among these, a phenyl group is preferred.

[0086] R in the above general formula (2) ２１ and R ２２ At least one of R is an alkyl group having 7 or more carbon atoms. ２１ and R ２２ The other of R is preferably a phenyl group. １１ and R １２ one of R is an alkyl group having 7 or more carbon atoms, ２１ and R ２２ A phenylenediamine-based antioxidant in which the other radical is a phenyl group can further improve the ozone resistance of the rubber composition and can further suppress the occurrence of cracks in rubber products to which the rubber composition is applied.

[0087] R in the above general formula (2) ２１ and R ２２At least one of R preferably has 7 or 8 carbon atoms. ２１ and R ２２ The phenylenediamine-based antioxidant, at least one of which has 7 or 8 carbon atoms, can further improve the ozone resistance of the rubber composition and can further suppress the occurrence of cracks in rubber products to which the rubber composition is applied.

[0088] Specific examples of the phenylenediamine-based antiaging agent represented by the general formula (1) include N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N-phenyl-N'-(1-methylheptyl)-p-phenylenediamine (8PPD), N-phenyl-N'-(1,4-dimethylpentyl)-p-phenylenediamine (7PPD), etc. These phenylenediamine-based antiaging agents may be used alone or in combination of two or more.

[0089] The proportion of the phenylenediamine-based antioxidant represented by general formula (2) in the antioxidant is preferably 0.1 to 80 mass%, more preferably 1 to 70 mass%. When the proportion of the phenylenediamine-based antioxidant represented by general formula (2) in the antioxidant is 0.1 to 80 mass%, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in rubber products using the rubber composition can be further suppressed.

[0090] Quinoline-Based Antiaging Agent: The antiaging agent preferably further contains a quinoline-based antiaging agent. The quinoline-based antiaging agent is an antiaging agent having a quinoline moiety or a derivative thereof (such as a dihydroquinoline moiety or a tetrahydroquinoline moiety). The quinoline-based antiaging agent has the effect of improving the ozone resistance of the rubber composition, and a rubber composition containing both the phenylenediamine-based antiaging agent represented by the general formula (1) and a quinoline-based antiaging agent can further suppress the occurrence of cracks in rubber products.

[0091] The quinoline-based antioxidant preferably has a dihydroquinoline moiety, and more preferably has a 1,2-dihydroquinoline moiety. Specific examples of the quinoline-based antioxidant include a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ) and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. The quinoline-based antioxidant preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ). Quinoline-based antioxidants containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline are highly effective in improving the ozone resistance of rubber compositions, and also have the advantage of being less likely to discolor the rubber composition. Therefore, a rubber composition containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline can further suppress the occurrence of cracks in rubber products and is also less susceptible to discoloration. 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.

[0092] The proportion of the quinoline-based antioxidant in the antioxidant is preferably 5 to 50% by mass, and more preferably 10 to 40% by mass. When the proportion of the quinoline-based antioxidant in the antioxidant is 5 to 50% by mass, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in rubber products using the rubber composition can be further suppressed.

[0093] Amine-based antiaging agent of formula (4) Furthermore, the antiaging agent may be an amine-based antiaging agent represented by the following general formula (4): [In the formula, R ４１ and R ４２ represents a phenyl group, and m4 represents an integer of 7 or more.]. The amine-based antioxidant represented by the general formula (4) has a higher molecular weight than conventional antioxidants, and as shown in the formula (4), it has a bridge moiety having a unique and relatively long chain length, i.e., "-NH-CH(CH ３ )-(CH ２ ) ｍ４-CH(CH ３ )-NH-". It is believed that the high molecular weight and the presence of specific bridge moieties of such amine-based antioxidants reduce the diffusion rate in the rubber composition, further suppressing migration to the rubber surface. Furthermore, the amine-based antioxidant (C4) has a moiety composed of "-CH(CH ３ )-(CH ２ ) ｍ４ -CH(CH ３ One hydrogen atom is bonded to each of the two nitrogen atoms present at both ends of "(2-amino-2-methyl-2-methyl-2-propanol)-" (forming a so-called secondary amino group), and the presence of this bond in the structure represented by formula (4) is thought to contribute to the specific effect of improving ozone resistance (weather resistance).

[0094] In the above general formula (4), R ４１ and R ４２ is a phenyl group. ４１ and R ４２ When is a phenyl group, the weather resistance of the rubber composition can be further improved, and discoloration of the rubber composition can be more reliably prevented.

[0095] In the general formula (4), m4 is an integer of 7 or more, and from the viewpoint of improving the weather resistance of the rubber composition and preventing discoloration, it is more preferably an integer of 8 to 16, and even more preferably an integer of 10 to 14.

[0096] Examples of the amine-based antiaging agent of the above formula (4) include N,N'-bis(4-anilinophenyl)dodecane-2,11-diamine, N,N'-bis(4-anilinophenyl)tetradecane-2,13-diamine, N,N'-bis(4-anilinophenyl)hexadecane-2,15-diamine, N,N'-bis(4-anilinophenyl)octadecane-2,17-diamine, etc. Among these, N,N'-bis(4-anilinophenyl)tetradecane-2,13-diamine and N,N'-bis(4-anilinophenyl)octadecane-2,17-diamine are particularly preferred.

[0097] The proportion of the amine-based antioxidant represented by the general formula (4) in the antioxidant is preferably 0.1 to 80% by mass, more preferably 1 to 70% by mass. When the proportion of the amine-based antioxidant represented by the general formula (4) in the antioxidant is 0.1 to 80% by mass, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in rubber products using the rubber composition can be further suppressed.

[0098] Nitrogen-containing cyclic compound, amine-based antiaging agent of formula (3) The rubber composition further comprises a nitrogen-containing cyclic compound not containing a benzene ring and a mercapto group, and an amine-based antiaging agent of the following general formula (3): [In the formula, R ３１ and R ３２ are each independently a monovalent saturated hydrocarbon group. ] and an amine-based antioxidant represented by the formula (1) (excluding the phenylenediamine-based antioxidant represented by the formula (1) above). Excellent adhesion can be achieved even when exposed to a deteriorating environment.

[0099] Here, the amine-based antioxidant represented by general formula (3) contains a phenylenediamine moiety like the general-purpose antioxidant N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD), but differs from antioxidant 6PPD in that it does not have a double bond other than the phenylenediamine moiety. The amine-based antioxidant represented by general formula (3) has the effect of improving the ozone resistance of the rubber composition.

[0100] In the above general formula (3), R ３１ and R ３２ are each independently a monovalent saturated hydrocarbon group. ３１ and R ３２ may be the same or different, but from the viewpoint of synthesis, they are preferably the same.

[0101] The number of carbon atoms in the monovalent saturated hydrocarbon group is preferably 1 to 20, more preferably 3 to 10, and particularly preferably 6 or 7. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass increases, which enhances the anti-aging effect and further improves the ozone resistance of the rubber composition. ３１ and R ３２ From the viewpoint of further improving the ozone resistance of the rubber composition, it is preferable that each of the groups independently represents a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms.

[0102] Examples of the monovalent saturated hydrocarbon group include an alkyl group and a cycloalkyl group. The alkyl group may be linear or branched, and 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, 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, 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.

[0103] Specific examples of the amine-based antiaging agent represented by the general formula (3) include N,N'-dicyclohexyl-p-phenylenediamine, etc. The amine-based antiaging agents represented by the formula (3) may be used alone or in combination of two or more.

[0104] The proportion of the amine-based antioxidant in the antioxidant is preferably 0.1 to 80% by mass, and more preferably 1 to 70% by mass. When the proportion of the amine-based antioxidant in the antioxidant is 0.1 to 80% by mass, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in rubber products using the rubber composition can be further suppressed.

[0105] 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, but 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.

[0106] 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.

[0107] 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.

[0108] Among these, triazole and triazole derivatives are preferred in terms of further exhibiting the effects of the present invention, and it is particularly preferred that they are 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 products (including reagents) are available, these commercially available products may be used, or the compounds may be synthesized by hand. The method for synthesizing a nitrogen-containing cyclic compound by hand would be obvious to a person skilled in the art in light of the common general technical knowledge at the time of filing.

[0109] 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 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 is highly compatible with rubber and cannot adequately protect the surface of metal materials.

[0110] The content of the nitrogen-containing cyclic compound is preferably 0.02 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the rubber component. When the content of the nitrogen-containing cyclic compound is 0.02 part by mass or more per 100 parts by mass of the rubber component, the effects of the present invention can be sufficiently obtained, while if the content is less than 0.02 part by mass, adhesion when exposed to a deterioration environment may not be ensured. On the other hand, when the content is 10 parts by mass or less, initial adhesion is good, and if the content exceeds 10 parts by mass, initial adhesion may deteriorate.

[0111] 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).

[0112] The inclusion of the nitrogen-containing cyclic compound free of benzene rings and mercapto groups improves initial adhesion and adhesion upon exposure to a deterioration environment, while the inclusion of the amine-based antioxidant represented by general formula (1) maintains adhesion for a long period of time, resulting in a synergistic effect that enables the adhesion between the rubber and the metal cord to be enhanced over a long period of time upon exposure to a deterioration environment. In other words, by satisfying the relationship 0.004≦A / B≦100, the metal cord-rubber composite of the present invention can stably achieve adhesion upon exposure to the environment. From the same perspective, the A / B ratio is preferably 0.04 to 10, and more preferably 0.2 to 2.

[0113] Other Antiaging Agents The rubber composition may or may not contain an antioxidant (other antioxidant) other than the phenylenediamine-based antioxidant of formula (1), the quinoline-based antioxidant, the amine-based antioxidant of formula (3), and the amine-based antioxidant of formula (4). Examples of other antioxidants include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and N,N'-diphenyl-p-phenylenediamine (DPPD). However, it is preferable not to include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD). Commercially available antioxidants can be used, including those from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., and Flexis. These antioxidants may be used alone or in combination of two or more. The ratio of the other antioxidants in the antioxidants is preferably 0 to 20% by mass, more preferably 0 to 10% by mass.

[0114] (Sulfur) The rubber composition preferably contains sulfur. When the rubber composition contains sulfur, it becomes vulcanizable, and the durability of the rubber composition is improved. Various types of sulfur can be used as the sulfur, but ordinary sulfur (soluble sulfur (powdered sulfur), etc.) is preferable to insoluble sulfur, and oil treat sulfur, etc., is also preferable. Here, insoluble sulfur is sulfur insoluble in carbon disulfide (amorphous polymeric sulfur), and soluble sulfur (powdered sulfur) is sulfur soluble in carbon disulfide. The sulfur content 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 even more preferably in the range of 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0115] (Carbon Black) Furthermore, the rubber composition may contain a filler as needed. Examples of the filler include carbon black. The carbon black reinforces the rubber composition and can improve the abrasion resistance of the rubber composition. Preferred carbon black is plant-derived carbon black or recycled carbon black (also called "recycled carbon black"). Examples of plant-derived carbon black include those derived from castor oil and pine oil. Recycled carbon black will be described in detail below.

[0116] From the viewpoint of further improving the abrasion resistance of the rubber composition and a tire using the same, the content of the carbon black (total of recycled carbon black and carbon black other than recycled carbon black) in the rubber composition of the present invention 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. Also, from the viewpoint of workability of the rubber composition, the content of the carbon black in the rubber composition is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less, per 100 parts by mass of the rubber component.

[0117] As used herein, "recycled carbon black" refers to carbon black recovered from recycled waste materials. Examples of such waste include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only waste generated from rubber products but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeled rubber. Buffing powder is fine rubber generated during the buffing process of scraping the tread portion remaining on the base tire during tire retreading, for example. Peeled rubber is a long piece of rubber, e.g., 1 to 2 cm wide, peeled from the surface of a rubber product such as a tire. Peeled rubber is generated by scraping the surface of a rubber product such as a tire using a U- or V-shaped knife like a peeler. Furthermore, waste rubber is not limited to crosslinked rubber but also includes unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, as well as rubber parts or components during the manufacturing process of final products. Used tires may be tires to be retreaded, or may be tires discarded for some reason, such as tires generated during tire replacement or scrapping, or ELTs (End-of-Life Tires) that have reached the end of their service life. Waste oils are not limited to those generated during the decomposition of plastics and rubber, but also include used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oils that contain no non-organic components, such as those derived from silicone rubber or polyvinyl chloride, are desirable. Furthermore, waste oils containing carbon black or rubber containing carbon black are desirable. "Recycled carbon black" differs from carbon black produced directly from hydrocarbons such as petroleum, natural gas, and coal, i.e., non-recycled carbon black. Note that "used" here refers not only to waste oils discarded after actual use, but also to waste oils that were produced but discarded without actually being used.

[0118] The recycled carbon black is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by pyrolysis of a vulcanized rubber product containing carbon black is readily available because vulcanized rubber products containing carbon black are readily available and can be easily obtained by pyrolysis. Furthermore, the recycled carbon black is preferably obtained from the solid residue produced by the pyrolysis of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and recycled carbon black can be recovered from either of them. When recovering carbon black from the volatile component, the oil component with a specific gravity suitable for producing carbon black can be recovered and used to produce carbon black using existing carbon black production methods (e.g., JP 2015-520259 A). Unlike carbon black recovered from solid residues, this method offers advantages such as no impurities and no mixed grades. In addition, in the production of environmentally friendly carbon black, various options are available, including oils obtained by recovering volatile components from rubber pyrolysis, as described above, as well as vegetable oils and oils derived from waste plastics. However, edible resources such as vegetable oils are needed for other uses, such as food, and there are challenges in securing sufficient quantities, as well as the environmental impact of expanding cultivated land. Furthermore, oils derived from waste plastics are also used for other purposes, such as horizontal plastic recycling, so supply issues are also a concern. On the other hand, using volatile components (oils) produced by the pyrolysis of vulcanized rubber products, particularly tires, allows for the continued use of existing materials due to the tire industry's ongoing system of using existing materials, thereby reducing the consumption of new materials in new tire production and contributing to a reduction in the industry's environmental impact. The grade of carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0119] Solid residues obtained by pyrolysis of waste materials such as used rubber and used tires contain ash in addition to carbon black. The ash is derived from non-volatile components contained in the rubber and tires. Therefore, recycled carbon black obtained from the solid residues has a relatively low carbon black content. On the other hand, considering the various physical properties required for tires manufactured using recycled carbon black, the higher the carbon content of the recycled carbon black, the better. The carbon content of the recycled carbon black is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and particularly preferably 89% by mass or more. Furthermore, the carbon content of the recycled carbon black is preferably 97% by mass or less. Note that the carbon content does not include adsorbed moisture.

[0120] Specific examples of the ash include zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, and magnesium oxide. In the case of recycled carbon black produced from solid residue obtained by pyrolysis of waste, a certain amount of ash remains even after various processes for removing the ash. In this embodiment, the recycled carbon black is allowed to contain ash. In one embodiment, the lower limit of the ash content of the recycled carbon black may be 0.5% by mass.

[0121] The recycled carbon black can also be obtained from a pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3,427,975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes that recycled carbon black can be obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (paragraph

[0027] ). Carbon black obtained from such pyrolysis processes typically lacks functional groups on its surface, as mentioned in paragraph

[0004] of Japanese Patent Publication No. 6,856,781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black and Commercially Available Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0122] The recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. The treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, carbon black obtained by a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, in Japanese Patent Publication No. 6,856,781, carbon black obtained by a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black according to this embodiment also includes carbon blacks treated to include functional groups on their surfaces.

[0123] Furthermore, examples of thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0124] The crosslinked rubber products used for the decomposition may be grouped by the type of rubber component previously compounded, and then the decomposition step may be performed for each group. Alternatively, the crosslinked rubber products may be grouped by the type of filler previously compounded (e.g., type of carbon black, type of silica, mixing ratio of carbon black and silica, etc.), and then the decomposition step may be performed for each group. Furthermore, the crosslinked rubber products may be grouped by both type of rubber component and type of filler, and then the decomposition step may be performed for each group. When the decomposition step is performed for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when the recycled carbon black is compounded again into a rubber component, a rubber composition with better performance can be obtained.

[0125] Furthermore, when the crosslinked rubber product used in the degradation is derived from tires, the tires may be grouped in advance by type (e.g., for passenger cars, for trucks and buses, for large vehicles such as off-road vehicles, for aircraft, for agricultural vehicles, etc.), and the degradation step may be carried out for each group. Alternatively, the tires may be grouped in advance by tire component (e.g., tread rubber, sidewall rubber, bead rubber, steel cord-coated rubber, organic fiber-coated rubber, pad rubber, cushion rubber, etc.), and the degradation step may be carried out for each group. Furthermore, the tires may be grouped both by type and by tire component, and the degradation step may be carried out for each group. When the degradation step is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and therefore, when the recycled carbon black is blended again into a rubber component, a rubber composition with better performance can be obtained.

[0126] The recycled carbon black has a nitrogen adsorption specific surface area of ​​40 to 100 m as measured by the BET method. ２ / g, and 50 to 90m ２ / g, and more preferably 55 to 75m ２ In this specification, the nitrogen adsorption specific surface area of ​​recycled carbon black measured by the BET method is a statistical thickness specific surface area (STSA) determined in accordance with ASTM D6556.

[0127] The pH of the recycled carbon black is preferably 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. In this specification, the pH of the recycled carbon black is determined in accordance with ASTM D1512.

[0128] The recycled carbon black preferably has a toluene color transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, the toluene color transmittance of recycled carbon black is determined in accordance with ASTM D1618.

[0129] The recycled carbon black preferably has a heat loss of 3% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less at 125°C. Herein, the heat loss of recycled carbon black at 125°C is determined in accordance with ASTM D1509.

[0130] The recycled carbon black preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0131] The recycled carbon black preferably has a 35 mesh sieve residue of 20 mass ppm or less, more preferably 15 mass ppm or less, and particularly preferably 10 mass ppm or less. Herein, the 35 mesh sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0132] The recycled carbon black preferably has a 325 mesh (44 μm) sieve residue of 1000 mass ppm or less, more preferably 700 mass ppm or less, and particularly preferably 300 mass ppm or less. Herein, the 325 mesh (44 μm) sieve residue of the recycled carbon black is determined in accordance with ASTM D1514.

[0133] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Herein, the pellet hardness of recycled carbon black is determined in accordance with ASTM D5230.

[0134] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. Herein, the pellet fine powder content of recycled carbon black is determined in accordance with ASTM D1508.

[0135] The particle size (D97) of the recycled carbon black is preferably 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Here, in this specification, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size distribution analyzer, assuming a refractive index of 1.33 for water and a refractive index of 1.75 for the filler.

[0136] The recycled carbon black preferably contains particles of 5 μm or less in a proportion of 50% by volume or more, more preferably 70% by volume or more, and particularly preferably 80% by volume or more.

[0137] The recycled carbon black preferably has an ash content of 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. When the ash content of the recycled carbon black is 25% by mass or less, the physical properties of the rubber product to which the rubber composition is applied can be improved. Herein, the ash content of the recycled carbon black is determined in accordance with ASTM D8474 and D1506.

[0138] The recycled carbon black preferably has a dibutyl phthalate (DBP) absorption of 70 to 120 mL / 100 g, more preferably 75 to 110 mL / 100 g, and particularly preferably 80 to 100 mL / 100 g. Herein, the DBP absorption of recycled carbon black is determined in accordance with ASTM D2414.

[0139] The recycled carbon black preferably has a compressed dibutyl phthalate (24M4DBP) absorption capacity of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Herein, the 24M4DBP absorption capacity of the recycled carbon black is determined in accordance with ASTM D3493.

[0140] Commercially available recycled carbon black can be used. For example, Enrestec's product name "PB365" can be mentioned as such a commercially available product. PB365 is a recycled carbon black produced through the thermal decomposition of used tires, and has a nitrogen adsorption specific surface area of ​​73.6 m2 as measured by the BET method. ２ / g and contains about 17% by mass of ash.

[0141] The amount of recycled carbon black is preferably 1 to 100 parts by mass, more preferably 5 to 80 parts by mass, even more preferably 5 to 50 parts by mass, still more preferably 5 to 30 parts by mass, and particularly preferably 5 to 20 parts by mass, per 100 parts by mass of the rubber component. When the amount of recycled carbon black is 5 parts by mass or more per 100 parts by mass of the rubber component, the effect of improving the proportion of sustainable materials in rubber products to which the rubber composition is applied is significant, and when the amount is 50 parts by mass or less, the fracture resistance of the rubber composition can be more reliably maintained.

[0142] (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 having a BET surface area in this range has the advantage of being able to achieve 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 / g. The content of the 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, per 100 parts by mass of the rubber component. 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.

[0143] 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 may be used, such as those from Tosoh Silica Corporation, Evonik Corporation, Solvay Corporation, Solvay Japan Co., Ltd., and Tokuyama Corporation. The silica may also be commercially available, such as Zeosil Premium 200MP (trade name) from Rhodia. The silica may be used alone or in combination of two or more.

[0144] From the viewpoint of reducing environmental impact, silica derived from siliceous plants is preferred as the silica. Examples of siliceous plants include mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Gramineae plants. 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 it easy to secure a sufficient supply. Therefore, from the viewpoint of availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred as silica. The use of rice husk silica allows for the effective use of rice husks, which are industrial waste, and also allows for the local procurement of raw materials near tire manufacturing plants, thereby reducing the energy and costs involved in transportation and storage, 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), and then 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 the method described in JP 2019-38728 A, for example.

[0145] Furthermore, the silica has a nitrogen adsorption specific surface area (N ２ SA) is 50m ２ / g or more, and ２ / g or more is more preferable, and 150m ２ / g or more, and ２ / g or less, and ２ / g or less is more preferable, and 230m ２ / g or less is more preferable, and 200m ２ / g or less. In this specification, the nitrogen adsorption specific surface area (N ２ SA) is a value measured by the BET method in accordance with ASTM D3037-93.

[0146] The content of the 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 is, relative to 100 parts by mass of the rubber component, 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 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.

[0147] (Silane Coupling Agent) When the rubber composition of this embodiment contains silica, in order to improve the effect of the silica, the rubber composition preferably contains a silane coupling agent. 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, Examples of such tetrasulfides 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. As the silane coupling agent, commercially available products can be used, and examples of commercially available silane coupling agents that can be used include products from Evonik, Momentive, Shin-Etsu Silicones Co., Ltd., Dow Corning Toray Co., Ltd., Tokyo Chemical Industry Co., Ltd., and Azumax Co., Ltd. These silane coupling agents may be used alone or in combination of two or more.

[0148] Bioethanol can also be used as a raw material for the silane coupling agent. Bioethanol is produced primarily using 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 a monomer component derived from a biological resource, a monomer component derived from a renewable resource, and a monomer component derived from a fossil resource. 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.

[0149] Furthermore, in terms of the effect as a coupling agent and prevention of gelation, the preferred blending amount of silane coupling agent is 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 preferred, and a mass ratio of (4 / 100) to (10 / 100) is particularly preferred.

[0150] (Boron Compound) The rubber composition may further contain a boron-containing compound from the viewpoint of further improving the adhesion durability between the steel cord and the coating rubber and 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 boron in the boron-containing compound is less than 0.005 parts by mass, the adhesion durability between the steel cord and the coating rubber may not be sufficiently improved. If the amount 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.

[0151] 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.

[0152] (Resin) The rubber composition may further contain a resin. Examples of the resin include terpene-based resin, rosin-based resin, C ５ based resin, C ５ -C ９ based resin, C ９ Examples of suitable resins include cyclopentadiene-based resins, aromatic resins, coumarone resins, indene resins, coumarone-indene-based resins, olefin-based resins, polyurethane resins, and acrylic resins. These resins may be used alone or in combination of two or more. Among these resins, terpene-based resins, rosin-based resins, and C ５ based resin, C ５ -C ９ based resin, C ９Preferred are cyclopentadiene-based resins, cyclopentadiene-based resins, and aromatic resins, with terpene-based resins and rosin-based resins being particularly preferred. Terpene-based resins and rosin-based resins are naturally derived, sustainable resins, and therefore can further reduce the environmental impact and further improve tire performance. ５ based resin, C ９ based resin, C ５ -C ９ The cyclopentadiene-based resin and the cyclopentadiene-based resin can improve reinforcement and fuel economy in a well-balanced manner, while the aromatic resin can improve rubber strength and the like.

[0153] 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.

[0154] 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.

[0155] The terpene resin is a solid resin obtained by blending turpentine, which is obtained simultaneously with the extraction of rosin from pine trees, or a polymerization component separated therefrom, and polymerizing the blend 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. The styrene-terpene resin 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.

[0156] 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.

[0157] Furthermore, a maleic acid-modified rosin resin 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).

[0158] 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 under the influence of air 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 and may form fracture nuclei, which is not preferable. 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.

[0159] 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 glass transition 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.

[0160] The weight-average molecular weight of the maleic acid-modified rosin resin is preferably 500 to 5,000, more preferably 1,000 to 4,000. By controlling 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 standards.

[0161] 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, Inc. 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.

[0162] Said C ５ As a resin based on C, there is C obtained by thermal decomposition of naphtha in the petrochemical industry. ５ and aliphatic petroleum resins obtained by (co)polymerizing the distillate. ５ The fraction usually contains 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.

[0163] Said C ５ -C９ The C-based resin is ５ -C ９ It refers to synthetic petroleum resin, ５ -C ９ Examples of the resin include petroleum-derived C ５ -C １１ The fraction was treated with AlCl ３ , B.F. ３ More specifically, copolymers containing styrene, vinyl toluene, α-methyl styrene, indene, etc. as the main component may be mentioned. ５ -C ９ As the resin, ９ Resins containing less of the above components are preferred from the viewpoint of compatibility with the rubber component. ９ "Low amount of the above components" means that the C ９ This means that the content of the above components is less than 50% by mass, preferably 40% by mass or less.

[0164] Said C ９ The C-based resin is ９ This refers to synthetic petroleum resins, such as AlCl ３ or BF ３ Using a Friedel-Crafts type catalyst such as C ９ It refers to a solid polymer obtained by polymerizing the fraction. ９ Examples of the resin include copolymers containing indene, α-methylstyrene, vinyltoluene, etc. as main components.

[0165] 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 and another monomer. Here, 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 is, for example, a copolymer of AlCl３ or BF ３ The term "dicyclopentadiene-based resin" refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as Benzene, etc. Dicyclopentadiene-based resins include homopolymers of dicyclopentadiene, copolymers of dicyclopentadiene and aromatic monomers, copolymers of dicyclopentadiene and C ９ Examples include copolymers with distillates (vinyl toluene, indene, etc.).

[0166] The aromatic resin refers to a resin containing units derived from aromatic monomers as monomer units. Examples of the aromatic resin include homopolymers of aromatic monomers, copolymers of two or more aromatic monomers, and copolymers of aromatic monomers with other monomers. Examples of the aromatic monomer include styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-phenylstyrene; phenol-based monomers such as phenol, alkylphenol, and alkoxyphenol; and naphthol-based monomers such as naphthol, alkylnaphthol, and alkoxynaphthol.

[0167] The resin may also be a mixture (mixed resin) of a hydrogenated styrene resin and an aromatic-modified terpene resin. The rosin-based resin may also be a maleic acid-modified rosin resin. The hydrogenated styrene resin is a resin obtained by hydrogenating a styrene resin made of a styrene monomer. Hydrogenating the styrene resin reduces the number of aromatic rings derived from styrene, improving dispersibility in the diene rubber and promoting 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.

[0168] 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.

[0169] The hydrogenated styrene resin is obtained by hydrogenating the aromatic rings in a styrene resin. The hydrogenation method is conventionally known 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 resulting from 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 measured by IR (infrared spectrophotometer) using the following formula: Hydrogenation rate (%) = {(C - D) / C} x 100, where C is the peak height of the absorbance derived from the aromatic rings before hydrogenation, and D is the peak height of the absorbance derived from the aromatic rings after hydrogenation. The hydrogenated styrene resins may be used alone or in combination of two or more.

[0170] The molecular weight of the hydrogenated styrene resin is, as measured by gel permeation chromatography (GPC), a weight average molecular weight (Mw) converted to polystyrene 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.

[0171] 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.

[0172] 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).

[0173] The resin preferably has a softening point of 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 resin preferably has a softening point of 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 the resin is the temperature at which the ball drops when the softening point as defined in JIS K 6220-1:2015 (ISO 28641:2010) is measured using a ring and ball softening point tester.

[0174] Commercially available resins can be used, and examples of commercially available resins include products from ENEOS Corporation, Arakawa Chemical Industries, Ltd., ExxonMobil Corporation, Kraton Corporation, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Kraton Polymers, Inc., Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., and Taoka Chemical Co., Ltd.

[0175] 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.

[0176] (Rubber Crumb) 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 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." The process of crushing vulcanized rubber to obtain rubber crumb may involve mechanical treatment or low-temperature treatment. 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. The rubber powder may be a commercially available product, such as those from Global Corporation or Nantong Huili Rubber Corporation. From the viewpoint of reducing the environmental impact, 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.

[0177] 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.

[0178] The rubber powder preferably has a volume average particle size of 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 with a laser diffraction particle size distribution analyzer, for example, a "CAPA500" manufactured by Horiba, Ltd.

[0179] The rubber crumb has an acetone extractable content of preferably 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 extractable content in the rubber crumb refers to the acetone extractable content (%) determined by the acetone extraction method in accordance with JIS K6350.

[0180] 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, still more preferably 15 parts by mass or less, even 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.

[0181] (Liquid Softener) The rubber composition may contain a liquid softener. Here, the "liquid softener" is 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.

[0182] 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. As the oil, commercially available products can be used, and examples of commercially available oils that can be used include 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.

[0183] 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.

[0184] 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.

[0185] (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 carboxylic acid metal salt (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): [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).] The durability of vulcanized rubber and heat-degradation adhesion between rubber and metal can be improved.

[0186] The metal carboxylate (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 function as adhesion promoters that promote good adhesion between steel cord and rubber even under hot and humid conditions. If the number of carbon atoms in the metal carboxylate (1) is less than 2, the compatibility of the metal carboxylate (1) with the rubber component is low, and high adhesive strength between the vulcanized rubber and the metal cannot be obtained. Furthermore, a metal carboxylate (1) having more than 25 carbon atoms is difficult to synthesize.

[0187] Examples of aliphatic carboxylic acids having 2 to 25 carbon atoms include aliphatic monocarboxylic acids and aliphatic dicarboxylic acids. The number of carbon atoms in an aliphatic carboxylic acid includes the number of carbon atoms in the carboxy group. Examples of aliphatic carboxylic acids having 2 to 25 carbon atoms include saturated aliphatic monocarboxylic acids and unsaturated aliphatic monocarboxylic acids.

[0188] 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 acids 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, dehydroabietic acid, etc. Examples of the aliphatic dicarboxylic acids 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, adipic acid, etc. Examples of the unsaturated aliphatic dicarboxylic acid include fumaric acid, maleic acid, etc.

[0189] 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. The use of a saturated aliphatic monocarboxylic acid is less likely to affect the sulfur crosslinking of the rubber, and can suppress 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.

[0190] The metal carboxylate (1) can be obtained, for example, by the following methods: 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 of producing aliphatic carboxylic acid (a) having 2 to 25 carbon atoms with sodium hydroxide in the presence of water to obtain a sodium salt of aliphatic carboxylic acid, and then reacting the sodium salt of aliphatic carboxylic acid with one or more selected from 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) (metathesis method).

[0191] Examples of 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 hydroxides (b-2) of metals (bismuth, copper, antimony, silver, niobium, and zirconium) include copper(II) hydroxide and zirconium hydroxide. Examples of carbonates (b-3) of metals (bismuth, copper, antimony, silver, niobium, and zirconium) include bismuth(III) carbonate, bismuth(III) carbonate oxide, and copper(II) carbonate. Examples of sulfates (c-1) of metals (bismuth, copper, antimony, silver, niobium, and 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), niobium chloride (V), etc. Examples of nitrates (c-3) of metals (bismuth, copper, antimony, silver, niobium, zirconium) include bismuth nitrate (III), bismuth subnitrate (III), silver nitrate (I), etc.

[0192] 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.

[0193] In Production Method 2, the reaction temperature when the aliphatic carboxylic acid (a) having 2 to 25 carbon atoms is reacted with sodium hydroxide in the presence of an organic solvent is usually 20 to 100°C. The reaction time is usually 1 to 5 hours. In Production Method 2, the reaction temperature when the sodium salt of the aliphatic carboxylic acid is reacted 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 the sodium salt of the aliphatic carboxylic acid is reacted with the compounds (c-1) to (c-3), the aqueous layer in the reaction system is separated. Thereafter, the solvent present in the oil layer is removed by distillation under reduced pressure to obtain the carboxylate metal salt (1).

[0194] (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.

[0195] 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 as described for carboxylic acid metal salt (1). Among the residues of aliphatic carboxylic acids, residues of saturated aliphatic monocarboxylic acids are preferred. Use of a residue of a saturated aliphatic monocarboxylic acid makes it easier for compound (2) to disperse in the vicinity of the steel cord, or for the vulcanized rubber to be adsorbed to 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.

[0196] 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 serves as an adhesion promoter that promotes good adhesion between steel cord and rubber even under moist and hot conditions.

[0197] Furthermore, x in the compound (2) represented by formula (A) is an integer of (the valence of M - 1).

[0198] Z in compound (2) represented by formula (A) is a structure selected from the above-described formulas (z-1) to (z-4). Among these, the structure represented by formula (z-1) is preferred because it makes it easier to obtain an adhesion promoter that exhibits high adhesive strength between vulcanized rubber and metal.

[0199] 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).

[0200] 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.

[0201] 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 esters (d-1) of lower alcohols include trimethyl borate, triethyl borate, tripropyl borate, and tributyl borate. Examples of the metaborate esters (d-2) of lower alcohols include trimethyl metaborate, triethyl metaborate, tripropyl metaborate, and tributyl metaborate. Examples of the phosphate esters (d-3) of lower alcohols include methyl phosphate, ethyl phosphate, propyl phosphate, and butyl phosphate. Examples of the phosphite esters (d-4) of lower alcohols 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.

[0202] 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 of the acid (e) include ethanoic acid, propanoic acid, and butanoic acid.

[0203] The metal compound M(f) is a metal source for compound (2), and can be, for example, the oxide (b-1), hydroxide (b-2), carbonate (b-3), etc., which have been described in the production method for metal carboxylate (1). 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.

[0204] The proportion of the inorganic acid ester (d) 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. 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.

[0205] 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.

[0206] An example of a method for mixing various components in multiple steps is a production method including the following steps 1 and 2. Step 1 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 reactant (h). Step 2 is a step of removing water from a reaction system containing the reactant (h) obtained in step 1, adding an inorganic acid ester (d) to the reaction system from which the water has been removed, and reacting the reactant (h) with the inorganic acid ester (d). Producing compound (2) through the above two steps can prevent hydrolysis of the inorganic acid ester (d) by the water generated in step 1, allowing compound (2) to be produced efficiently.

[0207] In the above-described 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.

[0208] Furthermore, 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, the content of the rubber-metal adhesion promoter in the rubber composition is preferably 0.01 parts by mass or more per 100 parts by mass of the rubber component. 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.

[0209] (Other Components) 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.

[0210] Among the other components, the rubber composition preferably further contains a vulcanization accelerator, which accelerates vulcanization and increases the strength of the rubber composition after vulcanization.

[0211] The type of 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, and xanthate-based vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. Among the above-mentioned vulcanization accelerators, 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, and N-decyl-2-benzothiazolylsulfenamide. N-dodecyl-2-benzothiazolyl sulfenamide, N-stearyl-2-benzothiazolyl sulfenamide, N,N-dimethyl-2-benzothiazolyl sulfenamide, N,N-diethyl-2-benzothiazolyl sulfenamide, N,N-dipropyl-2-benzothiazolyl sulfenamide, N,N-dibutyl-2-benzothiazolyl sulfenamide, N,N-dipentyl-2-benzothiazolyl sulfenamide, N,N-dihexyl 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, N,N-distearyl-2-benzothiazolylsulfenamide, etc. Among these, it is more preferable that the vulcanization accelerator contains at least N-cyclohexyl-2-benzothiazolylsulfenamide.

[0212] 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.

[0213] 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.

[0214] Among the other components, the hydrazide compound may be a hydrazide compound represented by the following general formula: (In the formula, R １ , R ２ are each independently an alkyl group having 1 to 18 carbon atoms.

[0215] 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 these may be methyl.

[0216] 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, 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, among which 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.

[0217] 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.

[0218] 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 can efficiently produce 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.

[0219] 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.

[0220] Among the other components, zinc oxide (ZnO) is used as a vulcanization accelerator. By further including zinc oxide in the rubber composition, 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.

[0221] 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.

[0222] 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.

[0223] 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.

[0224] 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 selected appropriately depending on the required performance. However, from the viewpoint of environmental impact, the rubber composition is preferably a cobalt-free rubber composition. "Not containing cobalt in the rubber composition" means that cobalt is not actively 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.

[0225] The method for producing the rubber composition is not particularly limited. For example, the rubber 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.

[0226] The method for coating the steel cord with the rubber composition is not particularly limited, but the following method can be used, for example: A predetermined number of plated steel cords are aligned in parallel at predetermined intervals, and these steel cords are coated from above and below with unvulcanized rubber sheets made of the rubber composition and having a thickness of about 0.5 mm. These steel cords are then vulcanized, for example, at a temperature of about 160°C for about 20 minutes. The steel cord-rubber composite obtained in this manner has excellent adhesion between the rubber and the cord.

[0227] The steel cord-rubber composite of the present invention may be used for any purpose, including, but not limited to, reinforcing materials for rubber articles that require particular strength, such as various automobile tires, hoses, and rubber crawlers. In particular, the steel cord-rubber composite can be suitably used as reinforcing members for belts, carcass plies, wire chafers, and the like, of various automobile radial tires.

[0228] <Tire> The tire of the present invention is characterized by including the above-described steel cord-rubber composite of the present invention. By using the steel cord-rubber composite of the present invention as a tire component, the adhesion between the rubber and the steel cord can be improved, and the excellent ozone resistance can improve the durability of the component using the steel cord-rubber composite.

[0229] Furthermore, the tire of the present invention is preferably a pneumatic tire, and the gas to be filled in 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 manufacturing the tire of the present invention is not particularly limited, and the tire may be manufactured by a conventional method. Generally, a rubber composition containing various components is processed into various components in the unvulcanized state, and these components are bonded and molded in a tire building machine using a conventional method to form a green tire. The green tire is then heated and pressurized in a vulcanizer to produce the tire. For example, a tire can be obtained by kneading the rubber composition, rubber-coating steel cords with the resulting rubber composition, laminating an unvulcanized belt, an unvulcanized carcass, and other unvulcanized components, and vulcanizing the unvulcanized laminate.

[0230] 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.

[0231] Examples 1 and 2, Comparative Example 1 According to Table 1, rubber composition samples were produced.

[0232] <Evaluation> The ozone resistance of the obtained rubber composition samples was evaluated using the following method. The evaluation results are shown in Table 1. - Evaluation of Ozone Resistance A dynamic ozone degradation test (a test in which repeated strain is applied) was conducted in accordance with ISO 1431 (JIS K 6259), and the sample was observed using a microscope at 20x magnification. The observed samples were ranked according to the size and depth of cracks and classified according to the following criteria (1 to 5), with smaller numbers indicating better results. (Ranking by Crack Size and Depth) 1: Not visible to the naked eye but visible with a 10x magnifying glass. 2: Visible to the naked eye. 3: Deep and relatively large cracks (less than 1 mm). 4: Deep and large cracks (1 mm or more but less than 3 mm). 5: Cracks of 3 mm or more or likely to cause breakage.

[0233]

[0234] *1 NR: Natural rubber *2 BR: Butadiene rubber, cis 1,4 bond content of 96% or more *3 Carbon black: Asahi Carbon Co., Ltd., product name "Asahi #65" *4 Antioxidant A: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD) *5 N-phenyl-N'-(1-methylheptyl)-p-phenylenediamine (8PPD) *6 Antioxidant C: Aminoquinoline-based antioxidant represented by the following formula (1-1) *7 Other chemicals: Total amount including at least oil, zinc oxide, stearic acid and vulcanization accelerator

[0235] The results in Table 1 show that the samples of the examples exhibited excellent ozone resistance, similar to the samples of the comparative examples.

[0236] 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 and excellent ozone resistance can be provided.Furthermore, according to the present invention, a tire having excellent durability of components using the steel cord and excellent ozone resistance 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, wherein the rubber composition comprises a rubber component and a rubber compound represented by the following general formula (1): [In the formula, is a single bond or 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; R １３ , R １４ , R １５ , R １６ , R １７ , R １８ , R １９ and R １１０ are each independently hydrogen or an alkyl group having 1 to 12 carbon atoms, and an aminoquinoline antioxidant represented by the following general formula (2): [In the formula, R ２１ and R ２２ are each independently an alkyl group or an aryl group having 7 or more carbon atoms, and R ２１ and R ２２ wherein at least one of the groups is an alkyl group having 7 or more carbon atoms.

2. The steel cord-rubber composite according to claim 1, wherein the steel cord has one or more steel filaments on which a plating layer containing copper, zinc, and cobalt is formed, and 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. Then, the atomic % of cobalt is analyzed at six equally spaced points in the longitudinal direction of the steel filament, over 100 nm from the bottom of the adhesive layer inward in the direction perpendicular to the longitudinal direction of the steel filament. A 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 analytical range (600 nm) of the six points B: The content of the aminoquinoline antioxidant in the rubber composition (parts by mass per 100 parts by mass of the rubber component) 3. The steel cord-rubber composite according to claim 1 or 2, characterized in that 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 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, the phosphorus content being 1.5 atomic % or less, and the ratio (A / B) of the phosphorus content (A (atomic %)) in the steel wire surface layer 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 the aminoquinoline-based antioxidant in the rubber composition per 100 parts by mass of the rubber component is 0.02 to 15.

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

5. The steel cord-rubber composite according to claim 1 or 2, characterized in that the rubber composition contains 0.01 part 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 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 compounds represented by the following formula (A): [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).] 6. The steel cord-rubber composite according to claim 1 or 2, characterized in that the content of the antioxidant is 0.5 to 10 parts by mass per 100 parts by mass of the rubber component, the antioxidant further contains a quinoline-based antioxidant, and the proportion of the quinoline-based antioxidant in the antioxidant is 5 to 50% by mass.

7. R in the above general formula (2) １１ and R １２ The steel cord-rubber composite body according to claim 1 or 2, wherein the other of the groups is a phenyl group.

8. R in the above general formula (2) １１ and R １２ 2. The steel cord-rubber composite according to claim 1, wherein at least one of the above groups has a carbon number of 7 or 8.

9. The rubber composition comprises a nitrogen-containing cyclic compound not containing a benzene ring or a mercapto group, and a compound represented by the following general formula (3): [In the formula, R ３１ and R ３２ and each independently represent a monovalent saturated hydrocarbon group.] (excluding the phenylenediamine-based antioxidants represented by general formula (1) above), and a proportion of the amine-based antioxidant represented by general formula (3) above in the antioxidants is 0.1 to 80 mass %.

10. The antioxidant is represented by the following general formula (4): [In the formula, R ４１ and R ４２ represents a phenyl group, and m4 represents an integer of 7 or greater. ], and a proportion of the amine-based antioxidant represented by general formula (4) in the antioxidants is 0.1 to 80 mass %.

11. A tire comprising the steel cord-rubber composite of claim 1 or 2.

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