Rubber compositions, rubber compositions for tires, vulcanized rubber, rubber-metal composites, tires, industrial belts, crawlers, and hoses

Abstract

This rubber composition contains a rubber component, an organic phosphate compound having at least one alkyl chain, a vulcanizing agent, and a vulcanization accelerator, contains a cobalt-containing compound in an amount of, with respect to 100 parts by mass of the rubber component, 0.00 parts by mass or more but less than 0.01 parts by mass in terms of the amount of cobalt, and contains N,N-dicyclohexyl-2-benzothiazolyl sulfonamide in an amount of, with respect to 100 parts by mass of the rubber component, 0.00 parts by mass or more but less than 0.08 parts by mass. The rubber composition enables manufacturing of a rubber-metal composite having excellent heat-resistant adhesiveness between a vulcanized rubber and a metal.

Description

[Technical Field]

[0001] The present invention relates to a rubber composition, a rubber composition for tires, a vulcanized rubber, a rubber-metal composite, a tire, an industrial belt, a crawler, and a hose. [Background technology]

[0002] Many different ideas and inventions have been devised to bond rubber and metal.

[0003] For example, in order to provide a radial tire that improves the initial adhesion and heat-resistant adhesion between the metal cord and the coating rubber while maintaining the fracture characteristics, heat aging resistance, and fatigue fracture resistance of the coating rubber, it is known to use a rubber composition in at least one of the belt layer and the carcass ply, in which the metal cord is coated with the coating rubber, in which 0.1 to 3.0 parts by mass of N,N'-diphenylmethane bismaleimide and 0.1 to 3.0 parts by mass of sodium pyrophosphate decahydrate are blended with 100 parts by mass of a rubber component made of a diene rubber (see, for example, Patent Document 1).

[0004] Also, for example, it has been disclosed that in order to obtain a rubber-metal composite having excellent initial adhesion and heat-resistant adhesion between a metal material and a rubber composition, the rubber composition contains 0.0025 to 0.05 parts by mass of a cobalt compound, calculated as cobalt, per 100 parts by mass of the rubber component (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-220188 [Patent Document 2] International Publication No. 2013 / 140820 Summary of the Invention [Problem to be solved by the invention]

[0006] In coating rubbers that use a large amount of organic acid cobalt salt, cobalt accelerates thermal degradation of the coating rubber, so bismaleimide and a sodium compound are used in Patent Document 1. In Patent Document 2, in order to provide tires with a reduced environmental impact, an attempt is made to improve the adhesion between vulcanized rubber and metal materials by reducing the amount of cobalt-containing compound used. However, the rubber compositions disclosed in Patent Documents 1 and 2 leave room for further investigation regarding the heat-resistant adhesion between vulcanized rubber and metal.

[0007] In view of the above circumstances, the present invention aims to provide a rubber-metal composite having excellent heat-resistant adhesion between vulcanized rubber and metal, a rubber composition and a rubber composition for tires from which the rubber-metal composite can be produced, vulcanized rubber of the rubber composition, and tires, industrial belts, crawlers, and hoses that use the rubber-metal composite, and an object of the present invention is to achieve the above objectives. [Means for solving the problem]

[0008] <1> A rubber composition comprising a rubber component, an organic phosphoric acid compound having at least one alkyl chain, a vulcanizing agent, and a vulcanization accelerator, wherein the content of the cobalt-containing compound is 0.00 part by mass or more and less than 0.01 part by mass, calculated as cobalt, per 100 parts by mass of the rubber component, and the content of N,N-dicyclohexyl-2-benzothiazolylsulfenamide is 0.00 part by mass or more and less than 0.08 part by mass, per 100 parts by mass of the rubber component.

[0009] <2> The alkyl chain has 1 to 20 carbon atoms. <1> The rubber composition according to claim 1. <3> The alkyl chain has 15 to 20 carbon atoms. <1> or <2> The rubber composition according to claim 1. <4> The content of the organic phosphoric acid compound is 0.05 to 10 parts by mass based on 100 parts by mass of the rubber component. <1> ~ <3> The rubber composition according to any one of the above.

[0010] <5> The rubber component contains a rubber having an isoprene skeleton. <1> ~ <4> The rubber composition according to any one of the above. <6> The rubber having an isoprene skeleton includes one or more selected from the group consisting of synthetic isoprene rubber and natural rubber. <5> The rubber composition according to claim 1. <7> The rubber component contains 50 to 100% by mass of the rubber having an isoprene skeleton. <5> or <6> The rubber composition according to claim 1.

[0011] <8> Further, the present invention contains at least one filler containing carbon black. <1> ~ <7> The rubber composition according to any one of the above. <9> The content of the carbon black is 1 to 80 parts by mass based on 100 parts by mass of the rubber component. <8> The rubber composition according to claim 1.

[0012] <10> <1> ~ <9> A rubber composition for tires, comprising the rubber composition according to any one of the above items. <11> <1> ~ <9> 2. A vulcanized rubber using the rubber composition according to any one of the above.

[0013] <12> <11> A rubber-metal composite comprising the vulcanized rubber according to claim 1 and a metal. <13> <12> A tire comprising the rubber-metal composite according to claim 1. <14> <12> An industrial belt comprising the rubber-metal composite according to claim 1. <15> <12> A crawler comprising the rubber-metal composite according to claim 1. <16> <12> A hose comprising the rubber-metal composite according to claim 1. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a rubber-metal composite having excellent heat-resistant adhesion between vulcanized rubber and metal, a rubber composition and a rubber composition for tires from which the rubber-metal composite can be produced, vulcanized rubber of the rubber composition, and tires, industrial belts, crawlers, and hoses that use the rubber-metal composite. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, the present invention will be illustrated and described in detail based on its embodiments. In the following description, the description of "A to B" indicating a numerical range represents a numerical range including the endpoints A and B, and represents "A or more and B or less" (when A < B), or "A or less and B or more" (when A > B). Also, parts by mass and mass% are synonymous with parts by weight and weight%, respectively.

[0016] <Rubber composition> The rubber composition of the present invention contains a rubber component, an organic phosphoric acid compound having at least one alkyl chain, a vulcanizing agent, and a vulcanization accelerator containing 0.08 to 2 parts by mass of a sulfenamide-based vulcanization accelerator with respect to 100 parts by mass of the rubber component, and the content of the cobalt-containing compound is 0.00 parts by mass or more and less than 0.01 parts by mass in terms of cobalt amount with respect to 100 parts by mass of the rubber component. The rubber composition may further contain a filler or the like.

[0017] As described in Patent Document 1, when the rubber composition contains many cobalt-containing compounds, coating rubber thermal deterioration can be promoted. On the other hand, since the cobalt-containing compound has a function of promoting the adhesion between the vulcanized rubber and the metal by being contained in the rubber composition, it has been difficult to improve the adhesion between the metal and the vulcanized rubber without adding the cobalt-containing compound to the rubber composition. Also, as shown in Patent Document 2, in order to provide a tire with a lower environmental load, reducing the usage amount of the cobalt-containing compound has been studied, but if the usage amount of the cobalt-containing compound is small, the adhesive force between the vulcanized rubber and the metal is likely to be suppressed.

[0018] In contrast, it has been found that when a rubber composition contains an organic phosphoric acid compound having at least one alkyl chain, the resulting vulcanized rubber exhibits excellent heat-resistant adhesion to metals, even when the rubber composition substantially does not contain a cobalt-containing compound or N,N-dicyclohexyl-2-benzothiazolylsulfenamide. While the reason for this is unclear, Patent Document 1 uses sodium pyrophosphate, an inorganic phosphoric acid compound, whereas the present invention uses an organic phosphoric acid compound having at least one alkyl chain. This facilitates dispersion of the organic phosphoric acid compound in the rubber component, and the rubber-metal composite exhibits excellent heat-resistant adhesion. Furthermore, the substantial absence of a cobalt-containing compound is believed to suppress thermal degradation of the vulcanized rubber and result in stronger heat-resistant adhesion. Furthermore, the substantial absence of a cobalt-containing compound and N,N-dicyclohexyl-2-benzothiazolylsulfenamide is believed to further reduce environmental impact. The rubber composition of the present invention will be described in detail below.

[0019] [Rubber component] The rubber composition of the present invention contains a rubber component. The rubber component includes at least one diene rubber selected from the group consisting of natural rubber (NR) and synthetic diene rubber, and the rubber component may be modified. Specific examples of synthetic diene rubbers include polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), butadiene-isoprene copolymer rubber (BIR), styrene-isoprene copolymer rubber (SIR), styrene-butadiene-isoprene copolymer rubber (SBIR), and modified rubbers thereof. From the viewpoint of adhesion between metal and vulcanized rubber, the rubber component is preferably natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, isobutylene-isoprene rubber, or modified rubbers thereof. Furthermore, from the viewpoint of mechanical strength of the vulcanized rubber, the rubber component preferably contains a rubber having an isoprene skeleton, and more preferably the rubber having an isoprene skeleton contains one or more selected from the group consisting of synthetic isoprene rubber and natural rubber. The rubber component may be used alone or in a blend of two or more.

[0020] The rubber component preferably contains 50 to 100% by mass of rubber having an isoprene skeleton, from the viewpoint of improving adhesion between the metal and the vulcanized rubber and improving the durability of the resulting rubber-metal composite. From the same viewpoint, the content of the rubber having an isoprene skeleton in the rubber component is more preferably 65% ​​by mass or more, even more preferably 75% by mass or more, and may be 100% by mass. The rubber component may contain a combination of natural rubber (NR) and polyisoprene rubber (IR) to improve adhesion between the metal and vulcanized rubber and thereby enhance durability of the resulting rubber-metal composite. In this case, the ratio of the two (mass of natural rubber:mass of polyisoprene rubber) is preferably 55:45 to 95:5, more preferably 65:35 to 93:17, and even more preferably 70:30 to 90:10. The rubber component may contain a non-diene rubber to the extent that the effects of the present invention are not impaired.

[0021] [Organophosphate compounds] The rubber composition of the present invention contains an organic phosphoric acid compound having at least one alkyl chain. When the rubber composition contains the organic phosphoric acid compound, the heat-resistant adhesion between the vulcanized rubber and the metal is improved. The organic phosphoric acid compound may have two or more alkyl chains, and specifically, it preferably has one to three alkyl chains, and more preferably has one to two alkyl chains. Specifically, the number of carbon atoms in the alkyl chain is preferably 1 to 20. The number of carbon atoms in the alkyl chain is more preferably 10 or more. When the organic phosphoric acid compound has a plurality of alkyl chains, the carbon atoms in the alkyl chains are independent of each other and may be the same or different. From the viewpoint of further enhancing the dispersibility of the organic phosphoric acid compound in the rubber component, the number of carbon atoms is more preferably 15 to 20. The alkyl chain may be linear, branched, or cyclic, but is preferably linear or branched, and more preferably linear, from the viewpoint of dispersibility in the rubber component. The organic phosphoric acid compound is preferably a non-aromatic organic phosphoric acid compound having no aromatic group. The organic phosphoric acid compound is preferably a phosphoric acid ester and preferably has at least one OH group. The phosphoric acid ester more preferably has one or two OH groups bonded to the phosphorus atom. In other words, the organic phosphoric acid compound is more preferably a phosphoric acid ester having one or two ester groups.

[0022] The content of the organic phosphoric acid compound in the rubber composition is preferably 0.05 to 10 parts by mass per 100 parts by mass of the rubber component. When the content of the organic phosphoric acid compound in the rubber composition is 0.05 part by mass or more per 100 parts by mass of the rubber component, the heat-resistant adhesion between the vulcanized rubber and metal can be improved, and even if the content exceeds 10 parts by mass, the performance is unlikely to change. From the viewpoints of heat-resistant adhesion between vulcanized rubber and metal, cost-effectiveness, etc., the content of the organic phosphoric acid compound in the rubber composition is more preferably 0.1 to 7 parts by mass, and even more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0023] [Cobalt-containing compounds] The content of the cobalt-containing compound in the rubber composition of the present invention is 0.00 to less than 0.01 parts by mass in terms of cobalt amount per 100 parts by mass of the rubber component, which means that the rubber composition of the present invention does not substantially contain the cobalt-containing compound except in the case of unavoidable inclusion such as impurities. The cobalt-containing compound may be an inorganic compound or an organic compound, but an organic compound is usually used, more specifically, an organic acid cobalt salt is used. Examples of organic acid cobalt salts include cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tallate, cobalt oleate, cobalt linoleate, cobalt linolenate, cobalt palmitate, etc. Examples of cobalt metal complexes include cobalt acetylacetonate.

[0024] From the viewpoint of further reducing the environmental burden, the content of the cobalt-containing compound in the rubber composition is preferably 0.00 part by mass in terms of the amount of cobalt per 100 parts by mass of the rubber component. For example, when cobalt stearate is used as the cobalt-containing compound, if the rubber composition contains 1 part by mass of cobalt stearate per 100 parts by mass of the rubber component, the rubber composition will contain 0.09 parts by mass of cobalt stearate in terms of the amount of cobalt.

[0025] [Vulcanizing agent] The rubber composition of the present invention contains a vulcanizing agent. The vulcanizing agent is not particularly limited, and examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur. The content of the vulcanizing agent in the rubber composition is preferably 2 to 10 parts by mass, more preferably 3 to 9 parts by mass, and even more preferably 4 to 9 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of further improving heat-resistant adhesion and further improving the durability of rubber-metal composites, tires, industrial belts, and crawlers.

[0026] [Vulcanization accelerator] The rubber composition of the present invention contains a vulcanization accelerator. However, the content of N,N-dicyclohexyl-2-benzothiazolylsulfenamide is 0.00 part by mass or more and less than 0.08 part by mass per 100 parts by mass of the rubber component, which means that the rubber composition of the present invention does not substantially contain N,N-dicyclohexyl-2-benzothiazolylsulfenamide except in the case of unavoidable inclusion such as impurities. N,N-dicyclohexyl-2-benzothiazolylsulfenamide has been widely used in the past because it can increase the reaction rate of the vulcanization reaction and improve the adhesion between vulcanized rubber and metal. However, by not using it, the environmental burden can be reduced. By not using N,N-dicyclohexyl-2-benzothiazolylsulfenamide, the improvement in the reaction rate of the vulcanization reaction due to this compound cannot be expected. However, in the present invention, an organic phosphoric acid compound having at least one alkyl chain is used, and therefore excellent heat-resistant adhesion can be achieved even without the use of this vulcanization accelerator.

[0027] As long as the content of N,N-dicyclohexyl-2-benzothiazolylsulfenamide is less than 0.08 parts by mass per 100 parts by mass of the rubber component, various vulcanization accelerators can be used in the rubber composition. Examples of vulcanization accelerators include sulfenamide vulcanization accelerators other than N,N-dicyclohexyl-2-benzothiazolylsulfenamide, thiuram vulcanization accelerators, guanidine vulcanization accelerators, aldehyde-amine vulcanization accelerators, aldehyde-ammonia vulcanization accelerators, thiazole vulcanization accelerators, thiourea vulcanization accelerators, dithiocarbamate vulcanization accelerators, xanthate vulcanization accelerators, etc. Only one type of vulcanization accelerator may be used, or two or more types may be used. Among the above, it is preferable to use a sulfenamide vulcanization accelerator other than N,N-dicyclohexyl-2-benzothiazolylsulfenamide (another sulfenamide vulcanization accelerator). When the rubber composition of the present invention contains another sulfenamide vulcanization accelerator, the vulcanization of the rubber component can be further accelerated and the heat-resistant adhesion between the vulcanized rubber and metal can be improved.

[0028] Other sulfenamide vulcanization accelerators include N-cyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide, N-ethyl-2-benzothiazolylsulfenamide, N-propyl-2-benzothiazolylsulfenamide, N-butyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N-heptyl-2-benzothiazolylsulfenamide, N-octyl-2-benzothiazolylsulfenamide, N-2-ethylhexyl-2-benzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide, and N-dodecyl-2-benzothiazolylsulfenamide. Examples of suitable benzothiazolylsulfenamide include N-stearyl-2-benzothiazolylsulfenamide, N,N-dimethyl-2-benzothiazolylsulfenamide, N,N-diethyl-2-benzothiazolylsulfenamide, N,N-dipropyl-2-benzothiazolylsulfenamide, N,N-dibutyl-2-benzothiazolylsulfenamide, N,N-dipentyl-2-benzothiazolylsulfenamide, N,N-dihexyl-2-benzothiazolylsulfenamide, N,N-diheptyl-2-benzothiazolylsulfenamide, N,N-dioctyl-2-benzothiazolylsulfenamide, N,N-di-2-ethylhexylbenzothiazolylsulfenamide, N,N-didecyl-2-benzothiazolylsulfenamide, N,N-didodecyl-2-benzothiazolylsulfenamide, and N,N-distearyl-2-benzothiazolylsulfenamide. The other sulfenamide vulcanization accelerators may be used alone or in combination of two or more. Among these, N-cyclohexyl-2-benzothiazolylsulfenamide is preferred from the viewpoint of reactivity.

[0029] The content of the vulcanization accelerator (excluding N,N-dicyclohexyl-2-benzothiazolylsulfenamide) in the rubber composition is preferably 0.1 to 5 parts by mass, more preferably 0.3 to 4 parts by mass, and even more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of further improving the heat-resistant adhesion between the vulcanized rubber and metal and further improving the durability of rubber-metal composites, tires, industrial belts, and crawlers.

[0030] [Filler] The rubber composition of the present invention preferably contains at least one filler containing carbon black. When the rubber composition contains a filler containing at least one type of carbon black, the reinforcement properties of the vulcanized rubber obtained from the rubber composition of the present invention can be improved, and the durability of rubber-metal composites, tires, industrial belts, and crawlers can be improved. The carbon black is not particularly limited and can be appropriately selected depending on the purpose. For example, the carbon black is preferably FEF, SRF, HAF, ISAF, or SAF grade, more preferably HAF, ISAF, or SAF grade, and even more preferably HAF grade. Only one type of carbon black may be used, or two or more types may be used.

[0031] The content of carbon black in the rubber composition is preferably 1 to 80 parts by mass per 100 parts by mass of the rubber component. When the content of carbon black in the rubber composition is 1 part by mass or more per 100 parts by mass of the rubber component, excellent reinforcement of the vulcanized rubber can be achieved, and when the content is 80 parts by mass or less, hysteresis caused by rubbing between carbon black particles can be further reduced. The content of carbon black in the rubber composition is more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, and more preferably 70 parts by mass or less, and even more preferably 65 parts by mass or less, per 100 parts by mass of the rubber component.

[0032] The filler may contain fillers other than carbon black, such as metal oxides such as silica, alumina, titania, and zirconia, and aluminum hydroxide.

[0033] The rubber composition of the present invention may contain, in addition to the rubber component, the organic phosphoric acid compound having at least one alkyl chain, the vulcanizing agent, the sulfenamide vulcanization accelerator other than N,N-dicyclohexyl-2-benzothiazolylsulfenamide, and the filler, compounding agents commonly used in the rubber industry, such as softeners, stearic acid, antioxidants, zinc oxide, resins, waxes, oils, etc., selected as appropriate within the scope that does not impair the object of the present invention. The resin preferably includes a thermosetting resin. The content of the thermosetting resin in the rubber composition of the present invention is preferably 0.1 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the rubber component.

[0034] [Preparation of Rubber Composition] The rubber composition of the present invention 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 amount of each component blended here is the same as the amount contained in the rubber composition as described above. The components may be kneaded in one stage or in two or more stages. For example, when kneading in two stages, the maximum temperature in the first stage of kneading is preferably 130 to 160°C, and the maximum temperature in the second stage is preferably 90 to 120°C.

[0035] The rubber composition of the present invention is preferably used as a rubber composition for coating metal cords, typified by steel cords.

[0036] <Rubber composition for tires> The rubber composition for a tire of the present invention includes the rubber composition of the present invention. The rubber composition for tires of the present invention is suitable for producing tires having a rubber-metal composite that has excellent heat-resistant adhesion between vulcanized rubber and metal, but the rubber composition for tires of the present invention may also be used for producing components such as tire tread portions and sidewall portions.

[0037] <Vulcanized rubber> The vulcanized rubber of the present invention is obtained by using the rubber composition of the present invention. Specifically, it can be obtained by vulcanizing the rubber composition of the present invention.

[0038] <Rubber-metal composite> The rubber-metal composite of the present invention comprises a vulcanized rubber of the rubber composition of the present invention and a metal. A rubber-metal composite in which a metal is coated with a vulcanized rubber is obtained by coating a metal with the rubber composition of the present invention and vulcanizing the rubber composition. The rubber composition of the present invention may coat at least a portion of the metal, but from the viewpoint of improving the durability of the rubber-metal composite, it is preferable to coat the entire surface of the metal. The metal of the rubber-metal composite is not particularly limited, and examples thereof include various metal members such as metal cords and metal plates. The rubber-metal composite is suitably used as a reinforcing material for rubber articles that require particular strength, such as various automobile tires, conveyor belts, hoses, etc. In particular, it is suitably used as a reinforcing member for belts, carcass plies, wire chafers, etc. of various automobile radial tires.

[0039] As a method for covering the steel cord, for example, the following method can be used. A predetermined number of preferably brass-plated steel cords are aligned in parallel at predetermined intervals, and the steel cords are coated from above and below with unvulcanized rubber sheets of the rubber composition of the present invention, each about 0.5 mm thick, to obtain a rubber-metal composite precursor (unvulcanized steel cord topping). This precursor is then heated and vulcanized. The composite of vulcanized rubber and steel cords thus obtained exhibits excellent heat-resistant adhesion.

[0040] The steel cord may be either a steel monofilament or a multifilament (twisted cord or a bundle of drawn cords), and its shape is not limited. When the steel cord is a twisted cord, the twist structure is also not particularly limited, and examples of twist structures include single twist, multi-twist, layer twist, and a composite twist of multi-twist and layer twist. From the viewpoint of ensuring favorable adhesion to vulcanized rubber, it is preferable that the surface of these steel cords is subjected to a surface treatment such as cleaning with an aqueous solution containing a transition metal compound, plating treatment, or adhesive treatment.

[0041] (Cleaning treatment with an aqueous solution containing a transition metal compound) By washing the surface of the steel cord with an aqueous solution containing a transition metal compound, the adhesion between the vulcanized rubber and the steel cord can be improved. Transition metals refer to metallic elements in the periodic table, from scandium (Sc) to zinc (Zn) in period 4, from yttrium (Y) to cadmium (Cd) in period 5, and from lutetium (Lu) to mercury (Hg) in period 6. Cobalt (Co) is preferred as this transition metal from the viewpoint of improving adhesion. The cobalt-containing compound contained in the aqueous solution for cleaning is preferably a compound selected from cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt citrate, cobalt gluconate, and cobalt acetylacetonate. Nitric acid, sulfuric acid, or acetate containing Fe and Ag can also be used as the transition metal compound contained in the aqueous solution.

[0042] The pH of the aqueous solution is preferably about 5 to 8. If the pH of the aqueous solution is in this range, the adhesion between vulcanized rubber and metal can be improved. Furthermore, if the pH is in the neutral range of about 5 to 8, the burden on the environment can be reduced. The washing conditions can be set appropriately depending on the concentration of the aqueous solution. For example, when using an aqueous solution containing cobalt acetate, the washing time is preferably 1 to 60 seconds at a concentration of 0.01 to 10 g / L.

[0043] (plating process) The surface of the steel filament may be plated. The type of plating is not particularly limited, and examples thereof 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 such as copper-zinc-tin (Cu-Zn-Sn) plating and copper-zinc-cobalt (Cu-Zn-Co) plating. Among these, brass plating and copper-zinc-cobalt ternary plating are preferred. Also, for example, a steel filament can be used in which the N atoms on the surface are 2 atomic % or more and 60 atomic % or less, and the Cu / Zn ratio on the surface is 1 or more and 4 or less. Also, the metal filament 1 can be one in which the amount of phosphorus contained as oxide up to 5 nm in the outermost layer of the filament radially inward is 7.0 atomic % or less as a proportion of the total amount excluding the amount of C. When an adhesive treatment is used, an adhesive treatment such as "Chemlock" (registered trademark) manufactured by Lord Corporation is preferred.

[0044] Among the above, the steel cord is preferably a steel cord the surface of which has been subjected to a cleaning treatment with an aqueous solution containing a transition metal compound or a plating treatment, more preferably a steel cord the surface of which has been subjected to a cleaning treatment with an aqueous solution containing a cobalt-containing compound or a cobalt ternary plating treatment, and even more preferably a steel cord the surface of which has been subjected to a cleaning treatment with an aqueous solution containing a cobalt-containing compound.

[0045] <Tires> The tire of the present invention comprises the rubber-metal composite of the present invention. The tire of the present invention has excellent durability because it contains the rubber-metal composite of the present invention. The method for producing the tire of the present invention is not particularly limited as long as it is a method that can produce a tire so that the rubber-metal composite of the present invention is contained within the tire. Generally, a rubber composition containing various components is processed into each component in the unvulcanized stage, and the components are attached and molded in a tire building machine by a conventional method to form a green tire. This green tire is heated and pressurized in a vulcanizer to produce a tire. For example, the rubber composition of the present invention is kneaded, and steel cords are rubber-coated with the resulting rubber composition. An unvulcanized belt layer, an unvulcanized carcass, and other unvulcanized components are laminated together, and the unvulcanized laminate is vulcanized to obtain a tire. The gas to be filled into the tire may be normal air, air with adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0046] <Industrial belts, hoses and crawlers> The industrial belt of the present invention comprises the rubber-metal composite of the present invention. The crawler of the present invention includes the rubber-metal composite of the present invention. The hose of the present invention comprises the rubber-metal composite of the present invention. The industrial belts, crawlers, and hoses of the present invention have excellent durability because they contain the rubber-metal composite of the present invention, which has excellent heat-resistant adhesiveness. Examples of industrial belts include conveyor belts. There are no particular limitations on the method for producing the industrial belt, crawler, and hose of the present invention. [Example]

[0047] <Examples 1 and 2 and Comparative Example 1> [Preparation of Rubber Composition] Each component was kneaded to prepare a rubber composition according to the formulation shown in Table 1. In Table 1, blank spaces indicate a numerical value of 0. Details of the components shown in Table 1 are as follows. In addition to the components shown in Table 1, each rubber composition also contains a total of 2.3 parts by mass of other components, including 0.6 parts by mass of stearic acid per 100 parts by mass of the rubber component.

[0048] Natural rubber: RSS#3 Carbon black: Tokai Carbon Co., Ltd., product name "Seast 300" (HAF-LS grade) Anti-aging agent: Ouchi Shinko Chemical Industry Co., Ltd., product name "Knocklac 6C" Organic phosphate compound: Organic phosphate compound having the following structure, manufactured by ADEKA Corporation, trade name "ADEKA STAB AX-71" Vulcanization accelerator: N-cyclohexyl-2-benzothiazolyl sulfenamide

[0049] [ka]

[0050] [Surface treatment of steel cord] A steel cord (3 + 9 + 15 × 0.23 mm (wire diameter)) consisting of five steel wires was produced that was brass-plated (thickness: 0.25 μm) with a copper and zinc content (Cu: 63 mass%, Zn: 37 mass%) in the entire brass-plated layer. The steel cord obtained was washed with an aqueous cobalt acetate solution and then dried to obtain a surface-treated steel cord.

[0051] <Production of rubber-metal composite> Surface-treated steel cords (3 + 9 + 15 × 0.23 mm (wire diameter)) were arranged in parallel at 12.5 mm intervals and coated with the prepared rubber composition to produce an unvulcanized rubber-metal composite precursor (unvulcanized steel cord topping) with a thickness of 7 mm. The rubber-metal composite precursor was then quickly vulcanized using standard methods to produce a rubber-metal composite containing vulcanized rubber.

[0052] 〔evaluation〕 The rubber-metal adhesion of rubber-metal composites was evaluated from the viewpoints of [1] initial adhesion and [2] heat-resistant adhesion. [1] For the initial adhesion evaluation, the steel cord of the prepared rubber-metal composite was raised at room temperature (25°C), and the state of the vulcanized rubber coating on the steel cord was visually observed, and the coverage rate was determined as 0 to 100 area %. [2] To evaluate heat-resistant adhesion, the rubber-metal composites were left in a nitrogen atmosphere at 110°C for 30 days to deteriorate. After that, the steel cords were removed from the rubber-metal composites at temperatures below -60°C, and the state of the vulcanized rubber coating on the steel cords was visually inspected to determine the coverage as a percentage between 0 and 100% by area. In both [1] initial adhesion and [2] heat-resistant adhesion, the coverage of the vulcanized rubber in Comparative Example 1 was set to 100, and the coverage of the vulcanized rubber in Examples 1 and 2 was indexed. The results are shown in Table 1.

[0053] [Table 1]

[0054] As can be seen from Table 1, the rubber-metal composites obtained from the rubber compositions of the Examples containing the organic phosphoric acid compound of the present invention have superior heat-resistant adhesion compared to the rubber-metal composites of the Comparative Examples. [Industrial Applicability]

[0055] The rubber composition of the present invention can be used to produce a rubber-metal composite having excellent heat-resistant adhesion. Therefore, the rubber-metal composite obtained using the rubber composition of the present invention is suitable for producing various tires such as heavy-duty tires such as truck tires and bus tires, and passenger car tires, as well as industrial belts, hoses, crawlers, etc.

Claims

1. A rubber component, an organophosphate compound having at least one alkyl chain; A vulcanizing agent; Vulcanization accelerator and Contains the content of the cobalt-containing compound is 0.00 parts by mass or more but less than 0.01 parts by mass in terms of cobalt amount per 100 parts by mass of the rubber component, A rubber composition having an N,N-dicyclohexyl-2-benzothiazolyl sulfenamide content of 0.00 parts by mass or more and less than 0.08 parts by mass per 100 parts by mass of the rubber component, the organic phosphoric acid compound is a phosphoric acid ester, The rubber composition for coating metal cords, wherein the alkyl chain has 15 to 20 carbon atoms (excluding 15 carbon atoms).

2. 2. The rubber composition according to claim 1, wherein the content of the organic phosphoric acid compound is 0.05 to 10 parts by mass per 100 parts by mass of the rubber component.

3. The rubber composition according to claim 1 or 2, wherein the rubber component contains a rubber having an isoprene skeleton.

4. The rubber composition according to claim 3 , wherein the rubber having an isoprene skeleton comprises at least one rubber selected from the group consisting of synthetic isoprene rubber and natural rubber.

5. The rubber composition according to claim 3 or 4, wherein the rubber component contains 50 to 100% by mass of the rubber having an isoprene skeleton.

6. The rubber composition according to any one of claims 1 to 5, further comprising a filler containing at least one kind of carbon black.

7. 7. The rubber composition according to claim 6, wherein the amount of the carbon black is 1 to 80 parts by mass per 100 parts by mass of the rubber component.

8. A rubber composition for tires, comprising the rubber composition according to any one of claims 1 to 7.

9. A vulcanized rubber made using the rubber composition according to any one of claims 1 to 7.

10. A rubber-metal composite comprising the vulcanized rubber according to claim 9 and a metal.

11. A tire comprising the rubber-metal composite of claim 10.

12. An industrial belt comprising the rubber-metal composite of claim 10.

13. A crawler comprising the rubber-metal composite according to claim 10.

14. A hose comprising the rubber-metal composite of claim 10.

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