Rubber compositions, rubber-metal composites, tires, hoses and crawlers

Abstract

This rubber composition contains: a rubber component; 0.01 parts by mass or more relative to 100 parts by mass of the rubber component of a rubber-metal adhesion promoter, said rubber-metal adhesion promoter containing a 2-25C metal carboxylate (1) wherein the type of metal is any selected from the group consisting of bismuth, copper, antimony, silver, niobium, and zirconium, and said rubber-metal adhesion promoter also containing at least one selected from the group consisting of compounds (2) represented by formula (A); and 4,4'-diphenylmethane bismaleimide. By using the rubber composition, it is possible to obtain vulcanized rubber such that a vulcanized rubber deterioration resistance property is good, a vulcanized rubber durability is excellent, and a rubber-metal heat deterioration adhesive property is excellent.

Description

[Technical Field]

[0001] This invention relates to rubber compositions, rubber-metal composites, tires, hoses, and crawlers. [Background technology]

[0002] Due to recent environmental regulations, there is an urgent need to investigate alternatives to cobalt salts (such as cobalt stearate and cobalt versatate), which are widely used as accelerators for rubber-metal bonding.

[0003] For example, a metal salt of an aliphatic carboxylic acid having 2 to 25 carbon atoms (1), wherein the metal is bismuth, copper, antimony, silver, or niobium, or a compound (2) represented by the following general formula (A) [wherein Z is a structure selected from the following formulas (z-1) to (z-4). M is bismuth, copper, antimony, silver, or niobium. (RCOO) is a residue of an aliphatic carboxylic acid having 2 to 25 carbon atoms. x is (valence of M - 1).] has been disclosed as an adhesion promoter between rubber and metal (see, for example, Patent Document 1).

[0004] Metal-organic compounds of the average formula: X(OMA′p)m(OMB′p)n [wherein M is cobalt, nickel, or bismuth, B′ is a residue of an aromatic carboxylic acid having 7-11 carbon atoms, A′ is a residue of an aliphatic carboxylic acid having 7-11 carbon atoms, p is 1 when M is cobalt or nickel, or 2 when M is bismuth, n is 0.5-2, and m is (3-n)] are disclosed (see, for example, Patent Document 2).

[0005] A method for increasing the viscosity of an aqueous medium containing a gellable polymeric substance having substituents with phenolic hydroxyl groups, or for inducing gelation, is disclosed, comprising adding an effective amount of laccase to the aqueous medium (see, for example, Patent Document 3).

[0006] A steel cord-rubber composite is disclosed, comprising a steel cord having one or more steel filaments formed on a plating layer containing copper, zinc, and cobalt, and a rubber bonded together, wherein the rubber and the plating layer are bonded together, and the layer in the plating layer containing a copper-sulfur compound is defined as the adhesive layer, and the sulfur content of the adhesive layer is analyzed from the plating layer toward the rubber perpendicular to the longitudinal direction of the steel filament, and the position of the inflection point where the sulfur content increases is defined as the bottom of the adhesive layer, and the atomic percentage of cobalt is analyzed at six equally spaced points in the longitudinal direction of the steel filament, 100 nm inward from the bottom of the adhesive layer perpendicular to the longitudinal direction of the steel filament, and the portion where the atomic percentage of cobalt is higher than the atomic percentage of cobalt of the entire plating layer is defined as a cobalt-rich region (nm), and the sum of the six cobalt-rich regions (nm) is 40% or more of the sum of the analysis ranges (nm) of the six points. (See, for example, Patent Document 4.) [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2016 / 039375 [Patent Document 2] Japanese Patent Application Publication No. 4-230397 [Patent Document 3] Special Publication No. 10-502962 [Patent Document 4] International Publication No. 2016 / 203886 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Even if only bismuth salts, etc., described in Patent Documents 1 to 4 are incorporated into the rubber composition, while thermal degradation adhesion between rubber and metal can be obtained, the degradation resistance of the vulcanized rubber decreases, and hysteresis loss increases. Therefore, there are many challenges in achieving both thermal degradation adhesion between rubber and metal and durability of vulcanized rubber.

[0009] In view of the above circumstances, the present invention aims to provide a rubber composition capable of obtaining a vulcanized rubber having good deterioration resistance, excellent durability of the vulcanized rubber, and excellent thermal deterioration adhesion of rubber-metal, a rubber-metal composite excellent in durability and rubber-metal adhesion, and a tire, hose, and crawler excellent in durability, and solving this problem is an issue.

Means for Solving the Problems

[0010] <1> A rubber-metal adhesion promoter containing a rubber component, a metal carboxylate (1) having 2 to 25 carbon atoms and any one selected from the group consisting of bismuth, copper, antimony, silver, niobium, and zirconium as the metal species; and at least one selected from the group consisting of the compound (2) represented by the following formula (A), with respect to 100 parts by mass of the rubber component, containing 0.01 parts by mass or more and 4,4'-diphenylmethane bismaleimide.

[0011]

Chemical formula

[0012] In formula (A), Z is a structure selected from formula (z-1) to formula (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 of (valence of M - 1).

[0013] <2> The rubber composition according to <1>, further containing at least one selected from the group consisting of sodium hexamethylenebisthiosulfate dihydrate, 1, m - bis(citraconimidomethyl)benzene, and 3-hydroxy-N'-(1,3-dimethylbutylidene)-2-naphthoic acid hydrazide. <3> The rubber composition according to <1> or <2>, containing a filler containing at least one selected from the group consisting of carbon black and silica. <4> The aforementioned rubber component includes natural rubber <1> ~ <3> A rubber composition as described in any one of the following.

[0014] <5> The rubber-metal adhesion promoter contains the metal carboxylate salt (1), and the metal species of the metal carboxylate salt (1) is bismuth or copper. <1> ~ <4> A rubber composition as described in any one of the following. <6> The rubber-metal adhesion promoter contains the carboxylate metal salt (1), and the aliphatic carboxylic acid in the carboxylate metal salt (1) is an aliphatic monocarboxylic acid or an aliphatic dicarboxylic acid. <1> ~ <5> A rubber composition as described in any one of the following. <7> The aliphatic monocarboxylic acid is a saturated aliphatic monocarboxylic acid having 2 to 20 carbon atoms. <6> The rubber composition described above. <8> The saturated aliphatic monocarboxylic acid having 2 to 20 carbon atoms is 2-ethylhexanoic acid, neodecanoic acid, hexadecanoic acid, or octadecanoic acid. <7> The rubber composition described above.

[0015] <9> The rubber-metal adhesion promoter contains the compound (2), wherein M in the compound (2) is bismuth or copper. <1> ~ <8> A rubber composition as described in any one of the following. <10> The rubber-metal adhesion promoter contains compound (2), and the structure of Z in compound (2) is represented by formula (z-1). <1> ~ <9> A rubber composition as described in any one of the following. <11> The rubber-metal adhesion promoter contains compound (2), wherein (RCOO) in compound (2) is a residue of a saturated aliphatic monocarboxylic acid having 2 to 20 carbon atoms. <1> ~ <10> A rubber composition as described in any one of the following. <12> In compound (2), (RCOO) is a residue of 2-ethylhexanoic acid, a residue of neodecanoic acid, a residue of hexadecanoic acid, or a residue of octadecanoic acid. <11> The rubber composition described above.

[0016] <13> <1> ~ <12> A rubber-metal composite comprising a vulcanized rubber and a metal, as described in any one of the rubber compositions. <14>A tire containing the rubber-metal composite described in <13>. <15>A hose containing the rubber-metal composite described in <13>. <16>A crawler containing the rubber-metal composite described in <13>.

Advantages of the Invention

[0017] According to the present invention, there can be provided a rubber composition capable of obtaining a vulcanized rubber having good deterioration resistance, excellent durability, and excellent heat deterioration adhesion of rubber-metal, a rubber-metal composite excellent in durability and rubber-metal adhesion, and a tire, a hose, and a crawler excellent in durability.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the present invention will be exemplified 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.

[0019] <Rubber Composition> The rubber composition of the present invention contains a rubber component, a metal carboxylate (1) having 2 to 25 carbon atoms and any one selected from the group consisting of bismuth, copper, antimony, silver, niobium, and zirconium as the metal species; and at least one selected from the group consisting of a rubber-metal adhesion promoter containing a compound (2) represented by the following formula (A). The rubber-metal adhesion promoter is contained in an amount of 0.01 part by mass or more with respect to 100 parts by mass of the rubber component, and contains 4,4'-diphenylmethane bismaleimide.

[0020]

Chemical Formula

[0021] 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 (valence of M - 1).

[0022] When a metal-containing compound such as bismuth is used as a substitute for a cobalt-containing compound in rubber-metal bonding adhesives, while rubber-metal adhesion is achieved, the durability of the vulcanized rubber decreases. In contrast, the rubber composition of the present invention, having the above-described structure, provides good resistance to degradation of the vulcanized rubber, excellent durability of the vulcanized rubber, and a rubber-metal composite with excellent thermal degradation adhesion between rubber and metal, as well as a tire with excellent durability. Although the reason for this is not entirely clear, it is presumed that the use of the aforementioned rubber-metal adhesion promoter containing bismuth, etc., and 4,4'-diphenylmethanebismaleimide complements the degradation resistance of the vulcanized rubber, resulting in excellent thermal degradation adhesion between rubber and metal for the vulcanized rubber and excellent durability for the rubber-metal composite.

[0023] In particular, even when an unvulcanized rubber-metal composite (referred to as a rubber-metal composite precursor) is prepared and then vulcanized after a period of time to obtain a rubber-metal composite, the rubber composition of the present invention suppresses metal corrosion, exhibits excellent rubber-metal adhesion, and yields a highly durable rubber-metal composite. The rubber composition, rubber-metal composite, and tire of the present invention will be described in detail below.

[0024] [Rubber components] The rubber composition of the present invention contains rubber components. The rubber component may be at least one diene rubber selected from the group consisting of natural rubber (NR) and synthetic diene rubber. The rubber component may be modified. 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 versions thereof. From the viewpoint of adhesion between metal and vulcanized rubber, the diene-based rubber is preferably natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, and isobutylene isoprene rubber, as well as modified versions thereof. Natural rubber, polyisoprene rubber, and polybutadiene rubber are more preferably, and natural rubber and polyisoprene rubber are even more preferably. Diene-based rubbers may be used individually or blended with two or more other types.

[0025] From the viewpoint of improving the adhesion between the metal and the vulcanized rubber and enhancing the durability of the resulting rubber-metal composite, the rubber component preferably contains 55% by mass or more of natural rubber, more preferably 65% ​​by mass or more, and even more preferably 75% by mass or more. The upper limit of the proportion of natural rubber in the rubber component may be 100% by mass. From the viewpoint of improving the adhesion between the metal and the vulcanized rubber and enhancing the durability of the resulting rubber-metal composite, it is preferable to use a combination of natural rubber (NR) and polyisoprene rubber (IR) as the rubber component. 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 include non-diene rubber to the extent that it does not impair the effects of the present invention.

[0026] [Rubber-metal bonding accelerator] The rubber composition of the present invention contains a rubber-metal adhesion promoter containing a carboxylate metal salt (1) having 2 to 25 carbon atoms and being selected from the group consisting of bismuth, copper, antimony, silver, niobium, and zirconium; and a compound (2) represented by the following formula (A).

[0027] [ka]

[0028] 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 (valence of M - 1).

[0029] The carboxylate metal salt (1) is a metal salt of an aliphatic carboxylic acid having 2 to 25 carbon atoms. Here, the metal species is bismuth, copper, antimony, silver, niobium, or zirconium. Among the metal species, bismuth, copper, antimony, or silver are preferred, and bismuth or copper are more preferred, because they act as adhesion promoters that provide good adhesion between steel cord and rubber even under humid heat conditions. If the number of carbon atoms in the carboxylate metal salt (1) is less than 2, the compatibility between the carboxylate metal salt (1) and the rubber component is low, and high adhesion between the vulcanized rubber and the metal cannot be obtained. Furthermore, carboxylate metal salts (1) with more than 25 carbon atoms are difficult to synthesize.

[0030] Examples of aliphatic carboxylic acids with 2 to 25 carbon atoms include aliphatic monocarboxylic acids and aliphatic dicarboxylic acids. Note that the carbon number of an aliphatic carboxylic acid refers to the total number of carbon atoms including the carboxyl group.

[0031] Examples of aliphatic carboxylic acids having 2 to 25 carbon atoms include saturated aliphatic monocarboxylic acids and unsaturated aliphatic monocarboxylic acids. Examples of saturated aliphatic monocarboxylic acids include ethaneic 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, naphthenic acid, and others.

[0032] Examples of 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, rosinic acid, abietic acid, neoabietic acid, parastric acid, pimaric acid, and dehydroabietic acid.

[0033] Examples of aliphatic dicarboxylic acids having 2 to 25 carbon atoms include saturated aliphatic dicarboxylic acids and unsaturated aliphatic dicarboxylic acids. Examples of saturated aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid. Examples of unsaturated aliphatic dicarboxylic acids include fumaric acid and maleic acid.

[0034] 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. Using a saturated aliphatic monocarboxylic acid has less impact on the sulfur crosslinking of rubber and can suppress the deterioration of the rubber properties of vulcanized rubber. Among 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.

[0035] The metal carboxylate salt (1) can be obtained, for example, by the method shown below. Method 1: A direct reaction 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).

[0036] Method 2: A method of production (double decomposition method) in which an aliphatic carboxylic acid (a) having 2 to 25 carbon atoms is reacted with sodium hydroxide in the presence of water to obtain a sodium salt of the aliphatic carboxylic acid, and then the sodium salt of the aliphatic carboxylic acid is reacted with one or more selected from metal sulfates (c-1) of metals (bismuth, copper, antimony, silver, niobium, zirconium), chlorides (c-2) of metals (bismuth, copper, antimony, silver, niobium, zirconium), and nitrates (c-3) of metals (bismuth, copper, antimony, silver, niobium, zirconium).

[0037] Examples of metal oxides (b-1) 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 metal hydroxides (b-2) include copper(II) hydroxide and zirconium hydroxide. Examples of metal carbonates (b-3) include bismuth(III) carbonate, bismuth(III) carbonate oxide, and copper(II) carbonate.

[0038] Examples of metal sulfates (c-1) (bismuth, copper, antimony, silver, niobium, zirconium) include copper(II) sulfate and zirconium sulfate. Examples of chlorides (c-2) of metals (bismuth, copper, antimony, silver, niobium, zirconium) include bismuth(III) chloride, copper(I) chloride, copper(II) chloride, antimony(III) chloride, antimony(V) chloride, silver(I) chloride, and niobium(V) chloride. Examples of nitrates (C-3) of metals (bismuth, copper, antimony, silver, niobium, zirconium) include bismuth(III) nitrate, bismuth(III) subnitrate, and silver(I) nitrate.

[0039] In method 1, the reaction temperature when reacting the aliphatic carboxylic acid (a) having 2 to 25 carbon atoms with compounds (b-1) to (b-3) is typically 50 to 150°C. The reaction time is typically 1 to 20 hours.

[0040] In method 2, the reaction temperature when reacting an aliphatic carboxylic acid (a) having 2 to 25 carbon atoms with sodium hydroxide in the presence of an organic solvent is typically 20 to 100°C. The reaction time is also typically 1 to 5 hours.

[0041] In method 2, the reaction temperature when reacting the sodium salt of the aliphatic carboxylic acid with compounds (C-1) to (C-3) is typically 20 to 100°C. The reaction time is typically 1 to 5 hours.

[0042] In method 2, the sodium salt of an aliphatic carboxylic acid is reacted with compounds (c-1) to (c-3), and then the aqueous layer in the reaction system is separated. Subsequently, the solvent present in the oil layer is removed by vacuum distillation to obtain the carboxylic acid metal salt (1).

[0043] Next, we will describe compound (2), represented by formula (A), in detail. The (RCOO) in compound (2) is an aliphatic carboxylic acid residue having 2 to 25 carbon atoms. If the aliphatic carboxylic acid residue has fewer than 2 carbon atoms, the compatibility between the rubber component and compound (2) is poor, resulting in reduced adhesion between the vulcanized rubber and the metal. If the aliphatic carboxylic acid residue has more than 25 carbon atoms, 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 onto the steel cord surface, resulting in reduced adhesion between the vulcanized rubber and the metal.

[0044] Examples of aliphatic monocarboxylic acid residues having 2 to 25 carbon atoms include aliphatic monocarboxylic acid residues, and the residues derived from aliphatic monocarboxylic acids described in the explanation of carboxylate metal salts (1) are preferably given as examples.

[0045] Among aliphatic carboxylic acid residues, saturated aliphatic monocarboxylic acid residues are preferred. Using saturated aliphatic monocarboxylic acid residues makes it easier for compound (2) to disperse near the steel cord, or for the vulcanized rubber to adsorb to the surface of the steel cord. Among saturated aliphatic monocarboxylic acid residues, residues of saturated aliphatic monocarboxylic acids having 2 to 20 carbon atoms are preferred, and residues of 2-ethylhexanoic acid, neodecanoic acid, hexadecanoic acid, or octadecanoic acid are more preferred.

[0046] In the compound represented by formula (A), M is a metal species, specifically bismuth, copper, antimony, silver, niobium, or zirconium. Among the metal species, bismuth, copper, antimony, or silver are preferred because they act as adhesion promoters that provide good adhesion between steel cords and rubber even under humid heat conditions, with bismuth or copper being more preferred.

[0047] Furthermore, x in compound (2) represented by formula (A) is an integer equal to (the valency of M minus 1).

[0048] In compound (2) represented by formula (A), Z is a structure selected from formulas (z-1) to (z-4) described above. In particular, the structure represented by formula (z-1) is preferred because it is easier to obtain an adhesion promoter that exhibits high adhesive strength between vulcanized rubber and metal.

[0049] Compound (2) represented by 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 then removing the volatile ester (g) obtained from the mixture.

[0050] Aliphatic carboxylic acids (a) having 2 to 25 carbon atoms include the aliphatic monocarboxylic acids having 2 to 25 carbon atoms as described above.

[0051] Examples of inorganic acid esters (d) include borate esters of lower alcohols having 1 to 5 carbon atoms (d-1), metaborate esters of lower alcohols having 1 to 5 carbon atoms (d-2), phosphoric acid esters of lower alcohols having 1 to 5 carbon atoms (d-3), and phosphorous acid esters of lower alcohols having 1 to 5 carbon atoms (d-4).

[0052] Examples of lower alcohol borate esters (d-1) include trimethyl borate, triethyl borate, tripropyl borate, and tributyl borate. Examples of lower alcohol metaboric acid esters (d-2) include trimethyl metaborate, triethyl metaborate, tripropyl metaborate, and tributyl metaborate. Examples of lower alcohol phosphate esters (d-3) include methyl phosphate, ethyl phosphate, propyl phosphate, and butyl phosphate. Examples of lower alcohol phosphite esters (d-4) include methyl phosphite, ethyl phosphite, propyl phosphite, and butyl phosphite. Among the above, metaboric acid ester (d-2) of a lower alcohol is preferred from the viewpoint of suppressing metal corrosion after treatment.

[0053] Acid (e) is an acid capable of forming a volatile ester (g) with a lower alcohol residue having 1 to 5 carbon atoms present in the inorganic acid ester (d). Specifically, examples include ethaneic acid, propanoic acid, and butanoic acid.

[0054] The metal compound M(f) is the metal source for compound (2), and for example, oxides (b-1), hydroxides (b-2), carbonates (b-3), etc., as described in the method for producing the carboxylate metal salt (1), can be used.

[0055] The proportion of the metal compound M(f), which is the metal source, used is, for example, 20 to 100 parts by mass per 100 parts by mass of aliphatic carboxylic acid (a) having 2 to 25 carbon atoms. For example, the proportion of inorganic acid ester (d) used is 10 to 50 parts by mass per 100 parts by mass of aliphatic carboxylic acid (a) having 2 to 25 carbon atoms. For example, the proportion of acid (e) used is 10 to 50 parts by mass per 100 parts by mass of aliphatic carboxylic acid (a) having 2 to 25 carbon atoms.

[0056] The mixing of 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) may be carried out in one step or in multiple steps. One example of a method for mixing various components in multiple steps is a manufacturing method that includes the following first and second steps.

[0057] The first step involves mixing an aliphatic carboxylic acid (a) having 2 to 25 carbon atoms, an acid (e), and a metal compound M (f), and heating the mixture to obtain a reaction product (h). The second step involves removing water from the reaction system containing the reactant (h) obtained in the first step, then adding the inorganic acid ester (d) to the water-free reaction system, and reacting the reactant (h) with the inorganic acid ester (d).

[0058] By producing compound (2) in the two steps described above, it is possible to prevent the inorganic acid ester (d) from being hydrolyzed by the water produced in the first step, and thus efficiently produce compound (2).

[0059] In the above two-step manufacturing 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, preferably 150 to 220°C. The reaction time is, for example, 1 to 20 hours, preferably 1 to 5 hours.

[0060] The content of the rubber-metal adhesion promoter in the rubber composition must be at least 0.01 parts by mass per 100 parts by mass of the rubber component, from the viewpoint of improving the adhesion between vulcanized rubber and metal and improving the durability of the metal-rubber composite and tires. If the content is less than 0.01 parts by mass, sufficient adhesion between vulcanized rubber and metal cannot be obtained. Furthermore, it is preferable that the rubber-metal adhesion promoter be 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.

[0061] [4,4'-Diphenylmethanebismaleimide] The rubber composition of the present invention contains 4,4'-diphenylmethanebismaleimide. If the rubber composition does not contain 4,4'-diphenylmethanebismaleimide, vulcanized rubber with excellent adhesion to metal cannot be obtained, and the rubber-metal composite and tires will not have good durability. Furthermore, if the rubber composition does not contain 4,4'-diphenylmethanebismaleimide, metal corrosion will progress after treatment, and the rubber-metal adhesion will decrease. The content of 4,4'-diphenylmethanebismaleimide in the rubber composition is preferably 0.3 to 2.0 parts by mass, more preferably 0.3 to 1.5 parts by mass, and even more preferably 0.5 to 1.2 parts by mass, per 100 parts by mass of the rubber component. 4,4'-Diphenylmethanebismaleimide can be purchased from Otsuka Chemical Co., Ltd., Tokyo Chemical Industries, Ltd., or Yamato Chemical Industries, Ltd. Yamato Chemical Industries, Ltd. sells it under the product name "BMI-1000". The ratio of 4,4'-diphenylmethanebismaleimide to rubber-metal adhesion promoter is not particularly limited, but the mass ratio of 4,4'-diphenylmethanebismaleimide to rubber-metal adhesion promoter (4,4'-diphenylmethanebismaleimide / rubber-metal adhesion promoter) is preferably 0.3 to 150, more preferably 0.5 to 100, even more preferably 0.7 to 50, and particularly preferably 0.9 to 20. By setting the ratio within the above range, it is expected that durability will be further improved.

[0062] The rubber composition of the present invention preferably contains at least one selected from the group consisting of hexamethylene bisthiosulfate disodium dihydrate, 1,3-bis(citraconimidomethyl)benzene, and 3-hydroxy-N'-(1,3-dimethylbutylidene)-2-naphthoate hydrazide (referred to as component B). The rubber composition containing one, two, or all of the following: hexamethylene bisthiosulfate disodium dihydrate, 1,3-bis(citraconimidomethyl)benzene, and 3-hydroxy-N'-(1,3-dimethylbutylidene)-2-naphthoate hydrazide, improves rubber-metal adhesion and enhances the durability of the rubber-metal composite and the tire. Component B preferably contains at least hexamethylene bisthiosulfate disodium dihydrate. The content of component B in the rubber composition is preferably 0.3 to 5.0 parts by mass, more preferably 0.5 to 3.0 parts by mass, and even more preferably 1.0 to 2.0 parts by mass, per 100 parts by mass of the rubber component.

[0063] [Cobalt-containing material] The rubber composition of the present invention may or may not contain a cobalt-containing material. Examples of organic cobalt acid salts include cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tolate, cobalt oleate, cobalt linoleate, cobalt linolenate, and cobalt palmitate. Examples of cobalt metal complexes include cobalt acetylacetonate.

[0064] As previously described, conventional methods have used cobalt-containing materials to achieve rubber-metal adhesion. However, the rubber composition of the present invention contains a rubber-metal adhesion promoter including bismuth, so the rubber composition exhibits excellent rubber-metal adhesion even without containing cobalt-containing materials. Furthermore, because the rubber composition does not contain cobalt-containing materials, metal corrosion after treatment can be suppressed, and the environmental burden can be reduced. Specifically, the cobalt atom content in the rubber composition of the present invention is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.01% by mass or less, and even more preferably 0% by mass. Furthermore, the cobalt element content in the rubber component is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.01% by mass or less, and even more preferably 0% by mass.

[0065] [Filling material] The rubber composition of the present invention preferably contains a filler. By including a filler in the rubber composition, the reinforcing properties of the vulcanized rubber obtained from the rubber composition of the present invention can be improved, thereby enhancing the durability of the rubber-metal composite and the tire. The type of filler is not particularly limited, and for example, a reinforcing filler that reinforces the rubber composition can be used. Examples of reinforcing fillers include metal oxides such as silica, alumina, titania, and zirconia, aluminum hydroxide, and carbon black. One type of filler may be used, or two or more types may be used. From the viewpoint of improving the reinforcing properties of vulcanized rubber and the durability of the rubber-metal composite and tire, it is preferable that the filler contains at least one selected from the group consisting of carbon black and silica.

[0066] (Carbon Black) The carbon black is not particularly limited and can be selected as appropriate depending on the purpose. For example, FEF, SRF, HAF, ISAF, and SAF grades of carbon black are preferred, HAF, ISAF, and SAF grades are more preferred, and HAF grade is even more preferred.

[0067] The carbon black content in the rubber composition is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 50 parts by mass or more, preferably 90 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. When the filler content in the rubber composition is 30 parts by mass or more per 100 parts by mass of the rubber component, the reinforcing properties of the vulcanized rubber are excellent, and when it is 90 parts by mass or less, hysteresis caused by friction between the fillers can be further reduced.

[0068] (silica) Examples of silica include wet silica (hydrated silica), dry silica (anhydrous silica), colloidal silica, calcium silicate, and aluminum silicate. Of these, wet silica is preferred. Silica may be used alone or in combination of two or more types. The silica content is preferably 1.0 to 10 parts by mass, more preferably 2.0 to 9.0 parts by mass, and even more preferably 4.0 to 8.0 parts by mass, per 100 parts by mass of rubber component.

[0069] [sulfur] The rubber composition of the present invention preferably contains sulfur. There are no particular restrictions on the type of sulfur used; examples include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur. From the viewpoint of further improving rubber-metal adhesion and further improving the durability of the rubber-metal composite and the tire, the sulfur content 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 8 parts by mass, per 100 parts by mass of rubber component.

[0070] [Vulcanization accelerator] The rubber composition of the present invention may contain a vulcanization accelerator to further promote the vulcanization of the rubber component. Specifically, examples of vulcanization accelerators include thiuram-based, guazinine-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, sulfenamide-based, thiourea-based, dithiocarbamate-based, and xantate-based accelerators, with sulfenamide-based accelerators being preferred among these. Examples of sulfenamide-based vulcanization accelerators include N-cyclohexyl-2-benzothiazolyl sulfenamide and N,N-dicyclohexyl-1,3-benzothiazole-2-sulfenamide, with N-cyclohexyl-2-benzothiazolyl sulfenamide being particularly preferred. One type of vulcanization accelerator may be used, or two or more types may be used. From the viewpoint of further improving rubber-metal adhesion and the durability of the rubber-metal composite and the tire, the content of the vulcanization accelerator 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.

[0071] The mixing ratio of the vulcanization accelerator to sulfur (vulcanization accelerator / sulfur) is not particularly limited, but is preferably 0.05 to 1, more preferably 0.1 to 0.9, and even more preferably 0.11 to 0.5.

[0072] The rubber composition of the present invention may optionally contain, in addition to rubber components, a rubber-metal adhesion promoter, 4,4'-diphenylmethane bismaleimide, fillers, and sulfur, hexamethylene bisthiosulfate disodium dihydrate and 1,3-bis(citraconimidomethyl)benzene, as well as compounding agents commonly used in the rubber industry, such as softeners, stearic acid, antioxidants, zinc oxide, silane coupling agents, resins, waxes, oils, etc., selected as appropriate within limits that do not impair the purpose of the present invention.

[0073] (Anti-aging agent) Among the above-mentioned formulations, the anti-aging agent is not particularly limited and includes, for example, amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as anti-aging agents such as metal carbamate salts.

[0074] Examples of amine-based antioxidants include phenylenediamine-based antioxidants having a phenylenediamine skeleton (-NH-Ph-NH-). Specifically, for example, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (sometimes called 6PPD), N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-bis(1,4-di Examples include methylpentyl-p-phenylenediamine, N,N'-dicyclohexyl-p-phenylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N-4-methyl-2-pentyl-N'-phenyl-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine, hindered diaryl-p-phenylenediamine, phenylhexyl-p-phenylenediamine, and phenyloctyl-p-phenylenediamine.

[0075] In particular, it is preferable that there are no double bonds other than the phenylenediamine portion (-NH-Ph-NH-), specifically the following formula (3)(R 1 -NH-Ph-NH-R 2 A preferred amine-based antioxidant is represented by ).

[0076] [ka]

[0077] In the above equation (3), R 1 and R 2 These are each independently monovalent saturated hydrocarbon groups. R 1 and R 2 These may be the same or different, but from a synthesis standpoint, it is preferable that they be the same.

[0078] 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 and 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 improves the ozone resistance of the vulcanized rubber of the rubber composition. R in equation (3) above 1 and R 2 From the viewpoint of further improving the ozone resistance of the vulcanized rubber of the rubber composition, it is preferable that each of these is independently a chain-like monovalent saturated hydrocarbon group having 1 to 20 carbon atoms or a cyclic monovalent saturated hydrocarbon group having 5 to 20 carbon atoms.

[0079] Examples of the monovalent saturated hydrocarbon group include alkyl groups and cycloalkyl groups. Alkyl groups may be linear or branched, and cycloalkyl groups may have further alkyl groups or the like bonded to them as substituents. Examples of the alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, n-pentyl group, isopentyl group, neopentyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,2-dimethylpentyl group, 1,3-dimethylpentyl group, 1,4-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,4-dimethylpentyl group, n-hexyl group, 1-methylhexyl group, 2-methylhexyl group, various octyl groups, various decyl groups, various dodecyl groups, etc., and among these, 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include cyclopentyl group, methylcyclopentyl group, cyclohexyl group, methylcyclohexyl group, cycloheptyl group, and cyclooctyl group, with the cyclohexyl group being preferred among these.

[0080] The amine-based antioxidant represented by formula (3) may be supported on any carrier. For example, the amine-based antioxidant represented by formula (3) may be supported on an inorganic filler such as silica or calcium carbonate. Furthermore, the amine-based antioxidant represented by formula (3) may also constitute a masterbatch together with the rubber component. The rubber component used in the masterbatch is not particularly limited and may be a diene rubber such as natural rubber (NR), or ethylene-propylene-diene rubber (EPDM), etc. Furthermore, the amine-based antioxidant represented by formula (3) may also be in the form of a salt with an organic acid. While there are no particular limitations on the organic acid used when forming the salt, examples include stearic acid.

[0081] Furthermore, quinoline-based antioxidants can also be suitably used. Examples of quinoline-based antioxidants include 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. The above anti-aging agents may be used individually or in combination of two or more. The anti-aging agent preferably contains one or more selected from the group consisting of amine-based anti-aging agents and quinoline-based anti-aging agents, and more preferably contains at least an amine-based anti-aging agent.

[0082] [Preparation of rubber composition] The rubber composition of the present invention can be manufactured by blending the above-mentioned components and kneading them using a kneading machine such as a Banbury mixer, roll mixer, or internal mixer. Here, the amounts of each component are the same as those previously described as being contained in the rubber composition. The mixing of each component may be carried out in a single stage or in two or more stages. For example, when mixing in two stages, the maximum temperature of the first stage of mixing is preferably 130 to 160°C, and the maximum temperature of the second stage is preferably 90 to 120°C.

[0083] The rubber composition of the present invention is preferably used as a rubber composition for covering metal cords, such as steel cords.

[0084] <Rubber-metal composite> The rubber-metal composite of the present invention comprises vulcanized rubber and metal from the rubber composition of the present invention. By coating a metal with the rubber composition of the present invention and vulcanizing the rubber composition, a rubber-metal composite is obtained in which the metal is coated with vulcanized rubber. The rubber composition of the present invention only needs to 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 in the rubber-metal composite is not particularly limited, but various metal components such as metal cords and metal plates can be used. Rubber-metal composites are suitably used as reinforcing materials in rubber products requiring particularly high strength, such as various automobile tires and hoses. In particular, they are suitably used as reinforcing members for belts, carcass plies, and wire chafers in various types of automobile radial tires.

[0085] For example, the following methods can be used to coat the steel cord. Preferably, a predetermined number of brass-plated steel cords are arranged in parallel at predetermined intervals, and these steel cords are coated from both the top and bottom with an uncrosslinked rubber sheet made of the rubber composition of the present invention, which is about 0.5 mm thick. This is then vulcanized at a temperature of, for example, about 160°C for about 20 minutes. The composite of the rubber composition and steel cords obtained in this way has excellent rubber-metal adhesion.

[0086] The steel cord described above may be either a monofilament or multifilament (twisted cord or bundled cord) made of steel, and its shape is not limited. There are also no particular restrictions on the twisting structure when the steel cord is a twisted cord, and examples of twisting structures include single twist, double twist, layer twist, and composite twist of double twist and layer twist. These steel cords are preferably surface-treated, such as by plating or adhesive treatment, from the viewpoint of ensuring suitable adhesion with the rubber composition. The surface of the steel filament may be plated. The type of plating is not particularly limited and includes, for example, zinc (Zn) plating, copper (Cu) plating, tin (Sn) plating, brass (copper-zinc (Cu-Zn)) plating, bronze (copper-tin (Cu-Sn)) plating, as well as ternary plating such as copper-zinc-tin (Cu-Zn-Sn) plating, copper-zinc-cobalt (Cu-Zn-Co) plating, and copper-zinc-iron (Cu-Zn-Fe) plating. Among these, brass plating, copper-zinc-cobalt ternary plating and copper-zinc-iron ternary plating are preferred, and copper-zinc-iron ternary plating is even more preferred. Furthermore, for example, a steel filament can be used in which the surface nitrogen atoms are between 2 atomic percent and 60 atomic percent, and the surface Cu / Zn ratio is between 1 and 4. In addition, as a metal filament 1, the amount of phosphorus contained as oxide up to the outermost 5 nm of the filament in the radial direction of the filament is 7.0 atomic percent or less in proportion to the total amount excluding the amount of carbon. Furthermore, if adhesive treatment is used, adhesive treatment such as "Chemrock" (registered trademark) manufactured by Road Co. is preferred.

[0087] A steel cord comprising one or more steel filaments as described above, wherein the filament comprises a steel filament substrate and a coating that partially or entirely covers the steel filament substrate, the coating comprises brass made of copper and zinc, the coating is reinforced with iron, the iron is present as particles in the brass, and the particles have a size of 10 to 10,000 nanometers. It is even more preferable that the particles have a size of 20 to 5,000 nanometers. "Reinforced with iron" means that the iron does not originate from the filamentous steel substrate. Here, the brass consists of copper and zinc, preferably contains at least 63% by mass of copper, with the remainder being zinc, more preferably contains 65% by mass or more of copper, and even more preferably contains 67% by mass or more of copper. Also, the amount of iron in the coating is preferably 1% or more and less than 10% by mass compared to the total mass of brass and iron, and more preferably 3% or more and less than 9% by mass compared to the total mass of brass and iron. The steel cord, which is characterized in that the coating substantially does not contain a zinc-iron alloy, is more preferable.

[0088] In the steel cord containing one or more of the above steel filaments, the amount of phosphorus present on the surface of the filament is P s and the amount of iron present on the surface of the filament is Fe s and the amount of (P s + Fe s ) is determined by gently etching the surface of the filament with a weak acid that dissolves phosphorus and iron according to the following methods (a) to (e). (a) Weigh approximately 5 grams of the steel cord, cut it into fragments approximately 5 cm long, and introduce them into a test tube. (b) Add 10 ml of 0.01 M hydrochloric acid HCl. (c) Shake the sample in the acid solution for 15 seconds. (d) Measure the amount present in the solution by ICP-OES. <00'00440>Here, ICP-OES refers to inductively coupled plasma - optical emission spectrometry (ICP-OES) that uses all of the standard solutions of (0;0;0), (2;0.02;1), (5;0.1;2), (10;0.5;5) mg / L of (Cu;Fe;Zn) in the matrix of a 10 mL stripping solution. (e) The result showing the mass of (P s + Fe s ) per unit surface area of the filament steel in milligrams per square meter (mg / m 2 ) is shown. The result may be referred to as (Fe s + P s ). The amount of phosphorus present on the surface of the filament is 4 mg / m². 2 The following is preferable for improving adhesion: 0 <P s ≤4 mg / m² 2 The amount of phosphorus (P s ) is 4 mg / m² 2 Less (P s <4mg / m 2 ) is preferable. A larger amount of phosphorus P s The amount reduces the growth of the adhesive layer. Phosphorus P s The amount is 3 mg / m². 2 It can be even lower, or 1.5 mg / m² 2 Even lower would be better. In a more preferred embodiment, the amount of iron present on the surface of the filament is 30 mg / m². 2 Preferably, it is 35 mg / m² or more. 2 It is more preferable if the presence of iron exceeding 40 mg / m² is present on the surface. 2 It is even more preferable if a certain amount of iron is present on the surface. Furthermore, the mass ratio of the amount of iron present on the surface of the filament to the amount of phosphorus present on the surface of the filament (Fe s / P s ) is preferably greater than 27. The filament surface coating weight SCW is the sum of the masses of brass and iron present in the coating per unit surface area, the coating weight is expressed in grams per square meter, and the mass ratio [Fe s / (SCW×P s ) is preferably greater than 13. As a method for obtaining a steel filament in which the iron exists as particles in the brass, an intermediate wire having a brass coating reinforced with iron particles is subsequently drawn out to a final diameter of 0.28 mm by wet wire drawing through a smaller die in a lubricant, thereby obtaining a steel filament. Lubricants generally contain high-pressure additives, including phosphorus, within the organic compound. Here, the die set to be used is a Set-D die, in which at least the head die is a sintered diamond die and the remaining dies are tungsten carbide dies.

[0089] The rubber composition of the present invention can suppress metal corrosion even after a certain period of time has elapsed since coating a metal. For example, a product can be distributed with a metal cord coated with the rubber composition, and then vulcanized at the distribution destination to produce a rubber-metal composite. Furthermore, because metal corrosion is suppressed in the rubber-metal composite produced in this way, the rubber-metal adhesion is less likely to be impaired, and it also has excellent durability.

[0090] <Tires> The tire of the present invention contains 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 manufacturing the tire of the present invention is not particularly limited, as long as it is a method that can manufacture the tire so that the rubber-metal composite of the present invention is contained within the tire. Generally, rubber compositions containing various components are processed into individual parts in an unvulcanized state, and then bonded and molded on a tire molding machine using conventional methods to form a green tire. This green tire is then heated and pressurized in a vulcanizing machine to produce a tire. For example, the rubber composition of the present invention is kneaded, and the resulting rubber composition is used to rubberize steel cords to create an unvulcanized belt layer, an unvulcanized carcass, and other unvulcanized components, which are then laminated together. A tire is then obtained by vulcanizing the unvulcanized laminate. In addition to ordinary air and air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium may also be used as the gas to fill the tires.

[0091] <Hoses and Crawlers> The hose 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 and crawler of the present invention are highly durable because they contain the rubber-metal composite of the present invention, which has excellent durability and rubber-metal adhesion. The method for manufacturing the hose and crawler of the present invention is not particularly limited. [Examples]

[0092] <Example 1> [Preparation of rubber composition] The rubber composition is prepared by kneading each component according to the formulation shown in Table 2.

[0093] <Examples 2-5, Comparative Example 1> [Preparation of rubber composition] A rubber composition was prepared by kneading each component according to the formulation shown in Table 2. Details of the components shown in Table 2 are as follows:

[0094] Natural rubber: RSS#3 Carbon Black: LS-HAF grade carbon black Vulcanization accelerator CBS: N-cyclohexyl-2-benzothiazolyl sulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noxellar CZ" 4,4'-Diphenylmethanebismaleimide: Manufactured by Otsuka Chemical Co., Ltd. Anti-aging agent: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Nocrac 6C" Co neodecanoate: Cobalt neodecanoate, structure shown in (i) below, molecular weight 401.5 Bi neodecanoate: Bismuth neodecanoate, structure (iii) below, molecular weight 722.8, carboxylate metal salt in which the metal species is bismuth (1)

[0095] [ka]

[0096] [ka]

[0097] <Method for fabricating rubber-metal composites> [Example 1] Steel cords (1 × 5 × 0.25 mm (wire diameter)) having the plating composition and surface phosphorus content shown in Table 2 are arranged in parallel at 12.5 mm intervals and coated with the prepared rubber composition to produce a 5 mm thick unvulcanized rubber-metal composite precursor (unvulcanized steel cord topping layer). Subsequently, the rubber-metal composite precursor is rapidly vulcanized at 145°C for 40 minutes to produce a rubber-metal composite (normal composite) containing vulcanized rubber. A 5mm thick rubber-metal composite precursor (unvulcanized steel cord topping) is prepared. Next, the rubber-metal composite precursor (unvulcanized steel cord topping) is left for one week in an environment of 40°C and 80% humidity. After the period of time, the rubber-metal composite precursor is vulcanized at 145°C for 40 minutes to prepare a rubber-metal composite containing vulcanized rubber (composite for treatment and standing evaluation). Furthermore, for the evaluation of the rubber degradation index described later, the rubber sample used will be the rubber sample after the rubber-metal adhesion evaluation following treatment and bonding.

[0098] [Examples 2-5, Comparative Example 1] Steel cords (1 × 5 × 0.25 mm (wire diameter)) having the plating composition and surface phosphorus content shown in Table 2 were arranged in parallel at 12.5 mm intervals and coated with the prepared rubber composition to produce a 5 mm thick unvulcanized rubber-metal composite precursor (unvulcanized steel cord topping layer). Subsequently, the rubber-metal composite precursor was rapidly vulcanized at 145°C for 40 minutes to produce a rubber-metal composite (normal composite) containing vulcanized rubber. A 5mm thick rubber-metal composite precursor (unvulcanized steel cord topping) was prepared. Next, the rubber-metal composite precursor (unvulcanized steel cord topping) was left for one week in an environment of 40°C and 80% humidity. After the period of time, the rubber-metal composite precursor was vulcanized at 145°C for 40 minutes to prepare a rubber-metal composite containing vulcanized rubber (composite for treatment and standing evaluation). Furthermore, for the evaluation of the rubber degradation index described later, rubber samples were used after the rubber-metal adhesion evaluation following treatment and bonding.

[0099] 〔evaluation〕 (Example 1) The evaluation will be performed using the method shown in Table 1. (Examples 2-5, Comparative Example 1) The evaluation was performed using the methods shown in Table 1.

[0100] [Table 1]

[0101] The evaluation methods used in Examples 1-5 and Comparative Example 1 are described below. Specifically, it is as follows: (Thermal degradation adhesion index of rubber-metal) [Example 1] The thermal degradation adhesion between rubber and metal is evaluated based on the state of adhesion under thermal degradation. In the evaluation of thermal degradation adhesion, a rubber-metal composite (conventional composite) with a thickness of 5 mm was prepared by bonding a steel cord topping sheet and each rubber to it. This composite was then degraded at 100°C for 60 days under a nitrogen partial pressure of 0.1 MPa (assuming atmospheric pressure of 0.1 MPa), and then the steel cord was pulled out from the rubber-metal composite in a -65 ± 5°C atmosphere. The results of each example and comparative example are expressed exponentially, with the result of Comparative Example 1 set to 100. [Examples 2-5, Comparative Example 1] The thermal degradation adhesion between rubber and metal was evaluated based on the state of adhesion under thermal degradation. In the evaluation of thermal degradation adhesion, a rubber-metal composite (conventional composite) with a thickness of 5 mm was prepared by bonding steel cord topping sheets and each type of rubber. This composite was then degraded at 100°C for 60 days under a nitrogen partial pressure of 0.1 MPa (assuming atmospheric pressure of 0.1 MPa), and the steel cord was then pulled out from the rubber-metal composite in a -65 ± 5°C atmosphere. The results of each example and comparative example were expressed as an index, with the result of Comparative Example 1 set to 100.

[0102] (Rubber degradation resistance index) [Example 1] The rubber composition is brought into contact with the metal, and after treatment under the conditions shown in Table 1, the rubber-metal adhesion is evaluated by pulling out a steel cord from the rubber-metal composite in a -65±5℃ atmosphere, cutting the vulcanized rubber from the rubber-metal composite used for adhesion evaluation, and determining the elongation at break (EB) (unit: %) and tensile strength at break (TB) (unit: MPa) of the obtained vulcanized rubber. The value obtained by multiplying the obtained EB and TB (EB×TB) is indexed for the examples and comparative examples, with the EB×TB of Comparative Example 1 set to 100. The larger the EB×TB index, the better the durability of the rubber-metal composite. The elongation at break (EB) (in %) and tensile strength (TB) (in MPa) are determined using the methods described in Table 1. [Examples 2-5, Comparative Example 1] After contacting a metal with a rubber composition and allowing it to be treated under the conditions shown in Table 1, the rubber-metal adhesion was evaluated by pulling a steel cord from the rubber-metal composite in a -65±5℃ atmosphere. The vulcanized rubber was then cut from the rubber-metal composite used for adhesion evaluation, and the elongation at break (EB) (unit: %) and tensile strength at break (TB) (unit: MPa) were determined for the obtained vulcanized rubber. The value obtained by multiplying the obtained EB and TB (EB×TB) was indexed for the examples and comparative examples, with the EB×TB of Comparative Example 1 set to 100. The larger the EB×TB index, the better the durability of the rubber-metal composite. The elongation at break (EB) (unit: %) and tensile strength (TB) (unit: MPa) were determined using the method described in Table 1.

[0103] (tanδ) [Example 1] In rubber-metal adhesion evaluation, a strip of vulcanized rubber is cut from the rubber-metal composite (conventional composite) used for initial adhesion evaluation. The tanδ of the obtained strip of vulcanized rubber is measured using a spectrometer viscoelasticity analyzer manufactured by Toyo Seiki Co., Ltd. The measurement conditions are a sine wave with a temperature of 100°C, a frequency of 15Hz, and a tensile strain of 5% on one side. The tanδ of Comparative Example 1 is set to 100, and the tanδ of each example and comparative example is expressed as an exponential value. A larger exponential value indicates superior durability of the rubber-metal composite. [Examples 2-5, Comparative Example 1] In rubber-metal adhesion evaluation, a strip of vulcanized rubber was cut from a rubber-metal composite (conventional composite) used for initial adhesion evaluation. The tanδ of the obtained strip of vulcanized rubber was measured using a spectrometer viscoelasticity analyzer manufactured by Toyo Seiki Co., Ltd. The measurement conditions were a sinusoidal wave with a temperature of 100°C, a frequency of 15Hz, and a tensile strain of 5% on one side. The tanδ of Comparative Example 1 was set to 100, and the tanδ of each example and comparative example was expressed as an exponential value. A higher exponential value indicates superior durability of the rubber-metal composite.

[0104] The results are shown in Table 2.

[0105] [Table 2]

[0106] In the plating composition shown in Table 2, "63 / 37 / -" means that the plating composition is "Cu / Zn" = "63 / 37". [Industrial applicability]

[0107] The rubber composition of the present invention has excellent thermal adhesion between rubber and metal, and can be used to produce rubber-metal composites with excellent durability. Therefore, rubber-metal composites obtained using the rubber composition of the present invention are suitable for the manufacture of various tires, such as heavy-duty tires for trucks and buses, and passenger car tires, as well as for the manufacture of hoses, crawlers, and the like.

Claims

1. Rubber components, A rubber-metal adhesion promoter containing a carboxylate metal salt (1) having 2 to 25 carbon atoms and being selected from the group consisting of bismuth, copper, antimony, silver, niobium, and zirconium; and at least one compound (2) represented by the following formula (A), is added in an amount of 0.01 parts by mass or more per 100 parts by mass of the rubber component. 4,4'-diphenylmethanebismaleimide and It contains, A rubber composition in which the mass ratio of 4,4'-diphenylmethanebismaleimide to the rubber-metal adhesion promoter is 0.5 to 100. 【Chemistry 1】 [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 (valence of M - 1).]

2. The rubber composition according to claim 1, further comprising at least one selected from the group consisting of hexamethylene bisthiosulfate disodium dihydrate, 1,3-bis(citraconimidomethyl)benzene, and 3-hydroxy-N'-(1,3-dimethylbutylidene)-2-naphthoate hydrazide.

3. The rubber composition according to claim 1 or 2, comprising a filler containing at least one selected from the group consisting of carbon black and silica.

4. The rubber composition according to any one of claims 1 to 3, wherein the rubber component comprises natural rubber.

5. The rubber composition according to any one of claims 1 to 4, wherein the rubber-metal adhesion promoter contains the metal carboxylate salt (1), and the metal species of the metal carboxylate salt (1) is bismuth or copper.

6. The rubber composition according to any one of claims 1 to 5, wherein the rubber-metal adhesion promoter contains the metal carboxylate salt (1), and the aliphatic carboxylic acid in the metal carboxylate salt (1) is an aliphatic monocarboxylic acid or an aliphatic dicarboxylic acid.

7. The rubber composition according to claim 6, wherein the aliphatic monocarboxylic acid is a saturated aliphatic monocarboxylic acid having 2 to 20 carbon atoms.

8. The rubber composition according to claim 7, wherein the saturated aliphatic monocarboxylic acid having 2 to 20 carbon atoms is 2-ethylhexanoic acid, neodecanoic acid, hexadecanoic acid, or octadecanoic acid.

9. The rubber composition according to any one of claims 1 to 8, wherein the rubber-metal adhesion promoter contains the compound (2), and M in the compound (2) is bismuth or copper.

10. The rubber composition according to any one of claims 1 to 9, wherein the rubber-metal adhesion promoter contains the compound (2), and Z in the compound (2) has a structure represented by the formula (z-1).

11. The rubber composition according to any one of claims 1 to 10, wherein the rubber-metal adhesion promoter contains the compound (2), and (RCOO) in the compound (2) is a residue of a saturated aliphatic monocarboxylic acid having 2 to 20 carbon atoms.

12. The rubber composition according to claim 11, wherein (RCOO) in compound (2) is a residue of 2-ethylhexanoic acid, a residue of neodecanoic acid, a residue of hexadecanoic acid, or a residue of octadecanoic acid.

13. A rubber-metal composite comprising a vulcanized rubber and a metal according to any one of claims 1 to 12.

14. A tire comprising the rubber-metal composite described in claim 13.

15. A hose comprising the rubber-metal composite according to claim 13.

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

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