Rubber composition and power steering hose

Abstract

To provide a rubber composition capable of satisfying both elongation at break and modulus at an excellent level when made into a cured product, and a power steering hose.SOLUTION: The rubber composition comprises a rubber component containing ≥ 60 mass% hydrogenated acrylonitrile-butadiene rubber, a compound represented by general formula (1), carbon black and a peroxide, and the power steering hose is produced using the rubber composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition and a power steering hose. [Background technology]

[0002] 2. Description of the Related Art Power steering hoses have traditionally been used in automobiles. On the other hand, a rubber composition for a hose and a hose having excellent oil resistance and low temperature properties have been proposed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-131899 Summary of the Invention [Problem to be solved by the invention]

[0004] Automotive power steering hoses expand and contract due to internal pressure (hydraulic pressure), so power steering hoses (especially the inner tube of a power steering hose) must have excellent toughness against internal pressure.To ensure excellent toughness against internal pressure, power steering hoses must have high elongation at break. Furthermore, power steering hoses are usually connected to metal piping, and metal fittings are attached to both ends of the power steering hose for connection. Therefore, in order to ensure excellent crimping sealability with the fittings used when connecting the power steering hose to the metal piping (hereinafter, the crimping sealability will also be referred to as "sealability with the fittings"), the power steering hose is also required to have a high modulus. To improve the elongation at break required to improve the toughness against internal pressure, methods such as reducing the crosslink density or the amount of filler can be used, but these methods lead to a decrease in modulus. As described above, achieving both high elongation at break and high modulus in a power steering hose is a trade-off, and is extremely difficult.

[0005] Therefore, an object of the present invention is to provide a rubber composition which, when cured, can achieve both excellent levels of elongation at break and modulus. Another object of the present invention is to provide a power steering hose that can achieve both excellent levels of elongation at break and modulus. [Means for solving the problem]

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that a desired effect can be obtained by a rubber composition containing a rubber component containing 60% by mass or more of hydrogenated acrylonitrile-butadiene rubber, a compound having a specific structure, carbon black, and a peroxide. Specifically, the present invention solves the above problems by the following configuration.

[0007] [1] A rubber composition comprising a rubber component containing 60% by mass or more of hydrogenated acrylonitrile butadiene rubber, a compound represented by the following general formula (1), carbon black, and a peroxide: [ka] [In general formula (1), R1, R2, R3, and R4 are the same or different and represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a heterocyclic group. R3 and R4 may be combined together to form an alkylidene group, or any two of R2, R3, and R4 may be combined together to form an alkylene group. Each of these groups may have one or more substituents.] [2] The rubber composition according to [1], wherein the content of the compound represented by the general formula (1) is 0.3 to 2.0 parts by mass per 100 parts by mass of the rubber component. [3] The carbon black has a nitrogen adsorption specific surface area of ​​60m 2The rubber composition according to [1] or [2], comprising one or more types of carbon black having a carbon black content of less than 1 / g. [4] The rubber composition according to any one of [1] to [3], wherein the content of the peroxide is 1.6 to 4.0 parts by mass per 100 parts by mass of the rubber component. [5] The rubber composition according to any one of [1] to [4], which is substantially free of sulfur. [6] The rubber composition according to any one of [1] to [5], which is for a hose. [7] A power steering hose produced using the rubber composition according to any one of [1] to [6]. [8] The power steering hose according to [7], having an inner tube formed using the rubber composition. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a rubber composition that, when cured, exhibits both excellent levels of elongation at break and modulus. The present invention also provides a power steering hose. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic perspective view of an example of a power steering hose of the present invention, with each layer cut away. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. The following description of the components may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In the present specification, each component can be used alone or in combination of two or more kinds. In this specification, when two or more types of a component are used in combination, the "content" of the component means the total content of those two or more types, unless otherwise specified. In the present specification, the method for producing each component is not particularly limited unless otherwise specified, and may be, for example, a conventionally known method. In this specification, the elongation at break when the product is cured may be simply referred to as "elongation at break." The modulus when the product is cured may be simply referred to as "modulus." In this specification, the term "the effect of the present invention is superior" may be used to mean that the cured product has both superior levels of elongation at break and modulus.

[0011] [Rubber composition of the present invention] The rubber composition of the present invention will be described below. The rubber composition of the present invention comprises: The rubber composition contains a rubber component containing 60% by mass or more of hydrogenated acrylonitrile butadiene rubber, a compound represented by the following general formula (1), carbon black, and a peroxide. [ka] [In general formula (1), R1, R2, R3, and R4 are the same or different and represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a heterocyclic group. R3 and R4 may be combined together to form an alkylidene group, or any two of R2, R3, and R4 may be combined together to form an alkylene group. Each of these groups may have one or more substituents.]

[0012] [Rubber component] The rubber composition of the present invention contains a rubber component containing 60% by mass or more of hydrogenated acrylonitrile butadiene rubber.

[0013] [Hydrogenated acrylonitrile butadiene rubber] In the present invention, the rubber component includes hydrogenated acrylonitrile butadiene rubber, which is also referred to as "HNBR" in this specification. The HNBR contained in the rubber composition of the present invention is a hydrogenated copolymer of acrylonitrile and butadiene. HNBR has acrylonitrile groups. The hydrogenation in HNBR is hydrogenation in the main chain, and the hydrogenation may be partial or complete.

[0014] (Acrylonitrile content) The acrylonitrile content (AN content) of HNBR is preferably 18 to 30 mass % and more preferably 18 to 25 mass % in HNBR, from the viewpoint of achieving better effects of the present invention and excellent low-temperature properties (flexibility under low-temperature conditions) and oil resistance. In the present invention, the amount of acrylonitrile in HNBR can be measured in accordance with the semi-micro Kjeldahl method based on JIS K6384:2016.

[0015] (hydrogenation rate) From the viewpoint of achieving better effects of the present invention, the hydrogenation rate of HNBR is preferably 95 to 100% of the double bonds (present in repeating units derived from butadiene) that the NBR has before hydrogenation. In the present invention, the hydrogenation rate of HNBR can be measured in accordance with JIS K6235:2006.

[0016] [Hydrogenated acrylonitrile butadiene rubber content] In the present invention, the content of the hydrogenated acrylonitrile butadiene rubber is 60% by mass or more and 100% by mass or less in the total amount of the rubber component. From the viewpoint of achieving superior effects of the present invention, the content of the hydrogenated acrylonitrile butadiene rubber is preferably 80 to 100% by mass, and more preferably 100% by mass, of the rubber component.

[0017] (Other rubber components) When the content of hydrogenated acrylonitrile butadiene rubber in the rubber component is 60% by mass or more but less than 100% by mass, other rubber components that the rubber component may further contain are not particularly limited. Examples of other rubber components include butadiene rubber, natural rubber (NR), isoprene rubber (IR), aromatic vinyl-conjugated diene copolymer rubber, butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), chlorinated polyethylene rubber (CM), acrylonitrile butadiene rubber (NBR; note that the above NBR does not include hydrogenated acrylonitrile butadiene rubber), and chlorosulfonated polyethylene rubber (CSM).

[0018] (Rubber content) The content of the rubber component is preferably 40 to 70% by mass of the total amount of the rubber composition of the present invention, from the viewpoint of achieving better effects of the present invention.

[0019] [Compound represented by general formula (1)] The rubber composition of the present invention contains a compound represented by the following general formula (1). [ka] [In general formula (1), R1, R2, R3, and R4 are the same or different and represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a heterocyclic group. R3 and R4 may be combined together to form an alkylidene group, or any two of R2, R3, and R4 may be combined together to form an alkylene group. Each of these groups may have one or more substituents.]

[0020] (R1, R2, R3, R4) In general formula (1), R1, R2, R3, and R4 are the same or different and represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a heterocyclic group. When R1, R2, R3, and R4 are hydrogen, the compound represented by general formula (1) is a 5-pyrazolone. In this specification, a compound having a 5-pyrazolone skeleton may be referred to as a "pyrazolone derivative."

[0021] (Alkyl group) In this specification, examples of the "alkyl group" include linear, branched, and cyclic alkyl groups. Specific examples include linear or branched alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, and 1-ethylpropyl; linear or branched alkyl groups having 1 to 18 carbon atoms, such as n-pentyl, isopentyl, neopentyl, n-hexyl, isohexyl, 3-methylpentyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, 5-propylnonyl, n-tridecyl, n-tetradecyl, n-pentadecyl, hexadecyl, heptadecyl, and octadecyl; and cyclic alkyl groups having 3 to 8 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl.

[0022] (aralkyl group) Examples of the "aralkyl group" include benzyl, phenethyl, trityl, 1-naphthylmethyl, 2-(1-naphthyl)ethyl, and 2-(2-naphthyl)ethyl groups.

[0023] (aryl group) Examples of the "aryl group" include phenyl, biphenyl, naphthyl, dihydroindenyl, 9H-fluorenyl, and the like.

[0024] (heterocyclic group) Examples of the "heterocyclic group" include pyridyl, pyrimidyl, triazyl, quinolyl, isoquinolyl, quinoxalyl, cinnolyl, quinazolyl, phthalazyl, tetrahydroquinolyl, pyrrolyl, furyl, thienyl, imidazolyl, pyrazolyl, oxazolyl, thiazolyl, isoxazolyl, isothiazolyl, thiadiazolyl, oxadiazolyl, triazolyl, tetrazolyl, indolyl, isoindolyl, benzimidazolyl, benzofuranyl, isobenzofuranyl, benzothienyl, benzoxazolyl, benzothiazolyl, indazolyl, morpholyl, piperazyl, 2-piperazyl, piperidyl, tetrahydropyranyl, tetrahydrothiopyranyl, pyrrolidyl, furanyl, tetrahydrofuranyl, tetrahydrothienyl, 5-methyl-3-oxo-2,3-dihydro-1H-pyrazol-4-yl group, and the like.

[0025] (Alkylidene group) Examples of the "alkylidene group" which may be formed by R3 and R4 together include methylidene, ethylidene, propylidene, isopropylidene, and butylidene groups.

[0026] (Alkylene group) Examples of the "alkylene group" that may be formed by any two of R2, R3, and R4 taken together include an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, etc. These alkylene groups may contain a nitrogen atom, an oxygen atom, or a sulfur atom, and may be connected via a phenylene group.

[0027] (substituent) Each of these alkyl groups, aralkyl groups, aryl groups, heterocyclic groups, alkylidene groups, and alkylene groups may have one or more substituents at any substitutable position. Examples of "substituents" include halogen atoms, amino groups, aminoalkyl groups, alkoxycarbonyl groups, acyl groups, acyloxy groups, amide groups, carboxyl groups, carboxyalkyl groups, formyl groups, nitrile groups, nitro groups, alkyl groups, hydroxyalkyl groups, hydroxyl groups, alkoxy groups, aryl groups, aryloxy groups, heterocyclic groups, thiol groups, alkylthio groups, and arylthio groups. The number of substituents may be preferably 1 to 5, and more preferably 1 to 3.

[0028] (Embodiments of the compound represented by general formula (1)) In general formula (1), R1, R2, R3 and R4 may be the same or different and may be a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, an aralkyl group, an aryl group or a heterocyclic group.

[0029] In the general formula (1), R1 is preferably a hydrogen atom. In general formula (1), R2 is preferably a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, an aralkyl group, an aryl group, or a heterocyclic group, more preferably a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a benzyl group, a phenyl group, a naphthyl group, or a furyl group, and particularly preferably a hydrogen atom or a linear alkyl group having 1 to 4 carbon atoms.

[0030] In the general formula (1), a compound in which at least one of R3 and R4 is a hydrogen atom is preferred, and a compound in which both R3 and R4 are hydrogen atoms is more preferred.

[0031] From the viewpoint of achieving superior effects of the present invention, the compound represented by general formula (1) more preferably includes at least one selected from the group consisting of compounds in which R1 is a hydrogen atom, R2 is a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, an aralkyl group, an aryl group, or a heterocyclic group, and R3 and R4 are both hydrogen atoms, and compounds in which R1 is a hydrogen atom, R2 is a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, an aralkyl group, an aryl group, or a heterocyclic group, and R3 and R4 together form an alkylidene group, and particularly preferably includes a compound in which R1 is a hydrogen atom, R2 is a hydrogen atom or a linear alkyl group having 1 to 4 carbon atoms, and R3 and R4 are both hydrogen atoms.

[0032] Examples of the compound represented by general formula (1) include 5-pyrazolone, 3-methyl-5-pyrazolone, 3-(naphthalen-2-yl)-1H-pyrazol-5(4H)-one, 3-(furan-2-yl)-1H-pyrazol-5(4H)-one, 3-phenyl-1H-pyrazol-5(4H)-one, and 3-propyl-1H-pyrazol-5(4H)-one.

[0033] Some compounds represented by general formula (1) produce tautomers, and these tautomers are also included. When tautomerization is possible (e.g., in solution), chemical equilibrium of the tautomers can be reached. Furthermore, salts of compounds represented by general formula (1) are also included. Examples of salts of compounds represented by general formula (1) include inorganic acid salts such as hydrochloride, sulfate, and nitrate; organic acid salts such as acetate and methanesulfonate; alkali metal salts such as sodium salt and potassium salt; alkaline earth metal salts such as magnesium salt and calcium salt; and ammonium salts such as dimethylammonium and triethylammonium.

[0034] (Content of compound represented by general formula (1)) The content of the compound represented by general formula (1) is preferably 0.3 to 2.0 parts by mass, more preferably 0.5 to 2.0 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of achieving better effects of the present invention.

[0035] [Carbon black] The rubber composition of the present invention contains carbon black.

[0036] (Nitrogen adsorption specific surface area) From the viewpoint of obtaining a more excellent effect of the present invention, the carbon black is selected from those having a nitrogen adsorption specific surface area (N2SA) of 60 m 2 The lower limit of the nitrogen adsorption specific surface area is, for example, 20 m 2 / g or more. In the present invention, the nitrogen adsorption specific surface area of ​​carbon black can be measured in accordance with JIS K6217-2:2017.

[0037] N2SA is 60m 2 Examples of carbon black having a densitometric coefficient of less than 1 / g include FEF carbon black, GPF carbon black, SRF carbon black, and FT carbon black. From the viewpoint of achieving better effects of the present invention, the carbon black preferably contains FEF carbon black and / or SRF carbon black.

[0038] (Carbon black content) The content of carbon black (when two or more types of carbon black are used in combination, the total amount of these) is preferably 40 to 150 parts by mass, more preferably 80 to 120 parts by mass, relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber, from the viewpoint of better effects of the present invention. When the carbon black contains FEF carbon black and SRF carbon black, the content of FEF carbon black can be 30 to 70 mass% of the total amount of carbon black, and the content of SRF carbon black can be the remainder of the total amount of carbon black other than FEF carbon black.

[0039] [Peroxide] The rubber composition of the present invention contains a peroxide. The peroxide contained in the rubber composition of the present invention is not particularly limited as long as it is a peroxide that can abstract protons from HNBR.

[0040] Examples of peroxides include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,3-bis(t-butylperoxypropyl)benzene, di(t-butylperoxyisopropyl)benzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, and 1,1-dibutylperoxy-3,3,5-trimethylsiloxane.

[0041] The peroxide can function as a crosslinking agent, and from the viewpoint of achieving superior effects of the present invention, it is preferable that the peroxide contains an organic peroxide having multiple peroxy groups, and more preferably contains at least one selected from the group consisting of di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,3-bis(t-butylperoxypropyl)benzene, and di(t-butylperoxyisopropyl)benzene.

[0042] (Peroxide content) The content of the peroxide is preferably 1.6 to 4.0 parts by mass, and more preferably 2.3 to 3.0 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of achieving better effects of the present invention.

[0043] The peroxide used in the rubber composition of the present invention may be a mixture of peroxide and silica, for example, Perkadox 14-40 (manufactured by Kayaku Akzo Co., Ltd.) as a commercially available product of the mixture of peroxide and silica. When the above mixture is used as the peroxide in the rubber composition of the present invention, the content of the peroxide contained in the rubber composition of the present invention refers to the net content of the peroxide in the above mixture.

[0044] (additives) The rubber composition of the present invention may further contain additives such as a crosslinking aid (e.g., zinc oxide), an antioxidant, stearic acid, an antioxidant, a plasticizer, a co-crosslinking agent, an antistatic agent, a flame retardant, and silica, as long as the object of the present invention is not impaired. The various additives are not particularly limited. For example, conventionally known additives can be used. The content of the various additives is not particularly limited and can be selected appropriately.

[0045] Co-crosslinking agent The co-crosslinking agent that may be further contained in the rubber composition of the present invention is not particularly limited as long as it is a compound that can crosslink HNBR. However, the co-crosslinking agent does not include an organic peroxide having multiple peroxy groups. Examples of the co-crosslinking agent include triallyl isocyanurate and diallyl compounds. When the rubber composition of the present invention further contains a co-crosslinking agent, the co-crosslinking agent preferably contains triallyl isocyanurate and / or a diallyl compound, and more preferably contains triallyl isocyanurate and a diallyl compound, from the viewpoint of achieving better effects of the present invention.

[0046] Triallyl isocyanurate The triallyl isocyanurate that can be contained in the rubber composition of the present invention is a compound having the following structure: [ka] When the rubber composition of the present invention further contains triallyl isocyanurate, the content of triallyl isocyanurate relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber is preferably 1.9 parts by mass or more, more preferably 2.5 to 5.0 parts by mass, and even more preferably 3.0 to 4.0 parts by mass, from the viewpoint of more excellent effects of the present invention.

[0047] Diallyl compounds From the viewpoint of achieving superior effects of the present invention, the rubber composition of the present invention preferably further contains a diallyl compound. The diallyl compound that can be contained in the rubber composition of the present invention is not particularly limited as long as it is a compound having two allyl groups, and examples thereof include aromatic compounds having two allyl groups such as diallyl phthalate. From the viewpoint of achieving better effects of the present invention, the diallyl compound preferably contains diallyl phthalate. When the rubber composition of the present invention further contains a diallyl compound, the content of the diallyl compound is preferably 3.0 to 20 parts by mass, more preferably 5.0 to 10.0 parts by mass, and even more preferably 7.0 to 10.0 parts by mass, relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber, from the viewpoint of more excellent effects of the present invention.

[0048] ·silica The rubber composition of the present invention may further contain silica. When the rubber composition of the present invention further contains silica, examples of the silica that the rubber composition of the present invention may further contain include silica derived from the mixture when the peroxide is a mixture of peroxide and silica, and silica added to the rubber composition of the present invention as simple silica (excluding silica derived from the mixture when the peroxide is a mixture of peroxide and silica; the same applies to simple silica hereinafter). The silica in the mixture or the silica itself is not particularly limited. In the rubber composition of the present invention, the content of silica (for example, when the peroxide is a mixture of peroxide and silica, the content of silica derived from the mixture, the content of silica as simple silica, or the total amount thereof; the same applies hereinafter for the content of silica) can be 0 to 10 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber.

[0049] The rubber composition of the present invention may be substantially free of sulfur. The rubber composition of the present invention being substantially free of sulfur means that the amount of sulfur is 0 to 0.5% by mass of the total amount of the rubber composition of the present invention.

[0050] The rubber composition of the present invention may be substantially free of a foaming agent. A foaming agent refers to a compound that can make the resulting cured product foamed. The foaming agent is not particularly limited, and examples thereof include organic chemical foaming agents such as organic acids and metal salts thereof, such as azodicarbonamide, N,N'-dinitrosopentanemethylenetetramine, p,p'-oxybisbenzenesulfonylhydrazide, paratoluenesulfonylhydrazide, p-toluenesulfonylsemicarbazide, diazoaminobenzene, hydrazodicarbonamide, barium azodicarboxylate, azobisisobutyronitrile, and monosodium citrate, and inorganic chemical foaming agents such as sodium bicarbonate, ammonium hydrogencarbonate, sodium carbonate, ammonium carbonate, aluminum acetate, ammonium nitrite, and sodium borohydride. The rubber composition of the present invention being substantially free of a foaming agent means that the amount of the foaming agent is 0 to 5 parts by mass relative to 100 parts by mass of the compound represented by the general formula (1) above.

[0051] In one preferred embodiment, the composition of the present invention is substantially free of magnesium oxide. The rubber composition of the present invention being substantially free of magnesium oxide means that the amount of magnesium oxide is 0 to 3 parts by mass per 100 parts by mass of the rubber component.

[0052] (Manufacturing method) The rubber composition of the present invention is not particularly limited in its production method. For example, the rubber composition of the present invention can be produced by mixing the above-mentioned HNBR, the compound represented by general formula (1), carbon black, a peroxide (the peroxide may be a mixture of peroxide and silica), and additives that can be used as needed, under conditions of 40 to 200°C using an internal mixer such as a Banbury mixer or a kneader, or a kneading roll mill.

[0053] The conditions for crosslinking the rubber composition of the present invention are not particularly limited. For example, the rubber composition of the present invention can be crosslinked under pressure at a temperature of 140 to 160°C.

[0054] (for hose) The rubber composition of the present invention can be used as a rubber composition for a hose. In particular, one preferred embodiment is to use the rubber composition of the present invention for the inner tube (innermost layer) of a hose. The hose may be, for example, a hose for an automobile, and specifically, for example, a power steering hose for an automobile (a hose used in a power steering system).

[0055] [Power steering hose] The power steering hose of the present invention is a power steering hose produced using the rubber composition of the present invention. The rubber composition used in the power steering hose of the present invention is not particularly limited as long as it is the rubber composition of the present invention.

[0056] The power steering hose of the present invention preferably has an inner tube, a reinforcing layer, and an outer tube as its constituent members. The power steering hose of the present invention may further have an intermediate rubber layer as its constituent members.

[0057] There are no particular restrictions on which component of the power steering hose of the present invention the rubber composition of the present invention is used for. However, from the viewpoint that the cured product obtained from the rubber composition of the present invention can achieve both excellent levels of elongation at break and modulus, one preferred embodiment of the power steering hose of the present invention is one in which the power steering hose has an inner tube formed using the rubber composition.

[0058] Examples of the power steering hose of the present invention will be described with reference to the accompanying drawings, in which, however, the present invention is not limited to the drawings. FIG. 1 is a schematic perspective view of an example of a power steering hose of the present invention, with each layer cut away. In FIG. 1, a power steering hose 10 has an inner tube 12, an intermediate rubber layer 14, and an outer tube 16, a reinforcing layer 18 between the inner tube 12 and the intermediate rubber layer 14, and a reinforcing layer 20 between the intermediate rubber layer 14 and the outer tube 16. It is preferable that at least the inner tube 12, which is the innermost layer of the power steering hose 10, is formed from the rubber composition of the present invention.

[0059] In the power steering hose of the present invention, the thickness of the inner tube can be, for example, about 0.5 to 5.0 mm, and is preferably 0.8 to 3.0 mm.

[0060] The power steering hose of the present invention may have a reinforcing layer. It is preferable for the power steering hose of the present invention to have a reinforcing layer, since this improves the tensile breaking strength, usable pressure range, and crimping sealability (fitting attachment). Examples of reinforcing layers include braided, spiral, net, and film structures. Examples of materials for the reinforcing layer include organic threads (reinforcing threads) such as aramid fiber, nylon, rayon, vinylon, and polyester; and metal wires such as brass-plated or zinc-plated steel wires.

[0061] In the power steering hose of the present invention, examples of materials that can be used to form the outer tube (outermost layer) include rubber compositions containing butyl rubber, halogenated butyl rubber, ethylene propylene rubber, brominated isobutylene-p-methylstyrene copolymer rubber (BIMS), or ethylene-acrylic ester copolymer rubber (AEM). The thickness of the outer tube is, for example, preferably 0.5 to 5.0 mm, and more preferably 0.8 to 3.0 mm.

[0062] The power steering hose of the present invention may optionally have an intermediate rubber layer. When the power steering hose of the present invention has an intermediate rubber layer, the material for the intermediate rubber layer is not particularly limited as long as it is, for example, a rubber composition that has excellent adhesion to the reinforcing layer. The thickness of the intermediate rubber layer may be, for example, 0.1 to 3 mm.

[0063] (Method of manufacturing the power steering hose of the present invention) A method for producing the power steering hose of the present invention includes, for example, placing the unvulcanized rubber composition of the present invention in a cylindrical shape around the outer periphery of a mandrel or the like, placing a reinforcing layer on that outer periphery, placing a rubber composition for an intermediate rubber layer in a cylindrical shape around that, placing a reinforcing layer on that outer periphery, and placing a rubber composition for an outer tube in a cylindrical shape around that, and then heating the entire power steering hose. The heating temperature is preferably 120°C or higher, more preferably 140 to 170°C. After sufficient cooling after heating, the power steering hose of the present invention can be obtained by removing it from the mandrel.

[0064] The fluid to be passed through the inside of the power steering hose of the present invention is not particularly limited. Examples of the fluid include a fluid containing oil with an aniline point of 90°C or higher, and a preferred embodiment includes a fluid containing oil with an aniline point of 105°C or higher. [Example]

[0065] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the following examples.

[0066] [Production of rubber composition] Each rubber composition was produced by mixing the components in the compositions (parts by mass) shown in Tables 1 and 2 below with a stirrer. In addition, in the Peroxide (14-40) column of Tables 1 and 2, *1 The figure in the upper right is the total amount of commercial peroxide used, and the figure in the lower right is the total amount of commercial peroxide used. *2 The number in parentheses is the net amount of peroxide in the above-mentioned commercial product, which will be described later.

[0067] (crosslinking) Each rubber composition produced as described above was press-crosslinked in a press molding machine at 160° C. for 90 minutes (surface pressure 3.0 MPa) to obtain a crosslinked sheet (thickness 2 mm) as a cured product.

[0068] [evaluation] The vulcanized sheets obtained as described above were subjected to the following evaluations, and the results are shown in Tables 1 and 2. Tensile properties JIS No. 3 dumbbell-shaped test pieces were punched out from each of the crosslinked sheets obtained as described above, and the tensile properties were evaluated using the test pieces obtained.

[0069] Tensile testing Using each test piece obtained as described above, a tensile test was carried out in accordance with JIS K6251:2017 under conditions of 23°C ± 2°C and a tensile speed of 500 mm / min, and the elongation at break (EB) [unit: %] and 50% modulus (M50) [unit: MPa] were measured.

[0070] [Evaluation criteria for balance between elongation at break and modulus] In the present invention, when the EB is 135% or more, the M50 is 3.0 MPa or more, and the value obtained by multiplying the EB and the M50 (the value is also referred to as "M50*EB"; the same applies hereinafter) is greater than the M50*EB when the compound represented by general formula (1) is not contained, it is evaluated that both the elongation at break and the modulus can be achieved at an excellent level. As described above, when the EB is 135% or more, the M50 is 3.0 MPa or more, and M50*EB is larger than M50*EB when the compound represented by general formula (1) is not contained, the larger M50*EB in the present invention is, the more excellent the balance between elongation at break and modulus can be achieved, which is preferable.

[0071] It is preferable that the EB is 135% or more, since this provides excellent toughness against internal pressure. The greater the EB is above 135%, the more excellent the toughness against internal pressure. When the M50 is 3.0 MPa or more, the sealing property with metal fittings is excellent, which is preferable. The greater the M50 is above 3.0 MPa, the better the sealing property with metal fittings.

[0072] (TR-10) Low temperature elastic recovery test Using each of the crosslinked sheets prepared as described above, a low-temperature elastic recovery test was carried out in accordance with ASTM D1329 to measure the temperature at which each sample recovered 10% of its elongation (TR-10). Evaluation criteria If the result of the low-temperature elastic recovery test is −25° C. or lower, the low-temperature properties (flexibility under low-temperature conditions) are excellent, which is preferable. In the above case, the lower the result of the low-temperature elastic recovery test, the better the low-temperature properties.

[0073] [Table 1]

[0074] [Table 2]

[0075] [Table 3]

[0076] Details of each component shown in Tables 1 and 2 are as follows: (HNBR) HNBR1 (LT2007 AN21%): Hydrogenated acrylonitrile butadiene rubber. Product name: THERBAN LT2007, manufactured by ARLANXEO. AN content: 21% by mass, hydrogenation rate: 99%

[0077] HNBR2 (Zetpol2000L, AN 36%): Hydrogenated acrylonitrile butadiene rubber. Product name: ZETPOL2000L, manufactured by Zeon Corporation. AN content: 36% by mass, hydrogenation rate: 99%

[0078] (carbon black) FEF: FEF carbon black (manufactured by Nippon Steel Carbon Co., Ltd.), nitrogen adsorption specific surface area 41m 2 / g SRF: SRF carbon black (product name Niteron #S, manufactured by Shin-Nichika Carbon Co., Ltd.), nitrogen adsorption specific surface area 25 m 2 / g

[0079] Magnesium oxide: Kyowa Chemical Industry Co., Ltd., Kyowa Mag 150 Zinc oxide: Zinc oxide No. 3 manufactured by Seido Chemical Industry Co., Ltd. Anti-aging agent: 2-mercaptobenzimidazole, manufactured by Ouchi Shinko Chemical Co., Ltd., Nocrac MBZ Stearic acid: Kao Corporation, Lunac YA

[0080] (Compound represented by general formula (1)) Pyrazolone derivative: 3-methyl-5-pyrazolone (structure shown below). Manufactured by Otsuka Chemical Co., Ltd., trade name EN-01 [ka]

[0081] Plasticizer (TP-95): Adipic acid bis[2-(2-butoxyethoxy)ethyl ester]. Trade name TP-95, manufactured by The HallStar Company. Co-crosslinking agent 1 (pure TAIC): Triallyl isocyanurate. Manufactured by Nippon Kasei Co., Ltd., product name: TAIC Co-crosslinking agent 2 (DAP): Diallyl phthalate, manufactured by Daiso Co., Ltd.

[0082] (peroxide) Peroxide (14-40): Perkadox 14-40 (trade name), manufactured by Kayaku Akzo Co., Ltd. This commercially available product is a mixture of di(t-butylperoxyisopropyl)benzene and silica, with the di(t-butylperoxyisopropyl)benzene content being 40% by mass and the silica content being 60% by mass. Di(t-butylperoxyisopropyl)benzene can also function as a crosslinking agent.

[0083] (Evaluation results) From the results in Tables 1 and 2, it was confirmed that the rubber composition of the present invention exhibits the desired effects.

[0084] On the other hand, Comparative Example 1, which did not contain the compound represented by general formula (1), had an insufficient M50. Comparative Example 2, which did not contain the compound represented by general formula (1), had a lower M50*EB than Examples 1 to 4. The results of M50*EB for Comparative Example 3 compared with Example 5, Comparative Example 4 compared with Example 6, Comparative Example 5 compared with Example 7, and Comparative Example 6 compared with Example 8 were similar to those above. Comparative Examples 5 and 6 also had insufficient EB. [Explanation of symbols]

[0085] 10 Power steering hose 12 Inner tube 14 Middle rubber layer 16 Outer tube 18, 20 Reinforcement layer

Claims

1. A rubber composition comprising a rubber component containing 60% by mass or more of hydrogenated acrylonitrile butadiene rubber, a compound represented by the following general formula (1), carbon black, and a peroxide: 【Chemistry 1】 [In general formula (1), R １ , R ２ , R ３ and R ４ are the same or different and represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a heterocyclic group. ３ and R ４ may be taken together to form an alkylidene group, and R ２ , R ３ and R ４ Any two of these may be combined to form an alkylene group. Each of these groups may have one or more substituents.

2. The rubber composition according to claim 1, wherein the content of the compound represented by the general formula (1) is 0.3 to 2.0 parts by mass per 100 parts by mass of the rubber component.

3. The carbon black has a nitrogen adsorption specific surface area of ​​60 m ２ The rubber composition according to claim 1, comprising one or more carbon blacks having a modulus of less than 1 / g.

4. The rubber composition according to claim 1, wherein the content of the peroxide is 1.6 to 4.0 parts by mass based on 100 parts by mass of the rubber component.

5. The rubber composition of claim 1, which is substantially free of sulfur.

6. The rubber composition according to claim 1, which is for a hose.

7. A power steering hose produced using the rubber composition according to any one of claims 1 to 6.

8. 8. The power steering hose according to claim 7, having an inner tube formed using the rubber composition.

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