Rubber composition for hose and hose

Abstract

To provide a rubber composition for a hose and the hose that are be able to become a hardened product exhibiting excellent durability under low-temperature conditions.SOLUTION: Provided is a rubber composition for a hose, which comprises a hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile content of not more than 24 mass%, carbon black, and a peroxide, in which the content of the peroxide is not less than 1.0 pt.mass and less than 2.4 pts.mass per 100 pts.mass of the hydrogenated acrylonitrile-butadiene rubber, and the content of magnesium oxide is not less than 0 pts.mass and less than 10.0 pts.mass per 100 pts.mass of the hydrogenated acrylonitrile-butadiene rubber, or alternatively, the content of the peroxide is from 1.0 to 3.5 pts.mass per 100 pts.mass of the hydrogenated acrylonitrile-butadiene rubber, and the content of magnesium oxide is from 0 to 3.0 pts.mass per 100 pts.mass of the hydrogenated acrylonitrile-butadiene rubber. Provided is also a hose produced using the rubber composition.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Since automobiles are used not only in warm environments but also in cold climates, strict low-temperature performance is required for the power steering hoses installed in automobiles. BACKGROUND ART Rubber compositions for hoses and hoses 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] The present inventors have studied the rubber composition for hoses and the hoses disclosed in Patent Document 1 and have found that there is room for further improvement in the durability under low-temperature conditions of hoses having components made from the cured product of the rubber composition for hoses (i.e., the toughness under low-temperature conditions of the hose or the cured product obtained from the rubber composition).

[0005] Therefore, an object of the present invention is to provide a rubber composition for a hose that can be cured to have excellent durability under low temperature conditions. Another object of the present invention is to provide a hose that has excellent durability under low temperature conditions. [Means for solving the problem]

[0006] As a result of extensive research to solve the above problems, the present inventors have found that A rubber composition for a hose containing hydrogenated acrylonitrile butadiene rubber having an acrylonitrile content of 24% by mass or less, carbon black, and a peroxide, The content of the peroxide is 1.0 part by mass or more and less than 2.4 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber, and the content of the magnesium oxide is 0 part by mass or more and less than 10.0 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber, or It has been found that the desired effect can be obtained when the content of the peroxide is 1.0 to 3.5 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber and the content of the magnesium oxide is 0 to 3.0 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber. Specifically, the present invention solves the above problems by the following configuration.

[0007] [1] A rubber composition comprising hydrogenated acrylonitrile butadiene rubber having an acrylonitrile content of 24% by mass or less, carbon black, and a peroxide; the content of the peroxide is 1.0 parts by mass or more and less than 2.4 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber, The rubber composition for hoses has a magnesium oxide content of 0 part by mass or more and less than 10.0 parts by mass per 100 parts by mass of the hydrogenated acrylonitrile butadiene rubber. In this specification, the rubber composition for a hose described in the above [1] may be referred to as the "first rubber composition of the present invention."

[0008] [2] A rubber composition comprising hydrogenated acrylonitrile butadiene rubber having an acrylonitrile content of 24% by mass or less, carbon black, and a peroxide; the content of the peroxide is 1.0 to 3.5 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber, The rubber composition for hoses has a magnesium oxide content of 0 to 3.0 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile butadiene rubber. In this specification, the rubber composition for a hose described in the above [2] may be referred to as the "second rubber composition of the present invention." Furthermore, the "first rubber composition of the present invention" and the "second rubber composition of the present invention" may be collectively referred to as the "rubber composition of the present invention."

[0009] [3] The rubber composition for hoses according to the above [2], wherein the content of the peroxide is 1.0 to 2.4 parts by mass per 100 parts by mass of the hydrogenated acrylonitrile butadiene rubber. [4] A hose produced using the rubber composition for a hose according to any one of [1] to [3]. [5] The hose according to [4], which is an automotive hose. [6] The hose according to [4] or [5], which is a piping for a power steering system for an automobile. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a rubber composition for a hose that can give a cured product having excellent durability under low temperature conditions. The present invention also provides a hose that is highly durable under low temperature conditions. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic perspective view showing an example of a hose of the present invention, with each layer cut away. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. 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 certain 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, superior durability under low temperature conditions may be referred to as "superior effects of the present invention."

[0013] Although the reason why the rubber composition of the present invention can solve the problems of the present invention is not necessarily clear, the present inventors speculate as follows. Note that the following speculation does not limit the mechanism by which the effects are obtained. In other words, even if the effects are obtained by a mechanism other than the one described below, it is still included in the scope of the present invention. First, magnesium oxide generally does not reinforce the rubber component in a cured product of a rubber composition, and therefore, if a large amount of magnesium oxide is present in the cured product, and the cured product is subjected to an impact under low temperature conditions, the magnesium oxide may act as a weak point in the cured product, causing the cured product to become brittle. On the other hand, since the rubber composition of the present invention does not contain magnesium oxide or the magnesium oxide content in the rubber composition of the present invention is within a predetermined range, the cured product obtained from the rubber composition of the present invention does not contain magnesium oxide or the magnesium oxide content in the cured product is low.Therefore, even if the cured product obtained from the rubber composition of the present invention is subjected to an impact under low temperature conditions, the cured product is less likely to break and has improved toughness, and therefore it is thought that it has excellent durability under low temperature conditions. Furthermore, since the rubber composition of the present invention has a peroxide content within a specified range, the crosslink density of the rubber in the cured product obtained from the rubber composition of the present invention is lower than when the rubber composition contains peroxide in an amount exceeding the above range. Therefore, even if the cured product obtained from the rubber composition of the present invention is subjected to an impact under low temperature conditions, the cured product is less likely to break and has improved toughness, and it is therefore thought that the durability under low temperature conditions is excellent.

[0014] [First rubber composition of the present invention] The first rubber composition of the present invention will be described below. The rubber composition for a hose of the present invention (the first rubber composition of the present invention) is The rubber contains hydrogenated acrylonitrile butadiene rubber having an acrylonitrile content of 24% by mass or less, carbon black, and a peroxide, the content of the peroxide is 1.0 parts by mass or more and less than 2.4 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber, The rubber composition for hoses has a magnesium oxide content of 0 part by mass or more and less than 10.0 parts by mass per 100 parts by mass of the hydrogenated acrylonitrile butadiene rubber.

[0015] [Hydrogenated acrylonitrile butadiene rubber] The first rubber composition of the present invention contains hydrogenated acrylonitrile butadiene rubber (HNBR) having an acrylonitrile amount (AN amount) of 24 mass% or less. In this specification, the hydrogenated acrylonitrile butadiene rubber having an acrylonitrile amount of 24 mass% or less is also referred to as "the above-mentioned HNBR." The HNBR contained in the first rubber composition of the present invention is a hydrogenated copolymer of acrylonitrile and butadiene. The HNBR has an acrylonitrile group. The hydrogenation in the HNBR is hydrogenation in the main chain, and the hydrogenation may be partial or complete.

[0016] [Acrylonitrile content] In the first rubber composition of the present invention, the amount of acrylonitrile (AN amount) contained in the HNBR is 24 mass % or less in the HNBR.

[0017] The AN amount of the HNBR is preferably 18 to 22 mass % of the HNBR, from the viewpoint of achieving better effects of the present invention and excellent 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.

[0018] (hydrogenation rate) From the viewpoint of achieving better effects of the present invention, the hydrogenation rate of the 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.

[0019] The first rubber composition of the present invention preferably contains only the above-mentioned HNBR as the rubber component, from the viewpoint of achieving better effects of the present invention and excellent oil resistance.

[0020] (Above HNBR content) The content of the HNBR is preferably 30 to 70 mass % of the total amount of the first rubber composition of the present invention, from the viewpoint of achieving better effects of the present invention and excellent oil resistance.

[0021] From the viewpoint of achieving superior effects of the present invention, the first rubber composition of the present invention preferably does not substantially contain alloyed HNBR. The rubber composition of the present invention being substantially free of alloyed HNBR means that the amount of alloyed HNBR is 0 to 1.0% by mass of the total amount of the rubber composition of the present invention.

[0022] [Carbon black] The first rubber composition of the present invention contains carbon black. In the present invention, the carbon black is not particularly limited.

[0023] (Nitrogen adsorption specific surface area of ​​carbon black) The nitrogen adsorption specific surface area of ​​the carbon black is preferably 5 to 50 m from the viewpoint of obtaining a more excellent effect of the present invention. 2 / g is preferred. In the present invention, the nitrogen adsorption specific surface area of ​​carbon black can be measured in accordance with JIS K6217-2:2017.

[0024] (Dibutyl phthalate oil absorption of carbon black) From the viewpoint of achieving a better effect of the present invention, the dibutyl phthalate oil absorption of the carbon black is preferably from 25 to 130 ml / 100 g, and more preferably from 50 to 120 ml / 100 g. The dibutyl phthalate oil absorption of carbon black can be measured in accordance with JIS K6217-4:2017.

[0025] Examples of carbon black include FTF grade (Fine Thermal Furnace), FEF grade (Fast Extruding Furnace), GPF grade (General Purpose Furnace), and SRF grade (Semi-Reinforcing Furnace) carbon black. The carbon blacks can be used either alone or in combination of two or more.

[0026] A preferred combination of carbon black is a combination of FEF grade carbon black and SRF grade carbon black, from the viewpoint of achieving a better effect of the present invention.

[0027] (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, per 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile content of 24% by mass or less, from the viewpoint of obtaining better effects of the present invention.

[0028] [Peroxide] The first rubber composition of the present invention contains a peroxide. The peroxide contained in the first rubber composition of the present invention is not particularly limited as long as it is a peroxide that can abstract protons from HNBR.

[0029] 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-butylperoxydiisopropyl)benzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, and 1,1-dibutylperoxy-3,3,5-trimethylsiloxane.

[0030] 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-butylperoxydiisopropyl)benzene.

[0031] [Peroxide content] In the first rubber composition of the present invention, the content of peroxide is 1.0 part by mass or more and less than 2.4 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 24% by mass or less. In the first rubber composition of the present invention, the content of peroxide is 1.0 part by mass or more, so that the hydrogenated acrylonitrile-butadiene rubber can be crosslinked. In the first rubber composition of the present invention, the content of the peroxide is preferably 1.1 to 2.2 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile content of 24% by mass or less, from the viewpoint of achieving better effects of the present invention.

[0032] The peroxide used in the first rubber composition of the present invention may be a mixture of peroxide and silica. Commercially available products of the mixture of peroxide and silica include Perkadox 14-40 (manufactured by Kayaku Akzo Co., Ltd.). When the above mixture is used as the peroxide in the first rubber composition of the present invention, the content of the peroxide contained in the first rubber composition of the present invention refers to the net content of the peroxide in the above mixture.

[0033] [Magnesium oxide content] In the first rubber composition of the present invention, the content of magnesium oxide is 0 part by mass or more and less than 10.0 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile butadiene rubber having an acrylonitrile amount of 24% by mass or less. In the first rubber composition of the present invention, magnesium oxide is an optional component. Therefore, in the first rubber composition of the present invention, the first rubber composition of the present invention does not contain magnesium oxide, or when the first rubber composition of the present invention contains magnesium oxide, the content of magnesium oxide is more than 0 part by mass and less than 10.0 parts by mass per 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber. From the viewpoint of achieving better effects of the present invention, the content of magnesium oxide is preferably 0 to 2.0 parts by mass, more preferably 0 to 1.0 part by mass, and even more preferably 0 part by mass, relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 24% by mass or less. When the first rubber composition of the present invention contains magnesium oxide, the content of magnesium oxide can be more than 3.0 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 24% by mass or less.

[0034] (Magnesium oxide) When the first rubber composition of the present invention contains magnesium oxide, the magnesium oxide (MgO) is not particularly limited. When the first rubber composition of the present invention contains magnesium oxide, the magnesium oxide can function as an adhesion promoter.

[0035] [Second rubber composition of the present invention] The rubber composition of the present invention (the second rubber composition of the present invention) is The rubber contains hydrogenated acrylonitrile butadiene rubber having an acrylonitrile content of 24% by mass or less, carbon black, and a peroxide, the content of the peroxide is 1.0 to 3.5 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber, The rubber composition for hoses has a magnesium oxide content of 0 to 3.0 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile butadiene rubber.

[0036] [Hydrogenated acrylonitrile butadiene rubber] The hydrogenated acrylonitrile-butadiene rubber containing in the second rubber composition of the present invention an acrylonitrile content of 24% by mass or less is the same as the hydrogenated acrylonitrile-butadiene rubber containing in the first rubber composition of the present invention an acrylonitrile content of 24% by mass or less, and therefore, a description of the hydrogenated acrylonitrile-butadiene rubber containing in the second rubber composition of the present invention an acrylonitrile content of 24% by mass or less will be omitted here. In this specification, the hydrogenated acrylonitrile-butadiene rubber containing in the second rubber composition of the present invention an acrylonitrile content of 24% by mass or less is also referred to as "the above HNBR".

[0037] [Carbon black] The carbon black contained in the second rubber composition of the present invention is the same as the carbon black contained in the first rubber composition of the present invention, so a description of the carbon black contained in the second rubber composition of the present invention will be omitted here.

[0038] [Peroxide] The second rubber composition of the present invention contains a peroxide. The peroxide contained in the second rubber composition of the present invention is not particularly limited as long as it is a peroxide that can abstract protons from HNBR.

[0039] 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-butylperoxydiisopropyl)benzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, and 1,1-dibutylperoxy-3,3,5-trimethylsiloxane.

[0040] 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-butylperoxydiisopropyl)benzene.

[0041] [Peroxide content] In the second rubber composition of the present invention, the content of peroxide is 1.0 to 3.0 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 24% by mass or less. In the second rubber composition of the present invention, the content of peroxide is 1.0 part by mass or more, so that the hydrogenated acrylonitrile-butadiene rubber can be crosslinked. In the second rubber composition of the present invention, the content of the peroxide is preferably 1.0 to 2.4 parts by mass, and more preferably 1.1 to 2.2 parts by mass, relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile content of 24% by mass or less, from the viewpoint of achieving better effects of the present invention.

[0042] The peroxide used in the second rubber composition of the present invention may be a mixture of peroxide and silica. Commercially available products of the mixture of peroxide and silica include Perkadox 14-40 (manufactured by Kayaku Akzo Co., Ltd.). When the above mixture is used as the peroxide in the second rubber composition of the present invention, the content of the peroxide contained in the second rubber composition of the present invention refers to the net content of the peroxide in the above mixture.

[0043] [Magnesium oxide content] In the second rubber composition of the present invention, the content of magnesium oxide is 0 to 3.0 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile butadiene rubber having an acrylonitrile amount of 24% by mass or less. In the second rubber composition of the present invention, magnesium oxide is an optional component. Therefore, in the second rubber composition of the present invention, the second rubber composition of the present invention does not contain magnesium oxide, or when the second rubber composition of the present invention contains magnesium oxide, the content of magnesium oxide is more than 0 part by mass and not more than 3.0 parts by mass per 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber. From the viewpoint of achieving better effects of the present invention, the content of magnesium oxide is preferably 0 to 2.0 parts by mass, more preferably 0 to 1.0 part by mass, and even more preferably 0 part by mass, relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 24% by mass or less.

[0044] (Magnesium oxide) When the second rubber composition of the present invention contains magnesium oxide, the magnesium oxide (MgO) is not particularly limited. When the second rubber composition of the present invention contains magnesium oxide, the magnesium oxide can function as an adhesion promoter.

[0045] In this specification, the matters described below are common to the first rubber composition of the present invention and the second rubber composition of the present invention unless otherwise specified, and therefore the matters below will be described as the rubber composition of the present invention. (additives) The rubber composition of the present invention may further contain additives such as antioxidants, antioxidants, antistatic agents, flame retardants, crosslinking aids such as zinc oxide, stearic acid, co-crosslinking agents, silica, and plasticizers, 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.

[0046] 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. 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.

[0047] 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 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 relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 24% by mass or less, from the viewpoint of more excellent effects of the present invention.

[0048] Diallyl compounds The rubber composition of the present invention preferably further contains a diallyl compound, from the viewpoint of achieving better effects of the present invention and excellent elongation of the resulting rubber. The diallyl compound 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. The diallyl compound preferably contains diallyl phthalate, from the viewpoint of achieving better effects of the present invention and excellent elongation of the resulting rubber. 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 having an acrylonitrile content of 24% by mass or less, from the viewpoint of more excellent effects of the present invention.

[0049] ·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, the content of silica derived from the mixture when the peroxide is a mixture of peroxide and silica, the content of silica as simple silica, or the total amount thereof; the same applies hereinafter to the content of silica) can be set to 0 to 10 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile content of 24% by mass or less. It has been confirmed that when the content of silica is within the above range, the excellent effect of the present invention (durability under low temperature conditions) can be maintained. Furthermore, in this specification, it has been confirmed that when the content of silica is within the above range and a mixture of peroxide and silica is used as the peroxide, the effect of both (durability under low temperature conditions) is equivalent whether or not simple silica is further used. When the rubber composition of the present invention further contains silica (for example, silica derived from the mixture when the peroxide is a mixture of peroxide and silica, silica as simple silica, or a combination thereof; the same applies hereinafter for silica), the content of silica is preferably 1.0 to 5.0 parts by mass based on 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 24% by mass or less. In addition, in the rubber composition of the present invention, the content of simple silica (excluding silica derived from the mixture when the peroxide is a mixture of peroxide and silica) is preferably 0 to 8 parts by mass, more preferably 0 to 3 parts by mass, and even more preferably 0 part by mass, relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 24% by mass or less.

[0050] 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.

[0051] (Manufacturing method) The rubber composition of the present invention can be produced without any particular limitation. For example, the rubber composition of the present invention can be produced by mixing the above-mentioned HNBR, carbon black, peroxide (the peroxide may be a mixture of peroxide and silica), and optionally used magnesium oxide and additives at 40 to 200°C using an internal mixer such as a Banbury mixer or a kneader, or a kneading roll mill. In addition, in the method for producing the rubber composition of the present invention, when the rubber composition of the present invention further contains silica (for example, when the peroxide is a mixture of peroxide and silica, silica derived from the mixture, silica as simple silica, or a combination thereof), the content (amount used) of silica can be more than 0 part by mass and 10 parts by mass or less, and is preferably 1.0 to 5.0 parts by mass, relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber. In addition, in the method for producing a rubber composition of the present invention, the content (amount used) of simple silica (excluding silica derived from the mixture when the peroxide is a mixture of peroxide and silica) is preferably 0 to 8 parts by mass, more preferably 0 to 3 parts by mass, and even more preferably 0 part by mass, relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber.

[0052] 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.

[0053] [Rubber composition for hoses] The rubber composition of the present invention can be used to produce a hose. In particular, one preferred embodiment is to use the rubber composition of the present invention in the inner tube (innermost layer) of the hose. The hose may be, for example, a hose for an automobile, and specifically, may be, for example, a pipe (hose) used in a power steering system for an automobile.

[0054] [hose] The hose of the present invention is a hose produced using the rubber composition for a hose of the present invention. The rubber composition for a hose used in the hose of the present invention is not particularly limited as long as it is the rubber composition of the present invention (the first rubber composition of the present invention or the second rubber composition of the present invention).

[0055] The hose of the present invention preferably has an inner tube, a reinforcing layer, and an outer tube as its constituent members. The hose of the present invention may further have an intermediate rubber layer as its constituent members.

[0056] In the hose of the present invention, there are no particular restrictions on which component of the hose of the present invention the rubber composition of the present invention is applied to. However, from the viewpoint that the cured product obtained from the rubber composition of the present invention has excellent durability under low-temperature conditions, one preferred embodiment of the hose of the present invention is one in which the hose has an inner tube formed using the rubber composition for a hose.

[0057] Examples of hoses of the present invention will now 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 showing an example of a hose of the present invention, with each layer cut away. In FIG. 1, a 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 hose 10, is formed from the rubber composition of the present invention.

[0058] In the 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.

[0059] The hose of the present invention may have a reinforcing layer. The reinforcing layer is preferable because it improves the tensile strength, usable pressure range, and metal fitting capability of the hose. 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 wire.

[0060] In the 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 acid 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.

[0061] The hose of the present invention may optionally have an intermediate rubber layer. When the 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.

[0062] (Method of manufacturing the hose of the present invention) A method for producing the 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 hose. The heating temperature is preferably 120°C or higher, more preferably 140 to 170°C. After sufficient cooling after heating, the hose of the present invention can be obtained by removing it from the mandrel.

[0063] The hose of the present invention can be used, for example, as a hose for automobiles, and specifically, for example, as a pipe (hose) used in a power steering system for an automobile.

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

[0065] The present invention will be described in more detail below with reference to 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 composition (parts by mass) shown in Table 1 below with a stirrer. In the peroxide column of Table 1, *1 is the total amount of commercial peroxide used, and the bottom *2 The value in parentheses is the net amount of peroxide in the commercial product, which will be described later.

[0067] [evaluation] The rubber compositions produced as described above were subjected to the following evaluations, and the results are shown in Table 1.

[0068] [Embrittlement temperature] Sample preparation Each rubber composition produced as described above was vulcanized for 90 minutes using a press molding machine at 160°C under a surface pressure of 3.0 MPa to produce a 2 mm thick vulcanized sheet, from which a strip sample measuring 26 to 40 mm in length and 6 mm in width was cut. Low temperature impact embrittlement test Using the samples prepared as described above, a low-temperature impact embrittlement test was performed in accordance with Method B (50% impact embrittlement temperature) of JIS K6261-2:2017, and the 50% impact embrittlement temperature (unit: °C) of the samples was determined. The 50% impact embrittlement temperature is shown in the embrittlement temperature column of Table 1. In this specification, the 50% impact embrittlement temperature is also simply referred to as the "embrittlement temperature."

[0069] [Low temperature elastic recovery temperature (TR10)] Sample preparation Each rubber composition produced as described above was vulcanized for 90 minutes using a press molding machine at 160°C under a surface pressure of 3.0 MPa to prepare a vulcanized sheet having a thickness of 2 mm, and an I-shaped sample was cut out from the sheet.

[0070] Low temperature elastic recovery test Using each sample 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 (low-temperature elastic recovery temperature, TR10). The low-temperature elastic recovery temperatures (TR10, unit: ° C.) measured as described above are shown in the column for low-temperature elastic recovery temperatures (TR10) in Table 1.

[0071] (brittle temperature - low-temperature elastic recovery temperature) *3 Using the brittle temperature and low-temperature elastic recovery temperature (TR10) measured as described above, subtract the low-temperature elastic recovery temperature (TR10) from the brittle temperature [(brittle temperature) - (low-temperature elastic recovery temperature (TR10))], and the resulting difference (°C) is recorded as (brittle temperature - low-temperature elastic recovery temperature) in Table 1. *3 shown in the column.

[0072] [Evaluation criteria for durability under low temperature conditions] In the present invention, when the brittleness temperature is −33°C or lower and is lower than the low-temperature elastic recovery temperature (TR10) (i.e., when the difference obtained by subtracting the low-temperature elastic recovery temperature (TR10) from the brittleness temperature is less than 0°C), the cured product obtained from the rubber composition is evaluated to have excellent durability under low-temperature conditions. The durability is more excellent when the brittle temperature is −33° C. or lower and the difference obtained by subtracting the low-temperature elastic recovery temperature (TR10) from the brittle temperature is smaller than 0° C. (In other words, the durability is more excellent when the brittle temperature is −33° C. or lower and the brittle temperature is lower than the low-temperature elastic recovery temperature (TR10) and the absolute value of the difference obtained by subtracting the low-temperature elastic recovery temperature (TR10) from the brittle temperature is larger than 0.)

[0073] [Table 1]

[0074] [Table 2]

[0075] [Table 3]

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

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

[0078] (carbon black) Carbon Black 1 FEF: FEF carbon black (manufactured by Nippon Steel Carbon Co., Ltd.), nitrogen adsorption specific surface area 41 m 2 / g, dibutyl phthalate oil absorption 121ml / 100g Carbon Black 2 SRF: SRF carbon black (product name Niteron #S, manufactured by Shin-Nichika Carbon Co., Ltd.), nitrogen adsorption specific surface area 25 m 2 / g, dibutyl phthalate oil absorption 72ml / 100g

[0079] Silica: Tosoh Silica Corporation, Nipsil AQ

[0080] Magnesium oxide: Kyowa Chemical Industry Co., Ltd., Kyowa Mag 150

[0081] Zinc oxide: Zinc oxide No. 3 manufactured by Seido Chemical Industry Co., Ltd. Anti-aging agent MBZ: 2-mercaptobenzimidazole. Ouchi Shinko Chemical Co., Ltd., Nocrac MBZ Stearic acid: Kao Corporation, Lunac YA

[0082] Co-crosslinking agent 1 TAIC (pure product): Triallyl isocyanurate. Manufactured by Nippon Kasei Co., Ltd., product name: TAIC Co-crosslinking agent 2 DAP: Diallyl phthalate, manufactured by Daiso Co., Ltd.

[0083] (peroxide) Crosslinking agent: Perkadox 14-40 (trade name), manufactured by Kayaku Akzo Co., Ltd. This commercially available product is a mixture of di(t-butylperoxydiisopropyl)benzene and silica, with the di(t-butylperoxydiisopropyl)benzene content being 40% by mass and the silica content being 60% by mass.

[0084] From the results in Table 1, it was confirmed that the rubber composition of the present invention exhibits the desired effects. Examples 1 to 4 and 8 to 13 correspond to the first rubber composition of the present invention. Examples 5 to 13 correspond to the second rubber composition of the present invention.

[0085] On the other hand, Comparative Examples 1 and 2, in which the content of magnesium oxide per 100 parts by mass of the above-mentioned HNBR was 10 parts by mass, did not correspond to the rubber composition of the present invention and did not satisfy the standard for durability under low temperature conditions. Comparative Examples 3 to 5, in which the net peroxide content per 100 parts by mass of the specified HNBR was 3.4 parts by mass and the magnesium oxide content per 100 parts by mass of the specified HNBR was 5 or 6 parts by mass, were not rubber compositions according to the present invention and did not satisfy the standards for durability under low temperature conditions. Comparative Examples 6 and 7, in which the net peroxide content exceeded 3.5 parts by mass per 100 parts by mass of the above-mentioned HNBR, were not rubber compositions of the present invention and did not satisfy the standard for durability under low temperature conditions. The hydrogenated acrylonitrile butadiene rubbers of Comparative Examples 8 and 9, which do not contain the above-mentioned specified HNBR but instead have an acrylonitrile content exceeding 24% by mass, do not correspond to the rubber compositions of the present invention and do not satisfy the standard for durability under low temperature conditions. In addition, since the rubber components were the same in Examples 1 to 13 and Comparative Examples 1 to 7, the low-temperature elastic recovery temperatures (TR10) were approximately the same, and no clear difference in durability under low-temperature conditions was observed based on the low-temperature elastic recovery temperatures (TR10) alone. [Explanation of symbols]

[0086] 10 Hose 12 Inner tube 14 Middle rubber layer 16 Outer tube 18, 20 Reinforcement layer

Claims

1. The rubber composition contains hydrogenated acrylonitrile butadiene rubber having an acrylonitrile content of 24% by mass or less, carbon black, and a peroxide, the content of the peroxide is 1.0 part by mass or more and less than 2.4 parts by mass with respect to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber, The rubber composition for hoses has a magnesium oxide content of 0 part by mass or more and less than 10.0 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile butadiene rubber.

2. The rubber composition contains hydrogenated acrylonitrile butadiene rubber having an acrylonitrile content of 24% by mass or less, carbon black, and a peroxide, the content of the peroxide is 1.0 to 3.5 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile-butadiene rubber, The rubber composition for hoses has a magnesium oxide content of 0 to 3.0 parts by mass relative to 100 parts by mass of the hydrogenated acrylonitrile butadiene rubber.

3. 3. The rubber composition for a hose according to claim 2, wherein the content of the peroxide is 1.0 to 2.4 parts by mass based on 100 parts by mass of the hydrogenated acrylonitrile butadiene rubber.

4. A hose manufactured using the rubber composition for a hose according to any one of claims 1 to 3.

5. 5. The hose of claim 4, which is a hose for an automobile.

6. 5. The hose according to claim 4, which is a piping for a power steering system of an automobile.

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