Rubber composition for hose and air hose

Abstract

To provide a rubber composition for a hose excellent in heat resistance, acid resistance and settling resistance, and various hoses obtained by using the same.SOLUTION: A rubber composition for a hose comprising the following components (A) to (C), wherein a content of the component (B) is from 1 to 3 parts by mass, and a content of the component (C) is from 0.05 to 0.4 parts by mass, per 100 parts by mass of the component (A): (A) an epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber having an ethylene oxide content of 50 mol% or less and an allyl glycidyl ether content of 5 mol% or more; (B) At least one of a quinoxaline-based crosslinking agent and a triazine-based crosslinking agent. (C) Sulfur.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for hoses, and more particularly to various hoses, particularly air hoses for automobiles (for example, turbo air hoses, blow-by gas hoses, emission control hoses, etc.). [Background technology]

[0002] Conventionally, epichlorohydrin polymer rubber (CO), epichlorohydrin-ethylene oxide copolymer rubber (ECO), epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber (GECO), and the like have sometimes been used as materials for hoses that require heat resistance, such as air hoses for automobiles (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-143299 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the environmental temperature inside an automobile engine compartment has tended to rise, and the materials used to make automobile hoses are required to have better heat resistance than ever before. However, technology for improving both the heat resistance and acid resistance of rubber compositions for hoses containing GECO has not yet been fully explored. In particular, no technology is known that can improve sag resistance (compression set) in addition to heat resistance and acid resistance.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rubber composition for hoses containing GECO that has excellent heat resistance, acid resistance, and settling resistance, and to provide various hoses obtained using the same. [Means for solving the problem]

[0006] In the course of extensive research to solve the above problems, the inventors of the present invention unexpectedly discovered that by setting the ratio of units constituting GECO within a specific range and blending sulfur and a specific cross-linking agent in specific proportions, not only can the resin have excellent heat resistance and acid resistance, but also excellent sag resistance, and thus arrived at the present invention.

[0007] That is, the gist of the present invention is the following [1] to [7]. [1] A rubber composition for a hose containing the following components (A) to (C): A rubber composition for a hose, comprising 1 to 3 parts by mass of component (B) and 0.05 to 0.4 parts by mass of component (C) per 100 parts by mass of component (A): (A) An epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber having an ethylene oxide content of 50 mol % or less and an allyl glycidyl ether content of 5 mol % or more. (B) At least one of a quinoxaline-based crosslinking agent and a triazine-based crosslinking agent. (C) Sulfur. [2] The rubber composition for a hose according to [1], which contains a quinoxaline-based crosslinking agent as the component (B). [3] The rubber composition for hoses according to [1] or [2], wherein the content of the component (C) is 0.1 to 0.4 parts by mass per 100 parts by mass of the component (A). [4] The rubber composition for a hose according to any one of [1] to [3], further containing magnesium oxide. [5] The rubber composition for a hose according to any one of [1] to [3], further comprising hydrotalcite. [6] Furthermore, the BET specific surface area is 30 to 50 m 2The rubber composition for a hose according to any one of [1] to [3], containing magnesium oxide and hydrotalcite in an amount of 1 / g. [7] An air hose having at least one rubber layer, the rubber layer being made of the rubber composition for hoses according to any one of [1] to [6]. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a rubber composition for a hose that is excellent in heat resistance, acid resistance, and resistance to setting. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, an embodiment of the present invention will be described in detail, but the present invention is not limited to this embodiment.

[0010] In this specification, when it is written "X to Y" (X and Y are any numbers), unless otherwise specified, it means "X or more and Y or less", and also means "preferably larger than X" or "preferably smaller than Y". In the present specification, when numerical ranges are described in stages, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In addition, in the numerical ranges described in the present specification, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples. In this specification, "X and / or Y (X and Y are any configurations)" means at least one of X and Y, and means X only, Y only, or X and Y.

[0011] The rubber composition for hoses of the present invention (hereinafter sometimes referred to as "the rubber composition for hoses") is a rubber composition for hoses containing components (A) to (C), characterized in that the content of component (B) is 1 to 3 parts by mass and the content of component (C) is 0.05 to 0.4 parts by mass per 100 parts by mass of component (A). (A) An epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber having an ethylene oxide content of 50 mol % or less and an allyl glycidyl ether content of 5 mol % or more. (B) At least one of a quinoxaline-based crosslinking agent and a triazine-based crosslinking agent. (C) Sulfur.

[0012] Rubber compositions for hoses containing GECO are known to be useful because of their excellent heat resistance. The inventors' investigations revealed that such rubber compositions for hoses have issues with acid resistance. Specifically, detailed investigations into the causes of deterioration in blow-by gas hoses through which exhaust gas condensates such as nitrogen oxides (NOx) flow revealed that acid components tend to cleave the unsaturated bonds in the main chain of GECO, leading to deterioration of various physical properties.

[0013] The present inventors have conducted extensive research aimed at improving the acid resistance of hose-forming materials containing GECO. As a result, they unexpectedly discovered that by adjusting the ratio of units constituting GECO to a specific range and blending sulfur and a specific cross-linking agent in specific proportions, the material can be made to have excellent heat resistance, acid resistance, and even resistance to settling, and have arrived at this invention.

[0014] The reason why the present rubber composition for hoses exhibits the above-mentioned excellent effects is not entirely clear, but the inventors speculate that the above-mentioned excellent effects are exhibited by reducing the EO content in the unit ratio that makes up GECO to reduce the degradation points caused by acid components, and by increasing the AGE content to suppress softening and degradation caused by acid components, and by setting the sulfur content for GECO of a specific composition within a specific range, which promotes re-crosslinking (self-repair) during the process of GECO main chain scission.

[0015] The rubber composition for hoses newly proposed by the present inventors has excellent heat resistance and acid resistance, and also has excellent resistance to settling. Therefore, for example, in one embodiment of the present invention, the composition can be suitably used as an air hose for vehicles, particularly as a blow-by gas hose for vehicles such as automobiles.

[0016] In one embodiment of the present invention, the use of a quinoxaline-based crosslinking agent can further enhance the above effects, particularly the heat resistance and settling resistance.

[0017] In one embodiment of the present invention, the above-mentioned effect can be further enhanced by using a specific acid acceptor. In particular, a low activity acid acceptor, for example, an acid acceptor having a relatively small BET specific surface area (for example, 30 to 50 m 2 / g) By using magnesium oxide or the like, acid resistance can be further improved.

[0018] Hereinafter, each material constituting the rubber composition for a hose will be described.

[0019] (A) Specific epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber The rubber composition for a hose contains an epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber having an ethylene oxide content of 50 mol % or less and an allyl glycidyl ether content of 5 mol % or more. If the ethylene oxide content of the GECO contained in the rubber composition for a hose exceeds 50 mol %, or if the allyl glycidyl ether content is less than 5 mol %, it tends to be difficult to achieve a high level of balance between heat resistance, acid resistance, and settling resistance.

[0020] The ethylene oxide content (hereinafter sometimes referred to as "EO content") of component (A) is 50 mol% or less, preferably 48 mol% or less, and more preferably 46 mol% or less. The EO content may also be 44 mol% or less, or 42 mol% or less. The lower limit of the EO content in the component (A) is, for example, preferably 35 mol % or more, more preferably 37 mol % or more, and even more preferably 39 mol % or more.

[0021] The allyl glycidyl ether content (hereinafter sometimes referred to as "AGE content") in component (A) is 5 mol% or more. The AGE content may be 5.2 mol% or more, or 5.4 mol% or more. The upper limit of the AGE content in component (A) is, for example, preferably 10 mol % or less, more preferably 8 mol % or less, even more preferably 7 mol % or less, and particularly preferably 6 mol % or less.

[0022] The epichlorohydrin content (hereinafter sometimes referred to as "CO content") in component (A) may be 40 mol% or more, 45 mol% or more, 50 mol% or more, etc. The upper limit of the CO content in component (A) may be, for example, 60 mol% or less, 58 mol% or less, 55 mol% or less, etc.

[0023] The content of component (A) is, for example, 30% by mass or more, preferably 35 to 80% by mass, more preferably 38 to 70% by mass, and even more preferably 40 to 60% by mass, based on the entire rubber composition for a hose (100% by mass).

[0024] When the rubber composition for a hose contains two or more GECOs, it is preferable that all of the two or more GECOs are the same as those described above, although this is not limited to the following. Specifically, it is preferable that all of the two or more GECOs have an EO content of 50 mol% or less and an AGE content of 5 mol% or more.

[0025] Furthermore, when the rubber composition for a hose contains two or more types of GECO, it is preferable to use the same GECO as above as at least one of the types of GECO, although this is not limited to the following. Specifically, it is preferable to use a GECO having an EO content of 50 mol% or less and an AGE content of 5 mol% or more as the at least one type of GECO, and the content of the one type of GECO is preferably 60 mass% or more of the total content of the two or more types of GECO (i.e., the total amount (100 mass%) of GECO contained in the rubber composition for a hose). The content of the one type of GECO can be appropriately set within the above range, for example, 65 mass% or more, 68 mass% or more, 70 mass% or more, 75 mass% or more, 80 mass% or more, 85 mass% or more, 90 mass% or more, or 90 to 99 mass% of the total content of the two or more types of GECO.

[0026] In this specification, the EO content, AGE content, and CO content of component (A) refer to the EO content, AGE content, and CO content of all GECOs contained in the rubber composition for a hose. Specifically, when the rubber composition for a hose contains one type of GECO, the EO content, AGE content, etc. of that one GECO correspond to the EO content, AGE content, etc. of component (A). When the rubber composition for a hose contains two or more types of GECO, the EO content, AGE content, etc. calculated based on the mass ratio of each GECO correspond to the EO content, AGE content, etc. of component (A).

[0027] Specifically, for example, if the rubber composition for a hose contains one type of GECO and that GECO has an EO content of 40.4 mol%, an AGE content of 5.6 mol%, and a CO content of 54 mol%, the EO content of component (A) will be 40.4 mol%, an AGE content of 5.6 mol%, and a CO content of 54 mol%. Alternatively, for example, if the rubber composition for a hose contains two types of GECO and one GECO has an EO content of 40.4 mol%, an AGE content of 5.6 mol%, and a CO content of 54 mol%, and the content of that GECO is 70 parts by mass, and the other GECO has an EO content of 53 mol%, an AGE content of 3.5 mol%, and a CO content of 43.5 mol%, and the content of that GECO is 30 parts by mass, the EO content of component (A) will be 44.2 mol%, an AGE content of 5.0 mol%, and a CO content of 50.9 mol%. The mole percentage of the EO content, etc., is rounded to the second decimal place.

[0028] (B) At least one of a quinoxaline-based crosslinking agent and a triazine-based crosslinking agent The rubber composition for a hose contains at least one of a quinoxaline-based crosslinking agent and a triazine-based crosslinking agent. The rubber composition for a hose contains a quinoxaline-based crosslinking agent and / or a triazine-based crosslinking agent.

[0029] Examples of quinoxaline-based crosslinking agents include 2,3-dimercaptoquinoxaline derivatives. Specific examples include quinoxaline-2,3-dithiocarbonate, 6-methylquinoxaline-2,3-dithiocarbonate, 6-ethyl-2,3-dimercaptoquinoxaline, 6-iopropylquinoxaline-2,3-dithiocarbonate, and 5,8-dimethylquinoxaline-2,3-dithiocarbonate. These may be used alone or in combination of two or more.

[0030] Examples of triazine crosslinking agents include 2,4,6-trimercapto-1,3,5-triazine, 2-hexylamino-4,6-dimercaptotriazine, 2-diethylamino-4,6-dimercaptotriazine, 2-cyclohexylamino-4,6-dimercaptotriazine, 2-dibutylamino-4,6-dimercaptotriazine, 2-anilino-4,6-dimercaptotriazine, 2-phenylamino-4,6-dimercaptotriazine, etc. These may be used alone or in combination of two or more.

[0031] Among the components (B), it is preferable to use a quinoxaline-based crosslinking agent from the viewpoint of further improving heat resistance and settling resistance.

[0032] The content of component (B) is 1 to 3 parts by mass per 100 parts by mass of component (A). The content of component (B) can be appropriately set within the above range, and may be, for example, 1.5 to 2.5 parts by mass, 1 to 2 parts by mass, etc. In particular, the content of component (B) is preferably 1.5 to 2.5 parts by mass, or 1 to 2 parts by mass, from the viewpoint of further improving heat resistance and acid resistance.

[0033] In this specification, "per 100 parts by mass of component (A)" means, when the rubber composition for a hose contains one type of GECO, per 100 parts by mass of the one type; or, when the rubber composition for a hose contains two or more types of GECO, per 100 parts by mass of the total of the two or more types of GECO.

[0034] 《(C) Sulfur》 The rubber composition for a hose contains (C) sulfur. The content of component (C) is 0.05 to 0.4 parts by mass per 100 parts by mass of component (A). If the content of component (C) is too low, acid resistance tends to be insufficient, while if the content of component (C) is too high, sag resistance (compression set) tends to be insufficient.

[0035] The content of component (C) can be appropriately set within the above range, and may be, for example, 0.1 to 0.4 parts by mass, 0.2 to 0.4 parts by mass, etc., per 100 parts by mass of component (A). From the viewpoint of achieving a high level of both heat resistance and acid resistance, an amount of 0.1 to 0.4 parts by mass is preferred.

[0036] Examples of component (C) include soluble sulfur and insoluble sulfur. Examples of insoluble sulfur include polymeric sulfur such as μ sulfur, π sulfur, and ω sulfur. These may be used alone or in combination of two or more. Commercially available insoluble sulfur products include Sanfel (manufactured by Sanshin Chemical Co., Ltd.) and Sanfel EX (manufactured by Sanshin Chemical Co., Ltd.).

[0037] Examples of soluble sulfur include sulfur having a cyclic structure, such as α-sulfur, β-sulfur, γ-sulfur, and λ-sulfur. These may be used alone or in combination of two or more. Commercially available soluble sulfur products include Sulfax T-10 (manufactured by Tsurumi Chemical Industry Co., Ltd.), Kinkajirushi Fine Sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd.), and Powdered Sulfur S (manufactured by Hosoi Chemical Industry Co., Ltd.).

[0038] In the present invention, insoluble sulfur refers to sulfur that is 90% by mass or more insoluble in carbon disulfide, preferably 95% by mass or more insoluble, more preferably 98% by mass or more insoluble, while soluble sulfur refers to sulfur that is 99.5% by mass or more soluble in carbon disulfide, preferably 99.9% by mass or more insoluble, more preferably 100% by mass.

[0039] (Other ingredients) In addition to the above components, the rubber composition for hoses may contain additives such as acid acceptors, antioxidants, plasticizers, fillers, vulcanization retarders, processing aids, flame retardants, colorants, etc. These may be used alone or in combination of two or more.

[0040] ((D) Acid acceptor) Examples of acid acceptors include metal oxides, metal hydroxides, metal carbonates, and composite metal hydroxides. These may be used alone or in combination of two or more. For example, a metal oxide and a composite metal hydroxide may be used in combination.

[0041] More specifically, examples of the acid acceptor include magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum hydroxide, calcium oxide, calcium hydroxide, calcium carbonate, calcium silicate, basic silicon dioxide, hydrotalcite, zeolite, etc., and these may be used alone or in combination of two or more. Among these, one or more selected from the group consisting of magnesium oxide and hydrotalcite are preferred, and it is more preferred to use both.

[0042] For example, magnesium oxide with a BET specific surface area of ​​100 m 2 Magnesium oxide having a BET specific surface area of ​​20 to 80 m / g or less is preferred. 2 / g, 30-70m 2 / g, 35-60m 2 / g, 30-50m 2 Among these, magnesium oxides having a low activity are preferred, from the viewpoint of achieving a high level of balance between the heat resistance, acid resistance, and fatigue resistance of the rubber composition for a hose, as well as improving water resistance. For example, magnesium oxides having a BET specific surface area of ​​30 to 70 m 2 / g or 30-50m 2 It is particularly preferred to use magnesium oxide in an amount of 1 / g.

[0043] Examples of hydrotalcite include compounds represented by the following general formula: [(M1 2+ ) 1-x M 3+ x (OH)2] x+ [A n- x / n mH2O] x- (In the formula, M1 2+is a divalent metal ion, M 3+ is a trivalent metal ion, A n- is an n-valent anion, x is a number satisfying 0 < x < 0.5, and m is a number satisfying 0 ≤ m.)

[0044] M1 2+ represents a divalent metal ion, for example, Mg 2+ , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ and the like can be mentioned.

[0045] M 3+ represents a trivalent metal ion, for example, Al 3+ , Fe 3+ , Cr 3+ , Co 3+ , In 3+ and the like can be mentioned.

[0046] A n- represents an n-valent anion, for example, OH - , F - , Cl - , Br - , NO3 - , CO3 2- , SO4 2- , Fe(CN)6 3- , CH3COO - and the like can be mentioned.

[0047] In the above formula, it is particularly preferable that M1 2+ is Mg 2+ and / or Zn 2+ , M 3+ is Al 3+ , and A n- is CO3 2- .

[0048] x is a number satisfying 0 < x < 0.5, preferably a number satisfying 0.2 ≤ x ≤ 0.4, and more preferably a number satisfying 0.2 ≤ x ≤ 0.33.

[0049] Specific examples of hydrotalcite include, but are not limited to, Mg 4.3 Al2(OH) 12.6 CO3·3.5H2O, Mg3ZnAl2(OH) 12 CO3·3H2O, Mg 4.5 Al2(OH) 13 CO3·3.5H2O, Mg 4.5 Al2(OH) 13 CO3, Mg4Al2(OH) 12 CO3·3.5H2O, Mg6Al2(OH) 16 CO3·4H2O, Mg5Al2(OH) 14 CO3·4H2O, Mg3Al2(OH) 10 CO3·1.7H2O, etc. Among them, Mg 4.3 Al2(OH) 12.6 CO3·3.5H2O, Mg3ZnAl2(OH) 12 Examples include CO3·3H2O.

[0050] The BET specific surface area of ​​hydrotalcite is, for example, 45 m 2 / g or less is preferable, and 3 to 35m 2 / g, 5-25m 2 / g, 8-20m 2 / g is preferred.

[0051] The content of the component (D) relative to 100 parts by mass of the component (A) is, for example, 2 to 10 parts by mass, preferably 3 to 8 parts by mass, and more preferably 4 to 7 parts by mass.

[0052] The content of magnesium oxide is, for example, 1 to 4 parts by mass, preferably 2 to 3.5 parts by mass, and more preferably 2.5 to 3.3 parts by mass, per 100 parts by mass of component (A), from the viewpoint of achieving a high level of balance between the heat resistance, acid resistance, and settling resistance of the rubber composition for a hose, as well as improving water resistance.

[0053] The content of hydrotalcite is, for example, 1 to 6 parts by mass, preferably 2 to 5.5 parts by mass, and more preferably 3 to 5 parts by mass, per 100 parts by mass of component (A).

[0054] (anti-aging agent) Examples of antioxidants include nickel dibutyldithiocarbamate (NiDBC), nickel diethyldithiocarbamate (NiDEC), polymerized-2,2,4-trimethyl-1,2-dihydroquinoline (TMDQ), 2-mercaptobenzimidazole (MBI), and 2-mercaptobenzimidazole zinc salt (ZnMBI).

[0055] The content of the antioxidant is not particularly limited, but may be, for example, 0.3 to 10 parts by mass, 0.5 to 8 parts by mass, or 1 to 6 parts by mass per 100 parts by mass of the component (A).

[0056] (plasticizer) Examples of the plasticizer include diisononyl phthalate (DINP), di-n-butyl phthalate (DBP), dioctyl adipate (DOA), dibutyl glycol adipate, dibutyl carbitol adipate, adipic acid polyester, and adipic acid ether ester plasticizers.

[0057] The content of the plasticizer is not particularly limited, but may be, for example, 4 to 20 parts by mass, 5 to 18 parts by mass, or 6 to 15 parts by mass per 100 parts by mass of the component (A).

[0058] (filler) Examples of fillers include carbon black, silicon dioxide, calcium carbonate, talc, clay, etc. Among these, carbon black is preferred.

[0059] Examples of carbon black include SAF grade, ISAF grade, HAF grade, MAF grade, FEF grade, GPF grade, SRF grade, FT grade, MT grade, etc. Of these, SRF grade is preferred.

[0060] The nitrogen adsorption specific surface area of ​​carbon black is, for example, 10 to 150 m 2 / g is preferable, and 15 to 100m 2 / g, more preferably 20 to 80m 2 / g. The nitrogen adsorption specific surface area of ​​carbon black can be measured in accordance with the method described in JIS K 6217-2.

[0061] The iodine adsorption capacity of carbon black is, for example, preferably 10 to 150 mg / g, more preferably 10 to 75 mg / g, and even more preferably 20 to 65 mg / g, and the DBP (dibutyl phthalate) absorption capacity of carbon black is, for example, preferably 20 to 180 mL / 100 g, and more preferably 20 to 150 mL / 100 g. The iodine adsorption amount of carbon black is a value measured in accordance with JIS K 6217-1 (method A), and the DBP absorption amount of carbon black is a value measured in accordance with JIS K 6217-4.

[0062] The content of the filler is not particularly limited, but may be, for example, 30 to 100 parts by mass, 40 to 100 parts by mass, 50 to 100 parts by mass, 60 to 90 parts by mass, or 65 to 85 parts by mass per 100 parts by mass of component (A).

[0063] (vulcanization retarder) Examples of vulcanization retarders include phthalic anhydride, benzoic acid, salicylic acid, N-nitrosodiphenylamine, N,N',N''-tris(isopropylthio)-N,N',N''-triphenylphosphoric triamide, N-cyclohexylthiophthalimide, and N-(trichloromethylthio)benzenesulfonamide.

[0064] The content of the vulcanization retarder is not particularly limited, but may be, for example, 0.1 to 5 parts by mass, 0.2 to 4 parts by mass, or 0.3 to 3 parts by mass per 100 parts by mass of the component (A).

[0065] (processing aids) Examples of processing aids include stearic acid, oleic acid, lauric acid, n-octadecylamine, polyoxyethylene stearyl ether phosphate, and glycerin fatty acid esters.

[0066] The content of the processing aid is not particularly limited, but may be, for example, 0.1 to 10 parts by mass, or 1 to 6 parts by mass, per 100 parts by mass of component (A).

[0067] (Flame retardant) Examples of the flame retardant include antimony oxide and chlorinated paraffin.

[0068] The content of the flame retardant is not particularly limited, but may be, for example, 3 to 20 parts by mass, or 5 to 12 parts by mass, per 100 parts by mass of the component (A).

[0069] (Preparation method) The rubber composition for a hose can be obtained, for example, by blending the above components (A) to (C) and, if necessary, other additives, and kneading the mixture using a kneading roll or the like.

[0070] (Hose manufacturing method) In a method for manufacturing a hose using the rubber composition for a hose, for example, in the case of a single-layer structure, the rubber composition for a hose is extruded onto a mandrel to form a tubular shape, and the uncrosslinked rubber hose extruded onto the mandrel is crosslinked with pressurized steam, and then the mandrel is removed to manufacture the desired hose. Note that while the above description concerns a hose with a single-layer structure having a single rubber layer, the rubber composition for a hose is not limited to this, and can also be suitably used as a material for forming a hose with a multi-layer structure (multi-layer structure) of two or more layers. That is, it is sufficient that the air hose has at least one rubber layer (one layer) made of the rubber composition for a hose. When the material is used to form a hose with a multi-layer structure of two or more layers, it is preferable, but not limited to, that the innermost layer be a rubber layer made of the rubber composition for a hose.

[0071] The inner diameter, thickness, and length of a hose obtained using the present rubber composition for a hose are not particularly limited. For example, in the case of a hose with a single-layer structure, the inner diameter is preferably in the range of 5.0 to 25.0 mm, and the thickness is preferably in the range of 2.0 to 5.0 mm. In the case of a hose of a multi-layer structure, although there are no particular limitations, the inner diameter of the rubber layer made of the rubber composition for a hose is in the range of 5.0 to 25.0 mm, and the thickness is in the range of 2.0 to 5.0 mm.

[0072] (Application) The rubber composition for hoses is useful as a hose-forming material for various hoses, for example, air hoses for automobiles, specifically, air hoses that exhaust a mixture of gasoline vapor, engine oil mist, and air from an engine and supply it to the engine for re-combustion, and more specifically, heat-resistant air hoses such as turbocharger hoses, blow-by gas hoses, and emission control hoses. [Example]

[0073] Next, examples of the present invention will be described together with comparative examples, but the present invention is not limited to these examples.

[0074] First, prior to the Examples and Comparative Examples, the following materials were prepared.

[0075] [Epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber] GECO(1) [Composition EO content: 40.4 mol%, AGE content: 5.6 mol%, CO content: 54.0 mol%] GECO(2) [Composition EO content: 44.2 mol%, AGE content: 5.0 mol%, CO content: 50.9 mol%]

[0076] GECO(3) [Composition EO content: 44.3 mol%, AGE content: 3.2 mol%, CO content: 52.6 mol%]

[0077] [Crosslinking agent] Quinoxaline crosslinking agent (Dysonet XL-60C, manufactured by Osaka Soda Co., Ltd.) Triazine-based crosslinking agent (Gisnet F, manufactured by Sankyo Kasei Co., Ltd.)

[0078] [sulfur] Sulfur (Sulfax T-10, manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0079] [Acid acceptor] Magnesium oxide (Kyowamag #30, manufactured by Kyowa Chemical Industry Co., Ltd., BET specific surface area 40 m 2 / g) Hydrotalcite (DHT-4A, manufactured by Kyowa Chemical Industry Co., Ltd., BET specific surface area 11 m 2 / g)

[0080] [Filler] Carbon black (SEAT S manufactured by Tokai Carbon Co., Ltd., nitrogen adsorption specific surface area: 27 m 2 / g, iodine adsorption: 26mg / g, DBP absorption: 68mL / 100g)

[0081] [Anti-aging agent] Nickel dibutyldithiocarbamate (Nocrac NBC, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0082] [Plasticizer] Ether ester oil (ADEKA Cizer RS-107, manufactured by ADEKA)

[0083] [Vulcanization retarder] N-cyclohexylthiophthalimide (retarder CTP, manufactured by Toray Industries, Inc.)

[0084] [Flame retardant] Ethylenebispentabromobenzene / antimony trioxide mixture (Firecut AT-3CN, manufactured by Suzuhiro Chemical)

[0085] The GECO(1) is GECO(a) [EO content: 40.4 mol%, AGE content: 5.6 mol%, CO content: 54.0 mol%]. The GECO(2) is a mixture of GECO(a) and GECO(b) [EO content: 53 mol%, AGE content: 3.5 mol%, CO content: 43.5 mol%] (mass ratio GECO(a):GECO(b) = 70:30). GECO(3) is a mixture of GECO(b) and GECO(c) [composition: EO content: 40.5 mol%, AGE content: 3.0 mol%, CO content: 56.5 mol%] (mass ratio GECO(b):GECO(c) = 30:70).

[0086] [Examples 1 to 8, Comparative Examples 1 to 3] The above components were blended in the proportions shown in Table 1 below, and kneaded using a mixing roll to prepare a rubber composition for a hose. Each property was evaluated according to the following criteria, and the results are shown in Table 1 below.

[0087] <Heat resistance test> Each rubber composition for hoses was press-molded (vulcanized) at 160°C for 30 minutes to prepare a sheet sample with a thickness of 2 mm. A JIS No. 5 dumbbell shape was punched out from this sample to prepare a test piece. The initial elongation at break (Eb) of this test piece was measured in a 23°C atmosphere in accordance with JIS K 6251. Next, the test piece was left to stand in a 125°C atmosphere for 72 hours, and then the elongation at break (Eb') was measured in the same manner as above. The rate of change (degree of reduction, ΔEb) of the elongation at break after heat aging relative to the initial elongation at break was calculated. A rate of change (ΔEb) of within -50% was evaluated as "Good," and a rate of change (ΔEb) of more than -50% (e.g., -60%) was evaluated as "Poor."

[0088] <Acid resistance test> Each rubber composition for hoses was press-molded (vulcanized) at 160°C for 30 minutes to prepare a 2 mm-thick sheet sample. A JIS No. 5 dumbbell shape was punched out from this sample to prepare a test piece. The initial elongation at break (Eb) of this test piece was measured in an atmosphere of 23°C in accordance with JIS K 6251. The test piece was then immersed in an acid aqueous solution (4000 ppm formic acid, 4000 ppm nitric acid, and 4000 ppm sulfuric acid) at 80°C for 72 hours, removed, and dried at 80°C for 72 hours. The elongation at break (Eb) was then measured in the same manner as above. The rate of change (degree of decrease, ΔEb) in elongation at break after acid aging relative to the initial elongation at break was then calculated. The change rate (ΔEb) was evaluated as "◎" when it was within -20%, "◯" when it was greater than -20% and less than -30%, and "×" when it was greater than -30% (for example, -40%).

[0089] <<Sag Resistance (Compression Set) Test>> Each rubber composition for hoses was press-molded (vulcanized) at 160°C for 30 minutes to prepare test specimens (29 mm diameter, 12 mm thickness). Compression set (%) of these test specimens was measured at 120°C for 70 hours at a compression rate of 25% in accordance with JIS K 6262. Compression set of 50% or less was evaluated as "◎", compression set of more than 50% but less than 60% was evaluated as "◯", and compression set of more than 60% (e.g., 70%) was evaluated as "×".

[0090] <Water pressure test> Each rubber composition for hoses was press-molded (vulcanized) at 160°C for 30 minutes to produce a sheet sample with a thickness of 2 mm. 20 mm x 25 mm test pieces were then prepared from these samples. The test pieces were immersed in water at 40°C for 24 hours, after which the volume change ΔV (%) was measured. A volume change ΔV (%) of +10% or less was marked "Good," and a volume change of more than +10% (e.g., +20%) was marked "Poor."

[0091] [Table 1]

[0092] From the results in Table 1 above, it can be seen that the rubber compositions for hoses of Examples 1 to 8 of the present invention were all excellent in heat resistance, acid resistance, and resistance to permanent compression set.

[0093] In contrast, the rubber composition for a hose of Comparative Example 1 had a low AGE content of GECO and did not satisfy the requirements of the present invention, resulting in poor acid resistance.

[0094] In addition, the rubber compositions for hoses in Comparative Examples 2 and 3 satisfy the requirements of the present invention for GECO, but the amount of sulfur blended does not satisfy the requirements of the present invention, resulting in poor acid resistance or fatigue resistance.

[0095] As the above results show, a rubber composition for a hose containing (A) GECO having an EO content of 50 mol% or less and an AGE content of 5 mol% or more, (B) at least one of a quinoxaline-based crosslinking agent and a triazine-based crosslinking agent, and (C) sulfur, in which the content of component (B) is 1 to 3 parts by mass and the content of component (C) is 0.05 to 0.4 parts by mass per 100 parts by mass of component (A), can achieve a high level of balance between heat resistance, acid resistance, and settling resistance. [Industrial Applicability]

[0096] The rubber composition for hoses of the present invention is useful as a forming material for various hoses, for example, air hoses for automobiles, more specifically, blow-by gas hoses that exhaust a mixture of gasoline vapor, engine oil mist, and air from an engine and supply it to the engine for re-combustion.

Claims

1. A rubber composition for a hose containing the following components (A) to (C): A rubber composition for a hose, wherein the content of the component (B) is 1 to 3 parts by mass and the content of the component (C) is 0.05 to 0.4 parts by mass per 100 parts by mass of the component (A). (A) An epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber having an ethylene oxide content of 50 mol % or less and an allyl glycidyl ether content of 5 mol % or more. (B) At least one of a quinoxaline-based crosslinking agent and a triazine-based crosslinking agent. (C) Sulfur.

2. 2. The rubber composition for a hose according to claim 1, wherein the component (B) contains a quinoxaline-based crosslinking agent.

3. 3. The rubber composition for a hose according to claim 1, wherein the content of the component (C) is 0.1 to 0.4 parts by mass per 100 parts by mass of the component (A).

4. The rubber composition for a hose according to claim 1 or 2, further comprising magnesium oxide.

5. The rubber composition for a hose according to claim 1 or 2, further comprising hydrotalcite.

6. Furthermore, the BET specific surface area is 30 to 50 m 2 3. The rubber composition for a hose according to claim 1, further comprising magnesium oxide and hydrotalcite in an amount of 1 / g.

7. 3. An air hose having at least one rubber layer, the rubber layer being made of the rubber composition for hoses according to claim 1 or 2.

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