Hose rubber composition and air hose

Abstract

Provided are: a hose rubber composition having excellent heat resistance, acid resistance, and permanent strain resistance; and various hoses obtained by using the same.　The present invention provides a hose rubber composition containing the following components (A) to (C), wherein the content of the component (B) is 1-3 parts by mass and the content of the component (C) is 0.05-0.4 parts by mass with respect to 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

Description

Rubber composition for hose and air hose

[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.).

[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 been used as materials for hoses that require heat resistance, such as air hoses for automobiles (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2004-143299

[0004] In recent years, the environmental temperature inside an automobile engine compartment has tended to become increasingly higher, and the materials used to form automobile hoses are required to have better heat resistance than ever before. However, in rubber compositions for hoses containing GECO, technology for improving both the heat resistance and acid resistance has not yet been fully explored, and 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 consideration of the above circumstances, and provides a rubber composition for hoses containing GECO that has excellent heat resistance, acid resistance, and settling resistance, as well as various hoses obtained using the same.

[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 resistance to sagging, 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): 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; and (C) sulfur. [2] The rubber composition for a hose according to [1], which contains a quinoxaline-based crosslinking agent as component (B). [3] The rubber composition for a hose according to [1] or [2], wherein the content of component (C) is 0.1 to 0.4 parts by mass per 100 parts by mass of 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 [4], further containing hydrotalcite. [6] The rubber composition for a hose according to any one of [1] to [4], further containing a BET specific surface area of ​​30 to 50 m ２ [7] An air hose having at least one rubber layer, the rubber layer comprising the rubber composition for hoses according to any one of [1] to [6].

[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 settling.

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

[0010] In this specification, when "X to Y" (X and Y are any numbers) is stated, unless otherwise specified, it means "X or more and Y or less," and also includes the meaning of "preferably greater than X" or "preferably smaller than Y." In this specification, with respect to numerical ranges described in stages, the upper limit or lower limit of a numerical range in one stage can be arbitrarily combined with the upper limit or lower limit of a numerical range in another stage. Furthermore, in the numerical ranges described in this specification, the upper limit or lower limit of the numerical range can also be replaced with a value shown in the examples. In this specification, "X and / or Y (X and Y are any configuration)" means at least one of X and Y, and can mean three possibilities: X only, Y only, or X and Y.

[0011] The rubber composition for a hose of the present invention (hereinafter sometimes referred to as "the rubber composition for a hose") is a rubber composition for a hose 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 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 among the units constituting 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 relative to a GECO of a specific composition within a specific range, which promotes re-crosslinking (self-repair) as the main chain scission of GECO progresses.

[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 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 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") in 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 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, for example. 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 in component (A) (hereinafter sometimes referred to as "CO content") 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) relative to the entire rubber composition for a hose (100% by mass) 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.

[0024] When the rubber composition for a hose contains two or more types of GECO, it is preferred that all of the two or more types of GECO are the same as those described above, although this is not limited thereto. Specifically, it is preferred that all of the two or more types of GECO 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 described above as at least one of the types of GECO, although this is not limited thereto. 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 relative to 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, and is, 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% relative to 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 the GECO 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 type of 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 the GECO has an EO content of 40.4 mol%, an AGE content of 5.6 mol%, and a CO content of 54 mol%, then the EO content of component (A) will be 40.4 mol%, the AGE content will be 5.6 mol%, and the CO content will be 54 mol%. For example, if the rubber composition for a hose contains two types of GECO, and one type of 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 another type of 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, then the EO content of component (A) will be 44.2 mol%, the AGE content will be 5.0 mol%, and the CO content will be 50.9 mol%. Note that mol% values ​​such as EO content are rounded to one 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. Among these, from the viewpoint of further improving heat resistance and acid resistance, the content of component (B) is preferably 1.5 to 2.5 parts by mass, 1 to 2 parts by mass, etc.

[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. Also, when the rubber composition for a hose contains two or more types of GECO, for example, it means 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 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 Components) In addition to the above components, the rubber composition for a hose may contain additives such as an acid acceptor, an antioxidant, a plasticizer, a filler, a vulcanization retarder, a processing aid, a flame retardant, a colorant, etc. These may be used alone or in combination of two or more.

[0040] (D) Acid Acceptor) Examples of the acid acceptor 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, it is preferable to use one or more selected from the group consisting of magnesium oxide and hydrotalcite, and it is more preferable to use both.

[0042] As magnesium oxide, for example, a magnesium oxide having 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 low activity are preferred from the viewpoint of achieving a high level of balance between 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 are preferred. 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) x+ [A n- x / n ・mH2O] x- (In the formula, M1 2+ is a divalent metal ion, and M 3+ is a trivalent metal ion, and 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+ , Mn2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ Examples include:

[0045] M 3+ represents a trivalent metal ion, for example, Al 3+ , Fe 3+ , Cr 3+ , Co 3+ , In 3+ Examples include:

[0046] A n- represents an anion with a valence of n, for example, OH - , F - , Cl - ,Br - , NO3 - , CO3 2- , SO4 2- , Fe(CN)6 3- , CH3COO - Examples include:

[0047] In the above formula, M 2+ is Mg 2+ and / or Zn 2+ and M 3+ Al 3+ and A n- is CO3 2- It is particularly preferred that:

[0048] x is a number that satisfies 0<x<0.5, preferably a number that satisfies 0.2≦x≦0.4, and more preferably a number that satisfies 0.2≦x≦0.33.

[0049] Specific examples of hydrotalcite include, but are not limited to, Mg 4.3 Al(OH) 12.6 CO3・3.5H2O, Mg3ZnAl2(OH) 12 CO3·3H2O, Mg 4.5 Al(OH) 13 CO3・3.5H2O, Mg 4.5 Al(OH) 13 CO3, Mg4Al2(OH) 12CO3・3.5H2O, Mg ６ Al(OH) 16 CO3・4H2O, Mg5Al2(OH) 14 CO3・4H2O, Mg3Al2(OH) 10 Among them, Mg 4.3 Al(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, 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 the anti-aging agent 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 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, adipate polyester, and adipate ether ester plasticizers.

[0057] The amount 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 component (A).

[0058] (Filler) Examples of the filler 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 preferred, and 15 to 100m 2 / g, more preferably 20 to 80 m 2 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. 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 capacity of carbon black is a value measured in accordance with JIS K 6217-1 (Method A), and the DBP absorption capacity 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 the vulcanization retarder 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 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 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 present 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 using pressurized steam, after which the mandrel is removed to produce the desired hose. While the above description concerns a hose with a single-layer structure having a single rubber layer, the present rubber composition for a hose is not limited thereto and can also be suitably used as a material for forming a hose with a multi-layer structure (composite layer structure) of two or more layers. That is, any air-type hose having at least one rubber layer (one layer) made of the present rubber composition for a hose may be used. Furthermore, when using the present rubber composition for a hose as a material for forming a hose with a multi-layer structure of two or more layers, it is preferable that the innermost layer be a rubber layer made of the present rubber composition for a hose, although this is not limited thereto.

[0071] The inner diameter, thickness, and length of a hose obtained using the rubber composition for a hose are not particularly limited, but 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 with a multi-layer structure, the inner diameter of the rubber layer made of the rubber composition for a hose is not particularly limited, but 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.

[0072] (Applications) The rubber composition for hoses is useful as a hose-forming material for various hoses, for example, air hoses for automobiles, specifically, air hoses for discharging a mixture of gasoline vapor, engine oil mist, and air from an engine and supplying 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.

[0073] Next, examples of the present invention will be described together with comparative examples, although 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-based 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: 26 mg / g, DBP absorption: 68 mL / 100 g)

[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 Corporation)

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

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

[0085] The GECO(1) is GECO(a) [composition: 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) [composition: EO content: 53 mol%, AGE content: 3.5 mol%, CO content: 43.5 mol%] (mass ratio: GECO(a):GECO(b) = 70:30). The 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 the mixture was kneaded using a mixing roll to prepare rubber compositions for hoses. Each property was evaluated according to the following criteria. The results are also 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. Using this test piece, the initial elongation at break (Eb) was measured in an atmosphere at 23°C in accordance with JIS K 6251. Next, the test piece was left to stand in an atmosphere at 125°C 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) in the elongation at break after heat aging relative to the initial elongation at break was calculated. A rate of change (ΔEb) of −50% or less 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 hose rubber composition was press-molded (vulcanized) at 160°C for 30 minutes to prepare a 2 mm-thick sheet sample. A JIS No. 5 dumbbell-shaped test piece was punched out from this sample. Using this test piece, the initial elongation at break (Eb) was measured in a 23°C atmosphere 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 (decrease, ΔEb) in elongation at break after acid degradation relative to the initial elongation at break was then calculated. A change rate (ΔEb) of −20% or less was evaluated as “⊚ (excellent)”, a change rate of more than −20% but less than −30% was evaluated as “◯ (good)”, and a change rate of more than −30% (for example, −40%) was evaluated as “× (poor)”.

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

[0090] <<Compressed Water 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. 20 mm x 25 mm test pieces were 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 evaluated as "○ (good)," and a volume change of more than +10% (e.g., +20%) was evaluated as "× (poor)."

[0091]

[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 in 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, wherein 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 an excellent balance of heat resistance, acid resistance, and settling resistance.

[0096] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0097] The rubber composition for hoses of the present invention is useful as a material for forming various hoses, for example, air hoses for automobiles, more specifically, blow-by gas hoses for discharging a mixture of gasoline vapor, engine oil mist, and air from an engine and supplying it to the engine for re-combustion.

Claims

1. A rubber composition for a hose containing the following components (A) to (C): 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; and (C) sulfur.

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

3. The rubber composition for hoses according to claim 1 or 2, wherein the content of said component (C) is 0.1 to 0.4 parts by mass per 100 parts by mass of said component (A).

4. The rubber composition for a hose according to any one of claims 1 to 3, further comprising magnesium oxide.

5. The rubber composition for a hose according to any one of claims 1 to 4, further comprising hydrotalcite.

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

7. An air hose having at least one rubber layer, said rubber layer being made of the rubber composition for hoses according to any one of claims 1 to 6.

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