Fuel hose

Abstract

To provide a fuel hose that has excellent adhesion between an inner layer of polyol cross-linked fluororubber and an outer layer of acrylonitrile-butadiene rubber even when stored in an uncross-linked state after extrusion. The rubber composition comprises a tubular inner layer 12 and an outer layer 14 provided in contact with the inner layer 12, wherein the inner layer 12 is made of a crosslinked body of a rubber composition containing the following (A) to (E), and the outer layer 14 is made of a crosslinked body of a rubber composition containing the following (F) to (I), wherein the total amount of (H) and (I) is 20 to 70 parts by mass per 100 parts by mass of (F), and the content of (H) is 30 to 95% by mass of the total amount of (H) and (I). (A) Polyol cross-linked fluororubber (B) Polyol crosslinker (C) Calcium hydroxide (D) Triallyl isocyanurate (E) Peroxide crosslinking agent (F) Acrylonitrile butadiene rubber (G) Paraffin wax (H) Carbon black with an oil absorption of less than 50 mL / 100 g (I) Carbon black with an oil absorption of 50 mL / 100 g or more

Description

[Technical Field]

[0001] The present invention relates to a fuel hose, and more particularly to a fuel hose used for transporting fuel for automobiles and the like. [Background technology]

[0002] Various types of hoses made of multiple laminated layers are used for fuel hoses used in transporting fuel for automobiles, etc. Among these, a multi-layer hose has been proposed that uses an inner layer of fluoroelastomer, which has excellent low fuel permeability (barrier properties), and an outer layer of acrylonitrile-butadiene rubber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-195040 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-273241 Summary of the Invention [Problem to be solved by the invention]

[0004] Polyol-crosslinked fluororubber is prone to scorching (discoloration) when calcium hydroxide, a crosslinking accelerator, is used. After extruding an inner layer of polyol-crosslinked fluororubber and an outer layer of acrylonitrile-butadiene rubber, if this laminate is stored in an uncrosslinked state, scorching (discoloration) of the inner layer will progress at the adhesive interface between the inner and outer layers, and as a result, the reaction between the polyol-crosslinked fluororubber and acrylonitrile-butadiene rubber during crosslinking will be inhibited, resulting in a problem of reduced adhesion between the inner and outer layers.

[0005] The problem to be solved by the present invention is to provide a fuel hose that has excellent adhesion between an inner layer of polyol-crosslinked fluororubber and an outer layer of acrylonitrile-butadiene rubber, even when stored in an uncrosslinked state after extrusion. [Means for solving the problem]

[0006] The fuel hose according to the present invention is a fuel hose comprising a tubular inner layer and an outer layer provided in contact with the outer peripheral surface of the inner layer, wherein the inner layer is made of a crosslinked product of a rubber composition containing the following (A) to (E), and the outer layer is made of a crosslinked product of a rubber composition containing the following (F) to (I), the total amount of (H) and (I) being 20 parts by mass or more and 70 parts by mass or less per 100 parts by mass of (F), and the content of (H) being 30% by mass or more and 95% by mass or less of the total amount of (H) and (I). (A) Polyol cross-linked fluororubber (B) Polyol crosslinker (C) Calcium hydroxide (D) Triallyl isocyanurate (E) Peroxide crosslinking agent (F) Acrylonitrile butadiene rubber (G) Paraffin wax (H) Carbon black with an oil absorption of less than 50 mL / 100 g (I) Carbon black with an oil absorption of 50 mL / 100 g or more

[0007] (G) is preferably a paraffin wax having a melting point of 45°C or higher and 75°C or lower. The content of (G) is preferably 0.5 parts by mass or higher and 6.0 parts by mass or lower relative to 100 parts by mass of (F). (H) is preferably carbon black having an oil absorption of 20 mL / 100g or higher and 45 mL / 100g or lower, and (I) is preferably carbon black having an oil absorption of 55 mL / 100g or higher and 120 mL / 100g or lower. The average particle size of (H) is preferably 75 nm or higher and 150 nm or lower, and the average particle size of (I) is preferably 15 nm or higher and 70 nm or lower.

[0008] (1) A fuel hose according to the present invention is a fuel hose comprising a tubular inner layer and an outer layer provided in contact with the outer peripheral surface of the inner layer, wherein the inner layer is made of a crosslinked product of a rubber composition containing the following (A) to (E), and the outer layer is made of a crosslinked product of a rubber composition containing the following (F) to (I), the total amount of (H) and (I) being 20 parts by mass or more and 70 parts by mass or less per 100 parts by mass of (F), and the content of (H) being 30% by mass or more and 95% by mass or less of the total amount of (H) and (I): (A) Polyol cross-linked fluororubber (B) Polyol crosslinker (C) Calcium hydroxide (D) Triallyl isocyanurate (E) Peroxide crosslinking agent (F) Acrylonitrile butadiene rubber (G) Paraffin wax (H) Carbon black with an oil absorption of less than 50 mL / 100 g (I) Carbon black with an oil absorption of 50 mL / 100 g or more

[0009] (2) In the above (1), (G) is preferably a paraffin wax having a melting point of 45°C or higher and 75°C or lower.

[0010] (3) In the above (1) or (2), the content of (G) is preferably 0.5 parts by mass or more and 6.0 parts by mass or less per 100 parts by mass of (F).

[0011] (4) In any one of (1) to (3) above, it is preferable that (H) is carbon black with an oil absorption of 20 mL / 100 g or more and 45 mL / 100 g or less, and (I) is carbon black with an oil absorption of 55 mL / 100 g or more and 120 mL / 100 g or less.

[0012] (5) In any one of (1) to (4) above, it is preferable that the average particle size of (H) is 75 nm or more and 150 nm or less, and the average particle size of (I) is 15 nm or more and 70 nm or less. [Effects of the Invention]

[0013] The fuel hose of the present invention has a tubular inner layer made of a crosslinked rubber composition containing the above-mentioned (A) to (E), and an outer layer provided in contact with the outer peripheral surface of the inner layer made of a crosslinked rubber composition containing the above-mentioned (F) to (I), wherein the total amount of (H) and (I) is a specific amount, and the content of (H) is a specific amount. By incorporating paraffin wax and two specific types of carbon black with different oil absorptions into the outer layer, the paraffin wax is unevenly distributed at the interface between the outer layer containing acrylonitrile-butadiene rubber and the inner layer, and appears at the adhesive interface between the inner layer and the outer layer. This paraffin wax suppresses scorching (discoloration) of the polyol-crosslinked fluororubber due to calcium hydroxide at the adhesive interface between the inner layer and the outer layer, resulting in excellent adhesion between the polyol-crosslinked fluororubber inner layer and the acrylonitrile-butadiene rubber outer layer, even when stored in an uncrosslinked state after extrusion.

[0014] Here, when (G) is a paraffin wax having a melting point of 45°C or more and 75°C or less, it tends to be unevenly distributed at the interface with the inner layer in the outer layer containing acrylonitrile-butadiene rubber, and is highly effective in suppressing scorch (discoloration) of the polyol-crosslinked fluororubber at the adhesive interface between the inner layer and the outer layer.

[0015] When the content of (G) is 0.5 parts by mass or more and 6.0 parts by mass or less per 100 parts by mass of (F), the effect of suppressing scorch (discoloration) of the polyol cross-linked fluororubber at the adhesive interface between the inner layer and the outer layer is excellent.

[0016] When (H) is carbon black having an oil absorption of 20 mL / 100 g or more and 45 mL / 100 g or less, and (I) is carbon black having an oil absorption of 55 mL / 100 g or more and 120 mL / 100 g or less, the bleeding amount of the paraffin wax in the outer layer is adjusted to an appropriate amount, and an appropriate amount of the paraffin wax is unevenly distributed at the adhesive interface with the fluororubber, thereby providing an excellent effect of suppressing scorch (discoloration) of the polyol-crosslinked fluororubber at the adhesive interface between the inner layer and the outer layer.

[0017] When the average particle size of (H) is 75 nm or more and 150 nm or less and the average particle size of (I) is 15 nm or more and 70 nm or less, the bleeding amount of the paraffin wax in the outer layer is adjusted to an appropriate amount, and an appropriate amount of the paraffin wax is unevenly distributed at the adhesive interface with the fluororubber, thereby achieving an excellent effect of suppressing scorch (discoloration) of the polyol cross-linked fluororubber at the adhesive interface between the inner layer and the outer layer. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a structural diagram showing a fuel hose according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0019] The fuel hose according to the present invention will now be described in detail.

[0020] A fuel hose according to one embodiment of the present invention is shown in Fig. 1. As shown in Fig. 1, the fuel hose 10 includes a tubular inner layer 12 and an outer layer 14 provided in contact with the outer peripheral surface of the inner layer 12.

[0021] The inner layer 12 is composed of a crosslinked rubber composition containing the following components (A) to (E): (A) Polyol cross-linked fluororubber (B) Polyol crosslinker (C) Calcium hydroxide (D) Triallyl isocyanurate (E) Peroxide crosslinking agent

[0022] The polyol-crosslinked fluororubber is a fluororubber having a polyol-crosslinkable moiety. Examples of the polyol-crosslinkable moiety include a moiety having a vinylidene fluoride unit. Examples of the fluororubber having a vinylidene fluoride unit include a copolymer of vinylidene fluoride and hexafluoropropylene, a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene, a copolymer of vinylidene fluoride and trifluorochloroethylene, a terpolymer of vinylidene fluoride, perfluoromethyl ether, and tetrafluoroethylene, and a terpolymer of vinylidene fluoride, tetrafluoroethylene, and propylene. Among these, a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene is particularly preferred. The polyol-crosslinked fluororubber may have a peroxide-crosslinkable moiety, in which case a peroxide crosslinking agent may be used.

[0023] Examples of polyol crosslinking agents include polyhydroxy compounds, such as 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)perfluoropropane, resorcinol, 1,3-dihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxystilbene, 2,6-dihydroxyanthracene, hydroquinone, catechol, 2,2-bis(4-hydroxyphenyl)butane, 4,4-bis(4-hydroxyphenyl)valeric acid, 2,2-bis(4-hydroxyphenyl)tetrafluorodichloropropane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ketone, tri(4-hydroxyphenyl)methane, 3,3',5,5'-tetrachlorobisphenol A, and 3,3',5,5'-tetrabromobisphenol A. Among these, polyhydroxy aromatic compounds are preferred from the viewpoint of excellent heat resistance, and 2,2-bis(4-hydroxyphenyl)propane is particularly preferred.

[0024] The amount of polyol cross-linking agent is preferably 0.2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of polyol cross-linked fluororubber. When the amount is 0.2 parts by mass or more, the cross-linking density can be increased and the compression set can be kept small. When the amount is 10 parts by mass or less, the cross-linking density can be prevented from becoming too high and cracking during compression can be suppressed. The amount is more preferably 0.5 parts by mass or more and 7.0 parts by mass or less, and even more preferably 1.0 parts by mass or more and 5.0 parts by mass or less.

[0025] Calcium hydroxide is used as a cross-linking accelerator for polyol-cross-linked fluororubber. The amount of calcium hydroxide is preferably 1.0 parts by mass or more and 10 parts by mass or less per 100 parts by mass of polyol-cross-linked fluororubber. The amount is more preferably 2.0 parts by mass or more and 8.0 parts by mass or less, and even more preferably 3.0 parts by mass or more and 7.0 parts by mass or less.

[0026] Triallyl isocyanurate is used as a co-crosslinking agent. By blending triallyl isocyanurate, the adhesive strength between the inner layer 12 and the outer layer 14 can be improved. The blending amount of triallyl isocyanurate is preferably 0.2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the polyol-crosslinked fluororubber. The blending amount is more preferably 0.3 parts by mass or more and 5.0 parts by mass or less, and even more preferably 0.4 parts by mass or more and 3.0 parts by mass or less.

[0027] The peroxide crosslinking agent can be used together with the co-crosslinking agent to improve the adhesive strength between the inner layer 12 and the outer layer 14. The amount of the peroxide crosslinking agent is preferably 0.1 to 5.0 parts by mass per 100 parts by mass of the polyol-crosslinked fluororubber. The amount is more preferably 0.2 to 3.0 parts by mass, and even more preferably 0.3 to 2.0 parts by mass.

[0028] Examples of peroxide crosslinking agents include 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)octane, n-butyl-4,4-bis(t-butylperoxy)butane, and n-butyl-4,4-bis(t peroxyketals such as di-t-butylperoxide, dicumyl peroxide, t-butylcumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, α,α'-bis(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, and the like; acetyl peroxide, isobutyryl peroxide, Diacyl peroxides such as octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and m-trioyl peroxide, as well as t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxylaurate, t-butyl peroxybenzoate, and di-t-butyl peroxy Examples include peroxyesters such as diisophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, and cumylperoxyoctate, and hydroperoxides such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, and 1,1,3,3-tetramethylbutyl peroxide. These may be used alone or in combination of two or more.

[0029] The rubber composition forming the inner layer 12 may contain additives that are typically compounded in fluororubbers, as needed. Examples of such additives include fillers, processing aids, plasticizers, colorants, stabilizers, adhesion aids, acid acceptors, mold release agents, electrical conductivity imparting agents, thermal conductivity imparting agents, surface anti-tack agents, flexibility imparting agents, heat resistance improving agents, and flame retardants. Examples of acid acceptors include magnesium oxide and hydrotalcite. Examples of fillers include carbon black.

[0030] The outer layer 14 is composed of a crosslinked rubber composition containing the following components (F) to (I). (F) Acrylonitrile butadiene rubber (G) Paraffin wax (H) Carbon black with an oil absorption of less than 50 mL / 100 g (I) Carbon black with an oil absorption of 50 mL / 100 g or more

[0031] Examples of acrylonitrile-butadiene rubber include acrylonitrile-butadiene rubber (NBR) and a blend of acrylonitrile-butadiene rubber and polyvinyl chloride (NBR+PVC). The higher the NBR content, the better the adhesion to the inner layer 12 containing polyol-crosslinked fluororubber. The inclusion of a PVC component tends to reduce adhesion to the inner layer 12 containing polyol-crosslinked fluororubber, but improves weather resistance such as ozone resistance. Of the acrylonitrile-butadiene rubbers, NBR is preferred from the standpoint of adhesion to the inner layer 12 containing polyol-crosslinked fluororubber, and NBR+PVC is preferred from the standpoint of weather resistance such as ozone resistance.

[0032] The PVC content in the NBR+PVC is preferably 15 to 45 parts by mass per 100 parts by mass of the blend rubber. When the PVC content is 15 parts by mass or more, weather resistance such as ozone resistance is excellent. When the PVC content is 45 parts by mass or less, the effect of improving adhesion to the inner layer 12 containing a polyol cross-linked fluororubber is excellent. From the above viewpoints, the PVC content in the NBR+PVC is more preferably 20 to 40 parts by mass per 100 parts by mass of the blend rubber.

[0033] The acrylonitrile content in acrylonitrile-butadiene rubber (NBR) is preferably 28% by mass to 42% by mass based on 100% by mass of NBR. When the acrylonitrile content is 28% by mass or more, excellent gasoline resistance is achieved. When the acrylonitrile content is 42% by mass or less, the effect of improving adhesion to the inner layer 12 containing polyol-crosslinked fluororubber is excellent. From the above viewpoints, the acrylonitrile content in NBR is preferably 30% by mass to 40% by mass based on 100% by mass of NBR.

[0034] Examples of crosslinking agents for acrylonitrile-butadiene rubber include sulfur and peroxide crosslinking agents. Examples of peroxide crosslinking agents include those exemplified in (E) above.

[0035] The amount of the crosslinking agent for the acrylonitrile-butadiene rubber to be compounded is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 4.0 parts by mass, per 100 parts by mass of the acrylonitrile-butadiene rubber, from the viewpoints of crosslinkability and suppression of scorch.

[0036] The above crosslinking agents may be used alone or in combination with a strong base, an acid acceptor, etc. Examples of strong bases include 1,8-diazabicyclo(5,4,0)undecene-7 salt (DBU salt).

[0037] Examples of DBU salts include DBU salts of carboxylic acids such as naphthoic acid, 2-hydroxynaphthoic acid, sorbic acid, 2-ethylhexyl acid, gallic acid, p-hydroxybenzoic acid, and cinnamic acid, and DBU salts of phenolic resins. Of these, DBU salts of naphthoic acid and phenolic resins are particularly preferred.

[0038] The amount of DBU salt to be compounded is preferably 0.1 to 5.0 parts by mass, more preferably 0.3 to 3.0 parts by mass, per 100 parts by mass of acrylonitrile-butadiene rubber, from the viewpoints of crosslinkability and suppression of scorch.

[0039] The paraffin wax is used to prevent scorching (discoloration) of the polyol-crosslinked fluororubber caused by calcium hydroxide at the adhesive interface between the inner layer 12 and the outer layer 14. Paraffin wax is a wax that is solid at room temperature and is separated and refined from vacuum distillate oil, and is primarily composed of linear hydrocarbons (normal paraffins). The "main component" refers to a component that accounts for 50% by mass or more of 100% by mass of the paraffin wax and is closely related to the properties of the paraffin wax. The "main component" refers to a component that accounts for 50% by mass or more of 100% by mass of the paraffin wax, more preferably 55% by mass or more, and even more preferably 60% by mass or more of 100% by mass of the paraffin wax. As long as the paraffin wax contains normal paraffin as the primary component, it may also contain other components such as branched hydrocarbons (isoparaffins) and cyclic hydrocarbons (cycloparaffins).

[0040] The paraffin wax preferably has a melting point of 45°C or higher and 75°C or lower. If the melting point is lower than 45°C, the effect of suppressing scorch (discoloration) of the polyol cross-linked fluororubber is likely to be reduced. If the melting point is higher than 75°C, the molecular weight is large and the wax is less likely to be unevenly distributed at the interface between the outer layer 14 and the inner layer 12, making it difficult to exhibit the effect of suppressing scorch (discoloration) of the polyol cross-linked fluororubber at the adhesive interface between the inner layer 12 and the outer layer 14. From the viewpoint of the effect of suppressing scorch (discoloration) of the polyol cross-linked fluororubber, the melting point of the paraffin wax is more preferably 50°C or higher and 75°C or lower, even more preferably 55°C or higher and 75°C or lower, and particularly preferably 60°C or higher and 75°C or lower.

[0041] The paraffin wax is preferably a hydrocarbon having 20 to 60 carbon atoms. If the carbon number is less than 20, the effect of suppressing scorch (discoloration) of the polyol cross-linked fluororubber is likely to be reduced. If the carbon number is more than 60, the molecular weight is large, making it difficult to be unevenly distributed at the interface between the outer layer 14 and the inner layer 12, and the effect of suppressing scorch (discoloration) of the polyol cross-linked fluororubber at the adhesive interface between the inner layer 12 and the outer layer 14 is unlikely to be achieved. From the viewpoint of the effect of suppressing scorch (discoloration) of the polyol cross-linked fluororubber, the paraffin wax preferably contains 3 to 60 mass% of hydrocarbons having 35 to 59 carbon atoms. This is more preferably 5 to 50 mass%, even more preferably 10 to 40 mass%, and particularly preferably 20 to 40 mass%. The carbon number of the paraffin wax is a value measured by gas chromatography.

[0042] The amount of paraffin wax to be blended is preferably 0.5 to 6.0 parts by mass, more preferably 0.5 to 4.0 parts by mass, and even more preferably 1.0 to 3.0 parts by mass, per 100 parts by mass of acrylonitrile-butadiene rubber, from the viewpoint of achieving a superior effect of suppressing scorching (discoloration) of the polyol-crosslinked fluororubber.

[0043] (I) Carbon black with an oil absorption of 50 mL / 100 g or more has a relatively small particle size and is added to reinforce acrylonitrile-butadiene rubber. (I) Carbon black with an oil absorption of 50 mL / 100 g or more has a high oil absorption, making it easy to retain paraffin wax. This tends to prevent paraffin wax from bleeding. On the other hand, (H) carbon black with an oil absorption of less than 50 mL / 100 g has a relatively large particle size, which leads to a decrease in the strength of acrylonitrile-butadiene rubber. Due to its large particle size and low oil absorption, it is difficult to retain paraffin wax. The amount of paraffin wax bleeding can be adjusted by combining (I) carbon black with an oil absorption of 50 mL / 100 g or more and (H) carbon black with an oil absorption of less than 50 mL / 100 g with paraffin wax. (H) Carbon black with an oil absorption of less than 50 mL / 100 g leads to a decrease in the strength of acrylonitrile-butadiene rubber. However, by using it, it is possible to optimize the amount of paraffin wax that bleeds out, thereby suppressing scorching (discoloration) of the polyol cross-linked fluororubber at the adhesive interface between the inner and outer layers.

[0044] From the above viewpoints, (I) carbon black having an oil absorption of 50 mL / 100 g or more preferably has an oil absorption of 55 mL / 100 g or more, even more preferably 60 mL / 100 g or more, and particularly preferably 65 mL / 100 g or more. On the other hand, the upper limit of the oil absorption of (I) carbon black having an oil absorption of 50 mL / 100 g or more is not particularly limited, but from the viewpoints of achieving the above-mentioned effects, it is preferably 120 mL / 100 g or less, more preferably 100 mL / 100 g or less, and even more preferably 80 mL / 100 g or less.

[0045] From the above viewpoints, (H) carbon black having an oil absorption of less than 50 mL / 100 g preferably has an oil absorption of 45 mL / 100 g or less, even more preferably 40 mL / 100 g or less, and particularly preferably 35 mL / 100 g or less. On the other hand, the lower limit of the oil absorption of (H) carbon black having an oil absorption of less than 50 mL / 100 g is not particularly limited, but from the viewpoint of achieving the above-mentioned effects, it is more preferably 20 mL / 100 g or more, even more preferably 25 mL / 100 g or more. The oil absorption of carbon black is calculated from the amount of DBP (dibutyl phthalate) absorbed by 100 g of carbon black in accordance with JIS K6221.

[0046] The total amount of (H) and (I) is preferably 20 to 70 parts by mass relative to 100 parts by mass of (F). The content of (H) is preferably 30 to 95% by mass relative to the total amount of (H) and (I). This optimizes the amount of bleeding of the paraffin wax and suppresses scorching (discoloration) of the polyol-crosslinked fluororubber at the adhesive interface between the inner layer and the outer layer. From this perspective, the total amount of (H) and (I) is more preferably 30 to 60 parts by mass, and even more preferably 40 to 60 parts by mass, relative to 100 parts by mass of (F). The content of (H) is more preferably 40 to 90% by mass, and even more preferably 50 to 80% by mass, relative to the total amount of (H) and (I).

[0047] The average particle size of (H) is preferably 75 nm or more and 150 nm or less, more preferably 75 nm or more and 130 nm or less, and even more preferably 75 nm or more and 100 nm or less. The average particle size of (I) is preferably 15 nm or more and 70 nm or less, more preferably 20 nm or more and 70 nm or less, and even more preferably 30 nm or more and 70 nm or less. This allows the amount of paraffin wax bleeding in the outer layer 14 to be properly adjusted, and the appropriate amount of paraffin wax is unevenly distributed at the adhesive interface with the fluororubber, thereby providing an excellent effect of suppressing scorch (discoloration) of the polyol-crosslinked fluororubber at the adhesive interface between the inner layer 12 and the outer layer 14. The average particle size of carbon black is expressed as the arithmetic mean diameter determined by observing the carbon black with an electron microscope.

[0048] The rubber composition forming the outer layer 14 may contain other components as needed, such as an acid acceptor, a plasticizer, a filler, a processing aid, a colorant, a stabilizer, an adhesion aid, a release agent, an electrical conductivity imparting agent, a thermal conductivity imparting agent, a surface anti-tack agent, a flexibility imparting agent, a heat resistance improving agent, an antioxidant, a pigment, a flame retardant, a crosslinking accelerator, and a crosslinking retarder.

[0049] As the plasticizer, an ester-based synthetic plasticizer can be used. Examples of the ester-based synthetic plasticizer include phthalate esters, adipate esters, and adipate polyesters. Examples of the phthalate esters include diisononyl phthalate (DINP) and di-n-butyl phthalate (DBP). Examples of the adipate esters include dioctyl adipate (DOA), dibutyl glycol adipate, and dibutyl carbitol adipate.

[0050] The amount of the plasticizer to be mixed is preferably 3 parts by mass or more and 30 parts by mass or less, and more preferably 5 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of the acrylonitrile-butadiene rubber.

[0051] The fuel hose 10 can be manufactured as follows. First, a rubber composition for forming the inner layer and a rubber composition for forming the outer layer are prepared, and the rubber composition for forming the inner layer is extruded into a cylindrical shape. After that, the rubber composition for forming the outer layer is directly extruded without applying an adhesive to the surface (outer periphery) of the extruded inner layer to form an uncrosslinked laminate. The uncrosslinked laminate can be stored as appropriate. Next, the layers are crosslinked to manufacture the fuel hose 10. The layers may also be formed by coextrusion.

[0052] The fuel hose 10 according to the present invention has a tubular inner layer 12 made of a crosslinked rubber composition containing the above-mentioned (A) to (E), an outer layer 14 provided in contact with the outer peripheral surface of the inner layer 12 made of a crosslinked rubber composition containing the above-mentioned (F) to (I), and the total amount of (H) and (I) is a specific amount, and the content of (H) is a specific amount. By incorporating paraffin wax and two specific types of carbon black with different oil absorptions into the outer layer 14, the paraffin wax is unevenly distributed at the interface with the inner layer 12 in the outer layer 14 containing acrylonitrile-butadiene rubber, and appears at the adhesive interface between the inner layer 12 and the outer layer 14. The paraffin wax prevents calcium hydroxide from scorching the polyol-crosslinked fluororubber at the adhesive interface between the inner layer 12 and the outer layer 14, resulting in excellent adhesion between the polyol-crosslinked fluororubber inner layer 12 and the acrylonitrile-butadiene rubber outer layer 14, even when stored in an uncrosslinked state after extrusion.

[0053] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention. [Example]

[0054] The present invention will be described in detail below using examples and comparative examples.

[0055] Example 1 <Preparation of Rubber Composition for Forming Inner Layer> For 100 parts by mass of polyol cross-linked fluororubber (containing polyol cross-linking agent), 6 parts by mass of calcium hydroxide (cross-linking accelerator), 1 part by mass of triallyl isocyanurate (co-cross-linking agent), 1 part by mass of peroxide cross-linking agent, 3 parts by mass of magnesium oxide (acid acceptor), and carbon black <3> The resulting mixture was kneaded using a kneader to prepare a rubber composition for forming an inner layer.

[0056] <Preparation of Rubber Composition for Forming Outer Layer> Acrylonitrile butadiene rubber <2> Paraffin wax per 100 parts by mass <1> 2.0 parts by mass of carbon black <1> 30 parts by mass of carbon black <3> 20 parts by mass of the above, 5 parts by mass of zinc oxide, 1 part by mass of stearic acid, 1 part by mass of antioxidant, 15 parts by mass of plasticizer, and 2 parts by mass of DBU salt (crosslinking accelerator) were blended and mixed using a Banbury mixer, and then 1 part by mass of crosslinking agent and 2 parts by mass of crosslinking accelerator were added. <1> 1.5 parts by mass of crosslinking accelerator <2> The mixture was kneaded using a roll to prepare a rubber composition for forming an outer layer.

[0057] <Production of fuel hose> The prepared rubber composition for forming the inner layer and the rubber composition for forming the outer layer were co-extruded to produce a fuel hose (inner diameter 25 mm, outer diameter 33 mm) in which an outer layer (thickness 3 mm) was laminated on the outer periphery of an inner layer (thickness 1 mm).

[0058] (Examples 2-3, Comparative Example 1) A fuel hose was produced in the same manner as in Example 1, except that the type of wax used in preparing the rubber composition for forming the outer layer was changed.

[0059] (Examples 4-5) A fuel hose was produced in the same manner as in Example 1, except that the amount of wax compounded was changed in the preparation of the rubber composition for forming the outer layer.

[0060] (Examples 6-10, Comparative Examples 2-5) A fuel hose was produced in the same manner as in Example 1, except that the type and amount of carbon black used in preparing the rubber composition for forming the outer layer were changed.

[0061] Example 11 A fuel hose was produced in the same manner as in Example 1, except that the type of acrylonitrile-butadiene rubber used in preparing the rubber composition for forming the outer layer was changed.

[0062] The materials used are as follows: (Fluororubber composition) Polyol cross-linked fluoroelastomer (containing polyol cross-linking agent): Daikin Industries, Ltd. "Daiel G-558" Calcium hydroxide Triallyl isocyanurate: "Taiku" manufactured by Mitsubishi Chemical Peroxide crosslinking agent: NOF's "Perhexa 25B-40" Magnesium oxide Carbon black <3> : Tokai Carbon "Seast S" (Acrylonitrile-butadiene rubber composition) Acrylonitrile butadiene rubber <1> (NBR): "Nipol DN202" manufactured by Nippon Zeon Acrylonitrile butadiene rubber <2> (Contains PVC, NBR+PVC) (NBR / PVC=70 / 30wt) Paraffin wax <1> : Seiko Chemical's "Suntite S" (melting point 68°C, normal paraffin 81% by mass, hydrocarbons with carbon numbers 35 to 59 29% by mass) Paraffin wax <2> : Nippon Seiro's "OZOACE-0062" (melting point 69°C, normal paraffin 76% by mass, hydrocarbons with carbon numbers 35 to 59 44% by mass) Paraffin wax <3> : Nippon Seiro's "Paraffin Wax-135" (melting point 59°C, normal paraffin 89% by mass, hydrocarbons with carbon numbers 35 to 59 4% by mass) Isoparaffin-based wax: Nippon Seiro "Hi-Mic-1080" (melting point 84°C) Carbon black <1> : Asahi Thermal manufactured by Asahi Carbon, oil absorption capacity 29mL / 100g, average particle size 80nm Carbon black <2> : Tokai Carbon "Seast TA", oil absorption capacity 42mL / 100g, average particle size 122nm Carbon black <3> : Tokai Carbon "Seat S", oil absorption capacity 68mL / 100g, average particle size 66nm Carbon black <4> : Tokai Carbon "SEAST 3", oil absorption 101mL / 100g, average particle size 28nm Carbon black <5> : Tokai Carbon "Seast 9", oil absorption capacity 115mL / 100g, average particle size 19nm Zinc oxide: Two types of zinc oxide Stearic acid: NOF Corporation's "Sakura Stearic Acid Beads" Anti-aging agent: Seiko Chemical's "Ozonone 3C" Plasticizer (ether ester type): ADEKA "Adeka Cizer RS107" DBU salt (crosslinking accelerator): Osaka Soda "DA-500" Crosslinker: Sulfur Crosslinking accelerator <1> : "Noccela TET" manufactured by Ouchi Shinko Chemical Industry Crosslinking accelerator <2> : "Noccela CZ" manufactured by Ouchi Shinko Chemical Industry

[0063] The interlayer adhesion and tensile strength of the manufactured fuel hoses were evaluated. The evaluation results are shown in the table together with the formulation.

[0064] (Interlayer adhesion) The prepared fuel hose (laminate) before crosslinking was subjected to wet heat treatment (50°C x 95% RH x 24 hours) and then heated at 160°C for 45 minutes to perform steam crosslinking. 25 mm wide test pieces were cut out from the resulting fuel hose, and the outer layer of each test piece was peeled off at a rate of 50 mm per minute using a tensile tester, and the state of fracture was observed. Those that showed base material fracture were rated as particularly good (◎), those that showed partial base material fracture were rated as good (○), and those that showed interfacial peeling were rated as poor (×).

[0065] (tensile strength) The prepared fuel hose (laminate) before crosslinking was heated at 160°C for 45 minutes to perform steam crosslinking. Samples were taken from the obtained fuel hose by slicing the outer rubber, and JIS No. 5 dumbbells were punched out from the samples. Using these dumbbells, the tensile strength at break was measured in accordance with JIS K6251. A tensile strength of 12 MPa or more was rated as particularly good (◎), a tensile strength of 8 MPa or more was rated as good (◯), and a tensile strength of less than 8 MPa was rated as poor (×).

[0066] [Table 1]

[0067] In Comparative Examples 1 to 4, during storage after extrusion of the inner and outer layers, the uncrosslinked fluororubber in the inner layer scorched at the adhesive interface with the outer layer due to calcium hydroxide (a basic component), resulting in discoloration. This resulted in poor interlayer adhesion between the inner layer containing polyol-crosslinked fluororubber and the outer layer containing acrylonitrile-butadiene rubber, resulting in interfacial delamination in a peel test. In Comparative Example 5, the material strength was insufficient. On the other hand, in the Example, such discoloration was not observed during storage after extrusion of the inner and outer layers, and the interlayer adhesion between the inner layer containing polyol-crosslinked fluororubber and the outer layer containing acrylonitrile-butadiene rubber was excellent, resulting in base material failure rather than interfacial delamination in a peel test. Furthermore, the material strength was also excellent.

[0068] Comparing the Examples and Comparative Examples, the Examples contain paraffin wax and two specific types of carbon black with different oil absorptions in the outer layer containing acrylonitrile-butadiene rubber, whereas Comparative Example 1 contains a wax whose main component is isoparaffin rather than paraffin wax in the outer layer containing acrylonitrile-butadiene rubber. Comparative Examples 4 and 5 contain only paraffin wax and one type of carbon black in the outer layer containing acrylonitrile-butadiene rubber. Comparative Example 2 contains paraffin wax and two specific types of carbon black with different oil absorptions in the outer layer containing acrylonitrile-butadiene rubber, but the proportion of carbon black with low oil absorptions is too low. Comparative Example 3 contains paraffin wax and two specific types of carbon black with different oil absorptions in the outer layer containing acrylonitrile-butadiene rubber, but the amount of carbon black blended is too high. From this, it can be said that by blending specific amounts of paraffin wax and two specific types of carbon black with different oil absorption amounts into the outer layer containing acrylonitrile-butadiene rubber, as in the examples, excellent adhesion can be achieved between the polyol-crosslinked fluororubber inner layer and the acrylonitrile-butadiene rubber outer layer, even if the inner and outer layers are stored in an uncrosslinked state after extrusion molding.

[0069] Next, comparing the Examples, Examples 1 to 3 show that the above-mentioned effect is particularly excellent when the melting point of the paraffin wax is 60°C or higher and 75°C or lower. Furthermore, Examples 1, 4, and 5 show that the above-mentioned effect is particularly excellent when the blending amount of the paraffin wax is 1 to 5 parts by mass per 100 parts by mass of the acrylonitrile-butadiene rubber. Furthermore, Examples 1 and 6 show that the above-mentioned effect is particularly excellent when the oil absorption of the (H) carbon black is 40 mL / 100 g or less. Furthermore, Examples 1, 7, and 8 show that the above-mentioned effect is particularly excellent when the oil absorption of the (I) carbon black is 100 mL / 100 g or less.

[0070] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various modifications are possible within the scope of the invention. [Explanation of symbols]

[0071] 10 Fuel hose 12 Inner layer 14 Outer layer

Claims

1. A fuel hose comprising a tubular inner layer and an outer layer provided in contact with an outer peripheral surface of the inner layer, the inner layer is composed of a crosslinked product of a rubber composition containing the following (A) to (E), the outer layer is composed of a crosslinked product of a rubber composition containing the following (F) to (I), the total amount of (H) and (I) is 20 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of (F); A fuel hose, wherein the content of the (H) is 30 mass % or more and 95 mass % or less based on the total amount of the (H) and the (I). (A) Polyol cross-linked fluororubber (B) Polyol crosslinking agent (C) Calcium hydroxide (D) Triallyl isocyanurate (E) Peroxide crosslinking agent (F) Acrylonitrile butadiene rubber (G) Paraffin wax (H) Carbon black having an oil absorption of less than 50 mL / 100 g (I) Carbon black with an oil absorption of 50 mL / 100 g or more

2. 2. The fuel hose according to claim 1, wherein the wax (G) is a paraffin wax having a melting point of 45° C. or higher and 75° C. or lower.

3. 3. The fuel hose according to claim 1, wherein an amount of the component (G) is 0.5 parts by mass or more and 6.0 parts by mass or less per 100 parts by mass of the component (F).

4. 3. The fuel hose according to claim 1, wherein the (H) is carbon black having an oil absorption of 20 mL / 100 g or more and 45 mL / 100 g or less, and the (I) is carbon black having an oil absorption of 55 mL / 100 g or more and 120 mL / 100 g or less.

5. 3. The fuel hose according to claim 1, wherein the average particle size of the (H) particles is 75 nm or more and 150 nm or less, and the average particle size of the (I) particles is 15 nm or more and 70 nm or less.

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