Composition for vehicle coolant transport hose, and vehicle coolant transport hose

Abstract

Provided is a composition for a vehicle coolant transport hose which ensures excellent permanent compression set properties and exhibits excellent heat resistance and extraction resistance; and a vehicle coolant transport hose.　The composition for a vehicle coolant transport hose contains components (A) to (F), and the content of component (F) is 0.02-0.5 parts by mass relative to a total of 100 parts by mass of components (A) to (C). The vehicle coolant transport hose is made of the composition for a vehicle coolant transport hose. (A) an ethylene·α-olefin·non-conjugated diene copolymer rubber, (B) an ethylene·α-olefin copolymer rubber having no non-conjugated diene unit, (C) one or more resins selected from among polyethylene and polypropylene-based resins, (D) an unsaturated silane compound, (E) a peroxide, and (F) an anti-aging agent having a melting point of 60ºC or higher.

Description

Composition for vehicle coolant transport hose and vehicle coolant transport hose

[0001] The present invention relates to a composition for a hose for transporting coolant for a vehicle and a hose for transporting coolant for a vehicle, and more particularly to a composition for a hose for transporting coolant for a vehicle and a hose for transporting coolant for a vehicle that are suitable as a hose for transporting coolant in a cooling system of an automobile or the like.

[0002] Coolant transport hoses are used to transport coolants in the cooling systems of gasoline-powered vehicles, electric vehicles, and the like. Polyamide resins are often used for coolant transport hoses due to their heat resistance. In recent years, cost-effective propylene-based resins have been considered as materials for coolant transport hoses. It is also known that dynamically crosslinked olefin-based thermoplastic elastomers (partially crosslinked TPVs) dynamically crosslinked using peroxides as a crosslinking agent are used for water hoses for fuel cells (Patent Document 1).

[0003] JP 2013-037972 A

[0004] When partially crosslinked TPV is used as a material for a coolant transport hose, it has poor compression set properties and problems with fastening when connecting the hose. To solve the fastening problem, when a dynamically crosslinked thermoplastic elastomer (water-crosslinked TPV) made from an unsaturated silane compound and peroxide is used as a material for a coolant transport hose, it has the problem of poor heat resistance. However, when an antioxidant is added to the material to improve heat resistance, components derived from the antioxidant tend to be extracted (eluted) into the coolant, which can lead to clogging of filters in the vehicle cooling system, and the extracted components can increase the conductivity of the coolant, causing short circuits and electric leakage.

[0005] The problem to be solved by the present invention is to provide a composition for a hose for transporting a coolant in a vehicle, which ensures excellent compression set properties, and which has excellent heat resistance and extraction resistance, and a hose for transporting a coolant in a vehicle.

[0006] The composition for a vehicle coolant transport hose according to the present invention contains the following (A) to (F), and the content of (F) is 0.02 parts by mass or more and 0.5 parts by mass or less relative to 100 parts by mass of the total of (A) to (C): (A) ethylene / α-olefin / non-conjugated diene copolymer rubber, (B) ethylene / α-olefin copolymer rubber containing no non-conjugated diene units, (C) one or more resins selected from polyethylene and propylene-based resins, (D) an unsaturated silane compound, (E) a peroxide, and (F) an antioxidant having a melting point of 60°C or more.

[0007] The melting point of (F) is preferably 90°C or higher. The (F) is preferably a phenol-based antioxidant. The (F) is preferably a hindered phenol-based antioxidant. The (C) is preferably a propylene-based resin having a melt flow rate of 0.1 g / 10 min or higher and 50 g / 10 min or lower, measured at 230°C under a load of 2.16 kg. The (C) is preferably a propylene-based resin having a melting point of 145°C or higher.

[0008] The hose for transporting a coolant for a vehicle according to the present invention comprises a crosslinked product of the above-mentioned composition for a hose for transporting a coolant for a vehicle.

[0009] (1) The composition for a vehicle coolant transport hose according to the present invention contains the following (A) to (F), and the content of (F) is 0.02 to 0.5 parts by mass per 100 parts by mass of the total of (A) to (C): (A) ethylene / α-olefin / non-conjugated diene copolymer rubber (B) ethylene / α-olefin copolymer rubber containing no non-conjugated diene units (C) one or more resins selected from polyethylene and propylene-based resins (D) unsaturated silane compound (E) peroxide (F) antioxidant having a melting point of 60°C or higher

[0010] (2) In the above (1), the melting point of (F) is preferably 90° C. or higher.

[0011] (3) In the above (1) or (2), (F) may be a phenol-based antioxidant.

[0012] (4) In any one of the above (1) to (3), the (F) may be a hindered phenol-based antioxidant.

[0013] (5) In any one of the above (1) to (4), (C) may be a propylene-based resin having a melt flow rate of 0.1 g / 10 min or more and 50 g / 10 min or less, measured at 230° C. under a load of 2.16 kg.

[0014] (6) In any one of the above (1) to (5), (C) may be a propylene-based resin having a melting point of 145° C. or higher.

[0015] (7) A hose for transporting a coolant for a vehicle according to the present invention comprises a crosslinked product of the composition for a hose for transporting a coolant for a vehicle according to any one of (1) to (6) above.

[0016] The composition for a vehicle coolant transport hose according to the present invention contains the above-mentioned components (A) to (F), with the content of (F) being a specific amount. That is, the composition is a dynamically crosslinked thermoplastic elastomer (water-crosslinked TPV) using an unsaturated silane compound and a peroxide, and a specific antioxidant is used. This ensures excellent compression set properties, as well as excellent heat resistance and extraction resistance.

[0017] When the melting point of (F) is 90° C. or higher, components derived from the antioxidant are less likely to be extracted (eluted) in the coolant, improving the effects of heat resistance and extraction resistance.

[0018] When (F) is a phenol-based antioxidant, components derived from the antioxidant are less likely to be extracted (eluted) in the coolant, improving the heat resistance and extraction resistance. When (F) is a hindered phenol-based antioxidant, the heat resistance is particularly excellent.

[0019] When (C) is a propylene-based resin having a melt flow rate of 0.1 g / 10 min or more and 50 g / 10 min or less, as measured at 230°C under a load of 2.16 kg, compatibility with the antioxidant (F) is increased, making it difficult for components derived from the antioxidant to be extracted (eluted) in the coolant, thereby improving the heat resistance and extraction resistance. When (C) is a propylene-based resin having a melting point of 145°C or more, compatibility with the antioxidant (F) is increased, making it difficult for components derived from the antioxidant to be extracted (eluted) in the coolant, thereby improving the heat resistance and extraction resistance.

[0020] The hose for transporting a vehicle coolant according to the present invention is made from a crosslinked product of the above-mentioned composition for a hose for transporting a vehicle coolant, and therefore has excellent compression set properties, heat resistance, and extraction resistance.

[0021] 1 is a structural diagram showing a vehicle coolant transport hose according to an embodiment of the present invention;

[0022] The composition for a hose for transporting a coolant for a vehicle and the hose for transporting a coolant for a vehicle according to the present invention will now be described in detail.

[0023] The composition for a vehicle coolant transport hose according to the present invention (hereinafter, sometimes referred to as the present composition) contains the following (A) to (F): (A) an ethylene / α-olefin / non-conjugated diene copolymer rubber; (B) an ethylene / α-olefin copolymer rubber containing no non-conjugated diene units; (C) one or more resins selected from polyethylene and propylene-based resins; (D) an unsaturated silane compound; (E) a peroxide; and (F) an antioxidant having a melting point of 60°C or higher.

[0024] The ethylene-α-olefin-non-conjugated diene copolymer rubber (A) is a copolymer containing ethylene, an α-olefin, and a non-conjugated diene compound as copolymerization components. The ethylene-α-olefin-non-conjugated diene copolymer rubber may be an oil-extended type or a non-oil-extended type. It may also be a mixture of an oil-extended type and a non-oil-extended type. The oil-extended type is a mixture of an ethylene-α-olefin-non-conjugated diene copolymer rubber and a hydrocarbon-based rubber softener. In the oil-extended type, the content of the hydrocarbon-based rubber softener may be 10 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the ethylene-α-olefin-non-conjugated diene copolymer rubber.

[0025] In (A), the α-olefin is preferably an α-olefin having 3 to 20 carbon atoms. More preferably, it is an α-olefin having 3 to 8 carbon atoms. Examples of α-olefins include propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, 1-octene, 1-decene, and 1-octadecene. These α-olefins may be used alone or in combination of two or more. Of these, from the viewpoints of excellent crosslinkability and resistance to blooming out, propylene, 1-butene, 3-methyl-1-butene, and 1-pentene are preferred. Propylene and 1-butene are more preferred.

[0026] In (A), examples of the non-conjugated diene compound include dicyclopentadiene, 1,4-hexadiene, cyclohexadiene, cyclooctadiene, dicyclooctadiene, 1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 1,3-cyclopentadiene, 1,4-cyclohexadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, tetrahydroindene, methyltetrahydroindene, 5-isopropylidene-2-norbornene, 5-vinyl-2-norbornene, vinylidene norbornene, ethylidene norbornenes such as 5-ethylidene-2-norbornene, and 5-methylene-2-norbornene. These may be used alone or in combination as the non-conjugated diene compound (A). Among these, dicyclopentadiene, ethylidene norbornene, and vinylidene norbornene are preferred from the viewpoint of excellent crosslinkability. Dicyclopentadiene, 5-ethylidene-2-norbornene, and vinylidene norbornene are more preferred.

[0027] Specific examples of the ethylene-α-olefin-non-conjugated diene copolymer rubber (A) include ethylene-propylene-non-conjugated diene copolymer rubbers (EPDM) such as ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber, ethylene-propylene-dicyclopentadiene copolymer rubber, ethylene-propylene-1,4-hexadiene copolymer rubber, and ethylene-propylene-5-vinyl-2-norbornene copolymer rubber, as well as ethylene-1-butene-5-ethylidene-2-norbornene copolymer rubber. These may be used alone as the ethylene-α-olefin-non-conjugated diene copolymer rubber (A), or two or more may be used in combination. Among these, ethylene-propylene-non-conjugated diene copolymer rubber (EPDM) is preferred from the viewpoints of excellent crosslinkability and resistance to blooming out.

[0028] The ethylene unit content in the ethylene / α-olefin / non-conjugated diene copolymer rubber (A) is preferably 50% by mass or more and 90% by mass or less, more preferably 55% by mass or more and 85% by mass or less, and even more preferably 60% by mass or more and 80% by mass or less, from the viewpoints of mechanical strength, rubber elasticity, etc.

[0029] The content of α-olefin units in the ethylene / α-olefin / non-conjugated diene copolymer rubber (A) is preferably 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 45% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less, from the viewpoints of mechanical strength, flexibility, rubber elasticity, etc.

[0030] The content of non-conjugated diene units in the ethylene / α-olefin / non-conjugated diene copolymer rubber (A) is preferably 0.5% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 20% by mass or less, and even more preferably 2% by mass or more and 10% by mass or less, from the viewpoints of mechanical strength, rubber elasticity, etc.

[0031] From the viewpoints of mechanical strength, rubber elasticity, etc., the ethylene-α-olefin-non-conjugated diene copolymer rubber (A) preferably has an ethylene unit content of 55% by mass to 75% by mass, a propylene unit content of 15% by mass to 40% by mass, and a non-conjugated diene unit content of 1% by mass to 10% by mass. In this case, the non-conjugated diene unit is preferably one or more of dicyclopentadiene, ethylidene norbornene, and vinylidene norbornene.

[0032] The content of each structural unit in the ethylene / α-olefin / non-conjugated diene copolymer rubber (A) can be determined by infrared spectroscopy.

[0033] The ethylene / α-olefin copolymer (B) is an ethylene / α-olefin copolymer rubber that does not contain non-conjugated diene units. The α-olefin in (B) is preferably an α-olefin having 3 to 10 carbon atoms. Examples of the α-olefin in (B) include those exemplified as the α-olefin in (A).

[0034] Specific examples of the ethylene / α-olefin copolymer (B) include an ethylene / propylene copolymer, an ethylene / 1-butene copolymer, an ethylene / 4-methyl-1-pentene copolymer, an ethylene / 1-hexene copolymer, and an ethylene / 1-octene copolymer. These may be used alone as the ethylene / α-olefin copolymer (B), or two or more may be used in combination. Of these, from the viewpoint of ease of crosslinking, an ethylene / 1-butene copolymer, an ethylene / 1-hexene copolymer, and an ethylene / 1-octene copolymer are preferred. From the viewpoint of excellent low-temperature properties, an ethylene / 1-octene copolymer is more preferred.

[0035] The content of ethylene units in the ethylene / α-olefin copolymer (B) is preferably 60% by mass or more and 99% by mass or less, more preferably 60% by mass or more and 90% by mass or less, and even more preferably 60% by mass or more and 85% by mass or less, from the viewpoints of mechanical strength, rubber elasticity, etc.

[0036] The content of α-olefin units in the ethylene / α-olefin copolymer (B) is preferably 1% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 40% by mass or less, and even more preferably 15% by mass or more and 40% by mass or less, from the viewpoints of mechanical strength, rubber elasticity, etc.

[0037] The content of each structural unit in the ethylene / α-olefin copolymer (B) can be determined by infrared spectroscopy.

[0038] The melt flow rate (MFR) of the ethylene / α-olefin copolymer (B) is preferably 0.01 g / 10 min or more and 30 g / 10 min or less from the viewpoints of compression set, productivity, etc., and more preferably 0.1 g / 10 min or more and 10 g / 10 min or less. The melt flow rate (MFR) of the ethylene / α-olefin copolymer is measured in accordance with JIS K7210 (1999) under conditions of a temperature of 230°C and a load of 2.16 kg.

[0039] The density of the ethylene-α-olefin copolymer (B) is set to 0.850 g / cm3 from the viewpoints of flexibility, compression set, etc. ３0.910g / cm or more ３ More preferably, it is 0.860 g / cm or less. ３ 0.900g / cm or more ３ More preferably, 0.850 g / cm ３ 0.880g / cm or more ３ The density of the ethylene / α-olefin copolymer (B) can be measured in accordance with JIS K 6922-1, 2:1997.

[0040] The melting end peak temperature of the ethylene / α-olefin copolymer (B) measured by a differential scanning calorimeter (DSC) is preferably 115°C or higher and 145°C or lower, from the viewpoints of being able to maintain the shape due to crystallization even at high temperatures and suppressing premature crystallization (melt fracture) during molding and cooling.

[0041] In the present composition, (A) is preferably 5 parts by mass or more and 70 parts by mass or less, relative to 100 parts by mass of the total of (A) and (B). More preferably, it is 5 parts by mass or more and 50 parts by mass or less. Furthermore, (B) is preferably 30 parts by mass or more and 95 parts by mass or less, relative to 100 parts by mass of the total of (A) and (B). More preferably, it is 50 parts by mass or more and 95 parts by mass or less. If the proportion of (A) is low, blocking tends to be difficult to suppress. If the proportion of (B) is low, it tends to be difficult to obtain a good appearance.

[0042] (C) is one or more resins selected from polyethylene and propylene-based resins. (C) is more preferably a propylene-based resin. While the strength of the rubbers (A) and (B) alone is low, the inclusion of resin (C) ensures the strength required for a single-layer hose.

[0043] In (C), examples of the polyethylene include high-density polyethylene (low-pressure polyethylene), low-density polyethylene (high-pressure polyethylene), and linear low-density polyethylene. These may be used alone or in combination of two or more as the polyethylene of (C). Of these, high-density polyethylene is preferred.

[0044] In (C), examples of the propylene-based resin include propylene homopolymers, propylene-α-olefin random copolymers, and propylene-α-olefin block copolymers. These may be used alone or in combination of two or more as the propylene-based resin of (C). Examples of the α-olefin include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Of these, ethylene, 1-butene, and 1-hexene are preferred. Ethylene is more preferred.

[0045] The content of propylene units in the propylene-based resin (C) is preferably 40% by mass or more, more preferably 50% by mass or more, from the viewpoint of moldability and the like. On the other hand, the upper limit of the content of propylene units is not particularly limited, and may be 100% by mass. The content of propylene units can be determined by infrared spectroscopy.

[0046] The propylene resin (C) preferably has a melt flow rate measured at 230°C under a load of 2.16 kg of 0.1 g / 10 min to 50 g / 10 min, more preferably 0.5 g / 10 min to 30 g / 10 min, and even more preferably 1.0 g / 10 min to 10 g / 10 min. Since the propylene resin (C) has high compatibility with the antioxidant (F) described below, components derived from the antioxidant are less likely to be extracted (eluted) in the coolant, improving the heat resistance and extraction resistance.

[0047] The propylene resin (C) preferably has a melting point of 145°C or higher. A melting point of 148°C or higher is more preferred, and a melting point of 150°C or higher, or even more preferred, is 155°C or higher. Since compatibility with the antioxidant (F), which will be described later, is improved, components derived from the antioxidant are less likely to be extracted (eluted) in the coolant, improving heat resistance and extraction resistance. The upper limit of the melting point of the propylene resin (C) is not particularly limited, but is preferably 175°C or lower. The melting point can be measured by a method in accordance with JIS K7121-2012.

[0048] In the present composition, from the viewpoints of smooth appearance and flexibility, the content of (C) is preferably 1 part by mass or more and 200 parts by mass or less, more preferably 5 parts by mass or more and 80 parts by mass or less, and even more preferably 10 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the total of (A) and (B).

[0049] The unsaturated silane compound (D) functions as a water cross-linking agent (B). By including (D), the present composition has excellent compression set characteristics and good fastening properties when connecting a hose. The unsaturated silane compound (D) is not particularly limited, but for example, an unsaturated silane compound represented by the following formula (1) is preferably used: RSi(R') ３ ...(1)

[0050] In formula (1), R is an ethylenically unsaturated hydrocarbon group, and R' are each independently a hydrocarbon group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms, and at least one of the R' is an alkoxy group having 1 to 10 carbon atoms.

[0051] In formula (1), R is preferably an ethylenically unsaturated hydrocarbon group having 2 to 10 carbon atoms, and more preferably an ethylenically unsaturated hydrocarbon group having 2 to 6 carbon atoms. Specific examples include alkenyl groups such as vinyl, propenyl, butenyl, and cyclohexenyl.

[0052] In formula (1), R' is preferably a hydrocarbon group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, more preferably a hydrocarbon group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. At least one of the R's is preferably an alkoxy group having 1 to 6 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms. The hydrocarbon group having 1 to 10 carbon atoms represented by R' may be an aliphatic group, an alicyclic group, or an aromatic group, but is preferably an aliphatic group. The alkoxy group having 1 to 10 carbon atoms represented by R' may be linear, branched, or cyclic, but is preferably linear or branched. When R' is a hydrocarbon group, specific examples include alkyl groups such as methyl, ethyl, isopropyl, t-butyl, n-butyl, i-butyl, and cyclohexyl, and aryl groups such as phenyl. When R' is an alkoxy group, specific examples include a methoxy group, an ethoxy group, an isopropoxy group, and a β-methoxyethoxy group.

[0053] When the unsaturated silane compound (D) is a compound represented by formula (1), at least one of the three R's is an alkoxy group, preferably two R's are alkoxy groups, and more preferably all R's are alkoxy groups.

[0054] As the unsaturated silane compound (D), among those represented by formula (1), vinyltrialkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, and propenyltrimethoxysilane are preferred. This is because the vinyl group enables modification of the ethylene-α-olefin copolymer of component (B), and the alkoxy group promotes the crosslinking reaction. That is, the alkoxy group introduced by graft modification of the ethylene-α-olefin copolymer (B) with the unsaturated silane compound reacts with water in the presence of a silanol condensation catalyst to hydrolyze and generate silanol groups, which then undergo dehydration condensation, bonding the ethylene-α-olefin copolymers together to cause the crosslinking reaction. These unsaturated silane compounds may be used alone or in combination of two or more.

[0055] In the present composition, the content of (D) is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 5 parts by mass, and even more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the total of (A) and (B), from the viewpoint of allowing the crosslinking reaction to proceed sufficiently.

[0056] Examples of the peroxide (E) include organic peroxides such as hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxy esters, and ketone peroxides.

[0057] Examples of hydroperoxides include cumene hydroperoxide and tertiary butyl hydroperoxide. Examples of dialkyl peroxides include dicumyl peroxide, ditertiary butyl peroxide, 2,5-dimethyl-2,5-ditertiary butylperoxyhexane, 2,5-dimethyl-2,5-ditertiary butylperoxyhexyne-3, and di(2-tertiary butylperoxyisopropyl)benzene. Examples of diacyl peroxides include lauryl peroxide and benzoyl peroxide. Examples of peroxy esters include tertiary peroxyacetate, tertiary butyl peroxybenzoate, and tertiary butyl peroxyisopropyl carbonate. Examples of ketone peroxides include cyclohexanone peroxide. These compounds may be used alone or in combination of two or more as the peroxide (E).

[0058] When the peroxide (E) is used in combination with a crosslinking aid, a radical generator having a high thermal decomposition temperature is preferred. From this viewpoint, di-tert-butyl peroxide, di(2-tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and dicumyl peroxide are preferred.

[0059] In the present composition, the content of (E) is preferably from 0.01 to 3 parts by mass, more preferably from 0.05 to 2 parts by mass, and even more preferably from 0.1 to 1 part by mass, from the viewpoints of allowing the crosslinking reaction to proceed sufficiently and obtaining a smooth appearance.

[0060] Examples of crosslinking aids include silicon hydride compounds such as metrohydrogen silicon, sulfur, p-quinone dioxime, p-dinitrosobenzene, 1,3-diphenylguanidine, divinylbenzene, triallyl cyanurate, triallyl isocyanurate, and diallyl phthalate, as well as polyfunctional (meth)acrylate compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and allyl (meth)acrylate, as well as compounds having a bismaleimide structure such as N,N'-m-phenylene bismaleimide and N,N'-m-toluylene bismaleimide, trimethylolpropane, trimethylolpropane trimethacrylate, and tin chloride. Among these, polyfunctional vinyl compounds and polyfunctional (meth)acrylate compounds are preferred. These crosslinking aids may be used alone or in combination of two or more.

[0061] Furthermore, a phenol resin can also be used as the crosslinking aid, and examples of the phenol resin include alkylphenol formaldehyde and brominated alkylphenol formaldehyde.

[0062] In the present composition, the content of the crosslinking aid is preferably 0.001 parts by mass or more and 2 parts by mass or less, more preferably 0.003 parts by mass or more and 1 part by mass or less, relative to 100 parts by mass of the total of (A) and (B), from the viewpoint of allowing the crosslinking reaction to proceed sufficiently.

[0063] The (F) antioxidant satisfies the heat resistance of the present composition, which is a dynamically crosslinked thermoplastic elastomer (water-crosslinked TPV) using an unsaturated silane compound and a peroxide. (F) is presumed to be unevenly distributed in (C) in the present composition. It is important that the (F) antioxidant has a melting point of 60°C or higher. If the melting point of the (F) antioxidant is lower than 60°C, components derived from the antioxidant tend to be extracted into the coolant, making it difficult to achieve both extraction resistance and heat resistance. From the above viewpoints, the melting point of the (F) antioxidant is preferably 70°C or higher, more preferably 75°C or higher, even more preferably 80°C or higher, and particularly preferably 90°C or higher. The melting point of the (F) antioxidant is preferably 300°C or lower, more preferably 250°C or lower.

[0064] The molecular weight of the antioxidant (F) is not particularly limited, but is preferably 550 to 1,300, more preferably 580 to 1,280, even more preferably 600 to 1,250, and particularly preferably 700 to 1,200.

[0065] Examples of the (F) antiaging agent include phenolic antiaging agents, amine antiaging agents, imidazole antiaging agents, and phosphoric acid antiaging agents. These may be used alone or in combination as the (F) antiaging agent. Among these, phenolic antiaging agents are preferred from the viewpoint of being superior in the effect of achieving both extraction resistance and heat resistance. Among the phenolic antiaging agents, hindered phenolic antiaging agents are particularly preferred from the viewpoint of heat resistance.

[0066] Examples of hindered phenol-based antioxidants include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (e.g., "Irganox 1010" manufactured by BASF Corporation; melting point: 110 to 125°C), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate (e.g., "Irganox 3114" manufactured by BASF Corporation; melting point: 218 to 223°C), 2,4,6-tris(4-hydroxy-3,5-di-tert-butylbenzyl)mesitylene (e.g., "Irganox 1330" manufactured by BASF Corporation; melting point: 240 to 245°C), and 6-(4-hydroxy-3,5-di-tert-butylanilino)-2,4-bis(octyl thio)-1,3,5-triazine (for example, "Irganox 565" manufactured by BASF Corporation; melting point 91 to 96°C), 2,2'-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (for example, "Irganox 1035" manufactured by BASF Corporation; melting point 63 to 78°C), N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide] ("Irganox 1098" manufactured by BASF Corporation; melting point 156 to 161°C), 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ("Irganox 259" manufactured by BASF Corporation; melting point 104 to 108°C), and the like.

[0067] In this composition, the content of (F) is 0.02 parts by mass or more and 0.5 parts by mass or less, relative to 100 parts by mass of the total of (A) and (B). It is important to keep the content of (F) relatively small. This allows for a high degree of compatibility between heat resistance and extraction resistance. If the content of (F) is too high, extraction resistance decreases. If the content of (F) is too low, heat resistance decreases. From the above viewpoints, the content of (F) is more preferably 0.03 parts by mass or more and 0.4 parts by mass or less, and even more preferably 0.05 parts by mass or more and 0.4 parts by mass or less, relative to 100 parts by mass of the total of (A) and (B).

[0068] In addition to the above components (A) to (F), the composition may contain other components within the scope of the present invention. Examples of other components that may be included include softeners and silanol condensation catalysts. Other components may also include heat stabilizers, UV absorbers, light stabilizers, antioxidants, antistatic agents, crystal nucleating agents, rust inhibitors, viscosity modifiers, foaming agents, lubricants, and pigments.

[0069] The silanol condensation catalyst can cause an intermolecular crosslinking reaction in the composition. The alkoxy groups introduced by graft-modifying (A) or (B) with the unsaturated silane compound (D) react with water in the presence of the silanol condensation catalyst to hydrolyze and generate silanol groups. The silanol groups then undergo dehydration condensation with each other, causing the crosslinking reaction to proceed, bonding the modified elastomers together to form a crosslinked elastomer composition with excellent heat resistance.

[0070] Examples of the silanol condensation catalyst include metal organic acid salts, titanates, borates, organic amines, ammonium salts, phosphonium salts, inorganic acids, organic acids, inorganic acid esters, etc. These may be used alone or in combination of two or more as the silanol condensation catalyst.

[0071] Examples of metal organic acid salts include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, stannous acetate, stannous octoate, cobalt naphthenate, lead octoate, lead naphthenate, zinc octoate, zinc caprylate, iron 2-ethylhexanoate, iron octoate, and iron stearate. Examples of titanates include tetrabutyl titanate, tetranonyl titanate, and bis(acetylacetonitrile)diisopropyl titanate. Examples of organic amines include ethylamine, dibutylamine, hexylamine, triethanolamine, dimethyl soya amine, tetramethylguanidine, and pyridine. Examples of ammonium salts include ammonium carbonate and tetramethylammonium hydroxide. Examples of phosphonium salts include tetramethylphosphonium hydroxide. Examples of inorganic and organic acids include sulfuric acid, hydrochloric acid, acetic acid, stearic acid, maleic acid, toluenesulfonic acid, alkylnaphthylsulfonic acid, and other sulfonic acids. Examples of inorganic acid esters include phosphate esters.

[0072] Among these, metal organic acid salts, sulfonic acids, and phosphates are preferred. Among these, metal carboxylates of tin, alkylnaphthylsulfonic acids, and ethylhexyl phosphate are particularly preferred. Examples of metal carboxylates of tin include dioctyltin dilaurate.

[0073] In the present composition, from the viewpoints of appearance and sufficient progression of the crosslinking reaction, the content of the silanol condensation catalyst is preferably from 0.001 to 0.5 parts by mass, more preferably from 0.001 to 0.1 parts by mass, per 100 parts by mass of the total amount of the present composition.

[0074] The silanol condensation catalyst is preferably used as a masterbatch containing a polyolefin and the silanol condensation catalyst. Examples of polyolefins that can be used in this masterbatch include polyethylene, polypropylene, and ethylene-α-olefin copolymers.

[0075] Examples of polyethylene include (branched or linear) ethylene homopolymers such as low-, medium-, and high-density polyethylene; ethylene-α-olefin copolymers such as ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-hexene copolymer, and ethylene-1-octene copolymer; and ethylene-based copolymer resins such as ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, and ethylene-(meth)acrylic acid ester copolymer. Among these, ethylene-α-olefin copolymers such as ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-hexene copolymer, and ethylene-1-octene copolymer are preferred.

[0076] Among these, high-pressure low-density polyethylene, high-density polyethylene, and ethylene-α-olefin copolymers are preferred, as they have an excellent balance between heat resistance and strength. More preferred ethylene-α-olefin copolymers are ethylene-α-olefin copolymers such as ethylene-1-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-hexene copolymer, and ethylene-1-octene copolymer, and these ethylene-α-olefin copolymers are more preferably copolymers of 2 to 60% by mass of one or more α-olefins with 40 to 98% by mass of ethylene. The masterbatch of the silanol condensation catalyst may contain only one of these polyolefins, or a blend of two or more of them.

[0077] When the silanol condensation catalyst is used as a masterbatch in which a polyolefin and the silanol condensation catalyst are blended, there are no particular restrictions on the content of the silanol condensation catalyst in the masterbatch, but it is usually preferably about 0.1 to 5.0 mass %.

[0078] The softener can improve the flexibility, processability, fluidity, and oil resistance of the present composition. Examples of the softener include mineral oil-based rubber softeners and synthetic resin-based rubber softeners. Among these, mineral oil-based rubber softeners are preferred from the viewpoint of affinity, etc.

[0079] Mineral oil-based rubber softeners are generally mixtures of aromatic hydrocarbons, naphthenic hydrocarbons, and paraffinic hydrocarbons. Those in which the proportion of carbon atoms in paraffinic hydrocarbons relative to the total carbon atoms is 50% by mass or more are called paraffinic oils, those in which the proportion of carbon atoms in naphthenic hydrocarbons is 30 to 45% by mass are called naphthenic oils, and those in which the proportion of carbon atoms in aromatic hydrocarbons is 35% by mass or more are called aromatic oils. As the softener, a liquid hydrocarbon-based rubber softener that is liquid at room temperature (23±2°C) is preferred, from the viewpoint of its excellent effect of improving the flexibility, processability, fluidity, and oil resistance of the present composition. Liquid paraffinic oil that is liquid at room temperature is more preferred.

[0080] The paraffinic oil is not particularly limited, but has a kinematic viscosity at 40°C of usually 10 cst (centistokes) or more, preferably 20 cSt or more, and usually 800 cSt or less, preferably 600 cSt or less. Furthermore, a paraffinic oil having a pour point of usually -40°C or more, preferably -30°C or more, and 0°C or less is preferably used. Furthermore, a paraffinic oil having a pour point of usually -40°C or more, preferably -30°C or more, and 0°C or less is preferably used. Furthermore, a paraffinic oil having a flash point (COC) of usually 200°C or more, preferably 250°C or more, and usually 400°C or less, preferably 350°C or less is preferably used.

[0081] The hydrocarbon rubber softener contained in the oil-extended type (A) is also generally included in the softener. A softener may be added separately to the oil-extended type (A). In this case, the softener may be the same as the hydrocarbon rubber softener contained in the oil-extended type (A), or a different softener may be added.

[0082] In the present composition, the content of the softener is preferably 0.5 parts by mass or more and 200 parts by mass or less, more preferably 1 part by mass or more and 100 parts by mass or less, and even more preferably 5 parts by mass or more and 80 parts by mass or less, relative to 100 parts by mass of the total of (A) and (B), from the viewpoints of improving flexibility, flowability, and oil resistance, suppressing bleed-out of the softener, etc. When (A) is an oil-extended type, the softener in (A) is also included in the amount of the softener.

[0083] The present composition can be obtained by blending (A) to (F) and melt-kneading them. A crosslinking aid, a softener, etc. can be blended into the present composition as needed. The melt-kneading temperature can be 120°C to 200°C. For melt-kneading, a common melt-kneader such as a Banbury mixer, various kneaders, or a single-screw or twin-screw extruder can be used. Before melt-kneading, the components may be mechanically mixed using a Henschel mixer, V blender, tumbler blender, or the like.

[0084] The present composition can be formulated with a silanol condensation catalyst, molded by various molding methods such as extrusion molding, injection molding, and press molding, and then exposed to an aqueous atmosphere to promote the crosslinking reaction between silanol groups, resulting in a crosslinked composition. Various conditions can be used for the exposure to an aqueous atmosphere, including leaving the composition in moist air, blowing air containing water vapor into the composition, immersing the composition in a water bath, and spraying warm water in a mist. The conditions for exposure to an aqueous atmosphere are typically a temperature range of 0 to 130°C and a time period ranging from 5 minutes to 1 week. Particularly preferred conditions are a temperature range of 40 to 90°C and a time period ranging from 30 minutes to 24 hours.

[0085] The present composition, which comprises (A) to (F), contains a specific amount of (F), and is a dynamically crosslinked thermoplastic elastomer (water-crosslinked TPV) using an unsaturated silane compound and a peroxide, and also uses a specific antioxidant, ensuring excellent compression set properties and excellent heat resistance and extraction resistance.

[0086] A vehicle coolant transport hose according to the present invention (hereinafter sometimes referred to as the present hose) can be obtained from the present composition. The present hose can be produced by melt-extrusion molding the present composition into a hose shape, followed by water crosslinking. The present hose is preferably implemented, for example, as a single-layer hose 10 as shown in FIG. 1. If necessary, other resin layers or reinforcing fiber layers may be further laminated to form a multi-layer hose.

[0087] From the viewpoint of its intended use, the present hose preferably has an inner diameter in the range of 2.5 to 30 mm, particularly 4 to 25 mm, and a thickness in the range of 0.5 to 5.0 mm, particularly 0.75 to 4.0 mm.

[0088] The hose is used, for example, for piping coolants inside automobiles, and specifically is suitable for use as a radiator hose, heater hose, air conditioner hose, etc., as well as a cooling hose for battery packs in electric vehicles and fuel cell vehicles.

[0089] 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.

[0090] The present invention will be described in detail below using examples and comparative examples.

[0091] (Examples 1-4, Comparative Examples 1-4) The components were blended in the blending ratios (parts by mass) shown in the table, and melt-blended at 120 to 200°C using a twin-screw kneading extruder (Toshiba Machine "TEM-18SS") to obtain a kneaded mixture. Next, 5 parts by mass of a polyolefin masterbatch blended with dioctyltin dilaurate was added to the kneaded mixture, and a 2 mm sheet was produced by injection molding. The mixture was then exposed to constant temperature and humidity conditions of 85°C and 85 RH for 24 hours to obtain a sheet for evaluation.

[0092] The materials used are as follows: (A) Ethylene-α-olefin-non-conjugated diene copolymer rubber Ethylene-propylene-non-conjugated diene copolymer rubber: Mitsui Chemicals' "Mitsui EPT3092M" (B) Ethylene-α-olefin copolymer rubber not containing non-conjugated diene units Ethylene-α-olefin copolymer rubber: Dow Chemical's "Engage XLT8677" (C) Resins Propylene-based resin <1>: Prime Polymer's "Prime Polypro E200GP" (MFR 2.0 g / 10 min) Propylene-based resin <2>: Prime Polymer's "Prime Polypro F113G" (MFR 3.0 g / 10 min) (D) Unsaturated silane compound Vinyltrimethoxysilane: Shin-Etsu Chemical's "KBM-1003" (E) Peroxide Crosslinking agent: NOF's "Perhexyne 25B" (F) Antioxidant Phenolic antioxidant <1>: 2,2'-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] manufactured by BASF "IRGANOX 1035" (melting point 63 to 78°C) Phenolic antioxidant <2>: pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] manufactured by BASF "IRGANOX 1010" (melting point 110 to 125°C) (F') Antiaging Agents Phenolic antioxidant <3>: n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate manufactured by BASF "IRGANOX 1076" (melting point 50 to 55°C) (Others) - Crosslinking agent: Nippon Steel Chemical's "DVB-570"

[0093] The properties of each material obtained were evaluated according to the following criteria, and the results are shown in Table 1 below.

[0094] <Extractability (elution)> A 2.8 cm square sample piece was punched out from the prepared sheet. 10 g of this sample piece was immersed in 100 ml of a cooling liquid (a 50% aqueous solution of ethylene glycol) and heat-treated at 100°C for 72 hours to examine whether the components in the sample piece were extracted into the cooling liquid. The sample was then filtered under reduced pressure using filter paper with a pore size of 8 μm and air-dried at 70°C for 24 hours. The amount of component extraction was calculated from the change in mass of the sample piece after air-drying. A sample with an extraction amount of 0.5 g or more was rated as "x" (large), a sample with an extraction amount of less than 0.5 g was rated as "◯" (small), and a sample with an extraction amount of 0.1 g or less among the small samples was rated as "◎" (very small).

[0095] <Heat Resistance> Sample pieces 10 mm wide and 15 cm long were punched out from the prepared sheet. These sample pieces were subjected to a heat aging treatment (heat treatment at 130°C for 500 hours), and then the elongation at break [Eb] was measured using a tensile tester (AGS-X, manufactured by Shimadzu Corporation) in accordance with JIS K 6251. Samples whose elongation at break after 500 hours was 100% or more were rated "Good", and samples whose elongation at break after 500 hours was less than 100% were rated "Poor".

[0096] <Compression Set> Compression set evaluation sheets were measured at 23°C for 24 hours under 25% compression conditions in accordance with JIS K 6262. Compression set of 40% or more was marked "X", and compression set of less than 40% was marked "O".

[0097]

[0098] In Comparative Example 4, (B) and (D) were not blended, and (F) was blended with (A), (C), and (E). That is, an antioxidant was blended with a dynamically crosslinked olefin-based thermoplastic elastomer (partially crosslinked TPV) that was dynamically crosslinked using a peroxide as a crosslinking agent. According to Comparative Example 4, since it is a partially crosslinked TPV, the compression set characteristics are poor, and there is a risk that the fastening ability when connecting a hose may be poor.

[0099] Comparative Examples 1 to 3 are blends of (A) to (E), and are dynamically crosslinked thermoplastic elastomers (water-crosslinked TPVs) using an unsaturated silane compound and a peroxide. Comparative Example 1 blends (A) to (E) with an antioxidant (F), but in an excessive amount. Comparative Example 2 blends (A) to (E) with no antioxidant (F). Comparative Example 3 blends (A) to (E) with an antioxidant, but the antioxidant has a low melting point. Comparative Example 1 has poor extractability because the amount of antioxidant (F) in the water-crosslinked TPV is too high. Comparative Example 2 has poor heat resistance because the amount of antioxidant (F) in the water-crosslinked TPV is not included. Comparative Example 3 has poor extractability because the melting point of the antioxidant in the water-crosslinked TPV is too low. Therefore, in Comparative Examples 1 to 3, both heat resistance and extractability cannot be achieved.

[0100] In contrast to Comparative Examples 1 to 3, Examples 1 to 4 incorporate a specific amount of antioxidant (F) with an appropriate melting point in a water-crosslinkable TPV containing (A) to (E). Examples 1 to 3 demonstrate that both heat resistance and extractability are achieved. Furthermore, because the TPV is water-crosslinkable, it is expected to have excellent compression set properties and fastening properties when connecting a hose.

[0101] 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.

[0102] 10. Vehicle coolant transport hose

Claims

1. A composition for a vehicle coolant transport hose, containing the following (A) to (F), wherein the content of (F) relative to 100 parts by mass in total of (A) to (C) is 0.02 parts by mass or more and 0.5 parts by mass or less. (A) Ethylene-α-olefin-non-conjugated diene copolymer rubber (B) Ethylene-α-olefin copolymer rubber not containing non-conjugated diene units (C) One or more resins selected from polyethylene and propylene-based resins (D) Unsaturated silane compound (E) Peroxide (F) Antioxidant having a melting point of 60 °C or higher 2. The composition for a vehicle coolant transport hose according to claim 1, wherein the melting point of (F) is 90 °C or higher.

3. The composition for a vehicle coolant transport hose according to claim 1 or 2, wherein (F) is a phenolic antioxidant.

4. The composition for a vehicle coolant transport hose according to claim 1 or 2, wherein (F) is a hindered phenolic antioxidant.

5. The composition for a vehicle coolant transport hose according to any one of claims 1 to 4, wherein (C) is a propylene-based resin having a melt flow rate measured at 230 °C under a load of 2.16 kg of 0.1 g / 10 min or more and 50 g / 10 min or less.

6. The composition for a vehicle coolant transport hose according to any one of claims 1 to 5, wherein (C) is a propylene-based resin having a melting point of 145 °C or higher.

7. A vehicle coolant transport hose comprising a crosslinked product of the composition for a vehicle coolant transport hose according to any one of claims 1 to 6.

Images