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

Abstract

To provide 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.SOLUTION: Provided is a composition for a vehicle coolant transport hose that contains components (A) to (F), where the content of component (F) is 0.02-0.5 pt.mass relative to a total of 100 pts.mass of components (A) to (C): (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 polyethylene and polypropylene resins, (D) an unsaturated silane compound, (E) a peroxide, and (F) an anti-aging agent having a melting point of 60°C or higher. Also provided is a vehicle coolant transport hose that is composed of the composition for a vehicle coolant transport hose.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] There is a coolant transport hose as a hose for transporting coolant in a cooling system of a gasoline vehicle, an electric vehicle, or the like. From the viewpoint of heat resistance, polyamide resin is often adopted for the coolant transport hose. In recent years, propylene-based resins, which are cost-effective, have been studied as materials for coolant transport hoses. In addition, although it is a water-based hose for a fuel cell, it is known to use a dynamically crosslinked olefin-based thermoplastic elastomer (partially crosslinked TPV) dynamically crosslinked using peroxide as a crosslinking agent (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a partially crosslinked TPV is used as the material for a coolant transport hose, the compression set characteristics are poor, and there are problems with the fastening property during hose connection. To solve the problem of fastening property, when a dynamically crosslinked thermoplastic elastomer (water crosslinked TPV) using an unsaturated silane compound and a peroxide is used as the material for a coolant transport hose, there is a problem of inferior heat resistance. Here, in order to improve the heat resistance, when an antioxidant is blended into the material, components derived from the antioxidant tend to be extracted (eluted) into the coolant, which may cause clogging of the filter in the vehicle cooling system or the like, or the extracted components may increase the conductivity of the coolant, leading to the risk of short circuit or leakage.

[0005] The problem to be solved by the present invention is to provide a composition for a vehicle coolant transport hose and a vehicle coolant transport hose that ensure excellent compression set characteristics and are excellent in heat resistance and extraction resistance.

Means for Solving the Problem

[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) with respect to a total of 100 parts by mass of (A) to (C) is 0.02 part by mass or more and 0.5 part by mass or less. (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

[0007] The melting point of (F) is preferably 90°C or higher. (F) is preferably a phenolic antioxidant. (F) is preferably a hindered phenolic antioxidant. (C) is preferably 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. (C) is preferably a propylene-based resin having a melting point of 145°C or higher.

[0008] The coolant transport hose for vehicles according to the present invention is composed of a crosslinked product of the above composition for the coolant transport hose for vehicles.

[0009] (1) The composition for the coolant transport hose for vehicles according to the present invention contains the following (A) to (F), and the content of (F) with respect to a total of 100 parts by mass of (A) to (C) is 0.02 part by mass or more and 0.5 part by mass or less. (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) is preferably a phenolic antioxidant.

[0012] (4) In any one of the above (1) to (3), (F) is preferably a hindered phenolic antioxidant.

[0013] (5) In any one of the above (1) to (4), (C) is preferably 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.

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

[0015] (7) The coolant transport hose for vehicles according to the present invention is composed of a crosslinked body of the composition for a coolant transport hose for vehicles described in any one of (1) to (6) above.

Effects of the Invention

[0016] The composition for a coolant transport hose for vehicles according to the present invention contains the above (A) to (F), and the content of (F) is a specific amount. That is, in a dynamically crosslinked thermoplastic elastomer (water-crosslinked TPV) using an unsaturated silane compound and a peroxide, a specific antioxidant is used. Therefore, excellent compression set characteristics are ensured, and heat resistance and extraction resistance are excellent.

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

[0018] When the above (F) is a phenolic antioxidant, the components derived from the antioxidant are less likely to be extracted (eluted) into the coolant, and the effects of heat resistance and extraction resistance are improved. Further, when the above (F) is a hindered phenolic antioxidant, it is particularly excellent in heat resistance.

[0019] When the above (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, the compatibility with the antioxidant of the above (F) is increased, so that the components derived from the antioxidant are less likely to be extracted (eluted) into the coolant, and the effects of heat resistance and extraction resistance are improved. Further, when the above (C) is a propylene-based resin having a melting point of 145°C or higher, the compatibility with the antioxidant of the above (F) is increased, so that the components derived from the antioxidant are less likely to be extracted (eluted) into the coolant, and the effects of heat resistance and extraction resistance are improved.

[0020] The coolant transport hose for vehicles according to the present invention is composed of a crosslinked body of the composition for a coolant transport hose for vehicles. Therefore, excellent compression set characteristics are ensured, and heat resistance and extraction resistance are excellent.

Brief Description of the Drawings

[0021]

Figure 1

Modes for Carrying Out the Invention

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

[0023] The composition for a coolant transport hose for a vehicle according to the present invention (hereinafter sometimes referred to as "this composition") contains the following (A) to (F). (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

[0024] (A) The ethylene·α-olefin·non-conjugated diene copolymer rubber is a copolymer containing ethylene, α-olefin, and non-conjugated diene compound as copolymerization components. The ethylene·α-olefin·non-conjugated diene copolymer rubber may be of an oil-extended type, a non-oil-extended type, or a mixture of an oil-extended type and a non-oil-extended type. The oil-extended type is a mixture of ethylene·α-olefin·non-conjugated diene copolymer rubber and a hydrocarbon rubber softening agent. In the oil-extended type, the content ratio of the hydrocarbon rubber softening agent may be 10 parts by mass or more and 200 parts by mass or less with respect to 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 the α-olefin 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, 1-octadecene, and the like. These may be used alone as the α-olefin in (A) or in combination of two or more. Among these, from the viewpoints of excellent crosslinkability and difficulty in blooming out, propylene, 1-butene, 3-methyl-1-butene, and 1-pentene are preferable. More preferably, they are propylene and 1-butene.

[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 norbornene such as 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, and the like. These may be used alone as the non-conjugated diene compound in (A) or in combination of two or more. Among these, from the viewpoint of excellent crosslinkability, dicyclopentadiene, ethylidene norbornene, and vinylidene norbornene are preferable. More preferably, they are dicyclopentadiene, 5-ethylidene-2-norbornene, and vinylidene norbornene.

[0027] Examples of the ethylene·α-olefin·non-conjugated diene copolymer rubber of (A) include specifically ethylene·propylene·5-ethylidene-2-norbornene copolymer rubber, ethylene·propylene·dicyclopentadiene copolymer rubber, ethylene·propylene·1,4-hexadiene copolymer rubber, ethylene·propylene·5-vinyl-2-norbornene copolymer rubber and other ethylene·propylene·non-conjugated diene copolymer rubbers (EPDM), and ethylene·1-butene·5-ethylidene-2-norbornene copolymer rubber and the like. These may be used alone as one kind of the ethylene·α-olefin·non-conjugated diene copolymer rubber of (A), or may be used in combination of two or more kinds. Among these, from the viewpoints of excellent crosslinkability and difficulty in blooming out, ethylene·propylene·non-conjugated diene copolymer rubber (EPDM) is preferable.

[0028] From the viewpoints of mechanical strength and rubber elasticity, the content of ethylene units in the ethylene·α-olefin·non-conjugated diene copolymer rubber of (A) is preferably 50% by mass or more and 90% by mass or less. More preferably, it is 55% by mass or more and 85% by mass or less, and still more preferably, it is 60% by mass or more and 80% by mass or less.

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

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

[0031] As the ethylene·α-olefin·non-conjugated diene copolymer rubber of (A), from the viewpoints of mechanical strength and rubber elasticity, those having an ethylene unit content of 55% by mass or more and 75% by mass or less, a propylene unit content of 15% by mass or more and 40% by mass or less, and a non-conjugated diene unit content of 1% by mass or more and 10% by mass or less are preferred. At this time, as the non-conjugated diene unit, it is preferably one or more of dicyclopentadiene, ethylidene norbornene, and vinylidene norbornene.

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

[0033] The ethylene·α-olefin copolymer of (B) is an ethylene·α-olefin copolymer rubber that does not contain a non-conjugated diene unit. 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 of (B) include ethylene·propylene copolymer, ethylene·1-butene copolymer, ethylene·4-methyl-1-pentene copolymer, ethylene·1-hexene copolymer, and ethylene·1-octene copolymer. These may be used alone as the ethylene·α-olefin copolymer of (B), or two or more of them may be used in combination. Among these, from the viewpoint of ease of crosslinking, etc., ethylene·1-butene copolymer, ethylene·1-hexene copolymer, and ethylene·1-octene copolymer are preferred. From the viewpoint of excellent low-temperature characteristics, etc., ethylene·1-octene copolymer is more preferred.

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

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

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

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

[0039] (B)'s density of the ethylene-α-olefin copolymer is preferably 0.850 g / cm 3 or more and 0.910 g / cm 3 or less. More preferably, it is 0.860 g / cm 3 or more and 0.900 g / cm 3 or less, and still more preferably, it is 0.850 g / cm 3 or more and 0.880 g / cm 3 or less. (B)'s density of the ethylene-α-olefin copolymer can be measured in accordance with JIS K 6922-1,2:1997.

[0040] (B)'s end melting peak temperature measured by differential scanning calorimetry (DSC) of the ethylene-α-olefin copolymer is preferably 115 °C or more and 145 °C or less from the viewpoints that the shape can be maintained by crystals even at high temperatures and early crystallization (melt fracture) during molding cooling can be suppressed.

[0041] In this composition, (A) is preferably 5 to 70 parts by mass, more preferably 5 to 50 parts by mass, based on 100 parts by mass in total of (A) and (B). Also, (B) is preferably 30 to 95 parts by mass, more preferably 50 to 95 parts by mass, based on 100 parts by mass in total of (A) and (B). When the proportion of (A) is small, blocking tends to be difficult to suppress. When the proportion of (B) is small, 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. The strength is low with only the rubber of (A)(B), but by including the resin of (C), the strength as a hose can be ensured even as a single layer.

[0043] In (C), examples of the polyethylene include high-density polyethylene (low-pressure method polyethylene), low-density polyethylene (high-pressure method polyethylene), linear low-density polyethylene, etc. These may be used alone as one kind of the polyethylene of (C), or may be used in combination of two or more kinds. Among these, high-density polyethylene is preferable.

[0044] In (C), examples of the propylene-based resin include a propylene homopolymer, a propylene·α-olefin random copolymer, and a propylene·α-olefin block copolymer. These may be used alone as one kind of the propylene-based resin of (C), or may be used in combination of two or more kinds. Examples of the α-olefin include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. Among these, ethylene, 1-butene, and 1-hexene are preferable. More preferably, it is ethylene.

[0045] In the propylene-based resin of (C), the content of propylene units 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-based resin of (C) preferably has 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. More preferably, it is 0.5 g / 10 min or more and 30 g / 10 min or less, and even more preferably 1.0 g / 10 min or more and 10 g / 10 min or less. Since the compatibility with the antioxidant (F) described later is high, components derived from the antioxidant are less likely to be extracted (eluted) into the coolant, and the effects of heat resistance and extraction resistance are improved.

[0047] Also, the propylene-based resin of (C) preferably has a melting point of 145 °C or more. More preferably, the melting point is 148 °C or more, even more preferably 150 °C or more, 155 °C or more. Since the compatibility with the antioxidant (F) described later is high, components derived from the antioxidant are less likely to be extracted (eluted) into the coolant, and the effects of heat resistance and extraction resistance are improved. The upper limit value of the melting point of the propylene-based resin of (C) is not particularly limited, but it is preferably 175 °C or less. The melting point can be measured by a method conforming to JIS K7121-2012.

[0048] In this composition, 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, based on 100 parts by mass in total of (A) and (B), from the viewpoints of a smooth appearance and flexibility.

[0049] The unsaturated silane compound of (D) functions as the water crosslinking agent of (B). By including (D), the present composition has excellent compression set characteristics and good fastening property during hose connection. The unsaturated silane compound of (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 independently of each other a hydrocarbon group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms, and at least one of 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, more preferably an ethylenically unsaturated hydrocarbon group having 2 to 6 carbon atoms. Specifically, alkenyl groups such as vinyl group, propenyl group, butenyl group, cyclohexenyl group and the like can be mentioned.

[0052] In formula (1), R’ are 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. Also, at least one of R’ 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 of R’ may be any of an aliphatic group, an alicyclic group, and an aromatic group, but is preferably an aliphatic group. Also, the alkoxy group having 1 to 10 carbon atoms of R’ may be linear, branched or cyclic, but is preferably linear or branched. When R’ is a hydrocarbon group, specifically, alkyl groups represented by methyl group, ethyl group, isopropyl group, t-butyl group, n-butyl group, i-butyl group, cyclohexyl group and the like, or aryl groups represented by phenyl group and the like can be mentioned. When R’ is an alkoxy group, specifically, methoxy group, ethoxy group, isopropoxy group, β-methoxyethoxy group can be mentioned.

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

[0054] As the unsaturated silane compound of (D), among those represented by the formula (1), vinyltrialkoxysilanes typified by vinyltrimethoxysilane, vinyltriethoxysilane, propenyltrimethoxysilane, etc. are preferred. This is because the vinyl group enables the modification of the ethylene-α-olefin copolymer of component (B), and the alkoxy group allows the cross-linking reaction to proceed. That is, the alkoxy group introduced by graft-modifying the ethylene-α-olefin copolymer of (B) with the unsaturated silane compound reacts with water and hydrolyzes in the presence of a silanol condensation catalyst to generate silanol groups, and the silanol groups undergo dehydration condensation with each other, whereby the ethylene-α-olefin copolymers are bonded to cause a cross-linking reaction. These unsaturated silane compounds may be used alone or in combination of two or more.

[0055] In this composition, from the viewpoint of allowing the cross-linking reaction to proceed sufficiently, the content of (D) is preferably 0.01 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass in total of (A) and (B). More preferably, it is 0.05 part by mass or more and 5 parts by mass or less, and still more preferably, it is 0.1 part by mass or more and 3 parts by mass or less.

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

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

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

[0059] In this composition, the content of (E) is preferably 0.01 part by mass or more and 3 parts by mass or less, more preferably 0.05 part by mass or more and 2 parts by mass or less, and still more preferably 0.1 part by mass or more and 1 part by mass or less, 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 methylhydrogensilicon, sulfur, p - quinonedioxime, p - dinitrosobenzene, 1,3 - diphenylguanidine, polyfunctional vinyl compounds such as divinylbenzene, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, 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, allyl (meth)acrylate, compounds having a bismaleimide structure such as N,N’ - m - phenylenebismaleimide, N,N’ - m - toluylenebismaleimide, trimethylolpropane, trimethylolpropane trimethacrylate, tin chloride, and the like. Among these, polyfunctional vinyl compounds and polyfunctional (meth)acrylate compounds are preferred. These may be used alone as a crosslinking aid or in combination of two or more.

[0061] In addition, a phenol resin can also be used as a crosslinking aid. Examples of the phenol resin include alkylphenol formaldehyde, brominated alkylphenol novolac formaldehyde, and the like.

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

[0063] The antioxidant of (F) satisfies the heat resistance of this 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 this composition. It is important that the melting point of the antioxidant of (F) is 60°C or higher. When the melting point of the antioxidant of (F) is less 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. Also, from the above perspective, the melting point of the antioxidant of (F) is preferably 70°C or higher, more preferably 75°C or higher, still more preferably 80°C or higher, and particularly preferably 90°C or higher. Also, the melting point of the antioxidant of (F) is preferably 300°C or lower. More preferably, it is 250°C or lower.

[0064] The molecular weight of the antioxidant of (F) is not particularly limited, but is preferably 550 to 1300, more preferably 580 to 1280, still more preferably 600 to 1250, and particularly preferably 700 to 1200.

[0065] Examples of the antioxidant of (F) include phenolic antioxidants, amine antioxidants, imidazole antioxidants, phosphate antioxidants, etc. These may be used alone as the antioxidant of (F), or in combination of two or more. Among these, phenolic antioxidants are preferred from the perspective of excellent effects such as achieving both extraction resistance and heat resistance. Among the phenolic antioxidants, hindered phenolic antioxidants are particularly preferred from the perspective of heat resistance.

[0066] Examples of hindered phenol antioxidants include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (e.g., "Irganox 1010", manufactured by BASF: melting point 110 - 125°C), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate (e.g., "Irganox 3114", manufactured by BASF: melting point 218 - 223°C), 2,4,6-tris(4-hydroxy-3,5-di-tert-butylbenzyl)mesitylene (e.g., "Irganox 1330", manufactured by BASF: melting point 240 - 245°C), 6-(4-hydroxy-3,5-di-tert-butylanilino)-2,4-bis(octylthio)-1,3,5-triazine (e.g., "Irganox 565", manufactured by BASF: melting point 91 - 96°C), 2,2'-thiodiethyl bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (e.g., "Irganox 1035", manufactured by BASF: melting point 63 - 78°C), N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide] ("Irganox 1098", manufactured by BASF: melting point 156 - 161°C), 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ("Irganox 259", manufactured by BASF: melting point 104 - 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 with respect to 100 parts by mass in total of (A) and (B). It is important to make the content of (F) relatively small. Thereby, high heat resistance and extraction resistance can be achieved simultaneously. If (F) is too much, the extraction resistance will decrease. If (F) is too little, the heat resistance will decrease. 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 with respect to 100 parts by mass in total of (A) and (B).

[0068] In addition to the above (A) to (F), other components can be blended in the composition as long as they do not inhibit the present invention. Examples of other components include plasticizers, silanol condensation catalysts, etc. Further, heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, crystal nucleating agents, rust preventives, viscosity modifiers, foaming agents, lubricants, pigments, etc. can be mentioned.

[0069] The silanol condensation catalyst can cause the composition to undergo a crosslinking reaction between molecules. The alkoxy groups graft-modified and introduced into (A) or (B) by the unsaturated silane compound of (D) react with water and hydrolyze in the presence of the silanol condensation catalyst to generate silanol groups, and further, the silanol groups undergo dehydration condensation, whereby the crosslinking reaction proceeds, and the modified elastomers are bonded to form a crosslinked elastomer composition having 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 as the silanol condensation catalyst or in combination of two or more.

[0071] Examples of the 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, iron stearate, etc. Examples of the titanates include tetrabutyl titanate ester, tetranonyl titanate ester, bis(acetylacetonitrile) di-isopropyl titanate, etc. Examples of the organic amines include ethylamine, dibutylamine, hexylamine, triethanolamine, dimethyl soyamine, tetramethylguanidine, pyridine, etc. Examples of the ammonium salts include ammonium carbonate, tetramethylammonium hydroxide, etc. Examples of the phosphonium salts include tetramethylphosphonium hydroxide, etc. Examples of the inorganic acids and organic acids include sulfonic acids such as sulfuric acid, hydrochloric acid, acetic acid, stearic acid, maleic acid, toluenesulfonic acid, alkylnaphthylsulfonic acid, etc. Examples of the inorganic acid esters include phosphate esters, etc.

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

[0073] In this composition, from the viewpoints of sufficiently advancing the appearance and crosslinking reaction, the content of the silanol condensation catalyst is preferably 0.001 part by mass or more and 0.5 part by mass or less with respect to 100 parts by mass of the total amount of this composition. More preferably, it is 0.001 part by mass or more and 0.1 part by mass or less.

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

[0075] Examples of the 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, ethylene-1-octene copolymer; ethylene-based copolymer resins such as ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylate 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, ethylene-1-octene copolymer are preferred.

[0076] Among these, high-pressure low-density polyethylene, high-density polyethylene, and ethylene-α-olefin copolymers, which are excellent in the balance between heat resistance and strength, are preferred. As the ethylene-α-olefin copolymer, more preferably, it is an ethylene-α-olefin copolymer such as ethylene-1-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, and it is more preferably a copolymer obtained by copolymerizing 2 to 60% by mass of one or more α-olefins and 40 to 98% by mass of ethylene. For the masterbatch of the silanol condensation catalyst, only one of these polyolefins may be used, or two or more of them may be blended and used.

[0077] When the silanol condensation catalyst is used as a masterbatch prepared by blending a polyolefin and a silanol condensation catalyst, the content of the silanol condensation catalyst in the masterbatch is not particularly limited, but it is usually preferably about 0.1 to 5.0% by mass.

[0078] The softening agent can improve the flexibility, processability, fluidity, and oil resistance of the present composition. Examples of the softening agent include softening agents for mineral oil-based rubbers and softening agents for synthetic resin-based rubbers. Among these, from the perspective of affinity and the like, softening agents for mineral oil-based rubbers are preferred.

[0079] Softening agents for mineral oil-based rubbers are generally mixtures of aromatic hydrocarbons, naphthenic hydrocarbons, and paraffinic hydrocarbons. Those with a paraffinic hydrocarbon carbon ratio of 50% by mass or more based on all carbon atoms are called paraffinic oils, those with a naphthenic hydrocarbon carbon ratio of 30 - 45% by mass are called naphthenic oils, and those with an aromatic hydrocarbon carbon ratio of 35% by mass or more are called aromatic oils. As the softening agent, from the perspective of excellent effects such as improving the flexibility, processability, fluidity, and oil resistance of the present composition, a liquid hydrocarbon-based softening agent for rubber that is liquid at normal temperature (23 ± 2°C) is preferred. More preferably, it is a liquid paraffinic oil that is liquid at normal temperature.

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

[0081] In addition, hydrocarbon-based softening agents contained in the oil-extended type (A) are generally also included in the softening agent. A softening agent may be separately added to the oil-extended type (A) as well. In this case, the same softening agent as the hydrocarbon-based softening agent contained in the oil-extended type (A) may be added, or a different one may be added.

[0082] In this composition, from the viewpoints of improving flexibility, fluidity, oil resistance, and suppressing the bleed-out of the softening agent, the content of the softening agent is preferably 0.5 parts by mass or more and 200 parts by mass or less with respect to a total of 100 parts by mass of (A) and (B). More preferably, it is 1 part by mass or more and 100 parts by mass or less, and even more preferably, it is 5 parts by mass or more and 80 parts by mass or less. When (A) is an oil-extended type, the softening agent in (A) is also included in the amount of the softening agent.

[0083] This composition can be obtained by blending (A) to (F) and melt-kneading them. To this composition, a crosslinking aid, a softening agent, etc. can be blended as necessary. The temperature of the melt-kneading can be 120°C to 200°C. For the melt-kneading, general melt-kneading machines such as a Banbury mixer, various kneaders, a single-screw or twin-screw extruder can be used. Before the melt-kneading, mechanical mixing may be performed using a Henschel mixer, a V blender, a tumbler blender, etc.

[0084] This composition is blended with a silanol condensation catalyst, and after being molded by various molding methods such as extrusion molding, injection molding, and press molding, it is exposed to a water atmosphere to cause the crosslinking reaction between silanol groups to proceed, thereby obtaining a crosslinked composition. As the method of exposing to a water atmosphere, various conditions can be adopted, including methods such as leaving it in air containing moisture, blowing air containing water vapor, immersing it in a water bath, and spraying warm water in a mist form. The conditions for exposing to a water atmosphere are usually in the temperature range of 0 to 130°C and the range of 5 minutes to 1 week. Particularly preferred conditions are in the temperature range of 40 to 90°C and the range of 30 minutes to 24 hours.

[0085] According to the composition having the above configuration, it contains (A) to (F), the content of (F) is a specific amount, and in a dynamic crosslinked thermoplastic elastomer (water-crosslinked TPV) using an unsaturated silane compound and a peroxide, a specific antioxidant is used. Therefore, excellent compression set characteristics are ensured, and it is excellent in heat resistance and extraction resistance.

[0086] The coolant transport hose for vehicles according to the present invention (hereinafter sometimes referred to as "this hose") can be obtained from this composition. This hose can be manufactured by melt-extruding this composition into a hose shape and then subjecting it to water crosslinking. This hose is preferably implemented as a hose 10 having a single-layer structure as shown in FIG. 1, for example. Further, if necessary, other resin layers or reinforcing thread layers may be further laminated to form a hose having a multi-layer structure.

[0087] From the viewpoint of its use, this 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] This hose is used, for example, for piping coolant in an automobile. Specifically, it is preferably used for radiator hoses, heater hoses, air conditioner hoses, etc., and for cooling hoses for battery packs of electric vehicles and fuel cell vehicles.

[0089] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments at all, and various modifications can be made without departing from the spirit of the present invention.

Examples

[0090] Hereinafter, the present invention will be described in detail using examples and comparative examples.

[0091] (Examples 1-4, Comparative Examples 1-4) Each component was blended at the blending ratios (parts by mass) shown in the table, and melt-kneaded at 120 to 200°C using a twin-screw kneading extruder ("TEM-18SS" manufactured by Toshiba Machine Co., Ltd.) to obtain a kneaded product. Next, 5 parts by mass of a polyolefin masterbatch containing dioctyltin dilaurate was added to the above kneaded product, and a 2 mm sheet was produced by injection molding. Further, it was exposed to a constant temperature and humidity atmosphere at 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 containing no non-conjugated diene units Ethylene-α-olefin copolymer rubber: Dow Chemical's "Engage XLT8677" (C) Resin Propylene-based resin <1> : Prime Polymer "Prime Polypro E200GP" (MFR 2.0g / 10min) Propylene-based resin <2> Prime Polymer "Prime Polypro F113G" (MFR 3.0g / 10min) (D) Unsaturated silane compounds Vinyltrimethoxysilane: Shin-Etsu Chemical Co., Ltd. "KBM-1003" (E) Peroxide Crosslinking agent: Perhexin 25B made by Nippon Oil & Fats (F) Antiaging Agent Phenolic antioxidant <1> : 2,2'-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] BASF "IRGANOX1035" (melting point 63-78°C) Phenolic antioxidant <2> Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] BASF "IRGANOX1010" (melting point 110-125°C) (F') Antioxidant Phenolic antioxidant <3> : n-Octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate BASF "IRGANOX1076" (melting point 50-55°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 (Dissolution)> 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 coolant (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 coolant. Then, vacuum filtration was performed using filter paper with a pore size of 8 μm, and air drying was carried out at 70 °C for 24 hours. The extraction amount of the components was calculated from the mass change of the sample piece after air drying. Those with an extraction amount of 0.5 g or more were marked as "×" for a large amount, those with an extraction amount of less than 0.5 g were marked as "〇" for a small amount, and among those with a small amount, those with an extraction amount of 0.1 g or less were marked as "◎" for a very small amount.

[0095] <Heat Resistance> A sample piece with a width of 10 mm and a length of 15 cm was punched out from the prepared sheet. After performing a heat aging treatment (heat treatment at 130 °C for 500 hours) on this sample piece, the elongation at break [Eb] at the time of fracture was measured using a tensile testing machine (AGS-X, manufactured by Shimadzu Corporation) in accordance with JIS K 6251. Those with an elongation at break after 500 hours of 100% or more were marked as "〇", and those with an elongation at break after 500 hours of less than 100% were marked as "×".

[0096] <Compression Set> For the sheet for compression set evaluation, measurement was carried out under the conditions of 23 °C × 24 hours and 25% compression in accordance with JIS K 6262. Those with 40% or more were marked as "×", and those with less than 40% were marked as "○".

[0097]

Table 1

[0098] Comparative Example 4 does not contain (B) and (D), and contains (F) with respect to (A), (C), and (E). That is, it is a composition in which an antioxidant is blended with a dynamically crosslinked olefin-based thermoplastic elastomer (partially crosslinked TPV) 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 of inferior fastening property during hose connection.

[0099] Comparative Examples 1 to 3 contain (A) to (E) and are dynamically crosslinked thermoplastic elastomers (water-crosslinked TPV) using an unsaturated silane compound and a peroxide. Comparative Example 1 contains an antioxidant (F) in addition to (A) to (E), but the blending amount is too large. Comparative Example 2 does not contain the antioxidant (F) with respect to (A) to (E). Comparative Example 3 contains an antioxidant in addition to (A) to (E), but it is an antioxidant with a low melting point. In Comparative Example 1, since there is too much antioxidant (F) in the water-crosslinked TPV, the extractability is poor. In Comparative Example 2, since the antioxidant (F) is not blended in the water-crosslinked TPV, the heat resistance is poor. In Comparative Example 3, since the melting point of the antioxidant in the water-crosslinked TPV is too low, the extractability is poor. Therefore, in Comparative Examples 1 to 3, it is impossible to achieve both heat resistance and extractability.

[0100] In contrast to Comparative Examples 1 to 3, Examples 1 to 4 contain a specific amount of an antioxidant (F) with an appropriate melting point in the water-crosslinked TPV containing (A) to (E). According to Examples 1 to 3, it can be seen that both heat resistance and extractability can be achieved. Also, since it is a water-crosslinked TPV, it can be expected to have excellent compression set characteristics and excellent fastening properties during hose connection.

[0101] As described above, the embodiments and examples of the present invention have been explained. However, the present invention is not limited to the above embodiments and examples, and various modifications are possible without departing from the spirit of the present invention.

Explanation of Signs

[0102] 10 Vehicle coolant transport hose

Claims

1. A composition for a coolant transport hose for vehicles, containing the following (A) to (F), wherein the content of (F) with respect to a total of 100 parts by mass of (A) to (C) is 0.02 part by mass or more and 0.5 part by mass or less. (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

2. The composition for a coolant transport hose for vehicles according to Claim 1, wherein the melting point of (F) is 90°C or higher.

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

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

5. The composition for a coolant transport hose for vehicles according to Claim 1 or Claim 2, wherein (C) is a propylene-based resin having a melt flow rate measured at 230°C and 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 coolant transport hose for vehicles according to Claim 1 or Claim 2, wherein (C) is a propylene-based resin having a melting point of 145°C or higher.

7. The melting point of (F) is 90°C or higher, (F) is a hindered phenolic antioxidant, and (C) is a propylene-based resin having a melt flow rate measured at 230°C and a load of 2.16 kg of 0.1 g / 10 min or more and 50 g / 10 min or less and a melting point of 145°C or higher. The composition for a coolant transport hose for vehicles according to Claim 1.

8. A coolant transport hose for vehicles comprising a crosslinked product of the composition for a coolant transport hose for vehicles according to Claim 1.

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