Resin composition for vehicle coolant delivery pipe, and vehicle coolant delivery pipe

Abstract

Provided are: a resin composition for a vehicle coolant delivery pipe, which has excellent heat resistance and extraction resistance; and a vehicle coolant delivery pipe obtained using the resin composition. A resin composition for a coolant delivery pipe for a vehicle, which contains the following components (A) and (B), and the content of the component (B) is 0.1-1 part by mass per 100 parts by mass of the component (A). (A) A polypropylene resin having a melt flow rate of 0.2 g / 10 minutes or more and less than 2.0 g / 10 minutes as measured under a load of 2.16 kg at 230 DEG C and a melting point of 145 DEG C or more. (B) An anti-aging agent having a melting point of 60 DEG C or higher.

Description

Technical Field

[0001] The present invention relates to a resin composition for a coolant delivery pipe for a vehicle and a coolant delivery pipe for a vehicle obtained by using the same. Specifically, it relates to a pipe for delivering a coolant in a cooling system of an automobile or the like, which is excellent in heat resistance and extraction resistance. Background Art

[0002] Conventionally, from the viewpoint of excellent heat resistance and the like, polyamide resin has been used as the material for coolant delivery pipes in fuel vehicles and electric vehicles (for example, refer to Patent Document 1). However, since polyamide resin has a problem in terms of price, polypropylene-based resin, which is a material having a cost advantage, has been studied (for example, refer to Patent Document 2).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2012-091730

[0006] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2006-194318 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] When using polypropylene-based resin as the material for a coolant delivery pipe for a vehicle, although it is excellent in terms of cost, it has a problem in heat resistance. Therefore, from the viewpoint of improving heat resistance, it is possible to consider compounding an antioxidant.

[0009] However, when compounding an antioxidant as the material for a coolant delivery pipe for a vehicle, since components derived from the antioxidant tend to be extracted (eluted) into the coolant, there is a possibility of causing clogging of the filter in the vehicle cooling system, etc., and there is a concern that the extracted components may increase the conductivity of the coolant, leading to short circuits or electric leakage, etc.

[0010] The present invention has been made in view of such circumstances, and provides a resin composition for a coolant delivery pipe for a vehicle, which is excellent in heat resistance and extraction resistance, and a coolant delivery pipe for a vehicle obtained by using the same.

[0011] Solutions to the Problems

[0012] In order to solve the above problems, the inventors, through repeated in-depth research, focused on the problem of the conflict between heat resistance and extraction resistance when using anti-aging agents. That is, from the perspective of improving heat resistance, an increase in the compounding amount of the anti-aging agent is required. However, if the compounding amount of the anti-aging agent is increased, it is difficult to suppress the extraction amount of the components derived from the anti-aging agent relative to the coolant, and thus extraction resistance cannot be ensured. The inventors conducted more in-depth research from the perspective of balancing heat resistance and extraction resistance, and as a result, found that if a specific polypropylene-based resin and a specific anti-aging agent are used in combination and the content ratios of both are set within a specific range, a coolant delivery pipe for vehicles with excellent heat resistance and extraction resistance can be obtained, thereby completing the present invention.

[0013] That is, the gist of the present invention is as follows in [1] to [7] below. [1]

[0015] A resin composition for a coolant delivery pipe for vehicles, which contains the following component (A) and component (B), and the content of component (B) is 0.1 to 1 part by mass relative to 100 parts by mass of component (A).

[0016] (A) A polypropylene-based resin having a melt flow rate of 0.2 g / 10 minutes or more and less than 2.0 g / 10 minutes and a melting point of 145°C or more as measured at 230°C under a load of 2.16 kg.

[0017] (B) An anti-aging agent having a melting point of 60°C or more. [2]

[0019] The resin composition for a coolant delivery pipe for vehicles according to [1], wherein the above-mentioned component (A) is a propylene-α-olefin block copolymer. [3]

[0021] The resin composition for a coolant delivery pipe for vehicles according to [1] or [2], wherein the melt flow rate of the above-mentioned component (A) is 0.2 g / 10 minutes or more and 1.5 g / 10 minutes or less. [4]

[0023] The resin composition for a coolant delivery pipe for vehicles according to any one of [1] to [3], wherein the melting point of the above-mentioned component (B) is 90°C or more. [5]

[0025] The resin composition for a coolant delivery pipe for vehicles according to any one of [1] to [4], wherein the above-mentioned component (B) is a phenolic anti-aging agent. [6]

[0027] The resin composition for a coolant delivery pipe for a vehicle according to any one of [1] to [5], wherein the component (B) is a hindered phenol antioxidant. [7]

[0029] A coolant delivery pipe for a vehicle, which is formed of the resin composition for a coolant delivery pipe for a vehicle according to any one of [1] to [6].

[0030] Effects of the Invention

[0031] According to the present invention, a coolant delivery pipe for a vehicle having excellent heat resistance and extraction resistance can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a view showing an example of the coolant delivery pipe for a vehicle according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to this embodiment.

[0034] The resin composition for a coolant delivery pipe for a vehicle according to one embodiment of the present invention (hereinafter, sometimes referred to as "the present resin composition") is characterized by containing the following component (A) and component (B), and the content of component (B) relative to 100 parts by mass of component (A) is limited to 0.1 to 1 part by mass.

[0035] (A) A polypropylene-based resin having a melt flow rate of 0.2 g / 10 minutes or more and less than 2.0 g / 10 minutes as measured at 230°C under a load of 2.16 kg and a melting point of 145°C or more.

[0036] (B) An antioxidant having a melting point of 60°C or more.

[0037] Since the coolant delivery pipe for a vehicle is disposed close to heat sources such as an engine and a battery, it is exposed to a high-temperature environment. At the same time, high-temperature coolant flows inside it, so excellent heat resistance is required.

[0038] On the other hand, when the coolant in the coolant delivery pipe for a vehicle has conductivity, there is a concern about causing an electrical short circuit, resulting in electric shock, and a reduction in power generation efficiency due to leakage. Therefore, the development of a technology for reducing the conductivity of the coolant is more important than before. Against this background, the coolant delivery pipe for a vehicle also strongly requires the development of a technology that contributes to the reduction of the conductivity of the coolant. In particular, in recent years, with the popularization of electric vehicles and the high voltage of batteries, considering the many problems that will occur when the coolant leaks, the insulation requirements for the coolant have become more and more strict, and it has become an urgent task for the coolant delivery pipe for a vehicle to meet these requirements.

[0039] This resin composition was obtained based on this background. The heat resistance of the coolant delivery pipe for vehicles obtained using this resin composition is excellent, and the extraction resistance of components (ionic components) that may have an adverse effect on the conductivity of the coolant is also excellent. Therefore, it is useful in contributing to the technology of reducing the conductivity of the coolant.

[0040] In addition, since the coolant delivery pipe for vehicles obtained using this resin composition has excellent extraction resistance, it is also useful in suppressing clogging of the filter in the cooling system and not interfering with the operation of the cooling system.

[0041] Moreover, the coolant delivery pipe for vehicles obtained using this resin composition uses a polypropylene-based resin with high cost competitiveness, so it is more useful in terms of excellent economy.

[0042] In the past, from the perspectives of heat resistance and economy, a multi-layered structure pipe having a polyamide resin layer and a polypropylene resin layer has also been proposed. However, since it is difficult to peel the layers during recycling, the recyclability is poor. The coolant delivery pipe for vehicles obtained using this resin composition can exhibit excellent properties such as heat resistance and economy even with a single-layer structure. Therefore, the coolant delivery pipe for vehicles obtained using this resin composition is also useful in that it has excellent heat resistance, economy, and recyclability.

[0043] Hereinafter, each material constituting this resin composition and the like will be described.

[0044] It should be noted that in this specification, "X and / or Y (X and Y are arbitrary components)" means at least one of X and Y, including three meanings: only X, only Y, and X and Y.

[0045] 《(A) Polypropylene-based resin》

[0046] Regarding the polypropylene-based resin used in this resin composition, importantly, the melt flow rate (hereinafter, sometimes simply referred to as "MFR") measured under the conditions of 230°C and a load of 2.16 kg is 0.2 g / 10 minutes or more and less than 2.0 g / 10 minutes, and at the same time, the melting point is 145°C or more.

[0047] By using a polypropylene-based resin with an MFR within the above range and a melting point within the above range in this resin composition, desired extraction resistance and heat resistance can be obtained. When the MFR of component (A) is 2.0 g / 10 minutes or more and when the melting point of component (A) is lower than 145°C, due to a decrease in the compatibility between component (A) and component (B) and the like, the extraction amount in the coolant tends to increase, so it is difficult to achieve a high balance between heat resistance and extraction resistance.

[0048] It should be noted that the above MFR was measured according to JIS K7210:1999 under the conditions of 230°C and a load of 2.16 kg.

[0049] From the perspective of significantly exerting the effects of the present invention, the MFR of component (A) is preferably 0.3 g / 10 min or more, more preferably 0.4 g / 10 min or more, and even more preferably 0.5 g / 10 min or more. In addition, it is preferably 1.8 g / 10 min or less, more preferably 1.6 g / 10 min or less, and even more preferably 1.5 g / 10 min or less.

[0050] From the perspective of significantly exerting the effects of the present invention, the melting point of component (A) is preferably 148°C or more, more preferably 150°C or more, and even more preferably 155°C or more. In addition, the upper limit value of the melting point of component (A) is not particularly limited, for example, it is about 175°C.

[0051] It should be noted that the melting point in this specification can be measured, for example, by the method according to JIS K7121:2012.

[0052] As a specific example of component (A), for example, one or more propylene-based polymers selected from the group consisting of propylene homopolymers, propylene-α-olefin random copolymers, and propylene-α-olefin block copolymers can be cited.

[0053] As the α-olefin used in these copolymers, for example, ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. can be cited. Among them, ethylene, 1-butene, and 1-hexene are preferred, and ethylene is particularly preferred.

[0054] In addition, as component (A), a modified polypropylene-based resin obtained by modifying the above polypropylene-based resin with at least one modifying compound selected from the group consisting of acids and acid derivatives can be cited.

[0055] As the acid or its derivative in the above acid-modified product, for example, unsaturated carboxylic acids and their derivatives can be cited. As the unsaturated carboxylic acid, for example, maleic acid, fumaric acid, acrylic acid, methacrylic acid, etc. can be cited. As the derivative of the unsaturated carboxylic acid, acid anhydrides, ester compounds, amide compounds, imide compounds, metal salts, etc. of the above unsaturated carboxylic acids can be cited.

[0056] In addition, as component (A), an alloy (mixture) having a sea-island structure in which a polypropylene component such as the above-mentioned homopolymer of propylene (homopolypropylene) is the sea phase and, for example, a polyethylene component, an ethylene-based rubber component, etc. are the island phases can be cited.

[0057] As the above-mentioned polyethylene component, for example, ethylene homopolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene copolymers with α-olefins (ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-octene copolymers), etc. can be cited. In addition, as the above-mentioned ethylene-based rubber component, for example, ethylene-propylene-diene terpolymers (EPDM), ethylene-propylene copolymers (EPR), ethylene-butene copolymers (EBR), ethylene-octene copolymers (EOR), etc. can be cited. Among the above-mentioned ethylene-based rubber components, ethylene-propylene copolymers (EPR) and ethylene-propylene-diene terpolymers (EPDM) are preferred. In addition, the content ratio of the polyethylene component and / or the ethylene-based rubber component relative to the entire alloy (100% by mass) is not limited, for example, it is 1 to 80% by mass, 1 to 70% by mass, 1 to 60% by mass, 1 to 55% by mass, etc., and preferably 1 to 49% by mass, 2 to 30% by mass, 2.5 to 20% by mass, etc.

[0058] In component (A), from the perspective of significantly exerting the effects of the present invention, a propylene-α-olefin block copolymer is preferred. As the propylene-α-olefin block copolymer, for example, an alloy (mixture) having a sea-island structure in which a polypropylene component such as a homopolymer of propylene is the sea phase and a polyethylene component and / or an ethylene-based rubber component is the island phase can be cited.

[0059] As the above-mentioned polyethylene component in the above-mentioned alloy, for example, ethylene homopolymers, ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-octene copolymers, etc. can be cited. In addition, as the above-mentioned ethylene-based rubber component, for example, ethylene-propylene-diene terpolymers (EPDM), ethylene-propylene copolymers (EPR), ethylene-butene copolymers (EBR), ethylene-octene copolymers (EOR), etc. can be cited. Among the above-mentioned ethylene-based rubber components, ethylene-propylene copolymers (EPR) and ethylene-propylene-diene terpolymers (EPDM) are preferred, and ethylene-propylene copolymers (EPR) are further preferred.

[0060] In addition, the content ratio of the polyethylene component and / or the ethylene-based rubber component relative to the entire alloy (100% by mass) is not limited to the following, for example, it is 1 to 80% by mass, 1 to 70% by mass, 1 to 60% by mass, 1 to 55% by mass, etc., and preferably 1 to 49% by mass, 2 to 30% by mass, 2.5 to 20% by mass, etc.

[0061] Among the above propylene-α-olefin block copolymers, a propylene-ethylene block copolymer is preferred. The propylene-ethylene block copolymer is produced, for example, by polymerizing propylene alone (pre-polymerization) and then copolymerizing ethylene (post-polymerization). In the above post-polymerization, components other than ethylene may also be copolymerized. The propylene-ethylene block copolymer has a sea-island structure in which ethylene blocks and ethylene-propylene copolymer blocks are dispersed in the sea phase after propylene polymerization, and is usually also referred to as a propylene block polymer or block polypropylene.

[0062] In this resin composition, these component (A) can be used alone or in combination of two or more. It should be noted that when two or more component (A) are used in combination, it is preferred that the MFR and melting point of the polyethylene-based resin mixture composed of two or more are within the above ranges. In addition, for example, when the above alloy (mixture) is used as component (A), it is preferred that the MFR and melting point of the alloy are within the above ranges.

[0063] This resin composition uses component (A) as the main component. For example, the content of component (A) relative to the whole resin composition (100% by mass) is usually 50% by mass or more, preferably 55-99.9% by mass, more preferably 60-90% by mass, and even more preferably 65-80% by mass.

[0064] <<(B) Antioxidant>>

[0065] As the (B) antioxidant used in this resin composition, it is important that the melting point is 60°C or higher. When the melting point of the (B) antioxidant is less than 60°C, there is a tendency for components derived from the antioxidant to be extracted into the coolant, and it is difficult to balance extraction resistance and heat resistance.

[0066] From the perspective of significantly exerting the effects of the present invention, the melting point of component (B) 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. In addition, it is preferably 300°C or lower, more preferably 250°C or lower.

[0067] The molecular weight of component (B) is not particularly limited. For example, it is preferably 550-1300, more preferably 580-1280, even more preferably 600-1250, and particularly preferably 700-1200.

[0068] Specific examples of component (B) include, but are not limited to, phenolic antioxidants, amine antioxidants, imidazole antioxidants, phosphoric acid antioxidants, etc. They can be used alone or in combination of two or more. Among them, from the perspective of significantly exerting the effects of the present invention, phenolic antioxidants are preferred. Among phenolic antioxidants, hindered phenolic antioxidants are particularly preferred from the perspective of heat resistance.

[0069] As hindered phenol antioxidants, for example, pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (for example, "Irganox 1010", manufactured by BASF, melting point 110 - 125°C), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid ester (for example, "Irganox 3114", manufactured by BASF, melting point 218 - 223°C), 2,4,6-tris(4-hydroxy-3,5-di-tert-butylbenzyl)mesitylene (for example, "Irganox 1330", manufactured by BASF, melting point 240 - 245°C), 6-(4-hydroxy-3,5-di-tert-butylaniline)-2,4-bis(octylthio)-1,3,5-triazine (for example, "Irganox 565", manufactured by BASF, melting point 91 - 96°C), 2,2'-thiobis(ethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) (for example, "Irganox 1035", manufactured by BASF, melting point 63 - 78°C), N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide] ("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), etc. can be cited.

[0070] From the perspective of achieving the effects of the present invention, it is important that the content of component (B) is a relatively small amount of 0.1 - 1 part by mass relative to 100 parts by mass of component (A) polypropylene-based resin. When the content of antioxidant (B) relative to component (A) is not within the above range, it is difficult to highly balance heat resistance and extraction resistance.

[0071] (Other components)

[0072] Within the range that does not impair the effects of the present invention, in addition to components (A) and (B), the forming materials of the present resin composition can be appropriately compounded with various additives such as fillers, weather stabilizers, lubricants, pigments, dyes, antistatic agents, plasticizers, crosslinking agents, crosslinking aids, etc. as needed.

[0073] As fillers, for example, inorganic fillers such as talc, silica, mica, kaolin, calcium carbonate, potassium titanate, apatite, mica, etc. can be cited. They can be used alone or in combination of two or more. Among them, talc is preferred from the perspectives of extrusion processability, reinforcement, etc.

[0074] The content of the filler is not particularly limited. From the perspective of strength, it is, for example, 1 to 100 parts by mass, preferably 10 to 70 parts by mass, relative to 100 parts by mass of the (A) polypropylene-based resin. Additionally, the content of the filler can be 10 to 50 parts by mass, etc.

[0075] As the crosslinking agent, for example, peroxide crosslinking agents such as ketone peroxides, peroxy esters, dialkyl peroxides, ketone peroxides, diacyl peroxides, and peroxydicarbonates can be cited. They can be used alone or in combination of two or more. The content of the crosslinking agent is not particularly limited. Relative to 100 parts by mass of the (A) polypropylene-based resin, it is, for example, 0.1 to 4 parts by mass, preferably 0.2 to 2 parts by mass.

[0076] (Manufacturing method)

[0077] This resin composition and the coolant delivery pipe for vehicles formed from this resin composition are manufactured, for example, by kneading the component (A), the component (B), and, if necessary, the above other components, and melt-extruding the obtained kneaded product into a tubular shape. For example, it can be favorably manufactured by successively performing the steps shown in the following [I] to [III].

[0078] [I] Step of kneading the component (A) and the component (B).

[0079] [II] Step of adding an inorganic filler to the kneaded product obtained in the above step [I] and kneading. [III] Step of melt-extruding the kneaded product obtained in the above step [II] into a tubular shape.

[0080] The above step [I] is a step of kneading the component (A), the component (B), etc. at, for example, 190 to 230 °C for 0.01 to 10 minutes by a twin-screw kneading extruder or the like.

[0081] The above step [II] is a step of adding an inorganic filler to the kneaded product obtained in the above step [I] and kneading. The above kneading conditions are, for example, using a twin-screw kneading extruder or the like, 190 to 270 °C, 0.01 to 10 minutes.

[0082] It should be noted that any component other than the component (A) and the component (B) can be added in any one of the steps [I] to [III] above, and it is preferably added and mixed after the above step [II]. It should be noted that a compound having a guanamine skeleton can be arbitrarily added to this resin composition, but from the perspective of extrusion processability, etc., it is preferably not added.

[0083] The above-mentioned step [III] is a step of melt-extruding and molding the kneaded product obtained in the above-mentioned step [II] into a tube shape at, for example, 190 to 270 °C by a melt extrusion molding machine equipped with a cylindrical die head. It should be noted that, from the perspective of productivity, it is preferable to use a granulated kneaded product as the above-mentioned kneaded product.

[0084] From the perspective of its use, the inner diameter of the vehicle coolant delivery pipe of the present invention thus obtained is preferably in the range of 2.5 to 30 mm, particularly preferably in the range of 4 to 25 mm, and the thickness is preferably in the range of 0.5 to 5.0 mm, particularly preferably in the range of 0.75 to 4.0 mm.

[0085] The vehicle coolant delivery pipe obtained from this resin composition is suitably implemented, for example, as a vehicle coolant delivery pipe having a single-layer structure as shown in Figure 1 In addition, other resin layers or reinforcing wire layers may be further laminated as needed to form a multi-layer vehicle coolant delivery pipe.

[0086] The vehicle coolant delivery pipe obtained from this resin composition is used, for example, for the piping of coolant in an automobile. Specifically, it is used for radiator hoses, heater hoses, air-conditioning hoses, etc., and cooling pipes for battery packs of electric vehicles and fuel cell vehicles.

[0087] Examples

[0088] Next, examples of the present invention will be described in combination with comparative examples. However, the present invention is not limited to these examples.

[0089] First, before implementing the examples and comparative examples, the following materials were prepared.

[0090] <(A) Polypropylene resin>

[0091] 〔Polypropylene resin (a)〕

[0092] Propylene-α-olefin block copolymer (E-702MG, manufactured by Prime Polymer Co., Ltd., MFR: 1.4 g / 10 minutes, melting point: 162 °C)

[0093] 〔Polypropylene resin (a’1)〕

[0094] Polypropylene homopolymer (E-200GP, manufactured by Prime Polymer Co., Ltd., MFR: 2.0 g / 10 minutes, melting point 164 °C)

[0095] 〔Polypropylene resin (a’2)〕

[0096] Random copolymer of propylene and α-olefin (B-241, manufactured by Prime Polymer Co., Ltd., MFR: 0.5 g / 10 min, melting point 143 °C)

[0097] <(B) Antioxidant>

[0098] 〔Phenolic antioxidant (b1)〕

[0099] Pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010, manufactured by BASF, melting point 110 - 125 °C)

[0100] 〔Phenolic antioxidant (b2)〕

[0101] 2,2'-Thiobis(ethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) (Irganox 1035, manufactured by BASF, melting point 63 - 78 °C)

[0102] 〔Phenolic antioxidant (b’)〕

[0103] n-Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1076, manufactured by BASF, melting point 50 - 55 °C)

[0104] <Filler>

[0105] 〔Inorganic filler〕

[0106] Talc (FH108, manufactured by Fuji Talc Industry Co., Ltd.)

[0107] [Examples 1 - 3, Comparative Examples 1 - 5]

[0108] Using the mass ratios and combinations shown in Table 1 below, each component except the inorganic filler was kneaded at 200 °C for 5 minutes by a twin-screw kneading extruder (TEM-18SS, manufactured by Toshiba Machine Co., Ltd.), then the inorganic filler was added, and further kneaded at 200 °C for 5 minutes by the above twin-screw kneading extruder to obtain a kneaded product (resin composition).

[0109] Next, by granulating the above kneaded product, the granules were melt-extruded into a tubular shape at 250 °C by a melt extrusion molding machine (GT-40, manufactured by PLABOR Research Laboratory of Plastics Technology Co., Ltd.) equipped with a cylindrical die to obtain a resin tube with an inner diameter of 18 mm and an outer diameter of 20 mm.

[0110] [Example 4]

[0111] Using the mass ratios and combinations shown in Table 1 below, the respective components were kneaded at 200°C for 5 minutes by a twin-screw kneading extruder (TEM-18SS, manufactured by Toshiba Machine Co., Ltd.) to obtain a kneaded product (resin composition).

[0112] Next, by granulating the above kneaded product, the granules were melt-extruded into a tubular shape at 250°C by a melt extrusion molding machine (GT-40, manufactured by PLABOR Research Laboratory of Plastics Technology Co., Ltd.) equipped with a cylindrical die to obtain a resin tube with an inner diameter of 18 mm and an outer diameter of 20 mm.

[0113] For the resin tubes of the examples and comparative examples thus obtained, the evaluation of each characteristic was carried out based on the following criteria. The results are shown together in Table 1 below.

[0114] 《Heat Resistance Test》

[0115] The resin tube was cut in half and punched into strips with a width of 10 mm and a length of 15 cm. After subjecting the obtained strip-shaped samples to heat aging treatment (heat treatment at 130°C for 500 hours, heat treatment at 130°C for 750 hours), according to JIS K6251, the elongation at break [Eb] of the above samples was measured by a tensile testing machine (AGS-X, manufactured by Shimadzu Corporation).

[0116] As a result, for the elongation of the above samples in the heat treatment at 130°C for 500 hours, those with an elongation of 50% or more of the sample length were evaluated as "〇 (very good)", and those less than 50% of the sample length were evaluated as "× (poor)".

[0117] In addition, for the elongation of the above samples in the heat treatment at 130°C for 750 hours, those with an elongation of 50% or more of the sample length were evaluated as "◎ (excellent)".

[0118] 《Extraction Resistance Test》

[0119] Using the obtained resin composition, an injection molded sheet (sample) with a thickness of 2 mm was produced under the condition of a temperature of 200°C. Then, a resin sheet with a side length of 2.8 cm was punched out from the sheet. The resin sheet (10 g) was sealed together with 100 ml of a coolant (50% ethylene glycol aqueous solution) in a covered 100 ml polypropylene container and heat-treated at 100°C for 72 hours to extract the components in the rubber sheet. After that, vacuum filtration was carried out using a filter paper with a pore size of 8 μm, and air drying (70°C × 24 hours) was carried out to measure the mass X (g) of the air-dried rubber sheet.

[0120] Based on the mass of the rubber sheet before extraction (10 g) and the above-mentioned mass X (g), calculate the extraction rate (%).

[0121] Extraction rate (%) = [10 (g) - X (g)] / 10 (g) × 100

[0122] As a result, those with an extraction rate (%) of 0.05% or more and less than 1.0% are evaluated as "〇 (very good)", and those with 1.0% or more are evaluated as "× (poor)".

[0123] In addition, those with an extraction rate (%) less than 0.05% are evaluated as "◎ (excellent)".

[0124] [Table 1]

[0125]

[0126] From the results of Table 1 above, it can be seen that the resin tubes of Examples 1 to 4 are all resin tubes with excellent heat resistance and extraction resistance.

[0127] In contrast, in Comparative Example 1, since a polypropylene resin with an MFR of 2.0 g / 10 minutes was used, the result was poor extraction resistance, and heat resistance and extraction resistance could not be balanced.

[0128] In Comparative Example 2, since a polypropylene resin with a melting point of 143 °C was used, the result was poor heat resistance, and heat resistance and extraction resistance could not be balanced.

[0129] In Comparative Example 3, since an antioxidant with a melting point of 50 - 55 °C was used, the result was poor extraction resistance, and heat resistance and extraction resistance could not be balanced.

[0130] In Comparative Examples 4 and 5, since the compounding ratio of the antioxidant relative to the polypropylene resin was "0.05 parts by mass" or "1.5 parts by mass", heat resistance and extraction resistance could not be balanced.

[0131] Based on the above test results, it was confirmed that by using a resin composition containing (A) a polypropylene resin having a melt flow rate measured at 230 °C and a load of 2.16 kg of "0.2 g / 10 minutes or more and less than 2.0 g / 10 minutes" and a melting point of "145 °C or more", and (B) an antioxidant having a melting point of "60 °C or more", and the content of component (B) relative to 100 parts by mass of component (A) being "0.1 - 1 part by mass", a coolant delivery pipe for vehicles with excellent heat resistance and extraction resistance can be obtained.

[0132] Although the specific embodiments of the present invention are shown in the above embodiments, the above embodiments are merely examples and are not subject to restrictive interpretation. Those skilled in the art can understand that various obvious variations are within the scope of the present invention.

[0133] Industrial Applicability

[0134] The coolant delivery pipe for vehicles obtained by the present invention is used, for example, in the piping of coolant in an automobile, specifically, in radiator hoses, heater hoses, air-conditioning hoses, etc., and in the cooling pipes for battery packs of electric vehicles or fuel cell vehicles. In addition, it can be used not only for automotive applications but also for cooling pipes of other transportation machinery (such as airplanes, forklifts, excavators, cranes, etc., industrial transport vehicles, railway vehicles, etc.), vending machines, etc.

Claims

1. A resin composition for a coolant delivery pipe for a vehicle, which contains the following component (A) and component (B), and the content of component (B) is 0.1 to 1 part by mass based on 100 parts by mass of component (A). (A) A polypropylene-based resin having a melt flow rate of 0.2 g / 10 min or more and less than 2.0 g / 10 min measured at 230 °C under a load of 2.16 kg and a melting point of 145 °C or more. (B) An antioxidant having a melting point of 60 °C or more.

2. The resin composition for a coolant delivery pipe for a vehicle according to claim 1. Wherein The above-mentioned component (A) is a propylene-α-olefin block copolymer.

3. The resin composition for a coolant delivery pipe for a vehicle according to claim 1 or 2. Wherein The melt flow rate of the above-mentioned component (A) is 0.2 g / 10 min or more and 1.5 g / 10 min or less.

4. The resin composition for a coolant delivery pipe for a vehicle according to any one of claims 1 to 3. Wherein The melting point of the above-mentioned component (B) is 90 °C or more.

5. The resin composition for a coolant delivery pipe for a vehicle according to any one of claims 1 to 4. Wherein The above-mentioned component (B) is a phenolic antioxidant.

6. The resin composition for a coolant delivery pipe for a vehicle according to any one of claims 1 to 5. Wherein The above-mentioned component (B) is a hindered phenolic antioxidant.

7. A coolant delivery pipe for a vehicle, which is formed of the resin composition for a coolant delivery pipe for a vehicle according to any one of claims 1 to 6.

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