Resin composition for vehicle coolant transport tubes and vehicle coolant transport tubes

Abstract

Provided are a resin composition for vehicle coolant transport tubes having superior heat resistance and extraction resistance, and a vehicle coolant transport tube obtained by employing said composition.　The present invention provides a resin composition for vehicle coolant transport tubes that contains (A) and (B) components indicated below, the (B) component content being 0.1 to 1 part by mass per 100 parts by mass of the (A) component.　(A) A polypropylene resin in which the melt flow rate measured at 230ºC and 2.16 kg load is 0.2 g / 10 min to less than 2.0 g / 10 min and the melting point is 145ºC or higher.　(B) An antioxidant in which the melting point is 60ºC or higher.

Description

Technical Field

[0001]

[0001] The present invention relates to a resin composition for a coolant transport tube for vehicles and a coolant transport tube for vehicles obtained using the same. Specifically, it relates to a tube for transporting coolant in a cooling system of an automobile or the like, which is excellent in heat resistance and extraction resistance.

Background Art

[0002] Conventionally, polyamide resin has been adopted as the material for coolant transport tubes in gasoline-powered vehicles and electric vehicles from the viewpoint of excellent heat resistance and the like (for example, see Patent Document 1). However, since polyamide resin has problems in terms of price, polypropylene-based resin, which is a cost-advantageous material, has been studied (for example, see Patent Document 2).

Prior Art Documents

Patent Documents

[0003] <00资源分配0016>

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a polypropylene-based resin is used as the material for a coolant transport tube for vehicles, although it is excellent in terms of cost, there are still problems with heat resistance. Therefore, from the viewpoint of improving heat resistance, it is conceivable to blend an antioxidant. However, when an antioxidant is blended as the material for a coolant transport tube for vehicles, 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 circuits and electric leakage.

[0005] The present invention has been made in view of these circumstances, and provides a resin composition for vehicle coolant transport tubes that is excellent in heat resistance and extractability, and a vehicle coolant transport tube obtained using the same. [Means for solving the problem]

[0006] In order to solve the above problems, the inventors of the present invention, through diligent research, focused on the conflicting challenges of heat resistance and extractability when using antioxidants. Specifically, from the viewpoint of improving heat resistance, it is necessary to increase the amount of antioxidant added, but if the amount of antioxidant is increased, it becomes difficult to suppress the extraction of components derived from the antioxidant into the coolant, and thus extractability cannot be guaranteed. As a result of further research from the viewpoint of achieving both heat resistance and extractability, the inventors of the present invention discovered that by using a specific polypropylene resin and a specific antioxidant in combination, and by keeping the content ratio of both within a specific range, it is possible to obtain a vehicle coolant transport tube with excellent heat resistance and extractability, thus arriving at the present invention.

[0007] In other words, the gist of the present invention is as follows: [1] to [7]. [1] A resin composition for transporting coolant in vehicles, comprising the following components (A) and (B), wherein the content of component (B) is 0.1 to 1 part by mass per 100 parts by mass of component (A). (A) A polypropylene 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 and a 2.16 kg load, and a melting point of 145°C or higher. (B) Anti-aging agent with a melting point of 60°C or higher. [2] The resin composition for vehicle coolant transport tubes according to [1], wherein the above component (A) is a propylene-α-olefin block copolymer. [3] A resin composition for vehicle coolant transport tubes according to [1] or [2], wherein the melt flow rate of component (A) above is 0.2 g / 10 min or more and 1.5 g / 10 min or less. [4] A resin composition for vehicle coolant transport tubes according to any one of [1] to [3], wherein the melting point of component (B) above is 90°C or higher. [5] A resin composition for vehicle coolant transport tubes according to any one of [1] to [4], wherein component (B) is a phenolic antioxidant. [6] A resin composition for vehicle coolant transport tubes according to any one of [1] to [5], wherein the above component (B) is a hindered phenol-based antioxidant. [7] A vehicle coolant transport tube comprising a resin composition for vehicle coolant transport tubes as described in any of [1] to [6]. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a vehicle coolant transport tube that has excellent heat resistance and extraction resistance. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of a vehicle coolant transport tube according to the present invention. [Modes for carrying out the invention]

[0010] Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to these embodiments.

[0011] A resin composition for vehicle coolant transport tubes according to one embodiment of the present invention (hereinafter sometimes referred to as "this resin composition") is characterized in that it contains the following components (A) and (B), and that the content of component (B) per 100 parts by mass of component (A) is specified to be 0.1 to 1 part by mass. (A) A polypropylene 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 and a 2.16 kg load, and a melting point of 145°C or higher. (B) Anti-aging agent with a melting point of 60°C or higher.

[0012] Since the coolant transport tube for vehicles is installed close to heat sources such as engines and batteries, it is exposed to a high-temperature environment. In addition, since high-temperature coolant flows inside the tube, excellent heat resistance is required. On the other hand, when the coolant in the vehicle coolant transport tube becomes conductive, it may cause an electrical short circuit, raising concerns such as the risk of electric shock and a decrease in power generation efficiency due to leakage. Therefore, the development of technology to reduce the conductivity of the coolant has become even more important than before. Against this backdrop, there is a strong demand for the development of technologies that can contribute to reducing the conductivity of the coolant in vehicle coolant transport tubes. In recent years, in particular, with the spread of electric vehicles and the increase in the voltage of batteries, assuming various problems that occur when the coolant leaks, the insulation requirements for the coolant have been tightened, and it has become an urgent task to address this issue in vehicle coolant transport tubes as well.

[0013] This resin composition is based on such a background. The vehicle coolant transport tube obtained by using this resin composition is excellent in heat resistance and also excellent in the extraction resistance of components (ionic components) that can adversely affect the conductivity of the coolant. Therefore, it is useful in that it can contribute to the technology for reducing the conductivity of the coolant.

[0014] In addition, the vehicle coolant transport tube obtained by using this resin composition is excellent in extraction resistance, so it is also useful in that it suppresses clogging of the filter in the cooling system and does not hinder the operation of the cooling system.

[0015] Moreover, the vehicle coolant transport tube obtained by using this resin composition uses a polypropylene-based resin with high cost competitiveness, so it is further useful in terms of excellent economic efficiency.

[0016] Conventionally, a tube with a multilayer structure having a polyamide resin layer and a polypropylene resin layer has been proposed from the viewpoints of heat resistance and economy. However, since it is difficult to peel each layer during recycling, it has poor recyclability. The coolant transport tube for vehicles obtained by using this resin composition can exhibit excellent properties such as heat resistance and economy even with a single-layer structure. Therefore, the coolant transport tube for vehicles obtained by using this resin composition is useful in that it is excellent in heat resistance, economy, and recyclability.

[0017] Hereinafter, each material and the like constituting this resin composition will be described. In this specification, "X and / or Y (X and Y are arbitrary configurations)" means at least one of X and Y, and means three cases: only X, only Y, and X and Y.

[0018] 《(A) Polypropylene-based resin》 The polypropylene-based resin used in this resin composition shows a melt flow rate (hereinafter, may be abbreviated as "MFR") measured under the conditions of 230°C and a load of 2.16 kg of 0.2 g / 10 min or more and less than 2.0 g / 10 min, and it is important that the melting point is 145°C or higher. By using a polypropylene-based resin in which the MFR is within the above range and the melting point is within the above range, this resin composition can obtain the desired extraction resistance and heat resistance. When the MFR of component (A) is 2.0 g / 10 min or more, or when the melting point of component (A) is lower than 145°C, the compatibility between component (A) and component (B) decreases, etc., and the extraction amount into the coolant tends to increase. Therefore, it is difficult to achieve both high heat resistance and extraction resistance. The above MFR is measured under the conditions of 230°C and a load of 2.16 kg in accordance with JIS K7210:1999.

[0019] (A) 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, from the viewpoint of significantly exhibiting the effects of the present invention. Furthermore, 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.

[0020] The melting point of component (A) is preferably 148°C or higher, more preferably 150°C or higher, and even more preferably 155°C or higher, from the viewpoint of significantly exhibiting the effects of the present invention. Furthermore, there is no particular upper limit to the melting point of component (A), but for example, it is about 175°C. The melting point in this specification can be measured, for example, by a method in accordance with JIS K7121:2012.

[0021] (A) Specific examples of component (A) include, 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.

[0022] Examples of α-olefins used in these copolymers include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Among these, ethylene, 1-butene, and 1-hexene are preferred, with ethylene being particularly preferred.

[0023] Furthermore, as component (A), examples include modified polypropylene resins obtained by modifying the above-mentioned polypropylene resin with at least one modified compound selected from the group consisting of acids and acid derivatives. Examples of acids or their derivatives in the above-mentioned acid-modified products include unsaturated carboxylic acids and their derivatives. Examples of unsaturated carboxylic acids include maleic acid, fumaric acid, acrylic acid, and methacrylic acid. Examples of derivatives of unsaturated carboxylic acids include acid anhydrides, ester compounds, amide compounds, imide compounds, and metal salts of the above-mentioned unsaturated carboxylic acids.

[0024] Furthermore, as component (A), examples of alloys (mixtures) include polypropylene components such as the homopolymer of propylene (homopolypropylene) described above, which form the sea phase, and alloys (mixtures) having a sea-island structure in which, for example, polyethylene components or ethylene-based rubber components form the island phase. Examples of the polyethylene component include ethylene homopolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and copolymers of ethylene and α-olefins (ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-octene copolymers). Examples of the ethylene-based rubber component include ethylene-propylene-diene terpolymer (EPDM), ethylene-propylene copolymer (EPR), ethylene-butene copolymer (EBR), and ethylene-octene copolymer (EOR). Among the above ethylene-based rubber components, ethylene-propylene copolymer (EPR) and ethylene-propylene-diene terpolymer (EPDM) are preferred. Furthermore, the content ratio of polyethylene components and / or ethylene-based rubber components relative to the entire alloy (100% by mass) is not limited, but is, for example, 1 to 80% by mass, 1 to 70% by mass, 1 to 60% by mass, 1 to 55% by mass, and preferably 1 to 49% by mass, 2 to 30% by mass, 2.5 to 20% by mass, etc.

[0025] (A) Among the components, propylene-α-olefin block copolymers are preferred from the viewpoint of significantly exhibiting the effects of the present invention. Examples of propylene-α-olefin block copolymers include alloys (mixtures) having a sea-island structure in which a polypropylene component such as a propylene homopolymer is the sea phase and a polyethylene component and / or an ethylene-based rubber component is the island phase. Examples of the polyethylene component in the above alloy include ethylene homopolymer, ethylene-propylene copolymer, ethylene-butene copolymer, and ethylene-octene copolymer. Examples of the ethylene-based rubber component include ethylene-propylene-diene terpolymer (EPDM), ethylene-propylene copolymer (EPR), ethylene-butene copolymer (EBR), and ethylene-octene copolymer (EOR). Among the above ethylene-based rubber components, ethylene-propylene copolymer (EPR) and ethylene-propylene-diene terpolymer (EPDM) are preferred, and ethylene-propylene copolymer (EPR) is more preferred. Furthermore, the content ratio of polyethylene components and / or ethylene-based rubber components relative to the entire alloy (100% by mass) is not limited to the following, but is for example 1 to 80% by mass, 1 to 70% by mass, 1 to 60% by mass, 1 to 55% by mass, and preferably 1 to 49% by mass, 2 to 30% by mass, 2.5 to 20% by mass, etc.

[0026] Among the propylene-α-olefin block copolymers mentioned above, propylene-ethylene block copolymers are preferred. Propylene-ethylene block copolymers are produced, for example, by polymerizing propylene alone (pre-polymerization) and then copolymerizing it with ethylene (post-polymerization). In the post-polymerization described above, components other than ethylene may also be copolymerized. Propylene-ethylene block copolymers have a sea-island structure in which island phases of ethylene blocks or ethylene-propylene copolymer blocks are dispersed in a sea phase where propylene is polymerized, and are generally also called propylene block polymers or block polypropylenes.

[0027] In this resin composition, these components (A) can be used individually or in combination of two or more. When two or more components (A) are used together, it is preferable that the MFR and melting point of the polyethylene resin mixture consisting of two or more components be within the above range. Furthermore, for example, when the above alloy (mixture) is used as component (A), it is preferable that the MFR and melting point of the alloy be within the above range.

[0028] This resin composition mainly consists of component (A). For example, the content of component (A) relative to the entire resin composition (100% by mass) is usually 50% by mass or more, preferably 55 to 99.9% by mass, more preferably 60 to 90% by mass, and even more preferably 65 to 80% by mass.

[0029] (B) Anti-aging agent It is important that the (B) antioxidant used in this resin composition has a melting point of 60°C or higher. If the melting point of the (B) antioxidant is below 60°C, components derived from the antioxidant tend to be extracted into the coolant, making it difficult to achieve both extractability and heat resistance.

[0030] 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, from the viewpoint of significantly exhibiting the effects of the present invention. It is also preferably 300°C or lower, and more preferably 250°C or lower.

[0031] The molecular weight of component (B) is not particularly limited, but is preferably 550 to 1300, more preferably 580 to 1280, even more preferably 600 to 1250, and most preferably 700 to 1200.

[0032] (B) Specific examples of component (B) include, but are not limited to, phenolic antioxidants, amine antioxidants, imidazole antioxidants, phosphate antioxidants, etc. These can be used alone or in combination of two or more. Among these, phenolic antioxidants are preferred from the viewpoint of significantly achieving the effects of the present invention. Among phenolic antioxidants, hindered phenolic antioxidants are particularly preferred from the viewpoint of heat resistance.

[0033] 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: melting point 110~125℃), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate (e.g., "Irganox 3114", manufactured by BASF: melting point 218~223℃), 2,4,6-tris(4-hydroxy-3,5-di-tert-butylbenzyl) mesitylene (e.g., "Irganox 1330", manufactured by BASF: melting point 240~245℃), and 6-(4-hydroxy-3,5-di-tert-butylanilino)-2,4-bis(oxy) Examples include thylthio)-1,3,5-triazine (e.g., "Irganox 565", manufactured by BASF: melting point 91-96°C), 2,2'-thiodiethylbis[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), and 1,6-hexanediolbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ("Irganox 259", manufactured by BASF: melting point 104-108°C).

[0034] (B) From the viewpoint of achieving the effects of the present invention, it is important that the content of component (B) be relatively small, such as 0.1 to 1 part by mass per 100 parts by mass of polypropylene resin (A). If the content of the antioxidant (B) relative to component (A) is outside the above range, it is difficult to achieve a high degree of both heat resistance and extractability.

[0035] (Other ingredients) In addition to components (A) and (B), various additives such as fillers, weather stabilizers, lubricants, pigments, dyes, antistatic agents, plasticizers, crosslinking agents, and crosslinking aids may be appropriately added to the forming material of this resin composition as needed, within limits that do not impede the effects of the present invention.

[0036] Examples of fillers include inorganic fillers such as talc, silica, mica, kaolin, calcium carbonate, potassium titanate, apatite, and mica. These can be used individually or in combination of two or more. Among these, talc is preferred from the viewpoint of extrusion processability and reinforcing properties.

[0037] The content of the filler is not particularly limited, but from the viewpoint of strength, it is, for example, 1 to 100 parts by mass, preferably 10 to 70 parts by mass, per 100 parts by mass of (A) polypropylene resin. Alternatively, the content of the filler may be 10 to 50 parts by mass, etc.

[0038] Examples of crosslinking agents include peroxide crosslinking agents such as peroxyketals, peroxyesters, dialkyl peroxides, ketone peroxides, diacyl peroxides, and peroxydicarbonates. These can be used alone or in combination of two or more. The content of the crosslinking agent is not particularly limited, but is, for example, 0.1 to 4 parts by mass, preferably 0.2 to 2 parts by mass, per 100 parts by mass of (A) polypropylene resin.

[0039] (Manufacturing method) The resin composition and the vehicle coolant transport tube made from this resin composition are manufactured, for example, by kneading component (A), component (B), and other components as needed, and then melt-extruding the resulting mixture into a tube. For example, they can be manufactured successfully by performing the steps shown in [I] to [III] below in this order. [I] A step of kneading component (A) and component (B). [II] A step of adding an inorganic filler to the kneaded material obtained in step [I] and kneading it. [III] A step of melt-extruding the kneaded material obtained in step [II] into a tube shape.

[0040] Step [I] described above is a step in which components (A) and (B), etc., are kneaded using a twin-screw kneading extruder or the like at, for example, 190 to 230°C for 0.01 to 10 minutes.

[0041] Step [II] above is a step in which an inorganic filler is added to the kneaded material obtained in Step [I] above and kneaded. The kneading conditions are, for example, 190 to 270°C for 0.01 to 10 minutes using a twin-screw extruder or the like. Any optional components other than components (A) and (B) may be added in any of steps [I] to [III] above, but it is preferable to add and mix them in step [II] or later. While compounds having a guanamine skeleton may be optionally added to this resin composition, it is preferable not to add compounds having a guanamine skeleton from the viewpoint of extrusion processability, etc.

[0042] Step [III] described above is a process of melt-extruding the kneaded material obtained in step [II] into a tubular shape at, for example, 190 to 270°C using a melt extrusion molding machine equipped with a cylindrical die. From the viewpoint of productivity, it is preferable to use pelletized kneaded material.

[0043] The vehicle coolant transport tube of the present invention obtained in this manner 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, from the viewpoint of its application.

[0044] The vehicle coolant transport tube obtained from this resin composition is preferably implemented as a single-layer vehicle coolant transport tube, for example, as shown in Figure 1. Alternatively, if necessary, other resin layers or reinforcing thread layers may be further laminated to create a multi-layer vehicle coolant transport tube.

[0045] The vehicle coolant transport tubes obtained from this resin composition can be used, for example, in coolant piping inside automobiles, specifically in radiator hoses, heater hoses, air conditioning hoses, and cooling tubes for battery packs in electric vehicles and fuel cell vehicles. [Examples]

[0046] Next, embodiments of the present invention will be described together with comparative examples. However, the present invention is not limited to these embodiments.

[0047] First, prior to the examples and comparative examples, the following materials were prepared.

[0048] <(A) Polypropylene resin> [Polypropylene resin (a)] Propylene-α-olefin block copolymer (E-702MG, manufactured by Prime Polymer, MFR: 1.4g / 10min, melting point: 162℃)

[0049] [Polypropylene resin (a'1)] Homopropylene homopolymer (E-200GP, manufactured by Prime Polymer, MFR: 2.0g / 10min, melting point 164℃) [Polypropylene resin (a'2)] Propylene-α-olefin random copolymer (B-241, manufactured by Prime Polymer, MFR: 0.5g / 10min, melting point 143℃)

[0050] <(B) Anti-aging agent> [Phenol-based antioxidant (b1)] Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010, manufactured by BASF, melting point 110-125°C) [Phenol-based antioxidant (b2)] 2,2'-Thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1035, manufactured by BASF, melting point 63-78°C)

[0051] [Phenol-based antioxidant (b')] n-Octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (Irganox 1076, manufactured by BASF, melting point 50-55°C)

[0052] <Filler> [Inorganic fillers] Talc (FH108, manufactured by Fuji Talc Co., Ltd.)

[0053] [Examples 1-3, Comparative Examples 1-5] In the mass ratios and combinations shown in Table 1 below, each component except the inorganic filler was kneaded at 200°C for 5 minutes using a twin-screw compound extruder (TEM-18SS, manufactured by Toshiba Machine Co., Ltd.). Then, the inorganic filler was added and kneaded again at 200°C for 5 minutes using the same twin-screw compound extruder to obtain a compound (resin composition). Next, the above-mentioned mixture was pelletized, and these pellets were melt-extruded into a tubular shape at 250°C using a melt extrusion molding machine (GT-40, manufactured by Plastics Engineering Research Institute Co., Ltd.) equipped with a cylindrical die, thereby obtaining a resin tube with an inner diameter of 18 mm and an outer diameter of 20 mm.

[0054] [Example 4] The components were kneaded at 200°C for 5 minutes using a twin-screw compound extruder (TEM-18SS, manufactured by Toshiba Machine Co., Ltd.) in the mass ratios and combinations shown in Table 1 below to obtain a compound (resin composition). Next, the above-mentioned mixture was pelletized, and these pellets were melt-extruded into a tubular shape at 250°C using a melt extrusion molding machine (GT-40, manufactured by Plastics Engineering Research Institute Co., Ltd.) equipped with a cylindrical die, thereby obtaining a resin tube with an inner diameter of 18 mm and an outer diameter of 20 mm.

[0055] The resin tubes of the examples and comparative examples obtained in this manner were evaluated for their respective properties according to the following criteria. The results are shown in Table 1 below.

[0056] Heat Resistance Test The resin tube was cut in half and punched out into strips 10 mm wide and 15 cm long. After subjecting these strip-shaped samples to heat aging treatment (heat treatment at 130°C for 500 hours and heat treatment at 130°C for 750 hours), the elongation [Eb] at break of the samples was measured using a tensile testing machine (AGS-X, manufactured by Shimadzu Corporation) in accordance with JIS K 6251. As a result, samples whose elongation during heat treatment at 130°C for 500 hours was 50% or more of the sample length were evaluated as "〇 (very good)", and those whose elongation was less than 50% of the sample length were evaluated as "× (poor)". Furthermore, samples whose elongation during heat treatment at 130°C for 750 hours was 50% or more of the sample length were marked with "◎ (excellent)".

[0057] ≪Extraction Resistance Test≫ Using the obtained resin composition, an injection-molded sheet (sample) with a thickness of 2 mm was prepared at a temperature of 200°C. Subsequently, a 2.8 cm square resin piece was punched out from this sheet. This resin piece (10 g) was sealed in a 100 ml polypropylene container with a lid, along with 100 ml of cooling liquid (50% aqueous solution of ethylene glycol), and heat-treated at 100°C for 72 hours to extract the components from the rubber piece. After that, it was filtered under reduced pressure using filter paper with a pore size of 8 μm, air-dried (70°C for 24 hours), and the mass X (g) of the air-dried rubber piece was measured. The extraction rate (%) was calculated based on the mass of the rubber piece before extraction (10g) and the above mass X (g). Extraction rate (%)=[10(g)-X(g)] / 10(g)×100 As a result, samples with an extraction rate (%) of 0.05% or more and less than 1.0% were rated as "〇 (very good)," while those with an extraction rate of 1.0% or more were rated as "× (poor)." Additionally, samples with an extraction rate (%) of less than 0.05% were marked with "◎ (excellent)".

[0058] [Table 1]

[0059] As shown in Table 1 above, the resin tubes of Examples 1 to 4 all exhibited excellent heat resistance and extractability.

[0060] In contrast, Comparative Example 1 used a polypropylene resin with an MFR of 2.0 g / 10 min, resulting in poor extraction resistance, and thus failing to achieve both heat resistance and extraction resistance. In Comparative Example 2, a polypropylene resin with a melting point of 143°C was used, resulting in poor heat resistance, and it was not possible to achieve both heat resistance and extractability.

[0061] In Comparative Example 3, an antioxidant with a melting point of 50-55°C was used, resulting in poor extractability, and it was not possible to achieve both heat resistance and extractability. In Comparative Examples 4 and 5, the blending ratio of the anti-aging agent to the polypropylene resin was "0.05 parts by mass" or "1.5 parts by mass," which meant that both heat resistance and extractability could not be achieved.

[0062] Based on the above test results, it was confirmed that a vehicle coolant transport tube with excellent heat resistance and extractability can be obtained by using a resin composition containing (A) a polypropylene resin with a melt flow rate of "0.2 g / 10 min or more and less than 2.0 g / 10 min" measured at 230°C and a 2.16 kg load, and a melting point of "145°C or higher", and (B) an antioxidant with a melting point of "60°C or higher", where the content of component (B) is "0.1 to 1 part by mass" per 100 parts by mass of component (A).

[0063] While the above embodiments illustrate specific forms of the present invention, these embodiments are merely illustrative and should not be interpreted restrictively. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention. [Industrial applicability]

[0064] The vehicle coolant transport tube obtained by the present invention can be used, for example, in the piping of coolant inside an automobile, specifically in radiator hoses, heater hoses, air conditioning hoses, etc., and as a cooling tube for battery packs in electric vehicles and fuel cell vehicles. Furthermore, it can be used not only for automobiles but also as a cooling tube for other transport machinery (industrial transport vehicles such as airplanes, forklifts, excavators, and cranes, railway vehicles, etc.) and vending machines.

Claims

1. A resin composition for vehicle coolant transport tubes, comprising the following components (A) and (B), wherein the content of component (B) is 0.1 to 1 part by mass per 100 parts by mass of component (A). (A) A polypropylene 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 and a 2.16 kg load, and a melting point of 145°C or higher. (B) Anti-aging agent with a melting point of 60°C or higher.

2. The resin composition for vehicle coolant transport tubes according to claim 1, wherein component (A) is a propylene-α-olefin block copolymer.

3. The resin composition for vehicle coolant transport tubes according to claim 1 or 2, wherein the melt flow rate of component (A) is 0.2 g / 10 min or more and 1.5 g / 10 min or less.

4. The resin composition for vehicle coolant transport tubes according to claim 1 or 2, wherein the melting point of component (B) is 90°C or higher.

5. The resin composition for vehicle coolant transport tubes according to claim 1 or 2, wherein component (B) is a phenolic antioxidant.

6. The resin composition for vehicle coolant transport tubes according to claim 1 or 2, wherein component (B) is a hindered phenol-based antioxidant.

7. A vehicle coolant transport tube comprising the resin composition for vehicle coolant transport tubes according to claim 1 or 2.

Images