JP2013037972A - Water hose for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water hose for fuel cell, capable of restraining generation of ion elution for ion exchange water as well as fuel cell cooling water while ensuring heat resistance and flexibility suitable as a water hose material for fuel cell.SOLUTION: The water hoses for fuel cell (water hoses 142a and 142b) are used in a cooling water system 142 for a fuel cell 110. Aqueous solution formed by adding glycol-based compound to ion exchange water or coolant formed from ion exchange water passes therethrough. Each of the water hoses for fuel cell is formed from dynamic crosslink olefinic thermoplastic elastomer dynamically crosslinked by using peroxide as crosslinking agent.

Description

  The present invention relates to an aqueous hose for a fuel cell used for a cooling system of a fuel cell, particularly a polymer electrolyte fuel cell.

  In recent years, development of fuel cell vehicles has been accelerated from the viewpoint of reducing environmental impact. The power plant of a fuel cell vehicle is mainly composed of a fuel cell that generates electricity by chemically reacting oxygen and hydrogen, and an electric system component that uses the electric power generated by the fuel cell as a driving force. A hydrogen system for supplying hydrogen, an air system for supplying air, and a cooling system for cooling the fuel cell are connected to the fuel cell.

  As a fuel cell mounted on a fuel cell vehicle, a solid polymer fuel cell having a solid polymer film is mainly used. In a polymer electrolyte fuel cell, a basic component (membrane / electrode assembly) composed of a fuel electrode (negative electrode), a solid polymer membrane (electrolyte), and an air electrode (positive electrode) is sandwiched between conductive plates (bipolar plates), One power generation unit called a single cell is configured, and a fuel cell stack in which a plurality of single cells are stacked and connected in series is used. Hereinafter, unless otherwise specified, the term “fuel cell” refers to the above-described polymer electrolyte fuel cell.

  In order to suppress the temperature rise due to the exothermic reaction of the fuel cell, in the fuel cell vehicle, a coolant is caused to flow through the fuel cell stack using a pump. The operating temperature of the fuel cell is maintained at an optimum value (for example, 80 ° C.) by radiating the heat absorbed by the coolant in a radiator installed in the cooling system. For example, in Patent Document 1, synthetic rubber is used as a flexible pipe for circulating this coolant through the cooling system of the fuel cell, that is, an aqueous hose for the fuel cell. Specifically, a peroxide additive containing carbon black as a reinforcing filler (hereinafter referred to as a reinforcing material) is added to an ethylene α-olefin copolymer (ethylene propylene copolymer rubber; hereinafter referred to as EPDM). A sulfur rubber compound (peroxide-crosslinked EPDM) is used.

  By the way, as described above, since the coolant flows in the fuel cell stack, a high conductivity causes a short circuit or a leakage of the battery. Therefore, the cooling liquid needs to have low conductivity (low conductivity). As a low-conductivity liquid that can be used as a cooling liquid, ion-exchanged water (for example, conductivity 1 μS / cm or less) is generally used. However, since it is assumed that the fuel cell vehicle is used in an environment where the temperature is zero degrees or less, there is a risk of freezing if ion-exchanged water is used as a coolant for a fuel cell mounted on the fuel cell vehicle. For this reason, a low-conductivity antifreeze solution (for example, a conductivity of 10 μS / cm or less) made of an aqueous solution in which a glycol compound and a low-conductivity inhibitor are added to ion-exchanged water is used as a coolant for a fuel cell mounted on a fuel cell vehicle. Is mainly used. Hereinafter, the low-conductivity antifreeze is referred to as a fuel cell coolant.

  However, no matter how low the conductivity of the coolant is, if the elution of ions from the fuel cell aqueous hose occurs, the conductivity will increase. Therefore, in order to maintain the low conductivity of the coolant, the fuel cell aqueous hose is required to have less ion elution. With the configuration of Patent Document 1, ions derived from carbon black or the like, which is a reinforcing material, are eluted and the conductivity of the coolant is increased. However, in order to improve the strength of synthetic rubber such as EPDM and to secure the physical properties of the hose, it is difficult to make the reinforcing agent non-compounding. Therefore, in the synthetic rubber hose as in Patent Document 1, there is a limit in reducing the elution property and thus maintaining the low conductivity of the coolant.

  Therefore, for example, in Patent Document 2, as a material having a small increase in electrical conductivity and excellent insulation, a polyolefin resin, a styrene thermoplastic elastomer (hereinafter referred to as SBC), and an olefin thermoplastic elastomer (hereinafter referred to as TPO) are used. It is proposed to use a thermoplastic elastomer (hereinafter referred to as TPE). For example, in patent document 3, the elution of the ion to a pure water is prevented by using a fluororesin for the inner layer side of the resin tube which supplies a pure water to a fuel cell.

Japanese Patent Laid-Open No. 2004-002682 JP-A-2005-149997 JP 2009-083288 A

  However, as described above, the fuel cell coolant (low conductivity antifreeze) is mainly used for cooling the fuel cell mounted on the fuel cell vehicle. The elution degree of ions from the fuel cell aqueous hose to the liquid flowing therethrough is affected by both the material of the fuel cell aqueous hose and the type of liquid. For this reason, in Patent Documents 2 and 3, it is not certain whether the increase in conductivity can be suppressed even in the fuel cell coolant (low conductivity antifreeze) even if the increase in conductivity of pure water can be suppressed. .

  In addition, fuel cell water hoses are required not only to have low elution properties but also to have basic physical properties such as heat resistance and flexibility. However, since SBC and TPO disclosed in Patent Document 2 are inferior in heat resistance as compared with synthetic rubber, there is a drawback that plastic deformation occurs in a high temperature environment (for example, about 80 ° C.). Moreover, since the fluororesin disclosed in Patent Document 3 is inferior in flexibility as compared with synthetic rubber, processing such as bellows processing for imparting it is necessary. As a result, the processing cost is increased, or the pump efficiency is reduced due to pressure loss or turbulent flow. That is, it has been difficult for the conventionally proposed materials to satisfy both low ion elution and basic physical properties as a hose.

  In view of such a problem, the present invention ensures the heat resistance and flexibility as a fuel cell water-based hose material, while leaching ions not only in ion exchange water but also in fuel cell cooling water. It aims at providing the water-system hose for fuel cells which can be suppressed.

  In order to solve the above problems, a typical configuration of a fuel cell water hose according to the present invention is used in a cooling system of a fuel cell, and consists of an aqueous solution obtained by adding a glycol compound to ion exchange water or ion exchange water. An aqueous hose for a fuel cell in which a coolant flows inside, and is characterized by comprising a dynamically crosslinked olefinic thermoplastic elastomer that is dynamically crosslinked using a peroxide as a crosslinking agent.

  TPE is a flexible component showing rubber elasticity (hereinafter referred to as a soft segment) and a molecular constrained component (hereinafter referred to as a hard segment) having a reinforcing effect that prevents plastic deformation corresponding to a crosslinking point of vulcanized rubber. .) TPE, a dynamically crosslinked olefinic thermoplastic elastomer (hereinafter referred to as TPV), is an ethylene-α-olefin copolymer rubber such as ethylene propylene rubber (EPM) or ethylene propylene diene rubber (EPDM). And olefinic thermoplastic elastomer (TPO) having a hard segment made of polyolefin such as polypropylene or polyethylene. Of these soft segments and hard segments, the soft segments can ensure the same flexibility as synthetic rubber. And since the reinforcement effect is acquired by a hard segment, the intensity | strength equivalent to or more than synthetic rubber can be obtained, without adding reinforcing materials, such as carbon black, which was essential in synthetic rubber. Therefore, sufficient strength can be secured while preventing elution of ions due to the reinforcing material.

  Moreover, high heat resistance can be obtained by subjecting TPO to TPV by dynamic crosslinking. In particular, by using a peroxide as a cross-linking agent in this dynamic cross-linking, it is possible to suppress elution of ions from the water hose for fuel cells for both ion-exchanged water and fuel cell coolant. Therefore, it is difficult for the conductivity of the fuel cell coolant to increase, so that the performance of the fuel cell is prevented from being lowered, and the ion exchange resin installed in the coolant system is extended to remove the eluted ions. It becomes possible to plan.

  In the above dynamically crosslinked olefin-based thermoplastic elastomer, the soft segment is preferably made of ethylene propylene copolymer rubber (EPDM), and the hard segment is preferably made of polypropylene (PP). As described above, since the olefinic thermoplastic elastomer composed of EPDM and PP is generally widely used, it is easy to procure raw materials and has advantages in terms of cost. In addition, it is difficult to recycle synthetic rubbers that have been used in the past, but thermoplastic elastomers are recyclable, so use highly versatile thermoplastic elastomers such as olefinic thermoplastic elastomers composed of EPDM and PP. Thus, it can be effectively reused.

  The fuel cell water-based hose has a soft segment and a hard segment so that the hardness measured with a type A durometer in accordance with the durometer hardness test described in item 6 of JIS-K6253 is in the range of 64-75. It is good that the ratio of is adjusted. Thereby, it becomes possible to satisfy the flexibility (softness) and heat resistance required for the fuel cell aqueous hose.

The water-based hose for fuel cells may have a volume resistivity of 1 × 10 ¹⁰ Ω · cm or more measured in accordance with the double ring electrode method described in item 6 of JIS-K6271. As a result, it is possible to avoid an electric shock even if a leakage occurs.

  The fuel cell aqueous hose may further include a carbon black masterbatch. Thereby, the weather resistance can be improved.

  According to the present invention, it is possible to suppress elution of ions not only in ion-exchanged water but also in fuel cell cooling water while suitably ensuring heat resistance and flexibility as a water-based hose material for fuel cells. A fuel cell aqueous hose can be provided.

It is the schematic which illustrates the structure of a fuel cell vehicle. It is a figure which shows the composition and physical property of an Example and a comparative example. It is a figure which shows evaluation of the Example of FIG. 2, and a comparative example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a schematic diagram illustrating the configuration of a fuel cell vehicle, FIG. 1 (a) is a schematic diagram of the overall configuration of the fuel cell vehicle, and FIG. 1 (b) is a schematic configuration of a cooling system of the fuel cell. FIG. As shown in FIG. 1A, the fuel cell vehicle 100 includes a fuel cell 110 (fuel cell stack) that is a power plant and an electrical system component 120. The fuel cell 110 is connected to a hydrogen system 132 that supplies hydrogen from the hydrogen tanks 130a and 130b and an air system 134 that supplies air, and chemically reacts oxygen and hydrogen supplied therefrom. Generate electricity.

  The electric system component 120 includes an inverter 122 and a motor 124, and uses electric power generated by the fuel cell 110 as a driving force. Specifically, the electric power generated by the fuel cell 110 is sent to the inverter 122 and converted from direct current to alternating current, and then supplied to the motor 124. The driving force for rotating the motor 124, that is, the fuel cell vehicle 100. Becomes a driving force for traveling. In addition, a secondary battery 128 is connected to the inverter 122 by an electric power system 126, and the electric power generated by the fuel cell 110 can be charged in the secondary battery 128 and the charged electric power can be used.

  In the fuel cell described above, a temperature rise occurs due to an exothermic reaction when generating power. In order to suppress this temperature rise, in the fuel cell vehicle 100 shown in FIG. 1A, the radiator 140 is connected to the fuel cell 110 by the cooling system 142, and the fuel cell 110 is cooled.

  As shown in FIG. 1B, the cooling system 142 uses two fuel cell water hoses (hereinafter, referred to as water hoses 142a and 142b) that connect the fuel cell 110 and the radiator 140, respectively. In this embodiment, the pump 144 is installed in the water system hose 142a in the cooling system 142, and the coolant is circulated to the fuel cell 110 and the radiator 140 through the water systems hoses 142a and 142b using the pump 144 as power. The water hose 142b is provided with an ion exchanger 146 (ion exchange resin) for removing ions contained in the coolant flowing through the water hoses 142a and 142b, and a conductivity meter 148 for measuring the conductivity of the coolant. ing.

  As the coolant supplied to the fuel cell 110, ion exchange water is well known. However, when the fuel cell 110 is mounted on the fuel cell vehicle 100 as in this embodiment, the ion exchange water is used. If it is, there is a risk of freezing. For this reason, in the fuel cell 110 mounted on the fuel cell vehicle 100, a low-conductivity antifreeze solution composed of an aqueous solution in which a glycol compound is added to ion-exchanged water (further, a low-conductivity inhibitor may be added) is cooled. Used as liquid (fuel cell cooling water). Therefore, in the present embodiment, even when a low-conductivity antifreeze is circulated through the cooling system 142 as the fuel cell cooling water, the elution of ions into the fuel cell cooling water is suppressed, and the heat resistance and possibility as a hose are reduced. Provided are fuel cell water hoses (water hose 142a and 142b) capable of sufficiently ensuring flexibility.

  That is, in the present embodiment, the water-based hoses 142a and 142b used in the cooling system 142 are dynamically cross-linked olefin-based thermoplastic elastomers obtained by dynamically cross-linking olefin-based thermoplastic elastomers (TPO) using peroxide as a cross-linking agent. (TPV). TPV is a kind of thermoplastic elastomer (TPE) characterized by having a soft segment and a hard segment. Therefore, the flexibility similar to that of the synthetic rubber can be imparted to the water-based hoses 142a and 142b by the rubber elasticity of the soft segment. On the other hand, due to the reinforcing effect of the hard segment, the water-based hoses 142a and 142b can have a strength equal to or higher than that of the synthetic rubber without adding a reinforcing material such as carbon black which is essential in the synthetic rubber. In addition, since TPV has a lower specific gravity than conventional synthetic rubber (EPDM hose: TPV hose = 1: 0.8), the weight of the water-based hoses 142a and 142b and the fuel cell vehicle 100 can be reduced. Can be planned.

  Further, as described above, as a feature of the present embodiment, the crosslinking method when TPO is TPV is dynamic crosslinking using a peroxide as a crosslinking agent. Dynamic cross-linking means that a cross-linking agent is added during the dissolution and kneading of the material constituting the soft segment and the material constituting the hard segment to carry out the cross-linking reaction of the soft segment (rubber component) and at the same time the rubber particles are made into TPE In the form, it is a cross-linking system in which fine dispersion is performed in TPO). By using such dynamic crosslinking, a TPV having high heat resistance can be obtained.

  As the crosslinking agent, sulfur, phenol resin (for example, phenol-formaldehyde resin), peroxide, and the like can be exemplified as those generally used. In particular, in the present embodiment, peroxide is used. Thereby, since elution of ions is suppressed for both ion-exchanged water and the fuel cell coolant, it is difficult for the conductivity of the fuel cell coolant to increase. Therefore, it is possible to prevent the performance of the fuel cell 110 from deteriorating and to prolong the life of the ion exchange resin of the ion exchanger 146.

  Examples of the peroxide crosslinking agent described above include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di- (tert-butylperoxy) hexane, and 2,5-dimethyl-2,5. -Di- (tert-butylperoxy) hexyne-3, 1,3-bis (tert-butylperoxyisopropyl) benzene, 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane, n- Butyl-4,4-bis (tert-butylperoxy) valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butylperoxybenzoate, tert-butylperbenzoate, tert-butylperoxyisopropyl carbonate Diacetyl peroxide, lauroyl peroxide, etc. tert- butyl cumyl peroxide. However, these are merely examples and do not exclude peroxide crosslinking agents other than those described above.

  There are various types of TPO used for TPV depending on the material of the soft segment and the hard segment. Particularly, the soft segment is made of ethylene propylene copolymer rubber (EPDM) and the hard segment is made of polypropylene (PP). TPO can be preferably used. Since TPO composed of EPDM and PP is generally widespread, it is easy to procure raw materials and has advantages in terms of cost. In addition, the characteristic of TPE is that it can be easily recycled compared to synthetic rubber. Therefore, by using TPE with high versatility such as TPO made of EPDM and PP, effective use after recycling can be achieved. Promoted.

  Furthermore, the TPV used for the water-based hoses 142a and 142b has a hardness measured by a type A durometer in which the ratio of the soft segment and the hard segment described above conforms to the durometer hardness test described in item 6 of JIS-K6253. (Hereinafter referred to as hardness (Shore A)) may be adjusted to be in the range of 64 to 75. Thereby, it is possible to achieve both flexibility (softness) and heat resistance required for the water-based hoses 142a and 142b.

Further, the TPV used for the water-based hoses 142a and 142b may have a volume resistivity of 1 × 10 ¹⁰ Ω · cm or more measured in accordance with the double ring electrode method described in JIS-K6271 item 6. . Thereby, even if a leakage occurs, an electric shock can be avoided and high safety can be obtained.

  A carbon black masterbatch can be added to the TPV of this embodiment for the purpose of improving weather resistance. Details of this will be described later using Examples and Comparative Examples.

[Examples and Comparative Examples]
Next, effects of the present embodiment will be described using examples and comparative examples. FIG. 2 is a diagram showing compositions and physical properties of Examples and Comparative Examples. FIG. 3 is a diagram showing the evaluation of the example and the comparative example of FIG. In the evaluation described below, in Examples 1 to 3 and Comparative Examples 1 to 9 shown in FIG. 2, the elution into the ion-exchange water, the elution into the fuel cell coolant shown in FIG. The material performance and product performance were tested and the results were compared.

  About the structure of Examples 1-3 shown in FIG. 2, and Comparative Examples 1-9, it is as follows. Example 1 is a TPV having a hardness (Shore A) of 64 obtained by peroxide crosslinking of TPO whose soft segment is EPDM and whose hard segment is PP. Example 2 is a TPV having a hardness (Shore A) of 75 obtained by peroxide crosslinking TPO having a soft segment of EPDM and a hard segment of PP. Example 3 is a TPV having a hardness (Shore A) of 74 obtained by peroxide crosslinking TPO having a soft segment of EPDM and a hard segment of PP.

  In Comparative Example 1, a trade name “EXCELLINK 3700” manufactured by JSR Corporation was used. Its composition is TPO that has not been cross-linked, and its hardness (Shore A) is 65. In Comparative Example 1, the configuration of the soft segment and the hard segment is not clear, but is exemplified as an uncrosslinked TPO for explaining the effect of dynamic crosslinking. In Comparative Example 2, a trade name “Santoprene 201-64” manufactured by ExxonMobil Corporation was used. The composition is a TPV having a soft segment made of EPDM, a hard segment made of PP, and resin-crosslinked, and a hardness (Shore A) of 69. In Comparative Example 3, a trade name “Santoprene 201-73” manufactured by ExxonMobil Corporation was used. The composition is a TPV having a soft segment made of EPDM and a hard segment made of PP and having undergone resin crosslinking, and the hardness (Shore A) is 78.

  In Comparative Example 4, a trade name “Sarlink 3160” manufactured by DSM was used. The composition is a TPV in which the soft segment is made of EPDM, the hard segment is made of PP, and the resin is crosslinked, and the hardness (Shore A) is 60. In Comparative Example 5, a trade name “Sarlink 4165” manufactured by DSM was used. The composition is a TPV in which the soft segment is made of EPDM, the hard segment is made of PP, and the resin is crosslinked, and the hardness (Shore A) is 61. In Comparative Example 6, a trade name “AR-875C” manufactured by Aron Kasei Co., Ltd. was used. The composition is a fully hydrogenated styrenic thermoplastic elastomer (SEBS) that has a soft segment made of polyethylene (PE) / polybutylene (PB), a hard segment made of polystyrene (PS), and is not crosslinked, and has a hardness (Shore). A) is 75.

  In Comparative Example 7, a trade name “AR-9070B” manufactured by Aron Kasei Co., Ltd. was used. Its composition is that the soft segment is made of polyethylene (PE) / polybutylene (PB), the hard segment is polystyrene (PS), and is a dynamically crosslinked fully hydrogenated styrene thermoplastic elastomer (SEBS-V) that has been subjected to peroxide crosslinking. And the hardness (Shore A) is 70. In Comparative Example 8, a trade name “Daiel Thermoplastic T-530” manufactured by Daikin Industries, Ltd. was used. Its composition is fluorine-based TPE (F-TPE) in which the soft segment is made of fluororubber, the hard segment is made of fluororesin, and is not crosslinked, and the hardness (Shore A) is 61. In Comparative Example 9, a product name “Daiel Thermoplastic T-550” manufactured by Daikin Industries, Ltd. was used. The composition is fluorine-based TPE (F-TPE) in which the soft segment is made of fluororubber, the hard segment is made of fluororesin, and is not crosslinked, and the hardness (Shore A) is 71.

  The test methods and test conditions for the evaluation items shown in FIG. 3 are as follows.

(1) Dissolvability (ion exchange water and fuel cell coolant)
The problem in elution of ions from the water hoses 142a and 142b, which are fuel cell cooling system components, into the coolant is the degree of increase in the conductivity of the coolant rather than the type of ions to be eluted. Therefore, in the elution evaluation, the conductivity value of the coolant was used regardless of the type of ions eluted.
Test liquid: ion-exchanged water and fuel cell coolant. As ion-exchanged water, ion-exchanged water having an initial conductivity of 0.6 μS / cm purified with an advantech Toyo pure water device GS-200 was used. As the fuel cell coolant, a low-conductivity antifreeze solution having an initial conductivity of 2 μS / cm in which ethylene glycol (50% by volume) and an azole compound as an inhibitor were added to the above ion-exchanged water was used.
Test piece: A 2 mm-thick flat plate produced by compression molding using the materials of Examples 1 to 3 and Comparative Examples 1 to 9 was punched into a size of 64 mmφ, and degreased and washed to obtain a test piece.
・ Test method: A test piece is immersed in a borosilicate glass container containing 200 mL of the test solution and stored in a thermostatic bath at 80 ° C. for 750 hours. It measured using Toledo conductivity meter InPro7001.
Criteria: Using the measured conductivity of the test solution, “elution degree = (conductivity of the test solution after the test (μS / cm) −the conductivity blank value of the test solution after the test (μS / cm)) In the case of ion-exchanged water, if the elution degree calculated from Equation 1 is 4.9 or less, “○ (pass)” is set, and if it exceeds 4.9, “× (fail)” is set. In the case of the cooling liquid, when it was 1.1 or less, it was set as “◯ (pass)”, and when it exceeded 1.1, it was set as “x (fail)”. In addition, the threshold value 4.9 in the case of ion-exchanged water and the threshold value 1.1 in the case of the fuel cell coolant are the hose welding area of the actual fuel cell vehicle and the test piece liquid contact area in the elution test condition, It is a numerical value obtained by conversion from the fuel cell coolant allowable value.

(2) Hot shape retainability A heat shape retainability test was conducted as a heat resistance evaluation. In this test, the temperature range to which the water-based hoses 142a and 142b that are fuel cell cooling system components are exposed is assumed to be a high temperature of about 80 ° C. to 100 ° C. Therefore, the temperature range during the test is as follows: Set to.
Test piece: JIS No. 3 dumbbell test pieces were produced using the materials of Examples 1 to 3 and Comparative Examples 1 to 9.
Test method: A test piece was suspended in a thermostat set to 80 ° C. to 160 ° C., and the amount of change in the vertical direction after 10 minutes was measured.
Criteria: Using the above measured change amount, the length change calculated from “length change = (test piece length after test (mm) −test piece length before test (mm))... When it was within 1 mm, the evaluation was “◯ (pass)”, and when it exceeded 1 mm, it was “x (fail)”.

(3) Material performance and product performance Examples 1 to 3 which passed the judgment criteria in the above-described dissolution and heat shape retention tests and Comparative Example 1 as a comparison target were designated as JIS D 2602 “Automotive Water”. The material performance test and the product performance test were conducted in accordance with “Hose”.
Test liquid: The above-mentioned ion-exchange water, ethylene glycol (50% volume), and inhibitor as an azole as a test liquid for a liquid resistance test, which is a test item for material performance, and a durability test, which is a test item for product performance A low-conductivity antifreeze solution having an initial conductivity of 2 μS / cm to which a system compound was added was used.
-Specimen: For product performance tests, the materials of Examples 1 to 3 and Comparative Example 1 were reinforced with polyethylene terephthalate yarn (trade name: Tetron), an inner diameter of 26 mmφ, an outer diameter of 34 mmφ, a wall thickness of 4 mm, and a length of 300 mm. The hose was extruded and used.
Judgment criteria: Pass / fail judgment was made based on the provisions of JIS D 2602. In addition, since the volume resistivity (material performance) prescribed | regulated by JISD2602 assumes synthetic rubber, it is not suitable for the water-system hose for fuel cells. Therefore, only the volume resistivity is provided separately, and 1 × 10 ¹⁰ Ω · cm or more is regarded as acceptable.

[Discussion]
Referring to FIGS. 2 and 3, in Examples 1 to 3, both elution to ion-exchanged water and the fuel cell coolant and shape retention during heat can be cleared. On the other hand, in Comparative Example 1, since no cross-linking is performed, elution to ion-exchanged water and fuel cell coolant can be cleared, but shape retention during heat cannot be cleared. From this, it can be seen that uncrosslinked TPO cannot satisfy the heat resistance required as a fuel cell cooling system component, and the necessity of dynamic crosslinking to TPO can be confirmed.

  Moreover, when Examples 1-3 are compared with Comparative Examples 2-5, the shape retention property at the time of heating can be cleared in all. From this, it is understood that mechanical properties such as heat resistance can be improved by dynamically cross-linking TPE into TPV. However, in the elution properties to ion-exchanged water and the fuel cell coolant, each of Examples 1 to 3 passed, but Comparative Examples 2 to 5 failed. From this, it can be seen that resin (phenolic resin) cross-linking results in significant elution of ions derived from cross-linking agents and cross-linking aids, leading to an increase in electrical conductivity, and peroxide cross-linking is optimal for dynamic cross-linking. I can understand.

  As described above, sulfur is generally used as a cross-linking agent, but it has been conventionally known that sulfur and vulcanization accelerators are likely to be eluted in sulfur cross-linking. Not adopted as an example.

  Referring to Comparative Examples 6 and 7, with styrene-based TPE, the elution into the fuel cell coolant can be cleared, but both the elution into ion-exchanged water and the shape retention during heat cannot be satisfied. Further, referring to Comparative Examples 8 and 9, although fluorine-based TPE can clear the shape retention during heat, it cannot satisfy the elution to ion-exchanged water or the fuel cell coolant. Therefore, it can be understood that styrene-based TPE and fluorine-based TPE are not suitable for the water-based hoses 142 a and 142 b that constitute the cooling system 142 of the fuel cell 110 mounted on the fuel cell vehicle 100.

  For Examples 1 to 3 that satisfy all of the elution properties to ion-exchanged water and the fuel cell coolant and the shape retention during heat, material performance tests and product performance tests were conducted in accordance with JIS D2602. went. As a result, all the examples were able to satisfy the criteria. Therefore, the TPV according to this embodiment can be suitably used for the cooling system 142a and 142b of the fuel cell 100.

  As described above, according to the fuel cell aqueous hose (aqueous hoses 142a and 142b) according to the present embodiment, a TPE dynamically crosslinked with a peroxide as a crosslinking agent, that is, a peroxide crosslinked TPV is used. Therefore, it is possible to sufficiently ensure material performance such as heat resistance and flexibility and product performance while suppressing elution of ions from the ion exchange water and the fuel cell coolant. Therefore, the water-system hose for the fuel cell according to the present embodiment is optimal as a cooling part for the fuel cell vehicle, and it is difficult for the conductivity of the fuel cell coolant to increase, so that the performance of the fuel cell is prevented and the ion exchange resin is prevented. This makes it possible to extend the service life.

  As described above, a carbon black masterbatch can be added to the TPV of this embodiment for the purpose of improving weather resistance. Carbon black masterbatch is composed of base resin such as low density polyethylene (LDPE) and linear low density polyethylene (LLDPE), and additives such as carbon black, metal soap, antioxidants, etc. of tens of weight. Composed. However, it is desirable to use a carbon black masterbatch containing no metal soap from the viewpoint of elution. Carbon black can also be added as long as it does not impair the TPV elution. These carbon black masterbatch and carbon black are sometimes referred to as a weather resistance improver or a synthetic resin material adhesive.

  The amount of carbon black compounded as a weather resistance improver for TPV can be greatly reduced as compared with the case of compounding such carbon black into a synthetic rubber as a reinforcing agent. For this reason, even if carbon black is blended with TPV as a weather resistance improver, ions are not eluted as much as synthetic rubber. However, when the carbon black masterbatch and the carbon black are compared, the carbon black masterbatch has a lower elution property. Therefore, it is desirable to use a carbon black masterbatch as a weather resistance improver.

  Long-term weather resistance can be improved by blending about 3% of the above-described carbon black masterbatch with TPV. Specifically, in the deterioration acceleration test using a sunshine arc lamp, cracks occur in about 500 hours when the carbon black masterbatch is not blended, whereas when the carbon black masterbatch is blended, cracks occur even after 2000 hours. Did not occur.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The above-described water-based hoses 142a and 142b do not necessarily need to be composed of only the layer made of the TPV of this embodiment. For example, the water-based hoses 142a and 142b have a laminated structure of two or more layers in the diametrical direction, the innermost layer in contact with the fuel cell coolant is constituted by the TPV of the present embodiment, and the other outer layers are different materials from the TPV. You may comprise by.

  Further, in both cases where the water-based hoses 142a and 142b are formed of one layer and a plurality of layers, polyester, rayon, aramid fiber, nylon, etc. are provided on the outer layer from the TPV layer of this embodiment. A reinforcing layer (fiber reinforcing layer) in which these fibers are knitted by a braiding method such as blade, spiral, or knit may be provided.

  INDUSTRIAL APPLICABILITY The present invention can be used for an aqueous hose for a fuel cell used for a cooling system of a fuel cell, particularly a polymer electrolyte fuel cell.

DESCRIPTION OF SYMBOLS 100 ... Fuel cell vehicle, 110 ... Fuel cell, 120 ... Electric system part, 122 ... Inverter, 124 ... Motor, 128 ... Secondary battery, 130a ... Hydrogen tank, 130b ... Hydrogen tank, 132 ... Hydrogen system, 134 ... Air system , 140: Radiator, 142 ... Cooling system, 142a ... Water-based hose, 142b ... Water-based hose, 144 ... Pump, 146 ... Ion exchanger, 148 ... Conductivity meter

Claims (5)

An aqueous hose for a fuel cell that is used in a cooling system for a fuel cell and in which an aqueous solution obtained by adding a glycol compound to ion-exchanged water or a cooling liquid comprising ion-exchanged water circulates inside,
An aqueous hose for a fuel cell comprising a dynamically crosslinked olefinic thermoplastic elastomer that is dynamically crosslinked using a peroxide as a crosslinking agent.   2. The fuel cell aqueous hose according to claim 1, wherein the dynamically crosslinked olefin-based thermoplastic elastomer has a soft segment made of ethylene-propylene copolymer rubber and a hard segment made of polypropylene.   The water segment hose for the fuel cell has the soft segment and the above-mentioned soft segment so that the hardness measured with a type A durometer in accordance with the durometer hardness test described in item 6 of JIS-K6253 is in the range of 64-75. The water-system hose for a fuel cell according to claim 1 or 2, wherein a ratio of the hard segments is adjusted. The volume resistivity measured in accordance with the double ring electrode method described in item 6 of JIS-K6271 is 1 × 10 ¹⁰ Ω · cm or more in the water-based hose for a fuel cell. The water-system hose for fuel cells according to any one of 1 to 3.   The water-based hose for a fuel cell according to any one of claims 1 to 4, further comprising a carbon black masterbatch.

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