Molded product for fuel cell

Abstract

To provide a molded product for fuel cells which prevents a decrease in tensile strength and is excellent in elution resistance even when being used as components of a cooling system for fuel cells.SOLUTION: There is provided a molded product for fuel cells, which is a molded product of a resin composition. The resin composition contains a resin component and the resin component substantially comprises polystyrene and polyphenylene ether. When S1 represents a tensile strength of a weld part of the molded product for fuel cells, and S2 represents a tensile strength of a molded product (A) for fuel cells, the molded product (A) being obtained by immersing the molded product for fuel cells into a long life coolant (LLC) cooling water and then being left for 2,000 hours at 110°C, a ratio of S2 to S1 is 70% or more and 100% or less. When a molded product (B) for fuel cells with a surface area of 50 cm2 / 100 mL is immersed into pure water and then left for 1,000 hours at 95°C, the pure water has a conductivity of 100 μS / cm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a molded article for a fuel cell. [Background technology]

[0002] Polyphenylene sulfide (hereinafter sometimes referred to as "PPS") is sometimes used as a material for cooling system components of fuel cells from the viewpoint of heat resistance and resistance to elution.

[0003] For example, Patent Document 1 describes a polyphenylene sulfide resin composition obtained by blending (A) a polyphenylene sulfide resin, (B) a modified diene copolymer, and (C) an elastomer containing an epoxy group. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-066346 Summary of the Invention [Problem to be solved by the invention]

[0005] In particular, PPS resin is sometimes used in cooling system parts bound with glass fiber for reinforcement. However, prolonged contact of cooling system parts with coolant may reduce the adhesive strength at the interface between the PPS resin and the glass fiber in the area in contact with the coolant, potentially reducing the tensile strength of the PPS resin-containing part of the cooling system part.

[0006] Furthermore, in order to reduce the space required for fuel cells, it is expected that it will also be necessary to miniaturize cooling system components that do not use bolts, but even when no bolts are used, they are required to have good tensile strength.

[0007] Furthermore, if one attempts to improve the output of a fuel cell, it is expected that the cooling capacity of the fuel cell will need to be improved. Increasing the cooling capacity is expected to increase the pressure of the cooling water flowing through the cooling system components. In addition, if one aims to extend the life of the cooling system components, the cooling system components will also need to have high tensile strength. Therefore, it is expected that tensile strength that can withstand such pressure and also withstand a long life will be required.

[0008] Resins used in fuel cells also need to be resistant to leaching. If the leaching resistance is low, ionic components will leach out of the resin, and if these ionic components enter the FC (Fuel Cell) stack, they may cause discharge, resulting in a decrease in cell performance.

[0009] Therefore, an object of the present invention is to provide a molded article for a fuel cell that suppresses a decrease in tensile strength and has excellent resistance to elution even when used as a cooling system part of a fuel cell. [Means for solving the problem]

[0010] In order to solve the above problems, the present inventors have conducted extensive research and have found that the above problems can be solved by providing a molded article using a resin composition containing a resin component essentially consisting of polystyrene and polyphenylene ether, which has a predetermined tensile strength and electrical conductivity.

[0011] That is, the present invention is as follows. [1] A molded product for a fuel cell, the molded article for a fuel cell is a molded article of a resin composition, The resin composition includes a resin component, the resin component consists essentially of polystyrene and polyphenylene ether, The tensile strength of the weld portion of the molded product for a fuel cell is S1, the molded article for a fuel cell is immersed in long-life coolant (LLC) cooling water, and the tensile strength of the weld of the molded article for a fuel cell (A) after 2000 hours at 110°C is defined as S2, and the ratio of S2 to S1 is 70% or more and 100% or less, Surface area 50cm 2 When 100 mL of the molded article (B) for a fuel cell is immersed in pure water at 95°C for 1000 hours, the conductivity of the pure water is 100 μS / cm or less. [2] The fuel cell molded product according to [1], having a welded portion at least in part thereof. [3] The fuel cell molded product according to [2], wherein the tensile strength of the welded portion is 30 MPa or more. [4] The molded article for a fuel cell according to any one of [1] to [3], which is a cooling system part for a fuel cell. [5] The molded product for a fuel cell according to [4], wherein the cooling system part is a pipe or a joint. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a molded article for a fuel cell that is excellent in elution resistance and that suppresses a decrease in tensile strength even when used as a cooling system part of a fuel cell. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1(A) is a plan view that schematically shows a test piece for laser welding, and FIG. 1(B) is a plan view that schematically shows a composite formed by laser welding. [Figure 2] Figure 2(A) is a plan view showing a schematic diagram of a test piece for vibration welding, Figure 2(B) is a plan view showing a schematic diagram of a composite formed by vibration welding, and Figure 2(C) is a plan view showing a schematic diagram of a composite cut into a length of 20 mm. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a detailed description will be given of an embodiment of the present invention (hereinafter referred to as "the present embodiment"). The present invention is not limited to the following embodiment, and various modifications can be made within the scope of the present invention.

[0015] In this specification, the molded article for a fuel cell after immersion in LLC cooling water at 110°C for 2000 hours will be referred to as "molded article for a fuel cell (A)" in order to distinguish it from the general molded article for a fuel cell of the present invention. 2 / 100mL is referred to as "molded article for fuel cell (B)".

[0016] Unless otherwise specified, the materials, components, compounds, resins, structural units, blocks, and solvents described in this specification may be used alone or in combination of two or more.

[0017] In this specification, unless otherwise specified, numerical ranges are intended to include the upper and lower limits of the range. For example, 70 to 100% means a range of 70% to 100%.

[0018] (Molded products for fuel cells) The molded article for a fuel cell of the present invention comprises: A molded article of a resin composition, The resin composition includes a resin component, the resin component consists essentially of polystyrene and polyphenylene ether, The tensile strength of the weld portion of the molded product for a fuel cell is S1, the tensile strength of the weld portion of the molded article for a fuel cell (A) after immersion in LLC cooling water at 110°C for 2000 hours is defined as S2, the ratio of S2 to S1 is 70% or more and 100% or less, Surface area 50cm 2 When 100 mL of the molded article for a fuel cell (B) is immersed in pure water at 95° C. for 1000 hours, the conductivity of the pure water is 100 μS / cm or less.

[0019] The molded article for a fuel cell of the present invention will be described below by way of example.

[0020] ·Resin composition The molded article for a fuel cell of the present invention is a molded article of a resin composition, and the resin composition contains a resin component consisting essentially of polystyrene and polyphenylene ether.

[0021] ·polystyrene Polystyrene (hereinafter sometimes referred to as "PS") refers to a homopolymer of a styrene-based compound, or a copolymer of a styrene-based compound and a compound copolymerizable with a styrene-based compound (excluding conjugated diene compounds; hereinafter, a "compound copolymerizable with a styrene-based compound" will be referred to as "compound CC"). The overlapping portion of polystyrene with the "block copolymer containing a styrene block and a hydrogenated conjugated diene compound block" described below is treated as a "block copolymer containing a styrene block and a hydrogenated conjugated diene compound block" rather than polystyrene. In other words, the polystyrene of this embodiment does not include a "block copolymer containing a styrene block and a hydrogenated conjugated diene compound block."

[0022] Examples of styrene compounds include styrene, α-methylstyrene, 2,4-dimethylstyrene, monochlorostyrene, p-methylstyrene, p-tert-butylstyrene, and ethylstyrene.

[0023] Examples of the compound CC include methacrylic acid esters such as methyl methacrylate and ethyl methacrylate; unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; and acid anhydrides such as maleic anhydride.

[0024] The styrene resin can be obtained by polymerizing a styrene compound, or a styrene compound and compound CC, optionally in the presence of a rubber polymer.

[0025] Examples of rubbery polymers include conjugated diene rubbers, copolymers of conjugated dienes and aromatic vinyl compounds, hydrogenated products thereof, and ethylene-propylene copolymer rubbers.

[0026] In this embodiment, the polystyrene is preferably polystyrene or high impact polystyrene reinforced with a rubber polymer, and more preferably polystyrene.

[0027] The amount of polystyrene in the resin composition may be adjusted as appropriate. For example, the amount of polystyrene is 30 to 70% by mass relative to the total amount of resin components. In one embodiment, the amount of polystyrene is 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, or 65% by mass or more relative to the total amount of resin components. In another embodiment, the amount of polystyrene is 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, or 35% by mass or less relative to the total amount of resin components. In yet another embodiment, the amount of polystyrene is 40 to 60% by mass relative to the total amount of resin components.

[0028] The amount of polystyrene blended is, for example, 20 to 70% by mass relative to the total amount of the resin component and fibrous filler contained in the resin composition. In one embodiment, the amount of polystyrene blended is 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, or 65% by mass or more relative to the total amount of the resin component and fibrous filler. In another embodiment, the amount of polystyrene blended is 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, or 25% by mass or less relative to the total amount of the resin component and fibrous filler. In yet another embodiment, the amount of polystyrene blended is 30 to 40% by mass relative to the total amount of the resin component and fibrous filler.

[0029] Polyphenylene ether The polyphenylene ether (hereinafter sometimes referred to as "PPE") is not particularly limited, and known polyphenylene ethers can be used. Examples of polyphenylene ethers include polyphenylene ethers modified with anhydrides, polyphenylene ether-based resins described in Japanese Patent Publication No. 7253122, polyphenylene ether-based resins described in Japanese Patent Publication No. 2021-038321, and polyphenylene ethers modified with α,β-unsaturated dicarboxylic acid anhydrides described in Japanese Patent Publication No. 2022-145815. A preferred polyphenylene ether is polyphenylene ether modified with anhydrides.

[0030] The amount of polyphenylene ether in the resin composition may be adjusted as appropriate. The amount of polyphenylene ether is, for example, 30 to 70% by mass relative to the total amount of resin components. In one embodiment, the amount of polyphenylene ether is 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, or 65% by mass or more relative to the total amount of resin components. In another embodiment, the amount of polystyrene is 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, or 35% by mass or less relative to the total amount of resin components. In yet another embodiment, the amount of polyphenylene ether is 40 to 60% by mass relative to the total amount of resin components.

[0031] Furthermore, when the resin composition contains a fibrous filler, the blending amount of polyphenylene ether is, for example, 20 to 50% by mass relative to the total amount of the resin component and the fibrous filler. In one embodiment, when the resin composition contains a fibrous filler, the blending amount of polyphenylene ether is 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more relative to the total amount of the resin component and the fibrous filler. In another embodiment, when the resin composition contains a fibrous filler, the blending amount of polyphenylene ether is 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, or 25% by mass or less relative to the total amount of the resin component and the fibrous filler. In yet another embodiment, when the resin composition contains a fibrous filler, the blending amount of polyphenylene ether is 30 to 40% by mass relative to the total amount of the resin component and the fibrous filler.

[0032] Other resins The resin composition may or may not contain other resins in addition to polystyrene and polyphenylene ether, such as polyphenylene sulfide resin, polyamide resin, acrylic resin, and polyether resin.

[0033] Examples of polyphenylene sulfide resins include polyphenylene sulfides described in JP 2011-057975 A and WO 2007 / 114056 A.

[0034] Examples of polyamide resins include aliphatic polyamides, aromatic polyamides, semi-aromatic polyamides, etc. Also included are the polyamides described in JP-A-2023-120914 and JP-A-2023-028726.

[0035] Examples of acrylic resins include polyacrylic acid, polyacrylic acid ester, and polymethyl methacrylate (polymethyl methacrylate).

[0036] Examples of polyether resins include polycarbonate, polyphenylene ether, polysulfone, and polyethersulfone.

[0037] When the resin composition contains other resins in addition to polystyrene and polyphenylene ether, the blending amount of the other resins is, for example, more than 0 mass % and 5 mass % or less relative to the total amount of the resin components.

[0038] ·Filling material The resin composition may or may not contain a filler. Examples of fillers include glass fiber, carbon fiber, glass flake, talc, kaolin, mica, calcium hydrogen phosphate, wollastonite, carbon nanotubes, graphite, calcium fluoride, montmorillonite, swellable fluoromica, and apatite. In one embodiment, the resin composition contains a filler. In another embodiment, the resin composition contains a fibrous filler. In yet another embodiment, the resin composition contains one or more fibers selected from the group consisting of glass fiber and carbon fiber.

[0039] When the resin composition contains a filler, the amount of the filler is, for example, greater than 0% by mass and 40% by mass or less, relative to the total amount of the resin components and the filler. In one embodiment, when the resin composition contains a filler, the amount of the filler is 1% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, or 35% by mass or more, relative to the total amount of the resin components and the filler. In another embodiment, when the resin composition contains a filler, the amount of the filler is 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, 5% by mass or less, or 1% by mass or less, relative to the total amount of the resin components and the filler.

[0040] Other ingredients The resin composition may or may not contain components other than the resin component and the filler, such as a "block copolymer containing a styrene block and a hydrogenated conjugated diene compound block," a plasticizer, an antistatic agent, a nucleating agent, a flow improver, a reinforcing agent, a peroxide, a spreading agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a moldability improver, a lubricant, a deterioration inhibitor, a nucleating agent, a heat stabilizer, and a colorant.

[0041] Block copolymer containing a styrene block and a hydrogenated conjugated diene compound block The resin composition may contain a block copolymer (hereinafter sometimes referred to as "elastomer") containing a styrene block and a hydrogenated conjugated diene compound block in order to improve impact resistance.

[0042] From the viewpoint of thermal stability, the conjugated diene compound block preferably has a hydrogenation rate of 50% or more, more preferably 80% or more, and even more preferably 95% or more.

[0043] Examples of the conjugated diene compound block include polybutadiene, polyisoprene, poly(ethylene-butylene), poly(ethylene-propylene), and vinyl-polyisoprene.

[0044] The arrangement of the repeating units constituting the block copolymer may be either linear or radial.

[0045] The block structure composed of the polystyrene block and the rubber intermediate block may be any of Type 2, Type 3, and Type 4. Among these, a Type 3 linear block copolymer (SEBS) composed of a polystyrene-poly(ethylene butylene)-polystyrene structure is preferred from the viewpoint of fully achieving the desired effects of this embodiment.

[0046] The conjugated diene compound block may contain butadiene units in an amount not exceeding 30% by mass in order to impart impact resistance.

[0047] From the viewpoint of improving impact resistance, the elastomer preferably has a weight average molecular weight Mw of 40,000 to 300,000, more preferably 50,000 to 280,000, and even more preferably 80,000 to 250,000. From the viewpoint of imparting sufficient impact resistance, it is preferably 40,000 or more, and from the viewpoints of flowability, appearance retention, and miscibility of the molded product, it is preferably 300,000 or less.

[0048] The bound styrene content of the elastomer is preferably 20 to 80% by mass, more preferably 50 to 70% by mass, and even more preferably 55 to 75% by mass. From the viewpoint of miscibility, the bound styrene content is preferably 20% by mass or more, and from the viewpoint of imparting impact resistance, it is preferably 80% or less.

[0049] (From the viewpoints of improving miscibility with the resin component and improving molding flowability, the elastomer more preferably contains an oil-extended styrene block-hydrogenated conjugated diene compound block copolymer. Specifically, the oil component is preferably contained in an amount of 5 to 100 parts by mass, more preferably 10 to 75 parts by mass, and even more preferably 20 to 50 parts by mass, per 100 parts by mass of the elastomer. From the viewpoint of dispersibility of the elastomer in the resin component, the content of the oil component is preferably 5 parts by mass or more per 100 parts by mass of the elastomer, and from the viewpoints of heat resistance and prevention of oil bleeding onto the surface of the molded article, it is preferably 100 parts by mass or less.)

[0050] Examples of oil components include paraffinic, naphthenic and aromatic process oils; and oils generally used as rubber softeners (for example, mineral oils such as liquid paraffin and castor oil).

[0051] The oil component may be incorporated into the elastomer in advance during production of the elastomer, or may be added during melt-kneading of the elastomer using an extruder or the like.

[0052] When using a high molecular weight elastomer (Mw: 200,000 to 300,000) as the elastomer, it is preferable to use it in combination with a medium molecular weight elastomer (Mw: 50,000 to 150,000) with a bound styrene content of 55 to 80 mass% or an oil-extended elastomer, rather than using the high molecular weight elastomer alone, from the viewpoint of improving miscibility in the resin composition.

[0053] The ratio of the high molecular weight elastomer to the medium molecular weight or oil-extended elastomer and the high molecular weight elastomer is preferably in the range of 10 to 70 mass %, more preferably 30 to 50 mass %, of the total mass of these.

[0054] From the viewpoint of improving impact resistance, the elastomer preferably contains a block copolymer E1 of a styrene block having a bound styrene content of 55% by mass or more and a hydrogenated conjugated diene compound block. In addition to the block copolymer E1, the resin composition may contain, as an elastomer component, a polyolefin resin (F) described in JP 2022-001624 A, for example.

[0055] When the resin composition contains components other than the resin component and the filler, the blending amount of such components is, for example, more than 0 mass % and 5 mass % or less relative to the total amount of the resin components.

[0056] Tensile strength of welded parts In the present invention, when the tensile strength of the weld of a molded article for a fuel cell is S1 and the tensile strength of the weld of molded article for a fuel cell (A) after the molded article for a fuel cell is immersed in long-life coolant (LLC) cooling water and left at 110°C for 2000 hours is S2, the ratio of S2 to S1 ((S2 / S1) × 100) is 70% or more and 100% or less. Hereinafter, the ratio of S2 to S1 may be referred to as the "retention rate."

[0057] A weld generally refers to a portion where molten resin meets in a molded product, and is weaker in strength than portions of the molded product other than the weld.

[0058] In the present invention, the tensile strength of the weld portion of the molded article for a fuel cell is measured by the measuring method described in the Examples.

[0059] In the fuel cell molded article of the present invention, the retention rate is 70% or more and 100% or less. A retention rate of 100% means that the tensile strength of the welded portion does not decrease even after the fuel cell molded article of the present invention is immersed in LLC cooling water at 110°C for 2000 hours.

[0060] In one embodiment, the retention is 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more.

[0061] One way to adjust the retention is to select polyphenylene ether and polystyrene as the resins to be kneaded and adjust the ratio accordingly, thereby taking advantage of their completely compatible nature and improving adhesion at the confluence of the molten resins. Polymer modification with maleic anhydride can also improve the compatibility and adhesion between resins. Another method involves adjusting the viscosity, for example, to improve the fluidity of the resin and thereby improve adhesion. Furthermore, optimization of the kneading conditions for elastomers such as SEBS, for example, by optimizing the timing of addition or the number of screw revolutions during extrusion, can reduce the particle size of the dispersed phase of elastomers such as SEBS relative to the resin, thereby improving adhesion at the resin interface.

[0062] ·conductivity In the present invention, the surface area is 50 cm 2 When a molded article for a fuel cell (B) having a conductivity of 100 mL / 100 mL is immersed in pure water at 95°C for 1000 hours, the conductivity of the pure water (hereinafter sometimes simply referred to as "conductivity (B)") is 100 μS / cm or less. As a result, when the molded article for a fuel cell of the present invention is used in a fuel cell, elution of ionic components from the molded article for a fuel cell is suppressed, resulting in excellent cell performance.

[0063] In the present invention, the electrical conductivity (B) is measured by the measurement method described in the Examples. The lower the electrical conductivity (B), the less ionic components will be eluted from the molded article, and the better the resistance to elution.

[0064] In one embodiment, the conductivity (B) is 100 μS / cm or less, 90 μS / cm or less, 80 μS / cm or less, 70 μS / cm or less, 60 μS / cm or less, 50 μS / cm or less, 40 μS / cm or less, 30 μS / cm or less, 20 μS / cm or less, or 10 μS / cm or less. In another embodiment, the conductivity (B) is 5 μS / cm or more, 10 μS / cm or more, 20 μS / cm or more, 30 μS / cm or more, 40 μS / cm or more, 50 μS / cm or more, 60 μS / cm or more, 70 μS / cm or more, 80 μS / cm or more, or 90 μS / cm or more. In yet another embodiment, the conductivity (B) is 5 to 70 μS / cm.

[0065] One way to adjust conductivity (B) is to use a resin with high hydrolysis resistance, which can prevent decomposition products from leaching out of the resin and thus prevent an increase in conductivity. When mixing two or more materials, compatibility is important; resins with high compatibility are more likely to prevent leaching from the resin interface, resulting in smaller changes in conductivity. Furthermore, adjusting the additive elastomer, such as SEBS, can be done by optimizing the timing of addition, such as by mixing at the beginning of compounding, or by increasing the screw rotation speed during mixing. This allows the resin and additive to be dispersed uniformly, preventing leaching of additives and resin components and preventing an increase in conductivity.

[0066] The molded article for a fuel cell of the present invention may or may not have a welded portion.

[0067] In the present invention, "welding" refers to melting at least the resin composition for forming the molded article for fuel cells of the present invention or the molded article for fuel cells of the present invention, and joining the molten molded article or resin composition by pressurizing and cooling. In welding, unlike welding, the molten part in the joined molded article cannot be discerned by the naked eye. On the other hand, in welding, the molten part in the joined molded article can be discerned by the naked eye. In the present invention, "welded part" refers to the welded part.

[0068] The method for forming the welded portion is not particularly limited, and examples thereof include vibration welding, laser welding, ultrasonic welding, induction welding, high-frequency welding, spin welding, etc. The laser welding is not particularly limited, and examples thereof include YAG laser welding, semiconductor laser welding, and diode laser welding.

[0069] The welding mode of the fuel cell molded article of the present invention is not particularly limited, and may be, for example, welding of a single resin composition for forming the fuel cell molded article of the present invention, i.e., welding between one portion of a single resin composition and another portion of the single resin composition; welding between multiple separate resin compositions for forming the fuel cell molded article of the present invention, such as welding between the first resin composition of the present invention and the second resin composition of the present invention; welding between the resin composition for forming the fuel cell molded article of the present invention and another conventional resin composition; welding between the resin composition for forming the first fuel cell molded article of the present invention and the second fuel cell molded article of the present invention; welding between the resin composition for forming the fuel cell molded article of the present invention and another conventional fuel cell molded article; welding between multiple separate fuel cell molded articles of the present invention, such as welding between the first fuel cell molded article of the present invention and the second fuel cell molded article of the present invention; or welding between the fuel cell molded article of the present invention and another conventional fuel cell molded article. The first resin composition and the second resin composition may be the same or different. The first and second fuel cell molded articles may be the same or different.

[0070] In one embodiment, the molded article for a fuel cell of the present invention has a welded portion at least in a part thereof.

[0071] The size and shape of the welded portion are not particularly limited and may be adjusted as appropriate.

[0072] When the molded article for a fuel cell of the present invention has a welded portion, the number of welded portions is not particularly limited, and may be one or more.

[0073] When the molded article for a fuel cell of the present invention has a welded portion, the molded article for a fuel cell of the present invention has excellent tensile strength, so that the tensile strength of the welded portion can be 30 MPa or more. In one embodiment, when the molded article for a fuel cell of the present invention has a welded portion, the tensile strength of the welded portion is 30 MPa or more, 35 MPa or more, 40 MPa or more, 45 MPa or more, 50 MPa or more, 55 MPa or more, or 60 MPa or more. In another embodiment, when the molded article for a fuel cell of the present invention has a welded portion, the tensile strength of the welded portion is 65 MPa or less, 60 MPa or less, 55 MPa or less, 50 MPa or less, 45 MPa or less, 40 MPa or less, or 35 MPa or less. In yet another embodiment, when the molded article for a fuel cell of the present invention has a welded portion, the tensile strength of the welded portion is 30 to 50 MPa.

[0074] In the present invention, the tensile strength of the welded portion is measured by the measurement method described in the Examples.

[0075] To increase the tensile strength of the welded part, it is better to increase the proportion of PS in the resin components, as long as the fluidity is not reduced. The resin has good fluidity during welding, resulting in a good weld interface. Furthermore, as molding conditions, it is preferable to have a high resin temperature or mold temperature, and a fast injection speed, as long as the resin does not deteriorate and the mold releasability is not impaired. The surface resin is uniformly aligned, resulting in a good weld interface during welding.

[0076] The molded article for a fuel cell of the present invention may be used for any fuel cell, for example, in cooling system components and FC stack components. Examples of cooling system components include pipes, joints, cooling water pumps, ion exchangers, and valves. Cooling system components such as pipes, joints, cooling water pumps, ion exchangers, and valves may have welded parts, but according to the present invention, a decrease in tensile strength is suppressed and the molded article for a fuel cell has excellent elution resistance.

[0077] The molded article for a fuel cell of the present invention may be any molded article for a fuel cell, such as a fuel cell automobile, a stationary fuel cell, a portable fuel cell, a high-temperature fuel cell, etc. In one embodiment, the molded article for a fuel cell of the present invention is a molded article for a fuel cell automobile.

[0078] The type of fuel cell using the molded article for fuel cells of the present invention is not particularly limited, and examples thereof include alkaline fuel cells (AFC), polymer electrolyte fuel cells (PEFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), and solid oxide fuel cells (SOFC). [Example]

[0079] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0080] The materials used in the present invention are as follows: Polyphenylene ether 1: Poly(2,6-dimethyl-1,4-phenylene) ether with a reduced viscosity of 0.52 dL / g, obtained by oxidative polymerization of 2,6-xylenol, was used. This is shown as "PPE-1" in Table 1. Polyphenylene ether 2: Poly(2,6-dimethyl-1,4-phenylene) ether with a reduced viscosity of 0.40 dL / g, obtained by oxidative polymerization of 2,6-xylenol, was used. This is shown as "PPE-2" in Table 1. Polystyrene 1: Product name "PSJ-Polystyrene GPPS 685", manufactured by PS Japan Co., Ltd., indicated as "GPPS" in Table 1. Polystyrene 2: Product name "Polystyrene CT60", manufactured by Petrochemical Co., Ltd., indicated as "HIPS" in Table 1. Polystyrene 3: Product name "Zalek 90ZC", manufactured by Idemitsu Kosan Co., Ltd., indicated as "SPS" in Table 1. Polyphenylene sulfide: Product name "DSP LR-1G", manufactured by DIC Corporation, indicated as "PPS" in Table 1. Polyamide: manufactured by Asahi Kasei Corporation, indicated as "PA" in Table 1. Carbon fiber: PAN-based carbon fiber bundled with an epoxy-based binder, fiber diameter 7 μm, cut length 6 mm, bundled number of 50,000 strands, indicated as "CF" in Table 1. Glass fiber: Average fiber diameter 13 μm, fiber length 3 mm, indicated as "GF" in Table 1. LLC Coolant: Product name: "Super Long Life Coolant", manufactured by Toyota The reduced viscosity of PPE is a value measured at 30°C using a 0.5 g / dL chloroform solution.

[0081] The apparatus used in the present invention is as follows: Twin-screw extruder: Werner & Pfleiderer, "ZSK-40" Laser welding machine: Panasonic, product name "Laser welding machine VL-W1 series" Vibration welding machine: Manufactured by Emerson Japan, product name "MICRO-CVT Kai" Injection molding machine: Sumitomo Heavy Industries, product name "SE-130D" Conductivity meter: DKK-TOA Corporation, product name "CM-30G" (electrode CT-57101C) Screw inline injection molding machine: Shibaura Machine Co., Ltd., product name "EC75SXII injection molding machine"

[0082] (Examples 1 to 9, Comparative Examples 1 to 4) The components in the formulation shown in Table 1 were melt-kneaded using a twin-screw extruder set at a temperature of 290 to 320° C. and a screw rotation speed of 500 rpm to obtain pellets of the resin compositions of the Examples and Comparative Examples.

[0083] -Measurement of tensile strength of welded parts A mold was prepared with test specimen dimensions of 127 mm in length, 12.7 mm in width, and 1.6 mm in thickness. Molten resin composition pellets were poured into the mold from both ends in the longitudinal direction, forming a weld in the center in the longitudinal direction. Molding was performed using an injection molding machine equipped with the mold, and test specimen A was obtained.

[0084] A tensile test was carried out on test piece A using a method in accordance with ISO 527, except that the chuck distance was 50 mm and the tensile speed was 50 mm / min, and the tensile strength S1 was determined. The measured value was the average of n=6 values.

[0085] Furthermore, the molded test piece A was immersed in LLC cooling water and maintained at 110°C for 2000 hours. After 2000 hours, the test piece A (i.e., the molded article for fuel cell (A)) was taken out. The tensile strength S2 of this test piece A was determined in the same manner as in the measurement of the tensile strength S1.

[0086] The tensile strength retention rate was calculated from the obtained S1 and S2. The results are also shown in Table 1.

[0087] Conductivity measurement The resin composition pellets were molded using an injection molding machine to obtain test pieces. 2 A test piece B (i.e., a molded article for a fuel cell (B)) of 100 mL / 100 mL was obtained. This test piece B was immersed in pure water and maintained at 95°C for 1000 hours. After 1000 hours had passed, the test piece B was taken out. Next, the conductivity of the pure water at 25°C was measured using a conductivity meter. The results are also shown in Table 1.

[0088] Measurement of tensile strength of welded joints (laser welding) (1) Preparation of test pieces for laser welding evaluation The resulting resin composition pellets were fed into a screw in-line injection molding machine set at 240°C to 330°C, and test pieces for measuring laser welding strength (transmitting material 1 and absorbing material 2) measuring 25 mm wide x 60 mm long x 2 mm thick were injection molded (see Figure 1 (A)). The injection speed was 50 mm / sec, and a surface-treated mold containing titanium nitride was used to produce the molded products.

[0089] (2) Preparation of the complex The obtained transmitting material 1 and absorbing material 2 were overlapped with their 25 mm wide x 60 mm long surfaces facing each other, so that the 25 mm wide x 20 mm long portions were in contact with each other, as shown in Figure 1(B). A 10 mm diameter circular portion in the center of the overlapping portion was irradiated with a 1064 nm laser at a laser output of 50 to 100 W and a laser scanning speed of 80 mm / sec, to produce a composite 3 with a laser-welded portion.

[0090] (3) Calculation of tensile strength Both ends of composite 3 were clamped with a support distance of 55 mm. Next, a shear test was performed along the longitudinal direction of composite 3 using an INSTRON tensile tester at a tensile speed of 5 mm / sec. The tensile strength per unit area of ​​composite 3 after the shear test was calculated from the weld area and shear stress values. The results are also shown in Table 1.

[0091] Measurement of tensile strength of welded parts (vibration welding) (1) Preparation of test pieces for vibration welding evaluation The resulting resin composition pellets were fed into a screw in-line injection molding machine set at 240°C to 330°C, and test pieces 4 and 5 for measuring vibration welding strength, each measuring 40 mm wide x 100 mm long x 3 mm thick, and 40 mm wide x 100 mm long x 5 mm thick, were injection molded (see Figure 2(A)). The injection speed was 50 mm / sec, and a surface-treated mold containing titanium nitride was used to produce the molded products.

[0092] (2) Preparation of the complex The obtained test pieces 4 and 5 were brought into contact at their 100 mm long sides, as shown in Figure 2(B). The interface was vibrated under the following conditions to produce composite 6 having a vibration-welded portion. Next, composite 6 was cut into 20 mm long pieces, as shown in Figure 2(C), to obtain composite 7. Vibration frequency: 240Hz Welding time: Ends when welding margin is reached Cooling time: 30 seconds Welding allowance: 2.0 mm Amplitude: 1.0 mm Pressure: 73 MPa

[0093] (3) Calculation of tensile strength The top and bottom ends of composite 7 in Figure 2(C) were clamped with chucks, and a shear test was performed on vibration-welded composite 7, just as with the laser-welded composite. The tensile strength per unit area of ​​composite 7 after the shear test was calculated from the welded area and shear stress values. The results are also shown in Table 1.

[0094] [Table 1]

[0095] According to the present invention, it is possible to provide a molded article for a fuel cell that is excellent in elution resistance and that suppresses a decrease in tensile strength even when used as a cooling system part of a fuel cell. [Industrial Applicability]

[0096] According to the present invention, it is possible to provide a molded article for a fuel cell that is excellent in elution resistance and that suppresses a decrease in tensile strength even when used as a cooling system part of a fuel cell. [Explanation of symbols]

[0097] 1: Transparent material 2: Absorbent material 3: Laser welded composite 4: Test piece for measuring vibration welding strength 5: Test piece for measuring vibration welding strength 6: Vibration-welded composite 7: Composite cut into 20 mm lengths

Claims

1. A molded product for a fuel cell, the molded article for a fuel cell is a molded article of a resin composition, The resin composition includes a resin component, the resin component consists essentially of polystyrene and polyphenylene ether, the tensile strength of the weld portion of the molded article for a fuel cell is S1, and the tensile strength of the weld portion of the molded article for a fuel cell (A) after the molded article for a fuel cell is immersed in long-life coolant (LLC) cooling water at 110°C for 2000 hours is S2, the ratio of S2 to S1 is 70% or more and 100% or less, Surface area 50cm ２ A molded article for a fuel cell (B) in which 100 mL of the molded article for a fuel cell (B) is immersed in pure water at 95°C for 1000 hours, and the conductivity of the pure water is 100 μS / cm or less.

2. The molded article for a fuel cell according to claim 1 , which has a welded portion at least in a part thereof.

3. 3. The molded article for a fuel cell according to claim 2, wherein the tensile strength of the welded portion is 30 MPa or more.

4. The molded article for a fuel cell according to any one of claims 1 to 3, which is a cooling system part of a fuel cell.

5. 5. The molded article for a fuel cell according to claim 4, wherein the cooling system part is a pipe or a joint.

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