JP2008068672A - Joint component for resin fuel tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joint component for a resin fuel tank exhibiting excellent fuel permeability resistance and a welding force in a welded part with an outer peripheral part of an opening part of the resin fuel tank. <P>SOLUTION: The joint component is composed of a body member 1 and a welding member 2 to be interposed, the body member 1 is formed of either one or two kinds or more of a low fuel permeability materials such as PA, polyester, LCP, PPS or the like, the welding member 2 is composed of a metal foil layer 21, alloy material (the alloy material where EVOH forms a matrix, and a modified HDPE forms a domain) layers 22 formed on both sides of the metal foil layer 21, and a modified HDPE layer 23 formed on the surface of each alloy material layer 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a joining part for a resin fuel tank such as a joining pipe and a joining valve joined to the resin fuel tank.

  Recently, resin-made parts are used as joint parts such as joint pipes and joint valves joined to the outer periphery of the mouth of a resin fuel tank for automobiles. The resin-made joining component is usually joined to the resin fuel tank by hot plate welding.

  In consideration of prevention of fuel transpiration, the resin fuel tank has a multilayer structure in which a fuel low permeability layer made of a low fuel permeability material such as ethylene-vinyl alcohol copolymer (EVOH) is usually incorporated. For the outer layer, high density polyethylene (HDPE) or the like is used as a material for reasons such as water resistance and cost.

For the joining parts such as the joining pipe, a low fuel permeation material such as polyamide 12 (PA12) is used. However, since the PA 12 and the like have a weak welding force with respect to HDPE or the like (the material of the outermost layer of the resin fuel tank), there is a possibility that the fuel leaks from the joint surface between both of them simply by welding them. Therefore, as shown in FIG. 5, a welding member 60 made of a polyethylene-based resin such as modified polyethylene having a strong welding power to both of them (joint component 50, the outermost layer of the resin fuel tank T) is interposed between the two. The thing welded in the made state is proposed (for example, refer patent document 1).
Japanese Patent No. 2715870

  Although the thickness of the welding member 60 is actually thin and it is difficult for the fuel to physically permeate, particularly fuel with high permeability such as alcohol-mixed gasoline penetrates the welding member 60. There is a difficulty. That is, polyethylene-based resin such as modified polyethylene, which is a material of the welding member 60, has high weldability, but is poor in fuel permeation resistance. Therefore, the fuel permeates through the welding member 60 and diffuses outside. There is a difficulty.

  The present invention has been made in view of such circumstances, and provides a joining part for a resin fuel tank that exhibits excellent fuel permeation resistance and welding power at the welded portion with the outer periphery of the mouth of the resin fuel tank. For that purpose.

In order to achieve the above-mentioned object, a joining part for a resin fuel tank according to the present invention includes a substantially cylindrical main body member and an opening of the resin fuel tank provided at or near one opening edge of the main body member. An annular portion positioned on the outer peripheral portion, and an annular welding member interposed between the outer peripheral portion of the mouth of the resin fuel tank and the annular portion of the main body member, and the main body member has the following ( A), the annular welding member is composed of a laminated material including a metal foil and a resin layer made of (B) described below formed on both surfaces of the metal foil.
(A) At least one selected from the group consisting of polyamide, polyester, liquid crystal polymer, and polyphenylene sulfide.
(B) An alloy material in which an ethylene-vinyl alcohol copolymer forms a matrix (sea) and a modified high-density polyethylene forms a domain (island).

  The inventor of the present invention has made a joint for a resin fuel tank so that the joint part for the resin fuel tank exhibits excellent fuel permeation resistance and welding force at the welded portion with the outer peripheral portion of the mouth of the resin fuel tank. Researched the composition of parts. In the course of the research, the joining part for the resin fuel tank is composed of a substantially cylindrical main body member made of (A), which is a low fuel permeation material, and a welding member interposed between the welding part of the resin fuel tank. Constructed as a separate unit, the welding member is designed not only to have excellent welding power to both (main body member, resin fuel tank), but also to have its own fuel permeation resistance Further research was conducted on the structure of the welding member. In the course of the research, as the above-mentioned welding member, modified HDPE having strong welding power to the outermost layer material (HDPE or the like) of an ethylene-vinyl alcohol copolymer (EVOH) which is a low fuel permeation material and a resin fuel tank, The idea was a laminate with a sandwich structure formed on the surface of a metal foil. However, in a laminated material having a two-layer structure in which the above EVOH or modified HDPE is used alone as a film and adhered to a metal foil, the metal foil and the EVOH or the like are not firmly bonded, so the adhesive strength is weak (10 N / cm It was found that it peeled off below. And further research was done. As a result, the EVOH and the modified HDPE are not used alone, but are kneaded together, and the EVOH forms a matrix (sea) and the modified HDPE forms an alloy material (island). It was found to adhere firmly to the foil. That is, when the alloy material is formed on the surface of the metal foil, the adhesive force between the metal foil and the layer made of the alloy material is strong (it does not peel off even at 20 N / cm), and there is no risk of fuel leaking from the interface. Moreover, the alloy material has excellent fuel permeation resistance, and further against the above (A) which is the material of the substantially cylindrical body member and HDPE which is the material of the outermost layer of the resin fuel tank. The present inventors have found that it has excellent welding power and have reached the present invention.

  The joint part for a resin fuel tank according to the present invention includes a substantially cylindrical main body member and an annular portion that is provided at or near one opening edge of the main body member and positioned on the outer peripheral portion of the mouth of the resin fuel tank. And an annular welding member interposed between the outer peripheral portion of the mouth of the resin fuel tank and the annular portion of the main body member, and the main body member is made of the fuel low-permeability material of (A). The annular welding member is composed of a laminated material composed of a metal foil and a resin layer made of the specific alloy material (B) formed on both surfaces of the metal foil. The welded portion exhibits excellent fuel permeation resistance and welding power.

  In particular, when a coating layer made of modified high-density polyethylene is formed on the surface of the resin layer made of (B) of the annular welding member, the modified high-density polyethylene exhibits water shielding properties, It is possible to prevent the specific alloy material (B) from absorbing moisture and to prevent a decrease in welding power due to moisture absorption. Further, when the coating layer made of the modified high-density polyethylene is welded in a state where the coating layer is in contact with the annular portion of the main body member made of (A), the welding force between the main body member and the welding member can be further increased.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to this.

  FIG. 1 schematically shows a state where the first embodiment of the joining part for a resin fuel tank of the present invention is welded to the outer peripheral portion of the mouth portion Ta of the resin fuel tank T. FIG. In this embodiment, a joined pipe for connecting a fuel hose (not shown) will be described as an example of a joined part for a resin fuel tank of the present invention. The joint pipe is composed of a substantially cylindrical main body member 1 on which a fuel hose is fitted and a welding member 2 for welding the main body member 1 to a resin fuel tank T. An annular portion 11 positioned integrally with the outer peripheral portion of the mouth portion Ta of the resin fuel tank T is integrally formed on the outer peripheral portion near the lower end opening edge of the main body member 1. The welding member 2 is formed in an annular shape and is interposed between the outer peripheral portion of the mouth portion Ta of the resin fuel tank T and the annular portion 11 of the main body member 1. In FIG. 1, the symbol R is an O-ring. The resin fuel tank T usually has a five-layer structure of HDPE layer / modified HDPE layer / EVOH layer / modified HDPE layer / HDPE layer from the outer surface.

  More specifically, the main body member 1 is made of a low fuel permeation material. Examples of the low fuel permeation material include polyamide (PA), polyester, liquid crystal polymer (LCP), polyphenylene sulfide (PPS) and the like, and these are used alone or in combination of two or more. Examples of the PA include polyamide 6 (PA6), polyamide 66 (PA66), polyamide 12 (PA12), polyphthalamide (PPA), and the like. Examples of the polyester include polybutylene terephthalate (PBT) and polybutylene naphthalate (PBN).

  Further, the low-permeability material of the main body member 1 may be filled with glass fiber (GF) in an amount of 10 to 60% by weight, preferably 15 to 50% by weight. As a result, the fuel permeation resistance can be improved, and the binding force of the externally fitted fuel hose can be maintained. Furthermore, it is preferable to perform plasma treatment on the portion of the main body member 1 where the annular portion 11 is in contact with the welding member 2. Thereby, the welding force of the annular portion 11 of the main body member 1 and the welding member 2 can be improved. And the thickness of the surrounding wall of the said main body member 1 is normally set in the range of 0.5-5 mm, and the thickness of the annular part 11 is normally set in the range of 1-20 mm.

  In the first embodiment, the welding member 2 has a five-layer structure, and each layer is, in order from the upper layer, a modified HDPE layer (coating layer) 23 / alloy material layer (resin layer) 22 / metal foil. Layer 21 / alloy material layer (resin layer) 22 / modified HDPE layer (coating layer) 23.

  The metal foil material of the metal foil layer 21 is not particularly limited. For example, aluminum, aluminum alloy, iron, stainless steel (SUS304, etc.), copper, copper alloy (including brass and phosphor bronze), nickel, nickel alloy, Examples include titanium and titanium alloys. Among these, aluminum, stainless steel, copper alloy and the like are preferably used from the viewpoint of corrosion resistance. In addition, in order to improve adhesiveness with the alloy material layer 22, you may perform pre-bonding processes, such as a chromate process and a texturing process, for example. And although the thickness of the metal foil layer 21 is not specifically limited, Usually, it sets in the range of 3-300 micrometers.

  The alloy material of the alloy material layer 22 is one in which EVOH is a matrix and modified HDPE forms a domain (a sea-island structure in which island phases composed of modified HDPE are finely dispersed in a sea phase composed of EVOH). . And although the thickness of this alloy material layer 22 is not specifically limited, Usually, it sets to the range of 10-500 micrometers.

  Although it does not specifically limit as said EVOH, From the point of the moldability at the time of alloy material shaping | molding, and a fuel-permeation resistance, the thing in the range whose ethylene copolymerization ratio is 25-50 mol% is preferable, Especially preferably, 30- It is within the range of 45 mol%. The EVOH is preferably one having a melting point in the range of 160 to 191 ° C, particularly preferably in the range of 165 to 185 ° C.

  The main component of the modified HDPE is any one of a maleic anhydride residue, a maleic acid group, an acrylic acid group, a methacrylic acid group, an acrylic ester group, a methacrylic ester group, a vinyl acetate group, and an amino group, or 2 A modified HDPE having a functional group of more than one species is preferred. In addition, the said main component means the component which occupies the majority of the whole, and is the meaning including the case where the whole consists only of a main component. Further, the modified HDPE is not particularly limited. For example, at least one of an unsaturated carboxylic acid and an unsaturated carboxylic acid derivative, or a modifying compound such as an amine-containing compound (methylenediamine or the like) is added to the HDPE as a radical initiator. Can be obtained by graft modification.

  The blending ratio of the modified HDPE is more preferably in the range of 80 to 300 parts by volume with respect to 100 parts by volume of EVOH. This reason is considered to facilitate the formation of the sea-island structure of the present invention. When the blending ratio of the modified HDPE is less than 80 parts by volume, the adhesive strength to the metal foil layer 21 and the modified HDPE layer 23 tends to decrease. On the contrary, if it exceeds 300 parts by volume, the fuel permeation resistance tends to deteriorate. Furthermore, the modification rate of the modified HDPE is more preferably in the range of 0.1 to 5% by weight. The reason for this is that if the modification rate is less than 0.1% by weight, the affinity between the EVOH and the modified HDPE tends to be poor, and the adhesion and fuel permeation resistance tend to be inferior. This is because the fuel permeation resistance tends to be inferior and the working environment such as kneading and molding tends to deteriorate. The modified HDPE preferably has a melting point (ISO 3146) in the range of 126 to 140 ° C, particularly preferably in the range of 128 to 136 ° C. The HDPE (high density polyethylene) in the modified HDPE usually has a specific gravity (ISO 1183) of 0.93 to 0.97, preferably 0.93 to 0.96, and a melting point ( ISO 3146) is in the range of 120 to 145 ° C.

  The alloy material can be obtained by kneading the EVOH and the modified HDPE with high shear below their melting points. The kneading with high shear can be realized by using, for example, a twin screw extruder (kneader). In addition, it is considered that the EVOH hydroxyl group and the modified HDPE modified group form a hydrogen bond or a covalent bond by the kneading. As a result, the affinity between EVOH and modified HDPE increases, the dispersion diameter of the island phase made of modified HDPE becomes extremely small (about 1 μm), and there is almost no dispersion diameter dispersion, indicating a finely dispersed sea-island structure. . Therefore, it is considered that the alloy material layer 22 has a small amount of fuel permeation and excellent fuel permeation resistance.

  In addition, the alloy material (alloy material layer 22) has a strong adhesion to the inner metal foil layer 21 and the outer modified HDPE layer 23 due to the finely dispersed sea-island structure. It is considered to be. In particular, the modified HDPE layer 23 which is the outermost layer contains the same modified HDPE in the alloy material. Therefore, the alloy material layer 22 and the modified HDPE layer 23 have good compatibility, and adhesion Power is also getting stronger. For this reason, each interface is not peeled off, and there is no possibility of fuel leaking from each interface.

  Furthermore, since the alloy material is easy to absorb moisture because EVOH forms a matrix, and the adhesive force may be reduced due to the moisture absorption, the surface of the alloy material layer 22 is a modified HDPE layer that provides water shielding. Since 23 is formed, moisture absorption is prevented in the storage state before welding, and there is no fear of a decrease in welding force due to moisture absorption after welding. The thickness of the modified HDPE layer 23 is not particularly limited, but is usually set in the range of 10 to 500 μm.

  The welding member 2 having such a five-layer structure can be obtained by laminating an alloy material and modified HDPE on the metal foil. In addition, the alloy material of the alloy material layer 22 formed on both surfaces of the metal foil layer 21 may be the same or different. Similarly, the modified HDPE of the modified HDPE layer 23 may be the same on both sides or different. And the thickness of the welding member 2 is normally set in the range of 50-1000 micrometers.

  And when welding the said joining pipe to the outer peripheral part of the opening | mouth part Ta of the resin-made fuel tank T, welding is performed in the state which interposed the said welding member 2 between the annular parts 11 of the said main body member 1. FIG. Is called. The welding method is not particularly limited, but from the viewpoint of obtaining high bonding strength, a hot plate welding method, a vibration welding method, an ultrasonic welding method, a laser welding method, and the like are suitable. The welding method can be used.

  By the above welding, the contact surface portion between the annular portion 11 of the main body member 1 made of the low-permeability fuel material and the modified HDPE layer 23 which is the uppermost layer of the welding member 2 is melted and welded. The contact surface portion between the HDPE layer as the outer layer and the modified HDPE layer 23 as the lowermost layer of the welding member 2 is melted and welded. Thereby, the thickness of the modified HDPE layer 23 that is the outermost layer of the welding member 2 is reduced, and the fuel is difficult to permeate from the modified HDPE layer 23. Furthermore, as described above, the adhesive force at the interface between the respective layers of the welding member 2 is strong, there is no risk of fuel leaking from each interface, and both the metal foil layer 21 and the alloy material layer 22 have fuel permeability resistance. Excellent. For these reasons, the bonded pipe exhibits excellent fuel permeability resistance and welding power.

  FIG. 2 schematically shows a state where the second embodiment of the joining part for a resin fuel tank of the present invention is welded to the outer peripheral portion of the mouth portion Ta of the resin fuel tank T. FIG. In this embodiment, the welding member 2 has a three-layer structure, and each layer is an alloy material layer 22 / metal foil layer 21 / alloy material layer 22 in order from the upper layer. The rest is the same as in the first embodiment, and the same reference numerals are given to the same parts.

  In the second embodiment, the contact surface portion between the annular portion 11 of the main body member 1 made of a low fuel permeation material and the alloy material layer 22 which is the uppermost layer of the welding member 2 is melted and welded. At the same time, the contact surface portion between the HDPE layer that is the outermost layer of the resin fuel tank and the alloy material layer 22 that is the lowermost layer of the welding member 2 is melted and welded. As described above, the adhesive force at the interface between the layers of the welding member 2 is strong, there is no risk of fuel leaking from each interface, and both the metal foil layer 21 and the alloy material layer 22 have fuel permeability. Excellent. For these reasons, the bonded pipe exhibits excellent fuel permeability resistance and welding power.

  FIG. 3 schematically shows a state in which the third embodiment of the joining part for a resin fuel tank of the present invention is welded to the outer peripheral portion of the mouth portion Ta of the resin fuel tank T. In this embodiment, the welding member 2 has a four-layer structure, and each layer is an alloy material layer 22 / metal foil layer 21 / alloy material layer 22 / modified HDPE layer 23 in order from the upper layer. That is, the modified HDPE layer 23 is formed on the lower surface of the welding member 2 in the second embodiment. Other than that is the same as that of the said 2nd Embodiment, and attaches | subjects the same code | symbol to the same part.

  In the third embodiment, the annular portion 11 of the main body member 1 made of a low fuel permeation material and the alloy material layer 22 which is the uppermost layer of the welding member 2 are welded in the same manner as in the second embodiment. The HDPE layer that is the outermost layer of the resin fuel tank and the modified HDPE layer 23 that is the lowermost layer of the welding member 2 are welded in the same manner as in the first embodiment. As in the above embodiments, the fuel permeation resistance and welding power are excellent.

  In each of the above embodiments, the annular part 11 formed integrally with the main body member 1 is formed in the vicinity of the lower end opening edge, but the position of the annular part 11 is not limited to this, It may be formed at the lower end opening edge, or may be formed at the center in the axial direction (height direction) of the main body member 1. In the present invention, “one opening edge of the body member or its vicinity” has such a meaning.

  The joint part for a resin fuel tank according to the present invention is not limited to the above-mentioned joining pipe. For example, a fuel filler valve, an ORVR (Onboard Refueling Vapor Recovery) valve, a VSF (Vent Shaft Float) valve, a V return It is suitably used for joint valves such as valves.

  Next, examples will be described together with comparative examples.

  First, the material of the main body member shown below was prepared.

[PA6-a]
Non-reinforced PA6 (manufactured by Ube Industries, UBE nylon 1013A).

[PA6-b]
PA6GF30 (Ube Industries, UBE nylon 1015GC6).

[PA66]
PA66GF33 (manufactured by Asahi Kasei Chemicals Corporation, Leona 14G33).

[PA12-a]
PA12GF30 (MMS Co., Ltd., Grillamide L25ANZ, GF was kneaded and blended with a 30 wt% twin screw extruder, terminal amino group equivalent: 63 μeq / g).

[PA12-b]
PA12GF30 (Ube Industries, Uvesta 3020GUX1, terminal amino group equivalent: 32 μeq / g).

  Moreover, the material of the welding member shown below was prepared.

[Metal foil]
Aluminum (Al) foil (thickness 0.1 mm) and SUS304 foil (thickness 0.1 mm) were prepared as metal foils.

[EVOH (for alloy material layer, for coating layer of comparative example)]
Two types (a, b) of EVOH having the characteristics (MFR, specific gravity, melting point, ethylene copolymerization ratio) shown in Table 1 below were prepared.

  The following maleic anhydride-modified HDPE was prepared.

[Maleic anhydride-modified HDPE (for alloy material layers and coating layers)]
HDPE (Nippon Polyethylene Co., Ltd., Novatec HY430, specific gravity: 0.956, melting point: 135 ° C.), maleic anhydride (content: 0.4% by weight) and 2,5-dimethyl-2,5 di (t- Butyl peroxy) hexane (content: 0.015 wt%) was blended and melt kneaded using a twin screw extruder (modification rate: 0.4 wt%, melting point: 135 ° C., maximum tensile strength) : 15 MPa).

[Alloy materials]
The above materials were blended in the proportions shown in Table 2 below, and kneaded at a kneading temperature of 80 ° C. using a twin-screw kneading extruder (manufactured by Nippon Steel Works, TEX30α), and five types (A to E) of alloy materials. The pellet which consists of was produced. Moreover, the dispersion state of the sea phase and the island phase of each pellet was observed using a scanning electron microscope (manufactured by Hitachi Technologies, S4800), and the results are also shown in Table 2.

[Examples 1-11, Comparative Examples 1-9]
As shown in Tables 3 to 6 below, a disk-shaped first test piece (diameter 50 mm, thickness 1 mm) 10 (see FIG. 4) was produced by injection molding using the material of the main body member. In addition, as shown in Tables 3 to 6 below, the material of the welding member [metal foil, alloy material (see Table 2), modified HDPE, etc.] is appropriately used to form an annular second test piece (outer diameter 80 mm, An inner diameter of 40 mm and the thickness of each layer are shown in Tables 3 to 6) 20 (see FIG. 4). Among these, the 2nd test piece 20 which formed the alloy material and modified | denatured HDPE in metal foil was produced by laminating | stacking using a roll coater.

  Using the test pieces 10 and 20 of Examples 1 to 11 and Comparative Examples 1 to 9 obtained in this manner, each characteristic was evaluated according to the following criteria. These results are shown in Tables 3 to 6 below.

[Fuel permeation amount]
As shown in FIG. 4, an annular sheet material 31 having the same shape as the above welding member, which is made of HDPE (manufactured by Nippon Polyethylene Co., Ltd., Novatec HB111R) corresponding to the outermost layer of the resin fuel tank, was prepared. Then, in the state where the first test piece (corresponding to the main body member) 10 is coaxially positioned on the surface of the sheet material 31 via the second test piece (corresponding to the welding member) 20, the hot plate welding (240 Each sample was prepared by welding at a temperature of 20 ° C. for 20 seconds. Next, a cup-shaped container 32 is prepared. In this container 32, a fuel mixture of Fuel C [toluene: isooctane = 50: 50 (volume basis)] and ethanol [Fuel C: ethanol = 90: 10 ( Capacity standard)] 33 was accommodated. The container 32 has a stepped portion with an enlarged upper end, and a female screw is threaded on the inner peripheral surface of the upper end opening. Then, the sample is stacked on the stepped portion of the container 32 via a ring-shaped seal rubber 34, and further, a ring-shaped screw lid 35 is screwed into the upper end opening, and the sheet material 31 of the sample and the second material The container 32 was sealed by tightening the portion of the test piece 20. In this way, a test apparatus for measuring the fuel permeation amount was produced. Then, with the test apparatus turned upside down, the atmosphere was kept at 40 ° C., and the weight of the test apparatus was measured once a day for one month to calculate the weight change per day. The change in weight per day when the change in weight was stable was taken as the fuel permeation amount.

(Interlayer adhesion)
Each sample obtained by welding the first test piece 10 to the sheet material 31 corresponding to the outermost layer of the resin fuel tank via the second test piece 20 is cut into a strip shape with a width of 10 mm, Each layer at the tip was peeled off, and the tip of each peeled layer was sandwiched between chucks of a tensile tester (Orientec Co., Ltd.), and a tensile test was performed at a tensile speed of 50 mm / min.

[Weldability with tank]
Each of the above samples is cut into a strip with a width of 10 mm, and the leading end of the sheet material 31 and the leading end of the first test piece 10 in each strip are sandwiched between the chucks of a tensile testing machine (Orientec Co., Ltd.) A tensile test was performed under the condition of a tensile speed of 50 mm / sec. As a result, the base material broke when the tensile strength was 13 MPa or more.

  From the above results, the second test piece (corresponding to the welding member) 20 of Examples 1 to 11 was interposed, and the first test piece (corresponding to the main body member) 10 was welded to the resin fuel tank. It can be seen that the welding force with the fuel tank is strong and the amount of fuel permeation is small. Moreover, it can be seen that the second test pieces of Examples 1 to 11 have stronger interlayer adhesion as compared with Comparative Examples 1 to 9.

It is sectional drawing which shows typically the state which 1st Embodiment of the joining components for resin fuel tanks of this invention welded to the resin fuel tank. It is sectional drawing which shows typically the state which 2nd Embodiment of the joining parts for resin fuel tanks of this invention welded to the resin fuel tank. It is sectional drawing which shows typically the state which 3rd Embodiment of the joining parts for resin fuel tanks of this invention welded to the resin fuel tank. It is sectional drawing which shows the test apparatus which measures the fuel permeation amount of the sample of an Example and a comparative example. It is sectional drawing which shows typically the state which the joining components for conventional resin fuel tanks welded to the resin fuel tank.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main body member 2 Welding member 21 Metal foil layer 22 Alloy material layer 23 Denatured HDPE layer

Claims (2)

A substantially cylindrical main body member, an annular portion provided at or near one opening edge of the main body member and positioned at the outer peripheral portion of the mouth portion of the resin fuel tank, and the outer peripheral portion of the mouth portion of the resin fuel tank And an annular welding member interposed between the annular portion of the main body member, the main body member is composed of the following (A), the annular welding member is a metal foil, and the metal foil A joining part for a resin fuel tank, characterized in that it is composed of a laminated material comprising a resin layer comprising the following (B) formed on both surfaces.
(A) At least one selected from the group consisting of polyamide, polyester, liquid crystal polymer, and polyphenylene sulfide.
(B) An alloy material in which an ethylene-vinyl alcohol copolymer forms a matrix and a modified high-density polyethylene forms a domain.   The joining part for resin fuel tanks according to claim 1, wherein a coating layer made of modified high-density polyethylene is formed on the surface of the resin layer made of (B) of the annular welding member.

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