JP7480863B2 - Automobile side door and manufacturing method thereof - Google Patents

Description

The present disclosure relates to an automotive side door and a method for manufacturing the same.

A known example of an automobile side door is the side door of Patent Document 1 (JP 2020-189505 A). The side door of Patent Document 1 is manufactured by joining one end of a front frame and one end of a rear frame to at least one door panel member, heating the joined at least one door panel member, the front frame, and the rear frame, and further joining the other end of the front frame to the other end of the rear frame.

JP 2020-189505 A

In the manufacture of the side door of Patent Document 1, the front frame and the rear frame are each joined to the door panel member by spot welding. Because joining the components of the side door to each other is troublesome, a simpler joining method using, for example, an adhesive is desired.

In addition, in recent years, in order to reduce the weight of vehicles, materials other than metal materials (e.g., resin materials) have been used as some of the components. However, when manufacturing a side door by joining a metal material and a resin material, it is preferable that the two materials are firmly joined in order to satisfy the strength (e.g., rigidity) required of the side door.

The present disclosure has been made in consideration of the above-mentioned technical background, and its purpose is to provide a lightweight automobile side door that includes a metal member and a resin member and has high bonding strength between the two members, and a manufacturing method thereof.

The present disclosure includes the following aspects:

[1] A metal member including one or more resin coating layers laminated on at least a part of a surface of a metal base, and a resin member bonded to a surface of the metal base of the metal member on the side of the resin coating layer,
1. An automobile side door, wherein at least one layer of the resin coating layer is a modified polyolefin layer formed from a resin composition containing a modified polyolefin, and the modified polyolefin layer is at least one selected from the group consisting of a layer containing a reaction product 1 of a maleic anhydride modified polyolefin, a bifunctional epoxy resin, and a bifunctional phenol compound, a layer containing a reaction product 2 of a maleic anhydride modified polyolefin and a thermoplastic epoxy resin, and a layer containing a mixture of a polyolefin and a thermoplastic epoxy resin.

[2] The automobile side door described in the preceding paragraph 1, wherein the reactant 1 is obtained by a polyaddition reaction of a bifunctional epoxy resin and a bifunctional phenol compound in a solution containing maleic anhydride-modified polyolefin.

[3] The automobile side door described in the preceding paragraph 1, wherein the reactant 2 is obtained by reacting a thermoplastic epoxy resin produced by a polyaddition reaction of a difunctional epoxy resin with a difunctional phenol compound with a maleic anhydride-modified polyolefin.

[4] An automobile side door as described in paragraph 1 above, wherein the mixture is a mixture of polypropylene and thermoplastic epoxy resin.

[5] An automobile side door according to any one of paragraphs 1 to 4 above, wherein the resin coating layer is composed of multiple layers including the modified polyolefin layer and a layer other than the modified polyolefin layer, and at least one of the layers other than the modified polyolefin layer is at least one selected from a thermoplastic epoxy resin layer formed from a resin composition containing a thermoplastic epoxy resin and a curable resin layer formed from a resin composition containing a curable resin.

[6] The automobile side door described in paragraph 5 above, wherein the curable resin is at least one selected from the group consisting of urethane resin, epoxy resin, vinyl ester resin, and unsaturated polyester resin.

[7] A functional group-containing layer is provided between the metal substrate and the resin coating layer and is laminated in contact with the metal substrate and the resin coating layer,
7. The automobile side door according to any one of items 1 to 6, wherein the functional group-containing layer contains at least one functional group selected from the group consisting of the following (1) to (7):
(1) At least one functional group derived from a silane coupling agent and selected from the group consisting of a glycidyl group, an amino group, a (meth)acryloyl group, and a mercapto group. (2) A functional group generated by reacting an amino group derived from a silane coupling agent with at least one selected from a glycidyl compound and a thiol compound. (3) A functional group generated by reacting a mercapto group derived from a silane coupling agent with at least one selected from the group consisting of a glycidyl compound, an amino compound, an isocyanate compound, a compound having a (meth)acryloyl group and a glycidyl group, and a compound having a (meth)acryloyl group and an amino group. (4) A functional group generated by reacting a (meth)acryloyl group derived from a silane coupling agent with a thiol compound. (5) A functional group generated by reacting a glycidyl group derived from a silane coupling agent with at least one selected from the group consisting of a compound having an amino group and a (meth)acryloyl group, an amino compound, and a thiol compound. (6) An isocyanato group derived from an isocyanate compound. (7) A mercapto group derived from a thiol compound.

[8] An automobile side door according to any one of paragraphs 1 to 7 above, wherein the surface of the metal base material has been subjected to at least one surface treatment selected from the group consisting of blasting, polishing, etching and chemical conversion treatment, and the resin coating layer is laminated on the surface-treated surface of the metal base material.

[9] An automobile side door as described in any one of paragraphs 1 to 8 above, wherein the metal substrate is made of an aluminum extrusion material of an A6000 series alloy and has properties of a tensile strength of 330 MPa or more and a Young's modulus of 65 GPa or more.

[10] An automobile side door as described in any one of paragraphs 1 to 8 above, wherein the metal substrate is made of an aluminum forging of an A4000 series alloy and has properties of a tensile strength of 350 MPa or more and a Young's modulus of 70 GPa or more.

[11] A vehicle seat cushion comprising a resin inner panel disposed inside a vehicle body, a resin outer panel disposed on an outer side of the vehicle body, and a metal reinforcing member disposed between the two panels,
Each of the panels is a resin member,
At least a contact surface of the reinforcing material with each panel is a surface on the resin coating layer side,
11. The automobile side door according to any one of claims 1 to 10, wherein each of the panels is joined to the contact surface of the reinforcing material.

[12] A method for manufacturing an automobile side door as described in any one of the preceding paragraphs 1 to 11, comprising joining a resin member to the resin coating layer side of a metal member when molding the resin member by injection molding, transfer molding, press molding, filament winding molding, or hand lay-up molding.

The automobile side door of the present disclosure is equipped with a metal member and a resin member, and therefore is lighter than a side door made entirely of metal. Furthermore, the resin member is bonded to the surface of the metal member on the resin coating layer side, and at least one layer of the resin coating layer is a modified polyolefin layer formed from a resin composition containing modified polyolefin, and the modified polyolefin layer is at least one selected from the group consisting of a layer containing a reaction product 1 of a maleic anhydride modified polyolefin, a bifunctional epoxy resin, and a bifunctional phenolic compound, a layer containing a reaction product 2 of a maleic anhydride modified polyolefin and a thermoplastic epoxy resin, and a layer containing a mixture of a polyolefin and a thermoplastic epoxy resin, so that the bonding strength between the metal member and the resin member is high. In addition, the side door of the present disclosure is obtained by bonding by interposing a resin coating layer as an adhesive between the metal member and the resin member, and therefore can be easily obtained without going through troublesome work such as welding as in the past.

FIG. 1 is a schematic front view of an automobile side door according to an embodiment of the present disclosure. FIG. 2 is an end view taken along line AA in FIG. FIG. 3 is a schematic perspective view showing a state in which the side door shown in FIG. 1 is separated into an inner panel, a reinforcing member, and an outer panel. FIG. 4 is a schematic cross-sectional view of the side door shown in FIG. 1 , showing a state in which a metal member (reinforcement member) is placed in a mold when the first resin member (inner panel) is molded by injection molding. FIG. 5 is a schematic cross-sectional view of the side door shown in FIG. 1 , showing a state in which a metal member (reinforcing material) is placed in a mold when the second resin member (outer panel) is molded by injection molding. FIG. 6A is a schematic cross-sectional view showing a state in which a resin coating layer is formed on the surface-treated surface of a metal substrate in a metal component. FIG. 6B is a schematic cross-sectional view showing a state in which a functional group-containing layer is formed on the surface-treated surface of a metal substrate in a metal component, and a resin coating layer is formed thereon. FIG. 7 is a schematic cross-sectional view of a state in which the metal member and the resin member are joined. FIG. 8 is a schematic cross-sectional view of a state in which a metal member and a resin member are joined via an adhesive layer. FIG. 9 is an SEM photograph of the boehmite coating.

Next, an embodiment of the present disclosure will be described below with reference to the drawings.

In this disclosure, unless otherwise specified, the term "metal" is used to include both pure metals consisting of a single metallic element and alloys in which a pure metal is mixed with one or more other elements. For example, the term "aluminum" includes pure aluminum metal and its alloys.

In this disclosure, joining means connecting objects together, and adhesion is a subordinate concept to adhesion, which means joining two adherends (things to be bonded) together using an organic material such as tape or adhesive (curable resin, thermoplastic resin, etc.).

As shown in Figure 1, the automobile side door 10 is opened and closed when the driver and passengers get in and out of the automobile. In this disclosure, the "automobile side door" is also referred to simply as the "side door."

In addition, the symbol "31" in these figures refers to glass installed in the side door 10.

As shown in Figures 2 and 3, the automobile side door 10 comprises a resin inner panel 21 arranged on the vehicle interior side (more specifically, inside the luggage compartment), a resin outer panel 22 arranged on the outside of the vehicle, and a metal reinforcing member 11 arranged between the two panels 21, 22, forming a sandwich structure in which the inner panel 21 and the outer panel 22 are integrated with the reinforcing member 11 sandwiched between the two panels 21, 22.

In the side door 10, the metal member 1 constitutes the reinforcing member 11 described above, and the resin members 8 (8A, 8B) constitute the panels 21, 22 described above. Therefore, the reinforcing member 11 is made of the metal member 1, and the panels 21, 22 are made of the resin members 8.

As described above, in the side door 10, each panel 21, 22 is made of a resin member 8, which ensures that the side door 10 is lightweight.

In addition, the side door 10 is connected to the vehicle body via a door hinge (not shown) provided at the front of the vehicle, and when the side door 10 is opened, the side door 10 is supported in a cantilevered manner by the door hinge, so high rigidity is required for the side door 10. Therefore, in order to supplement the rigidity of the side door 10, a reinforcing material 11 is sandwiched between both panels 21, 22 of the side door 10. Furthermore, the reinforcing material 11 and each panel 21, 22 are joined (glued) together, which further increases the rigidity of the side door 10.

Next, the configuration of each component of the side door 10 and the manufacturing method thereof will be described in detail. In the following, the reinforcing member 11 will also be referred to as the "metal member 1," and each panel (the inner panel 21, the outer panel 22) will also be referred to as the "resin member 8." Furthermore, when it is necessary to particularly distinguish between the resin member 8 constituting the inner panel 21 and the resin member 8 constituting the outer panel 22, the former will also be referred to as the "first resin member 8A" and the latter as the "second resin member 8B."

[Metal member 1]
As shown in FIGS. 6A and 6B, the metal member 1 (reinforcing material 11) has a metal base material 2 and one or more resin coating layers 4 laminated on the surface of the metal base material 2.

In Figures 6A and 6B, the resin coating layer 4 is laminated on the surface-treated surface of the metal substrate 2, and at least one layer of the resin coating layer 4 is a modified polyolefin layer 4a formed from a resin composition containing a modified polyolefin.

The resin coating layer 4 is formed with excellent adhesion to the surface of the metal substrate 2, and also exhibits excellent adhesion to polyolefin. This gives the metal substrate 2 excellent adhesion to the resin member 8 containing polyolefin (adhesion via the resin coating layer 4). Therefore, the resin coating layer 4 can be said to be a primer layer disposed on the joining surface of the metal substrate 2.

In this disclosure, a primer layer refers to a layer that is interposed between the metal substrate 2 and the resin member 8 when the metal substrate 1 and the resin member 8 are joined, and that improves the adhesion of the metal substrate 2 to the resin member 8 (bonding via the resin coating layer 4).

In addition, the resin coating layer 4 protects the surface of the metal substrate 2, which can suppress the adhesion of dirt to the surface of the metal substrate 2 and deterioration such as oxidation. Therefore, it is possible to obtain a metal component 1 that can maintain excellent adhesion to resin components even when stored for a long period of time such as several months.

In one embodiment, as shown in Figure 6A, in the metal component 1, the resin coating layer 4 may be laminated directly on the surface of the surface-treated portion 2a of the metal substrate 2. In another embodiment, as shown in Figure 6B, in the metal component 1, a functional group-containing layer 3 may be provided on the surface of the surface-treated portion 2a of the metal substrate 2, and a resin coating layer 4 may be further formed on the surface of the functional group-containing layer 3. That is, the functional group-containing layer 3 may be disposed between the surface-treated portion 2a of the metal substrate 2 and the resin coating layer 4.

2, the surface-treated surface of the metal substrate 2 is the surface of the metal member 1 (metal substrate 2) to be joined with at least the resin member 8, i.e., the contact surface of the metal member 1 (metal substrate 2) with at least the resin member 8, specifically, the contact surface 11a of the reinforcing material 11 with the inner panel 21 and the contact surface 11b of the reinforcing material 11 with the outer panel 22. Note that in the present disclosure, the surface-treated surface of the metal substrate 2 may alternatively be, for example, the entire surface of the metal substrate 2.

<Metal substrate 2>
The metal type of the metal substrate 2 is not particularly limited, and examples thereof include aluminum, iron, titanium, magnesium, stainless steel, copper, etc. Among these, aluminum is particularly preferably used from the viewpoints of light weight, ease of processing, etc. The application of aluminum will be described in detail below.

When aluminum is applied to the metal substrate 2, the type of aluminum material of the metal substrate 2 is not limited, and may be, for example, an aluminum material having an aluminum content of 50% by mass or more. Specifically, the aluminum material is preferably an A6000 series alloy (e.g., A6061, A6082, A6110), an A4000 series alloy, an A7000 series alloy, an A390 series alloy, etc., and more preferably an aluminum material having a Si content of 10 to 14% by mass.

In particular, it is preferable that the metal substrate 2 is made of an aluminum extrusion material of an A6000 series alloy and has the characteristics of a tensile strength of 330 MPa or more and a Young's modulus of 65 GPa or more. In this case, since the metal substrate 2 has high tensile strength (high strength) and high Young's modulus (high rigidity), the side door 10 can be made thinner, which contributes to reducing the weight of the side door 10. The upper limit of the tensile strength is not limited, and is, for example, 450 MPa. The upper limit of the Young's modulus is not limited, and is, for example, 75 GPa.

Furthermore, it is also preferable that the metal substrate 2 is made of an aluminum forged material of an A4000 series alloy, and has the characteristics of a tensile strength of 350 MPa or more and a Young's modulus of 70 GPa or more. In this case, since the metal substrate 2 has a very high tensile strength (high strength) and a very high Young's modulus (high rigidity), the side door 10 can be further thinned, which contributes greatly to reducing the weight of the side door 10. The upper limit of the tensile strength is not limited, and is, for example, 500 MPa. The upper limit of the Young's modulus is not limited, and is, for example, 85 GPa.

When the metal substrate 2 is made of aluminum forging, it is preferable that the metal substrate 2 is manufactured by the following method.

That is, in a preferred method for manufacturing the metal base material 2, the steps of continuously casting a cast rod by supplying a molten aluminum material having a predetermined characteristic to a continuous casting device, obtaining a billet (raw material) by cutting the cast rod to a predetermined length, homogenizing the billet, surface-cutting the billet, and hot die forging the billet to form a base material having a roughly flat bar shape as a forging material are performed in the order described above. When using a high-strength alloy such as an A6000 series alloy, an A7000 series alloy, or an A4000 series alloy as the metal base material 2, a T6 heat treatment (a combination of water-cooled quenching from a solution treatment and age hardening treatment (tempering)) is then performed. Next, welding grooves are machined (e.g., cutting) at predetermined locations (such as both ends) of the base material, and finishing is performed at predetermined locations (such as the surface to be joined with the resin member 8) of the base material by machining (e.g., cutting). A plurality of such preforms are produced and then joined together by MIG welding, friction stir welding, etc. In this way, the metal base material 2 made of an aluminum forged material is obtained.

[Surface Treatment (Part)]
When manufacturing the metal member 1, it is preferable to perform a surface treatment of the metal base material 2 before forming the resin coating layer 4. In the metal base material 2 shown in Figures 6A and 6B, a surface treatment portion 2a is formed at least on a surface to be joined with the resin member 8. The surface treatment portion 2a is regarded as a part of the metal base material 2.

Surface treatments include, for example, cleaning and degreasing treatments using solvents, blasting treatments, polishing treatments, plasma treatments, laser treatments, etching treatments, and chemical conversion treatments, and are preferably surface treatments that generate hydroxyl groups on the surface of the metal substrate 2. Only one of these surface treatments may be performed, or two or more types may be performed. As specific methods for these surface treatments, known methods can be used.

The surface treatment removes contaminants from the surface of the metal substrate 2 and/or roughens the surface of the metal substrate 2 by forming fine irregularities for the purpose of an anchoring effect. This improves the bonding strength between the surface of the metal substrate 2 and the resin coating layer 4, and as a result, the adhesion strength (bonding strength via the resin coating layer 4) between the metal member 1 and the resin member 8 to be bonded can also be improved. From this perspective, the surface treatment is preferably at least one selected from the group consisting of blasting, polishing, etching, and chemical conversion treatment.

(Cleaning and degreasing)
The cleaning/degreasing treatment using a solvent or the like may be, for example, degreasing the surface of the metal base material 2 with an organic solvent such as acetone, toluene, etc. The cleaning/degreasing treatment is preferably performed before other surface treatments.

(Blast treatment)
The blasting treatment includes, for example, shot blasting and sand blasting.

(Polishing process)
Examples of the polishing treatment include buff polishing using an abrasive cloth, roll polishing using abrasive paper (sandpaper), and electrolytic polishing.

(Plasma Treatment)
Plasma treatment is a method in which a plasma beam emitted from a rod called an electrode is directed onto the surface of a material using a high-voltage power source to first clean foreign matter or oil film present on the surface, and then the surface molecules are excited by inputting energy into a gas appropriate for the material. An example of the plasma treatment is atmospheric pressure plasma treatment, which can impart hydroxyl groups or other polar groups to the surface.

(Laser treatment)
Laser treatment is a technique for improving the surface characteristics of a material by rapidly heating and cooling only the surface layer by laser irradiation, and is an effective method for roughening the surface. Known laser treatment techniques can be used for the laser treatment.

(Etching process)
Examples of the etching treatment include chemical etching treatments such as an alkali method, a phosphoric acid-sulfuric acid method, a fluoride method, a chromic acid-sulfuric acid method, and an iron salt method, and electrochemical etching treatments such as an electrolytic etching method.

When the metal substrate 2 is aluminum, the etching process is preferably an alkali method using an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution as the etching solution, and more preferably a caustic soda method using an aqueous sodium hydroxide solution. The alkali method can be performed, for example, by immersing the metal substrate 2 in an aqueous sodium hydroxide or potassium hydroxide solution with a concentration of 3 to 20% by mass at 20 to 70°C for 1 to 15 minutes. Additives such as chelating agents, oxidizing agents, and phosphates may be added to the etching solution. After immersion, it is preferable to neutralize (de-smut) with an aqueous nitric acid solution of 5 to 20% by mass, rinse with water, and dry.

(Chemical conversion treatment)
The chemical conversion treatment is mainly to form a chemical conversion coating as the surface treatment portion 2a on the surface of the metal base material 2. Examples of the chemical conversion treatment include a boehmite treatment and a zirconium treatment. When the metal base material 2 is aluminum, the chemical conversion treatment is preferably a boehmite treatment.

In the boehmite treatment, the metal substrate 2 is subjected to hot water treatment to form a boehmite film on the surface of the metal substrate 2. Ammonia, triethanolamine, etc. may be added to the water as a reaction accelerator. For example, it is preferable to immerse the metal substrate 2 in hot water at 90 to 100°C containing triethanolamine at a concentration of 0.1 to 5.0 mass% for 3 seconds to 5 minutes.

In the zirconium treatment, the metal substrate 2 is immersed in a liquid containing a zirconium salt, such as zirconium phosphate, to form a film of a zirconium compound on the surface of the metal substrate 2. The metal substrate 2 is preferably immersed in a 45-70°C liquid of a zirconium treatment chemical (such as Pearl Coat 3762 or Pearl Coat 3796, manufactured by Nippon Parkerizing Co., Ltd.) for 0.5-3 minutes. The zirconium treatment is preferably performed after etching using a caustic soda method.

When the metal substrate 2 is aluminum, it is preferable that the metal substrate 2 has been subjected to at least one surface treatment selected from an etching treatment and a boehmite treatment.

<Functional Group-Containing Layer 3>
6B, a single or multiple functional group-containing layers 3 may be provided between the metal substrate 2 and the resin coating layer 4, and may be laminated in contact with the metal substrate 2 and the resin coating layer 4. When the functional group-containing layer 3 is provided, the functional groups of the functional group-containing layer 3 react with the hydroxyl groups on the surface of the metal substrate 2 and the functional groups of the resin constituting the resin coating layer 4 to form chemical bonds, thereby improving the adhesion between the surface of the metal substrate 2 and the resin coating layer 4. As a result, the adhesion between the metal member 1 and the resin member 8 to be joined (bonding via the resin coating layer 4) can also be improved.

〔process〕
The functional group-containing layer 3 is preferably formed by treating the surface of the metal substrate 2 with at least one selected from the group consisting of the following (1') to (7').
(1') A silane coupling agent containing at least one functional group selected from the group consisting of a glycidyl group, an amino group, and a mercapto group. (2') A combination of at least one selected from a glycidyl compound and a thiol compound with a silane coupling agent having an amino group. (3') A combination of at least one selected from the group consisting of a glycidyl compound, an amino compound, an isocyanate compound, a compound having a (meth)acryloyl group and a glycidyl group, and a compound having a (meth)acryloyl group and an amino group with a silane coupling agent having a mercapto group. (4') A combination of a thiol compound with a silane coupling agent having a (meth)acryloyl group. (5') A combination of at least one selected from the group consisting of a compound having an amino group and a (meth)acryloyl group, an amino compound, and a thiol compound with a silane coupling agent having a glycidyl group. (6') An isocyanate compound. (7') A thiol compound.

[Functional Group]
The functional group-containing layer 3 preferably contains a functional group introduced by the above-mentioned treatment, and specifically, it preferably contains at least one functional group selected from the group consisting of the following (1) to (7):
(1) At least one functional group derived from a silane coupling agent and selected from the group consisting of a glycidyl group, an amino group, a (meth)acryloyl group, and a mercapto group. (2) A functional group generated by reacting an amino group derived from a silane coupling agent with at least one selected from a glycidyl compound and a thiol compound. (3) A functional group generated by reacting a mercapto group derived from a silane coupling agent with at least one selected from the group consisting of a glycidyl compound, an amino compound, an isocyanate compound, a compound having a (meth)acryloyl group and a glycidyl group, and a compound having a (meth)acryloyl group and an amino group. (4) A functional group generated by reacting a (meth)acryloyl group derived from a silane coupling agent with a thiol compound. (5) A functional group generated by reacting a glycidyl group derived from a silane coupling agent with at least one selected from the group consisting of a compound having an amino group and a (meth)acryloyl group, an amino compound, and a thiol compound. (6) An isocyanato group derived from an isocyanate compound. (7) A mercapto group derived from a thiol compound.

Before forming the functional group-containing layer 3 on the metal substrate 2, the above-mentioned surface treatment portion 2a can be provided on the surface of the metal substrate 2. The adhesiveness between the surface of the metal substrate 2 and the resin coating layer 4, and the adhesiveness between the metal member 1 and the resin member 8 to be joined (bonding via the resin coating layer 4) can be further improved by the synergistic effect of the anchor effect due to the fine unevenness of the surface treatment portion 2a and the chemical bonds formed by the reaction of the functional groups of the functional group-containing layer 3 with the hydroxyl groups on the surface of the metal substrate 2 and the functional groups of the resin constituting the resin coating layer 4.

The method for forming the functional group-containing layer 3 using a silane coupling agent, an isocyanate compound, a thiol compound, etc. is not particularly limited, and examples include a spray coating method and an immersion method. Specifically, the functional group-containing layer 3 can be formed by immersing the metal substrate 2 in a solution of a silane coupling agent or the like having a concentration of 5 to 50% by mass at room temperature to 100°C for 1 minute to 5 days, and then drying at room temperature to 100°C for 1 minute to 5 hours.

〔Silane coupling agent〕
As the silane coupling agent, for example, a known agent used for surface treatment of glass fiber can be used. A silanol group generated by hydrolysis of the silane coupling agent, or a silanol group of an oligomer generated by condensation of the silanol group, reacts with and bonds to a hydroxyl group present on the surface of the metal substrate 2, whereby a functional group based on the structure of the silane coupling agent capable of chemically bonding with the resin coating layer 4 can be imparted (introduced) to the metal substrate 2.

The silane coupling agent is not particularly limited, and examples thereof include silane coupling agents having an amino group such as N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and 3-aminopropyltriethoxysilane; silane coupling agents having an epoxy group such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; 3-mercaptopropylmethyldimethoxysilane, 3-isocyanatopropyltriethoxysilane, dithi Silane coupling agents having a mercapto group or an isocyanato group, such as all-triazinepropyltriethoxysilane; silane coupling agents having a vinyl group, such as vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane; 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, hydrochloride salt of N-(vinylbenzyl)-2-aminopropyltrimethoxysilane, tris(trimethoxysilylpropyl)isocyanurate, and 3-ureidopropyltrialkoxysilane. The silane coupling agents may be used alone or in combination of two or more.

[Isocyanate Compound]
The isocyanate compound can impart (introduce) to the metal substrate 2 a functional group based on the structure of the isocyanate compound that can chemically bond with the resin coating layer 4 by reacting and bonding with the hydroxyl group present on the surface of the metal substrate 2 via the isocyanate group in the isocyanate compound.

The isocyanate compound is not particularly limited, and examples thereof include polyfunctional isocyanates such as diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), and isophorone diisocyanate (IPDI); and isocyanate compounds having radical reactive groups such as 2-isocyanatoethyl methacrylate (e.g., Karenz MOI (registered trademark) manufactured by Showa Denko K.K.), 2-isocyanatoethyl acrylate (e.g., Karenz AOI (registered trademark) and AOI-VM (registered trademark) manufactured by Showa Denko K.K.), and 1,1-(bisacryloyloxyethyl)ethyl isocyanate (e.g., Karenz BEI (registered trademark) manufactured by Showa Denko K.K.).

[Thiol compounds]
The mercapto group in the thiol compound reacts with and bonds to the hydroxyl group present on the surface of the metal substrate 2, thereby imparting (introducing) to the metal substrate 2 a functional group based on the structure of the thiol compound that can chemically bond with the resin coating layer 4.

The thiol compound is not particularly limited, and examples thereof include pentaerythritol tetrakis(3-mercaptopropionate) (e.g., "QX40" manufactured by Mitsubishi Chemical Corporation, and "QE-340M" manufactured by Toray Fine Chemicals Co., Ltd.), ether-based primary thiol (e.g., "Cupcure 3-800" manufactured by Cognis), 1,4-bis(3-mercaptobutyryloxy)butane (e.g., "Karenz MT (registered trademark) BD1" manufactured by Showa Denko K.K.), pentaerythritol tetrakis(3-mercaptobutyrate) (e.g., "Karenz MT (registered trademark) PE1" manufactured by Showa Denko K.K.), and 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (e.g., "Karenz MT (registered trademark) NR1" manufactured by Showa Denko K.K.).

<Resin coating layer 4>
A resin coating layer 4 is laminated on the metal substrate 2. The resin coating layer 4 may be a single layer or may be configured of multiple layers.

[Modified Polyolefin Layer 4a]
At least one layer of the resin coating layer 4 is a modified polyolefin layer 4a formed from a resin composition containing a modified polyolefin. Since the resin coating layer 4 contains the modified polyolefin layer 4a, the metal member 1 can exhibit excellent adhesion to the resin member 8 (bonding via the resin coating layer 4).

The resin coating layer 4 may be composed of multiple layers including a modified polyolefin layer 4a and a layer other than the modified polyolefin layer 4a, and the layer other than the modified polyolefin layer 4a may be at least one selected from a thermoplastic epoxy resin layer 4b formed from a resin composition containing a thermoplastic epoxy resin and a curable resin layer 4c formed from a resin composition containing a curable resin.

When the resin coating layer 4 is composed of multiple layers, it is preferable that the essential modified polyolefin layer 4a is laminated so as to be the outermost surface on the side opposite the metal substrate 2.

The modified polyolefin layer 4a is preferably at least one selected from the group consisting of a layer containing reactant 1 obtained by polyaddition reacting a bifunctional epoxy resin with a bifunctional phenol compound in the presence of maleic anhydride-modified polyolefin, while simultaneously reacting with the maleic anhydride in the maleic anhydride-modified polyolefin skeleton; a layer containing reactant 2 obtained by reacting a thermoplastic epoxy resin produced by polyaddition reacting a bifunctional epoxy resin with a bifunctional phenol compound, with the maleic anhydride in the maleic anhydride-modified polyolefin skeleton; and a layer containing a mixture of a thermoplastic epoxy resin and a polyolefin.

(Reactant 1)
Reactant 1 can be obtained by polyaddition reaction of a bifunctional epoxy resin and a bifunctional phenol compound in the presence of a catalyst in a solution of maleic anhydride-modified polyolefin. At this time, it is considered that the maleic anhydride-modified polyolefin also reacts with the bifunctional epoxy resin, the bifunctional phenol compound, and the thermoplastic epoxy resin produced from the bifunctional epoxy resin and the bifunctional phenol compound described later in the section on reactant 2.

(Maleic anhydride modified polyolefin)
The maleic anhydride-modified polyolefin is a polyolefin grafted with maleic anhydride, and examples thereof include maleic anhydride-modified polyethylene and maleic anhydride-modified polypropylene. Specific examples of the maleic anhydride-modified polyolefin include Kayabrid 002PP, 002PP-NW, 003PP, and 003PP-NW manufactured by Kayaku Akzo Co., Ltd., and Modic series manufactured by Mitsubishi Chemical Corporation. As a polypropylene additive functionalized with maleic anhydride, SCONA TPPP2112GA, TPPP8112GA, or TPPP9212GA manufactured by BYK Co., Ltd. may be used in combination with the maleic anhydride-modified polyolefin.

(Difunctional epoxy resin)
Examples of bifunctional epoxy resins include bisphenol type epoxy resins and biphenyl type epoxy resins. The bifunctional epoxy resins may be used alone or in combination of two or more. Specific examples of bifunctional epoxy resins include "jER (registered trademark) 828", "jER (registered trademark) 834", "jER (registered trademark) 1001", "jER (registered trademark) 1004", "jER (registered trademark) 1007", and "jER (registered trademark) YX-4000" manufactured by Mitsubishi Chemical Corporation.

(Bifunctional phenol compound)
Examples of bifunctional phenolic compounds include bisphenol and biphenol. The bifunctional phenolic compounds may be used alone or in combination of two or more. Examples of combinations of bifunctional phenolic compounds include bisphenol A type epoxy resin and bisphenol A; bisphenol A type epoxy resin and bisphenol F; biphenyl type epoxy resin and 4,4'-biphenol; and Nagase ChemteX Corporation's "WPE190" and "EX-991L."

Preferred catalysts for the polyaddition reaction of thermoplastic epoxy resins are, for example, tertiary amines such as triethylamine and 2,4,6-tris(dimethylaminomethyl)phenol; and phosphorus-based compounds such as triphenylphosphine.

(Reactant 2)
The reactant 2 can be obtained by reacting a thermoplastic epoxy resin produced by a polyaddition reaction of a difunctional epoxy resin and a difunctional phenol compound with a maleic anhydride-modified polyolefin. The maleic anhydride-modified polyolefin, the difunctional epoxy resin, and the difunctional phenol compound used in this reaction can be the same as those used to produce the reactant 1.

(Thermoplastic epoxy resin)
The thermoplastic epoxy resin used in the production of the reactant 2 is also called an in-situ polymerization type phenoxy resin, an in-situ curing type phenoxy resin, an in-situ curing type epoxy resin, etc., and forms a thermoplastic structure, i.e., a linear polymer structure, by a polyaddition reaction between a bifunctional epoxy resin and a bifunctional phenolic compound in the presence of a catalyst. Here, a linear polymer means a polymer that does not contain a crosslinked structure in the polymer molecule and is a one-dimensional linear chain. Unlike a curable resin that forms a three-dimensional network due to a crosslinked structure, a thermoplastic epoxy resin has thermoplasticity.

The total amount of the bifunctional epoxy resin and the bifunctional phenol compound used in producing reactant 1 or reactant 2 is preferably 5 to 100 parts by mass, more preferably 5 to 60 parts by mass, and even more preferably 10 to 30 parts by mass, per 100 parts by mass of maleic anhydride-modified polyolefin.

The reaction methods that occur when obtaining reactant 1 and reactant 2 are diverse, including the reaction of maleic anhydride-modified polyolefin with a bifunctional epoxy resin, the reaction of maleic anhydride-modified polyolefin with a bifunctional phenol compound, the reaction in which epoxy connects maleic anhydrides, the reaction of epoxy groups at the terminals of a thermoplastic epoxy resin with maleic anhydride, and the reaction of secondary hydroxyl groups in the skeleton of a thermoplastic epoxy resin with maleic anhydride, and it is not possible to comprehensively express specific aspects based on these combinations. Therefore, it is impossible or impractical to directly identify the modified polyolefin obtained as reactant 1 or reactant 2 by its structure or properties.

The mixture of thermoplastic epoxy resin and polyolefin can be obtained by mixing a thermoplastic epoxy resin similar to that used in the production of reactant 2 described above with a polyolefin in a conventional manner.

(Polyolefin)
The polyolefin used to form the mixture may be the same as that used in the resin member 8. The polyolefin is not particularly limited and may be a general synthetic resin. Examples of polyolefin include polyethylene and polypropylene.

The resin coating layer 4 is laminated on the surface of the metal substrate 2. As described above, the resin coating layer 4 may be laminated on the surface of the metal substrate 2 that has not been subjected to a surface treatment, or may be laminated on the surface of the metal substrate 2 that has been subjected to a surface treatment. The resin coating layer 4 may be laminated on the surface of the functional group-containing layer 3.

[Thermoplastic epoxy resin layer 4b]
The resin coating layer 4 can be composed of multiple layers including a modified polyolefin layer 4a and a layer other than the modified polyolefin layer 4a, and at least one of the layers other than the modified polyolefin layer 4a can be composed of a thermoplastic epoxy resin layer 4b formed from a resin composition containing a thermoplastic epoxy resin.

It is preferable that the resin composition containing the thermoplastic epoxy resin contains 40% by mass or more of the thermoplastic epoxy resin, and more preferably 70% by mass or more.

(Thermoplastic epoxy resin)
The thermoplastic epoxy resin is a resin that forms a thermoplastic structure, i.e., a linear polymer structure, by polyaddition reaction of a bifunctional epoxy resin and a bifunctional phenolic compound in the presence of a catalyst, similar to the thermoplastic epoxy resin used in the production of the reactant 2, and has thermoplasticity, unlike a curable resin that forms a three-dimensional network by a crosslinked structure. Because the thermoplastic epoxy resin has such characteristics, it can form a thermoplastic epoxy resin layer 4b by in-situ polymerization, which has excellent bonding properties with the metal substrate 2 and excellent bonding properties with the modified polyolefin layer 4a. Therefore, when producing the metal member 1, it is preferable to form the thermoplastic epoxy resin layer 4b by polyaddition reaction of a composition containing a monomer of the thermoplastic epoxy resin on the surface of the lower layer.

The polyaddition reaction of the composition containing the thermoplastic epoxy resin monomer is preferably carried out on the surface of the functional group-containing layer 3 as the lower layer. The resin coating layer 4 containing the thermoplastic epoxy resin layer 4b formed in this manner has excellent bonding properties with the metal substrate 2 and also has excellent bonding properties with the resin member 8 described below.

The method for forming the thermoplastic epoxy resin layer 4b using a composition containing a thermoplastic epoxy resin monomer is not particularly limited, and examples include a spray coating method and a dipping method.

The composition containing the thermoplastic epoxy resin monomer may contain a solvent and, if necessary, an additive such as a colorant in order to sufficiently advance the polyaddition reaction of the thermoplastic epoxy resin and form the desired resin coating layer. In this case, it is preferable that the thermoplastic epoxy resin monomer is the main component among the components other than the solvent of the composition. The main component means that the content of the thermoplastic epoxy resin monomer is 50 to 100 mass%. The content of the thermoplastic epoxy resin monomer is preferably 60 mass% or more, more preferably 80 mass% or more.

The monomer for obtaining a thermoplastic epoxy resin is preferably a combination of a difunctional epoxy resin and a difunctional phenolic compound.

The polyaddition reaction is preferably carried out by heating at a temperature of 120 to 200°C for 5 to 90 minutes, although this depends on the type of reactive compound. Specifically, after coating the composition, the solvent is appropriately volatilized, and then the mixture is heated to carry out the polyaddition reaction, thereby forming a thermoplastic epoxy resin layer.

[Curable resin layer 4c]
The resin coating layer 4 may be composed of multiple layers including a modified polyolefin layer 4a and a layer other than the modified polyolefin layer 4a, and the layer other than the modified polyolefin layer 4a may be composed of a curable resin layer 4c formed from a resin composition containing a curable resin.

The resin composition containing the curable resin may contain a solvent to sufficiently proceed with the curing reaction of the curable resin and form the desired resin coating layer, and may contain additives such as colorants as necessary. In this case, it is preferable that the curable resin is the main component of the resin composition other than the solvent. The main component means that the content of the curable resin is 40 to 100 mass%. The content of the curable resin is preferably 60 mass% or more, more preferably 70 mass% or more, and most preferably 80 mass% or more.

Examples of curable resins include urethane resins, epoxy resins, vinyl ester resins, and unsaturated polyester resins.

The curable resin layer 4c may be formed of one of these resins, or may be formed by mixing two or more of them. The curable resin layer 4c may be composed of multiple layers, and each layer may be formed of a resin composition containing a different type of curable resin.

The method for forming the curable resin layer 4c using a composition containing a curable resin monomer is not particularly limited, and examples include a spray coating method and a dipping method.

In this disclosure, a curable resin means a resin that cures by crosslinking, and is not limited to heat-curing types, but also includes room temperature curing types and light-curing types. Light-curing types can be cured in a short time by irradiation with visible light or ultraviolet light. Light-curing types may be used in combination with heat-curing types and/or room temperature curing types. Examples of light-curing types include vinyl ester resins such as "Lipoxy (registered trademark) LC-760" and "Lipoxy (registered trademark) LC-720" manufactured by Showa Denko K.K.

(urethane resin)
The urethane resin is usually a resin obtained by reacting the isocyanato group of an isocyanate compound with the hydroxyl group of a polyol compound, and is preferably a urethane resin that corresponds to the definition of "a coating material containing 10% by weight or more of polyisocyanate as a non-volatile component of a vehicle" in ASTM D16. The urethane resin may be of a one-component type or a two-component type.

Examples of one-component urethane resins include oil-modified types (those that cure by oxidative polymerization of unsaturated fatty acid groups), moisture-curing types (those that cure by reaction between isocyanato groups and water in the air), block types (those that cure by reaction between hydroxyl groups and isocyanato groups regenerated by dissociating a blocking agent when heated), and lacquer types (those that cure by evaporation of the solvent and drying). Of these, moisture-curing one-component urethane resins are preferably used from the viewpoint of ease of handling. A specific example of a moisture-curing one-component urethane resin is "UM-50P" manufactured by Showa Denko K.K.

Examples of two-component urethane resins include catalyst-curing types (which cure when isocyanato groups react with water in the air in the presence of a catalyst) and polyol-curing types (which cure when isocyanato groups react with hydroxyl groups of a polyol compound).

Examples of polyol compounds in the polyol curing type include polyester polyol and polyether polyol-phenol resin.

Examples of isocyanate compounds having an isocyanate group in the polyol curing type include aliphatic isocyanates such as hexamethylene diisocyanate (HDI), tetramethylene diisocyanate, and dimer acid diisocyanate; aromatic isocyanates such as 2,4- or 2,6-tolylene diisocyanate (TDI) or mixtures thereof, p-phenylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate (MDI) or its polynuclear mixture, polymeric MDI; and alicyclic isocyanates such as isophorone diisocyanate (IPDI).

The compounding ratio of polyol compound to isocyanate compound in a polyol-curing two-component urethane resin is preferably such that the molar equivalent ratio of hydroxyl group/isocyanato group is in the range of 0.7 to 1.5.

Examples of urethane catalysts used in two-component urethane resins include amine-based catalysts such as triethylenediamine, tetramethylguanidine, N,N,N',N'-tetramethylhexane-1,6-diamine, dimethyletheramine, N,N,N',N'',N''-pentamethyldipropylene-triamine, N-methylmorpholine, bis(2-dimethylaminoethyl)ether, dimethylaminoethoxyethanol, and triethylamine; and organotin-based catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin thiocarboxylate, and dibutyltin dimaleate.

In the polyol curing type, it is generally preferable to mix 0.01 to 10 parts by mass of a urethane catalyst per 100 parts by mass of polyol compound.

(Epoxy resin)
Epoxy resin is a resin having at least two epoxy groups in one molecule. Examples of prepolymers of epoxy resin before curing include ether-based bisphenol-type epoxy resins, novolac-type epoxy resins, polyphenol-type epoxy resins, aliphatic-type epoxy resins, ester-based aromatic epoxy resins, cyclic aliphatic epoxy resins, and ether-ester-based epoxy resins. Among these, bisphenol A-type epoxy resins are preferably used. The epoxy resins may be used alone or in combination of two or more kinds.

Specific examples of bisphenol A type epoxy resins include "jER (registered trademark) 828" and "jER (registered trademark) 1001" manufactured by Mitsubishi Chemical Corporation.

A specific example of a novolac type epoxy resin is "D.E.N.(registered trademark) 438(registered trademark)" manufactured by The Dow Chemical Company.

Examples of curing agents used for epoxy resins include aliphatic amines, aromatic amines, acid anhydrides, phenolic resins, thiols, imidazoles, and cationic catalysts. By using a curing agent in combination with a long-chain aliphatic amine and/or thiols, a resin coating layer 4 with high elongation and excellent impact resistance can be formed.

Specific examples of thiols include the same compounds as those exemplified as the thiol compounds for forming the functional group-containing layer 3. Among these, pentaerythritol tetrakis(3-mercaptobutyrate) (for example, Karenz MT (registered trademark) PE1 manufactured by Showa Denko K.K.) is preferred from the viewpoint of the elongation rate and impact resistance of the resin coating layer 4.

(Vinyl ester resin)
Vinyl ester resins are prepared by dissolving a vinyl ester compound in a polymerizable monomer (e.g., styrene). Vinyl ester resins are also generally called epoxy (meth)acrylate resins, but in the present disclosure, vinyl ester resins also include urethane (meth)acrylate resins.

Examples of vinyl ester resins that can be used include those described in the "Polyester Resin Handbook" (published by the Nikkan Kogyo Shimbun, 1988) and the "Paint Terminology Dictionary" (published by the Color Materials Association, 1993). Specific examples of vinyl ester resins include "Lipoxy (registered trademark) R-802," "Lipoxy (registered trademark) R-804," and "Lipoxy (registered trademark) R-806" manufactured by Showa Denko KK

An example of the urethane (meth)acrylate resin is a radical polymerizable unsaturated group-containing oligomer obtained by reacting an isocyanate compound with a polyol compound, followed by a hydroxyl group-containing (meth)acrylic monomer (and, if necessary, a hydroxyl group-containing allyl ether monomer). A specific example of the urethane (meth)acrylate resin is "Lipoxy (registered trademark) R-6545" manufactured by Showa Denko K.K.

Vinyl ester resins can be cured by radical polymerization through heating in the presence of a catalyst such as an organic peroxide.

Examples of organic peroxides include ketone peroxides, peroxyketals, hydroperoxides, diallyl peroxides, diacyl peroxides, peroxy esters, and peroxydicarbonates. By combining these organic peroxides with cobalt metal salts, etc., it is possible to cure at room temperature.

Examples of cobalt metal salts include cobalt naphthenate, cobalt octylate, and cobalt hydroxide. Among these, cobalt naphthenate and cobalt octylate are preferred.

(Unsaturated polyester resin)
The unsaturated polyester resin is prepared by dissolving a condensation product (unsaturated polyester) obtained by an esterification reaction between a polyol compound and an unsaturated polybasic acid (and optionally a saturated polybasic acid) in a polymerizable monomer (for example, styrene).

Examples of unsaturated polyester resins that can be used include those described in the "Polyester Resin Handbook" (published by Nikkan Kogyo Shimbun, 1988) and the "Paint Terminology Dictionary" (published by the Color Materials Association, 1993). A specific example of an unsaturated polyester resin is "Rigolac (registered trademark)" manufactured by Showa Denko K.K.

Unsaturated polyester resins can be cured by radical polymerization through heating in the presence of a catalyst similar to that of vinyl ester resins.

[Side door 10 (metal member-resin member joint)]
7, in the side door 10, a surface 4s of the metal member 1 on the side of the resin coating layer 4 is joined to a resin member 8. As described above, the resin coating layer 4 is a primer layer of the metal base material 2. Specifically, the surface 4s on the side of the resin coating layer 4, which is disposed on the contact surface of the metal base material 2 included in the metal member 1, is joined to the resin member 8 so as to be in direct contact with the resin member 8.

As described above, the surface 4s on the resin coating layer 4 side has excellent bonding properties with the resin member 8, making it possible to manufacture a side door 10 in which the metal member 1 and the resin member 8 are bonded with high bonding strength.

The thickness (dry thickness) of the resin coating layer 4 depends on the type of resin and bonding area of the resin member 8, but from the viewpoint of obtaining excellent bonding with the resin member 8 on the surface 4s on the resin coating layer 4 side, it is preferably 1 μm to 10 mm, more preferably 2 μm to 8 mm, and even more preferably 3 μm to 5 mm. When the resin coating layer 4 is made up of multiple layers, the thickness (thickness after drying) of the resin coating layer 4 is the total thickness of each layer.

Specifically, when joining and integrating the metal member 1 with a carbon fiber reinforced resin member (CFRP member) as the resin member 8, or when joining and integrating the metal member 1 with a glass fiber reinforced resin member (GFRP member) as the resin member 8, the thickness of the resin coating layer 4 is preferably 0.1 to 10 mm, more preferably 0.2 to 8 mm, and even more preferably 0.5 to 5 mm.

[Resin member 8]
The resin member 8 includes polyolefin. The polyolefin is not particularly limited, and examples thereof include polyethylene and polypropylene.

Polypropylene is generally classified into homopolymers with high rigidity, which are made by polymerizing only propylene; random polymers with high transparency and flexibility, which are made by copolymerizing a small amount of ethylene; and block copolymers with high impact resistance, in which a rubber component (EPR) is uniformly and finely dispersed in a homopolymer or random polymer. Polypropylene may include homopolymers, random polymers, or block copolymers, or mixtures thereof. Polypropylene may be a high-strength type containing talc, glass fiber, or carbon fiber. Examples of talc-containing polypropylene include TRC104N, a product of Sun Alloy Co., Ltd. Examples of glass fiber-containing polypropylene include PP-GF40-01 F02, a product of Daicel Miraize Co., Ltd. Examples of carbon fiber-containing polypropylene include PP-CF40-11 F008, a product of Daicel Miraize Co., Ltd.

Glass fiber-containing polypropylene is a type of glass fiber reinforced plastic (GFRP), and carbon fiber-containing polypropylene is a type of carbon fiber reinforced plastic (CFRP). Resins containing reinforcing fibers such as glass fiber and carbon fiber may be in the form of molded products such as sheet molding compounds (SMC) and bulk molding compounds (BMC). SMC is a sheet-like molded product obtained by impregnating reinforcing fibers such as glass fiber and carbon fiber with a resin composition containing polypropylene, a low shrinkage agent, a filler, etc.

One method for manufacturing the side door 10 is to manufacture the metal member 1 and the resin member 8 separately and then join (glue) them together to form an integrated unit.

A preferred method for manufacturing the side door 10 is to integrate the metal member 1 and the resin member 8 by simultaneously molding the resin member 8. Specifically, when molding the resin member 8 by a method such as injection molding (including insert molding), transfer molding, press molding, filament winding molding, or hand lay-up molding, the resin member 8 is joined to the surface 4s of the metal member 1 on the side of the resin coating layer 4, thereby integrating the metal member 1 and the resin member 8 to obtain the side door 10. In this case, the number of manufacturing steps for the side door 10 can be reduced.

Specifically, as shown in FIG. 4, when the first resin member 8A (i.e., the resin member 8 constituting the inner panel 21) and the second resin member 8B (i.e., the resin member 8 constituting the outer panel 22) are each molded by, for example, injection molding, a metal member 1 (i.e., reinforcing material 11) is placed in an injection molding die 40A, and the resin of the first resin member 8A is injected (injection direction 45A) into a cavity 41A of the die 40A by an injection device (not shown), thereby molding the first resin member 8A and simultaneously joining the metal member 1 and the first resin member 8A.

5, the metal member 1 to which the first resin member 8A is joined is placed in an injection mold 40B, and an injection device (not shown) injects the resin of the second resin member 8B into the cavity 41B of the mold 40B (injection direction 45B), thereby molding the second resin member 8B and simultaneously joining the metal member 1 and the second resin member 8B. The side door 10 is manufactured by the above method.

In Figures 4 and 5, the symbols "44A" and "44B" are knockout pins for removing the product from the mold.

In the manufacturing method for the side door 10 described above, the second resin member 8B may be molded after the first resin member 8A is molded as described above, or conversely, the first resin member 8A may be molded after the second resin member 8B is molded.

Next, another embodiment is described below.

As shown in FIG. 8, the side door 10 may be integrated by bonding the surface 4s of the metal member 1 facing the resin coating layer 4 to the resin member 8 via an adhesive layer 7.

In this way, depending on the type of resin used for the resin member 8, it is possible to obtain a side door 10 in which the metal member 1 and the resin member 8 are joined with higher joining strength by using an adhesive.

The adhesive for the adhesive layer 7 is appropriately selected depending on the type of resin of the resin member 8, but known adhesives such as epoxy resin-based, urethane resin-based, vinyl ester resin-based, etc. can be used.

Depending on the heating temperature during bonding (adhesion), the side door 10 may be thermally deformed during the process of cooling to room temperature after bonding (adhesion) due to the difference in thermal expansion coefficient between the metal base material 2 and the resin member 8. From the viewpoint of suppressing and mitigating such thermal deformation, it is desirable that the total thickness of the resin coating layer 4 and the adhesive layer 7 is 4 μm or more as a part having a large elongation rate characteristic between the metal base material 2 and the resin member 8. It is preferable that the above-mentioned total thickness is determined in consideration of the physical properties such as the elongation rate of the resin coating layer 4 and the adhesive layer 7 during the temperature change during bonding (the temperature change from the heating temperature during bonding to cooling at room temperature). The preferred upper limit of the total thickness of the resin coating layer 4 and the adhesive layer 7 is 10 mm.

In this disclosure, the layer involved in bonding between the metal member 1 and the resin member 8 is referred to as the bonding layer, and its thickness is referred to as the thickness of the bonding layer. When an adhesive layer 7 is formed on the surface 4s of the metal member 1 facing the resin coating layer 4, both the resin coating layer 4 and the adhesive layer 7 are bonding layers, and the total thickness of the resin coating layer 4 and the adhesive layer 7 is the thickness of the bonding layer. When an adhesive layer 7 is not formed on the surface 4s of the metal member 1 facing the resin coating layer 4, the resin coating layer 4 is the bonding layer, and the thickness of the resin coating layer 4 is the thickness of the bonding layer.

In another embodiment, at least one layer of the resin coating layer 4 is a layer derived from a film formed on a substrate other than the metal substrate 2. At least one layer of the film is the modified polyolefin layer 4a described above.

The film may be one layer or may be composed of multiple layers. The film may be composed of multiple layers including the modified polyolefin layer 4a and a layer other than the modified polyolefin layer 4a, and the layer other than the modified polyolefin layer 4a may be at least one selected from the thermoplastic epoxy resin layer 4b and the curable resin layer 4c. In this case, the modified polyolefin layer 4a of the film is bonded to the resin member 8, and the layer other than the modified polyolefin layer 4a of the film is bonded to the metal substrate 2 or the functional group-containing layer 3, which may or may not have a surface treatment.

The film can be produced, for example, by the following procedure. (1) A reactant 1 obtained by polyaddition reacting a bifunctional epoxy resin with a bifunctional phenolic compound in the presence of maleic anhydride-modified polyolefin and simultaneously reacting with maleic anhydride in the maleic anhydride-modified polyolefin skeleton, (2) a reactant 2 obtained by reacting a thermoplastic epoxy resin produced by polyaddition reacting a bifunctional epoxy resin with a bifunctional phenolic compound with maleic anhydride in the maleic anhydride-modified polyolefin skeleton, or (3) a film precursor composition 1 containing a mixture of a thermoplastic epoxy resin and a polyolefin and, if necessary, a solvent, is prepared. The reactant 1, the reactant 2, and the mixture of a thermoplastic epoxy resin and a polyolefin are the same as those described for the modified polyolefin layer 4a. The film precursor composition 1 is applied, sprayed, or extrusion laminated on a release film or release paper having a release coating such as a silicone-based coating so as to form a film having a thickness of 1 μm to 10 mm after drying. The application can be performed using a bar coater, a roll coater, or the like. The spraying can be performed using a spray coater, or the like. Extrusion lamination can be performed using a single-screw or twin-screw extrusion device. The film can then be formed on the release film or release paper by leaving the film in an environment of room temperature to 40° C. to volatilize the solvent. After the film is formed, the release film or release paper can be used as a carrier (support) for handling the film, or the film can be peeled off from the release film or release paper to obtain a free-standing film.

The modified polyolefin layer 4a of the film may contain reactant 1, reactant 2, or components that are structural units of the thermoplastic epoxy resin (e.g., bifunctional epoxy resin, bifunctional phenol compound, maleic anhydride modified polyolefin, etc.) in a completely reacted state, or may contain a portion of them in an unreacted state. In the latter case, when bonding the metal substrate 2 or resin member 8 to the film (resin coating layer 4), the unreacted components may be further reacted. The reaction of the unreacted components may increase the bonding strength between the film (resin coating layer 4) and the metal substrate 2 or resin member 8.

A film composed of multiple layers including the modified polyolefin layer 4a and layers other than the modified polyolefin layer 4a can be produced, for example, by the following procedure. (1a) A film precursor composition 2 containing a resin composition containing a thermoplastic epoxy resin, (1b) A composition containing a monomer of a thermoplastic epoxy resin, or (2) A resin composition containing a curable resin, and a solvent as necessary, is prepared. The resin composition containing a thermoplastic epoxy resin and the composition containing a monomer of a thermoplastic epoxy resin are the same as those described for the thermoplastic epoxy resin layer 4b. The resin composition containing a curable resin is the same as those described for the curable resin layer 4c. The film precursor composition 2 is applied, sprayed, or extrusion laminated on a release film or release paper having a release coating such as a silicone-based coating so that the film is in the form of a film having a thickness of 1 μm to 10 mm after drying. Thereafter, the thermoplastic epoxy resin layer 4b or the curable resin layer 4c is formed on the release film or release paper by leaving it in an environment of room temperature to 40° C. to volatilize the solvent, heating it to proceed with a polyaddition reaction or a curing reaction, or irradiating it with visible light or ultraviolet light to proceed with a curing reaction. By forming the modified polyolefin layer 4a on these layers by the above-mentioned procedure, it is possible to obtain a film constituted of multiple layers including the modified polyolefin layer 4a and a layer other than the modified polyolefin layer 4a.

The thermoplastic epoxy resin layer 4b or the curable resin layer 4c of the film may contain components (e.g., bifunctional epoxy resins, bifunctional phenolic compounds, polyols, isocyanate compounds, etc.) that are the structural units of these resins in a completely reacted state, or may contain a portion of them in an unreacted state. In the latter case, when bonding the metal substrate 2 and the film, the unreacted components may be further reacted. The reaction of these unreacted components may increase the bonding strength between the film and the metal substrate 2.

By placing the film on the metal substrate 2 and applying pressure and heat, a metal member 1 can be produced in which a resin coating layer 4 is laminated on the metal substrate 2. The metal substrate 2 may have the above-mentioned surface treatment and/or functional group-containing layer 3 as necessary, and a film may be placed on the metal substrate 2 and the resin coating layer 4 may be laminated by applying pressure and heat. A film composed of multiple layers including a modified polyolefin layer 4a and a layer other than the modified polyolefin layer 4a is laminated so that the layer other than the modified polyolefin layer 4a contacts the metal substrate 2 or the functional group-containing layer 3, which may or may not have a surface treatment.

The metal member 1 and the resin member 8 thus obtained are joined (adhered) together to form an integrated unit, thereby manufacturing the side door 10. The joining (adhering) of the metal member 1 and the resin member 8 can be carried out by at least one method selected from the group consisting of ultrasonic welding, vibration welding, electromagnetic induction, high frequency, laser, and heat pressing.

The side door 10 may be formed by molding a resin member 8 on top of the resin coating layer 4 (derived from a film) of the metal member 1 by a method such as injection molding (including insert molding), transfer molding, press molding, filament winding molding, hand lay-up molding, etc., and joining (bonding) the metal member 1 and the resin member 8 to form an integrated unit.

The side door 10 can also be manufactured by sandwiching a film between the metal substrate 2 and the resin member 8, and bonding (adhering) the metal substrate 2 and the resin member 8 together via the resin coating layer 4 (derived from the film) by at least one method selected from the group consisting of ultrasonic welding, vibration welding, electromagnetic induction, high frequency, laser, and heat pressing. In this case, the metal member 1 and the side door 10 are manufactured simultaneously. When the metal substrate 2 has a surface treatment and/or a functional group-containing layer 3, the film is arranged so as to contact the surface-treated surface or the functional group-containing layer 3 of the metal substrate 2.

Although several embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit and scope of the present invention.

For example, in the above-described embodiment, the number of resin members joined to the metal member is two, but in the present invention, the number of resin members is not limited to two, and may be, for example, one or more.

The following are examples of tests and comparative tests related to the present invention. However, the present invention is not limited to the following examples of tests.

<Production Example 1>
A flask was charged with 5 g of maleic anhydride-modified polypropylene (Mitsubishi Chemical Corporation's Modic (registered trademark) ER321P) and 95 g of xylene, and the mixture was heated to 125°C with stirring to dissolve. Next, 1.01 g of a bifunctional epoxy resin (Mitsubishi Chemical Corporation's jER (registered trademark) 1001: a polycondensate of bisphenol A and epichlorohydrin), 0.24 g of bisphenol A, and 0.006 g of 2,4,6-tris(dimethylaminomethyl)phenol were added to the flask and stirred at 125°C for 30 minutes to obtain a maleic anhydride-modified polypropylene modified with a thermoplastic epoxy resin, a bifunctional epoxy resin, and a bifunctional phenol compound: modified PP-1.

<Production Example 2>
A flask was charged with 5 g of maleic anhydride-modified polypropylene (Modic (registered trademark) ER321P manufactured by Mitsubishi Chemical Corporation) and 95 g of xylene, and the mixture was heated to 125° C. with stirring to dissolve. Next, a bifunctional epoxy resin (0.49 g of jER (registered trademark) 1004 manufactured by Mitsubishi Chemical Corporation, 0.06 g of bisphenol A, and 0.003 g of 2,4,6-tris(dimethylaminomethyl)phenol) was added to the flask and stirred at 125° C. for 30 minutes to obtain a maleic anhydride-modified polypropylene modified with a thermoplastic epoxy resin, a bifunctional epoxy resin, and a bifunctional phenol compound: Modified PP-2.

<Production Example 3>
A flask was charged with 5 g of talc-containing polypropylene (TRC104N manufactured by SunAllomer Co., Ltd.) and 95 g of xylene, which were then dissolved by heating to 125° C. with stirring. Next, 1.01 g of a bifunctional epoxy resin (jER (registered trademark) 1001 manufactured by Mitsubishi Chemical Co., Ltd.), 0.24 g of bisphenol A, and 0.006 g of 2,4,6-tris(dimethylaminomethyl)phenol were added to the flask and stirred at 125° C. for 30 minutes to obtain a mixture of thermoplastic epoxy resin (20% by mass) and polypropylene: Modified PP-3.

<Production Example 4>
A flask was charged with 95 g of xylene, 1.20 g of a bifunctional epoxy resin (jER1007 manufactured by Mitsubishi Chemical Corporation), 0.066 g of bisphenol A, and 0.003 g of 2,4,6-tris(dimethylaminomethyl)phenol, and the mixture was stirred and reacted at 125° C. for 30 minutes to obtain a thermoplastic epoxy resin solution. Next, 5 g of maleic anhydride-modified polypropylene (Modic (registered trademark) ER321P manufactured by Mitsubishi Chemical Corporation) was added to the flask and dissolved to obtain a maleic anhydride-modified polypropylene modified with a thermoplastic epoxy resin (20% by mass): Modified PP-4.

<Test Example 1>
An aluminum plate was formed by hot die forging, and its surface was smoothed by mechanical cutting to have dimensions of 45 mm in length, 18 mm in width, and 1.5 mm in thickness.

The material of the aluminum plate was "AHS (registered trademark)-1" manufactured by Showa Denko K.K., an A4000 aluminum alloy, with specific chemical composition of 11.0% by mass of Si, 0.23% by mass of Fe, 2.0% by mass of Cu, 0.6% by mass of Mg, with the remainder being Al and unavoidable impurities. The tensile strength of the aluminum plate was 400 MPa, and its Young's modulus was 78 GPa.

(surface treatment)
The aluminum plate was immersed in a 5% by mass aqueous sodium hydroxide solution for 1.5 minutes, neutralized with a 5% by mass aqueous nitric acid solution, washed with water, and dried to perform an etching treatment. The aluminum plate after the etching treatment was then boiled in pure water for 10 minutes and baked at 250° C. for 10 minutes to perform a boehmite treatment, thereby forming a boehmite film on the surface of the aluminum plate.

When the surface of the aluminum plate after the boehmite treatment was observed using an SEM photograph (scanning electron microscope photograph, observed at a 45° inclination), it was confirmed that a boehmite coating having whisker-like irregularities on the surface had been formed, as shown in Figure 9.

(Functional Group-Containing Layer 3)
Next, the aluminum plate after the boehmite treatment was immersed for 20 minutes in a silane coupling agent-containing solution at 70° C. in which 2 g of 3-aminopropyltrimethoxysilane ("KBM-903" manufactured by Shin-Etsu Silicones Co., Ltd.; a silane coupling agent) was dissolved in 1,000 g of industrial ethanol, and the aluminum plate was then taken out and dried, thereby forming a functional group-containing layer 3 on the surface of the boehmite coating.

(Resin coating layer 4)
Next, the modified PP-1 obtained in Production Example 1 was applied to the surface of the functional group-containing layer 3, the xylene was volatilized, and the mixture was held at 150°C for 30 minutes to produce a metal member 1 having a 30 µm-thick resin coating layer 4 of the modified PP-1 formed on the surface of the functional group-containing layer 3.

A talc-containing polypropylene resin (PP resin) (TRC104N manufactured by SunAllomer Co., Ltd.) (joint object) was injection molded on the surface 4s of the metal member 1 facing the resin coating layer 4 using an injection molding machine (SE100V manufactured by Sumitomo Heavy Industries, Ltd.; cylinder temperature 200°C, tool temperature 30°C, injection speed 50 mm/sec, peak/holding pressure 195/175 [MPa/MPa]) to join the resin member 8 to the metal member 1. This produced a test piece for a tensile test (PP resin, 10 mm x 45 mm x 3 mm, joint length 5 mm) (metal member 1-resin member 8 joint) in accordance with ISO19095.

[Adhesion Evaluation]
The prepared test piece (metal member 1-resin member 8 joint) was left at room temperature for 1 day, and then subjected to a tensile shear joint strength test in accordance with ISO19095 1-4 using a tensile tester (Shimadzu Corporation universal testing machine autograph "AG-IS"; load cell 10 kN, tensile speed 10 mm/min, temperature 23°C, 50% RH) to measure the joint strength. The measurement results are shown in Table 1.

<Test Example 2>
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 1 was carried out to form a functional group-containing layer 3 on the surface of the boehmite film.

(Resin coating layer 4: 1st layer)
A thermoplastic epoxy resin composition obtained by dissolving 100 g of a bifunctional epoxy resin (jER (registered trademark) 1001 manufactured by Mitsubishi Chemical Corporation), 24 g of bisphenol A, and 0.4 g of triethylamine in 250 g of acetone was spray-coated on the surface of the functional group-containing layer 3 so that the thickness after drying would be 30 μm. The coating was left in air at room temperature for 30 minutes to volatilize the solvent, and then left in a 150° C. oven for 30 minutes to carry out a polyaddition reaction, and then allowed to cool to room temperature to form a first resin coating layer (thermoplastic epoxy resin layer 4b).

(Resin coating layer 4: 2nd layer)
Next, the modified PP-2 obtained in Production Example 2 was applied to the surface of the thermoplastic epoxy resin layer 4b, the xylene was volatilized, and the mixture was held at 150°C for 30 minutes to produce a metal component 1 in which a 30 μm-thick resin coating layer of modified PP-2 (modified polyolefin layer 4a) was formed on the surface of the thermoplastic epoxy resin layer 4b.

A test piece for a tensile test (metal member 1 - resin member 8 joint) was prepared by carrying out the same operation as in Example Test 1 on the surface 4s of the second layer (modified polyolefin layer 4a) of the metal member 1 facing the resin coating layer 4. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 1.

<Test Example 3>
(surface treatment)
As the metal substrate 2, a copper plate having a size of 18 mm×45 mm and a thickness of 1.5 mm was subjected to a degreasing treatment with acetone.

(Functional Group-Containing Layer 3)
Next, the copper plate after the degreasing treatment was immersed in a silane coupling agent-containing solution at 70°C in which 0.5 g of 3-methacryloxypropyltrimethoxysilane (KBM-503; silane coupling agent, manufactured by Shin-Etsu Silicone Co., Ltd.) was dissolved in 100 g of industrial ethanol for 5 minutes, and then the copper plate was taken out and dried, and functional groups derived from the silane coupling agent were introduced onto the surface of the copper plate after the degreasing treatment. Furthermore, the copper plate was immersed in a solution in which 0.6 g of 1,4-bis(3-mercaptobutyryloxy)butane (Karens MT (registered trademark) BD1, manufactured by Showa Denko K.K.) and 0.05 g of 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), which are bifunctional thiol compounds, were dissolved in 150 g of toluene at 70°C for 10 minutes, and then pulled out and dried. In this way, two functional group-containing layers 3 were formed.

(Resin coating layer 4)
Next, the modified PP-3 obtained in Production Example 3 was applied to the surface of the functional group-containing layer 3 of the copper plate, the xylene was volatilized, and the mixture was held at 150°C for 30 minutes to produce a metal member 1 in which a 30 µm-thick resin coating layer 4 of the modified PP-3 was formed on the surface of the functional group-containing layer 3.

A test piece for a tensile test (metal member 1 - resin member 8 joint) was prepared by carrying out the same operation as in Example Test 1 on the surface 4s of the metal member 1 facing the resin coating layer 4. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 1.

<Test Example 4>
(surface treatment)
As the metal substrate 2, an iron plate having a size of 18 mm×45 mm and a thickness of 1.5 mm was subjected to a sanding treatment using #100 sandpaper to form fine irregularities on the surface of the iron plate.

(Resin coating layer 4: 1st layer)
The same operation as in Example Test 2 was carried out on the uneven surface of the iron plate to form a first resin coating layer (thermoplastic epoxy resin layer 4b).

(Resin coating layer 4: 2nd layer)
Next, the same operation as in Example Test 2 was carried out to prepare a metal member 1 having a 40 μm-thick resin coating layer (modified polyolefin layer 4a) of modified PP-2 formed on the surface of the thermoplastic epoxy resin layer 4b.

A test piece for a tensile test (metal member 1 - resin member 8 joint) was prepared by carrying out the same operation as in Example Test 1 on the surface 4s of the metal member 1 facing the resin coating layer 4. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 1.

<Test Example 5>
(surface treatment)
The aluminum plate used in Example 1 was immersed in a 5% by mass aqueous solution of sodium hydroxide for 1.5 minutes, neutralized with a 5% by mass aqueous solution of nitric acid, washed with water, and dried, thereby carrying out an etching treatment.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 1 was carried out to form a functional group-containing layer 3 on the surface of the aluminum plate after the etching treatment.

(Resin coating layer 4)
The same operation as in Experimental Test Example 1 was carried out to form a resin coating layer 4 on the surface of the functional group-containing layer 3 to prepare a metal member 1 .

A test piece for a tensile test (metal member 1 - resin member 8 joint) was prepared by carrying out the same operation as in Example Test 1 on the surface 4s of the metal member 1 facing the resin coating layer 4. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 1.

Comparative Test Example 1
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

An injection molding operation similar to that of Example Test 1 was carried out without providing a functional group-containing layer 3 and a resin coating layer 4 on the surface of the boehmite film of the aluminum plate. However, the PP resin did not bond to the surface of the boehmite film, and a metal member-resin member joint could not be produced.

Comparative Test Example 2
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 1 was carried out to form a functional group-containing layer 3 on the surface of the boehmite film.

(Resin coating layer)
Next, a solution prepared by dissolving 5 g of maleic anhydride-modified polypropylene (Modic (registered trademark) ER321P manufactured by Mitsubishi Chemical Corporation) in 95 g of xylene was applied to the surface of the functional group-containing layer 3, the xylene was volatilized, and the mixture was maintained at 150° C. for 30 minutes to produce a metal member in which a maleic anhydride-modified polypropylene layer having a thickness of 30 μm was formed on the surface of the functional group-containing layer.

A test piece for a tensile test (metallic member-resin member joint) was prepared by carrying out the same procedure as in Example Test 1 on the surface of the resin coating layer side of the metal member. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 1.

<Test Example 6>
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

(Functional Group-Containing Layer 3)
Next, the aluminum plate after the boehmite treatment was immersed for 20 minutes in a silane coupling agent-containing solution at 70° C. in which 2 g of 3-glycidoxypropyltrimethoxysilane ("KBM-403" manufactured by Shin-Etsu Silicones Co., Ltd.; a silane coupling agent) was dissolved in 1000 g of industrial ethanol, and the aluminum plate was then taken out and dried, thereby forming a functional group-containing layer 3 on the surface of the boehmite coating.

(Resin coating layer 4)
Next, the modified PP-4 obtained in Production Example 4 was applied to the surface of the functional group-containing layer 3, the xylene was volatilized, and the mixture was held at 150° C. for 30 minutes to produce a metal member 1 having a 30 μm-thick resin coating layer 4 of modified PP-4 formed on the surface of the functional group-containing layer 3.

A glass fiber reinforced polypropylene resin (PP resin) (pp-GF40-01 F02 manufactured by Daicel Miraize Co., Ltd.) (joint object) was injection molded on the surface 4s of the metal member 1 facing the resin coating layer 4 under the same conditions as in Example 1 to prepare a test piece for a tensile test (metal member 1 - resin member 8 joint). The joint strength of the test piece was measured using the same method as in Example 1. The measurement results are shown in Table 2.

<Test Example 7>
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 6 was carried out to form a functional group-containing layer 3 on the surface of the boehmite film.

(Resin coating layer 4: 1st layer)
A first resin coating layer (thermoplastic epoxy resin layer 4b) was formed on the surface of the functional group-containing layer 3 by the same operation as in Example 2, except that the epoxy resin was changed to jER (registered trademark) 1004 manufactured by Mitsubishi Chemical Corporation.

(Resin coating layer 4: 2nd layer)
Next, the same operation as in Example 2 was carried out to prepare a metal member 1 having a 30 μm-thick resin coating layer (modified polyolefin layer 4a) of modified PP-2 formed on the surface of the thermoplastic epoxy resin layer 4b.

A test piece for a tensile test (metal member 1 - resin member 8 joint) was prepared by carrying out the same operation as in Example Test 6 on the surface 4s of the second layer (modified polyolefin layer 4a) of the metal member 1 facing the resin coating layer 4. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 2.

<Test Example 8>
(surface treatment)
As the metal substrate 2, a magnesium plate having a size of 18 mm×45 mm and a thickness of 1.5 mm was subjected to a sanding treatment in the same manner as in Example 4 to form fine irregularities on the surface of the magnesium plate.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 3 was carried out on the irregular surface of the magnesium plate to form a functional group-containing layer 3 .

(Resin coating layer 4)
Next, the same operation as in Experimental Test Example 1 was carried out to prepare a metal member 1 having a 30 μm-thick modified PP-1 resin coating layer 4 formed on the surface of the functional group-containing layer 3 .

A test piece for a tensile test (metal member 1 - resin member 8 joint) was prepared by carrying out the same operation as in Example Test 6 on the surface 4s of the metal member 1 facing the resin coating layer 4. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 2.

<Test Example 9>
(surface treatment)
As the metal substrate 2, an aluminum plate (AHS alloy A6063) measuring 18 mm×45 mm and 1.5 mm thick was subjected to the same sanding treatment as in Example 4 to form fine irregularities on the surface of the aluminum plate.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 1 was carried out to form a functional group-containing layer 3 on the surface of the aluminum plate after the sanding treatment.

(Resin coating layer 4: 1st layer)
The same operation as in Experimental Test Example 7 was carried out to form a first resin coating layer (thermoplastic epoxy resin layer 4b).

(Resin coating layer 4: 2nd layer)
Next, the same operation as in Example Test 2 was carried out to prepare a metal member 1 having a 40 μm-thick resin coating layer (modified polyolefin layer 4a) of modified PP-2 formed on the surface of the thermoplastic epoxy resin layer 4b.

A test piece for a tensile test (metal member 1 - resin member 8 joint) was prepared by carrying out the same operation as in Example Test 6 on the surface 4s of the metal member 1 facing the resin coating layer 4. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 2.

Comparative Test Example 3
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

An injection molding operation similar to that of Example Test 6 was carried out without providing a functional group-containing layer 3 and a resin coating layer 4 on the surface of the boehmite film of the aluminum plate. However, the PP resin did not bond to the surface of the boehmite film, and a metal member-resin member joint could not be produced.

Comparative Test Example 4
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 1 was carried out to form a functional group-containing layer 3 on the surface of the boehmite film.

(Resin coating layer)
Next, the same operation as in Comparative Test Example 2 was carried out to prepare a metal member having a maleic anhydride-modified polypropylene layer having a thickness of 30 μm formed on the surface of the functional group-containing layer 3 .

A test piece for a tensile test (metallic member-resin member joint) was prepared by carrying out the same procedure as in Example Test 6 on the surface of the resin coating layer side of the metal member. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 2.

<Test Example 10>
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 1 was carried out to form a functional group-containing layer 3 on the surface of the boehmite film.

(Resin coating layer 4)
Next, the same operation as in Experimental Test Example 6 was carried out to prepare a metal member 1 having a 30 μm-thick modified PP-4 resin coating layer 4 formed on the surface of the functional group-containing layer 3 .

A carbon fiber-reinforced polypropylene resin (PP resin) (pp-GF40-01 F008 manufactured by Daicel Miraize Co., Ltd.) (joint object) was injection molded on the surface 4s of the metal member 1 facing the resin coating layer 4 under the same conditions as in Example Test 1 to prepare a test piece for a tensile test (metal member 1 - resin member 8 joint). The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 3.

<Test Example 11>
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 1 was carried out to form a functional group-containing layer 3 on the surface of the boehmite film.

(Resin coating layer 4: 1st layer)
A first resin coating layer (thermoplastic epoxy resin layer 4b) was formed on the surface of the functional group-containing layer 3 by the same operation as in Example 2, except that the epoxy resin was changed to jER (registered trademark) 1007 manufactured by Mitsubishi Chemical Corporation.

(Resin coating layer 4: 2nd layer)
Next, the same operation as in Example 2 was carried out to prepare a metal member 1 having a 30 μm-thick resin coating layer (modified polyolefin layer 4a) of modified PP-2 formed on the surface of the thermoplastic epoxy resin layer 4b.

A test piece for a tensile test (metal member 1 - resin member 8 joint) was prepared by carrying out the same operation as in Example Test 10 on the surface 4s of the second layer (modified polyolefin layer 4a) of the metal member 1 facing the resin coating layer 4. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 3.

<Test Example 12>
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

(Functional Group-Containing Layer 3)
Next, the same operation as in Example Test 1 was carried out to introduce functional groups derived from a silane coupling agent onto the surface of the boehmite film. Furthermore, the substrate was immersed in a solution of 1.2 g of 2-isocyanatoethyl methacrylate (Karenz MOI (registered trademark) manufactured by Showa Denko K.K.) and 0.05 g of 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) dissolved in 150 g of toluene at 70° C. for 5 minutes, and then pulled out and dried. In this way, a functional group-containing layer 3 in which functional groups capable of chemical bonding were extended in three-dimensional directions was formed.

(Resin coating layer 4)
Next, the same operation as in Experimental Test Example 1 was carried out to prepare a metal member 1 having a 30 μm-thick modified PP-1 resin coating layer 4 formed on the surface of the functional group-containing layer 3 .

A test piece for a tensile test (metal member 1 - resin member 8 joint) was prepared by carrying out the same operation as in Example Test 10 on the surface 4s of the metal member 1 facing the resin coating layer 4. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 3.

<Test Example 13>
(surface treatment)
As the metal substrate 2, a martensitic stainless steel (SUS403) plate measuring 18 mm×45 mm and 1.5 mm thick was subjected to sanding treatment in the same manner as in Example 4 to form fine irregularities on the surface of the stainless steel plate.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 1 was carried out to form a functional group-containing layer 3 on the surface of the stainless steel plate after the sanding treatment.

(Resin coating layer 4: 1st layer)
A thermoplastic epoxy resin composition obtained by dissolving 100 g of epoxy resin (jER (registered trademark) 1007 manufactured by Mitsubishi Chemical Corporation), 5.6 g of bisphenol A, and 0.4 g of triethylamine in 196 g of acetone was spray-coated on the surface of the functional group-containing layer 4 so that the thickness after drying would be 30 μm. The composition was left in air at room temperature for 30 minutes to volatilize the solvent, and then left in a 150° C. oven for 30 minutes to carry out a polyaddition reaction, and then allowed to cool to room temperature to form a first resin coating layer (thermoplastic epoxy resin layer 4b).

(Resin coating layer 4: 2nd layer)
Next, the same operation as in Example Test 2 was carried out to prepare a metal member 1 having a 40 μm-thick resin coating layer (modified polyolefin layer 4a) of modified PP-2 formed on the surface of the thermoplastic epoxy resin layer 4b.

A test piece for a tensile test (metal member 1 - resin member 8 joint) was prepared by carrying out the same operation as in Example Test 10 on the surface 4s of the metal member 1 facing the resin coating layer 4. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 3.

Comparative Test Example 5
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

An injection molding operation similar to that of Example Test 10 was carried out without providing a functional group-containing layer 3 and a resin coating layer 4 on the surface of the boehmite film of the aluminum plate. However, the PP resin did not bond to the surface of the boehmite film, and a metal member-resin member joint could not be produced.

Comparative Test Example 6
(surface treatment)
The same operation as in Example 1 was carried out to form a boehmite film having whisker-like irregularities on the surface of an aluminum plate (18 mm x 45 mm, 1.5 mm thick) of an AHS alloy.

(Functional Group-Containing Layer 3)
Next, the same operation as in Experimental Test Example 1 was carried out to form a functional group-containing layer 3 on the surface of the boehmite film.

(Resin coating layer)
Next, the same operation as in Comparative Test Example 2 was carried out to prepare a metal member having a maleic anhydride-modified polypropylene layer having a thickness of 30 μm formed on the surface of the functional group-containing layer 3 .

A test piece for a tensile test (metallic member-resin member joint) was prepared by carrying out the same operation as in Example Test 10 on the surface of the resin coating layer side of the metal member. The joint strength of the test piece was measured using the same method as in Example Test 1. The measurement results are shown in Table 3.

As can be seen from the evaluation results in Tables 1 to 3, all of the metal member-resin member joints in test examples 1 to 13 had high joint strength.

As the aluminum substrate, an aluminum plate made of another aluminum material was formed by hot extrusion, and the extruded aluminum plate was cut to a length of 45 mm, a width of 18 mm and a thickness of 1.5 mm, and its surface was smoothed by mechanical cutting.

The material of the aluminum plate was A6061-T6 aluminum alloy, specifically having a chemical composition of 0.6% by mass of Si, 0.25% by mass of Fe, 0.35% by mass of Cu, 1.0% by mass of Mg, with the remainder being Al and unavoidable impurities. The tensile strength of the aluminum plate was 340 MPa, and its Young's modulus was 68 GPa.

Next, test pieces for tensile tests (metallic member 1 - resin member 8 joints) were prepared by joining the aluminum plate and the resin member in the same manner as in Test Examples 1 to 5. The joint strength of these test pieces was measured using the same method as in Test Example 1, and all of them had high joint strength.

Therefore, according to the present disclosure, it is possible to manufacture a side door in which a metal member and a resin member are firmly joined.

The present invention can be used, for example, in side doors for hatchback automobiles and methods for manufacturing same.

1: Metal member 2: Metal substrate 2a: Surface treatment part 3: Functional group-containing layer 4: Resin coating layer (primer layer)
4a: Modified polyolefin layer 4b: Thermoplastic epoxy resin layer 4c: Curable resin layer 4s: Surface of resin coating layer 7: Adhesive layer 8: Resin member 8A: First resin member 8B: Second resin member 10: Side door (metal member-resin member joint)
11: Reinforcement material 21: Inner panel 22: Outer panel

Claims (12)

A metal member having one or more resin coating layers laminated on at least a part of the surface of a metal base, and a resin member bonded to a surface of the metal base of the metal member on the side of the resin coating layer,
1. An automobile side door, wherein at least one layer of the resin coating layer is a modified polyolefin layer formed from a resin composition containing a modified polyolefin, and the modified polyolefin layer is at least one selected from the group consisting of a layer containing a reaction product 1 of a maleic anhydride modified polyolefin, a bifunctional epoxy resin, and a bifunctional phenol compound, a layer containing a reaction product 2 of a maleic anhydride modified polyolefin and a thermoplastic epoxy resin, and a layer containing a mixture of a polyolefin and a thermoplastic epoxy resin. The automobile side door according to claim 1, wherein the reactant 1 is obtained by a polyaddition reaction of a difunctional epoxy resin and a difunctional phenol compound in a solution containing maleic anhydride-modified polyolefin. The automobile side door according to claim 1, wherein the reactant 2 is obtained by reacting a thermoplastic epoxy resin produced by a polyaddition reaction of a difunctional epoxy resin with a difunctional phenol compound with a maleic anhydride-modified polyolefin. The automobile side door according to claim 1, wherein the mixture is a mixture of polypropylene and a thermoplastic epoxy resin. The automotive side door according to any one of claims 1 to 4, wherein the resin coating layer is composed of multiple layers including the modified polyolefin layer and a layer other than the modified polyolefin layer, and at least one of the layers other than the modified polyolefin layer is at least one selected from a thermoplastic epoxy resin layer formed from a resin composition containing a thermoplastic epoxy resin and a curable resin layer formed from a resin composition containing a curable resin. The automobile side door according to claim 5, wherein the curable resin is at least one selected from the group consisting of urethane resin, epoxy resin, vinyl ester resin and unsaturated polyester resin. a functional group-containing layer is provided between the metal substrate and the resin coating layer and is laminated in contact with the metal substrate and the resin coating layer;
The automobile side door according to claim 1 , wherein the functional group-containing layer contains at least one functional group selected from the group consisting of the following (1) to (7):
(1) At least one functional group derived from a silane coupling agent and selected from the group consisting of a glycidyl group, an amino group, a (meth)acryloyl group, and a mercapto group. (2) A functional group generated by reacting an amino group derived from a silane coupling agent with at least one selected from a glycidyl compound and a thiol compound. (3) A functional group generated by reacting a mercapto group derived from a silane coupling agent with at least one selected from the group consisting of a glycidyl compound, an amino compound, an isocyanate compound, a compound having a (meth)acryloyl group and a glycidyl group, and a compound having a (meth)acryloyl group and an amino group. (4) A functional group generated by reacting a (meth)acryloyl group derived from a silane coupling agent with a thiol compound. (5) A functional group generated by reacting a glycidyl group derived from a silane coupling agent with at least one selected from the group consisting of a compound having an amino group and a (meth)acryloyl group, an amino compound, and a thiol compound. (6) An isocyanato group derived from an isocyanate compound. (7) A mercapto group derived from a thiol compound. The automobile side door according to any one of claims 1 to 7, wherein the surface of the metal base material is subjected to at least one surface treatment selected from the group consisting of blasting, polishing, etching and chemical conversion treatment, and the resin coating layer is laminated on the surface-treated surface of the metal base material. The automotive side door according to any one of claims 1 to 8, wherein the metal substrate is made of an aluminum extrusion material of an A6000 series alloy and has a tensile strength of 330 MPa or more and a Young's modulus of 65 GPa or more. The automotive side door according to any one of claims 1 to 8, wherein the metal substrate is made of an aluminum forging of an A4000 series alloy and has a tensile strength of 350 MPa or more and a Young's modulus of 70 GPa or more. The vehicle body includes a resin inner panel disposed inside the vehicle body, a resin outer panel disposed on the outside of the vehicle body, and a metal reinforcing member disposed between the two panels,
Each of the panels is a resin member,
At least a contact surface of the reinforcing material with each panel is a surface on the resin coating layer side,
11. The vehicle side door according to claim 1, wherein each panel is bonded to the contact surface of the stiffener. A method for manufacturing an automobile side door according to any one of claims 1 to 11, comprising joining a resin member to the resin coating layer side of a metal member when molding the resin member by injection molding, transfer molding, press molding, filament winding molding or hand lay-up molding.

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