Heat welding film, laminate, dissimilar material joined body, and method for producing dissimilar material joined body

Abstract

To provide a technique for joining a metal to a fiber-reinforced resin more simply and easily.SOLUTION: A heat welding film is used for joining a first member composed of metal to a second member composed of fiber-reinforced plastic. Both of one face and the other face are composed of a heat welding resin layer containing acid-modified polyolefin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a heat-weldable film, a laminate, a dissimilar material joint, and a method for manufacturing a dissimilar material joint. [Background technology]

[0002] Industrial product components are made up of various materials such as metals, resins, and ceramics. Conventionally, these components are first molded into the desired shape and then joined together using adhesives made of curable resins, screws, rivets, and other joining materials (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-111536 [Overview of the project] [Problems that the invention aims to solve]

[0004] Joining using mechanical fasteners such as screws and rivets is a cumbersome process. Adhesives, on the other hand, require time for application and are difficult to control in terms of adhesive thickness, leading to inconsistent adhesive strength. In contrast, adhesive bonding is preferable because it eliminates the need for mechanical fasteners, resulting in a more aesthetically pleasing joint. For these reasons, adhesive bonding remains the standard practice for joining two or more components, and this has been true for joining metals and fiber-reinforced resins, for example. In other words, a simpler method for joining metals and fiber-reinforced resins has not yet been discovered.

[0005] The inventors investigated a simpler method for joining metal and fiber-reinforced resin, and arrived at the novel idea of ​​using a heat-weldable film to join these materials. However, they encountered the problem that with conventional thermoplastic resins, the two components could not be joined together, as the resin would adhere to one material but not to the other at all.

[0006] Therefore, the main objective of the present invention is to provide a technology for more easily joining metal and fiber-reinforced resin. [Means for solving the problem]

[0007] The inventors of this invention conducted diligent research to solve the above-mentioned problems. As a result, they found that when an acid-modified polyolefin film is used as a heat-sealable film, it is possible to bond both metal and fiber-reinforced resin. This invention was completed by further research based on this finding.

[0008] In other words, the present invention provides inventions in the following embodiments. Item 1. A heat-weldable film for joining a first member made of metal and a second member made of fiber-reinforced plastic, A heat-weldable film in which both the surface on one side and the surface on the other side are composed of a heat-weldable resin layer containing acid-modified polyolefin. Item 2. The heat-sealable film according to Item 1, wherein the degree of acid modification of the acidic polyolefin is 0.005% by weight or more. Item 3. The heat-sealable film according to item 1 or 2, wherein the polyolefin to be modified in the acid-modified polyolefin is selected from the group consisting of polyethylene and polypropylene. Item 4. A heat-weldable film according to any one of items 1 to 3, wherein the matrix resin of the fiber-reinforced plastic is a thermosetting resin. Item 5. The heat-weldable film according to any one of items 1 to 3, wherein the matrix resin of the fiber-reinforced plastic is a thermoplastic resin. Item 6. The heat-weldable film according to any one of items 1 to 5, wherein the fibers in the fiber-reinforced plastic are glass fibers or carbon fibers. Item 7. A heat-weldable film according to any one of items 1 to 6, wherein fibers are exposed on the surface of the fiber-reinforced plastic. Item 8. A heat-sealable film according to any one of items 1 to 7, wherein the surface roughness of the fiber-reinforced plastic is 25 μm or more. Item 9. A heat-sealable film according to any one of items 1 to 8, wherein the melt mass flow rate of the heat-sealable resin layer is 2 to 20 g / 10 min. Item 10. A heat-weldable film according to any one of items 1 to 9, which is a single-layer film of the heat-weldable resin layer. Item 11. A method for manufacturing a dissimilar material joint, comprising: heating a laminate obtained by laminating a first member made of metal and a second member made of fiber-reinforced plastic via a heat-weldable film described in any of Items 1 to 10, and then performing heat welding to obtain a dissimilar material joint in which the first member and the second member are joined. Item 12. A method for manufacturing a dissimilar material joint, comprising: heating a laminate obtained by laminating a first member made of metal and a second member precursor made of fiber-reinforced plastic prepreg via a heat-weldable film as described in any of Items 1 to 10, thereby simultaneously performing heat welding, heat curing of the prepreg, and molding to obtain a dissimilar material joint in which the first member and the second member are joined. Item 13. A method for manufacturing a dissimilar material joint, comprising: heating a laminate obtained by laminating a first member made of metal and a second member made of fiber-reinforced plastic via a heat-weldable film as described in any of Items 1 to 10, thereby simultaneously performing heat welding and thermoforming to obtain a dissimilar material joint in which the first member and the second member are joined. Item 14. A laminate comprising a first member made of metal and a second member made of fiber-reinforced plastic or a precursor of a second member made of a fiber-reinforced plastic prepreg, laminated via a heat-weldable film as described in any of Items 1 to 10. Item 15. A dissimilar material joined body in which a first member made of metal and a second member made of fiber reinforced plastic are joined and formed through the heat-sealable film according to any one of Items 1 to 10.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a technique for more easily joining metal and fiber reinforced resin. That is, according to the present invention, by using a heat-sealable film using acid-modified polyolefin, it becomes possible to more easily join metal and fiber reinforced resin. Further, according to the present invention, it is also possible to provide a dissimilar material joined body of metal and fiber reinforced resin using the heat-sealable film.

Brief Description of the Drawings

[0010] [Figure 1] It is a schematic cross-sectional view of an example of the heat-sealable film of the present invention. [Figure 2] It is a schematic cross-sectional view of an example of the heat-sealable film of the present invention. [Figure 3] It is a schematic cross-sectional view of an example of the heat-sealable film of the present invention. [Figure 4] It is a schematic cross-sectional view of an example of the heat-sealable film of the present invention. [Figure 5] It is a schematic cross-sectional view of an example of the heat-sealable film of the present invention. [Figure 6] It is a schematic cross-sectional view of an example of the dissimilar material joined body of the present invention. [Figure 7] It is a schematic diagram for explaining a method of measuring seal strength. [Figure 8] It is a schematic diagram for explaining an example of a method for manufacturing the dissimilar material joined body of the present invention. [Figure 9] It is a schematic diagram for explaining an example of a method for manufacturing the dissimilar material joined body of the present invention. [Figure 10] It is a schematic cross-sectional view of an example of the dissimilar material joined body manufactured by the method for manufacturing the dissimilar material joined body of the present invention. [Figure 11] It is a schematic diagram for explaining a method of measuring shear strength. [Figure 12] This is a conceptual diagram of the positional change of the probe during probe displacement measurement. [Figure 13] This is a schematic diagram showing the position of the intermediate layer surface at the edge of the heat-sealable film where the probe is installed during probe displacement measurement. [Figure 14] This is a schematic diagram illustrating the method for measuring peel strength. [Modes for carrying out the invention]

[0011] The heat-weldable film of the present invention is a heat-weldable film for joining a first member made of metal and a second member made of fiber-reinforced plastic, and is characterized by comprising an acid-modified polyolefin heat-weldable resin layer 1. The heat-weldable film of the present invention, a dissimilar material joint using the heat-weldable film, and a method for manufacturing the same will be described in detail below.

[0012] In this specification, the numerical range indicated by "~" means "greater than or equal to" and "less than or equal to". For example, the notation 2~15mm means 2mm or more and 15mm or less.

[0013] 1. Heat-sealable film The heat-weldable film of the present invention is a heat-weldable film for joining a first member made of metal and a second member made of fiber-reinforced plastic. More specifically, the heat-weldable film of the present invention is used to join a first member made of metal and a second member made of fiber-reinforced plastic by placing the heat-weldable film between the first member made of metal and the second member made of fiber-reinforced plastic and heat-welding the first member and the second member through the heat-weldable film. In addition to the first member and the second member, other members may also be joined using the heat-weldable film of the present invention. That is, the heat-weldable film of the present invention is a heat-weldable film for joining a first member made of at least metal and a second member made of fiber-reinforced plastic by heat welding.

[0014] For example, as shown in the schematic diagram of Figure 1, the heat-weldable film 10 of the present invention is configured to include at least a heat-weldable resin layer 1 containing an acid-modified polyolefin. The heat-weldable film 10 shown in Figure 1 is configured as a single-layer film of the heat-weldable resin layer 1. Therefore, the heat-weldable resin layer 1 containing the acid-modified polyolefin constitutes both the surface on one side and the surface on the other side of the heat-weldable film 10.

[0015] The heat-weldable film 10 of the present invention may have a multilayer structure with other layers, as long as the heat-weldable resin layer 1 containing acid-modified polyolefin constitutes both one surface and the other surface of the heat-weldable film 10. When the heat-weldable film 10 of the present invention has a multilayer structure, the heat-weldable resin layer 1 containing acid-modified polyolefin of the heat-weldable film 10 of the present invention may be divided, as shown in the schematic diagrams of Figures 2 to 5, into a first heat-weldable resin layer 1a that constitutes one surface of the heat-weldable film 10 and a second heat-weldable resin layer 1b that constitutes the other surface of the heat-weldable film 10, via at least an intermediate layer 3. In other words, the heat-weldable film 10 of the present invention may be composed of a heat-weldable film comprising, in this order, at least a first heat-weldable resin layer 1a containing acid-modified polyolefin, an intermediate layer 3, and a second heat-weldable resin layer 1b containing acid-modified polyolefin.

[0016] Specific examples of the lamination configuration when the heat-weldable film 10 of the present invention has a multilayer structure include: a lamination configuration having a first heat-weldable resin layer 1a / intermediate layer 3 / second heat-weldable resin layer 1b in that order, as shown in Figure 2; a lamination configuration having a first heat-weldable resin layer 1a / intermediate layer 3 / thermoplastic resin layer 4 / second heat-weldable resin layer 1b in that order, as shown in Figure 3; a lamination configuration having a first heat-weldable resin layer 1a / thermoplastic resin layer 4 / intermediate layer 3 / second heat-weldable resin layer 1b in that order, as shown in Figure 4; and a lamination configuration having a first heat-weldable resin layer 1a / thermoplastic resin layer 4 / intermediate layer 3 / thermoplastic resin layer 4 / second heat-weldable resin layer 1b in that order, as shown in Figure 5. As will be described later, the first heat-weldable resin layer 1a and the second heat-weldable resin layer 1b may each contain an adhesive component and have adhesive properties. Furthermore, the thermoplastic resin layer 4 may also have heat-weldability, similar to the first heat-weldable resin layer 1a and the second heat-weldable resin layer 1b. The heat-weldable film of the present invention may have other layers laminated on it that are different from these layers. For example, although not shown in the figures, an adhesion promoter layer, as described later, may be provided on one or both sides of the intermediate layer 3.

[0017] From the viewpoint of low cost and simplification of the manufacturing process, the heat-weldable film of the present invention is preferably a single layer as shown in Figure 1. On the other hand, in the case of a multi-layer structure, from the viewpoint of low cost and simplification of the manufacturing process, it is preferable to make the heat-weldable film thin, and the heat-weldable film of the present invention preferably has a three-layer laminated structure comprising a first heat-weldable resin layer 1a / intermediate layer 3 / second heat-weldable resin layer 1b in this order, as shown in Figure 2. Furthermore, from the viewpoint of conformability to uneven shapes (i.e., the characteristic of smoothing out the uneven shape by allowing resin to enter the recesses in the uneven shape), it is preferable to make the heat-weldable film thicker, and the heat-weldable film of the present invention preferably has thermoplastic resin layers between each of the first heat-weldable resin layer 1a / intermediate layer 3 / second heat-weldable resin layer 1b. Specifically, it is preferable to have a four-layer laminate configuration comprising a first heat-weldable resin layer 1a / intermediate layer 3 / thermoplastic resin layer 4 / second heat-weldable resin layer 1b in that order, as shown in Figure 3; a four-layer laminate configuration comprising a first heat-weldable resin layer 1a / thermoplastic resin layer 4 / intermediate layer 3 / second heat-weldable resin layer 1b in that order, as shown in Figure 4; or a five-layer laminate configuration comprising a first heat-weldable resin layer 1a / thermoplastic resin layer 4 / intermediate layer 3 / thermoplastic resin layer 4 / second heat-weldable resin layer 1b in that order, as shown in Figure 5. Furthermore, if the first heat-weldable resin layer 1a contains an adhesive component to the extent that it does not affect the strength against shear stress parallel to the joint surface in the dissimilar material joint after joining, the heat-weldable film of the present invention may have a five-layer laminated structure in which the adhesive component is contained on both sides (specifically, a laminated structure comprising a first heat-weldable resin layer 1a containing an adhesive component, a thermoplastic resin layer 4, an intermediate layer 3, a thermoplastic resin layer 4, and a second heat-weldable resin layer 1b containing an adhesive component in this order), or a four-layer laminated structure in which the adhesive component is contained on one side (specifically, a laminated structure comprising a first heat-weldable resin layer 1a containing an adhesive component, a thermoplastic resin layer 4, an intermediate layer 3, a thermoplastic resin layer 4, and a second heat-weldable resin layer 1b not containing an adhesive component in this order).

[0018] From the viewpoint of low cost and minimizing the possibility of delamination, it is preferable that the number of layers in the heat-weldable film of the present invention be small, with a preferred lower limit of 1 or more and a preferred upper limit of 5 or less. From the viewpoint of reducing the thermal shrinkage rate in the high-temperature environment during heat welding and ensuring a good appearance after heat welding, and suitably heat-welding two or more members, the number of layers in the heat-weldable film of the present invention is preferably about 3 to 5, more preferably about 3 to 4.

[0019] Furthermore, the area of ​​one side of the heat-sealable film of the present invention can be appropriately set according to the size of the member to be heat-sealed.

[0020] <Seal strength> The heat-sealable film 10 of the present invention, when heat-sealed to the members described later (first member, second member), preferably has a seal strength of about 10 N / 15 mm or more between the heat-sealable film and the members, more preferably about 15 N / 15 mm or more, and even more preferably about 20 N / 15 mm or more. Furthermore, the seal strength between the heat-sealable film and the members is preferably about 10 N / 15 mm or more between both the first member and the second member. There is no particular upper limit to the preferred seal strength, but it is usually about 100 N / 15 mm or less. That is, the range of the seal strength is preferably about 10 to 100 N / 15 mm, more preferably about 15 to 100 N / 15 mm, and even more preferably about 20 to 100 N / 15 mm. In the heat-weldable film 10 of the present invention, which heat-welds a first member and a second member, the fact that the seal strength when heat-welded with these members has such a value means that in the resulting dissimilar material joint, the first member and the second member are suitably joined via the heat-weldable film 10 of the present invention. Note that if at least one of the first member and the second member, when joined by heat welding, is a solid member containing uncured resin, this refers to the seal strength when the heat-weldable film 10 is heat-welded to the member in which the uncured resin has been heat-cured. The specific method for measuring the seal strength is as follows. Note that the seal strength when the heat-weldable film 10 of the present invention and the members (first member, second member) described later are heat-welded is not limited to this range.

[0021] In measuring the seal strength, first, the heat-sealable film is cut to a size of 50 mm in the length direction (y direction) x 25 mm in the width direction (x direction). Next, the heat-sealable film 10 and each component 50 are heat-sealed with a depth of 7 mm (y direction) (heat sealing conditions: temperature 190°C, surface pressure 1 MPa, pressurization time 5 seconds) to obtain a test sample. In the schematic diagram of Figure 7, the area S enclosed by the dashed line indicates the heat-sealed area. A release sheet is placed in the area other than the area to be heat-sealed, so that the heat seal is applied with a depth of 7 mm. Next, the test sample is cut to a width of 15 mm as shown in Figure 7(a) so that the seal strength (N / 15 mm) in the width direction (x direction) can be measured. Next, using a tensile testing machine, the heat-sealable film 10 is peeled off from the fixed component 50 in the length direction (y direction) as shown in Figure 7(b). In this case, the peeling speed was set to 300 mm / min, and the maximum load until peeling was defined as the seal strength (N / 15 mm). For the materials used in the preparation of the test samples, a thickness of 4 mm was used for the fiber-reinforced plastic material and a thickness of 0.5 mm for the metal material. Each seal strength was defined as the average value (n=3) obtained by preparing three test samples in the same manner.

[0022] <Peel strength> When the heat-weldable film 10 of the present invention is heat-welded to the members described later (first member, second member), the peel strength between the first member and the second member is preferably about 10 N / 25 mm or more, more preferably about 20 N / 25 mm or more, and even more preferably about 25 N / 25 mm or more. There is no particular upper limit to the preferred peel strength, but it is usually about 100 N / 25 mm or less. That is, the range of the peel strength is preferably about 10 to 100 N / 25 mm, more preferably about 20 to 100 N / 25 mm, and even more preferably about 25 to 100 N / 25 mm. The specific method for measuring the peel strength is as follows. Note that the peel strength when the heat-weldable film 10 of the present invention is heat-welded to the members described later (first member, second member) is not limited to this range.

[0023] The peel strength is measured according to the methods specified in ISO 19095-2 and ISO 19095-3. Specifically, first, the heat-sealable film is cut to a size of 160 mm in length and 25 mm in width. Then, the first member 70 (if the thickness differs from the second member 80, the thinner one, such as metal, is used) is cut to a size of 250 mm in length and 25 mm in width, and the second member 80 is cut to a size of 200 mm in length and 25 mm in width. Next, Figure 14(i) As shown, the first or second heat-weldable resin layer of the heat-weldable film 10 is overlapped with the first member 70 and the second member 80 with their longitudinal directions aligned, and a test sample is obtained by heat-sealing a region of 160 mm in the length direction and 25 mm in the width direction (heat-sealing conditions: temperature 190°C, surface pressure 1 MPa, pressurizing time 30 seconds). Next, the test sample is fixed to a peel test fixture on the second member 80 side, and the first member 70 is peeled in the length direction using a tensile testing machine, as shown in Figure 14(ii). At this time, the peeling speed is set to 100 mm / min, and the average load in the area excluding the section from the peeling start point to a peeling length of 25 mm is defined as the peel strength (N / 25 mm). For the materials used in the preparation of the test sample, a fiber-reinforced plastic member with a thickness of 4 mm and a metal member with a thickness of 0.5 mm are used. Each peel strength is the average value (n=3) obtained by preparing three test samples in the same manner.

[0024] <Shear strength> Furthermore, the shear strength of the dissimilar material joint obtained by heat-welding the first member and the second member via the heat-weldable film 10 of the present invention is preferably about 5 MPa or more, more preferably about 8 MPa or more. There is no particular upper limit to the shear strength, but it is usually about 50 MPa or less. Preferred ranges for the shear strength are about 5 to 50 MPa and about 8 to 50 MPa. In the heat-weldable film 10 of the present invention used to heat-weld the first member and the second member, having such values ​​for shear strength when heat-welded with these members allows the resulting dissimilar material joint to maintain a good bond state.

[0025] Furthermore, when the heat-weldable film 10 of the present invention has an intermediate layer 3, the shear strength of the dissimilar material joint obtained by heat-welding the first member and the second member is preferably about 10 MPa or more, more preferably about 11 MPa or more. When the heat-weldable film 10 of the present invention has an intermediate layer 3, the preferred range for the shear strength is about 10 to 50 MPa or about 11 to 50 MPa. In the heat-weldable film 10 of the present invention used to heat-weld the first member and the second member, having such a shear strength when heat-welded with these members means that the resulting dissimilar material joint has excellent strength against shear stress parallel to the joint surface. In particular, a dissimilar material joint in which at least one of the first member and the second member has a thickness of 1 mm or more is susceptible to shear stress parallel to the joint surface, but having such shear strength allows the joint to maintain a good state even when subjected to such shear stress.

[0026] The shear strength is measured in accordance with the provisions of ISO 19095-2 and ISO 19095-3. The size of the first and second members in the preparation of the test sample is 45 mm in length and 10 mm in width, with a thickness of 1.5 mm for the metal member and 3 mm for the fiber-reinforced plastic member. The heat-sealable film is 5 mm in length and 10 mm in width. As shown in Figure 11, the heat-sealable film 10 is placed between the first member 70 and the second member 80 at their longitudinal ends, and the first member 70 and the second member 80 are heat-sealed via the heat-sealable film 10 to obtain a dissimilar material joint under the conditions of a temperature of 190°C, a surface pressure of 1.5 MPa, and a duration of 20 seconds. Furthermore, the heat-sealable film 10 is positioned so that both sides are heat-sealed to the first member 70 and the second member 80, respectively (i.e., the heat-sealed area is 5 mm in length and 10 mm in width on one side). Although not shown in Figure 11, in order to measure the joint in which the first member 70 and the second member 80 are joined in a parallel state, the first member 70 and the second member 80 are joined by adjusting their height using corrective members. The corrective member used to adjust the height of the first member 70 is made of the same material and shape as the first member 70, and the corrective member used to adjust the height of the second member 80 is made of the same material and shape as the second member 80. Next, the dissimilar material joint is pulled in the length direction using a tensile testing machine (tensile speed: 10 mm / min), the maximum load (N) is measured, and this is divided by the heat-sealed area (5 mm in length and 10 mm in width) to calculate the shear strength (MPa).

[0027] (Heat-weldable resin layer 1 (first heat-weldable resin layer 1a and second heat-weldable resin layer 1b)) In the present invention, the heat-weldable resin layer 1 is a layer that constitutes both one surface and the other surface of the heat-weldable film 10 of the present invention. That is, the heat-weldable resin layer 1 constitutes the outermost layer on both one and the other side of the heat-weldable film 10 of the present invention.

[0028] The heat-weldable resin layer 1 contains at least an acid-modified polyolefin. This enables dissimilar material joining by heat welding both a first member made of metal and a second member made of fiber-reinforced plastic. The presence of an acid-modified polyolefin in the resin constituting the heat-weldable resin layer 1 can be analyzed by methods such as infrared spectroscopy and gas chromatography-mass spectrometry, and the analytical method is not particularly limited. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a wavenumber of 1760 cm⁻¹ is used. -1 Nearby wave frequency 1780cm -1 A peak derived from maleic anhydride is detected in the vicinity.

[0029] Furthermore, examples of acid-modified polyolefins include polyolefins modified with unsaturated carboxylic acids or their anhydrides. Examples of unsaturated carboxylic acids or their anhydrides used for acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

[0030] The degree of acid modification of acid-modified polyolefins can be said to have a lower limit of, for example, about 0.005% by weight or more. From the viewpoint of better bonding of dissimilar materials, it is preferable that the lower limit be about 0.01% by weight or more, more preferably about 0.04% by weight or more, and even more preferably about 0.08% by weight or more. There is no particular preferred upper limit for the degree of acid modification, but it is usually about 0.5% by weight or less. That is, the range of the degree of acid modification can be said to be, for example, about 0.005 to 0.5% by weight, preferably about 0.01 to 0.5% by weight, more preferably about 0.04 to 0.5% by weight, even more preferably about 0.08 to 0.5% by weight, and even more preferably about 0.1 to 0.5% by weight. The degree of acid modification is the weight ratio of acid-modifying groups in the acid-modified polyolefin. For example, in the case of maleic acid-modified polyolefins, it is the weight ratio of maleic acid-modifying groups in the acid-modified polyolefin. The degree of acid modification is, 1 H-NMR The value is determined from the acid-derived peak area. Specifically, first, acid-modified polyolefins are treated with ODCB-d4 / C6D6 (volume ratio 4 / 1) solvent.1 H-NMR and the acid-modified polio Methyl esterified refin 1 1H-NMR and 1H-NMR are measured. 1 By comparing 1H-NMR spectra, the peaks of methyl esterified products with derivatized acids are identified. Furthermore, the acid-modified polyolefin (before methyl esterification) 1 From H-NMR, the methyl esterified product 1 In 1H-NMR, the area of ​​the impurity-derived peak that overlaps with the peak position of the methyl esterified product is identified. By subtracting the area of ​​the impurity-derived peak from the peak area at the peak position of the methyl esterified product, the peak area of ​​the methyl esterified product is determined. Based on this, the degree of acid modification is calculated from the ratio of the mass of the acid-modified group to the mass of the acid-modified polyolefin before methyl esterification.

[0031] The modified polyolefin is not particularly limited, but from the viewpoint of more favorably bonding dissimilar materials, preferred materials include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymer of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymer of propylene and ethylene); and ethylene-butene-propylene terpolymers. Among these, polypropylene is preferred as the modified polyolefin.

[0032] From the viewpoint of more effectively joining dissimilar materials, among the heat-weldable resins contained in the heat-weldable resin layer 1, maleic anhydride-modified polypropylene and maleic anhydride-modified polyethylene are particularly preferred.

[0033] The acid-modified polyolefin contained in the heat-weldable resin layer 1 may be of one type or of two or more types.

[0034] The proportion of acid-modified polyolefin contained in the heat-weldable resin layer 1 is not particularly limited, but preferably about 70% by mass or more, more preferably about 80% by mass or more, and preferably about 100% by mass or less as the lower limit. Furthermore, the range of the proportion of acid-modified polyolefin is preferably about 70 to 100% by mass or about 80 to 100% by mass. By having such a value for the proportion of acid-modified polyolefin contained in the heat-weldable resin layer 1, the heat-weldable film 10 of the present invention can suitably exhibit heat-welding properties to both metal members and fiber-reinforced plastics, and can more suitably join dissimilar materials.

[0035] The heat-weldable resin layer 1 may further contain an adhesive component, as long as it does not affect the strength against shear stress parallel to the joint surface in the dissimilar material joint after bonding. More specifically, the heat-weldable resin layer 1 may be composed of a heat-weldable resin composition containing an adhesive component. By including an adhesive component in the heat-weldable resin layer 1, the heat-weldable resin layer 1 of the heat-weldable film 10 can be suitably temporarily attached to the surfaces of the first and second members, thereby suppressing misalignment during heat welding and enabling more suitable bonding of dissimilar materials. In this invention, temporary attachment means temporarily bonding, and it is possible to peel it off even after it has been temporarily bonded.

[0036] The adhesive component is not particularly limited as long as it can impart tackiness to the heat-weldable resin layer 1. Examples include rosin or its derivatives such as rosin, hydrogenated rosin, polymerized rosin, and rosin esters; terpene resins such as α-pinene, β-pinene, and limonene; terpene phenol resins, coumarone-indene resins, styrene resins, xylene resins, phenolic resins, petroleum resins, and hydrogenated petroleum resins. Amorphous polyolefins can also be used as the adhesive component. Examples of amorphous polyolefins include amorphous polypropylene, or copolymers of amorphous propylene with other α-olefins. Specific examples include propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-butene-1-ethylene terpolymer, propylene-hexene-1-octene-1-terpolymer, propylene-hexene-1-4-methylpentene-1-terpolymer, propylene-hexene-1-4-methylpentene-1-terpolymer, and polybutene-1. The adhesive component may be used alone or in combination of two or more types.

[0037] When the heat-weldable resin layer 1 contains an adhesive component, the proportion of the adhesive component is not particularly limited, but the lower limit is preferably about 1% by mass or more, more preferably about 5% by mass or more, and the upper limit is preferably about 30% by mass or less, more preferably about 25% by mass or less. The range of the proportion of the adhesive component is preferably about 1 to 30% by mass, about 1 to 25% by mass, about 5 to 30% by mass, and about 5 to 25% by mass. Because the proportion of the adhesive component contained in the heat-weldable resin layer 1 has these values, the heat-weldable film of the present invention can suitably exhibit excellent adhesiveness and excellent heat-welding properties, so that the first member and the second member can be suitably temporarily bonded, and positional displacement during heat welding can be suppressed, allowing for more suitable bonding of dissimilar materials.

[0038] The melt mass flow rate (MFR) of the heat-weldable resin layer 1 is not particularly limited, but from the viewpoint of improving its conformability to the surface of the member and more favorably joining dissimilar materials, a lower limit of approximately 2 g / 10 min or more is preferred, and more preferably approximately 3 g / 10 min or more. In particular, from the viewpoint of favorably heat-welding the second member by improving the conformability of the heat-weldable resin layer 1 to the surface irregularities (surface roughness Ra) of the second member made of fiber-reinforced plastic and effectively obtaining an anchoring effect, the melt mass flow rate (MFR) of the heat-weldable resin layer constituting the surface on the side to be heat-welded to the second member (i.e., the heat-weldable resin layer 1, or the second heat-weldable resin layer 1b in the case where the heat-weldable film 10 has a multi-layer structure) is more preferably approximately 4 g / 10 min or more. From the viewpoint of preventing the outflow of molten resin during heat welding and more effectively joining dissimilar materials, a preferred upper limit for the melt mass flow rate (MFR) of the heat-weldable resin layer 1 is preferably about 20 g / 10 min or less, and more preferably about 15 g / 10 min or less. That is, the range of the melt flow rate is approximately 2 to 20 g / 10 min, 2 to 15 g / 10 min, 3 to 20 g / 10 min, 3 to 15 g / 10 min, 4 to 20 g / 10 min, or 4 to 15 g / 10 min. The melt mass flow rate (MFR) is a value measured using a melt indexer at a measurement temperature of 230°C and a load of 2.16 kg, in accordance with the provisions of JIS K7210:2014.

[0039] The softening point of the heat-weldable resin layer 1 is not particularly limited, but from the viewpoint of improving its conformability to the surface of the members and more effectively heat-welding two or more members, it is preferably about 180°C or lower, more preferably about 160°C or lower. The lower limit of the softening point of the heat-weldable resin layer 1 is, for example, about 80°C or higher, preferably 100°C or higher. Preferred ranges for the softening point of the heat-weldable resin layer 1 include about 80 to 180°C, about 80 to 160°C, about 100 to 180°C, and about 100 to 160°C.

[0040] In this invention, the softening point of the heat-weldable resin layer 1 is the temperature at which the deflection of the probe is maximum during the subsequent measurement of the probe's displacement. In measuring the softening point of the heat-weldable resin layer 1, the temperature at which the probe's deflection is maximum is read for five samples of the heat-weldable resin layer 1 to be measured, and the average of the three temperatures (excluding the maximum and minimum values) is taken as the softening point. In measuring the probe's displacement, first, as shown in the conceptual diagram in Figure 12, for example, the probe 90 is placed on the surface of the heat-weldable resin layer 1 at the edge of the heat-weldable film (for example, at position P in the heat-weldable resin layer 1 of the heat-weldable film 10 in Figure 13) (measurement start A in Figure 12). The edge at this time is the portion where the cross-section of the heat-weldable resin layer 1 is exposed, obtained by cutting the heat-weldable film in the thickness direction, passing through the center of the heat-weldable film. Cutting can be performed using a commercially available rotary microtome or the like. An atomic force microscope equipped with a nanothermal microscope consisting of a cantilever with a heating mechanism, such as the afm plus system from ANASIS INSTRUMENTS, can be used, and a probe from ANASIS INSTRUMENTS can be used. The tip radius of the probe should be 30 nm or less, the deflection setting of the probe should be -4 V, and the heating rate should be 5 °C / min. Next, when the probe is heated in this state, the heat from the probe 90 causes the surface of the heat-weldable resin layer 1 to expand as shown in Figure 12B, pushing up the probe 90, and the position of the probe 90 rises above its initial value (the position when the temperature of the probe 90 is 40 °C). If the heating temperature rises further, the heat-weldable resin layer 1 will soften, and as shown in Figure 12C, the probe 90 may pierce the heat-weldable resin layer 1, causing the position of the probe 90 to drop. In measuring the displacement of the probe 90 using an atomic force microscope equipped with a nanothermal microscope consisting of a cantilever with a heating mechanism, the heat-weldable film to be measured is at room temperature (25°C), and the probe 90, heated to 40°C, is placed on the surface of the heat-weldable resin layer 1 at the edge of the heat-weldable film to start the measurement.

[0041] The thickness of the heat-weldable resin layer 1 is not particularly limited, but from the viewpoint of reducing the thermal shrinkage rate in the high-temperature environment during heat welding and obtaining a dissimilar material joint with superior strength against shear stress parallel to the joint surface after joining, the lower limit is preferably about 5 μm or more, more preferably about 10 μm or more, and even more preferably about 20 μm or more, and the upper limit is preferably about 200 μm or less, and more preferably about 100 μm or less. Furthermore, the range of thickness of the heat-weldable resin layer 1 is preferably about 5 to 200 μm, about 5 to 100 μm, about 10 to 200 μm, about 10 to 100 μm, about 20 to 200 μm, and about 20 to 100 μm.

[0042] (First heat-weldable resin layer 1a and second heat-weldable resin 1b) When the heat-weldable film 10 of the present invention has a multilayer structure, the heat-weldable resin layer is divided into a first heat-weldable resin layer 1a and a second heat-weldable resin layer 1b via an intermediate layer 3. The first heat-weldable resin layer 1a is a layer that constitutes one side surface of the heat-weldable film 10, and the second heat-weldable resin layer 1b is a layer that constitutes the other side surface of the heat-weldable film 10. That is, in this case, the first heat-weldable resin layer 1a constitutes the outermost layer on one side of the heat-weldable film 10 of the present invention, and the second heat-weldable resin layer 1b constitutes the outermost layer on the other side of the heat-weldable film 10 of the present invention.

[0043] The first heat-weldable resin layer 1a and the second heat-weldable resin layer 1b are the same as the heat-weldable resin layer 1 described above, except that they are separated by an intermediate layer 3. Furthermore, the materials, such as the type of heat-modified polyolefin and resin composition, physical properties such as the melt mass flow rate (MFR), and thickness of the first heat-weldable resin layer 1a and the second heat-weldable resin layer 1b may be the same or different.

[0044] (Middle class 3) When the heat-weldable film 10 of the present invention has an intermediate layer 3, the intermediate layer 3 is located between the first heat-weldable resin layer 1a and the second heat-weldable resin layer 1b, thereby ensuring the excellent high tensile modulus of the heat-weldable film 10.

[0045] The material constituting the intermediate layer 3 is not particularly limited as long as it has a high tensile modulus, and examples include polyester, polyimide, polyamide, epoxy resin, polyvinyl alcohol, polyphenylene sulfide, polyarylate, polycarbonate, acrylic resin, fluororesin, silicone resin, phenolic resin, polyetherimide, and mixtures or copolymers thereof.

[0046] Specifically, examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolymer polyesters with ethylene terephthalate as the main repeating unit, and copolymer polyesters with butylene terephthalate as the main repeating unit. Furthermore, specific examples of copolymer polyesters with ethylene terephthalate as the main repeating unit include copolymer polyesters polymerized with ethylene isophthalate using ethylene terephthalate as the main repeating unit (hereinafter abbreviated as polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / isophthalate), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl dicarboxylate), and polyethylene (terephthalate / decanedicarboxylate). Furthermore, specific examples of copolymer polyesters with butylene terephthalate as the main repeating unit include copolymer polyesters polymerized with butylene isophthalate using butylene terephthalate as the main repeating unit (hereinafter abbreviated as polybutylene(terephthalate / isophthalate)), polybutylene(terephthalate / adipate), polybutylene(terephthalate / sebacate), polybutylene(terephthalate / decanedicarboxylate), and polybutylene naphthalate. These polyesters may be used individually or in combination of two or more types.

[0047] In addition to the above, other examples of polyesters include aromatic polyesters, which are polycondensates containing monomers selected from the group consisting of aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids in any composition ratio. Among aromatic polyesters, all-aromatic polyesters that do not have aliphatic hydrocarbons in the main chain are preferred. Specific examples of all-aromatic polyesters include polyarylates such as copolymers of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, and copolymers of p-hydroxybenzoic acid, terephthalic acid, and 4,4'-dihydroxybisphenyl.

[0048] From the viewpoint of reducing the thermal shrinkage rate in the high-temperature environment during heat welding and achieving a higher tensile modulus of elasticity for the heat-weldable film 10, among these, polyethylene terephthalate, polyethylene naphthalate, fully aromatic polyester, polyimide, polyphenylene sulfide, aramid, and vinylon (polyvinyl alcohol) are preferred as materials for the intermediate layer 3. These resins may be used individually or in combination of two or more.

[0049] The shape of the intermediate layer 3 is not particularly limited and can be a film, fiber, etc. A nonwoven fabric is preferred as a specific fiber shape. From the viewpoint of obtaining a higher tensile modulus of elasticity for the heat-sealable film 10, the intermediate layer 3 is preferably a film.

[0050] When the intermediate layer 3 is a film, it is preferable that the intermediate layer 3 is composed of polyethylene terephthalate film, polyethylene naphthalate film, and polyimide film.

[0051] When the intermediate layer 3 is made of fibers, it is preferable that the intermediate layer 3 is composed of polyphenylene sulfide fibers, aramid fibers, vinylon (polyvinyl alcohol) fibers, or fully aromatic polyester fibers.

[0052] Among these fibers, all-aromatic polyester fibers are preferable because all-aromatic polyester exhibits molecular orientation (melt anisotropy) in the molten state, and the resulting fibers (melt anisotropic all-aromatic polyester fibers) exhibit further molecular orientation. This makes them more prone to intertwining, resulting in a nonwoven fabric with high mechanical strength and low moisture absorption. Furthermore, the gaps created by the division and subdivision allow resin to easily penetrate, resulting in a nonwoven fabric with excellent resin impregnation properties. Consequently, the interlayer strength of the heat-weldable film 10 is extremely high. Therefore, among all-aromatic polyester fibers, nonwoven fabrics made of melt anisotropic all-aromatic polyester fibers are the most preferable.

[0053] The tensile modulus of the intermediate layer 3 is preferably about 1500 MPa or higher, more preferably about 2000 MPa or higher, even more preferably about 2900 MPa or higher, and particularly preferably about 5000 MPa or higher, from the viewpoint of obtaining a dissimilar material joint with excellent strength against shear stress parallel to the joint surface, by setting the heat-weldable film 10 to a specific tensile modulus. There is no particular upper limit to the tensile modulus, but it is usually about 10000 MPa or lower, preferably about 8000 MPa or lower, and more preferably 7000 MPa or lower. Specifically, the range of tensile modulus is approximately 1500-10000 MPa, 1500-8000 MPa, 1500-7000 MPa, 2000-10000 MPa, 2000-8000 MPa, 2000-7000 MPa, 2900-10000 MPa, 2900-8000 MPa, 2900-7000 MPa, 5000-10000 MPa, 5000-8000 MPa, and 5000-7000 MPa. The tensile modulus of intermediate layer 3 is a value obtained by measuring the material constituting intermediate layer 3 in accordance with the provisions of JIS K7161:2014.

[0054] The tensile modulus is a value measured in accordance with JIS K7161:2014. Specifically, a test piece (rectangular) cut from the film to a width of 2.5 mm and a length of 120 mm with the MD (medium-density) as the longer side is measured in a tensile-compression testing machine (Tensilon RTC-1250A, manufactured by Orientec Co., Ltd.) at a temperature of 25°C, under the conditions of a tensile speed of 200 mm / min and a chuck distance of 100 mm. The tensile modulus is calculated from the initial straight line portion of the tensile stress-strain curve obtained from this measurement, according to the following formula. E = Δρ / Δε E: Tensile modulus Δρ: Stress difference due to the original average cross-sectional area between two points on a straight line Δε: Difference in strain between the same two points

[0055] The method for confirming the MD of the intermediate layer 3 in the preparation of test specimens for measuring the tensile modulus is as follows: The intermediate layer 3 is observed using a transmission electron microscope to confirm the sea-island structure for each of the 10 cross-sections (a total of 10 cross-sections) of the heat-weldable film 10, by changing the angle by 10 degrees from a direction parallel to the cross-section in Furthermore, if the intermediate layer 3 of the heat-weldable film 10 is made of fibers, the MD can be determined based on the roll direction of the fiber material constituting the intermediate layer 3. However, if the MD cannot be determined, a test specimen can be prepared so that any direction is the longer side.

[0056] The thermal shrinkage rate of the intermediate layer 3, measured under the conditions of a test temperature of 200°C and a heating time of 10 seconds, is preferably about 10% or less, more preferably about 5% or less, even more preferably about 3% or less, and particularly preferably 2% or less, from the viewpoint of reducing the thermal shrinkage rate in the high-temperature environment during heat welding and obtaining a dissimilar material joint with superior strength against shear stress parallel to the joint surface after joining, and the lower limit is preferably about 0% or more and about 0.1% or more. The range of the thermal shrinkage rate is approximately 0-10%, 0-5%, 0-3%, 0-2%, 0.1-10%, 0.1-5%, 0.1-3%, and 0.1-2%. The thermal shrinkage rate can be measured by a method in accordance with the provisions of JIS K 7133:1999.

[0057] In the present invention, it is preferable that the above-mentioned thermal shrinkage rate is satisfied in at least two directions: one direction of the intermediate layer 3 (the planar direction of the intermediate layer 3) and a direction perpendicular to it (the planar direction of the intermediate layer 3). Specifically, when the intermediate layer 3 is a film, the MD of the intermediate layer 3 is defined as the one direction for measuring the thermal shrinkage rate. In the present invention, the method for confirming the MD of the intermediate layer 3 of the heat-weldable film 10 is as described above in the section on the tensile modulus of the intermediate layer 3. Furthermore, when the intermediate layer 3 of the heat-weldable film 10 is a fiber and the MD cannot be determined, any direction may be designated as the one direction.

[0058] The melting peak temperature of the intermediate layer 3 is not particularly limited, but from the viewpoint of further improving heat resistance, the melting peak temperature of the intermediate layer 3 is preferably about 200°C or higher, more preferably about 230°C or higher, and even more preferably about 240°C or higher. The upper limit of the melting peak temperature of the intermediate layer 3 is not particularly limited, but for example, it is about 300°C or lower. A preferred range for the melting peak temperature of the intermediate layer 3 is preferably about 200 to 300°C, more preferably about 230 to 300°C, and even more preferably about 240 to 300°C. In the present invention, the melting peak temperature is a value measured using a differential scanning calorimeter (DSC), with a heating rate of 10°C / min, a temperature measurement range of 100 to 350°C, and an aluminum pan used as the sample pan.

[0059] The thickness of the intermediate layer 3 is not particularly limited, but from the viewpoint of reducing the thermal shrinkage rate in the high-temperature environment during heat welding and obtaining a dissimilar material joint with excellent strength against shear stress parallel to the joint surface after joining, the lower limit is preferably about 5 μm or more, more preferably about 10 μm or more, and the upper limit is preferably about 200 μm or less, more preferably about 100 μm or less, and even more preferably about 50 μm or less. Furthermore, the range of the thickness of the intermediate layer 3 is preferably about 5 to 200 μm, about 5 to 100 μm, about 5 to 50 μm, about 10 to 200 μm, about 10 to 100 μm, and about 10 to 15 μm. In addition, if the intermediate layer 3 is a film, the upper limit of the thickness of the intermediate layer 3 may be preferably about 30 μm or less, more preferably about 20 μm or less. Furthermore, if the intermediate layer 3 is a film, the thickness range of the intermediate layer 3 can be approximately 5-30 μm, 10-30 μm, 5-20 μm, or 10-20 μm.

[0060] Furthermore, when the intermediate layer 3 is made of a nonwoven fabric, there are no particular restrictions on the basis weight of the nonwoven fabric. However, from the viewpoint of sufficiently impregnating the nonwoven fabric with the layers adjacent to the intermediate layer 3 (for example, the first heat-weldable resin layer 1a, the second heat-weldable resin layer 1b, the thermoplastic resin layer 4, etc.) and stabilizing the adhesive strength between the layers, a smaller basis weight is preferable, preferably about 5 g / m² as the lower limit.2 The above are listed. Further, from the viewpoint of reducing the heat shrinkage rate in the high-temperature environment during heat welding, a large basis weight is preferable, and the upper limit is 30 g / m 2 The following are listed. During heat welding In order to reduce the heat shrinkage rate in the high-temperature environment during heat welding and make the appearance after heat welding good, and to more preferably heat-weld two or more members, the range of the basis weight is preferably 5 to 30 g / m 2 or so, more preferably 7 to 25 g / m 2 or so.

[0061] <Tensile modulus> When the heat-sealable film 10 of the present invention has the intermediate layer 3, the tensile modulus of the heat-sealable film 10 of the present invention is 1500 MPa or more as the lower limit. Thereby, the joined dissimilar material joined body can be obtained as having excellent strength against the shear stress parallel to the joining surface. From the viewpoint of obtaining a joined dissimilar material joined body having more excellent strength against the shear stress parallel to the joining surface, the tensile modulus of the heat-sealable film 10 of the present invention is preferably about 1500 MPa or more, more preferably about 2000 MPa or more, further preferably about 3000 MPa or more, and particularly preferably about 5000 MPa or more as the lower limit. Note that there is no particular upper limit for the tensile modulus, but usually it is about 10000 MPa or less, preferably about 8000 MPa or less, more preferably about 7000 MPa or less. That is, the range of the tensile modulus includes about 1500 to 10000 MPa, about 1500 to 8000 MPa, about 1500 to 7000 MPa, about 2000 to 10000 MPa, about 2000 to 8000 MPa, about 2000 to 7000 MPa, about 3000 to 10000 MPa, about 3000 to 8000 MPa, about 3000 to 7000 MPa, about 5000 to 10000 MPa, about 5000 to 8000 MPa, about 5000 to 7000 MPa.

[0062] The method for measuring the tensile modulus is as described above in the section on the tensile modulus of the intermediate layer 3. In this measurement method, the direction corresponding to the MD of the heat-weldable film 10 may be the same as the MD of the intermediate layer 3 of the heat-weldable film 10, for example, if the intermediate layer 3 is a film. In this invention, the method for confirming the MD of the intermediate layer 3 of the heat-weldable film 10 is as described above in the section on the tensile modulus of the intermediate layer 3. Furthermore, if the intermediate layer 3 of the heat-weldable film 10 is a fiber, the direction corresponding to the MD of the heat-weldable film 10 may be the same as the MD of the heat-weldable resin layer 1. The method for confirming the MD of the heat-weldable resin layer 1 is the same as the method for confirming the MD of the intermediate layer 3.

[0063] <Thermal shrinkage rate> When the heat-weldable film 10 of the present invention has an intermediate layer 3, in order to reduce the thermal shrinkage rate in the high-temperature environment during heat welding and to obtain a dissimilar material joint with superior strength against shear stress parallel to the joint surface after joining, the thermal shrinkage rate of the heat-weldable film 10 of the present invention, measured under the conditions of a test temperature of 200°C and a heating time of 10 seconds, is preferably about 10% or less as an upper limit, more preferably about 3.0% or less, and even more preferably about 2.8% or less, and the lower limit is about 0% and about 0.1%. Furthermore, the range of the thermal shrinkage rate is preferably about 0-10%, about 0-3.0%, about 0-2.8%, about 0.1-10%, about 0.1-3.0%, and about 0.1-2.8%. The thermal shrinkage rate is measured by a method in accordance with the provisions of JIS K 7133:1999.

[0064] In the present invention, it is preferable that the above-mentioned thermal shrinkage rate is satisfied in at least two directions: one direction of the heat-weldable film 10 (the planar direction of the heat-weldable film 10) and a direction perpendicular thereto (the planar direction of the heat-weldable film 10). Specifically, when the intermediate layer 3 of the heat-weldable film 10 is a film, the direction corresponding to the MD of the intermediate layer 3 of the heat-weldable film 10 is defined as the one direction. In the present invention, the method for confirming the MD of the intermediate layer 3 of the heat-weldable film 10 is as described above in the section on the tensile modulus of the intermediate layer 3. Furthermore, when the intermediate layer 3 of the heat-weldable film 10 is a fiber, the same direction as the MD of the heat-weldable resin layer 1 may be defined as the one direction. The method for confirming the MD of the heat-weldable resin layer 1 is the same as the method for confirming the MD of the intermediate layer 3.

[0065] (Thermoplastic resin layer 4) In the present invention, the thermoplastic resin layer 4 is a layer that is laminated on the heat-weldable film 10 as needed. Preferably, the thermoplastic resin layer 4 is laminated between the first heat-weldable resin layer 1a and the intermediate layer 3, and between the intermediate layer 3 and the second heat-weldable resin layer 1b. The heat-weldable film 10 may have one layer of thermoplastic resin layer 4 laminated on it, or it may have two or more layers laminated on it. Preferably, the number of layers of thermoplastic resin layer 4 on the heat-weldable film 10 is about 0 to 2, more preferably about 0 to 1. If at least one of the first heat-weldable resin layer 1a and the second heat-weldable resin layer 1b contains an adhesive component, the adhesive strength between the layers can be stabilized by laminating the layer containing the adhesive component to the intermediate layer 3 via the thermoplastic resin layer 4. Therefore, for example, if the first heat-weldable resin layer 1a and the second heat-weldable resin layer 1b constitute both sides of the heat-weldable film 10, and the first heat-weldable resin layer 1a and the second heat-weldable resin layer 1b contain an adhesive component, it is preferable that the thermoplastic resin layer 4 is laminated in one layer each between the first heat-weldable resin layer 1a and the intermediate layer 3, and between the intermediate layer 3 and the second heat-weldable resin layer 1b, as shown in the laminate configuration of Figure 5. Also, for example, if the first heat-weldable resin layer 1a constitutes one side of the heat-weldable film 10, and the first heat-weldable resin layer 1a contains an adhesive component, it is preferable that the thermoplastic resin layer 4 is laminated in one layer between the first heat-weldable resin layer 1a and the intermediate layer 3, as shown in the laminate configuration of Figure 4.

[0066] The thermoplastic resin constituting the thermoplastic resin layer 4 is not particularly limited as long as it is thermoplastic. Examples of thermoplastic resins include polyolefins, polyesters, polyamides, acrylic resins, fluororesins, and silicone resins. Among these, the thermoplastic resin layer 4 is preferably composed of polyolefins, and more preferably of acid-modified polyolefins (i.e., having a polyolefin skeleton). As acid-modified polyolefins, the same ones exemplified in the heat-weldable resin layer 1 are preferably exemplified. That is, the resin constituting the thermoplastic resin layer 4 may or may not contain a polyolefin skeleton, but from the above viewpoint, it is preferable that it contains a polyolefin skeleton. Thermoplastic resins having a polyolefin skeleton are preferable as thermoplastic resins to be included in the thermoplastic resin layer 4 because they have excellent solvent resistance. Whether the resin constituting the thermoplastic resin layer 4 contains a polyolefin skeleton can be analyzed by, for example, infrared spectroscopy or gas chromatography-mass spectrometry, and the analytical method is not particularly limited. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a wavenumber of 1760 cm⁻¹ is used. -1 Nearby wave frequency 1780cm -1 A peak derived from maleic anhydride is detected in the vicinity.

[0067] Furthermore, the thermoplastic resin layer 4 may contain an adhesive component, as long as it does not affect the strength against shear stress parallel to the joint surface in the dissimilar material joint after bonding. When the thermoplastic resin layer 4 contains an adhesive component, the thermoplastic resin layer 4 can exhibit adhesive properties. When the thermoplastic resin layer 4 contains an adhesive component, there are no particular restrictions on the type of adhesive component, and the same components as those exemplified in the heat-weldable resin layer 1 are exemplified. Also, there are no particular restrictions on the proportion of the adhesive component in the thermoplastic resin layer 4, and the same proportion as in the heat-weldable resin layer 1 can be cited.

[0068] (Other layers) If the heat-weldable film 10 of the present invention has a multilayer structure, other layers different from the first heat-weldable resin layer 1a, the second heat-weldable resin layer 1b, the intermediate layer 3, and the thermoplastic resin layer 4 may be further laminated.

[0069] (Additives) The heat-sealable film 10 of the present invention may optionally contain various additives such as lubricants, antioxidants, ultraviolet absorbers, and light stabilizers. The type and amount of additives that do not cause discoloration of the heat-sealable film 10 can be appropriately selected by those skilled in the art.

[0070] (Method for manufacturing heat-sealable films) The heat-weldable film 10 of the present invention can be manufactured by melt extrusion and, if necessary, stretching of at least the heat-weldable resin layer 1. If the heat-weldable film 10 of the present invention has a multilayer structure, it can be manufactured by laminating at least a first heat-weldable resin layer 1a, an intermediate layer 3, a second heat-weldable resin layer 1b, and a thermoplastic resin layer 4, if necessary. The method of laminating these layers is not particularly limited and can be carried out using, for example, thermal lamination, sandwich lamination, or extrusion lamination.

[0071] Furthermore, when the heat-weldable film 10 of the present invention has a multilayer structure, and the intermediate layer 3 is made of a resin film, the adhesion strength with adjacent layers (for example, the first heat-weldable resin layer 1a, the second heat-weldable resin layer 1b, the thermoplastic resin layer 4, etc.) can be improved and the laminated structure can be stabilized by applying an adhesion promoter to both sides of the intermediate layer 3 (i.e., providing an adhesion promoter layer). In addition, the surface of the intermediate layer 3 can be subjected to well-known easy-adhesion methods such as corona discharge treatment, ozone treatment, or plasma treatment, as needed.

[0072] As the adhesion promoter for forming the adhesion promoter layer, well-known adhesion promoters such as isocyanate-based, polyethyleneimine-based, polyester-based, polyurethane-based, and polybutadiene-based promoters can be used. Furthermore, the adhesion promoter layer can also be formed using known adhesives such as two-component curing adhesives or one-component curing adhesives.

[0073] The adhesion promoter layer can be provided on one or both sides of the intermediate layer 3. The adhesion promoter layer can be formed by applying and drying using known coating methods such as bar coating, roll coating, or gravure coating.

[0074] (Component) The first member, which is joined by the heat-weldable film 10, is made of metal, and the second member is made of fiber-reinforced plastic.

[0075] Specific examples of metals that make up the first component include aluminum, iron, stainless steel, copper, and albino. Lead, silver, gold, magnesium, titanium, brass, nickel, or at least one of these. Examples include alloys containing one type, and among these, aluminum, iron, stainless steel, Titanium, brass, and nickel are preferred materials.

[0076] The surface roughness Ra of the metal is preferably about 10 nm or more, more preferably about 0.5 μm or more, and more preferably about 1 μm or more. There is no particular upper limit to the surface roughness Ra, but for example, it can be about 20 μm or less. Since the heat-weldable film 10 of the present invention can suitably bond dissimilar materials, even if the upper limit of the surface roughness Ra is about 10 μm or less, about 5 μm or less, or about 3 μm or less, it is possible to effectively bond dissimilar materials. That is, the range of the surface roughness Ra can be about 10 nm to 20 μm, about 10 nm to 10 μm, about 10 nm to 5 μm, about 10 nm to 3 μm, about 0.5 to 20 μm, about 0.5 to 10 μm, about 0.5 to 5 μm, about 0.5 to 3 μm, about 1 to 20 μm, about 1 to 10 μm, about 1 to 5 μm, and about 1 to 3 μm. Surface roughness Ra is the arithmetic mean roughness measured using a contact-type roughness meter in accordance with JIS B0601:2013. A Surfcom NEX manufactured by Tokyo Seimitsu Co., Ltd. can be used as the contact-type roughness meter.

[0077] The fiber-reinforced plastic constituting the second component can be any composite material whose strength is improved by incorporating fibers into the matrix resin. Examples of the matrix resin for the fiber-reinforced plastic include thermosetting resins (cured thermosetting resins) and thermoplastic resins, with thermosetting resins (cured thermosetting resins) being preferred.

[0078] Examples of thermosetting resins used as matrix resins for fiber-reinforced plastics include epoxy resins, unsaturated polyester resins, phenolic resins, silicone resins, urethane resins, and polyimide resins, with epoxy resins being preferred. These thermosetting resins can be used individually or in combination of two or more. Examples of thermoplastic resins used as matrix resins for fiber-reinforced plastics include polysulfone, polyethersulfone, polyetherimide, polyimide, and various thermoplastic elastomers. These thermoplastic resins can be used individually or in combination of two or more.

[0079] The fibers used in fiber-reinforced plastics are not particularly limited and include inorganic fibers such as carbon fibers and glass fibers, and organic fibers such as aramid fibers. Among these, carbon fibers and glass fibers are preferred, and carbon fibers are more preferred, from the viewpoint of obtaining a dissimilar material joint with superior strength against shear stress parallel to the joint surface after joining. The carbon fibers are not particularly limited and may be polyacrylonitrile (PAN) type, pitch type, etc., or mixtures thereof. The weave of the fibers may be any of the following: unidirectional long fibers, bidirectional woven fabric, multiaxial woven fabric, nonwoven fabric, mat, knit, braid, etc. Here, long fibers mean single fibers or fiber bundles that are substantially continuous for 10 mm or more.

[0080] For fiber-reinforced plastics, the surface roughness Ra can be, for example, about 1 μm or more. From the viewpoint of more effectively obtaining the anchoring effect by the heat-weldable resin layer 1 of the heat-weldable film 10 of the present invention following surface irregularities and more favorably joining dissimilar materials, the surface roughness Ra is preferably about 3 μm or more, more preferably about 8 μm or more, and even more preferably about 25 μm or more. There is no particular upper limit to the surface roughness Ra, but from the viewpoint of allowing the heat-weldable resin layer of the heat-weldable film to easily follow surface irregularities, it is, for example, about 100 μm or less. That is, the range of the surface roughness Ra can be, for example, about 1 to 100 μm, preferably about 3 to 100 μm, more preferably about 8 to 100 μm, and even more preferably about 25 to 100 μm. The surface roughness Ra is the arithmetic mean roughness measured using a contact-type roughness meter in accordance with JIS B0601:2013. For contact-type roughness metering, the Surfcom NEX manufactured by Tokyo Seimitsu Co., Ltd. can be used.

[0081] The surface of fiber-reinforced plastic may or may not have exposed fibers. For the same surface roughness Ra, exposed fibers are preferable in terms of more favorable bonding of dissimilar materials. Furthermore, the surface of fiber-reinforced plastic can be exposed for the purpose of adjusting the surface roughness Ra of the fiber-reinforced plastic. To expose the fibers of fiber-reinforced plastic, a process can be performed to remove the matrix resin from the surface of the fiber-reinforced plastic where the fibers are not exposed. The degree of fiber exposure on the surface of fiber-reinforced plastic, that is, the ratio of the area occupied by exposed fibers to the surface of the fiber-reinforced plastic, can be, for example, 0% or more, preferably about 5% or more, more preferably about 10% or more, even more preferably about 25% or more, and even more preferably about 40% or more. There is no particular upper limit to this degree of exposure, but it is usually about 90% or less. That is, the range of this degree of exposure can be, for example, about 0 to 90%, preferably about 5 to 90%, more preferably about 10 to 90%, even more preferably about 25 to 90%, and even more preferably about 40 to 90%.

[0082] Fiber-reinforced plastics may contain various additives as needed, such as lubricants, antioxidants, UV absorbers, light stabilizers, and colorants (pigments, dyes, etc.).

[0083] The thickness of the first and second members is not particularly limited, but as a lower limit, the thickness of each member should be about 0.1 mm or more, preferably at least one member should be about 1 mm or more. The thickness of a member refers to the maximum thickness of the member. Furthermore, if at least one member has a thickness of 1 mm or more, and especially if both members have a thickness of 1 mm or more, the dissimilar material joint will have a considerable thickness after joining, and the dissimilar material joint will easily be subjected to shear stress parallel to the joint surface. By joining such members with a thickness of 1 mm or more using the heat-weldable film 10 of the present invention, which preferably has an intermediate layer 3, a dissimilar material joint with excellent strength against such shear stress can be obtained. From a similar viewpoint, the thickness of at least one, preferably both members, should more preferably be 1.3 mm or more, and even more preferably 1.5 mm or more. There is no particular upper limit for the members, but for example, it is about 20 mm or less. In other words, the range of thickness can be, for example, about 0.1 to 20 mm, preferably about 1 to 20 mm, more preferably about 1.3 to 20 mm, and even more preferably about 1.5 to 20 mm.

[0084] The shape and size of the components are not particularly limited and should be appropriate for the dissimilar material joint manufactured by joining the components. Examples include components of various shapes such as plates, pin-shaped components like thumbtacks, concave, convex, and concave-convex shapes. Examples of components of various shapes include molded components. In the present invention, the dissimilar material joint manufactured by joining the components can be suitably used for applications such as interior and exterior components of automobiles. Therefore, the material, shape, and size of the components can be selected to suit these applications.

[0085] 2. Laminate, dissimilar material joint, and method for manufacturing dissimilar material joint The laminate of the present invention is characterized in that a first member 30 and a second member 40 or a precursor of the second member 40 are laminated via the heat-weldable film 10 of the present invention. Details of the heat-weldable film 10, the first member 30, and the second member 40 of the present invention are as described above. Furthermore, the precursor of the second member 40 refers to a fiber-reinforced plastic prepreg, which is the state before the thermosetting resin of the second member 40 hardens, as described as second member precursor 40a in Figure 8 below.

[0086] The laminate of the present invention may have a shape in which a first member 30 and a second member 40 or a precursor of the second member 40 are laminated via a heat-weldable film 10. For example, if there are two members to be laminated, the first member / heat-weldable film / second member or precursor of the second member may be laminated in that order. If there are three members to be laminated, the first member / heat-weldable film / second member or precursor of the second member / heat-weldable film / other members may be laminated in that order. Alternatively, the first member and the other members may be arranged side by side on one side of the heat-weldable film, and the second member or precursor of the second member may be arranged on the other side of the heat-weldable film, so that the three members are laminated via a single heat-weldable film. Furthermore, the heat-weldable film may be present over the entire area between the first member and the second member or precursor of the second member, and these members may be laminated, or it may be present over a part of the area between the first member and the second member or precursor of the second member, and these members may be laminated.

[0087] The laminate of the present invention is characterized by having a first member 30 and a second member 40 or a precursor of the second member 40 laminated via a heat-weldable film 10, and the first member 30 and the second member 40 or the precursor of the second member 40 may or may not be joined by heat welding via the laminated heat-weldable film 10 of the present invention.

[0088] The dissimilar material joint 20 of the present invention is characterized in that the first member 30 and the second member 40 are heat-welded together by the heat-weldable film 10 of the present invention, as shown in the schematic diagram of Figure 6, for example. That is, the dissimilar material joint 20 of the present invention is in a joined and molded state via the heat-weldable film 10 of the present invention. Details of the heat-weldable film 10, the first member 30, and the second member 40 of the present invention are as described above.

[0089] The dissimilar material joint 20 of the present invention can be molded into any shape. For example, Figure 6 shows an embodiment in which the dissimilar material joint 20 of the present invention is in the shape of a plate. Also, Figure 10 shows an embodiment in which the dissimilar material joint 20 of the present invention is molded by a mold.

[0090] The dissimilar material joint 20 of the present invention can be manufactured by heat-welding the first member 30 and the second member 40 or the precursor of the second member 40 in the laminate described above via a heat-weldable film 10. Specifically, in this case, the heat-weldable film 10 is placed between the first member 30 and the second member 40 or the precursor of the second member 40, and then heated and pressurized to heat-melt the surface of the heat-weldable film 10, or further heat-harden the precursor of the second member 40. After that, the heat-weldable film 10 is cooled to solidify the heat-melted surface, thereby obtaining a molded body 20 in which the first member 30 and the second member 40 are heat-welded (joined) via the heat-weldable film 10.

[0091] When the matrix resin of the fiber-reinforced plastic constituting the second member 40 is a thermosetting resin, the state of the member at the time of heat welding is the state after the thermosetting resin has hardened. In this case, a heat-weldable film 10 is sandwiched between a first metal member molded into a predetermined shape and a fiber-reinforced plastic (after hardening) molded into a predetermined shape, and heat welding is performed by applying pressure and heating to obtain a dissimilar material joint in which the first member and the second member are joined.

[0092] If the matrix resin of the fiber-reinforced plastic constituting the second member 40 is a thermosetting resin, the state of the member at the time of heat welding may be the state before the thermosetting resin hardens, that is, the second member precursor. In this case, the laminate formed by laminating the first member made of metal and the second member precursor made of fiber-reinforced plastic prepreg via a heat-weldable film 10 can be heated to perform heat welding, heat curing of the prepreg, and molding simultaneously, that is, in a single process, thereby obtaining a dissimilar material joint in which the first member and the second member are joined. More specifically, as shown in the series of schematic diagrams in Figures 8 to 10, a laminate is formed by laminating a metal member (first member 30) and a fiber-reinforced plastic prepreg (second member precursor 40a) with a heat-weldable film 10 in between (Figure 8). The laminate is deformed by pressing or heat-pressing it with a mold 60, and the laminate is heated to cause thermal curing of the fiber-reinforced plastic prepreg (second member precursor 40a) and thermal welding by melting the heat-weldable film 10 (Figure 9). After the mold 60 is cooled, a dissimilar material joint 20 is obtained in which the first member 30 and the second member 40 (after curing) are joined by the heat-weldable film 10, as shown in Figure 10.

[0093] When the matrix resin of the fiber-reinforced plastic constituting the second member 40 is a thermoplastic resin, a laminate formed by laminating a first member made of metal and a second member made of fiber-reinforced plastic via a heat-weldable film 10 can be heated to perform heat welding and thermoforming simultaneously, i.e., in a single step, thereby obtaining a dissimilar material joint in which the first member and the second member are joined. More specifically, the same process as shown in the series of schematic diagrams in Figures 8 to 10 can be performed, except that the fiber-reinforced plastic prepreg (second member precursor 40a) is changed to fiber-reinforced plastic 40. In other words, a laminate is formed by laminating a metal member (first member 30) and a fiber-reinforced plastic (second member 40) via a heat-weldable film 10, and the laminate is plastically deformed by heating and pressing with a mold or the like, and heat welding is performed by melting the heat-weldable film 10 by heating the laminate. After the mold is cooled, a dissimilar material joint 20 is obtained in which the first member 30 and the second member 40 are joined by the heat-weldable film 10.

[0094] The temperature at which the first member 30 and the second member 40 or the second member precursor 40a are heat-sealed via the heat-sealable film 10 is not particularly limited as long as it is the temperature at which the surface of the heat-sealable film 10 melts, but is preferably around 140 to 280°C, more preferably around 160 to 250°C. At this temperature, the curing temperature (in the case of thermosetting resins) or softening point (in the case of thermoplastic resins) of the matrix resin in the fiber-reinforced plastic is also taken into consideration as appropriate. The pressure (surface pressure) at which heat welding is performed is not particularly limited, but is preferably around 0.1 to 5 MPa, more preferably around 0.2 to 3 MPa. The heating and pressing time at which heat welding is performed is usually around 1 to 30 seconds. [Examples]

[0095] The present invention will be described in detail below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

[0096] <Materials for heat-weldable films, components to be joined, and measurement of their physical properties> In the examples and comparative examples, the degree of acid modification of the material, melt mass flow rate (MFR), melting peak temperature, softening point, tensile modulus, and thermal shrinkage coefficient, as well as the surface roughness of the members to be joined and the degree of fiber exposure of the fiber-reinforced plastic, were measured by the following methods.

[0097] (Measurement of the degree of acid denaturation) First, the target material (acid-modified polyolefin) was measured using ODCB-d4 / C6D6 (volume ratio 4 / 1) solvent. 1 1H NMR and the methyl ester of the acid-modified polyolefin 1 1H-NMR was measured. 1 Comparison of H-NMR showed that the acid-derivativeized methyl esterified product The peak was identified. Furthermore, the acid-modified polyolefin (before methyl esterification) 1 From H-NMR, the methyl esterified product 1 In 1H-NMR, the area of ​​impurity-derived peaks overlapping the peak position of the methyl esterified product was identified. By subtracting the area of ​​the impurity-derived peak from the peak area at the peak position of the methyl esterified product, the peak area of ​​the methyl esterified product was determined, and the degree of acid modification was calculated from the acid-derived peak area derived based on this. For polyolefins that were not acid-modified, the degree of acid modification was set to 0% by weight.

[0098] (Measurement of Meltmass Flow Rate (MFR)) The measurements were performed using a melt indexer for a heat-sealable resin layer, in accordance with the provisions of JIS K7210:2014. The melt indexer used was the "MiniLab" manufactured by HAAKE. The measurement conditions were a measurement temperature of 230°C and a load of 2.16 kg.

[0099] (Measurement of melting peak temperature) The melting peak temperature of the intermediate layer was measured using a differential scanning calorimeter (DSC). A Shimadzu DSC-60 Plus was used as the instrument. The measurement conditions were a heating rate of 10°C / min, a temperature measurement range of 100-350°C, and an aluminum pan used as the sample pan.

[0100] (Measurement of softening point) The softening point was measured using probe displacement measurement. First, as shown in the conceptual diagram of Figure 12, probe 90 was placed on the surface of the heat-weldable resin layer at the edge of the heat-weldable film (for example, in the case of the first heat-weldable resin layer 1a in the heat-weldable film 10 in Figure 13, this refers to position P. The following explanation will use the first heat-weldable resin layer 1a as a representative example). (Measurement start A in Figure 12). The edge at this time is the portion where the cross-section of the first heat-weldable resin layer 1a is exposed, obtained by cutting in the thickness direction so as to pass through the center of the heat-weldable film. Cutting was performed using a commercially available rotary microtome. An atomic force microscope equipped with a nanothermal microscope consisting of a cantilever with a heating mechanism, such as the afm plus system from ANASIS INSTRUMENTS, was used, and a probe from ANASIS INSTRUMENTS was used. The tip radius of the probe was 30 nm or less, the deflection setting of the probe was -4 V, and the heating rate was 5 °C / min. Next, when the probe was heated in this state, the heat from the probe 90 caused the surface of the first heat-weldable resin layer 1a to expand, as shown in Figure 12B, pushing up the probe 90 and raising its position above its initial value (the position when the probe 90 temperature was 40°C). As the heating temperature increased further, the first heat-weldable resin layer 1a softened, and as shown in Figure 12C, the probe 90 pierced the first heat-weldable resin layer 1a, causing the probe 90 to lower. In measuring the displacement of the probe 90, the heat-weldable film to be measured was at room temperature (25°C), and the probe 90, heated to 40°C, was placed on the surface of the first heat-weldable resin layer 1a to start the measurement. The softening point of the first heat-weldable resin layer 1a is the temperature at which the deflection of the probe 90 was maximum during the probe displacement measurement. In measuring the softening point of the first heat-weldable resin layer 1a, the temperature at which the deflection of the probe 90 reached its maximum was read for five samples of the first heat-weldable resin layer 1a to be measured. The average of the three temperatures obtained by excluding the maximum and minimum values ​​of the five temperatures was defined as the softening point.

[0101] (Measurement of tensile modulus) The tensile modulus of the intermediate layer was measured in the same manner as the measurement of the tensile modulus of the heat-sealable film described later.

[0102] (Measurement of thermal shrinkage rate) When the heat-sealable film has an intermediate layer and the intermediate layer is a film, the heat shrinkage rate was measured in two directions, MD (longitudinal direction) and TD (direction perpendicular to the longitudinal direction) in accordance with the provisions of JIS K 7133:1999, under the conditions of a test temperature of 200°C and a heating time of 10 minutes. When the intermediate layer is a fiber, the heat shrinkage rate was measured in two directions, MD (longitudinal direction of the nonwoven roll) and TD (direction perpendicular to the longitudinal direction of the nonwoven roll) in accordance with the provisions of JIS K 7133:1999, under the conditions of a test temperature of 200°C and a heating time of 10 minutes.

[0103] (Measurement of surface roughness) The surface roughness Ra of each component was measured using a contact-type roughness meter, Surfcom NEX, manufactured by Tokyo Seimitsu Co., Ltd., as the arithmetic mean roughness in accordance with JIS B0601:2013.

[0104] (Measurement of fiber exposure) The degree of fiber exposure in fiber-reinforced plastic components was measured by calculating the area ratio occupied by the exposed fibers through microscopic observation of the surface.

[0105] [Test Example 1: Test using a single-layer heat-sealable film] <Heat-sealable film> (Examples 1-18) Single-layer films (100 μm thick) of maleic anhydride-modified polypropylene resin (PPa) or maleic anhydride-modified polyethylene resin (PEa), as shown in Tables 1 and 2, were prepared as heat-sealable films.

[0106] (Comparative Example 1) As shown in Table 1, a single-layer film (100 μm thick) of unoriented polypropylene film (CPP) was prepared as a heat-sealable film.

[0107] <Measurement of various physical properties of dissimilar material joints> Test samples and dissimilar material joints were prepared under the conditions described below, and the seal strength and shear strength were measured. In Tables 1 and 2, AL for the first component refers to aluminum (JIS H 4000:2014 A1100), and SUS refers to stainless steel (JIS G 4305:2005 SUS304). Among the fiber-reinforced plastics of the second component, those where the resin material is epoxy and the fiber material is carbon refer to the cured fiber-reinforced plastic in which epoxy resin has impregnated carbon fibers. Furthermore, among the fiber-reinforced plastics of the second component, those where the resin material is PP and the fiber material is carbon refer to fiber-reinforced plastic in which carbon fibers have been impregnated with polypropylene resin.

[0108] (Measurement of seal strength) The seal strength (N / 15mm) between each surface of the heat-sealable films of the examples and comparative examples and the first and second members described in Tables 1 and 2 was measured. More specifically, first, each heat-sealable film was cut to a size of 50mm in the length direction (y direction) × 25mm in the width direction (x direction). Next, for example, when measuring the seal strength of the heat-sealable film of the example, as shown in Figure 7, each heat-sealable film 10 of the example and each member 50 were heat-sealed with a depth of 7mm (y direction) (heat sealing conditions: temperature 190℃, surface pressure 1MPa, pressurizing time 5 seconds) to obtain a test sample. In the schematic diagram of Figure 7, the area S enclosed by the dashed line indicates the heat-sealed area. A release sheet was placed in the area other than the area to be heat-sealed, and the area was heat-sealed with a depth of 7mm. Next, to measure the seal strength (N / 15mm) at a width of 15mm (x-direction), the test sample was cut to a width of 15mm as shown in Figure 7(a). Then, using a tensile testing machine, the heat-sealable film 10 was peeled from the fixed member 50 in the length direction (y-direction) as shown in Figure 7(b). At this time, the peeling speed was set to 300mm / min, and the maximum load until peeling was taken was defined as the seal strength (N / 15mm). For the materials used in the preparation of the test samples, a thickness of 4mm was used for the fiber-reinforced plastic member and a thickness of 0.5mm was used for the metal member. Each seal strength is the average value (n=3) obtained by preparing three test samples in the same manner and measuring them. The results are shown in Tables 1 and 2.

[0109] (Measurement of shear strength) The shear strength (MPa) of molded bodies obtained by heat-welding a first member and a second member using the heat-weldable films of the examples and comparative examples was measured under the following conditions. The shear strength was measured in accordance with the provisions of ISO 19095-2 and ISO 19095-3. The size of the first member and the second member in the preparation of the test samples was 45 mm in length and 10 mm in width, and the thickness was 3 mm for the fiber-reinforced plastic member and 1.5 mm for the metal member. In addition, each heat-weldable film was 5 mm in length and 10 mm in width. As shown in Figure 13, the heat-weldable film 10 was placed between the first member 70 and the second member 80 at their longitudinal ends, and the first member 70 and the second member 80 were heat-welded via the heat-weldable film 10 to obtain a molded body under the conditions of a temperature of 190°C, a surface pressure of 1.5 MPa, and a duration of 20 seconds. Furthermore, the heat-sealable film 10 was positioned so that the entire surface of both sides was heat-sealed (i.e., the heat-sealed area was 5 mm in length and 10 mm in width on one side). Although not shown in Figure 13, in order to measure the joint in which the first member 70 and the second member 80 were joined in a parallel state, the heights of the first member 70 and the second member 80 were adjusted using corrective members. The corrective member used to adjust the height of the first member 70 was made of the same material and shape as the first member 70, and the corrective member used to adjust the height of the second member 80 was made of the same material and shape as the second member 80. Next, the dissimilar material joint was pulled in the longitudinal direction using a tensile testing machine (tensile speed: 10 mm / min), and the maximum load (N) until delamination or fracture of the dissimilar material joint occurred was measured. This was then divided by the heat-sealed area (5 mm in length and 10 mm in width) to calculate the shear strength (MPa). The results are shown in Tables 1 and 2.

[0110] [Table 1]

[0111] [Table 2]

[0112] As shown in the results in Tables 1 and 2, the heat-weldable films (Examples 1-18) in which both surfaces consist of a heat-weldable resin layer containing acid-modified polyolefin, successfully bonded both the first member made of metal and the second member made of fiber-reinforced plastic. This demonstrated that by using such heat-weldable films, a dissimilar material joint can be easily obtained without the use of adhesives. On the other hand, the heat-weldable film (Comparative Example 1) made of a heat-weldable resin that does not contain acid-modified polyolefin bonded to the metal but not to the fiber-reinforced plastic at all. This demonstrated that a dissimilar material joint cannot be obtained using such a heat-weldable film.

[0113] [Test Example 2: Test using a heat-sealable film with an intermediate layer] <Manufacturing of heat-sealable films and measurement of their physical properties> (Example 19) A polyethylene naphthalate (PEN) film (tensile modulus 6000 MPa, peak melting temperature 262°C, thermal shrinkage coefficient TD 1.3%, MD 1.1%, thickness 12 μm) was used as an intermediate layer. A maleic anhydride-modified polypropylene resin (acid modification degree 0.09 wt%, MFR 8 g / 10 min, softening point 140°C) was extruded to a thickness of 44 μm using a T-die extruder to form a first heat-weldable resin layer (PPa). Next, the same maleic anhydride-modified polypropylene resin was extruded to a thickness of 44 μm on the other side of the intermediate layer using a T-die extruder to form a second heat-weldable resin layer (PPa). A laminated film was obtained in which the first heat-weldable resin layer (PPa, thickness 44 μm) / intermediate layer (PEN, thickness 12 μm) / second heat-weldable resin layer (PPa, thickness 44 μm) were laminated in this order, and this laminated film was obtained as a heat-weldable film.

[0114] (Example 20) As an intermediate layer, a melt-anisotropic fully aromatic polyester (polyarylate (PAR)) nonwoven fabric (tensile modulus 3000 MPa, melting peak temperature 250°C, thermal shrinkage coefficient TD 0.0%, MD 0.0%, basis weight 9 g / m²) is used. 2 Using a thickness of 40 μm, maleic anhydride is used as the heat-weldable resin. Except for using a modified polypropylene resin (acid modification degree 0.09% by weight, MFR 9g / 10 min, softening point 140°C), a laminated film was obtained as a heat-weldable film in which a first heat-weldable resin layer (PPa, thickness 20 μm) / intermediate layer (PAR, thickness 40 μm) / second heat-weldable resin layer (PPa, thickness 20 μm) were laminated in this order.

[0115] (Example 21) Except for using an unstretched polypropylene film (CPP, tensile modulus 1400 MPa, melting peak temperature 290°C, thermal shrinkage rate TD 3.0%, MD 81.0%) as the intermediate layer, a laminated film was obtained as a heat-weldable film in the same manner as in Example 1, in which a first heat-weldable resin layer (PPa, thickness 30 μm) / intermediate layer (CPP, thickness 40 μm) / second heat-weldable resin layer (PPa, thickness 30 μm) were laminated in this order.

[0116] (Measurement of tensile modulus) In accordance with JIS K7161:2014, a test specimen (rectangular) was cut from the film to a width of 25 mm and a length of 120 mm with the MD (medium-density) side as the longer side. This specimen was measured in a tensile-compression testing environment of 25°C using a tensile-compression testing machine (Tensilon RTC-1250A, manufactured by Orientec Co., Ltd.) under the conditions of a tensile speed of 200 mm / min and a chuck distance of 100 mm. The tensile stress-strain was calculated from the initial straight line portion of the obtained tensile stress-strain curve according to the following formula. E = Δρ / Δε E: Tensile modulus Δρ: Stress difference due to the original average cross-sectional area between two points on a straight line Δε: Difference in strain between the same two points

[0117] (Measurement of thermal shrinkage rate) The thermal shrinkage rate of each heat-sealable film obtained above was measured under the conditions of a test temperature of 200°C and a heating time of 10 seconds, in accordance with the provisions of JIS K 7133:1999. The results are shown in Table 1.

[0118] <Measurement of various physical properties of molded products> Test samples and molded bodies were prepared using the first and second components listed in Table 3 under the conditions described below, and the seal strength and peel strength were measured in the same manner as in Test Example 1. Furthermore, the shear strength was also measured as follows. In Table 3, AL for the first component indicates aluminum (JIS H 4000:2014 A1100), and fiber-reinforced plastic for the second component refers to the cured fiber-reinforced plastic in which epoxy resin is impregnated into carbon fibers.

[0119] (Measurement of peel strength) The peel strength (N / 25mm) between the first and second members of a dissimilar material joint composed of the first member, a heat-weldable film, and the second member as described in Table 1 was measured. More specifically, first, each heat-weldable film was cut to a size of 160mm in the length direction × 25mm in the width direction. The first member 70 was cut to a size of 250mm in the length direction × 25mm in the width direction, and the second member 80 was cut to a size of 200mm in the length direction × 25mm in the width direction. Next, as shown in Figure 14(i), each heat-weldable film 10 and the first member 70 and the second member 80 were cut longitudinally. The two components were aligned and stacked, and a region measuring 160 mm in length and 25 mm in width was heat-sealed (heat-sealing conditions: temperature 190°C, surface pressure 1 MPa, pressurization time 30 seconds) to obtain a test sample. Next, the test sample was fixed to a peel test fixture on the second component 80 side, and the first component 70 was peeled using a tensile testing machine as shown in Figure 14(ii). At this time, the peeling speed was set to 100 mm / min, and the average load in the area excluding the section from the peeling start point to a peeling length of 25 mm was defined as the peel strength (N / 25 mm). For the materials used in the preparation of the test samples, a thickness of 4 mm was used for the fiber-reinforced plastic component, and a thickness of 0.5 mm was used for the metal component. Each peel strength is the average value (n=3) measured by preparing three test samples in the same manner. The results are shown in Table 3. [Table 3]

[0120] Table 3 shows Examples 19-21 alongside Example 10. As shown in the results in Table 3, the heat-weldable films (Examples 19-21), in which both the surface of one side and the surface of the other side are composed of a heat-weldable resin layer containing acid-modified polyolefin, bonded both the first member made of metal and the second member made of fiber-reinforced plastic well. This demonstrated that by using such heat-weldable films, dissimilar material joints can be easily obtained without the use of adhesives. In particular, the heat-weldable films with a tensile modulus of 1500 MPa or higher (Examples 19 and 20) achieved a significantly superior shear strength of 10 MPa or higher after joining the members, compared to the heat-weldable film (Example 10) with the same heat-weldable resin layer but a tensile modulus of less than 1500 MPa. Therefore, the laminated films (heat-weldable films) of Examples 19 and 20 are particularly suitable for applications where members of 1 mm or more, which are susceptible to shear stress parallel to the joining surface, are joined to obtain molded articles. [Explanation of Symbols]

[0121] 1 Heat-fusible resin layer 1a First heat-fusible resin layer 1b Second heat-fusible resin layer 3. Middle Class 4 Thermoplastic resin layer 10 Heat-sealable film 20 Joined body of dissimilar materials 30. First component (metal) 40. Second component (fiber-reinforced plastic) 40a Second component precursor (fiber-reinforced plastic prepreg) 50 components 60 molds 70. First component (metal) 80. Second component (fiber-reinforced plastic) 90 probes S Heat-sealed area P: Position of the intermediate layer surface at the edge of the heat-sealed film.

Claims

1. A heat-weldable film for joining a first member made of metal and a second member made of fiber-reinforced plastic, Both the surface on one side and the surface on the other side are composed of a heat-weldable resin layer that contains only acid-modified polyolefin as the resin, and may also contain additives. A heat-weldable film wherein the heat-weldable resin layer has a melt mass flow rate of 3 to 9 g / 10 min at a temperature of 230°C and a load of 2.16 kg, and / or the degree of acid modification of the acid-modified polyolefin is 0.005 to 0.15% by weight.

2. The heat-sealable film according to claim 1, wherein the polyolefin to be modified in the acid-modified polyolefin is selected from the group consisting of polyethylene and polypropylene.

3. The heat-weldable film according to claim 1 or 2, wherein the matrix resin of the fiber-reinforced plastic is a thermosetting resin.

4. The heat-weldable film according to any one of claims 1 to 3, wherein the matrix resin of the fiber-reinforced plastic is a thermoplastic resin.

5. The heat-weldable film according to any one of claims 1 to 4, wherein the fibers in the fiber-reinforced plastic are glass fibers or carbon fibers.

6. The heat-weldable film according to any one of claims 1 to 5, wherein the heat-weldable resin layer is a single-layer film.

7. The heat-sealable film according to any one of claims 1 to 6, wherein the additive is selected from lubricants, antioxidants, ultraviolet absorbers, and light stabilizers.

8. A method for manufacturing a dissimilar material joint, comprising: heating a laminate obtained by laminating a first member made of metal and a second member made of fiber-reinforced plastic via a heat-weldable film according to any one of claims 1 to 7, and then performing heat welding to obtain a dissimilar material joint in which the first member and the second member are joined.

9. A method for manufacturing a dissimilar material joint, comprising: heating a laminate in which a first member made of metal and a second member made of fiber-reinforced plastic are laminated via a heat-weldable film according to any one of claims 1 to 7 to perform heat welding and thermoforming simultaneously, thereby obtaining a dissimilar material joint in which the first member and the second member are joined.

10. A dissimilar material joint in which a first member made of metal and a second member made of fiber-reinforced plastic are joined and molded via a heat-weldable film as described in any one of claims 1 to 7.

11. A method for manufacturing a dissimilar material joint, comprising: laminating a first member made of metal and a second member made of carbon fiber reinforced plastic having carbon fibers exposed on its surface via a heat-weldable film; heating the laminate for 1 to 30 seconds to perform heat welding; thereby obtaining a dissimilar material joint in which the first member and the second member are joined; A method for producing the heat-weldable film, wherein one surface and the other surface are both composed of a heat-weldable resin layer containing only acid-modified polyolefin as the resin and may also contain additives, and the melt mass flow rate of the heat-weldable resin layer at a temperature of 230°C and a load of 2.16 kg is 2 to 20 g / 10 min.

12. A method for manufacturing a dissimilar material joint, comprising: a first member made of metal and a second member made of carbon fiber reinforced plastic having carbon fibers exposed on its surface, laminated together via a heat-weldable film; heating the laminate for 1 to 30 seconds to simultaneously perform heat welding and thermoforming to obtain a dissimilar material joint in which the first member and the second member are joined; A method for producing the heat-weldable film, wherein one surface and the other surface are both composed of a heat-weldable resin layer containing only acid-modified polyolefin as the resin and may also contain additives, and the melt mass flow rate of the heat-weldable resin layer at a temperature of 230°C and a load of 2.16 kg is 2 to 20 g / 10 min.

13. A dissimilar material joint comprising a first member made of metal and a second member made of carbon fiber reinforced plastic having carbon fibers exposed on its surface, which are joined and molded together via a heat-weldable film, The heat-weldable film is composed of a heat-weldable resin layer on both its surface and the other surface, which may contain only acid-modified polyolefin as the resin and also contain additives, and the melt mass flow rate of the heat-weldable resin layer at a temperature of 230°C and a load of 2.16 kg is 2 to 20 g / 10 min, in a dissimilar material joint.

Images