JP2023174713A - Heat welding film, laminate, dissimilar material joined body, and method for producing dissimilar material joined body - Google Patents

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

The present invention relates to a heat-fusible film, a laminate, a bonded body of dissimilar materials, and a method for manufacturing a bonded body of dissimilar materials.

Components of industrial products are made of various materials such as metals, resins, and ceramics. Conventionally, these members have been formed into a desired shape in advance and then joined using an adhesive using a curable resin, or a joining member such as a screw or a rivet (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2008-111536

Joining using mechanical joining members such as screws and rivets is complicated. Furthermore, it takes time to apply the adhesive, and it is difficult to control the thickness of the adhesive layer, so adhesive strength tends to be uneven. On the other hand, the bonding method using adhesive is preferable because it does not require a mechanical bonding member and can provide a good design of the bonded body. Because of this preference, it is still common technical knowledge to use adhesives to join two or more members together, and the same holds true for joining metals and fiber-reinforced resins, for example. In other words, no technique has been found to date to more easily bond metal and fiber-reinforced resin.

The present inventors investigated a method for bonding metal and fiber-reinforced resin more easily, and came up with a new idea of using a heat-fusible film to bond these materials. However, with ordinary thermoplastic resins, we have encountered the problem that although we adhere to one material, we do not adhere to the other material at all, and that it is not possible to join both members together.

Therefore, the main object of the present invention is to provide a technique for bonding metal and fiber-reinforced resin more easily.

The present inventors conducted extensive studies to solve the above problems. As a result, it was found that when an acid-modified polyolefin film was used as a heat-fusible film, it was possible to bond both metal and fiber-reinforced resin. The present invention was completed through further studies based on this knowledge.

That is, the present invention provides the inventions of the following aspects.
Item 1. A heat-fusible film for joining a first member made of metal and a second member made of fiber-reinforced plastic, the film comprising:
A heat-fusible film in which one surface and the other surface are both composed of a heat-fusible resin layer containing acid-modified polyolefin.
Item 2. Item 2. The heat-fusible film according to Item 1, wherein the acidic polyolefin has a degree of acid modification of 0.005% by weight or more.
Item 3. Item 3. The heat-fusible 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. Item 4. The heat-fusible 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. Item 4. The heat-fusible 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. Item 6. The heat-fusible film according to any one of Items 1 to 5, wherein the fibers in the fiber-reinforced plastic are glass fibers or carbon fibers.
Section 7. Item 7. The heat-fusible film according to any one of Items 1 to 6, wherein fibers are exposed on the surface of the fiber-reinforced plastic.
Section 8. Item 8. The heat-fusible film according to any one of Items 1 to 7, wherein the fiber-reinforced plastic has a surface roughness of 25 μm or more.
Item 9. Item 9. The heat-fusible film according to any one of Items 1 to 8, wherein the heat-fusible resin layer has a melt mass flow rate of 2 to 20 g/10 minutes.
Item 10. Item 10. The heat-fusible film according to any one of Items 1 to 9, which is a single-layer film of the heat-fusible resin layer.
Item 11. Heat-welding a laminate in which a first member made of metal and a second member made of fiber-reinforced plastic are laminated via the heat-weldable film according to any one of Items 1 to 10. A method for manufacturing a joined body of dissimilar materials, wherein the joined body of dissimilar materials is obtained by joining the first member and the second member.
Item 12. Heating a laminate in which a first member made of metal and a second member precursor made of fiber-reinforced plastic prepreg are laminated via the heat-fusible film according to any one of Items 1 to 10. A method for producing a joined body of dissimilar materials, comprising performing thermal welding, thermosetting and molding of the prepreg simultaneously to obtain a joined body of dissimilar materials in which the first member and the second member are joined.
Item 13. Heat-welding a laminate in which a first member made of metal and a second member made of fiber-reinforced plastic are laminated via the heat-fusible film according to any one of Items 1 to 10. and thermoforming at the same time to obtain a dissimilar material assembly in which the first member and the second member are joined.
Section 14. The first member made of metal and the second member made of fiber-reinforced plastic or the second member precursor made of prepreg of fiber-reinforced plastic have the heat-weldability according to any one of Items 1 to 10. A laminate that is laminated with films interposed in between.
Item 15 The first member made of metal and the second member made of fiber-reinforced plastic are bonded and molded via the heat-fusible film according to any one of Items 1 to 10. , dissimilar material joints.

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-fusible film using acid-modified polyolefin, it becomes possible to more easily join metal and fiber-reinforced resin. Furthermore, 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-fusible film.

1 is a schematic cross-sectional view of an example of a heat-fusible film of the present invention. 1 is a schematic cross-sectional view of an example of a heat-fusible film of the present invention. 1 is a schematic cross-sectional view of an example of a heat-fusible film of the present invention. 1 is a schematic cross-sectional view of an example of a heat-fusible film of the present invention. 1 is a schematic cross-sectional view of an example of a heat-fusible film of the present invention. FIG. 1 is a schematic cross-sectional view of an example of a dissimilar material joined body of the present invention. FIG. 3 is a schematic diagram for explaining a method for measuring seal strength. FIG. 1 is a schematic diagram for explaining an example of a method for manufacturing a joined body of dissimilar materials according to the present invention. FIG. 1 is a schematic diagram for explaining an example of a method for manufacturing a joined body of dissimilar materials according to the present invention. 1 is a schematic cross-sectional view of an example of a dissimilar material joined body manufactured by the dissimilar material joined body manufacturing method of the present invention. FIG. 2 is a schematic diagram for explaining a method of measuring shear strength. FIG. 3 is a conceptual diagram of a change in the position of a probe in measuring the amount of displacement of the probe. FIG. 3 is a schematic diagram showing the position of the surface of the intermediate layer at the end of the heat-fusible film where the probe is placed in measuring the amount of displacement of the probe. FIG. 3 is a schematic diagram for explaining a method of measuring peel strength.

The heat-fusible film of the present invention is a heat-fusible film for joining a first member made of metal and a second member made of fiber-reinforced plastic, and the heat-fusible film is made of acid-modified polyolefin. It is characterized by having a heat-fusible resin layer 1. Hereinafter, the heat-fusible film of the present invention, the dissimilar material joined body using the heat-fusible film, and the manufacturing method thereof will be described in detail.

In this specification, the numerical range indicated by "~" means "more than" or "less than". For example, the expression 2 to 15 mm means 2 mm or more and 15 mm or less.

1. Heat-fusible film The heat-fusible film of the present invention is a heat-fusible film for joining a first member made of metal and a second member made of fiber-reinforced plastic. More specifically, in the heat-fusible film of the present invention, the heat-fusible film is placed between a first member made of metal and a second member made of fiber-reinforced plastic, and the heat-fusible film is placed between a first member made of metal and a second member made of fiber reinforced plastic. It is used for joining a first member and a second member by thermally welding the first member and the second member via the material. In addition to the first member and the second member, other members may be joined using the heat-fusible film of the present invention. That is, the heat-fusible film of the present invention is a heat-fusible film for joining at least a first member made of metal and a second member made of fiber-reinforced plastic by heat welding.

For example, as shown in the schematic diagram of FIG. 1, the heat-fusible film 10 of the present invention is configured to include at least a heat-fusible resin layer 1 containing acid-modified polyolefin. The heat-fusible film 10 shown in FIG. 1 is constructed as a single-layer film including a heat-fusible resin layer 1. The heat-fusible film 10 shown in FIG. Therefore, the heat-fusible resin layer 1 containing acid-modified polyolefin constitutes both one surface and the other surface of the heat-fusible film 10.

As long as the heat-fusible resin layer 1 containing acid-modified polyolefin constitutes both one surface and the other surface of the heat-fusible film 10, the heat-fusible film 10 of the present invention has no other layers. It may have a multi-layered structure in which it is embedded. When the heat-fusible film 10 of the present invention has a multilayer structure, the heat-fusible resin layer 1 containing acid-modified polyolefin of the heat-fusible film 10 of the present invention is formed in the schematic diagrams shown in FIGS. 2 to 5. As shown in , a first heat-fusible resin layer 1a forming one surface of the heat-fusible film 10 and a first heat-fusible resin layer 1a forming the other surface of the heat-fusible film 10 via at least the intermediate layer 3. The second heat-fusible resin layer 1b may be separated into the first heat-fusible resin layer 1a. That is, the heat-fusible film 10 of the present invention includes at least the first heat-fusible resin layer 1a containing acid-modified polyolefin, the intermediate layer 3, and the second heat-fusible resin layer 1b containing acid-modified polyolefin. The heat-fusible film may include the following in this order.

As a specific example of the laminated structure when the heat-fusible film 10 of the present invention has a multilayer structure, first heat-fusible resin layer 1a/intermediate layer 3/second heat-fusible resin layer as shown in FIG. Laminated structure including layers 1b in this order; Laminated structure including first heat-fusible resin layer 1a/intermediate layer 3/thermoplastic resin layer 4/second heat-fusible resin layer 1b in this order as shown in FIG. 3; Laminated structure including first heat-fusible resin layer 1a/thermoplastic resin layer 4/intermediate layer 3/second heat-fusible resin layer 1b in this order as shown in FIG. 4; first heat-fusible resin layer 1b as shown in FIG. Examples include a laminated structure including heat-fusible resin layer 1a/thermoplastic resin layer 4/intermediate layer 3/thermoplastic resin layer 4/second heat-fusible resin layer 1b in this order. Note that, as described later, the first heat-fusible resin layer 1a and the second heat-fusible resin layer 1b may each contain an adhesive component and have adhesive properties. Moreover, the thermoplastic resin layer 4 may have heat-fusibility like the first heat-fusible resin layer 1a and the second heat-fusible resin layer 1b. The heat-fusible film of the present invention may further include other layers different from these layers. For example, although not shown, an adhesion promoter layer, which will be described later, may be provided on one or both sides of the intermediate layer 3.

From the viewpoint of low cost and simplification of the manufacturing process, the heat-fusible film of the present invention is preferably a single layer as shown in FIG. 1. On the other hand, in the case of a multilayer structure, it is preferable to make the heat-fusible film thin from the viewpoint of low cost and simplification of the manufacturing process. It is preferable to have a three-layer laminated structure including first heat-fusible resin layer 1a/intermediate layer 3/second heat-fusible resin layer 1b in this order. In addition, from the viewpoint of conformability to uneven shapes (that is, the property of leveling out the uneven shapes by injecting resin into the recesses in the uneven shapes), it is preferable to make the heat-fusible film thicker. It is preferable that the fusible film includes a thermoplastic resin layer between each of the first heat-fusible resin layer 1a/intermediate layer 3/second heat-fusible resin layer 1b. Specifically, as shown in FIG. 3, a four-layer laminated structure including first heat-fusible resin layer 1a/intermediate layer 3/thermoplastic resin layer 4/second heat-fusible resin layer 1b in this order; A four-layer laminated structure including the first heat-fusible resin layer 1a/thermoplastic resin layer 4/intermediate layer 3/second heat-fusible resin layer 1b in this order; as shown in FIG. It is preferable to have a five-layer laminated structure including first heat-fusible resin layer 1a/thermoplastic resin layer 4/intermediate layer 3/thermoplastic resin layer 4/second heat-fusible resin layer 1b in this order. In addition, in the dissimilar material joined body after joining, if the first heat-fusible resin layer 1a contains an adhesive component as long as it does not affect the strength against shear stress parallel to the joining surface, the present invention The heat-fusible film has a laminate structure of five layers each containing an adhesive component on both sides (specifically, a first heat-fusible resin layer 1a containing an adhesive component/thermoplastic resin layer 4/intermediate layer 3/thermal layer). A laminate structure comprising plastic resin layer 4/second heat-fusible resin layer 1b containing an adhesive component in this order) or a 4-layer laminate structure having an adhesive component on one side (specifically, a 4-layer laminate structure containing an adhesive component on one side) Even if the laminate structure includes a first heat-fusible resin layer 1a/thermoplastic resin layer 4/intermediate layer 3/thermoplastic resin layer 4/second heat-fusible resin layer 1b that does not contain an adhesive component in this order, good.

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

Further, the area of one side of the heat-fusible film of the present invention can be appropriately set depending on the size of the member to be heat-welded.

<Seal strength>
The heat-fusible film 10 of the present invention has a sealing strength of approximately 10 N/15 mm or more between the heat-fusible film and the member when heat-welded to the members (first member, second member) described below. It is preferably about 15 N/15 mm or more, more preferably about 20 N/15 mm or more. Furthermore, it is preferable that the sealing strength between the heat-fusible film and the member is about 10 N/15 mm or more between both the first member and the second member. There is no particular upper limit to the preferable 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 still more preferably about 20 to 100 N/15 mm. In the heat-weldable film 10 of the present invention that heat-welds the first member and the second member, the sealing strength when heat-welded to these members has such a value, so that the obtained dissimilar materials In the joined body, it can be said that the first member and the second member are suitably joined via the heat-fusible film 10 of the present invention. Note that when at least one of the first member and the second member to be joined by heat welding is a solid member containing an uncured resin, the heat weldable film 10 is attached to the member in which the uncured resin is thermoset. This refers to the seal strength when heat welded. A specific method for measuring seal strength is as follows. Note that the sealing strength when the heat-fusible film 10 of the present invention and the members (first member, second member) described below are heat-welded is not limited to this range.

In measuring the seal strength, first, a heat-fusible film is cut out into a size of 50 mm in the length direction (y direction) x 25 mm in the width direction (x direction). Next, the heat-fusible film 10 and each member 50 are heat-sealed to a depth of 7 mm (y direction) (heat-sealing conditions: temperature 190°C, surface pressure 1 MPa, pressure time 5 seconds) to form a test sample. obtain. In the schematic diagram of FIG. 7, a region S surrounded by a broken line indicates a heat-sealed region. Note that a release sheet is sandwiched between the areas other than the area to be heat-sealed so that the area is heat-sealed to a depth of 7 mm. Next, the test sample is cut into a width of 15 mm as shown in FIG. 7(a) so that the seal strength (N/15 mm) in the width direction (x direction) of 15 mm can be measured. Next, using a tensile tester, the heat-fusible film 10 is peeled from the fixed member 50 in the length direction (y direction), as shown in FIG. 7(b). At this time, the peeling speed is 300 mm/min, and the maximum load until peeling is defined as the seal strength (N/15 mm). In addition, as for the members used in producing the test samples, fiber-reinforced plastic members with a thickness of 4 mm and metal members with a thickness of 0.5 mm are used. Each seal strength is the average value (n=3) of three test samples prepared and measured in the same manner.

<Peel strength>
When the heat-fusible film 10 of the present invention is thermally welded to members (first member, second member) to be described later, the peel strength between the first member and the second member is approximately 10 N/25 mm. It is preferably about 20 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. Note that there is no particular preferable upper limit for the peel strength, but it is usually about 100 N/25 mm or less. That is, the peel strength range is preferably about 10 to 100 N/25 mm, more preferably about 20 to 100 N/25 mm, and still more preferably about 25 to 100 N/25 mm. A specific method for measuring peel strength is as follows. Note that the peel strength when the heat-fusible film 10 of the present invention and the members (first member, second member) described below are heat-welded is not limited to this range.

Peel strength is measured by a method compliant with the regulations of ISO19095-2 and ISO19095-3. Specifically, first, a heat-fusible film is cut into a size of 160 mm in the length direction x 25 mm in the width direction. In addition, the first member 70 (if the thickness is different from the second member 80, the thinner one such as metal) is 250 mm in the length direction x 25 mm in the width direction, and the second member 80 is 200 mm in the length direction x 25 mm in the width direction. Cut it out to a size of 25mm in the width direction. Next, Figure 14(i)
As shown in the figure, the first heat-fusible resin layer or the second heat-fusible resin layer of the heat-fusible film 10, the first member 70, and the second member 80 are overlapped with their longitudinal directions aligned, and the length is 160 mm× A test sample is obtained by heat-sealing an area of 25 mm in the width direction (heat-sealing conditions: temperature 190° C., surface pressure 1 MPa, pressurization time 30 seconds). Next, the test sample is fixed to a peel test jig on the second member 80 side, and the first member 70 is peeled in the length direction using a tensile tester as shown in FIG. 14(ii). . At this time, the peeling speed is 100 mm/min, and the average load at the location excluding the location from the peeling start location to the peeling length of 25 mm is defined as the peel strength (N/25 mm). In addition, as for the members used in producing the test samples, fiber-reinforced plastic members with a thickness of 4 mm and metal members with a thickness of 0.5 mm are used. Each peel strength is the average value (n=3) of three test samples prepared and measured in the same manner.

<Shear strength>
Further, the shear strength of the dissimilar material joined body obtained by thermally welding the first member and the second member via the heat-fusible film 10 of the present invention is preferably about 5 MPa or more, more preferably about 8 MPa. The above can be mentioned. There is no particular upper limit to the shear strength, but it is usually about 50 MPa or less. Preferred ranges of the shear strength include about 5 to 50 MPa, and about 8 to 50 MPa. In the heat-fusible film 10 of the present invention that heat-welds the first member and the second member, the shear strength when heat-welded to these members has such a value, so that the resulting dissimilar material The bonded body can maintain a good bonded state.

Furthermore, when the heat-fusible film 10 of the present invention has the intermediate layer 3, the shear strength of the dissimilar material joined body obtained by heat-welding the first member and the second member is preferably about 10 MPa or more, More preferably, it is about 11 MPa or more. When the heat-fusible film 10 of the present invention has the intermediate layer 3, the preferable range of shear strength is about 10 to 50 MPa, and about 11 to 50 MPa. In the heat-fusible film 10 of the present invention that heat-welds the first member and the second member, the shear strength when heat-welded to these members has such a value, so that the resulting dissimilar material It can be said that the bonded body has excellent strength against shear stress parallel to the bonding surface. In particular, dissimilar material joined bodies in which at least one of the first member and the second member has a thickness of 1 mm or more are susceptible to shear stress parallel to the joint surfaces, but by having such shear strength, the shear stress The bonded state can be maintained well even when subjected to stress.

Shear strength is measured by a method that complies with the regulations of ISO19095-2 and ISO19095-3. The sizes of the first member and second member in the production of the test sample are each 45 mm in length x 10 mm in width, and the thickness is 1.5 mm in the case of a metal member and 3 mm in the case of a fiber-reinforced plastic member. Further, the heat-fusible film has a length of 5 mm and a width of 10 mm. As shown in FIG. 11, a heat-fusible film 10 is disposed between the first member 70 and the second member 80 at the longitudinal ends of the first member 70 and the second member 80, and The first member 70 and the second member 80 are thermally welded via the heat-fusible film 10 under the conditions of 1.5 MPa of surface pressure and 20 seconds to obtain a joined body of dissimilar materials. Further, the heat-fusible film 10 is arranged so that the entire both sides thereof are heat-sealed to the first member 70 and the second member 80, respectively (that is, the heat-sealed area is 5 mm in length x 10 mm in width on one side). Although not shown in FIG. 11, in order to perform measurements on a structure in which the first member 70 and the second member 80 are joined in parallel to each other, the first member 70 and the second member 80 are The height of each is adjusted using a compensating member and then joined. The compensation member for adjusting the height of the first member 70 is made of the same material and shape as the first member 70, and the compensation member for adjusting the height of the second member 80 is made of the same material and shape as the second member 80. Use shaped members. Next, using a tensile tester, the dissimilar material joined body was pulled in the length direction (pulling speed was 10 mm/min), the maximum load (N) was measured, and this was applied to the heat-sealed area (length 5 mm x width). 10 mm) to calculate the shear strength (MPa).

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

The heat-fusible resin layer 1 contains at least acid-modified polyolefin. This makes it possible to join dissimilar materials by thermally welding both the first member made of metal and the second member made of fiber-reinforced plastic. The fact that the resin constituting the heat-fusible resin layer 1 contains acid-modified polyolefin can be analyzed by, for example, infrared spectroscopy, gas chromatography-mass spectrometry, etc., and the analytical method is not particularly limited. For example, when a maleic anhydride-modified polyolefin is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected at wave numbers around 1760 cm ^-1 and around 1780 cm ^-1 wave numbers.

Further, specific examples of the acid-modified polyolefin include polyolefins modified with unsaturated carboxylic acids or their anhydrides. Examples of the unsaturated carboxylic acid or anhydride thereof used for acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

The lower limit of the degree of acid modification of the acid-modified polyolefin is, for example, about 0.005% by weight or more. From the viewpoint of better joining dissimilar materials, the lower limit is preferably about 0.01% by weight or more, more preferably about 0.04% by weight or more, and more preferably about 0.08% by weight or more. is even more preferable. There is no particular upper limit to 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 is, 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, and The amount is preferably about 0.08 to 0.5% by weight, more preferably about 0.1 to 0.5% by weight. The degree of acid modification is the weight ratio occupied by acid-modified groups in the acid-modified polyolefin. For example, in the case of a maleic acid-modified polyolefin, it is the weight ratio occupied by maleic acid-modified groups in the acid-modified polyolefin. Acid denaturation degree is ¹ H-NMR
It is determined from the value determined from the acid-derived peak area of . Specifically, first, ^{the 1} H-NMR of the acid-modified polyolefin and the ¹ H-NMR of the methyl ester of the acid-modified polyolefin are measured using an ODCB-d4/C ₆ D ₆ (volume ratio 4/1) solvent. . By comparing both ¹ H-NMR spectra, the peak of the methyl ester compound, which is an acid derivatized product, is identified. Furthermore, from ^{the 1} H-NMR of the acid-modified polyolefin (before methyl esterification), the area of impurity-derived peaks that overlap with the peak positions of the methyl ester in ^{the 1} H-NMR of the methyl ester is determined. The peak area of the methyl ester compound is determined by subtracting the peak area derived from impurities from the peak area at the peak position of the methyl ester compound, and the mass of the acid-modified group derived based on this is calculated from the mass of the acid-modified polyolefin before methyl esterification. The degree of acid denaturation is calculated from the ratio to the mass.

The polyolefin to be modified is not particularly limited, but from the viewpoint of more suitable joining of dissimilar materials, polyethylenes such as low density polyethylene, medium density polyethylene, high density polyethylene, and linear low density polyethylene; homopolypropylene; Crystalline or amorphous polypropylenes such as block copolymers of polypropylene (e.g. block copolymers of propylene and ethylene), random copolymers of polypropylene (e.g. random copolymers of propylene and ethylene); terpolymers of ethylene-butene-propylene. It will be done. Among these, polypropylene is preferred as the polyolefin to be modified.

From the viewpoint of bonding dissimilar materials more suitably, maleic anhydride-modified polypropylene and maleic anhydride-modified polyethylene are particularly preferred among the heat-fusible resins included in the heat-fusible resin layer 1.

The number of acid-modified polyolefins contained in the heat-fusible resin layer 1 may be one type, or two or more types.

The proportion of acid-modified polyolefin contained in the heat-fusible resin layer 1 is not particularly limited, but the lower limit is preferably about 70% by mass or more, more preferably about 80% by mass or more, and the upper limit is: Preferably, it is about 100% by mass or less. Further, the range of the ratio of the acid-modified polyolefin is preferably about 70 to 100% by mass, and about 80 to 100% by mass. Since the proportion of acid-modified polyolefin contained in the heat-fusible resin layer 1 has such a value, the heat-fusible film 10 of the present invention can be heat-welded to both metal members and fiber-reinforced plastics. properties can be suitably exhibited, and dissimilar materials can be more suitably joined.

The heat-fusible 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 joined body of dissimilar materials after joining. More specifically, the heat-fusible resin layer 1 may be made of a heat-fusible resin composition containing an adhesive component. Since the heat-fusible resin layer 1 contains an adhesive component, the heat-fusible resin layer of the heat-fusible film 10 can be suitably temporarily attached to the surfaces of the first member and the second member. It becomes possible to suppress misalignment and more appropriately join dissimilar materials. In the present invention, temporary attachment means temporary adhesion, and is a state that can be peeled off even after temporary adhesion.

The adhesive component is not particularly limited as long as it can impart adhesiveness to the heat-fusible resin layer 1, and includes, for example, rosin or its derivatives such as rosin, hydrogenated rosin, polymerized rosin, and rosin ester; α-pinene; Examples include terpene resins such as β-pinene and limonene; terpene phenol resins, coumaron/indene resins, styrene resins, xylene resins, phenol resins, petroleum resins, and hydrogenated petroleum resins. Moreover, an amorphous polyolefin can also be used as an adhesive component. Examples of amorphous polyolefins include amorphous polypropylene or copolymers of amorphous propylene and 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,tertiary copolymer, polybutene-1, and the like. One type of adhesive component may be used alone, or two or more types may be used in combination.

When the heat-fusible 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, The upper limit is preferably about 30% by mass or less, more preferably about 25% by mass or less. Further, 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. Since the proportion of the adhesive component contained in the heat-fusible resin layer 1 has such a value, the heat-fusible film of the present invention suitably exhibits excellent adhesiveness and excellent heat-weldability. As a result, the first member and the second member can be temporarily attached in a suitable manner, and positional displacement during thermal welding can be suppressed, and dissimilar materials can be joined more appropriately.

The melt mass flow rate (MFR) of the heat-fusible resin layer 1 is not particularly limited, but from the viewpoint of good followability to the surface of the member and more suitable joining of dissimilar materials, the lower limit is preferably about 2 g. /10 minutes or more, more preferably about 3g/10 minutes or more. In particular, even if the surface irregularities (surface roughness Ra) of the second member made of fiber-reinforced resin plastic increase, the thermofusible resin layer 1 can better follow the surface irregularities to effectively obtain an anchor effect. From the viewpoint of suitably heat-welding the second member, the heat-fusible resin layer (that is, the heat-fusible resin layer 1 or the heat-fusible film 10 constituting the surface of the side to be heat-welded to the second member) is In the case of having a layered structure, the melt mass flow rate (MFR) of the second heat-fusible resin layer 1b) is more preferably about 4 g/10 minutes or more. From the viewpoint of preventing the melted resin from flowing out during heat welding and bonding dissimilar materials more appropriately, the preferable upper limit of the melt mass flow rate (MFR) of the heat welding resin layer 1 is preferably about 20 g/10 minutes or less. , more preferably about 15 g/10 minutes or less. That is, the range of the melt flow rate is about 2 to 20 g/10 minutes, about 2 to 15 g/10 minutes, about 3 to 20 g/10 minutes, about 3 to 15 g/10 minutes, and about 4 to 20 g/10 minutes. , or about 4 to 15 g/10 minutes. The melt mass flow rate (MFR) is a value measured using a melt indexer at a measurement temperature of 230° C. and a weight of 2.16 kg, according to a method based on the regulations of JIS K7210:2014.

The softening point of the heat-fusible resin layer 1 is not particularly limited, but is preferably about 180°C or less, from the viewpoint of good followability to the surface of the member and more suitable heat-welding of two or more members. More preferably, the temperature is about 160°C or lower. Further, the lower limit of the softening point of the heat-fusible 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-fusible 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.

In the present invention, the softening point of the heat-fusible resin layer 1 is the temperature at which the deflection of the probe becomes maximum in the next probe displacement measurement. In addition, in measuring the softening point of the heat-fusible resin layer 1, for the five samples of the heat-fusible resin layer 1 to be measured, the temperature at which the probe deflection reaches the maximum is read, and the five temperatures are measured. The average value of the three temperatures excluding the maximum and minimum values is taken as the softening point. In measuring the amount of displacement of the probe, first, as shown in the conceptual diagram of FIG. 10, the probe 90 is installed at the position P) (measurement start A in FIG. 12). The end portion at this time is an exposed section of the heat-fusible resin layer 1 obtained by cutting in the thickness direction so as to pass through the center of the heat-fusible film. Cutting can be performed using a commercially available rotary microtome or the like. An atomic force microscope equipped with a nanothermal microscope composed of a cantilever with a heating mechanism, for example, an afm plus system manufactured by ANASIS INSTRUMENTS, can be used, and a probe manufactured by ANASYS INSTRUMMENTS can be used. The tip radius of the probe is 30 nm or less, the deflection setting value of the probe is −4 V, and the temperature increase rate is 5° C./min. Next, when the probe is heated in this state, the heat from the probe 90 causes the surface of the heat-fusible resin layer 1 to expand as shown in FIG. (the position when the temperature of the probe 90 is 40° C.). When the heating temperature further increases, the heat-fusible resin layer 1 softens, and the probe 90 may pierce the heat-fusible resin layer 1 as shown in C in FIG. 12, causing the position of the probe 90 to lower. Note that when measuring the displacement of the probe 90 using an atomic force microscope equipped with a nanothermal microscope configured from a cantilever with a heating mechanism, the heat-fusible film to be measured is in a room temperature (25°C) environment, and the temperature is 40°C. A probe 90 heated to 0.degree. C. is placed on the surface of the heat-fusible resin layer 1 at the end of the heat-fusible film, and measurement is started.

The thickness of the heat-fusible resin layer 1 is not particularly limited, but it reduces the thermal shrinkage rate in a high-temperature environment during heat-welding, and improves the strength of the bonded body of dissimilar materials after bonding against shear stress parallel to the bonding surface. From the viewpoint of obtaining the same, the lower limit is preferably about 5 μm or more, more preferably about 10 μm or more, and still more preferably about 20 μm or more, and the upper limit is preferably about 200 μm or less, more preferably about 100 μm or less. can be mentioned. Further, the thickness range of the heat-fusible 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. It will be done.

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

The first heat-fusible resin layer 1a and the second heat-fusible resin layer 1b are the same as the above-described heat-fusible resin layer 1 except that the intermediate layer 3 is interposed therebetween. In addition, the materials such as the type of heat-modified polyolefin and the resin composition, the physical properties such as melt mass flow rate (MFR), and the thickness of the first heat-fusible resin layer 1a and the second heat-fusible resin layer 1b are different from each other. They may be the same or different.

(Middle layer 3)
When the heat-fusible film 10 of the present invention has an intermediate layer 3, the middle layer 3 is located between the first heat-fusible resin layer 1a and the second heat-fusible resin layer 1b, and has a heat-fusible property. An excellent high tensile modulus of the film 10 can be ensured.

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, and fluororesin. , silicone resin, phenol resin, polyetherimide, and mixtures and copolymers thereof.

Specifically, polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolyesters whose repeating units are mainly ethylene terephthalate, and copolyesters whose repeating units are mainly butylene terephthalate. Examples include copolymerized polyester. In addition, as a copolymer polyester containing ethylene terephthalate as the main repeating unit, specifically, a copolymer polyester polymerized with ethylene isophthalate using ethylene terephthalate as the main repeating unit (hereinafter referred to as polyethylene (terephthalate/isophthalate)) ), polyethylene (terephthalate/isophthalate), polyethylene (terephthalate/adipate), polyethylene (terephthalate/sodium sulfoisophthalate), polyethylene (terephthalate/sodium isophthalate), polyethylene (terephthalate/phenyl-dicarboxylate) , polyethylene (terephthalate/decanedicarboxylate), and the like. In addition, as a copolymer polyester containing butylene terephthalate as a main repeating unit, specifically, a copolymer polyester polymerized with butylene isophthalate using butylene terephthalate as a main repeating unit (hereinafter referred to as polybutylene (terephthalate/isophthalate)) Polybutylene (terephthalate/adipate), polybutylene (terephthalate/sebacate), polybutylene (terephthalate/decanedicarboxylate), polybutylene naphthalate, etc. These polyesters may be used alone or in combination of two or more.

In addition to the above, examples of the polyester 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, wholly aromatic polyesters having no aliphatic hydrocarbon in the main chain are preferred. Specific examples of wholly aromatic polyesters include copolymers of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, copolymers of p-hydroxybenzoic acid, terephthalic acid, and 4,4'-dihydroxybisphenyl, etc. Examples include polyarylates.

From the viewpoint of reducing the thermal shrinkage rate in a high-temperature environment during thermal welding and making the thermal adhesive film 10 have a higher tensile modulus, polyethylene terephthalate and polyethylene nitride are preferably used as the material for the intermediate layer 3. Examples include phthalates, fully aromatic polyesters, polyimides, polyphenylene sulfides, aramids, and vinylon (polyvinyl alcohol). These resins may be used alone or in combination of two or more.

The shape of the intermediate layer 3 is not particularly limited, and examples thereof include films, fibers, and the like. As for the specific shape of the fibers, nonwoven fabric is preferred. From the viewpoint of obtaining a higher tensile modulus of the heat-fusible film 10, the shape of the intermediate layer 3 is preferably a film.

When the shape of the intermediate layer 3 is a film, it is preferable that the intermediate layer 3 is composed of a polyethylene terephthalate film, a polyethylene naphthalate film, or a polyimide film.

When the shape of the intermediate layer 3 is fiber, the intermediate layer 3 is preferably composed of polyphenylene sulfide fiber, aramid fiber, vinylon (polyvinyl alcohol) fiber, or wholly aromatic polyester fiber.

Among these fibers, wholly aromatic polyester fiber is a wholly aromatic polyester that exhibits molecular orientation (melt anisotropy) in the molten state, and fibers made by spinning this (melt anisotropic wholly aromatic polyester fiber). As the molecular orientation progresses further, the fibers become more easily intertwined with each other, resulting in a nonwoven fabric that not only has strong mechanical strength and low moisture absorption, but also has excellent resin impregnation properties, making it easy for resin to penetrate into the gaps created by division and subdivision. Therefore, it is preferable because the interlayer strength of the heat-fusible film 10 is extremely high. Therefore, among wholly aromatic polyester fibers, a nonwoven fabric made of melt anisotropic wholly aromatic polyester fibers is most suitable.

The lower limit of the tensile modulus of the intermediate layer 3 is set from the viewpoint of setting the heat-fusible film 10 to a specific tensile modulus and obtaining a bonded body of dissimilar materials with excellent strength against shear stress parallel to the bonding surface. It is preferably about 1,500 MPa or more, more preferably about 2,000 MPa or more, even more preferably about 2,900 MPa or more, and particularly preferably about 5,000 MPa or more. Although there is no particular preferable upper limit for the tensile modulus, it is usually about 10,000 MPa or less, preferably about 8,000 MPa or less, and more preferably 7,000 MPa or less. That is, the range of the tensile modulus is approximately 1500 to 10000 MPa, approximately 1500 to 8000 MPa, approximately 1500 to 7000 MPa, approximately 2000 to 10000 MPa, approximately 2000 to 8000 MPa, approximately 2000 to 7000 MPa, approximately 2900 to 10000 MPa, and 2900 to 80 MPa. Approximately 00MPa , about 2900 to 7000 MPa, about 5000 to 10000 MPa, about 5000 to 8000 MPa, and about 5000 to 7000 MPa. The tensile modulus of the intermediate layer 3 is a value obtained by measuring the material constituting the intermediate layer 3 in accordance with JIS K7161:2014 regulations.

The tensile modulus is a value measured in accordance with JIS K7161:2014 regulations, and specifically, a test piece ( Rectangle) was measured using a tensile compression tester (Tensilon RTC-1250A manufactured by Orientec Co., Ltd.) in a temperature environment of 25 ° C. at a tensile speed of 200 mm/min and a distance between chucks of 100 mm. It is calculated from the first straight line part of the tensile stress-strain curve according to the following formula.
E=Δρ/Δε
E: Tensile modulus Δρ: Stress difference between two points on a straight line due to original average cross-sectional area Δε: Strain difference between the same two points

In addition, in preparing the test piece for measuring the tensile modulus, the method for confirming the MD of the intermediate layer 3 is as follows. The longitudinal cross section of the heat-fusible film 10 and each cross section (10 cross sections in total) by changing the angle by 10 degrees from the direction parallel to the longitudinal cross section and the direction perpendicular to the longitudinal cross section. ), the sea-island structure is confirmed by observing the intermediate layer 3 using a transmission electron microscope photograph. Next, in each cross section, the shape of each island of the intermediate layer 3 is observed. Regarding the shape of each island, the straight line distance connecting the leftmost end in the direction perpendicular to the thickness direction of the heat-fusible film 10 and the rightmost end in the perpendicular direction is defined as the diameter y. In each cross section, the average of the top 20 diameters y of the island shape is calculated in descending order of diameter y. The direction parallel to the cross section where the average diameter y of the island shape is the largest is determined to be the MD. Further, when the intermediate layer 3 of the heat-fusible film 10 is made of fiber, the MD may be determined based on the roll direction of the fiber material that constitutes the intermediate layer 3. However, if the MD cannot be specified, The test piece may be prepared so that the long side is in any direction.

The heat shrinkage rate of the intermediate layer 3 measured at a test temperature of 200°C and a heating time of 10 seconds reduces the heat shrinkage rate in a high-temperature environment during thermal welding, and the bonded body of dissimilar materials after bonding is From the viewpoint of obtaining better strength against shear stress parallel to The lower limit includes about 0% or more and about 0.1% or more. In addition, the range of the heat shrinkage rate is about 0 to 10%, about 0 to 5%, about 0 to 3%, about 0 to 2%, about 0.1 to 10%, about 0.1 to 5%, Examples include about 0.1 to 3% and about 0.1 to 2%. The thermal shrinkage rate can be measured by a method compliant with the provisions of JIS K 7133:1999.

In the present invention, it is possible to satisfy the above heat shrinkage rate in at least two directions: one direction of the intermediate layer 3 (the plane direction of the intermediate layer 3) and a direction perpendicular thereto (the plane direction of the intermediate layer 3). preferable. Specifically, when the intermediate layer 3 is a film, the direction in which the heat shrinkage rate is measured and the direction perpendicular thereto is the MD of the intermediate layer 3. In the present invention, the method for confirming the MD of the intermediate layer 3 of the heat-fusible film 10 is as described in the above-mentioned tensile modulus of the intermediate layer 3. Furthermore, if the intermediate layer 3 of the heat-fusible film 10 is made of fiber and the MD cannot be specified, any direction may be set as the one direction.

The melting peak temperature of the intermediate layer 3 is not particularly limited, but from the viewpoint of further increasing 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 Preferably, the temperature is about 240°C or higher. The upper limit of the melting peak temperature of the intermediate layer 3 is not particularly limited, but may be, for example, about 300° C. or lower. The preferable range of 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 as a sample pan. Measured using

The thickness of the intermediate layer 3 is not particularly limited, but it is desirable to reduce the thermal shrinkage rate in a high-temperature environment during thermal welding, and to provide a bonded body of dissimilar materials with excellent strength against shear stress parallel to the bonding surface. From the viewpoint of obtaining the desired amount, 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 still more preferably about 50 μm or less. It will be done. Further, the thickness range 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. Furthermore, when the intermediate layer 3 is a film, the thickness of the intermediate layer 3 may be, as an upper limit, preferably about 30 μm or less, more preferably about 20 μm or less. Further, when the intermediate layer 3 is a film, the thickness range of the intermediate layer 3 includes approximately 5 to 30 μm, approximately 10 to 30 μm, approximately 5 to 20 μm, and approximately 10 to 20 μm.

In addition, when the intermediate layer 3 is made of a nonwoven fabric, the basis weight of the nonwoven fabric is not particularly limited, but the layers adjacent to the intermediate layer 3 (for example, the first heat-fusible resin layer 1a, the second heat-fusible resin layer 1a, the second heat-fusible resin layer From the viewpoint of sufficiently impregnating the nonwoven fabric with layer 1b, thermoplastic resin layer 4, etc. and stabilizing the adhesive strength between the layers, the basis weight is preferably small, and the lower limit is preferably about 5 g/m ²
The above can be mentioned. Further, from the viewpoint of reducing the thermal shrinkage rate in a high-temperature environment during thermal welding, the basis weight is preferably large, and the upper limit is 30 g/m ² or less. From the viewpoint of reducing the thermal shrinkage rate in a high-temperature environment during heat welding, giving a good appearance after heat welding, and better heat welding two or more members, the area weight range is preferably 5. About 30 g/m ² , more preferably about 7 to 25 g/m ² .

<Tensile modulus>
When the heat-fusible film 10 of the present invention has the intermediate layer 3, the lower limit of the tensile modulus of the heat-fusible film 10 of the present invention is 1500 MPa or more. As a result, it is possible to obtain a joined body of dissimilar materials after joining, which has excellent strength against shear stress parallel to the joined surfaces. From the viewpoint of obtaining a bonded body of different materials after bonding that has superior strength against shear stress parallel to the bonding surface, the lower limit of the tensile modulus of the heat-fusible film 10 of the present invention should be about 1500 MPa or more. It is preferably about 2,000 MPa or more, more preferably about 3,000 MPa or more, and particularly preferably about 5,000 MPa or more. Although there is no particular preferable upper limit to the tensile modulus, it is usually about 10,000 MPa or less, preferably about 8,000 MPa or less, and more preferably about 7,000 or less. That is, the range of the tensile modulus is approximately 1500 to 10000 MPa, approximately 1500 to 8000 MPa, approximately 1500 to 7000 MPa, approximately 2000 to 10000 MPa, approximately 2000 to 8000 MPa, approximately 2000 to 7000 MPa, approximately 3000 to 10000 MPa, and 3000 to 80 MPa. Approximately 00MPa , about 3000 to 7000 MPa, about 5000 to 10000 MPa, about 5000 to 8000 MPa, and about 5000 to 7000 MPa.

The method for measuring the tensile modulus is as described in the tensile modulus of the intermediate layer 3 above. In addition, in the measurement method, the direction corresponding to the MD of the heat-fusible film 10 may be the same direction as the MD of the middle layer 3 of the heat-fusible film 10, for example, when the intermediate layer 3 is a film. In the present invention, the method for confirming the MD of the intermediate layer 3 of the heat-fusible film 10 is as described in the above-mentioned tensile modulus of the intermediate layer 3. Further, when the intermediate layer 3 of the heat-fusible film 10 is made of fiber, the direction corresponding to the MD of the heat-fusible film 10 may be the same direction as the MD of the heat-fusible resin layer 1. The method for checking the MD of the heat-fusible resin layer 1 is also the same as the method for checking the MD of the intermediate layer 3.

<Heat shrinkage rate>
When the heat-fusible film 10 of the present invention has the intermediate layer 3, the heat shrinkage rate in a high-temperature environment during heat-welding is reduced, and the bonded body of dissimilar materials after bonding has superior strength against shear stress parallel to the bonding surface. From the viewpoint of obtaining the heat-fusible film 10 of the present invention, the heat shrinkage rate measured at a test temperature of 200° C. and a heating time of 10 seconds is preferably about 10% or less as an upper limit, and preferably about 10% or less. Preferably it is about 3.0% or less, more preferably about 2.8% or less, and the lower limit is about 0% and about 0.1%. Further, the range of the heat shrinkage rate is preferably about 0 to 10%, about 0 to 3.0%, about 0 to 2.8%, about 0.1 to 10%, and about 0.1 to 3.0%. Examples include about 0% and about 0.1 to 2.8%. The thermal shrinkage rate is measured by a method according to JIS K 7133:1999.

In the present invention, the heat is applied in at least two directions: one direction of the heat-fusible film 10 (the plane direction of the heat-fusible film 10) and a direction perpendicular thereto (the plane direction of the heat-fusible film 10). It is preferable that the shrinkage rate be satisfied. Specifically, the direction in which the heat shrinkage rate is measured and the direction perpendicular to this correspond to the MD of the intermediate layer 3 of the heat-fusible film 10 when the intermediate layer 3 of the heat-fusible film 10 is a film. The direction is the one direction. In the present invention, the method for confirming the MD of the intermediate layer 3 of the heat-fusible film 10 is as described in the above-mentioned tensile modulus of the intermediate layer 3. Further, when the intermediate layer 3 of the heat-fusible film 10 is made of fiber, the one direction may be the same direction as the MD of the heat-fusible resin layer 1. The method for checking the MD of the heat-fusible resin layer 1 is also the same as the method for checking the MD of the intermediate layer 3.

(Thermoplastic resin layer 4)
In the present invention, the thermoplastic resin layer 4 is a layer that is laminated on the heat-fusible film 10, if necessary. The thermoplastic resin layer 4 is preferably laminated between the first heat-fusible resin layer 1a and the intermediate layer 3, and between the intermediate layer 3 and the second heat-fusible resin layer 1b. The heat-fusible film 10 may have one thermoplastic resin layer 4 laminated thereon, or two or more thermoplastic resin layers 4 may be laminated thereon. The number of laminated thermoplastic resin layers 4 in the heat-fusible film 10 is preferably about 0 to 2, more preferably about 0 to 1. When at least one of the first heat-fusible resin layer 1a and the second heat-fusible resin layer 1b contains an adhesive component, the layer containing the adhesive component is laminated on the intermediate layer 3 via the thermoplastic resin layer 4. By doing so, the adhesive strength between the layers can be stabilized. Therefore, for example, the first heat-fusible resin layer 1a and the second heat-fusible resin layer 1b constitute both surfaces of the heat-fusible film 10, and the first heat-fusible resin layer 1a and the second heat-fusible resin layer When 1b contains an adhesive component, the thermoplastic resin layer 4 is placed between the first heat-fusible resin layer 1a and the intermediate layer 3, and between the intermediate layer 3 and the It is preferable that one layer is laminated between the two heat-fusible resin layers 1b. For example, when the first heat-fusible resin layer 1a constitutes one side of the heat-fusible film 10 and the first heat-fusible resin layer 1a contains an adhesive component, the laminated structure shown in FIG. Preferably, one thermoplastic resin layer 4 is laminated between the first heat-fusible resin layer 1a and the intermediate layer 3.

The thermoplastic resin constituting the thermoplastic resin layer 4 is not particularly limited as long as it has thermoplasticity. Examples of the thermoplastic resin include polyolefin, polyester, polyamide, acrylic resin, fluororesin, and silicone resin. Among these, the thermoplastic resin layer 4 is preferably made of polyolefin, and more preferably made of acid-modified polyolefin (that is, has a polyolefin skeleton). As the acid-modified polyolefin, the same ones as those exemplified for the heat-fusible 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 point of view, it is preferable that it contains a polyolefin skeleton. A thermoplastic resin having a polyolefin skeleton is preferable as the thermoplastic resin contained in the thermoplastic resin layer 4 because it has excellent solvent resistance. The fact that the resin constituting the thermoplastic resin layer 4 contains a polyolefin skeleton can be analyzed by, for example, infrared spectroscopy, gas chromatography mass spectrometry, etc., and the analytical method is not particularly limited. For example, when a maleic anhydride-modified polyolefin is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected at wave numbers around 1760 cm ^-1 and around 1780 cm ^-1 wave numbers.

Note that 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 joined body of different materials after joining. When the thermoplastic resin layer 4 contains an adhesive component, the thermoplastic resin layer 4 can exhibit adhesiveness. When the thermoplastic resin layer 4 contains an adhesive component, the type of the adhesive component is not particularly limited, and examples thereof include the same ones as those exemplified for the thermofusible resin layer 1. Further, the proportion of the adhesive component in the thermoplastic resin layer 4 is not particularly limited, and may be the same proportion as in the heat-fusible resin layer 1.

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

(Additive)
The heat-fusible film 10 of the present invention may contain various additives such as a lubricant, an antioxidant, an ultraviolet absorber, and a light stabilizer, if necessary. In addition, as the additive, the type and content thereof that do not discolor the heat-fusible film 10 are appropriately selected by those skilled in the art.

(Method for producing heat-fusible film)
The heat-fusible film 10 of the present invention can be manufactured by using a melt-extrusion method and, if necessary, a stretching method for at least the heat-fusible resin layer 1. When the heat-fusible film 10 of the present invention has a multilayer structure, at least the first heat-fusible resin layer 1a, the intermediate layer 3, and the second heat-fusible resin layer 1b are provided as necessary. It can be manufactured by laminating the thermoplastic resin layer 4. The method of laminating these layers is not particularly limited, and can be performed using, for example, a thermal lamination method, a sandwich lamination method, an extrusion lamination method, or the like.

Further, when the heat-fusible film 10 of the present invention has a multilayer structure and the intermediate layer 3 is made of a resin film, an adhesion promoter is applied to both surfaces of the intermediate layer 3 (i.e., an adhesion promoter layer) to improve adhesion strength with adjacent layers (for example, first heat-fusible resin layer 1a, second heat-fusible resin layer 1b, thermoplastic resin layer 4, etc.) and stabilize the laminated structure. be able to. In addition, the surface of the intermediate layer 3 may be subjected to known adhesion-facilitating means such as corona discharge treatment, ozone treatment, plasma treatment, etc., if necessary.

As the adhesion promoter forming the adhesion promoter layer, well-known adhesion promoters such as isocyanate-based, polyethyleneimine-based, polyester-based, polyurethane-based, polybutadiene-based, etc. can be used. Further, the adhesion promoter layer can also be formed using a known adhesive such as a two-component curing adhesive or a one-component curing adhesive.

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 coating and drying using a known coating method such as a bar coating method, a roll coating method, or a gravure coating method.

(Element)
The first member joined by the heat-fusible film 10 is made of metal, and the second member is made of fiber-reinforced plastic.

Specific examples of the metal constituting the first member include aluminum, iron, stainless steel, copper, zinc, silver, gold, magnesium, titanium, brass, nickel, or an alloy containing at least one of these. Among these, aluminum, iron, stainless steel,
Preferred examples include titanium, brass, and nickel.

The surface roughness Ra of the metal is preferably about 10 nm or more, preferably about 0.5 μm or more, more preferably about 1 μm or more. Note that there is no particular upper limit to the surface roughness Ra, but for example, it is about 20 μm or less. Since the heat-fusible film 10 of the present invention can suitably join 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, the effect can be achieved. It is possible to join dissimilar materials. That is, the range of the surface roughness Ra is 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, and about 0.5 to 10 μm. Examples include about 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. The surface roughness Ra is an arithmetic mean roughness measured using a contact roughness meter in accordance with JIS B0601:2013. As the contact roughness meter, Surfcom NEX manufactured by Tokyo Seimitsu Co., Ltd. can be used.

The fiber-reinforced plastic constituting the second member may be any composite material whose strength is improved by incorporating fibers into the matrix resin. Examples of the matrix resin of the fiber-reinforced plastic include thermosetting resins (cured products of thermosetting resins) and thermoplastic resins, preferably thermosetting resins (cured products of thermosetting resins).

Examples of thermosetting resins used as matrix resins for fiber-reinforced plastics include epoxy resins, unsaturated polyester resins, phenol resins, silicone resins, urethane resins, and polyimide resins, with epoxy resins being preferred. These thermosetting resins can be used alone 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 alone or in combination of two or more.

The fibers of 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 preferably mentioned, and carbon fibers are more preferably mentioned, from the viewpoint of obtaining a bonded body of dissimilar materials with excellent strength against shear stress parallel to the bonding surface. The carbon fiber is not particularly limited, and any of polyacrylonitrile (PAN) type, pitch type, etc. may be used, or a mixture thereof may be used. The weave of the fibers may be any of long fibers aligned in one direction, bidirectional fabrics, multiaxial fabrics, nonwoven fabrics, mats, knits, braids, and the like. The term "long fiber" as used herein means a substantially continuous single fiber or fiber bundle of 10 mm or more.

The surface roughness Ra of the fiber-reinforced plastic is, for example, about 1 μm or more. From the viewpoint of more effectively obtaining an anchor effect by the heat-fusible resin layer 1 of the heat-fusible film 10 of the present invention following the surface irregularities and more preferably bonding dissimilar materials, the surface roughness Ra is approximately It is preferably 3 μm or more, more preferably about 8 μm or more, and even more preferably about 25 μm or more. Note that there is no particular upper limit to the surface roughness Ra, but from the viewpoint of making the heat-fusible resin layer of the heat-fusible film easily follow the surface irregularities, it is, for example, about 100 μm or less. That is, the range of the surface roughness Ra is, for example, about 1 to 100 μm, preferably about 3 to 100 μm, more preferably about 8 to 100 μm, and still more preferably about 25 to 100 μm. The surface roughness Ra is an arithmetic mean roughness measured using a contact roughness meter in accordance with JIS B0601:2013. As the contact roughness meter, Surfcom NEX manufactured by Tokyo Seimitsu Co., Ltd. can be used.

The fibers may not be exposed on the surface of the fiber-reinforced plastic, or the fibers may be exposed. For the same surface roughness Ra, it is preferable for the fibers to be exposed in order to bond dissimilar materials more appropriately. Furthermore, the surface of the fiber-reinforced plastic can be exposed for the purpose of adjusting the surface roughness Ra of the fiber-reinforced plastic. In order to expose the fibers of the fiber-reinforced plastic, a treatment can be performed to remove the matrix resin on the surface of the fiber-reinforced plastic where the fibers are not exposed. The degree of exposure of the fibers on the surface of the fiber-reinforced plastic, that is, the ratio of the area occupied by exposed fibers to the surface of the fiber-reinforced plastic, is, for example, 0% or more, preferably about 5% or more, more preferably about 10% or more, and Preferably it is about 25% or more, more preferably about 40% or more. Note that there is no particular upper limit to the degree of exposure, but it is usually about 90% or less. That is, the range of the degree of exposure is, for example, about 0 to 90%, preferably about 5 to 90%, more preferably about 10 to 90%, still more preferably about 25 to 90%, even more preferably 40 to 90%. The degree is mentioned.

The fiber-reinforced plastic may contain various additives such as lubricants, antioxidants, ultraviolet absorbers, light stabilizers, and colorants (pigments, dyes, etc.) as necessary.

The thickness of the first member and the second member is not particularly limited, but the lower limit for each member is about 0.1 mm or more, preferably about 1 mm or more for at least one member. The thickness of the member refers to the maximum thickness of the member. Furthermore, if at least one member has a thickness of 1 mm or more, especially if both members have a thickness of 1 mm or more, the joined body of dissimilar materials will have a considerable thickness after joining. Easily subjected to shear stress parallel to the plane. By joining such members having a thickness of 1 mm or more using the heat-fusible film 10 of the present invention, preferably having the intermediate layer 3, it is possible to obtain a joined body of dissimilar materials having excellent strength against the shear stress. can. From the same viewpoint, the thickness of at least one, preferably both members is more preferably 1.3 mm or more, and even more preferably 1.5 mm or more. There is no particular preferable upper limit for the member, but it is, for example, about 20 mm or less. That is, the range of the thickness is, for example, about 0.1 to 20 mm, preferably about 1 to 20 mm, more preferably about 1.3 to 20 mm, and still more preferably about 1.5 to 20 mm.

The shape and size of the member are not particularly limited, and may be any shape and size that corresponds to the dissimilar material assembly to be manufactured by joining the members. Examples include members having various shapes such as a plate shape, a pin shape like a thumbtack, a concave shape, a convex shape, and an uneven shape. Examples of members having various shapes include molded members. In the present invention, a dissimilar material joined body manufactured by joining members can be suitably used, for example, as an interior member or an exterior member of an automobile. Therefore, the material, shape, size, etc. of the member can be selected to be suitable for these uses.

2. Laminate, dissimilar material joined body, and manufacturing method of dissimilar material joined body In the laminate of the present invention, the first member 30 and the second member 40 or the precursor of the second member 40 are made of the heat-fusible film of the present invention. It is characterized by being laminated with 10 layers interposed therebetween. Details of the heat-fusible film 10, the first member 30, and the second member 40 of the present invention are as described above. In addition, the precursor of the second member 40 refers to a fiber-reinforced plastic prepreg in a state before the thermosetting resin of the second member 40 is hardened, as will be explained later as a second member precursor 40a in FIG. 8. .

The laminate of the present invention may have a shape in which the first member 30 and the second member 40 or a precursor of the second member 40 are laminated with the heat-fusible film 10 in between, for example, the laminated member If there are two members, the first member/heat-fusible film/second member or a precursor of the second member are laminated in this order, and if there are three members to be laminated, the first An embodiment in which the member/heat-fusible film/second member or a precursor of the second member/heat-fusible film/other members are laminated in this order, or the first member and the other member are stacked on one side of the heat-fusible film. Examples include an embodiment in which three members are laminated with one heat-fusible film interposed therebetween, and a second member or a precursor of the second member is placed on the other side of the heat-fusible film. It will be done. Further, the heat-fusible film may be present on the entire surface between the first member and the second member or a precursor of the second member so that these members are laminated, or the heat-fusible film may be present on the entire surface between the first member and the second member or a precursor of the second member, or the first member and the second member or the precursor of the second member may be layered. These members may be stacked by being present in a part between the precursors of the second member.

In the laminate of the present invention, the first member 30 and the second member 40 or a precursor of the second member 40 may be laminated with the heat-fusible film 10 interposed therebetween, 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 thermal welding via the laminated heat-fusible film 10 of the present invention.

The dissimilar material joined body 20 of the present invention is characterized in that the first member 30 and the second member 40 are thermally welded by the heat-fusible film 10 of the present invention, as shown in the schematic diagram of FIG. 6, for example. It is said that That is, the dissimilar material joined body 20 of the present invention is in a bonded state and a molded state via the heat-fusible film 10 of the present invention. Details of the heat-fusible film 10, the first member 30, and the second member 40 of the present invention are as described above.

The dissimilar material joined body 20 of the present invention is formed into an arbitrary shape. For example, FIG. 6 shows an embodiment in which the dissimilar material joined body 20 of the present invention is plate-shaped. Moreover, FIG. 10 shows an embodiment in which the dissimilar material joined body 20 of the present invention is molded using a metal mold.

The dissimilar material joined body 20 of the present invention is manufactured by thermally welding the first member 30 and the second member 40 or a precursor of the second member 40 via the heat-fusible film 10 in the above-described laminate. be able to. In this case, specifically, with the heat-fusible film 10 disposed between the first member 30 and the second member 40 or the precursor of the second member 40, heat and pressure are applied to the heat-fusible film 10. The surface of the second member 40 is thermally melted, or the precursor of the second member 40 is further thermally hardened. Thereafter, the heat-fusible film 10 is cooled to solidify the heat-fused surface, thereby forming a molded body in which the first member 30 and the second member 40 are heat-welded (joined) via the heat-fusible film 10. 20 is obtained.

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 thermal welding includes the state after the thermosetting resin has hardened. In this case, a heat-fusible film 10 is sandwiched between a metal first member molded into a predetermined shape and a fiber-reinforced plastic (after hardening) molded into a predetermined shape, and the heat-fusible film 10 is heat-welded by pressure and heating. By doing this, it is possible to obtain a dissimilar material joined body in which the first member and the second member are joined.

When the matrix resin of the fiber-reinforced plastic that constitutes the second member 40 is a thermosetting resin, the state of the member at the time of thermal welding is the state before the thermosetting resin is cured, that is, the second member precursor. It may be. In this case, a laminate in which a first member made of metal and a second member precursor made of fiber-reinforced plastic prepreg are laminated with a heat-fusible film 10 interposed therebetween is heated to perform heat-welding and prepreg formation. The thermosetting and molding can be performed at the same time, that is, in one process, and thereby a dissimilar material joined body in which the first member and the second member are joined can be obtained. More specifically, as shown in a series of schematic diagrams in FIGS. 8 to 10, for example, a metal member (first member 30) and a fiber-reinforced plastic prepreg (second member precursor 40a) are coated with a heat-weldable material. The laminate is laminated with the film 10 interposed in between (FIG. 8), and the laminate is deformed by pressing or hot pressing with a mold 60, etc., and the laminate is heated to form a fiber-reinforced plastic prepreg (second member). Heat curing of the precursor 40a) and heat welding by melting the heat-fusible film 10 are performed (FIG. 9). After cooling the mold 60, as shown in FIG. 10, a dissimilar material assembly 20 is obtained in which the first member 30 and the second member 40 (after hardening) are joined with the heat-fusible film 10.

When the matrix resin of the fiber-reinforced plastic that constitutes the second member 40 is a thermoplastic resin, the first member made of metal and the second member made of fiber-reinforced plastic are connected via the heat-fusible film 10. By heating the laminated body and performing thermal welding and thermoforming simultaneously, that is, in one process, it is possible to obtain a dissimilar material joined body in which the first member and the second member are joined. More specifically, the same steps as those shown in the series of schematic diagrams of FIGS. 8 to 10 were performed except that the fiber-reinforced plastic prepreg (second member precursor 40a) was changed to the fiber-reinforced plastic 40. It can be carried out. In other words, a laminate is formed by laminating a metal member (first member 30) and a fiber-reinforced plastic (second member 40) with a heat-fusible film 10 in between, and the laminate is plastically deformed by hot pressing with a mold or the like. At the same time, the laminate is heated to perform thermal welding by melting the heat-fusible film 10. After cooling the mold, a dissimilar material assembly 20 is obtained in which the first member 30 and the second member 40 are joined with the heat-fusible film 10.

The temperature at which the first member 30 and the second member 40 or the second member precursor 40a are thermally welded via the thermally fusible film 10 is a temperature at which the surface of the thermally fusible film 10 is thermally melted. Although not particularly limited, the temperature is preferably about 140 to 280°C, more preferably about 160 to 250°C. At this temperature, the curing temperature (in the case of a thermosetting resin) or the softening point (in the case of a thermoplastic resin) of the matrix resin in the fiber-reinforced plastic is also appropriately considered. Further, the pressure (surface pressure) during thermal welding is not particularly limited, but is preferably about 0.1 to 5 MPa, more preferably about 0.2 to 3 MPa. The heating and pressurizing time during thermal welding is usually about 1 to 30 seconds.

The present invention will be explained in detail by showing Examples and Comparative Examples below. However, the present invention is not limited to the examples.

<Measurement of heat-fusible film materials, members to be joined, and their physical properties>
In Examples and Comparative Examples, the degree of acid modification, melt mass flow rate (MFR), melting peak temperature, softening point, tensile modulus and thermal shrinkage of the material, as well as the surface roughness of the members to be joined and the fiber-reinforced plastic The fiber exposure degree is a value measured by the following method.

(Measurement of acid denaturation degree)
First, ¹ H-NMR of the measurement target (acid-modified polyolefin) and ¹ H-NMR of the methyl ester of the acid-modified polyolefin were measured using ODCB-d4/C ₆ D ₆ (volume ratio 4/1) solvent. . By comparing both of the obtained ¹ H-NMRs, the peak of the methyl ester compound obtained by derivatizing the acid was identified. Furthermore, from ^{the 1} H-NMR of the acid-modified polyolefin (before methyl esterification), the area of impurity-derived peaks overlapping the peak positions of the methyl ester in ^{the 1} H-NMR of the methyl ester was determined. The peak area of the methyl ester compound was determined by subtracting the impurity-derived peak area from the peak area at the peak position of the methyl ester compound, and the degree of acid modification was calculated from the acid-derived peak area derived based on this. Note that for polyolefins that were not acid-modified, the degree of acid modification was 0% by weight.

(Measurement of melt mass flow rate (MFR))
The measurement was performed using a melt indexer for the heat-fusible resin layer in accordance with the regulations of JIS K7210:2014. As the melt indexer, "MiniLab" manufactured by HAAKE was used. The measurement conditions were a measurement temperature of 230° C. and a weight of 2.16 kg.

(Measurement of melting peak temperature)
The melting peak temperature of the intermediate layer was measured using a differential scanning calorimeter (DSC). The device used was "DSC-60 Plus" manufactured by Shimadzu Corporation. The measurement conditions were a temperature increase rate of 10° C./min, a temperature measurement range of 100 to 350° C., and an aluminum pan was used as the sample pan.

(Measurement of softening point)
The softening point was measured using probe displacement measurement. First, as shown in the conceptual diagram of FIG. 12, the position on the surface of the heat-fusible resin layer at the end of the heat-fusible film (for example, the first heat-fusible resin layer 1a in the heat-fusible film 10 of FIG. If so, the probe 90 is set at the position P (hereinafter, the first heat-fusible resin layer 1a will be explained as a representative) (measurement start A in FIG. 12). The end portion at this time is an exposed section of the first heat-fusible resin layer 1a obtained by cutting in the thickness direction so as to pass through the center of the heat-fusible film. The cutting was performed using a commercially available rotary microtome. An atomic force microscope equipped with a nanothermal microscope composed of a cantilever with a heating mechanism, for example, an afm plus system manufactured by ANASIS INSTRUMENTS, was used, and a probe manufactured by ANASYS INSTRUMENTS was used. The probe tip radius was 30 nm or less, the probe deflection setting was −4 V, and the temperature increase rate was 5° C./min. Next, when the probe is heated in this state, the surface of the first heat-fusible resin layer 1a expands as shown in B in FIG. 12 due to the heat from the probe 90, and the probe 90 is pushed up. has risen from the initial value (the position when the temperature of the probe 90 is 40° C.). When the heating temperature further increased, the first heat-fusible resin layer 1a softened, and the probe 90 penetrated into the first heat-fusible resin layer 1a, as shown in FIG. 12C, and the position of the probe 90 was lowered. Note that in measuring the displacement of the probe 90, the heat-fusible film to be measured is in a room temperature (25° C.) environment, and the probe 90 heated to 40° C. is placed on the surface of the first heat-fusible resin layer 1a. Then, the measurement started. The softening point of the first heat-fusible resin layer 1a is the temperature at which the deflection of the probe 90 becomes maximum in measuring the amount of displacement of the probe. In measuring the softening point of the first heat-fusible resin layer 1a, the temperature at which the deflection of the probe 90 reaches the maximum is read for the five samples of the first heat-fusible resin layer 1a to be measured. The average value of three temperatures excluding the maximum value and minimum value of the five temperatures was defined as the softening point.

(Measurement of tensile modulus)
The tensile modulus of the intermediate layer was measured in the same manner as the tensile modulus of the heat-fusible film described below.

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

(Measurement of surface roughness)
The surface roughness Ra of each member was measured as an arithmetic mean roughness based on JIS B0601:2013 using a contact roughness meter, Surfcom NEX manufactured by Tokyo Seimitsu Co., Ltd.

(Measurement of fiber exposure degree)
The degree of fiber exposure of the fiber-reinforced plastic member was measured by observing the surface under a microscope and calculating the area ratio occupied by the exposed portion of the fibers.

[Test Example 1: Test using a single layer heat-fusible film]
<Heat-fusible film>
(Examples 1 to 18)
A single-layer film (thickness: 100 μm) of maleic anhydride-modified polypropylene resin (PPa) or maleic anhydride-modified polyethylene resin (PEa) shown in Tables 1 and 2 was prepared as a heat-fusible film.

(Comparative example 1)
A single layer film (thickness: 100 μm) of unstretched polypropylene film (CPP) shown in Table 1 was prepared as a heat-fusible film.

<Measurement of various physical properties of dissimilar materials joined body>
Test samples and dissimilar material joined bodies were prepared under the conditions described below, and the seal strength and shear strength were measured. In Tables 1 and 2, AL of the first member indicates aluminum (A1100 of JIS H 4000:2014), and SUS indicates stainless steel (SUS304 of JIS G 4305:2005). Among the fiber-reinforced plastics of the second member, those in which the resin material is epoxy and the fiber material is carbon refer to cured fiber-reinforced plastics in which carbon fibers are impregnated with epoxy resin. Further, among the fiber-reinforced plastics of the second member, those in which the resin material is PP and the fiber material is carbon indicate fiber-reinforced plastics in which carbon fibers are impregnated with polypropylene resin.

(Measurement of seal strength)
The seal strength (N/15 mm) between each surface of the heat-fusible films of Examples and Comparative Examples and the first member and second member listed in Tables 1 and 2 was measured. More specifically, first, each heat-fusible film was cut into a size of 50 mm in the length direction (y direction) x 25 mm in the width direction (x direction). Next, when measuring the sealing strength of the heat-fusible film of the example as a heat-fusible film, as shown in FIG. 7, each heat-fusible film 10 of the example and each member 50 are A test sample was obtained by heat sealing (heat sealing conditions: temperature 190° C., surface pressure 1 MPa, pressurization time 5 seconds) at a depth (y direction) of . In the schematic diagram of FIG. 7, a region S surrounded by a broken line indicates a heat-sealed region. Note that a release sheet was sandwiched between the areas other than the area to be heat-sealed, so that the area was heat-sealed to a depth of 7 mm. Next, the test sample was cut into a width of 15 mm as shown in FIG. 7(a) so that the seal strength (N/15 mm) in the width direction (x direction) of 15 mm could be measured. Next, using a tensile testing machine, the heat-fusible film 10 was peeled from the fixed member 50 in the length direction (y direction), as shown in FIG. 7(b). At this time, the peeling speed was 300 mm/min, and the maximum load until peeling was defined as the seal strength (N/15 mm). In addition, as members used in the production of the test samples, fiber-reinforced plastic members with a thickness of 4 mm and metal members with a thickness of 0.5 mm were used. Each seal strength is an average value (n=3) measured by similarly preparing three test samples. The results are shown in Tables 1 and 2.

(Measurement of shear strength)
Using the heat-fusible films of Examples and Comparative Examples, the shear strength (MPa) of molded bodies obtained by heat-welding the first member and the second member was measured under the following conditions. The shear strength was measured in accordance with the regulations of ISO19095-2 and ISO19095-3. The size of the first member and the second member in the production of the test sample was 45 mm in length x 10 mm in width, and the thickness was 3 mm for the fiber-reinforced plastic member and 1.5 mm for the metal member. Further, each heat-fusible film had a length of 5 mm and a width of 10 mm. As shown in FIG. 13, a heat-fusible film 10 is disposed between the first member 70 and the second member 80 at the longitudinal ends of the first member 70 and the second member 80, and The first member 70 and the second member 80 were thermally welded together via the heat-fusible film 10 under conditions of 190° C., surface pressure of 1.5 MPa, and 20 seconds to obtain a molded body. Further, the heat-fusible film 10 was arranged so that the entire both sides were heat-sealed (that is, the heat-sealed area was 5 mm long x 10 mm wide on one side). Although not shown in FIG. 13, in order to measure the first member 70 and the second member 80 joined in parallel to each other, the first member 70 and the second member 80 are The height was adjusted using a compensating member and then joined. The compensation member for adjusting the height of the first member 70 is made of the same material and shape as the first member 70, and the compensation member for adjusting the height of the second member 80 is made of the same material and shape as the second member 80. A shaped member was used. Next, using a tensile tester, the dissimilar material assembly was pulled in the length direction (pulling speed: 10 mm/min), and the maximum load (N) until delamination or rupture of the dissimilar material assembly occurred was measured. The shear strength (MPa) was calculated by dividing this by the heat seal area (length 5 mm x width 10 mm). The results are shown in Tables 1 and 2.

As shown in the results in Tables 1 and 2, a heat-fusible film (Examples 1- 18) uses such a heat-fusible film to bond both the first member made of metal and the second member made of fiber-reinforced plastic without using an adhesive. In both cases, it was shown that a bonded body of dissimilar materials could be easily obtained. On the other hand, a heat-fusible film made of a heat-fusible resin that does not contain acid-modified polyolefin (Comparative Example 1) adheres to metal but does not adhere to fiber-reinforced resin at all. It was shown that even if a plastic film was used, a dissimilar material bonded body could not be obtained.

[Test Example 2: Test using heat-fusible film having intermediate layer]
<Manufacture of heat-fusible film and measurement of various physical properties>
(Example 19)
A heat-fusible resin was applied to one side of a polyethylene naphthalate (PEN) film (tensile modulus 6000 MPa, peak melting temperature 262°C, heat shrinkage rate TD 1.3%, MD 1.1%, thickness 12 μm) as an intermediate layer. As the first heat-fusible resin layer ( PPa) was formed. Next, on the other side of the intermediate layer, the same maleic anhydride-modified polypropylene resin was extruded and coated using a T-die extruder to a thickness of 44 μm to form a second heat-fusible resin layer (PPa), and the first heat-fusible resin layer (PPa) A laminated film in which a fusible resin layer (PPa, thickness 44 μm)/intermediate layer (PEN, thickness 12 μm)/second heat fusible resin layer (PPa, thickness 44 μm) are laminated in this order is used as a heat fusible film. Obtained.

(Example 20)
As the intermediate layer, a melting anisotropic wholly aromatic polyester (polyarylate (PAR)) nonwoven fabric (tensile modulus 3000 MPa, melting peak temperature 250°C, heat shrinkage rate TD 0.0%, MD 0.0%, basis weight 9 g/m ² , thickness Example 1 was carried out in the same manner as in Example 1, except that maleic anhydride-modified polypropylene resin (degree of acid modification 0.09% by weight, MFR 9g/10 minutes, softening point 140°C) was used as the heat-fusible resin. Then, a laminated film in which the first heat-fusible resin layer (PPa, thickness 20 μm)/intermediate layer (PAR, thickness 40 μm)/second heat-fusible resin layer (PPa, thickness 20 μm) were laminated in this order was made. It was obtained as a heat-fusible film.

(Example 21)
As the intermediate layer, an unstretched polypropylene film (CPP, tensile modulus 1400 MPa, peak melting temperature 290°C, heat shrinkage TD 3.0%, MD 81.0%) was used in the same manner as in Example 1, A laminated film in which the first heat-fusible resin layer (PPa, thickness 30 μm)/intermediate layer (CPP, thickness 40 μm)/second heat-fusible resin layer (PPa, thickness 30 μm) are laminated in this order is thermally welded. Obtained as a sex film.

(Measurement of tensile modulus)
In a method compliant with JIS K7161:2014, a test piece (rectangular) cut out from the film with a width of 25 mm and a length of 120 mm so that the MD becomes the long side was tested in a tensile compression tester ( Calculated according to the following formula from the first straight line part of the tensile stress-strain curve obtained by measuring using Tensilon RTC-1250A (manufactured by Orientech Co., Ltd.) at a tensile speed of 200 mm/min and a distance between chucks of 100 mm. did.
E=Δρ/Δε
E: Tensile modulus Δρ: Stress difference between two points on a straight line due to original average cross-sectional area Δε: Strain difference between the same two points

(Measurement of heat shrinkage rate)
In a method based on the regulations of JIS K 7133:1999, the heat shrinkage rate of each heat-fusible film obtained above was measured under conditions of a test temperature of 200° C. and a heating time of 10 seconds. The results are shown in Table 1.

<Measurement of physical properties of molded object>
Test samples and molded bodies were created using the first member and second member 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, shear strength was also measured as follows. In Table 3, AL of the first member indicates aluminum (A1100 of JIS H 4000:2014), and the fiber-reinforced plastic of the second member is a cured fiber-reinforced plastic in which carbon fibers are impregnated with epoxy resin. show something

(Measurement of peel strength)
The peel strength (N/25 mm) between the first member and the second member was measured in a dissimilar material assembly composed of the first member, heat-fusible film, and second member listed in Table 1. . More specifically, first, each heat-fusible film was cut into a size of 160 mm in the length direction x 25 mm in the width direction. The first member 70 was cut out into a size of 250 mm in the length direction x 25 mm in the width direction, and the second member 80 was cut out into a size of 200 mm in the length direction x 25 mm in the width direction. Next, as shown in FIG. 14(i), each heat-fusible film 10, the first member 70, and the second member 80 are stacked with their longitudinal directions aligned, and a size of 160 mm in the length direction x 25 mm in the width direction is formed. The area 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 jig on the second member 80 side, and the first member 70 was peeled off using a tensile tester as shown in FIG. 14(ii). At this time, the peeling speed was 100 mm/min, and the peel strength (N/25 mm) was the average load at a location excluding the peeling start location to a peeling length of 25 mm. In addition, as members used in the production of the test samples, fiber-reinforced plastic members with a thickness of 4 mm and metal members with a thickness of 0.5 mm were used. Each peel strength is an average value (n=3) measured by preparing three test samples in the same manner. The results are shown in Table 3.

In Table 3, Example 10 is also shown in parallel with Examples 19 to 21. As shown in the results in Table 3, the heat-fusible films (Examples 19 to 21) in which one surface and the other surface are both composed of a heat-fusible resin layer containing acid-modified polyolefin In order to bond both the first member made of metal and the second member made of fiber-reinforced plastic well, by using such a heat-fusible film, it is possible to easily bond the first member made of metal and the second member made of fiber-reinforced plastic without using an adhesive. It was shown that a composite of dissimilar materials could be obtained. In particular, heat-fusible films having a tensile modulus of 1500 MPa or more (Examples 19 and 20) are different from heat-fusible films having a tensile modulus of less than 1500 MPa (Example 10) even though they have the same heat-fusible resin layer. ), an extremely superior shear strength of 10 MPa or more was achieved after the members were joined. Therefore, the laminated films (heat-fusible films) of Examples 19 and 20 are shown to be particularly suitable for use in obtaining molded products by joining members of 1 mm or more that are susceptible to shear stress parallel to the joining surfaces. Ta.

1 Heat-fusible resin layer 1a First heat-fusible resin layer 1b Second heat-fusible resin layer 3 Intermediate layer 4 Thermoplastic resin layer 10 Heat-fusible film 20 Dissimilar material joined body 30 First member (metal)
40 Second member (fiber reinforced plastic)
40a Second member precursor (fiber reinforced plastic prepreg)
50 member 60 mold 70 first member (metal)
80 Second member (fiber reinforced plastic)
90 Probe S Heat sealed area P Position of surface of intermediate layer at end of heat welding film

Claims (12)

A heat-fusible film for joining a first member made of metal and a second member made of fiber-reinforced plastic in a heat-welding time of 1 to 30 seconds,
Both the surface of one side and the surface of the other side are composed of a heat-fusible resin layer made of acid-modified polyolefin which may contain additives,
The melt mass flow rate of the heat-fusible resin layer at a temperature of 230° C. and a load of 2.16 kg is 2 to 20 g/10 minutes,
A heat-fusible film in which fibers are exposed on the surface of the fiber-reinforced plastic. A heat-fusible film for joining a first member made of metal and a second member made of fiber-reinforced plastic in a heat-welding time of 1 to 30 seconds,
Both the surface of one side and the surface of the other side are composed of a heat-fusible resin layer made of acid-modified polyolefin which may contain additives,
The melt mass flow rate of the heat-fusible resin layer at a temperature of 230° C. and a load of 2.16 kg is 2 to 20 g/10 minutes,
A heat-fusible film, wherein the fiber-reinforced plastic has a surface roughness of 25 μm or more, which is an arithmetic mean roughness according to JIS B0601:2013. The heat-fusible film according to claim 1 or 2, wherein the acidic polyolefin has a degree of acid modification of 0.005% by weight or more. The heat-fusible film according to any one of claims 1 to 3, wherein the polyolefin to be modified in the acid-modified polyolefin is selected from the group consisting of polyethylene and polypropylene. The heat-fusible film according to claim 1, wherein the matrix resin of the fiber-reinforced plastic is a thermosetting resin. The heat-fusible film according to claim 1, wherein the matrix resin of the fiber-reinforced plastic is a thermoplastic resin. The heat-fusible film according to claim 1, wherein the fibers in the fiber-reinforced plastic are glass fibers or carbon fibers. The heat-fusible film according to claim 1, which is a single-layer film of the heat-fusible resin layer. The heat-fusible film according to any one of claims 1 to 8, wherein the additive is selected from a lubricant, an antioxidant, an ultraviolet absorber, and a light stabilizer. A laminate in which a first member made of metal and a second member made of fiber-reinforced plastic are laminated via the heat-fusible film according to any one of claims 1 to 9 is heated for 1 to 30 seconds. A method for manufacturing a joined body of dissimilar materials, comprising performing thermal welding to obtain a joined body of dissimilar materials in which the first member and the second member are joined. A laminate in which a first member made of metal and a second member made of fiber-reinforced plastic are laminated via the heat-fusible film according to any one of claims 1 to 9 is heated for 1 to 30 seconds. A method for manufacturing a joined body of dissimilar materials, wherein thermal welding and thermoforming are performed simultaneously to obtain a joined body of dissimilar materials in which the first member and the second member are joined. A first member made of metal and a second member made of fiber-reinforced plastic are bonded and molded via the heat-fusible film according to any one of claims 1 to 9. Joined body of dissimilar materials.