Hot-melt adhesive film, joined body, and method for producing joined body

Abstract

To provide a hot-melt adhesive film which is excellent in adhesive force in bonding materials of the same kind or materials of different kinds, and can suppress a decrease in adhesive force when an obtained bonded body is allowed to stand in a high-temperature and high-humidity environment.SOLUTION: The hot-melt adhesive film is composed of a resin composition containing a thermoplastic resin (A) and an inorganic filler (B), wherein a treatment layer composed of a hydrophobic surface treatment agent is provided on the surface of the inorganic filler (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hot melt adhesive film, a joint, and a method for producing the joint. [Background technology]

[0002] Hot melt adhesive film is a solvent-free adhesive whose main component is a film-like resin. The hot melt adhesive film is placed between components, heated and melted, and then pressed together to bond the components. After that, the hot melt adhesive film is cooled and solidified to bond the components together. Hot melt adhesive film is widely used because it is a solvent-free material with a low environmental impact.

[0003] Hot melt adhesive films are available in thermoplastic resin and thermosetting resin varieties, and thermoplastic resin hot melt adhesive films have been attracting attention from the viewpoint of simplifying the production process. However, since thermoplastic resin hot melt adhesive films have inferior adhesive strength compared to thermosetting resin hot melt adhesive films, Patent Document 1, for example, discloses a method of using a resin composition for hot melt adhesives that contains a specific terminal-modified polyamide resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-76487 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a bonded structure bonded with a hot-melt adhesive film made of a thermoplastic resin composition such as that described in Patent Document 1 is used in a high-temperature, high-humidity environment, the adhesive layer may be affected by water vapor and the adhesive strength may decrease. For this reason, there is a demand for a hot-melt adhesive film whose adhesiveness is less affected by humidity.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a hot melt adhesive film that has excellent adhesive strength when used to join the same or different materials and that can suppress a decrease in adhesive strength when the resulting joined body is left in a high-temperature and high-humidity environment, as well as a joined body using the hot melt adhesive film and a method for producing the joined body. [Means for solving the problem]

[0007] The present invention provides the following hot melt adhesive film, bonded body, and method for producing the bonded body.

[0008] Item 1: A hot-melt adhesive film made of a resin composition containing a thermoplastic resin (A) and an inorganic filler (B), wherein a treatment layer made of a hydrophobic surface treatment agent is provided on the surface of the inorganic filler (B).

[0009] Item 2. The hot melt adhesive film according to Item 1, wherein the thermoplastic resin (A) is a polyamide resin.

[0010] Item 3. The hot melt adhesive film according to item 1 or 2, wherein the hydrophobic surface treatment agent has a surface free energy of 50 mN / m or less.

[0011] Item 4. The hot melt adhesive film according to any one of Items 1 to 3, wherein the inorganic filler (B) is a fibrous particle or a non-fibrous particle.

[0012] Item 5. The hot melt adhesive film according to any one of Items 1 to 4, wherein the content of the inorganic filler (B) is 0.5% by mass or more and 50% by mass or less, based on 100% by mass of the total amount of the components contained in the resin composition.

[0013] Item 6: The hot melt adhesive film according to any one of Items 1 to 5, wherein the hydrophobic surface treatment agent is an alkoxysilane represented by the following general formula (I):

[0014] R 1 n Si(OR 2 ) 4-n ... Formula (I) [In general formula (I), n represents an integer selected from 1 to 3, and R 1 represents an alkyl group, an alkenyl group, or an aryl group, and R 2 represents an alkyl group.]

[0015] Item 7. The hot melt adhesive film according to any one of Items 1 to 6, wherein the hot melt adhesive film has a thickness of 10 μm or more and 300 μm or less.

[0016] Item 8: A joined body in which a first member to be joined and a second member to be joined, which is made of the same material as or a different material from the first member to be joined, are joined by the hot melt adhesive film according to any one of items 1 to 7.

[0017] Item 9: A method for producing a joined body, comprising the steps of preparing a first member to be joined and a second member to be joined, the second member being made of the same material as or a different material from the first member to be joined, and joining the first member to be joined and the second member to be joined using the hot melt adhesive film according to any one of items 1 to 7. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a hot melt adhesive film that has excellent adhesive strength when used to join materials of the same kind or different kinds, and that can suppress a decrease in adhesive strength when the resulting joined body is left in a high-temperature and high-humidity environment, as well as a joined body using the hot melt adhesive film and a method for producing the joined body. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a bonded body according to one embodiment of the present invention. [Figure 2]FIG. 2 is a graph showing the relationship between the heat treatment time and the adhesive strength retention rate when the bonded test piece prepared in Example 4 was heat treated at a temperature of 100° C. using a constant temperature air-blowing dryer. [Figure 3] FIG. 3 is a graph showing the relationship between the heat treatment time and the adhesive strength retention rate when the bonded body test piece produced in Example 4 was heat treated at a temperature of 150° C. using a constant temperature air-blowing dryer. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an example of a preferred embodiment of the present invention will be described. However, the following embodiment is merely an example, and the present invention is not limited to the following embodiment.

[0021] [Hot melt adhesive film] The hot melt adhesive film of the present invention is composed of a resin composition containing a thermoplastic resin (A) and an inorganic filler (B). A treatment layer composed of a hydrophobic surface treatment agent is provided on the surface of the inorganic filler (B). Furthermore, the resin composition constituting the hot melt adhesive film of the present invention may further contain other additives as necessary.

[0022] The present inventors have found that in a hot melt adhesive film composed of a resin composition containing a thermoplastic resin (A) and an inorganic filler (B), by providing a treatment layer composed of a hydrophobic surface treatment agent on the surface of the inorganic filler (B), excellent adhesive strength can be achieved when joining homogeneous or dissimilar materials, and further, the resulting joined body can be prevented from decreasing in adhesive strength when left in a high-temperature and high-humidity environment.

[0023] In the present invention, the thickness of the hot-melt adhesive film is not particularly limited, but is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, and preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less. When the thickness of the hot-melt adhesive film is equal to or greater than the above-mentioned lower limit, the adhesive strength can be further increased when joining the same or different materials, and the adhesive strength can be maintained at a higher level even when the resulting joined body is left in a high-temperature and high-humidity environment. When the thickness of the hot-melt adhesive film is equal to or less than the above-mentioned upper limit, the productivity of the hot-melt adhesive film can be further improved, and workability can be further improved. When the thickness of the hot-melt adhesive film is equal to or less than the above-mentioned upper limit, the shear adhesive strength can be further improved.

[0024] In order to further prevent a decrease in adhesive strength when the hot melt adhesive film is used at high temperatures for a long period of time, the thickness of the hot melt adhesive film is preferably 120 μm or less, more preferably 100 μm or less, even more preferably 70 μm or less, and particularly preferably 50 μm or less.

[0025] In general, a "film" refers to a thin, flat product that is extremely thin compared to its length and width, with an arbitrarily limited maximum thickness, and is usually supplied in roll form (Japanese Industrial Standard JIS K6900). Also, a "sheet," as defined in JIS, generally refers to a flat product that is thin and generally small in thickness relative to its length and width. For example, in the strict sense, a product with a thickness of less than 100 μm is referred to as a "film," while a product with a thickness of 100 μm or more is sometimes referred to as a "sheet." However, the boundary between "film" and "sheet" is unclear, and there is no need to completely distinguish between the two terms. Therefore, in this invention, when referring to a "film," the term "sheet" may also be included in the meaning, and when referring to a "sheet," the term "film" may also be included in the meaning.

[0026] Hereinafter, each of the components of the hot melt adhesive film of the present invention will be described.

[0027] The hot melt adhesive film of the present invention is composed of a resin composition containing a thermoplastic resin (A) and an inorganic filler (B). The resin composition constituting the hot melt adhesive film of the present invention may further contain other additives, if necessary.

[0028] (Thermoplastic resin (A)) The thermoplastic resin (A) is not particularly limited as long as it can be formed into a film. Examples of the thermoplastic resin (A) include polyolefin resins such as polypropylene (PP) resin, polyethylene (PE) resin, cyclic polyolefin (COP) resin, and cyclic olefin copolymer (COC) resin; polystyrene (PS) resin, syndiotactic polystyrene (SPS) resin, high impact polystyrene (HIPS) resin, acrylonitrile-butylene-styrene copolymer (ABS) resin, methyl methacrylate / styrene copolymer (MS), methyl methacrylate / butadiene / styrene copolymer (MBS), styrene / butadiene copolymer (SBR), styrene / isoprene copolymer (SIR), styrene / isoprene / butadiene copolymer (SIBR), styrene / butadiene / styrene copolymer (SBS), styrene / isoprene / styrene copolymer (SIS), styrene / ethylene / butylene / styrene copolymer (SEBS), and styrene / ethylene / propylene / styrene copolymer (SEPS); and polylactic acid (PLA) resin. Polyester resins such as polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, and polycyclohexene dimethylene terephthalate (PCT) resin; polyacetal (POM) resin; polycarbonate (PC) resin; polyamide 6 resin, polyamide 66 resin, polyamide 11 resin, polyamide 12 resin, polyamide 46 resin, polyamide 6C resin, polyamide 9C resin, and copolymers of polyamide 6 resin and polyamide 66 resin (polyamide 6 / 6 Aliphatic polyamide (PA) resins such as copolymers of polyamide 6 and polyamide 12 (polyamide 6 / 12 resin); semi-aromatic polyamide (PA) resins consisting of structural units with aromatic rings and structural units without aromatic rings, such as polyamide MXD6 resin, polyamide MXD10 resin, polyamide 6T resin, polyamide 9T resin, and polyamide 10T resin; polyphenylene sulfide (PPS) resin; polyethersulfone (PES) resin; liquid crystal polyester (LCP) resin;Examples of suitable thermoplastic resins include polyether aromatic ketone resins such as polyether ketone (PEK) resin, polyether ether ketone (PEEK) resin, polyether ketone ketone (PEKK) resin, and polyether ether ketone ketone (PEEKK); polyetherimide (PEI) resin; polyamide-imide (PAI) resin; thermoplastic polyimide (TPI) resin; and fluorine-based resins such as polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), and ethylene / tetrafluoroethylene copolymer (ETFE). These thermoplastic resins may be used alone or in combination. When multiple types of thermoplastic resins are used in combination, a polymer alloy, which is a mixture of two or more compatible thermoplastic resins, may be used as the thermoplastic resin (A).

[0029] When the thermoplastic resin (A) is a crystalline resin, the melting point of the thermoplastic resin (A) is preferably 150°C or higher, more preferably 170°C or higher, even more preferably 200°C or higher, and preferably 350°C or lower, more preferably 320°C or lower, and even more preferably 300°C or lower. When the melting point of the thermoplastic resin (A) is above the above-mentioned lower limit, the adhesive strength between the same or different materials can be further increased, and the decrease in adhesive strength when the bonded body is left in a high-temperature, high-humidity environment can be further suppressed. Furthermore, when the melting point of the thermoplastic resin (A) is below the above-mentioned upper limit, the moldability of the resin composition can be further improved. The melting point can be measured in accordance with JIS K7121.

[0030] When the thermoplastic resin (A) is a crystalline resin, the thermoplastic resin (A) is preferably a polyamide resin or a polyphenylene sulfide resin, more preferably a polyamide resin.

[0031] The term "crystalline" means that the value of the heat of fusion measured using a differential scanning calorimeter (DSC) in a nitrogen atmosphere after cooling from a molten state to 50°C at a rate of 10°C / min and then increasing the temperature at a rate of 10°C / min is greater than 30 J / g. The term "amorphous" means that the value of the heat of fusion measured using a DSC in a nitrogen atmosphere after cooling from a molten state to 50°C at a rate of 10°C / min and then increasing the temperature at a rate of 10°C / min is 30 J / g or less.

[0032] The shape of the thermoplastic resin (A) is not particularly limited as long as it can be melt-kneaded. Examples of the shape of the thermoplastic resin (A) include powder, granules, pellets, flakes, and beads.

[0033] The content of the thermoplastic resin (A) is preferably 70% by mass to 99.5% by mass, more preferably 75% by mass to 97% by mass, and even more preferably 80% by mass to 95% by mass, based on 100% by mass of the total amount of components contained in the resin composition. When the content of the thermoplastic resin (A) is within the above range, the moldability of the resin composition can be further improved, and the adhesive strength when joining the same or different materials can be further increased.

[0034] (Inorganic filler (B)) The main body of the inorganic filler (B) (excluding the treated layer) is, for example, a particulate inorganic filler. The particle shape of the inorganic filler (B) is not particularly limited as long as it improves the strength and rigidity of the resulting hot melt adhesive film. The inorganic filler (B) is preferably a fibrous particle or a non-fibrous particle. The particle shape of the inorganic filler (B) can be analyzed, for example, by observation with a scanning electron microscope (SEM).

[0035] In the present invention, a fibrous particle refers to a particle in which the longest side of the rectangular parallelepiped circumscribing the particle and having the smallest volume (circumscribing rectangular parallelepiped) is defined as the major axis L, the next longest side as the minor axis B, and the shortest side as the thickness T (B>T), where L / B and L / T are both 3 or greater. The major axis L corresponds to the fiber length, and the minor axis B corresponds to the fiber diameter. Non-fibrous particles refer to particles in which L / B is less than 3. Examples of non-fibrous particles include spherical particles (including those with slight surface irregularities and those with a substantially spherical cross section, such as an elliptical cross section), columnar particles (including those with an overall substantially columnar shape, such as a rod-like, cylindrical, prismatic, rectangular, rectangular, substantially cylindrical, or substantially rectangular shape), plate-like particles, block-like particles, particles with a shape having multiple protrusions (e.g., amoeba-like, boomerang-like, cross-like, or confetti-like), and particles of an irregular shape. The non-fibrous particles are preferably plate-like particles from the viewpoint of further improving strength and rigidity. Plate-like particles refer to non-fibrous particles having an L / T ratio of 3 or more. Note that the term "plate-like" encompasses not only a general plate-like shape but also a flake-like shape, a scale-like shape, and the like.

[0036] Specific examples of fibrous particles include inorganic fibers such as carbon fibers, glass fibers, potassium titanate fibers, wollastonite fibers, aluminum borate fibers, magnesium borate fibers, xonotlite fibers, zinc oxide fibers, basic magnesium sulfate fibers, alumina fibers, silicon carbide fibers, and boron fibers; and organic fibers such as aramid fibers and polyphenylene benzoxazole (PBO) fibers. From the viewpoint of further improving heat resistance, the fibrous particles are preferably inorganic fibers, and more preferably potassium titanate fibers and wollastonite fibers. These fibrous particles may be used alone or in combination.

[0037] From the viewpoint of further improving the strength and rigidity of the resulting hot melt adhesive film, the average fiber length of the fibrous particles is preferably 1 μm to 300 μm, more preferably 1 μm to 200 μm, even more preferably 3 μm to 100 μm, and particularly preferably 3 μm to 50 μm. The average aspect ratio of the fibrous particles is preferably 3 to 200, more preferably 3 to 100, even more preferably 3 to 50, and particularly preferably 3 to 40.

[0038] A wide variety of conventional potassium titanate fibers can be used, including, for example, potassium tetratitanate fiber, potassium hexatitanate fiber, and potassium octatitanate fiber. The dimensions of the potassium titanate fiber are not particularly limited as long as they are within the range of the dimensions of the fibrous particles described above. The average fiber length of the potassium titanate fiber is preferably 1 μm to 50 μm, more preferably 3 μm to 30 μm, and even more preferably 3 μm to 20 μm. The average fiber diameter of the potassium titanate fiber is preferably 0.01 μm to 1 μm, more preferably 0.05 μm to 0.8 μm, and even more preferably 0.1 μm to 0.7 μm. The average aspect ratio of the potassium titanate fiber is preferably 10 or more, more preferably 10 to 100, and even more preferably 15 to 35.

[0039] Wollastonite fiber is an inorganic fiber made of calcium metasilicate. The dimensions of the wollastonite fiber are not particularly limited as long as they are within the range of the dimensions of the fibrous particles described above. The average fiber length of the wollastonite fiber is preferably 5 μm to 180 μm, more preferably 7 μm to 100 μm, and even more preferably 9 μm to 40 μm. The average fiber diameter of the wollastonite fiber is preferably 0.1 μm to 15 μm, more preferably 1 μm to 10 μm, and even more preferably 2 μm to 7 μm. The average aspect ratio of the wollastonite fiber is preferably 3 or more, more preferably 3 to 30, and even more preferably 3 to 15.

[0040] The average fiber length and average fiber diameter can be measured by observation with a scanning electron microscope (SEM). The average aspect ratio (average fiber length / average fiber diameter) can be calculated from the average fiber length and average fiber diameter. To determine the average fiber length and average fiber diameter, for example, a plurality of fibrous particles are photographed with a scanning electron microscope (SEM), 300 fibrous particles are randomly selected from the observation image, and their fiber lengths and fiber diameters are measured. The average fiber length can then be calculated by accumulating all the fiber lengths and dividing by the number of particles, and the average fiber diameter can be calculated by accumulating all the fiber diameters and dividing by the number of particles.

[0041] As mentioned above, examples of non-fibrous particles include spherical particles (including those with slight surface irregularities and those with a roughly spherical cross section, such as an elliptical cross section), columnar particles (including those with an overall roughly columnar shape, such as rod-shaped, cylindrical, prismatic, rectangular, rectangular, roughly cylindrical, roughly rectangular), plate-shaped particles, block-shaped particles, particles with multiple protrusions (amoeba-shaped, boomerang-shaped, cross-shaped, confetti-shaped, etc.), and particles of irregular shape. However, from the viewpoint of further improving the strength and rigidity of the resulting hot-melt adhesive film, plate-shaped particles are preferred. These various particle shapes can be analyzed, for example, by observation with a scanning electron microscope (SEM).

[0042] Specific examples of non-fibrous particles include mica, sericite, illite, talc, kaolinite, montmorillonite, smectite, vermiculite, titanium dioxide, potassium titanate, lithium potassium titanate, magnesium potassium titanate, boehmite, etc. These non-fibrous particles may be used alone or in combination.

[0043] Talc is a hydrous magnesium silicate, generally represented by the chemical formula 4SiO2·3MgO·2H2O, and is usually a scaly particle with a layered structure. These talcs are also available commercially.

[0044] The average particle size of the non-fibrous particles is preferably 1 μm to 50 μm, more preferably 3 μm to 30 μm, and even more preferably 3 μm to 25 μm, from the viewpoint of further improving the strength and rigidity of the resulting hot melt adhesive film.

[0045] The average particle size of non-fibrous particles can be measured by a laser diffraction / scattering method. Specifically, the average particle size of non-fibrous particles is the particle size at 50% cumulative volume in the particle size distribution measured by the laser diffraction / scattering method (volume-based cumulative 50% particle size), i.e., D 50 (median diameter). This volume-based cumulative 50% particle diameter (D 50 ) is the particle size at which the cumulative value reaches 50% when the particle size distribution is calculated on a volume basis and the number of particles is counted from the smallest particle size on a cumulative curve with the total volume set to 100%.

[0046] The average maximum diameter (long diameter) of the plate-like particles is preferably 0.5 μm to 25 μm, more preferably 0.5 μm to 20 μm, from the viewpoint of further improving the strength and rigidity of the obtained hot melt adhesive film. The average thickness of the plate-like particles is preferably 0.05 μm to 2 μm, more preferably 0.05 μm to 1 μm. The average aspect ratio (average maximum diameter / average thickness) is preferably 10 to 400, more preferably 20 to 300.

[0047] As for the above-mentioned plate-like particles, the average maximum diameter (major axis) of the plate-like particles is preferably 0.5 μm to 25 μm, more preferably 0.5 μm to 20 μm, as described above. The average minor axis (minor axis) of the plate-like particles is usually 0.5 μm to 15 μm, preferably 0.5 μm to 10 μm. Although the terms "major axis" and "minor axis" are used here for convenience, particles having approximately the same length, i.e., square or nearly square, are also included in the plate-like particles.

[0048] The average major axis, average thickness, average minor axis, and average aspect ratio can be measured and calculated by observation using a scanning electron microscope (SEM).

[0049] In the present invention, a treatment layer composed of a hydrophobic surface treatment agent is provided on the surface of the inorganic filler (B). The treatment layer may cover only a portion of the surface of the main body of the inorganic filler (B) as long as the effects of the present invention are achieved. The treatment layer preferably covers 50% or more, and more preferably 80% or more, of the surface of the main body of the inorganic filler (B). However, it is even more preferable for the treatment layer to cover the entire main body of the inorganic filler (B).

[0050] The surface free energy of the hydrophobic surface treatment agent constituting the treatment layer of the inorganic filler (B) is preferably 50 mN / m or less. The surface free energy of the hydrophobic surface treatment agent is preferably 5 mN / m or more, more preferably 10 mN / m or more, even more preferably 15 mN / m or more, and is preferably 50 mN / m or less, more preferably less than 50 mN / m, even more preferably 45 mN / m or less.

[0051] The surface free energy can be determined by uniformly applying a surface treatment agent diluted 10 times with methanol to a glass plate, heating it at 85°C for 1 hour, and then heat-treating it at 110°C for 1 hour, and then measuring the static contact angle between the two liquids, water and decane, to calculate the surface free energy of the surface on which the surface treatment agent is applied.

[0052] The hydrophobic surface treatment agent constituting the treatment layer of the inorganic filler (B) can be, for example, a hydrophobic silane coupling agent. The hydrophobic silane coupling agent can be any agent having an essentially hydrophobic functional group such as an alkyl group or an aryl group and a hydrolyzable functional group that generates a group that can react with the hydrophilic group on the surface of the main body of the inorganic filler (B). A typical example of such a hydrophobic silane coupling agent can be, for example, an alkoxysilane represented by the following general formula (I):

[0053] R 1 n Si(OR 2 ) 4-n ... Formula (I) [In general formula (I), n represents an integer selected from 1 to 3, and R 1 represents an alkyl group, an alkenyl group, or an aryl group. 1 may have a substituent, R 1 When there are multiple R, they may be the same or different. 2 represents an alkyl group. 2 may have a substituent, R 2 When there are a plurality of groups, they may be the same or different.

[0054] R 1 Examples of the alkyl group represented by the formula (I) include alkyl groups such as heptyl, octyl, nonyl, decyl, dodecyl, hexadecyl, octadecyl, and icosyl. The number of carbon atoms in the alkyl group is preferably 6 or more, and more preferably 8 or more. The upper limit of the number of carbon atoms in the alkyl group is not particularly limited, but can be, for example, 20 or less.

[0055] These alkyl groups may have a cyclic structure or a branched structure. In general, the greater the number of carbon atoms in the linear chain of an alkyl group, the greater the degree of hydrophobicity. The alkyl group may have a substituent, as described below, at any position.

[0056] R 1 Examples of the alkenyl group represented by the formula (I) include a vinyl group and a butenyl group. These may have a cyclic structure or a branched structure. The alkenyl group may have a substituent, which will be described later, at any position.

[0057] R 1 Examples of the aryl group represented by the formula (I) include a phenyl group, a naphthyl group, etc. The aryl group may have a substituent, which will be described later, at any position.

[0058] R 1The groups represented by the formula (I) may each have a substituent, as long as it does not impair the hydrophobicity. Examples of the substituent include hydrophobic substituents such as a fluorine atom and a (meth)acryloxy group.

[0059] Furthermore, R 1 The alkyl group represented by the formula (I) may have the above-mentioned aryl group as a hydrophobic substituent. 1 The aryl group represented by the formula (I) may have an alkyl group as a hydrophobic substituent.

[0060] R 2 Examples of the alkyl group represented by the general formula (I) include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, a hexadecyl group, an octadecyl group, and an icosyl group. 2 ) is a hydrolyzable group, so from the viewpoint of hydrolysis, R 2 is preferably a lower alkyl group having 4 or less carbon atoms, more preferably an ethyl group or a methyl group, and even more preferably a methyl group.

[0061] n represents any integer selected from 1 to 3. n is preferably 1 from the viewpoint of further increasing the reactivity and hydrophobicity between the surface of the main body of the inorganic filler (B) and the treatment layer.

[0062] Specific examples of alkoxysilanes represented by general formula (I) include methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, heptyltrimethoxysilane, octyltrimethoxysilane, nonyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane, icosyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, hexyltriethoxysilane, heptyltriethoxysilane, octyltriethoxysilane, nonyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, hexadecyltriethoxysilane, octadecyltriethoxysilane, icosyltriethoxysilane, and phenyltriethoxysilane. Among these, the alkoxysilane is preferably heptyltrimethoxysilane, octyltrimethoxysilane, nonyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane, icosyltrimethoxysilane, heptyltriethoxysilane, octyltriethoxysilane, nonyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, hexadecyltriethoxysilane, octadecyltriethoxysilane, or icosyltriethoxysilane, and more preferably decyltrimethoxysilane or hexadecyltrimethoxysilane. These hydrophobic surface treatment agents may be used alone or in combination.

[0063] A known surface treatment method can be used to form a treatment layer made of a surface treatment agent on the surface of the main body constituting the inorganic filler (B). A dry method or a wet method can be used to form a coupling agent on the surface of the inorganic filler (B) in advance, and either method can be used.

[0064] The surface treatment is carried out, for example, by a dry method in which the main body constituting the inorganic filler (B) is placed in a device capable of high-speed stirring such as a Henschel mixer, and while stirring, a surface treatment agent (if liquid) or a solution in which the surface treatment agent is dissolved in a solvent that promotes hydrolysis (for example, water, alcohol, or a mixed solvent thereof) is sprayed onto the main body of the inorganic filler (B).

[0065] The amount of hydrophobic surface treatment agent used when treating the surface of the main body of the inorganic filler (B) is not particularly limited. In the case of a dry method, for example, a solution of the hydrophobic surface treatment agent may be sprayed so that the amount of the surface treatment agent is preferably 0.1% by mass to 20% by mass, more preferably 0.1% by mass to 10% by mass, more preferably 0.3% by mass to 5% by mass, and even more preferably 0.5% by mass to 3% by mass, relative to 100% by mass of the inorganic filler (B).

[0066] The content of the inorganic filler (B) in the resin composition of the present invention is preferably 0.1% by mass to 50% by mass, more preferably 0.5% by mass to 30% by mass, and even more preferably 3% by mass to 10% by mass, based on 100% by mass of the total amount of the resin composition.

[0067] When the content of the inorganic filler (B) is within the above range, the adhesive strength can be further increased when bonding the same or different materials, and the adhesive strength can be maintained at a higher level when the resulting bonded body is left in a high-temperature and high-humidity environment.

[0068] (Other additives) The resin composition constituting the hot melt adhesive film of the present invention may contain an olefin polymer (C) different from the thermoplastic resin (A). In this case, the adhesive strength obtained when joining the same or different materials can be further increased, and the adhesive strength can be maintained at a higher level when the joined body is left in a high-temperature and high-humidity environment.

[0069] Examples of the olefin polymer (C) include polyethylene, polypropylene, polymethylpentene, ethylene-butene copolymer, ethylene-propylene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-glycidyl methacrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-styrene copolymer, ethylene-methyl acrylate-glycidyl methacrylate copolymer, ethylene-ethyl acrylate-glycidyl methacrylate copolymer, and ethylene-vinyl acetate-glycidyl methacrylate copolymer. These olefin polymers (C) may be used alone or in combination of two or more.

[0070] The olefin polymer (C) preferably has a reactive functional group, in which case the olefin polymer (C) is likely to form an intermolecular bond with the thermoplastic resin (A).

[0071] The reactive functional group in the olefin polymer (C) is not particularly limited, and examples thereof include a vinyl group, an epoxy group, a glycidyl group, an ester group, an aldehyde group, a carbonyldioxy group, a haloformyl group, an alkoxycarbonyl group, an amino group, a hydroxyl group, a styryl group, a methacryl group, an acrylic group, a ureido group, a mercapto group, a sulfide group, an isocyanate group, and a hydrolyzable silyl group. Among these, the reactive functional group is preferably a hydroxyl group, an epoxy group, a glycidyl group, an acidic group (carboxy group), an amino group, or an isocyanate group, and more preferably an epoxy group or a glycidyl group. These reactive functional groups may be used alone or in combination.

[0072] From the viewpoint of facilitating the reaction with the thermoplastic resin (A), the amount of reactive functional groups contained in the olefin polymer (C) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, relative to 100% by mass of the total amount of the olefin polymer (C). The upper limit of the amount of reactive functional groups contained in the olefin polymer (C) is not particularly limited as long as the inherent properties of the olefin polymer (C) are not impaired, but in consideration of deterioration of flowability, etc., it is preferably 40% by mass or less, more preferably 30% by mass or less.

[0073] The MFR value of the olefin polymer (C) is not particularly limited as long as it can be melt-kneaded, but the MFR value measured under conditions of 190°C and a load of 2.16 kg is preferably 0.5 g / 10 min or more and preferably 500 g / 10 min or less. By setting the MFR value of the olefin polymer (C) within the above range, better fluidity is imparted to the olefin polymer (C) when the thermoplastic resin (A) is melted, and the compatibility between the olefin polymer (C) and the thermoplastic resin (A) can be further improved. In this case, the adhesive strength can be further improved when bonding homogeneous or dissimilar materials, and the resulting bonded body can maintain a higher level of adhesive strength when left in a high-temperature, high-humidity environment.

[0074] From the viewpoint of further improving the strength and rigidity of the resulting hot melt adhesive film, the content of the olefin polymer (C) is preferably 0.5% by mass to 15% by mass, and more preferably 1% by mass to 10% by mass, relative to 100% by mass of the total amount of the resin composition.

[0075] The resin composition may further contain other additives within the range that does not impair the preferable physical properties of the resin composition.

[0076] Other additives include, for example, inorganic fillers such as calcium carbonate, mica, palygorskite, pyrophyllite, hylosite, and diatomaceous earth (excluding inorganic filler (B)); laser direct structuring additives such as MgAl2O4, ZnAl2O4, FeAl2O4, CuFe2O4, CuCr2O4, MnFe2O4, NiFe2O4, TiFe2O4, FeCr2O4, and MgCr2O4; conductive fillers such as metal non-fibrous particles (e.g., aluminum flakes), metal fibrous particles, metal oxide non-fibrous particles, carbon fibrous particles, ionic liquids, and surfactants; antistatic agents such as anionic antistatic agents, cationic antistatic agents, and nonionic antistatic agents; antioxidants or heat stabilizers such as hindered phenols, hydroquinones, phosphites, thioethers, and their substituted derivatives; Examples of suitable flame retardants include ultraviolet absorbers such as phenones and triazines; light stabilizers such as hindered phenols and hindered amines; weathering agents; light stabilizers; release agents such as higher fatty acids, higher fatty acid esters, higher fatty acid amides, higher fatty acid metal salts (here, higher fatty acids refer to those having 10 to 25 carbon atoms), fatty acids, and fatty acid metal salts; lubricants; flow improvers; plasticizers such as polyester-based plasticizers, glycerin-based plasticizers, polycarboxylic acid ester-based plasticizers, phosphate ester-based plasticizers, polyalkylene glycol-based plasticizers, and epoxy-based plasticizers; impact modifiers; flame retardants such as phosphazene-based compounds, phosphate esters, condensed phosphate esters, inorganic phosphorus-based, halogen-based, and silicone-based flame retardants, metal oxide-based flame retardants, metal hydroxide-based flame retardants, organic metal salt-based flame retardants, nitrogen-based flame retardants, and boron compound-based flame retardants; dripping inhibitors; nucleating agents; dispersants; vibration dampers; neutralizing agents; and antiblocking agents. These may be used alone or in combination of two or more.

[0077] When the resin composition contains other additives, the content thereof is not particularly limited as long as it does not impair the preferable physical properties of the resin composition. The content of other additives is preferably 10% by mass or less, more preferably 5% by mass or less, based on 100% by mass of the total amount of the resin composition.

[0078] (Method of producing resin composition) The resin composition constituting the hot melt adhesive film of the present invention can be produced by heating and mixing (particularly melt-kneading) a mixture of a thermoplastic resin (A), an inorganic filler (B), and, if necessary, other additives. For melt-kneading, a known melt-kneading device such as a twin-screw extruder can be used.

[0079] More specifically, the resin composition can be produced by a method such as (1) premixing the components in a mixer (such as a tumbler or a Henschel mixer), melt-kneading the components in a melt-kneading device, and pelletizing the components in a pelletizing means (such as a pelletizer); (2) preparing a masterbatch of the desired components, mixing other components as needed, and melt-kneading the resulting mixture in a melt-kneading device to form pellets; or (3) supplying the components to a melt-kneading device and pelletizing the resulting mixture.

[0080] The processing temperature in the melt-kneading is not particularly limited as long as it is within a temperature range in which the thermoplastic resin (A) can be melted. Usually, the cylinder temperature of the melt-kneading device used for melt-kneading is adjusted to this temperature range. In this way, a resin composition exhibiting the desired effects is produced.

[0081] (Hot melt adhesive film manufacturing method and uses) The method for producing the hot melt adhesive film of the present invention is not particularly limited, and for example, a method can be adopted in which the above-mentioned resin composition in pellet form is used to produce the film by known melt film formation such as a T-die casting method, a calendar method, or a press method.

[0082] The processing temperature in the melt film formation is not particularly limited as long as it is within the temperature range in which the resin composition can be melted. Usually, the cylinder temperature of the melt film formation device used for melt film formation is adjusted to this temperature range. In this way, a hot melt adhesive film exhibiting the desired effects is produced.

[0083] The hot melt adhesive film of the present invention can be either a stretched film or an unstretched film, but a stretched film is preferred because it prevents wrinkles and sagging due to shrinkage during heat melting, thereby further improving the appearance of the molded product. The stretching ratio of the stretched film is preferably 2 to 15 times. In this specification, the stretching ratio of the stretched film is defined as the area ratio obtained by multiplying the stretching ratio in the transverse direction by the stretching ratio in the longitudinal direction, based on the dimensions of the film emerging from the casting roll during film formation.

[0084] The hot melt adhesive film of the present invention has excellent adhesive strength when joining materials of the same type or different types, and can also suppress a decrease in adhesive strength when the resulting joined body is left in a high-temperature and high-humidity environment, so it can be suitably used in applications such as adhesives for automotive parts, adhesives for optical parts, and adhesives for building materials.

[0085] [Jointed body and method for manufacturing the same] Fig. 1 is a schematic cross-sectional view showing a bonded body according to one embodiment of the present invention. As shown in Fig. 1, the bonded body 1 includes a first member to be bonded 2, a hot-melt adhesive film 4, and a second member to be bonded 3. The first member to be bonded 2 and the second member to be bonded 3 are bonded together with the hot-melt adhesive film 4. The bonded body 1 can be produced by bonding the first member to be bonded 2 and the second member to be bonded 3 together with the hot-melt adhesive film 4.

[0086] The second member to be joined 3 is made of the same or different material as the first member to be joined 2. The materials of the first member to be joined 2 and the second member to be joined 3 are not particularly limited, but examples include metal materials, ceramics, and resin materials. Examples of metal materials include simple metals such as iron, aluminum, and magnesium, or alloys thereof. Examples of resin materials include general plastic parts and carbon fiber reinforced plastic (CFRP, CFRTP) parts, and specific preferred resin types include polyamide resin, polyphenylene sulfide resin, liquid crystal polyester resin, polybutylene terephthalate resin, polyacetal resin, polycarbonate resin, thermoplastic polyurethane resin, polypropylene resin, epoxy resin, phenolic resin, and polyimide resin.

[0087] Examples of combinations of the first member to be joined 2 and the second member to be joined 3 include a combination in which both the first member to be joined 2 and the second member to be joined 3 are metal members, a combination in which the first member to be joined 2 is a metal member and the second member to be joined 3 is a resin member, and a combination in which both the first member to be joined 2 and the second member to be joined 3 are resin members.

[0088] In the bonded body 1, the first member to be bonded 2 and the second member to be bonded 3 are bonded by the hot-melt adhesive film 4, so that the first member to be bonded 2 and the second member to be bonded 3 have high adhesive strength and can maintain a high level of adhesive strength even when the bonded body 1 is left in a high-temperature and high-humidity environment.

[0089] The bonded body 1 of this embodiment can be suitably used particularly as an adhesive for automobile parts. [Example]

[0090] The present invention will be specifically explained below based on examples and comparative examples, but the present invention is not limited thereto. The raw materials used in the examples and comparative examples are as follows.

[0091] [raw materials] (Thermoplastic resin (A)) Polyamide resin 1: Polyamide MXD10 resin, melting point 215°C, manufactured by Mitsubishi Gas Chemical Company, Inc., product name "LEXTER 8500" Polyamide resin 2: Polyamide 12 resin elastomer, melting point 164°C, manufactured by Ube Industries, product name "UBESTA 9068X1"

[0092] (Raw material inorganic filler) Potassium titanate fiber: fibrous particles, average fiber length 15 μm, average fiber diameter 0.5 μm, manufactured by Otsuka Chemical Co., Ltd., product name "Tismo N" Talc: Plate-like particles, average particle diameter (D 50 ) 13 μm, manufactured by Fuji Talc Industries Co., Ltd., product name "ML112" Sodium titanate: porous spherical particles, average particle diameter (D 50 ): 10μm~40μm

[0093] (Inorganic filler (B)) Potassium titanate fiber A; Potassium titanate fibers were charged into a Henschel mixer and subjected to a dry surface treatment with decyltrimethoxysilane (surface free energy: 28 mN / m) at a concentration of 1.0 mass% relative to the entire potassium titanate fiber, thereby obtaining potassium titanate fiber A. Potassium titanate fiber B; Potassium titanate fibers were charged into a Henschel mixer and subjected to a dry surface treatment with 3-glycidyloxypropyltrimethoxysilane (γ-glycidoxypropyltrimethoxysilane) (surface free energy: 55 mN / m) at 1.0 mass% of the total potassium titanate fibers. This resulted in potassium titanate fibers B.

[0094] Talc A; Talc was charged into a Henschel mixer and subjected to a surface treatment using a dry method so that 1.0 mass % of the talc was treated with decyltrimethoxysilane (surface free energy: 28 mN / m). Talc A was thus obtained. Talc B; Talc was charged into a Henschel mixer and subjected to a surface treatment using a dry method so that 1.0 mass % of the entire talc was treated with hexadecyltrimethoxysilane (surface free energy: 20 mN / m). Thus, Talc B was obtained. Talc C; Talc was charged into a Henschel mixer and subjected to a surface treatment using a dry method so that 1.0 mass % of the talc was treated with 3-aminopropyltrimethoxysilane (surface free energy: 68 mN / m). This produced Talc C.

[0095] (Other inorganic fillers) Untreated potassium titanate fiber; The potassium titanate fibers were used as they were without any surface treatment. Untreated talc; The talc was used as is without any surface treatment. Untreated sodium titanate; The sodium titanate was used as is without any surface treatment.

[0096] (Olefin polymer (C)) Ethylene-glycidyl methacrylate copolymer: polyolefin with reactive functional groups, MFR: 3 g / 10 min (JIS K7210 compliant, 190°C, 2.16 kg load), melting point: 105°C, reactive functional group content: 6 mass%, specific gravity: 0.93 g / cm 3 , manufactured by Sumitomo Chemical Co., Ltd., product name "Bondfast 2C"

[0097] [Raw material evaluation method] The melting point of the thermoplastic resin (A) was measured in accordance with JIS K 7121. More specifically, the melting point of the thermoplastic resin (A) was measured using a differential scanning calorimeter (manufactured by Hitachi High-Tech Science Corporation, product name "DSC7000X") by placing 10 mg of a sample in a measurement aluminum cell, raising the temperature from room temperature to 50°C at a heating rate of 10°C / min under a nitrogen gas flow of 100 ml / min, holding at 50°C for 5 minutes, and then raising the temperature to 300°C at a heating rate of 10°C / min.

[0098] The average fiber length and average fiber diameter of the fibrous inorganic filler were determined from the average values ​​of 300 randomly selected fibers measured by observation with a scanning electron microscope (SEM).

[0099] The average particle size of each raw material (D 50 ) was measured using a laser diffraction particle size distribution analyzer (Shimadzu Corporation, trade name "SALD-2100").

[0100] (Examples 1 to 5 and Comparative Examples 1 to 7) The resin composition was melt-kneaded using a twin-screw extruder at the blending ratio shown in Table 1 to produce pellets of the resin composition. The cylinder temperature of the twin-screw extruder was 240°C. The resulting pellets were dried and then extruded from a T-die (width 150 mm, thickness 0.2 mm) using a film extruder (a Labo Plastomill (manufactured by Toyo Seiki Seisakusho, model "4C150") connected to a single-screw extruder (manufactured by Toyo Seiki Seisakusho, model "D20-25", L / D=25)) at a cylinder temperature of 240°C. The molten resin composition was uniaxially stretched using a film take-up device so that the film had the desired thickness, thereby obtaining a hot-melt adhesive film. The film thickness was 100 μm.

[0101] [evaluation] (Initial adhesive strength) Two metal plates (A5052 (Al-Mg alloy), 130 mm long x 13 mm wide x 1.5 mm thick) were prepared as the members to be joined. The hot melt adhesive film prepared as described above was cut into a size of 10 mm long x 10 mm wide.

[0102] Next, a hot-melt adhesive film was sandwiched between two metal plates. The two metal plates were arranged so that only the longitudinal ends overlapped, and the area of ​​the overlapping portion (bonding area) was 15 mm long x 13 mm wide. Next, in the bonding area, the hot-melt adhesive film was fixed with clips while still positioned between the two metal plates. In this state, the temperature was raised from 30°C to 245°C over one hour, and then held at 245°C for 10 minutes to melt and bond the plates, obtaining a bonded specimen.

[0103] The resulting bonded specimens were subjected to a tensile shear test at a rate of 10 mm / min using an autograph (Shimadzu Corporation, model number "AG-I"), and the maximum stress (MPa) obtained was taken as the adhesive strength. The test was performed five times, and the average value was taken as the initial adhesive strength. The results are shown in Table 1.

[0104] (Adhesive strength after exposure to high temperature and humidity) Bonded specimens prepared in the same manner as for the evaluation of initial adhesive strength were exposed to an environment of 85°C and 85% RH for 6 hours, and then the adhesive strength after exposure to high temperature and humidity was evaluated in the same manner as for the initial adhesive strength. The adhesive strength after exposure to high temperature and humidity was also calculated by dividing the obtained adhesive strength by the initial adhesive strength to determine the rate of change in adhesive strength. The results are shown in Table 1.

[0105] [Table 1]

[0106] As is clear from Table 1, the hot melt adhesive films of Examples 1 to 5, which are composed of a resin composition containing, in addition to a thermoplastic resin (A), an inorganic filler (B) having a treatment layer composed of a hydrophobic surface treatment agent, have excellent adhesive strength (initial adhesive strength) when joining metal members together, and are also able to suppress a decrease in adhesive strength when the resulting joined body is left in a high-temperature and high-humidity environment.

[0107] On the other hand, the hot melt adhesive films of Comparative Examples 1 and 4, which were made of a resin composition containing an inorganic filler provided with a treatment layer composed of a hydrophilic surface treatment agent, had excellent adhesive strength (initial adhesive strength) when joining metal members together, but were unable to sufficiently suppress the decrease in adhesive strength when the resulting joined body was left in a high-temperature and high-humidity environment.

[0108] Furthermore, the hot-melt adhesive films of Comparative Examples 2 and 5, which were made of a resin composition containing an untreated inorganic filler, had improved adhesive strength (initial adhesive strength) compared to the hot-melt adhesive films of Comparative Examples 6 and 7, which were made of a resin composition not containing an inorganic filler, but were unable to sufficiently suppress the decrease in adhesive strength when the resulting bonded body was left in a high-temperature and high-humidity environment. However, the hot-melt adhesive film of Comparative Example 3, which was made of a resin composition containing untreated sodium titanate, showed a decrease in adhesive strength (initial adhesive strength).

[0109] In this way, in the present invention, by using a hot melt adhesive film composed of a resin composition containing a thermoplastic resin (A) and an inorganic filler (B) provided with a treatment layer composed of a hydrophobic surface treatment agent, the hot melt adhesive film has excellent adhesive strength (initial adhesive strength) when joining materials of the same type or different types, and can also suppress a decrease in adhesive strength when the resulting joined body is left in a high-temperature and high-humidity environment.

[0110] FIG. 2 is a graph showing the relationship between the heat treatment time and the adhesive strength retention rate when the bonded specimens prepared in Example 4 were heat-treated at a temperature of 100°C using a constant-temperature air-blowing dryer (manufactured by Tokyo Rikakikai Co., Ltd., product name "EYELA WFO-500"). FIG. 3 is a graph showing the relationship between the heat treatment time and the adhesive strength retention rate when the bonded specimens prepared in Example 4 were heat-treated at a temperature of 150°C using a constant-temperature air-blowing dryer (manufactured by Tokyo Rikakikai Co., Ltd., product name "EYELA WFO-500"). Note that FIGS. 2 and 3 also show the results when the thickness t of the hot-melt adhesive film was changed to 50 μm. The adhesive strength retention rate was calculated by dividing the adhesive strength after heat treatment by the initial adhesive strength.

[0111] As shown in Figures 2 and 3, it can be seen that a high adhesive strength retention rate is achieved after heat treatment when the thickness t of the hot melt adhesive film is either 100 μm or 50 μm. In particular, Figure 3 shows that when heat treatment is performed at a high temperature, a hot melt adhesive film with a thinner thickness t of 50 μm has a higher adhesive strength retention rate.

[0112] [Evaluation of injection molded products] Each material was melt-kneaded using a twin-screw extruder in the blending ratios shown in Table 2 to produce pellets. The cylinder temperature of the twin-screw extruder was 240°C. The resulting pellets were injection-molded to produce JIS test pieces. The cylinder temperature of the injection molding machine was 240°C, and the mold temperature was 120°C.

[0113] (bending strength) The bending strength of the obtained JIS test pieces was measured by a three-point bending test with a support distance of 60 mm using an autograph (manufactured by Shimadzu Corporation, model number "AG-5000") in accordance with JIS K 7271. The results are shown in Table 2 below.

[0114] (tensile strength) The tensile strength of the obtained JIS test piece was measured in accordance with JIS K 7162. The results are shown in Table 2 below.

[0115] [Table 2]

[0116] In Table 2, comparing Reference Examples 1 to 3 with Reference Example 4, the strength of the injection-molded articles is reduced by surface-treating the inorganic filler. Furthermore, the strength is reduced more in those surface-treated with a hydrophobic surface-treatment agent (Reference Examples 1 and 2) than in those treated with a hydrophilic surface-treatment agent (Reference Example 3). The strength of the injection-molded article is thought to be correlated with the internal strength of the hot-melt adhesive film, and it is presumed that surface treatment makes cohesive failure more likely to occur or does not improve adhesive strength. However, contrary to expectations, as is clear from the evaluation results of adhesive strength shown in Table 1 above, the adhesive strength of the hot-melt adhesive film is significantly improved by surface-treating the inorganic filler with a hydrophobic surface-treatment agent. [Explanation of symbols]

[0117] 1...Zygote 2...First joining target member 3...Second joining target member 4...Hot melt adhesive film

Claims

1. A hot melt adhesive film comprising a resin composition containing a thermoplastic resin (A) and an inorganic filler (B), A hot melt adhesive film, wherein a treatment layer composed of a hydrophobic surface treatment agent is provided on the surface of the inorganic filler (B).

2. 2. The hot melt adhesive film according to claim 1, wherein the thermoplastic resin (A) is a polyamide resin.

3. 3. The hot melt adhesive film according to claim 1, wherein the hydrophobic surface treatment agent has a surface free energy of 50 mN / m or less.

4. 3. The hot melt adhesive film according to claim 1, wherein the inorganic filler (B) is a fibrous particle or a non-fibrous particle.

5. 3. The hot melt adhesive film according to claim 1, wherein the content of the inorganic filler (B) is 0.5% by mass or more and 50% by mass or less, based on 100% by mass of the total amount of components contained in the resin composition.

6. 3. The hot melt adhesive film according to claim 1, wherein the hydrophobic surface treatment agent is an alkoxysilane represented by the following general formula (I): R １ ｎ Si(OR ２ ) ４－ｎ … Formula (I) [In general formula (I), n represents an integer selected from 1 to 3, and R １ represents an alkyl group, an alkenyl group, or an aryl group; R ２ represents an alkyl group.]

7. 3. The hot melt adhesive film according to claim 1, wherein the thickness of the hot melt adhesive film is 10 μm or more and 300 μm or less.

8. A joined body in which a first joining target member and a second joining target member made of the same material as or a different material from the first joining target member are joined by the hot melt adhesive film according to claim 1 or 2.

9. A step of preparing a first member to be joined and a second member to be joined, the second member being made of the same material as or a different material from the first member to be joined; A step of joining the first joining target member and the second joining target member using the hot melt adhesive film according to claim 1 or 2; A method for manufacturing a bonded body, comprising:

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