Method for manufacturing bonded body

Abstract

Provided is a method for producing a bonded body, which is capable of producing a bonded body having a short bonding process time, a long opening time, and excellent bonding properties. A method for producing a bonded body in which a metal base material A, a film comprising an amorphous thermoplastic resin, and a metal base material B are bonded in this order, the amorphous thermoplastic resin being at least one type selected from the group consisting of thermoplastic epoxy resins and phenoxy resins, the method comprising a first bonding step and a second bonding step, a first bonding step in which the metal base material (A) and the film are bonded by melting and then solidifying the film in a state in which the film and the metal base material (A) are in surface contact; and a second bonding step for bonding the metal base material A and the metal base material B by melting and then curing the film in a state in which the film bonded to the metal base material A is in surface contact with the metal base material B. The amorphous thermoplastic resin has an epoxy equivalent of 1,600 g / eq or more or does not contain an epoxy group, and has a heat of fusion of 15 J / g or less.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a bonded body, which is suitable for applications that can firmly bond different types of metal materials. Background Art

[0002] In recent years, from the perspectives of weight reduction and high performance of products, in various fields such as automotive parts, medical devices, and home appliances, the multi-materialization of components has been promoted. Multi-materialization refers to a method of achieving weight reduction and high strength of materials by using materials with different functions and materials (hereinafter referred to as dissimilar materials). In order to achieve multi-materialization, a technology for firmly bonding dissimilar materials is indispensable.

[0003] As a means for firmly bonding dissimilar materials, thermosetting epoxy resin adhesives (Patent Document 1, etc.), which are liquid adhesives, have been widely used.

[0004] Bonding using a liquid adhesive requires a coating process for coating a liquid resin composition and a curing process for polymerizing and curing the resin composition after coating.

[0005] Therefore, in the case of bonding using a liquid adhesive, it takes time to coat the resin composition in the coating process, and it takes time to carry out the polymerization reaction in the curing process (that is, the bonding process time is long), and there is a problem of lack of convenience.

[0006] In the present specification, the bonding process time refers to the time from the start point when at least one base material constituting the bonded body comes into contact with the film to the end point when the bonded body is completed. For example, it includes the process of placing the base material on the film and the time required to bond the base materials to each other (for example, curing the film).

[0007] In addition, a technique for manufacturing a bonded body by impregnating or coating a base material with an epoxy resin composition and then semi-curing (B-staging) it to form a laminate with a B-stage adhesive layer has also been disclosed (Patent Document 2, etc.).

[0008] However, bonding using a B-stage adhesive also requires a curing process for polymerizing and curing the semi-cured adhesive layer, and there is a problem of a long bonding process time.

[0009] In addition, the storage stability of the B-stage adhesive is poor, and it cannot be stored at room temperature for a long time. It needs to be stored at a low temperature, and there are problems of a short open time and lack of convenience.

[0010] In this specification, the open time refers to the limited time from when the bonding agent is coated or placed on the metal substrate A until the metal substrate B is placed. If within the open time, the adhesive force of the bonding agent does not decrease, and the metal substrate A and the metal substrate B can be bonded with sufficient adhesive force. The longer the open time, the longer the limited time from when the bonding agent is coated or placed on the metal substrate A until the metal substrate B is placed, and the higher the convenience.

[0011] As a means for bonding dissimilar materials, a thermoplastic adhesive composition (hereinafter referred to as hot melt adhesive) is also used (Patent Document 3, etc.). By using a hot melt adhesive, specifically, since the hot melt adhesive is an adhesive that bonds by a phase change without a polymerization reaction, there is no need for a coating process, the curing time is fast (that is, the bonding process time is short), and the convenience is excellent. In addition, it can be stored at room temperature for a long time, and the convenience is also excellent in terms of the long open time.

[0012] However, as a conventional hot melt adhesive, it is formed of a crystalline resin or a resin containing a crystalline resin in order to reduce the melt viscosity. Therefore, the cohesive force in the adhesive resin is high, and there is no sufficient interaction with the substrate. In addition, when performing melt bonding, it becomes low viscosity at high temperature and easily flows out from the bonding surface, and it is difficult to control the viscosity. Therefore, the film thickness is unstable. Due to these factors, there is a problem that a high adhesive force cannot be stably obtained with the existing hot melt adhesives.

[0013] Prior Art Documents

[0014] Patent Documents

[0015] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-157018

[0016] Patent Document 2: Japanese Unexamined Patent Application Publication No. 10-17685

[0017] Patent Document 3: Japanese Unexamined Patent Application Publication No. 10-168417 Summary of the Invention

[0018] Problems to be Solved by the Invention

[0019] The present invention has been completed in view of the above technical background, and an object thereof is to provide a method for manufacturing a bonded body that is suitable for use in manufacturing a bonded body that firmly bonds even different types of metal materials, and the method has a short bonding process time, a long open time, and can manufacture a bonded body with excellent bondability.

[0020] Means for Solving the Problems

[0021] The present inventors have conducted in-depth research and as a result, found that the above problems can be solved by having a first bonding step and a second bonding step. The first bonding step is to bond the metal substrate A and the film by melting and then solidifying the film in a state where a specified film is in surface contact with the metal substrate A. The second bonding step is to bond the metal substrate A and the metal substrate B by melting and then solidifying the film in a state where the film bonded to the metal substrate A is in surface contact with the metal substrate B. The present invention has been completed based on this finding.

[0022] That is, the present invention provides the following [1] to [5].

[0023] [1] A method for manufacturing a bonded body, wherein the bonded body is formed by sequentially bonding a metal substrate A, a film containing an amorphous thermoplastic resin, and a metal substrate B, and the amorphous thermoplastic resin is at least one selected from a thermoplastic epoxy resin and a phenoxy resin;

[0024] This method has a first bonding step and a second bonding step,

[0025] The first bonding step: In a state where the film is in surface contact with the metal substrate A, the film is melted and then solidified, thereby bonding the metal substrate A and the film;

[0026] The second bonding step: In a state where the film bonded to the metal substrate A is in surface contact with the metal substrate B, the film is melted and then solidified, thereby bonding the metal substrate A and the metal substrate B;

[0027] The epoxy equivalent of the amorphous thermoplastic resin is 1,600 g / eq. or more or does not contain an epoxy group, and the heat of fusion is 15 J / g or less.

[0028] [2] The method for manufacturing a bonded body according to [1], wherein in the first bonding step, the film is melted and then solidified at a bonding temperature of 100 to 300 °C.

[0029] [3] The method for manufacturing a bonded body according to [1] or [2], wherein in the second bonding step, the film is melted and then solidified by at least one selected from contact heating, hot air heating, hot pressing, infrared heating, hot plate welding, ultrasonic welding, vibration welding, and high-frequency induction welding.

[0030] [4] The method for manufacturing a bonded body according to any one of [1] to [3], wherein in the second bonding step, the film is melted and then solidified at a temperature above the melting point of the film.

[0031] [5]According to the method for manufacturing a bonded body according to any one of [1] to [3], in the second bonding step, the film is melted and then solidified under a heating temperature of 100 to 400 °C and a pressure of 0.01 to 20 MPa.

[0032] Advantages of the Invention

[0033] According to the present invention, a method for manufacturing a bonded body can be provided, which has a short bonding process time, a long open time, and can manufacture a bonded body with excellent bondability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is an explanatory view showing the structure of a bonded body according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Hereinafter, embodiments of the present invention will be described in detail.

[0036] In this specification, "bonding" means connecting an object to an object, and "adhesion" and "welding" are subordinate concepts thereof. "Adhesion" means forming a bonded state between two adherends (materials to be adhered) by means of an organic material such as a tape or an adhesive (thermosetting resin, thermoplastic resin, etc.). "Welding" means melting the surface of a thermoplastic resin or the like by heat and cooling it, thereby forming a bonded state by entanglement based on molecular diffusion.

[0037] [Method for Manufacturing a Bonded Body]

[0038] The method for manufacturing a bonded body according to this embodiment is a method for manufacturing a bonded body formed by sequentially bonding a metal substrate A, a film containing an amorphous thermoplastic resin, and a metal substrate B. The amorphous thermoplastic resin is at least one selected from a thermoplastic epoxy resin and a phenoxy resin. The method includes a first bonding step and a second bonding step. In the first bonding step, the film is melted and then solidified in a state where the film is in surface contact with the metal substrate A, thereby bonding the metal substrate A and the film. In the second bonding step, the film bonded to the metal substrate A is melted and then solidified in a state where the film is in surface contact with the metal substrate B, thereby bonding the metal substrate A and the metal substrate B. Moreover, the metal material A is at least one of a metal and an inorganic substance, the epoxy equivalent of the amorphous thermoplastic resin is 1,600 g / eq. or more or does not contain an epoxy group, and the heat of fusion is 15 J / g or less.

[0039] The film preferably contains 50% by mass or more of a resin component, more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0040] When using this manufacturing method, the bonding of the metal substrate A and the metal substrate B utilizes the phase change (solid state - liquid state - solid state) of a film containing an amorphous thermoplastic resin selected from at least one of a thermoplastic epoxy resin and a phenoxy resin, without chemical reactions. Therefore, compared with conventional thermosetting epoxy resins, the bonding can be completed in a short time, and the open time is also long.

[0041] In addition, the thermoplastic epoxy resin and phenoxy resin contained in the film have low cohesive force within the resin and have hydroxyl groups, so they have a strong interaction with the substrate and can bond dissimilar materials with a higher bonding force than conventional crystalline hot melt adhesives.

[0042] In addition, in this manufacturing method, the process is divided into a first bonding process and a second bonding process for bonding. By separating in this way, bonding can be carried out at a temperature suitable for the bonding interface, and a bonded body with excellent bondability can be manufactured. In addition, compared with the case where the process is not separated, the control of the heating temperature becomes easier. Moreover, by pre-bonding the film on the metal substrate A, the metal substrate A and the metal substrate B can be bonded with high precision, and the generation of deviation at the bonding part can be suppressed.

[0043] <First bonding process>

[0044] The first bonding process is a process of bonding the metal substrate A and the film by melting and then curing the film in a state where the film is in surface contact with the metal substrate A.

[0045] In the first bonding process, by pre-bonding the metal substrate A and the film, the metal substrate A and the metal substrate B can be bonded with good precision.

[0046] It should be noted that in this specification, "curing" means being solid at normal temperature, that is, having no fluidity in the unpressurized state at 23°C. However, the film after the first bonding process may also have viscosity.

[0047] As a method for melting the film, at least one method selected from contact heating, hot air heating, hot pressing, hot plate welding, infrared heating, ultrasonic welding, vibration welding, and high-frequency induction welding can be cited. Among them, infrared heating is preferred in terms of manufacturing ease and shortening the bonding process.

[0048] When melting the film by heating, it is preferably melted at a temperature of 100 - 300°C, more preferably 120 - 250°C, and further preferably 150°C - 220°C for the temperature of the bonding surface between the metal substrate A and the film. By setting the temperature to 100 - 300°C, the film deforms and melts efficiently, wets and spreads effectively at the bonding surface, and thus a high bonding force can be obtained.

[0049] As a method for curing the molten film, a method of natural cooling at room temperature or a method of natural cooling using a cooling device can be cited. It should be noted that "room temperature" refers to the normal room temperature within the range of 5 to 30°C. Among them, from the aspect of manufacturing ease, a method of natural cooling at room temperature is preferred.

[0050] (film)

[0051] The film contains an amorphous thermoplastic resin, which is at least one selected from a thermoplastic epoxy resin and a phenoxy resin, and has an epoxy equivalent of 1600 or more and a heat of fusion of 15 J / g or less.

[0052] It should be noted that in this specification, "film" refers to a sheet having a thickness of 10 μm to 3 mm.

[0053] In addition, the amorphous thermoplastic resin in this embodiment refers to a resin having a heat of fusion of 15 J / g or less in the measurement using a differential scanning calorimeter (DSC). However, it also includes cases where the endothermic peak accompanying melting is below the detection limit or indistinguishable from the noise.

[0054] The heat of fusion is calculated from the area of the endothermic peak of the DSC (differential scanning calorimeter) and the weight of the thermoplastic resin component. In the case where an inorganic filler or the like is contained in the film, it is calculated from the weight of the thermoplastic resin component after removing the inorganic filler. Specifically, 2 - 10 mg of the sample can be weighed, placed in an aluminum pan, and heated from 23°C to 200°C or higher at 10°C / min using a DSC (DSC8231 manufactured by Rigaku Corporation) to obtain a DSC curve, and then calculated based on the area of the endothermic peak during melting obtained from this DSC curve and the above-mentioned weighed value.

[0055] From the aspect of fully imparting the characteristics of the amorphous thermoplastic resin to the film, for the content of the above-mentioned amorphous thermoplastic resin, it is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and most preferably 90% by mass or more in the resin component of the film.

[0056] The heat of fusion of the amorphous thermoplastic resin is 15 J / g or less, preferably 11 J / g or less, more preferably 7 J / g or less, further preferably 4 J / g or less, and most preferably the melting peak is below the detection limit.

[0057] The epoxy equivalent of the amorphous thermoplastic resin is 1,600 or more, preferably 2,000 or more, more preferably 5,000 or more, further preferably 9,000 or more, and most preferably above the detection limit and substantially no epoxy groups can be detected. It should be noted that the epoxy equivalent being above the detection limit means that no epoxy groups are detected when measuring the epoxy equivalent based on JIS K 7236:2001 described later.

[0058] By using a film containing an amorphous thermoplastic resin with an epoxy equivalent of 1600 or more and a heat of fusion of 15 J / g or less, the viscosity does not sharply decrease as in conventional hot melt adhesives during heating, and even in a high temperature region exceeding 200°C, it does not reach a low viscosity (0.001 to 100 Pa·s) state. Therefore, even in a molten state, the film does not flow out of the laminate, and the thickness of the bonding layer formed by curing after melting of the film can be stably ensured, and a high bonding strength can be stably obtained.

[0059] The epoxy equivalent (the weight of the above thermoplastic resin containing 1 mole of epoxy groups) mentioned here is the value of the epoxy equivalent of the thermoplastic resin contained in the film before bonding, and is a value measured by the method specified in JIS-K7236:2001 (unit "g / eq."). Specifically, using a potentiometric titration device, adding a tetraethylammonium bromide acetic acid solution, using a 0.1 mol / L perchloric acid - acetic acid solution, the solvent diluent (resin varnish) is a value obtained by calculating the solid content conversion value from the non-volatile components. It should be noted that in the case of a mixture of two or more resins, it can also be calculated from their respective contents and epoxy equivalents.

[0060] When the amorphous thermoplastic resin contained in the film has a melting point, the melting point is preferably 50 to 400°C, more preferably 60°C to 350°C, and further preferably 70°C to 300°C. By making the melting point within the range of 50 to 400°C, the above film is efficiently deformed and melted by heating, and wets and spreads effectively on the bonding surface, so a high bonding strength can be obtained.

[0061] In this specification, the melting point of the thermoplastic resin refers to the melting peak temperature measured by DSC. It should be noted that in the case where a melting peak cannot be obtained and the heat of fusion is 15 J / g or less, the temperature obtained by adding 70°C to the glass transition temperature is used as the melting point. The glass transition temperature refers to the temperature at the start of the decline of the DSC curve in the second cycle when heated to 200°C after cooling to 40°C or less after heating to 200°C by DSC. Specifically, it is a value measured by the method described in the examples.

[0062] In the case of conventional thermosetting adhesives, it is difficult to disassemble the bonded body, and it is difficult to separate and recycle the dissimilar materials constituting the bonded body (i.e., poor recyclability). In addition, in the case where there is a shift in the bonding part during the manufacturing process of the bonded body, and in the case where the content or the adherend has a defect and needs to be replaced, there are problems such as difficulty in re-bonding (i.e., poor reparability) and lack of convenience. However, the above-mentioned film can be softened and melted by heat and can be easily peeled off, so the recyclability is excellent. In addition, since the above-mentioned film is thermoplastic, it can be reversibly softened, melted, and cured repeatedly, and the reparability is also excellent.

[0063] "Thermoplastic Epoxy Resin"

[0064] The thermoplastic epoxy resin is preferably a polymer of (a) a bifunctional epoxy resin monomer or oligomer and (b) a bifunctional compound having two identical or different functional groups selected from a phenolic hydroxyl group, a carboxyl group, a mercapto group, an isocyanate group, and a cyanate group.

[0065] By using this compound, the polymerization reaction to form a linear polymer proceeds preferentially, and a thermoplastic epoxy resin having desired properties can be obtained.

[0066] The above-mentioned (a) bifunctional epoxy resin monomer or oligomer refers to an epoxy resin monomer or oligomer having two epoxy groups in the molecule.

[0067] As specific examples of the above (a), for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bifunctional phenol novolac type epoxy resin, bisphenol AD type epoxy resin, biphenyl type epoxy resin, bifunctional naphthalene type epoxy resin, bifunctional alicyclic epoxy resin, bifunctional glycidyl ester type epoxy resin (such as diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl dimer acid, etc.), bifunctional glycidyl amine type epoxy resin (such as diglycidyl aniline, diglycidyl toluidine, etc.), bifunctional heterocyclic epoxy resin, bifunctional diaryl sulfone type epoxy resin, hydroquinone type epoxy resin (such as hydroquinone diglycidyl ether, 2,5 - di - tert - butyl hydroquinone diglycidyl ether, resorcinol diglycidyl ether, etc.), bifunctional alkylene glycidyl ether compounds (such as butanediol diglycidyl ether, butenediol diglycidyl ether, butynediol diglycidyl ether, etc.), bifunctional glycidyl - containing hydantoin compounds (such as 1,3 - diglycidyl - 5,5 - dialkyl hydantoin, 1 - glycidyl - 3 - (epoxypropoxyalkyl) - 5,5 - dialkyl hydantoin, etc.), bifunctional glycidyl - containing siloxanes (such as 1,3 - bis(3 - epoxypropoxypropyl) - 1,1,3,3 - tetramethyldisiloxane, α,β - bis(3 - epoxypropoxypropyl) polydimethylsiloxane, etc.) and their modified products. Among them, from the aspects of reactivity and operability, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and biphenyl type epoxy resin are preferred.

[0068] As the bifunctional compound having a phenolic hydroxyl group of the above (b), for example, mononuclear aromatic dihydroxy compounds having one benzene ring such as catechol, resorcinol, hydroquinone, etc., bisphenols such as bis(4 - hydroxyphenyl) propane (bisphenol A), bis(4 - hydroxyphenyl) methane (bisphenol F), bis(4 - hydroxyphenyl) ethane (bisphenol AD), etc., compounds having a condensed ring such as dihydroxynaphthalene, bifunctional phenolic compounds having an allyl group introduced such as diallyl resorcinol, diallyl bisphenol A, triallyl dihydroxybiphenyl, etc., dibutyl bisphenol A, etc.

[0069] As specific examples of the carboxyl - containing compound of the above (b), for example, adipic acid, succinic acid, malonic acid, cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, and terephthalic acid, etc.

[0070] As the bifunctional compound having a mercapto group of the above (b), for example, ethylene glycol bis(mercaptoacetate), ethylene glycol bis(mercaptopropionate), etc.

[0071] Specific examples of the isocyanate group-containing bifunctional compound in (b) above include diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HMDI), toluene diisocyanate (TDI), and the like.

[0072] Specific examples of the cyanate group-containing bifunctional compound in (b) above include 2,2-bis(4-cyanatophenyl)propane, 1,1-bis(4-cyanatophenyl)ethane, bis(4-cyanatophenyl)methane, and the like.

[0073] In (b) above, from the viewpoint of obtaining a thermoplastic polymer, a bifunctional compound having a phenolic hydroxyl group is preferred. From the viewpoints of heat resistance and bonding properties, a bifunctional compound having two phenolic hydroxyl groups and having a bisphenol structure or a biphenyl structure is preferred. From the viewpoints of heat resistance and cost, bisphenol A, bisphenol F, or bisphenol S is preferred.

[0074] When (a) above is bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, or biphenyl type epoxy resin, and (b) above is bisphenol A, bisphenol F, or bisphenol S, the polymer obtained by the polymerization of (a) and (b) has a main chain formed by connecting p-phenylene structures and ether bonds with an alkylene group and hydroxyl groups generated by addition polymerization arranged on the side chains.

[0075] The linear structure composed of a p-phenylene skeleton can improve the mechanical strength of the polymer after polymerization, and the hydroxyl groups arranged on the side chains can improve the adhesion to the substrate. As a result, high bonding strength can be achieved while maintaining the workability of the thermosetting resin. Furthermore, in the case of a thermoplastic resin, it can be recycled and repaired by heating to soften and melt it, and the recyclability and reparability, which are problems of thermosetting resins, can be improved.

[0076] 《Phenoxy Resin》

[0077] Phenoxy resin is a polyhydroxy polyether synthesized from bisphenols and epichlorohydrin and has thermoplasticity. In the manufacture of phenoxy resin, a method using the direct reaction of a diphenol with epichlorohydrin and a method using the addition polymerization reaction of a diglycidyl ether of a diphenol with a diphenol are known, and the phenoxy resin used in the present invention can be obtained by any manufacturing method. In the case of the direct reaction of a diphenol with epichlorohydrin, examples of the diphenol include phenols such as bisphenol A, bisphenol F, bisphenol S, biphenol, biphenylenediol, fluorene diphenyl; aliphatic diols such as ethylene glycol, propylene glycol, and diethylene glycol. Among them, from the viewpoints of cost, bonding properties, viscosity, and heat resistance, bisphenol A, bisphenol F, and bisphenol S are preferred. They can be used alone or in combination of two or more.

[0078] The phenoxy resin has a chemical structure similar to that of the epoxy resin, having a main chain formed by connecting p-phenylene structures and ether bonds as the main skeleton and hydroxyl groups arranged on the main chain and side chains.

[0079] "Physical Properties of Thermoplastic Epoxy Resin and Phenoxy Resin"

[0080] For the above-mentioned thermoplastic epoxy resin and phenoxy resin, the weight-average molecular weight in terms of polystyrene obtained by GPC (gel permeation chromatography) measurement is preferably 10,000 to 500,000, more preferably 18,000 to 300,000, and further preferably 20,000 to 200,000. The weight-average molecular weight is calculated from the elution peak position detected by GPC and is a molecular weight value converted by standard polystyrene. If the weight-average molecular weight is within this range, the balance between thermoplasticity and heat resistance is good, and a bonded body can be efficiently obtained by melting, and its heat resistance is also increased. If the weight-average molecular weight is 10,000 or more, the heat resistance is excellent, and if the weight-average molecular weight is 500,000 or less, the viscosity during melting is low and the bonding property is increased.

[0081] "Components Other than the Resin Component in the Membrane"

[0082] As needed, the membrane may contain fillers and additives as components other than the resin component within the range that does not hinder the purpose of the present invention, or may not contain them.

[0083] Examples of the filler include inorganic fillers and organic fillers (resin powders).

[0084] Examples of the inorganic filler include, for example, spherical fused silica, metal powders of metals such as iron, silica sand, talc, calcium carbonate, mica, acid clay, diatomaceous earth, kaolin, quartz, titanium oxide, silica, phenolic resin microspheres, glass spheres, etc.

[0085] When the membrane contains a filler, the content of the filler in 100% by volume of the total amount of the membrane is preferably 50% by volume or less, more preferably 30% by volume or less, further preferably 20% by volume or less, and most preferably 10% by volume or less. It should be noted that the volume of the filler can be obtained by dividing the weight of the filler contained in the membrane by the true specific gravity of the filler.

[0086] The content of the resin component in 100% by volume of the total amount of the membrane is preferably 10% by volume or more, more preferably 20% by volume or more, further preferably 30% by volume or more, still more preferably 50% by volume or more, 80% by volume or more in one embodiment, 90% by volume or more in another embodiment, and 99% by volume or more in yet another embodiment.

[0087] Examples of the additive include defoamers, coupling agents such as silane coupling agents, pigments, etc., and one or more of them may be contained.

[0088] The content of the additive in the film is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 1% by mass or less.

[0089] The content of the resin component in the film is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, still more preferably 50% by mass or more, in one embodiment 80% by mass or more, in another embodiment 90% by mass or more, and in yet another embodiment 99% by mass or more.

[0090] "Morphology of the Film"

[0091] The film is a sheet having a thickness of 10 μm to 3 mm.

[0092] From the viewpoint of obtaining a bonded body with excellent bondability in a short bonding process time, the thickness of the film is preferably 1 mm or less, more preferably 0.5 mm or less, further preferably 0.3 mm or less, still more preferably 0.2 mm or less, and most preferably 0.1 mm or less.

[0093] If the size is within this range, it can be sandwiched between the metal substrate A and the metal substrate B, and can be efficiently expanded on the bonding surface by heating, pressing, etc., and a high bonding force can be obtained.

[0094] The film may be a single layer or a laminate including multiple layers, and is preferably a single layer from the viewpoints of ease of manufacture and improvement of the bonding force.

[0095] In addition, the film may have adhesiveness within the range that does not hinder the bonding force and its heat resistance.

[0096] "Method for Manufacturing the Film"

[0097] The method for manufacturing the film is not particularly limited. For example, a resin composition can be obtained by heating and polymerizing a monomer or oligomer of a bifunctional epoxy compound, a solvent is added to the obtained resin composition as needed, coated on a release film, etc., cured, dried, and pressed as needed to obtain the film.

[0098] <Second Bonding Process>

[0099] The second bonding process is a process of bonding the metal substrate A and the metal substrate B by melting and then curing the film that has been bonded to the metal substrate A in a state where the film is in surface contact with the metal substrate B.

[0100] From the perspective of obtaining a high bonding strength, in the second bonding process, it is preferable to melt and then solidify the film at a temperature above the melting point of the film.

[0101] As a method for melting the above-mentioned film, at least one method selected from contact heating, hot air heating, hot pressing, infrared heating, hot plate welding, ultrasonic welding, vibration welding, and high-frequency induction welding can be cited. Among them, hot pressing, ultrasonic welding, and high-frequency induction welding are preferable.

[0102] There are no particular restrictions on the conditions for hot pressing.

[0103] For example, the temperature is preferably 100 to 400 °C, more preferably 120 to 350 °C, and further preferably 150 °C to 300 °C. By heating at 100 to 400 °C, the above-mentioned film deforms and melts efficiently, and wets and spreads effectively on the bonding surface, so a high bonding strength can be obtained.

[0104] The pressing force in the above-mentioned hot pressing is preferably 0.01 to 20 MPa, more preferably 0.1 to 10 MPa, and further preferably 0.2 to 5 MPa. If it is within this pressure range, the above-mentioned film deforms efficiently, and wets and spreads effectively on the bonding surface, so a high bonding strength can be obtained.

[0105] There are no particular restrictions on the conditions for ultrasonic welding.

[0106] For example, the emission frequency is preferably 10 to 70 kHz, more preferably 15 to 40 kHz.

[0107] From the perspectives of adhesiveness and appearance, the ultrasonic application time is preferably 0.1 to 3 seconds, more preferably 0.2 to 2 seconds.

[0108] When pressurizing the metal substrate A and the metal substrate B during the application of ultrasonic waves, the applied pressure is preferably 0.01 to 20 MPa, more preferably 0.1 to 10 MPa, and further preferably 0.2 to 5 MPa. If it is within this pressure range, the above-mentioned solid-state bonding agent deforms efficiently, and wets and spreads effectively on the bonding surface, so a high adhesive strength can be obtained.

[0109] There are no particular restrictions on the conditions for ultrasonic welding.

[0110] For example, the oscillation frequency can be in the range of 1 to 1500 kHz. It is only necessary to adjust it to an appropriate oscillation frequency according to the sizes and types of the metal substrate A and the metal substrate B.

[0111] The output power can be in the range of 100 to 5000 W.

[0112] The oscillation time can be adjusted according to the sizes and types of the metal substrates A and B, and is preferably 1.0 to 10.0 seconds, more preferably 1.5 to 8.0 seconds.

[0113] As described above, the bonding between the metal substrate A and the metal substrate B utilizes the phase change of the film (solid state - liquid state - solid state) and does not involve chemical reactions. Therefore, compared with conventional thermosetting epoxy resins, the bonding can be completed in a short time.

[0114] [Bonded body]

[0115] Figure 1 An embodiment of the bonded body of the present invention is shown. Figure 1 The shown bonded body 1 is formed by bonding the metal substrate A (3) and the metal substrate B (4) together with a bonding layer 2. The bonding layer 2 is formed by melting and solidifying a film composed of an amorphous thermoplastic resin, and the amorphous thermoplastic resin is at least one selected from thermoplastic epoxy resins and phenoxy resins. For the bonded body of the present invention, even a bonded body of dissimilar materials shows excellent bonding strength. For the bonding strength, in addition to the strength of the interfacial interaction acting between the bonding layer and the metal substrate A and between the bonding layer and the metal substrate B, it is also affected by various factors such as the thickness of the bonding layer, the molecular weight, chemical structure, mechanical properties, and viscoelastic properties of the polymer constituting the film. Therefore, the detailed mechanism by which the bonded body of the present invention shows excellent bonding strength is not clear, but it is speculated that the main reason is that the cohesive force in the amorphous thermoplastic resin constituting the bonding layer 2 is low, and there are hydroxyl groups in the resin, forming chemical bonds and intermolecular forces such as hydrogen bonds and van der Waals forces at the interfaces between the bonding layer and the metal substrate A and between the bonding layer and the metal substrate B. However, in the above-mentioned bonded body, the state or characteristics of the interface of the bonded body are extremely thin chemical structures below the nanoscale and are difficult to analyze. At the current technical level, it is impossible or impractical to determine the mechanism so as to distinguish it from the case where the use of the film is not relied on and express it.

[0116] The recyclability and reparability of the bonded body of the present invention in which the bonding layer is composed of a thermoplastic resin are excellent, and by heating the bonded body, it can be easily disassembled into the metal substrate A and the metal substrate B.

[0117] (Metal substrate A, Metal substrate B)

[0118] The present invention is suitable for applications where different types of metal substrates are firmly bonded, but the combination of the metal substrate A and the metal substrate B is not particularly limited. It can also be applied to the bonding of the same type of metal substrates.

[0119] The metals constituting the metal substrates A and B are not particularly limited. For example, iron, aluminum, copper, magnesium, titanium, etc. can be cited. Among them, considering light weight and ease of processing, etc., aluminum and copper are particularly preferably used. It should be noted that in the present invention, the term "aluminum" is used in the sense of including aluminum and its alloys. Similarly, iron, copper, aluminum, magnesium, and titanium are also used in the sense of including their simple substances and their alloys (such as stainless steel, duralumin, etc.).

[0120] The shapes of the metal substrates A and B are also not particularly limited. The thickness of each is preferably 0.1 mm or more, more preferably 0.3 mm or more, further preferably 0.5 mm or more, and particularly preferably 1 mm or more. If it is 0.1 mm or more, a firm joined body can be obtained. The thickness of each of the metal substrates A and B is preferably 10 mm or less, more preferably 8 mm or less, further preferably 6 mm or less, and particularly preferably 4 mm or less. If it is 10 mm or less, it is easy to heat effectively and the manufacturing becomes easy.

[0121] (Pretreatment)

[0122] For the metal substrates A and B, it is preferred to perform a pretreatment on the surface for the purpose of removing surface contaminants and / or achieving an anchoring effect.

[0123] As the pretreatment, for example, degreasing treatment, UV ozone treatment, sandblasting treatment, polishing treatment, plasma treatment, corona discharge treatment, laser treatment, etching treatment, flame treatment, etc. can be cited.

[0124] As the pretreatment, it is preferred to perform a pretreatment for cleaning the surface of the substrate or a pretreatment for imparting irregularities to the surface. Specifically, when the substrate contains aluminum, glass, ceramic or iron, it is preferably at least one selected from degreasing treatment, UV ozone treatment, sandblasting treatment, polishing treatment, plasma treatment, and etching treatment; when the substrate contains FRP, polypropylene, polycarbonate, polymethyl methacrylate, polyetherimide, polyamide or polybutylene terephthalate, it is preferably at least one selected from degreasing treatment, UV ozone treatment, sandblasting treatment, polishing treatment, plasma treatment, and corona discharge treatment.

[0125] The pretreatment can be only one kind, or two or more kinds can be implemented. As specific methods of these pretreatments, known methods can be used.

[0126] It is generally considered that hydroxyl groups from the resin and reinforcing material exist on the surface of FRP, and hydroxyl groups originally exist on the surfaces of glass and ceramic, but new hydroxyl groups are generated through the above-mentioned pretreatment, and the hydroxyl groups on the substrate surface can be increased.

[0127] The above degreasing treatment refers to a method of dissolving and removing dirt such as grease on the surface of the substrate with organic solvents such as acetone and toluene.

[0128] The above UV ozone treatment refers to a method of cleaning or modifying the surface with the energy of short-wavelength ultraviolet rays emitted by a low-pressure mercury lamp and the power of ozone (O3) generated therefrom. In the case of glass, it becomes one of the surface cleaning methods for removing organic impurities on the surface. Usually, a surface cleaning and modification device using a low-pressure mercury lamp is called a "UV ozone cleaner", "UV cleaning device", "ultraviolet surface modification device", etc.

[0129] As the above sandblasting treatment, for example, wet sandblasting treatment, shot peening treatment, sandblasting treatment, etc. can be cited. Among them, the wet sandblasting treatment can obtain a denser surface compared with the dry sandblasting treatment, so it is preferred.

[0130] As the above grinding treatment, for example, polishing using a polishing cloth, roll grinding using abrasive paper (sandpaper), electrolytic grinding, etc. can be cited.

[0131] The above plasma treatment refers to a method of making a plasma beam with a high-voltage power supply and a rod, making it collide with the surface of the raw material, exciting the molecules to a functional state, and for example, an atmospheric pressure plasma treatment method capable of imparting hydroxyl groups and polar groups to the surface of the raw material can be cited.

[0132] The above corona discharge treatment can be cited as a method for surface modification of a polymer film, which is a method of generating hydroxyl groups and polar groups on the surface starting from free radicals generated by cutting the main chain and side chain of the polymer surface layer by electrons released from the electrode.

[0133] The above laser treatment is a technique for improving surface characteristics by rapidly heating and cooling only the surface of the substrate by laser irradiation, and is an effective method for roughening the surface. Known laser treatment techniques can be used.

[0134] As the above etching treatment, for example, chemical etching treatments such as an alkali method, a phosphoric acid-sulfuric acid method, a fluoride method, a chromic acid-sulfuric acid method, a ferric chloride method, and an electrochemical etching treatment such as an electrolytic etching method can be cited.

[0135] The above flame treatment refers to a method of making the oxygen in the air plasma by burning a mixed gas of a combustion gas and air, applying oxygen plasma to the object to be treated, and thereby achieving surface hydrophilization. Known flame treatment techniques can be used.

[0136] Examples

[0137] Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

[0138] [Manufacture of the film]

[0139] [Production Example 1]

[0140] Into a reaction apparatus equipped with a stirrer, a reflux condenser, a gas inlet tube, and a thermometer, 1.0 equivalent (203 g) of jER (registered trademark) 1007 (manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, weight average molecular weight of about 10,000), 1.0 equivalent (12.5 g) of bisphenol S, 2.4 g of triphenylphosphine, and 1,000 g of methyl ethyl ketone were added. While stirring, the temperature was raised to 100 °C under a nitrogen atmosphere. After visually confirming dissolution, it was cooled to 40 °C to obtain a resin composition having a solid content of about 20% by mass. The solvent was removed therefrom to obtain a solid. A non-stick fluororesin film (Nitoflon (registered trademark) No. 900UL, manufactured by Nitto Denko Corporation) was set on the upper and lower plates of a press. After placing the above solid on the non-stick fluororesin film on the lower plate, the above press was heated to 160 °C, and the above resin composition was heated and compressed for 2 hours to obtain a film P-1 having a solid content of 100% by mass and a thickness of 100 μm. The measurement results of the weight average molecular weight, epoxy equivalent, melting point, and heat of fusion of the obtained film P-1 are shown in Table 1. It should be noted that for the measurement of the weight average molecular weight, the obtained film was dissolved in tetrahydrofuran for measurement.

[0141] In addition, the same measurements were also performed on the films and adhesives obtained by other production examples described later, and the results are also shown in Tables 1 and 2.

[0142] [Production Example 2]

[0143] Into a reaction apparatus equipped with a stirrer, a reflux condenser, a gas inlet tube, and a thermometer, 20 g of Enotote (registered trademark) YP-50S (manufactured by Nippon Steel Chemical & Material Co., Ltd., phenoxy resin, weight average molecular weight of about 50,000) and 80 g of cyclohexanone were added. While stirring, the temperature was raised to 60 °C. After visually confirming dissolution, it was cooled to 40 °C to obtain a resin composition having a solid content of 20% by mass. The solvent was removed therefrom to obtain a film P-2 having a solid content of 100% by mass and a thickness of 100 μm.

[0144] [Production Example 3]

[0145] The above film P-2 and crystalline epoxy resin YSLV-80XY (manufactured by Nippon Steel Chemical & Material Co., Ltd.) were respectively pulverized, mixed at a mass ratio of 98 to 2, and pressed with a vise and heated to 50 °C to obtain a film P-3 having a solid content of 100% by mass and a thickness of 100 μm.

[0146] [Production Example 4]

[0147] The above-mentioned film P-2 and crystalline epoxy resin YSLV-80XY (manufactured by Nippon Steel Chemical & Material Co., Ltd.) were respectively pulverized, mixed at a mass ratio of 94:6, pressed with a vise, and heated to 50 °C, thereby obtaining a film P-4 with 100% by mass of solids and a thickness of 100 μm.

[0148] <Production Example 5>

[0149] The above-mentioned thin film P-2 and crystalline epoxy resin YSLV-80XY (manufactured by Nippon Steel Chemical & Material Co., Ltd.) were respectively pulverized, mixed at a mass ratio of 89:11, pressed with a vise, and heated to 50 °C, thereby obtaining a thin film P-5 with 100% by mass of solids and a thickness of 100 μm.

[0150] <Production Example 6>

[0151] In a reaction apparatus equipped with a stirrer, a reflux condenser, a gas inlet tube, and a thermometer, 203 g (1.0 equivalent) of jER (registered trademark) 1007 (a bisphenol A type epoxy resin, molecular weight about 4060, manufactured by Mitsubishi Chemical Corporation), 12.5 g (0.6 equivalent) of bisphenol S (molecular weight 250), 2.4 g of triphenylphosphine, and 1000 g of methyl ethyl ketone were added. While stirring under a nitrogen atmosphere, the temperature was raised to 100 °C. After visually confirming dissolution, it was cooled to 40 °C to obtain a resin composition with about 20% by mass of solids. The solvent was removed from the resin composition, and it was heated at 160 °C for 2 hours to obtain a film-like solid binder (P-6) with 100% by mass of solids and a thickness of 100 μm.

[0152] <Comparative Production Example 1>

[0153] Two liquids of a thermosetting liquid epoxy adhesive E-250 (a two-component type of bisphenol type epoxy resin and amine curing agent, manufactured by Konishi Co., Ltd.) were mixed, coated on a release film, cured at 100 °C for 1 hour, then cooled, and peeled off from the release film to obtain a film Q-1 with a thickness of 100 μm.

[0154] For film Q-1, no heat of fusion peak was detected by DSC measurement, and the epoxy equivalent and weight average molecular weight could not be measured because it was insoluble in solvents.

[0155] <Comparative Production Example 2>

[0156] An amorphous polycarbonate film (Iupilon (registered trademark) FE2000, manufactured by Mitsubishi Engineering-Plastics Corporation, thickness 100 μm) was cut to obtain a film Q-2.

[0157] For thin film Q-2, no heat of fusion peak was detected by DSC measurement, and the epoxy equivalent and weight average molecular weight could not be measured because it was insoluble in solvents.

[0158] <Comparative Production Example 3>

[0159] A sheet was obtained by pressing the crystalline epoxy resin YSLV-80XY (manufactured by Nippon Steel Chemical & Material Co., Ltd.) at room temperature, and then cut to obtain a film Q-3 with a thickness of 100 μm.

[0160] The measurement results of the weight average molecular weight, epoxy equivalent, and heat of fusion of the obtained film Q-3 are shown in Table 2.

[0161] <Comparative Production Example 4>

[0162] The thermosetting liquid epoxy adhesive E-250 (manufactured by Konishi Co., Ltd., a two-component type of bisphenol type epoxy resin and amine curing agent) was directly used as the liquid adhesive Q-4.

[0163] For the adhesive Q-4, no heat of fusion peak was detected by DSC measurement, and the epoxy equivalent and weight average molecular weight could not be measured because it was insoluble in the solvent.

[0164] <Comparative Production Example 5>

[0165] 1.0 equivalent (203 g) of jER (registered trademark) 1007 (manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, weight average molecular weight of about 10,000), 1.0 equivalent (12.5 g) of bisphenol S, 2.4 g of triphenylphosphine, and 1,000 g of methyl ethyl ketone were added to a flask and stirred at room temperature to obtain a liquid adhesive Q-5 with a solid content of about 20% by mass.

[0166] It should be noted that for the adhesive Q-5, the weight average molecular weight, epoxy equivalent, heat of fusion, and melting point were measured using the thermoplastic epoxy resin polymer formed on the surface of resin A in Comparative Example 5 described later.

[0167] <Comparative Production Example 6>

[0168] 20 g of Phenotote (registered trademark) YP-50S (manufactured by Nippon Steel Chemical & Material Co., Ltd., phenoxy resin, weight average molecular weight of about 50,000) and 80 g of cyclohexanone were added to a reaction apparatus equipped with a stirrer, reflux condenser, gas inlet tube, and thermometer, and the temperature was raised to 60 °C with stirring. After visually confirming dissolution, it was cooled to 40 °C to obtain a liquid adhesive Q-6 with a solid content of 20% by mass.

[0169] It should be noted that for the adhesive Q-6, the weight average molecular weight, epoxy equivalent, heat of fusion, and melting point were measured using the phenoxy resin coating layer formed on the surface of resin A in Comparative Example 6 described later.

[0170] For the adhesive Q-6, no heat of fusion peak was detected by DSC measurement, and the epoxy equivalent was above the detection limit.

[0171] <Comparative Production Example 7>

[0172] The crystalline polyamide-based hot melt adhesive film NT-120 (manufactured by Nippon MatTai Co., Ltd., thickness 100 μm) was cut to obtain film Q-7 with a thickness of 100 μm.

[0173] For film Q-7, since it is insoluble in solvents, the epoxy equivalent and weight average molecular weight could not be measured. The results of the heat of fusion measurement are shown in Table 2.

[0174] <Evaluation Method>

[0175] The weight average molecular weight, heat of fusion, and epoxy equivalent of the film and the binder were determined as follows. In addition, the thickness of the film was measured by the following method.

[0176] (Weight Average Molecular Weight)

[0177] The film and the binder were dissolved in tetrahydrofuran, and measurement was carried out using Prominence 501 (manufactured by Showa Kagaku Co., Ltd., Detector: Shodex (registered trademark) RI-501 (manufactured by Showa Denko K.K.)) under the following conditions.

[0178] Column: LF-804 (manufactured by Showa Denko K.K.) × 2 columns

[0179] Column temperature: 40 °C

[0180] Sample: 0.4 mass% tetrahydrofuran solution of the resin

[0181] Flow rate: 1 ml / min

[0182] Eluent: Tetrahydrofuran

[0183] Calibration method: Conversion based on standard polystyrene

[0184] (Heat of Fusion and Melting Point)

[0185] Weigh 2 - 10 mg of the film and the binder, place them in an aluminum dish, and heat from 23 °C to 200 °C at a rate of 10 °C / min using a DSC (DSC8231 manufactured by Rigaku Corporation) to obtain a DSC curve. Calculate the heat of fusion from the area of the endothermic peak during melting on this DSC curve and the above-mentioned weighed value. Additionally, take the melting peak temperature of the obtained DSC curve as the melting point. It should be noted that in the case where no melting peak can be obtained or when the heat of fusion is 15 J / g or less, the temperature obtained by adding 70 °C to the glass transition temperature is taken as the melting point. The glass transition temperature is specified as the temperature at the start of the descent of the DSC curve in the second cycle when heating to 200 °C using DSC, cooling to below 40 °C, and then heating to 200 °C again. It should be noted that for thermosetting resins that do not melt upon heating, no melting point is considered.

[0186] (Epoxy equivalent)

[0187] Measure according to JIS K - 7236:2001 and convert to the value as the resin solids. Additionally, in the case of a simple mixture without a reaction, calculate from the respective epoxy equivalent and content.

[0188] (Thickness of the film)

[0189] For the thickness of the film, after placing it in an atmosphere of 23 °C and 50% humidity for 24 hours, measure using MDC - 25MX manufactured by Mitutoyo Corporation.

[0190] [Manufacture of the bonded body]

[0191] <Metal substrate A>

[0192] As the metal substrate A, use the following substrates.

[0193] 《Aluminum》

[0194] Perform sandblasting on the surface of A6061 - T6 to obtain a test piece with a width of 18 mm, a length of 45 mm, and a thickness of 1.6 mm.

[0195] 《Copper》

[0196] Perform sandblasting on the surface of C1100 to obtain a test piece with a width of 18 mm, a length of 45 mm, and a thickness of 1.6 mm.

[0197] <Metal substrate B>

[0198] As the metal substrate B, use the following substrates.

[0199] 《Iron》

[0200] Perform sandblasting on the surface of SPCC - SD to obtain a test piece with a width of 10 mm, a length of 45 mm, and a thickness of 3.0 mm.

[0201] <Example 1-1>

[0202] Aluminum was used as metal substrate A, and iron was used as metal substrate B. The above-mentioned film P-1 cut into a size of 10×15 mm was arranged on metal substrate A, heated in such a way that the temperature of the film became 200°C, melted the film, and then naturally cooled at room temperature for 1 minute to cure the film, and the metal substrate A was joined to the film.

[0203] Next, metal substrate B was brought into surface contact with the film joined to metal substrate A. The overlap of these substrates with each other was set to a width of 10 mm and a depth of 5 mm. For the above-mentioned film P-1, it was arranged so as to entirely cover the overlapping area of these substrates with each other. That is, a laminate in which metal substrate B and the film were not joined was prepared in a state where metal substrate A and metal substrate B did not directly contact each other and the above-mentioned film was sandwiched between them.

[0204] A high-frequency induction welder (manufactured by Seidensha Electronics Industry Co., Ltd., oscillator UH-2.5K, press JIIP30S) was used to heat the metal by high-frequency induction, and the test pieces were joined together by heating and pressing. The applied pressure was set to 110 N (pressure 2.2 MPa), the oscillation frequency was set to 900 kHz, and the oscillation time was set to 2 seconds.

[0205] In addition, for the evaluation of the open time, after leaving the film joined to the above-mentioned metal substrate A standing for 3 days, metal substrate B was brought into surface contact with the film joined to metal substrate A, and metal substrate A and metal substrate B were joined. Except for this, the joined body was produced in the same manner.

[0206] <Example 1-2>

[0207] Copper was used as metal substrate A, and iron was used as metal substrate B. A joined body was obtained through the same operation as in <Example 1-1>.

[0208] <Examples 2 to 5, Comparative Examples 1 to 3>

[0209] As the film, the films in Table 1 and Table 2 were used, and except for this, the same operation as in Example 1 was performed to produce a joined body.

[0210] <Comparative Example 4>

[0211] Aluminum was used as metal substrate A, and iron was used as metal substrate B.

[0212] The adhesive Q-4, which is a mixture of two liquids of a thermosetting liquid epoxy adhesive E-250 (manufactured by Konishi Co., Ltd., a two-component type of bisphenol epoxy resin and amine curing agent), was respectively coated on the surfaces of the metal substrate A and the metal substrate B, and the bonding was carried out within 1 minute over an area of 10 mm in length × 18 mm in width. Then, it was left standing in an oven at 100 °C for 1 hour in a state fixed by a jig, thereby curing the bonding agent. Then, it was cooled to room temperature. Thus, a bonded body was produced. The thickness of the adhesive layer was 0.1 mm.

[0213] In addition, for the evaluation of the open time, the bonding agent Q-4 was respectively coated on the metal substrate A and the metal substrate B, and after standing for 3 days, it was left standing in an oven at 100 °C for 1 hour in a state where the metal substrate A and the metal substrate B were overlapped and fixed by a jig. Except for this, the same operations as in <Example 1-1> were carried out to produce a bonded body for open time evaluation.

[0214] <Comparative Example 5>

[0215] Aluminum was used as the metal substrate A, and iron was used as the metal substrate B.

[0216] The liquid adhesive Q-5 was rod-coated on the metal substrate A, and after drying at room temperature for 30 minutes, it was left standing in an oven at 160 °C for 2 hours, thereby forming a solid thermoplastic epoxy resin polymer coating layer with a length of 20 mm × a width of 18 mm × a thickness of 50 μm on the surface of the metal substrate A.

[0217] Next, after the metal substrate A and the metal substrate B were overlapped, the same operations as in <Example 1-1> were carried out to obtain a bonded body by ultrasonic welding.

[0218] In addition, for the evaluation of the open time, after the metal substrate A with the above-mentioned thermoplastic epoxy resin polymer coating layer formed on its surface was left standing for 3 days, the metal substrate A and the metal substrate B were overlapped, and except for this, the same operations as in <Example 1-1> were carried out to produce a bonded body for open time evaluation.

[0219] <Comparative Example 6>

[0220] Aluminum was used as the metal substrate A, and iron was used as the metal substrate B.

[0221] The above-mentioned liquid resin composition was rod-coated on the metal substrate A and left standing in an oven at 70 °C for 30 minutes, thereby forming a phenoxy resin coating layer with a length of 20 mm × a width of 18 mm × a thickness of 50 μm on the surface of the metal substrate A.

[0222] The coating layer on the metal substrate A was overlapped with the metal substrate B, and except for this, the same operations as in Comparative Example 5 were carried out to produce a bonded body.

[0223] In addition, for the evaluation of the open time, the metal substrate A with the above-mentioned phenoxy resin coating layer formed on its surface was allowed to stand for 3 days, and then the metal substrate A was laminated with the metal substrate B. Except for this, the same operations as in <Example 1-1> were carried out to produce a bonded body for open time evaluation.

[0224] <Comparative Example 7>

[0225] Using Film Q-7 as the film, except for this, the same operations as in <Example 1-1> were carried out to produce a bonded body and a bonded body for open time evaluation.

[0226] <Comparative Examples 8 to 11>

[0227] The metal substrate A was not bonded to the film, and a laminate was prepared by sequentially laminating the metal substrate A, the film, and the metal substrate B. Except for this, the same operations as in Example 1 were carried out to produce a bonded body and a bonded body for open time evaluation.

[0228] <Bonded Body Evaluation Method>

[0229] The obtained bonded bodies were evaluated as follows. The evaluation results are shown in Tables 1 and 2.

[0230] (Shear Bonding Strength)

[0231] After allowing the bonded bodies obtained in the examples and comparative examples to stand for 30 minutes or more at the measurement temperature (23°C or 80°C), according to ISO19095, a tensile shear bonding strength test was carried out in an atmosphere of 23°C and 80°C using a tensile testing machine (universal testing machine Autograph “AG-X plus” (manufactured by Shimadzu Corporation), load cell 10 kN, tensile speed 10 mm / min) to measure the bonding strength. The measurement results are shown in Tables 1 and 2.

[0232] (Bonding Process Time)

[0233] For the bonding process time, starting from when at least one of the substrates constituting the bonded body came into contact with the bonding agent and ending when the production of the bonded body was completed, the time from the start point to the end point was measured. The measurement results are shown in Tables 1 and 2.

[0234] (Recyclability)

[0235] After heating the bonded body on a hot plate at 200°C for 1 minute, it was judged whether it could be easily peeled off with a force of 1 N or less. If it could be peeled off, it was evaluated as good (A), and if it could not be peeled off, it was evaluated as inappropriate (B). The evaluation results are shown in Tables 1 and 2.

[0236] (Repairability)

[0237] For each bonded body produced in the examples and comparative examples, the base materials A and B whose bonding had been released by the test at 23°C in the above tensile shear strength test were used, and the bonded body was produced again by the same operation as in each example and each comparative example, thereby obtaining a repaired bonded body.

[0238] The shear bonding force at 23°C of this repaired bonded body was measured in the same manner as the above test method. If it was 80% or more of the first shear bonding force, it was evaluated as good (A). If it was less than 80%, it was evaluated as inappropriate (B). The measurement results are shown in Tables 1 and 2.

[0239] (Open time evaluation)

[0240] Using the bonded body for open time evaluation, the above tensile shear bonding strength test was carried out at 23°C. Compared with the test pieces produced by the methods of the above examples and comparative examples, if the shear bonding force was 80% or more, it was good (A). If it was less than 80%, it was inappropriate (B). A good open time evaluation (A) means a long open time and excellent convenience.

[0241] The measurement results are shown in Tables 1 and 2.

[0242]

[0243]

[0244] Industrial applicability

[0245] The bonded body obtained by the production method of the present invention can be used as, for example, automotive components such as door side panels, engine hoods, tailgates, steering hangers, A-pillars, B-pillars, C-pillars, D-pillars, crash boxes, power control unit (PCU) housings, electric compressor components (inner wall parts, air inlets, exhaust control valve (ECV) insertion parts, mounting boss parts, etc.), lithium-ion battery (LIB) spacers, battery cases, LED headlamps, etc., but is not particularly limited to these exemplified uses.

[0246] Symbol description

[0247] 1 Bonded body

[0248] 2 Bonding layer

[0249] 3 Metal base material A

[0250] 4 Metal base material B

Claims

1. A method for manufacturing a bonded body, the bonded body being formed by sequentially bonding a metal substrate A, a film containing an amorphous thermoplastic resin, and a metal substrate B, the amorphous thermoplastic resin being at least one selected from a thermoplastic epoxy resin and a phenoxy resin; This method includes a first bonding step and a second bonding step, The first bonding step: In a state where the film is in surface contact with the metal substrate A, the film is melted and then solidified, thereby bonding the metal substrate A and the film; The second bonding step: In a state where the film bonded to the metal substrate A is in surface contact with the metal substrate B, the film is melted and then solidified, thereby bonding the metal substrate A and the metal substrate B; The epoxy equivalent of the amorphous thermoplastic resin is 1,600 g / eq. or more or does not contain an epoxy group, and the heat of fusion is 15 J / g or less.

2. The method for manufacturing a bonded body according to claim 1, wherein in the first bonding step, the film is melted and then solidified at a bonding temperature of 100 to 300 °C.

3. The method for manufacturing a bonded body according to claim 1, wherein in the second bonding step, the film is melted and then solidified by at least one selected from contact heating, hot air heating, hot pressing, infrared heating, hot plate welding, ultrasonic welding, vibration welding, and high-frequency induction welding.

4. The method for manufacturing a bonded body according to claim 1, wherein in the second bonding step, the film is melted and then solidified at a temperature above the melting point of the film.

5. The method for manufacturing a bonded body according to claim 1, wherein in the second bonding step, the film is melted and then solidified under heating at a temperature of 100 to 400 °C and under pressure of 0.01 to 20 MPa.

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