Metal-resin bond, metal-resin laminate, and method for manufacturing a metal-resin bond

Abstract

The present invention aims to provide a metal-resin bond using a resin film that exhibits good adhesion to a metal layer and good dielectric breakdown characteristics under high voltage. [Solution] The present invention relates to a metal-resin bond having a metal layer and a resin layer laminated on the metal layer, wherein the resin layer contains a carboxylic acid-modified polyolefin and the value obtained by dividing the tracking resistance index of the surface of the resin layer by the thickness of the resin layer is 4.0 or more.

Description

Technical Field

[0005] , , ,

[0001] The present invention relates to a metal-resin bonded body, a metal-resin laminate, and a method for manufacturing a metal-resin bonded body.

Background Art

[0002] In recent years, due to environmental regulations and global warming issues, there has been an increasing tendency to improve fuel efficiency and reduce the weight of automobiles. For the purpose of reducing the weight of automobiles, conventionally, the use of high-strength steel materials and the use of light metals such as aluminum have been studied. In addition, weight reduction by utilizing resin materials has also been studied, and composite materials of metal and resin are used as automobile parts.

[0003] For example, Patent Document 1 discloses using a PPS sheet as an electrical insulating material, and here, a laminate in which a polyphenylene sulfide layer (A) and a polyphenylene sulfide alloy layer (B) are laminated is disclosed. Also, regarding the bonding method of metal and resin in a composite material of metal and resin, various proposals have been made conventionally. For example, Patent Document 2 discloses a laminate including a resin layer containing a polyarylene sulfide-based resin and a metal layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, Patent Document 1 proposes a resin film having an alloy structure of polyphenylene sulfide and an olefin copolymer. While the tensile strength of the film is good, its adhesion to the metal layer is insufficient. In addition, Patent Document 2 has problems with adhesion to metal, and improvements in the manufacturing process, such as increasing the temperature during hot pressing, were necessary to improve adhesion.

[0006] Furthermore, when using laminated metal and resin layers as automotive parts, the increasing prevalence of electric vehicles (EVs) necessitates designs that can handle even greater currents. Additionally, the voltage tends to rise with increasing power consumption. In particular, EVs are increasingly shifting towards higher voltages to shorten charging times. Therefore, metal-resin laminates are required to possess properties that prevent short circuits and dielectric breakdown in the resin layer, even under higher voltages.

[0007] Therefore, the present invention has been made in view of the above problems, and aims to provide a metal-resin joint having good adhesion between the metal layer and the resin layer, and having a resin layer that does not undergo dielectric breakdown even under high voltage. [Means for solving the problem]

[0008] As a result of diligent research, the inventors of the present invention have found that the above problems can be solved by employing a metal-resin bonded body in which a resin film of a specific configuration and a metal layer are joined, and have completed the present invention described below. In other words, the present invention provides the following [1] to

[14] . [1] Having a metal layer and a resin layer laminated on the metal layer, The resin layer comprises a carboxylic acid-modified polyolefin, A metal-resin bond in which the value obtained by dividing the tracking resistance index of the surface of the resin layer by the thickness of the resin layer is 4.0 or more. [2] The metal-resin bond according to [1] above, wherein the 180° peel strength of the resin layer against the metal layer is 1.0 N / 20 mm or more when rolled to a reduction ratio of 50-60%. [3] The metal-resin bond according to [1] or [2] above, wherein the tracking resistance index of the resin layer surface is 160 or higher. [4] The metal-resin bond according to any one of [1] to [3] above, wherein the thickness of the resin layer is 5 to 200 μm. [5] The metal-resin bond according to any one of [1] to [4] above, wherein the metal layer includes aluminum or an aluminum alloy. [6] The metal-resin bond according to any one of [1] to [4] above, wherein the metal layer contains copper or a copper alloy. [7] A metal-resin bond according to any of [1] to [6] above, wherein the thickness of the metal layer is 0.05 to 2.0 mm. [8] The metal-resin composite according to any one of [1] to [7] above, wherein the carboxylic acid-modified polyolefin is an anhydrous carboxylic acid-modified polyolefin. [9] The metal-resin composite according to [8] above, wherein the carboxylic acid-modified polyolefin is maleic acid-modified polypropylene.

[10] A metal-resin composite body according to any of the above [1] to [9], for use in automotive parts.

[11] A method for manufacturing a metal-resin bond according to any of the above [1] to

[10] , A method for manufacturing a metal-resin bond, comprising a step of joining a metal layer and a resin layer directly or via another layer.

[12] A method for manufacturing a metal-resin bond according to

[11] , comprising: step 1 of surface-treating at least one surface selected from the metal layer and the resin layer with a silane coupling agent treatment solution; and step 2 of laminating an untreated resin layer onto the surface-treated metal layer, or laminating an untreated metal layer onto a surface-treated resin layer and joining them by thermocompression bonding.

[13] A metal-resin laminate obtained by stacking n metal-resin bonded bodies described in any of [1] to

[10] above (where n is an integer of 2 or more).

[14] A metal-resin laminate as described in

[13] above, for use in automotive parts. [Effects of the Invention]

[0009] According to the present invention, a metal-resin joint can be obtained in which the adhesion between the metal layer and the resin layer is good and the resin layer does not undergo dielectric breakdown even under high voltage. [Modes for carrying out the invention]

[0010] Next, an example of an embodiment of the present invention will be described. However, the present invention is not limited to the embodiment described below, and can be modified and implemented as such without departing from the spirit of the invention. In this specification, when "X~Y" (where X and Y are any numbers) is used, unless otherwise specified, it includes the meaning of "X or more and Y or less," as well as "preferably greater than X" or "preferably less than Y." Also, when "X or more" (where X is any number) or "Y or less" (where Y is any number) is used, it also includes the intention that "it is preferable that it be greater than X" or "it is preferable that it be less than Y." In the following description, "film" and "sheet" are not clearly distinguished, and the term "film" includes "sheet," and the term "sheet" includes "film."

[0011] <Metal-resin bonded body> This embodiment relates to a metal-resin composite having a metal layer and a resin layer laminated on the metal layer. In the metal-resin composite of this embodiment, the resin layer contains a carboxylic acid-modified polyolefin, and the value obtained by dividing the tracking resistance index of the resin layer surface by the thickness of the resin layer is 4.0 or higher.

[0012] The metal-resin bond of this embodiment is a metal-resin bond having at least one metal layer and one resin layer. The metal-resin bond of this embodiment has excellent adhesion between the metal layer and the resin layer. Furthermore, the metal-resin bond of this embodiment has a resin layer that does not undergo dielectric breakdown even under high voltage. In other words, the resin layer in the metal-resin bond of this embodiment has good tracking resistance. For this reason, the metal-resin bond of this embodiment is particularly preferably used for automotive parts (e.g., automotive interior materials, automotive exterior materials, busbars).

[0013] Furthermore, in the metal-resin joint of this embodiment, the adhesion between the metal layer and the resin layer is excellent. For example, even when the metal-resin joint is subjected to harsh deformation such as rolling, bending, or pressing, the resin layer follows the metal layer, resulting in good workability.

[0014] When the metal-resin bond of this embodiment is rolled to obtain a rolled sample with a reduction ratio of 50-60%, the 180° peel strength of the resin layer is preferably 1.0 N / 20 mm or more, more preferably 1.5 N / 20 mm or more, and even more preferably 2.0 N / 20 mm or more. The upper limit of the 180° peel strength of the resin layer relative to the metal layer when rolled to a reduction ratio of 50-60% is not particularly limited, but for example, it is preferably 10 N / 20 mm or less. When a rolling process is involved, the resin layer needs to follow the thinned metal layer. If the peel strength at a reduction ratio of 50-60% is within the above range, it means that the adhesion between the metal layer and the resin layer is good even under harsh conditions, and that the followability of the resin layer is excellent. For this reason, the metal-resin bond of this embodiment can also be applied to laminate molding applications that include deformation such as rolling processes. The reduction ratio when measuring the 180° peel strength can be appropriately adjusted depending on the type of metal layer, but the measurement method described in the examples can be used for specific measurement methods.

[0015] In the metal-resin bonded body of this embodiment, the tracking resistance index of the resin layer surface is preferably 160 or more, more preferably 200 or more, further preferably 300 or more, still more preferably 400 or more, and particularly preferably 500 or more. The upper limit value of the tracking resistance index of the resin layer surface is not particularly limited, but the tracking resistance index is preferably 1000 or less. The measurement of the tracking resistance index is carried out referring to JIS C 2134 (2007). Specifically, the resin layer surface of the metal-resin bonded body cut out to 20 mm square is connected to the platinum electrodes of the tracking resistance tester, and after applying a voltage, 30 drops of 0.1% ammonium chloride solution are dropped onto the resin layer. The highest voltage at which no tracking breakdown occurs after 30 drops are dropped is taken as the tracking resistance index.

[0016] In this embodiment, it is sufficient that the value obtained by dividing the tracking resistance index of the resin layer surface by the thickness of the resin layer (tracking resistance index / thickness) is 4.0 or more, more preferably 4.5 or more, further preferably 5.0 or more, still more preferably 5. A value of 5 or more is even more preferable, a value of 6.0 or more is still more preferable, a value of 6.5 or more is even more preferable, and a value of 7.0 or more is particularly preferable. The upper limit value of the value obtained by dividing the tracking resistance index of the resin layer surface by the thickness of the resin layer is not particularly limited, but the value obtained by dividing the tracking resistance index of the resin layer surface by the thickness of the resin layer (tracking resistance index / thickness) is preferably 30 or less. If the value of the tracking resistance index / thickness is not less than the above lower limit value, the resin layer can exhibit excellent tracking resistance, and as a result, it is possible to suppress dielectric breakdown under high voltage.

[0017] [Resin layer] The metal-resin bonded body of this embodiment has a resin layer, and the resin layer contains a carboxylic acid-modified polyolefin. By including the carboxylic acid-modified polyolefin in the resin layer, the adhesion between the metal layer and the resin layer can be more effectively enhanced, and the followability of the resin layer to the metal layer can be more effectively enhanced. Further, by including the carboxylic acid-modified polyolefin in the resin layer, the tracking resistance of the resin layer can be effectively enhanced, and as a result, it is possible to suppress breakdown under high voltage.

[0018] In this specification, the resin layer is a layer that directly contacts the metal layer or a layer laminated on the metal layer via a primer layer or the like. Among these, it is preferable that the resin layer and the metal layer are laminated so as to directly contact. Thus, by containing a carboxylic acid-modified polyolefin in the resin layer laminated directly or indirectly on the metal layer, the adhesion between the metal layer and the resin layer can be more effectively enhanced, and the followability of the resin layer to the metal layer can be more effectively enhanced.

[0019] The carboxylic acid-modified polyolefin contained in the resin layer is preferably an anhydrous carboxylic acid-modified polyolefin, more preferably maleic anhydride-modified polypropylene. By including the above resin in the resin layer, the adhesion between the resin layer and the metal layer can be more effectively enhanced. Further, by including the above resin in the resin layer, the tracking resistance of the resin layer can be effectively enhanced, and as a result, it is possible to suppress breakdown under high voltage.

[0020] The thickness (total thickness) of the resin layer is preferably 5 μm or more, more preferably 7 μm or more. On the other hand, regarding the upper limit, considering handling properties and the like, it is preferably 200 μm or less, more preferably 100 μm or less, still more preferably 80 μm or less, and particularly preferably 60 μm or less. By setting the thickness of the resin layer within the above range, the adhesion between the metal layer and the resin layer can be more effectively enhanced. Further, by setting the thickness (total thickness) of the resin layer within the above range, the tracking resistance of the resin layer can be effectively enhanced, and as a result, it is possible to suppress breakdown under high voltage.

[0021] In the metal-resin bond of this embodiment, the resin layer may be a single layer or a multilayer structure. When the resin layer is a multilayer structure, it is preferable that the layer arranged on the metal layer side of the resin layer contains a resin having a carboxylic acid-modified polyolefin. This makes it possible to more effectively improve the adhesion between the resin layer and the metal.

[0022] When the resin layer has a multilayer structure, it may be, for example, a single-type, two-layer structure consisting of two layers (A / A), a two-type, two-layer structure consisting of two layers (A / B), a two-type, three-layer structure consisting of three layers (A / B / A), or a three-type, three-layer structure consisting of three layers (A / B / C). Below, we will describe in detail each component in the case of a two-type, two-layer structure consisting of two layers (A / B). Note that when the resin layer is a single layer, the resin layer consists only of resin layer A.

[0023] <Resin layer A> In a multilayer structure, resin layer A is the layer located on the metal layer side of the resin layer, and resin layer A contains a carboxylic acid-modified polyolefin. When the resin layer is a single layer, the resin layer consists only of resin layer A. The content of carboxylic acid-modified polyolefin in resin layer A is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on the total mass of resin layer A. The content of carboxylic acid-modified polyolefin in resin layer A may also be 100% by mass, based on the total mass of resin layer A.

[0024] <Carboxylic acid-modified polyolefin> Examples of carboxylic acid-modified polyolefins include modified polymers obtained by copolymerizing (e.g., graft polymerization) polyolefins with unsaturated carboxylic acids or their derivatives. Examples of polyolefins include homopolymers of olefins, crosspolymers, and copolymers with other copolymerizable monomers (e.g., other vinyl monomers).

[0025] Here, "graft polymerization" means bonding an unsaturated carboxylic acid and / or its derivative to a polyolefin. The bonding position of the unsaturated carboxylic acid and / or its derivative in the carboxylic acid-modified polyolefin is not particularly limited; it is sufficient that it is introduced to at least one of the main chain ends and side chains of the polyolefin. The notation "unsaturated carboxylic acid and / or its derivative" may also be written as "at least one selected from the group consisting of unsaturated carboxylic acids and their derivatives."

[0026] The acid modification rate (graft amount) in carboxylic acid-modified polyolefins is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, based on the total mass (100% by mass) of the carboxylic acid-modified polyolefin. Furthermore, the acid modification rate (graft amount) in carboxylic acid-modified polyolefins is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 7% by mass or less, even more preferably 5% by mass or less, and particularly preferably 4% by mass or less. Note that the acid modification rate (graft amount) in carboxylic acid-modified polyolefins represents the ratio of the mass content of units derived from unsaturated carboxylic acid or its derivatives to the total mass of the carboxylic acid-modified polyolefin. By setting the carboxylic acid modification rate (graft amount) within the above range, it becomes easier to obtain a resin layer A with excellent adhesion to the metal layer. Furthermore, by setting the carboxylic acid modification rate (graft amount) within the above range, the tracking resistance of resin layer A can be effectively improved, and as a result, dielectric breakdown under high voltage can be suppressed.

[0027] The acid value of the carboxylic acid-modified polyolefin is preferably 0.01 mg KOH / g or higher, more preferably 0.1 mg KOH / g or higher, and even more preferably 0.2 mg KOH / g or higher. Furthermore, the acid value of the carboxylic acid-modified polyolefin is preferably 100 mg KOH / g or less, more preferably 80 mg KOH / g or less, and even more preferably 50 mg KOH / g or less. The acid value of the carboxylic acid-modified polyolefin serves as an indicator of the acid modification rate (graft amount) of the carboxylic acid-modified polyolefin. By setting the acid value of the carboxylic acid-modified polyolefin within the above range, it becomes easier to obtain resin layer A with excellent adhesion to the metal layer. In addition, by setting the acid value of the carboxylic acid-modified polyolefin within the above range, the tracking resistance of resin layer A can be effectively improved, and as a result, dielectric breakdown under high voltage can be suppressed. The acid value of the carboxylic acid-modified polyolefin is measured in accordance with the method described in JIS K0070:1992.

[0028] The melting point of the carboxylic acid-modified polyolefin is preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. While there is no particular upper limit to the melting point of the carboxylic acid-modified polyolefin, it is preferably, for example, 170°C or lower. By setting the melting point of the carboxylic acid-modified polyolefin within the above range, it becomes easier to obtain a resin layer A with excellent adhesion to the metal layer.

[0029] <Polyolefin> The unmodified polyolefins used as raw materials for carboxylic acid-modified polyolefins are not particularly limited, but include ethylene, propylene, butene-1, pentene-1, 2-methylbutene-1, 3-methylbutene-1, hexene-1, 3-methylpentene-1, 4-methylpentene-1, 3,3-dimethylbutene-1, heptene-1, methylhexene-1, dimethylpentene-1, trimethylbutene-1, ethylpentene-1, octene-1, methylpentene-1, and dimethylhexene. Examples include homopolymers of α-olefins such as -1, trimethylpentene-1, ethylhexene-1, methylethylpentene-1, diethylbutene-1, putopropylpentene-1, decene-1, methylnonene-1, dimethyloctene-1, trimethylheptene-1, ethyloctene-1, methylethylheptene-1, diethylhexene-1, dodecene-1, and hexadodecene-1, or copolymers using any two or more of these α-olefins as raw material monomers. Among these, propylene-based polymers with propylene as the main component monomer are preferred, and propylene homopolymers (homopolypropylene), propylene-ethylene random copolymers, and propylene-butene-1 random copolymers are more preferred.

[0030] Carboxylic acid-modified polyolefins preferably contain propylene units as constituent monomer units, more preferably 50 mol% or more, even more preferably 60 mol% or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more. Carboxylic acid-modified polyolefins also preferably contain 100 mol% propylene units as constituent monomer units. In other words, carboxylic acid-modified polyolefins are preferably homopolypropylene.

[0031] <Unsaturated carboxylic acids and / or their derivatives> Unsaturated carboxylic acids and / or derivatives used with polyolefins include unsaturated compounds having one or more carboxylic acid groups, esters of unsaturated carboxylic acid compounds having carboxylic acid groups with alkyl alcohols, and unsaturated compounds having one or more carboxylic anhydride groups (for example, an anhydride of an unsaturated dicarboxylic acid). Examples of unsaturated groups include vinyl groups, vinylene groups, and unsaturated cyclic hydrocarbon groups. Unsaturated carboxylic acids and / or derivatives may be used alone or in combination of two or more. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, and aconitic acid.

[0032] Furthermore, the unsaturated carboxylic acid and / or its derivatives are not limited to unsaturated carboxylic acids in the form of free carboxylic acids, but may also be in the form of corresponding derivatives. For example, corresponding acid anhydrides such as maleic anhydride and citraconic anhydride may also be used. In addition, for example, acid halides, amides, imides, esters, etc., may also be used, and specific examples of unsaturated carboxylic acid derivatives include malenyl chloride, malenylimide, maleic anhydride, citraconic anhydride, monomethyl maleate, and dimethyl maleate. Among these, unsaturated dicarboxylic acids or their acid anhydrides are preferred, maleic acid or its acid anhydrides are particularly preferred, and among these, maleic anhydride is particularly preferred.

[0033] From the viewpoint of achieving good adhesion to the metal layer, unsaturated carboxylic acids and / or their derivatives are preferably those having a nonpolar group, and more preferably the nonpolar group is a hydrocarbon group having 1 to 30 carbon atoms. Specific examples of hydrocarbon groups having 1 to 30 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, neopentyl, and n-hexyl.

[0034] (organic peroxide) When obtaining carboxylic acid-modified polyolefins by graft polymerization, organic peroxides can be used as radical initiators during graft polymerization. Specific examples of organic peroxides include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-amyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-hexyl peroxypivalate, and t-butyl peroxypivalate.

[0035] The amount of organic peroxide used is preferably 0.01 to 30 parts by mass, more preferably 1 to 20 parts by mass, and more preferably 2 to 15 parts by mass, per 100 parts by mass of polyolefin.

[0036] The method for grafting unsaturated carboxylic acids and / or their derivatives onto polyolefins is not particularly limited, and conventionally known grafting methods such as solution methods, melt-kneading methods, and solid-phase methods can be employed. More specifically, any of the following methods may be used: a melt-kneading method in which the polymer is melted and the graft monomer is added thereto and the graft reaction is carried out in the presence of an organic peroxide; a solution method in which the polymer is dissolved in a solvent to form a solution, and then the graft monomer is added thereto and the graft reaction is carried out in the presence of an organic peroxide; or a solid-phase method in which the graft monomer is added to a solid polymer and the graft reaction is carried out in the presence of an organic peroxide at a temperature below the melting point of the polymer.

[0037] Alternatively, the carboxylic acid-modified polyolefin may be graft polymerized using a grafting method, and the resulting graft-modified product may be further melt-kneaded with an unmodified resin to obtain a carboxylic acid-modified polyolefin composition.

[0038] (optional ingredient) The resin layer may contain various additives, such as heat stabilizers, antioxidants, ultraviolet absorbers, ultraviolet stabilizers, light stabilizers, antibacterial and antifungal agents, antistatic agents, lubricants, pigments, dyes, fillers, nucleating agents, flame retardants, plasticizers, weather-resistant agents, and conductive agents, to the extent that it does not impair the spirit of the present invention. Preferably, the content of additives is 5% by mass or less of the total mass of the resin layer.

[0039] The resin layer may further contain unmodified polyolefins in addition to carboxylic acid-modified polyolefins. The unmodified polyolefin is not particularly limited, but any polyolefin similar to the modified polyolefin described above, but without modification, can be used. Examples of unmodified polyolefins include homopolymers of olefins, crosspolymers, and copolymers with other copolymerizable monomers (e.g., other vinyl monomers). Specifically, examples of polyolefins include polyethylene (LDPE, LLDPE, etc.), polypropylene, polybutene, crosspolymers thereof, ionomer resins, etc. Furthermore, cyclic olefin polymers and methylpentene polymers can also be used as unmodified polyolefins. Among these, it is preferable that the unmodified polyolefin contains at least one monomer unit selected from the group consisting of propylene, methylpentene, and cyclic olefins as constituent monomer units. The content of the unmodified polyolefin is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total mass of the resin components constituting the resin layer.

[0040] The resin layer may contain other resins besides modified polyolefins and unmodified polyolefins. Examples of other resins include styrene resins, vinyl resins, and acrylic resins. Examples of styrene resins include polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS), and acrylonitrile-styrene copolymer (AS). An example of a vinyl resin is polyvinyl chloride. An example of an acrylic resin is polymethyl methacrylate (PMMA). The content of the other resins is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on the total mass of the resin components constituting the resin layer.

[0041] [Metal layer] The metal-resin bond of this embodiment has a metal layer. The metal constituting the metal layer can be a commercially available product and is not particularly limited. Specific examples include iron, steel, tinplate, tin-free steel (TFS), copper, aluminum, stainless steel, or alloys containing these as one component.

[0042] From the viewpoint of corrosion resistance and adhesion to the resin layer, the surface of the metal layer may be plated with one or more types of metals, or it may be provided with an inorganic oxide coating, such as a chemical conversion coating represented by chromic acid treatment, phosphoric acid treatment, chromic acid / phosphoric acid treatment, electrolytic chromic acid treatment, or chromate treatment, which are commonly performed. Furthermore, the metal layer may be subjected to other treatments such as electrochemical treatment or physical treatment.

[0043] From the viewpoint of electrical properties, etc., it is preferable that the metal layer contains aluminum or an aluminum alloy, or that the metal layer contains copper or a copper alloy. In particular, considering the processability, cost, environmental friendliness, and lightweight properties, it is preferable that the metal layer contains aluminum or an aluminum alloy.

[0044] Specific examples of aluminum alloys include non-heat-treatable or heat-treatable aluminum alloys specified in or conforming to JIS standards, which can be appropriately selected and used. Examples of non-heat-treatable aluminum alloys include pure aluminum (1000 series), Al-Mn alloys (3000 series), Al-Si alloys (4000 series), and Al-Mg alloys (5000 series). Examples of heat-treatable aluminum alloys include Al-Cu-Mg alloys (2000 series), Al-Mg-Si alloys (6000 series), and Al-Zn-Mg alloys (7000 series).

[0045] Specific examples of copper or copper alloys include high-purity materials such as tough pitch copper, oxygen-free copper, and phosphorus-deoxidized copper, as well as copper alloys such as brass, phosphor bronze, Cu-Fe alloys, Cu-Fe-P alloys, and Cu-Ni-Si alloys, but are not particularly limited. In particular, from the viewpoint of further improving electrical properties, it is preferable that the copper or copper alloy has a copper purity of 99.90% or higher.

[0046] The thickness of the metal layer is preferably 0.05 mm or more, and more preferably 0.1 mm or more. Furthermore, the thickness of the metal layer is preferably 3.0 mm or less, more preferably 2.5 mm or less, even more preferably 2.0 mm or less, even more preferably 1.5 mm or less, and particularly preferably 1.0 mm or less. By setting the thickness of the metal layer within the above range, the formability can be more effectively improved.

[0047] [Method for manufacturing a metal-resin bond] The manufacturing method for a metal-resin bond involves forming the aforementioned resin layer on at least one surface of a metal layer. The manufacturing method is not particularly limited, but examples include a method of extruding a molten resin, which is a resin layer-forming composition, into a film-like layer on the surface of a metal layer and laminating it, or a method of laminating a pre-formed resin film for resin layer formation onto a metal layer. As for the manufacturing method of the resin film for resin layer formation, general molding methods can be used. For example, it can be molded into a desired shape, such as a film or sheet, by extrusion molding, lamination molding, casting molding such as molten casting, or press molding. In each molding method, the apparatus and processing conditions are not particularly limited, and known methods can be used. Furthermore, in order to improve adhesion, various surface treatments such as corona treatment or painting, or treatments such as metal vapor deposition, may be applied to the surface of the resin layer.

[0048] In particular, the manufacturing method of the metal-resin bond of this embodiment preferably includes a step of joining the metal layer and the resin layer directly or via another layer. The step of joining the metal layer and the resin layer is not particularly limited, but it is preferable that the resin layer and the metal layer are passed between a pair of heating rolls (compression rolls) to perform thermocompression bonding. The temperatures of the pair of heating rolls may be the same or different. The width between the pair of heating rolls can be appropriately adjusted according to the thickness of the laminate. The temperature during thermocompression bonding is preferably 3°C or higher than the melting point of the resin constituting the resin layer, more preferably 5°C or higher than the melting point of the resin, and even more preferably 10°C or higher than the melting point of the resin. This allows the resin layer to melt sufficiently and enhances the adhesion strength with the metal layer.

[0049] The metal layer and the resin layer may be heat-pressed together so that they are directly laminated. In this case, there is no need to provide an adhesive layer or the like between the metal layer and the resin layer, which makes it possible to make the metal-resin joint thinner and lighter. On the other hand, when the metal layer and the resin layer are laminated via another layer, the other layer may be an adhesive layer such as a hot-melt type or primer, or a reactive adhesive layer such as a urethane type or acrylic type.

[0050] The metal layer may be treated with a primer. Applying a primer to the surface of the metal layer further enhances its adhesion to the resin layer. Examples of primers used in the primer treatment include silane coupling agents, titanium coupling agents, or various epoxy, urethane, and acrylic coating agents having functional groups such as epoxy, amino, and acrylic groups. From the viewpoint of adhesion to the resin layer, silane coupling agents are preferred.

[0051] A method for manufacturing a metal-resin bond may include a step 1 in which at least one surface selected from the metal layer and the resin layer is surface-treated with a silane coupling agent treatment solution. In this case, it is preferable to include a step 2 in which an untreated resin layer is laminated onto the surface of the metal layer surface-treated in step 1, or an untreated metal layer is laminated onto the resin layer surface-treated in step 1, and then bonded by thermocompression. In step 1, it is preferable to surface-treat at least one surface selected from the metal layer and the resin layer with a silane coupling agent treatment solution, and among these, it is preferable to surface-treat the surface of the metal layer with a silane coupling agent treatment solution.

[0052] The silane coupling agent treatment solution used in step 1 contains a silane coupling agent. The silane coupling agent is an organosilicon compound having an organic functional group and a hydrolysis group such as an alkoxy group in a single molecule. For example, epoxy group-containing compounds such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; vinyl group-containing compounds such as vinyltrimethoxysilane and vinyltriethoxysilane; styryl group-containing compounds such as p-styryltrimethoxysilane and p-styryltriethoxysilane; (meth)acrylic group-containing compounds such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)- Examples include amino group-containing compounds such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltriethoxysilane; isocyanurate group-containing compounds such as tris(trimethoxysilylpropyl)isocyanurate and tris(triethoxysilylpropyl)isocyanurate; and mercapto group-containing compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane. Among the above compounds, amino group-containing silane coupling agents are more preferred from the viewpoint of achieving both adhesion to the metal layer and adhesion to the resin layer. The silane coupling agent may be used alone or in combination of two or more types.

[0053] The silane coupling agent is applied to the metal layer surface as a liquid coating solution and dried as necessary. The silane coupling agent treatment solution is preferably diluted with a solvent to form a coating solution. The silane coupling agent treatment solution may be dissolved in the solvent or dispersed in the solvent. The silane coupling agent content in the silane coupling agent treatment solution is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, based on the total mass of the silane coupling agent treatment solution. Furthermore, the silane coupling agent content is preferably 1% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.5% by mass or less, based on the total mass of the silane coupling agent treatment solution.

[0054] The solvent contained in the silane coupling agent treatment solution is not particularly limited, but either water or an organic solvent may be used. Among these, from the viewpoint of environmental protection, an aqueous coating solution using water as the solvent is preferred. The aqueous coating solution may contain a small amount of organic solvent. The specific amount of organic solvent should be less than that of water by mass, but for example, it is preferably less than 30% by mass of the total mass of the solvent, more preferably less than 20% by mass, and even more preferably less than 10% by mass.

[0055] Examples of organic solvents used in combination with water include alcohols such as ethanol, isopropanol, ethylene glycol, and glycerin; ethers such as ethyl cellosolve, t-butyl cellosolve, propylene glycol monomethyl ether, and tetrahydrofuran; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and amines such as dimethylethanolamine. These can be used individually or in combination. By appropriately selecting and including these organic solvents in the aqueous coating solution as needed, the stability and applicability of the coating solution can be improved.

[0056] Conventional coating methods such as air doctor coating, blade coating, rod coating, bar coating, knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss roll coating, cast coating, spray coating, curtain coating, calender coating, and extrusion coating can be used as methods for applying the silane coupling agent treatment solution to the metal layer surface.

[0057] Furthermore, in order to improve the applicability or adhesion of the silane coupling agent treatment solution to the metal layer surface, surface treatments such as chemical treatment, corona discharge treatment, plasma treatment, ozone treatment, chemical treatment, or solvent treatment may be applied to the metal layer surface before applying the treatment solution.

[0058] In this embodiment, the amount of silane coupling agent treatment solution applied is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 15 μm or more, as a coating thickness in a wet state. Furthermore, the amount of silane coupling agent treatment solution applied is preferably 30 μm or less, and more preferably 20 μm or less, as a coating thickness in a wet state.

[0059] It is preferable to include a drying step after applying the silane coupling agent treatment solution. The drying step is preferably a step to remove the solvent contained in the silane coupling agent treatment solution. By removing the solvent from the silane coupling agent treatment solution, the surface of the metal layer or resin layer is treated with the silane coupling agent. The silane coupling agent chemically bonds the metal layer and the resin layer.

[0060] In step 2, an untreated resin layer is laminated onto the surface of the metal layer treated in step 1, or an untreated metal layer is laminated onto the resin layer treated in step 1, and then joined by thermocompression bonding. In particular, step 2 is preferably a step in which an untreated resin layer is laminated onto the surface of the metal layer treated in step 1, and then joined by thermocompression bonding. In step 2, the laminated metal layer / resin layer can be treated as one set, and multiple sets (multiple layers) may be laminated by thermocompression bonding after one set has been laminated, or multiple metal layers and multiple resin layers (multiple sets) may be laminated from the beginning. In step 2, it is preferable to laminate the laminated metal layer / resin layer so that the metal layer and resin layer are laminated alternately, but for example, the resin layers may be in contact with each other so that the exposed surface at the end in the thickness direction is the metal layer.

[0061] In the thermocompression bonding process, it is preferable to perform thermocompression bonding by passing one or more sets of laminates between a pair of heating rolls (compression rolls). The temperatures of the pair of heating rolls may be the same or different. The width between the pair of heating rolls can be appropriately adjusted according to the thickness of the laminate. In this embodiment, the thermocompression bonding process (silane bonding) may be a compression process using rolls or a heat press bonding process. Alternatively, the thermocompression bonding process using rolls and the heat press bonding process described above may be combined. For example, one set of laminates consisting of a metal layer and a resin layer may be prepared, and then the metal layer and resin layer may be laminated and subjected to the heat press bonding process.

[0062] [Metal-resin laminate] This embodiment may also relate to a metal-resin laminate obtained by stacking n (where n = an integer of 2 or more) of the above-described metal-resin bonded bodies. The above-described metal-resin bonded body may be a constituent unit (PM) in which a resin layer and a metal layer are stacked one layer at a time, or a constituent unit in which a resin layer is further stacked on a metal layer. In this case, the metal-resin bonded body may be a constituent unit (PMP) in which a resin layer (P), a metal layer (M), and a resin layer (P) are stacked. That is, the metal-resin laminate of this embodiment is preferably a laminate containing n (where n = an integer of 2 or more) constituent units (PM) or constituent units (PMP). Because the metal-resin laminate of this embodiment has the above-described configuration, it has a configuration in which resin layers (P) and metal layers (M) are stacked alternately.

[0063] The metal-resin laminate of this embodiment has a structure in which n metal-resin bonded bodies are laminated (where n = an integer of 2 or more). Here, n may be an integer of 1 or more, preferably an integer of 2 or more, more preferably an integer of 3 or more, even more preferably an integer of 4 or more, even more preferably an integer of 5 or more, and particularly preferably an integer of 6 or more. The upper limit of n is not particularly limited, but it is preferably an integer of 50 or less, more preferably an integer of 40 or less, and even more preferably an integer of 30 or less.

[0064] The metal-resin laminate of this embodiment also includes the following configuration. Examples include M(PM)n, M(PM)nP, P(PM)n, P(PM)nP, MP(PM)n, MP(PM)nP, (PMP)n, M(PMP)n, M(PMP)nP, M(PMP)nM, P(PMP)n, P(PMP)nP, P(PMP)nPM, P(PMP)nMP, MP(PMP)n, MP(PMP)nM, MP(PMP)nPM, PM(PMP)n, PM(PMP)nM, PM(PMP)nPM, PM(PMP)nMP, and PM(PMP)nMP. The outermost layer of the metal-resin laminate is preferably selected appropriately, taking into consideration, for example, the adhesion to the components that make up the area in which the metal-resin laminate is incorporated. In the above configuration, if there are two or more metal layers (M), each layer may have any configuration, and a combination of dissimilar metal layers (for example, a combination of copper and aluminum) may be used. In the above configuration, if there are two or more resin layers (P), each layer may have any configuration, and different resins, resin blends, and various additives may be used.

[0065] The total thickness of the metal-resin laminate is preferably 0.5 mm or more, and more preferably 1.0 mm or more. On the other hand, the upper limit of the total thickness of the metal-resin laminate is preferably 5.0 mm or less, more preferably 4.0 mm or less, and even more preferably 3.0 mm or less.

[0066] [How to use metal-resin joints] The metal-resin bonded or metal-resin laminated bodies described above are particularly preferred for use in automotive parts (e.g., automotive interior materials, automotive exterior materials, busbars). [Examples]

[0067] Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples described below.

[0068] <Evaluation Method> The methods for measuring and evaluating various physical properties and characteristics are as follows:

[0069] (1) Peel strength of the resin layer over the metal layer Metal-resin composites were rolled to a reduction ratio of 60% when the metal layer was aluminum, and to a reduction ratio of 50% when the metal layer was copper, and rolled samples were prepared. The reduction ratio is calculated by dividing the difference in thickness of the composite before and after rolling by the original thickness of the composite, and the thickness was measured using a micrometer. Two cuts were made with a cutter blade to allow the resin layer to be peeled off in 20 mm widths, and 180° peel test pieces were prepared. Then, the peel strength (N / 20 mm) was determined by a 180° peel test at a tensile speed of 50 mm / min. In the comparative example, if the metal layer and resin layer could not be bonded, it was marked as "not bonded".

[0070] (2) The value obtained by dividing the tracking resistance index by the thickness of the resin layer. The tracking resistance index was measured in accordance with JIS C 2134 (2007). Specifically, a Yamayo HAT-112-3 tracking resistance tester was used, and the resin layer surface of a 20mm square metal-resin joint was connected to a platinum electrode. After applying a voltage, a 0.1% ammonium chloride solution was dropped onto the resin layer. The highest voltage at which tracking breakdown did not occur after 30 drops was defined as the tracking index, and this value was calculated by dividing it by the thickness of the resin layer.

[0071] The raw materials used in each example and comparative example are as follows: <Resin layer> (a) Film having a maleic anhydride-modified polypropylene / polypropylene mixture ratio of 80 / 20 wt% Thickness: 50 μm Melting point: 165℃ Acid value: 0.3mgKOH / g (b) Polyphenylene sulfide film Thickness: 50 μm Melting point: 286℃ (c) Copolymerized polyphenylene sulfide film Thickness: 38 μm Melting point: 252℃

[0072] <Metal layer> (d) Aluminum sheet material A1100P-H16 Thickness: 0.3mm Chromate phosphate treated material (e) Copper plate material C1020P-1 / 4H Thickness: 0.1mm

[0073] [Example 1] A metal layer (d) was cut to A4 size, and resin layer (a) was placed on one surface. After heat-pressing one side between rolls set to 200°C, the joint was passed through a heating furnace set to 250°C for 126 seconds to obtain a metal-resin bond.

[0074] [Example 2] (e), cut to A4 size as a metal layer, was annealed by passing it through a heating furnace set to 290°C for 18 seconds. Then, (a) was placed on one surface of (e) as a resin layer, and one side was heat-compressed between rolls set to 165°C. Finally, the furnace was passed through a heating furnace set to 250°C for 126 seconds to obtain a metal-resin bond.

[0075] [Comparative Example 1] An attempt was made to superimpose a resin layer (b) onto one surface of (d), which was cut to A4 size as a metal layer, and then heat-press it between rolls set to 290°C on one side. However, the metal layer and the resin layer did not adhere, and a metal-resin bond could not be obtained.

[0076] [Comparative Example 2] Hydrolyzed 3-aminopropyltriethoxysilane was mixed with water and ethanol to prepare a 0.15 wt% solution, which was then applied to one surface of (d), cut to A4 size as the metal layer, using a #9 bar coater. The water was then dried by heating in an oven at 130°C for 1.5 minutes. A resin layer (c) was placed on top of the metal layer coated with the solution, and after heat-pressing one side between rolls set to 250°C, the joint was passed through a heating furnace set to 400°C for 40 seconds to obtain a metal-resin bond.

[0077] [Table 1]

[0078] In this example, the peel strength of the metal-resin bond after thinning was evaluated under conditions of a reduction ratio of 50-60%. The metal-resin bond in Examples 1 and 2 showed good adhesion even under conditions of a reduction ratio of 50-60%. Furthermore, Example 1 demonstrates good tracking resistance of the resin layer, indicating that dielectric breakdown is unlikely to occur even under high voltage. On the other hand, in all of the comparative examples, it was found that it is difficult to achieve both good adhesion of the resin layer to the metal layer and good tracking resistance. In particular, Comparative Example 2 had poor tracking resistance, making it difficult to apply to EV applications where shortening charging time is desired. [Industrial applicability]

[0079] The metal-resin bond of the present invention exhibits excellent adhesion between the metal layer and the resin layer, and good tracking resistance of the resin layer. Therefore, dielectric breakdown is less likely to occur even under high voltage, making it particularly suitable for applications requiring large currents. It is especially suitable for automotive parts (e.g., automotive interior materials, automotive exterior materials, busbars), and among these, it is particularly suitable for EVs where shortening charging time is desired and high voltage resistance is required, thus possessing high industrial value.

Claims

1. It has a metal layer and a resin layer laminated on the metal layer, The resin layer comprises a carboxylic acid-modified polyolefin, A metal-resin bond in which the value obtained by dividing the tracking resistance index of the surface of the resin layer by the thickness of the resin layer is 4.0 or more.

2. The metal-resin bond according to claim 1, wherein the 180° peel strength of the resin layer against the metal layer is 1.0 N / 20 mm or more when rolled to a reduction ratio of 50 to 60%.

3. The metal-resin bond according to claim 1, wherein the tracking resistance index of the surface of the resin layer is 160 or more.

4. The metal-resin bond according to claim 1, wherein the thickness of the resin layer is 5 to 200 μm.

5. The metal-resin bond according to claim 1, wherein the metal layer comprises aluminum or an aluminum alloy.

6. The metal-resin bond according to claim 1, wherein the metal layer comprises copper or a copper alloy.

7. The metal-resin bond according to claim 1, wherein the thickness of the metal layer is 0.05 to 2.0 mm.

8. The metal-resin bond according to claim 1, wherein the carboxylic acid-modified polyolefin is a carboxylic acid-modified polyolefin.

9. The metal-resin bond according to claim 8, wherein the carboxylic acid-modified polyolefin is maleic anhydride-modified polypropylene.

10. A metal-resin bond according to claim 1, for use in automotive parts.

11. A method for manufacturing a metal-resin bond according to any one of the above claims 1 to 10, A method for manufacturing a metal-resin bond, comprising a step of joining a metal layer and a resin layer directly or via another layer.

12. A method for manufacturing a metal-resin bond according to claim 11, comprising: step 1 of surface-treating at least one surface selected from the metal layer and the resin layer with a silane coupling agent treatment solution; and step 2 of laminating an untreated resin layer onto the surface-treated metal layer, or laminating an untreated metal layer onto a surface-treated resin layer, and joining them by thermocompression bonding.

13. A metal-resin laminate obtained by stacking n metal-resin bonded bodies according to any one of claims 1 to 10 (where n = an integer of 2 or more).

14. A metal-resin laminate according to claim 13, for use in automotive parts.

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