Multi-layer sheet and method for producing same

Abstract

The present invention addresses the problem of providing a multi-layer sheet comprising: an adhesive agent layer that contains an acid modified polyolefin; and a base material layer that contains a polyphenylene ether. The peeling strength of the adhesive agent layer and the base material layer is high. This multi-layer sheet is characterized by comprising: a base material layer (A) which contains 40-99.9 mass% polyphenylene ether (a1), 0-59.9 mass% polystyrene (a2), and an amino-group-containing polymer (a3); and an adhesive agent layer (B) which contains an acid modified polyolefin.

Description

Multilayer sheet and method for producing the same

[0001] The present invention relates to a multilayer sheet having excellent adhesiveness and heat resistance that can be used for bonding or sealing various parts and can be used as a sheet-like member itself, and to a method for producing the same.

[0002] In recent years, hot melt adhesive compositions have come to be used as adhesive films or sheets (hereinafter collectively referred to as "adhesive members") in chemical batteries such as lithium ion batteries and fuel cells incorporated into notebook computers, smartphones, tablets, automobiles, etc., as well as physical batteries such as solar cells and capacitors. It is known that relatively good adhesive strength can be obtained by using hot melt adhesive compositions containing an acid-modified olefin thermoplastic resin (hereinafter also referred to as "acid-modified polyolefin") as the main component to bond metal substrates such as iron, aluminum, titanium, other metals, and alloys thereof used as the base materials for the components of these batteries.

[0003] In battery applications, hot melt adhesive compositions are required to have not only adhesive strength but also durability against the battery's constituent materials. In lithium ion batteries, lithium hexafluorophosphate, used as an electrolyte, may react with moisture to generate hydrofluoric acid. In fuel cells, acids such as hydrofluoric acid may be generated from the electrolyte membrane, a constituent component of the battery, so acid resistance is required. Furthermore, lithium ion batteries require durability against ethylene carbonate or diethyl carbonate, which are used as electrolyte solvents, and nickel-metal hydride batteries require durability against strong alkaline aqueous solutions. Furthermore, fuel cells require durability against ethylene glycol or propylene glycol, etc., because a coolant containing such ethylene glycol or propylene glycol is circulated inside the battery to cool the battery that generates heat during power generation.

[0004] Patent Document 1 discloses a resin composition comprising 50 to 99% by mass of a low-viscosity propylene-based base polymer satisfying specific properties and 1 to 50% by mass of an acid-modified propylene-based elastomer satisfying specific properties, as well as a hot-melt adhesive containing the resin composition. This resin composition has excellent adhesion to polyolefin substrates and also excellent adhesion to metal substrates. Patent Document 2 discloses acid-modified polypropylene as an adhesive between metal and nylon-based resin.

[0005] By laminating an acid-modified polyolefin adhesive film or sheet on a substrate layer to form a multilayer sheet, it is possible to obtain an adhesive member with even higher performance and functionality. An engineering plastic with excellent rigidity and heat resistance is used for the substrate layer of this multilayer sheet. By forming the acid-modified polyolefin adhesive into such a multilayer sheet, strength, rigidity, gas barrier properties, chemical resistance, acid / alkali resistance, heat resistance, etc. are improved, making it suitable for use in applications requiring durability, such as the above-mentioned lithium ion batteries and fuel cells. Furthermore, by using the multilayer sheet as an adhesive member for lithium ion batteries and fuel cells, it is possible to reduce the number of constituent members and parts, thereby reducing costs and improving productivity.

[0006] Engineering plastics used as the substrate of multilayer sheets have included polyethylene naphthalate, heat-resistant polyolefins such as cycloolefin polymers, polyphenylene ether alloys, and aromatic polyamide resins, due to their heat resistance, rigidity, dimensional stability, and cost. For example, Patent Document 3 describes a laminate sheet for sealing electronic devices, which comprises a first sheet and a second sheet laminated together, the first sheet containing an acid-modified polyolefin thermoplastic resin, the second sheet having a higher melting point than the first sheet, and the peel strength of the second sheet relative to the first sheet at 25°C being 0.5 to 10.0 [N / 15 mm]. Patent Document 3 also describes polyethylene naphthalate as a specific example of the second sheet.

[0007] JP 2013-060521 A JP 2017-109613 A International Publication No. 2011 / 013389

[0008] As described above, multilayer sheets formed by laminating an adhesive layer containing an acid-modified polyolefin and a substrate layer containing a heat-resistant polyolefin such as polyethylene naphthalate or a cycloolefin polymer, or an engineering plastic such as polyphenylene ether or an aromatic polyamide resin have been used as adhesive members. However, polyethylene naphthalate and aromatic polyamide resins hydrolyze during long-term use, and have problems with durability in environments where they come into contact with moisture. Cycloolefin polymers have a problem in that their softening point is not sufficiently high, limiting the compression bonding temperature. Furthermore, cycloolefin polymers have low toughness, making them prone to problems such as cracking during long-term use.

[0009] Polyphenylene ether does not have the degradation problems seen with other engineering plastics over long periods of use, but it does not adhere well to the acid-modified polyolefin used in the adhesive layer, resulting in easy delamination.

[0010] The problem to be solved by the present invention is to provide a multilayer sheet comprising an adhesive layer containing an acid-modified polyolefin and a substrate layer containing a polyphenylene ether, wherein the adhesive layer and the substrate layer have high peel strength.

[0011] The present inventors have conducted extensive research to solve the above problems in developing a multilayer sheet comprising an adhesive layer containing an acid-modified polyolefin and a substrate layer containing polyphenylene ether. Specifically, they have conducted various research on multilayer sheets in which functional groups have been introduced into the substrate layer containing polyphenylene ether, and have been able to complete the present invention.

[0012] Means for solving the above problems include the following aspects. [1] A multilayer sheet comprising a substrate layer (A) containing 40 to 99.9 mass% of polyphenylene ether (a1), 0 to 59.9 mass% of polystyrene (a2), and an amino group-containing polymer (a3), and an adhesive layer (B) containing an acid-modified polyolefin. [2] The multilayer sheet according to [1], wherein the content of the amino group-containing polymer (a3) ​​in the substrate layer (A) is 2 to 40 mass%. [3] The multilayer sheet according to [1] or [2], wherein the softening point of the substrate layer (A) is 175°C or higher. [4] The multilayer sheet according to any one of [1] to [3], wherein the storage modulus of the substrate layer (A) at 160°C is 500 MPa or higher. [5] The multilayer sheet according to any one of [1] to [4], wherein the amino group-containing polymer (a3) ​​in the substrate layer (A) contains a polystyrene chain having an amino group at its terminal. [6] The multilayer sheet according to [5], wherein the amino group-containing polymer (a3) ​​of the base layer (A) is a styrene-diene-styrene block copolymer. [7] The multilayer sheet according to any one of [1] to [6], wherein the acid-modified polyolefin is a maleic anhydride-modified polyolefin. [8] The multilayer sheet according to any one of [1] to [7], wherein the base layer (A) has a thickness of 50 to 300 μm and the adhesive layer (B) has a thickness of 10 to 100 μm. [9] A method for producing a multilayer sheet, comprising the step of contacting a base layer (A) containing 40 to 99.9 mass% of polyphenylene ether (a1), 0 to 59.9 mass% of polystyrene (a2), and an amino group-containing polymer (a3) ​​with an adhesive layer (B) containing an acid-modified polyolefin in a molten state at 160° C. or higher.

[0013] According to the present invention, it is possible to provide a multilayer sheet which includes an adhesive layer containing an acid-modified polyolefin and a substrate layer containing a polyphenylene ether, and which has high peel strength between the adhesive layer and the substrate layer.

[0014] By including the base material layer (A) containing the amino group-containing polymer (a3) ​​and the adhesive layer (B) containing the acid-modified polyolefin, a multilayer sheet having excellent adhesive strength and heat resistance can be produced, thereby providing a high-performance and economical sheet-like battery component, etc.

[0015] 1 is a calibration curve for converting the absorbance ratio of ethylene units and propylene units into a mass ratio.

[0016] The multilayer sheet of the present invention comprises a substrate layer (A) containing polyphenylene ether (a1) and an adhesive layer (B) containing an acid-modified polyolefin. The substrate layer (A) is an intermediate layer or a surface layer, and the adhesive layer (B) is a surface layer. Here, the surface layer is a layer disposed on either the upper or lower surface, and the intermediate layer is a layer other than the surface layer. When the adhesive layer (B) is disposed on only one surface layer, the intermediate layer may be omitted, and both the substrate layer (A) and the adhesive layer (B) may be surface layers. Typical layer configurations include a two-layer sheet of substrate layer (A) / adhesive layer (B) and a three-layer sheet of adhesive layer (B) / substrate layer (A) / adhesive layer (B). If the interfacial strength between the substrate layer (A) and the adhesive layer (B) is insufficient, a tie layer (C) may be disposed between the two layers. The tie layer (C) firmly bonds the substrate layer (A) and the adhesive layer (B). Typical layer configurations when a tie layer (C) is provided include a three-layer sheet of substrate layer (A) / tie layer (C) / adhesive layer (B) and a five-layer sheet of adhesive layer (B) / tie layer (C) / substrate layer (A) / tie layer (C) / adhesive layer (B). In one embodiment of the present invention, the substrate layer (A) and the adhesive layer (B) are preferably in direct contact without the intermediary of the tie layer (C). In one embodiment of the present invention, the tie layer (C) may contain a functional group capable of bonding with an amino group, such as a carboxylic acid or a carboxylic anhydride. For example, the tie layer (C) may be a layer containing an acid-modified polyolefin.

[0017] The substrate layer (A) contains polyphenylene ether (a1). The polyphenylene ether (a1) may be a major component accounting for 40 to 99.9% by mass of the substrate layer (A). The mass ratio of polyphenylene ether (a1) in the substrate layer (A) is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. When the mass ratio of polyphenylene ether (a1) is within this range, the heat resistance of the multilayer sheet can be improved. The mass ratio of polyphenylene ether (a1) in the substrate layer (A) is preferably 98% by mass or less, more preferably 95% by mass or less. When the mass ratio of polyphenylene ether (a1) is within this range, the formability of the multilayer sheet can be improved.

[0018] The substrate layer (A) may further contain polystyrene (a2). The polystyrene (a2) is different from the amino group-containing polymer (a3) ​​and does not contain an amino group. The polystyrene (a2) may be a minor component occupying 0 to 55.9% by mass of the substrate layer (A). The polystyrene (a2) is an optional component, and the substrate layer (A) may not contain polystyrene (a2). The mass ratio of polystyrene (a2) in the substrate layer (A) is preferably 50% by mass or less, more preferably 40% by mass or less, and particularly preferably 30% by mass or less. When the mass ratio of polystyrene (a2) is within this range, the heat resistance of the multilayer sheet can be improved.

[0019] Typical examples of polystyrene (a2) include general-purpose polystyrene (GPPS), which is a polymer of styrene alone, and high-impact polystyrene (HIPS), which is made by adding rubber to GPPS to impart impact resistance. However, copolymers of styrene and acrylonitrile or (meth)acrylic acid esters can also be used. The copolymer used as polystyrene (a2) contains monomer units derived from styrene as the main component (e.g., 50% by mass or more of the total monomer units). When polystyrene (a2) is a copolymer, the mass ratio of monomer units derived from comonomers other than styrene in polystyrene (a2) is preferably 20% by mass or less, more preferably 10% by mass or less. By having the mass ratio of monomer units derived from comonomers be 20% by mass or less, compatibility with polyphenylene ether (a1) is improved, and phase separation can be prevented.

[0020] The total amount of polyphenylene ether (a1) and polystyrene (a2) in the substrate layer (A) is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. The total amount of polyphenylene ether (a1) and polystyrene (a2) in the substrate layer (A) is preferably 99.9% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less.

[0021] The substrate layer (A) further contains an amino group-containing polymer (a3). The mass ratio of the amino group-containing polymer (a3) ​​in the substrate layer (A) is preferably 0.1 mass% or more, more preferably 2 mass% or more, and particularly preferably 5 mass% or more. When the mass ratio of the amino group-containing polymer (a3) ​​is within this range, the amino group-containing polymer (a3) ​​sufficiently reacts with the acid-modified polyolefin in the adhesive layer (B), thereby improving the interlayer adhesive strength. The mass ratio of the amino group-containing polymer (a3) ​​in the substrate layer (A) is preferably 40 mass% or less, more preferably 30 mass% or less. When the mass ratio of the amino group-containing polymer (a3) ​​is within this range, the heat resistance of the substrate can be maintained and the formability of the multilayer sheet can be improved.

[0022] The amino group-containing polymer (a3) ​​is not particularly limited as long as it has an amino group. The weight average molecular weight of the amino group-containing polymer (a3) ​​is preferably 1,000 or more. The weight average molecular weight of the amino group-containing polymer (a3) ​​is preferably 200,000 or less. When the weight average molecular weight is 1,000 or more, moldability and thermal stability are improved, and when the weight average molecular weight is 200,000 or less, adhesive strength with the adhesive layer (B) or tie layer (C) is improved. When the weight average molecular weight is within this range, both the physical properties of the base layer (A) and adhesiveness with the adhesive layer (B) can be achieved. The weight average molecular weight is a standard polystyrene equivalent value obtained using gel permeation chromatography (GPC).

[0023] The amino group-containing polymer (a3) ​​is preferably a polymer having an amino group at the molecular end, more preferably a polymer containing a polystyrene chain having an amino group at the end, and particularly preferably a polymer containing a polystyrene chain having a molecular weight of 1,000 or more and having an amino group at the end. In the polymer having an amino group at the molecular end, the amino group may be present at only one end or at both ends. Primary amines or secondary amines are preferably used as the terminal amino groups.

[0024] Methods for synthesizing polystyrene chains having terminal amino groups include a method in which the active terminals are capped with a modifying agent after anionic living polymerization or radical living polymerization, and a method in which styrene is radically polymerized in the presence of a chain transfer agent having an amino group.

[0025] The polymer synthesized by the method of introducing amino groups into active terminals using a modifying agent after living polymerization is not limited to styrene homopolymers, but may also be a block copolymer containing a styrene chain. However, in the case of a block copolymer, it is preferable that the chain to which the amino group is bonded is a styrene chain. In terms of ease of commercial availability, styrene-diene block copolymers having amino groups at their terminals are preferably used.

[0026] One example of a method for end-capping active terminals with a modifier after anionic living polymerization is to anionically polymerize styrene with an initiator such as butyllithium in a hydrocarbon solvent, add a modifier such as 1,3-dimethyl-2-imidazolidinone after polymerization to cause an addition reaction with the terminal anions, and then treat the reaction product with protons. In the case of styrene-diene block copolymers, a diene such as butadiene is anionically polymerized in the first stage, and styrene is added and anionically polymerized in the second stage, and a modifier is similarly added to introduce amino groups. As styrene-diene block copolymers, block copolymers having polystyrene blocks in the terminal chains, such as styrene-diene diblock copolymers and styrene-diene-styrene triblock copolymers, are preferred. Triblock copolymers are particularly preferred due to their commercial availability.

[0027] Specific examples of polydiene blocks include polybutadiene and its hydrogenated product poly(ethylene-butylene), polyisoprene and its hydrogenated product poly(ethylene-propylene), and poly(butadiene-butylene) which is a partially hydrogenated product of polybutadiene.

[0028] An example of a method for radically polymerizing styrene in the presence of a chain transfer agent having an amino group is a method in which 2-aminoethynthiol or its hydrochloride is used as the chain transfer agent and styrene is radically polymerized in an organic solvent using an azo initiator or organic peroxide. When a hydrochloride is used as the chain transfer agent, it is neutralized with an equivalent amount of alkali to convert it to an amine.

[0029] The amino group concentration of the base layer (A) is preferably 1 μeq or more, more preferably 5 μeq or more. When the amino group concentration is within this range, the interlayer adhesive strength with the adhesive layer (B) or the tie layer (C) can be improved. The amino group concentration of the base layer (A) is preferably 200 μeq or less, more preferably 100 μeq or less. When the amino group concentration is within this range, the heat resistance of the base layer (A) can be improved and problems such as discoloration can be prevented.

[0030] To the base layer (A), a polymer other than (a1) to (a3) ​​(hereinafter referred to as "other polymer (A)") may be added for the purposes of improving toughness and molding stability at low temperatures, and improving adhesion to the adhesive layer (B) or the tie layer (C).

[0031] Examples of the other polymer (A) include styrene-based block copolymers such as styrene-butadiene-styrene block copolymers and hydrogenated products thereof, and styrene-isoprene-styrene block copolymers and hydrogenated products thereof, and graft copolymers in which a styrene homopolymer or copolymer is grafted onto a polyolefin. These copolymers contain styrene units as a minor component (e.g., 40% by mass or less of the total monomer units). The presence of a polystyrene chain enables the other polymer (A) to have high miscibility with the polyphenylene ether (a1).

[0032] As the other polymer (A), unmodified polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers may be used. By including a polyolefin in the base layer (A), improved adhesion to the adhesive layer (B) or tie layer (C), both of which contain the same polyolefin resin, can be expected. Because these polyolefins are completely incompatible with polyphenylene ether (a1), it is preferable to use the aforementioned copolymer containing a styrene unit in combination as a compatibilizer.

[0033] When the other polymer (A) is used, the content of the other polymer (A) in the base layer (A) is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more. When the added amount is within this range, the improving effect of the other polymer (A) is enhanced.

[0034] When the other polymer (A) is used, the content of the other polymer (A) in the base layer (A) is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less. When the added amount is within this range, the multilayer sheet can have high heat resistance and high adhesive strength at high temperatures.

[0035] The softening point of the substrate layer (A) is preferably 175° C. or higher, more preferably 180° C. or higher, and particularly preferably 185° C. or higher. When the softening point is within this range, the heat resistance of the multilayer sheet is improved.

[0036] The storage modulus of the base layer (A) is preferably 500 MPa or more at 160° C. It is more preferable that the storage modulus of the base layer (A) is 500 MPa or more at 170° C. When the storage modulus in this temperature range is 500 MPa or more, deformation and damage of the multilayer sheet due to thermocompression bonding during adhesion can be prevented.

[0037] The softening point and storage modulus in the present invention are values ​​determined using a tensile viscoelasticity analyzer (DMS6100 manufactured by Hitachi High-Tech Sanence Corporation). Specifically, the temperature is raised from room temperature to 250°C at a frequency of 1 Hz and a heating rate of 2°C / min, and the changes in storage modulus, loss modulus, and tan Δ with temperature are recorded. The softening point in the present invention refers to the temperature at which tan Δ reaches its maximum value.

[0038] The melt flow rate of the substrate layer (A) is preferably 1 g / 10 min or more, more preferably 2 g / 10 min or more. The melt flow rate of the substrate layer (A) is preferably 50 g / 10 min or less, more preferably 30 g / 10 min or less. If the melt flow rate of the substrate layer (A) is below the lower limit, the melt viscosity becomes high, making sheet molding difficult, and if it is above the upper limit, the melt tension becomes too low, making sheet molding difficult as well.

[0039] Here, the melt flow rate is a value measured in accordance with JIS K7210: 2014. The melt flow rate of the base layer (A) was measured at a resin temperature of 300°C and a load of 2.16 kg.

[0040] The substrate layer (A) may further contain an additive selected from the group consisting of an antioxidant, an ultraviolet absorber, a filler, a reinforcing fiber, a release agent, a processing aid, a flame retardant, a plasticizer, a nucleating agent, an antistatic agent, a pigment, a dye, a foaming agent, and a combination thereof.

[0041] The adhesive layer (B) contains an acid-modified polyolefin, which is an unmodified polyolefin (hereinafter also simply referred to as "polyolefin") graft-modified with an acid compound selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and combinations thereof.

[0042] Examples of monomer units constituting polyolefins include monomer units derived from monomers selected from the group consisting of α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene, diene monomers such as butadiene, isoprene, and chloroprene, aromatic vinyl compounds such as styrene, and combinations thereof. The number of carbon atoms in the monomer is preferably 2 to 10, and more preferably 2 to 5.

[0043] Among these, polyolefins selected from the group consisting of polymer blends of polyethylene and polypropylene, ethylene-propylene copolymers, and combinations thereof are preferred because they have high adhesive strength to the adherend.

[0044] Polyethylene is a polymer containing ethylene units as a main component, and may be a homopolymer or a copolymer. When it is a copolymer, the content of ethylene units in the polyethylene is preferably 50% by mass or more, and may be 70% by mass or more. Specific examples of polyethylene include homopolymers such as low-density polyethylene, high-density polyethylene, and linear low-density polyethylene; copolymers such as ethylene-diene monomer copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid ester copolymers, and ethylene-methacrylic acid ester copolymers; and halogen-modified polyethylenes such as chlorinated polyethylene.

[0045] Polypropylene is a polymer containing propylene units as a main component, and may be a homopolymer or a copolymer. In the case of a copolymer, the content of propylene units in the polypropylene is preferably 50% by mass or more, and may be 70% by mass or more. Specific examples of polypropylene include homopolymers such as amorphous polypropylene and crystalline polypropylene, copolymers such as propylene-diene monomer copolymer, and halogen-modified products such as chlorinated polypropylene.

[0046] An ethylene-propylene copolymer is a polymer containing ethylene units and propylene units, and may be composed only of ethylene units and propylene units, or may further contain other monomer units in addition to ethylene units and propylene units. An example of an ethylene-propylene copolymer containing other monomer units is an ethylene-propylene-diene monomer copolymer. The total amount of ethylene units and propylene units in the ethylene-propylene copolymer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may even be 100% by mass.

[0047] Polyolefins include physical blends of these resins, reactive blends in which functional groups are reacted between different polymers in a molding machine, graft copolymers and block copolymers consisting of multiple segments, and compositions in which physical blends of these copolymers are microdispersed as compatibilizers.

[0048] Of all the monomer units contained in the polyolefin, the total amount of ethylene units and propylene units is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass.

[0049] The mass ratio of ethylene units to propylene units (ethylene units / propylene units) contained in the polyolefin is preferably 10 / 90 to 40 / 60, more preferably 15 / 85 to 35 / 65. When the mass ratio of ethylene units is equal to or greater than the lower limit of this range, the thermocompression bondability of the acid-modified polyolefin is improved, thereby improving adhesive strength. When the mass ratio of ethylene units is equal to or less than the upper limit of this range, adhesive strength at high temperatures can be improved. By setting the mass ratio of ethylene units to propylene units within the above range, it is possible to achieve both high-temperature and low-temperature adhesive durability. Note that when the polyolefin is a polymer blend of polyethylene and polypropylene, the "mass ratio of ethylene units to propylene units contained in the polyolefin" means the mass ratio of ethylene units to propylene units in all ethylene units and propylene units contained in the polyethylene and polypropylene.

[0050] The mass ratio of ethylene units and propylene units can be determined by the characteristic absorption of polyethylene in the IR spectrum (719 cm －１ ) and the characteristic absorption of polypropylene (1167 cm －１ ) is determined from the absorbance ratio of the ethylene unit and the propylene unit. Specifically, a calibration curve is used to convert the absorbance ratio of the ethylene unit and the propylene unit into a mass ratio. The calibration curve can be created by blending commercially available polyethylene and polypropylene at various ratios and plotting the blending ratio and the absorbance ratio. For specific details, see the examples described below.

[0051] Polyethylene, polypropylene, and ethylene-propylene copolymers may contain monomer units other than ethylene units and propylene units. Examples of other monomers that form monomer units other than ethylene units and propylene units include α-olefins such as 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene; diene monomers such as butadiene, isoprene, and chloroprene; unsaturated carboxylic acids and derivatives thereof such as vinyl acetate, acrylic acid esters, acrylic acid, methacrylic acid, and methacrylic acid esters; and aromatic vinyl compounds such as styrene. The content of monomer units other than ethylene units and propylene units in polyolefins is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less. When the content of monomer units other than ethylene units and propylene units is within this range, the properties of the polyolefin, such as water resistance, chemical resistance, and durability, are improved, and polyolefins can be produced at low cost.

[0052] Methods for producing polyolefins include known production methods using polymerization catalysts. Examples of polymerization catalysts include Ziegler catalysts and metallocene catalysts, and examples of polymerization methods include slurry polymerization and gas phase polymerization. Impact-resistant polypropylene, also known as polypropylene block polymer, is essentially a mixture of polypropylene and a propylene-ethylene random copolymer, and can be produced by a process consisting of a first step of obtaining a propylene homopolymer and a second step of obtaining a propylene-ethylene random copolymer.

[0053] The acid compound used in producing the acid-modified polyolefin is selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and combinations thereof.

[0054] The unsaturated carboxylic acid is a compound having an ethylenic double bond and a carboxylic acid group in the same molecule, and examples thereof include various unsaturated monocarboxylic acids and unsaturated dicarboxylic acids. These acid compounds may be used alone or in combination of two or more.

[0055] Specific examples of unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid.

[0056] Specific examples of unsaturated dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid, and endic acid.

[0057] The unsaturated carboxylic acid anhydride is a compound having an ethylenic double bond and a carboxylic acid anhydride group in the same molecule, and examples thereof include the acid anhydrides of the unsaturated dicarboxylic acids described above. Specific examples of the acid anhydrides of unsaturated dicarboxylic acids include maleic anhydride, fumaric anhydride, itaconic anhydride, citraconic anhydride, nadic anhydride, and endic anhydride.

[0058] Among these, maleic acid and maleic anhydride are preferably used because of their high modifying effect, and maleic anhydride is particularly preferably used.

[0059] The graft modification may be carried out by a known method, for example, by grafting an acid compound together with a polyolefin in a molten or solution state in the presence of a radical polymerization initiator such as an organic peroxide or an aliphatic azo compound.

[0060] The temperature of the grafting reaction is preferably 80 to 160° C. when the reaction is carried out in a solution state, and 150 to 300° C. when the reaction is carried out in a melt state. In both the solution state and the melt state, the reaction rate is high at or above the lower limit of the reaction temperature range described above, while a decrease in the molecular weight of the resin can be suppressed at or below the upper limit of the reaction temperature range described above, and the mechanical strength of the resulting acid-modified polyolefin can be maintained.

[0061] The radical polymerization initiator to be used may be selected from commercially available organic peroxides, taking into consideration the reaction temperature and the like.

[0062] If a portion of the acid compound used for graft modification remains unreacted, it is preferable to remove the unreacted acid compound by a known method such as distillation under reduced pressure in order to prevent adverse effects on adhesive strength.

[0063] The amount of the acid compound grafted to the acid-modified polyolefin is preferably 0.2% by mass or more, more preferably 0.4% by mass or more. When the amount of the grafted acid compound is within this range, the adhesiveness of the adhesive layer (B) can be improved.

[0064] The amount of the acid compound grafted onto the acid-modified polyolefin is preferably 5% by mass or less, more preferably 2% by mass or less. When the amount of the grafted acid compound is within this range, deterioration of physical properties due to a decrease in molecular weight can be suppressed.

[0065] In this specification, the amount of acid compound grafted to the acid-modified polyolefin is defined by the acid value of the acid-modified polyolefin using the following formula: Graft amount (mass%) = Acid value × M × 100 / (1000 × 56.1 × V) In the formula, M and V are defined by the following formulas: M = (Molecular weight of acid compound) + (Number of unsaturated groups in acid compound) × 1.008 V = Valence of acid group (however, in the case of containing acid anhydride groups, V is the valence of the acid group when the acid anhydride groups are completely hydrolyzed) The acid value indicates the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 g of sample, and is measured in accordance with JIS K 0070:1992.

[0066] The melting point of the acid-modified polyolefin is preferably 130° C. or higher, more preferably 135° C. or higher. When the melting point of the acid-modified polyolefin is within this range, the heat resistance and adhesive strength at high temperatures of the adhesive layer (B) can be improved.

[0067] The melting point of the acid-modified polyolefin is preferably 160° C. or lower, more preferably 150° C. or lower. When the melting point of the acid-modified polyolefin is within this range, good thermocompression bondability can be obtained, and adhesion durability at low temperatures can be improved.

[0068] In the present invention, the melting point refers to the temperature at the top of an endothermic peak that occurs in the process of first holding the sample at 180°C for several minutes, then cooling it to 0°C, and then raising the temperature to 200°C at a rate of 10°C per minute using a differential scanning calorimeter (DSC).

[0069] The melt flow rate of the acid-modified polyolefin is preferably 3 g / 10 min or more, more preferably 7 g / 10 min or more, and is preferably 50 g / 10 min or less, more preferably 30 g / 10 min or less.

[0070] Here, the melt flow rate is a value measured in accordance with JIS K7210: 2014. The melt flow rate of the adhesive layer (B) was measured at a resin temperature of 230°C and a load of 2.16 kg.

[0071] The content of the acid-modified polyolefin in the adhesive layer (B) may be 2% by mass or more. For example, the acid-modified polyolefin may be used in combination with an unmodified polyolefin, and when a highly acid-modified polyolefin is used, a small amount of about 2% by mass may be used. In one embodiment, the content of the acid-modified polyolefin in the adhesive layer (B) is preferably 30% by mass or more, more preferably 70% by mass or more, particularly 90% by mass or more, and may even be 100% by mass.

[0072] To the adhesive layer (B), a polymer other than the acid-modified polyolefin (hereinafter referred to as "other polymer (B)") can be added for the purpose of improving the adhesive strength at low temperatures, adhesive durability, molding stability, and adhesion to the base layer (A). Examples of the other polymer (B) include styrene-based block copolymers such as styrene-butadiene-styrene block copolymers and hydrogenated products thereof, styrene-isoprene-styrene block copolymers and hydrogenated products thereof, and styrene-isobutylene-styrene block copolymers and hydrogenated products thereof, as well as styrene-based graft copolymers in which a styrene homopolymer or copolymer is grafted onto a polyolefin. In addition, unmodified polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers may also be added as the other polymer (B).

[0073] When the other polymer (B) is used, the lower limit of the content of the other polymer (B) in the adhesive layer (B) is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more. When the added amount is within this range, the improving effect of the other polymer (B) is enhanced.

[0074] When another polymer (B) is used, the upper limit of the content of the other polymer (B) in the adhesive layer (B) is preferably 50% by mass or less, more preferably 30% by mass or less, and particularly preferably 10% by mass or less. When the amount added is within this range, the adhesive layer (B) can obtain high heat resistance and high adhesive strength at high temperatures. As described above, when an acid-modified polyolefin with a high degree of acid modification is used, the content of the acid-modified polyolefin can be reduced. In such a case, the content of the unmodified polyolefin may be high, and the upper limit of the content of the unmodified polyolefin in the adhesive composition may be 98% by mass.

[0075] The adhesive layer (B) may further comprise an additive selected from the group consisting of an antioxidant, an ultraviolet absorber, a filler, a reinforcing fiber, a release agent, a processing aid, a flame retardant, a plasticizer, a nucleating agent, an antistatic agent, a pigment, a dye, a foaming agent, and combinations thereof.

[0076] The multilayer sheet of the present invention can be firmly bonded to an adherend. When the adhesive layer (B) of the multilayer sheet is bonded to an adherend, particularly a 0.1 mm thick SUS304 plate, to produce a bonded structure, the room temperature peel strength between the multilayer sheet and the adherend, particularly a 0.1 mm thick SUS304 plate, is 2 N / 10 mm or more, more preferably 5 N / mm or more. Here, room temperature is 23°C, and the room temperature peel strength is measured under the conditions described in the Examples below.

[0077] The substrate layer (A) preferably has a thickness within the range of 50 to 300 μm. When the thickness of the substrate layer (A) is equal to or greater than this lower limit, sufficient rigidity can be obtained. When the thickness of the substrate layer (A) is equal to or less than this upper limit, the effect on the thickness of an article incorporating the multilayer sheet, such as a battery, can be reduced. On the other hand, the thickness of the adhesive layer (B) preferably has a thickness of 10 to 100 μm. When the thickness of the adhesive layer (B) is equal to or greater than this lower limit, the occurrence of poor adhesion can be suppressed. When the thickness of the adhesive layer (B) is equal to or less than this upper limit, the adhesive can be prevented from extruding from the multilayer sheet, preventing defects in an article incorporating the multilayer sheet, such as a battery. By controlling the thickness of the multilayer sheet within this range, the multilayer sheet and the bonded body using it can exhibit excellent adhesive performance, durability, productivity, and economy.

[0078] The base material layer (A) and the adhesive layer (B) are generally each produced from a resin composition as a raw material. The resin compositions that are the raw materials for the base material layer (A) and the adhesive layer (B) are compositions whose main component is a resin, consisting of the components of the base material layer (A) or the adhesive layer (B) described above. The resin composition can be produced by melt-kneading the main component resin and, if necessary, other components, using an extruder, Banbury mixer, or heated roll, and then cooling and solidifying the extruded strands with water or the like while pulling them through the nozzle holes of a die head, and cutting them into pellets.

[0079] The melt-kneading temperature of the resin composition used for the substrate layer (A) is preferably 150 to 320°C, more preferably 180 to 300°C, and the kneading time is usually 0.5 to 20 minutes, preferably 1 to 15 minutes.

[0080] The temperature for melt-kneading the resin composition used for the adhesive layer (B) is preferably 150 to 270°C, more preferably 170 to 250°C, and the kneading time is usually 0.5 to 20 minutes, preferably 1 to 15 minutes.

[0081] The resin composition used for the substrate layer (A) and the resin composition used for the adhesive layer (B) thus obtained can be formed into multilayer sheets of various shapes depending on the application by a conventionally known method, such as compression molding, injection molding, extrusion molding, multilayer extrusion molding, profile extrusion molding, or blow molding.

[0082] The substrate layer (A), adhesive layer (B), and optionally tie layer (C) may be prepared as sheets and then thermally laminated to form a multilayer structure, or may be formed by simultaneously forming a sheet and laminating the layers as in multilayer extrusion molding. In either case, it is preferable to bring the adjacent layers into contact with each other while the layers are in a molten state. The contact temperature is preferably 160°C or higher, more preferably 190°C or higher, and particularly preferably 220°C or higher. If the contact temperature is higher than the lower limit, the acid group or acid anhydride group contained in the adhesive layer (B) and the amino group contained in the substrate layer (A) may form a bond, thereby improving the interlayer adhesive strength.

[0083] The multilayer sheet of the present invention is preferably produced by multilayer extrusion molding in terms of productivity and production costs. In general extrusion molding, layered molten resin extruded from a T-die is cooled and stretched by rolls or the like to form a sheet. Multilayer molding is possible by "co-extrusion," in which multiple resins are extruded simultaneously. Specific co-extrusion techniques include the "feedblock method," in which resins are joined just before the T-die, and the "multi-manifold method," in which the single layers are spread in manifolds and then joined at the lip, which is the discharge outlet of the T-die. Either of these techniques, or other techniques, may be used to produce the multilayer sheet of the present invention.

[0084] The multilayer sheet of the present invention can be bonded to adherends made of various materials such as metal, glass, ceramics, or plastic. This allows for the production of a bonded body including the multilayer sheet and the adherend. For example, the bonded body including the multilayer sheet can be used as a member or part of a layered battery.

[0085] The metal used as the adherend may be a commonly known metal plate, metal flat plate, or metal foil, and may be iron, copper, aluminum, lead, zinc, titanium, chromium, stainless steel, etc. Among these, iron, aluminum, titanium, and stainless steel are particularly preferred.

[0086] The plastic used as the adherend may be any of various thermoplastic or thermosetting resins. Composite materials may also be used, in which inorganic materials such as glass or ceramics, or fillers or fibers such as metals or carbon are combined with a resin.

[0087] The present invention will be described in more detail below with reference to examples. Unless otherwise specified, "parts" means parts by mass and "%" means % by mass. Unless otherwise specified, "PPE" means polyphenylene ether, "PS" means polystyrene, "PP" means polypropylene, "PE" means polyethylene, and "MAH" means maleic anhydride.

[0088] [Adhesive layer (B)] Maleic anhydride-modified polyolefins A to B, each of which mainly contains polypropylene, polyethylene, an ethylene-propylene copolymer, and maleic anhydride-modified versions of these, were prepared. The PE / PP blending ratio and the amount of maleic anhydride in the maleic anhydride-modified polyolefins A to B were confirmed by the procedures described in (1) and (2) below.

[0089] (1) PE / PP Blending Ratio Commercially available polyethylene resin (P9210 manufactured by Keiyo Polyethylene Co., Ltd.) and polypropylene resin (Waymax MFX3 manufactured by Japan Polypropylene Corporation) were melt-mixed in an extruder at various blending ratios, and the resulting resin mixture was molded using a bench press molding machine to produce a resin sheet with a thickness of approximately 2 mm.

[0090] An IR spectrum was obtained from the cut surface of the resin sheet by the attenuated total reflection method (ATR method) using a Spectrum 100 manufactured by PerkinElmer. －１ (PE characteristic absorption) and 1167 cm －１The PE absorbance ratio was calculated from the absorbance of (PP characteristic absorption). A calibration curve was created by plotting this absorbance ratio against the blending ratio during melt-kneading. The results of the PE blending ratio and PE absorbance ratio are shown in Table 1, and the plot results are shown in Figure 1.

[0091] In consideration of measurement error, the number of repetitions was set to 4 or more. The approximate curve of this plot was used as a calibration curve for determining the PE / PP blend ratio.

[0092]

[0093] The maleic anhydride-modified polyolefins A and B were molded into resin sheets with a thickness of 2 mm, and their cross sections were used as the measurement surfaces to measure the IR spectra in the same manner. Based on the obtained IR spectra, a calibration curve was created and the PE / PP blending ratios of the maleic anhydride-modified polyolefins A and B were determined. The results are shown in Table 2.

[0094] (2) Amount of maleic anhydride The amount of maleic anhydride grafted into the maleic anhydride-modified polyolefins A to B was quantified by neutralization titration. In the neutralization titration, the maleic anhydride-modified polyolefins A to B as samples were dissolved in xylene by heating, and the resulting solution was titrated with an ethanol solution of potassium hydroxide using phenol red as an indicator. The amount of maleic anhydride was calculated from the titration results. The results of the maleic anhydride amount are shown in Table 2.

[0095] (3) Melt Flow Rate The melt flow rate (MFR) was measured using a commercially available melt indexer (G-02 manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS K7210: 2014 at a resin temperature of 230 ° C. and a load of 2.16 kg. The results are shown in Table 2.

[0096]

[0097] [Base layer (A)] First, amino-terminated polystyrene (AT-PS) used for the base layer (A) was prepared according to the synthesis example below. The other materials used were commercially available products. Details of these will be described later.

[0098] [Synthesis Example] Synthesis of Amino-Terminated Polystyrene (AT-PS) A mixed solvent consisting of 90 parts isopropyl alcohol (IPA) and 10 parts distilled water was prepared. 30 parts of styrene, 40 parts of the mixed solvent, and 1.5 parts of 2-aminoethanethiol hydrochloride were placed in a glass flask equipped with a reflux condenser, a nitrogen inlet tube, a thermometer, two dropping funnels, and a stirrer, and the mixture was stirred, heated, and refluxed. 70 parts of styrene were placed in one dropping funnel, and a solution of 3.5 parts of 2-aminoethanethiol hydrochloride and 0.2 parts of 2,2'-azobis-(2-methylbutyronitrile) (hereinafter referred to as ABN-E) dissolved in 17.5 parts of the mixed solvent was placed in the other dropping funnel, and both were added dropwise under reflux over 2 hours. Subsequently, a solution consisting of 0.1 parts ABN-E and 2.5 parts of the mixed solvent was added dropwise over 1 hour, and then a solution consisting of 0.8 parts ABN-E and 40 parts of the mixed solvent was added dropwise over 2 hours. The mixture was then refluxed for 2 hours to complete the polymerization, and sodium hydroxide equivalent to the total amount of 2-aminoethanethiol hydrochloride charged was added to convert it to an amine. The polymerization solution was diluted with methyl ethyl ketone until it became transparent, and a large amount of methanol was poured into it to precipitate polystyrene. The polystyrene-terminated polystyrene powder was obtained by filtration, washing, and drying. The molecular weight calculated as polystyrene by gel permeation chromatography was a number average molecular weight of 3,000 and a weight average molecular weight of 5,100.

[0099] The resins (PPE / PS and amino group-containing polymer) shown in the "Composition of base layer (A)" in Table 3 below were melt-kneaded in the blending ratios (% by mass) shown in Table 3 to obtain a resin composition for the base layer (A). The melt flow rate, softening point, storage modulus, creep amount, and thermal change rate of the obtained resin composition for the base layer (A) were measured as described in (1) to (4) below. The results are shown in Table 3 together with the composition.

[0100] (1) Melt Flow Rate The melt flow rate (MFR) was measured using a commercially available melt indexer (G-02 manufactured by Toyo Seiki Seisaku-sho, Ltd.) in accordance with JIS K7210:2014 at 300°C and a load of 2.16 kg.

[0101] (2) Softening Point and Storage Modulus The softening point and storage modulus were determined using a tensile viscoelasticity analyzer (DMS6100 manufactured by Hitachi High-Tech Sanence Corporation). Specifically, the temperature was raised from room temperature to 250°C at a frequency of 1 Hz and a heating rate of 2°C / min, and the changes in storage modulus, loss modulus, and tan Δ with temperature were recorded. The softening point was determined as the temperature at which tan Δ reached its maximum value.

[0102] (3) Compression Creep Test The resin composition for the base layer (A) was molded into a sheet with a thickness of 1 mm using a bench press molding machine. This resin sheet was cut into a size of 10 mm x 10 mm, and five sheets were stacked to form a sample with a thickness of 5 mm. Using a heat press device (Digital Press CYPT-50 manufactured by Shinto Kogyo Co., Ltd.), the sample was heated at a temperature of 170 ° C and a pressure of 6 MPa for 12 hours, and the creep amount (%) was calculated from the change in thickness.

[0103] (4) Thermal Shrinkage Test The resin composition for the base layer (A) was molded into a sheet with a thickness of approximately 100 μm using a bench press molding machine. This resin sheet was cut into a size of 200 mm × 100 mm to prepare a sample. The prepared sample was hung in a dryer at 180 ° C for 30 seconds, and the thermal change rate was calculated from the dimensional change before and after heating. The thermal change rate is the average of the absolute value of the change rate of the long side and the absolute value of the change rate of the short side.

[0104] [Three-layer sheet] In each example, a three-layer sheet was produced as described below using the resin composition for the base layer (A) and the maleic anhydride-modified polyolefin for the adhesive layer (B) shown in Table 3, and evaluated.

[0105] The resin composition for the base layer (A) was formed into a base layer (A) with a thickness of approximately 150 μm using a bench press molding machine. The maleic anhydride-modified polyolefin for the adhesive layer (B) was formed into an adhesive layer (B) with a thickness of approximately 50 μm using a bench press molding machine. The base layer (A) and adhesive layer (B) were superimposed in the order of adhesive layer (B) / base layer (A) / adhesive layer (B) and thermocompressed for 10 seconds using the same bench press molding machine at the compression temperature listed in Table 3 to obtain a three-layer sheet.

[0106] [Test Piece] A 0.1 mm thick SUS304 plate was used as the adherend, and both sides of the three-layer sheet were sandwiched between SUS304 plates and thermocompression bonded (160°C, 10 seconds, 0.3 MPa) using a precision press to produce a bonded assembly. This bonded assembly was cut into 10 mm wide strips to prepare test pieces. The bonded portion of the test piece was 10 mm wide and 15 mm long. The room temperature peel strength, hot water peel strength, and constant load immersion drop time of the obtained test piece were measured as described below in (1) to (3).

[0107] (1) Room-temperature peel test In the room-temperature peel test, a tensile testing device (Instron 5564) manufactured by Instron was used to peel off a SUS304 plate at a tensile speed of 50 mm / min, and the peel force in the stable region was taken as the peel strength. The results are shown in Table 3 as room-temperature peel strength (N / 10 mm).

[0108] (2) Hot Water Peel Test In the hot water peel test, a load cell eDPU-50N manufactured by Imada Co., Ltd. was attached to a measurement stand MX2-1000N manufactured by the same company, and a heated water bath with a hook attached to the bottom was filled with hot water at 95°C, and the test piece was immersed in the water and peeled off, and the peel strength was evaluated in the same manner. The results are shown in Table 3 as hot water peel strength (N / 10 mm).

[0109] (3) Adhesion Durability in Water A constant-load immersion test was conducted to evaluate adhesion durability in water. The constant-load immersion test involves placing a test specimen in 95°C hot water under a constant peel load, and evaluating the adhesion durability based on the time (drop time) until the SUS304 plate peeled off. The test specimens were the same as those used to measure peel strength. One end of the handle of the test specimen was connected to a fixed stand with a wire, and the other end was connected to a weight. The test specimen and the weight were suspended from a fixed stand placed above the water surface into 95°C hot water, and a peel load (1 N) was applied by the weight in the water. The time (drop time) required for the adherend SUS304 plate to completely separate was measured. The results are shown in Table 3 as the constant-load immersion drop time (hr).

[0110]

[0111] Details of the resins used in the substrate layer (A) in Table 3 are as follows: 1000H: PPE-PS alloy ZYLON 1000H manufactured by Asahi Kasei Corporation, Tg = 184°C (DSC) PX100F: PPE PX100F manufactured by Mitsubishi Engineering Plastics Corporation, Tg = 204°C (DSC) MP10: amine-terminated hydrogenated styrene-based thermoplastic elastomer (SEBS) Tuftec MP10 manufactured by Asahi Kasei Corporation, styrene content 30% AT-PS: amine-terminated polystyrene obtained by the method shown in the synthesis example

[0112] As can be seen from the results in Table 3, the addition of the amino group-containing polymer significantly improved the adhesive strength and durability with the adhesive layer (B).

[0113] The multilayer sheet of the present invention is useful for bonding or sealing metals and other materials, and can be suitably used in applications where the resulting bonded body may be in continuous or intermittent contact with moisture. Because it has a substrate layer (A) with excellent rigidity and heat resistance, it is useful as a component of a battery, contributing to reducing the number of battery parts and costs, and significantly improving productivity.

[0114] Other uses include, for example, electric wires and cables in which metal conductors or optical fibers are coated with resin molded products, automobile mechanical parts, automobile exterior parts, automobile interior parts, molded power supply substrates, light reflectors for reflecting light sources, fuel cases for solid methanol batteries, heat insulating materials for metal pipes, heat insulating materials for vehicles, fuel cell water pipes, decorative molded products, water cooling tanks, boiler exterior cases, peripheral parts and members for printer ink, water piping, joints, secondary battery alkaline storage battery tanks, gasket sealants for various layered batteries, and the like.

[0115] The disclosure of Japanese Patent Application No. 2021-075960, filed on April 28, 2021, is incorporated herein by reference in its entirety.

Claims

1. A substrate layer (A) containing 40 to 99.9% by mass of polyphenylene ether (a1), 0 to 59.9% by mass of polystyrene (a2), and an amino group-containing polymer (a3); An adhesive layer (B) containing an acid-modified polyolefin; A multi-layer sheet comprising:

2. The multilayer sheet according to claim 1, wherein the content of the amino group-containing polymer (a3) ​​in the substrate layer (A) is 2 to 40% by mass.

3. 2. The multilayer sheet according to claim 1, wherein the softening point of the substrate layer (A) is 175°C or higher.

4. 2. The multilayer sheet according to claim 1, wherein the storage modulus of the substrate layer (A) at 160°C is 500 MPa or more.

5. 2. The multilayer sheet according to claim 1, wherein the amino group-containing polymer (a3) ​​of the substrate layer (A) contains a polystyrene chain having an amino group at its terminal.

6. 6. The multilayer sheet according to claim 5, wherein the amino group-containing polymer (a3) ​​of the substrate layer (A) is a styrene-diene-styrene block copolymer.

7. 2. The multilayer sheet of claim 1, wherein the acid-modified polyolefin is a maleic anhydride-modified polyolefin.

8. The multilayer sheet according to any one of claims 1 to 7, wherein the substrate layer (A) has a thickness of 50 to 300 µm, and the adhesive layer (B) has a thickness of 10 to 100 µm.

9. A method for producing a multilayer sheet, comprising a step of contacting a substrate layer (A) containing 40 to 99.9 mass % of polyphenylene ether (a1), 0 to 59.9 mass % of polystyrene (a2), and an amino group-containing polymer (a3) ​​with an adhesive layer (B) containing an acid-modified polyolefin in a molten state at 160° C. or higher.