Multilayer sheet and method for manufacturing the 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

Technical Field

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

Background Art

[0002] In recent years, hot-melt adhesive compositions have been 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 in notebook computers, smartphones, tablets, automobiles, etc., and physical batteries such as solar cells and capacitors (capacitors). It has come to be used. In order to adhere metal substrates such as iron, aluminum, titanium and other metals, and alloys thereof, which are used for the base materials of the constituent members of these batteries, a hot-melt adhesive composition mainly composed of an olefin-based thermoplastic resin modified with an acid (hereinafter also referred to as "acid-modified polyolefin") is used. It is known that a relatively good adhesive force can be obtained.

[0003] In battery applications, in addition to the adhesive force, durability against the constituent materials of the battery is also required for the hot-melt adhesive composition. In a lithium-ion battery, lithium hexafluorophosphate used as an electrolyte may react with moisture to generate hydrofluoric acid, and in a fuel cell, an acid such as hydrofluoric acid may be generated from an electrolyte membrane which is a constituent member of the battery, and acid resistance is required. Further, in a lithium-ion battery, durability against ethylene carbonate or diethyl carbonate used as a solvent of the electrolyte, and in a nickel-metal hydride battery, durability against a strong alkaline aqueous solution are required. In addition, in a fuel cell, for the purpose of cooling the battery heated by power generation, a coolant containing ethylene glycol or propylene glycol is circulated inside the battery, so durability against the ethylene glycol or the like is also required.

[0004] Patent Document 1 discloses a resin composition comprising 50 to 99% by mass of a low-viscosity propylene-based 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 this resin composition. This composition exhibits excellent adhesion to polyolefin-based substrates while also having excellent adhesion to metal substrates. Patent Document 2 describes acid-modified polypropylene as an adhesive between metal and nylon-based resins.

[0005] By laminating acid-modified polyolefin adhesive films or sheets onto a substrate layer to form a multilayer sheet, it is possible to obtain even higher-performance and more functional adhesive components. Engineering plastics with excellent rigidity and heat resistance are used for the substrate layer of this multilayer sheet. By using acid-modified polyolefin adhesives in such multilayer sheets, strength, rigidity, gas barrier properties, chemical resistance, acid / alkali resistance, and heat resistance are improved, making them suitable for applications requiring durability, such as lithium-ion batteries and fuel cells. Furthermore, using multilayer sheets as adhesive components in lithium-ion batteries and fuel cells reduces the number of constituent components and parts, leading to cost reduction and improved productivity.

[0006] As engineering plastics used as substrates for multilayer sheets, polyethylene naphthalate, heat-resistant polyolefins such as cycloolefin polymers, polyphenylene ether alloys, and aromatic polyamide resins have been used in terms of heat resistance, rigidity, dimensional stability, and cost. For example, Patent Document 3 describes a laminated sheet for sealing electronic equipment, in which a first sheet and a second sheet are laminated, characterized in that the first sheet contains an acid-modified polyolefin thermoplastic resin, the second sheet has a higher melting point than the first sheet, and the peel strength of the second sheet relative to the first sheet at 25°C is 0.5 to 10.0 [N / 15mm]. Patent Document 3 describes polyethylene naphthalate as a specific example of the second sheet. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2013-060521 [Patent Document 2] Japanese Patent Publication No. 2017-109613 [Patent Document 3] International Publication No. 2011 / 013389 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] As described above, multilayer sheets are used as adhesive members, consisting of an adhesive layer containing acid-modified polyolefin and a substrate layer containing engineering plastics such as heat-resistant polyolefins (e.g., polyethylene naphthalate, cycloolefin polymer), polyphenylene ether, and aromatic polyamide resin. However, polyethylene naphthalate and aromatic polyamide resins undergo hydrolysis during long-term use, posing problems with durability in environments exposed to moisture. Cycloolefin polymers have a low softening point, which limits the bonding temperature. Furthermore, cycloolefin polymers have low toughness, making them prone to cracking and other problems during long-term use.

[0009] Polyphenylene ether does not exhibit the same long-term degradation problems seen in other engineering plastics. However, polyphenylene ether has the problem of not adhering well to acid-modified polyolefins used in adhesive layers, leading to easy delamination.

[0010] The problem that the present invention aims to solve is to provide a multilayer sheet comprising an adhesive layer containing an acid-modified polyolefin and a substrate layer containing polyphenylene ether, wherein the adhesive layer and the substrate layer have high peel strength. [Means for solving the problem]

[0011] The inventors of the present invention diligently studied to solve the above problems in developing a multilayer sheet comprising an adhesive layer containing an acid-modified polyolefin and a substrate layer containing a polyphenylene ether. Specifically, they were able to complete the present invention by studying various multilayer sheets in which functional groups were introduced into the substrate layer containing a polyphenylene ether.

[0012] The means for solving the above problems include the following embodiments. [1] A base layer (A) comprising 40-99.9% by mass of polyphenylene ether (a1), 0-59.9% by mass of polystyrene (a2), and an amino group-containing polymer (a3), An adhesive layer (B) containing an acid-modified polyolefin, A multilayer sheet containing [a specific component]. [2] The multilayer sheet according to [1], wherein the content of the amino group-containing polymer (a3) ​​in the base layer (A) is 2 to 40% by mass. [3] A multilayer sheet according to [1] or [2], wherein the softening point of the base layer (A) is 175°C or higher. [4] A multilayer sheet according to any one of items [1] to [3], wherein the storage modulus of the base layer (A) at 160°C is 500 MPa or more. [5] A multilayer sheet according to any one of [1] to [4], wherein the base layer (A) contains an amino group-containing polymer (a3) ​​comprising 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] A multilayer sheet according to any one of [1] to [6], wherein the acid-modified polyolefin is a maleic anhydride-modified polyolefin. [8] A multilayer sheet according to any one of items [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 manufacturing a multilayer sheet, comprising a step of bringing a base material 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) into contact with an adhesive layer (B) containing an acid-modified polyolefin in a molten state at 160°C or higher.

Advantages of the Invention

[0013] According to the present invention, a multilayer sheet including an adhesive layer containing an acid-modified polyolefin and a base material layer containing polyphenylene ether, and having high peel strength between the adhesive layer and the base material layer can be provided.

[0014] By including a base material layer (A) containing an amino group-containing polymer (a3) and an adhesive layer (B) containing an acid-modified polyolefin, a multilayer sheet excellent in adhesive strength and heat resistance can be manufactured. Thereby, members of a high-performance and economical sheet-like battery or the like can be provided.

Brief Description of the Drawings

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

Embodiments for Carrying Out the Invention

[0016] The multilayer sheet of the present invention includes a base material layer (A) containing polyphenylene ether (a1) and an adhesive layer (B) containing an acid-modified polyolefin. The base material 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 surface or the lower surface, and the intermediate layer is a layer other than the surface layer. When the adhesive layer (B) is provided only on one surface layer, the intermediate layer may not exist, and both the base material layer (A) and the adhesive layer (B) may be surface layers. Typical layer configurations include a two-layer sheet of base material layer (A) / adhesive layer (B) and a three-layer sheet of adhesive layer (B) / base material layer (A) / adhesive layer (B). When the interfacial strength between the base material layer (A) and the adhesive layer (B) is insufficient, a tie layer (C) may be provided between the two layers. The tie layer (C) is a layer that firmly adheres the base material layer (A) and the adhesive layer (B). Typical layer configurations when the tie layer (C) is provided include a three-layer sheet of base material layer (A) / tie layer (C) / adhesive layer (B) and a five-layer sheet of adhesive layer (B) / tie layer (C) / base material layer (A) / tie layer (C) / adhesive layer (B). In one embodiment of the present invention, it is preferable that the base material layer (A) and the adhesive layer (B) are in direct contact without passing through the tie layer (C). In one embodiment of the present invention, the tie layer (C) may contain a functional group capable of bonding to 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 base material layer (A) contains polyphenylene ether (a1). The polyphenylene ether (a1) may be the main component accounting for 40 to 99.9% by mass of the base material layer (A). The mass ratio of the polyphenylene ether (a1) in the base material 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 the polyphenylene ether (a1) is within such a range, the heat resistance of the multilayer sheet can be improved. The mass ratio of the polyphenylene ether (a1) in the base material layer (A) is preferably 98% by mass or less, more preferably 95% by mass or less. When the mass ratio of the polyphenylene ether (a1) is within such a range, the moldability of the multilayer sheet can be improved.

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

[0019] Typical polystyrene (a2) includes general-purpose polystyrene (GPPS), which is a polymer of styrene alone, and high-impact polystyrene (HIPS), which is GPPS with added rubber for impact resistance. However, copolymers of styrene and acrylonitrile or (meth)acrylic acid esters can also be used. Copolymers used as polystyrene (a2) contain monomer units derived from styrene as the main component (for example, 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, and more preferably 10% by mass or less. A mass ratio of monomer units derived from comonomers of 20% by mass or less improves compatibility with polyphenylene ether (a1) and prevents phase separation.

[0020] The total amount of polyphenylene ether (a1) and polystyrene (a2) in the base 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 base 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 base layer (A) further contains an amino group-containing polymer (a3). The mass ratio of the amino group-containing polymer (a3) ​​in the base layer (A) is preferably 0.1% by mass or more, more preferably 2% by mass or more, and particularly preferably 5% by mass or more. By having the mass ratio of the amino group-containing polymer (a3) ​​within this range, the amino group-containing polymer (a3) ​​reacts sufficiently with the acid-modified polyolefin in the adhesive layer (B), thereby improving the interlayer adhesion. The mass ratio of the amino group-containing polymer (a3) ​​in the base layer (A) is preferably 40% by mass or less, more preferably 30% by mass or less. By having the mass ratio of the amino group-containing polymer (a3) ​​within this range, the heat resistance of the base material can be maintained and the moldability of the multilayer sheet can be improved.

[0022] The amino group-containing polymer (a3) ​​is not particularly limited as long as it has amino groups. The weight-average molecular weight of the amino group-containing polymer (a3) ​​is preferably 1000 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 1000 or more, moldability and thermal stability are improved, and when the weight-average molecular weight is 200,000 or less, the adhesion strength with the adhesive layer (B) or tie layer (C) is improved. By having the weight-average molecular weight within this range, it is possible to achieve both the physical properties of the base layer (A) and the adhesion with the adhesive layer (B). 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 amino groups at its molecular ends, more preferably a polymer containing polystyrene chains having amino groups at their ends, and particularly preferably a polymer containing polystyrene chains with a molecular weight of 1000 or more having amino groups at their ends. In a polymer having amino groups at its molecular ends, the amino groups may be present only at one end or at both ends. Primary amines or secondary amines can be preferably used as terminal amino groups.

[0024] Methods for synthesizing polystyrene chains having amino groups at their termini include methods of anionic living polymerization or radical living polymerization followed by termination of the active termini with a denaturing agent, and methods of radical polymerization of styrene in the presence of a chain transfer agent containing amino groups.

[0025] Polymers synthesized by introducing amino groups to the active ends with a modifying agent after living polymerization are not limited to styrene homopolymers, but may also be block copolymers containing styrene chains. However, in the case of block copolymers, the chain to which the amino groups are bonded is preferably a styrene chain. From the standpoint of readily available commercial products, styrene-diene block copolymers having amino groups at the ends are preferably used.

[0026] One example of a method for terminal occlusion of the active end after anionic living polymerization is to anionically polymerize styrene in a hydrocarbon solvent with an initiator such as butyllithium, add a modifying agent such as 1,3-dimethyl-2-imidazolidinone after polymerization is complete to cause an addition reaction to the terminal anion, and then treat the reaction product with a proton. In the case of styrene-diene block copolymers, a diene such as butadiene can be anionically polymerized in the first step, styrene can be charged and anionically polymerized in the second step, and an amino group can be introduced by adding a modifying agent in the same way. As styrene-diene block copolymers, block copolymers having polystyrene blocks in the terminal chain, such as styrene-diene diblock copolymers and styrene-diene-styrene triblock copolymers, are preferably used. Triblock copolymers are particularly preferred due to their availability as commercially available products.

[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), a partially hydrogenated product of polybutadiene.

[0028] An example of a method for radical polymerization of styrene in the presence of a chain transfer agent containing an amino group is to use 2-aminoethinthiol or its hydrochloride salt as the chain transfer agent and radically polymerize styrene in an organic solvent using an azo initiator or organic peroxide. When a hydrochloride salt 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. Having an amino group concentration within this range improves the interlayer adhesion with the adhesive layer (B) or tie layer (C). The amino group concentration of the base layer (A) is preferably 200 μeq or less, more preferably 100 μeq or less. Having an amino group concentration within this range improves the heat resistance of the base layer (A) and prevents problems such as discoloration.

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

[0031] Other polymers (A) include, for example, styrene-butadiene-styrene block copolymers and their hydrogenated products, styrene-isoprene-styrene block copolymers and their hydrogenated products, and graft copolymers obtained by grafting styrene homopolymers or copolymers onto polyolefins. These copolymers contain styrene units as a minor component (for example, 40% by mass or less of the total monomer units). The presence of polystyrene chains enables other polymers (A) to have high miscibility with polyphenylene ether (a1).

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

[0033] When using other polymers (A), the content of other polymers (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 amount added is within this range, the improvement effect of other polymers (A) is enhanced.

[0034] When using other polymers (A), the content of other polymers (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 amount added 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 base layer (A) is preferably 175°C or higher, more preferably 180°C or higher, and particularly preferably 185°C or higher. Having the softening point within this range improves the heat resistance of the multilayer sheet.

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

[0037] Here, the softening point and storage modulus in this invention are values ​​obtained using a tensile viscoelastic device (DMS6100, manufactured by Hitachi High-Tech Science & Engineering Co., Ltd.). 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 temperature-dependent changes in storage modulus, loss modulus, and tanΔ are recorded. In this invention, the softening point refers to the temperature at which the value of tanΔ is at its highest.

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

[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 base layer (A) may further contain additives selected from the group consisting of antioxidants, ultraviolet absorbers, fillers, reinforcing fibers, mold release agents, processing aids, flame retardants, plasticizers, nucleating agents, antistatic agents, pigments, dyes, foaming agents, and combinations thereof.

[0041] The adhesive layer (B) contains an acid-modified polyolefin. The acid-modified polyolefin is an unmodified polyolefin (hereinafter also simply referred to as "polyolefin") that has been 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 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, more preferably 2 to 5.

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

[0044] Polyethylene is a polymer that mainly contains ethylene units, and may be a homopolymer or a copolymer. In the case of a copolymer, the ethylene unit content in 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 products such as chlorinated polyethylene.

[0045] Polypropylene is a polymer that mainly contains propylene units, and may be either a homopolymer or a copolymer. In the case of a copolymer, the propylene unit content in 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 copolymers, and halogen-modified products such as chlorinated polypropylene.

[0046] Ethylene-propylene copolymers are polymers containing ethylene units and propylene units, and may consist only of ethylene units and propylene units, or may further contain other monomer units in addition to ethylene units and propylene units. Examples of ethylene-propylene copolymers containing other monomer units include ethylene-propylene-diene monomer copolymers. The total amount of ethylene units and propylene units in an 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 also be 100% by mass.

[0047] Polyolefins include not only physical blends consisting of multiple components of these resins, but also reaction blends produced by reacting functional groups between different polymers in a molding machine, graft copolymers and block copolymers consisting of multiple segments, and compositions in which physical blends using these as compatibilizers are microdispersed.

[0048] In the total monomer units contained in the polyolefin, the sum 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, and particularly preferably 90% by mass or more, and may also be 100% by mass.

[0049] The mass ratio of ethylene units to propylene units (ethylene units / propylene units) contained in polyolefins is preferably 10 / 90 to 40 / 60, and more preferably 15 / 85 to 35 / 65. A mass ratio of ethylene units above the lower limit of this range improves the thermocompression properties of acid-modified polyolefins and enhances adhesive strength. A mass ratio of ethylene units below the upper limit of this range improves adhesive strength at high temperatures. By keeping the mass ratio of ethylene units to propylene units within the above range, both high-temperature and low-temperature adhesive durability can be achieved. Note that when the polyolefin is a polymer blend of polyethylene and polypropylene, "mass ratio of ethylene units to propylene units contained in the polyolefin" refers to the mass ratio of ethylene units to propylene units in all ethylene units and propylene units contained in polyethylene and polypropylene.

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

[0051] Polyethylene, polypropylene, and ethylene-propylene copolymers may contain monomer units other than ethylene and propylene units. Examples of other monomers that form monomer units other than ethylene 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 their derivatives 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 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 and propylene units is within this range, the properties of the polyolefin, such as water resistance, chemical resistance, and durability, are improved, and it becomes possible to manufacture polyolefins at a low cost.

[0052] Known methods for producing polyolefins include those 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 propylene-ethylene random copolymer, and can be produced by a process consisting of a first step to obtain a propylene homopolymer and a second step to obtain a propylene-ethylene random copolymer.

[0053] The acid compounds used in the production of acid-modified polyolefins are selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and combinations thereof.

[0054] Unsaturated carboxylic acids are compounds that contain both an ethylenic double bond and a carboxylic acid group within the same molecule, and include various unsaturated monocarboxylic acids and unsaturated dicarboxylic acids. These acid compounds may be used individually 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] Unsaturated carboxylic acid anhydrides are compounds that have an ethylenic double bond and a carboxylic acid anhydride group within the same molecule, and examples include acid anhydrides of unsaturated dicarboxylic acids. Specific examples of acid anhydrides of unsaturated dicarboxylic acids include maleic anhydride, fumaric anhydride, itaconic anhydride, citraconic anhydride, nadic anhydride, and endicic anhydride.

[0058] Among these, maleic acid and maleic anhydride are preferred due to their high denaturing effect, with maleic anhydride being particularly preferred.

[0059] Known methods can be used for graft modification. For example, one method involves 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 preferred temperature for the graft reaction is 80-160°C when the reaction is carried out in solution, and 150-300°C when the reaction is carried out in molten state. In both the solution and molten states, the reaction rate is high above the lower limit of the above reaction temperature range, and the decrease in molecular weight of the resin can be suppressed below the upper limit of the above reaction temperature range, thereby maintaining the mechanical strength of the resulting acid-modified polyolefin.

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

[0062] If some of the acid compounds used for graft modification remain unreacted, it is preferable to remove the unreacted acid compounds by known methods such as reduced-pressure distillation in order to suppress adverse effects on adhesion.

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

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

[0065] In this specification, the amount of acid compound grafted onto an acid-modified polyolefin is defined from the acid value of the acid-modified polyolefin by 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 equations. M = (Molecular weight of the acid compound) + (Number of unsaturated groups in the acid compound) × 1.008 V = Valency of the acid group (however, if an acid anhydride group is included, it is the valency of the acid group when the acid anhydride group is completely hydrolyzed). The acid value indicates the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 g of the 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 high-temperature adhesive strength 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 properties can be obtained, and the adhesive durability at low temperatures can be improved.

[0068] In this invention, the melting point refers to the temperature at the peak of the endothermic peak generated when a differential scanning calorimeter (DSC) is used to hold a sample at 180°C for several minutes, then cool it to 0°C, and then raise the temperature by 10°C per minute up to 200°C.

[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. The melt flow rate of the acid-modified polyolefin 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 adhesive layer (B) was measured at a resin temperature of 230°C and a load of 2.16 kg.

[0071] The content of 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 mixture with unmodified polyolefin, and when using an acid-modified polyolefin with a high degree of acid modification, a small amount of about 2% by mass may be used. In one embodiment, the content of 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 be 100% by mass.

[0072] To improve the adhesive layer (B) with properties such as low-temperature adhesion, adhesive durability, molding stability, and adhesion to the substrate layer (A), polymers other than acid-modified polyolefins (hereinafter referred to as "other polymers (B)") may be added. Examples of other polymers (B) include styrene-butadiene-styrene block copolymers and their hydrogenated products, styrene-isoprene-styrene block copolymers and their hydrogenated products, and styrene-isobutylene-styrene block copolymers and their hydrogenated products, as well as styrene-based graft copolymers obtained by grafting styrene homopolymers or copolymers onto polyolefins. Unmodified polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers may also be added as other polymers (B).

[0073] When using other polymers (B), the lower limit of the content of other polymers (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 amount added is within this range, the improvement effect of other polymers (B) is enhanced.

[0074] When using other polymers (B), the upper limit of the content of other polymers (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 using acid-modified polyolefins with a high degree of acid modification, the content of acid-modified polyolefins can be reduced. In such cases, the content of unmodified polyolefins may be high, and the upper limit of the content of unmodified polyolefins in the adhesive composition may be 98% by mass.

[0075] The adhesive layer (B) may further contain additives selected from the group consisting of antioxidants, ultraviolet absorbers, fillers, reinforcing fibers, mold release agents, processing aids, flame retardants, plasticizers, nucleating agents, antistatic agents, pigments, dyes, foaming agents, and combinations thereof.

[0076] The multilayer sheet of the present invention can adhere firmly to an adherend. When the adhesive layer (B) of the multilayer sheet is adhered to an adherend, particularly a SUS304 plate with a thickness of 0.1 mm, to create a joint, the peel strength at room temperature between the multilayer sheet and the adherend, particularly the SUS304 plate with a thickness of 0.1 mm, is 2 N / 10 mm or more, more preferably 5 N / mm or more. Here, room temperature is 23°C, and the peel strength at room temperature is measured under the conditions described in the examples below.

[0077] The base layer (A) preferably has a thickness in the range of 50 to 300 μm. When the thickness of the base layer (A) is above this lower limit, sufficient rigidity can be obtained. When the thickness of the base layer (A) is below this upper limit, the influence on the thickness of articles incorporating multilayer sheets such as batteries 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 above this lower limit, the occurrence of adhesion defects can be suppressed. When the thickness of the adhesive layer (B) is below this upper limit, the leakage of adhesive from the multilayer sheet can be prevented, and the occurrence of defects in articles incorporating multilayer sheets such as batteries can be prevented. By controlling the thickness of the multilayer sheet within this range, the multilayer sheet and the joint using it can exhibit excellent adhesive performance, durability, productivity, and economic efficiency.

[0078] The base layer (A) and the adhesive layer (B) are generally manufactured from a resin composition, which is the raw material. The resin composition, which is the raw material for the base layer (A) and the adhesive layer (B), is a resin-based composition consisting of the components of the base layer (A) or adhesive layer (B) described above. The resin composition can be manufactured by melting and kneading the main resin component and other components as needed in an extruder, Banbury mixer, or hot roll, then cooling and solidifying the strand extruded from the nozzle hole of the die head with water while pulling it, and finally cutting it into pellets.

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

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

[0081] The resin composition used in the base layer (A) and the resin composition used in the adhesive layer (B) obtained in this manner can be formed into multilayer sheets of various shapes according to the application by conventionally known methods, such as compression molding, injection molding, extrusion molding, multilayer extrusion molding, shape extrusion molding, or hollow molding.

[0082] The base layer (A), adhesive layer (B), and optionally tie layer (C) may be prepared separately as sheets and then heat-laminated to form a multilayer structure, or they may be formed by simultaneously forming sheets and multilayer structures, such as through multilayer extrusion molding. In either case, it is preferable to bring at least one of the adjacent layers into contact while it is 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. When the contact temperature is above the lower limit, the acid groups or acid anhydride groups contained in the adhesive layer (B) and the amino groups contained in the base layer (A) can bond together, potentially improving the interlayer adhesion.

[0083] The multilayer sheet of the present invention is preferably formed by multilayer extrusion molding from the viewpoint of productivity and manufacturing cost. 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," which extrudes multiple resins simultaneously. Specific co-extrusion methods include the "feed block method," in which the resins are merged before reaching the T-die, and the "multi-manifold method," in which each single layer is spread in a manifold before being merged at the lip, which is the discharge port of the T-die. In the manufacture of the multilayer sheet of the present invention, either of these methods may be used, or other methods may be used.

[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 creation of a bonded structure including the multilayer sheet and the adherend. For example, a bonded structure including the multilayer sheet can be used as a component or part of a layered battery.

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

[0086] Various thermoplastic or thermosetting resins can be used as the adherend. Composite materials may also be used, which are resins compounded with inorganic materials such as glass or ceramics, or with fillers or fibers such as metal or carbon. [Examples]

[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 mass percent. 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, mainly composed of polypropylene, polyethylene, ethylene-propylene copolymers, and their maleic anhydride-modified products, were prepared. The PE / PP blending ratio and the amount of maleic anhydride in maleic anhydride-modified polyolefins A to B were confirmed using the procedures described in (1) to (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 Nippon Polypropylene Co., Ltd.) were melt-mixed in an extruder at various mixing ratios, and the resulting resin mixture was molded using a tabletop press molding machine to produce resin sheets with a thickness of approximately 2 mm.

[0090] An IR spectrum was obtained from the cross-section of a resin sheet using the Total Internal Reflection Absorption (ATR) method with a PerkinElmer Spectrum100. The obtained IR spectrum was obtained at 719 cm⁻¹. -1 (PE characteristic absorption) and 1167cm -1 The PE absorbance ratio was determined from the absorbance of the PP (PP characteristic absorption). A calibration curve was created by plotting this absorbance ratio against the mixing ratio during melt mixing. The results for the PE mixing ratio and PE absorbance ratio are shown in Table 1, and the plot results are shown in Figure 1.

[0091] To account for measurement errors, the number of repetitions was set to four or more. The approximation curve of this plot was used as a calibration curve to determine the PE / PP blending ratio.

[0092] [Table 1]

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

[0094] (2) Amount of maleic anhydride Furthermore, the amount of maleic anhydride grafted into maleic anhydride-modified polyolefins A and B was quantified by neutralization titration. In the neutralization titration, the maleic anhydride-modified polyolefins A and B, which were the samples, were heated and dissolved in xylene, 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 for the amount of maleic anhydride 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] [Table 2]

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

[0098] [Synthesis Example] Synthesis of terminal amino polystyrene (AT-PS) A mixed solvent consisting of 90 parts isopropyl alcohol (IPA) and 10 parts distilled water was prepared. In a glass flask equipped with a reflux condenser, nitrogen inlet tube, thermometer, two dropping funnels, and stirrer, 30 parts styrene, 40 parts mixed solvent, and 1.5 parts 2-aminoethanethiol hydrochloride were placed and stirred, heated, and refluxed. 70 parts styrene was placed in one dropping funnel, and a solution of 3.5 parts 2-aminoethanethiol hydrochloride and 0.2 parts 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. Both were added dropwise over 2 hours under reflux. Subsequently, a solution consisting of 0.1 parts ABN-E and 2.5 parts mixed solvent was added dropwise over 1 hour, and then a solution consisting of 0.8 parts ABN-E and 40 parts mixed solvent was added dropwise over 2 hours. The polymerization was then completed under reflux for 2 hours, and an equivalent amount of sodium hydroxide was added to the total amount of 2-aminoethanethiol hydrochloride to convert it to an amine. The polymerization solution was diluted with methyl ethyl ketone until clear, and a large amount of methanol was added to precipitate the polystyrene. The solution was then filtered, washed, and dried to obtain a powder of terminal amino-type polystyrene. The polystyrene-equivalent molecular weight, determined by gel permeation chromatography, was 3000 (number average molecular weight) and 5100 (weight average molecular weight).

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

[0100] (1) 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 300°C and under a load of 2.16 kg.

[0101] (2) Softening point and storage modulus The softening point and storage modulus were determined using a tensile viscoelastic device (DMS6100, Hitachi High-Tech Science & Engineering Co., Ltd.). 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 temperature-dependent changes in storage modulus, loss modulus, and tanΔ were recorded. The softening point was defined as the temperature at which the value of tanΔ was highest.

[0102] (3) Compression creep test A resin composition for the base layer (A) was formed into a 1 mm thick sheet using a desktop press molding machine. This resin sheet was cut into 10 mm x 10 mm pieces, and five pieces were stacked to create a 5 mm thick sample. Using a hot press (Shinto Kogyo Co., Ltd. Digital Press CYPT-50), 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) Heat shrinkage test A resin composition for the base layer (A) was formed into a sheet approximately 100 μm thick using a tabletop press molding machine. This resin sheet was cut into 200 mm x 100 mm size samples. The prepared samples were suspended in a 180°C dryer for 30 seconds, and the thermal change rate was calculated from the dimensional changes before and after heating. The thermal change rate is the average of the absolute values ​​of the change rate on the long side and the absolute values ​​of the change rate on the short side.

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

[0105] A resin composition for the base layer (A) was used to form a base layer (A) with a thickness of approximately 150 μm using a desktop press molding machine. A maleic anhydride-modified polyolefin for the adhesive layer (B) was used to form an adhesive layer (B) with a thickness of approximately 50 μm using a desktop press molding machine. The base layer (A) and the adhesive layer (B) were stacked in the order of adhesive layer (B) / base layer (A) / adhesive layer (B), and a three-layer sheet was obtained by heat-pressing them together for 10 seconds at the pressure temperature shown in Table 3 using the same desktop press molding machine.

[0106] [Test piece] A SUS304 plate with a thickness of 0.1 mm was used as the adherend. A three-layer sheet was sandwiched between two SUS304 plates and heat-pressed using a precision press (160°C, 10 seconds, 0.3 MPa) to create a bonded body. This bonded body was cut into strips with a width of 10 mm to create test specimens. The bonded portion of the test specimen was 10 mm wide and 15 mm long. The peel strength at room temperature, the peel strength in hot water, and the constant load immersion drop time of the obtained test specimens were measured as described in (1) to (3) below.

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

[0108] (2) Hot water peeling test In the hot water peel test, an IMADA Corporation MX2-1000N measuring stand was fitted with an IMADA Corporation eDPU-50N load cell. A heated water bath with a hook attached to the bottom was filled with 95°C hot water, and the test specimen was immersed in the bath and peeled off to evaluate the peel strength in the same manner. The results are shown in Table 3 as hot water peel strength (N / 10mm).

[0109] (3) Adhesion durability underwater To evaluate the adhesive durability in water, a constant load immersion test was conducted. The constant load immersion test is a method of evaluating adhesive durability by holding a test specimen in 95°C hot water under a constant peel load and measuring the time (drop time) until the SUS304 plate peels off. The test specimen was the same as the one used for measuring peel strength. One end of the handle of the test specimen was connected to a fixed stand with wire, and the other end was connected to a weight. The test specimen, along with the weight, was suspended from the fixed stand installed above the water surface into 95°C hot water, and a peel load (1N) was applied by the weight in the water. At this time, the time required for the adherend, the SUS304 plate, to completely separate (drop time) was measured. This result is shown in Table 3 as constant load immersion drop time (hr).

[0110] [Table 3]

[0111] The details of the resin used in the base layer (A) in Table 3 are as follows. 1000H: PPE-PS alloy Zylon 1000H manufactured by Asahi Kasei Corporation, Tg=184℃ (DSC) PX100F: PPE PX100F manufactured by Mitsubishi Engineering Plastics Corporation, Tg=204℃ (DSC) MP10: Terminal amine-modified hydrogenated styrene-based thermoplastic elastomer (SEBS) manufactured by Asahi Kasei Corporation, ToughTec MP10, styrene content 30% AT-PS: Terminal amino polystyrene obtained by the method shown in the synthesis example.

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

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

[0114] Other applications include, for example, electric wires and cables with metal conductors or optical fibers covered with resin molded products, automotive mechanical parts, automotive exterior parts, automotive interior parts, molded substrates for power supply, light reflectors for light source reflection, fuel cases for solid methanol batteries, insulation materials for metal pipes, insulation materials for vehicles, fuel cell water distribution pipes, decorative molded products, water cooling tanks, boiler exterior cases, ink peripheral parts and components for printers, water piping, fittings, alkaline battery tanks for secondary batteries, and gasket sealing materials for various layered batteries.

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

Claims

1. A base layer (A) is a thermoplastic resin 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 multilayer sheet containing [a specific component].

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

3. The softening point of the base layer (A) is 175°C or higher. The softening point is the temperature at which the tanΔ value is highest when the temperature is raised from room temperature to 250°C at a frequency of 1 Hz and a heating rate of 2°C / min, as determined using a tensile viscoelastic device. This is the multilayer sheet according to claim 1.

4. The multilayer sheet according to claim 1, wherein the storage modulus of the substrate layer (A) at 160°C is 500 MPa or more, as measured by heating from room temperature to 250°C under the conditions of a tensile viscoelasticity measuring device with a frequency of 1 Hz and a heating rate of 2°C / min.

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

6. The multilayer sheet according to claim 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 claim 1, wherein the acid-modified polyolefin is a maleic anhydride-modified polyolefin.

8. A multilayer sheet according to any one of claims 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 bringing a base layer (A), which is a thermoplastic resin 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), into contact with an adhesive layer (B) containing an acid-modified polyolefin in a molten state at 160°C or higher.

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