Multilayer sheet and method for manufacturing the same

Abstract

The present invention addresses the problem of providing an adhesive multilayer sheet which comprises an adhesive layer including an acid-modified polyolefin and a substrate layer including a poly(phenylene ether) and which has high interlaminar peeling strength. This multilayer sheet comprises a substrate layer (A) including a poly(phenylene ether) and an adhesive layer (B) including an acid-modified polyolefin, and is characterized by further including, between the substrate layer (A) and the adhesive layer (B), a tie layer (C) comprising a polyolefin / poly(phenylene ether)-based alloy.

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 type 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 (condensers). In order to adhere metal substrates such as iron, aluminum, titanium, and other metals, and their alloys, which are used for the base materials of the constituent members of these batteries, it is known that a hot-melt type adhesive composition mainly composed of an olefin-based thermoplastic resin modified with an acid (hereinafter also referred to as "acid-modified polyolefin") can obtain relatively good adhesive strength.

[0003] In battery applications, in addition to adhesive strength, durability against the constituent materials of the battery is also required for hot-melt type adhesive compositions. In a lithium-ion battery, lithium hexafluorophosphate used as an electrolyte may react with moisture to generate hydrofluoric acid. In a fuel cell, an acid such as hydrofluoric acid may be generated from an electrolyte membrane, which is a constituent member of the fuel cell, 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 is required, and in a nickel-metal hydride battery, durability against a strong alkaline aqueous solution is required. 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, and thus 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 project] [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] While polyphenylene ether does not exhibit the long-term degradation problems seen in other engineering plastics, it had a significant problem: it did not adhere to the acid-modified polyolefin used in the adhesive layer, 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 a polyphenylene ether, wherein the multilayer sheet has high peel strength between the layers. [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 explored various resin materials with the idea of ​​newly providing a tie layer with excellent adhesive strength between the adhesive layer containing the acid-modified polyolefin and the substrate layer containing the polyphenylene ether, and bonding the adhesive layer and the substrate layer with this tie layer. They discovered a resin composition suitable for the tie layer and completed the present invention.

[0012] The means for solving the above problems include the following embodiments. [1] A multilayer sheet comprising a base layer (A) containing polyphenylene ether and an adhesive layer (B) containing an acid-modified polyolefin, further comprising a tie layer (C) containing a polyolefin / polyphenylene ether alloy between the base layer (A) and the adhesive layer (B). [2] The multilayer sheet according to [1], wherein the base layer (A) comprises 40 to 99.9% by mass of polyphenylene ether, 0 to 59.9% by mass of polystyrene, and a polymer different from the polyphenylene ether and the polystyrene. [3] The multilayer sheet according to [1] or [2], wherein the softening point of the base material layer (A) is 175°C or higher. [4] A multilayer sheet according to any one of [1] to [3], wherein the storage modulus of the base material layer (A) at 160°C is 500 MPa or more. [5] The multilayer sheet according to any one of [1] to [4], wherein the acid-modified polyolefin is a maleic anhydride-modified polyolefin. [6] The multilayer sheet according to [1] to [5], wherein the mass ratio of polyolefin to polyphenylene ether contained in the tie layer (C) is 15 / 85 to 80 / 20. [7] A multilayer sheet according to any one of [1] to [6], wherein the tie layer (C) comprises a styrene-diene block copolymer, a hydrogenated styrene-diene block copolymer, or polyethylene. [8] The multilayer sheet according to any one of [1] to [7], wherein the base material layer (A) has a thickness of 50 to 300 μm, the adhesive layer (B) has a thickness of 10 to 100 μm, and the tie layer (C) has a thickness of 2 to 50 μm. [9] Step (1) of preparing a base material layer (A) containing polyphenylene ether, an adhesive layer (B) containing an acid-modified polyolefin, and a tie layer (C) containing a polyolefin / polyphenylene ether alloy, Step (2) of bringing at least one of the base material layer (A) and the tie layer (C) into a molten state at 160°C or higher and bringing the base material layer (A) into contact with the tie layer (C), and Step (3) of bringing at least one of the tie layer (C) and the adhesive layer (B) into a molten state at 160°C or higher and bringing the tie layer (C) into contact with the adhesive layer (B) at the same time as or at a different time from step (2) A method for manufacturing a multilayer sheet, comprising:

Advantages of the Invention

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

[0014] By providing a tie layer mainly composed of a polyolefin / polyphenylene ether alloy between the adhesive layer and the base material layer, the interface between the adhesive layer and the base material layer can be firmly adhered, and a multilayer sheet excellent in adhesive strength and heat resistance can be manufactured. Thereby, members of a high-performance and economical sheet-like battery 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. [Figure 2] It is a calibration curve for converting the absorbance ratio of polypropylene and polyphenylene ether 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 and an adhesive layer (B) containing an acid-modified polyolefin, and further has a tie layer (C) containing a polyolefin / polyphenylene ether alloy between the base material layer (A) and the adhesive layer (B). The tie layer is a layer disposed between the base material layer and the adhesive layer, firmly bonding them, and enhancing the peel strength of the multilayer sheet. The base material layer (A) is an intermediate layer or a surface layer, the adhesive layer (B) is a surface layer, and the tie layer (C) is an intermediate 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, only the tie layer (C) becomes the intermediate layer, and the base material layer (A) and the adhesive layer (B) may both be surface layers. Typical layer configurations 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).

[0017] The base material layer (A) contains polyphenylene ether. The polyphenylene ether is typically a homopolymer or copolymer containing monomer units represented by the following formula.

[0018] [Chemical formula] In the formula, R1 to R4 are selected from H and alkyl groups having 1 to 6 carbon atoms, R1 and R3 are preferably H, and R2 and R4 are preferably CH3.

[0019] The mass ratio of polyphenylene ether in the base layer (A) is preferably 50% by mass or more, more preferably 60% by mass or more, particularly preferably 70% by mass or more, and may be 100% by mass. Having the mass ratio of polyphenylene ether in the base layer (A) within this range can improve the heat resistance of the multilayer sheet. There is no particular upper limit to the mass ratio of polyphenylene ether in the base layer (A), but for example, when a polymer other than polyphenylene ether is used in the base layer (A), the mass ratio of polyphenylene ether in the base layer (A) is preferably 99.9% by mass or less, more preferably 98% by mass or less, and particularly preferably 95% by mass or less. Having the mass ratio of polyphenylene ether within this range can improve the moldability of the multilayer sheet.

[0020] The base layer (A) may further contain polystyrene. Polystyrene is an optional component, and the base layer (A) does not have to contain polystyrene. The mass ratio of polystyrene 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 within this range improves the heat resistance of the multilayer sheet.

[0021] Typical polystyrenes include 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 contain monomer units derived from styrene as the main component (for example, 50% by mass or more of the total monomer units). When polystyrene is a copolymer, the mass ratio of monomer units derived from comonomers other than styrene in the polystyrene 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 and prevents phase separation.

[0022] The total amount of polyphenylene ether and polystyrene in the base layer (A) is preferably 60% by mass or more, more preferably 70% by mass or more. There is no particular upper limit to the total amount of polyphenylene ether and polystyrene in the base layer (A), but in one embodiment of the present invention, the total amount of polyphenylene ether and polystyrene 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.

[0023] The base layer (A) may contain polymers other than polyphenylene ether and polystyrene (hereinafter referred to as "other polymers (A)") for the purpose of improving toughness and molding stability at low temperatures, as well as improving adhesion with the tie layer (C).

[0024] Other polymers (A) include, for example, styrene-based block copolymers such as 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 allows other polymers (A) to have high miscibility with polyphenylene ether. These block copolymers and graft copolymers may be modified with functional groups such as carboxylic acid (anhydride) groups, epoxy groups, and amino groups by acid modification with maleic anhydride, epoxy modification using an oxidizing agent, or terminal amine modification. These functional groups may be effective in improving interfacial adhesion with the tie layer.

[0025] Other examples of polymers (A) include unmodified or acid-modified polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers. The inclusion of polyolefins in the substrate layer (A) is expected to improve toughness and chemical resistance. Since these polyolefins are incompatible with polyphenylene ether, it is preferable to use the aforementioned block copolymer or grout copolymer containing styrene units as a compatibilizer.

[0026] When using other polymers (A), the content of other polymers (A) in the base layer (A) may be, for example, 0.1% by mass or more, 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.

[0027] 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.

[0028] When using other polymers (A), the base layer (A) may contain 40 to 99.9% by mass of polyphenylene ether and 0 to 59.9% by mass of polystyrene, preferably containing 50 to 98% by mass of polyphenylene ether and 0 to 50% by mass of polystyrene, and more preferably containing 60 to 95% by mass of polyphenylene ether and 0 to 40% by mass of polystyrene, from the viewpoint of improving the moldability and heat resistance of the multilayer sheet.

[0029] 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.

[0030] The storage modulus of the base layer (A) at 160°C is preferably 500 MPa or more, more preferably 700 MPa or more, and particularly preferably 1000 MPa or more. The storage modulus of the base layer (A) at 170°C is preferably 500 MPa or more, more preferably 700 MPa or more, and particularly preferably 1000 MPa or more. If the storage modulus in this temperature range is 500 MPa or more, deformation and damage to the multilayer sheet due to thermocompression during bonding can be prevented.

[0031] From the viewpoint of heat resistance, the thickness change rate in the compression creep test of the base layer (A) is preferably 30% or less, more preferably 25% or less, and particularly preferably 20% or less. The thickness change rate is measured according to the method described in the examples shown below.

[0032] From the viewpoint of heat resistance, the rate of change in heat in the thermal shrinkage test of the base material layer (A) is preferably 0.50% or less, more preferably 0.30% or less, and particularly preferably 0.20% or less. The rate of change in heat is measured according to the method described in the examples shown below.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The adhesive layer (B) of the present invention contains an acid-modified polyolefin. The acid-modified polyolefin is obtained by graft-modifying an unmodified polyolefin (hereinafter also simply referred to as "polyolefin") with an acid compound selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and combinations thereof.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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) -1This 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 more details, please refer to the examples described later.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] Specific examples of unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid.

[0052] Specific examples of unsaturated dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid, and endic acid.

[0053] 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.

[0054] Among these, maleic acid and maleic anhydride are preferred due to their high denaturing effect, with maleic anhydride being particularly preferred.

[0055] 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.

[0056] 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.

[0057] The radical polymerization initiator used may be selected from commercially available organic peroxides, taking into consideration the reaction temperature and other factors.

[0058] 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.

[0059] The amount of acid compound grafted onto the acid-modified polyolefin is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, and particularly preferably 0.6% 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.

[0060] The amount of acid compound grafted onto the acid-modified polyolefin is preferably 5% by mass or less, more preferably 2% by mass or less, and particularly preferably 1% 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] In this invention, 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.

[0067] 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 preferably 90% by mass or more, and may be 100% by mass.

[0068] The adhesive layer (B) may contain polymers other than acid-modified polyolefins (hereinafter referred to as "other polymers (B)") for the purpose of improving adhesive strength at low temperatures, adhesive durability, molding stability, and adhesion to the substrate layer (A). 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, 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).

[0069] 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.

[0070] 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.

[0071] 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.

[0072] The tie layer (C) contains a polyolefin / polyphenylene ether alloy. In this specification, the term "polyolefin / polyphenylene ether alloy" refers to a polymer alloy containing a polyolefin and a polyphenylene ether. When polypropylene is used as the polyolefin, the polyolefin / polyphenylene ether alloy may also be described as a polypropylene / polyphenylene ether alloy. A polymer alloy is a composite resin material in which two or more polymers are mixed. The mass ratio of polyolefin to polyphenylene ether (polyolefin / polyphenylene ether) in the tie layer (C) is preferably 15 / 85 or higher, more preferably 20 / 80 or higher, and particularly preferably 25 / 75 or higher. By keeping the mass ratio of polyolefin to polyphenylene ether within these ranges, the tie layer (C) can be firmly bonded to the adhesive layer (B). The mass ratio of polyolefin to polyphenylene ether (polyolefin / polyphenylene ether) in the tie layer (C) is preferably 80 / 20 or less, more preferably 70 / 30 or less, and particularly preferably 60 / 40 or less. By keeping the mass ratio of polyolefin to polyphenylene ether within these ranges, the tie layer (C) can be firmly adhered to the substrate layer (A). The mass ratio of polyolefin to polyphenylene ether can be determined from the absorbance ratio of their respective characteristic absorptions in the IR spectrum. For example, when polypropylene is used as the polyolefin, the mass ratio of polypropylene to polyphenylene ether is such that the characteristic absorption of polypropylene in the IR spectrum is (2920 cm⁻¹). -1 ) and the properties of polyphenylene ether (1604cm) -1 This is determined from the absorbance ratio of polypropylene and polyphenylene ether. Specifically, a calibration curve is used to convert the absorbance ratio of polypropylene and polyphenylene ether to a mass ratio. The calibration curve can be created by blending commercially available polypropylene and polyphenylene ether in various ratios and plotting the blending ratio against the absorbance ratio. For more details, please refer to the examples described later.

[0073] The total amount of polyolefin and polyphenylene ether in the tie layer (C) is preferably 50% by mass or more, more preferably 70% by mass or more, and may be 100% by mass.

[0074] Since polyolefins and polyphenylene ethers are incompatible, the miscibility of the two resins may be improved by adding a compatibilizer to the tie layer (C) or by introducing functional groups through chemical modification (modification) of the polyolefin or polyphenylene ether.

[0075] Typical compatibilizers include styrene-diene block copolymers and their hydrogenated products. Specifically, these include styrene-butadiene binary block copolymers, styrene-butadiene-styrene ter-block copolymers, styrene-isoprene binary block copolymers, styrene-isoprene-styrene ter-block copolymers, and their hydrogenated products. Among these block copolymers, styrene-ethylene-butylene block copolymers, which are hydrogenated products of styrene-butadiene block copolymers, and styrene-ethylene-propylene block copolymers, which are hydrogenated products of styrene-isoprene block copolymers, are preferably used. Due to their easy availability as commercially available products, styrene-ethylene-butylene-styrene ter-block copolymers (hereinafter sometimes abbreviated as SEBS) and styrene-ethylene-propylene-styrene ter-block copolymers (hereinafter sometimes abbreviated as SEPS) are particularly preferred.

[0076] An example of chemical modification (denaturation) is the introduction of polar groups into polyolefins or polyphenylene ethers by grafting maleic anhydride, thereby conferring polar interactions such as hydrogen bonds and ionic bonds.

[0077] Examples of monomer units that constitute 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.

[0078] Polypropylene is particularly preferred as the polyolefin. That is, the polyolefin / polyphenylene ether alloy is preferably a polypropylene / polyphenylene ether alloy. Polypropylene is a polymer mainly composed of propylene units, and may be a homopolymer or copolymer, or an alloy or blend with other polymer components. When polypropylene is a copolymer or alloy, the propylene unit content is preferably 60% by mass or more, and more preferably 75% by mass or more.

[0079] Specific examples of polypropylene include homopolymers such as amorphous polypropylene and crystalline polypropylene, copolymers mainly composed of propylene such as ethylene-propylene copolymers and propylene-diene monomer copolymers, halogen-modified products such as chlorinated polypropylene, and alloys or blends of polypropylene with other polymers.

[0080] Other monomer units that constitute polypropylene copolymers and alloys include monomers selected from the group consisting of ethylene, α-olefins such as 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene, diene monomers such as butadiene, isoprene, chloroprene, and diene monomers, aromatic vinyl compounds such as vinyl acetate, (meth)acrylic acid esters, and styrene, and combinations thereof. The number of carbon atoms in the monomer is preferably 2 to 10, more preferably 2 to 5. Among these monomer units, ethylene units are frequently used, and it is preferable that the total amount of propylene units and ethylene units accounts for 70% by mass or more, and more preferably 85% by mass or more.

[0081] When polypropylene is an alloy or blend of polypropylene and other polymers, typical examples of other polymers include polyolefins other than polypropylene, such as polyethylene. Polyethylene is a polymer that mainly contains ethylene units and may be a homopolymer or a copolymer such as an ethylene-propylene 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. By including polyolefins other than polypropylene together with polypropylene, improvements in toughness and chemical resistance can be expected.

[0082] 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.

[0083] The method for manufacturing polypropylene has already been described in the explanation of the adhesive layer (B).

[0084] The polypropylene may be acid-modified polypropylene. Acid modification increases its affinity with the adhesive layer (B), and an improvement in interfacial adhesion can also be expected.

[0085] The acid compounds used for acid modification, the methods and conditions for acid modification, and the amount of acid modification have already been described in the explanation of adhesive layer (B).

[0086] The polyphenylene ether may be the same as the polyphenylene ether used in the substrate layer (A).

[0087] An alloy of polyphenylene ether and polystyrene (sometimes called modified polyphenylene ether) can be used as the polyphenylene ether, and the polyolefin / polyphenylene ether alloy may also contain polystyrene. In this case, the mass ratio of polystyrene in the tie layer (C) 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 within this range improves the heat resistance of the multilayer sheet. Polystyrene is an optional component, and the polyolefin / polyphenylene ether alloy does not have to contain polystyrene, nor does the tie layer (C) have to contain polystyrene.

[0088] Typical polystyrenes include 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 contain monomer units derived from styrene as the main component (for example, 50% by mass or more of the total monomer units). When polystyrene is a copolymer, the mass ratio of monomer units derived from comonomers other than styrene in the polystyrene 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 and prevents phase separation.

[0089] In the tie layer (C), polymers other than the polyolefins and polyphenylene ethers described above (hereinafter referred to as "other polymers (C)") may be added for the purpose of improving toughness at low temperatures, molding stability, and adhesion to the substrate layer (A) and adhesive layer (B).

[0090] Other polymers (C) include, for example, styrene-based block copolymers such as styrene-butadiene-styrene block copolymers and their hydrogenated derivatives, styrene-isoprene-styrene block copolymers and their hydrogenated derivatives, and graft copolymers obtained by grafting styrene homopolymers or copolymers onto polyolefins, as described in the explanation of compatibilizers. These copolymers contain styrene units as a minor component (e.g., 40% by mass or less of the total monomer units). The presence of polystyrene chains allows other polymers (C) to exhibit high miscibility with polyphenylene ether. These block copolymers and graft copolymers may be modified with reactive groups such as carboxylic acid (anhydride) groups, epoxy groups, and amino groups by acid modification with maleic anhydride, epoxy modification using an oxidizing agent, or terminal amine modification. These reactive groups can sometimes be used to improve interfacial adhesion with the adhesive layer.

[0091] When using other polymers (C), the content of other polymers (C) in the tie layer (C) 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 (C) is enhanced.

[0092] When using other polymers (C), the content of other polymers (C) in the tie layer (C) is preferably 50% 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.

[0093] The melt flow rate of the tie layer (C) is preferably 1 g / 10 min or more, more preferably 2 g / 10 min or more. The melt flow rate of the tie layer (C) is preferably 50 g / 10 min or less, more preferably 30 g / 10 min or less. If the melt flow rate of the tie layer (C) is below the lower limit, the melt viscosity is too 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.

[0094] Here, the melt flow rate is a value measured in accordance with JIS K7210:2014. The melt flow rate of the tie layer (C) was measured at a resin temperature of 300°C and a load of 2.16 kg.

[0095] The tie layer (C) 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.

[0096] 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 room-temperature peel strength between the multilayer sheet and the adherend, particularly the SUS304 plate with a thickness of 0.1 mm, is preferably 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.

[0097] The base layer (A) preferably has a thickness in the range of 50 to 300 μm, more preferably in the range of 70 to 250 μm, and particularly preferably in the range of 100 to 200 μm. Sufficient rigidity can be obtained when the thickness of the base layer (A) is above this lower limit. When the thickness of the base layer (A) is below this upper limit, the impact on the thickness of articles incorporating multilayer sheets such as batteries can be reduced.

[0098] The adhesive layer (B) preferably has a thickness in the range of 10 to 100 μm, more preferably in the range of 20 to 80 μm, and particularly preferably in the range of 30 to 70 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 adhesive can be prevented from seeping out from the multilayer sheet, and defects in articles incorporating multilayer sheets such as batteries can be prevented.

[0099] The tie layer (C) preferably has a thickness in the range of 2 to 50 μm, more preferably in the range of 5 to 40 μm, and particularly preferably in the range of 10 to 30 μm. When the thickness of the tie layer (C) is above this lower limit, sufficient adhesion can be obtained. When the thickness of the tie layer (C) is below this upper limit, the impact on the thickness of the article incorporating the multilayer sheet, such as a battery, can be reduced.

[0100] By controlling the thickness of each layer of a multilayer sheet within this range, the multilayer sheet and the bonded structure using it can exhibit excellent adhesive performance, durability, productivity, and cost-effectiveness.

[0101] The base layer (A), adhesive layer (B), and tie layer (C) are generally manufactured from a resin composition, which is the raw material. The resin composition that is the raw material for the base layer (A), adhesive layer (B), and tie layer (C) is a resin-based composition consisting of the components of the base layer (A), adhesive layer (B), and tie layer (C) 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 a die head with water while pulling it, and finally cutting it into pellets.

[0102] 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.

[0103] 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.

[0104] The melt-mixing temperature of the resin composition used in the tie layer (C) is preferably 150 to 320°C, more preferably 170 to 300°C, and the mixing time is usually 0.5 to 20 minutes, preferably 1 to 15 minutes.

[0105] The resin composition used in the base layer (A), the resin composition used in the adhesive layer (B), and the resin composition used in the tie layer (C) 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.

[0106] The base layer (A), adhesive layer (B), and 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 base layer (A) and tie layer (C) into contact with the base layer (A) and at least one of the tie layer (C) and adhesive layer (B) into contact with the tie layer (B) while both are in a molten state. It is even more preferable to bring both the base layer (A) and tie layer (C), and both the tie layer (C) and adhesive layer (B) into contact while both 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 below the lower limit, the fusion between the adhesive layer (B) and the tie layer (C), and between the tie layer (C) and the substrate layer (A), may not proceed sufficiently, potentially resulting in insufficient interlayer adhesion. Contact between the substrate layer (A) and the adhesive layer (B) and the tie layer (C) may be performed simultaneously or separately.

[0107] 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 a roll 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 production of the multilayer sheet of the present invention, either of these methods may be used, or other methods may be used. Furthermore, the multilayer sheet extruded by multilayer extrusion molding may be subsequently heat-laminated (thermally bonded) using a heated roll. Adding a heat lamination step may further improve the interlayer adhesion strength. The preferred temperature conditions for the heat lamination step are as described above.

[0108] 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.

[0109] 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.

[0110] 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]

[0111] 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.

[0112] [Adhesive layer (B)] Ethylene-propylene-based maleic anhydride polyolefin B1 was prepared. The PE / PP blending ratio and the amount of maleic anhydride in maleic anhydride-modified polyolefin B1 were confirmed using the procedures described in (1) and (2) below.

[0113] (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.

[0114] 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.

[0115] 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.

[0116] [Table 1]

[0117] Maleic anhydride-modified polyolefin B1 was molded into a 2 mm thick resin sheet, and its cross-section was used as the measurement surface to measure the IR spectrum in the same manner. Based on the obtained IR spectra, the PE / PP blending ratio of maleic anhydride-modified polyolefin B1 was determined using a prepared calibration curve. The results are shown in Table 2.

[0118] (2) Amount of maleic anhydride The amount of maleic anhydride grafted into maleic anhydride-modified polyolefin B1 was quantified by neutralization titration. In the neutralization titration, the maleic anhydride-modified polyolefin B1 sample was 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, and the results of the maleic anhydride amount are shown in Table 2.

[0119] (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.

[0120] [Table 2]

[0121] [Thai layer (C)] We prepared PP / PPE alloys C1 to C6 with different PP / PPE blending ratios. The PP / PPE blending ratio of PP / PPE alloys C1 to C6 was confirmed using the procedure described below.

[0122] Commercially available polypropylene resin (Waymax MFX3, manufactured by Nippon Polypropylene Co., Ltd.) and polyphenylene ether resin (PX100F, manufactured by Mitsubishi Engineering Plastics Corporation) were heated and dissolved in xylene in various mass ratios, precipitated with methanol, solidified, and dried to obtain PP / PPE blends.

[0123] The IR spectrum of the PP / PPE blend was obtained using the Total Internal Reflection Absorption (ATR) method with a PerkinElmer Spectrum100. -1 (PP characteristic absorption) and 1604cm -1 The PP absorbance ratio was determined from the absorbance of the PPE characteristic absorption. A calibration curve was created by plotting this absorbance ratio against the blending ratio during solution blending. The results for PP blending ratio and PP absorbance ratio are shown in Table 3, and the plot results are shown in Figure 2. The approximation curve of this plot was used as a calibration curve to determine the PP / PPE blending ratio.

[0124] [Table 3]

[0125] PP / PPE alloys C1 to C6 were molded into 2 mm thick resin sheets, and their cross-sections were used as the measurement surface for IR spectra. Based on the obtained IR spectra, the PP / PPE blending ratios of PP / PPE alloys C1 to C6 were determined using a calibration curve. The results are shown in Table 4. In Example 10, an alloy prepared by melt-kneading PP / PPE alloy C3 and hydrogenated styrene-diene block copolymer (SEBS) in a mass ratio of 70 / 30 was used as the resin composition for the tie layer (C). In the other examples, one of the PP / PPE alloys C1 to C6 was used as the resin composition for the tie layer (C).

[0126] [Table 4]

[0127] [Base material layer (A)] The resins listed in "Base Layer (A) Composition" in Table 5 below were melt-kneaded at the mixing ratio (mass%) shown in Table 5 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 5.

[0128] (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.

[0129] (2) Softening point and storage modulus A resin composition for the base layer (A) was formed into a sheet approximately 0.2 mm thick using a benchtop press molding machine. This resin sheet was cut to a size of 10 mm x 4.5 mm, and its viscoelastic properties were measured using a tensile viscoelasticity 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.

[0130] (3) Compression creep test A resin composition for the base layer (A) was formed into a 1 mm thick sheet using a tabletop 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 ratio of the change in thickness before and after the test to the thickness before the test was calculated as the creep amount (%).

[0131] (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.

[0132] [Multilayer sheet] In each example, a five-layer multilayer sheet described below was prepared and evaluated using the resin composition for the base layer (A), the maleic anhydride-modified polyolefin for the adhesive layer (B), and the resin composition for the tie layer (C) as described in Table 5.

[0133] A resin composition for the base layer (A) was formed into a base layer (A) with a thickness of approximately 150 μm using a desktop press molding machine. 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 desktop press molding machine. PP / PPE alloy for the tie layer (C) was formed into a tie layer (C) with a thickness of approximately 25 μm using a desktop press molding machine. The base layer (A), adhesive layer (B), and tie layer (C) were stacked in the order of adhesive layer (B) / tie layer (C) / base layer (A) / tie layer (C) / adhesive layer (B), and then heat-pressed for 10 seconds at the pressure temperature shown in Table 5 using the same desktop press molding machine to obtain a 5-layer sheet. In Comparative Example 1, a 3-layer sheet consisting of adhesive layer (B) / base layer (A) / adhesive layer (B) was prepared and evaluated without the tie layer (C).

[0134] [Test piece] A SUS304 plate with a thickness of 0.1 mm was used as the adherend. A multilayer sheet was sandwiched between SUS304 plates on both sides 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.

[0135] (1) Room temperature peel test In the room-temperature peel test, a SUS304 plate was peeled at 23°C using an Instron tensile testing apparatus (Instron 5564) 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 5 as room-temperature peel strength (N / 10 mm).

[0136] (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 5 as hot water peel strength (N / 10mm).

[0137] (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 5 as constant load immersion drop time (hr).

[0138] [Table 5]

[0139] The details of the resins used in the base layer (A) and tie layer (C) in Table 5 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, 100% by mass of polyphenylene ether, Tg = 204℃ (DSC) MP10: Terminal amine-modified hydrogenated styrene-based thermoplastic elastomer (SEBS) manufactured by Asahi Kasei Corporation, ToughTec MP10, styrene content 30% H1221: Hydrogenated styrene-diene block copolymer (SEBS) manufactured by Asahi Kasei Corporation, ToughTec H1221

[0140] As can be seen from the results in Table 5, using PP / PPE alloy in the tie layer (C) significantly improved adhesion to the substrate and durability. In particular, using PP / PPE alloys C2 to C5 with a PP / PPE mass ratio of 30 / 70 to 49 / 51 made it possible to create multilayer sheets with high peel strength. [Industrial applicability]

[0141] 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. The multilayer sheet has a base layer (A) with excellent rigidity and heat resistance, and by applying a tie layer (C) of a specific formulation to it, the interfacial strength between the base layer (A) and the adhesive layer (B) is improved, allowing for the formation of a strong bond. Therefore, the multilayer sheet of the present invention is useful as a component of batteries and can contribute to reducing the number of battery parts and costs, as well as significantly improving productivity.

[0142] 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.

[0143] The disclosure of Japanese Patent Application No. 2021-102181, filed on 21 June 2021, is incorporated herein by reference in its entirety.

Claims

1. A multilayer sheet comprising a substrate layer (A) containing polyphenylene ether and an adhesive layer (B) containing acid-modified polyolefin, further comprising a tie layer (C) containing a polyolefin / polyphenylene ether alloy between the substrate layer (A) and the adhesive layer (B).

2. The multilayer sheet according to claim 1, wherein the base layer (A) comprises 40 to 99.9% by mass of polyphenylene ether, 0 to 59.9% by mass of polystyrene, and a polymer different from the polyphenylene ether and the polystyrene.

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

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

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

6. The multilayer sheet according to claim 1, wherein the mass ratio of polyolefin to polyphenylene ether contained in the tie layer (C) is 15 / 85 to 80 / 20.

7. The multilayer sheet according to claim 1, wherein the tie layer (C) comprises a styrene-diene block copolymer, a hydrogenated styrene-diene block copolymer, or polyethylene.

8. The multilayer sheet according to any one of claims 1 to 7, wherein the base layer (A) has a thickness of 50 to 300 μm, the adhesive layer (B) has a thickness of 10 to 100 μm, and the tie layer (C) has a thickness of 2 to 50 μm.

9. Step (1) involves preparing a substrate layer (A) containing polyphenylene ether, an adhesive layer (B) containing acid-modified polyolefin, and a tie layer (C) containing a polyolefin / polyphenylene ether alloy. Step (2) of bringing the base layer (A) and the tie layer (C) into contact by melting at least one of them at 160°C or higher, and Step (3) involves bringing at least one of the tie layer (C) and the adhesive layer (B) into contact with each other by melting them at a temperature of 160°C or higher, simultaneously with or at a different time from step (2). A method for manufacturing multilayer sheets, including [the specified element].

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