Multilayer sheet and production method therefor

Abstract

The present invention addresses the problem of providing a multilayer sheet that exhibits a high interlayer peel strength and that comprises: an adhesive layer containing an acid-modified polyolefin; and a substrate layer containing a polyphenylene ether. The multilayer sheet according to the present invention characteristically comprises a substrate layer (A) containing a polyphenylene ether and an adhesive layer (B) containing an acid-modified polyolefin, and further comprises, between the substrate layer (A) and the adhesive layer (B), a tie layer (C) containing a styrene-diene block copolymer.

Description

Multilayer sheet and method for producing the same

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

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

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

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

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

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

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

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

[0009] Although polyphenylene ether does not have the problems of deterioration over long-term use seen with other engineering plastics, it does have the serious problem of not adhering to the acid-modified polyolefin used in the adhesive layer and easily undergoing interlayer delamination.

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

[0011] The present inventors conducted extensive research to solve the above problems in developing a multilayer sheet comprising an adhesive layer containing an acid-modified polyolefin and a substrate layer containing polyphenylene ether. Specifically, they searched for various resin materials with the idea of ​​providing a tie layer with excellent adhesive strength between the adhesive layer containing an acid-modified polyolefin and the substrate layer containing polyphenylene ether, and discovered a resin composition suitable for the tie layer, thereby completing the present invention.

[0012] Means for solving the above problems include the following aspects. [1] A multilayer sheet comprising a substrate layer (A) containing polyphenylene ether and an adhesive layer (B) containing an acid-modified polyolefin, further comprising a tie layer (C) between the substrate layer (A) and the adhesive layer (B) containing a styrene-diene block copolymer, a hydrogenated styrene-diene block copolymer, a modified styrene-diene block copolymer, or a modified hydrogenated styrene-diene block copolymer. [2] The multilayer sheet according to [1], wherein the substrate layer (A) contains 40 to 99.9% by mass of polyphenylene ether and 0 to 59.9% by mass of polystyrene. [3] The multilayer sheet according to any one of [1] to [2], wherein the softening point of the substrate layer (A) is 175°C or higher. [4] The multilayer sheet according to any one of [1] to [3], wherein the storage modulus of the substrate layer (A) at 160°C is 500 MPa or higher. [5] The multilayer sheet according to any one of [1] to [4], wherein the acid-modified polyolefin is a maleic anhydride-modified polyolefin. [6] The multilayer sheet according to any one of [1] to [5], wherein the tie layer (C) comprises a modified product of the styrene-diene block copolymer or a modified product of a hydrogenated styrene-diene block copolymer, and the modified product of the styrene-diene block copolymer or the modified product of a hydrogenated styrene-diene block copolymer has a functional group selected from the group consisting of a carboxylic acid group, a carboxylic acid anhydride group, an epoxy group, an amino group, and combinations thereof. [7] The multilayer sheet according to any one of [1] to [6], wherein the tie layer (C) further comprises a polyphenylene ether. [8] The multilayer sheet according to any one of [1] to [7], wherein the substrate 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] A method for producing a multilayer sheet, comprising: a step (1) of preparing a substrate layer (A) containing polyphenylene ether, an adhesive layer (B) containing an acid-modified polyolefin, and a tie layer (C) containing a styrene-diene block copolymer, a hydrogenated styrene-diene block copolymer, a modified styrene-diene block copolymer, or a modified hydrogenated styrene-diene block copolymer; a step (2) of bringing at least one of the substrate layer (A) and the tie layer (C) into a molten state at 160°C or higher and contacting the substrate layer (A) with the tie layer (C); and a 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 contacting the tie layer (C) with the adhesive layer (B) simultaneously with or at a different time from the step (2).

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

[0014] By providing a tie layer mainly composed of a styrene-diene block copolymer, its hydrogenated product, and / or modified product thereof between the adhesive layer and the substrate layer, the interface between the adhesive layer and the substrate layer is firmly bonded, allowing the production of a multilayer sheet with excellent adhesive strength and heat resistance, thereby providing high-performance and economical sheet-type battery components, etc.

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

[0016] The multilayer sheet of the present invention comprises a substrate layer (A) containing polyphenylene ether and an adhesive layer (B) containing an acid-modified polyolefin. The multilayer sheet further comprises a tie layer (C) between the substrate layer (A) and the adhesive layer (B) containing a styrene-diene block copolymer, a hydrogenated product thereof, and / or a modified product thereof. The tie layer is disposed between the substrate layer and the adhesive layer, firmly bonding them together and increasing the peel strength of the multilayer sheet. The substrate 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 or lower surface, and the intermediate layer is a layer other than the surface layer. When the adhesive layer (B) is disposed on only one surface layer, only the tie layer (C) may be an intermediate layer, and both the substrate layer (A) and the adhesive layer (B) may be surface layers. Typical layer configurations include a three-layer sheet of substrate layer (A) / tie layer (C) / adhesive layer (B) and a five-layer sheet of adhesive layer (B) / tie layer (C) / substrate layer (A) / tie layer (C) / adhesive layer (B).

[0017] The substrate layer (A) contains a polyphenylene ether, which is typically a homopolymer or copolymer containing a monomer unit represented by the following formula:

[0018] In the formula, R １ ~R ４ is selected from H and alkyl groups having 1 to 6 carbon atoms; R １ and R ３ is preferably H, and R ２ and R ４ is preferably CH ３ is.

[0019] The mass ratio of polyphenylene ether in the substrate 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. When the mass ratio of polyphenylene ether in the substrate layer (A) is within this range, the heat resistance of the multilayer sheet can be improved. There is no particular upper limit for the mass ratio of polyphenylene ether in the substrate layer (A). However, for example, when a polymer other than polyphenylene ether is used in the substrate layer (A), the mass ratio of polyphenylene ether in the substrate 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. When the mass ratio of polyphenylene ether is within this range, the formability of the multilayer sheet can be improved.

[0020] The substrate layer (A) may further contain polystyrene. Polystyrene is an optional component, and the substrate layer (A) does not necessarily contain polystyrene. The mass ratio of polystyrene in the substrate layer (A) is preferably 50 mass% or less, more preferably 40 mass% or less, and particularly preferably 30 mass% or less. When the mass ratio of polystyrene is within this range, the heat resistance of the multilayer sheet can be improved.

[0021] Typical examples of polystyrene include general-purpose polystyrene (GPPS), which is a polymer of styrene alone, and high-impact polystyrene (HIPS), which is GPPS with added rubber to impart impact resistance. However, copolymers of styrene and acrylonitrile or (meth)acrylic acid esters can also be used. The copolymer used as polystyrene contains monomer units derived from styrene as the main component (e.g., 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, more preferably 10% by mass or less. By having the mass ratio of monomer units derived from comonomers be 20% by mass or less, compatibility with polyphenylene ether is improved, and phase separation can be prevented.

[0022] The total amount of polyphenylene ether and polystyrene in the substrate layer (A) is preferably 60% by mass or more, more preferably 70% by mass or more. There is no particular upper limit on the total amount of polyphenylene ether and polystyrene in the substrate layer (A), but in one embodiment of the present invention, the total amount of polyphenylene ether and polystyrene in the substrate layer (A) is preferably 99.9% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less.

[0023] A polymer other than polyphenylene ether and polystyrene (hereinafter referred to as other polymer (A)) may be added to the base layer (A) for the purposes of improving toughness and molding stability at low temperatures and improving adhesion to the tie layer (C).

[0024] Examples of the other polymer (A) include styrene-based block copolymers such as styrene-butadiene-styrene block copolymers and hydrogenated products thereof, styrene-isoprene-styrene block copolymers and hydrogenated products thereof, and graft copolymers in which a styrene homopolymer or copolymer is grafted onto a polyolefin. These copolymers contain styrene units as a minor component (e.g., 40% by mass or less of the total monomer units). The presence of polystyrene chains allows the other polymer (A) to have high miscibility with polyphenylene ether. These block copolymers and graft copolymers may be modified with an acid such as maleic anhydride, epoxy modified with an oxidizing agent, or terminal amine modified to have functional groups such as carboxylic acid groups, carboxylic anhydride groups, epoxy groups, or amino groups. These functional groups may be effective in improving interfacial adhesion with the tie layer.

[0025] Other examples of the other polymer (A) that can be used include unmodified or acid-modified polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers. By including a polyolefin in the base layer (A), improvements in toughness and chemical resistance can be expected. Because these polyolefins are not compatible with polyphenylene ether, it is preferable to use the aforementioned block copolymer or graft copolymer containing styrene units in combination as a compatibilizer.

[0026] When the other polymer (A) is used, the content of the other polymer (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 added amount is within such a range, the improving effect of the other polymer (A) is enhanced.

[0027] When the other polymer (A) is used, the content of the other polymer (A) in the base layer (A) is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less. When the added amount is within this range, the multilayer sheet can have high heat resistance and high adhesive strength at high temperatures.

[0028] When the other polymer (A) is used, the base layer (A) may contain 40 to 99.9 mass% of polyphenylene ether and 0 to 59.9 mass% of polystyrene, and from the viewpoint of improving the formability and heat resistance of the multilayer sheet, it preferably contains 50 to 98 mass% of polyphenylene ether and 0 to 50 mass% of polystyrene, and more preferably contains 60 to 95 mass% of polyphenylene ether and 0 to 40 mass% of polystyrene.

[0029] The softening point of the substrate layer (A) is preferably 175° C. or higher, more preferably 180° C. or higher, and particularly preferably 185° C. or higher. When the softening point is within this range, the heat resistance of the multilayer sheet is improved.

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

[0031] In terms of heat resistance, the thickness change rate of the substrate layer (A) in a compression creep test 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 below.

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

[0033] The softening point and storage modulus in the present invention are values ​​determined using a tensile viscoelasticity analyzer (DMS6100 manufactured by Hitachi High-Tech Sanence Corporation). Specifically, the temperature is raised from room temperature to 250°C at a frequency of 1 Hz and a heating rate of 2°C / min, and the changes in storage modulus, loss modulus, and tan δ with temperature are recorded. The softening point in the present invention refers to the temperature at which tan δ reaches its maximum value.

[0034] The melt flow rate of the substrate layer (A) is preferably 1 g / 10 min or more, more preferably 2 g / 10 min or more. The melt flow rate of the substrate layer (A) is preferably 50 g / 10 min or less, more preferably 30 g / 10 min or less. If the melt flow rate of the substrate layer (A) is below the lower limit, the melt viscosity becomes high, making sheet molding difficult, and if it is above the upper limit, the melt tension becomes too low, making sheet molding difficult as well.

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

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

[0038] Examples of monomer units constituting polyolefins include monomer units derived from monomers selected from the group consisting of α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene, diene monomers such as butadiene, isoprene, and chloroprene, aromatic vinyl compounds such as styrene, and combinations thereof. The number of carbon atoms in the monomer is preferably 2 to 10, and more preferably 2 to 5.

[0039] Among these, polyolefins selected from the group consisting of polymer blends of polyethylene and polypropylene, ethylene-propylene copolymers, and combinations thereof are preferred because they have high adhesive strength to the adherend.

[0040] Polyethylene is a polymer containing ethylene units as a main component, and may be a homopolymer or a copolymer. When it is a copolymer, the content of ethylene units in the polyethylene is preferably 50% by mass or more, and may be 70% by mass or more. Specific examples of polyethylene include homopolymers such as low-density polyethylene, high-density polyethylene, and linear low-density polyethylene; copolymers such as ethylene-diene monomer copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid ester copolymers, and ethylene-methacrylic acid ester copolymers; and halogen-modified polyethylenes such as chlorinated polyethylene.

[0041] Polypropylene is a polymer containing propylene units as a main component, and may be a homopolymer or a copolymer. In the case of a copolymer, the content of propylene units in the polypropylene is preferably 50% by mass or more, and may be 70% by mass or more. Specific examples of polypropylene include homopolymers such as amorphous polypropylene and crystalline polypropylene, copolymers such as propylene-diene monomer copolymer, and halogen-modified products such as chlorinated polypropylene.

[0042] An ethylene-propylene copolymer is a polymer containing ethylene units and propylene units, and may be composed only of ethylene units and propylene units, or may further contain other monomer units in addition to ethylene units and propylene units. An example of an ethylene-propylene copolymer containing other monomer units is an ethylene-propylene-diene monomer copolymer. The total amount of ethylene units and propylene units in the ethylene-propylene copolymer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may even be 100% by mass.

[0043] Polyolefins include physical blends of these resins, reactive blends in which functional groups are reacted between different polymers in a molding machine, graft copolymers and block copolymers consisting of multiple segments, and compositions in which physical blends of these copolymers are microdispersed as compatibilizers.

[0044] Of all the monomer units contained in the polyolefin, the total amount of ethylene units and propylene units is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass.

[0045] The mass ratio of ethylene units to propylene units (ethylene units / propylene units) contained in the polyolefin is preferably 10 / 90 to 40 / 60, more preferably 15 / 85 to 35 / 65. When the mass ratio of ethylene units is equal to or greater than the lower limit of this range, the thermocompression bondability of the acid-modified polyolefin is improved, thereby improving adhesive strength. When the mass ratio of ethylene units is equal to or less than the upper limit of this range, adhesive strength at high temperatures can be improved. By setting the mass ratio of ethylene units to propylene units within the above range, it is possible to achieve both high-temperature and low-temperature adhesive durability. Note that when the polyolefin is a polymer blend of polyethylene and polypropylene, the "mass ratio of ethylene units to propylene units contained in the polyolefin" means the mass ratio of ethylene units to propylene units in all ethylene units and propylene units contained in the polyethylene and polypropylene.

[0046] The mass ratio of ethylene units and propylene units can be determined by the characteristic absorption of polyethylene in the IR spectrum (719 cm －１ ) and the characteristic absorption of polypropylene (1167 cm －１ ) is determined from the absorbance ratio of the ethylene unit and the propylene unit. Specifically, a calibration curve is used to convert the absorbance ratio of the ethylene unit and the propylene unit into a mass ratio. The calibration curve can be created by blending commercially available polyethylene and polypropylene at various ratios and plotting the blending ratio and the absorbance ratio. For more details, see the examples below.

[0047] Polyethylene, polypropylene, and ethylene-propylene copolymers may contain monomer units other than ethylene units and propylene units. Examples of other monomers that form monomer units other than ethylene units and propylene units include α-olefins such as 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene; diene monomers such as butadiene, isoprene, and chloroprene; unsaturated carboxylic acids and derivatives thereof such as vinyl acetate, acrylic acid esters, acrylic acid, methacrylic acid, and methacrylic acid esters; and aromatic vinyl compounds such as styrene. The content of monomer units other than ethylene units and propylene units in polyolefins is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less. When the content of monomer units other than ethylene units and propylene units is within this range, the properties of the polyolefin, such as water resistance, chemical resistance, and durability, are improved, and polyolefins can be produced at low cost.

[0048] Methods for producing polyolefins include known production methods using polymerization catalysts. Examples of polymerization catalysts include Ziegler catalysts and metallocene catalysts, and examples of polymerization methods include slurry polymerization and gas phase polymerization. Impact-resistant polypropylene, also known as polypropylene block polymer, is essentially a mixture of polypropylene and a propylene-ethylene random copolymer, and can be produced by a process consisting of a first step of obtaining a propylene homopolymer and a second step of obtaining a propylene-ethylene random copolymer.

[0049] The acid compound used in producing the acid-modified polyolefin is selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and combinations thereof.

[0050] The unsaturated carboxylic acid is a compound having an ethylenic double bond and a carboxylic acid group in the same molecule, and examples thereof include various unsaturated monocarboxylic acids and unsaturated dicarboxylic acids. These acid compounds may be used alone or in combination of two or more.

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

[0054] Among these, maleic acid and maleic anhydride are preferably used because of their high modifying effect, and maleic anhydride is particularly preferably used.

[0055] The graft modification may be carried out by a known method, for example, by grafting an acid compound together with a polyolefin in a molten or solution state in the presence of a radical polymerization initiator such as an organic peroxide or an aliphatic azo compound.

[0056] The temperature of the grafting reaction is preferably 80 to 160° C. when the reaction is carried out in a solution state, and 150 to 300° C. when the reaction is carried out in a melt state. In both the solution state and the melt state, the reaction rate is high at or above the lower limit of the reaction temperature range described above, while a decrease in the molecular weight of the resin can be suppressed at or below the upper limit of the reaction temperature range described above, and the mechanical strength of the resulting acid-modified polyolefin can be maintained.

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

[0058] If a portion of the acid compound used for graft modification remains unreacted, it is preferable to remove the unreacted acid compound by a known method such as distillation under reduced pressure in order to prevent adverse effects on adhesive strength.

[0059] The amount of the acid compound grafted to the acid-modified polyolefin is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, and particularly preferably 0.6% by mass or more. When the amount of the grafted acid compound is within this range, the adhesiveness of the adhesive layer (B) can be improved.

[0060] The amount of the acid compound grafted onto the acid-modified polyolefin is preferably 5% by mass or less, more preferably 2% by mass or less, and particularly preferably 1% by mass or less. When the amount of the grafted acid compound is within such a range, deterioration in physical properties due to a decrease in molecular weight can be suppressed.

[0061] In this specification, the amount of acid compound grafted to the acid-modified polyolefin is defined by the acid value of the acid-modified polyolefin using the following formula: Graft amount (mass%) = Acid value × M × 100 / (1000 × 56.1 × V) In the formula, M and V are defined by the following formulas: M = (Molecular weight of acid compound) + (Number of unsaturated groups in acid compound) × 1.008 V = Valence of acid group (however, in the case of containing acid anhydride groups, V is the valence of the acid group when the acid anhydride groups are completely hydrolyzed) The acid value indicates the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 g of sample, and is measured in accordance with JIS K 0070:1992.

[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 adhesive strength at high temperatures 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 bondability can be obtained, and adhesion durability at low temperatures can be improved.

[0064] In the present invention, the melting point refers to the temperature at the top of an endothermic peak that occurs in the process of first holding the sample at 180°C for several minutes, then cooling it to 0°C, and then raising the temperature to 200°C at a rate of 10°C per minute using a differential scanning calorimeter (DSC).

[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, and is preferably 50 g / 10 min or less, more preferably 30 g / 10 min or less.

[0066] In the present 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 the acid-modified polyolefin in the adhesive layer (B) may be 2% by mass or more. For example, the acid-modified polyolefin may be used in combination with an unmodified polyolefin, and when a highly acid-modified polyolefin is used, a small amount of about 2% by mass may be used. In one embodiment, the content of the acid-modified polyolefin in the adhesive layer (B) is preferably 30% by mass or more, more preferably 70% by mass or more, particularly preferably 90% by mass or more, and may even be 100% by mass.

[0068] To the adhesive layer (B), a polymer other than the acid-modified polyolefin (hereinafter referred to as "other polymer (B)") can be added for the purpose of improving the adhesive strength at low temperatures, adhesive durability, molding stability, and adhesion to the base layer (A). Examples of the other polymer (B) include styrene-based block copolymers such as styrene-butadiene-styrene block copolymers and hydrogenated products thereof, styrene-isoprene-styrene block copolymers and hydrogenated products thereof, and styrene-isobutylene-styrene block copolymers, as well as styrene-based graft copolymers in which a styrene homopolymer or copolymer is grafted onto a polyolefin. In addition, unmodified polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers may also be added as the other polymer (B).

[0069] When the other polymer (B) is used, the lower limit of the content of the other polymer (B) in the adhesive layer (B) is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more. When the added amount is within this range, the improving effect of the other polymer (B) is enhanced.

[0070] When another polymer (B) is used, the upper limit of the content of the other polymer (B) in the adhesive layer (B) is preferably 50% by mass or less, more preferably 30% by mass or less, and particularly preferably 10% by mass or less. When the amount added is within this range, the adhesive layer (B) can obtain high heat resistance and high adhesive strength at high temperatures. As described above, when an acid-modified polyolefin with a high degree of acid modification is used, the content of the acid-modified polyolefin can be reduced. In such a case, the content of the unmodified polyolefin may be high, and the upper limit of the content of the unmodified polyolefin in the adhesive composition may be 98% by mass.

[0071] The adhesive layer (B) may further comprise an additive selected from the group consisting of an antioxidant, an ultraviolet absorber, a filler, a reinforcing fiber, a release agent, a processing aid, a flame retardant, a plasticizer, a nucleating agent, an antistatic agent, a pigment, a dye, a foaming agent, and combinations thereof.

[0072] The tie layer (C) contains a styrene-diene block copolymer or a hydrogenated styrene-diene block copolymer (hereinafter, these are collectively referred to as "SBP"), or a modified styrene-diene block copolymer or a modified hydrogenated styrene-diene block copolymer (hereinafter, these are collectively referred to as "modified SBP"). The modified SBP is obtained by modifying SBP to introduce a reactive group. One of these may be used alone, or a mixture of two or more may be used. SBP and modified SBP are preferably the main components of the tie layer (C). In the tie layer (C), particularly, of all the resin components constituting the tie layer (C), the total amount of SBP and modified SBP is preferably 30% by mass or more, more preferably 50% by mass or more, and particularly preferably 60% by mass or more. There is no particular upper limit on the total amount of SBP and modified SBP, but the total amount of SBP and modified SBP in the tie layer (C), particularly, of all the resin components constituting the tie layer (C), may be 80% by mass or less.

[0073] Specific examples of SBP include styrene-butadiene diblock copolymers, styrene-butadiene-styrene triblock copolymers, styrene-isoprene diblock copolymers, styrene-isoprene-styrene triblock copolymers, and polymers in which some or all of the double bonds in the molecular chains have been hydrogenated. Triblock copolymers are preferably used because commercially available products are easily available.

[0074] Among these block copolymers, a styrene-ethylene-butylene-styrene terblock copolymer (hereinafter sometimes abbreviated as SEBS), which is a hydrogenated product of a styrene-butadiene diblock copolymer, and a styrene-ethylene-propylene-styrene terblock copolymer (hereinafter sometimes abbreviated as SEPS), which is a hydrogenated product of a styrene-isoprene diblock copolymer, are preferably used because they are easily miscible with the acid-modified polyolefin, which is the main component of the adhesive layer (B).

[0075] The SBP described above is suitable as a resin contained in the tie layer (C) that bonds the two layers together because it contains, in the same molecule, a polystyrene chain that is compatible with the polyphenylene ether, which is the main component of the base layer (A), and a polyolefin chain that is compatible with the acid-modified polyolefin of the adhesive layer (B). However, by using a modified SBP in which a reactive group has been added to the SBP, the adhesive effect to the adhesive layer (B) can be further enhanced.

[0076] The reactive group is preferably a functional group that forms a hydrogen bond, an ionic bond, or a covalent bond by interacting with or reacting with a carboxylic acid group or a carboxylic acid anhydride group contained in the adhesive layer (B), and specific examples thereof include a carboxylic acid group, a carboxylic acid anhydride group, an epoxy group, and an amino group. Among these, the epoxy group and the amino group are preferred, and the amino group is particularly preferred.

[0077] The preferred method for modifying SBP to introduce carboxylic acid groups or carboxylic acid anhydride groups is the acid modification described in the description of the adhesive layer (B). For specific raw materials, methods, reaction conditions, etc., please refer to the description of the adhesive layer (B). By retaining at least a portion of the double bonds in the polydiene chain of the SBP, the acid modification reaction with maleic anhydride or the like becomes easier. The acid modification adds carboxylic acid groups or carboxylic acid anhydride groups to the diene block chain. As a result, the interaction, primarily via hydrogen bonding, between the carboxylic acid groups or carboxylic acid anhydride groups in the modified SBP and the carboxylic acid groups or carboxylic acid anhydride groups in the adhesive layer (B) is enhanced, improving the adhesive strength between the adhesive layer (B) and the tie layer (C).

[0078] A preferred method for modifying SBP to introduce epoxy groups is to oxidize and epoxidize the double bonds of the polydiene block of the SBP with an organic peroxide such as peracetic acid. The SBP used as the raw material for epoxidation may be hydrogenated, as long as at least a portion of the double bonds remain. An epoxidized product of a styrene-diene block copolymer can generally be produced by dissolving the raw material styrene-diene block copolymer in an organic solvent, adding an epoxidizing agent, reacting at a temperature of 80°C or less, and then removing the organic solvent by evaporation after the reaction. The epoxy groups introduced into the polydiene block react with carboxylic acid groups or carboxylic anhydride groups in the adhesive layer (B) to form covalent bonds, thereby improving the adhesive strength between the adhesive layer (B) and the tie layer (C).

[0079] A method for modifying SBP to introduce amino groups includes capping the active terminals with a modifying agent during the anionic living polymerization process, which is the basic synthesis method for SBP. Specifically, a method includes adding a modifying agent such as 1,3-dimethyl-2-imidazolidinone during the SBP synthesis process to cause an addition reaction with the terminal anions, and treating the product with protons.

[0080] When amine modification is performed using this method, an amine-modified SBP having an amino group at the end of the polystyrene block is obtained. The amino group may be present at only one end of the SBP molecule or at both ends. The terminal amino group may be a primary amine (-NH ２ ) and secondary amines (—NHR (where R is any group other than hydrogen, preferably an alkyl group)) are preferably used. Furthermore, triblock copolymers are more preferably used than diblock copolymers because of their commercial availability. Modified SBPs into which amino groups have been introduced interact or react with carboxylic acid groups or carboxylic anhydride groups in the adhesive layer (B) to form hydrogen bonds, ionic bonds, and even covalent bonds, thereby improving the adhesive strength between the adhesive layer (B) and the tie layer (C).

[0081] The tie layer (C) preferably contains polyphenylene ether. The amount of polyphenylene ether contained in the tie layer (C) is preferably 10% by mass or more, more preferably 20% by mass or more. The amount of polyphenylene ether contained in the tie layer (C) is preferably less than 70% by mass, more preferably less than 50% by mass. Polyphenylene ether is an optional component and may not be used in some cases.

[0082] The polyphenylene ether used in the tie layer (C) may be the same polyphenylene ether as that used in the substrate layer (A). By adding the polyphenylene ether to the tie layer (C), miscibility with the substrate layer (A) can be improved, and the interfacial adhesion can be increased.

[0083] The polyphenylene ether used in the tie layer (C) may have a lower molecular weight than commonly used polyphenylene ethers. The use of a low-molecular-weight polyphenylene ether improves moldability and enhances miscibility with SBP or modified SBP, an essential component of the tie layer (C). Furthermore, miscibility with the substrate layer (A) is enhanced, preventing interfacial delamination between the substrate layer (A) and the tie layer (C). The weight-average molecular weight of the low-molecular-weight polyphenylene ether is preferably 300 to 20,000, more preferably 500 to 10,000. By ensuring that the weight-average molecular weight is equal to or greater than the lower limit, the generation of volatile impurities can be suppressed, while by ensuring that the weight-average molecular weight is equal to or less than the upper limit, moldability can be improved. The weight-average molecular weight in this case is a polystyrene-equivalent molecular weight measured using gel permeation chromatography.

[0084] The low-molecular-weight polyphenylene ether preferably has an MFR of 1 g / 10 min or more, more preferably 10 g / 10 min or more, measured at 230° C. Controlling the MFR within this range improves the miscibility with the SBP and modified SBP, as well as the base layer (A).

[0085] In addition to SBP, modified SBP, and polyphenylene ether, other polymers (hereinafter referred to as other polymers (C)) can be added to the tie layer (C) for the purpose of adjusting moldability, interfacial strength, etc. Examples of other polymers (C) include polystyrene, unmodified polyolefins, and styrene-based graft copolymers in which a styrene homopolymer or copolymer is grafted onto a polyolefin.

[0086] When polystyrene is used as the other polymer (C), a homopolymer of styrene alone, a high-impact polystyrene to which rubber has been added to impart impact resistance, or a copolymer of styrene with acrylonitrile or a (meth)acrylic acid ester can be used. When polystyrene is a copolymer, the mass ratio of monomer units derived from comonomers other than styrene in the polystyrene is preferably 20 mass% or less, more preferably 10 mass% or less. By having the mass ratio of monomer units derived from comonomers be 20 mass% or less, compatibility with polyphenylene ether can be improved and phase separation can be prevented.

[0087] When an epoxy-modified SBP is used for the tie layer (C), if an epoxy group-containing styrene copolymer is used as the other polymer (C), the epoxy group concentration can be further increased, thereby enhancing the adhesive strength with the adhesive layer (B). A specific example of a styrene copolymer containing epoxy groups is a copolymer of styrene and glycidyl (meth)acrylate.

[0088] When the other polymer (C) is used, the content of the other polymer (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 improving effect of the other polymer (C) is enhanced.

[0089] When the other polymer (C) is used, the content of the other polymer (C) in the tie layer (C) is preferably 40% by mass or less, more preferably 20% by mass or less. When the amount added is within this range, the improving effect of the other polymer (C) is enhanced.

[0090] The melt flow rate of the tie layer (C) is preferably 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more. The melt flow rate of the tie layer (C) is preferably 100 g / 10 min or less, more preferably 60 g / 10 min or less. If the melt flow rate of the tie layer (C) is below the lower limit, the melt viscosity becomes high, making sheet molding difficult. If the melt flow rate is above the upper limit, the melt tension becomes too low, making sheet molding difficult.

[0091] 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 260°C and a load of 2.16 kg.

[0092] The tie layer (C) may further comprise 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, blowing agents, and combinations thereof.

[0093] The multilayer sheet of the present invention can be firmly bonded to an adherend. When the adhesive layer (B) of the multilayer sheet is bonded to an adherend, particularly a 0.1 mm thick SUS304 plate, to produce a bonded structure, the room temperature peel strength between the multilayer sheet and the adherend, particularly a 0.1 mm thick SUS304 plate, is 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.

[0094] The substrate 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. When the thickness of the substrate layer (A) is equal to or greater than this lower limit, sufficient rigidity can be obtained. When the thickness of the substrate layer (A) is equal to or less than this upper limit, the influence on the thickness of an article incorporating the multilayer sheet, such as a battery, can be reduced.

[0095] 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 equal to or greater than this lower limit, the occurrence of poor adhesion can be suppressed. When the thickness of the adhesive layer (B) is equal to or less than this upper limit, the adhesive can be prevented from squeezing out of the multilayer sheet, and defects can be prevented in articles incorporating the multilayer sheet, such as batteries.

[0096] The thickness of the tie layer (C) is preferably 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 equal to or greater than this lower limit, sufficient adhesiveness can be obtained. When the thickness of the tie layer (C) is equal to or less than this upper limit, the effect on the thickness of an article incorporating the multilayer sheet, such as a battery, can be reduced.

[0097] By controlling the thickness of each layer of the multilayer sheet within such a range, the multilayer sheet and the bonded body using the same can exhibit excellent adhesive performance, durability, productivity, and economy.

[0098] The base layer (A), adhesive layer (B), and tie layer (C) are generally each produced from a resin composition as a raw material. The resin compositions that are the raw materials for the base layer (A), adhesive layer (B), and tie layer (C) are compositions whose main component is a resin, consisting of the components of the base layer (A), adhesive layer (B), and tie layer (C) described above. The resin composition can be produced by melt-kneading the main component resin and, if necessary, other components using an extruder, Banbury mixer, or heated roll, and then cooling and solidifying the extruded strands with water or the like while pulling them through the nozzle holes of a die head, and cutting them into pellets.

[0099] The melt-kneading temperature of the resin composition used for the substrate layer (A) is preferably 150 to 320°C, more preferably 180 to 300°C, and the kneading time is usually 0.5 to 20 minutes, preferably 1 to 15 minutes.

[0100] The temperature for melt-kneading the resin composition used for the adhesive layer (B) is preferably 150 to 270°C, more preferably 170 to 250°C, and the kneading time is usually 0.5 to 20 minutes, preferably 1 to 15 minutes.

[0101] The melt-kneading temperature of the resin composition used for the tie layer (C) is preferably 150 to 320°C, more preferably 170 to 300°C, and the kneading time is usually 0.5 to 20 minutes, preferably 1 to 15 minutes.

[0102] The resin composition used for the substrate layer (A), the resin composition used for the adhesive layer (B), and the resin composition used for the tie layer (C) thus obtained can be formed into multilayer sheets of various shapes depending on the application by a conventionally known method, such as compression molding, injection molding, extrusion molding, multilayer extrusion molding, profile extrusion molding, or blow molding.

[0103] The substrate layer (A), adhesive layer (B), and tie layer (C) may be prepared as individual sheets and then thermally laminated to form a multilayer structure. Alternatively, they may be formed into a multilayer structure by simultaneously forming a sheet and laminating the layers, as in multilayer extrusion molding. In either case, it is preferable to bring the substrate layer (A) and the tie layer (C) into contact with each other while at least one of the substrate layer (A) and the tie layer (C) is in a molten state, and to bring the tie layer (C) and the adhesive layer (B) into contact with each other while at least one of the tie layer (C) and the adhesive layer (B) is in a molten state. It is more preferable to bring the substrate layer (A) and the tie layer (C), and the tie layer (C) and the 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 temperature at which they are brought into contact 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 base layer (A) may not proceed sufficiently, resulting in insufficient interlayer adhesive strength. The base layer (A) and the adhesive layer (B) may be brought into contact with the tie layer (C) simultaneously or separately.

[0104] The multilayer sheet of the present invention is preferably produced by multilayer extrusion molding in terms of productivity and manufacturing costs. In general extrusion molding, layered molten resins extruded from a T-die are cooled and stretched by rolls or the like to form a sheet. Multilayer molding is possible by "coextrusion," in which multiple resins are extruded simultaneously. Specific coextrusion techniques include the "feedblock method," in which resins are joined just before the T-die, and the "multi-manifold method," in which the individual layers are spread in manifolds and then joined at the lip, which is the discharge outlet of the T-die. Either of these techniques, or other techniques, may be used to produce the multilayer sheet of the present invention. The multilayer sheet extruded by the above-described multilayer extrusion molding may subsequently be thermally laminated (thermocompression bonded) using a heated roll. The addition of a thermal lamination step may further improve interlayer adhesion. The preferred temperature conditions for the thermal lamination step are as described above.

[0105] The multilayer sheet of the present invention can be bonded to adherends made of various materials such as metal, glass, ceramics, or plastic. This allows for the production of a bonded body including the multilayer sheet and the adherend. For example, the bonded body including the multilayer sheet can be used as a member or part of a layered battery.

[0106] The metal used as the adherend may be a commonly known metal plate, metal flat plate, or metal foil, and may be iron, copper, aluminum, lead, zinc, titanium, chromium, stainless steel, etc. Among these, iron, aluminum, titanium, and stainless steel are particularly preferred.

[0107] The plastic used as the adherend may be any of various thermoplastic or thermosetting resins. Composite materials may also be used, in which inorganic materials such as glass or ceramics, or fillers or fibers such as metals or carbon are combined with a resin.

[0108] The present invention will be described in more detail below with reference to examples. Unless otherwise specified, "parts" means parts by mass and "%" means % by mass. Unless otherwise specified, "PPE" means polyphenylene ether, "PS" means polystyrene, "PP" means polypropylene, "PE" means polyethylene, and "MAH" means maleic anhydride.

[0109] [Adhesive layer (B)] An ethylene-propylene-based maleic anhydride polyolefin B1 was prepared. The PE / PP blend ratio and the amount of maleic anhydride in the maleic anhydride-modified polyolefin B1 were confirmed by the following procedures (1) and (2).

[0110] (1) PE / PP Blending Ratio Commercially available polyethylene resin (P9210 manufactured by Keiyo Polyethylene Co., Ltd.) and polypropylene resin (Waymax MFX3 manufactured by Japan Polypropylene Corporation) were melt-mixed in an extruder at various blending ratios, and the resulting resin mixture was molded using a bench press molding machine to produce a resin sheet with a thickness of approximately 2 mm.

[0111] An IR spectrum was obtained from the cut surface of the resin sheet by the attenuated total reflection method (ATR method) using a Spectrum 100 manufactured by PerkinElmer. －１ (PE characteristic absorption) and 1167 cm －１ The PE absorbance ratio was calculated from the absorbance of (PP characteristic absorption). A calibration curve was created by plotting this absorbance ratio against the blending ratio during melt-kneading. The results of the PE blending ratio and PE absorbance ratio are shown in Table 1, and the plot results are shown in Figure 1.

[0112] In consideration of measurement error, the number of repetitions was set to 4 or more. The approximate curve of this plot was used as a calibration curve for determining the PE / PP blend ratio.

[0113]

[0114] The maleic anhydride-modified polyolefin B1 was molded into a resin sheet with a thickness of 2 mm, and the cross section of the sheet was used as the measurement surface for IR spectroscopy. Based on the obtained IR spectrum, a calibration curve was created to determine the PE / PP blending ratio of the maleic anhydride-modified polyolefin B1. The results are shown in Table 2.

[0115] (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 dissolved in xylene by heating, and the resulting solution was titrated with an ethanol solution of potassium hydroxide using phenol red as an indicator. The amount of maleic anhydride was calculated from the titration results, and the results are shown in Table 2.

[0116] (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.

[0117]

[0118] [Tie layer (C)] The resins shown in the "Tie layer (C) composition" in Table 3 below were melt-kneaded in the blending ratios (mass%) shown in Table 3 to prepare a resin composition for the tie layer (C).

[0119] [Base layer (A)] A commercially available PPE / PS alloy, Zylon 1000H (Tg = 184°C (DSC)) manufactured by Asahi Kasei Corporation, was used as the resin for the base layer (A). The melt flow rate, softening point, storage modulus, creep amount, and thermal change rate were measured as described in (1) to (4) below, and the following results were obtained.

[0120] (1) Melt Flow Rate The melt flow rate (MFR) was measured using a commercially available melt indexer (G-02 manufactured by Toyo Seiki Seisaku-sho, Ltd.) in accordance with JIS K7210:2014 at 300°C and a load of 2.16 kg. The melt flow rate was 5.7 (g / 10 min).

[0121] (2) Softening Point and Storage Modulus The resin composition for the base layer (A) was molded into a sheet of approximately 0.2 mm thickness using a bench press molding machine. This resin sheet was cut into a size of 10 mm x 4.5 mm, and the viscoelastic properties were measured using a tensile viscoelasticity device (Hitachi High-Tech Sanence Corporation DMS6100). Specifically, the temperature was raised from room temperature to 250 ° C at a frequency of 1 Hz and a heating rate of 2 ° C / min, and the changes in storage modulus, loss modulus, and tan δ with temperature were recorded. The softening point was defined as the temperature at which the tan δ value reached its maximum. As a result of the measurement, the softening point was 196 ° C, the storage modulus at 160 ° C was 1,985 MPa, and the storage modulus at 170 ° C was 1,779 MPa.

[0122] (3) Compression Creep Test The resin composition for the base layer (A) was molded into a sheet with a thickness of 1 mm using a bench press molding machine. This resin sheet was cut into a size of 10 mm x 10 mm, and five sheets were stacked to form a sample with a thickness of 5 mm. Using a heat press device (Digital Press CYPT-50 manufactured by Shinto Kogyo Co., Ltd.), the sample was heated at a temperature of 170 ° C and a pressure of 6 MPa for 12 hours, and the ratio of the thickness change before and after the test to the thickness before the test was calculated as the creep amount (%). As a result of the measurement, the compression creep amount was 14%.

[0123] (4) Thermal Shrinkage Test The resin composition for the base layer (A) was molded into a sheet approximately 100 μm thick using a bench press molding machine. This resin sheet was cut into a size of 200 mm x 100 mm to prepare a sample. The prepared sample was hung in a dryer at 180°C for 30 seconds, and the thermal change rate was calculated from the dimensional change before and after heating. The thermal change rate is the average of the absolute value of the change rate of the long side and the absolute value of the change rate of the short side. As a result of the measurement, the thermal change rate was only 0.07%.

[0124] [Multilayer Sheet] In each example, a five-layer multilayer sheet was produced and evaluated by the following method using the resin for the base layer (A), the resin for the adhesive layer (B) described above, and the resin for the tie layer (C) having the composition shown in Table 3. Note that the multilayer sheet of Comparative Example 1 did not have a tie layer (C).

[0125] The resin for the base layer (A) was formed into a base layer (A) with a thickness of approximately 150 μm using a bench press molding machine. The resin for the adhesive layer (B) was formed into an adhesive layer (B) with a thickness of approximately 50 μm using a bench press molding machine. The resin composition for the tie layer (C) was formed into a tie layer (C) with a thickness of approximately 25 μm using a bench 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 thermocompressed for 10 seconds at a compression temperature of 260 ° C. using the same bench press molding machine to obtain a five-layer sheet.

[0126] [Test Piece] A 0.1 mm thick SUS304 plate was used as the adherend, and both sides of the multilayer sheet were sandwiched between SUS304 plates and thermocompression bonded (160°C, 10 seconds, 0.3 MPa) using a precision press to produce a bonded assembly. This bonded assembly was cut into 10 mm wide strips to prepare test pieces. The bonded portion of the test piece was 10 mm wide and 15 mm long. The room temperature peel strength, hot water peel strength, and constant load immersion drop time of the obtained test piece were measured as described below in (1) to (3).

[0127] (1) Room-temperature peel test In the room-temperature peel test, a tensile tester (Instron 5564) manufactured by Instron Corporation was used to peel a SUS304 plate at a tensile speed of 50 mm / min at 23°C, 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).

[0128] (2) Hot Water Peel Test In the hot water peel test, a load cell eDPU-50N manufactured by Imada Co., Ltd. was attached to a measurement stand MX2-1000N manufactured by the same company, and a heated water bath with a hook attached to the bottom was filled with hot water at 95°C, and the test piece was immersed in the water and peeled off, and the peel strength was evaluated in the same manner. The results are shown in Table 3 as hot water peel strength (N / 10 mm).

[0129] (3) Adhesion Durability in Water A constant-load immersion test was conducted to evaluate adhesion durability in water. The constant-load immersion test involves placing a test specimen in 95°C hot water under a constant peel load, and evaluating the adhesion durability based on the time (drop time) until the SUS304 plate peeled off. The test specimens were the same as those used to measure peel strength. One end of the handle of the test specimen was connected to a fixed stand with a wire, and the other end was connected to a weight. The test specimen and the weight were suspended from a fixed stand placed above the water surface into 95°C hot water, and a peel load (1 N) was applied by the weight in the water. The time (drop time) required for the adherend SUS304 plate to completely separate was measured. The results are shown in Table 3 as the constant-load immersion drop time (hr).

[0130]

[0131] Details of the resins used in the tie layer (C) in Table 3 are as follows: PX100F: PPE PX100F manufactured by Mitsubishi Engineering Plastics Corporation, Tg = 204°C (DSC) SA120: Low-molecular-weight PPE manufactured by SABIC Japan LLC, product name Noryl SA120, MFR measured at 230°C = 48 g / 10 min MP10: Amine-terminated hydrogenated styrene-based thermoplastic elastomer manufactured by Asahi Kasei Corporation (modified hydrogenated styrene-diene block copolymer <SEBS>) Tuftec MP10, styrene content 30%, MFR measured at 230°C = 3.8 g / 10 min

[0132] As can be seen from the results in Table 3, the use of a tie layer containing an amine-terminated hydrogenated styrene-based thermoplastic elastomer significantly improved adhesion strength and durability to the adherend. Furthermore, the inclusion of polyphenylene ether in the tie layer improved the peel strength and adhesion durability of the multilayer sheet in water. In particular, as shown in Examples 2 to 4, when the tie layer contained 25 to 40 mass % polyphenylene ether, the peel strength and adhesion durability of the multilayer sheet in water were significantly improved.

[0133] 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 bonded body may be in continuous or intermittent contact with moisture. The multilayer sheet has a substrate layer (A) with excellent rigidity and heat resistance, and the addition of a tie layer (C) with a specific composition improves the interfacial strength with the adhesive layer (B), resulting in a strong bonded body. Therefore, the multilayer sheet is useful as a component of a battery, contributing to reducing the number of battery parts and costs, and significantly improving productivity.

[0134] Other uses include, for example, electric wires and cables in which metal conductors or optical fibers are coated with resin molded products, automobile mechanical parts, automobile exterior parts, automobile interior parts, molded power supply substrates, light reflectors for reflecting light sources, fuel cases for solid methanol batteries, heat insulating materials for metal pipes, heat insulating materials for vehicles, fuel cell water pipes, decorative molded products, water cooling tanks, boiler exterior cases, peripheral parts and members for printer ink, water piping, joints, secondary battery alkaline storage battery tanks, gasket sealants for various layered batteries, and the like.

[0135] The disclosure of Japanese Patent Application No. 2021-116318, filed on July 14, 2021, is incorporated herein by reference in its entirety.

Claims

1. A multilayer sheet comprising a base material layer (A) containing a polyphenylene ether and an adhesive layer (B) containing an acid-modified polyolefin, and between the base material layer (A) and the adhesive layer (B), a tie layer (C) containing a styrene-diene block copolymer, a hydrogenated product of a styrene-diene block copolymer, a modified product of a styrene-diene block copolymer, or a modified product of a hydrogenated product of a styrene-diene block copolymer.

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

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

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

5. The multilayer sheet according to claim 1, wherein the tie layer (C) contains a modified product of the styrene-diene block copolymer or a modified product of a hydrogenated product of the styrene-diene block copolymer, and the modified product of the styrene-diene block copolymer or the modified product of a hydrogenated product of the styrene-diene block copolymer has a functional group selected from the group consisting of a carboxylic acid group, a carboxylic anhydride group, an epoxy group, an amino group, and combinations thereof.

6. The multilayer sheet according to claim 1, wherein the tie layer (C) further contains a polyphenylene ether.

7. The multilayer sheet according to any one of claims 1 to 6, 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.

8. A 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 styrene-diene block copolymer, a hydrogenated product of the styrene-diene block copolymer, a modified product of the styrene-diene block copolymer, or a modified product of the hydrogenated product of the styrene-diene block copolymer, A step (2) of bringing the base material layer (A) and the tie layer (C) into contact with each other by melting at least one of the base material layer (A) and the tie layer (C) at 160°C or higher, and A step (3) of bringing the tie layer (C) and the adhesive layer (B) into contact with each other by melting at least one of the tie layer (C) and the adhesive layer (B) at 160°C or higher at the same time as or at a different time from the step (2). A method for manufacturing a multilayer sheet, comprising the above steps.