Multilayer sheet

Abstract

A multilayer sheet comprises a base material layer, a primer layer disposed on at least one surface side of the base material layer, and an adhesive layer in this order. The base material layer contains a polymer having a structural unit including at least one structure selected from the group consisting of an imide structure, a sulfone structure, an amide structure, and a sulfide structure. The primer layer contains an acid-modified polyolefin.

Description

Multilayer sheet

[0001] The present disclosure relates to multilayer sheets.

[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] For example, Patent Document 1 describes a hot melt adhesive resin laminate comprising a first surface layer containing an acid-modified polyolefin resin, a first intermediate layer, a substrate layer, a second intermediate layer, and a second surface layer containing an acid-modified polyolefin resin, laminated in this order, and characterized in that the peel strength when subjected to a peel test under specified conditions is 0.8 Nmm or more.

[0004] Regarding battery applications, for example, fuel cells operate in a humidified atmosphere to improve the proton conductivity of the electrolyte membrane, and since water is generated during the power generation reaction, high hydrolysis resistance is required for the components that make up the fuel cell. Furthermore, since the output density can be improved by increasing the operating temperature of the fuel cell, use in high-temperature environments (e.g., 100°C or higher) is required from the perspective of miniaturizing the fuel cell.

[0005] As a technology for addressing the hydrolysis resistance of gasket members in high-temperature environments among the components that make up a fuel cell, for example, Patent Document 2 describes a gasket member for a polymer electrolyte fuel cell that is composed of a laminate including at least a base layer and adhesive layers disposed on both sides of the base layer, and the laminate has a breaking elongation retention rate of 60% or more after being left standing in water at 120°C for 300 hours.

[0006] Patent Document 1: JP 2018-135467 A Patent Document 2: WO 2022 / 172983

[0007] The hot melt adhesive resin laminate described in Patent Document 1 uses a hydrolyzable resin such as PEN for the substrate layer, and has problems with adhesion durability in a moisture-containing environment. The gasket member for a polymer electrolyte fuel cell described in Patent Document 2 has insufficient adhesion between the substrate layer and the adhesive layer, and has problems with adhesion durability at high temperatures. The problem to be solved by one embodiment of the present disclosure is to provide a multilayer sheet with excellent adhesion durability in a moisture-containing environment at high temperatures.

[0008] Means for solving the above problems include the following aspects. [1] A multilayer sheet comprising, in this order, a substrate layer, a primer layer disposed on at least one surface of the substrate layer, and an adhesive layer, wherein the substrate layer comprises a polymer having a structural unit containing at least one structure selected from the group consisting of an imide structure, a sulfone structure, an amide structure, and a sulfide structure, and the primer layer comprises an acid-modified polyolefin. [2] The multilayer sheet according to [1], wherein the primer layer further comprises a curing agent. [3] The multilayer sheet according to [2], wherein the curing agent comprises at least one selected from an isocyanate compound and an epoxy compound. [4] The multilayer sheet according to any one of [1] to [3], wherein the acid-modified polyolefin contained in the primer layer is a maleic anhydride-modified polyolefin. [5] The multilayer sheet according to any one of [1] to [4], wherein the multilayer sheet is used as a gasket member for a fuel cell.

[0009] According to one embodiment of the present disclosure, a multilayer sheet having excellent adhesion durability in a high-temperature and moisture-containing environment can be provided.

[0010] The multilayer sheet according to the present disclosure will be described in detail below. The following description may be based on representative embodiments of the multilayer sheet according to the present disclosure, but the multilayer sheet according to the present disclosure is not limited to such embodiments and can be modified as appropriate within the scope of the object of the present disclosure.

[0011] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0012] In the present disclosure, the upper or lower limit of a numerical range described in stages may be replaced by the upper or lower limit of another numerical range. In the present disclosure, the upper or lower limit of a numerical range may be replaced by a value shown in the examples.

[0013] In the present disclosure, unless otherwise specified, the molecular weight of a compound having a molecular weight distribution is the weight average molecular weight (Mw). In the present disclosure, "mass%" and "weight%" are synonymous, and "parts by mass" and "parts by weight" are synonymous. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0014] [Multilayer Sheet] The multilayer sheet according to the present disclosure comprises, in this order, a base layer, a primer layer disposed on at least one surface of the base layer, and an adhesive layer, wherein the base layer contains a polymer having a structural unit including at least one structure selected from the group consisting of an imide structure, a sulfone structure, an amide structure, and a sulfide structure, and the primer layer contains an acid-modified polyolefin.

[0015] The primer layer is a layer that is disposed between the substrate layer and the adhesive layer and contributes to improving the adhesive strength between the substrate layer and the adhesive layer.

[0016] The substrate layer is an intermediate layer or a surface layer, the adhesive layer is a surface layer, and the primer layer is an intermediate layer.

[0017] Here, in the multilayer sheet, 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.

[0018] When the adhesive layer is provided on only one of the surface layers, only the primer layer may be the intermediate layer, and both the base layer and the adhesive layer may be surface layers.

[0019] Typical layer configurations of the multilayer sheet include a three-layer sheet of substrate layer / primer layer / adhesive layer, and a five-layer sheet of adhesive layer / primer layer / substrate layer / primer layer / adhesive layer.

[0020] The multilayer sheet according to the present disclosure is configured to comprise, in this order, a base layer, a primer layer arranged on at least one side of the base layer, and an adhesive layer. It is presumed that the base layer contains a specified polymer and the primer layer contains an acid-modified polyolefin, thereby improving hydrolysis resistance even in high-temperature and moisture-containing environments and providing excellent adhesive durability.

[0021] In the present disclosure, adhesive durability is evaluated by preparing a test piece from a bonded assembly obtained by bonding the adhesive layer of a multilayer sheet to an adherend (specifically, a 0.1 mm thick SUS304 plate), and then holding the test piece in water at 120° C. for 1,500 hours, and then measuring the peel strength. Details of the evaluation method and conditions for adhesive durability will be described in the Examples below.

[0022] (Substrate Layer) The substrate layer contains a polymer (hereinafter also referred to as "specific polymer") having a structural unit containing at least one structure selected from the group consisting of an imide structure, a sulfone structure, an amide structure, and a sulfide structure. By containing the specific polymer, the substrate layer has excellent heat resistance and hydrolysis resistance, and also excellent adhesion to a primer layer containing an acid-modified polyolefin.

[0023] The structural unit of the specific polymer may include one type of structure selected from the group consisting of an imide structure, a sulfone structure, an amide structure, and a sulfide structure (hereinafter also referred to as a "specific structure"), or may include two or more types of structures.

[0024] Examples of the specific polymer include polyimide (PI), polyamideimide (PAI), polyphenylsulfone (PPSU), polyethersulfone (PESU), polysulfone (PSU), polyamide (PA), polyphenylene sulfide (PPS), polyetherimide (PEI), and polymethacrylimide (PMI). From the viewpoint of adhesive durability in a high-temperature, moisture-containing environment, polyimide (PI) and polyphenylsulfone (PPSU) are more preferred.

[0025] The total amount of the specific polymer in the substrate layer 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 the specific polymer in the substrate layer, but in one embodiment of the present disclosure, the total amount of the specific polymer in the substrate layer is preferably 99.9% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less.

[0026] The substrate layer may contain a polymer other than the specific polymer (hereinafter also referred to as "other polymer A") for the purposes of heat resistance, hydrolysis resistance, ease of molding, and the like.

[0027] Other examples of the polymer A include phenolic resins, urea resins, melamine resins, benzoguanamine resins, alkyd resins, unsaturated polyester resins, vinyl ester resins, diallyl terephthalate resins, silicone resins, urethane resins, furan resins, ketone resins, xylene resins, benzoxazine resins, active ester resins, aniline resins, cyanate ester resins, styrene-maleic anhydride (SMA) resins, polyethylene resins, polypropylene resins, polystyrene resins, rubber-modified polystyrene resins, acrylonitrile-butadiene-styrene (ABS) resins, acrylonitrile-styrene (AS) resins, polymers Examples of the resin include methyl methacrylate resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyethylene terephthalate resin, ethylene vinyl alcohol resin, cellulose acetate resin, ionomer resin, polyacrylonitrile resin, polyacetal resin, polybutylene terephthalate resin, polylactic acid resin, polyphenylene ether resin, modified polyphenylene ether resin, polycarbonate resin, polyarylate resin, polyether ether ketone resin, polyketone resin, liquid crystal polyester resin, fluororesin, syndiotactic polystyrene resin, cyclic polyolefin resin, α-olefin copolymer, propylene-based elastomer, polyisoprene, hydrogenated polyisoprene, polybutadiene, cycloolefin polymer, cycloolefin copolymer, polyamine, polyamide, melamine resin, urea resin, styrene-based thermoplastic resin, hydroxyl group-modified polyolefin resin, and glycidyl methacrylate-modified polyolefin resin.

[0028] When the other polymer A is contained, the content of the other polymer in the base layer may be, for example, 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and particularly preferably 5% by mass or more. When the content of the other polymer A is within this range, the improving effect of the other polymer A in the multilayer sheet is enhanced.

[0029] When the other polymer A is contained, the content of the other polymer A in the base layer is preferably 50% by mass or less, more preferably 35% by mass or less, and particularly preferably 20% by mass or less. When the content of the other polymer A is within this range, the heat resistance, hydrolysis resistance, and formability of the multilayer sheet can be further improved.

[0030] The softening point of the substrate layer 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.

[0031] The storage modulus of the base layer 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 at 170° C. is preferably 500 MPa or more, more preferably 700 MPa or more, and particularly preferably 1000 MPa or more. When the storage modulus in this temperature range is 500 MPa or more, deformation and damage of the multilayer sheet due to thermocompression bonding during adhesion can be prevented.

[0032] From the viewpoint of heat resistance, the thickness change rate of the substrate layer in a compression creep test is preferably 30% or less, more preferably 25% or less, and particularly preferably 20% or less.

[0033] From the viewpoint of heat resistance, the thermal change rate of the substrate layer in a heat shrinkage test is preferably 0.50% or less, more preferably 0.30% or less, and particularly preferably 0.20% or less.

[0034] In the present disclosure, the softening point and storage modulus are values ​​determined using a tensile viscoelasticity analyzer (DMS6100 manufactured by Hitachi High-Tech Sanence Corporation). Specifically, the object to be measured is heated 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. In the present disclosure, the softening point refers to the temperature at which tan δ reaches its maximum value.

[0035] The melt flow rate of the substrate layer is preferably 1 g / 10 min or more, more preferably 2 g / 10 min or more. The melt flow rate of the substrate layer 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 is below the lower limit, the melt viscosity becomes high, making sheet formation difficult, while if the melt flow rate is above the upper limit, the melt tension becomes too low, making sheet formation difficult as well.

[0036] The melt flow rate of the base material layer is a value measured in accordance with JIS K7210:2014 (ISO 1133 2011). The melt flow rate of the base material layer was measured at a resin temperature of 300°C and a load of 2.16 kg.

[0037] The substrate layer 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.

[0038] (Primer layer) The primer layer contains an acid-modified polyolefin. The content of the acid-modified polyolefin in the primer layer is preferably 50% by mass or more, more preferably 70% by mass or more, based on the total amount of the primer layer. When the content of the acid-modified polyolefin is within this range, the effect of improving the adhesion durability of the primer layer is enhanced.

[0039] In the present disclosure, the acid-modified polyolefin is an unmodified polyolefin (hereinafter also simply referred to as "polyolefin") that has been graft-modified with an acid compound selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid anhydrides, and combinations thereof.

[0040] In the acid-modified polyolefin contained in the primer layer, examples of the monomer units constituting the polyolefin include monomer units derived from a monomer 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.

[0041] As the polyolefin, polypropylene is particularly preferred. Polypropylene is a polymer containing propylene units as a main component, and may be a homopolymer or copolymer, or may be 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, more preferably 75% by mass or more.

[0042] Specific examples of polypropylene include homopolymers such as amorphous polypropylene and crystalline polypropylene, copolymers containing propylene as the main component, halogen-modified products such as chlorinated polypropylene, alloys or blends of polypropylene with other polymers, etc. In one embodiment, the polypropylene is preferably a copolymer containing propylene as the main component, and an example of a copolymer containing propylene as the main component is a propylene-1-butene copolymer.

[0043] Other monomer units constituting polypropylene copolymers or alloys include monomer units derived from monomers selected from the group consisting of α-olefins such as ethylene, 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, and more preferably 2 to 5.

[0044] Polyolefins can be produced by known methods using a polymerization catalyst, such as a Ziegler catalyst or a metallocene catalyst, and by a polymerization method such as slurry polymerization or gas phase polymerization.

[0045] 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.

[0046] 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.

[0047] Specific examples of unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid.

[0048] Specific examples of unsaturated dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid, and endic acid.

[0049] 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.

[0050] Among these, maleic acid and maleic anhydride are preferably used because of their high modifying effect, and maleic anhydride is particularly preferably used. That is, the acid-modified polyolefin contained in the primer layer is preferably a maleic anhydride-modified polyolefin.

[0051] 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.

[0052] 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.

[0053] The radical polymerization initiator to be used may be selected from commercially available organic peroxides, taking into consideration the reaction temperature and the like.

[0054] 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.

[0055] 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 adhesion of the primer layer can be improved.

[0056] The amount of the acid compound grafted onto the acid-modified polyolefin is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% 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.

[0057] 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.

[0058] In the primer layer, the melting point of the acid-modified polyolefin is preferably 50° C. or higher, more preferably 60° 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 primer layer can be further improved.

[0059] In the primer layer, the melting point of the acid-modified polyolefin is preferably 160° C. or lower, more preferably 100° 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.

[0060] In the present disclosure, the melting point refers to the temperature at the top of an endothermic peak that occurs in the process of first holding the temperature at 180°C for several minutes, then cooling 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).

[0061] The weight average molecular weight (Mw) of the acid-modified polyolefin contained in the primer layer is preferably from 10,000 to 300,000, more preferably from 30,000 to 250,000, and even more preferably from 50,000 to 200,000.

[0062] The acidic polyolefin contained in the primer layer may be a commercially available product. Examples of commercially available acidic polyolefins include "MODIC" manufactured by Mitsubishi Chemical Corporation, "ADMER" and "UNISTOR" manufactured by Mitsui Chemicals, Inc., "TOYOTAC" manufactured by Toyobo Co., Ltd., "UMEX" manufactured by Sanyo Chemical Industries, Ltd., "REXPERL EAA" and "REXPERL ET" manufactured by Japan Polyethylene Corporation, "PRIMACOL" manufactured by Dow Chemical Co., Ltd., "NUCREL" manufactured by DuPont-Mitsui Polychemicals, and "BONDINE" manufactured by Arkema.

[0063] The primer layer may contain a polymer other than the above-described acid-modified polyolefin (hereinafter also referred to as "other polymer B") for the purposes of improving adhesion, hydrolysis resistance, heat resistance, etc. When the primer layer contains the other polymer B, the other polymer B may be one type or two or more types.

[0064] Other examples of the polymer B include phenolic resins, urea resins, melamine resins, benzoguanamine resins, alkyd resins, unsaturated polyester resins, vinyl ester resins, diallyl terephthalate resins, silicone resins, urethane resins, furan resins, ketone resins, xylene resins, thermosetting polyimide resins, benzoxazine resins, active ester resins, aniline resins, cyanate ester resins, styrene-maleic anhydride (SMA) resins, polyethylene resins, polypropylene resins, polystyrene resins, rubber-modified polystyrene resins, acrylonitrile-butadiene-styrene (ABS) resins, acrylonitrile-styrene (AS) resins, polymethyl methacrylate resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyethylene terephthalate resins, ethylene vinyl alcohol resins, cellulose acetate resins, ionomer resins, polyacrylonitrile resins, poly Examples of the resin include amide resins, polyacetal resins, polybutylene terephthalate resins, polylactic acid resins, polyphenylene ether resins, modified polyphenylene ether resins, polycarbonate resins, polysulfone resins, polyphenylene sulfide resins, polyetherimide resins, polyethersulfone resins, polyarylate resins, thermoplastic polyimide resins, polyamideimide resins, polyetheretherketone resins, polyketone resins, liquid crystal polyester resins, fluororesins, syndiotactic polystyrene resins, cyclic polyolefin resins, α-olefin copolymers, propylene-based elastomers, polyisoprene, hydrogenated polyisoprene, polybutadiene, cycloolefin polymers, cycloolefin copolymers, polyamines, polyamides, melamine resins, urea resins, styrene-based thermoplastic resins, hydroxyl group-modified polyolefin resins, and glycidyl methacrylate-modified polyolefin resins.

[0065] When the other polymer B is contained, the content of the other polymer B in the primer layer is preferably 0.1 mass % or more, more preferably 1 mass % or more, and particularly preferably 5 mass % or more, based on the total amount of the primer layer. When the content of the other polymer B is within this range, the improving effect of the other polymer B is enhanced.

[0066] When the other polymer B is contained, the content of the other polymer B in the primer layer is preferably 50% by mass or less, more preferably 35% by mass or less, and particularly preferably 20% by mass or less, based on the total amount of the primer layer. When the content of the other polymer B is within this range, the multilayer sheet can have further improved adhesion, hydrolysis resistance, and heat resistance.

[0067] The primer layer preferably further contains a curing agent. The curing agent is preferably a compound capable of forming a crosslinked structure between acidic polyolefins. From the viewpoint of improving adhesion durability, examples of the curing agent include isocyanate compounds, epoxy compounds, carbodiimide compounds, and oxazoline compounds, and it is more preferable that the curing agent be at least one selected from isocyanate compounds and epoxy compounds.

[0068] The isocyanate compound is preferably a compound having two or more isocyanate groups (—NCO) (i.e., a polyfunctional isocyanate compound), and examples thereof include bifunctional diisocyanates, and trifunctional or higher isocyanates having a structure such as an adduct structure, an isocyanurate structure, or a biuret structure.

[0069] The isocyanate compound may be a commercially available product, such as Duranate TPA-100, Duranate T4900-70B, Duranate MFA-75B, Duranate MHG80B, or Duranate 21S-75E (manufactured by Asahi Kasei Corporation), Takenate A-3, Takenate A-50, Takenate 500, Takenate 600, Stabio D-370N, or Stabio D-376N (manufactured by Mitsui Chemicals, Inc.).

[0070] Examples of epoxy compounds include bisphenol type epoxy resins such as bisphenol A type epoxy resins (different from hydrogenated bisphenol A type epoxy resins) and bisphenol F type epoxy resins; hydrogenated bisphenol type epoxy resins; novolac type epoxy resins; biphenyl type epoxy resins; stilbene type epoxy resins; hydroquinone type epoxy resins; naphthalene skeleton type epoxy resins; tetraphenylolethane type epoxy resins; trishydroxyphenylmethane type epoxy resins; dicyclopentadiene phenol type epoxy resins; 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate alicyclic epoxy resins such as 1,2-epoxy-4-(2-oxiranyl)cyclohexane adducts of 2,2-bis(hydroxymethyl)-1-butanol; polyglycidyl esters of polybasic acids such as diglycidyl esters of hexahydrophthalic anhydride; glycidyl ethers such as sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, pentaerythritol polyglycidyl ether, trimethylolpropane polyglycidyl ether, polypropylene glycol diglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, and cyclohexanedimethanol diglycidyl ether; diene polymer epoxy resins such as polybutadiene or polyisoprene; tetraglycidyldiaminodiphenylmethane, tetraglycidylbisamino ... Examples of epoxy resins include glycidylamine-type epoxy resins such as diglycidylcyclohexane, diglycidylaniline, and tetraglycidylmetaxylylenediamine; and heterocycle-containing epoxy resins such as triazine or hydantoin.

[0071] As the epoxy compound, commercially available products may be used, such as EPICLON HP7200, EPICLON HP4700, EPICLON HP4710 (manufactured by DIC Corporation), jER828, jER157S70 (manufactured by Mitsubishi Chemical Corporation), JP-100, JP-200 (manufactured by Nippon Soda Co., Ltd.), EPPN-501H, NC-7000 (manufactured by Nippon Kayaku Co., Ltd.), TETRAD-C, TETRAD-X (Mitsubishi Gas Chemical Company, Inc.), and the like.

[0072] The amount of the curing agent to be added can be appropriately determined depending on the type and content of the acidic polyolefin, the type and content of the other polymer B, etc. Only one type of curing agent may be used, or two or more types may be used.

[0073] When an isocyanate compound is used in the primer layer, the amount of the isocyanate compound added is preferably 0.1% by mass to 50% by mass, more preferably 5% by mass to 40% by mass, and even more preferably 10% by mass to 35% by mass, relative to the content of the acid-modified polyolefin. When the amount of the isocyanate compound added is in the above range, the adhesive durability of the multilayer sheet tends to be improved and shape stability tends to be easily obtained.

[0074] When an epoxy compound is used in the primer layer, the amount of the epoxy compound added is preferably 0.1% by mass to 40% by mass, more preferably 1% by mass to 30% by mass, and even more preferably 5% by mass to 20% by mass, relative to the content of the acid-modified polyolefin. When the amount of the epoxy compound added is within the above range, the adhesive durability of the multilayer sheet tends to be improved and overcuring tends to be easily suppressed.

[0075] From the viewpoint of curability, an additive selected from imidazole compounds, dioctyl tin laurate, amine compounds, phosphorus compounds, etc. (hereinafter also referred to as "additive X") may be added to the primer layer. Additive X may be a catalyst added from the viewpoint of promoting the reaction of the curing agent.

[0076] The amount of additive X to be added can be appropriately determined depending on the type and amount of curing agent used, the type and amount of acid-modified polyolefin used, etc. Only one type of additive X may be used, or two or more types may be used.

[0077] The primer layer 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, foaming agents, and combinations thereof.

[0078] <Adhesive Layer> The adhesive layer is a layer that exhibits adhesion to an adherend. The adhesive layer is preferably a layer containing at least one selected from polyethylene, polypropylene, an ethylene-propylene copolymer, a styrene-based thermoplastic elastomer, polyester, polyamide, and an acid-modified polyolefin, and more preferably a layer containing an acid-modified polyolefin.

[0079] In the acid-modified polyolefin contained in the adhesive layer, examples of the monomer units constituting the polyolefin include monomer units derived from a monomer 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.

[0080] 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.

[0081] Polyethylene is a polymer containing ethylene units as a main component, and may be a homopolymer or a copolymer. When polyethylene 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.

[0082] Polypropylene is a polymer containing propylene units as a main component, and may be a homopolymer or a copolymer. When the polypropylene is a copolymer, the content of propylene units in the polypropylene is 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.

[0083] 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.

[0084] Polyolefins include physical blends of these resins, reactive blends in which functional groups are reacted between different polymers in a molding machine, graft copolymers or block copolymers consisting of multiple segments, and compositions in which physical blends using these as compatibilizers are microdispersed.

[0085] 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 even be 100% by mass. The mass ratio of ethylene units to propylene units contained in the polyolefin (ethylene units / propylene units) 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, and adhesive strength can be improved. 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, adhesive durability at both high temperatures and low temperatures can be achieved. 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 among all ethylene units and propylene units contained in the polyethylene and polypropylene.

[0086] 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 The absorbance ratio is determined from the absorbance ratio of the ethylene unit and propylene unit. Specifically, a calibration curve is used to convert the absorbance ratio of the ethylene unit and propylene unit into a mass ratio. The calibration curve can be created by blending commercially available polyethylene and polypropylene in various ratios and plotting the blend ratio and absorbance ratio.

[0087] 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.

[0088] Methods for producing polyolefins include known production methods using a polymerization catalyst. Examples of the polymerization catalyst include a Ziegler catalyst or a metallocene catalyst, and examples of the polymerization method 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.

[0089] The acid compound used when acid-modifying the polyolefin, the method and conditions for acid-modification, and the amount of acid-modification are as already described in the description of the primer layer, and therefore further description is omitted here.

[0090] The weight average molecular weight (Mw) of the acid-modified polyolefin contained in the adhesive layer is preferably 50,000 to 1,000,000, more preferably 100,000 to 750,000, and even more preferably 150,000 to 500,000.

[0091] In the adhesive layer, 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 can be improved.

[0092] In the adhesive layer, 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.

[0093] 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.

[0094] The melt flow rate of the adhesive layer is a value measured in accordance with JIS K7210:2014 (ISO 1133 2011). The melt flow rate of the adhesive layer was measured at a resin temperature of 230°C and a load of 2.16 kg.

[0095] The content of the acid-modified polyolefin in the adhesive layer may be 2% by mass or more. For example, the acid-modified polyolefin may be used in combination with an unmodified polyolefin. For example, when using an acid-modified polyolefin with a high degree of acid modification, a small amount of about 2% by mass of the acid-modified polyolefin may be used. In one embodiment, the content of the acid-modified polyolefin in the adhesive layer 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.

[0096] A polymer other than the acid-modified polyolefin (hereinafter referred to as "other polymer C") can be added to the adhesive layer for the purpose of improving the adhesive strength at low temperatures, adhesive durability, molding stability, and adhesion to the base layer. Examples of other polymer C 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 C.

[0097] When the other polymer C is used, the lower limit of the content of the other polymer C in the adhesive layer is preferably 1 mass % or more, more preferably 2 mass % or more, and particularly preferably 3 mass % or more. When the added amount is within this range, the improving effect of the other polymer C is enhanced.

[0098] When another polymer C is used, the upper limit of the content of the other polymer C in the adhesive layer 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 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.

[0099] A crosslinkable resin may be added to the adhesive layer, but it is preferable that the content of the crosslinkable resin in the adhesive layer is small or completely absent. A low content of the crosslinkable resin increases the crystallinity of the acid-modified polyolefin, improving heat resistance and hydrolysis resistance. A low content of the crosslinkable resin can prevent excessive increase in molecular weight due to crosslinking formation, improving the formability of the adhesive layer. The content of the crosslinkable resin in the adhesive layer is preferably less than 3% by mass, more preferably less than 1% by mass, particularly preferably less than 0.5% by mass, and may even be 0% by mass. The crosslinkable resin is capable of crosslinking the main component of the adhesive layer, and examples thereof include resins having multiple functional groups such as phenol novolac-modified epoxy resins, oxazoline group-containing styrene resins, and epoxy group-containing polyolefin resins.

[0100] The adhesive layer may further comprise additives selected from the group consisting of antioxidants, ultraviolet absorbers, fillers, reinforcing fibers, release agents, processing aids, flame retardants, plasticizers, nucleating agents, antistatic agents, pigments, dyes, blowing agents, and combinations thereof.

[0101] The substrate layer preferably has a thickness in the range of 10 μm to 300 μm, more preferably in the range of 30 μm to 250 μm, and particularly preferably in the range of 50 μm to 200 μm. When the thickness of the substrate layer is equal to or greater than this lower limit, sufficient rigidity can be obtained. When the thickness of the substrate layer 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.

[0102] The primer layer preferably has a thickness in the range of 1 μm to 20 μm, more preferably in the range of 5 μm to 20 μm, and particularly preferably in the range of 10 μm to 20 μm. When the thickness of the primer layer is equal to or greater than this lower limit, sufficient adhesion can be obtained. When the thickness of the primer layer 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.

[0103] The adhesive layer preferably has a thickness in the range of 10 μm to 200 μm, more preferably in the range of 20 μm to 150 μm, and particularly preferably in the range of 30 μm to 100 μm. When the thickness of the adhesive layer is equal to or greater than this lower limit, the occurrence of poor adhesion can be suppressed. When the thickness of the adhesive layer 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.

[0104] 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.

[0105] The total thickness of the multilayer sheet is preferably 30 μm to 400 μm, more preferably 50 μm to 350 μm, and particularly preferably 50 μm to 300 μm.

[0106] In the present disclosure, the thickness of the multilayer sheet and each layer constituting the multilayer sheet is defined as the arithmetic mean value of the thicknesses at three locations obtained by preparing a slice having a cross section perpendicular to the main surface of the multilayer sheet and measuring the thicknesses using a digital microscope VHS-8000 (manufactured by Keyence Corporation).

[0107] The base layer and adhesive layer are generally produced from a resin composition as a raw material, which is a composition mainly composed of the components of the base layer and adhesive layer described above.

[0108] The resin composition that forms the base layer and the adhesive layer can be produced by melt-kneading the main component resin and, if necessary, other components using an extruder, a Banbury mixer, a heated roll, or the like, and then cooling and solidifying the strands extruded from the nozzle holes of the die head with water or the like while pulling them, and then cutting them into pellets.

[0109] The temperature for melt-kneading the resin composition used for the base layer is preferably 150°C to 320°C, more preferably 180°C to 300°C, and the kneading time is usually 0.5 to 20 minutes, preferably 1 to 15 minutes.

[0110] The temperature for melt-kneading the resin composition used for the adhesive layer is preferably 150°C to 270°C, more preferably 170°C to 250°C, and the kneading time is usually 0.5 to 20 minutes, preferably 1 to 15 minutes.

[0111] The base layer and adhesive layer can be obtained by molding the resin composition used for the base layer and the resin composition used for the adhesive layer obtained in this manner into a film using a conventionally known method (e.g., extrusion molding).

[0112] The primer layer is preferably formed on at least one surface of the substrate layer by a coating method. That is, the primer layer is preferably a coated layer. For example, the primer layer can be formed by dissolving or dispersing the components of the primer layer described above in a solvent to prepare a primer layer-forming composition, applying the primer layer-forming composition onto the substrate layer using a coating means, volatilizing the solvent to form a substrate layer with a coating film, adhering the obtained substrate layer with the coating film to an adhesive layer, and then curing the coating film.

[0113] The solvent may be an organic solvent capable of dissolving or dispersing the components of the primer layer. The means for applying the primer layer-forming composition may be a bar coater, a spray gun, a dispenser, a roll coater, a curtain coater, a dip coater, or the like.

[0114] The temperature and time for volatilizing the solvent can be appropriately set in consideration of the type of solvent, etc., and can be, for example, 50° C. to 200° C. and 0.1 to 5 minutes.

[0115] The multilayer sheet according to the present disclosure can be produced as follows. First, a substrate layer with a coating film and an adhesive layer are each prepared in advance. Next, the surface of the substrate layer on which the coating film is disposed is placed opposite the adhesive layer, and a multilayer laminate is obtained by thermal lamination. Next, the laminate is cured to harden the coating film, thereby obtaining a multilayer sheet.

[0116] Thermal lamination can be performed using a known laminator. There are no limitations on the lamination conditions, and general conditions can be applied. The lamination temperature is preferably 50°C to 200°C, and more preferably 80°C to 150°C. The conveying speed during lamination is preferably 0.01 m / min to 200 m / min, and more preferably 0.1 m / min to 100 m / min. The lamination pressure is preferably 0.01 MPa to 10 MPa, and more preferably 0.1 MPa to 5 MPa.

[0117] By curing the laminate after thermal lamination, the curing of the coating film progresses, and a multilayer sheet in which the substrate layer, primer layer, and adhesive layer are more firmly bonded can be obtained. The curing conditions may be, for example, leaving the laminate at rest at a temperature of 40°C to 150°C for 0.5 to 7 days.

[0118] The multilayer sheet according to the present disclosure can be bonded to an adherend formed of various materials such as metal, glass, ceramics, or plastic. This allows for the production of an assembly including the multilayer sheet and the adherend. For example, an assembly including the multilayer sheet can be used as a member or part of a layered battery. In one embodiment, the multilayer sheet according to the present disclosure is preferably used as a gasket member for a fuel cell.

[0119] 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.

[0120] 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.

[0121] The multilayer sheet according to the present disclosure will be described in more detail below with reference to examples, although the multilayer sheet according to the present disclosure is not limited to the following examples.

[0122] 1. Substrate layer materials Polyphenylsulfone film (PPSU): Radel R-5000 (manufactured by Solvay) was used as the PPSU film, and a film with a thickness of 70 μm was produced using a T-die extruder. Polyimide film (PI): Upilex 125RN (thickness 125 μm, manufactured by UBE) was used as the PI film. Polyethylene naphthalate film (PEN): Teonex Q51 (thickness 100 μm, manufactured by Toyobo) was used as the PEN film.

[0123] 2. Primer layer materials <Main component> Acid-modified polyolefin-1 (PO-1) Propylene-butene-1 copolymer, melting point: 70°C, molecular weight: Mw 100,000, maleic anhydride modification rate: 1.1% by mass Acid-modified polyolefin-2 (PO-2) Propylene-butene-1 copolymer, melting point: 80°C, molecular weight: Mw 90,000, maleic anhydride modification rate: 1.1% by mass Polycarbonate diol-1 (PD-1) Duranol T5652 (manufactured by Asahi Kasei Corporation) Polycarbonate diol-2 (PD-2) Duranol T5650J (manufactured by Asahi Kasei Corporation) Polycarbonate diol-3 (PD-3) Duranol T3452 (manufactured by Asahi Kasei Corporation)

[0124] <Curing agent> Isocyanate compound-1 Duranate TPA-100 (manufactured by Asahi Kasei Corporation) Epoxy compound-1 EPICLON HP-7200 (manufactured by DIC Corporation)

[0125] <Additive X> Imidazole compound-1 Curezol C11Z (manufactured by Shikoku Chemicals Co., Ltd.) Dioctyltin laurate reagent (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0126] <Two-component urethane adhesive> Takelac A-1143 (Mitsui Chemicals, Inc. polyester polyol) Takenate A-3 (Mitsui Chemicals, Inc. aromatic isocyanate compound) Takenate A-50 (Mitsui Chemicals, Inc. aliphatic isocyanate compound)

[0127] 3. Adhesive Layer Material: TM55 (Aronmelt (registered trademark) TM55, manufactured by Toagosei Co., Ltd., melting point 142°C) was used to produce a film having a thickness of 55 μm using a T-die extruder.

[0128] <Film surface treatment> Base layer: Corona treatment machine (Navidas, Polydyne 1, discharge amount: 81.5 W min / m ２ Adhesive layer: Corona treatment machine (Navidas, Polydyne 1, discharge amount: 81.5 W min / m) ２ , once back and forth) and one side (only the side to be stuck to the primer layer) was treated.

[0129] <Primer Layer-Forming Composition> Primer 1 (P-1) to Primer 7 (P-7) were prepared as primer layer-forming compositions as follows.

[0130] Preparation of Primer 1 (P-1) 14.9 g of acid-modified polyolefin (PO-1) was dissolved in a mixed solvent of 36.2 g of methyl ethyl ketone and 50.8 g of methylcyclohexane at 60°C, and then 0.3 g of dioctyl tin laurate, 2.4 g of isocyanate compound-1, and 2.4 g of isocyanate compound-2 were dissolved therein to obtain Primer 1 (PO-1).

[0131] Preparation of Primer 2 (P-2) 20.0 g of acid-modified polyolefin (PO-2) was dissolved in a mixed solvent of 35.5 g of toluene, 8.3 g of methyl ethyl ketone, and 82.9 g of methylcyclohexane at 60°C, and then 2.0 g of epoxy compound-1 and 0.03 g of imidazole compound-1 were dissolved therein to obtain Primer 2 (PO-2).

[0132] Preparation of Primer 3 (P-3) 50.0 g of polycarbonate diol-1 (PD-1) was dissolved in a mixed solvent of 50.0 g of toluene and 5.0 g of methyl ethyl ketone, and then 10.0 g of isocyanate compound-1 was dissolved therein to obtain Primer 3 (P-3).

[0133] Preparation of Primer 4 (P-4) 67.0 g of polycarbonate diol-2 (PD-2) was dissolved in a mixed solvent of 33.0 g of toluene and 14.9 g of methyl ethyl ketone, and then 30.1 g of isocyanate compound-1 was dissolved therein to obtain Primer 4 (P-4).

[0134] Preparation of Primer 5 (P-5) 50.0 g of polycarbonate diol-3 (PD-3) was dissolved in a mixed solvent of 50.0 g of toluene and 5.0 g of methyl ethyl ketone, and then 10.0 g of isocyanate compound-1 was dissolved therein to obtain Primer 5 (P-5).

[0135] The compositions of Primer 1 (P-1) to Primer 5 (P-5) are summarized in Table 1 below. In Table 1, P-1 to P-5 correspond to Primer 1 (P-1) to Primer 5 (P-5), respectively. The unit of composition is "g."

[0136]

[0137] Preparation of Primer 6 (P-6) As a two-component urethane adhesive, Takelac A-1143 (polyester polyol; manufactured by Mitsui Chemicals, Inc.) and Takenate A-3 (aromatic isocyanate; manufactured by Mitsui Chemicals, Inc.) were mixed in a mass ratio of 9:1 to obtain Primer 6 (P-6), a two-component urethane adhesive.

[0138] Preparation of Primer 7 (P-7) Primer 7 (P-7) was obtained by mixing Takelac A-1143 (polyester polyol; manufactured by Mitsui Chemicals, Inc.) and Takenate A-50 (aliphatic isocyanate; manufactured by Mitsui Chemicals, Inc.) as a two-component urethane adhesive in a mass ratio of 9:1.

[0139] Example 1 Primer 1 (P-1) was applied to one side of a polyphenylsulfone film (PPSU, thickness 70 μm) using a bar coater to a coating thickness of 10 μm (dry), and the solvent was evaporated at 100°C for 1 minute to obtain a coated film (coated substrate layer). The coated surface of the obtained coated film was then bonded to TM55 (an acid-modified polypropylene film; thickness 55 μm) by thermal lamination (100°C, 0.3 m / min, 0.3 MPa). Primer 1 (P-1) was also applied to the uncoated side of the PPSU film in the same manner, and the film was bonded to TM55 to obtain a laminate. The obtained laminate was then aged at 100°C for 4 days to cure the coating. As a result of the above, a multilayer sheet (thickness 200 μm) was obtained in which the adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / base layer (thickness 70 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in this order.

[0140] Example 2 Primer 2 (P-2) was applied to one side of a polyphenylsulfone film (PPSU, thickness 70 μm) using a bar coater to a coating thickness of 10 μm (dry), and the solvent was evaporated at 100°C for 1 minute to obtain a coated film (coated substrate layer). The coated surface of the obtained coated film was then bonded to TM55 (an acid-modified polypropylene film; thickness 55 μm) by thermal lamination (100°C, 0.3 m / min, 0.3 MPa). Primer 2 (P-2) was also applied to the uncoated side of the PPSU film in the same manner, and the film was bonded to TM55 to obtain a laminate. The resulting laminate was then cured at 80°C for 2 days to harden the coating, thereby obtaining a multilayer sheet (thickness 200 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 70 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in this order.

[0141] Example 3 Primer 1 (P-1) was applied to one side of a polyimide film (PI, thickness 125 μm) using a bar coater to a coating thickness of 10 μm (dry), and the solvent was evaporated at 100°C for 1 minute to obtain a coated film (coated substrate layer). Thereafter, the coated surface of the obtained coated film was bonded to TM55 (an acid-modified polypropylene film; thickness 55 μm) by thermal lamination (100°C, 0.3 m / min, 0.3 MPa). Primer 1 (P-1) was also applied to the uncoated side of the PI film in the same manner, and the PI film was bonded to TM55 to obtain a laminate. The resulting laminate was then cured at 100°C for 4 days to harden the coating, thereby obtaining a multilayer sheet (thickness 255 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 125 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in that order.

[0142] Example 4 Primer 2 (P-2) was applied to one side of a polyimide film (PI, 125 μm thick) using a bar coater to a coating thickness of 10 μm (dry), and the solvent was evaporated at 100°C for 1 minute to obtain a coated film (coated substrate layer). The coated surface of the obtained coated film was then bonded to TM55 (an acid-modified polypropylene film; 55 μm thick) by thermal lamination (100°C, 0.3 m / min, 0.3 MPa). Primer 2 (P-2) was also applied to the uncoated side of the PI film in the same manner, and the PI film was bonded to TM55 to obtain a laminate. The resulting laminate was then cured at 80°C for 2 days to harden the coating, thereby obtaining a multilayer sheet (thickness 255 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 125 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in that order.

[0143] Comparative Example 1 Primer 3 (P-3) was applied to one side of a polyphenylsulfone film (PPSU, thickness 70 μm) using a bar coater to a coating thickness of 10 μm (dry), and the solvent was evaporated at 100° C. for 1 minute to obtain a coated film. The coated surface of the obtained coated film was then bonded to TM55 (an acid-modified polypropylene film; thickness 55 μm) by lamination (roll room temperature, 0.3 m / min, 0.3 MPa). Primer 3 (P-3) was also applied to the uncoated side of the PPSU film in the same manner, and the film was bonded to TM55 to obtain a laminate. The resulting laminate was then cured at 60°C for 2 days to harden the coating, thereby obtaining a multilayer sheet (thickness 200 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 70 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in this order.

[0144] Comparative Example 2 A multilayer sheet (thickness 200 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 70 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in this order was obtained in the same manner as in Comparative Example 1, except that "Primer 4 (P-4)" was used instead of "Primer 3 (P-3)" as the resin composition forming the primer layer.

[0145] Comparative Example 3 A multilayer sheet (thickness 200 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 70 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in this order was obtained in the same manner as in Comparative Example 1, except that "Primer 5 (P-5)" was used instead of "Primer 3 (P-3)" as the resin composition for forming the primer layer.

[0146] Comparative Example 4 A multilayer sheet (thickness 200 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 70 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in this order was obtained in the same manner as in Comparative Example 1, except that "Primer 6 (P-6)" was used instead of "Primer 3 (P-3)" as the resin composition forming the primer layer.

[0147] Comparative Example 5 A multilayer sheet (thickness 200 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 70 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in this order was obtained in the same manner as in Comparative Example 1, except that "Primer 7 (P-7)" was used instead of "Primer 3 (P-3)" as the resin composition forming the primer layer.

[0148] (Comparative Example 6) Primer 3 (P-3) was applied to one side of a polyimide film (PI, thickness 125 μm) using a bar coater to a coating thickness of 10 μm (dry), and the solvent was evaporated at 100° C. for 1 minute to obtain a coated film (coated substrate layer). Thereafter, the coating surface of the obtained coated film was bonded to TM55 (acid-modified polypropylene film; thickness 55 μm) by lamination (roll room temperature, 0.3 m / min, 0.3 MPa). Primer 3 (P-3) was also applied to the uncoated side of the PI film in the same manner, and the PI film was bonded to TM55 to obtain a laminate. The resulting laminate was then cured at 60°C for 2 days to harden the coating, thereby obtaining a multilayer sheet (thickness 255 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 125 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in this order.

[0149] Comparative Example 7 A multilayer sheet (thickness 255 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 125 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in this order was obtained in the same manner as in Comparative Example 6, except that "Primer 4 (P-4)" was used instead of "Primer 3 (P-3)" as the resin composition forming the primer layer.

[0150] (Comparative Example 8) A multilayer sheet (thickness 255 μm) in which an adhesive layer (thickness 55 μm) / a primer layer (thickness 10 μm) / a base layer (thickness 125 μm) / a primer layer (thickness 10 μm) / an adhesive layer (thickness 55 μm) were laminated in this order was obtained in the same manner as in Comparative Example 6, except that "Primer 5 (P-5)" was used instead of "Primer 3 (P-3)" as the resin composition forming the primer layer.

[0151] Comparative Example 9 Primer 2 (P-2) was applied to one side of a polyethylene naphthalate (PEN) film (thickness 100 μm) using a bar coater to a coating thickness of 10 μm (dry), and the solvent was evaporated at 100° C. for 1 minute to obtain a coated film. The coated surface of the obtained coated film was then bonded to TM55 (an acid-modified polypropylene film; thickness 55 μm) by lamination (roll room temperature, 0.3 m / min, 0.3 MPa). Primer 3 (P-3) was similarly applied to the uncoated side of the PEN film, and the film was bonded to TM55 to obtain a laminate. The resulting laminate was then cured at 80°C for 2 days to harden the coating, thereby obtaining a multilayer sheet (thickness 230 μm) in which an adhesive layer (thickness 55 μm) / primer layer (thickness 10 μm) / substrate layer (thickness 100 μm) / primer layer (thickness 10 μm) / adhesive layer (thickness 55 μm) were laminated in this order.

[0152] (Evaluation) The multilayer sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 8 were subjected to the following measurements and evaluations.

[0153] <Initial Peel Strength> The initial peel strength was measured by the hot water peel test described below. Using 0.1 mm thick SUS304 plates as adherends, the multilayer sheets produced in the Examples and Comparative Examples were sandwiched between the SUS304 plates and thermocompression bonded (180°C, 3 seconds, 1 MPa) using a precision press to produce a bonded structure. This bonded structure was cut into 10 mm wide strips to prepare test specimens. The bonded portion of the test specimen was 10 mm wide and 15 mm long. 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 Imada Co., Ltd.), and a heated water bath with a hook attached to the bottom was filled with 95°C hot water. The test specimen was immersed in the water and peeled at 30 mm / min to measure the initial peel strength (N / mm). The results are shown in Table 2.

[0154] <Adhesion durability in water> To evaluate adhesion durability at high temperatures and in water, the test pieces prepared above were placed in a pressure-resistant container filled with pure water, and the pressure-resistant container was heated in an oven at 120°C. After holding for 1500 hours, the test pieces were removed from the pressure-resistant container and subjected to the above-mentioned hot water peel test to measure the peel strength (N / mm). The obtained results were evaluated according to the following evaluation criteria. The results are shown in Table 2.

[0155] [Evaluation criteria] A: Peel strength after immersion for 1500 hours is 0.50 N / mm or more. B: Peel strength after immersion for 1500 hours is 0.40 N / mm or more and less than 0.50 N / mm. C: Peel strength after immersion for 1500 hours is 0.30 N / mm or more and less than 0.40 N / mm. D: Peel strength after immersion for 1500 hours is less than 0.30 N / mm or cannot be measured.

[0156]

[0157] In Table 2, P-1 to P-7 correspond to primer 1 (P-1) to primer 7 (P-7), respectively.

[0158] As shown in Table 2, the multilayer sheets of the examples in which the base layer contains a specific polymer and the primer layer contains an acid-modified polyolefin have superior adhesion durability in high-temperature and humid environments compared to the comparative examples in which the primer layer does not contain an acid-modified polyolefin.

[0159] The multilayer sheet according to the present disclosure is useful for bonding and sealing metals and other materials, and is suitable for use in applications where the resulting bonded body may be in continuous or intermittent contact with moisture. The multilayer sheet according to the present disclosure has excellent adhesive durability even in high-temperature, moisture-containing environments, and therefore has a wide range of applications.

[0160] Applications of the multilayer sheet according to the present disclosure include, for example, electric wires and cables in which metal conductors or optical fibers are coated with a resin molded product, 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, insulation materials for metal pipes, insulation materials for vehicles, fuel cell water pipes, decorative molded products, water cooling tanks, boiler exterior cases, peripheral parts and components for printer ink, water piping, joints, secondary battery alkaline storage battery tanks, gasket sealants for various layered batteries, and the like.

[0161] The disclosure of Japanese Patent Application No. 2023-111757, filed on July 6, 2023, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A multilayer sheet comprising, in this order, a base layer, a primer layer disposed on at least one surface side of the base layer, and an adhesive layer, wherein the base layer comprises a polymer having a structural unit including at least one structure selected from the group consisting of an imide structure, a sulfone structure, an amide structure, and a sulfide structure, and the primer layer comprises an acid-modified polyolefin.

2. The multilayer sheet according to claim 1, wherein said primer layer further comprises a curing agent.

3. The multilayer sheet according to claim 2, wherein the curing agent comprises at least one selected from an isocyanate compound and an epoxy compound.

4. The multilayer sheet according to claim 1 or 2, wherein the acid-modified polyolefin contained in the primer layer is a maleic anhydride-modified polyolefin.

5. The multilayer sheet according to claim 1 or 2, which is used as a gasket member for a fuel cell.